The response of Calanus finmarchicus populations to climate variability in the Northwest Atlantic: basin-scale forcing associated with the North Atlantic Oscillation

The North Atlantic Oscillation (NAO) is associated with decadal-scale forcing of climate and physical oceanography throughout the North Atlantic. Oceanographers have recently established correlations between the NAO and various processes at work in the shelf ecosystems of the NE Atlantic, correlations that have led them to suggest several hypotheses explaining the mechanistic basis of ecosystem and population responses to the NAO. Here, we incorporate these ideas into a new conceptual framework for interpreting the responses of shelf ecosystems to climate variability on both sides of the North Atlantic. This conceptual framework, contrasting the relative importance of internal ecological dynamics versus advective exchange processes, is used to examine the trans-Atlantic responses of Calanus finmarchicus populations to the NAO. We conclude by proposing an NAO-based explanation for the trends in C. finmarchicus abundance observed from 1961 to 1989 on the NW Atlantic Shelf.