Marine Aerosol Contribution to Ice-Wedge Geochemistry: Potential for Paleo-Sea Ice and Paleogeography Reconstructions in the Canadian Arctic

Marine aerosol records from glacial ice cores have recently been used in the Arctic to provide insight into marine productivity and sea ice dynamics prior to the satellite era. However, these terrestrial archives of paleo-sea ice conditions are limited to glaciated coastal sites, which precludes most areas of the Arctic, leaving only marine records to infer sea-ice conditions in other Arctic coastal regions. A recent study has demonstrated the potential of ice wedges-a widespread form of Arctic ground ice that integrates the winter snowpack-as a long-term archive for marine aerosols, and thus winter sea ice conditions, in non-glaciated regions. Here we develop a late Holocene ion geochemistry record from a coastal ice wedge in the northwestern Canadian Arctic (Beaufort Sea coast). Dissolved organic radiocarbon dating of the ice revealed a systematic increase in age from the center to the outside of the ice wedge, allowing for the construction of a linear age model spanning ~4,600 to ~640 yr b2k. Major ion species show a moderate to strong positive correlation with each other, indicating a marine origin. The Cl^-/Na⁺ ratio (1.27) is similar to bulk seawater (1.16), while the enrichment of bulk Mg²⁺ and Ca²⁺ suggests a large lithogenic component, particularly during early ice-wedge development. Depleted SO₄^2­- values likely indicate a large contribution of blowing snow from the marine snowpack to the terrestrial snowpack over the period of ice-wedge formation. Cl^-, Na⁺ and the sea-salt component of Mg²⁺ and Ca²⁺ reveal a systematic increase in concentrations over the period of the record (0.08 mmol L^-1·kyr^-1 for Cl^-). Potential drivers of this enrichment may include a reduction in sea-ice duration over the late Holocene until 2,000 yr b2k in the southern Beaufort Sea proximal to the study site and/or decreased continentality up to ~1 km inland due to high rates of coastal erosion. Future research aimed at better understanding the spatial variability of snowpack marine aerosol concentrations in this region will help to refine interpretations of paleogeography and sea ice conditions from this record. This study highlights the potential of ice wedges as a novel marine aerosol archive where glacial ice core records are unavailable.