期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：35
DOI：10.1073/pnas.2201871119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Our results identify an exceptionally large warming of the equatorial Atlantic intermediate waters and strong evidence of methane release and oxidation almost certainly due to massive methane hydrate destabilization during the early part of the penultimate warm episode (126,000 to 125,000 y ago). This major warming was caused by reduced advection of cold water from high latitudes and enhanced downward heat diffusion in response to a brief episode of meltwater-induced weakening of the Atlantic meridional overturning circulation and amplified by a warm mean climate. Our results highlight climatic feedback processes associated with the penultimate climate warming that can serve as a paleoanalog for modern ongoing warming.
The stability of widespread methane hydrates in shallow subsurface sediments of the marine continental margins is sensitive to temperature increases experienced by upper intermediate waters. Destabilization of methane hydrates and ensuing release of methane would produce climatic feedbacks amplifying and accelerating global warming. Hence, improved assessment of ongoing intermediate water warming is crucially important, especially that resulting from a weakening of Atlantic meridional overturning circulation (AMOC). Our study provides an independent paleoclimatic perspective by reconstructing the thermal structure and imprint of methane oxidation throughout a water column of 1,300 m. We studied a sediment sequence from the eastern equatorial Atlantic (Gulf of Guinea), a region containing abundant shallow subsurface methane hydrates. We focused on the early part of the penultimate interglacial and present a hitherto undocumented and remarkably large intermediate water warming of 6.8 °C in response to a brief episode of meltwater-induced, modest AMOC weakening centered at 126,000 to 125,000 y ago. The warming of intermediate waters to 14 °C significantly exceeds the stability field of methane hydrates. In conjunction with this warming, our study reveals an anomalously low δ
13C spike throughout the entire water column, recorded as primary signatures in single and pooled shells of multitaxa foraminifers. This extremely negative δ
13C excursion was almost certainly the result of massive destabilization of methane hydrates. This study documents and connects a sequence of climatic events and climatic feedback processes associated with and triggered by the penultimate climate warming that can serve as a paleoanalog for modern ongoing warming.
关键词：enmethane hydrate destabilizationoceanic intermediate water warmingGulf of Guineameltwater-induced AMOC weakeningThe Eemian
