To be an oral-presentation at
European Geophysical Society XXVI, Nice 2001
Long term sea level change in Mediterranean Sea from multi-mission altimetry and tde gauges
1Institute of Physical Geodesy;
Tecnical
University Darmstadt
The long term sea level variation and its coupling
with sea surface temperature, wind speed and atmospheric pressure
variations are investigated regionally in the Mediterranean Sea.
Nine years, from 1991 to 2000, of altimetric sea level data
from the ERS-1, ERS-2 and Topex/Poseidon missions are used
after an adjustment and a consistency check of the multi-mission data.
The results are compared with eight years, from 1992 to 2000,
of the single-mission
Topex/Poseidon data and with sea level heights from tide gauges to detect
bias and drifts in the multi-mission altimetry system.
The dominant characteristics of the variability of each field and the
coupled variability between the fields are analysed.
In the single-field study
a parametric and a non parametric method for spectral estimation are used
as well as the statistical method of principal component analysis.
The short and medium parts of the spectra are eliminated and the
long-term scales investigated.
Positive sea level trends are found in most of the Mediterranean Sea
with exception of the Ionian sea. The highest positive trends occurs in the
eastern Mediterranean in correspondence to oceanographic features.
In the coupled-field study both the linear regression analysis and the
canonical correlation analysis show a hight correlation between the sea level
height and the sea surface temperature both
at medium and at long-term scales.
%At long time scales
%also the correlation between air pressure and sea level is significant.
Reconstruction of sea level height using the first components of the
spectral and of the
statistical decompositions shows an agreement on the level of 2 cm locally.
The extrapolated canonical correlation model derived using the
sea surface as the predictor has an agreement of 3-4 cm.
Based on the observed correlation between the sea level and the sea surface
temperature,
the sea level trends can be due to the steric effect. Other causes for the
negative trends are analysed.
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