Simulated Arctic atmospheric feedbacks associated with late summer sea ice anomalies

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Abstract

[1] The coupled regional climate model HIRHAM-NAOSIM is used to investigate feedbacks between September sea ice anomalies in the Arctic and atmospheric conditions in autumn and the subsequent winter. A six-member ensemble of simulations spanning the period 1949–2008 is analyzed. The results show that negative Arctic sea ice anomalies are associated with increased heat and moisture fluxes, decreased static stability, increased lower tropospheric moisture, and modified baroclinicity, synoptic activity, and atmospheric large-scale circulation. The circulation changes in the following winter display meridionalized flow but are not fully characteristic of a negative Arctic Oscillation pattern, though they do support cold winter temperatures in northern Eurasia. Internally generated climate variability causes significant uncertainty in the simulated circulation changes due to sea ice-atmosphere interactions. The simulated atmospheric feedback patterns depend strongly on the position and strength of the regional sea ice anomalies and on the analyzed time period. The strongest atmospheric feedbacks are related to sea ice anomalies in the Beaufort Sea. This work suggests that there are complex feedback mechanisms that support a statistical link between reduced September sea ice and Arctic winter circulation. However, the feedbacks depend on regional and decadal variations in the coupled atmosphere-ocean-sea ice system.

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