Nitrate isotope investigations reveal future impacts of climate change on nitrogen inputs and cycling in Arctic fjords: Kongsfjorden and Rijpfjorden (Svalbard)

• Published in: Biogeosciences
• Main Authors: Santos-Garcia, Marta, Ganeshram, Raja S., Tuerena, Robyn E., Debyser, Margot C. F., Husum, Katrine, Assmy, Philipp, Hop, Haakon
• Format: Text
• Language: English
• Published: 2022
• Subjects: Arctic; Rijpfjorden; Svalbard; Climate change; glacier; Kongsfjord*; Kongsfjorden; Rijpfjord*; Tidewater
• Online Access: https://doi.org/10.5194/bg-19-5973-2022; https://bg.copernicus.org/articles/19/5973/2022/

Ongoing climate change in the Arctic has caused tidewater glaciers to retreat while increasing the discharge of freshwater and terrestrial material into fjords. This can affect both nutrient inputs and cycling within the fjord systems. In particular, tidewater glaciers and the presence of associated subglacial meltwater plumes can have a large impact on fjord circulation and biogeochemistry. In this study, we assess the influence of tidewater glaciers on nitrogen inputs and cycling in two fjords in Svalbard during the summer using stable isotopic analyses of dissolved nitrate ( δ 15 N and δ 18 O) in combination with nutrient and hydrographic data. Kongsfjorden receives inputs from tidewater glaciers, whereas Rijpfjorden mainly receives surface inputs from land-terminating glaciers. Results showed that both fjords are enriched in nutrients from terrestrial inputs. Nutrient ratios indicate excess Si and P relative to N. In both fjords, terrestrial nitrate from snowpack and glacier melting are identified as the dominant sources based on high δ 18 O-NO <math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" dspmath="mathimg" md5hash="0723f17b5be9fc41c36a5585631feb47"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-5973-2022-ie00001.svg" width="9pt" height="16pt" src="bg-19-5973-2022-ie00001.png"/></svg:svg> and low δ 15 N-NO <math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi/><mn mathvariant="normal">3</mn><mo>-</mo></msubsup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="9pt" height="16pt" class="svg-formula" ...