Reductions in Strong Upwelling-Favorable Wind Events in the Pliocene
Abstract
Proxy records of the Pliocene show significant warm anomalies of sea surface temperatures (SST) near midlatitude upwelling sites at the eastern boundaries of the Pacific and Atlantic Oceans. Weaker upwelling‐favorable mean winds or a deeper thermocline have been proposed as explanations, yet the mechanisms involved are still not clear and the dramatic warmings of up to 9°C are only partially accounted for. Here we quantify the response of strong "transient" upwelling‐favorable wind events, defined to have a wind velocity over 5 m s⁻¹ and a duration of at least 3 days, to two reconstructions of Pliocene SST. Such events are responsible for much of the modern upwelling SST signal and may therefore be a more relevant measure than the climatological winds. We find that both the amplitude and duration of upwelling‐favorable events are reduced in the Pliocene scenarios. Using Pliocene Reconstruction Interpretation and Synoptic Mapping SST, we find an annual reduction in upwelling flux between 7.4% and 13.2%, depending on model resolution. With an idealized Pliocene SST, the reduction in upwelling flux is between 46.7% and 50.3%. This reduction is shown to be closely related to changes in anticyclonic atmospheric activity, associated in turn with a weaker large‐scale meridional SST gradient.
Additional Information
© 2019 American Geophysical Union. Received 21 AUG 2019; Accepted 12 OCT 2019; Accepted article online 1 NOV 2019; Published online 5 DEC 2019. We thank two anonymous reviewers and associate editor Chris Poulsen for most helpful comments. This work was funded by the NSF P2C2 program, grant OCE-1602864, and by the Harvard Global Institute. ET thanks the Weizmann Institute for its hospitality during parts of this work. We would like to acknowledge high-performance computing support from Cheyenne provided by NCAR's Computational and Information Systems Laboratory, sponsored by the National Science Foundation. Data availability: all GCM input files used to produce the runs analyzed in the manuscript, post processing scripts used for the analysis are available under https://osf.io/ and under http://www.seas.harvard.edu/climate/eli/Downloads/.Attached Files
Published - Li_et_al-2019-Paleoceanography_and_Paleoclimatology.pdf
Supplemental Material - palo20797-sup-0001-2019pa003760-si.pdf
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Additional details
- Eprint ID
- 99628
- Resolver ID
- CaltechAUTHORS:20191101-151047200
- OCE-1602864
- NSF
- Harvard Global Institute
- Created
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2019-11-01Created from EPrint's datestamp field
- Updated
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2021-11-16Created from EPrint's last_modified field