Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations
Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations
复制标题
DOI：
10.1029/2010pa002055
复制
发表时间：
2011-11-16
期刊：
影响因子：
--
通讯作者：
Zeebe, Richard E.
中科院分区：
文献类型：
--
作者：
Bartoli, Gretta;Hoenisch, Baerbel;Zeebe, Richard E.
人们提出了几种假说来解释格陵兰岛、斯堪的纳维亚半岛和北美在360万年前至270万年前的上新世期间发生的强烈冰川作用。大气中二氧化碳的减少可能在冰川作用开始期间发挥了作用，但同时发生的其他构造和海洋事件也可能发挥了作用。在这里，我们提出了详细的大气CO2估计从硼同位素在南极有孔虫壳跨越4.6-2.0马。最大上新世大气CO2的估计值逐渐下降，从410个大气压左右的值，早更新世的值为300亩大气压在2.0马。在北方半球出现大规模冰盖后，最大pCO（2）估计值仍为2.5 Ma + 90 mu atm，高于早更新世间冰期的特征值。相比之下，上新世最小的大气CO2逐渐减少，从310至245毫米，在3.2马，正好与格陵兰岛上的短暂冰川的开始。值特征的早更新世冰川大气CO2的200亩大气压突然达到后2.7马在上新世晚期过渡。这一趋势与2.7 Ma后北太平洋和南大洋海洋分层和铁肥化增加的建议一致，并可能导致2.7 Ma后海洋深渊中冰川CO2储存量增加。
Several hypotheses have been put forward to explain the onset of intensive glaciations on Greenland, Scandinavia, and North America during the Pliocene epoch between 3.6 and 2.7 million years ago (Ma). A decrease in atmospheric CO2 may have played a role during the onset of glaciations, but other tectonic and oceanic events occurring at the same time may have played a part as well. Here we present detailed atmospheric CO2 estimates from boron isotopes in planktic foraminifer shells spanning 4.6-2.0 Ma. Maximal Pliocene atmospheric CO2 estimates gradually declined from values around 410 matm to early Pleistocene values of 300 mu atm at 2.0 Ma. After the onset of large-scale ice sheets in the Northern Hemisphere, maximal pCO(2) estimates were still at 2.5 Ma + 90 mu atm higher than values characteristic of the early Pleistocene interglacials. By contrast, Pliocene minimal atmospheric CO2 gradually decreased from 310 to 245 matm at 3.2 Ma, coinciding with the start of transient glaciations on Greenland. Values characteristic of early Pleistocene glacial atmospheric CO2 of 200 mu atm were abruptly reached after 2.7 Ma during the late Pliocene transition. This trend is consistent with the suggestion that ocean stratification and iron fertilization increased after 2.7 Ma in the North Pacific and Southern Ocean and may have led to increased glacial CO2 storage in the oceanic abyss after 2.7 Ma onward.