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Temporal Variations of the Marine Geoid
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  • Frank Siegismund,
  • Armin Köhl,
  • Reiner Rummel,
  • Detlef Stammer
Frank Siegismund
Technical University Munich

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Armin Köhl
Uni Hamburg
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Reiner Rummel
Technical University Munich
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Detlef Stammer
University Hamburg, Centrum für Erdsystemforschung und Nachhaltigkeit (CEN)
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The effects of temporal changes in the marine geoid on estimates of the ocean dynamic topography is being investigated. Influences from changes of land hydrology, ice sheets, Post-Glacial Rebound (PGR), and ocean and atmospheric dynamics are considered and the associated crustal deformation is included. The strongest signals are associated with the seasonal cycle caused by changes in terrestrial water content and ice sheets as well as the redistribution of atmospheric mass. Second to this is the importance of an overall trend caused by PGR and decreasing ice sheets over Greenland and Antarctica. On long spatial scales, the amplitude of regional trends estimated for the geoid height have a sizable fraction of those from Sea Level Anomaly (SLA) for the period 1993–2016, also after subtraction of steric height of the upper 1000m to analyze trends in deep ocean geostrophic currents. The estimated strong negative geoid height trend south of Greenland for the period 1993–2016 opposes changes in dynamic sea level for the same period thereby affecting past studies on changes of both the strength of the Subpolar Gyre based on SLA and the meridional overturning circulation on a section between Cape Farewell and Portugal applying ocean dynamic topography and hydrography. We conclude that temporal geoid height trends should be considered in studies of (multi-)decadal trends in sea level and circulation on large spatial scales based on altimetry data referenced to a geoid field.
Nov 2020Published in Journal of Geophysical Research: Oceans volume 125 issue 11. 10.1029/2020JC016433