Arctic Surface Radiation Budget, Clouds, and Sea Ice Extent
Arctic Research Initiative
2009 Funded Project
The Arctic sea ice waxes and wanes in accordance with the annual cycle of the solar radiation. The sea ice partly melts in the summer when days are long, and then grows back during the winter when sunlight is low or absent. One of the most important characteristics of sea ice is the high albedo, causing sea ice to reflect more incoming solar radiation back to the atmosphere than the darker ocean water. Because of the large difference in albedo between sea ice and open water, any small changes in the Arctic surface albedo would affect strongly the surface energy budget and thus, the sea ice extent. This icealbedo feedback is regarded as a dominant mechanism for the continuing sea ice loss in the Arctic. On the other hand, the Arctic is one of the cloudiest regions on the earth. Radiative properties of clouds are somewhat similar to ice, because both have high visible albedo and high longwave emissivity. Clouds affect the surface radiation budget via two ways: they reflect incoming solar radiation and reduce the downwelling shortwave radiation at the surface (i.e., a cooling effect), and they trap heat emitted by the earth and re-emit some of that energy back to the surface, leading to an increase of the downwelling longwave (i.e., a warming effect). This cloud-radiation feedback, although it has been suggested to play an important role in polar amplification of the Arctic climate change, remains as one of the least understood processes.
The new and continuing satellite radiation programs (ISCCP, GEWEX-SRB, and NASA’s CERES) developed in past years have led to rich archives of the surface radiative fluxes with high temporal and spatial resolution for multiple years (1983-present). Preliminary study based on these satellite archives suggested that albedo, surface temperature, and clouds have intertwined in a complex manner in affecting the Arctic Ocean surface radiative fluxes, and that the seemingly dominant sea icealbedo feedback mechanism may have been enhanced by the cloud-radiation feedback process.
The aim of this proposed study is to utilize the satellite-based radiation archives to gain a better understanding of the sea ice-albedo feedback, cloud-radiation feedback, and their coupled interactions, with particular focus on the effects of the two feedback processes on the surface radiation budget over the Arctic Ocean. The proposed study is built upon the ongoing Objectively Analyzed air-sea Fluxes (OAFlux) project which the PI has been leading. It is expected that results from the proposed study would not only expand the OAFlux project to the polar oceans but also likely open the doors for new funding opportunities targeted for high-latitude climate change. Since the surface radiative fluxes are a key driver for changes in sea ice and Arctic Ocean heat budget, the expertise developed here could ultimately benefit WHOI Arctic research programs.