A Pulse of Meteoric Subsurface Fluid Discharging Into the Chukchi Sea During the Early Holocene Thermal Maximum (EHTM)

Abstract

The response of Arctic Ocean biogeochemistry to subsurface flow driven by permafrost thaw is poorly understood. We present dissolved chloride and water isotopic data from the Chukchi Sea Shelf sediments that reveal the presence of a meteoric subsurface flow enriched in cations with a radiogenic Sr fingerprint. This subsurface fluid is also enriched in dissolved inorganic carbon and methane that bear isotopic compositions indicative of a carbon reservoir modified by reactions in a closed system. Such fluid characteristics are in stark contrast with those from other sites in the Chukchi Sea where the pore water composition shows no sign of meteoric input, but reflect typical biogeochemical reactions associated with early diagenetic sequences in marine sediment. The most likely source of the observed subsurface flow at the Chukchi Sea Shelf is from the degradation of permafrost that had extended to the shelf region during the Last Glacial Maximum. Our data suggest that the permafrost‐driven subsurface flow most likely took place during the 2–3°C warming in the Early Holocene Thermal Maximum. This time scale is supported by numerical simulation of pore water profiles, which indicate that a minimum of several thousand years must have passed since the cessation of the subsurface methane‐bearing fluid flow.

Influence of sedimentary deposition on the microbial assembly process in Arctic Holocene marine sediments

“…In geochemical tests, major and trace elements and total organic carbon (TOC) in the solid phase were determined using inductively couple plasma optical emission spectroscopy (ICP-OES) and Rock-Eval analyses at 30 cm depth intervals ( n = 35, each 1 g dried sediment) for JPC1. Headspace methane and pore water chemistry (liquid phase) were selectively presented by Kim et al (2021) . Details of geochemical experiments were described in Supplementary Information (geochemical experiment).…”

Impact of High Methane Flux on the Properties of Pore Fluid and Methane-Derived Authigenic Carbonate in the ARAON Mounds, Chukchi Sea

“…It is expected that rapid global warming will continuously amplify in the future (Schuur et al, 2015;Kim et al, 2021a). We can also predict that the seafloor morphology and regional hydrology including the formation of GHs and MDACs of the ARAON Mounds as well as other regions of the Arctic Ocean, will rapidly change in association with future climate change.…”

“…All analyzed δ 18 O MDAC values from Sites ARA07C-St 13 and ARA07C-St 14 are higher than these calculated equilibrium values (Figure 5; Table 2), suggesting the incorporation of enriched 18 O fluid during MDAC precipitation. The enriched 18 O fluid may originate from either clay mineral dehydration, opal diagenesis, or GH dissociation (Hesse and Harrison, 1981;Kastner et al, 1991;Ussler and Paull, 1995;Hesse, 2003;Kim et al, 2013;Kim et al, 2021a). In general, the 87 Sr/ 86 Sr ratio tends to be lower than that of the ambient present seawater by clay dehydration, and the δ 18 O value increases with a relatively constant δD value by opal diagenesis (Kastner et al, 1991;Kim et al, 2013;Kim et al, 2021a).…”

“…The enriched 18 O fluid may originate from either clay mineral dehydration, opal diagenesis, or GH dissociation (Hesse and Harrison, 1981;Kastner et al, 1991;Ussler and Paull, 1995;Hesse, 2003;Kim et al, 2013;Kim et al, 2021a). In general, the 87 Sr/ 86 Sr ratio tends to be lower than that of the ambient present seawater by clay dehydration, and the δ 18 O value increases with a relatively constant δD value by opal diagenesis (Kastner et al, 1991;Kim et al, 2013;Kim et al, 2021a). Since most 87 Sr/ 86 Sr ratios in pore fluids are similar to the present bottom seawater of ARA09C-St 04 and the values of δ 18 O and δD are relatively constant in the non-GH-bearing intervals, irrespective of sampling depth (Figures 3, 4; Supplementary Table 1), we excluded clay mineral dehydration and opal diagenesis as the primary sources for enriched 18 O fluid in the ARAON Mounds.…”

“…The shrinkage of the cryosphere extent is expected to accelerate continuously in the future, releasing a large amount of CH 4 . This CH 4 released from the sediment column will play a critical positive feedback role in global warming, marine geology, (bio)geochemistry, and microbial activities, linked to the ebullition of gas transport (Schuur et al, 2015;Argentino et al, 2021;Kim et al, 2021a;Lee et al, 2021;Sauer et al, 2021).…”