Rapid decline in Antarctic sea ice in recent years hints at future change

Eayrs, Clare; Li, Xichen; Raphael, Marilyn; Holland, David M.

doi:10.1038/s41561-021-00768-3

Cited by 144 publications

(166 citation statements)

References 54 publications

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“…A subsurface ocean warming has contributed to the melting and thinning of West Antarctic ice shelves in recent decades [34,35]. While Southern Ocean sea-ice extent has increased slowly at the end of the 20th century and until 2016, it has abruptly decreased since then [36], hinting at an accelerated warming of the Southern Ocean. In addition, modern observations indicate the surface southern polar ocean has freshened since the 1950s due to increased melting of AIS, thus weakening deep ocean convection and AABW formation [27].…”

Section: Discussionmentioning

confidence: 99%

Last Interglacial subsurface warming on the Antarctic shelf triggered by reduced deep-ocean convection

Yeung

Menviel

Meißner

et al. 2022

Preprint

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The global mean sea-level was likely ∼3-6 m higher at the Last Interglacial (LIG) compared to pre-industrial (PI), with an Antarctic contribution estimated at 3 to 5 m sea-level equivalent. Antarctic ice-sheet modelling studies suggest that such an ice-mass loss from Antarctica requires a subsurface warming on the Antarctic shelf of ∼3◦C compared to PI. Here we show that such a subsurface warming is simulated in an equilibrium experiment of the LIG performed with a comprehensive Earth System Model. Reduced deep-ocean convection in the Weddell and Ross Seas, arising from reduced sea-ice cover, are the primary drivers of this subsurface warming, reaching +2.4◦C at 430 m depth. The associated changes in meridional density gradients and surface winds lead to a weakened Antarctic Circumpolar Current but strengthened Antarctic Slope Current, which further impact subsurface temperatures around both East and West Antarctica, with a maximum warming of +3.1◦C at 125 m depth on the East Antarctic shelf. Higher SST and reduced sea-ice formation in the Southern Ocean thus increase ocean stratification and lead to a subsurface warming on the Antarctic shelf, with the potential to trigger ice-mass loss from the Antarctic ice-sheet.

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Section: Discussionmentioning

confidence: 99%

Last Interglacial subsurface warming on the Antarctic shelf triggered by reduced deep-ocean convection

Yeung

Menviel

Meißner

et al. 2022

Preprint

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“…After years of increasing extent, there was an exceptional decline in Antarctic sea-ice extent in 2016 (Parkinson et al, 2019), especially in the Weddell and Ross seas (Hao et al 2021). The 2016 minimum has been attributed to a combination of factors, including decades of ocean warming, weakening of Southern Hemisphere Westerly winds, and increased advection of warmer air masses from low latitudes (Doddridge and Marshall, 2017;Nicolas et al, 2017;Stuecker et al, 2017;Turner et al, 2017;Alkama et al 2020;Eayrs et al 2021;Sabu et al, 2021). A small rebound in sea-ice extent has been observed in 2020 (Parkinson et al, 2021).…”

Section: Recent Sea-ice Changesmentioning

confidence: 99%

“…Finally, the diversity in simulated sea-ice conditions may arise from different model responses to climatic modes of variability and atmosphere-ocean-ice interactions at different timescales (Holland et al, 2017;Kusahara et al, 2019). Given the shortcoming mentioned above, models cannot currently robustly assess whether the observed changes in sea ice over the last decades are part of natural climate variability, or a response to anthropogenic forcing (Polvani and Smith, 2013;Hobbs et al, 2014;Jones et al, 2016;Eayrs et al, 2021).…”

Section: Recent Sea-ice Changesmentioning

confidence: 99%

Antarctic sea ice over the past 130,000 years, Part 1: A review of what proxy records tell us

Crosta

Kohfeld

Bostock

et al. 2022

Preprint

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Abstract. Antarctic sea ice plays a critical role in the Earth system, influencing energy, heat, and freshwater fluxes, air-sea gas exchange, ice shelf dynamics, ocean circulation, nutrient cycling, marine productivity, and global carbon cycling. However, accurate simulation of recent sea-ice changes remains challenging, and therefore projecting future sea-ice changes and their influence on the global climate system is uncertain. Reconstructing past changes in sea-ice cover can provide additional insights into climate feedbacks within the Earth system at different timescales. This paper is the first of two review papers from the Cycles of Sea Ice Dynamics in the Earth system (C-SIDE) Working Group. In this first paper, we review marine- and ice core-based sea-ice proxies and reconstructions of sea-ice changes throughout the last glacial-interglacial cycle. Antarctic sea-ice reconstructions rely mainly on diatom fossil assemblages and highly branched isoprenoid (HBI) alkenes in marine sediments, supported by chemical proxies in Antarctic ice cores. Most reconstructions for the Last Glacial Maximum (LGM) suggest winter sea-ice expanded all around Antarctica and covered almost twice its modern surface extent. In contrast, LGM summer sea-ice expanded mainly in the regions off the Weddell and Ross seas. The difference between winter and summer sea ice during the LGM led to a larger seasonal cycle than today. More recent efforts have focused on reconstructing Antarctic sea-ice during warm periods, such as the Holocene and the Last Interglacial (LIG), which may serve as an analogue the future. Notwithstanding regional heterogeneities, existing reconstructions suggest sea-ice cover increased from the warm mid-Holocene to the colder Late Holocene, with pervasive decadal-to-millennial scale variability throughout the Holocene. Sparse marine and ice core data, supported by proxy modelling experiments, suggest that sea-ice cover was halved during the warmer LIG, when global average temperatures were ~2 °C above the pre-industrial (PI). There are limited marine (14) and ice core (4) sea-ice proxy records covering the complete 130,000 year (130 ka) last glacial cycle. The glacial-interglacial pattern of sea-ice advance and retreat appears relatively similar in each basin of the Southern Ocean. Rapid retreat of sea ice occurred during Terminations II and I, while the expansion of sea ice during the last glaciation appears more gradual, especially in cores data sets. Marine records suggest that the first prominent expansion occurred during Marine Isotope Stage (MIS) 4 and that sea ice reached maximum extent during MIS 2. We however note that additional sea-ice records and transient model simulations are required to better identify the underlying drivers and feedbacks of Antarctic sea-ice changes over the last 130 ka. This understanding is critical to improve future predictions.

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“…At the same time, the annual duration and extent of sea-ice coverage off the western and northeastern Peninsula have shown negative trends since 1979 [19,20], in broad contrast to other Antarctic regions. The response of Antarctic sea ice to climate variability and change is characterised by complexities, regional variations and recent high interannual variability [21,22], which is emphasised by the consecutive years of record highs (peaking in 2014) closely followed by record lows (from 2016) [20]. Contemporary models are unable to reproduce the observed behaviours of Antarctic sea ice accurately, resulting in low confidence in projections of future trends in Antarctic sea ice coverage [2,23].…”

Section: Introductionmentioning

confidence: 99%

Sea ice-free corridors for large swell to reach Antarctic ice shelves

Teder

Bennetts

Reid

et al. 2022

Environ. Res. Lett.

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Sea ice can attenuate Southern Ocean swell before it reaches Antarctic ice shelves and imposes flexural stresses, which promote calving of outer ice-shelf margins and influence ice shelf stability. An algorithm is developed to identify sea ice-free corridors that connect the open Southern Ocean to Antarctic ice shelves from daily satellite sea ice concentration data between 1979–2019. Large swell in the corridors available to impact the ice shelves is extracted from spectral wave model hindcast data. For a selection of ice shelves around the Antarctic coastline, corridors are assessed in terms of duration and areal extent. The availability of large swell to impact certain ice shelves through the corridors is evaluated from spectral wave data for daily statistical properties and the number of large swell days per year. Results integrated over a large number of ice shelves are used to assess overall trends. Large variations are found between individual ice shelves for both corridors and available swell, with contrasting trends between the West and East Antarctic Ice Sheets. The findings indicate ice shelves likely to experience prolonged periods of appreciable outer margin flexure due to large swell action, such as the Fimbul, Shackleton and Ross Ice Shelves, which could exacerbate climate-driven weakening and decreasing buttressing capacity, with implications for sea-level rise.

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Rapid decline in Antarctic sea ice in recent years hints at future change

Cited by 144 publications

References 54 publications

Last Interglacial subsurface warming on the Antarctic shelf triggered by reduced deep-ocean convection

Last Interglacial subsurface warming on the Antarctic shelf triggered by reduced deep-ocean convection

Antarctic sea ice over the past 130,000 years, Part 1: A review of what proxy records tell us

Sea ice-free corridors for large swell to reach Antarctic ice shelves

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