Evaluating pressure gauges as a potential future replacement for electromagnetic cable observations of the Florida Current transport at 27°N

ABSTRACT For 30+ years, submarine cable voltage measurements have been a critical measurement system used to produce a highly valuable time series of daily Florida Current volume transport at 27°N in the Florida Straits. However, the high cost associated with replacing the measurement system, should the existing telecommunications cable break, represents a significant vulnerability to the continuation of this important transport time series. Six years of data from tide gauges near the ends of the cable at 27°N have been used to test the potential of a paired tide gauge system to replace the cable in the event of a future problem. Validations against the daily cable observations, and against snapshot transport estimates from ship sections, suggest that the tide gauges do represent a viable replacement, however, the accuracy of the transports determined from the tide gauges is lower than for the cable observations (2.7 Sv vs. 1.7 Sv, respectively). The tide gauges capture roughly 55% of the total variance observed by the cable. The correlation between the cable data and the tide gauge differences is fairly constant (r ≈ 0.75) after low-pass filtering the data at periods from 3 to 365 days, illustrating a lack of coherence sensitivity to those time scales.