Evidence for elevated alkalinity in the glacial Southern Ocean

Journal article

An increase in whole ocean alkalinity during glacial periods could account, in part, for the drawdown of atmospheric CO₂ into the ocean. Such an increase was inevitable due to the near elimination of shelf area for the burial of coral reef alkalinity. We present evidence, based on downcore measurements of benthic foraminiferal B/Ca and Mg/Ca from a core in the Weddell Sea, that the deep ocean carbonate ion concentration, [CO²⁻₃], was elevated by ~25 μmol/kg during each glacial period of the last 800 kyr. The heterogeneity of the preservation histories in the different ocean basins reflects control of the carbonate chemistry of the deep glacial ocean in the Atlantic and Pacific by the changing ventilation and chemistry of Weddell Sea waters. These waters are more corrosive than interglacial northern sourced waters but not as undersaturated as interglacial southern sourced waters. Our infrared increase in whole ocean alkalinity can be reconciled with reconstructions of glacial saturation horizon depth and the carbonate budget if carbonate burial rates also increased above the saturation horizon as a result of enhanced pelagic calcification. The Weddell records display low[CO²⁻₃] and act to trigger the deglacial rise in pCO₂.

Authors: Rickaby, R; Elderfield, H; Roberts, N; Hillenbrand, C; Mackensen, A

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Geophysical Union
• Journal: Paleoceanography
• Volume: 25
• Article number: PA1209
• Publication date: 2010-03-01
• DOI: 10.1029/2009PA001762
• ISSN: 0883-8305
• Language: English
• Subjects: Earth sciences