Sea Ice Albedo Feedback: Comparison of Model and Observational Based Estimates
Abstract
The sea ice albedo feedback (SIAF) is the product of the ice sensitivity (IS) -- how much the sea ice concentration changes as the planet warms-- and the radiative sensitivity (RS) -- how much the top of atmosphere radiation changes as the surface albedo changes. We demonstrate that the RS calculated from radiative kernels in climate models is reproduced from calculations that use the climatological radiative fluxes at the top of atmosphere and the assumption that the atmosphere is isotropic to shortwave radiation. This method allows us to calculate an observational based RS from satellite estimates of climatological radiative fluxes and compare the resultant RS across a full suite of coupled climate models. We find that the model-ensemble mean RS is close to the observed satellite-based RS despite a large model spread in RS that differs by a factor of two between climate models in both the Arctic and Southern Ocean. Observed trends in Arctic sea ice over the historical record are used to estimate IS which, in conjunction with the satellite-based RS yields an observed SIAF parameter of 0.16 ± 0.04 W m-2 K-1. This observational estimate of SIAF is slightly smaller but not statistically different from the ensemble average SIAF of coupled climate models (0.13 ± 0.09 W m-2 K-1) assessed using the same methodology. The observed Arctic SIAF would result in a modest amplification of future global surface temperature change of approximately 15%.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.C21C..03D
- Keywords:
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- 3349 Polar meteorology;
- ATMOSPHERIC PROCESSES;
- 0750 Sea ice;
- CRYOSPHERE;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 4207 Arctic and Antarctic oceanography;
- OCEANOGRAPHY: GENERAL