Download Ocean-atmosphere interactions related to the AMO caused

Ocean-atmosphere interactions related to the AMO caused simultaneous ‘regime shift’-like
changes in ecosystems of eastern North Atlantic and Mediterranean in the mid-1990s
Jürgen Alheit1, Joachim Groeger2, Priscilla Licandro3, Ian H. McQuinn4, Thomas Pohlmann5,
Athanassios C. Tsikliras6
1
Leibniz Institute for Baltic Sea Research, Warnemünde, Germany. E-mail: [email protected]
2
Thünen Institute for Sea Fisheries, Hamburg, Germany
3
Sir Alister Hardy Foundation for Ocean Science, Plymouth, UK
4
Maurice Lamontagne Institute, DFO, Mont Joli, Canada
5
Institute of Oceanography, Hamburg University, Hamburg, Germany
6
School of Biology, Aristotle University, Thessaloniki, Greece
Northeast Atlantic marine ecosystems such as the Bay of Biscay, Celtic Sea, English Channel,
Subpolar Gyre region, Icelandic waters and the North Sea as well as the Mediterranean show
concomitant ‘regime shift’-like changes around the mid-1990s, which involved all biota of the
pelagial: phytoplankton, zooplankton, pelagic fish assemblages, demersal fish assemblages and
top predators. These shifts were caused by complex ocean-atmosphere interactions initiating largescale changes in the strength and direction of the current system that move water masses around
the North Atlantic and involved the North Atlantic Oscillation (NAO), the Atlantic Meridional
Overturning Circulation (AMOC), and the subpolar gyre (SPG). The contractions and expansions
of the SPG most likely played a key role in the coupled atmosphere-ocean system of the North
Atlantic. Fluctuations in the AMO seem to be a driver for these complex processes and small
pelagic fish population trends were the sentinels of these mid-1990s changes.