Date and Time
Bath Royal Literary and Scientific Institution, 16-18 Queen Square, Bath BA1 2HN
Coastal seawater (and lake water) temperature (SST) adjacent to urban centres is rising up to 10 times faster than the observed global trend of 0.13 degrees C/decade (IPCC, 2007). Much of this trend is linked to upward trends in air temperature due to the heat island effect, which are well in excess of the global trends (Gonzalez et al., 2007). Global models of SST avoid or “homogenize” coastal datasets because of these local effects and thus they are not good proxies for coastal impacts. It is possible that in coastal regions of high urban development, human activity is directly warming adjacent coastal waters and that this contribution is equal to, or greater than, that due to greenhouse gasses or advection/mixing by surface currents (Shearman et al., 2010).
If this is true, then future changes in SST in the coastal zone, especially adjacent to urban regions, are likely to be poorly predicted by global trends. Thus there appears to be a blind-spot in our understanding of future coastal vulnerability that could be addressed by a synthesis of SST change in the coastal ocean. The impact of this on fines sedimentation is three-fold: changes in seawater density (and hence buoyancy); changes in fluid viscosity; and changes in flocculation rates. The sum total of these changes can alter sedimentation patterns profoundly, especially in the silt/clay size ranges. The impact of these effects will be discussed in the context of sedimentation patterns in Venice lagoon.
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