Changes in sediment connectivity following glacial debuttressing in an Alpine valley system

Abstract

Increasing air temperature and declining winter snowfalls are resulting in rapid glacier recession and the expansion of proglacial margins in Alpine regions. Such margins include substantial debris accumulations (e.g. frontal/lateral moraine ridges; till-covered and steep valley sidewalls) which may be unstable due to glacial debuttressing. Rainfall, snowmelt and ice melt out may then cause mass movements. Here, we quantify the decadal-scale erosion and deposition patterns and changes in connectivity for two valley sidewall geomorphological systems following retreat of the Glacier d'Otemma, Switzerland. We apply archival digital photogrammetric methods to the period 1964 to 2009 to determine high resolution digital elevation models. These were differenced to calculate patterns of erosion and deposition and to quantify the evolution of sediment connectivity. We found that gully headward erosion (rates between ca. -10.6 mm/yr and -1002.1 mm/year) was the main geomorphological process during glacier thinning but increasing depositional rates downslope of the gullies (ca. +21.3 to +298.5 mm/yr) were recorded in the following years associated with significant alluvial fan growth at the slope base. Whilst gullying enhanced connectivity by removing glacially conditioned sediment transfer buffers, so connecting sideslopes to upstream sediment sinks (the upslope contributing area between 1964 and 2009 increased by +73.8% and +195.1% in each subsystem), alluvial fans reduced the rates of

Evidence of glacier-permafrost interactions associated with hydro-geomorphological processes and landforms at Snøhetta, Dovrefjell, Norway

“…Oversteepened rock-faces are impacted both by paraglacial processes grounded in the loss of glacial overburden and periglacial processes exerting frost weathering on the bedrock at different rates, creating an assemblage of paraglacial subsystems (cf. Mancini and Lane 2020). Talus slopes are abundant and indicative of a glacial-periglacial transition zone extending to lower elevations.…”

“…Additionally, some parts may currently be reacting to more recent changes, whereas other parts may still be in incomplete transition from past perturbations (Hewitt 2002;Bierman and Montgomery 2014). Often in the paraglacial phase of a landscape, subsystems operate at different, context specific response rates (Mancini and Lane 2020). Therefore, even supposedly simple landscapes may be the composite result of many interacting subsystems (Allen 2005).…”

BEGEOSCIENTIST a young network - I Congresso Nazionale dei Giovani Geoscienziati

“…Sapropel deposits represent an important perturbation of the carbon cycle; despite more than 50 years of intense studies, the triggering mechanism of sapropel deposition is still under debate. In particular, two models explaining the mechanisms promoting the Messinian sapropel deposition were proposed: the first relies on the Pleistocene-Holocene sapropels depositional model, which invoked humid and warm conditions as necessary for the sapropel deposition (Sierro et al, 2003); the second points to a cold and highly productive environment as a trigger for the sapropel deposition (Mancini et al, 2020).…”

“…Running waters action contributes to these dynamics favoring unconsolidated sediments dismantling and genesis of proglacial lakes in correspondence of morphological hollow, later becoming potential sediment sinks. The highly geodiversity of such environments hence complicate the analysis of sediment connectivity which could reflect very local patterns (Mancini & Lane, 2020).To perform a multitemporal evaluation of dynamics affecting a proglacial region, the focus has been put on the last seventy years evolution of the adjoining Aurona and Leone proglacial areas, in the Alpe Veglia area (Lepontine Alps, Italy), characterized by different geomorphological features and approachable along a glaciological trail (Zanoletti et al, 2017). A multitemporal analysis on the historical archives allows to identify the main evolution stages of the proglacial areas, individuating the hot-spots of changes in the time span 1952-2018, among which LIA moraines, permafrost-related debris bodies, proglacial lakes.…”

Glacial Lake Outburst Floods (GLOFs) in the Cordillera Huayhuash, Peru: Historic Events and Current Susceptibility

“…The vast majority of glacierized high mountains have experienced glacier shrinkage in past decades (e.g., [1][2][3]). Lakes commonly develop in front or on top of receding or thinning glaciers (e.g., [4,5]), and these lakes can represent a threat of glacial lake outburst floods (GLOFs), i.e., a sudden release of water retained within a glacial lake regardless of trigger, failure mechanism, or glacial lake sub-type (e.g., [6,7]).…”