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Shrinking Ice: The Global Impact of Polar Warming
World Meteorological Day PresentationGeneva 23rd March 2007
Shrinking Ice: The Global Impact of Polar Warming
World Meteorological Day PresentationGeneva 23rd March 2007
Chris Rapley
Director
British Antarctic Survey
Chris Rapley
Director
British Antarctic Survey
IPCC Fourth Assessment ReportClimate Change 2007 : The Physical Science
Basis – Summary for Policy Makers
IPCC Fourth Assessment ReportClimate Change 2007 : The Physical Science
Basis – Summary for Policy Makers
Atmospheric GHG concentrations far exceed levels of last 650,000y as a result of human emissions
Warming of the climate system is “Unequivocal”
Current climate forcing primarily Human
Agreed by delegates of 113 nations
In a Warmer World Ice MeltsIn a Warmer World Ice Melts
Global Warming - Amplification at PolesGlobal Warming - Amplification at Poles
“Ice-Albedo” amplifier as ice and snow cover reduces
Hansen et al - 2005
Arctic Sea Ice CoverArctic Sea Ice Cover
Reduction of Arctic Sea Ice summer extent 1978 to 2006 ~8% per decadeAccelerating?
Ice-free during summer by 2050?
OpportunitiesOpportunities
0
10
20
30
40
50
60
70S
ea-le
vel e
quiv
alen
t (m
etre
s)
Glaciers and ice caps Greenland Antarctica
West Antarctica
East Antarctica
Antarctic Peninsula
0
10
20
30
40
50
60
70S
ea-le
vel e
quiv
alen
t (m
etre
s)
Glaciers and ice caps Greenland Antarctica
West Antarctica
East Antarctica
Antarctic Peninsula
Sea Level Rise PotentialSea Level Rise Potential
0.5m7m
57m
Summer melt area increased on average by 25% from 1979 to 2005Modest increased snowfall in interior
Greenland Ice Sheet Surface Melt and Glacier Discharge
Greenland Ice Sheet Surface Melt and Glacier Discharge
Space radar and gravity data indicate that ice discharge by melting AND SLIDING increased from 1996 to 2005
Net contribution to sea level rise ~0.28mm/y Shepherd & Wingham 2007
AntarcticaAntarctica
Antarctic Peninsula Glacier ResponsesAntarctic Peninsula Glacier Responses
244 glaciers : 87% have retreated over last 50y
Cook et al., 2005
Antarctic Peninsula Ice
Shelf Disintegrations
Antarctic Peninsula Ice
Shelf Disintegrations
• Summer surface melting the key
• Northern ones absent 3-5ky ago
• Larsen B in place for 10(s)ky
Peninsula Warming and Ice Shelf Break-Up
Peninsula Warming and Ice Shelf Break-Up
Progressive warming attributed to human-induced enhanced greenhouse effect and ozone hole
Marshall et al (2006)
Glaciersaccelerated
Glacier stable
Larsen B CollapseLarsen B Collapse
Antarctic Surface Elevation Change Antarctic Surface Elevation Change
Pine Island Glacier Iceberg CalvingPine Island Glacier Iceberg Calving
Marine Ice Sheet
How Much?
How Quickly?
2005 Survey by BAS and U. Texas2005 Survey by BAS and U. Texas
How Much?How Much?
Ice accessible for discharge ~1.5m msl equivalent
How Quickly?How Quickly?• Current Antarctic sea level contribution:
– 0.2mm/y (IPCC 2007)– 0.07mm/y (Shepherd and Wingham 2007)
• Numerical ice sheet models provide no insight:– Ice dynamics not included– Numerical stability problems near grounding line
Sea Level Rise since Last Glacial Maximum
Sea Level Rise since Last Glacial Maximum
• 9k years at ~10mm/y
• two bursts at ~20mm/y or greater
• last 3ky - 0.1 to 0.2mm/y
• since 1900 1.8mm/y
• last decade ~3mm/y
• Predict 0.18 - 0.59m by 2100• BUT - models exclude increased ice sheet dynamical flow • Even if GHG concentrations stabilised sea level rise will continue
for centuries• 2 - 4.5oC global warming if maintained for millennia would result
in virtually complete elimination of the Greenland ice sheet and sea level rise of 7m.
• Comparable to interglacial period 125ky ago when polar land ice extent reduced and sea level 4-6m higher
IPCC Fourth Assessment ReportClimate Change 2007 : The Physical Science Basis –
Summary for Policy Makers
IPCC Fourth Assessment ReportClimate Change 2007 : The Physical Science Basis –
Summary for Policy Makers
Long-Term CommitmentLong-Term Commitment
Long-Term CommitmentLong-Term Commitment
Impact of Sea Level RiseImpact of Sea Level Rise
Rowley et al 2007
Global ImpactsGlobal Impacts
• Population Affected– 1m ~ 110M
– 6m ~ 430M
• Cost?
Impact on Major Cities - LondonImpact on Major Cities - London
Estimated bill for one flood : £30bn = 2%GDP
Is This The Future?Is This The Future?
International Polar Year 2007-2008International Polar Year 2007-2008
International Polar Year 2007-2008International Polar Year 2007-2008
An intensive burst of internationally coordinated, interdisciplinary, scientific research and
observations focussed on the Earth’s Polar regions
www.ipy.org
Intensive ObservationsIntensive Observations
IPY LegacyIPY Legacy
International Year of Planet Earth
International Heliophysical Year
EXISTING POLAR ACTIVITIES
Electronic Geophysical Year
2007 2008 2009 2010200620052004
IPY SNAPSHOT LONG TERM IMPLEMENTATIONIPY PLANNING
IPY2007-2008
OBSERVING SYSTEMSOBSERVING SYSTEMS
“Observing networks established or improved during the IPY should be kept in operational mode for as many years
as possible to provide data for the detection and projection of climate change”
(Recommendation of WMO EC–LVI, June 2004)
“Observing networks established or improved during the IPY should be kept in operational mode for as many years
as possible to provide data for the detection and projection of climate change”
(Recommendation of WMO EC–LVI, June 2004)
If the Earth were only a few feet in diameter, floating a few feet above a field somewhere, people would come from everywhere to marvel at it. … they would declare it as sacred because it was the only one, and they would
protect it so that it would not be hurt.
Joe Miller