Upper-ocean-to-atmosphere radiocarbon offsets imply fast deglacial carbon dioxide release
Upper-ocean-to-atmosphere radiocarbon offsets imply fast deglacial carbon dioxide release
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DOI：
10.1038/nature09288
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发表时间：
2010-08
期刊：
影响因子：
64.8
通讯作者：
K. A. Rose;E. Sikes;T. Guilderson;P. Shane;T. Hill;R. Zahn;H. Spero
中科院分区：
文献类型：
--
作者：
K. A. Rose;E. Sikes;T. Guilderson;P. Shane;T. Hill;R. Zahn;H. Spero
Radiocarbon in the atmosphere is regulated largely by ocean circulation, which controls the sequestration of carbon dioxide (CO2) in the deep sea through atmosphere–ocean carbon exchange. During the last glaciation, lower atmospheric CO2levels were accompanied by increased atmospheric radiocarbon concentrations that have been attributed to greater storage of CO2in a poorly ventilated abyssal ocean,. The end of the ice age was marked by a rapid increase in atmospheric CO2concentrations that coincided with reduced14C/12C ratios (Δ14C) in the atmosphere, suggesting the release of very ‘old’ (14C-depleted) CO2from the deep ocean to the atmosphere. Here we present radiocarbon records of surface and intermediate-depth waters from two sediment cores in the southwest Pacific and Southern oceans. We find a steady 170 per mil decrease in Δ14C that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial–interglacial climatic transition. The atmospheric decrease in the radiocarbon signal coincides with regionally intensified upwelling and marine biological productivity, suggesting that CO2released by means of deep water upwelling in the Southern Ocean lost most of its original depleted-14C imprint as a result of exchange and isotopic equilibration with the atmosphere. Our data imply that the deglacial14C depletion previously identified in the eastern tropical North Pacific must have involved contributions from sources other than the previously suggested carbon release by way of a deep Southern Ocean pathway, and may reflect the expanded influence of the14C-depleted North Pacific carbon reservoir across this interval. Accordingly, shallow water masses advecting north across the South Pacific in the early deglaciation had little or no residual14C-depleted signals owing to degassing of CO2and biological uptake in the Southern Ocean.
