Using Downscaled Global Climate Models to Perform a Long-Term Analysis of North Atlantic Tropical Cyclones and Their Impacts on Coastal Inundation to New York City
Open Access
- Author:
- Reed, Andra Jenn
- Graduate Program:
- Meteorology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 06, 2016
- Committee Members:
- Michael Mann, Dissertation Advisor/Co-Advisor
Michael Mann, Committee Chair/Co-Chair
David W Titley, Committee Member
Raymond Gabriel Najjar Jr., Committee Member
Richard B Alley, Outside Member - Keywords:
- Tropical Cyclones
NYC
Flooding
Storm surge
Atlantic Basin
New York
Historical
Future Risk
Flood Height - Abstract:
- In a changing climate, the impact of tropical cyclones on the United States’ Atlantic and Gulf Coasts will be affected by both how intense and how frequent these storms become. The observational record of tropical cyclones in the North Atlantic basin is too short (1851 CE – present) to accurately assess long-term trends of low-frequency variability in storm activity. To overcome this limitation, I use synthetic tropical cyclone data sets for the North Atlantic basin downscaled from Coupled Model Intercomparison Project Phase 5 (CMIP5) models; driving climate conditions span 850 CE – 2005 CE. Using these long-term synthetic tropical cyclone data sets, I investigate the relationship between power dissipation and ocean temperature metrics, as well as the relationship between basin-wide and landfalling tropical cyclone count statistics over the past millennium. Contrary to previous studies, I find only a very weak relationship between power dissipation and main development region sea surface temperature in the Atlantic basin. Consistent with previous studies, I find that basin-wide and landfalling tropical cyclone counts are significantly correlated with one another, lending further support for the use of paleohurricane landfall records to infer long-term basin-wide tropical cyclone trends. Additionally, I investigate the changing risk of inundation to the United States’ Atlantic coast, dependent upon both storm surges during tropical cyclones, and the rising sea levels on which those surges occur. Focusing our study on New York City, I compare pre-anthropogenic era (850 CE – 1800 CE) and anthropogenic era (1970 CE – 2005 CE) storm-surge model results, exposing links between increased rates of sea-level rise and storm flood heights. I find that mean flood heights increased by ~1.24 m at The Battery in New York City (due mainly to sea level rise) from ~AD 850 to the anthropogenic era, a result that is significant at the 99% confidence level. Additionally, changes in tropical cyclone characteristics have led to increases in the extremes of the types of storms that create the largest storm surges for New York City. As a result, flood risk has greatly increased for the region; for example, the 500 year return period for a ~2.25 m flood height during the pre-anthropogenic era has decreased to less than 25 years in the anthropogenic era. Finally, as sea levels continue to rise over the next several centuries, we expect additional risk of coastal flooding for the United States’ Atlantic Coast in general, and for New York City in particular, associated with storm surge events. I thus turn to an analysis of future projections of storm surge heights in New York City through the year 2300 in the context of my long-term historical analysis. Using CMIP5 model projections that extend to 2300 CE, I generate large datasets of downscaled tropical cyclones. Combining storm surge model results with several potential sea level rise scenarios for the New York City region through the year 2300, I find greatly increased risk of flooding for the metropolitan area. I show that mean flood heights are projected to increase by ~0.24 to ~0.97 meters across three CMIP5 models through the year 2100. By 2300, mean flood heights could increase by as much as ~2.85- ~4.99 meters. These results are significant at the 99% confidence level. I show that, although it is possible that shifting storm tracks could spare NYC from increases in severe storm surge heights in coming centuries, rising relative sea levels are likely to greatly increase overall flood heights, regardless of changes in TCs and their resultant storm-surge heights. Results from this research indicate the impacts of climate change on coastal inundation, and call for advanced risk management strategies in our coastal communities, especially in the New York City region.