Accelerating Change

in the Arctic?Perspectives from Observations

and Global Climate Models

David Lawrence

NCAR

With contributions from Marika Holland,

Mark Serreze, Don Perovich

Greenland Ice Sheet Melt

• 16% increase in melt area between 1979 and 2002 • new record in 2007 (60% increase in area)

Arctic sea ice is disappearing

Stroeve et al. 2008

Permafrost FeaturesWarmer climate leads to soil warming and Warmer climate leads to soil warming and permafrost degradationpermafrost degradation

http://www.arctic.noaa.gov/reportcard/index.html

Peering into the future ….

NCAR-based Community Climate System Model (CCSM3)

Coupled Ocean-Atmosphere-Land- Sea Ice model

• ~1.4o longitude x 1.4o latitude resolution

• 30 minute time step

• 26 atmosphere levels

• 40 ocean levels

• 10 soil levels

• ~1.2 million points

• Archive data (monthly, daily, hourly) for over 100 geophysical fields:

- Surface air temperature

- Sea ice thickness

- Snow age

Abrupt reductions in the September sea ice cover

“Abrupt”transition

Holland et al., 2006

Ice E

xte

nt

( 1

06 k

m2 )

September sea ice extent

9 events

across 8-

member

CCSM3 A1B

ensembleSSMI observed

CCSM3

CCSM3 – smoothed

Observed rate of loss is faster than projected

Adapted from Stroeve et al., 2007

What impact does sea ice loss have on Arctic?

Impacts on Polar Bears

…and on broader Arctic climate … in the 1970’s

D. Perovich, CRREL

Not far from today…

D. Perovich, CRREL

Arctic Land Area: Surface Air Temperature Change (CCSM3)

}

Glo

bal

Warming is ~2x faster in Arctic compared to global average

September Sea- ice Extent

3.5-fold increase in rate of warming over land during rapid sea ice loss

Lawrence et al. 2008

‘Present-day’ permafrost distribution

IPA Permafrost Distribution Map

Continuous (90 – 100% coverage)

Discontinuous (50 – 90%)

Sporadic (10 – 50%)

Isolated (0 – 10%)

Brown et al. 1998

Near-Surface Permafrost in CCSM3

IPA Permafrost Distribution Map

Continuous Discontinuous Sporadic Isolated

CCSM3(1980 – 1999)

CCSM3 Projections of Degradation of Near-Surface Permafrost

Lawrence and Slater, 2005

Lakes drain, soil dries

Arctic terrestrial climate-change feedbacks

Enhanced[nitrogen]

CO2

efflux

Globalwarming

CH4

efflux

Microbial activity

increases

Shrubgrowth

Expandedwetlands

Carbonsequester

Arctic runoffincreases Thermohaline

slows

Permafrost warms and

thaws

ArcticArcticwarmingwarming

Lakes drain, soil dries

Arctic terrestrial climate-change feedbacks

CO2

efflux

Globalwarming

CH4

efflux

Expandedwetlands

Permafrost warms and

thaws

ArcticArcticwarmingwarming

Carbon stocks in permafrost soil

~ 800 – 1300 PgC

Atmospheric carbon content

~ 750 PgC + 8-9 PgC yr-1

What happens to soil carbon as soil warms and permafrost thaws?

If soils get drier aerobic decomposition CO2 emissions

If more wetlands anaerobic microbial activity CH4 production (25x GWP)

19781978

19981998Bubier et al. 1995

Lakes drain, soil dries

Arctic terrestrial climate-change feedbacks

Enhanced[nitrogen]

CO2

efflux

Globalwarming

CH4

efflux

Microbial activity

increases

Shrubgrowth

Expandedwetlands

Carbonsequester

Arctic runoffincreases Thermohaline

slows

Permafrost warms and

thaws

ArcticArcticwarmingwarming

Bernhard Edmaier National Geographic

Summary

• Observations and models indicate system-wide change in the Arctic that is consistent with warming

• In some cases the observed rate of change exceeds modeled rates (e.g. sea ice) “Sea ice melt unnerves experts” – NY Times

• Complex array of interrelationships and feedbacks across systems continues to challenge our models and motivates further model development

Timeline of Climate Model Development

Timeline of Climate Model Development

Permafrost “Humor”

ChemistryClimate

ChemistryClimate

BioGeoChemistryBioGeoChemistry

Software EngineeringSoftware Engineering

Climate VariabilityClimate Variability

Polar ClimatePolar

ClimateLand ModelLand Model

PaleoClimate PaleoClimate

Ocean Model Ocean Model

CCSM Working GroupsCCSM Working GroupsCCSM Working GroupsCCSM Working Groups DevelopmentDevelopmentDevelopmentDevelopment

ApplicationApplication ApplicationApplication

AtmModel

AtmModel

Climate ChangeClimate Change

CCSM is primarily sponsored by the National Science Foundation

and the Department of Energy

Mountain Glaciers are Melting / Retreating

Pasterze Gletscher, Austria

2003

1900

CO2 emissions and concentrations increasing faster than expected

Fraction of CO2 emissions staying in atmosphere is increasing (0.4 to 0.45)

Is the earth system losing its capability to soak up CO2?

1960 2000

Appearing and Disappearing Lakes in Siberia (Smith et al.

2005)

Smith et al., 2005

Impacts on Infrastructure

Permafrost: Soil or rock that remains below freezing for two or more years

Continuous (90 – 100% coverage)

Discontinuous (50 – 90%)

Sporadic (10 – 50%)

Isolated (0 – 10%)

IPA Permafrost Distribution Map

Continuous Discontinuous

Brown et al. 1998