Linkages between Transient Atmospheric Eddy Activities and the Retreat of Arctic Sea Ice in Different Circulation Patterns

In response to increasing CO2 concentrations, the perturbed climate system has experienced a wide range of warming worldwide with the largest in the Arctic. The “Arctic amplification” that features a sharp retreat of Arctic sea ice is usually attributed to enhanced local radiative forcing by clouds and aerosols, and enhanced meridional transport of energy into the Arctic. Meanwhile, the changes of sea ice can exert a forcing to modify atmospheric circulation patterns as well. Dominant atmospheric circulation patterns defined by Arctic Oscillation (AO), North Atlantic Oscillation (NAO), or North Annular Mode (NAM) are linked with the variability of atmospheric poleward transport of heat and moisture, which contributes to the sea ice retreat. The increased meridional moisture transport can result in an additional local radiative heating, and alter the circulation pattern. This negative feedback mechanism has been found in many previous studies. However, it remains uncertain why the Arctic sea ice has continued to decline during the period of positive NAO mode (1980-1995) as well as the period of negative NAO mode (2001-2008). To understand how the climate system operates that leads to Arctic amplification, we compute the energy budget from two new reanalysis datasets, MERRA (Modern Era Retrospective-Analysis for Research and Applications) and ERA-Interim (European Centre for Medium-Range Weather Forecasts ReAnalysis- Interim), and from CESM (Community Earth System Model) and WRF (Weather Research and Forecasting) model results. We will focus on the connection between sea ice retreat and transient eddy activities, which affect atmospheric meridional energy transport and local radiative forcing of water vapor, clouds, and aerosols. In different circulation patterns, we will investigate how atmospheric meridional energy transport affects the sea ice, how local radiative forcing affects sea ice and circulation patterns, and how the change of sea ice alters the circulation patterns as a feedback.