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Zusammenfassung:
We investigate sea level change and variability in some areas of the
Arctic region over the 1950-2009 period. Analysis of 62 long tide gauge
records available during the studied period along the Norwegian and
Russian coastlines shows that coastal mean sea level (corrected for
Glacial Isostatic Adjustment and inverted barometer effects) in these
two areas was almost stable until about 1980 but since then displayed a
clear increasing trend. Until the mid-1990s, the mean coastal sea level
closely follows the fluctuations of the Arctic Oscillation (AO) index,
but after the mid-to-late 1990s the co-fluctuation with the AO
disappears. Since 1995, the coastal mean sea level (average of the
Norwegian and Russian tide gauge data) presents an increasing trend of
similar to 4 mm/yr. Using in situ ocean temperature and salinity data
down to 700 m from three different databases, we estimated the
thermosteric, halosteric and steric (sum of thermosteric and halosteric)
sea level since 1970 in the North Atlantic and Nordic Seas region
(incomplete data coverage prevented us from analyzing steric data along
the Russian coast). We note a strong anti-correlation between the
thermosteric and halosteric components both in terms of spatial trends
and regionally averaged time series. The latter show a strong change as
of similar to 1995 that indicates simultaneous increase in temperature
and salinity, a result confirmed by the Empirical Orthogonal Function
decomposition over the studied region. Regionally distributed steric
data are compared to altimetry-based sea level over 1993-2009. Spatial
trend patterns of observed (altimetry-based) sea level over 1993-2009
are largely explained by steric patterns, but residual spatial trends
suggest that other factors contribute, in particular regional ocean mass
changes. Focusing again on Norwegian tide gauges, we then compare
observed coastal mean sea level with the steric sea level and the ocean
mass component estimated with GRACE space gravimetry data and conclude
that the mass component has been increasing since 2003, possibly because
of the recent acceleration in land ice melt.
