The science of hypoxia in the Northern Gulf of Mexico: a review.

Progress in numerical models of the Loop Current, rings, and related circulation during the past three decades is critically reviewed with emphasis on physical phenomena and processes

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

An 8-year database of sea surface temperature (SST), 7 years of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color images, wind fields, and numerical model results are analyzed to identify regions and periods of coastal upwelling on the western and southern shelves of the Gulf of Mexico. On the seasonal scale, it is found that on the Tamaulipas, Veracruz, and southwestern Texas–Louisiana shelves there are upwelling favorable winds from April to August, when southeasterly winds are dominant and cold SST anomalies associated with upwelling are observed along their coasts. However, during summer, values of chlorophyll-a concentration are lower than those in autumn and winter, which are high due to advection of old bloom biological material from upstream. During winter, there is a cold front on the Tamaulipas shelf produced by advection of cold water from the Texas–Louisiana shelf and not due to upwelling. On the eastern Campeche Bank, persistent upwelling is observed due to favorable winds throughout the year with cold SST and large chlorophyll-a content along the inner shelf from May to September. On the Tamaulipas shelf, the summer upwelling delays the annual SST peak until September, while in most of the Gulf SST peaks in August. This difference is due to the end of the upwelling favorable wind conditions and the September seasonal current reversal.

Seasonal upwelling on the Western and Southern Shelves of the Gulf of Mexico

Circulation over the continental shelf in the northern Gulf of Mexico

A climatology of various ocean features in the Gulf of Mexico (GOM) was developed using the combination of satellite remote sensing and in situ data that spanned periods as long as 32 years. Twelve separate statistics were created, some of which described characteristics of the Loop Current, while others are involved with warm core rings that separate from the Loop Current and cold core rings. These statistics examined the frequency with which the Loop Current was found in the GOM, the orientation of the Loop Current, the frequency of intrusion of Loop Current water onto the west Florida shelf and into the GOM common water region, ring separation period from the Loop Current, ring dissipation, ring speed, ring path, frequency of ring water in the western GOM, and the frequency of warm and cold core rings (WCRs and CCRs, respectively) in the GOM. The results indicate that CCRs were principally responsible for mass and heat redistribution in the eastern GOM (EGOM) and WCRs are responsible for mass and heat redistribution in the western GOM (WGOM). The average period for WCR separation from the Loop Current was 11 months and the range from 5 to 19 months. WCRs moved through the WGOM most often using the central path (i.e., their trajectory was found between 24° and 26°N latitude) and they decreased to about 55% of their initial size when they reach the western wall of the GOM. CCRs were most often found in the EGOM, and their frequency of occurrence in the EGOM surpassed that of WCRs anywhere in the GOM.

Climatology of Ocean Features in the Gulf of Mexico Using Satellite Remote Sensing Data

Anticyclones originating from the Loop Current are known to propagate into the western Gulf of Mexico. Their frequency of generation, their long lifetimes, and satellite data suggest that at any one time one or more eddies may occupy the Gulf. Given the eddy sizes (100–200 km) and geometric confinement of the Gulf, it would appear that there may be significant interactions of individual eddies and/or interactions of the eddies with bottom topography. These possibilities are explored through the use of a two-layer primitive equation model. Variable parameters in this model study are eddy strength, vertical structure, lateral friction, and initial location relative to topography. Results indicate that eddy motion is governed by two dynamical regimes depending on its lower layer rotational strength. Anticyclones with significant lower layer anticyclonic structure develop offshore directed self advective tendencies associated with topographic dispersion which induces asymmetry in the eddy. Eddies wit...

A Numerical Study of Loop Current Eddy Interaction with Topography in the Western Gulf of Mexico

The spatial structure and temporal characteristics of sea breeze and the associated coastal ocean response in the northwest Gulf of Mexico are investigated using moored instruments, hydrographic stations, and wind measurements. Near the study area of 30°N, motions in the diurnal–inertial band (DIB) may be significantly enhanced by a near-resonant condition between local inertial and diurnal forcing frequencies. Wavelet analysis is used to quantify the results. Results indicate that diurnal sea-breeze variability peaks in summer and extends at least 300 km offshore with continuous seaward phase propagation. The maximum DIB oceanic response occurs in June when there is a shallow mixed layer, strong stratification, and an approximately 10-day period of continuous sea-breeze forcing. DIB current variance decreases in July and August as the consequence of the deepening of the mixed layer and a more variable phase relationship between the wind and current. River discharge varies interannually and can s...

Near-Resonant Ocean Response to Sea Breeze on a Stratified Continental Shelf

Near the vicinity of 30° latitude, the coincidence of the period of sea breeze and the inertial period of the ocean leads to a maximum near-inertial ocean response to sea breeze. This produces a propagating inertial internal (Poincare) wave response that transfers energy laterally away from the coast and provides significant vertical mixing. In this paper, the latitudinal dependence of this wave propagation and its associated vertical mixing are investigated primarily using a nonlinear numerical ocean model. Three-dimensional idealized simulations show that the coastal oceanic response to sea breeze is trapped poleward of 30° latitude; however, it can propagate offshore as Poincare waves equatorward of 30° latitude. Near 30° latitude, the maximum oceanic response to sea breeze moves offshore slowly because of the near-zero group speed of Poincare waves at this latitude. The lateral energy flux convergence plus the energy input from the wind is maximum near the critical latitude, leading to increa...

David C. Smith

Papers

A Numerical Study of Loop Current Eddy Interaction with Topography in the Western Gulf of Mexico

Near-Resonant Ocean Response to Sea Breeze on a Stratified Continental Shelf

A Numerical Study of Sea-Breeze-Driven Ocean Poincare Wave Propagation and Mixing near the Critical Latitude

Sea breeze driven ocean Poincare wave propagation and mixing near the critical latitude with application to the Gulf of Mexico