Stable oxygen isotope record and Calcium concentrations of sediment core GeoB3910-2

There is increasing evidence that the preceding Holocene climate was as unstable as the last glacial period, although variations occurred at much lower amplitudes. However, low-latitude climate records that confirm this variability are sparse. Here we present a radiocarbon-dated Holocene marine record from the tropical western Atlantic. Aragonite dissolution derived from the degree of preservation of the pteropod Limacina inflata records changes in the corrosiveness of the bottom water at the core site due to the changing influence of northern versus southern water masses. The delta18O difference between the shallow-living planktonic foraminifera Globigerinoides sacculifer and the deep-living Globorotalia tumida is used as proxy for changes in the vertical stratification of the surface water, hence the trade wind strength at this latitude. We compared our data to high-latitude records of the North Atlantic region. A good agreement is found between the aragonite dissolution and the strength in the Island-Scotland Overflow Water, which contributes significantly to the North Atlantic Deep Water. This suggests that large-scale variations in the Atlantic thermohaline circulation occurred throughout the Holocene. Concurrently, the comparison of our Delta delta18O with the GISP2 glaciochemical records points to global Holocene atmospheric reorganizations seen in both the tropics and high northern latitudes.

越来越多的研究证据表明，全新世（Holocene）气候的不稳定性可与末次冰期（last glacial period）相媲美，尽管其波动幅度远低于后者。然而，证实这一气候变异性的低纬度气候记录仍较为匮乏。本研究报道了来自热带西大西洋的、经放射性碳定年的全新世海洋沉积记录。基于翼足类（pteropod）膨胀海若螺（Limacina inflata）的保存程度推算的文石溶解作用，可记录岩心站位处底水腐蚀性的变化——这一变化源于北方与南方水团的影响此消彼长。研究采用浅居浮游有孔虫袋拟抱球虫（Globigerinoides sacculifer）与深居有孔虫膨胀圆辐虫（Globorotalia tumida）之间的δ¹⁸O差值，作为该纬度带表层水体垂直层化强度的代用指标，进而反映信风（trade wind）强度的变化。我们将本次研究的数据与北大西洋高纬度地区的气候记录进行了对比。结果显示，文石溶解作用的变化与冰岛-苏格兰溢流水体（Island-Scotland Overflow Water, ISOW）的强度具有良好的对应关系，而该溢流水体是北大西洋深层水（North Atlantic Deep Water, NADW）的重要组成部分。这一发现表明，全新世期间大西洋温盐环流（thermohaline circulation）发生了大规模的波动。与此同时，将我们得到的Δδ¹⁸O数据与格陵兰冰芯计划2号（GISP2）的冰芯化学记录进行对比后发现，全新世全球大气环流重组的信号在热带与北极高纬度地区均有体现。