Tracing the role of Arctic shelf processes in Si and N cycling and export through the Fram Strait: insights from combined silicon and nitrate isotopes

• Published in: Biogeosciences
• Main Authors: Debyser, Margot C. F., Pichevin, Laetitia, Tuerena, Robyn E., Dodd, Paul A., Doncila, Antonia, Ganeshram, Raja S.
• Format: Text
• Language: English
• Published: 2022
• Subjects: Arctic; Arctic Ocean; Climate change; Fram Strait; Sea ice
• Online Access: https://doi.org/10.5194/bg-19-5499-2022; https://bg.copernicus.org/articles/19/5499/2022/

Nutrient cycles in the Arctic Ocean are being altered by changing hydrography, increasing riverine inputs, glacial melt and sea-ice loss due to climate change. In this study, combined isotopic measurements of dissolved nitrate ( δ 15 N-NO 3 and δ 18 O-NO 3 ) and silicic acid ( δ 30 Si(OH) 4 ) are used to understand the pathways that major nutrients follow through the Arctic Ocean. Atlantic waters were found to be isotopically lighter ( δ 30 Si(OH) <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi/><mn mathvariant="normal">4</mn></msub><mo>=</mo><mo>+</mo></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="27pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="1a40839ccef088eeb629cb2b48ad95cd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-5499-2022-ie00001.svg" width="27pt" height="10pt" src="bg-19-5499-2022-ie00001.png"/></svg:svg> 1.74 ‰) than their polar counterpart ( δ 30 Si(OH) <math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi/><mn mathvariant="normal">4</mn></msub><mo>=</mo><mo>+</mo></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="27pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="f65eb36be258f76aabb6be3a2cd3fb19"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-5499-2022-ie00002.svg" width="27pt" height="10pt" src="bg-19-5499-2022-ie00002.png"/></svg:svg> 1.85 ‰) owing to partial biological utilisation of dissolved Si (DSi) within the Arctic Ocean. Coupled partial benthic denitrification and nitrification on Eurasian Arctic shelves lead to the enrichment of δ 15 N-NO 3 and lighter δ 18 O-NO 3 in the polar surface waters ( δ 15 N-NO 3 = 5.44 ‰, δ 18 O-NO 3 ...