Pan-Arctic Ocean Primary Production Constrained by Turbulent Nitrate Fluxes

• Published in: Frontiers in Marine Science
• Main Authors: Achim Randelhoff, Johnna Holding, Markus Janout, Mikael Kristian Sejr, Marcel Babin, Jean-Éric Tremblay, Matthew B. Alkire
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2020
• Subjects: Arctic; turbulence; nitrate; flux; primary production; climate change; Science; Q; General. Including nature conservation; geographical distribution; QH1-199.5; Arctic Ocean; Laptev Sea; Baffin Bay; Greenland; Baffin; Climate change; East Greenland; laptev; Sea ice
• Online Access: https://doi.org/10.3389/fmars.2020.00150; https://doaj.org/article/316ce113e49f42fda9cfadef50e1bf7d

Arctic Ocean primary productivity is limited by light and inorganic nutrients. With sea ice cover declining in recent decades, nitrate limitation has been speculated to become more prominent. Although much has been learned about nitrate supply from general patterns of ocean circulation and water column stability, a quantitative analysis requires dedicated turbulence measurements that have only started to accumulate in the last dozen years. Here we present new observations of the turbulent vertical nitrate flux in the Laptev Sea, Baffin Bay, and Young Sound (North-East Greenland), supplementing a compilation of 13 published estimates throughout the Arctic Ocean. Combining all flux estimates with a Pan-Arctic database of in situ measurements of nitrate concentration and density, we found the annual nitrate inventory to be largely determined by the strength of stratification and by bathymetry. Nitrate fluxes explained the observed regional patterns and magnitudes of both new primary production and particle export on annual scales. We argue that with few regional exceptions, vertical turbulent nitrate fluxes can be a reliable proxy of Arctic primary production accessible through autonomous and large-scale measurements. They may also provide a framework to assess nutrient limitation scenarios based on clear energetic and mass budget constraints resulting from turbulent mixing and freshwater flows.