Figure 2: Relationship between algal Ba/Ca and δ13C. | Nature Communications

Figure 2: Relationship between algal Ba/Ca and δ13C.

From: Multicentennial record of Labrador Sea primary productivity and sea-ice variability archived in coralline algal barium

Figure 2

(a) Annual and 10-year mean algal Ba/Ca ratios were derived from sample Kil and δ13C values from sample 2013-15–4 (plotted inversely on secondary x axis). The post-1960s departure to negative δ13C values is due to the anthropogenic introduction of isotopically light fossil fuels into the biosphere (‘Suess Effect’). A δ13C decline starting 1970 has commonly been observed in marine proxy archives throughout the North Atlantic1. Note that outliers defined as ±four times of interquartile range of raw δ13C values were removed from the comparison. Correlations between algal Ba/Ca and δ13C before the Suess Effect are displayed as scatter plots on (b) annual timescales (1870–1960; r=−0.53, P<0.001; Padj=0.0038; s.e. of Ba/Ca ±0.2e−5); and (c) Decadal timescales (1870–1960; r=−0.89, Padj=0.003). Significance levels were adjusted for loss in degrees of freedom using a lag-1 test that takes into account the temporal autocorrelation of the underlying time series (Padj=adjusted for loss of degrees of freedom).

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