O1: Advancing the knowledge on the ground air circulation (and subsurface permafrost changes) in relation to environmental drivers
We previously proved with the use of thermal measurements and smoke air experiments the occurrence of an intense ground air circulation; the specific thermal regimes of cold air absorption zones with large negative ATA and of warm air evacuation zones with positive ATA were also presented together with other relevant site observations and measurements during both the cold and warm seasons (Popescu et al., 2017a). Till present, the ground air currents were directly monitored using anemometers only in one site (Dreveneuse, Swiss Alps) but for a too short period of time (including instruments failure in the field) which did not allow for significant conclusions to be drawn (Lambiel, 2006). In these conditions, we plan to install several ultrasonic 3D-anemometers with high sensitivity and accuracy in order to monitor both aspiration and exhalation during the cold and warm seasons and to identify ground air circulation patterns in relation to temperature offset (between atmosphere and ground temperatures), talus slope morphometry and debris texture. Detunata is a perfect site as a natural laboratory to study the ground air circulation in relation to ATA variability and already mentioned controlling factors due to its complex and rare morphology (talus slope – rock glacier system) expanded on a large surface and to regular basaltic clasts imposing extraordinary high porosities (Popescu et al, 2017a). Within the current project we expect to bring a substantial progress for the global understanding of the mechanisms governing the chimney circulation at low altitude permafrost sites by using accurate and detailed DEM, smoke experiments, ultrasonic anemometers and thermal sensors. In addition, several BTS campaigns will be performed during winter to capture the hypothesized thermal zones expansion and contraction. Intensive ERT survey will be performed in order to detect the perfect site for borehole.
O2: Starting a long-term temperature monitoring program of the permafrost and cold reservoir at Detunata site as a key site for monitoring the climate variability impact on cold screes;
Mountain permafrost is usually investigated by indirect measurements, with thermal and geophysical methods but the ideal case is represented by drilling. The latter provide direct evidence of permafrost and offer a unique opportunity to get insight of permafrost characteristics that cannot be otherwise known: temperature profile, active layer depth, zero annual amplitude depth, ice content and mean clast-size. Moreover, by installing thermistors arrays in a sealed and stabilized borehole, one can monitor the permafrost changes (seasonal, annual, and multiannual) and the impact of climate variability. Even though we know how temperature, precipitation, snow cover and other meteorological variables evolve in time by accurate measurements, we cannot precisely estimate the impact on ground thermal regime which is the result of the complex interplay between the meteorological factors, land cover types, topography and vegetation. That is why permafrost is one of the 13 terrestrial essential climate variables (ECVs) and why the Global Terrestrial Network for Permafrost (GTN-P) was developed in 1990s by the International Permafrost Association with the “long-term goal of obtaining a comprehensive view of the spatial structure, trends and variability of changes in the active layer thickness and permafrost temperature”. Thus, taking the opportunity of relatively accessible Detunata scree, we aim to perform the first borehole in permafrost in the Carpathians (and in the Eastern Europe) as a contribution of Romania to the GTN-P data base and in a relatively rare geologic feature (rectangular basaltic columns deposit) and complex geomorphologic landform (talus slope-rock glacier system). One or two drillings will be performed and the stratigraphy will be described in situ in order to infer the formation and palaeoevolution of the deposit and to draw palaeoclimatic information later on. Further, terrestrial cosmogenic nuclides (TCN) datings will be performed in order to determine the absolute age of the landform. The borehole(s) will be equipped with thermistors array connected to a main logger at the ground surface.
O3: Inter-site analysis and comparison of multiple LAP sites
Several studies have concentrated on documenting the permafrost occurrence at low altitude cold screes but only a few attempted to look comparatively at several locations (e.g. Morard, 2011). Thus, the causes that determine different thermal anomalies in cold screes remain insufficiently understood. In this context, we plan to test our hypothesis that lithology via debris texture and porosity is the key factor in establishing the magnitude of thermal anomalies. Our preliminary inventory of cold screes already indicated that large ATAs can be found on basalts, granites and marbles (-6…-9.1°C), medium ATA on limestone (-4.06… -5.25°C) and reduced ATA on crystalline schist (> -3.05°C). Thus, we plan to assess the influence of different rock types and topography on ATA by several investigations at several cold screes from Central Europe by: (i) detailed DEMs (basic morphometry), (ii) clast-size and the surface debris porosity measurements and (iii) determination of the mechanical (hardness, joint network, cleavage) and thermal (conductivity) properties of rocks. Identification and analyzing of other cold screes susceptible for permafrost preservation in different lithological contexts from Romanian Carpathians is also intended as an original component of the project.
The second inter-site analysis will be focused on dendrologic investigations. We previously proposed a method to evaluate the climate fluctuations impact on low altitude permafrost sites thermal regime by dendrogeomorphology (tree ring width analysis; Popescu et al., 2017a) showing that during colder time intervals the cold scree environments are slightly warmer and the dwarf trees have a better growth and vice versa. We now intend to test the validity of this finding in other cold screes sites by analyzing the collected samples and by collecting and analyzing new ones. The dendrologic series could be also used to document natural events impact on climate change like major volcanic eruptions around the world from the last centuries.