Migration of the Antarctic Polar Front through the mid-Pleistocene transition: evidence and climatic implications
Migration of the Antarctic Polar Front through the mid-Pleistocene transition: evidence and climatic implications
复制标题
DOI：
10.1016/j.quascirev.2010.04.027
复制
发表时间：
2010-08-01
影响因子：
4
通讯作者：
Garabato, A. C. Naveira
中科院分区：
文献类型：
--
作者：
Kemp, A. E. S.;Grigorov, I.;Garabato, A. C. Naveira
南极极锋是南大洋重要的地球化学分界线。层压硅藻垫存款记录事件的大量流量的硅藻Thalassiothrix南极极地锋下，并提供了一个标记，通过时间来跟踪前的迁移。大洋钻探计划1091、1093和1094号站点是迄今为止从环极生物蛋白石带沉积物中取样的唯一深活塞岩心记录。对这些地点之间的硅藻垫沉积物进行的绘图表明，在更新世早期/中期，冰川-间冰期锋面发生了高达6个纬度的迁移。中更新世的过渡标志着极锋的轨迹逐步向北迁移至少7度，持续了大约45万年，直到突然向南返回到一个与现代位置相似的轨迹，并且比任何中更新世轨迹都更南。从900 ka事件（海洋大幅冷却和三角洲C-13最小值）到424 ka中Brunhes事件（终止V）的这段时间似乎也具有以下特征：1）亚热带南大西洋碳酸盐持续减少，2）南极深层纬向环流强度减弱。3)间冰期温度和间冰期大气CO2水平比过去400 kyr低（约30/mil），证明冰川消退不完全。这一证据与间冰期期间深海仅部分通风的长期持续450 kyr是一致的，并表明，最近的假设所强调的机制，将中纬度大气条件与深海通风的程度和冰川-间冰期循环的碳固存联系起来，可能在中更新世过渡的较长时间尺度特征中起作用。启动“900 ka事件”的冷却可能是由最小的太阳能振幅相关的偏心率调制的岁差，也影响了低纬度气候的阈值变化在非洲季风系统的标志。在地球系统的行为通过中更新世过渡的主要阈值可能是由100 kyr和400 kyr的偏心率的岁差调制的相互作用。(C)2010爱思唯尔有限公司保留所有权利。
The Antarctic Polar Front is an important biogeochemical divider in the Southern Ocean. Laminated diatom mat deposits record episodes of massive flux of the diatom Thalassiothrix antarctica beneath the Antarctic Polar Front and provide a marker for tracking the migration of the Front through time. Ocean Drilling Program Sites 1091, 1093 and 1094 are the only deep piston cored record hitherto sampled from the sediments of the circumpolar biogenic opal belt. Mapping of diatom mat deposits between these sites indicates a glacial-interglacial front migration of up to 6 degrees of latitude in the early/mid Pleistocene. The mid-Pleistocene transition marks a stepwise minimum 7 degrees northward migration of the locus of the Polar Front sustained for about 450 kyr until an abrupt southward return to a locus similar to its modern position and further south than any mid-Pleistocene locus. This interval from a "900 ka event" that saw major cooling of the oceans and a delta C-13 minimum through to the 424 ka Mid-Brunhes Event at Termination V is also seemingly characterised by 1) sustained decreased carbonate in the sub-tropical south Atlantic, 2) reduced strength of Antarctic deep meridional circulation. 3) lower interglacial temperatures and lower interglacial atmospheric CO2 levels (by some 30 per mil) than those of the last 400 kyr, evidencing less complete deglaciation. This evidence is consistent with a prolonged period lasting 450 kyr of only partial ventilation of the deep ocean during interglacials and suggests that the mechanisms highlighted by recent hypotheses linking mid-latitude atmospheric conditions to the extent of deep ocean ventilation and carbon sequestration over glacial-interglacial cycles are likely in operation during the longer time scale characteristic of the mid-Pleistocene transition. The cooling that initiated the "900 ka event" may have been driven by minima in insolation amplitude related to eccentricity modulation of precession that also affected low latitude climates as marked by threshold changes in the African monsoon system. The major thresholds in earth system behaviour through the mid-Pleistocene transition were likely governed by an interplay of the 100 kyr and 400 kyr eccentricity modulation of precession. (C) 2010 Elsevier Ltd. All rights reserved.