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Climate warming does not force sea-level rise (SLR) at the same rate everywhere. Rather, there are spatial variations of SLR superimposed on a global average rise. These variations are forced by dynamic processes 1-4 , arising from circulation and variations in temperature and/or salinity, and by static equilibrium processes 5 , arising from mass redistributions changing gravity and the Earth's rotation and shape. These sealevel variations form unique spatial patterns, yet there are very few observations verifying predicted patterns or fingerprints 6 . Here, we present evidence of recently accelerated SLR in a unique 1,000-km-long hotspot on the highly populated North American Atlantic coast north of Cape Hatteras and show that it is consistent with a modelled fingerprint of dynamic SLR. Between 1950Between -1979Between and 1980Between -2009, SLR rate increases in this northeast hotspot were ∼3-4 times higher than the global average. Modelled dynamic plus steric SLR by 2100 at New York City ranges with Intergovernmental Panel on Climate Change scenario from 36 to 51 cm (ref. 3); lower emission scenarios project 24-36 cm (ref. 7). Extrapolations from data herein range from 20 to 29 cm. SLR superimposed on storm surge, wave run-up and set-up will increase the vulnerability of coastal cities to flooding, and beaches and wetlands to deterioration.We test the hypothesis that a statistically significant observed northeast hotspot (NEH) of accelerated SLR exists by determining its position and dimensions and comparing them with model projections 1-4 . We explore correlations between rate changes of observed NEH SLR and of climate indices potentially relevant to NEH formation.In the late twentieth century, sea levels were relatively low along the North American east coast, particularly north of Cape Hatteras 8,9 . Sea-surface gradients sloped down towards the coast away from the Gulf Stream and its continuation to the northeast, the North Atlantic Current 10 . The sharp pressure gradients balance the Coriolis force to sustain these narrow and strong geostrophic currents, leading to low coastal sea levels.These low levels could rise with warming and/or freshening of surface water in the subpolar north Atlantic, where less dense water inhibits deep convection associated with the Atlantic Meridional Overturning Current (AMOC). The AMOC weakens and pressure gradients along the North American east coast decrease, raising sea levels. The models considered here simulate this dynamic SLR using Intergovernmental Panel for Climate Change (IPCC) Special Report on Emissions Scenarios warming scenarios 2-4 and/or assumed freshening scenarios 1,4 . Gyre system weakening by changes in the North Atlantic Oscillation 11,12 (NAO) could also reduce sea-level gradients and raise sea levels.To establish the observed NEH, we analyse tide-gauge records along the North American Atlantic coast for increasing rates of SLR (see Methods and Supplementary Information). With leastsquares linear regression, rates of SLR were found for the first an...

Increases in concentrations of greenhouse gases projected for the 21st century are expected to lead to increased mean global air and ocean temperatures. The National Assessment of Potential Consequences of Climate Variability and Change (NAST 2001) was based on a series of regional and sector assessments. This paper is a summary of the coastal and marine resources sector review of potential impacts on shorelines, estuaries, coastal wetlands, coral reefs, and ocean margin ecosystems. The assessment considered the impacts of several key drivers of climate change: sea level change; alterations in precipitation patterns and subsequent delivery of freshwater, nutrients, and sediment; increased ocean temperature; alterations in circulation patterns; changes in frequency and intensity of coastal storms; and increased levels of atmospheric CO •. Increasing rates of sea-level rise and intensity and frequency of coastal storms and hurricanes over the next decades will increase threats to shorelines, wetlands, and coastal development. Estuarine productivity will change in response to alteration in the timing and amount of freshwater, nutrients, and sediment delivery. Higher water temperatures and changes in freshwater delivery will alter estuarine stratification, residence time, and eutrophication. Increased ocean temperatures are expected to increase coral bleaching and higher CO. levels may reduce coral calcification, making it more difficult for corals to recover from other disturbances, and inhibiting poleward shifts. Ocean warming is expected to cause poleward shifts in the ranges of many other organisms, including commercial species, and these shifts may have secondary effects on their predators and prey. Although these potential impacts of climate change and variability will vary from system to system, it is important to recognize that they will be superimposed

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Wave setup and swash statistics were calculated from 154 runup time series measured on a moderately steep beach under incident waves varying from 0.4 to 4.0 m significant wave height. When scaled by the incident wave height, setup, swash height, and total runup (the sum of setup and half the swash height) were found to vary linearly with the surf zone similarity parameter ξ0 = β(H0/L0)−1/2. The foreshore slope appeared the appropriate value for the calculation of ξ0, although the setup data showed some influence of an offshore bar at low tide. For low Irribaren numbers the swash height in the incident frequency band becomes saturated, while for high Irribaren numbers, no such signs of saturations were seen. Thus the infragravity band appears to become dominant in the swash below some value of ξ0. For these data, that value is approximately 1.75, although there is considerable scatter associated with that estimate.