Abstract

The sea ice thickness is recognized as an early indicator of climate changes. The mean Arctic sea ice thickness has been declining for the past four decades, and a sea ice thickness record minimum is confirmed occurring in autumn 2011. We used a daily sea ice thickness reanalysis data covering the melting season to investigate the dynamic and thermodynamic processes leading to the minimum thickness. Ice thickness budget analysis demonstrates that the ice thickness loss is associated with an extraordinarily large amount of multiyear ice volume export through the Fram Strait during the season of sea ice advance. Due to the loss of multiyear ice, the Arctic ice thickness becomes more sensitive to atmospheric anomalies. The positive net surface energy flux anomalies melt roughly 0.22 m of ice more than usual from June to August. An analysis of clouds and radiative fluxes from ERA5 reanalysis data reveals that the increased net surface energy absorption supports the enhanced sea ice melt. The enhanced cloudiness led to positive anomalies of net long-wave radiation. Furthermore, the enhanced sea ice melt reduces the surface albedo, triggering an ice–albedo amplifying feedback and contributing to the accelerating loss of multiyear ice. The results demonstrate that the dynamic transport of multiyear ice and the subsequent surface energy budget response is a critical mechanism actively contributing to the evolution of Arctic sea ice thickness.

Highlights

  • Arctic sea ice plays an important role in the climate system

  • The results demonstrate that the dynamic transport of multiyear ice and the subsequent surface energy budget response is a critical mechanism actively contributing to the evolution of Arctic sea ice thickness

  • Most regions were subject of enhanced divergence, while increased convergence is indicated around the coast of the Beaufort Sea (BS). 120 Advection anomalies transported sea ice from BS, Chukchi Sea (CS), and East Siberian Sea (ESS) to the Fram Strait along the Central Arctic (CA) coast, resulting in increased sea ice thickness north of Spitsbergen and the Fram Strait

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Summary

Introduction

Arctic sea ice plays an important role in the climate system. The thinning of Arctic sea ice well reflects recent climate 25 changes. The Arctic sea ice thickness declined sharply in 2005 and 2007, while the thinning trend deaccelerated in the years of the CryoSat-2 record (Kwok, 2018). 50 From mid-June in 2011, the melt pond fraction exhibits values up to two standard deviations above the mean values for the years 2000–2011, which are even higher than in summer 2007 (Rösel and Kaleschke, 2012). To advance upon these existing studies, we utilized sea ice thickness budgets to further assess the dynamic and thermodynamic mechanisms involved in the sea ice thickness anomaly in summer 2011.

Data and methods
Results
Dynamic transportation of the Sea Ice Anomaly
Thermodynamic forcing and thermodynamic feedback
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