Remote climate forcing of decadal‐scale regime shifts in Northwest Atlantic shelf ecosystems

Abstract

Decadal-scale regime shifts in Northwest Atlantic shelf ecosystems can be remotely forced by climateassociated atmosphere-ocean interactions in the North Atlantic and Arctic Ocean Basins. This remote climate forcing is mediated primarily by basin-and hemispheric-scale changes in ocean circulation. We review and synthesize results from process-oriented field studies and retrospective analyses of time-series data to document the linkages between climate, ocean circulation, and ecosystem dynamics. Bottom-up forcing associated with climate plays a prominent role in the dynamics of these ecosystems, comparable in importance to that of topdown forcing associated with commercial fishing. A broad perspective, one encompassing the effects of basin-and hemispheric-scale climate processes on marine ecosystems, will be critical to the sustainable management of marine living resources in the Northwest Atlantic.

Synchronous marine pelagic regime shifts in the Northern Hemisphere

“…In addition to the role of temperature, both atmospheric and oceanic circulations have been shown to play a key role in the long-term changes of marine populations [6,43,79,95], and may also influence the regime dynamics of the areas we studied. Our results support the hypothesis that climate dynamics may have a relevant role.…”

“…This phenomenon explains why all species in an ecosystem do not exhibit a shift [45,87], and, if a limited 2002 2003 1999 2000 2001 1989 1990 1991 1996 1997 1998 1992 1993 1994 1995 1984 1986 1985 1987 1988 1977 1978 1976 1979 1980 1981 1982 1983 1972 1973 1974 1971 1975 1960 1961 1962 1963 1968 1970 1969 1964 1965 1966 To address this question, we analysed the first three PCs originating from the PCAs performed for each ecosystem to reveal the NH biological state (BioPC), together with climate indicators (NHT, AO, PDO and AMO) and with long-term spatial variations in NHTs and SLPs. These variables were chosen because previous studies have suggested that temperature may affect the biogeographical distribution of many pelagic organisms [7,69], while changes in the main pressure centres can influence ocean circulation and the biological processes [41,43,[88][89][90], as well as local temperature [6]. We searched for potential lags in the responses of all regions to large-scale hydro-climatic forcing but no lag was observed using cross-correlation analysis and cross-correlograms.…”

“…esrl.noaa.gov/psd/data/timeseries/AMO/). Each of these indices track phenomena that have been assumed to play a role in some of the reported regime shifts [6,8,19,43,65].…”

“…of appropriate length for our multi-decadal investigation. Even if the data used in this investigation represent mostly one trophic level, it has to be noted that other studies have identified ecosystemwide regime shifts in most of these areas [6,8,9,11,36,43,44,47]. Second, we identified temporal shifts in all these systems, individually and in aggregate, and examined their relationships to (i) large-scale climatic indices (Northern Hemisphere temperature (NHT) anomalies, Arctic Oscillation (AO), Atlantic Multi-decadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO)), and (ii) spatial patterns of change in sea surface temperature (SST) and sea-level pressure (SLP) over the NH.…”

“…Regime shifts have been reported for the North Pacific (1976/1977 and 1989) [6,[26][27][28][29], specifically the northeast Pacific (1976/1977) [30,31], (1998/1999) [32,33] and the northwest Pacific (1976/1977, 1988/1989 and 1998) [34][35][36]; the Humboldt Current in the southern Pacific (1968/1970 and 1984/1986) [37,38]; and the northwest Atlantic (1989Atlantic ( /1990 [39][40][41][42][43]. In addition, regime shifts were observed in the late 1980s around all European seas [8]: the North Sea [44,45], the Baltic Sea [9,46], the northwest European shelf seas (1987/1990) [47,48], the western [49] and eastern (Adriatic) Mediterranean Sea [8,50,51] and the Black Sea [52,53].…”