Disentangling abrupt deglacial hydrological changes in northern South America: Insolation versus oceanic forcing
Disentangling abrupt deglacial hydrological changes in northern South America: Insolation versus oceanic forcing
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DOI：
10.1130/g35562.1
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发表时间：
2014-07
期刊：
影响因子：
5.8
通讯作者：
J. Hoffmann;A. Bahr;S. Voigt;J. Schönfeld;D. Nürnberg;J. Rethemeyer
中科院分区：
文献类型：
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作者：
J. Hoffmann;A. Bahr;S. Voigt;J. Schönfeld;D. Nürnberg;J. Rethemeyer
古环境研究和气候模型表明，在加勒比腹地的径流和水分供应的气候变化非常敏感的反应。晚更新世和全新世的气候记录表明，南美洲热带地区的干湿期明显，这主要是由热带辐合带（ITCZ）的移动造成的。然而，强制改变ITCZ立场的机制仍然存在争议。在这里，我们提出了高分辨率有孔虫Ba/Ca和δ 18 O海水记录从位于奥里诺科河外流记录在奥里诺科河流域在冰消期和全新世水文突变的核心。我们的数据，从表面居住的有孔虫Globigerinoides红（粉红色），显示在全新世早期的Ba/ Ca比值突然增加，开始约600年后的新仙女木（YD）冷间隔结束约。10.8 ka，并表明在南美洲北方的水汽来源的大规模重组。与此相反，同一样品的δ 18 O随盐度的变化从YD末期开始逐渐降低。我们的Ba/Ca峰值的偏移不包括融水的释放与北方安第斯山脉冰川退缩以及年底前的YD作为一个强制机制。我们认为，Ba/Ca记录文件突然增加，富Ba的沃茨的北方安第斯山脉源所造成的太阳能驱动的ITCZ和/或增强季风活动的转变。
Paleoenvironmental studies and climate models demonstrate that fl uvial runoff and moisture availability in the Caribbean hinterland react very sensitively to climatic variations. Late Pleistocene and Holocene climate records document pronounced dry and wet periods over tropical South America mainly caused by shifts of the Intertropical Convergence Zone (ITCZ). However, forcing mechanisms for changes in the ITCZ position remain controversial. Here we present high-resolution foraminiferal Ba/Ca and δ18Oseawater records from a core located within the Orinoco River outfl ow documenting abrupt hydrological changes in the Orinoco catchment area during the deglacial and Holocene. Our data, obtained from the surface-dwelling foraminifera Globigerinoides ruber (pink), show an abrupt increase in Ba/ Ca ratios in the early Holocene, starting ~600 yr after the end of the Younger Dryas (YD) cold interval at ca. 10.8 ka and suggesting a massive reorganization of moisture sources in northern South America. In contrast, the salinity dependent δ18Oseawater from the same samples shows a gradual decrease starting at the end of the YD. The offset of our Ba/Ca peak excludes meltwater release in conjunction with the northern Andean glacier retreat well before the end of the YD as a forcing mechanism. We suggest that the Ba/Ca record documents an abrupt increase in Ba-rich waters of a northern Andean source caused by the insolation-driven shift of the ITCZ and/or enhanced monsoon activity.