Gas escape features off New Zealand: Evidence of massive release of methane from hydrates

Davy, Bryan; Pecher, Ingo; Wood, Ray; Carter, Lionel; Gohl, Karsten

doi:10.1029/2010gl045184

Cited by 66 publications

(93 citation statements)

References 31 publications

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“…Such a steep slope could result from strong contour currents but, as we discuss below, physical oceanographic measurements do not offer convincing evidence of strong present-day currents. We show that west of where Davy et al (2010) noted a steep slope, a trough with a steep slope on its north side closely follows the c. 1200 m contour and seems to result from erosion by a contour current, which we presume to flow eastwards.…”

Section: Pockmarksmentioning

confidence: 96%

“…Judd & Hovland 2007;Pilcher & Argent 2007). Recently, Davy et al (2010) recognised pockmarked seafloor topography near the Urry Knolls on Chatham Rise (Figs. 1, 3) from the similarity of their topographic signatures on a few multibeam swaths and high-resolution sub-bottom profiles to pockmarks recognised elsewhere.…”

Section: Pockmarksmentioning

confidence: 99%

“…Deep submarine erosion on the Chatham Rise Davy et al (2010) noted that the pockmarks on the Chatham Rise seem to be confined to seafloor shallower than c. 1200 m, where the south side of the Rise is bounded by a steep slope. Such a steep slope could result from strong contour currents but, as we discuss below, physical oceanographic measurements do not offer convincing evidence of strong present-day currents.…”

Section: Pockmarksmentioning

confidence: 99%

“…Loncke et al 2004;Pilcher & Argent 2007;Davy et al 2010). Hovland & Judd (1988, p. 116) stated that there is no dependence of pockmark size on water depths.…”

Section: Submarine Volcanoes Near the Urry Knollsmentioning

confidence: 99%

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Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Collins

Molnár

Sheehan

2011

New Zealand Journal of Geology and Geophysics

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Multibeam bathymetric surveys east of the South Island of New Zealand yield images of submarine volcanoes and pockmarks west of Urry Knolls on the Chatham Rise, and evidence of submarine erosion on the southern margin of the Chatham Rise. Among numerous volcanic cones, diameters of the largest reach c. 2000 m, and some stand as high as 400 m above the surrounding seafloor. The tops of most of the volcanic cones are flat, with hints of craters, and some with asymmetric shapes may show flank collapses. There are hints of both northeastÁsouthwest and northwestÁsoutheast alignments of volcanoes, but no associated faulting is apparent. Near and to the west of these volcanoes, huge pockmarks, some more than c. 1 km in diameter, disrupt bottom topography. Pockmarks in this region seem to be confined to seafloor shallower than c. 1200 m, but we see evidence of deeper pockmarks at water depths of up to 2100 m on profiles crossing the Bounty Trough. The pockmark field on the Chatham Rise seems to be bounded on the south by a trough at almost 1200 m depth; like others, we assume that contour currents have eroded the margin and created the trough.

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Section: Pockmarksmentioning

confidence: 96%

Section: Pockmarksmentioning

confidence: 99%

Section: Pockmarksmentioning

confidence: 99%

“…Loncke et al 2004;Pilcher & Argent 2007;Davy et al 2010). Hovland & Judd (1988, p. 116) stated that there is no dependence of pockmark size on water depths.…”

Section: Submarine Volcanoes Near the Urry Knollsmentioning

confidence: 99%

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Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Collins

Molnár

Sheehan

2011

New Zealand Journal of Geology and Geophysics

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“…Since its main sink, tropospheric OH, has negligible long-term change, this implies a stabilisation of the emissions (Forster et al, 2007). However, a flare-up of the methane concentration was observed recently (Schneising et al, 2011) and concern by climate feedback effects in a warmer atmosphere has risen (Heimann, 2010;Davy et al, 2010).…”

mentioning

confidence: 99%

Sensitivity studies for a space-based methane lidar mission

et al. 2011

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Abstract.Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modestsize lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1 % over vegetation. The use of a methane absorption trough at 1.65 µm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, keyCorrespondence to: C. Kiemle (christoph.kiemle@dlr.de) regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised.

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Shallow methane hydrate system controls ongoing, downslope sediment transport in a low‐velocity active submarine landslide complex, Hikurangi Margin, New Zealand

Mountjoy

Pecher

Henrys

et al. 2014

Geochem Geophys Geosyst

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Morphological and seismic data from a submarine landslide complex east of New Zealand indicate flow-like deformation within gas hydrate-bearing sediment. This ''creeping'' deformation occurs immediately downslope of where the base of gas hydrate stability reaches the seafloor, suggesting involvement of gas hydrates. We present evidence that, contrary to conventional views, gas hydrates can directly destabilize the seafloor. Three mechanisms could explain how the shallow gas hydrate system could control these landslides. (1) Gas hydrate dissociation could result in excess pore pressure within the upper reaches of the landslide. (2) Overpressure below low-permeability gas hydrate-bearing sediments could cause hydrofracturing in the gas hydrate zone valving excess pore pressure into the landslide body. (3) Gas hydrate-bearing sediment could exhibit time-dependent plastic deformation enabling glacial-style deformation. We favor the final hypothesis that the landslides are actually creeping seafloor glaciers. The viability of rheologically controlled deformation of a hydrate sediment mix is supported by recent laboratory observations of time-dependent deformation behavior of gas hydrate-bearing sands. The controlling hydrate is likely to be strongly dependent on formation controls and intersediment hydrate morphology. Our results constitute a paradigm shift for evaluating the effect of gas hydrates on seafloor strength which, given the widespread occurrence of gas hydrates in the submarine environment, may require a reevaluation of slope stability following future climate-forced variation in bottom-water temperature.

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Gas escape features off New Zealand: Evidence of massive release of methane from hydrates

Cited by 66 publications

References 31 publications

Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Multibeam bathymetric surveys of submarine volcanoes and mega-pockmarks on the Chatham Rise, New Zealand

Sensitivity studies for a space-based methane lidar mission

Shallow methane hydrate system controls ongoing, downslope sediment transport in a low‐velocity active submarine landslide complex, Hikurangi Margin, New Zealand

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