Dissociation of oceanic methane hydrate as a cause of the carbon isotope excursion at the end of the Paleocene

Isotopic records across the “Latest Paleocene Thermal Maximum“ (LPTM) indicate that bottom water temperature increased by more than 4°C during a brief time interval (<104 years) of the latest Paleocene (∼55.6 Ma). There also was a coeval −2 to −3‰ excursion in the δ13C of the ocean/atmosphere inorganic carbon reservoir. Given the large mass of this reservoir, a rapid δ13C shift of this magnitude is difficult to explain within the context of conventional hypotheses for changing the mean carbon isotope composition of the ocean and atmosphere. However, a direct consequence of warming bottom water temperature from 11 to 15°C over 104 years would be a significant change in sediment thermal gradients and dissociation of oceanic CH4 hydrate at locations with intermediate water depths. In terms of the present-day oceanic CH4 hydrate reservoir, thermal dissociation of oceanic CH4 hydrate during the LPTM could have released greater than 1.1 to 2.1 × 1018 g of carbon with a δ13C of approximately −60‰. The release and subsequent oxidation of this amount of carbon is sufficient to explain a −2 to −3‰ excursion in δ13C across the LPTM. Fate of CH4 in oceanic hydrates must be considered in developing models of the climatic and paleoceanographic regimes that operated during the LPTM.

[1]  R. Corfield.  Palaeocene oceans and climate: An isotopic perspective , 1994 .

[2]  G. Dickens,et al.  Methane hydrate stability in seawater , 1994 .

[3]  K. Kaiho.  Planktonic and benthic foraminiferal extinction events during the last 100 m.y , 1994 .

[4]  I. Fung,et al.  Potential distribution of methane hydrates in the world's oceans , 1994 .

[5]  J. Brooks,et al.  Gas hydrate that breaches the sea floor on the continental slope of the Gulf of Mexico , 1994 .

[6]  J. Zachos,et al.  Evolution of Early Cenozoic marine temperatures , 1994 .

[7]  M. Rowe,et al.  Faulted Structure of the Bottom Simulating Reflector on the Blake Ridge, Western North Atlantic , 1993 .

[8]  Youxue Zhang,et al.  Distribution and evolution of carbon and nitrogen in Earth , 1993 .

[9]  W. Broecker,et al.  A search for an early Holocene CaCO3 preservation event , 1993 .

[10]  Ellen Thomas,et al.  Environmental impact of volcanic margin formation , 1993 .

[11]  M. Lilley,et al.  Methane oxidation in deep-sea hydrothermal plumes of the endeavour segment of the Juan de Fuca Ridge , 1993 .

[12]  K. Kvenvolden.  Gas hydrates—geological perspective and global change , 1993 .

[13]  G. Keller,et al.  The Paleocene-Eocene transition in the Antarctic Indian Ocean: Inference from planktic foraminifera , 1993 .

[14]  J. Zachos,et al.  Abrupt Climate Change and Transient Climates during the Paleogene: A Marine Perspective , 1993, The Journal of Geology.

[15]  K. Miller,et al.  Paleocene to Eocene benthic foraminiferal isotopes and assemblages: Implications for deepwater circulation , 1992 .

[16]  P. Gingerich,et al.  Correlation between isotope records in marine and continental carbon reservoirs near the Palaeocene/Eocene boundary , 1992, Nature.

[17]  J. Cartlidge,et al.  Oceanographic and climatic implications of the Palaeocene carbon isotope maximum , 1992 .

[18]  R. Larson.  Geological consequences of superplumes , 1991 .

[19]  J. P. Kennett,et al.  Abrupt deep-sea warming, palaeoceanographic changes and benthic extinctions at the end of the Palaeocene , 1991, Nature.

[20]  W. Dillon,et al.  Is the extent of glaciation limited by marine gas-hydrates , 1991 .

[21]  G. MacDonald.  Role of methane clathrates in past and future climates , 1990 .

[22]  K. Louden,et al.  CRC Handbook of Seafloor Heat Flow , 1988 .

[23]  K. Kvenvolden.  Methane hydrate — A major reservoir of carbon in the shallow geosphere? , 1988 .

[24]  K. Miller,et al.  Abyssal circulation and benthic foraminiferal changes near the Paleocene/Eocene boundary , 1987 .

[25]  P. Novelli,et al.  Methane oxidation and methane fluxes in the ocean surface layer and deep anoxic waters , 1987, Nature.

[26]  R. Fairbanks,et al.  Tertiary oxygen isotope synthesis, sea level history, and continental margin erosion , 1987 .

[27]  S. Leavitt.  Annual volcanic carbon dioxide emission: An estimate from eruption chronologies , 1982 .

[28]  J. Wright,et al.  The measurement of marine geothermal heat flow by a multipenetration probe with digital acoustic telemetry and insitu thermal conductivity , 1979 .

[29]  U. Siegenthaler.  Modelling the Present-Day Oceanic Carbon Cycle , 1993 .

[30]  W. Broecker,et al.  What Caused the Glacial to Interglacial CO2 Change , 1993 .

[31]  M. Khalil,et al.  Methane Sinks Distribution , 1993 .

[32]  M. Shearer,et al.  Sources of Methane: An Overview , 1993 .

[33]  E. Nisbet.  The end of the ice age , 1990 .

[34]  C. Gregor.  Chemical cycles in the evolution of the earth , 1988 .

[35]  N. Shackleton.  Carbon-13 in Uvigerina: Tropical Rainforest History and the Equatorial Pacific Carbonate Dissolution Cycles , 1977 .