Understanding projections of sea level rise in a Hadley Centre coupled climate model

Sea level changes resulting from CO2-induced climate changes in ocean density and circulation have been investigated in a series of idealised experiments with the Hadley Centre HadCM3 AOGCM. Changes in the mass of the ocean were not included. In the global mean, salinity changes have a negligible effect compared with the thermal expansion of the ocean. Regionally, sea level changes are projected to deviate greatly from the global mean (standard deviation is 40% of the mean). Changes in surface fluxes of heat, freshwater and wind stress are all found to produce significant and distinct regional sea level changes, wind stress changes being the most important and the cause of several pronounced local features, while heat and freshwater flux changes affect large parts of the North Atlantic and Southern Ocean. Regional change is related mainly to density changes, with a relatively small contribution in mid and high latitudes from change in the barotropic circulation. Regional density change has an important contribution from redistribution of ocean heat content. In general, unlike in the global mean, the regional pattern of sea level change due to density change appears to be influenced almost as much by salinity changes as by temperature changes, often in opposition. Such compensation is particularly marked in the North Atlantic, where it is consistent with recent observed changes. We suggest that density compensation is not a property of climate change specifically, but a general behavior of the ocean.

Twentieth-century global-mean sea-level rise: is the whole greater than the sum of the parts?

Confidence in projections of global-mean sea level rise (GMSLR) depends on an ability to account for GMSLR during the twentieth century. There are contributions from ocean thermal expansion, mass loss from glaciers and ice sheets, groundwater extraction, and reservoir impoundment. Progress has been made toward solving the ���enigma��� of twentieth-century GMSLR, which is that the observed GMSLR has previously been found to exceed the sum of estimated contributions, especially for the earlier decades. The authors propose the following: thermal expansion simulated by climate models may previously have been underestimated because of their not including volcanic forcing in their control state; the rate of glacier mass loss was larger than previously estimated and was not smaller in the first half than in the second half of the century; the Greenland ice sheet could have made a positive contribution throughout the century; and groundwater depletion and reservoir impoundment, which are of opposite sign, may have been approximately equal in magnitude. It is possible to reconstruct the time series of GMSLR from the quantified contributions, apart from a constant residual term, which is small enough to be explained as a long-term contribution from the Antarctic ice sheet. The reconstructions account for the observation that the rate of GMSLR was not much larger during the last 50 years than during the twentieth century as a whole, despite the increasing anthropogenic forcing. Semiempirical methods for projecting GMSLR depend on the existence of a relationship between global climate change and the rate of GMSLR, but the implication of the authors' closure of the budget is that such a relationship is weak or absent during the twentieth century.

Uncertainties in tidally adjusted estimates of sea level rise flooding (bathtub model) for the Greater London

Sea-level rise (SLR) from global warming may have severe consequences for coastal cities, particularly when combined with predicted increases in the strength of tidal surges. Predicting the regional impact of SLR ���ooding is strongly dependent on the modelling approach and accuracy of topographic data. Here, the areas under risk of sea water ���ooding for London boroughs were quanti���ed based on the projected SLR scenarios reported in Intergovernmental Panel on Climate Change (IPCC) ���fth assessment report (AR5) and UK climatic projections 2009 (UKCP09) using a tidally-adjusted bathtub modelling approach. Medium- to very high-resolution digital elevation models (DEMs) are used to evaluate inundation extents as well as uncertainties. Depending on the SLR scenario and DEMs used, it is estimated that 3%���8% of the area of Greater London could be inundated by 2100. The boroughs with the largest areas at risk of ���ooding are Newham, Southwark, and Greenwich. The differences in inundation areas estimated from a digital terrain model and a digital surface model are much greater than the root mean square error differences observed between the two data types, which may be attributed to processing levels. Flood models from SRTM data underestimate the inundation extent, so their results may not be reliable for constructing ���ood risk maps. This analysis provides a broad-scale estimate of the potential consequences of SLR and uncertainties in the DEM-based bathtub type ���ood inundation modelling for London boroughs.

ESTIMATING THE IMPACT OF CATASTROPHIC SEA LEVEL RISE IN MAINE

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Estimating the Impact of Catastrophic Sea Level Rise in Maine

Maine's 3,500 miles of coastline is the longest coastline in the continental US. The goal of our study was to use GIS to estimate the impact future global sea level rise could potentially have on our state. We show the area of coastline and some of the economic and social impacts that would result from a rise of one meter and six meters. We used roads to estimate the impact on infrastructure and public building, including schools, libraries, hospitals, police and fire stations, as a measure of social impact. A sea level rise of six meters would result in a loss of over 650 km��2 from coastal communities and cost the state of Maine over 3 million in repaving costs. Through our study, we hope coastal communities will be able to prepare for and react to the predicted changes in global sea level.

Effects of nutrients and sea-level rise on salt marshes of different soil types

The present thesis analyses the effects of the enrichment of the soil with fertilizer and sea level rise (SLR) on salt marsh vegetation. We simulated different conditions of the salt marshes under current and projected sea level rise. These habitats are colonised by various types of plants, we focused on species belonging to the genus Spartina. This plant seems to be particularly sensitive to eutrophication due to human activities, as experiments have documented a loss of habitat associated with altered nutrient conditions. We manipulated experimentally the types of sediment, the concentration of nutrients and sea level rise. We wanted to test whether eutrophication can affect the aboveground/belowground growth of the vegetation, and indirectly the erosion of the sediment, with potentially interacting effects with soil type and SLR in affecting the loss of the habitats and species. The study lasted from July to October. The data were analysed using Permanova. The results showed that the plants were placed in growth spiked sediment different from those raised in the untreated sediment. Furthermore, the sediment underwent a level of erosion differently depending on the growth of plants and the condition they were in the pots, current or future sea levers. These results suggest that the total salt marsh habitat is very sensitive to changes caused by human activities, and that excessive eutrophication, combined with SLR will likely facilitate further loss of salt marsh vegetation.