Deglacial bottom water warming intensified Arctic methane seepage in the NW Barents Sea

Abstract

Changes in the Arctic climate-ocean system can rapidly impact carbon cycling and cryosphere. Methane release from the seafloor has been widespread in the Barents Sea since the last deglaciation, being closely linked to changes in pressure and bottom water temperature. Here, we present a post-glacial bottom water temperature record (18,000–0 years before present) based on Mg/Ca in benthic foraminifera from an area where methane seepage occurs and proximal to a former Arctic ice-sheet grounding zone. Coupled ice sheet-hydrate stability modeling shows that phases of extreme bottom water temperature up to 6 °C and associated with inflow of Atlantic Water repeatedly destabilized subsurface hydrates facilitating the release of greenhouse gasses from the seabed. Furthermore, these warming events played an important role in triggering multiple collapses of the marine-based Svalbard-Barents Sea Ice Sheet. Future warming of the Atlantic Water could lead to widespread disappearance of gas hydrates and melting of the remaining marine-terminating glaciers.

Northeast Greenland: ice‐free shelf edge at 79.4°N around the Last Glacial Maximum 25.5–17.5 ka

“…2007; El bani Altuna et al . 2021a). These records show dominance of C. neoteretis together with C. reniforme , E. clavatum and some C. lobatulus and M. barleeanus , and bottom water temperatures reconstructed from Mg/Ca reach 4.4 °C.…”

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

“…4b, 6a,b). Widespread occurrences of low δ 13 C values during the Bølling-Allerød interstadials indicate that similar emissions occurred simultaneously over large areas of the western Svalbard margin 40,55 including shelf areas 29 . Another contributory cause to the widespread and strong emission of methane during the Bølling and Allerød interstadials could be tectonic movements due to the proximity of the Knipovich Ridge spreading zone 37,45,70 , isostatic rebound [71][72][73] and/or high sedimentation rates 35 .…”

“…Facilitated by faults and porous sediments, free and dissolved gas in the pore water can migrate upward through the GHSZ and through overlying sediments with the potential to reach the atmosphere [21][22][23] . Growing concern about the effect of greenhouse gases on the global warming, rising surface and deep ocean temperatures and on the increasing deep-ocean acidi cation [24][25][26] has fostered an intensi ed interest on the future stability of the GHSZ in a warmer ocean 23,[27][28][29][30][31] .…”

The phylogeography and ecology of Oligobrachia frenulate species suggest a generalist chemosynthesis-based fauna in the arctic

“…Similarly, bottom water temperature on Arctic shelves, where methane seeps are increasingly being recognized as being common, vary considerably between seasons, with methane release at shelf seeps decreasing dramatically (by 43%) in colder, winter months [ 84 ]. Though temperature does not always impact gas hydrate dissociation [ 85 ], Mg/Ca of benthic foraminifera indicate that the gas hydrate stability zone can shift by at least 50 m water depth [ 86 ]. The latter case would result in extensive areas among seep sites having only a summertime exposure to sediment methane release.…”