Causes and Impacts of Sea Ice Variability in the Sea of Okhotsk Assessed with CESM

Abstract:

Interannual variability in Arctic sea ice is driven by a variety of coupled atmosphere-ocean-sea ice processes. In this study, we investigate the mechanisms responsible for generating interannual variability in sea ice coverage in the Sea of Okhotsk as well as the atmospheric response to these anomalies. We analyze Community Earth System Model Large Ensemble (LENS) simulations over the period of 1980-2000. Using 30 ensemble members, we estimate weekly lead-lag composite analyses with robust statistics. We identify how key thermodynamic processes involving anomalous ocean-atmosphere heat fluxes affect the timing of initial sea ice growth in the Sea of Okhotsk as early as November. In the winter, low-level wind anomalies help determine the extent to which sea ice fully develops, both through advection of the sea ice itself and through changes in the transport of air masses over the Sea of Okhotsk. Associated with anomalous sea ice conditions, we are also able to identify a Rossby wave response that extends over North America. This response is similar to that shown in more idealized model simulations with prescribed sea ice and sea surface temperature and demonstrates that the interannual sea ice variability in the SOK can impact atmospheric circulations.