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Abstract. Over recent decades Antarctic sea-ice extent has increased, alongsidewidespread ice shelf thinning and freshening of waters along the Antarcticmargin. In contrast, Earth system models generally simulate a decrease insea ice. Circulation of water masses beneath large-cavity ice shelves is notincluded in current Earth System models and may be a driver of thisphenomena. We examine a Holocene sediment core off East Antarctica thatrecords the Neoglacial transition, the last major baseline shift ofAntarctic sea ice, and part of a late-Holocene global cooling trend. Weprovide a multi-proxy record of Holocene glacial meltwater input, sedimenttransport, and sea-ice variability. Our record, supported by high-resolutionocean modelling, shows that a rapid Antarctic sea-ice increase during themid-Holocene (∼ 4.5 ka) occurred against a backdrop ofincreasing glacial meltwater input and gradual climate warming. We suggestthat mid-Holocene ice shelf cavity expansion led to cooling of surfacewaters and sea-ice growth that slowed basal ice shelf melting.Incorporating this feedback mechanism into global climate models will beimportant for future projections of Antarctic changes.
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Accelerated sea ice loss in the Wandel Sea points to a change in the Arctic’s Last Ice Area
The Arctic Ocean’s Wandel Sea is the easternmost sector of the Last Ice Area, where thick, old sea ice is expected to endure longer than elsewhere. Nevertheless, in August 2020 the area experienced record-low sea ice concentration. Here we use satellite data and sea ice model experiments to determine what caused this record sea ice minimum. In our simulations there was a multi-year sea-ice thinning trend due to climate change. Natural climate variability expressed as wind-forced ice advection and subsequent melt added to this trend. In spring 2020, the Wandel Sea had a mixture of both thin and -- unusual for recent years -- thick ice, but this thick ice was not sufficiently widespread to prevent the summer sea ice concentration minimum. With continued thinning, more frequent low summer sea ice events are expected. We suggest that the Last Ice Area, an important refuge for ice-dependent species, is less resilient to warming than previously thought.
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- PAR ID:
- 10233904
- Date Published:
- Journal Name:
- Communications earth environment
- ISSN:
- 2662-4435
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s43247-021-00197-5
