Observed mesoscale eddy signatures in Southern Ocean surface mixed-layer depth
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Hausmann_et_al-2017-Journal_of_Geophysical_Research__Oceans.pdf
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Author(s)
Hausmann, U.
McGillicuddy, Dennis J.
Marshall, John C
Date Issued
January 2017
Journal
Journal of Geophysical Research: Oceans
Publisher
American Geophysical Union (AGU)
Citation
Hausmann, U. et al. “Observed Mesoscale Eddy Signatures in Southern Ocean Surface Mixed-Layer Depth.” Journal of Geophysical Research: Oceans 122, 1 (January 2017): 617–635 © 2016 American Geophysical Union
Version
Final published version
Abstract
Combining satellite altimetry with Argo profile data a systematic observational estimate of mesoscale eddy signatures in surface mixed-layer depth (MLD) is provided across the Southern Ocean (SO). Eddy composite MLD anomalies are shallow in cyclones, deep in anticyclones, and increase in magnitude with eddy amplitude. Their magnitudes show a pronounced seasonal modulation roughly following the depth of the climatological mixed layer. Weak eddies of the relatively quiescent SO subtropics feature peak late-winter perturbations of ±10 m. Much larger MLD perturbations occur over the vigorous eddies originating along the Antarctic Circumpolar Current (ACC) and SO western boundary current systems, with late-winter peaks of −30 m and +60 m in the average over cyclonic and anticyclonic eddy cores (a difference of ≈ 100 m). The asymmetry between modest shallow cyclonic and pronounced deep anticyclonic anomalies is systematic and not accompanied by corresponding asymmetries in eddy amplitude. Nonetheless, the net deepening of the climatological SO mixed layer by this asymmetry in eddy MLD perturbations is estimated to be small (few meters). Eddies are shown to enhance SO MLD variability with peaks in late winter and eddy-intense regions. Anomalously deep late-winter mixed layers occur disproportionately within the cores of anticyclonic eddies, suggesting the mesoscale heightens the frequency of deep winter surface-mixing events along the eddy-intense regions of the SO. The eddy modulation in MLD reported here provides a pathway via which the oceanic mesoscale can impact air-sea fluxes of heat and carbon, the ventilation of water masses, and biological productivity across the SO.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
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DOI of Published Version
https://doi.org/10.1002/2016JC012225
