The Potential for High Resolution Climate Records From Ice Deposits in Saline Lakes of the Central Andes

在玻利维亚南部和智利北部的浅盐湖中发现的层状冰层可能提供了安第斯山脉干旱-亚热带地区气候变化的第一个高分辨率记录。冰层高出浅水盐湖表面7米，并延伸到未知的深度。沉积物被白色的碳酸盐结壳覆盖，各层在淡水冰和混合了沉积物的冰之间交替。这些地点位于一个非常干旱的地区(年平均降雨量为100毫米A.1)，年平均气温在3.6摄氏度到9.6摄氏度之间。这些沉积物目前正在融化，这表明它们与现代气候制度不平衡。从科罗拉达拉古纳湖(22o10‘S，4289米)发现的最大的冰层开始，将从冰层中提取冰芯，以确定这些冰层作为高分辨率气候变化档案的潜力。横跨沉积物的岩心横断面将表明这些层是否水平连续。这些岩芯还将为同位素、化学和矿物分析提供材料，这些分析是确定地层形成的时间和方式所必需的。单脉冲雷达探测将有助于确定沉积物的厚度，以及可能需要机械钻探来获得长期记录。高湖面和冰川推进表明，在晚更新世，安第斯山脉亚热带地区的水文收支发生了重大变化。这种变化可能是由两个因素引起的：热带辐合带南移，延长了雨季，以及较低的气温。初步结果表明，层状冰层可能是在晚更新世时期开始形成的，因此可能为该地区的气候变化提供了独特的记录。

Layered ice deposits found in shallow saline lakes in southern Bolivia and northern Chile may provide the first high-resolution record of climatic change from the arid-subtropical region of the Andes. The ice deposits rise as much as 7 m above the surface of shallow saline lakes and extend to unknown depths. The deposits are covered by a white carbonate crust and the layers alternate between freshwater ice and ice mixed with sediment. The sites are located in a very arid region (100 mm a.1 mean annual precipitation) where mean annual temperatures range from 3.6o to 9.6oC. The deposits are presently melting, which indicates they are not in equilibrium with the modern climatic regime. Ice cores will be retrieved from the ice deposits beginning with the largest deposit, which is found in Laguna Colorada (22o10'S,4289m), to determine the potential of these deposits as archives of high- resolution climatic change. A transect of cores across the deposits will indicate whether or not the layers are horizontally continuous. The cores will also provide the material for isotopic, chemical, and mineral analyses, which are needed to determine when and how the layers formed. Mono-pulse radar soundings will help to determine how thick the deposits are and the potential need for a mechanical drill to obtain a long record. High lake levels and glacial advances indicate there was a significant change in the hydrologic budget in the subtropical region of the Andes during the late Pleistocene. This change was probably caused by two factors: a southward shift of the Intertropical Convergence Zone, which lengthened the rainy season, and colder temperatures. Pr1eliminary results indicate that the layered ice deposits may have started to form during this late-Pleistocene interval and therefore could provide a unique record of climatic change for this region.