Likely weakening of the Florida Current during the past century revealed by sea-level observations

The Florida Current marks the beginning of the Gulf Stream at Florida Straits, and plays an important role in climate. Nearly continuous measurements of Florida Current transport are available at 27 degrees N since 1982. These data are too short for assessing possible multidecadal or centennial trends. Here I reconstruct Florida Current transport during 1909-2018 using probabilistic methods and principles of ocean physics applied to the available transport data and longer coastal sea-level records. Florida Current transport likely declined steadily during the past century. Transport since 1982 has likely been weaker on average than during 1909-1981. The weakest decadal-mean transport in the last 110 y likely took place in the past two decades. Results corroborate hypotheses that the deep branch of the overturning circulation declined over the recent past, and support relationships observed in climate models between the overturning and surface western boundary current transports at multidecadal and longer timescales. Understanding trends in ocean circulation and dynamics is hampered by a lack of long-term records. Here the author uses probabilistic reanalysis of available data to show that transport by the Florida Current has declined over the past 110 years, indicating a slowdown of Atlantic Ocean circulation.