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Ocean Surface Topography from Space
SCIENCE
Basin Scale Geostrophy: a challenge for GOCE and altimetry data. The case of the Mediterranean Sea


Author:

Isabel Vigo - (Applied Mathematics - Space Geodesy Laboratory - University of Alicante)

Co-Investigator(s):
  Ole B. Andersen
Ben Chao
Yun-Hao Wu
José M. Ferrandiz
David Garcia
José M. Sanchez-Reales
Mariot Rottini
(Technical University of Denmark - Geodetic Department)
(Academia Sinica)
(Academia Sinica)
(University of Alicante)
(University of Alicante)
(University of Alicante)
(University of Alicante)

Abstract:
Basin Scale Geostrophy: a challenge for GOCE and altimetry data. The case of the Mediterranean Sea
Southern Ocean velocities estimated (a) using a GOCE-derived geoid; (b) a GRACE-derived geoid; and (c) in-situ drifters measurements. For comparison, table shows absolute velocities at different locations.

The ocean exhibits variability at different scales in time and space, affecting significantly mass and heat transport, exchanges with the atmosphere, and consequently the climate. Sea surface topography as measured by altimetry has a resolution mainly limited (at open ocean areas) by the geoid to which it should be referred. GOCE satellite gravity mission has recently increased the quality and resolution of the geoid up to 83 km for middle-high latitudes. In order to determine the absolute Surface Geostrophic Current (SGC,) it is needed to have at our disposal an Ocean Dynamic Topography (ODT) as good as possible. The ODT can be improved by means of two ways: (i) a more accurate (less noisy) geoid allowing us to work in higher resolutions; and (ii) the use of appropriate filters to remove the noise from the surface. Accurateness and resolution will be improved at the same time that GOCE increases its life- time (and more observation are collected by the satellite). Together with this, combining solutions provided by several satellites will held into an improvement of the geoid, especially for the lower degrees (some harmonics of very-low degree cannot be estimated accurately with GRACE and GOCE data). On the other side, to continue the investigation about suitable filters is the key requirement to meet with success the main objective of the determination and monitoring of the SGC at basin scale.

Paying an especial attention to the Mediterranean region seems adequate given its singular geographical distribution (short space scales are predominant) and physical characteristics (more or less weak flow) that will help to understand the real improvement in the upcoming data (small spatial scales quality of the GOCE data; quality of altimetric data at coastal and mesoescale resolution); as well its value to Europe and the significance of the results to generate valuable insight into the regional Climate Change.



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