Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change
Proceedings of the National Academy of Sciences
National Academy of Sciences
Marine ecosystems are sensitive to stochastic environmental variability, with higher-amplitude, lower-frequency--i.e., "redder"--variability posing a greater threat of triggering large ecosystem changes. Here we show that fluctuations in the Pacific Decadal Oscillation (PDO) index have slowed down markedly over the observational record (1900-present), as indicated by a robust increase in autocorrelation. This "reddening" of the spectrum of climate variability is also found in regionally averaged North Pacific sea surface temperatures (SSTs), and can be at least partly explained by observed deepening of the ocean mixed layer. The progressive reddening of North Pacific climate variability has important implications for marine ecosystems. Ecosystem variables that respond linearly to climate forcing will have become prone to much larger variations over the observational record, whereas ecosystem variables that respond nonlinearly to climate forcing will have become prone to more frequent "regime shifts." Thus, slowing down of North Pacific climate variability can help explain the large magnitude and potentially the quick succession of well-known abrupt changes in North Pacific ecosystems in 1977 and 1989. When looking ahead, despite model limitations in simulating mixed layer depth (MLD) in the North Pacific, global warming is robustly expected to decrease MLD. This could potentially reverse the observed trend of slowing down of North Pacific climate variability and its effects on marine ecosystems.
National Centers for Environmental Prediction (NCEP) Reanalysis Derived data were provided by the National Oceanic and Atmospheric Administration/Ocean and Atmospheric Research/Earth System Research Laboratory Physical Sciences Division (NOAA/OAR/ERSL PSD), Boulder, CO. The PDO index was provided by the Joint Institute for the Study of the Atmosphere and Ocean (JISAO), University of Washington/NOAA. HadISST and HadSST3 data were provided by the Met Office, Exeter, United Kingdom. ERSST data were provided by the NOAA. MLD data were provided by S. A. Grodsky, University of Maryland. C.A.B. and T.M.L. were supported by the Research on Changes of Variability and Environmental Risk (RECoVER), funded by EPSRC (EP/M008495/1). C.A.B. was also supported by a PhD Studentship funded by the University of Exeter, United Kingdom. T.M.L.’s contribution was also supported by a Royal Society Wolfson Research Merit Award and EU FP7/2007-2013 under Grant Agreement 603864 (HELIX).
This is the final version of the article. Available from the publisher via the DOI in this record.
Vol. 112, pp. 11496 - 11501
PubMed Central ID
Place of publication