Transience in cascading paraglacial systems

Abstract

AbstractTwo main ways in which the progress of deglaciation in mountains can be identified and monitored are through (a) meltwater loss over time as glaciers and permafrost melt and (b) enhanced sediment yield over time as loose sediments are released downslope. Conceptually, both these outcomes of glacier retreat can be considered through their relationship to models of paraglacial landscape evolution, which describe how volume fluxes of meltwater and sediments change over time in mountains that are becoming deglacierized, and the different landforms that exist during different stages of landscape evolution. This paper critically reconsiders paraglacial landscape evolution models with respect to the separate timings and magnitudes of meltwater and sediment fluxes, drawing from examples from past and present deglacierizing mountains worldwide. This analysis shows that constructions of paraglacial systems simply as sediment cascades cannot be uncritically supported and that paraglacial systems can be best considered as reflecting transient stages of evolution in which meltwater and sediment fluxes vary over time and space. These transient properties of paraglacial systems have important implications for the ways in which the dynamics of these systems are conceptualized and modelled, with respect to the paraglacial evolution of mountain landscapes and mountain geohazards, especially under conditions of global warming and glacier recession.