Decreasing stability of the Gulf Stream (GS) has resulted in more frequent interations between its meanders and the Mid-Atlantic Bight (MAB) continental shelf and slope region. While these intrusions could have been thought to reduce primary productivity by transporting relatively nutrient-poor water to the otherwise productive shelf edge region, we present evidence of widespread, anomalously high-chlorophyll subsurface diatom hotspots in the slope sea that likely resulted from the intursion of a GS meander in July 2019. The water mass properties associated with the subsurface hotspots were characteristic of deeper GS water; we propose that the hotspots resulted from upwelling of GS water while being transported towards the shelf. The GS stream meander intruding towards the shelf east of where the hotspots were found is likely to have driven the upwelling of this deeper, nutrient-rich water into the slope sea euphotic zone, though multiple potential transport mechanisms are possible. Further work is thus needed to understand how changing western boundary current behavior could influence coastal and slope sea marine ecosystems.

Oliver, H., Zhang, W. G., Smith, W. O., Alatalo, P., Chappell, P. D., Hirzel, A. J., et al. (2021). Diatom hotspots driven by western boundary current instability. Geophysical Research Letters, 48, e2020GL091943. https://doi.org/10.1029/2020GL091943