Abstract
AbstractThe lack of long‐term, highly resolved (annual to subannual) and absolutely dated baseline records of marine variability extending beyond the instrumental period (last ~50–100 years) hinders our ability to develop a comprehensive understanding of the role the ocean plays in the climate system. Specifically, without such records, it remains difficult to fully quantify the range of natural climate variability mediated by the ocean and to robustly attribute recent changes to anthropogenic or natural drivers. Here we present a 211 year (1799–2010 C.E.; all dates hereafter are Common Era) seawater temperature (SWT) reconstruction from the northeast Atlantic Ocean derived from absolutely dated, annually resolved, oxygen isotope ratios recorded in the shell carbonate (δ18Oshell) of the long‐lived marine bivalve molluskGlycymeris glycymeris. The annual record was calibrated using subannually resolved δ18Oshellvalues drilled from multiple shells covering the instrumental period. Calibration verification statistics and spatial correlation analyses indicate that the δ18Oshellrecord contains significant skill at reconstructing Northeast Atlantic Ocean mean summer SWT variability associated with changes in subpolar gyre dynamics and the North Atlantic Current. Reconciling differences between the δ18Oshelldata and corresponding growth increment width chronology demonstrates that 68% of the variability inG.glycymerisshell growth can be explained by the combined influence of biological productivity and SWT variability. These data suggest thatG.glycymeriscan provide seasonal to multicentennial absolutely dated baseline records of past marine variability that will lead to the development of a quantitative understanding of the role the marine environment plays in the global climate system.
Highlights
North Atlantic seawater temperature (SWT) variability plays a significant role in the global climate system with the propagation of heat through the northward flowing surface currents (Gulf Stream/North Atlantic Current) acting as a ‘bottom-up’ mechanism for driving atmospheric climate variability (Tandon and Kushner, 2015)
Whilst it is important to assess the degree of coherence across all frequency domains, to account for the high degree of autocorrelation in both the T 18Oshell series and the instrumental datasets, which can lead to an overestimate of the significance of the correlation between the two series, we examined the correlations using both the raw non-detrended data and linear detrended data
In this study we demonstrate that sub-annual and annually resolved 18O analyses derived from the growth increments of the long-lived marine bivalve G. glycymeris can reconstruct past summer SWTs on sub-annual to multi-centennial timescales
Summary
North Atlantic seawater temperature (SWT) variability plays a significant role in the global climate system with the propagation of heat through the northward flowing surface currents (Gulf Stream/North Atlantic Current) acting as a ‘bottom-up’ mechanism for driving atmospheric climate variability (Tandon and Kushner, 2015). Kamenos, 2010; Halfar et al, 2011), and the typically lower resolution (multi-decadal) reconstructions from marine sediment cores that rely on radiocarbon (14C) derived age models Whilst these latter sediment archives provide invaluable information regarding the amplitude and potential processes of past climate variability (e.g. Lund et al, 2006; Hall et al, 2010; Sicre et al, 2011; Moffa-Sanchez et al., 2014a,b; Mjell et al, 2016) the large uncertainties associated with radiocarbon derived age models typically hinder the application of these data in resolving high frequency (decadal to sub-decadal) spatiotemporal variability and robustly assessing potential leads/lags within the marine system and in the ocean-atmosphere coupling. Hitherto marine bivalve sclerochronological archives have provided robust reconstructions of past SWTs (Schöne et al, 2004; Brocas et al, 2013; Reynolds et al, 2013; Mette et al, 2016; Reynolds et al, 2017), oceanic carbon dynamics (Schöne et al, 2011), marine radiocarbon reservoir ages (Wanamaker et al, 2012), coupled ocean and terrestrial ecosystem dynamics (Helama et al., 2007; Black, 2009; Black et al, 2014) and to investigate the mechanisms and drivers of ocean variability (Lohmann and Schöne, 2013; Reynolds et al, 2016; Reynolds et al, 2017)
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