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: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2023
• Subjects: article; Verlagsveröffentlichung; North Atlantic
• Online Access: https://doi.org/10.5194/egusphere-2023-987; https://noa.gwlb.de/receive/cop_mods_00066841; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00065311/egusphere-2023-987.pdf; https://egusphere.copernicus.org/preprints/2023/egusphere-2023-987/egusphere-2023-987.pdf

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 northwest 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 illustrate 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.