No evidence for a deglacial intermediate water Delta C-14 anomaly in the SW Atlantic

作者：Sortor Rachel N; Lund David C^*

来源：Earth and Planetary Science Letters, 2011, 310(1-2): 65-72.

DOI：10.1016/j.epsl.2011.07.017

• Radiocarbon
• Deglaciation
• Southwest Atlantic

The last deglaciation was characterized by an increase in atmospheric pCO(2) and decrease in atmospheric radiocarbon activity. One hypothesis is that these changes were due to out-gassing of C-14-depleted carbon from the abyssal ocean. Reconstructions; of foraminiferal Delta C-14 from the eastern tropical Pacific, Arabian Sea, and high latitude North Atlantic show that severe depletions in C-14 occurred at intermediate water depths during the last deglaciation. It has been suggested that C-14-depleted water from the abyss upwelled in the Southern Ocean and was then carried by Antarctic Intermediate Water (AAIW) to these sites. However, locations in the South Pacific in the direct path of modern-day AAIW do not exhibit the Delta C-14 excursion and therefore cast doubt upon the AAIW mechanism (De Pol-Holz et al., 2010; Rose et al., 2010). Here we evaluate whether or not a deglacial C-14 anomaly occurred at intermediate depths in the Southwest Atlantic. We find that the deglacial benthic Delta C-14 trend at our site is similar to the atmospheric Delta C-14 trend. Our results are also largely consistent with results from U/Th-dated corals at shallower water depths on the Brazil Margin (Mangini et al., 2010). We find no evidence in the southwestern Atlantic of a similar to 300% decrease in intermediate water Delta C-14 from 18 to 14 kyr BP like that observed in the eastern tropical Pacific (Marchitto et al., 2007). When our results are paired with those from the South Pacific, it appears AAIW did not carry a highly C-14-depleted signal during the deglaciation. Another source of carbon is apparently required to explain the intermediate-depth Delta C-14 anomalies in the North Atlantic, Indian, and Pacific Oceans.

• 出版日期2011-10-1