(^76) Coastal Zone and Sea-Level Rise Human Development Report - Croatia 2008
5.3. Potential impacts of future
climate change on the coastal
zone in Croatia
In the long term, sea-level rise may be among the
most costly impacts of climate change on the Croatian
coast, along with the effects of a warmer, drier climate
on tourism and an increased frequency of extreme
weather events. Sea-level is the average height of the
ocean between high and low tide. Sea-level rise is the
change of the average height of the ocean over a long
period of time. However, a rise in sea-level is not only a
rise in this average. It can also mean that storm surges,
flooding, and erosion become more pronounced.
Monitoring and re-assessing historical, sea-level data
has recently become more important due to the
changes in sea-level triggered by climate change. Fig-
ure 5-2 shows past changes in global sea-level and
projections for the future.
There are two basic reasons why mean sea-level rises:
- The total volume of seawater increases because
of the thermal expansion of seawater due to sur-
face warming.^8 According to the IPCC (2007a),
since 1993 thermal expansion of the oceans has
contributed to about 57% of sea-level rise, with
decreases in glaciers and ice caps contributing to
about 28% and losses from the polar ice sheets
contributing to the remainder. This means ther-
mal expansion of water is currently the number
one factor in sea-level rise. Since the same report
states that global temperatures are expected to
continue to rise, we can surmise that sea-level
rise is also highly probable. The crucial question
is how much it will rise and how quickly. - The warming of the Earth’s atmosphere is caus-
ing accelerated melting of the Earth’s ice sheets
and alpine glaciers, contributing to an increase in
the total volume of seawater.
Both these factors produce a rise in global sea-level,
which affects the Adriatic Sea as well. Measurements
have shown a steady rise in sea-level over the last de-
cade. However, observations of such a small time pe-
riod make it difficult to conclude whether this is part
of an overall trend in sea-level rise or just a decadal
variation of sea-level.
The Croatian coast is a tectonically and seismically
active zone characterised by local uplifting and sub-
sidence. Therefore, monitoring the mean sea-level
should take these factors into account. The analysis
of the tide gauge stations at four points along the
Croatian Adriatic coast (Rovinj, Bakar, Split and Du-
brovnik), over several decades (from 1956 to 1991),
showed very different trends. For example, at Rovinj
and Split sea-level is falling relative to the land by a
rate of -0.50 mm/y and -0.82mm/y respectively, while
in Bakar and Dubrovnik sea-level is rising relative to
the land by a rate of +0.53mm/y and +0.96mm/y, re-
spectively.^9-200-10001002001800 1850 1900 1950 2000 2050 2100300400500Sea level change (mm)YearEstimates
of the pastInstrumental record Projections of the
futureFigure 5-2: Time series of global mean sea-level (deviation
from the 1980-1999 mean) in the past and as projected
for the future. The shaded areas show the uncertainty in
the estimated long-term rate of sea-level change (light
grey) and the range of model projections for the SRES A1B
scenario for the 21st century relative to the 1980 to 1999
mean (dark grey). Future projections have been calculated
independently from the observations. The green shading
denotes the range of variations from a smooth curve
(light green line), which is a reconstruction of global mean
sea level from tide gauges. The black line shows global
mean sea-level observed from satellite altimetry. Beyond
2100, the projections are increasingly dependent on the
emissions scenario. Over many centuries or millennia, sea-
level could rise by several metres.Source: Bindoff et al. 2007.In the long term,
sea-level rise
may be among
the most costly
impacts of
climate change
on the Croatian
coast, along
with the effects
of a warmer,
drier climate
on tourism and
an increased
frequency of
extreme weather
events