Cold-season Arctic amplification driven by Arctic Ocean-mediated seasonal energy transfer

Seminar by Eui-Seok Chung from Korea Polar Research Institute

06 November 2020
13:30 — 14:30

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

During recent decades, the Arctic has been warming at a much faster rate than the global average. Interestingly, this accelerated warming in response to greenhouse gas forcing is most pronounced in boreal fall and winter, when the sea-ice albedo feedback is not active due to a lack of incoming solar radiation at the top of the atmosphere. Furthermore, some previous studies show that in idealized model simulations, Arctic amplification can occur even without the surface albedo feedback, which has led numerous studies to emphasize the role of either positive local longwave feedback processes or poleward energy transport from lower latitudes. However, the physical processes governing Arctic amplification and its seasonality still remain elusive. Here, we present observational and modeling evidence that the seasonal evolution of Arctic amplification cannot be explained by a single mechanism such as lapse-rate feedback or sea-ice albedo feedback. We show that ocean-atmosphere heat exchanges associated with sea-ice reduction are essential for Arctic amplification and its seasonality. In particular, our analysis shows that the warm-season ocean heat uptake and cold-season ocean heat release link and integrate the summer surface-albedo and winter longwave feedbacks, thereby explaining the seasonal evolution of Arctic amplification, and its peak in the cold season. This connected nature of climate feedback processes in conjunction with ice insulation effect implies a substantial weakening of Arctic amplification and its seasonal contrast in a future ice-free climate as well as during ice-free states in the geological past.