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| Le Grand, Pascal. |
| One long-standing difficulty in estimating the large-scale ocean circulation is the inability to observe absolute current velocities. Both conventional hydrographic measurements and altimetric measurements provide observations of currents relative to an unknown velocity at a reference depth in the case of hydrographic data, and relative to mean currents calculated over some averaging period in the case of altimetric data. Space gravity missions together with altimetric observations have the potential to overcome this difficulty by providing absolute estimates of the velocity of surface oceanic currents. The absolute surface velocity estimates will in turn provide the reference level velocities that are necessary to compute absolute velocities at any depth... |
| Tipo: Text |
Palavras-chave: Inverse modeling calculation; Surface oceanic current; Current velocity; Oceanic fluxes. |
| Ano: 2003 |
URL: http://archimer.ifremer.fr/doc/2003/publication-494.pdf |
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| Johannessen, J; Balmino, G; Le Provost, C; Rummel, R; Sabadini, R; Sunkel, H; Tscherning, C; Visser, P; Woodworth, P; Hughes, C; Le Grand, Pascal; Sneeuw, N; Perosanz, F; Aguirre Fernandez, M; Rebhan, H; Drinkwater, M. |
| Current knowledge of the Earth's gravity field and its geoid, as derived from various observing techniques and sources, is incomplete. Within a reasonable time, substantial improvement will come by exploiting new approaches based on spaceborne gravity observation. Among these, the European Space Agency (ESA) Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission concept has been conceived and designed taking into account multi-disciplinary research objectives in solid Earth physics, oceanography and geodesy. Based on the unique capability of a gravity gradiometer combined with satellite-to-satellite high-low tracking techniques, an accurate and detailed global model of the Earth's gravity field and its corresponding geoid will... |
| Tipo: Text |
Palavras-chave: M1; M1; M1. |
| Ano: 2003 |
URL: https://archimer.ifremer.fr/doc/2003/publication-493.pdf |
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| Hughes, Chris; Le Grand, Pascal. |
| A summary is offered of the potential benefits of future measurements of temporal variations in gravity for the understanding of ocean dynamics. Two types of process, and corresponding amplitudes are discussed: ocean basin scale pressure changes, with a corresponding amplitude of order 1 cm of water, or 1 mm of geoid height, and changes in along-slope pressure gradient, at cross-slope length scales corresponding to topographic slopes, with a corresponding amplitude of order 1 mm of water, or a maximum of about 0.01 mm of geoid. The former is feasible with current technology and would provide unprecedented information about abyssal ocean dynamics associated with heat transport and climate. The latter would be a considerable challenge to any foreseeable... |
| Tipo: Text |
Palavras-chave: Satellite gravity; Ocean bottom pressure; Ocean circulation changes; Abyssal. |
| Ano: 2004 |
URL: http://archimer.ifremer.fr/doc/2004/publication-1351.pdf |
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| Le Grand, Pascal. |
| The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission, by providing a precise estimate of the marine geoid height, will allow the determination of absolute geostrophic velocities at the surface of the ocean with unprecedented accuracy. The resulting impact on oceanic flux estimates is quantified within a climatological inverse model of the Atlantic in terms of reduction of uncertainties in volume transports. These uncertainty reductions are obtained by replacing the error spectrum of present-day geoid models by the error spectrum expected for the GOCE mission. The impact is large in the Circumpolar Current, with relative uncertainty reductions reaching 50% in the upper layers of the ocean, and 40% in the whole water column. It is... |
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| Ano: 2001 |
URL: http://archimer.ifremer.fr/doc/00000/10280/9574.pdf |
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