Abstract
Glaciers are highly effective agents of erosion that have profoundly shaped Earth’s surface, but there is uncertainty about how glacial erosion should be parameterised in landscape evolution models. Glacial erosion rate is usually modelled as a function of glacier sliding velocity, but the empirical basis for this relationship is weak. In turn, climate is assumed to control sliding velocity and hence erosion, but this too lacks empirical scrutiny. Here, we present statistically robust relationships between erosion rates, sliding velocities, and climate from a global compilation of 38 glaciers. We show that sliding is positively and significantly correlated with erosion, and derive a relationship for use in erosion models. Our dataset further demonstrates that the most rapid erosion is achieved at temperate glaciers with high mean annual precipitation, which serve to promote rapid sliding. Precipitation has received little attention in glacial erosion studies, but our data illustrate its importance.
Highlights
Glaciers are highly effective agents of erosion that have profoundly shaped Earth’s surface, but there is uncertainty about how glacial erosion should be parameterised in landscape evolution models
The rate of shear at the ice-bed interface is widely agreed to be the most important control on erosion rates, but glacial erosion of bedrock is achieved via several distinct mechanisms, and theoretical treatments of these processes are constrained poorly by actual observations[1,8,9]. This complexity means that glacial landscape evolution models (LEMs) use a very simple erosion rule that relates glacial erosion rate (E) to glacier sliding velocity (Us), or surface velocity as its surrogate[4,7,9,10,11,12,13,14,15,16]
This rule is usually expressed as E 1⁄4 KGUSl, where KG is a bedrock erodibility constant and l is an exponent that is usually taken to be between one and two, values of up to four have been used in LEMs depending on the value of KG (e.g. 1,4,8,13,14)
Summary
Glaciers are highly effective agents of erosion that have profoundly shaped Earth’s surface, but there is uncertainty about how glacial erosion should be parameterised in landscape evolution models. Our global dataset encompasses a wide range of climatic and geological environments (Fig. 1), and provides a robust empirical context within which to examine both glacial and non-glacial controls on glacial erosion We use these data to examine the strength of the relationship between glacial erosion rate and glacier sliding velocity, enabling us to determine a value for the exponent l that allows models of glacial landscape evolution to be more reliably based on realworld relationships. We hypothesise that higher precipitation rates would lead to greater erosion rates because liquid precipitation reaching the glacier bed will enhance sliding and sediment flushing[22], and higher rates of snowfall in the accumulation zone will result in thicker ice and steeper mass balance gradients, which should lead to greater
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