Carbon isotopic evidence for rapid methane clathrate release recorded in coals at the terminus of the Late Palaeozoic Ice Age

Abstract

The end of the Late Palaeozoic Ice Age (LPIA) ushered in a period of significant change in Earth’s carbon cycle, demonstrated by the widespread occurrence of coals worldwide. In this study, we present stratigraphically constrained organic stable carbon isotope (δ13Corg) data for Early Permian coals (312 vitrain samples) from the Moatize Basin, Mozambique, which record the transition from global icehouse to greenhouse conditions. These coals exhibit a three-stage evolution in atmospheric δ13C from the Artinskian to the Kungurian. Early Kungurian coals effectively record the presence of the short-lived Kungurian Carbon Isotopic Excursion (KCIE), associated with the proposed rapid release of methane clathrates during deglaciation at the terminus of the Late Palaeozoic Ice Age (LPIA), with no observed disruption to peat-forming and terrestrial plant communities. δ13Corg variations in coals from the Moatize Basin are cyclic in nature on the order of 103–105 years and reflect changes in δ13Corg of ~±1‰ during periods of stable peat accumulation, supporting observations from Palaeozoic coals elsewhere. These cyclic variations express palaeoenvironmental factors constraining peat growth and deposition, associated with changes in base level. This study also demonstrates the effectiveness of vitrain in coal as a geochemical tool for recording global atmospheric change during the Late Palaeozoic.

Sustained and intensified lacustrine methane cycling during Early Permian climate warming

“…In addition to the contribution of CO 2 (refs. [15][16][17] and potential methane clathrate release 55 , our results suggest that the injection of the terrestrial greenhouse gas CH 4 into the atmosphere may have facilitated the demise of the LPIA and played a direct role in forcing the turnover from a long-lived icehouse to a greenhouse world.…”

Parametric Study of Prompt Methane Release Impacts III: AOGCM Results Which Respect Historical PIOMAS Measurements

“…Although controversy exists, shallow continental shelf methane releases from a seasonally ice-free Arctic ocean have been measured. [8][9][10][11][12] The potential impacts of a sudden methane burst were applied to the results already presented, using an offline method -that is, not included in the sources/dynamics/feedbacks of the model itself. Instead, the model results are adjusted after-the-fact, based on previously-modeled methane-induced Arctic ocean-basin surface air temperature increases (Figure 8).…”

Parametric Study of Prompt Methane Release Impacts III: AOGCM Results Which Respect Historical PIOMAS Measurements

“…Although controversy exists, rapid methane releases from shallow continental-shelf methane clathrates in a seasonally ice-free Arctic ocean are of concern, and some have been measured. [8][9][10][11][12] Arctic permafrost-capped natural gas provinces, which may be released by melting permafrost, have also been observed. [28,31] The potential impacts of a sudden methane release were applied to the results already presented here by using an offline method -that is, not included in the numerics of the AOGCM model itself.…”

“… Risk: Northern Hemisphere growing season disruption  Arctic Ocean Cloud Brightening may extend modeled zero-ice dates [6]  Probably required to facilitate any realistic carbon-reduction actions [8,15,16,[24][25][26][27]  A methane burst (clathrates/provinces) moves these dates considerably closer Narrative Summary The importance of forecasting the approaching seasonal zero-ice condition in the Arctic (ca 2035) is the significant potential for periodic disruption of Northern Hemisphere (NH) food production, which is especially grave given that the global NH food production rate already has a decreasing trajectory. [15][16][17] Additionally, based on previous work, it is estimated that if large scale seasonal Arctic ocean warming and permafrost melt facilitates a rapid increase in the atmospheric methane burden [6,[8][9][10][11][12]28,31], the modelestimated dates for Arctic phase changes could be accelerated to 2030 and 2038, respectively, depending on the resulting atmospheric burden of methane as well as the precise rate of increase and timing of release. Even in the absence of a methane burst, the modeled acceleration of global temperature rise by loss of a seasonal sea-ice cover associated with the onset of Arctic phase change (i.e., Figure 1a) is of concern.…”