Seasonality in pH and temperature for shallow zones of the Bering Sea from measurements of coral Clathromorphum nereostratum

Increasing atmospheric CO2 concentrations are potentially affecting marine ecosystems twofold, by warming and acidification. The rising amount of CO2 taken up by the ocean lowers the saturation state of calcium carbonate, complicating the formation of this key biomineral used by many marine organisms to build hard parts like skeletons or shells. Reliable time-series data of seawater pH are needed to evaluate the ongoing change and compare long-term trends and natural variability. For the high-latitude ocean, the region facing the strongest CO2 uptake, such time-series data are so far entirely lacking. Our study provides, to our knowledge, the first reconstruction of seasonal cycle and long-term trend in pH for a high-latitude ocean obtained from 2D images of stable boron isotopes from a coralline alga.

(Figure 3d) Export production reconstruction based on planktonic foraminiferal sampled in surface sediments

To reconstruct Export Productivity (Pexp), 27 taxonomic categories of the planktonic foraminifera census data were used with the modern analog technique SIMMAX 28 (Pflaumann et al., 1996, doi:10.1029/95PA01743; 2003, doi:10.1029/2002PA000774). To the 26 taxonomic groups widely used and listed in Kucera et al. (2005, doi:10.1016/j.quascirev.2004.07.014), Turborotalita humilis was added in our calibration as it is associated with the PCC source region (Meggers et al., 2002, doi:10.1016/S0967-0645(02)00103-0). The modern analog file is based on the Iberian margin database (Salgueiro et al., 2008, doi:10.1016/j.marmicro.2007.09.003) combined with the North Atlantic surface samples used by the MARGO project (Kucera et al., 2005). This results in a total of 999 analogs for Pexp. Modern oceanic primary productivity (PP) is obtained for each site by averaging 12 monthly primary productivity values for a 8-year period (1978-1986) that were estimated from satellite color data (CZCS) and gridded at 0.5° latitude - longitude fields (Antoine et al., 1996, doi:10.1029/95GB02832). Export Productivity (Pexp) was calculated from the PP values following the empirical relationship Pexp = PP**2/400 for primary production below 200 gC/m**2/yr, and Pexp = PP/2 for primary production above 200 gC/m2/yr (Eppley and Peterson, 1979, doi:10.1038/282677a0; Sarnthein et al., 1988, doi:10.1029/PA003i003p00361). The residuals gives the differences between satellite based Pexp and foraminiferal Pexp.