Remote-sensing evaluation of geophysical anomaly sites in the outer continental slope, northern Gulf of Mexico

Garcia-Pineda, Oscar; MacDonald, Ian R.; Zimmer, B.; Shedd, Bill; Roberts, Harry H.

doi:10.1016/j.dsr2.2010.05.005

Cited by 73 publications

(78 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We suspect that this crude oil was derived from active seeps in the vicinity of the Seep site trap and was scavenged during its ascent by sinking marine snow. As seep activity fluctuates in time (Garcia-Pineda et al, 2010, seepage is temporally and spatially very heterogeneous. Heterogeneous seepage combined with strongly variable small scale currents (Diercks et al, 2017) likely cause irregular advection of hydrocarbon-enriched waters and explain the intermittent nature of these crude-oil flux periods.…”

Section: Effect Of Seepage On Particle Fluxmentioning

confidence: 99%

The ecosystem baseline for particle flux in the Northern Gulf of Mexico

Giering¹,

Yan

Sweet

et al. 2018

Elementa: Science of the Anthropocene

View full text Add to dashboard Cite

Response management and damage assessment during and after environmental disasters such as the Deepwater Horizon (DWH) oil spill require an ecological baseline and a solid understanding of the main drivers of the ecosystem. During the DWH event, a large fraction of the spilled oil was transported to depth via sinking marine snow, a routing of spilled oil unexpected to emergency response planners. Because baseline knowledge of particle export in the Northern Gulf of Mexico and how it varies spatially and temporally was limited, we conducted a detailed assessment of the potential drivers of deep (~1400 m depth) particle fluxes during 2012-2016 using sediment traps at three contrasting sites in the Northern Gulf of Mexico: near the DWH site, at an active natural oil seep site, and at a site considered typical for background conditions. The DWH site, located ~70 km from the Mississippi River Delta, showed flux patterns that were strongly linked to the Mississippi nitrogen discharge and an annual subsequent surface bloom. Fluxes carried clear signals of combustion products, which likely originated from pyrogenic sources that were transported offshore via the Mississippi plume. The seep and reference sites were more strongly influenced by the open Gulf of Mexico, did not show a clear seasonal flux pattern, and their overall sedimentation rates were lower than those at the DWH site. At the seep site, based on polycyclic aromatic hydrocarbon data, we observed indications of three different pathways for "natural" oiled-snow sedimentation: scavenging by sinking particles at depth, weathering at the surface before incorporation into sinking particles, and entry into the food web and subsequent sinking in form of detritus. Overall, sedimentation rates at the three sites were markedly different in quality and quantity owing to varying degrees of riverine and oceanic influences, including natural seepage and contamination by combustion products.

show abstract

Section: Effect Of Seepage On Particle Fluxmentioning

confidence: 99%

The ecosystem baseline for particle flux in the Northern Gulf of Mexico

Giering¹,

Yan

Sweet

et al. 2018

Elementa: Science of the Anthropocene

View full text Add to dashboard Cite

show abstract

“…However, the lack of sea level verification of algorithm results has constrained opportunities for spill classification. For example, natural oil seeps reliably generate layers of floating oil useful for testing the effectiveness of algorithms, but their low discharge rates do not produce very thick oil-emulsion layers (De Beukelaer et al, 2003;Garcia-Pineda et al, 2010). Tanker spills often produce (Jernelöv and Lindén, 1981) or the Exxon Valdez spill in Alaska (Xia and Boufadel, 2010).…”

Section: Resolution Imaging Spectroradiometer (Modis) and Medium Resomentioning

confidence: 99%

Detection of Floating Oil Anomalies From the Deepwater Horizon Oil Spill With Synthetic Aperture Radar

Garcia-Pineda¹,

MacDonald²,

Hu³

et al. 2013

oceanog

Self Cite

107

View full text Add to dashboard Cite

show abstract

“…The texture of the image was then examined in order to estimate the wind conditions present during the time of the collection of radar data and to make a judgment whether an image had been collected under sea-state conditions that were compliant with detection of floating oil layers. Based on previous experience, oil layers can be detected in SAR images when wind speeds were between 2 and 10 m/s [Garcia-Pineda et al, 2010]. For wind speeds higher than this range, the layers of oil tended to fragment and disappear into the heightened backscatter caused by chop and rough seas.…”

Section: Image Data and Processingmentioning

confidence: 99%

“…Geophysical anomalies generated by seeps in the geologic past exceed 5000 possible sites [Frye, 2008] whereas preliminary results for seeps detected by remote sensing (see the detailed method in [Garcia-Pineda et al, 2010]) suggest a maximum number of active vents at about 1500. Assuming that each of the 1500 -5000 seeps in the northern Gulf of Mexico has a daily net sea-to-air flux of 300 mol d -1 , and they persistently emit methane to the atmosphere at the same rate over a one-year period, the total diffusive net sea-to-air flux from deepwater hydrocarbon seeps in the northern Gulf of Mexico is about 3 -9 Gg yr -1 .…”

Section: And 46)mentioning

confidence: 99%

See 1 more Smart Citation

Remote Sensing and Sea-Truth Measurements of Methane Flux to the Atmosphere (HYFLUX project)

MacDonald¹

2011

View full text Add to dashboard Cite

A multi-disciplinary investigation of distribution and magnitude of methane fluxes from seafloor gas hydrate deposits in the Gulf of Mexico was conducted based on results obtained from satellite synthetic aperture radar (SAR) remote sensing and from sampling conducted during a research expedition to three sites where gas hydrate occurs (MC118, GC600, and GC185). Samples of sediments, water, and air were collected from the ship and from an ROV submersible using sediments cores, niskin bottles attached to the ROV and to a rosette, and an automated sea-air interface collector.The SAR images were used to quantify the magnitude and distribution of natural oil and gas seeps that produced perennial oil slicks on the ocean surface. A total of 176 SAR images were processed using a texture classifying neural network algorithm, which segmented the ocean surface into oil-free and oilcovered water. Geostatistical analysis indicates that there are a total of 1081 seep formations distributed over the entire Gulf of Mexico basin. Oil-covered water comprised an average of 780.0 sq. km (sd 86.03) distributed with an area of 147,370 sq. km. Persistent oil and gas seeps were also detected with SAR sampling on other ocean margins located in the Black Sea, western coast of Africa, and offshore Pakistan.Analysis of sediment cores from all three sites show profiles of sulfate, sulfide, calcium and alkalinity that indicated anaerobic oxidation of methane with precipitation of authigenic carbonates. Difference among the three sampling sites may reflect the relative magnitude of methane flux.Methane concentrations in water column samples collected by ROV and rosette deployments from MC118 ranged from ~33,000 nM at the seafloor to ~12 nM in the mixed layer with isolated peaks up to ~13,670 nM coincident with the top of the gas hydrate stability field. Average plume methane, ethane, and propane concentrations in the mixed layer are 7, 630, and 9,540 times saturation, respectively. Based on the contemporaneous wind speeds at this site, contemporary estimates of the diffusive fluxes from the mixed layer to the atmosphere for methane, ethane, and propane are 26.5, 2.10, and 2.78 µmol/m 2 d, respectively.Continuous measurements of air and sea surface concentrations of methane were made to obtain high spatial and temporal resolution of the diffusive net sea-to-air fluxes. The atmospheric methane fluctuated between 1.70 ppm and 2.40 ppm during the entire cruise except for high concentrations (up to 4.01 ppm) sampled during the end of the occupation of GC600 and the transit between GC600 and GC185. Results from interpolations within the survey areas show the daily methane fluxes to the atmosphere at the three sites range from 0.744 to 300 mol d-1.Considering that the majority of seeps in the GOM are deep (>500 m), elevated CH 4 concentrations in near-surface waters resulting from bubble-mediated CH 4 transport in the water column are expected to be widespread in the Gulf of Mexico. HYFLUX Final Report iiTexas A&M University -Corpus Christi...

show abstract

Remote-sensing evaluation of geophysical anomaly sites in the outer continental slope, northern Gulf of Mexico

Cited by 73 publications

References 16 publications

The ecosystem baseline for particle flux in the Northern Gulf of Mexico

The ecosystem baseline for particle flux in the Northern Gulf of Mexico

Detection of Floating Oil Anomalies From the Deepwater Horizon Oil Spill With Synthetic Aperture Radar

Remote Sensing and Sea-Truth Measurements of Methane Flux to the Atmosphere (HYFLUX project)

Contact Info

Product

Resources

About