Quantifying Feedback Mechanisms on Glacier Mass Balance across High Mountain Asia

Abstract:

One major challenge to modeling Earth’s climate system is the proliferation of complex feedbacks that can both dampen and amplify the effects of forcing mechanisms acting on it. While these types of feedbacks are regularly addressed in general climate studies, they are often neglected in climate-dependent studies where feedback impacts are potentially similarly significant. A primary example of this is found in studies involving glacier mass balances, where numerous temperature and albedo feedbacks (in particular) are recognized, yet remain poorly quantified in many glacier mass balance studies. This study develops a robust, fully distributed surface- and energy-mass balance model to quantify the influence of glacier mass balance feedbacks across High Mountain Asia (HMA), and thereby provides a quantitative estimate for the variability of mass balance feedbacks under differing climate settings. HMA is chosen here primarily because it is a region whose climate is especially heterogeneous, largely due to its complex topography. The surface- and energy-mass balance model follows well-known methods described in previous mass balance studies, but allows individual feedback mechanisms to be independently switched on or off. The sensitivity of glacier mass balance to each feedback is then independently tested by comparing the model-predicted mass balance when only a single feedback is included, to that of a control in which no feedbacks are included. By this means, the magnitude of the contribution of each individual feedback is directly comparable one to another, as is the variability in glacier sensitivity to these feedbacks from one region to another. In addition, the interdependence of feedbacks is assessed. The results provide a self-consistent assessment of the impact of feedbacks on glacier surface mass balance, highlight which regions of HMA are most sensitive to feedback processes, and identify which feedbacks are likely to have the biggest impacts on glacier response to future climate scenarios.