NDLI: Ocean methane hydrates as a slow tipping point in the global carbon cycle

Content Provider	PubMed Central
Author	Archer, David Buffett, Bruce Brovkin, Victor
Abstract	We present a model of the global methane inventory as hydrate and bubbles below the sea floor. The model predicts the inventory of CH4 in the ocean today to be ≈1600–2,000 Pg of C. Most of the hydrate in the model is in the Pacific, in large part because lower oxygen levels enhance the preservation of organic carbon. Because the oxygen concentration today may be different from the long-term average, the sensitivity of the model to O2 is a source of uncertainty in predicting hydrate inventories. Cold water column temperatures in the high latitudes lead to buildup of hydrates in the Arctic and Antarctic at shallower depths than is possible in low latitudes. A critical bubble volume fraction threshold has been proposed as a critical threshold at which gas migrates all through the sediment column. Our model lacks many factors that lead to heterogeneity in the real hydrate reservoir in the ocean, such as preferential hydrate formation in sandy sediments and subsurface gas migration, and is therefore conservative in its prediction of releasable methane, finding only 35 Pg of C released after 3 °C of uniform warming by using a 10% critical bubble volume. If 2.5% bubble volume is taken as critical, then 940 Pg of C might escape in response to 3 °C warming. This hydrate model embedded into a global climate model predicts ≈0.4–0.5 °C additional warming from the hydrate response to fossil fuel CO2 release, initially because of methane, but persisting through the 10-kyr duration of the simulations because of the CO2 oxidation product of methane.
Related Links	http://dx.doi.org/10.1073/pnas.0800885105
Ending Page	20601
Page Count	6
Starting Page	20596
File Format	PDF
ISSN	00278424
e-ISSN	10916490
Journal	Proceedings of the National Academy of Sciences of the United States of America
Issue Number	49
Volume Number	106
Language	English
Publisher	National Academy of Sciences
Publisher Date	2009-12-08
Access Restriction	Open
Rights Holder	National Academy of Sciences
Subject Keyword	General Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Multidisciplinary

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
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4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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