Quantification of Arctic Sea-Ice-Driven Atmospheric Circulation Variability in Coordinated Large Ensemble Hindcast Simulations

A coordinated set of large ensemble atmosphere-only simulations is used to investigate the impacts of the observed Arctic sea ice-driven variability (SIDV) on the atmospheric circulation for the 1979-2014 period. The experimental protocol permits a clean separation of internal atmospheric variability from SIDV and those driven by other forcings including sea-surface temperature and greenhouse gases. The geographic pattern of SIDV is consistent across seven participating models, but its magnitude strongly depends on ensemble size. Based on 130 members, the results suggest that about 100 members are needed to robustly separate SIDV from other variability components for dynamical or thermodynamical variable. SIDV in the Arctic Circle explains only ~3% of the total variance for sea-level pressure and ~23% for surface air temperature in boreal winter at interannual and longer time scales. Nevertheless, SIDV is one-and-half to twice as large as the variability driven by other forcings over the Arctic and northern Eurasia.