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Critical role of snow on sea ice growth in the Atlantic sector of the Arctic Ocean
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  • Mats Granskog,
  • Ioanna Merkouriadi,
  • Bin Cheng,
  • Robert M. Graham,
  • Anja Rösel
Mats Granskog

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Ioanna Merkouriadi
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Bin Cheng
Ilmatieteen Laitos
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Robert M. Graham
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Anja Rösel
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During the Norwegian young sea ICE (N-ICE2015) campaign, which took place in the first half of 2015 north of Svalbard, a deep winter snow pack (50 cm) on sea ice was observed, that was 50% thicker than earlier climatological studies suggested for this region. Moreover, a significant fraction of snow contributed to the total ice mass in second-year ice (SYI) (9% snow by mass), while very little snow was present in first-year ice (FYI) (3% snow by mass). We use a 1-D snow/ice thermodynamic model forced with reanalyses data in autumn and winter 2014/15. We show that snow-ice would form on SYI even with an initial ice thickness of 2 m in autumn. By the end of winter snow-ice can contribute up to 24-44% of the total thickness of SYI, if the ice is thin in autumn (0.6 m). This is important, especially in the absence of any bottom thermodynamic growth due to the thick insulating snow cover. We also show that growth of FYI north of Svalbard is controlled by the timing of growth onset relative to snow precipitation events and cold spells. These usually short-lived conditions are largely determined by the frequency of storms entering the Arctic from the Atlantic Ocean. In our case, a later freeze onset was favorable for FYI growth, due to less snow accumulation in early autumn. This limits snow accumulation on FYI but promotes bottom thermodynamic growth. We show our findings are related to regionally higher precipitation in the Atlantic sector of the Arctic, where frequent storms bring lot of precipitation in autumn and winter, and also affect the duration of cold temperatures required for ice growth in winter. We discuss the implications and the importance of snow-ice in the future Arctic, formerly believed to be non-existent in the central Arctic, due to thick perennial ice and little snow precipitation. The combination of sea ice thinning and high precipitation in the “Transpolar Drift region” highlights the need to understand the regionality of these processes across the Arctic.