Variations in deep-sea methane seepage linked to millennial-scale changes in bottom water temperatures ~ 50–6 ka, NW Svalbard margin

• Published in: Scientific reports 2024-09, Vol.14 (1), p.22184-17, Article 22184
• Main Authors: Rasmussen, Tine L., El bani Altuna, Naima, Thomsen, Erik
• Format: Article
• Language: English
• Subjects: 704/172; 704/47; 704/829; Bottom water; Deep sea; Gas hydrates; Gas seepage; Glaciation; High pressure; Humanities and Social Sciences; Hydrates; Low temperature; Methane; multidisciplinary; Ocean floor; Ocean temperature; Science; Science (multidisciplinary); Water depth; Water temperature
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-024-72865-3

During the last glaciation, the northern hemisphere experienced profound millennial-scale changes (termed Dansgaard-Oeschger (DO) events) in atmospheric and oceanic temperatures. In the North Atlantic, the fluctuations resulted in extremely unstable bottom water conditions with bottom water temperatures (BWT) varying up to > 5 °C. We have studied these changes in a core from 1,300 m water depth at Vestnesa Ridge, northwestern Svalbard margin to investigate a possible connection between BWT and seepage of methane from the seafloor covering the period ~ 50–6 ka. Beneath Vestnesa Ridge, gas hydrates containing vast amounts of methane are kept stable due to the high pressure and low temperatures. Release of gas is shown by numerous pockmarks on the seafloor. The pockmarks at 1,300 m water depth are presently inactive, but they bear witness of earlier activity. Our study shows that from ~ 50–6 ka, the core site experienced repeated increases in BWT and in the emissions of gas, both following the pattern of the DO events. This correspondence in time scale indicates that BWT was the primary forcing factor for the variability in methane release. However, the releases were delayed by up to > 1,000 years compared to the initial increase in BWT.