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 AR Rate of rise ± 0.7 mm year -1 Varmaútþensla Thermal expansion Glaciers outside north and south polar regions Greenland Antarctica ? ? Sea level change Contributions: h ~20-30 cm h: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 ( ) of sea level rise: 3.3 ± 0.7 mm yr -1 Thermal expansion less than 50% Antarctica 0.3 mm yr -1 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

Estimated average annual mass balance, m w.e. a -1 Red: DEM Black: annual mass balance measurements Glaciers cover 11% of Iceland, 11,000 km 2, 3,600 km 3

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, o C 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 Mass balance ± 0.15 m w.e. a -1 Sea temperature Near zero mass balance

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 tephraaerosols Maritime climate outlets decreasing faster than inland

Annual total mass loss of Iceland‘s glaciers to 25.3 ± 1.5 Gt a to -2.2 ± 0.15 m w.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 : 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

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 precipitation from nearby meteorological stations and calibrated with seasonal stake measurements of winter and summer mass balance winter summer DEM

Future 0.2 °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 oCoC 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 values Specific 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?

mm ár /- 0.4 frá Varmaútþensla 1.6 mm ár -1 Jöklar utan heimskauta 0.8 mm ár -1 Grænlandsjökull 0.6 mm ár -1 Suðurskautslandið 0.3 mm ár -1 Hlutur jökla orðinn meiri en útþensla hafs ?