Alpine rockwall erosion patterns follow elevation-dependent climate trajectories

Abstract

Mountainous topography reflects an interplay between tectonic uplift, crustal strength, and climate-conditioned erosion cycles. During glaciations, glacial erosion increases bedrock relief, whereas during interglacials relief is lowered by rockwall erosion. Here, we show that paraglacial, frost cracking and permafrost processes jointly drive postglacial rockwall erosion in our research area. Field observations and modelling experiments demonstrate that all three processes are strongly conditioned by elevation. Our findings on catchment scale provide a potential multi-process explanation for the increase of rockwall erosion rates with elevation across the European Alps. As alpine basins warm during deglaciation, changing intensities and elevation-dependent interactions between periglacial and paraglacial processes result in elevational shifts in rockwall erosion patterns. Future climate warming will shift the intensity and elevation distribution of these processes, resulting in overall lower erosion rates across the Alps, but with more intensified erosion at the highest topography most sensitive to climate change.

Debris‐flow fan development and geomorphic effects in alpine canyons under a changing climate

“…Alpine environments, especially glacier, permafrost and snow‐related landforms, are highly sensitive to the rising temperatures, which have undergone general glacier retreat and permafrost degradation over the past decades due to global climate change (Harris et al, 2001; Magnin et al, 2019; Scapozza, 2016). The corresponding exposure of a large amount of unconsolidated, unvegetated and sometimes ice‐cored glacial deposits may significantly increase the potential of slope instability and consequently favour the occurrence of high‐frequency mass movement (Chiarle et al, 2007; Draebing et al, 2022; East & Sankey, 2020; Zhang et al, 2022). The debris flows in typical alpine areas such as the European Alps and Southeast Tibet, China, in the past century have clearly demonstrated such trend (Lu et al, 2021; Pavlova et al, 2014; Stoffel et al, 2005; Willi et al, 2015).…”

Elevation‐Dependent Periglacial and Paraglacial Processes Modulate Tectonically‐Controlled Erosion of the Western Southern Alps, New Zealand

“…In steady‐state orogens, long‐term (∼10 6 yr) erosion rates balance rock‐uplift rates, and hence are largely dictated by tectonics (Willett & Brandon, 2002). However, over timescales shorter than ∼10 6 yr, climate cycles and their related erosional processes can influence rates and patterns of erosion (Delunel et al., 2010; Draebing et al., 2022; Herman et al., 2015; Marshall et al., 2015; Moon et al., 2011).…”

“…Periglacial processes (predominantly frost‐cracking) occur commonly in regions experiencing paraglacial landscape adjustment, and they can help pre‐condition bedrock for paraglacial landsliding (Draebing et al., 2022; Geng et al., 2022; Grämiger et al., 2017; Hartmeyer et al., 2020a). Compared to paraglacial landsliding, which represents lower‐frequency, higher‐magnitude erosional events that deliver a wide range of grain sizes, including meter‐scale boulders (Ben‐Yehoshua et al., 2022), periglacial frost‐cracking represents higher‐frequency, lower‐magnitude erosional events that deliver narrower and finer grain size distributions (P. A. Allen et al., 2015; Sklar et al., 2017).…”

“…Bedrock strength, porosity and pre‐existing fracture networks further modulate frost‐cracking intensity (Andersen et al., 2015; Draebing & Mayer, 2021). Direct rock temperature measurements are only available in a few monitored sites (Draebing & Mayer, 2021; Draebing et al., 2022; Hartmeyer et al., 2020a), and variables such as snow/regolith cover, daily temperature cycles, bedrock strength, and fracture networks are challenging or impossible to constrain at the landscape scale and over >10 2 yr timescales. Consequently, studies comparing long‐term (>10 2 yr) erosion rates to frost‐cracking predictions generally use models that consider only MAAT and annual temperature fluctuations (Delunel et al., 2010; Geng et al., 2022; Hales & Roering, 2005, 2009; Marshall et al., 2015, 2021; Savi et al., 2015).…”

Influences Driving and Limiting the Efficacy of Ice Segregation in Alpine Rocks

“…These rates are in the same order of magnitude as glacial erosion rates (0.5–36 mm a −1 ; Cook et al., 2020) suggesting that rockfall processes are key agents of alpine landscape evolution. Rockwall erosion is controlled by permafrost (Krautblatter et al., 2013), glacier retreat (Hartmeyer et al., 2020), frost cracking (Hales & Roering, 2005) or a combination of these processes (Draebing et al., 2022). Ice segregation is a dominant frost weathering process capable of breaking rocks (Matsuoka & Murton, 2008).…”