| Summary: | The contribution of small Canadian Arctic rivers to the total freshwater flux through the Canadian Arctic Archipelago (CAA) is unknown and remains a significant gap in the growing data set addressing the freshwater budget of the Arctic and subarctic oceans. Limited geochemical data have been collected from the CAA, Nares Strait, and Baffin Bay, and the existing data sets are too sparse to differentiate among the various freshwater sources thought to contribute to the total freshwater pool (i.e., Pacific water, sea-ice meltwater, and meteoric water derived from the Mackenzie River, Eurasian rivers, and local runoff). New programs have begun to collect requisite geochemical data in Davis Strait and other regions. However, interpretation of these measurements may be biased by typical endmember assignments associated with Eurasian and North American river runoff. Characterizing the geochemical signature of local freshwater inputs is essential for distinguishing these contributions from those of Arctic Ocean origin, but virtually no studies have sampled small Arctic rivers discharging into the CAA. Available data collected from Baffin Bay and Hudson Strait suggest local rivers do not resemble the Mackenzie and Yukon Rivers typically assumed to represent North American runoff. While the annual discharge of any given river is relatively small, the combined discharge of all rivers is sufficient to support nearshore, narrow boundary currents, which provide an important, but often neglected, transport mechanism. Thus, local contributions of freshwater may impact the total volume flux and geochemistry of the Canadian Arctic throughflow that has historically been attributed entirely to export from the Arctic Ocean. The project consists of a three-year study to characterize the total alkalinity, barium, DOC, major ion and isotope (δ18O, 87Sr/86Sr) geochemistry of remote CAA rivers and estuaries with the ultimate aim of resolving the contribution of local freshwater inputs to CAA boundary currents. River sampling will occur during different flow regimes, but emphasize the spring freshet, the time of year when terrestrial runoff from local CAA rivers maximally impacts coastal waters. Estuarine sampling will include both horizontal and vertical profiles. The study focuses on eight rivers: the Coppermine, Ellice, Back, Hayes, Kuujuua, Thomsen, Cunningham, and Clyde Rivers. During summer field seasons of 2014-2016, four researchers are transported to each site via Twin Otter aircraft. Field operations begin at Kugluktuk (Coppermine River) in early July 2014 (river sampling only) and in early August of 2015 and 2016 (river and estuary sampling). Researchers spend 3-5 days at each site. The team utilizes airports located at Kugluktuk, Clyde River, and Ulukhaktok. More remote sites near the Thomsen, Ellice, Cunningham, and Back Rivers are accessed via equipping the Twin Otter with tundra tires. River water samples are collected by wading into the river and using an extendable pole to collect bulk (1L) samples from the central current. Bulk samples are then immediately filtered using a peristaltic pump and small subsamples are collected. Weekly samples are also collected by local workers in the more populated regions surrounding the Coppermine and Clyde Rivers to gain insight into the changes in river chemistry over the course of the spring and summer flow periods. Samples are collected from estuaries adjoining the river mouths from small, inflatable boats and a peristaltic pump equipped with multiple lengths of C-FLEX tubing.
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