Persistent Lagrangian Transport Patterns in the Northwestern Gulf of Mexico

Abstract

Persistent Lagrangian transport patterns at the ocean surface are revealed from Lagrangian Coherent Structures (LCSs) computed from daily climatological surface current velocities in the northwestern Gulf of Mexico (NWGoM). The velocities are produced by a submesoscale permitting regional ocean model of the Gulf of Mexico. The significance of the climatological LCSs (cLCSs) is supported with ensemble-mean drifter density evolutions from simulated and historical satellite-tracked drifter trajectories. A persistent attracting barrier between the NWGoM shelf and the deep ocean is effectively identified by a hook-like pattern associated with groups of overall strongly attracting cLCSs that extend along the shelf break.Localized reductions in the attraction rate along these overall strongly attracting cLCSs proximal to cross-shore oriented cLCSs identify a pathway for potential transport across the shelf break.Groups of overall weakly-attracting cLCSs are not seen to strongly constrain material transport.Tracers originating over the shelf tend to be trapped there by the hook-like pattern as they spread cyclonically. Tracers originating beyond the shelf tend to be initially attracted to the hook-like pattern as they spread anti-cyclonically and eventually over the deep ocean. The findings have important implications for the mitigation of contaminant accidents such as oil spills.

Ocean Circulation in the Western Gulf of Mexico Using Self‐Organizing Maps

“…The main feature is a medium-size LCE in the impact area with an intensified northward current traveling along the continental slope, thus forming a hook-like pattern in the northwestern portion of the WGoM (Duran et al, 2018). This anticyclonic gyre was detected with drifter trajectories by Hamilton et al (1999) and with altimetry by Hyunn and Hogan (2008), who associated the gyre with the topographic effect of the northwestern corner, which formed a semienclosed slope shape between 26-28°N and 94-96°W; additionally, the gyre was identified by climatological Lagrangian coherent structures (cLCSs) nearly year-round (Gough et al, 2019), thus demonstrating that the shelf is isolated from the circulation beyond the shelf break. The pattern was not visible at 200-m depth in the presence of cyclones formed by the current stream (offshore direction) of the northern portion of the LCE.…”

Assessment of Mesophotic Coral Ecosystem Connectivity for Proposed Expansion of a Marine Sanctuary in the Northwest Gulf of Mexico: Population Genetics

“…Our observed panmictic migration pattern hypothesizes that multiple larval dispersal patterns may be effective to enable gene flow over time among all banks in the study. The LCC experiences seasonal variability, and in rarer cases, eastward transport following impingement on the continental shelf (Jarosz and Murray, 2005;Gough et al, 2017). The LCC may reverse direction during summer months (June-August) and flow eastward at a weaker speed.…”

“…Most of these habitats are at mesophotic depths (∼30-150 m), but notably West and East Flower Garden Banks (FGB), approximately 180 km from the Texas coast, also have relatively shallow coral reef habitats from 17 to 30 m. While at higher latitudes than most other reefs in the Tropical Western Atlantic (TWA) and therefore spatially isolated, coral populations in the NW GOM are thought to persist due to thermal stability and relatively high larval dispersal potential from the Gulf of Mexico Loop Current (Oey et al, 2005;Atchison et al, 2008;Nunes et al, 2011;Precht et al, 2014;Rippe et al, 2017). Westward-moving eddy formations and coastal currents are also quite common in the NW GOM and may connect reef populations along the continental margin (Ohlmann and Niiler, 2005;Schmahl et al, 2008;Gough et al, 2017). Despite residing at sub-tropical latitudes, reefs in the NW GOM have relatively stable seasonal temperatures between 18 and 30 • C due to persistence of currents, and major coral bleaching events are rare (Rezak et al, 1990;Schmahl et al, 2008).…”

Observation and quantification of inertial effects on the drift of floating objects at the ocean surface

“…The assessment of motions of floating matter in the ocean is of importance for a number of key reasons. These range from improving search-and-rescue operations at sea 1,2 ; to better understanding the drift of flotsam of different nature including macroalgae such as Sargassum [3][4][5] , plastic litter 6,7 , airplane wreckage 8,9 , tsunami debris 10,11 , sea-ice pieces 12 , larvae 13,14 , and oil 15,16 ; to better interpreting "Lagrangian" observations in the ocean 17,18 . At present, largely piecemeal, ad-hoc approaches are taken to simulate the effects of ocean currents and winds on the drift of floating objects.…”