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

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70S

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Glaciers and ice caps Greenland Antarctica

West Antarctica

East Antarctica

Antarctic Peninsula

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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