Download Arctic Climate and Water Change: Information Relevance for Assessment and Adaptation Arvid Bring

Arctic Climate and Water Change:
Information Relevance for Assessment and
Adaptation
Arvid Bring
Department of Physical Geography and Quaternary Geology
Stockholm University
Stockholm 2013
c Arvid Bring
ISSN: 1653-7211
ISBN: 978-91-7447-638-5
Cover: Bank of the Ob River at Salekhard, Russia.
Layout: Summary: Arvid Bring based on a LATEX template by Rickard Petterson. Papers II and IV: Arvid
Bring using LATEX. Paper I: Wiley Blackwell. Paper III: Springer. Paper V: AGU. Reprinted with permission.
Printed by Universitetsservice US-AB, 2013
Doctoral dissertation 2013
Arvid Bring
Department of Physical Geography and Quaternary Geology
Stockholm University
Abstract. The Arctic is subject to growing economic and political interest. Meanwhile,
its water and climate systems are in rapid transformation. Relevant and accessible information about water and climate is therefore vital to detect, understand and adapt to the
changes. This thesis investigates hydrological monitoring systems, climate model data, and
our understanding of hydro-climatic change, for adaptation to water system changes in the
Arctic. Results indicate a lack of harmonized water chemistry data, which may impede
e↵orts to understand transport and origin of key waterborne constituents. Further development of monitoring cannot rely only on a reconciliation of observations and projections
on where climate change will be the most severe, as they diverge in this regard. Climate
model simulations of drainage basin temperature and precipitation have improved between
two recent model generations, but large inaccuracies remain for precipitation projections.
Late 20th-century discharge changes in major Arctic rivers generally show excess of water
relative to precipitation changes. This indicates a possible contribution of stored water from
permafrost or groundwater to sea level rise. The river contribution to the increasing Arctic
Ocean freshwater inflow matches that of glaciers, which underlines the importance of considering all sources when assessing change. To provide adequate information for research
and policy, Arctic hydrological and hydrochemical monitoring needs to be extended, better
integrated and made more accessible. This especially applies to hydrochemistry monitoring,
where a more complete set of monitored basins is motivated, including a general extension for the large unmonitored areas close to the Arctic Ocean. Improvements in climate
model parameterizations are needed, in particular for precipitation projections. Finally, further water-focused data and modeling e↵orts are required to resolve the source of excess
discharge in Arctic rivers.
Keywords: Arctic, hydrology, monitoring, climate change, water management, general circulation models, adaptation.
Svensk sammanfattning
Arktis är för närvarande föremål för ett tilltagande intresse, både från ekonomiskt och politiskt håll. Samtidigt genomgår den arktiska regionen snabba och genomgripande förändringar
i klimat och miljö. Dessa förändringar kommer inte bara att påverka Arktis, utan också ge
upphov till långtgående globala e↵ekter.
Vatten har en central roll i många av de mest uppmärksammade förändringar som nu observeras. Som exempel kan nämnas den kraftigt minskande utbredningen av sommaristäcket
i Norra ishavet, och den tinande permafrosten i delar av Sibirien och Alaska. I och med
vattnets sammanlänkande roll är det av stor vikt med relevant och tillgänglig information
om förändringar i vatten och klimat.
I denna avhandling undersöks hydrologiska övervakningssystem och data från globala
klimatmodeller för Arktis, med avseende på vår förståelse för de förändringar som nu pågår
och vår förmåga att anpassa samhället till dem. Resultaten visar bland annat på en brist
av sammanställda och jämförbara vattenkemiska data för de floder som rinner ut i Norra
ishavet. Detta kan försvåra försök att förstå hur ämnen transporteras i Arktis, och vad deras
ursprung är.
För att prioritera en utveckling av vattenövervakningen behövs robust information om
vilka områden som kommer att beröras mest av förändringar i klimatet. I det här avseendet
pekar dock observationer och modeller i olika riktningar, vilket gör att det inte tillförlitligt
går att identifiera särskilt utsatta områden dit övervakningen bör prioriteras.
Globala klimatmodellers projektioner av temperatur och nederbörd har förbättrats mellan två successiva generationer av modeller, men stora avvikelser finns fortfarande i deras
simuleringar av nederbörd. Även om nederbördsprojektionerna skulle bli mer noggranna
finns det andra svårigheter i att översätta nederbörden till prognoser för förändringar i vattenflödet. Under senaste delen av 1900-talet har ett antal stora arktiska floder nämligen uppvisat ett överskott på vatten i jämförelse med de förändringar som observerats i nederbörd.
Detta indikerar ett möjligt bidrag från grundvattenförråd eller permafrost till floderna, och
en förbättrad förståelse behövs för dessa komplexa samband i vattensystemet.
Under de senaste decennierna har sötvatteninflödet till Norra ishavet ökat, både från
floder, glaciärer och den grönländska inlandsisen. Ökningen av flödet från floderna är av
samma storleksordning som ökningen i glaciäravsmältning, vilket understryker vikten av att
ta hänsyn till alla källor när man söker en fullständig förståelse av förändringarna.
För att bidra med bättre information för forskning och policybeslut behöver övervakningen av vattensystemet i Arktis förstärkas. En bättre integration mellan olika system
och databaser skulle bidra till ökad tillgänglighet och överblick. Detta gäller i synnerhet
för vattenkemi, där stora områden nära Norra ishavet idag är helt oövervakade. För att få
en mer representativ bild av förändringarna behöver sammansättningen av de avrinningsområden som övervakas också bli mer heltäckande. Vad gäller klimatmodeller krävs en fortsatt förbättring, i synnerhet av hur nederbörd simuleras. Det är också motiverat med ytterligare ansträngningar som fokuserar på vattendata och modellering av vattensystemet,
för att förstå ursprunget till överskottet på vatten i arktiska floder.
Arctic Climate and Water Change: Information Relevance
for Assessment and Adaptation
Arvid Bring
This doctoral dissertation consists of this summary and the following papers, which
are referred to by their roman numbers in the text.
I
Bring, A. & Destouni, G., 2009. Hydrological and hydrochemical observation
status in the pan-Arctic drainage basin. Polar Research 28, 327–338.
II
Bring, A. & Destouni, G., 2013. Hydro-climatic changes and their monitoring in the Arctic: Observation-model comparisons and prioritization
options for monitoring development. Accepted for publication in Journal of Hydrology.
III
Bring, A. & Destouni, G., 2011. Relevance of hydro-climatic change projection and monitoring for assessment of water cycle changes in the Arctic.
Ambio 40, 361–369.
IV
Bring, A. & Destouni, G., Manuscript. Evaluation of IPCC AR4 climate
model performance over 14 major Arctic watersheds. Appendix to Paper
III.
V
Dyurgerov, M.B., Bring, A. & Destouni, G., 2010. Integrated assessment of
changes in freshwater inflow to the Arctic Ocean. Journal of Geophysical Research 115, D12116.
The co-authorship of the papers reflects the collaborative nature of the underlying
research. For Papers I–IV, I was responsible for all analysis and had the main responsibility for designing the study and writing the paper. For Paper V, I had the
main responsibility for the design, analysis and writing of the river component of
the paper, and contributed to the interpretation and writing of the remainder of the
paper.
Other related peer-reviewed publications by the author:
Karlsson, J.M., Bring, A., Peterson, G.D., Gordon, L.J. & Destouni, G., 2011.
Opportunities and limitations to detect climate-related regime shifts in inland Arctic ecosystems through eco-hydrological monitoring. Environmental
Research Letters 6, 014015.
Rennermalm, Å.K., Bring, A. & Mote, T.L., 2012. Spatial and scale-dependent
controls on North American pan-Arctic minimum river discharge. Geographical Analysis 44, 202–218.
Jarsjö, J., Asokan, S.M., Prieto, C., Bring, A. & Destouni, G., 2012. Hydrological
responses to climate change conditioned by historic alterations of land-use
and water-use. Hydrology and Earth System Sciences 16, 1335–1347.
Abbreviations
AHC
Arctic Hydrological Cycle
AR4
Fourth Assessment Report
AR5
Fifth Assessment Report
CRU
Climate Research Unit
GCM
General Circulation Model
GRIS
Greenland Ice Sheet
IPCC
Intergovernmental Panel on Climate Change
MG&IC
Mountain Glaciers and Ice Caps
PADB
Pan-Arctic Drainage Basin
SAON
Sustaining Arctic Observation Networks
SRES
Special Report on Emission Scenarios
TAR
Third Assessment Report
UNECE
United Nations Economic Commission for Europe
Introduction
A multitude of global-scale changes, including climate change, are currently transforming the Earth
system. This is clearly evident in the Arctic, where
temperatures over the last half-century have increased at a rate 50% higher than the Northern hemisphere average (McBean et al., 2005), and where
future climate change is expected to be most pronounced (Kattsov et al., 2005). Coupled to the
changes in the physical environment, the Arctic is
also increasingly becoming a focal point of economic
and geopolitical interest.
These transformations present a considerable
challenge. The critical role of the Arctic in the global
climate system implies that Arctic changes will have
far-reaching consequences for, and feedbacks to, the
Earth system (McGuire et al., 2006). To understand
the changes, and to the degree possible, adapt to
them, is therefore of large importance to the global
community.
Water is a key integrating, propagating and regulating factor, and therefore plays a central role in
the changing Arctic and the wider global climate
system. It is a shared component in the most important and recognized Arctic indications of global
change. These indications include rapidly diminishing extent of sea ice (Comiso et al., 2008; Stroeve et
al., 2012a), increased mass loss from glaciers (Kaser
et al., 2006; Gardner et al., 2011), increasing river
flows (Peterson et al., 2002; 2006; McClelland et
al., 2006; Shiklomanov & Lammers, 2009; Overeem
& Syvitski, 2010) and increasing groundwater contribution to those flows (Smith et al., 2007; Lyon
and Destouni, 2010), permafrost degradation (Hinzman et al., 2005; White et al., 2007; Brutsaert and
Hiyama, 2012), ecosystem regime shifts (Smol et al.,
2005; Karlsson et al., 2011), and shorter extent of
snow cover season (Brown et al., 2010; Callaghan et
al., 2011).
In order to observe, assess and plan for adaptation to the changes to the Arctic Hydrological Cycle
(AHC) over the Pan-Arctic Drainage Basin (PADB),
it is vital that observation systems and models can
provide adequate information of relevance to scientists, environmental managers and policymakers.
The importance of data and observation systems in
particular has recently been emphasized at intergovernmental summits (GEO, 2010) and recognized as
one of five ”grand challenges” for Earth system science and science policy over the next decade (Reid
et al., 2010; ICSU, 2010).
Assessing previous and ongoing change in the water system requires observations of river discharge,
as well as sediment and water chemistry data to
estimate the waterborne mass fluxes of important
global cycle constituents such as carbon, nitrogen
and phosphorus. The collection of such hydrological and hydrochemical data is normally conducted
through continuous monitoring programs by various
government agencies.
However, in many countries, hydrological observation systems have been in decline during recent
decades. The extent of monitoring generally peaked
around 1980, after the significant increases in monitoring e↵orts during the International Hydrological
Decade 1965–1974. Since then, budget constraints
and failure to maintain existing systems have resulted in a general decline of monitoring, which has
been reported in several studies (Brown, 2002; Fekete
& Vörösmarty, 2002; Maurer, 2003; Hannerz, 2008;
FAO, 2009).
The global trend of declining discharge monitoring is also evident in the Arctic (Lammers et
al., 2001; Shiklomanov et al., 2002; Hinzman et al.,
2005; Walsh et al., 2005, Arctic-HYDRA consortium,
2010). However, the particular situation in the Arctic has received relatively much attention in the scientific community, partly due to the rapid changes
and the general scientific interest in the region. Also,
the accessibility to discharge data has been improved
more in the Arctic than in many other parts of the
world, due to concentrated international e↵orts and
collaborations, in particular at the University of New
Hampshire.
In contrast to discharge monitoring, a clear picture of the status of water chemistry data for that
discharge has been lacking. Previous e↵orts have
tried to establish a status for particular parameters (e.g., Holmes et al., 2000; Holmes et al., 2002;
Raymond et al., 2007), and estimated the quality
of existing data (Zhulidov et al., 2000; Holmes et
al., 2001; Zhulidov et al., 2003). Although particular data sets have been made accessible for parts
of the PADB (e.g., Holmes et al., 2000; Holmes
& Peterson, 2002), and in at least one case for
the wider PADB (McClelland et al., 2008; data at
http://www.arcticgreatrivers.org), no international
repository and data host exists for all accessible Arctic water chemistry data. Neither has any initiative yet been launched to develop a common set
of indicators, such as the Millenium Development
Goals-related UN Federated Water Monitoring System (FWMS) and its Key Water Indicators Portal
(KWIP).
The decline in station numbers and the lack of
integrated hydrological and hydrochemical information, together with the grand challenge of improving
Earth observation systems, constitute an imperative
1
ARVID BRING
to develop Arctic hydrological monitoring networks,
and to ensure their relevance under conditions of climate change. To formulate a rational strategy to improve monitoring in the Arctic, one then either has
to rely on some degree of certainty in the distribution of future changes, or acknowledge that other potential bases for prioritization may exist and try to
harmonize them. Despite its importance for robust
improvement of monitoring networks, this question
has so far received little attention.
To address this problem, and also the direct
adaptation-central issue of projecting present and
past hydro-climatic changes to the future, relevant
and robust climate data are required. The primary
information basis for global climate projections is the
Intergovernmental Panel on Climate Change (IPCC)
ensemble of general circulation models (GCMs),
which form the basis for the IPCC assessment reports. The two most recent reports are the Third
Assessment Report (TAR; 2001) and the Fourth Assessment Report (AR4; 2007). The fifth report (AR5)
is scheduled for release in 2013.
The performance of GCMs in the Arctic has been
the subject of intensive discussion. Assessments of
TAR and AR4 model performance in the Arctic have
shown improvements between successive generations
of models, but also indicated that significant shortcomings remain in simulating observed climate parameters (Christensen et al., 2007). There have been
several assessments of simulations of sea ice processes
(Zhang & Walsh, 2006; Overland & Wang, 2007;
Stroeve et al., 2007; Eisenman et al., 2007, Holland
et al., 2010, Stroeve et al., 2012b), the surface radiation budget (Sorteberg et al., 2007, Boé et al.,
2010) and surface temperature (Lui et al., 2008) over
the Arctic Ocean, while there are fewer studies explicitly examining GCM performance related to hydrological components of the Arctic hydrological cycle over drainage basin scales. Kattsov et al. (2007)
analysed the output of the AR4 model ensemble for
four major basins in the PADB, and Roesch (2006)
evaluated AR4 simulations of snow cover. Holland et
al. (2007) investigated ten AR4 GCMs to estimate
change in freshwater budget of the Arctic Ocean, including pan-Arctic scale runo↵, and Rawlins et al.
(2010) used the same GCMs combined with reanalysis and observational data in a pan-Arctic analysis of
Arctic hydrological cycle intensification. However, no
basin-wise investigation and comparison of GCM results between the TAR and AR4 has been performed
for a larger set of basins within the PADB, and no
benchmark of AR4 GCM performance over such a
set of basins exists for comparison with the upcoming AR5 set of models.
2
Climate
data
Water
information
Water flow
data
Glacier
change data
Paper I
Paper II
Paper III
Paper IV
Paper V
Figure 1. Integrative links between water information
and other components of climate and water change understanding. Connections investigated in this thesis are
shown with arrows, which are colored according to the appended papers where the analyses are carried out. Potential subsequent assessment and adaptation applications
that derive from water information, and apply to the
understanding of changes across other terrestrial, atmospheric and marine systems, are illustrated with dashed
arrows.
Assessment of AHC change, including projection
of hydro-climatic system changes to the future, is
central to adaptation. It has also been a question of
considerable scientific interest in the recent decades.
Component studies and integrative system assessments (e.g., Vörösmarty et al., 2001; Serreze et al.,
2006; Slater et al., 2007; Rawlins et al., 2009; 2010)
have greatly improved understanding of the AHC,
but several inconsistencies, understanding gaps and
open questions remain (Arctic-HYDRA consortium,
2010).
The importance of the water system in Arctic and
global change implies that the hydrological drainage
basin is a fundamental and relevant unit of scale,
both for water management, adaptation and basic research (Pahl-Wostl, 2007; UNECE, 2009). This thesis links and analyses several components required
to provide reliable water information for change
adaptation and assessment (Figure 1), consistently
at drainage basin scales. This basin-scale water information and understanding then also has important ensuing applications in understanding coupled
ARCTIC CLIMATE AND WATER CHANGE
changes across other terrestrial, atmospheric and marine systems (e.g., Karlsson et al., 2011), illustrated
in Figure 1 by dashed arrows from the water information box.
The thesis is centered on the following two overarching research questions:
1. Are current surface water system observations
representative, accessible and relevant for assessing changes to the Arctic environment and
connections to global systems? What critical
gaps and key limitations exist, and is there a
basis to robustly prioritize how to address these
limitations?
2. Are climate model results and our understanding of water budget changes in major Arctic
basins and the wider pan-Arctic ocean drainage
system sufficient for adaptation of society to climate and other global change?
Methods and data
The hydrological drainage basin has been the fundamental basis when investigating the research questions of this thesis. The drainage basin constitutes
a physically consistent boundary for closing the
flow balance of water and the mass balances of
constituents transported by water, which makes it
a relevant scale for addressing both scientific and
management-related problems.
The study area of the thesis is centered on the
14 largest Arctic watersheds in the PADB, covering an area of at least 200,000 km2 each and with a
combined drainage of 13.8 million km2 (see map of
study area in Figure 2). These basins are common to
the analysis in Papers II–IV. In Paper I, the entire
PADB is included. For paper V, the analysis focuses
on the central Arctic Ocean drainage, a subset of
the PADB, and includes 17 basins, of which 11 are in
common with the 14 major basins and the remainder
are smaller ones. Paper V also separately incorporates mountain glaciers and ice caps (MG&IC) that
contribute water directly to the Arctic Ocean, as well
as the Greenland ice sheet (GRIS). Figure 3 shows
the characteristic temperature and precipitation conditions, and recent observed changes for those parameters, in the 14 major basins.
Basin-scale climate data in the form of observations and GCM projections were analyzed for the 14
major basins in Papers II–IV. Papers III and V contain synthesis and analysis of discharge data for the
basins included in the respective studies. Paper I also
includes a characterization of basin properties based
180°
120°W
Ma
Ne
120°E
Ko
Yu
Le
In
Ol
Ch
Ya
Ye
Kh
Ob
Pe
60°W
SD
60°E
0°
Watersheds included
Glaciers (Paper V)
Papers II-V
MG&IC
Papers II-IV
Paper V
GRIS
Remaing PADB
Figure 2. Map indicating studied areas of the PADB.
Basins common to Papers II–V are shown in red, and additional studied basins in blue (Papers II–IV) and green
(Paper V). Paper I includes all areas within the PADB,
demarcated by the combined area of all colored basins
and the dark gray area. The glaciers (crosses) and the
GRIS (light blue) are also included in Paper V. Basin
names are abbreviated as Ne: Nelson, Ch: Churchill, Ma:
Mackenzie, Ko: Kolyma, Kh: Khatanga, Ol: Olenek, Le:
Lena, Ya: Yana, In: Indigirka, Ye: Yenisey, SD: Severnaya
Dvina, Pe: Pechora, and Yu: Yukon. Lambert azimuthal
equal-area projection; approximate scale 1:150 000 000.
on a range of data sources, and Paper V includes
analysis of glacier change data.
Climate observation data were in the form of
global gridded datasets of temperature and precipitation at half-degree resolution. For paper III, the Climate Reseach Unit (CRU) TS 2.1 dataset (Mitchell
& Jones, 2005) was used, and for Papers II and IV
both the CRU TS 3.10 (Harris et al., in review) and
the Willmott & Matsuura 3.1 (method first described
in Willmott & Matsuura, 1995; data available at
http://climate.geog.udel.edu/ climate) datasets were
used. For climate projections in Papers II–IV, IPCC
TAR (Paper III only) and AR4 global climate model
30-year means from the IPCC data distribution center (http://www.ipcc-data.org) were used.
3
ARVID BRING
Summary of papers
Paper I
Bring, A. & Destouni, G., 2009. Hydrological and
hydrochemical observation status in the panArctic drainage basin. Polar Research 28, 327–
338.
Figure 3. Climate characteristics of the 14 major Arctic basins. The top panel shows average annual temperature; the bottom one shows annual average precipitation,
for the periods 1961–1990 and 1991–2009. Data from
CRU (Harris et al., in review) and Willmott & Matsuura
(http://climate.geog.udel.edu/⇠climate).
Paper I presents a synthesis of all accessible discharge
and water chemistry data for the PADB, with lists
of data sources and specifics of each data set. The
extent of accessible data is further presented in map
form, illustrating the maximum length of time series
and latest data year for the PADB. Characteristics
of monitored and unmonitored areas are summarized
for, and compared between, North America, Europe
and Asia.
The general picture derived from the analysis in
Paper I shows a considerable di↵erence between accessible water chemistry monitoring and discharge
monitoring, both in terms of total extent and characteristics of the data. In general, discharge data are
available for a wide range of di↵erent basins, from
small catchments of a few square kilometers in size
to the major river basins in the PADB. In contrast,
accessible water chemistry monitoring is limited to
a much smaller set of stations, which cover a significantly smaller area and also a much less complete
range of basin sizes.
Figure 4 shows a summary of the accessible
length of time series for discharge, sediment and carbon monitored areas. The average length of time series for the various parameters, and the corresponding share of the PADB that is monitored, is further
summarized in Table 1.
Table 1. Average length of time series and monitored
share of total area for discharge, carbon and sediment
data in the PADB.
Parameter
For Papers III and V, discharge data from the RArcticNET (Lammers et al., 2001) and ArcticRIMS
(http://rims.unh.edu) databases were used. Paper V
also includes discharge data from the Water Survey
of Canada HYDAT database (Environment Canada,
2004).
Glacier data in Paper V consist of data on annual direct mass balance observations carried out
for MG&IC (Dyurgerov & Meier, 2005; Glazovsky
& Macheret, 2006; Fluctuations of Glaciers (FoG),
2008), and of several recent modeling studies for the
GRIS (Rignot et al., 2008; Hanna et al., 2008, 2009;
Box et al., 2006; Mernild et al., 2009).
4
Discharge
Sediment
Carbon
Average timeseries
length (years)
29
7
5
Area
monitored
73%
63%
51%
Results from Paper I also show a marked di↵erence in characteristics of monitored and unmonitored
areas (Figure 5). For example, monitored areas are
distinctly dominated by the taiga eco-region, while
unmonitored areas are generally strongly defined by
tundra type vegetation. This tendency is particularly
evident for discharge monitoring in all regions, and
for all monitoring parameters in Asia. The most balanced monitoring, in terms of eco-region proportions,
ARCTIC CLIMATE AND WATER CHANGE
a
c
b
1 - 10
21 - 40
11 - 20
41 - 70
71 -
partly monitored
unmonitored or not accessible
Figure 4. Overview of the maximum length of accessible data series (years) for the pan-Arctic monitoring
of (a) water discharge, (b) sediment, and (c) carbon. Cells containing stations with drainage areas smaller
than five cells are indicated as partly monitored.
Figure 5. Distribution of terrestrial eco-regions in monitored (M) and unmonitored (U) areas, by monitoring parameter and continent.
is for carbon monitoring in Europe, while the most
unbalanced monitoring is found in North America
and Asia. Such regional monitoring di↵erences complicate the interpretation of observation data di↵erences between di↵erent parts of the PADB.
Paper II
Bring, A. & Destouni, G., 2013. Hydro-climatic
changes and their monitoring in the Arctic:
Observation-model comparisons and prioritization options for monitoring development. Accepted for publication in Journal of Hydrology.
In this paper we analyze the prioritization basis
for planning of monitoring development under conditions of climate change. We formulate two alternate
final stages of possible climate change in the next
half-century by selecting the five warmest or wettest
models from the most severe IPCC Special Report on
Emission Scenarios (SRES) scenario (A2), and the
five coldest or driest models from the least severe
scenario (B1). For these two cases, we analyze the
relative distribution of climate change severity across
the 14 largest Arctic drainage basins, and compare
this distribution with hitherto observed changes.
5
ARVID BRING
Temperature change
mm!yr
Precipitation change
100
Warm!wet A2
50
Cool!dry B1
0
Nelson
Churchill
Mackenzie
Kolyma
Khatanga
Olenek
Lena
Yana
Indigirka
Yenisey
Ob
S.Dvina
Pechora
Yukon
Observations
Nelson
Churchill
Mackenzie
Kolyma
Khatanga
Olenek
Lena
Yana
Indigirka
Yenisey
Ob
S.Dvina
Pechora
Yukon
K
6
5
4
3
2
1
Figure 6. Changes to temperature (left) and precipitation (right) from 1961–1990 to 1991–2009 for observations and to 2040–2069 for GCM projections across 14 major Arctic basins. Error bars indicate one
standard deviation of di↵erent GCM results from the model ensemble mean for each basin.
Results from Paper II indicate that observations
and projections of climate change severity across the
pan-Arctic are not in agreement, when comparing
the relative order of basins (rank correlations of basin
orders are close to zero, or negative; Table 2). Both
directional (in the case of precipitation) and temporal shifts are required to bring observed changes in
line with projections (Figure 6). Some continued directional changes are naturally expected, however, as
observations and projections concern di↵erent time
periods.
In Paper II, we also analyze how the present distribution of hydrological monitoring network density
relates to observed and projected climate change. Results from this analysis show that current network
density is more adapted to prioritize monitoring capacity for the so far observed precipitation changes
than the observed temperature changes, or the projected future changes in either temperature or precipitation.
Table 2. Spearman’s correlation of GCM-projected climate change ranking with observed climate change ranking.
Scenario
Temperature
Cool B1
Hot A2
⇢
0.01
-0.03
Scenario
Precipitation
Dry B1
Wet A2
⇢
-0.10
-0.23
Paper III
Bring, A. & Destouni, G., 2011. Relevance of
hydro-climatic change projection and monitoring for assessment of water cycle changes in the
Arctic. Ambio 40, 361–369.
6
Paper III first presents a comparison of IPCC TAR
and AR4 GCM projections for precipitation and
temperature in the 14 largest Arctic basins. Areaweighted basin average projections were summarized and compared with observed changes. Paper
III results also include a comparison of precipitationdischarge changes for the studied basins, as well as an
analysis of the evolution of the discharge-monitoring
network in relation to projected climate changes.
Figure 7 illustrates GCM projections and CRU
observations for the 14 major basins. Temperature
projections seem compatible with observed changes
during the late 20th and early 21st century, both for
the TAR and AR4, while precipitation projections indicate an increase that is hitherto not evident in observations. The absolute GCM results compare well
with observations for temperature, but the models
considerably overestimate precipitation.
A further result of Paper III is that the responses
in discharge to changes in precipitation vary widely
for the major basins in the PADB (Figure 8). The
majority of basins exhibit excess flow changes in relation to precipitation changes; that is, discharge has so
far increased more (or decreased less) than precipitation within each basin. These disagreements between
precipitation and discharge changes are in some cases
large; therefore, an essential question for forthcoming investigation is: where does the extra water come
from?
Finally, Paper III presents an analysis of the development of the discharge monitoring system in relation to projected climate change. A comparison
of monitoring station density between the period
of peak extent of monitoring and a recent period
shows that the weight of discharge monitoring systems has shifted towards the basins where the ex-
2
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ARCTIC CLIMATE AND WATER CHANGE
ARCTIC CLIMATE AND WATER CHANGE
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-8
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20102039
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Runoff change mm yr 1 ⇥
Figure
. .Changes
temperature (left)
(left)and
andprecipitation
precipitation
(right)
from
1961–1990
to 1991–2002
for
Figure77
Changes to
to temperature
(right)
from
1961–1990
to 1991–2002
for obobservations
and
to
2010–2039
for
GCM
projections
across
the
14
major
Arctic
basins.
Error
bars
indicate
servations and to 2010–2039 for GCM projections across 14 major Arctic basins. Error bars indicate one
one
standard
deviation
of di↵erent
GCM
results
the model
ensemble
standard
deviation
of di↵erent
GCM
results
fromfrom
the model
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mean.mean for each basin.
Ol
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Yu
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R 2 ⇥0.46
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50
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Ko
Ne
Ye
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Ch
40
20
0
20
Precipitation change mm yr 1 ⇥
Figure 8. Changes from 1961–1990 to 1991–2002 in observed 8annual
average
corresponding
Figure
. Changes
fromprecipitation
1961–1990 toand
1991–2002
in obruno↵
for
13
major
Arctic
basins.
The
dashed
line indiserved annual average precipitation and corresponding
catesfor
a 1:1
precipitation
and dashed
runo↵. The
runo↵
13 change
major in
Arctic
basins. The
line solid
indiline is a linear best-fit regression of actual changes in all
cates a 1:1 change in precipitation and runo↵. The solid
basins except the Ch (Churchill) watershed, which is afline is a linear best-fit regression of actual changes in all
fected by major artificial water diversions. Abbreviations
basins except the Ch (Churchill) watershed, which is afof basin names are the same as in Figure 2.
fected by major artificial water diversions. Abbreviations
of basin names are the same as in Figure 6.
pectedIV
changes to temperature and precipitation are
Paper
the smallest. If one aims to follow up and capture the
Bring,
& Destouni,
G. change
Manuscript.
Evaluation
actualA.
e↵ects
of climate
on the
AHC, this is
of
IPCC
AR4
climate
model
performance
over
not a desirable development.
14 major Arctic watersheds. Appendix to Paper
III.
Paper
Paper
IVIV is an appendix to and extension of the
analysis
made in Paper III. Here, we perform an exBring, A. & Destouni, G. Manuscript. Evaluation
plicitoferror
of IPCC
IPCCand
AR4performance
climate modelanalysis
performance
over AR4
GCMs
over
the
14
largest
Arctic
watersheds.
14 major Arctic watersheds. Appendix to Paper Mean
III. Error (MAE), Mean Bias Error (MBE)
Absolute
and a dimensionless index of model performance (dr ;
Paper et
IVal.,
is an
appendix
to and extension
of the
Willmott
2012)
are evaluated
against observaanalysis
made in Paper
III.precipitation
Here, we perform
anreferextions
of temperature
and
for the
plicitperiod
error and
performanceWe
analysis
of IPCC
AR4
ence
of 1961–1990.
also analyze
the
corGCMs over
the 14ranking
largest of
Arctic
watersheds.
Mean
relation
between
model
performance
for
Absolute Error
Mean simulations.
Bias Error (MBE)
temperature
and (MAE),
precipitation
andResults
a dimensionless
of model
performance
(dr ; is
from thisindex
analysis
indicate
that there
Willmott
et
al.,
2012)
are
evaluated
against
observaa large spread in error and relative performance betions of
and precipitation
refertween
thetemperature
models forming
the basis for for
the the
AR4
(Figence period of 1961–1990. We also analyze the corure 9). For some basins, and for the pan-Arctic in
relation between ranking of model performance for
general, an above-average model performance in temtemperature and precipitation simulations.
perature simulation does not correlate particularly
Results from this analysis indicate that there is
strongly
with performance in simulating precipitaa large spread in error and relative performance betion
(MAE
and drforming
rank correlations
Table
tween the models
the basis for negative;
the AR4 (Fig3).
implies
choosing
a ”best”
model is in
difureThis
9). For
somethat
basins,
and for
the pan-Arctic
ficult
if
one
wants
to
have
consistently
good
perforgeneral, an above-average model performance in temmance
in simulating
over
the Arctic.
perature
simulation both
does parameters
not correlate
particularly
strongly with performance in simulating precipitation (MAE and dr rank correlations negative; Table
3). This implies that choosing a ”best” model is difficult if one wants to have consistently good performance in simulating both parameters over the Arctic.
Table
. Spearman rank correlation coefficient ⇢ bePaper3V
tween
the
pan-Arctic
temperature
and precipitation
Dyurgerov,
M., Bring,
A. & Destouni,
G., 2010. values ofIntegrated
MAE, MBE
and dr . of changes in freshwater
assessment
inflow to the Arctic Ocean. Journal of Geophys⇢MAE
⇢MBE
⇢d r
ical Research
115, D12116.
-0.29
0.37
-0.29
7
7
Cumulative deviation from
1961-1992 mean Hkm3 L
ARVID BRING
2500
2000
1500
MG&IC
GRIS
Rivers
1000
500
0
-500
1960 1970 1980 1990 2000
year
Figure 9. Mean Absolute Error (MAE; top panel), Mean
Bias Error (MBE; middle panel) and model performance
index (dr ; bottom panel) for 14 GCMs across the PADB.
In this paper we perform an integrated analysis of
freshwater inflow to the Arctic Ocean, and separately assess the contribution of rivers and glaciers
to this inflow over the period 1961–2006. We specifically investigate the periods 1961–1991 and 1992–
2006, where the break coincides with a shift in magnitude of glacier mass loss (Lemke et al., 2007).
Results from this assessment are generally in line
with other studies that indicate an increase in freshwater inflow to the Arctic Ocean. However, our analysis also highlights that the magnitude of the increase in inflow from the 1961–1991 to the 1992–
2006 period is similar for the river contributions and
the glacier contributions (Figure 10). This underlines
the importance of also accounting for river discharge
Table 3. Spearman rank correlation coefficient ⇢ between the pan-Arctic temperature and precipitation values of MAE, MBE and dr .
⇢
8
MAE
-0.29
MBE
0.37
dr
-0.29
Figure 10. Above: Total meltwater runo↵ and total river
runo↵ into the Arctic Ocean. Below: Cumulative deviations in annual freshwater flows from MG&IC, GRIS, and
rivers relative to average values for 1961–1992.
changes that are not related to glacial melt water
changes as a potentially contributing source for sealevel rise and the freshening of the Arctic Ocean waters.
Discussion
Robust scientific understanding of climate and water
systems is a prerequisite for informed policy decisions in assessing and adapting to the large-scale environmental changes currently transforming the Arctic and other regions. This in turn requires access
to relevant information on changes to flows of water
and waterborne constituents. This thesis has aimed
to contribute to a more complete picture of several important components required for AHC change
monitoring and adaptation planning. This has been
done by investigating two overarching research questions pertaining to the adequacy and information relevance of water monitoring systems, and of climate
model and hydro-climatic change understanding, for
change assessment and adaptation.
ARCTIC CLIMATE AND WATER CHANGE
Regarding the first research question on the relevance of hydro-climatic data, the results from Papers
I–III point to some important shortcomings, but also
to certain opportunities and results of relevance for
future research and monitoring improvement e↵orts.
The synthesis of monitoring data in Paper I indicates a lack of water chemistry data, compared
with the more extensively accessible discharge data.
The range of basin sizes, sampling frequency, and
length of time series for water chemistry data overall compare negatively with corresponding attributes
for discharge data. Together, these shortcomings imply that the full potential of translating the existing
discharge data to also calculate mass fluxes of important constituents is hindered.
Furthermore, the di↵erence in characteristics of
monitored areas found in Paper I indicate that existing monitoring data are not representative of the
PADB as a whole. This constitutes a limitation to
the value and reliability of the modeling that must
be used for interpreting and projecting changes in
the AHC in unmonitored areas.
From the perspective of an integrative pan-Arctic
analysis, the limited accessibility to water chemistry
data is remarkable, given the high profile of and
international commitment to research into Arctic
environmental changes. While discharge data have
been compiled into pan-Arctic datasets (most importantly, R-ArcticNET (Lammers et al., 2001) and
the ARDB (http://ardb.bafg.de)) and also made accessible in near-real time through the ArcticRIMS
project (http://rims.unh.edu), water chemistry data
remain fragmented, although the recent continuation
of the PARTNERS project as the Arctic Great Rivers
Observatory (http://www.arcticgreatrivers.org) constitutes an important improvement.
Several factors may explain these results. Firstly,
although the research community emphasizes a system perspective on the pan-Arctic domain, no international body has formal responsibility for an integrated monitoring system. Instead, monitoring efforts must build upon undertakings by separate government agencies in at least the eight di↵erent nations of the Arctic Council, and for hydrology also
Mongolia and Kazakhstan, which constitute parts of
the PADB. Even if all national hydrometeorological agencies were committed to promoting a coordinated Arctic observation e↵ort, domestic budget limitations and conflicting information goals may still
interfere with ambitions being met.
Secondly, public agencies that apply costrecovery principles to their environmental data may
be reluctant to undermine this rule by freely sharing
their data with international repositories. Thirdly,
in a previously isolated Arctic that is now rapidly
becoming more accessible to activities such as natural resource exploration, shipping and tourism, water
data may be viewed as increasingly sensitive information from both political and economic perspectives.
Occasionally, pressure from international organizations on member states to disclose water chemistry
information viewed as sensitive has rebounded and
instead caused delays in the progress of sharing other
water data (Vladimir Ryabinin, personal communication).
All the same, member states of the Arctic Council
have in the Tromsø Declaration recently committed
to facilitate data access, as a legacy of the International Polar Year during 2007–2009. The organizational form for this commitment is the Sustaining
Arctic Observation Networks (SAON) process, which
is currently in its implementation phase. The European Commission has also expressed support for
SAON (European Commission, 2008; 2012). It remains to be seen to which extent the SAON process
can contribute to increased accessibility to monitored
water chemistry data in the PADB, but it is now established as a platform for policy dialogue on Arctic monitoring issues, for example through recurring
Arctic Observation Summits.
Whether through institutional pan-Arctic initiatives or through other channels at various levels and
scales, any remediation of the present-day monitoring system shortcomings identified in Paper I requires a strategy to improve observation networks
under conditions of climate change. This issue is investigated in Paper II, which centers on the prioritization of hydro-climatic change monitoring across
the Arctic.
Improvements of monitoring and observing capacity in the Arctic, and elsewhere, must incorporate
climate change projections in order to take the nonstationary nature of the environment into account
(Milly et al., 2008). For the case of the Arctic, however, results from Paper II indicate that the relative
distribution of climate change severity, as simulated
by GCM projections, does not agree with the distribution of actually observed changes across the major
Arctic basins, which places obstacles for a robust prioritization strategy based on reconciliation of observations and projections for an assessment of which
basins that will be most a↵ected by climate change.
An alternative strategy to the aforementioned
one could be to prioritize basins where the disagreement between observations and projections is particularly large, as such a strategy would yield important information on the hydro-climatic system functioning and changes regardless of whether there is
actual convergence of observations and projections
in the end or not. Alternatively, one could argue
9
ARVID BRING
for prioritizing monitoring of basins with greater observed changes so far, as these are actual experienced
changes where increased e↵orts at understanding and
adaptation can be intrinsically motivated. Such a prioritization is to some degree evident in the present
distribution of monitoring, specifically with respect
to precipitation changes, although this situation is
most likely not by design but by coincidence.
The divergent rationales and prioritization bases
that can be argued for based on the results of Paper
II underline the importance of attempting to formulate win-win or no-regret solutions in any strengthening of hydro-climatic monitoring e↵orts under climate change conditions (UNECE, 2009), incorporating also other relevant parameters, in addition to
the temperature and precipitation data studied here,
and explicitly identifying set information goals to be
achieved. The results presented here can inform observation assessments connected to strategic Arctic
initiatives and programs, such as SAON and the upcoming Third International Conference on Arctic Research Planning (ICARP III) in 2015, where continued evaluation of monitoring e↵orts will be a priority.
The second research question about climate
model and water budget change understanding is
explored in Papers III–V. Paper III highlights improvements in basin-scale climate model simulation
of temperature and precipitation, but also identifies some key remaining limitations, which are further examined in Paper IV. Also in Paper III, some
challenges to water system understanding through
the precipitation-discharge change relation are presented, and Paper V extends the discharge assessment of these changes to a full Arctic Ocean freshwater inflow synthesis, including a glacier-independent
river change component in addition to the change
contributions from melting glaciers, ice caps, and the
Greenland ice sheet.
Considerable improvements have been made between the two successive generations of model ensemble runs that underlie the most recent IPCC Assessment Reports, the TAR and the AR4. Examples
include improved parameterization of land surface
schemes and snowpack, as well as the inclusion of
canopy processes in most models (Randall et al.,
2007). However, important uncertainties remain in
the representation of cryospheric feedbacks, which
explain part of the range of model responses at mid
and high latitudes (Randall et al., 2007).
These improvements are evident in that Paper III
results indicate a lower spread among the ensemble
members for the AR4 models, and in the case of precipitation, a marked improvement in the agreement
with absolute observed values. However, despite the
improvement in precision, accuracy remains insuffi10
cient for precipitation projections, which, even if they
were correct, are still difficult to translate to subsequent changes in the water cycle without further
and finer resolved hydrological modeling. It should
be noted that observations also are associated with
uncertainty, for example gauge undercatch of primarily solid precipitation due to wind (e.g., Yang et al.,
2005; Tian et al., 2007), which may explain part of
the remaining di↵erence between observations and
the improved AR4 results. Based on a global precipitation bias adjustment by Adam & Lettenmaier
(2003), the annual e↵ect seems generally to be about
10–25% over the latitudes of the whole PADB, but
may amount to higher values in the most northern
parts of some basins.
The large span in model performance, evident
from the explicit error and performance analysis
of AR4 models in Paper IV, also indicates that
large uncertainties and shortcomings remain for reliable simulations of hydro-climatic parameters on
basin scales. The analysis furthermore underlines
that models may yield good output results on these
scales for the wrong reasons. For example, the panArctic bias error of both temperature and precipitation for the GIER model is close to zero, which would
place it at the top of a basin-scale simulation performance ranking. At the same time, the absolute error
and the performance index for the same model are
among the worst of the ensemble, implying large deviations from observations at individual grid points,
even though the deviations happen to almost cancel out across the PADB. Overall, the evaluation in
Paper IV can serve as a benchmark for evaluating
the performance change against the subsequent generation of climate models, which underlies the forthcoming IPCC AR5 report.
Notwithstanding further improvement in GCM
simulations, full understanding of hydro-climatic
change, and transfer of this understanding back into
model development, requires basin-scale understanding of precipitation-discharge change patterns. In
the Arctic, certain counterintuitive hydro-climatic
changes have caused intense investigation and discussion in the scientific community. The fact that most
of the rivers analyzed in Paper III can be termed
so-called ”excess” rivers (that is, the increase in discharge has been greater than the increase in precipitation) is consistent with findings by Milliman et
al. (2008) for a related set of Arctic rivers. This,
and other studies (e.g., Dyurgerov & Carter, 2004;
McClelland et al., 2006; Smith et al., 2007; Lyon et
al., 2009; Brutsaert & Hiyama, 2012) indicate that
both specific climatic and subsurface processes pertaining to the Arctic, such as permafrost degradation, as well as other anthropogenic changes, and
ARCTIC CLIMATE AND WATER CHANGE
general atmospheric patterns such as increased moisture transport from outside the PADB, are responsible for the range in discharge patterns, but the relative importance of the di↵erent contributing factors
is not definitely established. Undercatch of snow, in
combination with increases in winter precipitation
(Bulygina et al., 2009; Rawlins et al., 2009), is also
a potential contributing factor. The wide spread in
discharge responses to precipitation changes indicate
a need for further concerted modeling and field investigation e↵orts aimed at increasing the process
knowledge of hydrological regimes particular to the
Arctic domain, including simulations of evaportranspiration and permafrost processes, considering also
e↵ects of scale (Rennermalm et al., 2012). Improved
parameterization, in particular with precipitation focus, is also critical to the development of GCMs, and
continued water-balance assessments and closure experiments in Arctic catchments are motivated.
The extended water budget changes of the entire PADB and its Arctic Ocean drainage including
glacier contributions, studied in Paper V, also has
implications for global climate system changes, and
sea level rise influencing both the Arctic region and
the wider Earth system. The fact that increases in
river freshwater contribution are of the same order of
magnitude as increases from MG&IC and GRIS underlines the importance of accurately understanding
the reasons for river flow changes, and the potentially
contributing components of frozen and liquid water
storage changes in major Arctic basins (e.g., Muskett & Romanovsky, 2009). Such changes could have
large implications on the pan-Arctic hydro-climatic
system, but also on scales beyond the Arctic through
contribution to sea level rise or thermohaline circulation functioning.
The review of literature and analysis in this thesis confirms a picture of advances in our knowledge about the Arctic environment and its functioning during recent decades. International efforts at making discharge information accessible,
e.g. through the ArcticRIMS project, have contributed to a more timely access to river flow data
for a number of important basins and sub-basins.
Similarly, the PARTNERS monitoring campaign
(http://ecosystems.mbl.edu/partners), now semipermanently established as the Arctic Great Rivers
Observatory (http://www.arcticgreatrivers.org) has
provided a multi-season dataset of concentrations of
a range of important water chemistry constituents
for six major Arctic rivers. Climate model advances
have improved in precision and alignment with observations in the Arctic, and numerous studies have contributed to a fuller understanding of hydro-climatic
changes. These developments, which coincide with a
time of increasing focus on the Arctic as an arena for
important changes, imply improvements also in our
ability to understand the AHC and the associated
PADB.
Nevertheless, considerable challenges for understanding and managing the rapidly changing Arctic
water system still remain. A critical priority must be
to continue improving the accessibility to water data,
in particular for water chemistry, for the PADB. Observations must be made at the right places, and improvements should be based on clearly stated information goals, striving in their achievement for winwin and no-regret approaches that do not rely on a
single most likely scenario of future hydro-climatic
conditions. Improved coverage of unmonitored areas
in the northern rims of the PADB is also motivated,
particularly as these areas are expected to become increasingly accessible and also subject to exploration
with a warming climate (Andreeva, 1998). In addition, improved monitoring here may yield information on the unclear role of these areas in the total
flux of water chemistry constituents to the ocean,
as near-ocean catchments have in other regions been
shown to contribute an unproportionately large share
of coastal pollution in relation to the drainage basin
as a whole (Destouni et al., 2008).
Conclusions
This thesis has investigated the adequacy of water
flow and water chemistry observations and climate
model projections in the PADB, with the purpose
of establishing a quantitative picture of the status
of these observations and model results for understanding and management of water cycle changes in
the Arctic. The main findings of the thesis can be
summarized in the following conclusions:
• There is a lack of long-term and accessible water
chemistry data for large regions of the PADB,
and discharge data is also limited for considerable areas. The data that are accessible do not
constitute a representative sample of the PADB
environment.
• There is a need to extend monitoring and to
make data more accessible, in particular for the
relatively unmonitored but large areas on the
northern rim of the Eurasian continent.
• Establishing regional priorities for hydrological
monitoring systems with regard to the specific
issue of climate changes in the Arctic can currently not be achieved based solely on a reconciliation of observations and projections. When
11
ARVID BRING
taking di↵erent data and system/change perspectives as starting points, di↵erent conclusions
about what constitutes rational priorities, and
related strategies, arise.
• The precision in predicting precipitation and
temperature change on drainage basin scales
has improved between successive generations of
the IPCC model ensemble. However, that improvement is relatively unimportant next to
the large inaccuracy that still remains in precipitation projections. Individual model performance varies greatly, and models can be right
for the wrong reasons when relatively large errors cancel out on basin scales for some models. Further investigation and benchmarking of
model performance in the GCMs underlying
the IPCC AR5 could indicate whether certain
hydro-climatological model shortcomings in the
Arctic have been addressed.
• Hitherto observed changes in precipitation do
not translate into similar changes in discharge
even over the large scales of the studied basins.
The discrepancy between precipitation and discharge changes, and the fact that this discrepancy principally is expressed as excess in discharge compared to available precipitation, indicate that a component of the variation in discharge may be due to changes in permafrost or
groundwater storage.
• Even though the increase in river inflow to the
Arctic Ocean during 1993–2006 is small in relative terms compared to the average flow for
1961–1992, in absolute terms it is of the same
order of magnitude as the meltwater increase
from glaciers, which underlines the importance
of also accounting for river discharge changes
as a potentially contributing source for sea-level
rise and Arctic Ocean freshening.
Financial support
The research in this thesis has been funded through
grants from the Swedish research council Formas
(project number 2007-1263) and the Swedish Research Council (VR; project number 2007-8393), and
has been linked to the Bert Bolin Centre for Climate Research (in turn supported by VR and Formas
through a Linneaus grant) and the strategic research
project EkoKlim at Stockholm University. I gratefully acknowledge travel support from the Graduate
Research School of the Bolin Centre, C F Liljevalchs
foundation, Knut and Alice Wallenbergs foundation,
12
L & E Kinanders foundation, John Söderbergs foundation, the government of the Yamalo-Nenets Autonomous Okrug, and the Arctic Research Council
of the U.S.
Acknowledgements
I am very grateful for the invaluable support I have
had from my main advisor, Georgia Destouni. Without your insight, enthusiasm and guidance, Gia, this
thesis would not have come about. You have always
had time for extensive comments and feedback on
my work, and I appreciate all the discussions we’ve
had, on the specific research issues at hand but particularly also on the larger picture, strategic science
matters and science-policy interactions.
I have also much appreciated collaboration and
discussions with my co-supervisors Jerker Jarsjö,
Steve Lyon, Garry Peterson, and with my co-authors
Johanna Mård Karlsson, Line Gordon and Mark
Dyurgerov. Sadly Mark passed away too soon, before we had an opportunity to continue our collaboration. Åsa Rennermalm I would like to thank
for stimulating discussions at my first international
scientific meeting in Washington, DC, and the collaboration that followed. A special thanks to Johan
Kuylenstierna for introducing me to the world of international environmental negotiations. I would also
particularly like to thank Fredrik Hannerz, Christoffer Carstens and Klas Persson for many enjoyable
lunches with inspiration on water-related topics.
I’ve always enjoyed going to work at the Department of Physical Geography & Quaternary Geology.
Thanks to everyone for your contribution to a stimulating work environment. A particular thanks to the
technical and administrative sta↵, who are invaluable in keeping things together, and to the whole
community of PhD students, past and present, for
the support and discussions. Unfortunately I have
been able to join all too few pub nights!
I also want to acknowledge the interdisciplinary
group for environmental science PhD students. The
atmosphere at our gatherings really stimulated an
academic discussion, and remains one of my best
memories from the doctoral studies at Stockholm
University. I am very glad for the continued network
that we have established, and for the perspectives on
my research you have given.
The Association of Polar Early Career Scientists
(APECS) also played an important role during my
PhD studies. Stina and Sussie got me involved with
APECS and have continued to be good friends and
colleagues. Thanks to you and all other wonderful
ARCTIC CLIMATE AND WATER CHANGE
APECS people I have had the opportunity to get to
know and work with.
To my sisters and brother, Nina, Torun, Hedda
and Johan, and all other friends, thank you for the
important support and encouragement. I would also
like to thank my parents Lena and Axel. Your erudition remains a paragon to me, and I can only hope
that age shall endow me too with some sagacity.
Since I started work on this thesis, I have had
two wonderful sons, Valter and Tage. The two years
I spent at home with them I would not trade for any
career outcome in the world. But I have been away,
too, particularly at conferences around the world.
At these times, my wife Eva has had much support
from my parents-in-law Helena and Weine, for which
I (and Eva) are very grateful.
And to Eva, with whom I’ve shared ten wonderful years and hope to share many more, thank you,
above all—for all the days, of love, light and joy.
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