A new paper by multiple Russian authors, including Shakhova and Semilitov (remember them) came out recently.
Key finding: Sediment temperatures are as high at +5.0 C in large regions. Methane burst risks…
Here are the relevant links:
“Abstract
Features of sediment temperature on the shelf and continental slope areas of the Russian Arctic seas and its physical properties are important for understanding the current state of subsea permafrost and the gas hydrates stability zone. New data are reported for the Kara Sea region where the bottom sediment temperatures are influenced by warming effects from great Siberian rivers and the Atlantic currents. The data collected during marine expeditions in 2019–2022 are combined with results of earlier marine studies, drilling operations, and geophysical surveys in the Laptev and East Siberian seas, in order to identify major trends of in situ temperature and properties distribution of bottom sediments in the Russian Arctic region.
Most (85%) of bottom sediments in the Kara Sea shelf, as well as in the Laptev and East Siberian shelves, consist of water-saturated silty clay and silt with rather uniform particle size distribution. The obtained thermal conductivity and heat capacity values for the Kara Sea sediments agree with the values of 1.0 W/(m·K) and 2900 kJ/m3, respectively, obtained previously from other Arctic seas. Thermal conductivity becomes up to 40% higher depthward from 0 to 2 m subbottom depth, possibly, because of lower moisture content and porosity in more lithified sediments.
The bottom sediment temperatures in the Arctic seas are distributed unevenly, especially in the Kara Sea shelf (from +5.0 °C in the west to −1.4 °C in the east), where the high sediment temperatures in the western and central parts of the Kara Sea being due to the effect of warm water inputs. The distribution of bottom sediment temperatures correlates well with distribution of relic subsea permafrost. Ice-bearing permafrost in the Siberian Arctic shelf extends from the shoreline till sea depths of 80–100 m, within the respective offshore distances of ∼800–1000 km in some areas, but permafrost remnants may exist locally at sea depths within 120 m. Buried 100–600 m thick continuous subsea permafrost may occur in the Kara, Laptev, and East Siberian shelves under unfrozen (cryotic) saline shallow sediments. However, subsea permafrost is discontinuous and sporadic at sea depths ∼70 m and more. Thus, the bottom sediment temperature features in the Arctic seas can be used as a proxy of subsea permafrost extent contenting intrapermafrost and subpermafrost gas and gas hydrate accumulations.”
“Warming of the ESAS began over 12 thousand years (kyr) ago in the earliest Holocene after the area had been submerged as a result of sea level rise. The temperature of terrestrial permafrost in the Holocene Arctic changed as the mean annual air temperature has become 6–7 °C warmer since the last glacial maximum. Subsea permafrost has been subjected to additional warming induced by sea water which has much warmer mean annual temperatures than air in the ESAS area: −1 °C against −10 °C, respectively. Consequently, the subsea permafrost has grown up to 17 °C warmer for the last 12 kyrs. The evolution of subsea permafrost may have multiple controls: the time when it was submerged relative to the time of emergence; thermal state and thickness of permafrost before inundation; coastal morphology and hydro- and lithodynamics; shoreline configuration and retreat rate; pre-existing thermokarst (particular landforms produced by thawing of ice-rich permafrost or melting of ground ice) and thaw lakes; temperature and salinity of bottom water; composition of sediments, including ice content, etc.”
“Current state of subsea permafrost in the Kara sea vs laptev and East Siberian seas”: [ Ссылка ]
Arctic region maps: [ Ссылка ]
Peer reviewed paper on methane gas migration underneath the permafrost; the paper studies Svalbard but results apply widely across the Arctic: “Permafrost trapped natural gas in Svalbard, Norway”: [ Ссылка ]
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