The footprint of Asian monsoon dynamics in the mass and energy balance of a Tibetan glacier

Abstract

Abstract. Determinations of glacier-wide mass and energy balance are still scarce for the remote mountains of the Tibetan Plateau, where field measurements are challenging. Here we run and evaluate a physical, distributed mass balance model for Zhadang Glacier (central Tibet, 30 • N) based on in-situ measurements over 2009-2011 and an uncertainty estimate by Monte Carlo and ensemble strategies. The model application aims to provide the first quantification of how the Indian Summer Monsoon (ISM) impacts an entire glacier over the various stages of the monsoon's annual cycle. We find a strong and systematic ISM footprint on the interannual scale. Early (late) monsoon onset causes higher (lower) accumulation, and reduces (increases) the available energy for ablation primarily through changes in absorbed shortwave radiation. By contrast, only a weak footprint exists in the ISM cessation phase. Most striking though is the core monsoon season: local mass and energy balance variability is fully decoupled from the active/break cycle that defines large-scale atmospheric variability during the ISM. Our results demonstrate quantitatively that monsoon onset strongly affects the ablation season of glaciers in Tibet. However, we find no direct ISM impact on the glacier in the main monsoon season, which has not been acknowledged so far. This result also adds cryospheric evidence that, once the monsoon is in full swing, regional atmospheric variability prevails on the Tibetan Plateau in summer.

Mass balance observations and reconstruction for Batysh Sook Glacier, Tien Shan, from 2004 to 2016

“…At decadal scale as well, summer air temperatures were identified an important driving force of mass balance for Chhota Shigri (Azam et al, 2014b). Furthermore, on the Tibetan Plateau an early onset of the summer monsoon precipitation could be associated with reduced ablation mainly through changes in absorbed shortwave radiation (Mölg et al, 2012). Additionally, for Batysh Sook, a difference in inter-annual mass balance variability depending on elevation can be observed (Fig.…”

High-resolution interactive modelling of the mountain glacier–atmosphere interface: an application over the Karakoram

“…The initial subsurface temperature was specified through linear interpolation of the input data to the Noah LSM, available at 0.1, 0.4, 1.0, and 2.0 m depths, and assigning a constant value of 268.6 K below this level. The lower boundary is specified at 268.6 K during the simulation, based on measurements taken from a Tibetan glacier (Mölg et al, 2012a). We address uncertainties in the subsurface temperature initialization by including a long (25 day) model spin-up period.…”

“…2.1) and the process-based surface-energy and CMB model of Mölg et al (2008, 2012a Here we use the term interactive to denote surface-atmosphere exchanges through heat, moisture and momentum fluxes only and not through topographic feedbacks, as glacier geometry is held constant over our brief simulation. As a first approximation, we focused on the meteorologically driven fluctuations of mass balance and neglected the influence of debris cover.…”

“…The CMB model is described fully by Mölg et al (2008Mölg et al ( , 2009 with the most recent updates in Mölg et al (2012a), but we will review some important features here. The model computes the column specific mass balance from solid precipitation, surface deposition and sublimation, surface and subsurface melt, and refreeze of both meltwater and liquid precipitation.…”

Climatic controls and climate proxy potential of Lewis Glacier, Mt. Kenya

“…The model used in this study originates from an energy balance model (Mölg and Hardy, 2004), that was developed into a mass balance model suitable for single point or glacier-wide applications (Mölg et al, 2008(Mölg et al, , 2009b. The model structure used in this study is explained in detail by Mölg et al (2012) with the latest model version (2.4) used by Mölg (2015). The model calculates the surface and near-subsurface mass and energy fluxes and has been successfully applied to address various questions in a range of climatic conditions (Collier et al, 2013;Conway and Cullen, 2015;Cullen et al, 2007Cullen et al, , 2014Gurgiser et al, 2013a, b;MacDonell et al, 2013;Mölg et al, 2014;Nicholson et al, 2013).…”