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thermal expansion, with only a conservative estimate of the contribution from ice sheet melt (Rahmstorf,<br />
2007).<br />
Recent studies that observed acceleration in ice discharge (e.g. Rignot <strong>and</strong> Kanargaratnam, 2006) <strong>and</strong><br />
observed rates of SLR in response to global warming (Rahmstorf, 2007), suggest that ice sheets respond<br />
highly-non linearly to atmospheric warming. We might therefore expect continued acceleration of the large<br />
ice sheets resulting in considerably more rapid rates of SLR. Rahmstorf (2007) is perhaps the most well<br />
cited example of such a study <strong>and</strong> suggests that future SLR might be in the order of twice the maximum<br />
level that the IPCC, indicating up to 1.4 m by 2100.<br />
Table 3.11.2: Projected increases in sea level rise from the IPCC AR4<br />
Scenario Global Mean Sea Level Rise<br />
by 2100 relative to 1980-<br />
1999.<br />
31<br />
Caribbean Mean Sea Level Rise<br />
by 2100 relative to 1980-1999<br />
(+/ 0.05m relative to global<br />
mean)<br />
IPCC B1 0.18-0.38 0.13-0.43<br />
IPCC A1B 0.21-0.48 0.16-0.53<br />
IPCC A2 0.23-0.51 0.18- 0.56<br />
Rahmstorf, 2007 Up to 1.4m Up to 1.45m<br />
(Source: Meehl et al., 2007 contrasted with those of Rahmstorf, 2007).<br />
3.12. Storm Surge<br />
Changes to the frequency or magnitude of storm surge experienced at coastal locations in Cockburn Town<br />
are likely to occur as a result of the combined effects of:<br />
1. Increased mean sea level in the region, which raises the base sea level over which a given storm<br />
surge height is superimposed<br />
2. Changes in storm surge height, or frequency of occurrence, resulting from changes in the<br />
severity or frequency of storms<br />
3. Physical characteristics of the region (bathymetry <strong>and</strong> topography) which determine the<br />
sensitivity of the region to storm surge by influencing the height of the storm surge generated<br />
by a given storm.<br />
Sections 3.10 <strong>and</strong> 3.11 discuss the potential changes in sea level <strong>and</strong> hurricane intensity that might be<br />
experienced in the region under (global) warming scenarios. The high degree of uncertainty in both of<br />
these contributing factors creates difficulties in estimating future changes in storm surge height or<br />
frequency.<br />
Further impacts on storm surge flood return period may include:<br />
Potential changes in storm frequency: some model simulations indicate a future reduction in storm<br />
frequency, either globally or at the regional level. If such decreases occur they may offset these<br />
increases in flood frequency at a given elevation.<br />
Potential increases in storm intensity: evidence suggests overall increases in the intensity of storms<br />
(lower pressure, higher near storm rainfall <strong>and</strong> wind speeds) which would cause increases in the<br />
storm surges associated with such events, <strong>and</strong> contribute further to increases in flood frequency at<br />
a given elevation.
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