Automated gas bubble imaging at sea floor – a new method of in situ gas flux quantification

Thomanek, K.; Sahling, Heiko; Bohrmann, Gerhard

doi:10.5194/osd-7-291-2010

Cited by 7 publications

(3 citation statements)

References 33 publications

(14 reference statements)

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“…For the size evaluation, we calculated equivalent spherical bubble diameter using ellipse fitting [ Leifer and MacDonald , ] and area equivalence [ Thomanek et al ., ] approaches. Statistically, both approaches provided consistent result in estimating bubble size, but the equivalent bubble diameter computed using ellipse fitting was systematically lower than that computed with the area equivalence method (with ratio of 0.93:1 for our data) [see Wang and Socolofsky , ].…”

Section: Methodsmentioning

confidence: 99%

Observations of bubbles in natural seep flares at MC 118 and GC 600 using in situ quantitative imaging

et al. 2016

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This paper reports the results of quantitative imaging using a stereoscopic, high‐speed camera system at two natural gas seep sites in the northern Gulf of Mexico during the Gulf Integrated Spill Research G07 cruise in July 2014. The cruise was conducted on the E/V Nautilus using the ROV Hercules for in situ observation of the seeps as surrogates for the behavior of hydrocarbon bubbles in subsea blowouts. The seeps originated between 890 and 1190 m depth in Mississippi Canyon block 118 and Green Canyon block 600. The imaging system provided qualitative assessment of bubble behavior (e.g., breakup and coalescence) and verified the formation of clathrate hydrate skins on all bubbles above 1.3 m altitude. Quantitative image analysis yielded the bubble size distributions, rise velocity, total gas flux, and void fraction, with most measurements conducted from the seafloor to an altitude of 200 m. Bubble size distributions fit well to lognormal distributions, with median bubble sizes between 3 and 4.5 mm. Measurements of rise velocity fluctuated between two ranges: fast‐rising bubbles following helical‐type trajectories and bubbles rising about 40% slower following a zig‐zag pattern. Rise speed was uncorrelated with hydrate formation, and bubbles following both speeds were observed at both sites. Ship‐mounted multibeam sonar provided the flare rise heights, which corresponded closely with the boundary of the hydrate stability zone for the measured gas compositions. The evolution of bubble size with height agreed well with mass transfer rates predicted by equations for dirty bubbles.

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Section: Methodsmentioning

confidence: 99%

Observations of bubbles in natural seep flares at MC 118 and GC 600 using in situ quantitative imaging

et al. 2016

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“…Using a fast lens, which means a high aperture, is not a solution, because this lowers the depth of field and leads to potentially defocused images. To overcome this problems, so called bubble boxes have been developed (Thomanek et al, 2010). A bubble box as shown in Figure 1 includes a camera, channeling elements to concentrate the bubbles in the cameras depth of focus, and a backlight illumination.…”

Section: Introductionmentioning

confidence: 99%

Blind Deconvolution on Underwater Images for Gas Bubble Measurement

Zelenka

Koch

2015

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:Marine gas seeps, such as in the Panarea area near Sicily (McGinnis et al., 2011), emit large amounts of methane and carbon-dioxide, greenhouse gases. Better understanding their impact on the climate and the marine environment requires precise measurements of the gas flux. Camera based bubble measurement systems suffer from defocus blur caused by a combination of small depth of field, insufficient lighting and from motion blur due to rapid bubble movement. These adverse conditions are typical for open sea underwater bubble images. As a consequence so called 'bubble boxes' have been built, which use elaborate setups, specialized cameras and high power illumination. A typical value of light power used is 1000W (Leifer et al., 2003). In this paper we propose the compensation of defocus and motion blur in underwater images by using blind deconvolution techniques. The quality of the images can be greatly improved, which will relax requirements on bubble boxes, reduce their energy consumption and widen their usability.

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“…-27-Texas A&M University -Corpus Christi Hydrocarbon fluid seepage has been detected in the thrust faulting regime generated in the Makran subduction zone offshore Pakistan [Ding et al, 2010b] and active gas venting was observed in depths of 1020 m [Thomanek et al, 2010]. The HYFLUX project examined the archive of SAR images with the goal of determining whether the SAR technique of detecting potential gas hydrate bearing areas would be effective on a geologically active margin.…”

Section: Hyflux Final Reportmentioning

confidence: 99%

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

MacDonald¹

2011

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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...

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Automated gas bubble imaging at sea floor – a new method of in situ gas flux quantification

Cited by 7 publications

References 33 publications

Observations of bubbles in natural seep flares at MC 118 and GC 600 using in situ quantitative imaging

Observations of bubbles in natural seep flares at MC 118 and GC 600 using in situ quantitative imaging

Blind Deconvolution on Underwater Images for Gas Bubble Measurement

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

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