The influence of sea ice aerosol deposition and melt ponds on the Arctic surface heat budget and surface albedo feedback in CCSM4
Abstract
The Community Climate System Model, 4 incorporates a new sea ice shortwave radiative transfer scheme, which uses inherent optical properties to define scattering and absorption characteristics of snow, ice and included shortwave absorbers. This explicitly allows for melt pond and aerosol radiative impacts on sea ice. As such, the deposition and cycling of aerosols in sea ice is now included and a new parameterization derives ponded water from the surface meltwater flux. Taken together, this provides a more sophisticated, accurate, and complete treatment of sea ice radiative transfer, shortwave heat budgets, and surface albedo. We discuss the radiative impacts of ponds and aerosols on Arctic sea ice in equilibrated simulations with different atmospheric CO2 levels and in transient 20th century runs. We find that the presence of melt ponds enhances the surface albedo feedback as more surface melting in a warming climate leads to more ponding and a lower surface albedo. In simulations with constant aerosol deposition but higher atmospheric CO2, the aerosol radiative forcing is reduced as more melt-out of aerosols occurs. This acts to weaken the surface albedo feedback. However, diagnosis of a 20th century simulation, with changing aerosol deposition, indicates an increased radiative forcing from aerosols and melt ponds, which could play a role in the simulated 20th century Arctic sea ice reductions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.C41F..01H
- Keywords:
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- 0748 CRYOSPHERE / Ponds;
- 0750 CRYOSPHERE / Sea ice;
- 1626 GLOBAL CHANGE / Global climate models