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Abstract This study investigates how clouds and their atmospheric radiative effects respond to meridional shifts in the Southern Hemisphere (SH) mid‐latitude jet, represented by the Southern Annular Mode (SAM), using reanalysis data, CloudSat/CALIPSO observations, and CMIP6 models. Consistent with previous studies, poleward jet shifts displace storm‐track clouds, creating lower tropospheric radiative heating anomalies poleward of the mean jet latitude and cooling anomalies on the equatorward side of the mean jet latitude where large‐scale subsidence increases low cloud fraction. Whether these radiative heating anomalies can affect SAM persistence is also investigated in CMIP6 models. If observed sea surface temperatures are prescribed, models that simulate low cloud responses more realistically show less SAM persistence, aligning more closely with observations. Our results based on CMIP6 models agree with a recent idealized modeling study and suggest that atmospheric cloud radiative heating anomalies, induced by the poleward jet shift, contribute to a reduction in SAM persistence.
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Interannual SAM Modulation of Antarctic Sea Ice Extent Does Not Account for Its Long‐Term Trends, Pointing to a Limited Role for Ozone Depletion
Abstract The expansion of Antarctic sea ice since 1979 in the presence of increasing greenhouse gases remains one of the most puzzling features of current climate change. Some studies have proposed that the formation of the ozone hole, via the Southern Annular Mode, might explain that expansion, and a recent paper highlighted a robust causal link between summertime Southern Annular Mode (SAM) anomalies and sea ice anomalies in the subsequent autumn. Here we show that many models are able to capture this relationship between the SAM and sea ice, but also emphasize that the SAM only explains a small fraction of the year‐to‐year variability. Finally, examining multidecadal trends, in models and in observations, we confirm the findings of several previous studies and conclude that the SAM–and thus the ozone hole–are not the primary drivers of the sea ice expansion around Antarctica in recent decades.
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- PAR ID:
- 10366513
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 48
- Issue:
- 21
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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