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Webinar: Gulf Stream variability and trends: From the Florida Current to past Cape Hatteras

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Tuesday, 09 November 2021, 2:00

Tuesday, November 9, 2021. 2:00 PM. Webinar: Gulf Stream variability and trends: From the Florida Current to past Cape Hatteras. Christopher Wolfe, Stony Brook University. Sponsored by NOAA. Complete details here. Register here.

Abstract: Previous work linking interannual variations in Florida Current transport (FCT) to changes in atmospheric forcing have focused on the North Atlantic Oscillation (NAO). The NAO is a one-dimensional representation of fluctuations in the strengths and positions of the Icelandic Low and Azores High and considering its components independently has the potential to provide new insights. When considering the full record, FCT is not significantly correlated (i.e., p > 0.05) with the NAO at any lag or any season; however, wintertime FCT is significantly correlated (p < 0.05) with Icelandic Low longitude in the same season. Perturbation experiments with an ocean model reveal that wind perturbations associated with changes in Icelandic Low latitude drive coastal up/downwelling (through longshore winds) and offshore sea level anomalies (through wind stress curl) that are rapidly transmitted to Florida Strait, inducing transport changes by altering the sea level gradient across the Strait. Wintertime FCT is also correlated with latitude variations in both the Icelandic Low and Azores High with a lag of four years, likely due mid- ocean wind stress curl anomalies which excite baroclinic Rossby waves.

Further downstream, climate models have forecast that the Gulf Stream past Cape Hatteras will slow and shift northward as the AMOC weakens under climate change. While several studies have indirectly inferred a slowing Gulf Stream, the picture revealed by in situ and altimetric observations is more mixed. We examine the trends in Gulf Stream latitude, speed, surface transport, and width using along-track altimetry and find very few significant trends in these quantities during the altimetry era. Further, the nature and geographic location of significant trends is very sensitive to the length of the record used in the analysis. These results suggest that any possible trends are too small to be detectable above the Gulf Stream's natural variability. Supposing that the calculated trends are real (even though not currently statistically significant) and continue at the current rate, detection of trends at more than half of the altimetry tracks would require 22"23 additional years of observations for latitude and transport and 44 additional years for speed.

Bio(s): Dr. Christopher L.P. Wolfe is a physical oceanographer and an associate professor of marine science in the School of Marine and Atmospheric Sciences at Stony Brook University. He received his Ph.D. from Oregon State University in 2006 and was formerly a postdoc (2006"2012) and assistant research oceanographer (2012"2013) at the Scripps Institution of Oceanography, UCSD.

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