TY - JOUR
T1 - Disentangling carbon concentration changes along pathways of North Atlantic subtropical mode water
AU - Reijnders, Daan
AU - Bakker, Dorothee C. E.
AU - van Sebille, Erik
N1 - Data Availability Statement: The code to reproduce the results and figures from this paper is stored in YODA, Utrecht University's persistent data storage platform, see Reijnders et al. (2024) or https://doi.org/10.24416/UU01-05B2AT. The physical hindcast product FREEGLORYS2V4 was made available by Mercator Ocean International on request, and the biogeochemical hindcast product FREEBIORYS2V4 is available at https://doi.org/10.48670/moi-00019 (E.U. Copernicus Marine Service Information (CMEMS), 2023). Bottle and DIC data used for model-data comparison in Text S1 in Supporting Information S1 are available through the CLIVAR and Carbon Hydrographic Data Office at https://cchdo.ucsd.edu (Pickard, 2022; Swift et al., 2022; Toole & MacDonald, 2022). WOA18 data is available at https://www.ncei.noaa.gov/access/world-ocean-atlas-2018/ (Boyer et al., 2018). WOA23 data is available at https://www.ncei.noaa.gov/access/world-ocean-atlas-2023/ (Reagan & NOAA National Centers for Environmental Information, 2023). The Parcels Lagrangian framework version 2.4.1 is available at https://doi.org/10.5281/ZENODO.7680187 (Van Sebille et al., 2023).
Acknowledgements: DR and EvS were supported through funding from the Netherlands Organization for Scientific Research (NWO), Earth and Life Sciences, through project OCENW.KLEIN.085. DCEB was supported by UKRI's (UK Research and Innovation) CHALKY project NE/Y004388/1. We thank Siren Rühs and Jamie Palter for useful discussions and feedback, and Coralie Perruche for help with the FREEBIORYS2V4 product. This study has been conducted using E.U. Copernicus Marine Service Information. Bottle and CTD data along A20 in 2003 and 2012 was supported by the NSF/NOAA funded U.S Global Ocean Carbon and Repeat Hydrography Program.
PY - 2024/7
Y1 - 2024/7
N2 - North Atlantic subtropical mode water (NASTMW) serves as a major conduit for dissolved carbon to penetrate into the ocean interior by its wintertime outcropping events. Prior research on NASTMW has concentrated on its physical formation and destruction, as well as Lagrangian pathways and timescales of water into and out of NASTMW. In this study, we examine how dissolved inorganic carbon (DIC) concentrations are modified along Lagrangian pathways of NASTMW on subannual timescales. We introduce Lagrangian parcels into a physical‐biogeochemical model and release these parcels annually over two decades. For different pathways into, out of, and within NASTMW, we calculate changes in DIC concentrations along the path (ΔDIC), distinguishing contributions from vertical mixing and biogeochemical processes. The strongest ΔDIC is during subduction of water parcels (+101 μmol L-1 in 1 year), followed by transport out of NASTMW due to increases in density in water parcels (+10 μmol L-1). While the mean ΔDIC for parcels that persist within NASTMW in 1 year is relatively small at +6 μmol L-1, this masks underlying dynamics: individual parcels undergo interspersed DIC depletion and enrichment, spanning several timescales and magnitudes. Most DIC enrichment and depletion regimes span timescales of weeks, related to phytoplankton blooms. However, mixing and biogeochemical processes often oppose one another at short timescales, so the largest net DIC changes occur at timescales of more than 30 days. Our new Lagrangian approach complements bulk Eulerian approaches, which average out this underlying complexity, and is relevant to other biogeochemical studies, for example, on marine carbon dioxide removal.
AB - North Atlantic subtropical mode water (NASTMW) serves as a major conduit for dissolved carbon to penetrate into the ocean interior by its wintertime outcropping events. Prior research on NASTMW has concentrated on its physical formation and destruction, as well as Lagrangian pathways and timescales of water into and out of NASTMW. In this study, we examine how dissolved inorganic carbon (DIC) concentrations are modified along Lagrangian pathways of NASTMW on subannual timescales. We introduce Lagrangian parcels into a physical‐biogeochemical model and release these parcels annually over two decades. For different pathways into, out of, and within NASTMW, we calculate changes in DIC concentrations along the path (ΔDIC), distinguishing contributions from vertical mixing and biogeochemical processes. The strongest ΔDIC is during subduction of water parcels (+101 μmol L-1 in 1 year), followed by transport out of NASTMW due to increases in density in water parcels (+10 μmol L-1). While the mean ΔDIC for parcels that persist within NASTMW in 1 year is relatively small at +6 μmol L-1, this masks underlying dynamics: individual parcels undergo interspersed DIC depletion and enrichment, spanning several timescales and magnitudes. Most DIC enrichment and depletion regimes span timescales of weeks, related to phytoplankton blooms. However, mixing and biogeochemical processes often oppose one another at short timescales, so the largest net DIC changes occur at timescales of more than 30 days. Our new Lagrangian approach complements bulk Eulerian approaches, which average out this underlying complexity, and is relevant to other biogeochemical studies, for example, on marine carbon dioxide removal.
U2 - 10.1029/2023JC020814
DO - 10.1029/2023JC020814
M3 - Article
SN - 2169-9275
VL - 129
JO - Journal of Geophysical Research: Oceans
JF - Journal of Geophysical Research: Oceans
IS - 7
M1 - e2023JC020814
ER -