Plankton verses the blob: Impact of the 2014/15 warm water anomaly on the Northern Gulf of Alaska Shelf

We consider the anomalous conditions in the subarctic Pacific in the context of 18 years of observations along the Seward Line in the Northern Gulf of Alaska. May 2014 conditions on the shelf, were unremarable, but stronger signals emerged over the summer and through the fall. The September 2014 temperatures averaged over the upper 100m along the Seward Line were 1°C above normal. At that time, the Seward Line showed significant increases in the four copepods taxa normally associated with southern influence: Clausocalanus sp., Calanus pacificus, Mesocalanus tenuicornis, and Paracalanus parva. For all but the latter species, values were the highest observed in the 17-year time series. Warm waters persisted over the winter with May 2015 still over 1°C above normal. By September 2015, the thermal anomaly had declined to only 0.5°C more typical of previous El Nino’s. Like 2014, atypical abundances of warm water species occurred, but with disruption of typical spring phenology. We speculate on the ecosystem impact of such warm water events, given that their frequency may be expected to increase in future decades.