The Miocene-Pliocene boundary (∼5.3 million years ago, Ma) represents a climate transition, where global warming resulted in a rise in sea surface temperatures from near modern values in the late Miocene, to sustained, warmer than modern values in the early Pliocene. Estimated atmospheric CO2 concentrations were within the range of anthropogenic values. Thus, this transition provides an opportunity to evaluate hydroclimate responses to warming, when the Earth system was in equilibrium with near modern atmospheric CO2 levels. Here, we utilize lacustrine carbonate stable and clumped isotope methods, and palynology, to investigate hydroclimate trends within the western Altiplano of Chile during the late Miocene and early Pliocene. The results provide observational support for a warmer and wetter-than-modern climate over these timeframes. However, increasing aridity across the Miocene-Pliocene boundary suggests a hydroclimate response to global climate forcing. Given the sensitivity of the region's climate to disturbances in tropical Pacific, ocean-atmospheric processes, we speculate that this aridification may reflect progressive weakening of the Pacific Walker Circulation, in response to global warming.

中文翻译：

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智利北部高原西部的晚中新世-上新世早期水文气候演变：气候变暖条件下对干旱化趋势的影响


中新世-上新世边界（约 530 万年前，马）代表气候过渡，其中全球变暖导致海面温度从中新世晚期的接近现代值上升到上新世早期的持续、比现代值更暖。估计的大气 CO2 浓度在人为价值范围内。因此，这种转变为评估水文气候对变暖的响应提供了机会，当时地球系统与接近现代大气 CO2 水平处于平衡状态。在这里，我们利用湖相碳酸盐稳定和聚集同位素方法以及古生物学来研究智利西部高原地区中新世晚期和上新世早期的水文气候趋势。结果为这些时间范围内比现代气候更温暖、更潮湿的气候提供了观测支持。然而，中新世-上新世边界的日益干旱表明水文气候对全球气候强迫的反应。鉴于该地区的气候对热带太平洋海洋-大气过程干扰的敏感性，我们推测这种干旱化可能反映了太平洋沃克环流对全球变暖的响应而逐渐减弱。