Abstract
Accurate estimates of albedo can be crucial for energy balance models of glaciers. A number of algorithms exist which are often site dependent and rely on accurate measurements or estimates of snow depth. Using the well-established COSIMA model we simulate the energy and mass balance of the Laohugou Glacier No.12 in the Qilian Mountains, on the northern fringe of the Qinghai-Tibetan Plateau, a glacier that has been well studied in the past. Using energy flux and mass balance measurements between 2010 and 2015 we were able to validate the model over multiple seasons. Using the original albedo parametrization, the model fails to reproduce the observed mass balance. We show that this is due to the failure to estimate snow depth accurately. We therefore applied two alternative albedo algorithms, one well established example and one new parametrization only dependent on temperature and time since last snow fall. As a result, mass balance simulations improve considerably from a RMSE of 0.53 m w.e. for the original parametrization to 0.39 and 0.19 m w.e. for the uncalibrated established and the new calibrated model respectively. Modelled albedo during the ablation period (NSE = 0.05, R2 = 0.33) is more accurate than during the accumulation period (NSE = −0.37, R2 = 0.04). Testing the new model at another glacier on the Tibetan Plateau shows that a local recalibration of parameters remains necessary to achieve satisfying results. Investigations into the effect of impurities in snow, regional moisture sources and changing surface characteristics with rising temperatures will be crucial for accurate projections into the future.
Highlights
Mass loss of glaciers on the Tibetan plateau has been very variable in recent decades, with a strong negative balance in the South-East and near balance in the South-West (Kääb et al, 2012; Brun et al, 2017; Li et al, 2019)
In this study we try to reach the three following specific aims: (a) we investigate how suitable the standard approach in the COSIMA model based on Oerlemans and Knap (1998) is to reproduce the mass balance accurately; (b) we discuss its shortcoming and test an alternative approach; (c) we propose a new parametrization that is able to account for the variability of albedo and (d) discuss the implications the choice of different models has on mass balance estimates
In this paper we show how a mass and energy balance model applied on a glacier in the Qilian Shan, on the northern fringes of the Tibetan Plateau, fails due to the use of an albedo scheme that is dependent on accurate snow depth data that is not available in our case and in many other field sites
Summary
Mass loss of glaciers on the Tibetan plateau has been very variable in recent decades, with a strong negative balance in the South-East and near balance in the South-West (Kääb et al, 2012; Brun et al, 2017; Li et al, 2019). This heterogeneous response can be explained with different dominant drivers of accumulation and ablation (Yao et al, 2012). As it is relatively accessible compared to the rest of the plateau, a number of glaciers have been researched in more detail including the Ningchanhe glaciers (Liu et al, 2012), the Bayi glacier (Liu et al, 2020), the Qiyi glacier (Chen et al, 2007) as well as the Laohugou Glacier No 12 (Sun et al, 2012; Zhang et al, 2012; Sun et al, 2014; Qin et al, 2015; Wang et al, 2018; Liu et al, 2019)
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