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Abstract. The melt of snow and sea ice during the Arctic summer is a significant source of relatively fresh meltwater in the central Arctic. The fate of this freshwater – whether in surface melt ponds, or thin layers underneath the ice and in leads – impacts atmosphere-ice-ocean interactions and their subsequent coupled evolution. Here, we combine analyses of datasets from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition (June–July, 2020) to understand the key drivers of the sea ice freshwater budget in the Central Arctic and the fate of this water over time. Freshwater budget analyses suggest that a relatively high fraction (58 %) is derived from surface melt. Additionally, the contribution from stored precipitation (snowmelt) significantly outweighs by five times the input from in situ summer precipitation (rain). The magnitude and rate of local meltwater production are remarkably similar to that observed on the prior Surface Heat Budget of the Arctic Ocean (SHEBA) campaign. A relatively small fraction (10 %) of freshwater from melt remains in ponds, which is higher on more deformed second-year ice compared to first-year ice later in the summer. Most meltwater drains via lateral and vertical drainage channels, with vertical drainage enabling storage of freshwater internally in the ice by freshening of brine channels. In the upper ocean, freshwater can accumulate in transient meltwater layers on the order of 10 cm to 1 m thick in leads and under the ice. The presence of such layers substantially impacts the coupled system by reducing bottom melt and allowing false bottom growth, reducing heat, nutrient and gas exchange, and influencing ecosystem productivity. Regardless, the majority fraction of freshwater from melt is inferred to be ultimately incorporated into upper ocean (75 %) or stored internally in the ice (14 %). Comparison of key source and sink terms with estimates from the CESM2 climate model suggest that simulated freshwater storage in melt ponds is dramatically underestimated. This suggests pond drainage terms should be investigated as a likely explanation.
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Meltwater sources and sinks for multiyear Arctic sea ice in summer
Abstract. On Arctic sea ice, the melt of snow and sea ice generate asummertime flux of fresh water to the upper ocean. The partitioning of thismeltwater to storage in melt ponds and deposition in the ocean hasconsequences for the surface heat budget, the sea ice mass balance, andprimary productivity. Synthesizing results from the 1997–1998 SHEBA fieldexperiment, we calculate the sources and sinks of meltwater produced on amultiyear floe during summer melt. The total meltwater input to the systemfrom snowmelt, ice melt, and precipitation from 1 June to 9 August wasequivalent to a layer of water 80 cm thick over the ice-covered and openocean. A total of 85 % of this meltwater was deposited in the ocean, and only 15 %of this meltwater was stored in ponds. The cumulative contributions ofmeltwater input to the ocean from drainage from the ice surface and bottommelting were roughly equal.
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- PAR ID:
- 10297231
- Date Published:
- Journal Name:
- The Cryosphere
- Volume:
- 15
- Issue:
- 9
- ISSN:
- 1994-0424
- Page Range / eLocation ID:
- 4517 to 4525
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/tc-15-4517-2021
