Variations of heat availability in the Western Caucasus in the past 1500 years inferred from a high-resolution record of bromine in the sediment of Lake Karakel

Abstract

The Caucasus region lacks climate-sensitive chronologies that are continuous, high-resolution and covering more than several centuries at the same time. This paper presents the first high-resolution curve reflecting the variations of heat availability in the Western Caucasus over the past 1500 years. The chronology of bottom sediment of Lake Karakel is based on the two precisely overlapped sediment cores, constrained by ten 14C dates with a temporal resolution of around 3 years. Bromine content in the sediment is interpreted as a proxy for variations of heat availability based on its coherence with the broadleaved tree pollen content in the same deposits. Lake Karakel Br curve showed distinct agreement with hemispheric and regional temperature reconstructions starting from 500 CE, as well as with the tree-ring temperature reconstructions available for the Caucasus. It allowed a constraint of the time frames for the main climatic events in the Western Caucasus during the past 1500 years: Medieval Climate Anomaly (ca. 960–1270 CE) and Little Ice Age with its three separate stages (LIA 1 ca. 1270–1310 and 1370–1410; LIA 2 ca. 1500–1630; LIA 3 ca. 1750–1840). Br-derived variations of heat availability are also supported by the recent cosmogenic glacier moraine dates in the Caucasus.