Late Glacial and Holocene landscape and permafrost evolution of the Barentsburg area, West Spitsbergen

Abstract. The postglacial landscape evolution on West Spitsbergen provides insights into the interplay among glacial retreat and rebound, marine transgression, and permafrost aggradation, all of which are driven, or at least superimposed, by climate dynamics. To gain a new understanding of this interplay, a total of 19 permafrost drill cores, complemented by one natural exposure reaching depths of 5–25 m below the surface, were studied. The sampling heights span from 74 m above sea level to 4 m below sea level. The drill transect extends approximately 20 km inland from the marine terraces at Isfjorden (sub-area A), along the Grønfjorden (sub-area B), the Grøndalen (sub-area C), and the Hollendardalen (sub-area D) valleys in the wider Barentsburg area. Detailed cryolithological descriptions, hydrochemical and sedimentological analyses, and radiocarbon dating were employed to infer the spatial and temporal evolution of regional permafrost following deglaciation and sea-level adjustment.

The sediment composition is highly variable, ranging from clayey silt to gravelly sand (mean grain size: ca. 10–10,000 µm). Instead, the biogeochemical composition reveals relatively small differences in total organic carbon (TOC) and total nitrogen (TN) contents, as well as in stable carbon isotope ratios (δ13C) and in the TOC/TN ratio of organic matter. Likewise, the mass-specific magnetic susceptibility data exhibit relatively low variability. Ice and water extracts with low electrical conductivity, relatively low anion and cation concentrations, and a wide spread on the PIPER plot suggest a terrestrial origin of the ground ice. However, in some places, high conductivity and a dominant sodium-chloride composition indicate marine and/or cryopeg influence. Applicable radiocarbon dates are younger than 11 cal kyr BP. Older radiocarbon dates, starting from 37.8 cal kyr BP, are disputable and very likely contaminated by carbon from surrounding Tertiary coal deposits and, therefore, not considered in the present study. Three major stages of Late Glacial and Holocene landscape evolution were identified: (1) deglaciation, (2) marine transgression, and (3) permafrost formation. The latter differentiates into three sub-stages characterized by (a) periglacial, fluvial, and alluvial deposition, (b) pingo formation, and (c) slope and alluvial deposition and pingo degradation.

As the High Arctic and thus the permafrost have recently experienced strong warming and substantial landscape changes, their evolution over geologic timescales warrants fundamental research to better understand climate-permafrost interactions. In this context, the present study provides insights into permafrost's response to Late Glacial and Holocene environmental changes.