Andrew Shepherd School of Geosciences, Edinburgh
Sea Subglacial level contribution lakes of Antarctica & Greenland
Climate change Satellite observations Ice Sheets and Sea level
Climate change
Climate Change Slow climate change Mt Kilimanjaro, 1993
Climate Change Slow climate change Mt Kilimanjaro, 2000
Climate Change Abrupt climate change
Climate Change Abrupt climate change Larsen Ice Shelf, 2002
Abrupt climate change Larsen Ice Shelf, 2002
Abrupt climate change Larsen embayment, 2005
Climate Change Abrupt climate change Larsen sea bed, 2005 Domack et al., 2005
Climate Change IPCC Assessment reports (1990, 1995, 2001) 0.6 C rise since 1900 Global warming IPCC, 2001
Climate Change IPCC Assessment reports (1990, 1995, 2001) 15 cm rise since 1900 Global sea level rise IPCC, 2001
IPCC 2007 1961-2003 1993-2003 Measured sea level Thermal expansion Glaciers & ice caps Greenland Antarctica
IPCC 2007
IPCC 2007
IPCC 2007 (i) Models used to date do not include the full effects of changes in ice sheet flow, because a basis in published literature is lacking. (ii) Dynamical processes related to ice flow suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. (iii) Understanding of these processes is limited and there is no consensus on their magnitude.
Zwally effect
Payne effect
Climate Change UK today
Climate Change UK today No Polar Ice Sheets
Satellite observations
Sea Polar level ice sheets contribution and sea of level Antarctica rise & Greenland Altimetry Interferometry Gravimetry
Altimetry
Altimetry Mass change from volume change
Gravimetry
Gravimetry Mass change from orbit change
Interferometry
Interferometry
Interferometry Mass change from glacier flow
Sea level contribution
Sea level Range of -366 to 53 Gt yr -1 equals 1.0 to -0.15 mm yr -1 sea level contribution Factor 3 poorer certainty than last two IPCC reports
Sea level All methods are all sensitive to snowfall: Interferometry compares snowfall to, runoff &ice discharge Altimetry requires knowledge of density, which ranges from 350 to 900 kg m -3 Gravimetry measures change in snow and ice mass, and suffers from short time period (<3 years)
Sea level All methods are all sensitive to snowfall: Interferometry compares snowfall to, runoff &ice discharge Altimetry requires knowledge of density, which ranges from 350 to 900 kg m -3 Gravimetry measures change in snow and ice mass, and suffers from short time period (<3 years) Ice cores show 15 % fluctuations in MAR over short time periods Antarctica MAR = 6 mm esl Greenland MAR = 0.5 mm esl
Greenland
Greenland EAIS = - 100 Gt yr -1 (+0.3 mm yr -1 ) Altimetry misses coast Gravimetry studies do not concur InSAR shows acceleration 1995-2005
Greenland InSAR shows large and rapid fluctuations in Greenland glacier discharge Complicates estimates of decadal imbalance Recent (2007) decelleration shows signal to be non-secular
Greenland InSAR shows large and rapid fluctuations in Greenland glacier discharge Complicates estimates of decadal imbalance Recent (2007) decelleration shows signal to be nonsecular
Antarctica
Antarctica EAIS = + 25 Gt yr -1 (-0.07 mm yr -1 ) WAIS = - 50 Gt yr -1 (+0.14 mm yr -1 ) Altimetry & interferometry concur Gravimetry overestimates loss (-150 Gt yr -1 ), because of recent snowfall shortfall (100 Gt yr -1 )
Antarctica
Antarctica PIG thinning due to <0.5 C ocean warming Has triggered 50 Gt yr -1 ice loss from 2 glaciers (0.14 mm yr -1 ) 21 st C warming up to 4 C
Summary Recent sea level contribution of Antarctica and Greenland is 0.35 mm yr -1 Half of this is due to recent acceleration of Greenland, which has since abated Only submarine-based & coastal Antarctic glaciers show secular trend Evolution of these glaciers poses immediate threat to future sea levels