Preprints
https://doi.org/10.5194/tc-2022-134
https://doi.org/10.5194/tc-2022-134
 
31 Aug 2022
31 Aug 2022
Status: this preprint is currently under review for the journal TC.

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

Dotan Rotem1,2, Vladimir Lyakhovsky3, Hanne Hvidtfeldt Christiansen2, Yehudit Harlavan3, and Yishai Weinstein1 Dotan Rotem et al.
  • 1Department of Geography and Environment, Bar-Ilan University, Ramat-Gan, 52900, Israel
  • 2Geology Department, the University Centre in Svalbard, UNIS, Longyearbyen 9170, Norway
  • 3Geological Survey of Israel, 32 Yesha'yahu Leibowitz, Jerusalem 9692100, Israel.

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.

Dotan Rotem et al.

Status: open (until 26 Oct 2022)

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Dotan Rotem et al.

Dotan Rotem et al.

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Short summary
The relatively warm climate of the Early to mid-Holocene question permafrost aggradation in the high Arctic. Permafrost ground ice from Svalbard, preserved a fresh-saline water interface. The site proximity to the sea and high rebound rates of that period, seawater should have been washed seawards. Freezing model confirmed that freezing could progress relatively fast down the exposed sediments, to 15–33 m within 200 years. We conclude that permafrost aggradation did take place in fjord valleys.