Twentieth century <i>&delta;</i>¹³C variability in surface water dissolved inorganic carbon recorded by coralline algae in the northern North Pacific Ocean and the Bering Sea

• Main Authors: W. Adey, P. Lebednik, S. Hetzinger, R. S. Steneck, U. G. Wortmann, J. Halfar, B. Williams, M. Joachimski
• Format: Article
• Language: English
• Published: Copernicus Publications 2011-01-01
• Series: Biogeosciences
• Online Access: http://www.biogeosciences.net/8/165/2011/bg-8-165-2011.pdf
• ISSN: 1726-4170; 1726-4189

The oxygen isotopic composition and Mg/Ca ratios in the skeletons of long-lived coralline algae record ambient seawater temperature over time. Similarly, the carbon isotopic composition in the skeletons record <i>&delta;</i>¹³C values of ambient seawater dissolved inorganic carbon. Here, we measured <i>&delta;</i>¹³C in the coralline alga <i>Clathromorphum nereostratum</i> to test the feasibility of reconstructing the intrusion of anthropogenic CO₂ into the northern North Pacific Ocean and Bering Sea. The <i>&delta;</i>¹³C was measured in the high Mg-calcite skeleton of three <i>C. nereostratum</i> specimens from two islands 500 km apart in the Aleutian archipelago. In the records spanning 1887 to 2003, the average decadal rate of decline in <i>&delta;</i>¹³C values increased from 0.03&permil; yr⁻¹ in the 1960s to 0.095&permil; yr⁻¹ in the 1990s, which was higher than expected due to solely the <i>&delta;</i>¹³C-Suess effect. Deeper water in this region exhibits higher concentrations of CO₂ and low <i>&delta;</i>¹³C values. Transport of deeper water into surface water (i.e., upwelling) increases when the Aleutian Low is intensified. We hypothesized that the acceleration of the <i>&delta;</i>¹³C decline may result from increased upwelling from the 1960s to 1990s, which in turn was driven by increased intensity of the Aleutian Low. Detrended <i>&delta;</i>¹³C records also varied on 4–7 year and bidecadal timescales supporting an atmospheric teleconnection of tropical climate patterns to the northern North Pacific Ocean and Bering Sea manifested as changes in upwelling.