The Southern Hemisphere westerly winds influence deep ocean circulation and carbon storage. While the westerlies are hypothesized to play a key role in regulating atmospheric CO2over glacial‐interglacial cycles, past changes in their position and strength remain poorly constrained. Here, we use a compilation of planktic foraminiferal δ18O from across the Southern Ocean and emergent relationships within an ensemble of climate models to reconstruct changes in the Southern Hemisphere surface westerlies over the last deglaciation. We infer a 4.8° (2.9–7.1°, 95% confidence interval) equatorward shift and about a 25% weakening of the westerlies during the Last Glacial Maximum (20 ka) relative to the mid‐Holocene (6.5 ka). Climate models from the Palaeoclimate Modeling Intercomparison Project substantially underestimate this inferred equatorward wind shift. According to our reconstruction, the poleward shift in the westerlies over deglaciation closely mirrors the rise in atmospheric CO2(
Many studies have documented the trends in the latitudinal position and strength of the midlatitude westerlies in the Southern Hemisphere. However, very little attention has been paid to the longitudinal variations of these trends. Here, we specifically focus on the zonal asymmetries in the southern hemisphere wind trends between 1980 and 2018. Meteorological reanalyses show a large strengthening and a statistically insignificant equatorward shift of peak near‐surface winds over the Pacific, in contrast to a weaker strengthening and significant poleward shift over the Atlantic and Indian Ocean sectors. The reanalysis trends fall within the ensemble spread for historical climate model simulations, showing that climate models are able to capture the observed trends. Climate model simulations indicate that the differential movement of the peak westerlies is a manifestation of internal variability and is not a forced response. Implications of these asymmetries for other components of the climate system are discussed.
more » « less- Award ID(s):
- 1902409
- PAR ID:
- 10450180
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 18
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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This article is categorized under:
Paleoclimates and Current Trends > Earth System Behavior
