Department of Geosciences, Princeton University, Princeton, NJ 08544, USA.
Climate Geochemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany.
Science. 2020 Dec 11;370(6522):1348-1352. doi: 10.1126/science.abd2115.
Previous studies have suggested that during the late Pleistocene ice ages, surface-deep exchange was somehow weakened in the Southern Ocean's Antarctic Zone, which reduced the leakage of deeply sequestered carbon dioxide and thus contributed to the lower atmospheric carbon dioxide levels of the ice ages. Here, high-resolution diatom-bound nitrogen isotope measurements from the Indian sector of the Antarctic Zone reveal three modes of change in Southern Westerly Wind-driven upwelling, each affecting atmospheric carbon dioxide. Two modes, related to global climate and the bipolar seesaw, have been proposed previously. The third mode-which arises from the meridional temperature gradient as affected by Earth's obliquity (axial tilt)-can explain the lag of atmospheric carbon dioxide behind climate during glacial inception and deglaciation. This obliquity-induced lag, in turn, makes carbon dioxide a delayed climate amplifier in the late Pleistocene glacial cycles.
先前的研究表明，在更新世冰期晚期，南大洋南极区的表-深层交换不知为何减弱，这减少了深层封存的二氧化碳的泄漏，从而导致冰期大气二氧化碳水平降低。在这里，南极区印度扇区的高分辨率硅藻结合氮同位素测量结果显示，南风驱动上升流发生了三种变化模式，每种模式都对大气二氧化碳产生影响。此前已经提出了两种模式，一种与全球气候和两极跷跷板有关，另一种与地球倾斜（轴向倾斜）影响的经向温度梯度有关的第三种模式可以解释冰期开始和冰消期间大气二氧化碳滞后于气候的现象。这种由倾斜引起的滞后反过来又使二氧化碳成为更新世冰期旋回后期的一个延迟气候放大器。
