Search

In this paper, we present a reconstruction of climate conditions during the Last Glacial Maximum on a karst plateau Snežnik, which lies in Dinaric Mountains (southern Slovenia) and bears evidence of glaciation. The reconstruction merges geomorphological ice limits, classified as either clear or unclear, and a computer modelling approach based on the Parallel Ice Sheet Model (PISM). Based on extensive numerical experiments where we studied the agreements between simulated and geomorphological ice extent, we propose using a combination of a high-resolution precipitation model that accounts for orographic precipitation combined with a simple elevation-based temperature model. The geomorphological ice extent can be simulated with climate to be around 6 °C colder than the modern day and with a lower-than-modern-day amount of precipitation, which matches other state-of-the art climate reconstructions for the era. The results indicate that an orographic precipitation model is essential for the accurate simulation of the study area, with moist southern winds from the nearby Adriatic Sea having a predominant effect on the precipitation patterns. Finally, this study shows that transforming climate conditions towards wetter and warmer or drier and colder does not significantly change the conditions for glacier formation. [ABSTRACT FROM AUTHOR]

In this paper we present a reconstruction of climate conditions during the Last Glacial Maximum on a karst plateau in Dinaric Mountains (southern Slovenia) that bares evidence of glaciation. The reconstruction merges geomorphological ice limits, classified as either clear or unclear, and computer modelling approach based on Parallel Ice Sheet Model, which is an established numerical model for simulating glacier dynamics ranging from ice sheets to alpine glaciers. Based on extensive numerical experiments, where we studied the agreements between simulated and geomorphological ice extent, we propose to use a combination of high resolution precipitation model that accounts for orographic precipitation combined with simple elevation based temperature model. The geomorphological ice extent can be simulated with climate around 6 °C colder than modern and with a lower than modern amount of precipitation, which matches other state-of-the art climate reconstructions for the era. The results indicate that orographic precipitation model is essential for accurate simulation of the Snežnik with moist southern winds from the nearby Adriatic Sea having predominant effect on the precipitation patterns. Finally, this study shows that transforming climate conditions towards wetter and warmer or drier and colder does not significantly change conditions for glacier formation. [ABSTRACT FROM AUTHOR]

Evidence that during the Last Glacial Maximum (LGM) glaciers extended well into the piedmont planes is still identifiable in the alpine foreland as a system of well-preserved moraines. Glaciers are strongly affected by temperature and precipitation and therefore they are excellent indicators of climate change. Here we use a regional climate model (RCM) to investigate the physical processes sustaining the glacier extent during the LGM. We find a predominance of convection during summer and increased southwesterly stratiform precipitation over the southern Alps compared to pre-industrial conditions. This precipitation pattern, along with lower temperatures, determined summer snowfall extending to low elevations with a consequent substantial drop of the equilibrium line altitude (ELA) consistent with the estimated LGM glacier extent. Our RCM based estimates of the ELA at the LGM yield excellent consistency with Alpine glacier reconstructions, further demonstrating the great potential of this technique for use in paleoclimate studies. [ABSTRACT FROM AUTHOR]

Geomorphological and geological mapping have long been used to study the glacial history of the Slovenian Alps, but many uncertainties remain regarding the time and extent of Pleistocene glaciations there. Glacial landforms and undisturbed glacial deposits are rare in the areas of the former glacier terminus, especially in the Soča Valley, where large discrepancies in the interpretation of the extent of the former Soča Glacier have been reported. Early studies proved inconclusive as to whether one or two glaciations extended into the Soča Valley as far as Most na Soči. In order to answer this question, the Quaternary sedimentary succession and landforms in the Modrejce Valley near Most na Soči were investigated. New geological and geomorphological field data allow the interpretation of the sedimentary environment and the stratigraphic relationships between different units. In response to glacial dynamics, the sedimentation developed from glaciofluvial and glaciolacustrine to fully glacial environments, followed by slope deposition. At higher altitudes lateral moraines are preserved, while the staircase-like slope below has been carved into older glacial, glaciofluvial and glaciolacustrine deposits by glacial and post-glacial processes, including fluvial erosion and slope dynamics. We conclude that the succession studied here was deposited over the course of two different glacial advances – LGM and pre-LGM. Our study thus suggests that the Soča Glacier extended as far as the area of Most na Soči twice over the course of the late Quaternary. [ABSTRACT FROM AUTHOR]

The highest sections of the Slovenian part of Dinaric Mountains were glaciated during Pleistocene. Traces of extensive glacial erosion and accumulation are preserved on Snežnik Mountain, while glaciation of Trnovski Gozd Plateau occupied only the highest, north-facing areas as well as large karst depressions. We established that the equilibrium line altitude on both plateaus was within the elevation range from 1220 to 1360 m, which explains an absence of glaciation in other lower sections of the Dinaric Mountains. [ABSTRACT FROM AUTHOR]

Snežnik and Gorski Kotar are mountainous areas in the Northern Dinaric Alps. We investigated this remote and densely forested area on the border between Slovenia and Croatia between 2011 and 2014. The result of the fieldwork campaign is a 1:30,000 geomorphological map covering almost 600 km2. The study area mainly consists of Mesozoic age limestone and dolostone. Karstified carbonate lithology results in almost the complete absence of surface run-off and a dominance of typical karst morphology. The extensive karstified area was modified by Quaternary glaciations; therefore, the recent landscape is characterized as a glaciokarst. The focus of the presented map is to provide a basis for further research of Quaternary glaciations in the areas of Snežnik and Gorski Kotar. Along with the map, we propose a legend for glaciokarst landscape mapping. [ABSTRACT FROM PUBLISHER]

Understanding subglacial systems is essential for making predictions of glacier motion andthe contribution of glacier melt to stream runoff in the context of overall glacier response toclimate change. Several studies have shown that subglacial hydrology is one of the keycontrols on basal sliding, but how the ice bed geology influences the subglacial drainagesystem and therefore the basal sliding, is still poorly understood. The drainage system at thebase of a glacier usually consists of two main components with complex interactions: 1) adistributed system of linked cavities and 2) a channelized system that depends on thedevelopment of Röthlisberger channels into the basal ice. Both systems are expected toevolve during the melt season in response to variable water flux, effective pressure, andsliding speed. In this study, we use a two-dimensional finite element model to simulate theseasonal evolution of a hydrological system at the base of a glacier. The sliding velocity ofthe ice is allowed to vary as a function of the contact area between the ice and itsbed. Our computational experiments consider a range of groundwater transmissivities in orderto explore the effect of groundwater flow on the seasonal variability of sliding velocity. Usinglow groundwater transmissivities (< 10−5 m2 s−1), typical of non-carbonate rocks, asubglacial drainage system evolves from an inefficient drainage system in winter withrelatively slow sliding, a high contact area, and moderate effective pressure, followed by thespring event with enhanced sliding as the capability of the drainage system is exceeded by theincreasing surface melt. In summer, channels gradually develop as the subglacial systemadapts to the increased water flux. The development of channels cause cavities to shrink andsliding consequently slows towards the winter level. On the other hand, by applyinggroundwater transmissivities typical of carbonate rocks (> 10−5 m2 s−1), the waterdischarge through bedrock prevails over the entire year, leaving the channelized systemlargely undeveloped. As a result, the sliding velocity remains low and stable throughout ayear. Warm-based glaciers typically exhibit a distinct seasonal variation in sliding velocity,with spring-summer sliding velocities sometimes two or three times faster than winteraverages. However, glaciers resting on carbonate rocks, where the meltwater dischargethrough bedrock accounts for more than 90% of the total meltwater flux, are, at least in somecases known to show reduced seasonality. Our results demonstrate how groundwater flow caneffectively remove the seasonal variation of glaciers flowing on carbonate rocks such aswell-karstified limestone. [ABSTRACT FROM AUTHOR]