Forschungsprojekt ::

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

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.

In the first project phase (3 years), the research unit will concentrate on changes of process dynamics since the end of the LIA (ca. 1850; c.f. Knight & Harrison 2014), based on the investigation of recent and past processes and their relationship with triggers and geofactors. This database will be further improved in the second project phase of the research group (year 4 to 6). Based on these results related to the coupling of (hydro-) meteorological, geomorphic and successional process dynamics, we further aim at predictive scenarios of geosystem development in the second project phase using dynamically downscaled climate model projections until the year 2050. This timescale was chosen since (i) scenario-uncertainty plays a relatively small role until then, (ii) uncertainty from internal variability is getting smaller on these multidecadal timescales, and (iii) time-lagged, not yet fully visible consequences of climate changes that already occurred in the recent past provide a reasonable amount of predictability. Such consequences are largely independent of future climate changes, for example subsequent effects of irreversible cryospheric changes (glacier melt, permafrost degradation)

The intricate interaction of atmospheric forcing, hydro- and cryospheric changes and the detection of their consequences for different geomorphic processes in alpine geosystems calls for concerted action, leading to a multidisciplinary structure of the research unit (Fig. 1).

We investigate three main research questions:

I. Is it possible to identify significant changes of single processes in alpine geosystems related to climate change considering the uncertainty affecting experimental data and model analysis?
a. How has the meteorological forcing (e.g., precipitation, temperature, and atmospheric circulation patterns) changed locally/regionally on a decadal scale?
b. Can we detect significant changes in the spatial distribution and magnitude-frequency relationships of geomorphic and hydrological processes in the study areas? If so, when did they occur?
c. Can we detect local/regional vegetation/landcover changes (since 1850) that can be attributed to climate change? Which functional responses are relevant for the vegetational feedback to climatic, geomorphic and hydrological changes?

II. How do system compartments (Cryosphere, Lithosphere, Hydrosphere, Vegetation/Landcover, Pedosphere) , their properties and processes interact, and do such interactions enhance or attenuate the impact of climate change?
a. How do cryospheric changes (glacier, permafrost, snow) influence geomorphic (mass movements), vegetation cover and hydrological processes and rates (discharge dynamics, channel evolution, terraces, rills) in time and space?
b. What is the effect of alpine climate change on runoff, sediment transport capacity and channel evolution?
c. How do changes in vegetation cover on the one hand and hydrological and geomorphic dynamics on the other interact? Does vegetation growth attenuate morphodynamics, or do the latter inhibit vegetation growth?

III. How do changes of single compartments (I) or through interactions (II) propagate through the system, specifically with respect to sediment delivery?
a. Can we find evidence that and how connectivity (as assessed through field work, maps and indices) modifies the propagation of changes (increased or decreased sediment flux) along sediment cascades, towards the catchment outlet?
b. Has connectivity itself changed through time?
c. Has sediment delivery changed, and how did that affect the sediment yield at the outlet or reservoir?

The following topics have to be considered when answering the questions above:

• The knowledge of system evolution since ca. 1850 serves as a basis for the second project phase in which future scenarios will be modelled.
• There might be differences in geosystem reaction to (i) the initial warming after the end of the LIA and (ii) the recent warming phase since the 1980s.

Within the second working phase of the research group (2022-2024) we will investigate prognostic statements considering the amplitude of projected climatic changes, their uncertainties, and the signal/noise ratio we find in the relation between forcing and response of the geosystem. All SP will continue to conduct field measurements and to retrieve and evaluate historical photos, augmenting knowledge of past and present dynamics gained during phase 1 (see also dedicated sections in SP proposals that refer to phase 2).

Zu diesem Forschungsprojekt gibt es mehrere Teil- oder Unterprojekte.