The Early to Mid-Holocene experienced marked climate change over the northern hemisphere mid-latitudes in response to changing insolation and declining ice volume. Oxygen isotopes from lake sediments provide a valuable climate proxy, encoding information regarding temperature, hydroclimate and moisture source. We present oxygen-isotope records from two lakes in western Ireland that are strongly influenced by the North Atlantic. Excellent replication between the records suggests they reflect regional, not local, influences. Carbonate oxygen-isotope values peaked at the start of the Holocene, between 11.2 and 11.1 cal ka bp, and then decreased markedly until 6 cal ka bp at both sites. Palaeoecological evidence supports only modest change in temperature or hydroclimate during this interval and we therefore explain the decrease primarily by a reduction in the oxygen-isotope composition of precipitation (δ¹⁸O_ppt). We show a similar decrease in δ¹⁸O values in a forward model of carbonate isotopes between 12–11 and 6–5 cal ka bp. However, the inferred reduction in δ¹⁸O_ppt between the Early and Mid-Holocene in the model is mainly linked to a decrease in the δ¹⁸O of the ocean source water from ice sheet melting whereas the lake carbonate isotope records are more consistent with changes in the transport pathway of moisture associated with atmospheric circulation change as the dominant cause.

中文翻译：

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根据爱尔兰西部湖泊碳酸盐氧同位素记录推断全新世早期和中期的气候和大气环流

全新世早期到中期，由于日照变化和冰量减少，北半球中纬度地区经历了显着的气候变化。湖泊沉积物中的氧同位素提供了有价值的气候指标，编码有关温度、水文气候和水分来源的信息。我们提供了爱尔兰西部两个受北大西洋强烈影响的湖泊的氧同位素记录。记录之间的出色复制表明它们反映了区域而不是本地的影响。碳酸盐氧同位素值在全新世开始时达到峰值，在 11.2 和 11.1 cal ka bp之间，然后显着下降，直到两个地点的 6 cal ka bp。古生态学证据支持在此期间温度或水文气候仅发生适度变化，因此我们主要通过降水的氧同位素组成的减少（δ ¹⁸ O _ppt）来解释这种减少。我们在 12-11 和 6-5 cal ka bp 之间的碳酸盐同位素正演模型中显示 δ ¹⁸ O 值也有类似的下降。然而，模型中推断的早全新世和中期全新世之间δ ¹⁸ O _ppt的减少主要与冰盖融化导致海洋源水 δ ¹⁸ O 的减少有关，而湖泊碳酸盐同位素记录与与大气环流变化相关的水分输送路径的变化是主要原因。