Age constraints of rock glaciers in the Southern Alps/New Zealand – Exploring their palaeoclimatic potential

Two rock glaciers in the valley head of Irishman Stream in the central Ben Ohau Range, Southern Alps/New Zealand, have been investigated using the electronic Schmidt-hammer (SilverSchmidt). Longitudinal profiles on both features reveal a consistent trend of decreasing R(Rebound)-values and, hence, increasing weathering intensity and surface-exposure age on their numerous transverse surface ridges from rooting zone towards the front. Previously published numerical ages obtained by terrestrial cosmogenic nuclide dating (TCND) allowed the calculation of a local Schmidt-hammer exposure-age dating (SHD) age-calibration curve by serving as the required fixed points. Age estimates for the lowermost rock glacier surface ridges fall within the early Holocene between 12 and 10.5 ka and indicate a fast disappearance of the Late Glacial glacier formerly occupying the valley head, followed by the initiation of rock glacier formation around or shortly after the onset of the Holocene. Although it cannot be judged whether the rock glaciers investigated were active within the entire Holocene or only repeatedly during multiple episodes within, their location and intact morphology exclude any substantial glacial activity at Irishman Stream during the Holocene. This has considerable regional palaeoclimatic implications because it opens for the hypothesis that climatic conditions during early Holocene were possibly comparatively dry and favourable for rock glacier initiation, but less so for glaciers. It would also challenge the view that air temperature is the sole major climate driver of glacier variability in the Southern Alps. More work utilising the palaeoclimatic potential of rock glaciers in the Southern Alps is advised. </jats:p

Influence of microclimate and geomorphological factors on alpine vegetation in the Western Swiss Alps

Among the numerous environmental factors affecting plant communities in alpine ecosystems, the influence of geomorphic processes and landforms has been minimally investigated. Subjected to persistent climate warming, it is vital to understand how these factors affect vegetation properties. Here, we studied 72 vegetation plots across three sites located in the Western Swiss Alps, characterized by high geomorphological variability and plant diversity. For each plot, vascular plant species were inventoried and ground surface temperature, soil moisture, topographic variables, earth surface processes (ESPs) and landform morphodynamics were assessed. The relationships between plant communities and environmental variables were analysed using non-metric multidimensional scaling (NMDS) and multivariate regression techniques (generalized linear model, GLM, and generalized additive model, GAM). Landform morphodynamics, growing degree days (sum of degree days above 5°C) and mean ground surface temperature were the most important explanatory variables of plant community composition. Furthermore, the regression models for species cover and species richness were significantly improved by adding a morphodynamics variable. This study provides complementary support that landform morphodynamics is a key factor, combined with growing degree days, to explain alpine plant distribution and community composition

Permafrost in Switzerland 2004/2005 and 2005/2006

The present report covers the period from October 2004 to September 2006. It is the last report of the pilot phase 2000–2006 of the network for permafrost monitoring in Switzerland (PERMOS). At this point, PERMOS includes (a) 11 drill sites (including 22 boreholes and geophysical monitoring at 4 of the sites), (b) 11 surface temperature sites (including measurements in loose debris at 9 sites, in bedrock at 5 sites, and at the bottom of the snow cover (BTS) at 3 sites), and (c) aerial photographs taken by Swisstopo. Winter 2004/2005 was characterized by an early and thin snow cover in the higher alpine regions and an early snow melt in spring. A long phase of above average air temperatures followed, which lasted until July and made summer 2005 the second warmest on record. Winter 2005/2006 started late, had a long lasting thick snow cover, and was followed by a warm summer with the hottest July ever measured. Active layer thicknesses in summer 2004 were similar to those before 2003 at most sites. Hence, thermal changes in the subsurface from the 2003 heat wave were not sustained, although the ice content at the permafrost table may have been permanently modified. The active layer deepened again in several boreholes in summer 2005, reaching values similar to 2003, and remained more or less stable in summer 2006. At ca. 10 m depth, ground temperatures at the drill sites displayed a warming until the beginning of 2005, which results from the preceding heat period in summer 2003. Then, mainly as a result of the snow conditions in winter, a cooling period followed. Since 2005, temperature observations are complemented by electrical resistivity tomography (ERT) measurements at 4 drill sites to monitor physical properties of the ground (e.g., ice content or unfrozen water content). The ERT monitoring strategy is outlined and discussed in this report. Ground surface temperatures (GST) were low in both years of the reporting period, especially during winter. In 2005, GST temporarily dropped to new minima and reached about mean values of the past decade at the end of the reporting period. Rock surface temperatures (RST) were integrated into PERMOS in summer 2004 and are presented and discussed in detail in this report. Temperature values in steep rock clearly display the cold conditions in winter 2004/2005 as well as the warm summer 2006. The chapter on special aspects of permafrost monitoring is dedicated to the observed acceleration of rock glaciers in the past two decades. The destabilization of several landforms shows that permafrost creep conditions in the Alps are changing. In general, both, surface temperatures and ground temperatures in the uppermost meters decreased to pre-2003 conditions at all sites during the reporting period, which is mainly a result of the snow conditions

Pregnancy-induced Changes in Corneal Biomechanics and Topography Are Thyroid Hormone Related

To identify biomechanical and topographic changes of the cornea during pregnancy and the postpartum period and its association to hormonal changes