Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change.
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.
Earth System Science, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QE, United Kingdom c.a.boulton@exeter.ac.uk t.m.lenton@exeter.ac.uk.
Chris A
CA
Boulton
Earth System Science, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QE, United Kingdom c.a.boulton@exeter.ac.uk t.m.lenton@exeter.ac.uk.
Timothy M
TM
Lenton
D000465:Algorithms; D002980:Climate; D057231:Climate Change; D017753:Ecosystem; D005398:Fisheries; D057232:Global Warming; D016014:Linear Models; D010140:Pacific Ocean; D013269:Stochastic Processes; D013696:Temperature; D013997:Time Factors; D014867:Water
D014867:Water
North Pacific; abrupt change; climate change; marine ecosystems; regime shifts