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沉积物可能提供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。冰沉积物高出浅盐湖表面7米，并延伸到未知的深度。这些沉积物被一层白色的碳酸盐外壳覆盖，在淡水冰和混合沉积物的冰之间交替存在。这些站点位于非常干旱的地区（年平均降水量100毫米），年平均气温在3.6℃至9.6℃之间。这些沉积物目前正在融化，这表明它们与现代气候状况不平衡。将从最大的冰沉积物中提取冰芯，该沉积物发现于拉古纳科罗拉多（2210s,4289m），以确定这些沉积物作为高分辨率气候变化档案的潜力。横贯矿床的岩心样带将表明各层是否水平连续。岩心还将为同位素、化学和矿物分析提供材料，这些都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层的厚度，以及是否需要机械钻头来获得长记录。高湖泊水位和冰川推进表明，晚更新世期间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：热带辐合带向南移动，延长了雨季，以及气温下降。初步结果表明，层状冰沉积可能在晚更新世期间开始形成，因此可以为该地区提供独特的气候变化记录。

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.