Lateglacial and Holocene mountain glacier fluctuations near Cape Farewell South Greenland inferred from 10Be moraine dating

Abstract

We report 43 new 10Be exposure ages and six 26Al/10Be measurements from replicates from a small piedmont mountain glacier located at Cape Farewell (south Greenland) and temperature anomalies estimated from equilibrium-line altitude (ELA) changes derived from 3D glacier reconstruction carried out using the ‘GlaRe’ toolbox. Both ELA-derived temperature estimations and climate conditions documented from the transient simulation TraCE-21ka help us to explore the causes of glacier changes during the investigated period. Exposure ages span from the Oldest Dryas to the Late Holocene, revealing that the GrIS retreat in this valley permitted the individualisation or formation of a mountain glacier early in the Lateglacial. Interestingly, four of the six 26Al/10Be ratios come from samples located on the oldest moraines do not reveal inheritance. The two other ratios suggest inheritance up to 6 ka. The oldest moraine combining a frontal and a lateral remain is dated to 18.4 ± 0.8 ka. Between 18 ka and ~14.7 ka, the glacier experienced a significant retreat interrupted by at least three minor advances or stillstands. We did not find any moraine formed either during the Younger Dryas, or during the Early and the Mid Holocene. The largest Holocene glacier advance occurred ~4.4 ka. Two other younger moraines were formed at ~2.9 ka and probably during the LIA. Temperatures of 3.3°C and 1.7°C colder than today may explain the glacier extent during the Lateglacial and the Holocene, respectively. Complementary dry regional climate conditions estimated from TraCE-21ka simulations during the Early Holocene may explain why the glacier was smaller than during the Late Holocene.