Abstract
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°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.
Highlights
The Florida Current marks the beginning of the Gulf Stream at Florida Straits, and plays an important role in climate
I found that Florida Current transport probably declined steadily over the past century, such that transport since 1982 was likely weaker on average than it was during 1909–1981, and the weakest decadalmean transport in the last 110 y probably took place in the past two decades
While past changes in the gyre circulation are uncertain, these results corroborate earlier hypotheses based on proxy indicators that the deep branch of the Atlantic meridional overturning circulation weakened continuously during the twentieth century[23,24,25,26,27]
Summary
The Florida Current marks the beginning of the Gulf Stream at Florida Straits, and plays an important role in climate. 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. Later fulldepth transport measurements[18,19,20,21,22] were made variously between Florida and Havana, Cay Sal Bank, the Cat Cays, or Bimini, which captured the flow through Yucatán Channel, but omitted transports through Nicholas, Santaren, or Northwest Providence Channels, all of which contribute to the transport at 27°N (Fig. 1) Such disparities make it difficult to produce a stable instrumental estimate of Florida Current transport through time. Thin black lines are locations of in situ measurements from past studies[18,19,20,21]
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