Accelerating Change in the Arctic? Perspectives from Observations and Global Climate Models David...
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Transcript of Accelerating Change in the Arctic? Perspectives from Observations and Global Climate Models David...
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)
Permafrost FeaturesWarmer climate leads to soil warming and Warmer climate leads to soil warming and permafrost degradationpermafrost degradation
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
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)
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
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
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