This data set describes geochemical data collected from 53 rivers, lakes, and glaciers throughout the Canadian Arctic Archipelago (CAA) and Hudson Bay. CAA rivers were sampled through access either (i) on foot from nearby communities; (ii) by small local boats; (iii) via float planes or helicopters; (iv) and/or aboard larger marine vessels, including: the RV Martin Bergmann as part of the Canadian Arctic Archipelago Rivers Program (CAA-RP; 2016 – 2019); aboard the CCGS Amundsen as part of the ArcticNet / Amundsen Science biogeochemical surveys (2017-2019); and aboard the MV Polar Prince as part of the Canada 150 C3 Expedition (2017). Hudson Bay rivers were sampled from the CCGS Amundsen as part of the BaySys project (2018). Time series observations were collected from the Coppermine River in Kugluktuk, Nunavut (NU) (year-round; Sept 14, 2016 to Sept 17, 2018), and from Freshwater Creek in Cambridge Bay, NU (open water only; June 8, 2017 to Aug 23, 2019). Water samples were collected according to methods developed by the Arctic Great Rivers Observatory (http://www.arcticgreatrivers.org/), described in detail in Brown et al., 2020. Briefly, water was collected at each site using pre-rinsed 60 mL syringes (Fisher Scientific) either by filling the syringe (1) directly from just below the surface of the river; or, (2) with the aid of a Niskin bottle deployed just below the surface; (3) using a submersible or peristaltic pump and tubing fastened to a pole; or (4) after collecting a bulk water sample by pump (as in 3) into a clean 500 mL glass bottle, stored in coolers in the dark, and then subsampling immediately after returning to the ship. Water collected for geochemical analyses of dissolved constituents was filtered through 0.22 μm Sterivex cartridges (Millipore) into triply rinsed glass or HDPE plastic vials. Vials used for the determination of Dissolved Organic Carbon (DOC) and Nutrients (Nitrate + Nitrite, Phosphate, Silicate) were acid cleaned prior to use. Samples for the determination of DOC and Nutrients were frozen until analyses, whereas dissolved ion and stable isotope samples were stored in the dark at room temperature or refrigerated until analyses. Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TA) samples were filtered directly into glass sample bottles using a 0.45 μm cartridge installed in-line with a peristaltic pump. Where indicated, water Temperature and Conductivity at the time of sampling were determined as described in the dataset metadata file. Analytical methods are described in detail in Brown et al., 2020. Deviations in the laboratory facilities and methods used since Brown et al., 2020 are listed in the dataset metadata file. Additional information on Freshwater Creek sampling methods can be found in Jones et al., (in progress).

Two more datasets will be added to this collection later: Canadian Arctic Archipelago Rivers Program: Major Ion and Inorganic Carbon Data 2016-2019 Canadian Arctic Archipelago Rivers Program: Coppermine River and Freshwater Creek Data 2016-2019-------------------------------------------------Acknowledgments:This sampling program would not be possible without the help of many enthusiastic and supportive partners who have carried sampling kits with them across the CAA! Many thanks go to the Captain and Crew of the CCGS Amundsen, the Captain and Crew of the RV Martin Bergmann, the Captain Crew of the MV Polar Prince, and the staff at the Canadian High Arctic Research Station, as well as Austin Maniyogina, Amanda Dumond, Patrick Duke, Shawn Marriott, Francis Emingak, Araleigh Cranch, Richard Sims, Peter Van Buren, Geraint Element, Kathleen Munson, Mohamed Ahmed, Kate Yezhova, ArcticNet, Amundsen Science, Adrian Schimnowski, Tara Mascarenhas, Mark Graham, Eddy Carmack, Mike Dempsey, and Baba Pedersen for sample collection and logistical assistance, as well as Sarah-Ann Quesnel, Cynthia Wright, Owen Cowling, Joseph Orchardo, Gretchen Swarr, Jean-Eric Tremblay, Jonathan Gagnon, Gabriele Deslongchamps, Helmuth Thomas, Monica Nelson, Tonya Burgers, Jacoba Mol, and Araleigh Cranch for assistance with laboratory analyses. The Canadian Arctic Archipelago Rivers Program was supported by the Department of Fisheries and Oceans Canada, the Woods Hole Oceanographic Institution Coastal Ocean Institute, the Arctic Research Foundation, and Polar Knowledge Canada.