The Southern Westerlies in Central Chile:: Holocene precipitation estimates based on a water balance model for Laguna Aculeo (33°50′S)
The Southern Westerlies in Central Chile:: Holocene precipitation estimates based on a water balance model for Laguna Aculeo (33°50′S)
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DOI：
10.1007/s00382-002-0267-3
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发表时间：
2003-01-01
期刊：
影响因子：
4.6
通讯作者：
Valero-Garcés, BL
中科院分区：
文献类型：
--
作者：
Jenny, B;Wilhelm, D;Valero-Garcés, BL
智利中部（南纬32- 35度）位于西风环流带（西风带）的强烈影响的北方边界，因此具有陡峭的降水梯度。在这一地区，定量重建全新世降水是稀缺的。因此，本研究估计降水量的变化，根据湖水位波动的拉古纳Aculeo（33度50'S，70度54 'W）。通过对湖泊沉积物的多指标研究，重建了湖泊水位曲线。湖平面的变化已经使用一个简单的水平衡模型进行了模拟。因此，古降水量可以估计：有关输入参数和过去的条件的不确定性限制了降水量估计的精度。结果表明，全新世初期，湖平面较低（<1.5m）时，降水量< 200 mm/a。在8000 cal yr BP之前，湖泊经常干涸。在8000和6000 cal yr BP之间，降水量似乎较高（150-300 mm/年），大约6000 cal yr BP之后，降水量急剧增加（350-450 mm/年）。大约3000 cal yr BP，现代湖泊水位和降水量（450-550 mm/年）一般成立。早全新世和中全新世的干燥条件与智利中部和北方巴塔哥尼亚的其他记录一致。在全新世中、早期，西风带可能受到东南太平洋副热带高压环流的影响而向南偏转。随后，在智利中部的水分增加，在晚全新世似乎是密切相关的西风活动加强，也可能增加厄尔尼诺活动。
Central Chile (32-35degreesS) lies at the northern border of strong influence of the Westerly circulation belt (Westerlies) and is therefore characterized by a steep precipitation gradient. In this region, quantitative reconstructions of Holocene precipitation are scarce. Hence, the present study estimates precipitation changes, based on lake level fluctuations of Laguna Aculeo (33degrees50'S, 70degrees54'W). The lake level curve has been reconstructed using a multi-proxy study of lake sediments. Lake level changes have been simulated using a simple water balance model. As a result, palaeo-precipitation could be estimated: uncertainties concerning the input parameters and past conditions have limitated the precision of precipitation estimates. The results suggest that during the beginning of the Holocene, when the lake level (< 1.5 m) was low, precipitation was < 200 mm/year. Before 8000 cal yr BP, the lake frequently dried out. Between 8000 and 6000 cal yr BP, precipitation appeared to be higher (150-300 mm/year) and after about 6000 cal yr BP, precipitation increased dramatically (350-450 mm/year). Around 3000 cal yr BP, modern lake level and precipitation (450-550 mm/year) were generally established. The dry conditions during the early and mid-Holocene are in good agreement with other records from Central Chile and northern Patagonia. The Westerlies were probably deflected southward by the southeast Pacific subtropical high-pressure cell during the mid- and early Holocene. Subsequently, the increase in moisture in Central Chile during the late Holocene appears to be strongly related to intensified Westerly activity and probably also to increased El Nino activity.