The drilling of the 10.5 m high Nori pingo that stands at 32 m asl in Grøndalen Valley (Spitsbergen) performed in April 2019 reached a depth of 21.8 m bs (core #13, starting from 42.5 m asl, 77.99483 °N, 14.59009 °E) and revealed 16.1 m thick massive ice. The core was obtained with a portable gasoline-powered rotary drilling rig (UKB 12/25, Vorovskiy Machine Factory, Ekaterinburg, Russia). The core pieces with diameter 112-76 mm were lifted for sampling to the surface every 30–50 cm. After documentation and cryolithological description core pieces were sealed in zip lock bags. Ice samples were split in two parts - one part for stable isotope analyses, another part for ion content measurement. They were kept frozen for transportation while sediment samples were kept unfrozen. Moisture content was analyzed in laboratory by measuring sediment samples weight before and after drying.
The stable water isotope composition (δ18O and δD) of massive pingo ice was analyzed at the Climate and Environmental Research Laboratory (CERL, Arctic and Antarctic Research Institute, St. Petersburg, Russia) using a Picarro L2120- i analyzer. After every five samples the working standard (SPB-2, δ18O = -9.66 ‰ and δD = -74.1 ‰) was measured. SPB-2 is made of distilled St. Petersburg tap water and is calibrated against the International Atomic Energy Agency (IAEA) standards VSMOW-2 (Vienna Standard Mean Ocean Water 2), GISP (Greenland Ice Sheet Precipitation), and SLAP-2 (Standard Light Antarctic Precipitation 2). The reproducibility of the results is 0.08 ‰ for δ18O and 0.4 ‰ for δD and was assessed by re-measuring a random selection of 10% of the total samples. The measurement error is thus 1-2 orders of magnitude less than the natural isotopic variability of pingo ice, which is satisfactory for the purpose of this study. The δ18O and δD values are given as per mil (‰) difference to the VSMOW-2 standard. The deuterium excess (d) is calculated as d = δD - 8δ18O29.
The ion content of sedimentary permafrost samples from core #13 was estimated after water extraction at the analytical laboratory of RAE-S, Barentsburg. The material was dried and sieved at 1 mm. About 20 g of the sediment were suspended in 100 ml of de-ionized water and filtered through 0.45 μm nylon mesh within 3 minutes after stirring. Electrical conductivity (EC, measured in μS cm-1) and pH values were estimated with a Mettler Toledo Seven Compact S 220. EC values were transformed automatically by the instrument into general ion content (mineralization) values given as mg L-1. Major anions and cations in the water extracts were analyzed by an ion chromatograph (Shimadzu LC-20 Prominence) equipped with the Shimadzu CDD-10AVvp conductometric detector and ion exchange columns for anions (Phenomenex Star-ion A300) and for cations (Shodex ICYS-50). Bicarbonate content was measured by a Shimadzu TOC-L analyzer via catalytic oxidizing at +680o C and subsequent infrared detecting. Melted pingo ice samples from core #13 and spring water samples were analyzed after filtration through 0.45 μm nylon mesh on the same equipment using the same techniques for pH, EC, and ion composition as for sedimentary permafrost samples.
Analyses and research were aimed at determining major characteristics of the Nori pingo including its internal structure, groundwater source, and geochemical and isotopic stages of formation.
