Investigation of the Relationship Between the Yucatan Channel Transport and the Loop Current Area in a Multi-Decadal Numerical Simulation

A hypothesis by Maul [1977], stating the rate of change of Loop Current (LC) volume is related to deep Yucatan Channel (YC) transport, is examined and validated with a continuous 54-year simulation of the regional 1/25˚ Gulf of Mexico (GoM) Hybrid Coordinate Ocean Model (HYCOM). The hypothesis states that the imbalance of transport between the upper YC and the Florida Straits controls the rate of change of the LC volume and that the imbalance is compensated by transport through the deep YC. Previous studies have investigated the relationship between deep YC transport and LC area (used as a proxy for the volume). The first attempt by Maul et al. [1985] using a single mooring was unsuccessful in finding a relationship. However, Bunge et al. [2002] using data from the Canek observing program, which deployed 8 moorings across the YC, found a strong relationship between the deep YC transport and the LC area. The data used in Bunge et al. [2002] was for a period of 7.5 months, which is relatively short compared to the time scale of LC variability. A multi-decadal (54 years) HYCOM simulation of the Gulf of Mexico provides long term data to study LC variability and allows one to validate the Maul [1977] theory. Time evolution of the LC between two shedding events can be viewed as a combination of relatively high-frequency (on the order of about 40 days) fluctuations superimposed on a low-frequency trend. The high frequency portions of the modeled variability are shown to be related when the LC-area time derivative and the deep YC transport are compared. The low frequency variability is examined by comparing the LC-area time series with integrated transport in the deep YC, and statistically similar trends are identified. The results support the Maul [1977] theory.