Vulnerability, Impacts and Adaptation of Coastal Zones to Global Change - Vulnerability of Coastal Ecosystems and Adaptation - page 142

Sea level estimates
Proxy reconstructions
Observations (tide gauges)
Model

Rate of sea
level rise
(mm/year)

0 (mm/year) +0.6 (mm/year) -0.1 (mm/year) +2.1

Year

Figure 4.3. Evolution of GMSL over the last 2,100 years
(adapted from [KEM 11]) (see color section)

The variation in GMSL has been measured since the 18th Century
by tide gauges and since 1992 by satellites using radar altimeters, in
particular by the satellites TOPEX/Poseidon and Jason 1 and 2.
According to the IPCC AR5 report [IPC 13], during the 20th Century
the mean annual increase of the GMSL was 1.7 mm, but since 1993 it
has been situated between 2.8 and 3.6 mm. We are therefore observing
an accelerated rise of the GMSL that has recently been quantified
[CAL 13].

The increase in mean sea level is not spatially uniform. For
example, the rate of increase in the mean sea level in the western
Pacific equatorial region is around three times greater than the rate of
increase in GMSL. However, on the eastern Pacific equatorial region,
the rate of increase is less than the global rate, as Figure 4.4 shows for
the period 1993-2012. These spatial variations of the local mean sea
level, relative to the center of the Earth, occur on small timescales -
from a day to several years - and are associated with storms and
climate variability, especially with the El Niño southern oscillation
and the Pacific decadal oscillation. The climate variability induces
changes in winds at the ocean surface, changes in oceanic currents, in
sea surface temperature and salinity. All these changes lead to a
variation in the local mean sea level. On this short-term spatial
variability is superimposed the long-term variation resulting from