Atmospheric drivers of sea-level fluctuations and nuisance floods along the mid-Atlantic coast of the USA

Abstract

As sea levels have risen and continue to rise, the risk of coastal flooding has increased in turn. While many studies have examined specific extreme flooding events, far fewer have explored the systematic associations between weather events and smaller, nuisance flood events. In this research, we take a synoptic climatological approach to assess this connection. We utilize self-organizing maps (SOMs) to separately cluster two atmospheric fields, sea-level pressure and 700-hPa geopotential height. We then utilize the output from these classifications to assess the impact of atmospheric conditions on the short-term fluctuations of sea level for the period 1979–2012, as well as the likelihood of nuisance flood occurrence, at five tidal gauges from Cape May, NJ, to Charleston, SC, along the mid-Atlantic coast of the USA. Results show the impacts of both the inverted barometer effect as well as surface wind forcing. Beyond this, the SOM nodes show a clear spatial continuum of associations between circulation and anomalous sea level, including some significant sea-level anomalies associated with relatively ambiguous pressure patterns. Moreover, the transitions from 1 day to the next are also analyzed, with results showing that rapidly deepening cyclones, or persistent onshore flow, can be associated with the greatest likelihood of nuisance floods. Results are generally weaker with 700-hPa height than sea-level pressure; however, in some cases, it is clear that the mid-tropospheric circulation can modulate the connection between sea-level anomalies and surface circulation.