| Summary: | Anthropogenic forcing is predicted to increase climate variability. As many biological processes, such as recruitment to fish populations, are sensitive to variability in environmental conditions, such an increase in climate variability has the potential for ecological effects. In this study, we evaluate the evidence for ecologically-important increases in climate variability across the North Pacific (20°-66°N) over recent decades (1951-2010). Our climate data are SST values on a 1°x1° grid from the HADISST data set, which we standardized by the mean and SD of the 1951- 1980 climatology. Analysis of basin-wide SD over sliding windows at three temporal scales (month, year, decade) shows similar, nonlinear trends in variability at all three scales. Variability increased during a period of warming in the 1970s-1990s, then decreased during the 2000s and 2010s, when mean temperatures were generally stable. To test the hypothesis that biological variability has tracked these changes in climatic variability, we collected a set of long-term data sets from a diverse set of populations (zooplankton, ichthyoplankton, groundfish, salmon, seabirds, pinnipeds) from a variety of ecosystems (Oyashio Current and Transition; Bering Sea; Gulf of Alaska; California Current). Analysis of variability trends across these time series allows us to test for community-level changes in variability, across multiple taxa and trophic levels, over large spatial scales. Further analysis of trends in SST variability at the scale of individual large marine ecosystems also allows us to assess the coherence of the basin-scale patterns at ecologically-relevant spatial scales.
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