The ecological impact of the Great Salinity Anomaly in the northern North-west Atlantic

In a number of recent papers Cushing has advocated that the Great Salinity Anomaly (GSA), which entered the northern North Atlantic in the early 1970s, adversely affected the recruitment of a number of deep-water fish stocks of this ocean. Cushing envisages that a temperature anomaly accompanying the GSA slowed and/or delayed growth in the spring phytoplankton bloom which sequentially affected zooplankton growth and fish recruitment. We test a number of hypotheses relating to Cushing's picture, focusing on the waters of the West Greenland, Labrador and Newfoundland Shelves. We find that, south of Greenland waters, there were no significant temperature anomalies corresponding to the GSA. In addition we show that stability of the shelf waters increased during the GSA, casting doubt on the contention that the phytoplankton bloom was delayed by retardation of the spring stabilization of the water column due to the influence of cold water. Our analysis indicates that the food chain coupling of environment to recruitment (climate to phytoplankton to zooplankton to fish) is not strong in the study region.