Hugh Corr

1
Antarctica, recent observations of change

• Hugh Corr
• British Antarctic Survey

2
Arctic vs. Antarctic
Antarctica 13,661,000 km² Greenland 2,160,086
km² Ireland 70,280 km²
Source Unpublished
3
Major uncertainties exist regarding the impact
of human-induced climate change on the Polar
Regions. Intergovernmental Panel on Climate
Change The Physical Science Basis, 2007

• Estimated Sea Level Rise from
• Total Loss of Ice Sheets
• Greenland 7
  meters
• West Antarctica (WAIS) 5 meters
• East West Antarctica 70 meters

4
Collapse of the West Antarctic ice sheet?
Subglacial topography sea level
2000 m
-2000 m
Source Unpublished
5
(No Transcript)
6

• The isotopic content of the water molecules
  themselves (18O/16O and D/H) is determined mainly
  by the temperature at the time of snowfall
• 2. Soluble and insoluble impurities are trapped
  at the surface by falling snow, dry deposition
  and gaseous uptake onto the surface
• 3. Trapped air

7
(No Transcript)
8
Recent past CO2
9
Recent changes - methane
Etheridge et al 1998, JGR 103, 15979.
10
Greenhouse gases
11
But we are out of the range of the last 800 kyr
9oC
Siegenthaler et al., Science 2005 (EPICA gas
consortium)
12
For CH4 also
Spahni et al., Science 2005, EPICA gas consortium
13
MIS11 analogue for Holocene?
14
George VI Ice Shelf
Prince Gustav Channel Ice Shelf 1995
Wilkins 1998
Larsen A 1995
Wordie 1980s
Larsen B 1998 2002
Larsen Inlet 1998/9
Jones 2002
15
Antarctic Peninsula
87 of 244 glaciers retreated over 50 year period
South Pole station (trend -0.1 C/decade)
Faraday/Vernadsky Station, Antarctic Peninsula,
(trend 0.5C/decade)
16
Collapse of the West Antarctic ice sheet?
Subglacial topography sea level
2000 m
-2000 m
Source Unpublished
17
Antarctica and sea level
Surface elevation change 1992-2003
Source Curt Davis et al., Science, 2005
18
(No Transcript)
19
Perspective view of the new bed topography for
Pine Island and Twaites Glaciers
20
150 Subglacial Lakes Identified (so far)
Lake Vostok 15,690 km² N. Ireland 13,843 km²
21
"Sooner or later the lakes will go off like
champagne corks," Wingham et al. Nature 440,
1033-1036, 2006 Over 16 months, 1.8 km3 of water
was transferred over 290 km to at least two
other subglacial lakes at a rate of 50 m3 s-1
22
Tidal Modulation of Stick-Slip Ice Stream Motion
Bindschadler et al, Science 2003
Accelerates to 1 m/hr Comes to a stop in
minutes Slip propagates at 88 m/s
Motion linked to spring tides
23
Spaceborne high-resolution laser altimeter
Launched 2003
24
An Active Subglacial Water System Mapped from
Space Fricker et al, Science 2007
Subglacial lake near a grounding line. Dynamic
subglacial water system Controls ice flow.
Lubricant between the ice and bed
25
Effect of Sedimentation on Ice-Sheet
Grounding-Line Stability Alley et al. Science,
2007.
Sedimentation beneath ice shelves at grounding
lines (where ice begins to float) provides
stability against advance or retreat
for sea-level changes of up to a few meters or
more.
26
Conclusions
Glaciological changes at the Antarctic Peninsula
Ice Shelves thinned and some have collapsed
Restraint is removed accelerating ice discharge
However any sea-level rise negated by increased
snowfall
East Antarctica is gaining 25 Gt year1 West
Antarctica is losing 50 Gt year1 Greenland
is losing 100 Gt year1.
These trends provide a sea-level contribution of
0.35 mm year1 a modest component of the
present rate of sea-level rise of 3.0 mm year1.
Losses are dominated by ice dynamics NOT the
balance between accumulation and
ablation Satellite observations show glacier
accelerations of 20 to 100 over the past decade.

Our predictive ability is limited, continued
observation is essential Numerical models that
include the detailed mechanics are required