climate change on UAE - Stockholm Environment Institute-US Center

y 2100. Figure ‎2‐6 captures this observation of
sea level <strong>change</strong>, where each study reviewed is
represented by a different line in the graph. The
shaded area and the vertical red and green error
bars represent the 90% confidence interval. The
black and red curves denote the deviation from
their 1961-1990 average, the shorter green curve
the deviation from the average of the black
curve for the period 1993 to 2003 (IPCC, 2007).
Warmer SST will lead to thermal expansion in
the Gulf and <strong>change</strong>s in mean sea level. Sea level
data collected from 11 stations in the Arabian
Gulf already indicate rising levels. Increased
SST could lead to higher peaks of storm surges,
increased cyclone intensity, and a greater risk
of coastal disasters; warmer waters also undermine
temperature-sensitive coastal ecosystem
functioning.
Thermosteric sea level is high in the summer
(June, July, and August) and autumn
(September, October, and November) and
low during spring (May, April, and March) and
winter (December, January, and February).
The distribution of the thermosteric sea
level shows larger variations in sea level in
spring than in winter. “Worst case scenario”
adaptation measures will need to target spring
mean sea levels due to both larger thermosteric
variations layered on top of large spring tidal
means (as will be explored in Section ‎2.4).
2.4. Increase in the tidal variation
around the mean
Tidal dynamics in the Arabian Gulf are
admittedly unusual. At most tidal stations, the
tidal range maximum occurs in July (summer)
and the minimum in February for most stations.
In northern and southern mid-latitudes, the
lowest sea level in the annual cycle occurs
during spring and is highest in the autumn
(Hassanzadeh, 1997; Tabata et al., 1998), but over
the Arabian Gulf, this feature is different. The
vertical extent of the intertidal zone depends
mainly on the tidal range, wave action and
slope of the shore. On sheltered steeply sloping
shores, the height of the intertidal corresponds
closely to the tidal range, narrow throughout
much of the UAE. Along unprotected coasts,
strong wave action causes the intertidal zone to
extend upwards above normal high-tide levels.
The tide waves entering the Straits of Hormuz
generate two large rotary waves for the
semidiurnal tide (two highs and two lows each
day), and a single large rotary wave for the
diurnal tide inside the Gulf. This leads to two
distinct tide patterns in the Iranian coast of
Arabian Gulf. One is found at eastern boundary
(the Strait of Hormuz) and the other at the
northern Gulf or western. Seas of up to 5.4m
swells in the Eastern Gulf tend to predominate
from NW and SE, and swells of 1.8m and higher
occur in the Central Gulf.
Baseline sea level elevation and subsequent tidal
variation around a mean is best determined by
the monthly mean sea level (mmsl). In Figure
‎2‐7, we can see how mmsl <strong>change</strong>s: the blue
line shown in the figure at left represents the
predicted (astronomical) tide. By subtracting the
predicted hourly tide from the observed hourly
water levels (red line), the researchers obtained
the residual <strong>change</strong> in water level (green line).
Improved estimates of sea level trends rely on
improving tidal gauge data collection the in the
Arabian Gulf. Mmsl data is publicly available
for only three years for the UAE (PSMSL, 2008).
As such data is insufficient for a tidal analysis;
this report relies on existing analysis of tidal
dynamics found in the literature, as synthesized
below, to best understand how tidal variation
may shift with <strong>climate</strong> <strong>change</strong> induced sea level
rise.
Figure ‎2‐7. Residual <strong>change</strong> in water level based
on observed and predicted water levels.
In Safaniya, a coastal town less than two
hundred kilometers to the northwest of Ras
Tanura, the tide is mixed, though mainly diurnal.
Whereas in Ras Tanura, a major oil terminal on
the west side of the Arabian Gulf, has a large
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Climate Change Impacts, Vulnerability & Adaptation