Simulations of black carbon (BC) aerosol impact over Hindu-Kush Himalayan sites: validation, sources, and implications on glacier runoff

Abstract

<p><strong>Abstract.</strong> We estimated the black carbon (BC) concentration over the Hindu Kush Himalayan region (HKH), its impact on snow-albedo reduction and sensitivity on annual glacier runoff over the identified glaciers. These estimates were based on free-running aerosol simulations (<i>freesimu</i>) and constrained aerosol simulations (<i>constrsimu</i>) from an atmospheric general circulation model, combined with numerical simulations of glacial mass balance model. BC concentration estimated from <i>freesimu</i> performed better over higher altitude (HA) HKH stations than that over lower altitude (LA) stations. The estimates from <i>constrsimu</i> mirrored well the measurements when implemented for LA stations. Estimates of the spatial distribution of BC concentration in the snowpack (<i>BC</i><sub><i>c</i></sub>) over the HKH region led to identifying a hot-spot zone located around Manora peak. Among glaciers over this zone, <i>BC</i><sub><i>c</i></sub> (> 60 μg kg<sup>−1</sup>) and BC-induced snow-albedo reduction (≈ 5 %) were estimated explicitly being high during the pre-monsoon for Pindari, Poting, Chorabari, and Gangotri glaciers (which are major sources of fresh water for the Indian sub-continent). The rate of increase of <i>BC</i><sub><i>c</i></sub> in recent years (i.e. over the period 1961–2010) was, however, estimated being the highest for the Zemmu glacier. Sensitivity analysis with glacial mass balance model indicated the increase in annual runoff from debris-free glacier area due to BC-induced snow albedo reduction (SAR) corresponding to <i>BC</i><sub><i>c</i></sub> estimated for the HKH glaciers was 4 %–18 %, with the highest being for the Milam and Pindari glacier. The rate of increase in annual glacier runoff per unit BC-induced percentage SAR was specifically high for Milam, Pindari, and Shunkalpa glacier. The source-specific contribution to atmospheric BC aerosols by emission sources led to identifying the potential emission source being primarily from the biofuel combustion in the Indo-Gangetic plain south to 30° N, but also from open burning in a more remote region north to 30° N.</p>

Impact of light-absorbing particles on snow albedo darkening and associated radiative forcing over high-mountain Asia: high-resolution WRF-Chem modeling and new satellite observations

“…Many of these studies used online global model simulations at coarse spatial resolutions of ∼ 50-150 km (Flanner and Zender, 2005;Ming et al, 2008;Qian et al, 2011;Kopacz et al, 2011;Zhang et al, 2015). Other studies employed offline simulation of the snow albedo effect using measured or modeled concentrations of deposited LAPs in surface snow or estimated from atmospheric loading and ice cores Nair et al, 2013;He et al, 2014;Santra et al, 2019;Thind et al, 2019). The complex terrain of HMA, seasonal snowfall and near-surface air circulation are not well resolved by coarse global climate models (Kopacz et al, 2011;Ménégoz et al, 2014).…”

APCC Data Report I: Black carbon and organic carbon dataset from atmosphere, glaciers, snow cover, precipitation, and lake sediment cores over the Third Pole

“…Historical BC records from the Tibetan glacier ice cores revealed the impact of anthropogenic emissions, with BC concentrations increased by 2−3 times since the 1950s (Kaspari et al, 2011;Wang et al, 2015. Light absorbing BC and OC (including water soluble organic carbon (WSOC) and water insoluble organic carbon (WIOC)) deposited on the glacier and snow cover induced surface darkening and enhanced melting (Flanner et al, 2007;Kang et al, 2020;Lau and Kim, 2018;Santra et al, 2019;Xu et al, 2009;Zhang et al, 2020b). Estimates indicated that BC in snow resulted in accelerated glacier melt by approximately 15−20% in the southeast/central TP and Central Asia (Li et al, 2020;Zhang et al, , 2020b reduced snow cover duration by 3−4 days across the TP and 3−6 days in Northern Xinjiang (Zhang et al, 2018a;Zhong et al, 2019).…”

Biomass-Derived Provenance Dominates Glacial Surface Organic Carbon in the Western Himalaya

“…3,4 In addition to this warming, the reduction of surface ice albedo by ice surface deposits of dark colored impurities constitutes an additional control of glacier melting rate. [5][6][7] Impurities that darken the ice surface and directly increase the heat absorption and thus enhance ice melting comprise dust, BC (black carbon, e.g., soot), and other forms of OC not derived from combustion. [8][9][10][11] In this study, OC refers to the total organic 51 carbon that comprises the entire pool of organic carbon including both organic and elemental 52 carbon.…”

“…Further, we classify the OC as OC ff (fossil fuel) and OC bio (biomass) referring to OC derived from either fossil fuel or biomass sources, such as biomass burning derived particles, atmospheric organic matters, and glacial microbes. 5 The contribution to glacier surface darkening by particle matter and its attendant impact on glacial melt across high Asian mountain glaciers is variable. For example, the main contributor to glacier surface warming in Eastern Himalaya and Central Asia is BC, while mineral dust is a dominant factor in the western Himalaya.…”