Collaborative Research: The Role of the North Atlantic Oscillation (NAO) in Modulating Major Hurricane Activity in the U.S. on Interannual to Millennial Timescales

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Records from the 20th century indicate considerable variations in coastal hurricane activity along the Gulf and Atlantic coastlines of North America. A decade of strong hurricanes on the Gulf coast is followed by a decade of severe hurricanes on the East coast. Preliminary research suggests that these cycles are related to the location and strength of the subtropical Atlantic high-pressure cell (Bermuda High), perhaps controlled by the strength of the North Atlantic Oscillation (NAO). To explore the dynamics of these relationships, it is necessary to consider records of past hurricane activity that predate the 20th century. This research project will examine the role of the Bermuda High and the North Atlantic Oscillation in modulating major U.S. coastal hurricane activity on time scales ranging from the inter-annual to the millennial. Lakes and marshes along the Atlantic coast and Gulf of Mexico coast will be cored, and the overwash sand deposits preserved in these coastal sediments will be studied to produce proxy records of past hurricane activity. These geological records and evidence from historical documents will be collated with the modern instrumental records using geographic information systems (GIS) and statistics. Past climate patterns will be inferred from measured and proxy indices. The objectives of this project are to better understand climate patterns associated with variations in coastal hurricane activity and to improve return-period estimates of catastrophic events. GIS will be used to collate the disparate historical archives into an electronic document. Statistical models will be used to distinguish periods of activity from inactivity locally and regionally. A probabilistic framework will be adopted to capture the varying levels of uncertainty in the data.Strong hurricanes have enormous societal impact. High winds, heavy rain, and storm surge combine to create a catastrophic threat to life and property. Coastal populations are growing faster than the population at large, thereby continually accentuating problem associated with strong hurricanes. Careful examination of historical documents and fresh geological evidence gathered from Cape Cod and the Gulf coast through this project will provide valuable clues about the regularity of hurricanes in the distant past. A careful study of these records will result in new knowledge about the relationship between climate variability and hurricane frequency, which will lead to a better understanding of the future threat of a hurricane disaster in the United States and nearby nations.