- 1University Of Toronto Mississauga, Department of Geography, Geomatics and Environment, Mississauga, Canada
- 2Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
Recent retrogressive thaw slump activity in the Richardson Mountains (northwestern Canada), induced by climate warming, has exposed a stratigraphic record of landscape evolution and permafrost development since the last glaciation. Horizontal profiles of five relict ice wedges and one rejuvenation-stage (ca. modern) ice wedge were collected from the headwalls of four thaw slumps in the Willow Creek area of the Richardson Mountains to study post-glacial changes in winter climate. The ice wedges contain vertically elongated bubbles, indicating a likely snowmelt origin. δ2H and δ18O measurements, sampled every ~1.5 cm across the profiles (n = 325), fall well within the range of local winter precipitation values, thereby confirming winter precipitation as the probable source water. Detrital plant macrofossils from several pristine ice samples were AMS 14C dated (n = 16) and confirm at least 2 generations of relict wedge ice dating to the Younger Dryas (YD) and Late Holocene; this is only the second study from the Western Arctic to document YD wedge ice. YD wedge ice is ~2.2‰ more negative in δ18O compared to Late Holocene wedge ice, which could be explained by one or a combination of plausible factors: (i) winter temperatures were up to ~5°C colder on average (e.g., assuming a δ18Oprecip-T sensitivity of 0.41‰·°C-1); (ii) a greater proportion of snow fell during the coldest winter months; or (iii) the moisture source region varied in response to changing atmospheric circulation, moderated by the collapse of the last ice sheet. However, no significant difference is observed in dexcess between YD and Late Holocene wedge ice, which may suggest the precipitation seasonality and moisture source region were comparable. Conversely, the rejuvenation-stage wedge ice, which likely formed in the last few decades, is 1.7‰ more positive in δ18O than Late Holocene wedge ice, while dexcess is statistically indifferent. The strong increase in δ18O in modern wedge ice relative to Late Holocene wedge ice reflects the impact of recent Arctic warming, especially in winter, a pattern that has been previously observed in other ice wedge records from the Canadian and Siberian Arctic. In summary, this study provided insights on winter climate variability in the northwestern Canadian Arctic, with a focus on the YD, Late Holocene and recent times, and demonstrates the potential to use ice wedges to further our knowledge of cold-season climate dynamics in the circum-Arctic more broadly.
How to cite: Porter, T., Changulani, A., Opel, T., and Meyer, H.: Younger Dryas and Holocene winter conditions in the Richardson Mountains, Canadian Arctic, reconstructed from precipitation isotopes in relict ice wedges, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13380, https://doi.org/10.5194/egusphere-egu25-13380, 2025.