DISSOLVED ORGANIC NITROGEN AND CARBON DISTRIBUTIONS AND DYNAMICS ACROSS THE ARCTIC OCEAN POLAR SURFACE LAYER

The Arctic Ocean is notably deficient in inorganic nutrients, making dissolved organic nitrogen (DON) stand out as the principal reservoir of fixed nitrogen in this environment. However, due to the region’s inaccessibility, our understanding of the distributions and dynamics of DON in the Arctic Ocean remains limited. Here we combine hydrographic sections (GEOTRACES section GN01 and GN04; US GO-SHIP section ARC01; occupied in 2015) for the first trans-Arctic examination of DON in the polar surface layer (PSL). The Transpolar Drift harbors the highest concentrations of DON of all basins, alongside elevated dissolved organic carbon (DOC), meteoric water fractions (i.e., from rivers), and inorganic nutrients. This influence extends into the adjacent Amundsen Basin, where DON and DOC concentrations remain high. Conversely, the Nansen Basin and the Barents Sea, largely influenced by inflowing Atlantic water, exhibit the lowest DON and DOC of all basins. In the Amerasian Basin, we observe a non-conservative behavior between meteoric water and DON, likely due to the extended residence time in the PSL, deepening of the nutricline by the Beaufort Gyre, and influence of seasonal ice melt. This study also reports the first trans-Arctic measurements of δ¹⁵N of DON, with values ranging from 0.14‰ to 9.21‰. Overall, these findings underscore the significant role that regional hydrology and biogeochemical processes play in shaping the distributions of DON in the Arctic Ocean and highlight the complexity of Arctic nitrogen dynamics.

Presentation Preference: Oral

Primary Presenter: Claire Fandel, University of Miami (caf185@miami.edu)

Authors:

Claire Fandel, University of Miami  (caf185@miami.edu)

Dennis Hansell, University of Miami  (dhansell@miami.edu)

Annie Bourbonnais, University of South Carolina  (abourbonnais@seoe.sc.edu)

Mariana Bif, University of Miami  (mariana@mbari.org)

Kimberly Popendorf, University of Miami  (kpopendorf@earth.miami.edu)