Sea ice growth and decay are critical processes in the Arctic climate system, but comprehensive observations are very sparse. We analyzed data from 23 sea ice mass balance buoys (IMBs) deployed during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019–2020 to investigate the seasonality and timing of sea ice thermodynamic mass balance in the Arctic Transpolar Drift. The data reveal four stages of the ice season: (I) onset of ice basal freezing, mid-October to November; (II) rapid ice growth, December–March; (III) slow ice growth, April–May; and (IV) melting, June onward. Ice basal growth ranged from 0.64 to 1.38 m at a rate of 0.004–0.006 m d–1, depending mainly on initial ice thickness. Compared to a buoy deployed close to the MOSAiC setup site in September 2012, total ice growth was about twice as high, due to the relatively thin initial ice thickness at the MOSAiC sites. Ice growth from the top, caused by surface flooding and subsequent snow-ice formation, was observed at two sites and likely linked to dynamic processes. Snow reached a maximum depth of 0.25 ± 0.08 m by May 2, 2020, and had melted completely by June 25, 2020. The relatively early onset of ice basal melt on June 7 (±10 d), 2019, can be partly attributed to the unusually rapid advection of the MOSAiC floes towards Fram Strait. The oceanic heat flux, calculated based on the heat balance at the ice bottom, was 2.8 ± 1.1 W m–2 in December–April, and increased gradually from May onward, reaching 10.0 ± 2.6 W m–2 by mid-June 2020. Subsequently, under-ice melt ponds formed at most sites in connection with increasing ice permeability. Our analysis provides crucial information on the Arctic sea ice mass balance for future studies related to MOSAiC and beyond.
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A Synthesis of Observations and Models to Assess the Time Series of Sea Ice Mass Balance in the Beaufort Sea
Over the past four decades, there has been a substantial thinning of the summer sea ice cover in the Beaufort Sea. Variations in sea ice mass balance reflect these changes and give insight to the environmental forcings which caused them. In this work, the time series results from eight Lagrangian mass balance sites that operated in the Beaufort Sea over the years 1997–2015 are analyzed. Direct measurements from the sites are combined with estimates of ice/ocean heat input to examine the roll of solar heating on ice loss, growth, and melt rates. Comparisons between ice and snow conditions and mass balance event timing, for example, surface and bottom melt onset, melt peak, and melt end, are also made. From the late 1990s to the present, a general increase in bottom melting and solar heat input to the upper ocean was observed. All sites showed a net loss of ice (ranging from 29 to 271 cm), and all but one site saw the majority of this loss from bottom melting. Bottom melt onset occurred within a relatively narrow 13‐day window between 1 and 13 June at all sites. The amount of observed bottom melt was also related to the heat deposited in the ocean available for melting, underscoring the increasingly important role of ocean thermodynamics in determining sea ice mass balance.
more » « less- PAR ID:
- 10453531
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 125
- Issue:
- 11
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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