North Atlantic Oscillation dynamics recorded in shells of a long-lived bivalve mollusk

Abstract

Existing reconstructions of the winter North Atlantic Oscillation (WNAO) are based on terrestrial proxies and historical documents. No direct high-resolution, long-term records from marine settings are available for this major climate-dictating phenomenon, which severely affects a variety of economic aspects of our society. Here we present a 245 yr proxy WNAO index based on shells of the long-lived marine bivalve mollusk Arctica islandica. Variations in annual rates of shell growth are positively correlated with WNAO-related changes in the food supply. Maximum amplitudes in frequency bands of 7-9 and 5-7 yr fall exactly within the range of instrumental and other proxy WNAO indices. These estimates were obtained for specimens collected live, 2000 km apart, in the central North Sea and on the Norwegian Shelf. Hence, the WNAO influences hydrographic regimes of large regions of the ocean. Our study demonstrates that A. islandica can reliably reconstruct WNAO dynamics for time intervals and regions without instrumental records. Our new tool functions as a proxy for the WNAO index prior to the twentieth-century greenhouse forcing and has the potential to further validate other proxy-based WNAO records.

A seasonally resolved bottom‐water temperature record for the period AD 1866–2002 based on shells of Arctica islandica (Mollusca, North Sea)

“…Based on similar growth patterns, growth-increment time series of synchronous trees with overlapping life spans can be strung together to form mean and master chronologies spanning centuries and millennia. Similar techniques were recently applied to a variety of different bivalve mollusc species (Jones et al, 1989;Marchitto et al, 2000;Schöne, 2003;Schöne et al, 2003aSchöne et al, ,b, 2004bStrom et al, 2004).…”

“…In a previous study, Schöne et al (2003a) demonstrated that variable growth rates of shells of A. islandica record changes of the WNAO. Here, we show that the shells contain another proxy archive of the changes of the WNAO, i.e.…”

“…Oxygen isotope-derived temperatures and microgrowth increment counts were previously used to assign calendar dates to shell sections (Goodwin et al, 2001;Schöne et al, 2003aSchöne et al, ,b, 2004a. Knowing the time contained in a certain shell section provides the prerequisite for using geochemical data of bivalve shells, such as A. islandica, for palaeoclimate reconstructions.…”

“…tree data are summer biased, because they do not grow during winter), and clear seasonal time constraints do not exist. Recently, Schöne et al (2003a) presented the first marine proxy for the WNAO based on shell growth rates of the bivalve mollusc Arctica islandica L. collected alive from bottom waters of the North Sea and the Norwegian Sea.…”

Evaluation of CMIP5 models over the northern North Atlantic in the context of forthcoming paleoclimatic reconstructions

“…In addition to the high temporal resolution of Arctica islandica, the reconstructions derived from its records can be crossvalidated, absolutely dated (Scourse et al 2006;Butler et al 2010) and offer significant advantages in evaluating long-term NA marine climate dynamics ). Records of Arctica islandica can be used to reconstruct sea water temperatures (Eagle et al 2013;Wanamaker et al 2016), salinity (Gillikin et al 2006), major NA climate modes like the Atlantic Multidecadal Oscillation (AMO) , ocean dynamics (see for NAO in Schöne et al 2003; see for AMOC in; Wanamaker et al 2012), hydrographic changes and ecosystem dynamics (Witbaard 1996;Witbaard et al 2003).…”