Impact of Vertical Mixing on Summertime Net Community Production in Canadian Arctic and Subarctic Waters: Insights From In Situ Measurements and Numerical Simulations

Abstract

Arctic and Subarctic oceanic waters contain highly-productive ecosystems that contribute significantly to the global air-sea exchange of carbon dioxide (e.g., Ahmed & Else, 2019;Fennel et al., 2018). Strong variability in these ecosystems is driven, in part, by seasonal cycles in marine primary production (PP) associated with large-amplitude changes in mixed layer (ML) nutrient inventories, solar irradiance, and sea ice dynamics (R. Ji et al., 2013;Tremblay et al., 2015). On longer timescales, atmospheric warming and the acceleration of the polar

Design Update to “The Pressure of In-Situ Gases Instrument (PIGI) for Autonomous Shipboard Measurement of Dissolved O2 and N2 in Surface Ocean Waters”

“…During the cruise, we compared oxygen measurements taken from the ship's seawater line against surface bottle samples to evaluate any potential discrepancies resulting from the ship's sampling system (Figure 2a; Izzet and Tortell, 2021;Cynar et al, 2022;Izett et al, 2022). This was done using Winkler titrations (Culberson, 1991;Dickson, 1994) of triplicate samples taken from the inline system and from a Niskin bottle at 3 m, which is the same depth as the seawater b a intake location on the hull.…”

“…Similar to O 2 /Ar sampling, the PIGI system's NCP estimates assume that N 2 , like Ar, is a biologically inert analog for O 2 , meaning that the O 2 /N 2 ratio is unaffected by temperature and salinitydependent solubility effects, and that there is no biological impact on N 2 . Izett and Tortell (2021) and Izett et al (2022) tested the validity of these assumptions in model and field tests, demonstrating a negligible impact of biological N 2 cycling on mixed layer O 2 /N 2 signals. They also found near-equivalence between surface O 2 /Ar-and O 2 /N 2 -derived NCP estimates.…”

Canada's marine carbon sink: an early career perspective on the state of research and existing knowledge gaps

“…Moreover, coastal margins and the ice edge can also be important pathways for carbon export (Nishino et al 2011), particularly as phytoplankton blooms may be stimulated by nutrients derived from coastal rivers or seeded by ice algae (Matthes et al 2021). There is, however, some evidence that rivers may drive localized marine organic carbon respiration (Izett et al 2022), suggesting that some Arctic regions may experience periodic net CO 2 outgassing (Manning et al 2020). Finally, it is likely that future Arctic CO 2 fluxes will exhibit varied responses to ongoing permafrost thawing and changes in river runoff, through various effects on nutrient and organic matter inputs, and changes to local marine stratification (Vonk and Gustafsson 2013;Prowse et al 2015).…”