Mean Upper-Ocean Circulation of the Southern Hemisphere Oceans Based on Goce Data
Abstract
One of the main goals of the Gravity and steady-state Ocean Circulation Explorer (GOCE) satellite mission launched in 2009 is to improve the previous estimates of the global ocean circulation structures determined from Mean Dynamic Topographies (MDTs). Recently published studies suggest that the GOCE-based MDTs and their respective mean geostrophic circulation fields (MGCs) are superior to those obtained from GRACE (Gravity Recovery and Climate Experiment)-only data. These studies focus mostly on the circulation of the North Atlantic and North Pacific oceans with emphasis on the strong western boundary current systems. In contrast, no detailed assessment has yet been made to determine the impact of the GOCE models in the southern hemisphere (SH) upper-ocean circulation especially in the subtropical region. It is generally recognized that the SH circulation is still not well established even at large scales, and the new GOCE and GRACE products can contribute to increase our understanding of the dominant currents in these regions, which may have even greater impact on the global climate than the NH counterparts. In the present work, we compute five global GOCE-derived MDTs with a 0.25 x 0.25 degree spatial grid based on three GOCE geoid models (TIM3, GOCO02S, GOCO3S) and three mean sea surfaces (CLS01, CLS11, DTU10) using the standard spectral approach (MSS minus Geoid). These MDTs do not have the well-known large-amplitude striation-type noise that plagued all of the GRACE-only MDTs with he same resolution, but still present commission errors which are filptered out with Singular Spectrum Analysis methods. Additionally, the MGCs were calculated by use of a Anderssen-Hegland averaging scheme for estimation of derivatives, which is able to filter out the well-known high amplitude noise caused by standard finite-difference methods. Comparisons with previous GRACE-only MGCs show that GOCE permits retrieval of currents with much higher intensities (e.g. the Agulhas Current reaches 50-60cm/s in the GOCE-only solution as compared to 20cm/s in the GRACE-only MGCs). GOCE-based MGCs show all known SH current systems in a very clear way: the weak Brazil Current, Falkland Current, the Zapiola Anticyclone, Tristan da Cunha Current, Benguela, and South Atlantic Currents, the Agulhas and its retroflection, the East Madagascar, the South Indian Countercurrent, the East Australian, the South Pacific Tropical Countercurrent, Humboldt and South Equatorial Currents and the Antarctic Circumpolar Current.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.G31B0927M
- Keywords:
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- 1240 GEODESY AND GRAVITY / Satellite geodesy: results;
- 4223 OCEANOGRAPHY: GENERAL / Descriptive and regional oceanography