Remote Western Arctic Nutrients Fuel Remineralization in Deep Baffin Bay. Issue 6 (7th June 2019)

• Record Type: Journal Article
• Authors: Lehmann, N.; Kienast, M.; Granger, J.; Bourbonnais, A.; Altabet, M. A.; Tremblay, J.‐É.
• Is Part Of: Global biogeochemical cycles. Volume 33:Issue 6(2019:Jun.)
• Page Start: 649
• Page End: 667
• Publication Date: 2019-06-07
• Subjects: Arctic Ocean -- GEOTRACES -- nutrients -- nitrate isotopes -- nitrous oxide -- isotopomers; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1029/2018GB006134
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: The oceanic nitrogen cycle is critically important for the partitioning of greenhouse gases between ocean and atmosphere. Baffin Bay connects ocean regions that are major sources (North Atlantic) and sinks (North Pacific and western Arctic) of biologically available nitrogen and further harbors supersaturation of nitrous oxide and a coincident deficit in nitrate in the deep basin. Isotopic tracer profiles of both nitrogen species presented here provide novel insights into the origin and cycling of reactive nitrogen in Baffin Bay, highlighting the connectivity between different Arctic systems and horizontal components of basin‐scale nutrient transport. Baffin Bay bottom water properties are derived from export production in northern Baffin Bay, which is largely fueled by Pacific‐derived nutrients. In situ remineralization at depth gives rise to benthic denitrification, evidenced by a pronounced accumulation of nitrous oxide with a distinctively high site preference (<44‰) in the deep basin. Nutrients supplied to Baffin Bay are hence stripped from surface waters and trapped at depth over long timescales, where sedimentary denitrification further adds to the N removal capacity of the Arctic Ocean. Key Points: Nitrate isotope ratios indicate substantial remineralization of organic matter in deep Baffin Bay, fueled by Pacific‐derived nutrients Nitrous oxide isotopomers support a predominantly sedimentary source of N2 O propagating well into the oxygenated water column Sedimentary denitrification is a significant sink of dissolved inorganic nitrogen in deep Baffin Bay