Abstract
AbstractThe tilt of mean sea level along the North American east coast has been a subject of debate for many decades. Improvements in geoid and ocean circulation models, and GPS positioning of tide gauge benchmarks, provide an opportunity to produce new tilt estimates. Tilts estimated using tide gauge measurements referenced to high‐resolution geoid models (the geodetic approach) and ocean circulation models (the ocean approach) are compared. The geodetic estimates are broadly similar, with tilts downward to the north through the Florida Straits and at Cape Hatteras. Estimates from the ocean approach show good agreement with the geodetic estimates, indicating a convergence of the two approaches and resolving the long standing debate as to the sign of the tilt. These tilts differ from those used by Yin and Goddard (2013) to support a link between changing ocean circulation and coastal sea level rise.
Highlights
The geodetic approach is based on the difference between mean sea level observed at coastal tide gauges and the height of the geoid, with both heights expressed relative to the same reference ellipsoid
In this study we have built on the work of W12 by means of a more detailed analysis of the tilts along the east coast of North America, an area with a long history of attempts to measure the tilts
Using a clustering technique we show an encouraging level of agreement between a group of estimates from the geodetic approach and the ocean approach
Summary
There is a long history of attempts to measure the tilt of mean sea level along the east coast of North America and to relate it to the circulation of the adjacent shelf and deep ocean [e.g., Bowie, 1927; Montgomery, 1938; Sturges, 1974; Scott and Csanady, 1976; Sturges, 1977; Csanady, 1978; Chapman et al, 1986; Lentz, 2008; Xu and Oey, 2011]. Bowie [1927] used geodetic leveling surveys to argue that coastal mean sea level tilted upward toward the north and suggested a link to meteorological conditions and ocean density variations. Montgomery [1938] used the difference in mean sea level between tide gauges on the east and west coasts of Florida, linked by leveling, to estimate the mean speed of the Florida Current. Two of the most prominent are in the Florida Straits and at Cape Hatteras, both regions where the Gulf Stream passes close to the coastline, there are considerable differences in the magnitude of the tilts between different estimates Their estimates from the ocean approach around Cape Hatteras (between Springmaid Pier and Duck tide gauges, E and F in Figure 1a) range from 1.1 × 10−7 upward to the north to 3.2 × 10−7 downward. Dynamical explanations for the main features of the tilts are proposed in section 4, and in section 5 the new contributions from this study are discussed
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