External Forcing, Internal Climate
Variability and the Arctic’s Rapidly
Shrinking Sea Ice Cover
Mark Serreze
National Snow and Ice Data Center, Cooperative
Institute for Research in Environmental Sciences at
the University of Colorado Boulder
The National Snow and Ice Data Center (NSIDC)
The view from NSIDC
The National Snow and Ice Data Center…
Manages and
distributes
scientific data
Performs scientific
research
Supports data
users
Creates tools for
data access
Educates the public
about the cryosphere
The Arctic sea ice cover
AMSR-E data, plots by Univ. Bremen
End of summer ice extent is rapidly declining
Sept 16, 2007:
Sept 14, 2008:
Sept 12, 2009:
Sept 19, 2010:
4.13 million sq. km
4.51 million sq. km
5.10 million sq. km
4.60 million sq. km
Sept 11, 2011: 4.34 million sq. km
Left: Univ. Bremen; Right: Updated from Stroeve et al. (2007); Top: NSIDC
Conservative models and large between-model scatter
Updated from Stroeve et al. (2007)
Arctic warming and ice-albedo feedback
Cumulative anomalies in absorbed solar radiation,
2005-2010, based on JRA-25
From Stroeve et al., 2011
JRA-25 925 hPa temperature
anomalies, 1979-2010
Black carbon aerosols
newsbusters.org
With the advent of cleaner combustion techniques, sulfate aerosol concentrations have
declined, but black carbon aerosol concentrations have increased, largely because of
increasing emissions from Asia. In contrast to sulfate aerosols, black carbon aerosols
strongly absorb solar radiation and hence have a warming effect on the atmosphere. Results
from the modeling study of Shindell and Faluvegi (2009) suggest that the combination of
decreasing concentrations of sulfate aerosols and increasing concentrations of black carbon
aerosols in the Arctic has contributed to Arctic warming over the past three decades.
ALSO – soot on snow.
Clouds and atmospheric energy transport
Francis and Hunter (2006): Increased
spring cloud cover, more abundant
water containing clouds and
increased water vapor have
augmented to the downward
longwave flux to the surface,
contributing to retreat of the sea ice
margin.
Graversen et al. (2008), Yang et al.
(2010): Links between recent
temperature change and altered
atmospheric energy transport.
http://campaign.arm.gov/altos/
A puzzle: enhanced Atlantic inflow
Moorings at Svinoy and Fram Strait
I. Polyakov et. al, 2005
The “dipole” circulation of summer 2007
 High pressure over central Arctic Ocean
 Low pressure over Siberia
A very warm Arctic
NCEP/NCAR Reanalysis; NOAA/ESRL Physical Sciences Division
Observed autumn temperature trends, 1960-2010
GISS Analysis
Effects of sea ice loss
•Ocean picks up more heat in summer
•Releases more heat back to the atmosphere in autumn and winter
•Albedo feedback signal on temperature is seasonally delayed
Increasing tropospheric water vapor
MERRA anomalies by month
and year for the polar cap
(the region north of 70 deg.
N) of a) surface to 500 hPa
precipitable water; b) 850
hPa air temperature; c) 850
hPa specific humidity; d) 850
hPa relative humidity.
Anomalies are with respect
to 1979-2008 means.
A complex set of interconnected processes
Warmer air temperatures in all seasons (GHG
forcing)
Enhanced ice-albedo feedback
More open water in
September
Warmer autumn temperatures
Earlier development of open water
Thinner spring ice
Adapted from Stroeve et al., 2011
Will sea ice loss affect circulation patterns?
The NCAR Community Atmospheric Model (CAM) was used to perform
two 30-year simulations, one with a climatological late 20th century
seasonal cycle in sea ice fraction, and one using the 2007 seasonal cycle.
Circulation differences were most prominent in autumn and winter.
E. Cassano, J. Cassano and M. Higgins
Conclusions
We are quickly losing the ice cover
•Impacts are already being felt
Ice-free summers by 2030? Earlier?
•We seem to be in the fast lane
Both external forcing and internal variability are at work
•Atmospheric circulation patterns – dipole anomaly
•Ocean heat flux convergence
•Atmospheric heat flux convergence
•Black carbon aerosols and soot on snow
•Cloud cover and water vapor
Thank You