Late winter biogeochemical conditions under sea ice in the Canadian High Arctic

Abstract

With the Arctic summer sea-ice extent in decline, questions are arising as to how changes in sea-ice dynamics might affect biogeochemical cycling and phenomena such as carbon dioxide (CO₂) uptake and ocean acidification. Recent field research in these areas has concentrated on biogeochemical and CO₂ measurements during spring, summer or autumn, but there are few data for the winter or winter–spring transition, particularly in the High Arctic. Here, we present carbon and nutrient data within and under sea ice measured during the Catlin Arctic Survey, over 40 days in March and April 2010, off Ellef Ringnes Island (78° 43.11′ N, 104° 47.44′ W) in the Canadian High Arctic. Results show relatively low surface water (1–10 m) nitrate (<1.3 µM) and total inorganic carbon concentrations (mean±SD=2015±5.83 µmol kg⁻¹), total alkalinity (mean±SD=2134±11.09 µmol kg⁻¹) and under-ice pCO_2sw (mean±SD=286±17 µatm). These surprisingly low wintertime carbon and nutrient conditions suggest that the outer Canadian Arctic Archipelago region is nitrate-limited on account of sluggish mixing among the multi-year ice regions of the High Arctic, which could temper the potential of widespread under-ice and open-water phytoplankton blooms later in the season.

• Sea ice
• carbon cycling
• biogeochemical cycles
• nutrients
• Arctic Ocean
• ocean acidification

Acknowledgements

The Catlin Arctic Survey was funded by Catlin Ltd. and coordinated by Geo Mission Ltd. HSF was supported by the Plymouth Marine Laboratory Lord Kingsland Fellowship and received the Ralph Brown Expedition Grant from the Royal Geographical Society (with IBG) and a Royal Society Travel Grant. CL was supported by a Natural Environment Research Council (NERC) Fellowship (NE/G014728/1). LAE was supported by the NERC's National Centre for Earth Observation and received fieldwork funds from the World Wide Fund for Nature. LAM, GC and SV were supported by the Department of Fisheries and Oceans, Canada. The authors are extremely grateful to the Ice Base staff and Geo Missions support staff, especially A. Daniels, C. Paton and M. Hartley. We also express our thanks to E.M.S. Woodward at the Plymouth Marine Laboratory for nutrient analytical assistance, C. Michel from the Department of Fisheries and Ocean, Canada (Discovery Grant, Natural Sciences and Engineering Research Council of Canada) for lending us their ice corer and for advice on the data, M. Davelaar and K. Johnson at the Institute of Ocean Sciences for logistical and analytical assistance, M. Gosselin for advice on the chlorophyll and phytoplankton dynamics and B. Else and anonymous reviewers for their constructive advice. The data from this study are available from the British Oceanographic Data Centre, NERC (www.bodc.ac.uk/data/published_data_library/catalogue/10.5285/03167d6f-a9cc-2e1a-e053-6c86abc0753b/).