Last Glacial Maximum paleochemistry and deepwater circulation in the Southern Ocean: Evidence from foraminiferal cadmium
Last Glacial Maximum paleochemistry and deepwater circulation in the Southern Ocean: Evidence from foraminiferal cadmium
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末次盛冰期古化学和南大洋深水环流：来自有孔虫镉的证据
DOI：
10.1029/97pa02508
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发表时间：
1997
期刊：
影响因子：
--
通讯作者：
L. Labeyrie
中科院分区：
文献类型：
--
作者：
Y. Rosenthal;E. Boyle;L. Labeyrie
南大西洋底栖有孔虫Cd/Ca没有显示冰期间冰期变化，表明北大西洋深水对南大洋的冰川贡献与现在没有太大差异。相比之下，东南印度洋脊的Cd/Ca显示出较低的冰川底水Cd，与北大西洋中深度相当，显著低于南大西洋深处。在浮游有孔虫中也记录到低的冰川Cd/Ca，这表明在冰期极大期，亚南极地表水的营养物质浓度大幅下降，这很可能是由于生物生产力的增加造成的。Cd数据与较低的冰川底栖有孔虫δ13C不一致，表明营养物浓度较高。我们认为，东南印度洋脊记录中的低Cd/Ca反映了末次盛冰期由南极极锋附近的开放海洋对流形成的营养物质枯竭的深水的局地来源，南极极锋位于Kerguelene高原下游。如果这个来源仅限于东南印度盆地，那么它对冰川环极深水的整体化学影响是相当小的。然而，如果在冰期，开放海洋对流成为底层水形成的主要模式，它可能对CPDW化学产生更大的影响。
South Atlantic benthic foraminiferal Cd/Ca shows no glacial-interglacial variation, suggesting that the glacial contribution of North Atlantic Deep Water to the Southern Ocean was not much different than at present. In contrast, Cd/Ca in southeast Indian Ridge cores show lower glacial bottom water Cd, comparable to levels in intermediate depths of the North Atlantic and significantly lower than in the deep South Atlantic. Low glacial Cd/Ca was also recorded in planktonic foraminifera, suggesting a substantial decrease in the nutrient concentration of Subantarctic surface water during the glacial maximum which most likely was caused by increased biological productivity. The Cd data are inconsistent with low glacial benthic foraminiferal δ13C which suggest higher nutrient concentration. We propose that the low Cd/Ca in the Southeast Indian Ridge records reflects a local source of nutrient-depleted deepwater, formed during the last glacial maximum by open-ocean convection near the Antarctic Polar Front, downstream of the Kerguelene Plateau. If this source was limited to the southeast Indian basin then its impact on the overall chemistry of glacial Circumpolar Deepwater was rather small. However, if during glaciations open-ocean convection became the dominant mode of bottom water formation, it might have had a greater impact on CPDW chemistry.