Benthic foraminifera stable isotope data from the South Pacific sediment cores PS75/059-2 and PS75/056-1

Investigating the inter-basin deep water exchange between the Pacific and Atlantic Oceans over glacial-interglacial climate cycles is important for understanding circum-Antarctic Southern Ocean circulation changes and their impact on the global Meridional Overturning Circulation. We use benthic foraminiferal d13C records from the southern East Pacific Rise to characterize the d13C composition of Circumpolar Deep Water in the South Pacific, prior to its transit through the Drake Passage into the South Atlantic. A comparison with published South Atlantic deep water records from the northern Cape Basin suggests a continuous water mass exchange throughout the past 500 ka. Almost identical glacial-interglacial d13C variations imply a common deep water evolution in both basins suggesting persistent Circumpolar Deep Water exchange and homogenization. By contrast, deeper abyssal waters occupying the more southern Cape Basin and the southernmost South Atlantic have lower d13C values during most, but not all, stadial periods. We conclude that these values represent the influence of a more southern water mass, perhaps AABW. During many interglacials and some glacial periods, the gradient between Circumpolar Deep Water and the deeper southern Cape Basin bottom water disappears suggesting either no presence of AABW or indistinguishable d13C values of both water masses.研究冰期-间冰期气候旋回背景下太平洋与大西洋之间的盆间深水交换，对于理解环南极南大洋环流变化及其对全球经向翻转环流（Meridional Overturning Circulation）的影响具有重要学术价值。本研究利用东太平洋海隆（East Pacific Rise）南部海域的底栖有孔虫δ¹³C记录，刻画南太平洋环极深水（Circumpolar Deep Water）在经德雷克海峡（Drake Passage）输入南大西洋之前的δ¹³C组成特征。将该记录与已发表的开普盆地北部的南大西洋深水记录对比后发现，过去500 ka以来两个盆地间始终存在持续的水团交换。二者近乎一致的冰期-间冰期δ¹³C变化特征表明，两个盆地的深水具有共同的演化过程，暗示环极深水一直存在持续的交换与均一化作用。相比之下，占据更南部开普盆地与最南南大西洋的更深层深渊水，在多数（但并非全部）冰阶时期的δ¹³C值更低。本研究认为，这些较低的δ¹³C值代表了更南源水团的影响，可能为南极底层水（Antarctic Bottom Water, AABW）。在多数间冰期与部分冰期阶段，环极深水与南部开普盆地深层底层水之间的δ¹³C梯度消失，这意味着要么不存在南极底层水，要么两种水团的δ¹³C值难以区分。