Increased terrestrial methane cycling at the Palaeocene–Eocene thermal maximum

Abstract

The Palaeocene-Eocene thermal maximum (PETM), a period of intense, global warming about 55 million years ago, has been attributed to a rapid rise in greenhouse gas levels, with dissociation of methane hydrates being the most commonly invoked explanation. It has been suggested previously that high-latitude methane emissions from terrestrial environments could have enhanced the warming effect, but direct evidence for an increased methane flux from wetlands is lacking. The Cobham Lignite, a recently characterized expanded lacustrine/mire deposit in England, spans the onset of the PETM and therefore provides an opportunity to examine the biogeochemical response of wetland-type ecosystems at that time. Here we report the occurrence of hopanoids, biomarkers derived from bacteria, in the mire sediments from Cobham. We measure a decrease in the carbon isotope values of the hopanoids at the onset of the PETM interval, which suggests an increase in the methanotroph population. We propose that this reflects an increase in methane production potentially driven by changes to a warmer and wetter climate. Our data suggest that the release of methane from the terrestrial biosphere increased and possibly acted as a positive feedback mechanism to global warming.

Late Paleocene–early Eocene Tethyan carbonate platform evolution — A response to long- and short-term paleoclimatic change

“…The oxidation of organic-rich sediments during the India-Asia collision may also have acted as a driving mechanism for enhanced CO 2 concentrations (Beck et al, 1998;Thomas et al, 2000). Finally, methane release from wetlands and methane dissociation during the PETM and similar subsequent events from sea floor gas hydrate reservoirs are also considered as important contributors for increase in greenhouse gases (Sloan et al, 1992;Pearson and Palmer, 2000;Pancost et al, 2007).…”

Acerca de la biotecnología ambiental

“…Este fenómeno, previsto por Joseph Fourier en 1824, fue descubierto en 1860 por John Tyndall, estudiado cuantitativamente por Svante Arrhenius en 1896 y sacado a la luz pública por Guy Stewart Callendar en 1960, el denominado efecto Callendar, al que en principio achacó un efecto beneficioso y no perjudicial. Los estudios paleoclimáticos han revelado episodios de cambio climático global, el denominado PEMT, aunque lento por ser debido a causas naturales como emisiones de CH 4 acumulado como hidrato en el manto terrestre (Pancost et al, 2007). Por otra parte, el seguimiento del clima desde épocas históricas hasta la actualidad ha revelado que existe una tendencia al aumento de temperatura, relativamente rápido en este caso por ser presuntamente debido a causas antropogénicas (Pla y Catalan, 2005).…”

Geomicrobial functional groups: A window on the interaction between life and environments

“…The greenhouse effect from oxidation of CH 4 released from a tremendous volume of gas hydrate has been proposed widely to have triggered this warm event [161,162], although this hypothesis is rejected by other researchers [163]. Pancost et al [164] identified the bloom of methanotrophic bacteria in wetlands cross the Paleocene-Eocene boundary, indicated by the occurrence of 13 C-depleted hopanes. These studies revealed a potential causal connection among CH 4 -related GFGs, gas hydrate release and the thermal climate, in which GFGs might show positive or negative feedback to climate change by regulating the CH 4 cycle.…”