Permafrost saline water and Early to Mid-Holocene permafrost aggradation in Svalbard

Abstract

Abstract. Deglaciation in Svalbard was followed-up by seawater ingression and the deposition of marine (deltaic) sediments in fjord valleys, while elastic rebound resulted in fast land uplift and the exposure of these sediment to the atmosphere, therefore the formation of epigenetic permafrost. This was then followed by the accumulation of aeolian sediments, which froze syngenetically. The permafrost was drilled in the east Adventdalen valley, Svalbard, 3–4 km from the maximum up-valley reach of post-deglaciation seawater ingression, and its ground ice was measured for chemistry. While ground ice in the syngenetic part is basically fresh the epigenetic part reveals a frozen fresh-saline water interface (FSI), with chloride concentrations increasing from the top of the epigenetic part (depth of 5.5 m) to about 15 % that of seawater at 11 m. We applied a one-dimensional freezing model in order to examine the rate of top-down permafrost aggradation, which could accommodate with the observed frozen FSI. The model examined permafrost development under different scenarios of mean average air temperature, water-freezing temperature and the degree of pore-water freezing. We found that even at the relatively high temperatures of the Early to mid-Holocene, permafrost could aggrade quite fast, e.g. down to 15 to 33 m in 200 years, therefore allowing freezing of the fresh-saline water interface despite of the relatively fast rebound rate and the resultant increase in topographic gradients toward the sea. This could be aided by non-complete pore water freezing, which possibly lead to slightly faster aggradation, resulting in the freezing of the entire marine section at that location (23 m) within less than 200 years. We conclude that freezing should have occurred immediately after the exposure of the marine sediment to atmospheric conditions.

Massive ground ice of glacial meltwater origin in raised marine-deltaic sediments, Fosheim Peninsula, high Arctic Canada

“…7). In addition, thermal modeling of permafrost aggradation during the Early to Middle Holocene in marine sediments of a fjord in Svalbard using mean annual air temperature in the −6 to −4°C range showed that permafrost could aggrade tens of meters in a relatively short time period (~200 yr) (Rotem et al, 2022).…”

“…7). In addition, thermal modeling of permafrost aggradation during the Early to Middle Holocene in marine sediments of a fjord in Svalbard using mean annual air temperature in the −6 to −4°C range showed that permafrost could aggrade tens of meters in a relatively short time period (∼200 yr) (Rotem et al, 2022). The development of tabular massive ice in the ESL raised marine-deltaic sediments involves glacial meltwater recharging an aquifer in the poorly consolidated weathered sandstone beneath the Holocene marine sediments.…”