Lake La Thuile, in the Northern French Prealps (874 m a.s.l.), provides an 18-m long sedimentary sequence spanning the entire Lateglacial/Holocene period. The high-resolution multi-proxy (sedimentological, palynological, and geochemical) analysis of the uppermost 6.2 m reveals the Holocene dynamics of erosion in the catchment in response to landscape modifications. The mountain belt is at relevant altitude to study past human activities, and the watershed is sufficiently disconnected from large valleys to capture a local sedimentary signal. From 12,000 to 10,000 cal. BP (10–8 kyr cal. BC), the onset of hardwood species triggered a drop in erosion following the Lateglacial/Holocene transition. From 10,000 to 4500 cal. BP (8–2.5 kyr cal. BC), the forest became denser and favored slope stabilization, while erosion processes were very weak. A first erosive phase was initiated at ca. 4500 cal. BP without evidence of human presence in the catchment. Then, the forest declined at approximately 3000 cal. BP, suggesting the first human influence on the landscape. Two other erosive phases are related to anthropic activities: approximately 2500 cal. BP (550 cal. BC) during the Roman period and after 1600 cal. BP (350 cal. AD) with a substantial accentuation in the Middle Ages. In contrast, the lower erosion produced during the ‘Little Ice Age’, when climate deteriorations are generally considered to result in an increased erosion signal in this region, suggests that anthropic activities dominated the erosive processes and completely masked the natural effects of climate on erosion in the late Holocene.

ABSTRACT. In the mid-1990s, excellent results from the GRIP and GISP2 deep drilling projects in Greenland opened up funding for continued ice-coring efforts in Antarctica (EPICA) and Greenland (NorthGRIP). The Glaciology Group of the Niels Bohr Institute, University of Copenhagen, was assigned the task of providing drilling capability for these projects, as it had done for the GRIP project. The group decided to further simplify existing deep drill designs for better reliability and ease of handling. The drill design decided upon was successfully tested on Hans Tausen Ice Cap, Peary Land, Greenland, in 1995. The 5.0 m long Hans Tausen (HT) drill was a prototype for the 11 m long EPICA and NorthGRIP versions of the drill which were mechanically identical to the HT drill except for a much longer core barrel and chips chamber. These drills could deliver up to 4 m long ice cores after some design improvements had been introduced. The Berkner Island (Antarctica) drill is also an extended HT drill capable of drilling 2 m long cores. The success of the mechanical design of the HT drill is manifested by over 12 km of good-quality ice cores drilled by the HT drill and its derivatives since 1995.

Abstract. The temperature at the Antarctic Ice Sheet bed and the temperature gradient in subglacial rocks have been directly measured only a few times, although extensive thermodynamic modeling has been used to estimate the geothermal heat flux (GHF) under the ice sheet. During the last 5 decades, deep ice-core drilling projects at six sites – Byrd, WAIS Divide, Dome C, Kohnen, Dome F, and Vostok – have succeeded in reaching or nearly reaching the bed at inland locations in Antarctica. When temperature profiles in these boreholes and steady-state heat flow modeling are combined with estimates of vertical velocity, the heat flow at the ice-sheet base is translated to a geothermal heat flux of 57.9 ± 6.4 mW m−2 at Dome C, 78.9 ± 5.0 mW m−2 at Dome F, and 86.9 ± 16.6 mW m−2 at Kohnen, all higher than the predicted values at these sites. This warm base under the East Antarctic Ice Sheet (EAIS) could be caused by radiogenic heat effects or hydrothermal circulation not accounted for by the models. The GHF at the base of the ice sheet at Vostok has a negative value of −3.6 ± 5.3 mW m−2, indicating that water from Lake Vostok is freezing onto the ice-sheet base. Correlation analyses between modeled and measured depth–age scales at the EAIS sites indicate that all of them can be adequately approximated by a steady-state model. Horizontal velocities and their variation over ice-age cycles are much greater for the West Antarctic Ice Sheet than for the interior EAIS sites; a steady-state model cannot precisely describe the temperature distribution here. Even if the correlation factors for the best fitting age–depth curve are only moderate for the West Antarctic sites, the GHF values estimated here of 88.4 ± 7.6 mW m−2 at Byrd and 113.3 ± 16.9 mW m−2 at WAIS Divide can be used as references before more precise estimates are made on the subject.