Origin, burial and preservation of late Pleistocene-age glacier ice in Arctic permafrost (Bylot Island, NU, Canada)

Abstract

Abstract. Over the past decades, observations of buried glacier ice exposed in coastal bluffs and headwalls of retrogressive thaw slumps of the Arctic have indicated that considerable amounts of late Pleistocene glacier ice survived the deglaciation and are still preserved in permafrost. In exposures, relict glacier ice and intrasedimental ice often coexist and look alike but their genesis is strikingly different. This paper aims to present a detailed description and infer the origin of a massive ice body preserved in the permafrost of Bylot Island (Nunavut). The massive ice exposure and core samples were described according to the cryostratigraphic approach, combining the analysis of permafrost cryofacies and cryostructures, ice crystallography, stable O-H isotopes and cation contents. The ice was clear to whitish in appearance with large crystals (cm) and small gas inclusions (mm) at crystal intersections, similar to observations of englacial ice facies commonly found on contemporary glaciers and ice sheets. However, the δ18O composition (-34.0±0.4 ‰) of the massive ice was markedly lower than contemporary glacier ice and was consistent with the late Pleistocene age ice in the Barnes Ice Cap. This ice predates the aggradation of the surrounding permafrost and can be used as an archive to infer palaeo-environmental conditions at the study site. As most of the glaciated Arctic landscapes are still strongly determined by their glacial legacy, the melting of these large ice bodies could lead to extensive slope failures and settlement of the ground surface, with significant impact on permafrost geosystem landscape dynamics, terrestrial and aquatic ecosystems and infrastructure.

Thermokarst lake development in syngenetic ice-wedge polygon terrain in the Eastern Canadian Arctic (Bylot Island, Nunavut)

“…14 C-dated at 9860 yr BP, and found within ice-contact deposits (sands, gravels and pebbles) with lithological properties corresponding to the surrounding Precambrian and Cretaceous-Tertiary rocks. Lacelle et al (2018) and Coulombe et al (2019) later proposed that Laurentide ice and Bylot ice were converging in the valley. Glacial retreat was then accompanied by a marine transgression phase, associated with the deposition of silts and clays, and which lasted until about 6000 yr BP ( 14 C ages in shells at different altitudes ranging from 9860 to 6100 yr BP).…”

Reconstructing 15 Myr of environmental change in the McMurdo Dry Valleys through permafrost geochemistry

“…This has been observed in multiple locations in the Arctic, particularly in the Canadian Arctic, where ice from the Laurentide Ice Sheet and other Pleistocene glaciers have been preserved for thousands of years (e.g. French and Harry, 1990, Sharpe, 1992, Dredge et al, 1999, St-Onge and McMartin, 1999, Dyke and Savelle, 2000, Kokelj et al, 2017, Lacelle et al, 2018, Coulombe et al, 2019 and in northwestern Siberia, where ice from the Barents-Kara Ice Sheet has been preserved for 80 to 90 kyr (e.g. Kaplanskaya and Tarnogradskiy, 1986, Astakhov and Isayeva, 1988, Svendsen et al, 2004.…”

Cryostratigraphical studies of ground ice formation and distribution in a High Arctic polar desert landscape, Resolute Bay, Nunavut1

“…Recent advances in ground ice research show a striking concentration of North American investigations sites in Alaska and the western Canadian Arctic (Gilbert et al 2016). Very few recent studies have addressed specifically the Canadian Arctic Archipelago (Coulombe et al 2019), underlining a persistent lack of knowledge on ground ice distribution and cryostratigraphy in the High Arctic (Pollard 2000). This region might be very sensitive to thermal degradation, as it lacks a thick insulating vegetation cover and because the low heat budget of its soils, which can be rapidly unbalanced during warm summers (Farquharson et al 2019).…”

“…In the High Arctic, warm summers during which active layer depths reached segregated ice formations have recorded thermokarst events such as ground subsidence (Farquharson et al 2019), active layer detachments (Lewkowicz 2007;Lamoureux and Lafrenière 2009) and retrogressive thaw slumps, (Couture and Pollard 1998). These events have at times exposed massive ice bodies of segregated and buried origin (Pollard 1991;Coulombe et al 2019). The degradation of such ice rich ground near the surface has important ramifications in terms of landscape stability and habitability, for soil and water geochemistry and for greenhouse gas emission (Kokelj and Lewkowicz 1999;Pollard et al 2015;Vonk et al 2015;Becker et al 2016;Cochand et al 2019;Lafrenière and Lamoureux 2019;Plaza et al 2019).…”