Abstract The steppe of northern Tierra del Fuego is an important region for studying climate variability in the Southern Hemisphere, due to its position at the southern margin of the Southern Hemisphere Westerly Wind belt. Here we present a multiproxy analysis of a sedimentary sequence from Laguna Carmen (53°S, 68°W) which provides evidence of the progressive aridity and strengthening of the low-level Westerlies during the Late Holocene. We identified three prominent phases in the climatic record from Laguna Carmen: a cold and wet period between ~4000 cal. BP and ~2200 cal. BP, evidenced by a relative high lake level, periodic runoff into the lake, and oligohaline (mean: 2554 μS/cm) salinities; a step-change towards warmer and drier conditions after ~2200 cal. BP, reflected by limited runoff and oligo-mesohaline salinities (mean: 4799 μS/cm); and finally, the establishment of modern semi-arid conditions some time after ~1000 cal. BP, when the lake became a shallow lake that sometimes dried out during the summer. Our results coincide with paleoclimatic numerical models that suggest a progressive aridification of the southern Patagonian steppe since 6000 cal. BP due to stronger Westerlies and higher temperatures associated with changes in solar irradiance.

中文翻译：

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南半球西风带对火地岛（阿根廷）草原全新世水文气候变化的作用

摘要 火地岛北部草原位于南半球西风带南缘，是研究南半球气候变率的重要区域。在这里，我们展示了对 Laguna Carmen (53°S, 68°W) 沉积序列的多重代理分析，它提供了在全新世晚期低层西风带逐渐干旱和加强的证据。我们在 Laguna Carmen 的气候记录中确定了三个突出阶段：约 4000 卡路里之间的寒冷和潮湿时期。BP 和 ~2200 卡路里。BP，由相对较高的湖水位、周期性流入湖中的径流和寡盐（平均值：2554 μS/cm）盐度证明；大约 2200 卡路里后，向更温暖和更干燥的条件迈进。BP，由有限的径流和低中盐度盐度反映（平均值：4799 μS/cm）；最后，在大约 1000 卡路里后的一段时间内建立了现代半干旱条件。BP，当湖泊变成浅湖时，有时会在夏季干涸。我们的结果与古气候数值模型一致，该模型表明自 6000 cal 以来南部巴塔哥尼亚草原逐渐干旱化。BP 由于更强的西风和与太阳辐照度变化相关的更高温度。