12 research outputs found
Synchronous marine pelagic regime shifts in the Northern Hemisphere.
Regime shifts are characterized by sudden, substantial and temporally persistent
changes in the state of an ecosystem. They involve major biological
modifications and often have important implications for exploited living
resources. In this study, we examine whether regime shifts observed in
11 marine systems from two oceans and three regional seas in the Northern
Hemisphere (NH) are synchronous, applying the same methodology to all.
We primarily infer marine pelagic regime shifts from abrupt shifts in zooplankton
assemblages,with the exception of the East Pacificwhere ecosystemchanges
are inferred fromfish. Our analyses provide evidence for quasi-synchronicity of
marine pelagic regime shifts both within and between ocean basins, although
these shifts lie embedded within considerable regional variability at both
year-to-year and lower-frequency time scales. In particular, a regime shift was
detected in the late 1980s in many studied marine regions, although the exact
year of the observed shift varied somewhat from one basin to another. Another
regime shift was also identified in the mid- to late 1970s but concerned less
marine regions.We subsequently analyse themain biological signals in relation
to changes in NH temperature and pressure anomalies. The results suggest that
the main factor synchronizing regime shifts on large scales is NH temperature;
however, changes in atmospheric circulation also appear important. We propose
that this quasi-synchronous shift could represent the variably lagged
biological response in each ecosystem to a large-scale,NHchange of the climatic
system, involving both an increase in NH temperature and a strongly positive
phase of the Arctic Oscillation. Further investigation is needed to determine
the relative roles of changes in temperature and atmospheric pressure patterns
and their resultant teleconnections in synchronizing regime shifts at large scales