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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

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accelerating change in the arctic perspectives from observations and global climate models

Accelerating Changein the Arctic?Perspectives from Observationsand Global Climate Models

David Lawrence

NCAR

With contributions from Marika Holland, Mark Serreze, Don Perovich

slide2

Greenland Ice Sheet Melt

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

Warmer climate leads to soil warming and permafrost degradation

ncar based community climate system model ccsm3
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
slide8

9 events across 8-member CCSM3 A1B ensemble

Abrupt reductions in the September sea ice cover

September sea ice extent

Ice Extent ( 106 km2 )

SSMI observed

CCSM3

CCSM3 – smoothed

“Abrupt”

transition

Holland et al., 2006

observed rate of loss is faster than projected
Observed rate of loss is faster than projected

Adapted from Stroeve et al., 2007

slide13

Not far from today…

D. Perovich, CRREL

arctic land area surface air temperature change ccsm3
Arctic Land Area: Surface Air Temperature Change (CCSM3)

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

}

Global

slide15

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

September Sea- ice Extent

Lawrence et al. 2008

present day permafrost distribution
‘Present-day’ permafrost distribution

Continuous (90 – 100% coverage)

Discontinuous (50 – 90%)

Sporadic (10 – 50%)

Isolated (0 – 10%)

IPA Permafrost Distribution Map

Brown et al. 1998

near surface permafrost in ccsm3
Near-Surface Permafrost in CCSM3

IPA Permafrost

Distribution Map

CCSM3

(1980 – 1999)

Continuous

Discontinuous

Sporadic

Isolated

arctic terrestrial climate change feedbacks
Arctic terrestrial climate-change feedbacks

Arctic

warming

Arctic runoff

increases

Thermohaline

slows

Carbon

sequester

Global

warming

CO2

efflux

CH4

efflux

Permafrost

warms and

thaws

Enhanced

[nitrogen]

Expanded

wetlands

arctic terrestrial climate change feedbacks1
Arctic terrestrial climate-change feedbacks

Carbon stocks in permafrost soil

~ 800 – 1300 PgC

Atmospheric carbon content

~ 750 PgC + 8-9 PgC yr-1

Arctic

warming

Global

warming

CO2

efflux

CH4

efflux

Permafrost

warms and

thaws

Expanded

wetlands

slide21

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)

1978

Bubier et al. 1995

1998

arctic terrestrial climate change feedbacks2
Arctic terrestrial climate-change feedbacks

Arctic

warming

Arctic runoff

increases

Thermohaline

slows

Carbon

sequester

Global

warming

CO2

efflux

CH4

efflux

Permafrost

warms and

thaws

Enhanced

[nitrogen]

Expanded

wetlands

slide23

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

Bernhard Edmaier

National Geographic

ccsm working groups
CCSM Working Groups

Chemistry

Climate

BioGeo

Chemistry

Atm

Model

Land

Model

Polar

Climate

Ocean

Model

Climate Change

PaleoClimate

Climate Variability

Development

Application

Software Engineering

CCSM is primarily sponsored by

the National Science Foundation

and the Department of Energy

slide28

Mountain Glaciers are Melting / Retreating

Pasterze Gletscher, Austria

2003

1900

co 2 emissions and concentrations increasing faster than expected
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?

2000

1960

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

IPA Permafrost Distribution Map

Continuous Discontinuous

Continuous (90 – 100% coverage)

Discontinuous (50 – 90%)

Sporadic (10 – 50%)

Isolated (0 – 10%)

Brown et al. 1998