Impact of abrupt climate change in the tropical southeast Atlantic during Marine Isotope Stage (MIS) 3
Impact of abrupt climate change in the tropical southeast Atlantic during Marine Isotope Stage (MIS) 3
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DOI：
10.1029/2011pa002118
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发表时间：
2011-12
期刊：
影响因子：
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通讯作者：
I. Hessler;S. Steinke;J. Groeneveld;L. Dupont;G. Wefer
中科院分区：
文献类型：
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作者：
I. Hessler;S. Steinke;J. Groeneveld;L. Dupont;G. Wefer
对安哥拉外海ODP 1078站点的高分辨率浮游有孔虫Mg/Ca古温度和氧同位素进行了重建，揭示了末次冰期（50-23.5 ka BP）安哥拉海流（AC）、安哥拉-本格拉锋（ABF）和本格拉海流（BC）的季节热演化。特别强调的时间间隔可能与北大西洋海因里希地动（HS）有关，这被认为是由于大西洋经向翻转环流（AMOC）的减少而导致南大西洋热量的积累。在测年的不确定性范围内，基于gloigerinoides rubber（粉色）Mg/ ca的海表温度（SST）估计代表南半球夏季表面条件，显示出与北大西洋高温相吻合的几次变暖事件，从而支持两极热跷跷板的概念。而代表南半球冬季ABF/BC系统海温的球藻Mg/ ca基温度对北大西洋HS的响应不明显。我们认为，冬季地表水的冷却是由于较冷水团的上升流增强或上升流增强，这很可能减轻了高温期间ABF/BC系统的变暖。我们进一步推测，海温记录的季节不对称是由于在北方高纬度降温期间大气和海洋遥相关优势的季节差异造成的。
[1] High resolution planktonic foraminifera Mg/Ca paleotemperatures and oxygen isotopes of seawater of Ocean Drilling Program (ODP) Site 1078 (off Angola) have been reconstructed and reveal insights into the seasonal thermal evolution of the Angola Current (AC), the Angola-Benguela Front (ABF), and the Benguela Current (BC) during the last glacial (50–23.5 ka BP). Special emphasis is put on time intervals possibly associated with the North Atlantic Heinrich Stadials (HS), which are thought to lead to an accumulation of heat in the South Atlantic due to a reduction of the Atlantic Meridional Overturning Circulation (AMOC). Within dating uncertainties, Globigerinoides ruber (pink) Mg/Ca-based sea surface temperature (SST) estimates that represent southern hemisphere summer surface conditions show several warming episodes that coincide with North Atlantic HS, thus supporting the concept of the bipolar thermal seesaw. In contrast, the Mg/Ca-based temperatures of Globigerina bulloides, representing the SST of the ABF/BC system during southern hemisphere winter, show no obvious response to the North Atlantic HS in the study area. We suggest that surface water cooling during the winter season is due to enhanced upwelling or upwelling of colder water masses which has most likely mitigated a warming of the ABF/BC system during HS. We further speculate that the seasonal asymmetry in our SST record results from seasonal differences in the dominance of atmospheric and oceanic teleconnections during periods of northern high latitude cooling.