Download GGOS, ECGN and NGOS: Global and regional geodetic observing

Geodetic observations of land uplift
Markku Poutanen
Finnish Geodetic Institute
National Geographics, November 2013
Facts and faults of climate change
 If glaciers melt, the sea level will rise
 Melting is a slow process, glacier calving is more effective
 Time scales 1000’s of years;
 Greenland, dynamic response 1000-10000 years
 W.Antarctica 100-1000 years
 E.Antarctica 10000-100000 years
 Amount of water:
Facts and faults of climate change
 Antarctica glaciers are melting (climate should warm up +20C for this to
happen. Precipitation may increase, more snowing, ice mass may
increase…)
 Meltwater is evenly distributed in the world’s oceans (NO!)
 Amount of the sea level rise can directly be computed from the amount
of melted ice (muuuchh more complicated)
 Coastal lines of Finland are in danger (not as long as the sea level rise
is below 5-10 mm/y)
 Thermal expansion of oceans
will cause sea level rise at
coastal areas (NO.
Potential is not changed,
water will not flow anywhere)
Sea level trends, 1992-2009. Cazenave
Scenario if the Greenland glacier
is melting
Land uplift and geodetic measurements
Geodetic techniques
Terrestrial techniques:
- Levelling (height determination)
- Gravity measurements
- Precise distances, baselines
- Triangulation, trilateration
- GNSS, permanent networks
Space geodesy
Geodetic Observing systems
and multi technique sites




To observe various aspects of GIA we
need several techniques; in geodesy
we observe 3D-motions, gravity, EOP,
sea level, …
This implies: GNSS, SLR, VLBI, AG,
SCG, levelling, relative gravimetry,
altimetry, InSAR, …
Geodetic Observing Systems: GGOS,
ECGN, NGOS, …
Special projects (BIFROST, COST
ES0701, DynaQlim…)
+ terrestrial
levelling, AG, SCG,
rel.g, tide gauges, …
Motivation for multi-technique
sites
VLBI
SLR
Global
Reference
Frames
GNSS
BGI
Geodynamics
Postglacial rebound
Earth structure
Gravity changes
Vertical datums
Local coordinates
Observing techniques
IAG SERVICE (IVS)
IAG SERVICE (ILRS)
IAG SERVICE (IGS), EPN, NKG
IAG SERVICE (IDS)
UELN, Nordic
PSML
AG plan + archive (developing)
GGP (OK, IAG PROJECT )
Many sources, partly available
Meta-databases, data archives, partly available
Permanent
GNSS-networks
 Built in Nordic countries 1994-1996
 Renewal now
Repeated precise levellings
Land uplift
1892-1910
N00
1935-1975
N60
1978-2006
N2000
Terrestrial gravimetry
15
Earth’s gravity field, global changes
Glacial Isostatic Adjustment
• Land uplift is just one consequence of the physical
process called the Glacial Isostatic Adjustment, GIA
• GIA-related phenomena originate to the large-scale
mass transportation; Waxing and waning of the Northern
hemisphere glaciers in about 100 000 year cycles cause
up to 135 m of global sea level rise and fall. This
corresponds about 5×1019 kg of mass
• The mass transportation causes cyclic variation on the
surface load resulting in the viscoelastic mantle flow and
elastic effects on the upper crust
• No single technique or observing network will give
enough information on all aspects and consequences of
GIA
Glacial Isostatic Adjustment

GIA with its unique temporal signatures is one of the
great opportunities in geosciences to retrieve
information about earth processes.

GIA contains information about recent climate forcing,
being dependent on the geologically recent on- and
off-loading of ice sheets.

GIA gives a unique chance to study the dynamics and
rheology of the lithosphere and asthenosphere with an
increasingly detailed modelling

GIA is of fundamental importance in geodesy, since
reference frames, physical heights, Earth rotation and
polar motion are influenced by it.
Phenomena and disciplines affected
by GIA
• Earth orientation parameters: reference frames
• Post-glacial uplift, contemporary movements and gravity:
heights and height systems
• Dynamic ice sheets, glaciology
• Quaternary paleoenvironments and climate
• Neotectonics and seismotectonics
• Dynamics, structure, properties and composition of the
lithosphere
Other signals
 The GIA signal is contaminated by several other spatially
and temporally varying mass changes and crustal
deformation. These include seismic deformation, mantle
convection and plate tectonics
 Sea level change is an example of a phenomenon which
is related to GIA but mixed with other signals.
 The observed sea level change relative to the
benchmark on the ground contains components of GIA
related crustal vertical motion, eustatic rise of the sea
level, changes in semi-permanent sea surface
topography and geoid changes.
The uplift changes both heights
and gravity
Uplift rate
mm/y
Gravity Change (Vaasa ja Joensuu)
Land uplift – gravity lines
Courtesy J. Mäkinen at al 2004
Postglacial rebound,
viscoelastic phase
Slow viscoelastic phase, flow of
upper mantle material
Elastic rebound happens immediately after the deglaciation. Mass flow
of upper mantle are slow, and and this viscoelastic phase takes tens
on thousands of years. The Fennoscandian uplift is now in this phase.
Gravity change combined with uplift information will give hints what
happens in the lithosphere/upper mantle.
Postglacial rebound, 3-D modelling
Maps of vertical motion have traditionally been based on
long time series of tide gauges and repeated precise
levellings over several decades. Today we can observe
3-D motions with GNSS
Courtesy Martin Lidberg / BIFROST
Uplift rate vs. distance
We get different values when using different techniques;
Blue = GPS time series, Green = tide gauge data, Red = model
12.00
10.00
Uplift [mm/yr]
8.00
6.00
4.00
2.00
0.00
-2.00
0
200
400
600
800
1000
1200
Distance from uplift center [km]
1400
1600
BIFROST
BIFROST (Baseline Inferences for Fennoscandian
Rebound Observations, Sea level, and Tectonics)
project uses a network of permanent GPS
stations in Finland and Sweden to measure
crustal deformation due to glacial isostatic
adjustment (GIA).
Project was initiated in 1993 taking advantage of
tens of permanent GPS stations both in Finland
and Sweden.
Horizontal and vertical rates and
model; BIFROST project
Courtesy Glenn Milne, Martin Lidberg
DynaQlim
Upper Mantle Dynamics and Quaternary
Climate in Cratonic Areas
A regional co-ordination committee of the International
Lithosphere Program (ILP)
Markku Poutanen and the DynaQlim Group*
* Søren Gregersen, Sören Haubrock, Erik Ivins, Matt King, Volker Klemann, Ilmo Kukkonen,
Juha-Pekka Lunkka, Christophe Pascal, Hans-Georg Scherneck, Bert Vermeersen
Objectives of DynaQlim
 to collect existing relevant geo-data for
improving geophysical models,

to improve kinematic 3-D models, and in general,
understand better the dynamics of the Earth's crust,

to better understand the relations between the
upper mantle dynamics, mantle composition, physical
properties, temperature and rheology,

to study the effect of Quaternary climate,
glaciation cycles and ice thickness on contemporary
climate, rebound rate,…

to study the Quaternary climate variations and
Weichselian (Laurentian and other) glaciations,
Objectives of DynaQlim

to study the response of the gravity field with
different ice loads and to understand the secular
change of gravity in the rebound area and especially in
its margin areas,

to apply the results in the polar regions, like the
glaciation history in Antarctica and Greenland and the
Holocene rebound history in deglaciated areas,

to offer reliable data for other disciplines in
geoscience and for studies of the global change, sea
level rise and climate variation
Ancient shorelines can be
used to reconstruct
rebound / sea level
changes during last 10 ky
But:
Land uplift/subsidence
and sea level variations
can not be separated in
this data alone
Tikkanen, Oksanen
Back to the sea level rise…
Sea level rise
Wikipedia
Observational evidences
Wikipedia
Observational evidences
Wikipedia
Observational evidences
Wikipedia
Sea level in Baltic Sea /Helsinki
Courtesy Kimmo Kahma /
Finnish Marine Research Institute
Melting;
where the meltwater is going?
Top: Antarctica glaciers are melting
Middle: Greenland glaciers are
melting
Bottom: Mountain glaciers are
melting
We see practically nothing of the
Greeenland melting in the Baltic Sea
Growth and decay of a glacier
Vertical uplift of Fennoscandian far-field
J.-M. Nocquet, E. Calais, B. Parsons (2005). GRL 32,L06308.
Sea level rise, melting of glaciers
Initial phase
0 m water has added
in the ocean
Ocean
Oceanic crust
Viscoelastic upper mantle
Sea level at its
initial height
Continental crust
Sea level rise, melting of glaciers
Added water
1 m water has added
in the ocean
Sea level rises at
shore line
Continental crust
Ocean
Oceanic crust
Viscoelastic upper mantle
Sea bottom is pressed down
Upper mantle viscoelastic flow under continents
Summary
• GIA is very complicated in the viewpoint of precise
observations and reference frames
• No single observing technique is sufficient
• Geodetic observing systems (GGOS, ECGN, NGOS, …)
offer (or will/should offer) multi-technique data/sites in a
coordinated way
• Many GIA-related phenomena are global but many
consequences are local and may have also serious societal
aspects (sea level rise, earth quakes, …) or which are
laborous and expensive (new height systems)
• We need also regional and local dense networks
• Sub-mm accuracy in ten years + levelling for height control
Summary 2
• Sea level is rising unevenly; depends on where the
glaciers are melting
• At shoreline we see less effect than calculated by the melt
water
•
•
•
•
Elastic loading of the sea bottom (immedeate)
Viscoelastic flow of upper mantle (slow)
Push of continents up
Volume of oceans increased
• Land uplift in Finland 2-9 mm/y = 20 – 90 cm / 100 y
• Most sea level rise is absorbed by the uplift
• Greenland effect almost zero here