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

• Published in: Biogeosciences
• Main Authors: K. Rutherford, K. Fennel, L. Garcia Suarez, J. G. John
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2024
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; North Atlantic
• Online Access: https://doi.org/10.5194/bg-21-301-2024; https://doaj.org/article/06b4972cb40b47fdb20b9667228f2e4e

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.