Speleothem paleoclimate records from the Peruvian Andes have been interpreted to reflect the strength of the South American monsoon. While these interpretations have been verified through comparison with other regional and global climate records, the mechanics of the cave environment that facilitate the preservation of this signal with such consistency remain unstudied. Here, we present four years of environmental data from Huagapo and Pacupahuain cave, and one year from Antipayarguna cave. The data reveal that the cave environment is very stable with little to no change in temperature and 100% relative humidity year-round. This stability in cave air is juxtaposed with the monsoonal drip water pulse that increases drip rates over 40 times on average across all seven monitored drip sites. Compared to the amount-weighted precipitation average δO value, the cave drip water δO values are evaporatively O enriched during infiltration through the soil/epikarst. As the monsoonal precipitation pulse fades and drip rates decrease, changes in the drip water chemistry (trace elements Mg/Ca and Sr/Ca, dissolved inorganic carbon δC, and δO values) indicate that prior calcite precipitation (PCP) drives the trace element and δC variability. The δC and δO values of farmed slide calcite are highly variable. However, high drip rate and lower cave air CO during the monsoon combine to increase calcite precipitation rates. This causes speleothem records from these caves to be weighted toward annual monsoon conditions. Calcite isotope values from actively growing stalagmite tops support this finding. These results suggest that speleothems from these caves are sensitive to changes in monsoon precipitation amount, because it determines the duration of the monsoon drip water pulse, and therein, the extent of dry season PCP. Further, these data indicate that heterogeneity in the dolomitic limestone massif causes offsets between the carbon isotopes and trace metal concentrations between the caves, highlighting the need to normalize these datasets when chronology-stacking these proxies.

中文翻译：

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秘鲁安第斯山脉的洞穴监测揭示了洞穴方解石中保存的季风气候


秘鲁安第斯山脉的洞穴古气候记录被解释为反映了南美季风的强度。虽然这些解释已通过与其他区域和全球气候记录的比较得到验证，但有助于以这种一致性保存该信号的洞穴环境机制仍未得到研究。在这里，我们提供了 Huagapo 和 Pacupahuain 洞穴四年的环境数据，以及 Antipayarguna 洞穴一年的环境数据。数据显示，洞穴环境非常稳定，温度几乎没有变化，全年相对湿度为100%。洞穴空气的这种稳定性与季风滴水脉冲并存，季风滴水脉冲使所有七个监测滴水点的滴水率平均增加了 40 倍以上。与量加权降水平均 δ18O 值相比，洞穴滴水 δ18O 值在渗透土壤/表层岩溶过程中蒸发富集 O。随着季风降水脉冲减弱和滴水率降低，滴水化学成分（微量元素 Mg/Ca 和 Sr/Ca、溶解无机碳 δ13C 和 δ18O 值）的变化表明，先前的方解石沉淀 (PCP) 驱动微量元素和δ13​​C 变异性。养殖滑坡方解石的 δ13C 和 δ18O 值变化很大。然而，季风期间高滴水率和较低的洞穴空气二氧化碳结合起来增加了方解石的沉淀率。这导致这些洞穴的洞穴记录会根据年度季风条件进行加权。活跃生长的石笋顶部的方解石同位素值支持了这一发现。 这些结果表明，这些洞穴的洞穴对季风降水量的变化很敏感，因为它决定了季风滴水脉冲的持续时间，以及其中旱季PCP的程度。此外，这些数据表明，白云质石灰岩地块的异质性导致洞穴之间碳同位素和痕量金属浓度之间的偏移，突出显示在按年代顺序堆叠这些代理时需要对这些数据集进行标准化。