CASPO Seminar: Katsuro Katsumata

04/25/2018 - 3:30pm

Topic: Eddies observed by Argo floats

Abstract: Argo floats measure horizontal current velocities at the parking depth (mostly 1000 m) and vertical profiles of temperature and salinity. The data are sufficient for simultaneous estimates of velocities and vertical displacements of isopycnal surfaces. More than 980000 of such pairs were used to calculate eddy transport of volume and momentum and its uncertainties based on the Temporal Residual Mean framework. Two results are highlighted.
First, the eddy transport perpendicular to the density contours at 1000 m had a large northward component in the southern Indian Ocean. The velocity and thickness correlations suggested that this transport was a northward intrusion of Antarctic Intermediate Water.
Second, zonal momentum budget in the Southern Ocean showed that approximately half of zonal momentum input from the wind was transferred downward by eddy form stress across the isopycnal whose mean depth was 1000 m. The eddy transfer was spatially localized, particularly on the eastern flanks of meridional ridges. The power of Argo floats in reducing the sampling error thus provides a new way to quantitatively describe the turbulent ocean.

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Theresa Morrison
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Nierenberg Hall 101