The North Atlantic experiences climate variability on multidecadal scales, which is sometimes referred to as Atlantic multidecadal variability. However, the relative contributions of external forcing such as changes in solar irradiance or volcanic activity and internal dynamics to these variations are unclear. Here we provide evidence for persistent summer Atlantic multidecadal variability from AD 800 to 2010 using a network of annually resolved terrestrial proxy records from the circum-North Atlantic region. We find that large volcanic eruptions and solar irradiance minima induce cool phases of Atlantic multidecadal variability and collectively explain about 30% of the variance in the reconstruction on timescales greater than 30 years. We are then able to isolate the internally generated component of Atlantic multidecadal variability, which we define as the Atlantic multidecadal oscillation. We find that the Atlantic multidecadal oscillation is the largest contributor to Atlantic multidecadal variability over the past 1,200 years. We also identify coherence between the Atlantic multidecadal oscillation and Northern Hemisphere temperature variations, leading us to conclude that the apparent link between Atlantic multidecadal variability and regional to hemispheric climate does not arise solely from a common response to external drivers, and may instead reflect dynamic processes.
Key Laboratory of Desert and Desertification, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China; Department of History, Stockholm University, Stockholm, Sweden; Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden; Department of Geography, Climatology, Climate Dynamics and Climate Change, Justus Liebig University of Giessen, Senckenbergstrasse 1, Giessen, Germany; Centre for International Development and Environmental Research, Justus Liebig University Giessen, Senckenbergstrasse 3, Giessen, Germany; Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom; Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
Recommended Citation:
Wang J.,Yang B.,Ljungqvist F.C.,et al. Internal and external forcing of multidecadal Atlantic climate variability over the past 1,200 years[J]. Nature Geoscience,2017-01-01,10(7)