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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. [ABSTRACT FROM AUTHOR]

Three paleosols buried in the left lateral moraines of the Greater Azau Glacier (Northern Caucasus) were identified in an excavated outcrop (43.2658 N, 42.4766 E, 2370 m a.s.l.). When the glacier was overlying the surface of the lateral moraines at this site, the thickness of the ice was 50 m and more above the valley floor. Fragments of charcoal from the uppermost soil (S1) buried 0.6 m below the surface yielded the radiocarbon date 130 ± 20 yr BP (IGANAMS-6826) (AD 1680–1939). The middle soil (S2), buried at the depth of 13 m yielded two 14C dates 320 ± 20 yr BP (IGANAMS-8127) (bark of birch) (AD 1496–1641) and 1190 ± 20 yr BP (IGANAMS-8126) (AD 774–889) (charcoal). We suggest that the soil S2 has been formed between these dates during the Medieval Warm Period and in the early Little Ice Age. The lowermost (S3) unit lying 15 m below the surface is the thickest (0.4–0.6 m), well-developed paleosol. Charcoal collected at the top of S3, yielded the date 1300 ± 20 yr BP (IGANAMS-6826) (AD 663–773), indicating a prominent glacier advance occurred shortly before this date. Two dates from the charcoal buried at the bottom of S3 (2855 ± 20 yr BP (IGANAMS-8125) and 2880 ± 20 yr BP (IGANAMS-6827) mark the beginning of a long episode of restricted glacier extent that lasted for about 1600 years. The dates at the bottom of the S3 paleosol constrain the end of glacier advance that occurred before 2800–2900 14C yr BP. The timing of most prominent advances of the Greater Azau Glacier in the past 3500 years is in general agreement with the Late-Holocene glacial chronologies in the European Alps, Scandinavia and other regions of the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

A global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions (excluding Antarctica) highlights the nature of glacier fluctuations during the late Holocene. The dataset includes 275 time series of glacier fluctuations based on historical, tree ring, lake sediment, radiocarbon and terrestrial cosmogenic nuclide data. The most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and, when available, winter precipitation reconstructions, the most important parameters for glacier mass balance. In many cases major glacier advances correlate with multi-decadal periods of decreased summer temperature. In a few cases, such as in Arctic Alaska and western Canada, some glacier advances occurred during relatively warm wet times. The timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region. However, the number of glacier advances shows a clear pattern for the high, mid and low latitudes and, hence, points to common forcing factors acting at the global scale. Globally, during the first millennium CE glaciers were smaller than between the advances in 13th to early 20th centuries CE. The precise extent of glacier retreat in the first millennium is not well defined; however, the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th/early 21st centuries. Other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the European Alps, in the 3rd–6th and 9th centuries in Norway, during the 10th–13th centuries in southern Alaska, and in the 18th century in Spitsbergen. However, no single period of common global glacier retreat of centennial duration, except for the past century, has yet been identified. In contrast, the view that the Little Ice Age was a period of global glacier expansion beginning in the 13th century (or earlier) and reaching a maximum in 17th–19th centuries is supported by our data. The pattern of glacier variations in the past two millennia corresponds with cooling in reconstructed temperature records at the continental and hemispheric scales. The number of glacier advances also broadly matches periods showing high volcanic activity and low solar irradiance over the past two millennia, although the resolution of most glacier chronologies is not enough for robust statistical correlations. Glacier retreat in the past 100–150 years corresponds to the anthropogenic global temperature increase. Many questions concerning the relative strength of forcing factors that drove glacier variations in the past 2 ka still remain. [ABSTRACT FROM AUTHOR]