Preprints
https://doi.org/10.5194/egusphere-2023-2538
https://doi.org/10.5194/egusphere-2023-2538
14 Dec 2023
 | 14 Dec 2023

Contribution of physical processes to variability of dissolved silicate in the Labrador Sea between 1980 and 2015

Alizée Dale, Marion Gehlen, Douglas W. R. Wallace, Germain Bénard, Christian Éthé, and Elena Alekseenko

Abstract. We use output of an eddy-permitting biogeochemical ocean general circulation model to investigate the drivers of the observed decline in the pre-bloom inventory of dissolved silicate (DSi) and its InterAnnual Variability (IAV) over the period 1980–2015. Specifically, the relative impacts of an abrupt decrease in Deep Winter Convection (DWC) and changes in Arctic inflow on DSi concentrations at the regional scale are examined. The IAV of the upper layer DSi inventory covaries with both the Arctic inflow and DWC, however, the pre-bloom decline seems driven primarily by the DWC and associated winter vertical mixing, while the contribution of Arctic inflow is negligible. Our study suggests that the inventory responds to natural decadal variability which is influenced by two major climate modes, the North Atlantic and the Arctic Oscillations, with the former appearing to be the main control.

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Alizée Dale, Marion Gehlen, Douglas W. R. Wallace, Germain Bénard, Christian Éthé, and Elena Alekseenko

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  • RC1: 'Comment on egusphere-2023-2538', Anonymous Referee #1, 04 Feb 2024
  • RC2: 'Comment on egusphere-2023-2538', Anonymous Referee #2, 24 Feb 2024
  • RC3: 'Comment on egusphere-2023-2538', Anonymous Referee #3, 24 Feb 2024
Alizée Dale, Marion Gehlen, Douglas W. R. Wallace, Germain Bénard, Christian Éthé, and Elena Alekseenko
Alizée Dale, Marion Gehlen, Douglas W. R. Wallace, Germain Bénard, Christian Éthé, and Elena Alekseenko

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Short summary
Diatom, which is at the base of a productive food chain that supports valuable fisheries, dominates the total primary production of the Labrador Sea (LS). The synthesis of biogenic silica frustules makes them peculiar among phytoplankton but also dependent on dissolved silicate (DSi). Regular oceanographic surveys show declining DSi concentrations since the mid-1990s. With a model-based approach, we show that weakening deep winter convection was the proximate cause of DSi decline in the LS.