Spatial variation in shallow sediment methane sources and cycling on the Alaskan Beaufort Sea Shelf/Slope

Coffin, Richard B.; Smith, Joseph P.; Plummer, Rebecca E.; Yoza, Brandon A.; Larsen, Randolph K.; Millholland, L. C.; Montgomery, Michael T.

doi:10.1016/j.marpetgeo.2013.05.002

Cited by 39 publications

(81 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Of particular interest to this study are locations in the Beaufort Sea, where indications for gas hydrate manifest on seismic profiles (Grantz et al, 1976(Grantz et al, , 1982Weaver and Stewart, 1982;Hart et al, 2011;Phrampus et al, 2014), and pore water profiles have been generated using shallow piston cores (Coffin et al, 2013). Striking contrasts exist between pore water profiles of the Beaufort Sea and those of SNESS (Table 2).…”

Section: General Absence Of Methanementioning

confidence: 98%

“…Ryan et al, 2009). Observed sulfatemethane transitions during the MITAS 1 expedition shown in black diamonds (Coffin et al, 2013) and Arctic Coring Expedition (ACEX) shown as red squares (Backman and Moran, 2009). …”

Section: East Siberian Margin Geologymentioning

confidence: 99%

“…Where CH 4 fluxes toward the seafloor are high, the SMT is located at shallow depth. For example, in cores from the continental shelf and slope of the Beaufort Sea, where seismic profiles indicate gas hydrate, Coffin et al (2008Coffin et al ( , 2013 have documented SMTs in shallow sediment (< 10 mbsf).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Pore water geochemistry along continental slopes north of the East Siberian Sea: inference of low methane concentrations

et al. 2017

View full text Add to dashboard Cite

Abstract. Continental slopes north of the East Siberian Sea potentially hold large amounts of methane (CH 4 ) in sediments as gas hydrate and free gas. Although release of this CH 4 to the ocean and atmosphere has become a topic of discussion, the region remains sparingly explored. Here we present pore water chemistry results from 32 sediment cores taken during Leg 2 of the 2014 joint Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions (SWERUS-C3) expedition. The cores come from depth transects across the slope and rise extending between the Mendeleev and the Lomonosov ridges, north of Wrangel Island and the New Siberian Islands, respectively. Upward CH 4 flux towards the seafloor, as inferred from profiles of dissolved sulfate (SO 2− 4 ), alkalinity, and the δ 13 C of dissolved inorganic carbon (DIC), is negligible at all stations east of 143 • E longitude. In the upper 8 m of these cores, downward SO 2− 4 flux never exceeds 6.2 mol m −2 kyr −1 , the upward alkalinity flux never exceeds 6.8 mol m −2 kyr −1 , and δ 13 C composition of DIC (δ 13 C-DIC) only moderately decreases with depth (−3.6 ‰ m −1 on average). Moreover, upon addition of Zn acetate to pore water samples, ZnS did not precipitate, indicating a lack of dissolved H 2 S. Phosphate, ammonium, and metal profiles reveal that metal oxide reduction by organic carbon dominates the geochemical environment and supports very low organic carbon turnover rates. A single core on the Lomonosov Ridge differs, as diffusive fluxes for SO 2− 4 and alkalinity were 13.9 and 11.3 mol m −2 kyr −1 , respectively, the δ 13 C-DIC gradient was 5.6 ‰ m −1 , and Mn 2+ reduction terminated within 1.3 m of the seafloor. These are among the first pore water results generated from this vast climatically sensitive region, and they imply that abundant CH 4 , including gas hydrates, do not characterize the East Siberian Sea slope or rise along the investigated depth transects. This contradicts previous modeling and discussions, which due to the lack of data are almost entirely based on assumption.

show abstract

Section: General Absence Of Methanementioning

confidence: 98%

Section: East Siberian Margin Geologymentioning

confidence: 99%

See 1 more Smart Citation

Pore water geochemistry along continental slopes north of the East Siberian Sea: inference of low methane concentrations

et al. 2017

View full text Add to dashboard Cite

show abstract

“…In some systems, however, there may be a departure from this balance due to natural and/or anthropogenic influences. For example, regional climate change in the Arctic has led to significant changes of OM cycling in shelf sediments and changes in the inputs of tundra-derived, permafrost-derived, and shallow hydrate-derived carbon [20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Spatial Variation in Sediment Organic Carbon Distribution across the Alaskan Beaufort Sea Shelf

et al. 2017

Self Cite

View full text Add to dashboard Cite

Abstract:In September 2009, a series of sediment cores were collected across the Alaskan Beaufort Sea shelf-slope. Sediment and porewater organic carbon (OC) concentrations and stable carbon isotope ratios (δ 13 C) were measured to investigate spatial variations in sediment organic matter (OM) sources and distribution of these materials across the shelf. Cores were collected along three main nearshore (shelf) to offshore (slope) sampling lines (transects) from east-to-west along the North Slope of Alaska: Hammerhead (near Camden Bay), Thetis Island (near Prudhoe Bay), and Cape Halkett (towards Point Barrow). Measured sediment organic carbon (TOC) and porewater dissolved organic carbon (DOC) concentrations and their respective δ 13 C values were used to investigate the relative contribution of different OM sources to sediment OC pool cycled at each location. Sources of OM considered included: water column-sourced phytodetritus, deep sediment methane (CH 4 ), and terrestrial, tundra/river-sourced OM. Results of these measurements, when coupled with results from previous research and additional analyses of sediment and porewater composition, show a pattern of spatial variation in sediment OC concentrations, OM source contributions, and OM cycled along the Alaskan Beaufort Sea shelf. In general, measured sediment total organic carbon (TOC) concentrations, δ 13 C TOC values, porewater DOC concentrations, and δ 13 C DOC values are consistent with an east-to-west transport of modern Holocene sediments with higher OC concentrations primarily sourced from relatively labile terrestrial, tundra OM sources and phytodetritus along the Alaskan Beaufort shelf. Sediment transport along the shelf results in the medium-to-long term accumulation and burial of sediment OM focused to the west which in turn results in higher biogenic CH 4 production rates and higher upward CH 4 diffusion through the sediments resulting in CH 4 − AMO-sourced contribution to sediment OC westward along the shelf. Understanding current OM sources and distributions along the Alaskan Beaufort shelf is important for enhancing models of carbon cycling in Arctic coastal shelf systems. This will help support the prediction of the climate response of the Arctic created in the face of future warming scenarios.

show abstract

“…Vast reserves of methane hydrate, a crystalline form of methane-water complex (molar ratio 1:6) exist within the marine sediments at suitable temperature-pressure conditions subject to the availability of methane in excess of solubility (Kvenvolden, 1993;Sloan, 1998;Kvenvolden and Lorenson, 2001). Whereas, methane from shallow sub-seafloor (Hovland and Judd, 1992;Mazumdar et al, 2009a;Coffin et al, 2013) are additional sources of marine methane to the global budget.The terrestrial sources influencing the global methane budget include volcanic eruptions, natural wetlands, rice and paddy fields, enteric fermentation, coal mining, biomass burning, soil microseepage, geothermal activity (Chanton and Whiting, 1996;Judd et al, 2002;Kaplan, 2002;Etiope et al, 2008;Sanchez Goni et al, 2008) and ebullition from thermokarst lakes (Walter et al, 2006). Carbon stable isotope ratios of foraminifera (Kennett and Stott, 1991;Kennett et al, 2000;Kennett et al, 2003;De Garidel-Thoron et al, 2004;Hill et al, 2004a;Uchida et al, 2004;Cook et al, 2011) as well as measurement of methane concentrations in the Greenland and Antarctic ice deposits (Chappellaz et al,1997;Dällenbach et al,2000;Wolf and Spahni, 2007) suggest repeated enrichment of methane concentrations in the ocean-atmosphere system.…”

Section: Introductionmentioning

confidence: 99%

Gas hydrate destabilization and methane release events in the Krishna–Godavari Basin, Bay of Bengal

Joshi¹,

Mazumdar²,

Peketi³

et al. 2014

Marine and Petroleum Geology

View full text Add to dashboard Cite

Methane release events have been linked to global warming, alteration of the carbon cycle and influence on biota. However, unequivocal evidence of paleomethane release events are limited. We report several negative carbon stable isotope excursions in planktic and benthic foraminifera in a core (MD161-8) from the Krishna-Godavari (K-G) Basin, Bay of Bengal. The most negative δ 13 C spikes are recorded during the marine isotope stages MIS-4 and at the transition of MIS-5 to 4. Occurrence of highly 13 C depleted (average δ 13 C = -48±2.4 ‰ VPDB) authigenic high magnesian calcite are also reported within this time window from the core MD161-8. In the present work an unequivocal explanation for the observed 13 C depletion in the marine planktic and benthic foraminifera is difficult to achieve solely from the optical/ electron microscopy or C-O stable isotope ratio analyses due to possible influence of diagenetic alteration. We attribute the observed episodic methane expulsion events, as inferred from the negative δ 13 C excursions and earlier reports on the occurrence chemosynthetic bivalves and Mo concentration anomaly to the destabilization of the base of gas hydrate stability zone (BGHSZ). Sea level drop and shale tectonics induced focused fluid flow are the two possible causes of hydrate destabilization discussed here. Shale tectonics were possibly responsible for creating fault systems which acted as the conduit for gas flow through the sediment column and subsequent seepage. Shale and salt tectonics in the passive continental margins being a globally observed phenomenon, its role as an important driving force for enhanced methane emission needs detailed investigation to understand the climatic perturbations through geologic time. Additional evidence of methane emission from site MD161-15 further supports the link between shale tectonics and methane emission.

show abstract

Spatial variation in shallow sediment methane sources and cycling on the Alaskan Beaufort Sea Shelf/Slope

Cited by 39 publications

References 62 publications

Pore water geochemistry along continental slopes north of the East Siberian Sea: inference of low methane concentrations

Pore water geochemistry along continental slopes north of the East Siberian Sea: inference of low methane concentrations

Spatial Variation in Sediment Organic Carbon Distribution across the Alaskan Beaufort Sea Shelf

Gas hydrate destabilization and methane release events in the Krishna–Godavari Basin, Bay of Bengal

Contact Info

Product

Resources

About