Structure and Variability of the Antilles Current at 26.5°N

Observations from five different systems provide a robust picture of the structure and variability of the Antilles Current, an important contributor to the oceanic flux budget, at 26.5 degrees N during 2005-2015. The analysis includes three direct measurement technologies (current meters, shipboard acoustic Doppler current profilers, and lowered acoustic Doppler current profilers) and two geostrophy-based measurement technologies (conductivity-temperature-depth profilers and pressure-equipped inverted echo sounders). The direct systems are shown to produce weaker, and less variable, Antilles Current transport estimates than the geostrophy-based systems. The record-length-mean geostrophic estimate for the Antilles Current is 4.7 Sverdrups (Sv; 1 Sv = 10(6) m(3)/s), and the daily temporal standard deviation is 7.5 Sv. The variations of the Antilles Current transport exceed those of the entire basin-wide meridional overturning circulation, illustrating the impact of this unusual current. Seasonal variability shows a maximum northward transport in August-September; however, the seasonal component of the variability is weak, and aliasing of higher frequencies is still a problem even with 10.5 years of data. The dominant time scales of variability in the spectra are at 70 and 180 days, and there is indication of westward propagation of Rossby Wave-like features into the region at a speed of 9 cm/s. There is no significant correlation between the Antilles Current transport variations and those of the Florida Current at 27 degrees N, in phase or at lags/leads of up to 5 years, likely reflecting the varying coastal wave/wall jet time scales for information to pass from the basin interior through the Bahamas Islands. Plain Language Summary The Antilles Current carries waters northward and northwestward around the Bahamas Islands. While scientists have known that the Antilles Current existed for decades, it has not been studied nearly as much as the stronger Florida Current to the west, even though studies have suggested that the Antilles Current plays a significant role in the north-south exchange of heat and salt within the North Atlantic. This study uses five different types of measurement systems to quantify how much water is being carried by the Antilles Current every day, how variable that flow is over a 10.5-year time period, and what typical salinity, temperature, and dissolved oxygen contents are for the waters carried by the flow. The study finds that on average, this current is carrying 4.7 x10(6) m(3) of water per second northward and that this flow can vary by more than 100% from day to day (i.e., some days the flow can actually reverse and go southward). The study reveals the time scales on which the current tends to vary, and it also provides some tantalizing evidence that the physics of the current may not be as simple as has been previously thought.