Can Arctic Sea Ice Summer Melt be Accelerated by

Changes in Spring Cloud Properties?

I. Gorodetskaya1, B. Tremblay1,2, B. Liepert1, M. Cane1

1Lamont-Doherty Earth Observatory, New York2McGill University, Montreal

yes

surface radiative

fluxes

Data: SHEBA Atmospheric Surface Fluxes Group

atmosphere

Cloud phase and long-wave:

February March April

WINTER->SPRING

Cloud phase and long-wave:

SPRING->SUMMER

May June July

Cloud LW forcing (CFL) as a function of cloud properties

Chen, Aires, Francis, Miller, J Climate 2006

Liquid water path: data and models

Gorodetskaya et al, accepted to J Climate

Total variance in the perennial ice edge attributable to anomalies in forcing parameters, 1980-2004

also see: Francis, Hunter, Key, Wang, JRL 2005

J. A. Francis and E Hunter

- Spring: large positive trend

Schweiger, GRL 2004

- Summer: no trend …

Cloud cover over the Arctic Ocean:

April and May have the largest trends in both Cloud % and LW flux

R(LW,CLT)=0.6

TOVS

Changes in Arctic (white bars) annual mean sea ice extent

at the end of the 21st century

Arzel, Fichefet, Goosse, Ocean Modelling 2006

CCSM3: predicts a large increase in the Arctic annual mean downwelling LW flux

in the 21st century

CCSM3: predicts a large increase in the Arctic annual mean downwelling LW flux

in the 21st century

Winter&SPRING!

increase in cloud liquid water path:

increase in LW flux down:

Total downwelling fluxdifference between the last and first

decades of 21st century

0-layer thermodynamics model: sea ice thickness and concentration

evolution

Ta - from NP drifting stations (Lindsay, J Climate 1998)

LW, SW

ice: A,h Fc

Ti

Tb=-1.8

LW, SW, Fsens, FlatFsens(Ta-Ti), Flat

Scale the forcing with the CCSM-predicted changes in downwelling LW and SW fluxes

Sea ice thickness change:

conclusions and outlook

• Clouds increase: Apr 21%, May 12% (1980-2004) => Arctic Ocean gains ~15 W/m2 more

LW radiation (TOVS data)

• NCAR CCSM3: - Arctic - more liquid clouds in 2xCO2 world - spring cloud LW warming overwhelms SW

cooling

• with the above cloud response alone (LW forcing strongest in winter and spring), a 1D ice model reduces an equilibrium sea ice thickness from 4.5 to 2.5 m

• positive feedbacks not included! e.g., snow(T) -> surface albedo

Arctic Sea Ice Summer Melt can be accelerated by an

increase in Spring cloud liquid water path...

Big Thanks: Yonghua Chen, Jennifer Francis, Kirstie Stramler, Martin Vancoppenolle, Richard Cullather

Photo from Peter Minnett