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4th TPE workshop, Dehradun, India, 1-4 April 2013 Contribution of Icelandic ice caps to sea level rise: trends and variability since the Little Ice Age GRL 2013 Helgi Björnsson, Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland Contribution to studies of global changes of glaciers in the hydrological cycle 0,001% 0,01% 2,15% 0,63% 97,2% Present rising rate Sea level change Dh:20-50 cm Rate of rise 1993-2003 Varmaútþensla 3.1 ± 0.7 mm year-1 Contributions: ? Dh ~20-30 cm Antarctica Greenland ? Glaciers outside north and south polar regions Thermal expansion IPCC AR4 2007 Latest reports (2005-2010) of sea level rise: 3.3 ± 0.7 mm yr-1 Thermal expansion less than 50% West-Antarctica and Greenland reacting faster to global warming than models have been able to predict Antarctica 0.3 mm yr-1 Future prognoses of rising sea level 0,8 – 1 m ? Greenland 0.6 mm yr-1 Other ice masses 0.8 mm yr-1 Thermal expansion of oceans 1.6 mm yr-1 Glacier recession outside polar regions since 1970 Iceland Glaciers cover 11% of Iceland, 11,000 km2, 3,600 km3 Estimated average annual mass balance, mw.e. a-1 Red: DDEM Black: annual mass balance measurements 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, oC Inter-annual variability in mass balance may be expected in the North Atlantic area forced by fluctuations in atmospheric circulation and ocean currents Air temperature Precipitation Sea temperature Mass balance ± 0.15 mw.e. a-1 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 Maritime climate outlets decreasing faster than inland Deposition of tephra aerosols 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 related 13% (20 Gt) due to lowering of albedo by tephra aerosols < 3% melted by geothermal heat 2% melted by volcanic eruptions Observed summer temperature and winter precipitation Observed sea temperature Observed mass balance Modelled mass balance Coupled mass-balance-ice-flow model Mass balance related to climate through mass balance measurements and meteorological observations Accumulation area Firnline Ablation area Runoff Mass-balance evolution simulated with a coupled mass-balance-ice-flow model forced by daily mean temperature records and accumulated precipitation from nearby meteorological stations and calibrated with seasonal stake measurements of winter and summer mass balance winter DDEM summer Distributed snow accumulation and temperature-index melt (positive degree-day model, PDD) Climate change scenario (A1B) for Icelandic highland Future 0.2 °C/decade 3.4 mm/decade. Predicted glacier response Interannual variations in mass balance may be expected in the Glaciers in a cold temperate climate North Atlantic area, forced by fluctuations in atmospheric circulation and ocean currents, superimposed on the projected trend of increasingly negative glacier mass balance Iceland oC Sea surface temperature Iceland 2200? Predicted response to the A1B climate change scenario Mass balance model coupled with a ice-flow model (given geometry) Model responses shown for three Icelandic ice caps: Vatnajökull, Langjökull and Hofsjökull Year 2060: sea level rise 0,06 mm/a Note: Volumes and areas are normalized to present day values Specific runoff is from the present day glacier covered area Mass balance modelling Mass balance related to climate Meteorological observations Iceland 2200? Hlutur jökla orðinn meiri en útþensla hafs 1961-2003 1.8 +/- 0.5 mm ár-1 1.7 +/- 0.3 frá 1950-2009 Varmaútþensla 0.42 +/- 0.12 mm ár-1 1993-2003 3.3 +/- 0.4 frá 1993-2009 Grænlandsjökull 0.21 +/- 0.12 mm ár-1 ? Suðurskautslandið 0.21+/- 0.35 mm ár-1 ? ? Suðurskautslandið Jöklar utan heimskauta 0.14 +/- 0.41 mm ár-1 0.5 +/- 0.18 mm ár-1 Grænlandsjökull 0.05 +/- 0.12 mm ár-1 2005-2010 3.1 +/- 0.7 mm ár-1 Jöklar utan heimskauta 0.77 +/- 0.22 mm ár-1 Varmaútþensla 1.6 +/- 0.5 mm ár-1 3.3 mm ár-1 3.3 +/- 0.4 frá 1993-2009 Grænlandsjökull 0.6 mm ár-1 Suðurskautslandið 0.3 mm ár-1 Jöklar utan heimskauta 0.8 mm ár-1 ? Varmaútþensla 1.6 mm ár-1