Future glacier lakes in the Swiss Alps: a projection of their evolution

Abstract

<p>With the ongoing, rapid glacier retreat, high-alpine landscapes are poised to change drastically over the coming decades. The newly exposed areas will not only give rise to new environments that can be eventually colonized by plants and organisms, but also to characteristic landforms. Amongst these, future glacier lakes forming in topographical depressions left behind by glacier retreat, have already been in the focus of earlier studies. The interest in these features is given by a number of factors, ranging from the ecological significance of such high-alpine lakes, over the potential hazards posed by such newly emerging water bodies, to their optical appeal in terms of landscape elements.</p><p>Here, we add to the existing body of literature dealing with the formation of new glacier lakes, and do so by leveraging both (1) a recently released, measurement-based estimate for the subglacial topography of all glaciers in the Swiss Alps, and (2) the results of a regional-scale glacier evolution model driven by different climate scenarios. Whilst the first point significantly increases the robustness of our projections, the second allows for a first quantification of the timing by which such new glacier lakes are expected to emerge. In this time-dependent analysis, we also include the possibility for newly emerging lakes to disappear again due to re-filling with sediments – a process neglected by studies so far.</p><p>Our results indicate that, if glaciers were to disappear entirely from the Swiss Alps, up to 683 new glacier lakes could emerge. These hold the potential of storing up to 1.16 ± 0.16 km<sup>3</sup> of water, for a total lake area of 45 ± 9 km<sup>2</sup>. For a middle-of-the-road climate scenario, we estimate that about 14% of the total volume (i.e. 0.16 ± 0.07 km<sup>3</sup>) could emerge by 2050. For 2100, the number changes to 57% (0.66 ± 0.17 km<sup>3</sup>), indicating a substantial increase in the pace by which new lakes will emerge after mid-century. Our first-order assessment of lake re-sedimentation indicates that about 45% of the newly emerging glacier lakes (ca. 260 out of ca. 570) could disappear again before the end of the century, and that between 12 to 20% of the newly emerging lake volume could be lost again due to this process. This suggests that sedimentation processes have to be taken into account when aiming at anticipating how future glacier landscapes will look like.</p>