Climate change impacts and vulnerability in Europe 2016

Climate change impacts on environmental systems
Past trends: mean sea level along the European
coastline
Sea level measurements for the European region
are available from satellite altimeter observations
(Map 4.3) and from tide gauges (Map 4.4). Satellite
observations, which show changes in absolute sea
level, are available from 1993. Tide gauge records can
be more than 100 years long; they show changes in
relative sea level considering also land changes, which
is more relevant for coastal protection than absolute
sea level. Most European coastal regions experience
increases in both absolute and relative sea level, but
there are sizeable differences between the rates of
absolute and relative sea level change across Europe.
Map 4.3 shows linear trends in absolute sea level
from 1992 to 2014 as observed by satellites. The main
differences between regional seas and basins are
primarily the result of different physical processes
being the dominant cause of sea level change at
different locations. For instance, the Mediterranean
Sea is a semi-closed, very deep basin, exchanging
water with the Atlantic Ocean through only the
narrow Gibraltar Strait. Salinity in the Mediterranean
Sea may increase in the future and this will tend to
offset rises in sea level due to thermal expansion
from warming. The NAO, interannual wind variability,
changes in ocean circulation patterns, and the location
of large‐scale gyres and small-scale eddies are
further factors that can influence local sea level in the
European seas. Obviously, sea level changes in coastal
zones are most relevant for society.
Map 4.4 shows linear trends in relative sea level from
1970 to 2014 as observed by tide gauge stations in
Europe. These trends can differ from those measured
by satellites because of the longer time period
covered and because tide gauge measurements
are influenced by vertical land movement whereas
satellite measurements are not. In particular, since the
last ice age, the lands around the northern Baltic Sea
have been, and are still, rising owing to the post-glacial
rebound (Johansson et al., 2002).
Map 4.3
Trend in absolute sea level across Europe based on satellite measurements
-30°
-20°
-10°
0°
10°
20°
30°
40°
50°
60°
70°
Trend in absolute sea
level across Europe
based on satellite
measurements,1992–2014
mm/year
< – 4
60°
– 4 to – 3
– 3 to – 2
50°
– 2 to – 1
– 1 to – 0.5
– 0.5 to 0.5
50°
0.5 to 1
1 to 2
2 to 3
40°
3 to 4
> 4
40°
Outside coverage
0 500 1000 1500 km
0°
10°
20°
30°
40°
Note:
Source:
The map shows the linear trend in sea level change over the period 1992–2014. Data uncertainty is higher along coastal zones than in
areas further away from the coast. In some regions of the Mediterranean Sea, the depicted trends reflect long-term variability in gyres
(i.e. rotating ocean currents) rather than the effects of climate change.
Data supplied by CLS/CNES/LEGOS group (also available through CMEMS).
Climate change, impacts and vulnerability in Europe 2016 | An indicator-based report
127