Geochemical Weathering and Atmospheric CO2 Drawdown in Canadian Alpine and Arctic Proglacial Freshwater Systems (Banff, Jasper, and Quttinirpaaq National Parks)

Alpine and polar glaciers are melting at unprecedented rates due to climate change, with glacier-fed rivers transporting large quantities of comminuted sediments downstream. These sediments are then available for carbonate and silicate geochemical weathering reactions that can consume atmospheric carbon dioxide (CO₂) in proglacial freshwater systems. This differs greatly from rivers in non-glacierized watersheds that receive fewer inputs of comminuted sediments, and greater terrestrial runoff of organic matter, typically resulting in net CO₂ emissions as heterotrophic respiration overwhelms autotrophy. Yet, despite these known biogeochemical differences between proglacial and non-glacial freshwater systems, and observations that weathering-driven CO₂ consumption can occur sub-glacially, this phenomenon has rarely been examined downstream in glacial rivers and lakes. We recently showed, however, that weathering of comminuted sediments was responsible for glacier-fed freshwaters being a net annual CO₂ sink in the Canadian High Arctic watershed of Lake Hazen, Quttinirpaaq National Park.

Building from this, we continue to investigate the prevalence of this phenomenon across glacierized regions, and will present new data on weathering and CO₂ drawdown in the Canadian Rockies in Banff and Jasper National Parks. Using detailed monthly water quality surveys of glacier-fed freshwater systems in this mid-latitude alpine region, we have observed that weathering-driven CO₂ drawdown occurs at least up to 25 kilometers downstream of glacial termini. We will also present updated data from Lake Hazen, where we continue to quantify the extent of CO₂ drawdown across years of low and high glacial melt. These interannual and cross-regional data will be used to determine if Canadian arctic and western alpine proglacial freshwaters, which originate from glaciers with different thermal regimes and underlying geologies, have a similar capacity for CO₂ drawdown.

Geochemical weathering reactions in glacial meltwaters could have important implications for carbon cycling in glacierized regions. Thus, identifying the CO₂ drawdown capacity of proglacial freshwaters as glacial melt accelerates is essential for understanding annual carbon budgets at the watershed-scale in these rapidly changing regions.