The flow of the Florida Current, one of the most powerful ocean currents in the world, has been measured by a submarine telecommunications cable between Florida and the Bahamas since 1982. Unfortunately, this record was interrupted in November 2023 due to a mechanical failure of the cable. Building on prior research, a new study presents an alternative method to continue providing the Florida Current daily transport estimates until the cable can be repaired.
The Florida Current is the beginning of the Gulf Stream—a powerful ocean current that flows through the Florida Straits and moves large amounts of warm water, salt, carbon, and nutrients northward. Scientists monitor the Florida Current because of its proximity to land and influence on societal issues, including changes in coastal sea level and flooding events, as well as its role in weather and climate patterns. In addition, the Florida Current transport estimates are a key component for calculating the Atlantic Meridional Overturning Circulation (AMOC) at 26.5°N.
Because of its importance, observations of the Florida Current daily transport date back to 1982 using the decommissioned submarine telecommunications cable. This system has provided over 40 years of data, making it the longest, nearly continuous observational record of a major ocean current ever collected. Nowadays, these observations are carried out as part of the NOAA’s Western Boundary Time Series (WBTS) program, which works to measure both the warm upper and cold lower limbs of the AMOC near the western boundary of the Atlantic Ocean at 27°N.
Unfortunately, data collection ceased in November 2023 due to a mechanical failure of the cable. While efforts are underway to restore the cable system, there is an urgent need to continue providing the Florida Current daily transport estimates using an alternative method.
In a new study, scientists at the University of Miami-NOAA Cooperative Institute for Marine and Atmospheric Studies (CIMAS) and NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) present a new method based on underwater pressure sensors and satellite measurements of sea level.
A pair of pressure gauges has been deployed on either side of the Florida Current since July 2008 at depths of approximately 12m. The western instrument is located off the east coast of Florida at 27°N, and the eastern instrument is positioned over the Little Bahama Bank at 27°N. Both instruments record pressure every 5 minutes. The instruments are regularly refreshed by scuba divers who recover them, remove biofouling, replace the batteries, and redeploy them. Satellite altimetry has provided accurate, homogeneous‐quality measurements of sea surface height since October 1992.
In this study, scientists combine data from the pair of pressure gauges with satellite altimetry to extend daily transport estimates and fill gaps in the cable record. The study shows that transport estimates based on crossflow sea level gradients from pressure gauges adjusted by satellite altimetry represent a suitable temporary substitute for cable‐based measurements.
Relying solely on pressure gauges to study low‐frequency variability (longer than ∼1 year) is problematic, as pressure sensors are susceptible to false drifts, making it difficult to combine records from different deployments. This shortcoming is addressed by employing satellite altimetry that provides quality data across multiple missions. The combination of the two observational records serves as a viable interim solution until the cable measurements are resumed.
“The new transport estimates build on previous efforts by leveraging the daily resolution of moored pressure gauge records together with the reliable low-frequency variability captured by satellite altimetry,” said Denis Volkov, lead author of the study and CIMAS scientist.
Resuming cable measurements remains a high priority, as they represent the most accurate and cost‐effective method for monitoring the Florida Current to date. This approach is particularly valuable for maintaining continuity in the daily Florida Current transport estimates used in calculating the AMOC at ∼26.5°N. The updated Florida Current transport time series is freely available on the WBTS project website.