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1. Impact of downward longwave radiative deficits on Antarctic sea-ice extent predictability during the sea ice growth period

   https://doi.org/10.1088/1748-9326/ac7d66  

   Cerovečki, Ivana ; Sun, Rui ; Bromwich, David H. ; Zou, Xun ; Mazloff, Matthew R. ; Wang, Sheng-Hung ( July 2022 , Environmental Research Letters)

   Forecasting Antarctic atmospheric, oceanic, and sea ice conditions on subseasonal to seasonal scales remains a major challenge. During both the freezing and melting seasons current operational ensemble forecasting systems show a systematic overestimation of the Antarctic sea-ice edge location. The skill of sea ice cover prediction is closely related to the accuracy of cloud representation in models, as the two are strongly coupled by cloud radiative forcing. In particular, surface downward longwave radiation (DLW) deficits appear to be a common shortcoming in atmospheric models over the Southern Ocean. For example, a recent comparison of ECMWF reanalysis 5th generation (ERA5) global reanalysis with the observations from McMurdo Station revealed a year-round deficit in DLW of approximately 50 Wm⁻²in marine air masses due to model shortages in supercooled cloud liquid water. A comparison with the surface DLW radiation observations from the Ocean Observatories Initiative mooring in the South Pacific at 54.08° S, 89.67° W, for the time period January 2016–November 2018, confirms approximately 20 Wm⁻²deficit in DLW in ERA5 well north of the sea-ice edge. Using a regional ocean model, we show that when DLW is artificially increased by 50 Wm⁻²in the simulation driven by ERA5 atmospheric forcing, the predicted sea ice growth agrees much better with the observations. A wide variety of sensitivity tests show that the anomalously large, predicted sea-ice extent is not due to limitations in the ocean model and that by implication the cause resides with the atmospheric forcing.

    

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2. Addendum: Impact of downward longwave radiative deficits on Antarctic sea-ice extent predictability during the sea ice growth period (2022 Environ. Res. Lett. 17 084008)

   https://doi.org/10.1088/1748-9326/acb162  

   Cerovečki, Ivana ; Sun, Rui ; Bromwich, David H. ; Zou, Xun ; Mazloff, Matthew R. ; Wang, Sheng-Hung ( January 2023 , Environmental Research Letters)
3. A regime shift in seasonal total Antarctic sea ice extent in the twentieth century

   https://doi.org/10.1038/s41558-021-01254-9  

   Fogt, Ryan L. ; Sleinkofer, Amanda M. ; Raphael, Marilyn N. ; Handcock, Mark S. ( January 2022 , Nature Climate Change)
4. Modeling the annual cycle of daily Antarctic sea ice extent

   https://doi.org/10.5194/tc-14-2159-2020  

   Handcock, Mark S. ; Raphael, Marilyn N. ( January 2020 , The Cryosphere)

   Abstract. The total Antarctic sea ice extent (SIE) experiences a distinct annual cycle, peaking in September and reaching its minimum in February. In thispaper we propose a mathematical and statistical decomposition of this temporal variation inSIE. Each component is interpretable and, when combined,gives a complete picture of the variation in the sea ice. We consider timescales varying from the instantaneous and not previously defined to themulti-decadal curvilinear trend, the longest. Because our representation is daily, these timescales of variability give precise information about thetiming and rates of advance and retreat of the ice and may be used to diagnose physical contributors to variability in the sea ice. We definea number of annual cycles each capturing different components of variation, especially the yearly amplitude and phase that are major contributors toSIE variation. Using daily sea ice concentration data, we show that our proposed invariant annual cycle explains 29 % more of the variation indaily SIE than the traditional method. The proposed annual cycle that incorporates amplitude and phase variation explains 77 % more variation thanthe traditional method. The variation in phase explains more of the variability in SIE than the amplitude. Using our methodology, we show that theanomalous decay of sea ice in 2016 was associated largely with a change of phase rather than amplitude. We show that the long term trend inAntarctic sea ice extent is strongly curvilinear and the reported positive linear trend is small and dependent strongly on a positive trend thatbegan around 2011 and continued until 2016. 

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5. Seasonal Antarctic Sea Ice Extent Reconstructions, 1905-2020, Version 1

   https://doi.org/10.7265/55x7-we68  

   Fogt, R.L. ; Raphael, M.N. ; Handcock, M.S. ( January 2023 , National Snow and Ice Data Center)