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Foredrag
AerOzClim Module II:
Description of aerosol particles and their physical properties in a
atmospheric global climate model (CCM-Oslo).
Trond Iversen, Øyvind Seland, Alf Kirkevåg, Jon Egill Kristjansson
Department of Geosciences, University of Oslo, P.O. Box 1022, Blindern, N-0315 Oslo.
([email protected])
The potential influence of anthropogenic aerosol particle on climate is designated by
IPCC TAR as an important source of climate model uncertainty. There are several reasons for
this. Particles are partly realeased directly into air and partly produced in situ by gas-toparticle physico-chemical reactions. They are subject to quick depletion by precipitation
scavenging, and their tropospheric residence times are generally only a few days to a week.
Also they can be produced and processed otherwise in cloud droplets. Hence, the space-time
distribution of aerosols is strongly influenced by clouds, and clouds and their properties are
themselves very uncertain in atmospheric numerical models.
One potential climate effect of aerosols is the particles’ reflection and absorption of
solar radiation; the direct effect. To calculate the radiative forcing due to this requires
knowledge of particle composition as a function of particle size, in order to estimate the
reflectivity and absorptivity for each wavelength of light. Another potential climate effect of
aerosols is linked to the particles’ ability to extract water from water vapor and thus act as
cloud condensation nuclei (CCN). More CCNs may cause smaller and more reflective cloud
droplets (first indirect effect), less efficient precipitation release and thus more cloudiness
(second indirect effect).
In AerOzClim we develop new methods that are simplified compared to “first
principles”, but still more accurate than in earlier climate models. In this presentation we will
demonstrate the principles behind the schemes along with results from designed experiments
for the ongoing intercomparison exercise that prepares for the next IPCC report (Aerocom).
CHEMCLIM: Tropospheric chemistry and climate
Ivar S.A. Isaksen
Department of Geosciences, University of Oslo, P.O. Box 1022, Blindern, N-0315 Oslo.
([email protected])
In CHEMCLIM the overall focus is on how natural emission and emission of pollutants affect
oxidation processes in the atmosphere and the distribution of chemical active greenhouse gases
(e.g. ozone, methane), particles from natural (sea salt, mineral dust) and anthropogenic (e.g.
sulfate, organics) sources, and how changes in the emission contribute to the global radiative
forcing. Global model studies are being performed in three main areas: Studies of the oxidation
potential of the troposphere and how it is changing due to changes in the emission of pollutants.
The OsloCTM2 model has been updated with the newest and best emission inventories that are
available. The purpose is to be able to make sensitivity studies of different emission source
categories impact on current, past and future climate and pollution levels. The oxidation studies
include particular model studies of ozone and sulfate particle formation due to ship emissions and
studies of changes in sulfate burden due to emission changes over the last 10 to 15 years. Studies
of sources of mineral dust and temporal changes in the global distribution have been performed in
collaboration with University of California, Irvine. Studies of climate-chemistry interactions of
water vapour in the upper troposphere and lower stratosphere (UTLS) region are being performed
in collaboration with State University of New York (SUNY), Albany, using the NCAR CCM3
climate model. Most of the modeling studies in the CHEMCLIM project are performed by PhD
students as part of their thesis work, and include a significant part of basic process studies and
model development. The Oslo CTM2 has been developed to include extensive physical and
chemical schemes to study chemical active gaseous and aerosol compounds. Comparisons with
observations show that the models developed are able to realistically reproduce the distribution of
major chemically active compounds in the troposphere. The modeling activities performed in
CHEMCLIM are the basis for particle studies and ozone climate–chemistry studies performed in
AerOzClim. Results from the modeling activities in the different areas will be presented.
CHEMCLIM: Studier av kjemisk active klimagasser (ozon, methan) og partikler (sulfat,
organiske partikler, sjøsalt, mineralstøv) i atmosfæren og deres innvirkning på strålingen.
Combined Observational and Modeling Based Studies of
the Aerosol Indirect Effect (COMBINE)
Jón Egill Kristjánsson1, Trude Storelvmo1, Mona Johnsrud2, Gunnar Myhre1,2, Frode
Stordal1, Ann-Mari Fjæraa2
1
Department of Geosciences, University of Oslo
2
Norwegian Institute for Air Research, Kjeller
Humans influence the climate in various ways, e.g., by releasing so-called greenhouse gases
into the atmosphere and by introducing new particles (aerosols) into the atmosphere. In this
way the number of cloud condensation nuclei (CCN) is enhanced, leading to smaller and more
numerous cloud droplets, which reflect more solar radiation. The impact of this “indirect
effect” of aerosols is, by current estimates, only surpassed in magnitude by greenhouse gas
forcing, but with opposite sign. At present, there is great uncertainty concerning many aspects
of the indirect effect. This is due to a combination of poorly understood physics, insufficient
measurements and oversimplified model treatments. In Norway, the modeling aspect has been
addressed within the RegClim project, and will be worked on further in AerOzClim. To
strengthen the research in this area, we have introduced an integrated effort combining
climate modeling and the use of satellite observations. To improve the simulations of the
indirect effect, prognostic equations will be developed for cloud droplet number and ice
crystal number. The satellite observations will serve to identify and evaluate the magnitude of
the indirect effect, as well as to validate crucial model parameters, such as aerosol optical
depth, cloud optical depth, liquid water path and CCN. These quantities are obtained from the
MODIS instrument onboard the Terra and Aqua satellites.
Deep water ventilation processes
Peter M. Haugan, Tor Eldevik, Bjørn Ådlandsvik on behalf of the ProClim participants
The deep parts of the world oceans are ventilated from the surface in limited areas at
high latitudes. Small scale ocean mixing processes, mesoscale variability, sea ice formation
and salt release are involved in setting the properties of the deep water and the pathways of
circulation between low and high latitudes. Since this circulation is crucial to the ocean heat
transport, the surface temperature and the sea ice distribution, there is a need to understand the
physics of the processes and their sensitivity to atmospheric conditions. Studies in the Polar
Ocean Climate Processes (ProClim) project focusses on process studies in the Storfjord area
and the western Barents Sea, Norwegian Sea, and Greenland Sea.
The sea ice production and salt release in Storfjorden is primarily determined by the
strength of northeasterly winds locally each winter. The resulting dense water volume and
properties also depend upon the Arctic and Atlantic water masses advected into the area, i.e.
on larger and longer time scale conditions. Mixing in the outflow is primarily determined by
shear instability between the dense flow and ambient water above. This first order description
based on measurements gives a good basis for modelling based on appropriate atmospheric
forcing, although predictive capability for the whole system still remains to be tested.
Deep convection in the open ocean involves small net vertical volume flow but is
nevertheless important for deep water properties and large scale pressure fields. The
variability in the strength of the different ventilation processes and pathways on shelves and
in the deep ocean is large. The possibility for alternation between different modes and shift
between different areas in closing the overturning circulation will be addressed in later parts
of the project but remains a motivation for the ongoing work.
ECOBE 2003-2006 (Effects of North Atlantic Climate Variability On the
Barents Sea Ecosystem) – preliminary results from the first year of the
project.
Svein Sundby
Institute of Marine Research and Bjerknes Centre for Climate Research
The over-all goal of this integrated project is to understand and quantify the impacts of Arctic
climate variability on trophic transfer and ecosystem structure of the Barents Sea in order to
improve the prediction of growth and recruitment on key fish species. Inflow of Atlantic
plankton-rich water from the Norwegian Sea onto the Norwegian continental shelves is of
major importance for the growth and survival of fish stocks along the Norwegian coast and in
the Barents Sea. Additionally, ocean climate parameters as temperature, light conditions,
wind-induced mixing and turbulence are important abiotic parameters for individual growth
of marine organisms. In the ECOBE project, we use integrated physical-biological models to
explore influence of the various processes of importance for growth and recruitment in fish.
Laboratory experiments produce important input data to the coupled models. The model
results are compared to survey data of pelagic juveniles from the region. Here, we present
preliminary results after the first year of the project. A first-generation individual-based model
simulates growth and survival of larval fish from the spawning areas along the Norwegian
coast till the stage of pelagic juveniles when they are spread out in the Barents Sea.
Ecological and nutrient feedbacks to anthropogenic ocean acidification
from rising atmospheric CO2
Richard Bellerby – Bjerknes Centre for Climate Research, University of Bergen
The surface oceans are increasing in carbon dioxide, in concert with rising atmospheric
concentrations, and there is a consequentially reduction in the seawater pH. Models show that
within this century, the anticipated drop in pH will reach levels not seen for the last 420,000
years. Laboratory and field studies have shown that such pH levels have a considerable effect
on plankton physiology and community structure. Further into the next century ocean pH will
reduce to levels that severely effect the survival of certain marine organisms, particularly
benthic and polar species. Decreased pH results in changes in nutrient utilisation and export
production which will have consequences for food web structure and ultimately for fisheries.
Such planktonic biogeochemical responses will have pronounced feedback to atmospheric
carbon dioxide concentrations.
ECOSYSTEM MANIPULATIONS AS A TOOL IN CLIMATE
RESEARCH
Arne Stuanes1, Richard F. Wright2, Heleen de Wit3, Lars Hole4, Øyvind Kaste2 & Jan
Mulder1
1
Department of Plant and Environmental Sciences, Agricultural University of Norway,
2
Norwegian Institute for Water Research, 3 Norwegian Institute for Land Inventory,
4
Norwegian Institute for Air Research
Large-scale ecosystem experiments are a powerful tool to study environmental effects
on ecosystems. Norway has a long experience with large-scale experiments in forest, lake and
heathland ecosystems and has an international reputation in this field. Large-scale ecosystem
experiments started in the 1970s with research on effects of acid rain on forest and fish (SNSF
project). In the SNSF project large field experiments included addition of artificial acid rain in
forests and manipulations in small catchments. This was followed by the RAIN project (198493) where a small upland catchment with trees was covered by a roof to study the reversibility
of acidification. Later, ecosystem-scale experiments with nitrogen (addition and exclusion) in
forest (NITREX) and acidification of lakes (HUMEX) were established. In another largescale experiment in forest aluminium was added to study the effect of this metal on a closed
forest stand. Experiments to study the effects of climate change began in the 1990s with the
CLIMEX project (glass house covering a forested catchment where CO2 concentration and air
temperature were increased) and the THERMOS project (manipulation of heat budget for a
whole lake).
Results and experiences gained from these large-scale ecosystem experiments have
led to use of this approach in the new Norwegian climate change effects project “Effect of
climate change on flux of N and C: air-land-freshwater-marine links (CLUE)”. In the CLUE
project we will manipulate snow cover, freeze-thaw cycles, and soil wetness in minicatchments to simulate future climate scenarios of increased frequency of freezing and
thawing cycles in winter, melting episodes due to increased temperature in winter and
increased summer and autumn precipitation.
Such controlled large-scale experiments give direct information on effects of different
environmental factors on an ecosystem level. They are necessary for evaluation of long-term
effects in a short-term perspective. Such experiments are also essential for testing of models
that later can be used for extrapolations in time and space.
Ecosystem process modeling with input data from climate
scenarios, preliminary experiences.
Lars Bakken
GCM simulations of the present and future global climate can be downscaled to provide local
“weather forecasts”. Such downscaled global warming scenarios are like manna from heaven
for ecosystem process modellers because they allow us to explore the effects of future global
warming on ecosystem functions, including their feedback on the global warming. These
phenomena are not predictable by simple statistical climate information (average temperature,
annual precipitation etc), because of various non linear responses of interacting components
within the ecosystems. We need real weather scenarios (daily weather information) to run our
models! The Norwegian research program Regclim has produced such regionalized weather
scenarios for the period 2030-2049, based on the basic global scenario from Max-PlanckInstitute (MPI) in Germany.
We have used these “weather forecasts” for 2030-49 (SIM3049) as driving data in a cluster of
physical, biological, and economical models for agroecosystems. Such exercises necessarily
requires an investigation of validity of the weather forecasts as well as our ecosystem
forecasts. As a control, we used downscaled MPI simulations for the period 1980-99
(SIM8099), which were compared to observed weather in the same period (OBS8099). Some
problematic characteristics of the SIM8099-weather were identified, which had severe
consequences for the simulation of water transport, plant growth and soil erosion. Some of
these problems were solved by adjustments based on empirical downscaling, and the RegClim
project plans for further improvements in the near future. Other problems experienced were
the lack of transparency and a large annual variability (20 years scenarios are too short to test
relevant changes).
Assuming that the contrast between SIM3049 and SIM8099 is an adequate prediction of the
climate change in response to future global warming, we find that soil erosion will increase
dramatically and nitrate leaching may increase substantially. The latter is a result of an altered
economic optimum for N-fertilization due to slight changes in the product functions. This was
not statistically significant, however.
Fører klimaendring til at fjellreven forsvinner?
Nina E. Eide, John D.C. Linnell, Unni S. Lande, Vidar Grøtan, Olav Strand og Pål
Prestrud
Arctic fox populations declined rapidly around 1900 throughout Fennoscandia and were close
to extinction around the 1920s. Despite more than 70 years of protection there has been no
recovery of the arctic foxes. The decline was extremely pronounced in Fennoscandia.
Although less pronounced, the decline in arctic foxes was observed throughout the whole
Arctic. The changes in population sizes across several continents happen approximately at the
same time; around 1900, implying a common change happening at larger spatial scales. Many
hypotheses have been put forward to explain the non-recovery of the arctic fox; one of them is
indirect effects of a warmer climate. The southerly (and lower altitudinal) distribution of
arctic foxes is probably constrained by the distribution of the dominant competitor, the red
fox, with arctic foxes only surviving in areas that have too low productivity for red fox to
survive. At the same time as arctic foxes declined, there was a general temperature rise from
1900 over the whole northern hemisphere. A general temperature rise is expected to result in a
vertical rise in productivity zones; which also lead to the expectation that red fox distribution
will expand vertically, leading to a decrease in potential arctic fox habitat. The main objective
of this study has been to improve our understanding of possible influences of climate changes
on community structure in alpine ecosystems, with main focus on the relationship between the
arctic fox (a “polar” species) and the red fox (a “temperate” species). Changes at the level of
species could in the long run lead to changes in species diversity, shorter food chains and a
simplification of alpine ecosystems. The red fox as a typical generalist predator is also a
pronounced keystone species, and an increase and expansion of the red fox population could
hence have large influence on both the structure and the dynamic of the alpine ecosystem. We
explore coincident changes in the abundance of species having the same specialist food niche
as the arctic fox; snowy owl, rough-legged buzzard, long-tailed skua; which could indicate
larger changes in the structure of alpine ecosystems, and if these changes relate to the climatic
changes that have occurred over the last 100-150 years. Could further climate change result in
loss of the arctic fox and typical alpine habitat niches?
PAST CLIMATE OF THE NORWEGIAN REGION (NORPAST-2):
STATUS & RESULTS
Morten Hald
Project coordinator, Department of Geology, University of Tromsø
NORPAST-2 is a nationally coordinated NFR-project that aims to advance the knowledge of
patterns and variability of past climate in the Norwegian Region (Norway and adjoining
continental margin and fjords), and to contribute to the understanding of climate forcing
factors. The studies focus on quantitative climate reconstructions during the last deglaciation,
the Holocene and the Recent Past. We investigate a limited number of high-resolution sites
from terrestrial and marine archives; by improving paleoclimatic proxies; and by synthesising
existing and new data. The instrumental record of climate variability is too short and spatially
incomplete to reveal the full range of seasonal to millennial-scale climate variability, or to
provide empirical examples of how the climate system responds to large changes in climate
forcing. This recent record is also a complex reflection of both natural and anthropogenic
forcing (e.g., trace gases and aerosols). Various proxy sources, on the other hand, provide the
much wider range of realisations needed to describe and understand the full range of natural
climate system behaviour.
In this presentation I will give some examples from some new results form the first year of the
project. This will include: 1) Climate variations over the last 1500 years; 2) Reconstructions
of snow avalanche during the Holocene, Jostedalen inner Sogn; 3) Quantitative
reconstructions of winter precipitation at Jostedalsbreen and Hardangerjøkulen during the
Holocene; 4) Glacier variations during the Holocene; 5) Reconstructions of surface and
bottom water temperatures along the Norwegian continental margin during the Holocene. 6)
Age models for paleoclimatic proxy records.
The reconstructions clearly show that climate in the Norwegian Region has been both
significantly warmer and cooler that it is today during the Holocene. Both rapid (decadal)
changes, as well as more gradual (century-millennial) changes have been observed during the
past. Possible climate forcing mechanisms will be discussed.
RegClim Phase III: A focus on risks and uncertainties in climate
projections for Northern Europe and parts of the Arctic.
Trond Iversen
Project leader of RegClim, Department of Geosciences, University of Oslo, P.O. Box 1022,
Blindern, N-0315 Oslo. ([email protected])
RegClim’s main emphasis is to produce scenarios for climate development in Norway
and adjacent sea areas, including parts of the Arctic. The purpose is to enable quantitative
assessments of potential impacts of climate change in the region on the natural environment
and on society. There are, however, considerable uncertainties associated with such scenarios
due to natural climate variability or “chaos” (I), errors resulting from inadequate process
descriptions in climate models (II), and future assumptions resulting in radiative forcing of the
climate system (III). These uncertainties will manifest as a statistical spread in the estimates
of all climate relevant parameters. Statistical spread connected with I and III is unavoidable,
but the spread caused by III must be kept at a reasonable level. Spread caused by II should,
however, be as small as possible by improving the models. Statistical spread is closely related
to risks for extreme events, and large model uncertainties produce wrong assessments of risk.
In this presentation we will present plans for RegClim Phase III, along with selected
results so far. In particular we will present results from a combination of two dynamically
downscaled scenarios. Finally, we will briefly mention results from climate response of
aerosol particles and from theoretical studies of regional climate predictability. Results from
studies of the Atlantic Meridional Overturning Circulations and from empirical downscaling
of a large ensemble of IPCC climate scenarios will be presented in separate talks.
RegClim: Local and regional climate scenarios for Norway:
Evaluation of uncertainties
Eirik J. Førland, Rasmus Benestad, Inger Hanssen-Bauer & Torill E. Skaugen.
Norwegian Meteorological Institute, P.O.Box 43 Blindern, N-0313 Oslo, Norway
(e-mail: [email protected])
A survey of downscaled daily and monthly scenarios for Norway will be given, including
both available and planned projections. Presently available downscaled scenario data from
RegClim are available at: http://noserc.met.no/effect/. The presentation will focus on
uncertainties of climate scenarios in our region evaluated by empirical downscaling of 17
global climate projections made for IPCC TAR.
Climate scenarios in general and local scenarios in particular are encumbered with several
sources of uncertainty: a). Internal variations in the climate system leads to unpredictable
natural variability. b). Uncertainties concerning future changes in climate forcings (Natural
forcings, i.e. solar radiation, volcanoes, Anthropogenic release of gases and particles, Changes
in land-use), c). Imperfect climate models (Imperfect knowledge about forcing and processes,
Imperfect physical and numerical treatment of processes, Poor resolution in the global
models) and d). Weaknesses in downscaling techniques.
Different AOGCM simulations may thus produce quite different regional climate scenarios,
and examples will be given of spread in temperature and precipitation projections for Norway.
Some of the pitfalls in deducing local projections from the spatial scale (55x55km) in the
present RegClim Regional Climate Model (RCM) will also be discussed.
During phase 3 of RegClim, it will be established a RCM with finer spatial resolution, and
methods for empirical downscaling of daily values will be improved. Special focus will be on
developing methods for analysing risk of changes in frequency distributions and extreme
values of temperature, precipitation and wind. This is an important component for evaluations
of societal and natural impacts of climate change. However, tailoring of climate scenarios for
specific impact studies is not a part of the planned RegClim activities.
RegClim: Trends and internal variability in a cmip2 ensemble
simulated with the Bergen Climate Model
A. Sorteberg, H. Drange*, N.G.Kvamstø, T. Furevik
Bjerknes Center for Climate Resear ch, University of Bergen.
*Also NERSC, Bergen.
An ensemble of five climate change simulations of each 80 years has been carried out with
the Bergen Climate Model (BCM). The 5 ensemble members have all been integrated with a
1% increase per year in CO2 content with 353ppm as initial level. But they have been started
from different initial physical states (taken from a control run).
The spread between the ensemble members in simulated regional (and zonal mean) climate
changes seem to be a function of the ensemble mean response. The relation we see is that
large ensemble mean response is associated with large ensemble spread and vice versa for
small mean response. We observe the largest spread in wintertime over land in the mid and
high latitudes.
Furthermore, the spread in zonal mean trends are a strong function of sampling time. Our data
show that the trend spread between the ensemble members is reduced by a factor of 2 by
increasing sample time from 50 to 70 years and a reduction of 80-90% is found by reducing
sampling time from 20 to 75 years.
The regional climate warming pattern in individual ensemble members showed increased
similarities with increasing sampling time. For Europe the pattern correlation increased with a
factor of about 1.5 by increasing sampling period from 20 to 75 years. However, with a
sampling period of 75 years the mean pattern correlation for individual ensemble members is
less that 0.8.
Our findings suggest that climate change projections over a period of less than 50 years will
be strongly influenced by chaotic (or unpredictable) internal climate variability. Thus multimodel spread on these time-scales may partly be influenced by real model differences and
internal (natural) chaotic variations.
Salt and Freshwater transport in the Arctic Ocean and the Nordic Seas
Svein Østerhus, ([email protected])
Bjerknes Centre for Climate Research, University of Bergen
The main fluxes of salt/freshwater between the North Atlantic, the Nordic Seas and the Arctic
Ocean are measured by means of instrumented moorings in the Scotland-Greenland Gap, the
Barents Sea opening, and in the Fram Strait. As a result relative accurate flux estimates of salt
and heat can be given for the Atlantic inflow to the Nordic Seas. The cooling and freezing in
the Arctic converts the Atlantic Water into a fresh surface layer (ice) and a salty deep water.
Freshwater is added to the surface layers by atmospheric transport and river runoff. The
inflow of low saline water from the Pacific Ocean through the Bering Strait and transport
from the Baltic Sea via the Norwegian Costal current also add freshwater into this system.
The relative salty deep water returns to the Atlantic Ocean by overflowing the ScotlandGreenland ridge and the fresh surface layer returns via the East Greenland Current and
through the Canadian Archipelagos. The main of the freshwater leaves the Arctic Ocean
through the Fram Strait as ice and liquid water. The spreading of the freshwater in the
Greenland and Iceland seas is thought to play an important role in the deepwater formation
taking place in these seas. A freshening of the intermediate water is observed in the
Norwegian Sea since the mid 70’s and the density is decreasing. As a consequence the
overflow through the Faroe Bank Channel is reduced.
The impacts of climatic changes on nature and socioeconomic impacts of
climate change: an awkward relationship.
Asbjørn Aaheim
This presentation questions the observed trend of bringing studies of social and economic
impacts of climate change closer to the knowledge about physical changes in the natural
environment by narrowing the scope and focus. It is pointed out that the advantage of
delimiting the focus for the purpose of utilising the best available knowledge about the
physical changes usually has a cost in terms of neglecting vital socioeconomic relationships.
With examples from impacts assessments of climate change it is shown that there is no oneto-one relationship between physical changes and socioeconomic impacts. It is emphasised
that there is a need for a framework to systematically organising data and characterising
impacts of climate change in order to prepare them for socioeconomic analysis. It is suggested
to transform results about impacts into the framework of national accounting. The advantages
are, firstly, that results from independent impacts studies are made comparable, and the
contribution from each of them can be analysed in a broader socioeconomic context. Second,
it provides a checkpoint for the availability of data about impacts on the national scale, and a
reference for an evaluation of the data quality. Third, putting impacts assessments into the
frames of traditional economic analysis enables evaluation of climate change in familiar
terms, such as GDP, and analysis of impacts with established analytical tools.
The new IGBP programme IMBER (Integration of Marine
Biogeochemistry and Ecosystems Research).
Svein Sundby
Institute of Marine Research and Bjerknes Centre for Climate Research
The work with developing the IMBER Science Plan and Implementation Strategy, the new
IGBP programme, is now being finalised and submitted to the IGBP Council and Secretariat.
The work with the plan has been carried on over the last two years. The IMBER project is
being formed as an activity jointly sponsored by IGBP and SCOR (Scientific Committee on
Oceanic Research). The IMBER project goal is to understand how interactions between
marine biogeochemical cycles and ecosystems respond to and force global change. To achieve
this goal it will be important to understand the mechanisms by which marine biogeochemical
cycles control marine life and, in turn, how marine life controls biogeochemical cycles. In this
light, IMBER research aims to identify key feedbacks from marine biogeochemical cycles and
ecosystems to other components of the Earth System. Included in the IMBER plan is to
explore the effects of global change on human activities and welfare. IMBER will collaborate
with a number of other international programmes, particularly GLOBEC Global Ocean
Ecosystem Dynamics), SOLAS (Surface Ocean – Lower Atmosphere Study) og CLIVAR
(Climate Variability and Prediction) under World Climate Research Programme.
The Nordic Seas; a gateway between the North Atlantic
and Arctic Oceans
Cecilie Mauritzen, Trond Dokken, Helge Drange, Peter M. Haugan and Solfrid S. Hjøllo
The Nordic Seas (here defined as including the Norwegian, Greenland, Iceland and
Barents Seas) can be considered a gateway between the North Atlantic and Arctic Oceans,
and quantifying and understanding the variability of the fluxes between these regions is
considered an important component of understanding the global climate system. Within
Norwegian Ocean and Climate Project (NOClim) processes which govern oceanic heat
transport towards the Nordic Seas, and which provide the basis for atmospheric heat transport
from the Atlantic sector towards northern Europe, are investigated.
To examine the forcing, structure and sensitivity of the Atlantic Meridional
Overturning Circulation in response to buoyancy forcing, internal mixing and wind driving,
numerical modelling experiments in idealized and realistic basin configurations will be
performed. The Nordic Seas represents a (fairly) well-sampled end-member of the AMOC.
Therefore, the inflow and outflow properties across the Greenland-Scotland Ridge serve as
one – the northern – check-point of climate GCMs.
NOClim investigates the relevant processes that led to large and abrupt amplitude
climatic shifts. Climate transitions are identified by reconstructing oceanographic variables
across three different climate transitions that are all easily detectable in the paleo-record, and
where each climate transition represents a transition from different initial conditions. Each
event will be identified in all the cores, and will be subject for detailed investigation and
chemical/sedimentological/ biological analysis. Proxy data collected from surface samples are
calibrated with present day hydrography. Vertical temperature and salinity profiles through
the main inflow and outflow areas between Iceland, the Faroes and Shetland during three
major climate transitions are estimated, and quantitative reconstructions of the transport of
surface and deep water through the channels connecting the Nordic Seas and the North
Atlantic during climate transitions will be deduced from this study.
Historical data is assessed in order to investigate whether significant change to our
high-latitude (specifically the Nordic Seas) climate system is presently underway. Emphasis is
on the oceanic part of the climate system, and the goal is to contribute to the understanding of
the physical conditions that do (or do not) influence the oceanic heat fluxes in the Nordic
Seas. Analysis shows that there have been very significant hydrographic changes in the
Nordic Seas in the 20th century, and there is a need to establish whether the pathways or their
strength may have changed.
Postere
A study of the Arctic Upper Troposphere/Lower Stratosphere (UTLS)
region
K. Stebel ([email protected]), G.H. Hansen, A. F. Vik, and Y. Orsolini,
Institute for Air Research (NILU)
The tropopause region, the narrow transition layer between the troposphere and the stratosphere, plays
an important role in climate and radiation processes. Cross-tropopause transport of trace gases have
been intensively studied in the tropics and mid-latitudes. Only in recent years, motivated by the
increasing efforts to clarify the role of dynamical patterns or equivalently, changes in tropopause
altitude, in ozone trends, the tropopause in polar regions has got into the focus of scientific attention.
Here, we present the Arctic Upper Troposphere/Lower Stratosphere (UTLS) project, which started
during 2003. The scientific results will be obtained in collaboration with research groups from
Germany, Sweden and Finnland. The main objectives of this study are to further characterize the
Arctic tropopause trends, using the most recent comprehensive meteorological dataset from the
ECMWF and local meteorological measurements from radiosondes, ozonsondes, lidar and radar at
high-latitude stations, and to achieve understanding of the processes leading to the high variability of
the Arctic tropopause and Arctic UTLS temperatures in the last decade. Besides improving the
quality of trend studies, the 1990s/early 2000s data set will be utilized to investigate Arctic
stratosphere-troposphere coupling processes based on the thermal structure throughout the UTLS
region, with emphasis on their dependence on hemispheric circulation patterns and wave propagation
conditions. Furthermore, an investigation of meso-scale tropopause properties including stratospheretroposphere exchange processes in the vicinity of the Scandinavian mountain ridge is planned.
We give a general overview of the background and status of the Arctic UTLS projects, including a
presentation of the data sets available. Further, we show results from the algorithm implementation for
the determination of the thermal, ozone and radar tropopause. First, very preliminary, geophysical
outcomes will be presented.
Atmosphere-Ice-Ocean Interaction Studies in frozen Svalbard fjords
S. Gerland1, K. Widell2, P. Haugan2, F. Nilsen3, J-G. Winther1, K. Edvardsen4, M. McPhee5,
& J. Morison6
1: Norwegian Polar Institute, Polar Environmental Centre, Tromsø, Norway
2: Bjerknes Centre for Climate Research and Geophysical Institute, University of Bergen, Norway
3: University Courses on Svalbard, Longyearbyen, Norway
4: Norwegian Institute for Air Research, Polar Environmental Centre, Tromsø, Norway
5: McPhee Research Company, Naches, USA
6: Applied Physics Laboratory, University of Washington, Seattle, USA
The project Atmosphere-Ice-Ocean Interaction Studies (acronym “AIO”, duration 20022005), is designed to provide a rigorous basis for selected sea ice-related aspects of climate
hypotheses. The Norwegian project partner’s activities are funded by the Research Council of
Norway, whereas the complementary U.S. activities are funded by the National Science
Foundation under a US-Norway collaboration scheme.
The main thrust of the project is to perform controlled field experiments using Svalbard fjords
as a natural laboratory. The scientific objects include (1) to test proposed parameterizations
for ice-ocean heat exchange during conditions of ice freezing, (2) to measure vertical heat and
salt fluxes and develop parameterizations of ice-ocean heat exchange during melting, and in
conditions when sea ice is exposed to saline water which is colder than the melting
temperature of the fresher ice, (3) to investigate the role of penetrating solar radiation, in
particular effects of albedo and snow cover, in determining under-ice ocean temperature
structure and bottom ablation of sea ice, and (4) to study polynya processes where the
atmosphere-ice-ocean processes are interactively linked to water mass formation and
movement. Preliminary results from the first set of field campaigns, conducted in
Kongsfjorden and van Mijenfjorden, show generally different hydrographic conditions for the
two studied systems on large, medium and small scales. These differences can be explained
by the principal settings of the fjords, resulting in different ice formation and current
patterns/strengths.
Comparing methane data from Ny-Ålesund with results from a
regional transport model (MATCH)
Ine-Therese Pedersena,b, Kristina Enerotha, Erik Kjellströma,
Ove Hermansenb, Kim Holménb
a Department
b
of Meteorology, Stockholm University (MISU), S-106 91 Stockholm, Sweden.
Norwegian Institute for Air Research (NILU), N-9296 Tromsø, Norway.
E-mail: [email protected]
Methane (CH4) is an important greenhouse gas and a key molecule in tropospheric
photochemistry. The global burden of atmospheric CH4 has risen dramatically since the
preindustrial era, and recent measurements show global CH4 mixing ratios continuing to rise
although the rate of increase has slowed over the past decade (Dlugokencky et al., 2001). The
effect of methane transport source/sinks regions has been investigated on several stations in
the CMDL network. In the Arctic, north of the polar front, winter meteorology is somewhat
stagnant, with few storms and little precipitation to mix and clean the atmosphere (Raatz,
1991). Furthermore, the polar front limits how midlatitude surface sources can influence
tracer fields in the Arctic. In this project the in situ methane measurements from the Zeppelin
station in Ny-Ålesund (ZEP) on Svalbard (78°58´ N, 11°53´ E) are studied by comparing
continuous gas chromatograph data and flask data to simulated CH4 concentrations from an
atmospheric transport model. The model is used to investigate the distribution and transport of
CH4 in and out of the Arctic region. The model is a 3-dimensional Eulerian transport model
called Multiple-scale Atmospheric Transport and Chemistry modelling system (MATCH)
from Robertson et al. (1999). The meteorological fields (wind, temperature and pressure) are
taken from the European Centre for Medium range Weather Forecasts, ECMWF, available
every 6 hours. The chosen domain covers most of the Arctic. Emission and boundary
conditions for CH4 are taken from a global tracer transport model developed at "Centre for
Atmospheric Science" in Cambridge, U.K, on 5 x 5 resolution (Warwick et al., 2002). The
Zeppelin station is a part of the CMDL cooperative Air Sampling Network (Dlugokencky et
al., 1994) and at least once a week flask samples are collected and analysed at NOAA CMDL
in Boulder, Colorado by a GC/FID (http://www.cmdl.noaa.gov/). In addition to this a
trajectory climatology for Svalbard will be used to investigate how the atmospheric flow
patterns influence the observed CH4 concentration (Eneroth et al., 2003). By combining the
climatology with the MATCH model, emission scenarios can be tested to identify region
variability. One essential question being pursued is whether the high concentration of CH4 in
wintertime in the Arctic are mainly caused by leakage from gas fields in Western Siberia, or
originates from industrial activities further away in Russia or Europe.
References
Dlugokencky, E.J., Steele, L.P., Lang, P.M. and Masarie, K.A., 1994. The growth rate and distribution
of atmospheric methane. J. Geophys. Res. 99: 17,021-17,043
Dlugokencky, E.J., Walter, B.P., Masarie, K.A., Lang, P.M. and Kasischke, E.S., 2001. Measurements
of an anomalous global methane increase during 1998. Geophys. Res. Letters 28:499-509
Eneroth, K., Kjellström, E., Holmén, K., 2003. A trajectory climatology for Svalbard; investigating
how atmospheric flow patterns influence observed tracer concentrations. Physics and chemistry
of the Earth, in press.
Raatz, W.E., 1991. The climatology and meteorology of Arctic air pollution. Pollution of the Arctic
Atmosphere, edited by J.W. Sturges, pp. 13-42, Elsvier Sci., New York.
Robertson, L., Langner, J. and Engardt, M., 1999. An Eulerian Limited-Aewa Atmospheric Transport
Model. J. Appl. Meteo. 38:190-210
Warwick, N.J., Bekki, S., Law, K. S., Nisbet, E.G. and Phyle, J.A. 2002. The impact of meteorology
on the interannual growth rate of atmospheric methane. Geophys. Res. Letters 29 (20): Art. No.
1947OCT 15 2002
Keywords : methane; Arctic; transport model; tropospheric photochemistry; trajectory; Svalbard
Dynamical downscaling of marine climate
Bjørn Ådlandsvik and W. Paul Budgell,
Institute of Marine Research
To study the climate effects on economically important activities such as
petroleum, fisheries, and aquaculture high quality future climate scenarios
are needed. In RegClim we will provide such scenarios by dynamical
downscaling from larger scale coupled ocean-atmosphere models. This will be
done by forcing a high resolution regional ocean circulation model with
results from the large scale couples model at the surface and the lateral
boundaries.
The model tool chosen in the Regional Ocean Model System (ROMS). This model
uses a terrain-following vertical coordinate. As an adaption to the
downscaling use for Norwegian Waters, we have
implemented a dynamic-thermodynamic sea ice model and the FRS
boundary condition for the lateral boundaries.
Preliminary results will be presented where ROMS has been forced by the
NCAR/NCEP reanalysis at the surface and climatology laterally. In
particular, a 50+ year hindcast simulation has been performed for the North
Atlantic Ocean. Results with finer resolution for the North Sea and the
Barents Sea is also presented.
Economy and Ecology of Agriculture in a Changing
Climate: The Norwegian project EACC (2003-2008)
Forfattere:
Bleken Marina A, Bakken LR, Haugen LE, Lundekvam H, Rørstad PK,
Sørensen R, Vatn A.
Abstract: EACC is an interdisciplinary project which explores the possible consequences of
climate change for the economic and environmental performance of Norwegian agriculture.
The environmental factors included are soil erosion, nitrate leaching and the sinks and sources
of greenhouse gases. The integrated economic and ecological modelling allows an inspection
of economic outcome, farmers decisions and their effects on the environmental variables in a
future climate. The project also includes an investigation of the past: erosion and P losses
during the past 2000 years is investigated by sediment core analyses. The patterns of the past
soil erosion will be compared with documented changes in the climate and agronomy.
Effects of climatic change on the spruce bark beetle, an economically
important forest pest
Bjørn Økland, Paal Krokene og Erik Christiansen, alle ved Skogforsk i Ås
The spruce bark beetle (Ips typographus) is by far the most serious insect pest on mature
spruce in Eurasia. Studies of how various climate change scenarios may affect its population
dynamics have shown good progress during the first project year. A large-scaled time series
analysis revealed a dominance of lag 1 density dependence, and a marked shift in population
dynamics after a large-scaled windfall episode. These results indicate that the population
dynamics of the spruce bark are determined by resource availability rather than parasite-host
interactions. A strong regional synchrony in spatio-temporal analysis also indicates that some
large-scale climatic factor influence the dynamics. Among different climatic variables tested,
windfelling was the external variable showing the most parallel pattern of spatio-temporal
correlation to beetle dynamics. Thus, large windfall events may be a major synchronizer of
beetle outbreaks in areas subjected to regionalized weather systems, which may override
temperature and drought. The results are now used in the development of a resource-based
model that can be used to extrapolate to alternate climatic scenarios of the future. Test runs of
the model agree with historical data for length of outbreak periods and intervals between
outbreaks. A second model that is under construction sets the number of generations per year
as a function of local temperature, and attempts to predict the geographical distribution of
bivoltism in Norway under climatic change. Two papers from the project have been accepted
for publication in international journals.
Emission from International Sea Transportation and Environmental
Impact
Stig B. Dalsøren , Jostein K. Sundet, Ivar S. A. Isaksen and Tore F. Berglen,
Department of Geosciences, University of Oslo, P.O. Box 1022, Blindern, N-0315 Oslo.
([email protected])
Øyvind Endresen, Eirik Sørgård and Gjermund Gravir
Det Norske Veritas, Veritasveien 1, N-1322 Høvik, Norway
The impacts of emissions from cargo and passenger carrying ships in international trade are studied in
collaboration with Det Norske Veritas. Emissions from ships in international trade are not subject to
regulations as part of the Kyoto agreement. The International Maritime Organisation (IMO) has
introduced and is planning restrictions for specific areas (sulphur content in fuel) and new ship engines
(nitrogen oxides). Bearing in mind that ship emissions are one of the most rapidly increasing emission
sectors, it is also of interest to evaluate the predicted future importance compared to other sectors.
Perturbations of the global distribution of ozone, methane, sulphur and nitrogen compounds due to
ship emissions are estimated using the global 3-D CTM with interactive ozone and sulphur chemistry.
Ozone perturbations are highly non-linear, being most efficient in regions of low background
pollution. Different data sets are used as input for the model studies (e.g. AMVER, COADS), leading
to highly different regional perturbations. Maximum perturbation of ozone is obtained in the North
Atlantic and in the North Pacific during summer months. In contrast to the AMVER data the COADS
data gives particularly large enhancements over the North Atlantic. Ship emissions reduce global
methane lifetime by approximately 5 %. CO2 and O3 give positive radiative forcing (RF), and CH4
and sulfate give negative. The total RF is small (0.01 - 0.02 W/m2), but connected with large
uncertainties. Increase in acidification due to increased sulfate deposition is in average 3% and up to
10% in certain coastal areas.
Factors controlling UV radiation in Norway (FARIN)
A. Kylling, B. Kjeldstad, A. Dahlback, B. Johnsen, O. Engelsen, K.
Edvardsen, A. Bagheri, B.-A. Høiskar, T. Danielsen, L.-T. Nilsen
Norway, including Svalbard, covers more than 20 degrees of latitude. The
climate is quite diverse with little snow throughout the year in the far
south and often snow cover well into the summer in the far north.
Furthermore, the northern location makes Norway exposed to low ozone levels
during the Arctic spring. Thus, it is a unique laboratory for studying how
clouds, ozone, surface albedo, aerosols, latitude, and geometry of the
exposed surface control the UV radiation levels. The FARIN project aims to
study these factors by
1) quantifying how UV radiation is affected by clouds, snow and
ozone as a function of latitude and season and identify and quantify
any possible longterm changes in UV radiation and parameters that
control UV radiation.
2) quantifying how aerosols affect surface UV radiation, with
emphasis on coastal regions.
3) measuring and analyse the distribution of diffuse sky radiation
for a coastal site in Norway.
4) measuring and analyse the UV radiation on horizontal and
vertical surfaces.
5) performing a comprehensive instrument comparison with spectral
and broad band meters included in the project .
The project is presented including obtained results.
IMPACTS OF CLIMATE CHANGE ON NITROGEN LEACHING FROM
UPLAND ECOSYSTEMS
Øyvind Kaste1, Arne O. Stuanes2, Richard F. Wright1, Lars Hole3, Ståle Haaland2 & Jan
Mulder2
1
Norwegian Institute for Water Research, 2 Department of Plant and Environmental Sciences,
Agricultural University of Norway, 3 Norwegian Institute for Air Research
Elevated levels of inorganic nitrogen (N) in runoff water may have negative
environmental effects in both freshwater and marine ecosystems. In acid-sensitive areas,
leaching of nitrate (NO3-) contributes to surface water acidification by mobilising hydrogen
and inorganic aluminium ions from soil. Increased NO3- output to surface waters will also
alter the nutrient balance and possibly cause eutrophication problems in coastal waters, where
N commonly is the limiting element for primary production.
Non-forested upland catchments (typical for large areas in southern Norway) often
have a restricted capacity to retain N from atmospheric sources, owing to their thin and patchy
soils, sparse vegetation cover, high precipitation amounts and short growing season. In such
marginal areas, the predicted change in ambient climate might have significant effects on
catchment N cycling and subsequent losses of inorganic N to surface waters.
Long-term increases in air temperatures and precipitation amounts, as predicted by the
REGCLIM project, will have several implications for production, consumption and mobility
of N in catchments. In the recently started climate project ‘Effect of climate change on flux of
N and C: air-land-freshwater-marine links (CLUE)’ two major hypotheses will be tested: (1)
increased frequency of freezing-thawing events (due to reduced snow accumulation in
marginal areas) will increase the leaching of N from soil to water; (2) more frequent drought
and re-wetting events during summer will increase decomposition/mineralisation and subsequent losses of N from the soils. These hypotheses will be tested by large-scale
manipulation experiments (snow removal, insulation, irrigation) of upland mini-catchments
(30-300 m2) at Storgama, Telemark.
IMPACT OF CLIMATE CHANGE ON SURFACE WATERS AND
FJORDS
Øyvind Kaste, Nils R. Sælthun, Richard F. Wright, Line J. Barkved, Birger Bjerkeng,
Jan Magnusson & Jarle Molvær
Norwegian Institute for Water Research (NIVA)
In this project we apply a linked-model approach to assess possible impacts of
predicted climate change towards 2050 on hydrology and water quality in a river-fjord system
(the Bjerkreim River + Estuary in Rogaland). The work is part of a Strategic Institute
Programme (SIP) at NIVA (2002-2004), funded by the Norwegian Research Council. The
basic concept here is to 1) calibrate and link four existing models to simulate hydrology and
water quality at present climate, and 2) use this model platform to simulate possible effects of
various climate change scenarios on the same river-fjord system. Implementation of climate
scenarios is carried out in close collaboration with a research team from the Norwegian
Meteorological Institute (met.no). The four models included are HBV, MAGIC, INCA and
the NIVA Fjord Model. HBV uses catchment characteristics together with climate data
(observations + scenarios) to produce hydrological time series (daily time steps). The MAGIC
model uses deposition data, soil chemistry and climatic data to simulate runoff chemistry at
present (1990-2000), in the past (1860-1990), and in the future (2000-2050). INCA, which is
an integrated nitrogen (N) model for catchments, takes hydrological data from HBV,
carbon/nitrogen dynamics from MAGIC, deposition + point source data, and simulates daily
concentrations of inorganic N in the river. Finally, the NIVA Fjord model uses morphological
data, climate observations, together with time series data from HBV and INCA to simulate
effects of changed climate forcing, hydrology and N inputs on physical, chemical and
biological conditions in the estuarine area.
Impact of different dust production mechanisms on
downwind dust size distributions
Alf Grini
Department of Geosciences, University of Oslo, P.O. Box 1022, Blindern, N-0315 Oslo.
([email protected])
C. Zender
Department of Earth System Sciences, University of California, Irvine
A tracer transport model has been run with several different dust production schemes to try to explain
the discrepancy between modelled and measured aerosols at remote sites. The focus is in particular on
the difference between statical production schemes in which all dust particles have the same size
distribution, and dynamical schemes in which the size distribution can vary as a function of wind
speed and soil size distributions. Comparisons are made with campaign data. It is found that the type
of soil adopted has a significant influence on the distribution downwind.
Increased organic matter in surface waters of south-eastern
Norway - a change in the quality of freswaters due to climate
change?
Gunnhild Riise1, Dag Hongve2, Jan Mulder1, Ståle Haaland1, Dolly Kothawala1 and
Arne Stuanes1
1
Agric, Univ. of Norway, Dep. of Plant and Environmental Sci., P.O. Box 5003, 1432 Ås
Norwegian Institute of Public Health, P.O. Box 4404, 0403 Oslo
2
Clean, high quality surface water is an important resource for current and future
generations. During the last few decades several countries in North-western Europe
have reported increasing colour and concentration of organic matter (OM) in surface
water (Forsberg and Petersen 1990, Freeman et al. 2001, Liltvedt et al. 2001, Riise
and Hongve 2002). In Norway the strongest increase in colour has been found in the
southern and eastern part of the country, especially in the period1997-2001, but
there are also considerable increases in western Norway and Trøndelag. It has been
hypothesized that the increase in OM is associated with climate change, but
research on this topic is very limited. Others have suggested that decreases in
global sulphate deposition (acid rain) and large-scale changes in land-use may
explain the increase in OM.
OM in runoff represents an important problem because it affects physical and
chemical properties of surface water. Reduced transmission of light affects primary
production in water as well as biodiversity. Some waterworks have experienced a
three-fold increase in colour, which causes increased demands on water treatment
facilities.
Climate change may affect the dynamics of OM in soil water and catchment runoff in two different
ways. Increased temperature and wetter summers may cause increased decomposition of soil organic
matter, potentially resulting in increased production of CO2 and mobile organic compounds (Michalzik
et al., 2003). More intensive precipitation events in autumn results in a greater proportion of
streamflow being generated as surface runoff, which has greater concentrations of OM, and OM with
more hydrophobic properties than percolation water from deeper soil layers. The observed increase in
colour relative to OM, which is typical for episodes with increased precipitation, is probably related to
increased content of high molecular weight compounds (Riise and Hongve 2002), but more research is
needed. In the project “Effect of climate change on flux of N and C: air-land-freshwater-marine links
(CLUE)" this will be studied by large-scale manipulation (snow removal, insulation, irrigation) of
upland mini-catchments.
References:
Forsberg, C. and Petersen, R.C., 1990. A darkening of Swedish lakes due to increased humus
inputs during the last 15 years. Verh. Internat. Verein. Limnol. 24: 289-292
Freeman, C., Evans, C.D., Monteith, D.T., Reynolds, B. and Fenner, N., 2001. Export of
organic carbon from peat soils. Nature 412:785.
Liltvedt, H., Wright, R. and Gjessing, E., 2001. Monitoring increasing colour in Norwegian
surface waters – possible causes. VANN 36:70-77 (in Norwegian)
Riise, G. and Hongve, D. 2002. Influence of hydrological flow pattern versus atmospheric
sulphate deposition on water chemistry in low ionic forest lakes. Proceeding XXII Nordic
Hydrological Conference, Røros 2002, NHP Report no. 47: 337-342.
Michalzik, B., Tipping, E., Mulder, J. Gallardo-Lancho, J.F., Matzner, E., Bryant, C.L.,
Clarke, N.,Lofts, S. and Vicente Esteban, M.A. 2003. Modelling the production and transport
of dissolved organic carbon in forest soils. Biogeochemistry (in press).
Intercomparison of dynamic heights in the Nordic Seas from
observations and climate model simulations between 1950 and 1990.
Korablev, A., H. Drange, J. A. Johannessen and O. M. Johannessen.
The dynamic height D, defined as the product of the depth difference between two surfaces of
constant pressure and gravity, is a powerful quantity to derive the ocean circulation on both
regional and global scales. The dynamic height can be readily derived from 3-dimensional
observations of temperature and salinity, or from Ocean General Circulation Models
(OGCMs). It can also be derived from remotely sensed sea surface height and the Earth's
geoide. In the project, a unique Russian data set with about 130.000 hydrography observations
covering the 20th century has been used to compute the mean value and the decadal
variability of D of the Nordic Seas, i.e., from the ocean region between the GreenlandScotland Ridge and south and the Fram Strait in north. Similar computations are made from
an OGCM driven by daily atmospheric forcing fields from the period 1948 to present.
Analyses of the observed and simulated D-fields show many temporal and spatial similarities
between the two D-products. It is particularly evident that D varies on decadal time scales.
The degree of variability in the region over the last 50 years is quantified. This quantification
is of importance because it provides bounds on the accuracy of sea surface height determined
by satellites and the Earth's geoide if reliable estimates of the remotely sensed ocean
circulation are to be made.
Local temperature and precipitation scenarios for Norway
Inger Hanssen-Bauer, Eirik J.Førland and Ole Einar Tveito
Norwegian Meteorological Institute, P.O.Box 43 Blindern, N-0313 Oslo, Norway.
Local temperature and precipitation scenarios may be deduced by applying empirical
downscaling. The basic idea within empirical downscaling is that local climate is conditioned
by large-scale climate and by local physiographic features as topography, distance to coast
and vegetation. At a definite locality, links should thus exist between large-scale and local
climate. Empirical downscaling consists of revealing empirical links between large-scale
patterns of climate elements (predictors) and local climate (predictands), and applying them
on output from global or regional climate models. Successful empirical downscaling is thus
dependent on long reliable series of predictors and predictands. Within RegClim, scenarios
from several global climate models are empirically downscaled for the Nordic region.
The downscaled scenarios in this presentation are based upon the GSDIO-integration with the
ECHAM4/OPYC3 climate model. These scenarios indicate an average annual warming rate
of 0.2-0.5ºC/decade up to 2050 in Norway. The rates are generally smallest in southern
Norway along the western coast. They increase in the inland and in the northern parts. The
highest rates are found in the northernmost parts and in the inland valleys (0.5ºC/decade).
The precipitation scenarios for Norway indicate an average annual increase of 0.3-2.7% /
decade during the next 50 years. The changes are largest and highly significant along the
western and northwestern coasts. They are smallest and not statistically significant in
southeastern Norway. Both temperature and precipitation scenarios show a seasonal variation.
Corresponding author:
Eirik J. Førland, met.no, P.O.Box 43 Blindern, N-0313 Oslo, Norway
e-mail: [email protected]
Meridional Overturning Exchange with the Nordic Seas
MOEN (ASOF-EU-E)
By
Svein Østerhus
The mild climate of north western Europe is, to a large extent, governed by the influx of warm
Atlantic water to the Nordic Seas. Model simulations predict that this influx and the return of
flow of cold deep water to the Atlantic may weaken as a consequence of global warming.
MOEN (http://www.bjerknes.uib.no/research/MOEN/) will assess the effect of anthropogenic
climate change on the Meridional Overturning Circulation by monitoring the flux exchanges
between the North Atlantic and the Nordic Seas and by assessing its present and past
variability in relation to the atmospheric and thermohaline forcing. This information will be
used to improve predictions of regional and global climate changes. MOEN is a selfcontained project of the intercontinental Arctic-Subarctic Ocean Flux (ASOF,
http://asof.npolar.no) Array for European Climate project, which aims at monitoring and
understanding the oceanic fluxes of heat, salt and freshwater at high northern latitudes and
their effect on global ocean circulation and climate.
MOEN will contribute to a better long-term observing system to monitor the exchanges
between the North Atlantic and the Nordic Seas from direct and continuous measurements in
order to allow an assessment of the effect of anthropogenic climate change on the Meridional
Overturning Circulation. This we will be done by measuring and modelling fluxes and
characteristics of total Atlantic inflow to the Nordic Seas and of the Iceland-Scotland
component of the overflow from the Nordic Seas to the Atlantic.
MOEN objectives:
 To contribute to a better long-term observing system to monitor the exchanges
between the North Atlantic and the Nordic Seas.
 To assess the effect of anthropogenic climate change on the Meridional Overturning
Circulation
MOEN Tasks:
 Measure the total flux and characteristic of Atlantic water passing into the Nordic Seas
across the Greenland- Scotland Ridge
 Measure the flux and characteristic of the eastern component of the overflows from
the Nordic Seas to the North-Atlantic
 Estimate the contribution of meso- and small scale processes to these fluxes
 Model the fluxes and reconstruct their variability since the onset of the 20th century
 To relate strengths and variability of the fluxes to local and remote forcing
mechanisms as well as to internal modes of oscillations
Monitoring the Ice Shelf water overflow:
Importance for Antarctic ice cap melting and thermohaline circulation.
by
Tor Gammelsrød, Svein Østerhus and Povl Abrahamsen
Ice Shelf Water (ISW) is the final product of the melting process underneath the floating ice
shelves in the Antarctica. Recent drastic break-ups of the Larsen ice-shelf in the Weddell Sea
has vitalised the question if this melting has increased. The most efficient production of ISW
takes place under the immense Ronne – Filchner Ice shelves in the Southern Weddell Sea.
The corresponding ISW flow out of the region was located in 1977, and a key location for
long term monitoring was identified. Since then we have succeeded in occupying this station
with instrumented moorings for about 5 years, which have given us valuable information of
variability of the sub-ice shelf and continental shelf circulation. However, in addition to serve
as an indicator for Antarctic ice-cap melting, it turns out that the ISW flow contribute to the
formation of the Antarctic bottom water. Therefore it is driving the thermohaline circulation,
which has a great impact on the global climate. There are several processes and regions in the
Antarctic of importance for the bottom water formation. However, recent international efforts
indicate that the ISW overflow and its cascading towards large oceans depths as a bottom
trapped jet entrain waters from above, increasing the volume transport by a factor of about
2.5. The resulting volume transport estimates indicate that the processes involving ISW is
dominating the deep and bottom water formation in the Antarctic.
Norwegian Ocean and Climate project
Solfrid Sætre Hjøllo, NOClim Scientific Coordinator, Bjerknes Centre for Climate
Research
Norwegian Ocean and Climate project (NOClim) is a continuation of the NOClim Phase I project, but
focussing all available resources on the fundamental and overarching issue of Atlantic Water flow towards and
into the Nordic Seas. Active partners are Bjerknes Centre for Climate Research, Institute of Marine Research,
Nansen Environmental and Remote Sensing Center, Norwegian Meteorological Institute, Norwegian Polar
Institute and University of Bergen. The principal objective of the project is to significantly improve our
understanding of processes which govern oceanic heat transport towards the Nordic Seas, and which provide the
basis for atmospheric heat transport from the Atlantic sector towards northern Europe. The subgoals are i) to
elucidate how stable the Atlantic Meridional Overturning Circulation (AMOC) is to human induced greenhouse
warming, ii) to identify whether rapid climate transitions in the past were associated with changes in the
overturning rate in the Nordic Seas and iii) to investigate whether the balance of evidence (from observations,
process understanding and models) indicates that abrupt changes are underway or likely to happen in the near
future.
The project will be executed by combining theory and numerical modelling with analyses of recent
instrumental data and reconstructions from proxy data. The project is organised in three modules:



Module A: Theory and modelling of meridional oceanic heat transport
Module B: Analysis of abrupt changes in the past
Module C: Analysis of modern variability and detection of significant changes
The Polar Ocean Climate Processes (ProClim) project is integrated with NOClim as its module D. However,
ProClim is funded and reported separately.
NOClim intends to serve as an authoritative source of information and advice to the Research Council
and the public concerning the difficult issues of possible rapid climate change related to ocean circulation. More
information can be found at the project web-pages www.noclim.org
OCTAS: Ocean Circulation and Transport Between North Atlantic
and the Arctic Sea
Plag, H.-P., Drange, H., Gidskehaug, A., Johannessen, J.,
Nahavandchi, H., Omang, O.C.D., Pettersen, B.R., Solheim, D.
The Norwegian OCTAS Project running from 2003 to 2006 focuses on the ocean circulation
in the Fram Strait and adjacent sea with the main objective to improve sea surface topography
determination and to study the impact on ocen modelling. Up to the expected launch of
GOCE in 2005 the gravimetric geoid is not known with sufficient accuracy to allow full use
of the massive sea surface height information, which several satellite altimetry missions have
regularly provided since the early 90-ies, in global analysis of the ocean circulation. However,
in a few marine regions in the world sufficient in-situ information about the Earths gravity
field exists to compute a more accurate geoid. The region covering the Northern North
Atlantic and the Nordic seas between Greenland, Iceland, Norway and the UK, including the
Fram Strait is one of those regions. One goal of the OCTAS Project is therefore to determine
an accurate geoid in the Fram Strait and the adjacent seas. Together with the results from the
on-going EU-funded project GOCINA, where in a similar approach an accurate geoid is
determined for the region between Greenland and the UK, this will create a platform for
validation of future GOCE Level 2 data and higher order scientific products. The new and
accurate geoid is used together with an accurate Mean Sea Surface (MSS) to determine the
Mean Dynamic Topography (MDT).
Another major goal of OCTAS is to use this new and accurate MDT for improved analysis of
the ocean circulation. The ocean transport through the Fram Strait is known to play an
important role in the global circulation. Gulf Stream water flows into the Nordic seas and
feeds the formation of heavy bottom water that returns back into the Atlantic Ocean. Recent
results have shown that changes in this bottom water transport may cause the inflow of Gulf
Stream water to slow down or change into another stable circulation mode over a few
decades. Such a change of the Gulf Stream with even a possible shut down of the heat
transport towards high latitudes would have a huge impact on the North European climate.
The OCTAS project, in coordination with the GOCINA project, attempts to ellucidate the role
of the water exchange between the Arctic and Greenland Seas in this process.
Phenology as an indicator of climate change effects,
PhenoClim
K.A. Høgda, S. R. Karlsen, and I. Solheim.
Norut IT, N-9291 Tromsø, Norway
Fennoscandia is characterized by high climatic diversity and comprises nemoral zone in south
to southern arctic zone in north. The contrast in climate and vegetation from coast to inland
and along the altitude gradient is high. Accordingly, the region is well suited for studying
effects of climatic change.
The PhenoClim project started in 2003 and will last for five years. PhenoClim is financed by
The Research Council of Norway. Eight different institutes in Norway participate. The project
includes scientists in physics, biology, computer science, economy, and sociology. The
project is presented on web at: http://www.itek.norut.no/projects/phenology/index.html.
The objective of the PhenoClim project is to use in-situ and satellite data to establish
knowledge about ongoing large-scale changes in the phenological cycle and primary
production on a national and regional level. Phenological changes are studied in order to
investigate selected biological, economical, and social consequences of observed and
predicted climate changes.
In the first year of the project most of the work has been concentrated on collecting data (that
as far as legally possible will be made available on internet). Phenological data is collected by
more than 150 schools and 5 Planteforsk stations around Norway. In cooperation with the
national parks on Kola Peninsula unique historical phenological data series, the longest going
back to the 1930thies, are made available for the project. Satellite data from 1981-2003
(NOAA AVHRR 8 km resolution), 1998-2002 (Spot 1 km resolution) and 2000-2003
(MODIS 250 meter resolution) have been collected and is at present being analyzed.
In southern Fennoscandia results indicate a surprisingly high change in the start of spring
during the period from the beginning of 1980 to today. In most of southern Fennoscandia, the
spring now starts more than two weeks earlier compared to the early eighties. In addition, we
have also detected a delay trend in mountain areas in southern Norway and in continental
parts of northern Fennoscandia. This trend is also supported by the in-situ phenological data
from Kola Peninsula. Even more important, the phenological data from Kola Peninsula is also
indicating cyclic trends in the onset of spring (the last 20 years on the delay phase of the
trend), and earlier autumn. These trends are now to be further analyzed against meteorological
data.
Polar Ocean Climate Processes
Solfrid Sætre Hjøllo (Bjerknes Centre for Climate Research)
Polar Ocean Climate Processes (ProClim) is addressing climate processes in the geographical region of the
Polar Climate Research Programme by means of observations, process modelling, parameterization, analyses
of observations/model fields and synthesis. The principal objective of the project is to quantify and understand
climate processes in polar marginal seas, with emphasis on the western Barents Sea, Svalbard region and
Greenland Sea in order to improve our understanding of future regional and global climate and its
predictability. Sub-goals:
 To identify the parameters setting the mode of Greenland Sea convection.
 To understand dense water formation on polar shelves, and develop high resolution atmosphere, ice and
ocean model tools which properly describe the processes.
 To measure major cold outflows from the shelf region and understand the mixing processes determining
their fate.
 To assess the variable contributions to deep mixing and sinking from shelves and in the deep ocean and
understand the regional interaction between the processes.
The project is organized in four work packages: 1) Deep mixing and sinking, 2) Water mass formation on
shelves, 3) Slope convection and overflows off shelves and 4) Integration by (basin scale) models, observations
and theory. Work packages 1 to 3 will provide in-depth understanding of those regional components of global
thermohaline ocean circulation which are believed to be especially important for ocean heat transport and sea ice
extent in the northern seas. The fourth work package will use large scale models and observations to quantify the
variability and understand the interaction between processes.
The project team will use their unique field experience and facilities in Svalbard waters, the Greenland and
Barents Seas, in combination with theoretical and modelling. The project is funded by Norwegian Research
Council, Polar Climate Research Programme, and the duration is 2003-2006. More information can be found on
http://www.gfi.uib.no/ProClim
Sea Ice Fluxes through the Fram Strait
By
Karolina Widell, Svein Østerhus and Tor Gammelsrød
Ice velocity in the Fram Strait has been monitored by use of a new method using moored
Doppler Current Meters since 1996. Three years of data from 79 N 5 W in the period 19962000 are here presented and analysed with respect to the atmospheric driving force. A
correlation between the ice velocity and the cross-strait sea level pressure (SLP) difference
was R = 0.76 for daily means and R = 0.79 for monthly means is found and this result is used
to formulate a simple linear model of the ice area flux. The model gives a mean ice area
export for the period 1950-2000 of 850 000 km2/year, using NCEP/NCAR reanalysis SLP
data. The cross-strait SLP difference exhibits a positive trend since 1950 of 10 % of the mean
per decade indicating increased ice area export. We combine the modelled area flux with 10
years of ice thickness recordings from Upward looking Sonars to compute the ice volume flux
which is found to be 200 km3/month during the last decade, without any significant trend.
Sea Ice Thickness Measurements with ULS in the Barents Sea
by
Povl Abrahamsen, Svein Østerhus, and Tor Gammelsrød
Moored upward-looking sonar (ULS) is one of the most promising tools for monitoring
long-term, as well as interannual and seasonal changes in ice thickness. Annual
moorings with a current meter and a ULS were deployed in the Northwestern Barents
Sea around 77°55'N 28°20'E by the Norwegian Polar Institute from 1993-1996. This
yielded a two-year time series of ice drafts, which was processed and analyzed at the
Geophysical Institute, Univ. of Bergen. As preliminary processing, using algorithms
developed at the Norwegian Polar Institute primarily for use with data from Fram
Strait, proved unreliable, a new algorithm for processing this sort of data using
satellite-derived ice concentrations from the SSM/I sensor was developed. The
resulting data appears, as least subjectively, to result in significantly lower errors.
While we believe that in its current form this algorithm works best for data from the
Barents Sea, we do have some suggestions for applying it to other regions. The
processed data set shows significant differences in draft between the two years.
While the mean ice draft (including open water) for February-May 1995 was 2.61 m,
the corresponding value for 1996 was 1.56 m. Although there was a difference in
instrumentation, this cannot account for such large differences in draft. Thus, we
believe there was a significant change in circulation patterns between the two years,
affecting the inflow of Atlantic water, which largely controls the ice conditions of the
Barents Sea.
Seasonal forecast of the North Atlantic Oscillation with stratospheretroposphere models
Ina K. Thorstensen Kindem1,2
Yvan Orsolini 2
Nils Gunnar Kvamstø 2,1
Franscisco J. Doblas-Reyes 4
1. Bjerknes Centre for Climate Reseach
2. Geophysical Insitute, University of Bergen
3. Norwegian Institute for Air Research (NILU)
4. ECMWF, Reading, United Kingdom
The North Atlantic Oscillation (NAO) is one of the most important factors controlling the
North-Atlantic and European climate. Hence, improved seasonal predictability of the NAO
will be important to society. Attempts to forecast the NAO on medium to seasonal time scale
using troposphere-only models with boundary conditions of observed sea surface
temperatures (SSTs) have not proven too successful, as documented in the PROVOST project
(PRediction Of climate Variations On Seasonal to interannual Timescales). However, recent
statistical analysis has suggested that predictability of the NAO may be obtained from the
state of the stratospheric Arctic Oscillation. We have run the atmospheric general circulation
model ARPEGE with a well-resolved stratosphere and observed SSTs to investigate if we
improve upon the predictability scores from the troposphere-only models presented in
PROVOST. The technique for generating our model data set is similar to that in PROVOST.
Preliminary results of how our modelled NAO index compares to both the NAO index from
the PROVOST results and the observed NAO index from ERA-40 data will be presented.
Simulation of Erosion under 2 observed and 2 simulated Climates in the
Follo Region Southeast Norway.
Lundekvam, Helge Egil,
Agricultural University of Norway, E-mail: [email protected]
As part of the research program “Ecology and economy under a changing climate” (EACC)
(2003-2007) at the Agricultural University, also soil erosion on agricultural land is simulated.
In the following 4 climates were used: A) observed climate 1980-98 for Follo, B) simulated
present climate 1980-98, C) simulated future climate 2030-48, D) observed climate (1980-98)
at Ås in Follo (30 km south of Oslo). Climates A-C were provided May 2003 by the
REGCLIM group in Oslo based on dynamic/empirical downscaling of GCM-simulations.
Hydrological models used were the Swedish COUP model and AVRJUST3 (Lundekvam,
2002). Erosion model was ERONOR (Lundekvam, 2002). 2 soil types with slope 13% and
length 100 m were used, but only data from the most erodible soil is given in the poster. Over
20 different tillage systems were simulated, but only 7 are presented.
An evaluation of the simulated present climate B showed that precipitation was overestimated
by 140-200 mm/year especially during the months July and August. The frequency of days
with precipitation intensities less than 12 mm/day were also greatly overestimated. If
realistic, this would sometimes seriously postphone essential field operations such as sowing
and tillage. The frequency distribution of precipitation intensities greater than 12 mm were
similar to observed climate. Comparing simulated future and present climates showed similar
precipitation, an increase in temperature (+1.1 degrees), reduced snow cover and increased
frequency of rain or snowmelt on soil with little or no snow cover. This increases the climatic
erosion risk. Depending on hydrology model, soil type and tillage system used in the
simulations, surface runoff will increase by 4-70%, soil loss by fallow (best expressing
climatic erosion risk) will increase 40-60%, soil loss by ploughing autumn will increase 120200%, soil loss by other systems will increase 40-150%. The increase will mostly happen
during late autumn, winter and early spring. Thus agricultural systems with no till in autumn
will reduce soil losses even more in future than at present compared with traditional autumn
ploughing.
References:
Lundekvam, H., 2002. ERONOR/USLENO-Empirical erosion models for Norwegian
conditions. Report 6/2002. Agric. Univ. of Norway. ISBN 82-483-0022-6.
The Ocean beneath the Ronne Ice Shelf, Antarctica.
Svein Østerhus
Early in the history of modern oceanography it was realised that the bottom waters occupying
the abyss of the world oceans were renewed from sources at high latitudes. In the north these
sources were located in the Nordic Seas and in the south they were traced back to the Weddell
Sea. The formation processes for the coldest source water are connected with the
Filchner-Ronne Ice Shelf in the southern Weddell Sea. This is a large floating glacier
comparable in area to the North Sea and with a thickness ranging from 300 m at the seaward
edge (the barrier) to more than 2000 m where it initially goes afloat at its southern boundary.
The water mass characteristics in front of the ice shelf are determinded by advection and local
modification due to interaction with the atmosphere by heat and freshwater exchange, as well
as by freezing and melting of sea ice. Under the ice shelf melting and refreezing at the iceocean interface cause further modifications. These natural conditions are unique to the region
and result in the formation of large quantities of extremely cold sea water. This poster contain
results from the recent years of investigations in the sea water beneath the Ronne Ice Shelf
The role of climatic variation in the dynamics and
persistence of an Arctic predator – prey / host –parasite
system
Nigel G. Yoccoz *†, Eva Fuglei ‡, Rolf A. Ims †, Audun Stien †, Jan-Gunnar Winther ‡
* Norwegian Institute for Nature Research, Polar Environmental Centre, Tromsø
† Institute of Biology, University of Tromsø
‡ Norwegian Polar Institute, Tromsø
Microtus voles and lemmings are functionally important species in most terrestrial Arctic ecosystems:
they are both prey and predators (herbivores), and are the hosts of many parasites. The key role of
these small mammals is primarily due to their population dynamics with recurrent years with high
numbers/biomass. Population dynamics patterns and consequently their function in the ecosystem vary
geographically and temporally. It has been suggested that such large-scale and long-term patterns are
at least in part due to winter climate through properties of the snow cover. However, the links between
population dynamics patterns in arctic small mammals and qualitative and quantitative characteristics
of the snow cover, as determined by primary climatic variables such as temperature, precipitation and
wind, have yet to be established. The project started in 2002 in order to elucidate such links and to
predict how climate change may affect the ecosystem functions of arctic small mammals through the
properties of ice and snow. For this purpose we study a closed metapopulation of the sibling vole
Microtus rossiameridionalis at Svalbard and its interactions with a predator, the arctic fox, and a
parasite, the tape-worm Echinococcus multilocularis. The parasite has both the vole (intermediate) and
the fox (final) as host species. This predator-prey/host-parasite system has many favourable model
system characteristics that should enable us to establish:
(1) How the variability of winter climate determines qualitative/quantitative properties of the snow
cover in space and time,
(2) How properties of the snow cover in turn shape the spatio-temporal density dynamics in the vole
populations,
(3) How the spatio-temporal variation in vole dynamics and the snow cover in turn shapes the
functional response of the arctic fox to their vole prey, and
(4) Finally, how this chain of processes (1-3) determines spatially and temporally varying prevalence
of Echinococcus multilocularis both in its intermediate (i.e. the vole) and final host (i.e. the arctic
fox).
The Significance of the North Atlantic Oscillation (NAO) for Sea-salt
Episodes and Acidification-related effects in Norwegian Rivers.
ATLE HINDAR1, KJETIL TØRSETH2, ARNE HENRIKSEN3, AND YVAN ORSOLINI2
1
Norwegian Institute for Water Research, Grimstad, 2Norwegian Institute for Air Research,
3
Norwegian Institute for Water Research, Oslo
Acidification of Norwegian surface waters, as indicated by elevated concentrations of
sulphate and a corresponding reduction in acid neutralising capacity and pH, is a result of
emission and subsequent deposition of sulphur and nitrogen compounds. Episodic sea-salt
deposition during severe weather conditions may increase the effects of acidification by
mobilising more toxic aluminium during such episodes. Changes in climatic conditions may
increase the frequency and strength of storms along the coast thus interacting with
acidification effects on chemistry and biota. We found that the North Atlantic Oscillation
(NAO) is linked to sea-salt deposition and sea-salt induced water chemistry effects in five
rivers. Particularly, toxic levels of aluminium in all rivers were significantly correlated with
higher NAO index values. Further, temporal trends were studied by comparing tendencies for
selected statistical indices (i.e. frequency distributions) with time. The selected indices
exhibited strong correlations between the NAO index, sea-salt deposition and river data such
as chloride, pH and inorganic monomeric aluminium, pointing at the influence of North
Atlantic climate variability on water chemistry and water toxicity. The potentially toxic
effects of sea-salt deposition in rivers seem to be reduced as the acidification is reduced. This
suggests that sea-salt episodes have to increase in strength in order to give the same potential
negative biological effects in the future, if acid deposition is further reduced. More extreme
winter precipitation events have been predicted in the northwest of Europe as a result of
climate change. If this change will be associated with more severe sea-salt episodes is yet
unknown.
Transport of mass and heat from the North Atlantic toward the
Nordic Seas and the Arctic Ocean.
Svein Østerhus, Bjerknessenteret
The flow of Atlantic water towards the Arctic crosses the Greenland-Scotland Ridge in three
current branches. By the heat that it carries along, it keeps the subarctic regions abnormally
warm and by its import of salt, it helps maintain a high salinity and hence high density in the
surface waters as a precondition for thermohaline ventilation. In mid 1990’s an extensive
monitoring program for all three branches was lunched as a Nordic contribution to WOCE
and is still going on. The western branch, the Irminger Current, has been monitored by means
of traditional current meters moorings on a section crossing the current northwest of Iceland.
A number of ADCPs have been moored on a section going north from the Faroes, crossing the
Faroes Current. The eastern branch, the Continental Slope Current, is monitored by ADCPs
moorings across the Faroe-Shetland Channel. CTD observations from research vessels along
all the current meter sections are obtained on seasonal basis. Here we present results from all
the branches and offer numbers for the Atlantic water transport and present new tools for cost
efficient monitoring of the currents.
Validation and Analysis of the Models for the Mean Dynamic Topography,
the Mean Sea Surface Height and the Geoid in the Northern North Atlantic.
Solheim, D., Drange, H., Johannessen, J.A., Nahavandchi, H.,
Omang, O.C.D., Plag, H.-P.
The primary goal for the NFR funded project OCTAS, Ocean Circulation and Transport
Between North Atlantic and the Arctic Sea, is to determine the Mean Dynamic Topography
(MDT), which is the difference between the mean sea surface and the geoid.
The MDT provides the absolute reference surface for the ocean circulation. The improved
determination of the mean circulation will advance the understanding the role of the ocean
mass and heat transport in climate research.
Existing geoid, Mean Sea Surface (MSS) and MDT models have been collected and
intercompared. Best combinations of models have been determined and synthetic geoid, MSS
and MDT models have been computed. These models will be compared with the relevant state
of the art models for the OCTAS study area.