Forschungsprojekt ::

Research Unit SEHAG - Sensitivity of high Alpine geosystems to climate change since 1850 (SEHAG) - Phase II

Projektbeschreibung

The research unit sets out to test the central hypothesis that the consequences of climate changes since the LIA can be detected already today in the Alpine geosystem. The aforementioned data and knowledge gaps need to be closed for pursuing this aim. Specifically, we will investigate to what extent the activity of geomorphic and hydrological processes has changed spatially and temporally (i.e. with respect to magnitude and frequency, time lag). The analysis will be conducted in highly sensitive study areas north and south of the Alpine divide; this study design will enable the investigation of different climatic changes conditioned by the topography of the orogen, and the differentiated response within the respective geosystem. The selected study areas cover the altitudinal zones between the treeline ecotone and the nival zone. We consider them especially suitable for our research due to (i) extensive data collections and experience from previous projects (e.g. SEDAG, PROSA), (ii) the high intensity of morphodynamics combined with a relatively low degree of human impact, (iii) the comparatively high density of climate monitoring stations in the greater region, and (iv) the availability of photogrammetric and remote sensing data.
Based on the central research hypothesis that the effects of climatic changes since 1850 are already detectable in reactions of the alpine geosystem, the research group investigates these systems exemplarily in three catchments south and north of the main Alpine ridge, which were selected due to extensive preliminary work, high morphodynamics with low anthropo-genic influences and good data situation.

The ongoing investigations in the first project phase focus on changes in geosystems and their causes from 1850 to the present day and will be continued in the second application phase (years 4-6) in order to further improve the data situation. However, the focus of the work in the continuation phase will be on the model-based analysis of future developments in the ge-osystems up to 2050, based on the data from dynamically downscaled climate model projec-tions and the models for subsystems in complex alpine catchments calibrated in the first pro-ject phase (cf. subprojects). The project period of three decades in the second project phase was chosen because the expected forecast uncertainties (climate scenarios) and the internal variabilities of the processes in the geosystems are still low, but irreversible changes that have already begun and are expanding, e.g. in the cryosphere, will have consequences especially in the forecast period.

The complex interplay of atmospheric forcing, hydro- and cryospheric changes and the de-tection of their consequences for different geomorphological processes in alpine geosystems requires a concerted approach, which leads to a multidisciplinary structure of the research group.

The research group's investigations are guided by three main research questions:

I. Is it possible to identify significant responses of individual processes in alpine geosys-tems in the context of climate change, even taking into account the spatial and temporal un-certainties in experimental data and model analyses?

II. How do climatically induced changes in system compartments (cryosphere, litho-sphere, hydrosphere, vegetation/land cover) influence the properties of geosystems with re-spect to process dynamics? Do interactions strengthen or weaken the effects of climate change?

III How do changes in individual compartments and process dynamics (I), possibly ampli-fied or weakened by process interactions (II), propagate through the system (connectivity), especially with regard to sediment delivery? Is there a development of increasing dynamics or weakening of the formation?

The knowledge about the system development since about 1850 will be acquired in the first project phase, completed in the second project phase and forms the prerequisite for the mod-elling of future scenarios in the second project phase. The selection of the study areas and their mesoscale size ensures that the influence of local factors on the reaction of the geosys-tems can also be worked out. Important aspects here are the location of the areas in relation to the main Alpine ridge (meteorological influences) and the varying degrees of involvement of cryospheric changes (especially of glaciers and permafrost) in the development of the ge-osystems and parts of them. The degree of connectivity, which can be spatially and temporal-ly variable, determines whether local changes in individual processes dominate or whether the entire geosystem responds to climatic changes. In order to record and forecast the develop-ment at catchment level, the use of a Landscape Evolution Model is planned in the second project phase (cf. SP 8).

For the second application phase of the research group (2022-2024), the focus is on prognos-tic model-based analyses. Knowledge of the amplitude of projected climatic changes, their uncertainties and the signal-to-noise ratio we find in the relationship between forcing and geosystem response must be taken into account. All SPs will continue to conduct field meas-urements and evaluate historical photos to increase knowledge of past and present dynamics and improve model calibrations in the subprojects (see also specific sections in SP pro-posals).