Understanding measured sea level rise by data assimilation
Manfred Wenzel(1) and Jens Schroeter(1)
Work at AWI that is related to altimetric measurements focusses on
the estimation of the global oceans circulation, its sea level change and
finally its mass budget. This presentation will shortly review the findings
achieved so far.
Sea surface elevations as measured by the altimeter are together with hydrographic
measurements are assimilated into a global OGCM that has a free surface, i.e.
that conserves mass rather than volume. The combination of both types of measurements
appeared to be necessary to get a reasonable estimate of the oceanic circulation.
Furthermore referencing the altimeter data to the GRACE geoid improves the modelling
Further improvement in estimating sea level change was achieved by including the steric
effects (thermosteric AND halosteric) into the modelled sea surface elevation, because
local sea level trends vary substatial in space anmd time. They are closely associated
to heat and salt anomalies in the ocean. This finally allowed to estimate the temporally
variing oceanic mass budget from sea surface elevations.