can arctic sea ice summer melt be accelerated by changes in spring cloud properties? i. gorodetskaya...
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TRANSCRIPT
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