Uncertainty in the evolution of northwest North Atlantic circulation leads to diverging biogeochemical projections

• Main Authors: Rutherford, Krysten, Fennel, Katja, Garcia Suarez, Lina, John, Jasmin G.
• Format: Text
• Language: English
• Published: 2024
• Subjects: North Atlantic
• Online Access: https://doi.org/10.5194/egusphere-2023-987; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-987/

The global ocean's coastal areas are rapidly experiencing the effects of climate change. These regions are highly dynamic, with relatively small-scale circulation features like shelf break currents playing an important role. Projections can produce widely diverging estimates of future regional circulation structures. Here, we use the northwestern North Atlantic, a hotspot of ocean warming, as a case study to illustrate how the uncertainty in future estimates of regional circulation manifests itself and affects projections of shelf-wide biogeochemistry. Two diverging climate model projections are considered and downscaled using a high-resolution regional model with intermediate biogeochemical complexity. The two resulting future scenarios exhibit qualitatively different circulation structures by 2075 where along-shelf volume transport is reduced by 70 % in one of them and while remaining largely unchanged in the other. The reduction in along-shelf transport creates localized areas with either amplified warming ( +3 ∘ C) and salinification ( +0.25 units) or increased acidification ( −0.25 units) in shelf bottom waters. Our results suggest that a wide range of outcomes is possible for continental margins and suggest a need for accurate projections of small-scale circulation features like shelf break currents in order to improve the reliability of biogeochemical projections.