Abstract. High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of BC and OC with higher respective concentrations but a lower OC / BC ratio in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source-receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia has the largest contribution to the presentday (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) mean BC deposition at the ice-core drilling site during the non-monsoon season (October to May) (81 %) and all year round (74 %), followed by East Asia (14 % to the non-monsoon mean and 21 % to the annual mean). The icecore record also indicates stable and relatively low BC and OC deposition fluxes from the late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia (as the primary contributor to annual mean BC deposition). Moreover, the increasing trend of the OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and/or biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing potential influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice-core record.

Improved daily precipitation and temperature data at 5 × 5‐km grids for 1960–2015 were developed for the Upper Yarkant basin (UYB) based on observations of precipitation gradients and temperature lapse rates. The developed climate data are then used to drive the VIC‐Glacier hydrological model to simulate the runoff process for the UYB. A large altitudinal dependence is observed in both precipitation and temperature, with three altitudinal patterns of precipitation gradient for the elevation bands of <2,000 m, 2,000–3,000 m, and >3,000 m, respectively, and a strong seasonal variation in temperature lapse rate ranging from 0.4 to 0.8 °C/100 m. Basin precipitation and temperature data are greatly improved in both amount and spatial variations after the orographic adjustments. Glacier melt runoff is the dominant water source of the UYB accounting for about 52% of annual total flows, followed by snowmelt (about 26%), and rainfall runoff (about 22%). About 60% of basin runoff originates from the high altitudes (>5,000 m), and about 32% and 8% of runoff originate from middle (4,000–5,000 m) and low (<4,000 m) altitudes, respectively. The variations in annual runoff in the UYB were mainly controlled by glacier melt runoff, middle and high altitudes, and temperature in warm seasons during 1965–2015. However, rainfall and snowmelt runoff, and low altitudes, were playing an increasingly important role in total flow variations of the UYB due to the increase of warm season temperatures in 1994–2015 and precipitation in the entire simulation period.

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