scholarly journals Water Column Stability and the Role of Velocity Shear on a Seasonally Stratified Shelf, Mississippi Bight, Northern Gulf of Mexico

2018 ◽  
Vol 123 (8) ◽  
pp. 5777-5796 ◽  
Author(s):  
Brian Dzwonkowski ◽  
Severine Fournier ◽  
Kyeong Park ◽  
Steven L. Dykstra ◽  
John T. Reager
Keyword(s):  
Gulf Of Mexico ◽  
Water Column ◽  
Velocity Shear ◽  
Northern Gulf Of Mexico ◽  
Water Column Stability

Oxygen consumption in the water column and sediments of the northern Gulf of Mexico hypoxic zone

2013 ◽  
Vol 123 ◽  
pp. 46-53 ◽  
Author(s):  
Mark J. McCarthy ◽  
Stephen A. Carini ◽  
Zhanfei Liu ◽  
Nathaniel E. Ostrom ◽  
Wayne S. Gardner
Keyword(s):  
Oxygen Consumption ◽  
Gulf Of Mexico ◽  
Water Column ◽  
Northern Gulf Of Mexico ◽  
Hypoxic Zone

scholarly journals Role of Near-Inertial Internal Waves in Subthermocline Diapycnal Mixing in the Northern Gulf of Mexico

2015 ◽  
Vol 45 (12) ◽  
pp. 3137-3154 ◽  
Author(s):  
Zhao Jing ◽  
Ping Chang ◽  
Steven F. DiMarco ◽  
Lixin Wu
Keyword(s):  
Gulf Of Mexico ◽  
Hurricane Katrina ◽  
Internal Waves ◽  
Dominant Role ◽  
Deep Ocean ◽  
Diapycnal Mixing ◽  
Northern Gulf Of Mexico ◽  
Weather Patterns ◽  
The Impact

AbstractMoored ADCP data collected in the northern Gulf of Mexico are analyzed to examine near-inertial internal waves and their contribution to subthermocline diapycnal mixing based on a finescale parameterization of deep ocean mixing. The focus of the study is on the impact of near-inertial internal waves generated by an extreme weather event—that is, Hurricane Katrina—and by month-to-month variation in weather patterns on the diapycnal mixing. The inferred subthermocline diapycnal mixing exhibits pronounced elevation in the wake of Katrina. Both the increased near-inertial (0.8–1.8f, where f is the Coriolis frequency) and superinertial (>1.8f) shear variances contribute to the elevated diapycnal mixing, but the former plays a more dominant role. The intense wind work on near-inertial motions by the hurricane is largely responsible for the energetic near-inertial shear variance. Energy transfer from near-inertial to superinertial internal waves, however, appears to play an important role in elevating the superinertial shear variance. The inferred subthermocline diapycnal mixing in the region also exhibits significant month-to-month variation with the estimated diffusivity in January 2006 about 3 times the values in November and December 2005. The subseasonal change in the diapycnal mixing mainly results from the subseasonal variation of the near-inertial wind work that causes intensification of the near-inertial shear in January 2006.

scholarly journals Laboratory growth of denitrifying water column microbial consortia from deep-sea shipwrecks in the northern Gulf of Mexico

F1000Research ◽  
2017 ◽  
Vol 6 ◽  
pp. 1834
Author(s):  
Dhanya Haridas ◽  
Justin C. Biffinger ◽  
Thomas J. Boyd ◽  
Preston A. Fulmer ◽  
Leila J. Hamdan ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Water Column ◽  
Deep Sea ◽  
Amplicon Sequencing ◽  
Microbial Consortia ◽  
Microbial Populations ◽  
Northern Gulf Of Mexico ◽  
Metabolic Adaptations ◽  
16S Amplicon Sequencing ◽  
Growth Profiles

Background: Shipwrecks serve as a rich source for novel microbial populations that have largely remained undiscovered. Low temperatures, lack of sunlight, and the availability of substrates derived from the shipwreck’s hull and cargo may provide an environment in which microbes can develop unique metabolic adaptations.  Methods: To test our hypothesis that shipwrecks could influence the microbial population involved in denitrification when a consortium is grown in the laboratory, we collected samples proximate to two steel shipwrecks in the northern Gulf of Mexico. Then under laboratory conditions, we grew two independent denitrifying microbial consortia. Each consortium was grown by using the BART assay system and analyzed based on growth kinetics, ion chromatography and 16S amplicon sequencing.Results: Both denitrifying consortia were different from each other based on varied growth profiles, rates of nitrate utilization and 16S amplicon sequencing.Conclusions: Our observations conclude that the laboratory grown water column microbial consortia from deep-sea shipwrecks in the Gulf of Mexico are able to undergo aggressive denitrification.

scholarly journals Volumetric Mapping of Methane Concentrations at the Bush Hill Hydrocarbon Seep, Gulf of Mexico

2021 ◽  
Vol 9 ◽  
Author(s):  
William P. Meurer ◽  
John Blum ◽  
Greg Shipman
Keyword(s):  
Gulf Of Mexico ◽  
Water Column ◽  
Acoustic Doppler Current Profiler ◽  
Field Studies ◽  
Methane Seepage ◽  
Current Profiler ◽  
Methane Fluxes ◽  
Methane Concentrations

The role of methane as a green-house gas is widely recognized and has sparked considerable efforts to quantify the contribution from natural methane sources including submarine seeps. A variety of techniques and approaches have been directed at quantifying methane fluxes from seeps from just below the sediment water interface all the way to the ocean atmosphere interface. However, there have been no systematic efforts to characterize the amount and distribution of dissolved methane around seeps. This is critical to understanding the fate of methane released from seeps and its role in the submarine environment. Here we summarize the findings of two field studies of the Bush Hill mud volcano (540 m water depth) located in the Gulf of Mexico. The studies were carried out using buoyancy driven gliders equipped with methane sensors for near real time in situ detection. One glider was equipped with an Acoustic Doppler Current Profiler (ADCP) for simultaneous measurement of currents and methane concentrations. Elevated methane concentrations in the water column were measured as far away as 2 km from the seep source and to a height of about 100 m above the seep. Maximum observed concentrations were ∼400 nM near the seep source and decreased away steadily in all directions from the source. Weak and variable currents result in nearly radially symmetric dispersal of methane from the source. The persistent presence of significant methane concentrations in the water column points to a persistent methane seepage at the seafloor, that has implications for helping stabilize exposed methane hydrates. Elevated methane concentrations in the water column, at considerable distances away from seeps potentially support a much larger methane-promoted biological system than is widely appreciated.

scholarly journals Submesoscale Dynamics in the Northern Gulf of Mexico. Part I: Regional and Seasonal Characterization and the Role of River Outflow

2017 ◽  
Vol 47 (9) ◽  
pp. 2325-2346 ◽  
Author(s):  
Roy Barkan ◽  
James C. McWilliams ◽  
Alexander F. Shchepetkin ◽  
M. Jeroen Molemaker ◽  
Lionel Renault ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Gulf Of Mexico ◽  
Root Mean Square ◽  
Mean Square ◽  
Layer Depth ◽  
Mean Values ◽  
Northern Gulf Of Mexico ◽  
River Outflow ◽  
Submesoscale Currents

AbstractRealistic, submesoscale-resolving numerical simulations are used to characterize the flow’s statistics and the geography of surface submesoscale currents in the northern Gulf of Mexico. This study examines the role of the Mississippi–Atchafalaya River system in driving submesoscale currents during winter and summer, on and off the shelf, by investigating two sets of statistically equilibrated solutions, with and without river forcing. In this paper, the first of three, the authors analyze vorticity ζ, horizontal divergence δ, and available potential energy to eddy kinetic energy conversion and show that river forcing has an important effect on the spatial distribution and magnitudes of submesoscale currents in both seasons. During winter, solutions without river forcing display an increase in seasonal-mean values of ζ, δ and compared to solutions with river forcing, particularly east of the Mississippi River delta and offshore. On the contrary, during summer, seasonal-mean values are larger in solutions with river forcing throughout the entire region. The river effects can be rationalized in terms of scaling arguments that relate submesoscale current magnitudes to the surface boundary layer depth and lateral buoyancy gradients. River outflow enhances submesoscale currents by increasing lateral buoyancy gradients but suppresses them by decreasing the boundary layer depth. A discussion of the submesoscale-generating mechanisms that in each season may determine whether the enhancement effect overcomes the suppression effect or vice versa is presented. Regional comparisons of horizontal velocity spectra, root-mean-square ζ, root-mean-square δ, and root‐mean‐square across different resolutions show no sign of convergence even at 150-m horizontal resolution. This demonstrates the numerical challenge of modeling the full range of submesoscale currents.

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