The long-term and far-reaching impact of hurricane Dorian (2019) on the Gulf Stream and the coast

Hurricane Dorian (28-August to 6-September 2019) was one of the most powerful hurricanes ever recorded in the Atlantic Ocean; it had disastrous impact on the Bahamas, before moving along the southeastern coast of the U.S. The unusual track of Dorian followed the track of hurricane Matthew (2016)- both hurricanes moved along the Gulf Stream (GS) without making a significant landfall and both seemed to weaken the flow of the GS by almost 50%. In the case of Dorian, the transport of the Florida Current (FC) measured by the cable across the Florida Straits had dropped from 34.7 Sv (1 Sv = 10(6) m(3)/s) on 22-August before the storm, to 17.1 Sv on 4-September (the lowest recorded value since measurements started in 1982). Two questions that this study tried to answer are: 1. Did the disruption that Dorian caused to ocean currents off the Florida coast affect the large-scale Gulf Stream (GS) dynamics downstream? and 2. Was there a long-term impact on the GS flow and on coastal sea level? Satellite altimeter data showed that the signal of the hurricane's impact on reducing the GS flow near the Florida coast is seen as far as 4000 km downstream along the GS path 50 days later. This long period of a weakened GS flow can elevate coastal sea level and increase flooding in the days and weeks after offshore storms already disappeared. The observed FC transport was found to be significantly correlated with the downstream GS velocity as far as 50 degrees W and was anti-correlated with sea level along the entire U.S. East Coast. The density and velocity anomaly created by the hurricane's cooling and mixing near the Florida coast seemed to propagate downstream with the GS flow at similar to 1 m/s, but slow-moving baroclinic waves with propagation speed of similar to 0.1 m/s were also observed along the GS path. The results of this study may have implications for the indirect impact of storms on large-scale ocean circulation, coastal processes and the response of coastal ecosystems to offshore changes.