Seminar: Dr. Jesse McNinch, Army Corps of Engineers

ENSO variance and cyclone frequency in the North Atlantic: a complex relationship (Host: Chris Martens)

Assessing the skill of climate models predicting future cyclone occurrence has been a challenge, in large part, because historical and paleo-records of cyclones have either been too coarse or too short to capture the long, subtle cycles of climate forces affecting cyclone frequency. Sediment cores from two drainage basins on the island of St. Croix, USVI contain a sub-decadal, five hundred year record of cyclones in the Eastern Caribbean. Data from both basins show a significant temporal correlation between cyclone frequency and decadal ENSO variance beginning in the early eighteenth century and persisting today. Interestingly, it is the decadal time periods experiencing substantial swings between strong El Niña and strong La Niña events (expressed as high ENSO variance) that show the greatest correlation to cyclone frequency in the North Atlantic. These data also suggest a shift in the relationship between decadal ENSO variance and cyclone frequency in the early eighteenth century; becoming highly correlated in time, post ~1710, while being out of phase for the prior 150-200 years. Simply put, periods of high ENSO variance appear to be better predictors of elevated cyclone frequency in the North Atlantic than just single years with strong La Niña values, and the relationship between ENSO and cyclones may shift over long time periods. Results presented here independently support investigations suggesting that the influence of ENSO on global climate and cyclone development is dynamic and complex, and may change on time scales longer than historical meteorological observations.