Helgi Björnsson,Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland
Contribution of Icelandic ice caps to sea level rise:trends and variability since the Little Ice Age
4th TPE workshop, Dehradun, India, 1-4 April 2013
GRL 2013
2,15%
97,2%
0,001%
0,63%
0,01%
Contribution to studies of global
changes of glaciers in the hydrological cycle
Present rising rate
IPCC AR4 2007
Rate of rise 1993-2003
3.1 ± 0.7 mm year-1
Varmaútþensla
Thermal expansion
Glaciers outside north and south polar regions
Greenland
Antarctica ??
Sea level change
Contributions:Dh ~20-30 cm
Dh:20-50 cm
Future prognoses of rising sea level
0,8 – 1 m ?
West-Antarctica and Greenland reacting faster to global warming than models have been able to predict
Latest reports (2005-2010) of sea level rise: 3.3 ± 0.7 mm yr-1
Thermal expansion less than 50%
Antarctica 0.3 mm yr-1
Greenland0.6 mm yr-1
Other ice masses0.8 mm yr-1 Thermal expansion of oceans
1.6 mm yr-1
Glacier recession outside polar regions since 1970
Iceland
Estimated average annual mass balance, mw.e. a-1
Red: DDEMBlack: annual mass balance measurements
Glaciers cover 11% of Iceland, 11,000 km2, 3,600 km3
Iceland
at the boundary between polar and mid-latitude atmospheric circulation cells in the westerlies
and confluence of warm and cold sea currents
Sea surface temperature, oCInter-annual variability in mass balance
may be expected in the North Atlantic areaforced by fluctuations in atmospheric circulation and ocean currents
Air temperature
Precipitation
Mass balance ± 0.15 mw.e. a-1
Sea temperature
Near zero mass balance 1980-1995
1900
General mass loss reflects: Higher summer temperature Longer melting seasons Warm winters reducing proportion of precipitation falling as snow Earlier exposure of low albedo
glacier ice (radiation:3/4 of melt energy)
Higher sea temperatures
Fluctuations relate to:
Cold springs, late exposure of low albedo glacier ice
Snowfall during summers
Deposition of tephra aerosolsMaritime climate outlets decreasing faster than inland
Annual total mass loss of Iceland‘s glaciers 1995-2011
2.7 to 25.3 ± 1.5 Gt a-1
-0.2 to -2.2 ± 0.15 mw.e. a-1
Average 9.5 ± 1.5 Gt a-1 (0.03 mm a-1 SLE)
Annual total mass loss of Iceland‘s glaciers
Total ice melt 1995-2010:85% directly climate related13% (20 Gt) due to lowering of albedo by tephra aerosols< 3% melted by geothermal heat2% melted by volcanic eruptions
Modelled mass balance
Observed mass balance
Observed summer temperature and winter precipitation
Observed sea temperature
Firnline
Ablation area
Accumulation area
Ice flow
Runoff
through mass balance measurements
and meteorological observations
Coupled mass-balance-ice-flow model
Mass balance related to climate
Distributed snow accumulation and temperature-index melt (positive degree-day model, PDD)
Mass-balance evolution simulated with a coupled mass-balance-ice-flow model
forced by daily mean temperature records and accumulated precipitationfrom nearby meteorological stations and
calibrated with seasonal stake measurements of winter and summer mass balance
winter
summer
DDEM
Future0.2 °C/decade
3.4 mm/decade.
Climate change scenario (A1B) for Icelandic highland
Predicted glacier response
Sea surface temperature
Glaciers in a cold temperate climate
Iceland
oC
Interannual variations in mass balance may be expected in the North Atlantic area, forced by fluctuations in atmospheric circulation and ocean currents,
superimposed on the projected trend of increasingly negative glacier mass balance
Iceland 2200?
Note:Volumes and areas are normalized to present day valuesSpecific runoff is from the present day glacier covered area
Predicted response to the A1B climate change scenario
Model responses shown for three Icelandic ice caps:Vatnajökull, Langjökull and Hofsjökull
Mass balance model coupled with a ice-flow model (given geometry)
Year 2060: sea level rise 0,06 mm/a
Mass balance modelling Mass balance related to climate
Meteorological observations
Iceland 2200?
2005-2010
3.3 mm ár-1
3.3 +/- 0.4 frá 1993-2009
Varmaútþensla1.6 mm ár-1
Jöklar utan heimskauta0.8 mm ár-1
Grænlandsjökull0.6 mm ár-1
Suðurskautslandið 0.3 mm ár-1
Hlutur jökla orðinn meiri en útþensla hafs
?
1961-2003
1.8 +/- 0.5 mm ár-1
1.7 +/- 0.3 frá 1950-2009
Varmaútþensla0.42 +/- 0.12 mm ár-1
Jöklar utan heimskauta0.5 +/- 0.18 mm ár-1
Grænlandsjökull0.05 +/- 0.12 mm ár-1
Suðurskautslandið0.14 +/- 0.41 mm ár-1
?
1993-2003
3.1 +/- 0.7 mm ár-1
3.3 +/- 0.4 frá 1993-2009
Varmaútþensla1.6 +/- 0.5 mm ár-1
Jöklar utan heimskauta0.77 +/- 0.22 mm ár-1
Grænlandsjökull0.21 +/- 0.12 mm ár-1
Suðurskautslandið0.21+/-0.35 mm ár-1
??