© 1998 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Common signals between physical and atmospheric variables and zooplankton biomass in the Subarctic Pacific
Marine Sciences Research Center, State University of New York Stony Brook, New York, 11794-5000, USA
Correspondence to A. Conversi: tel: +39 187 536275; fax: +39 187 536273; e-mail: conversi{at}estosf.santateresa.enea.it
There is increasing evidence that zooplankton inter-annual variability is related to changes in the physical and atmospheric environments. Here, we analyse and compare the inter-annual variations of zooplankton biomass and of two environmental properties – surface temperature and surface salinity – at Station P, Gulf of Alaska (50°N 145°W). This 1956–1980 data set was gathered by Canadian weatherships, with a frequency of approximately 1 month. Spectral analysis shows that the annual cycle dominates the variations of zooplankton biomass, as well as temperature and salinity. However, most of the inter-annual variability in all three properties is contained in frequency bands corresponding to periods near 12–24 years, 
6 years, 29 months, and 14.5 months. These frequencies correspond to those found in well-known oscillations in the atmosphere–ocean system. In this article we summarize some of the results of our work, compare our results with others reported in the literature and discuss possible mechanisms for the relationships between zooplankton, salinity, and temperature.
Keywords: climate–ocean interactions, copepod, Gulf of Alaska, inter-annual variations, North Pacific, Quasi Biennial Oscillation, salinity, SST, time series, zooplankton biomass