Closing the transport budget of the Florida Straits

Abstract

Closing the mean mass budget of the Florida Straits is fundamental to understanding the source waters of the Gulf Stream and for constraining ocean simulations and forecasts in a region of complex topography. Existing transport time series of the inflow through Yucatan Channel and the outflow at 27°N yield a 9 Sv difference in the mean, which cannot be reconciled by the two minor inflows between. Here we present a synthesis of transport estimates from throughout the Florida Straits, using velocity data collected aboard the cruise ship Explorer of the Seas. Our transports form a consistent mass budget and conform with the northern outflow from the Straits of 32.1 ± 3.3 Sv, as measured continuously by cable. In particular, we find an average of 30.0 ± 5.3 Sv for the inflow to southern Florida Straits and estimate that Old Bahama Channel contributes less than an additional 2 Sv.

Interannual variability in the Yucatan Channel flow

“…Transport calculations from moorings suggest a considerable range of interannual transport variations (~5 Sv), higher than the one suggested by Rousset and Beal []. The AVISO‐120 transport proxy has a standard deviation of 1.2 Sv and a range of 4–5 Sv but recall this proxy underestimates the annual means of the CANEK transports.…”

“…Recent measurements (2001 to 2006) from shipboard acoustic Doppler current profiler (ADCP) through Yucatan Channel and Florida Straits suggest a ~30 Sv transport in both passages and a ~2.7 Sv seasonal variation [ Rousset and Beal , , , ]. These shipboard measurements combined with model data imply a small contribution (~3 Sv) from the OB and NWP channels.…”

“…These shipboard measurements combined with model data imply a small contribution (~3 Sv) from the OB and NWP channels. Rousset and Beal [, , ] argue that sampling errors and biases of their shipboard ADCP observations, as well as interannual variability at 27°N from cable measurements, cannot account for a transport as low as the 23 Sv measured by CANEK at Yucatan Channel; since in their view, these factors together represent no more than 2 Sv of the transport deficit observed.…”

Neogene palaeoceanographic changes recorded in a carbonate contourite drift (Santaren Channel, Bahamas)

“…Current measurements show a northward‐flowing contour current at the east side of the SC and a weaker countercurrent at the margin of CSB (Leaman et al ., ; Lüdmann et al ., ). Approximately less than 2 × 10 6 m³ sec −1 of inflow enters the Florida Straits via the SC, fed by the OBC, with a strong subsurface current and a maximum speed at 300 m water depth (Rousset & Beal, ). The inflow of the subsurface water masses of the North Atlantic Central Water (Talley et al ., ) through the OBC is propelled by the thermohaline subtropical gyre and wind‐driven currents (Johns et al ., ).…”

Compensation between meridional flow components of the Atlantic MOC at 26° N

“…The FC carries most of the waters of the Gulf Stream across 26 • N. The origins of this water come from the Yucatan Channel and Old Bahama Channel, across complex topography west of the Bahamas (Rousset and Beal, 2014). At similar latitudes, the flow through the Yucatan Channel has been found to compensate flow around Cuba (Lin et al, 2009), while variations in the FC have, at times, shown compensation east of the Bahamas in bottom pressure variations ) and in top 1000 m velocities (FrajkaWilliams et al, 2013).…”