The Role of Clouds in Linking the Summer AO and Arctic Dipole to Summer Arctic Sea Ice Extent Variability on Seasonal and Interannual Timescales

Abstract:

The current skill of seasonal and long-term sea ice predictions from coupled general circulation models (GCMs) are limited due to insufficient initial conditions, insufficient model physics, and the influence of chaotic atmospheric variability. Since atmospheric variability is a limiting factor in sea ice extent prediction, an improvement in the understanding of the relationship between atmospheric variability and sea ice will help improve seasonal and long-term sea ice forecasting. As a first step to better understand this relationship, we investigate the link between atmospheric variability and sea ice during the summer melt season on seasonal and interannual timescales, facilitated by a connecting (or bridging) physical mechanism. We characterize the summer atmospheric variability by both atmospheric eddy activity and by the two dominant modes of summer Arctic atmospheric variability, the Arctic Oscillation (AO) and the Arctic Dipole (AD). We hypothesize that anomalies in cloud fraction and the cloud liquid/ice water content driven by atmospheric eddies and the AO/AD are an important bridging physical mechanism. Cloud fraction and cloud liquid/ice water content anomalies change the downwelling radiation at the sea ice surface, and thus affect the surface energy budget and sea ice melt. Associated large-scale cloud property anomalies and surface cloud radiative effects are identified using a CloudSAT-CALIPSO-CERES-MODIS fusion cloud data set. Atmospheric eddies are defined in MERRA reanalysis data, and are classified by frequency into high-, low-, and seasonal-scale eddies. Preliminary results suggest that in individual years, high-frequency atmospheric eddies help initiate sea ice melt through associated total downwelling radiation anomalies. These downwelling radiation anomalies are associated with anomalously low and high cloud fraction.