The Cold Fresh Pulse in the Northwest Atlantic in 2023/2024
G. Gawarkiewicz, E. Perez, L. Enders, P. Fratantoni, K. Chen, L. Stoltz, N. Olsen, F. Bahr, K. Hyde, S. Salois, A. Gangopadhyay, A. SilverAbstract
The Northwest Atlantic Ocean has been warming at an accelerated rate since 2010. However, in summer 2023 a cold fresh signal concentrated along the shelfbreak advected into the Middle Atlantic Bight from the Scotian Shelf and Grand Banks region. By spring of 2024 the entire continental shelf in the Middle Atlantic Bight had a significant fresh salinity anomaly. A second cold fresh pulse appeared primarily located over the continental slope in May 2024. Shipboard observations in early June 2024 show that near surface salinity across the entire slope region was typical of mid‐shelf salinities (31–33 PSU). The fresh anomalies were greatly reduced by October 2024. The unusual water mass conditions, including cold anomalies in May/June 2024, led to major changes to the shelf/slope ecosystem in 2024 including significant decreases in shortfin and longfin squid landings and the re‐appearance of cold water fish such as mackerel and herring. There were direct economic impacts in terms of reduced revenue to major fishing ports in the northeast U.S. In addition, a substantial fresh water anomaly was injected into the Gulf Stream, with potential impacts further downstream in terms of stratification in the North Atlantic.