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Volume 11, issue 4 | Copyright
Clim. Past, 11, 669-685, 2015
https://doi.org/10.5194/cp-11-669-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 17 Apr 2015

Research article | 17 Apr 2015

Carbon isotope (δ13C) excursions suggest times of major methane release during the last 14 kyr in Fram Strait, the deep-water gateway to the Arctic

C. Consolaro1,2, T. L. Rasmussen1, G. Panieri1, J. Mienert1, S. Bünz1, and K. Sztybor1 C. Consolaro et al.
  • 1CAGE – Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geology, UiT the Arctic University of Norway, Dramsveien 201, 9037 Tromsø, Norway
  • 2School of Geography, Earth & Environmental Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK

Abstract. We present results from a sediment core collected from a pockmark field on the Vestnesa Ridge (~ 80° N) in the eastern Fram Strait. This is the only deep-water gateway to the Arctic, and one of the northernmost marine gas hydrate provinces in the world. Eight 14C AMS dates reveal a detailed chronology for the last 14 ka BP. The δ 13C record measured on the benthonic foraminiferal species Cassidulina neoteretis shows two distinct intervals with negative values termed carbon isotope excursion (CIE I and CIE II, respectively). The values were as low as −4.37‰ in CIE I, correlating with the Bølling–Allerød interstadials, and as low as −3.41‰ in CIE II, correlating with the early Holocene. In the Bølling–Allerød interstadials, the planktonic foraminifera also show negative values, probably indicating secondary methane-derived authigenic precipitation affecting the foraminiferal shells. After a cleaning procedure designed to remove authigenic carbonate coatings on benthonic foraminiferal tests from this event, the 13C values are still negative (as low as −2.75‰). The CIE I and CIE II occurred during periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere. CIEs with similar timing have been reported from other areas in the North Atlantic, suggesting a regional event. The trigger mechanisms for such regional events remain to be determined. We speculate that sea-level rise and seabed loading due to high sediment supply in combination with increased seismic activity as a result of rapid deglaciation may have triggered the escape of significant amounts of methane to the seafloor and the water column above.

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A sediment core collected from a pockmark field on the Vestnesa Ridge (~80N) in the Fram Strait is presented. Our results show an undisturbed sedimentary record for the last 14 ka BP and negative carbon isotope excursions (CIEs) during the Bølling-Allerød interstadials and during the early Holocene. Both CIEs relate to periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere, suggesting an apparent correlation with warm climatic events.
A sediment core collected from a pockmark field on the Vestnesa Ridge (~80N) in the Fram Strait...
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