Ice-wedge evidence of Holocene winter warming in the Canadian Arctic

• Main Authors: Porter, Trevor, Holland, Kira, Buchanan, Casey, Froese, Duane, Kokelj, Steven
• Format: Dataset
• Language: unknown
• Published: Canadian Cryospheric Information Network 2021
• Subjects: Arctic; Tuktoyaktuk; Pelly Island; Climate change; Ice; permafrost; Richards Island; wedge*
• Online Access: https://dx.doi.org/10.21963/13163; https://www.polardata.ca/pdcsearch/?doi_id=13163

In this study, we sampled lateral cross-sections of four relict ice wedges from retrogressive thaw slump and coastal bluf exposures on Hooper Island, Pelly Island, Richards Island and the mainland coast near Tuktoyaktuk. Ice blocks capturing the entire growth sequences of the ice wedges (i.e., ice wedge center to ice-sediment contact) were collected by chainsaw and kept frozen in field coolers, and later sub-sampled at high-resolution in a cold lab. The ice wedges were sub-sampled at 1-1.5 cm horizontal resolution, integrating ~1-3 ice veins per sample on average. We analysed the stable hydrogen- and oxygen-isotope ratios (δ2H and δ18O) of each sample (N = 803). The age of the ice was estimated by AMS-DO14C dating of 6 to 10 samples per ice wedge, evenly distributed across each wedge to capture the full range of ages. A composite δ18O record spanning the period 7,400-600 cal yr BP was also constructed using the dated samples only (N = 36). The all-sample co-isotope (δ2H-δ18O) data are defined by a regression line that is remarkably similar to the Local Meteoric Water Line, suggesting the ice wedges reliably preserve the isotopic composition of local precipitation, which is strongly influenced by mean air temperatures. The composite record shows a increase in δ18O over the last 7,400 years which we interpret as a long-term warming trend of the mean winter climate. This warming trend is largely explained by increasing November-April insolation at 69°N and increasing greenhouse gas concentrations over the same period, a result that is corroborated by two independent high-resolution ice wedge records from the Siberian Arctic and is also in agreement with model-based simulations of the winter climate. This record, the first of its kind in the North American Arctic. It provides a more seasonally holistic perspective on Holocene climate change and highlights the potential to use permafrost isotope records to fill paleoclimate knowledge gaps in Arctic regions were more traditional precipitation isotope archives such as ice cores do not exist.