Twenty years of European mountain permafrost dynamics-the PACE legacy

This paper reviews and analyses the past 20 years of change and variability of European mountain permafrost in response to climate change based on time series of ground temperatures along a south-north transect of deep boreholes from Sierra Nevada in Spain (37°N) to Svalbard (78°N), established between 1998 and 2000 during the EU-funded PACE (Permafrost and Climate in Europe) project. In Sierra Nevada (at the Veleta Peak), no permafrost is encountered. All other boreholes are drilled in permafrost. Results show that permafrost warmed at all sites down to depths of 50 m or more. The warming at a 20 m depth varied between 1.5 °C on Svalbard and 0.4 °C in the Alps. Warming rates tend to be less pronounced in the warm permafrost boreholes, which is partly due to latent heat effects at more ice-rich sites with ground temperatures close to 0 °C. At most sites, the air temperature at 2 m height showed a smaller increase than the near-ground-surface temperature, leading to an increase of surface offsets (SOs). The active layer thickness (ALT) increased at all sites between c. 10% and 200% with respect to the start of the study period, with the largest changes observed in the European Alps. Multi-temporal electrical resistivity tomography (ERT) carried out at six sites showed a decrease in electrical resistivity, independently supporting our conclusion of ground ice degradation and higher unfrozen water content

Unlocking the time capsule of historic aerial photography to measure changes in Antarctic Peninsula glaciers

Recent studies have reported widespread retreat and acceleration of glaciers on the Antarctic Peninsula, attributed to regional warming. The loss of ice is a contributor to sea-level rise, but its volume and impact on sea level is poorly known. There are few ground measurements of ice thickness change and existing satellite altimeters are ineffective over the mountainous terrain. An accurate assessment of changes in surface height, and hence ice volume, of glaciers on the Antarctic Peninsula over past decades is needed to aid better estimates of their past impact on sea-level rise and predictions of their future contribution. There is an archive of over 30,000 aerial photographs going back to the 1940s for parts of the Antarctic Peninsula and photogrammetry of time-series of these historic photographs is now the only way to reconstruct changes in glacier surface height over the last fifty years. However, the historic aerial photographs are difficult to use for detailed measurements due to inadequate ground control, unfavourable sortie characteristics, incomplete calibration data and use of paper prints. This paper describes a method to provide control for historic photos without ground fieldwork by linking them to a newly-acquired, highly-accurate photogrammetric model adjusted through direct kinematic GPS positioning of the camera. It assesses the achievable accuracy through a worked example using a glacier on the Antarctic Peninsula with typical aerial photography at five dates from 1947 to 2005. Overall measurement accuracy of better than 2 m RMSE in X, Y and Z was achieved for all the photography types, which is precise enough to allow reliable measurement of changes in ice thickness for the glacier over decadal periods. The principal constraints are image quality of the historic photographs and using paper prints

Iceland

Within the high North Atlantic region, Iceland is the natural nexus between Scandinavia and Greenland. Its location at the meeting point of polar and temperate air masses and cold and warm sea currents makes this island very sensitive to climatic oscillations. The spreading of permafrost and periglacial environments throughout the island began at the first ice-free coastal lowland areas uncovered by the Icelandic Ice Sheet at the onset of the deglaciation following the Last Glacial Maximum (LGM, hereafter). Post-glacial periglacial dynamics varied in intensity and resulted in a wide variety of periglacial phenomena associated to both permafrost and seasonal frost regimes. Today, the lower limit of permafrost ranges between 850–900 m in the north and 950–1000 m in the south. The shifts of the lower permafrost limit and the extent of the seasonal frost areas since the LGM has generated a wide range of periglacial landforms from the coastal areas (700 m; e.g. palsas, sorted nets, stripes), north-western and northern Iceland (solifluction, relict and active rock glaciers, talus slopes). The current atmospheric warming and the changes in the general weather pattern are leading to the fast retreat of outlet glaciers and the degradation of permafrost and snow cover, contributing also to catastrophic phenomena such as complex landslides, debris slides and slush avalanches. Periglacial dynamics has also been affected by widespread human activities over the last millennia or all the way since the Norse settlement (grazing, deforestation, etc.). In addition, projected warming for the next decades will likely increase the frequency of such events

Doctoriales du Sophiapol, 15 avril 2015, Paris Ouest

Le laboratoire Sophiapol organise une journée d’étude dédiée aux travaux de ses doctorant-e-s. Ces doctoriales visent, d’une part, à échanger sur la diversité des travaux du laboratoire, et, d’autre part, à valoriser les problématiques transversales à la philosophie et la sociologie. À la suite du séminaire « Pratiques croisées », nous chercherons à faire dialoguer ces deux disciplines, autour de quatre axes : 1. Critique de la marchandise ; 2. Rejet de l'essentialisme ; 3. Mise en crise de l..

The Thermal State of Permafrost in the Nordic Area during the International Polar Year 2007-2009

This paper provides a snapshot of the permafrost thermal state in the Nordic area obtained during the International Polar Year (IPY) 2007-2009. Several intensive research campaigns were undertaken within a variety of projects in the Nordic countries to obtain this snapshot. We demonstrate for Scandinavia that both lowland permafrost in palsas and peat plateaus, and large areas of permafrost in the mountains are at temperatures close to 0 degrees C, which makes them sensitive to climatic changes. In Svalbard and northeast Greenland, and also in the highest parts of the mountains in the rest of the Nordic area, the permafrost is somewhat colder, but still only a few degrees below the freezing point. The observations presented from the network of boreholes, more than half of which were established during the IPY, provide an important baseline to assess how future predicted climatic changes may affect the permafrost thermal state in the Nordic area. Time series of active-layer thickness and permafrost temperature conditions in the Nordic area, which are generally only 10 years in length, show generally increasing active-layer depths and risings permafrost temperatures. Copyright (C) 2010 John Wiley & Sons, Ltd

A Disc-DIRC Cherenkov Detector With High Resolution Micro Channel Plate Photomultiplier Tubes

The upcoming PANDA Experiment at FAIR in Germany will be equipped with a novel Cherenkov detector type for high-energy particle identification. This very compact Disc-DIRC detector uses a large disc-shaped fused silica plate of 2 cm thickness as its Cherenkov radiator. The internally reflected Cherenkov light is transported to the rim of the disc where it is focused by quartz light guides onto microchannel plate photomultiplier tubes (MCP-PMTs) with high spatial resolution (pitch 0.5 mm) and high time resolution (σ ≈ 100 ps). The device has an active area of about 3 m2 and will be able to identify pions and kaons with a separation power of more than 3σ in the momentum range up to 4 GeV/c. It has 32400 individual pixels and each can handle a mean photon rate of up to about 100 kHz. The presented design deals with numerous challenges that come with the very hostile environment in which the detector has to function properly, caused by the presence of high magnetic fields of up to 2 Tesla, high levels of radiation, high particle and background rates and a tight spatial volume. First test measurements have shown the performance of the design