Deep flows in the Yucatan Channel and their relation to changes in the Loop Current extension

Abstract

The first attempt to establish a relation between the Loop Current extension and deep flows in Yucatan Channel was made by Maul et al. [1985]; it was unsuccessful, probably because of the low spatial resolution of their observations. From September 8, 1999, to June 17, 2000, eight moorings with acoustic Doppler current profilers, current meters, and thermometers were deployed across the Yucatan Channel. The data from these arrays were used to compute time series of the transports below the level of the deepest isotherm observed in the Florida Straits, as required by a simple box model that restricts deep exchanges with the Gulf of Mexico to the Yucatan Channel. The surface extension of the Loop Current was inferred from 3 day advanced very high resolution radiometer imagery from October to May, when temperature gradients were sufficient to map the warm water unambiguously. The deep transports appear at first unrelated to the rate of change of the Loop Current extension, but filtering the series with a 20 day running mean increases the correlation between the low‐pass series to 0.62, and up to 0.83 with a lag of 8.5 days, with Loop Current changes leading the deep flows. The cumulative deep transport, a quantity that favors lower frequencies, is very well related (correlations >0.9) to the surface extension of the Loop Current, also with a lag of about a week. These lags are not statistically significant but suggest a timescale for internal adjustment processes in the Gulf of Mexico. The empirical orthogonal function of the current best related to the area extension of the Loop Current represents a unidirectional flow across the entire deep section, flowing either toward or from the Gulf of Mexico, and includes a strong expression of the Yucatan Undercurrent.

Loop Current, Rings and Related Circulation in the Gulf of Mexico: A Review of Numerical Models and Future Challenges

“…Maul et al [985] observed similar southward (deep) events and the apparent relation of these events to eddy shedding. More recent data and analyses [Bunge et al 2002;Ezer et al, 2003] support Maul et al's and Oey's [996] findings. Second, Oey noted that these transport fluctuations occurred at shorter periods (weeks ~ months) than eddy-shedding, i.e., not every Loop Current extension (and deep southward flow) resulted in shedding.…”

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

“…Bunge et al, [2002] found a very strong relationship between LC area and deep YC flows for their time frame. They attributed the lack of a relationship found…”

“…Maul and Vukovich [1993] examined volume transport through the FLS and also did not find a significant relation to the LC area rate of change. Bunge et al, [2002] used a simple box model to illustrate Maul's [1977] theory. They investigated data from the Canek observing program, which deployed eight moorings with acoustic doppler current profilers and current meters across the YC from 8 September 1999 to 17…”

Temporal variability of chlorophyll distribution in the Gulf of Mexico: bio-optical data from profiling floats

“…-T6 is in the lower thermocline and has been used as the interface for a two-layer system, separating deep waters from the more energetic upper layer containing mesoscale structures and the LC (Bunge et al, 2002;Donohue et al, 2008;Hamilton et al, 2016a, b). …”