Winter Mixing Controls Carbon Sequestration by the Biological Pump in the Subpolar North Atlantic.
Saved in:
| Title: | Winter Mixing Controls Carbon Sequestration by the Biological Pump in the Subpolar North Atlantic. |
|---|---|
| Authors: | Fogaren, K. E.1 (AUTHOR) fogaren@bc.edu, Palevsky, H. I.1 (AUTHOR), Yoder, M.1 (AUTHOR), Nicholson, D. P.2 (AUTHOR), Cuevas, J. M.1 (AUTHOR), Wanzer, L.3 (AUTHOR) |
| Source: | Journal of Geophysical Research. Oceans. May2026, Vol. 131 Issue 5, p1-21. 21p. |
| Subject Terms: | *Carbon sequestration, *Biogeochemistry, *Carbon cycle, Oceanic mixing, Natural heat convection |
| Geographic Terms: | North Atlantic Ocean |
| Abstract: | Year‐round, full water‐column hydrodynamic and biogeochemical observations at the Ocean Observatories Initiative's Irminger Sea Array provide a unique opportunity to examine the drivers of ocean carbon sequestration via the biological carbon pump in a region with deep winter convection. We use daily resolution oxygen and optical backscatter profiles to quantify carbon remineralization and large particles sinking throughout the water column from 2015 to 2022, during which deep winter convection ranged from 440 to 1,430 dbar. We use calibrated oxygen time series to determine depth‐resolved remineralization rates, finding 6.4 ± 2.0 mol C m−2 yr−1 were exported seasonally from the surface and remineralized at depth. However, 65%–100% of this remineralized carbon was re‐entrained into the mixed layer in the subsequent winter, such that only 0.8 ± 1.2 mol C m−2 yr−1 was sequestered annually below the winter mixing depth. The remineralized carbon sequestered each year depends on winter mixing and carbon transfer efficiency through the thermocline, quantified as remineralization length scale (z∗ ${z}^{\ast }$). Interannual variability in z∗ ${z}^{\ast }$ is correlated with the maximum mixing depth of the previous winter, suggesting detrainment of biomass during spring shoaling is an important pathway for export to the mesopelagic. Backscatter profiles reveal a carbon pool of large particles that is efficiently transferred to depth, with sinking particle pulses sequestering ∼0.6–1.5 mol C m−2 yr−1 of carbon that is not captured in our oxygen‐based estimates. These results underscore the importance of sustained multi‐parameter biogeochemical time series data to unravel the intertwined biological and physical drivers of carbon cycling in this highly dynamic region. Plain Language Summary: In this study, we examined how carbon moves from the surface ocean into the deep sea in a region of the subpolar North Atlantic known for intense mixing each winter. We use two types of measurements to track carbon both sinking and being consumed by microbes, which were collected on buoys and underwater robots nearly every day for 7 years. We find that the amount of carbon that leaves the surface each year is high, but most of it is consumed by microbes within the layer that mixes to the surface the next winter. We find two different types of carbon that move from the surface to the deep ocean in different ways. One type comes from big particles that form during the spring growing season and sink to the deep ocean very quickly. The other type is from biological growth earlier in the year, which gets into the deep ocean primarily by physical mixing rather than sinking. Our results show the power of the long‐term, continuous measurements used for this study, and the importance of continuing to collect these data to further investigate how the ocean absorbs carbon. Key Points: 8,914 oxygen and 6,157 backscatter profiles are used to estimate seasonal carbon export and annual sequestration in the Irminger Sea65%–100% of the carbon remineralized within the seasonal thermocline was re‐entrained into the mixed layer the following winterBiomass detrainment after deep winter mixing and sinking of large particles drives efficient transfer to depth of two separate carbon pools [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Geophysical Research. Oceans is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | GreenFILE |
Be the first to leave a comment!
