Modeling the evolution of climate‐sensitive Arctic subsea permafrost in regions of extensive gas expulsion at the West Yamal shelf

Abstract

Thawing subsea permafrost controls methane release from the Russian Arctic shelf having a considerable impact on the climate-sensitive Arctic environment. Expulsions of methane from shallow Russian Arctic shelf areas may continue to rise in response to intense degradation of relict subsea permafrost. Here we show modeling of the permafrost evolution from the Late Pleistocene to present time at the West Yamal shelf. Modeling results suggest a highly dynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions, e.g., geothermal heat flux from below and/or bottom water temperature changes from above permafrost. Scenarios of permafrost evolution show a potentially nearest landward modern extent of the permafrost at the West Yamal shelf limited by~17 m isobaths, whereas its farthest seaward extent coincides with~100 m isobaths. The model also predicts seaward tapering of relict permafrost with a maximal thickness of 275-390 m near the shoreline. Previous field observations detected extensive emissions of free gas into the water column at the transition zone between today's shallow water permafrost (<20 m) and deeper water nonpermafrost areas (>20 m). The model adapts well to corresponding heat flux and ocean temperature data, providing crucial information about the modern permafrost conditions. It shows current locations of upper and lower permafrost boundaries and evidences for possible release of methane from the seabed to the hydrosphere in a warming Arctic.

Subsea ice‐bearing permafrost on the U.S. Beaufort Margin: 1. Minimum seaward extent defined from multichannel seismic reflection data

“…The model of continuous IBPF rapidly thinning seaward of the modern shoreline with subsequent thin and discontinuous occurrences is also suggested by recent studies in the South Kara Sea [ Portnov et al ., ]. In addition to using high‐resolution seismic data, Portnov et al .…”

Subsea ice‐bearing permafrost on the U.S. Beaufort Margin: 2. Borehole constraints

“…Some contemporary Arctic Ocean continental shelves host subsea permafrost that originally formed in subaerially exposed tundra (in unglaciated areas [e.g., Romanovskii et al, 1998;Hunter and Hobson, 1974;Hunter et al, 1978;Rekant et al, 2005;Brothers et al, 2012;Portnov et al, 2013Portnov et al, , 2014) or beneath glaciers (e.g., Norwegian margin [Portnov et al, 2016]) in Late Pleistocene time. With the end of the last glaciation and subsequent sea level rise of up to $120 m [Fairbanks, 1989], these areas have now been inundated.…”

Estimation of the permafrost stability on the East Arctic shelf under the extreme climate warming scenario for the XXI century

“…При моделировании подводной мерзлоты на арктическом шельфе традиционно используют ся модели, в которых учитывается представление об изменении уровня океана и положении бере говой линии [1,10,12,17,19,22,25,26] . Предпо лагается, что подводная мерзлота шельфа моря Лаптевых и ВосточноСибирского моря сфор мировалась на суше в холодную эпоху в период понижения уровня океана и осушения шельфа .…”

“…В первом (S0) не учи тывается солёность поровых вод донных осадков и принимается температура фазовых переходов T F = 0 °C . Во втором (S11) и третьем (S30) экспери ментах предполагается, что пресные грунты шель фа после затопления морем подвергались засоле нию, а процессы оттаивания донных отложений могли протекать при отрицательной температуре пород по аналогии с исследованиями работы [25] . а -изменения по времени (с момента начала трансгрессии и до 2100 г .)…”