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Sea Level Budget

Sea level changes are a key indicator for climate change and per se an important monitoring quantity. We aim at quantifying spatial and temporal scales of sea level variability. In order to gain a better understanding the driving mechanisms of sea level changes are studied. Sea level is governed by changes in oceanic heat content and in mass redistribution in the System Earth, where changes in mass originate from the combined effects of ocean dynamics and freshwater in- and export.

Sea level has been monitored globally by satellite altimeters since the mid 1980's. By means of the progress of the art, the continuous correction of previous measurement data and the harmonization of altimeter data from different missions the estimation of sea level trends has been improved and consolidated. In contrast it has not been feasible to measure the steric and mass components on large spatial scales until recently. From 2002 onwards monthly oceanic mass changes have been derived from the GRACE satellites. The steric component can be inferred from temperature and salinity profiles measured in-situ by the Argo drifter array.

We study total, steric and mass components of the monthly sea level variability starting from end of 2002 using Jason-1 and Jason-2 altimeter data processed by the ADS system, GRACE derived equivalent water level (GFZ-RL05, CSR-RL05) and gridded Argo data from Met Office Hadley Centre for Climate Change. The consistency of the different means of measurements is investigated on global scales, basin-scale mass changes have been studied in the North Atlantic in more detail.

Global mean sea level (total, steric and mass)

Global mean oceanic mass component

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