Hydrothermal combination and geometry control the spatial and temporal rhythm of glacier flow.

The dynamic response of glacier to atmospheric change has varied both spatially and temporally. While some of this variability is likely related to regional climate signals, the geometry of this particular glacier also appears to be important. In this study, we investigated the hydrothermal conditions and geometric controls on the temporal and spatial evolution of Baishui River Glacier No.1's velocity from 2012 to 2019. To do this, we combined field investigations and remote sensing observations to measure the velocity of the glacier, and factors controlling this velocity. Annual changes showed that, from 2012 to 2019, the Baishui River Glacier No. 1 experienced continuous shrinkage, accompanied by decreasing ice velocities. Seasonal changes showed that the glacier velocity during the monsoon period was significantly higher than during the non-monsoon period. Spatially, the glacier's dynamic variability decreased toward its terminus, but increased toward the upper reaches of the glacier, along a longitudinal axis. We would suggest that the interannual velocity variation of Baishui River Glacier No.1 corresponded to thinning of the glacier, which in turn affected its gravitational force. Given that surface melt-induced basal lubrication, basal friction controlled by freezing rate, and dynamic thickening can alter seasonal patterns of movement, these variations may be important for understanding the seasonal evolution of this, and other glaciers. Our results further indicated that glacier width, slope, surface meltwater and crevasses were important constraints on any spatial movement patterns.

Investigation of the spatio-temporal heterogeneity and optical property of water-soluble organic carbon in atmospheric aerosol and snow over the Yulong Snow Mountain, southeastern Tibetan Plateau.

Atmospheric aerosols are a branch of active research in recent decades. The deposition of light-absorbing substances on high-altitude glaciers causes substantial adverse impacts on the cryospheric environment, cryosphere-hydrology, and climate system. Although, the concentrations of water-soluble organic carbon (WSOC) in snow/ice on glaciers of Tibetan Plateau (TP) have been reported, their transfer processes and optical properties in the context of summer precipitation-atmosphere-snow-river water continuum are seldom studied. In this study, we have systematically examined some scientific issues associated with WSOC concentrations and light absorption properties of WSOC in various forms of samples from the Mt. Yulong region. Statistical results demonstrate that the spatial distribution of WSOC in the snow of Baishui glacier was heterogeneous. The average WSOC concentrations of each snowpit were significantly decreased, and its light-absorbing properties were significantly elevated with the time extension. Aerosol WSOC concentrations and light absorption have distinct spatial disparity and seasonal variation. Pre-monsoon and monsoon have the highest and lowest WSOC content, respectively. Whereas the light-absorbing properties present contrasting seasonal trends. Rivers of which runoff was supplied by glacier meltwater have significantly lower WSOC concentrations (e.g., 0.42 ± 0.03 mg L-1) compared with other forms of water bodies. Mass absorption cross-section of WSOC (MAC-WSOC) in multiple snow and meltwater samples was significantly different and type-dependent. Atmospheric aerosol has the lowest MAC-WSOC value among the four types of samples, which was likely associated with exhaust emissions from private vehicles and tour buses. Statistical results indicated that the average AAE330-400 values of various snow/ice samples are subequal. Snow of glaciers supplies a desirable platform for the deposition of gaseous materials which experienced long-range transport in high altitude zones. Biomass-burning emissions made an immense contribution to the WSOC deposition over the study area, as demonstrated by the distribution of active fire points. However, this preliminary study represents the first systematic investigation of WSOC deposition in southeastern TP. Further robust in-situ field investigations and laboratory measurements are urgently necessary to improve our understanding of the transfer process and optical property of WSOC.

Light-absorbing impurities accelerating glacial melting in southeastern Tibetan Plateau.

Deposition of light-absorbing particles on glacier surfaces poses a series of adverse impacts on the cryospheric environment, climate and human health. Broad attention of the scientific community has been paid on insoluble light-absorbing impurities (ILAIs) in snow and ice on glaciers over the Tibetan Plateau (TP). However, systematic investigation of ILAIs in snowpack of glaciers on the TP is scarce. In this study, the properties and darkening effect of ILAIs in snowpack on glaciers are extensively investigated in the southeast of TP. Results show that ILAIs concentrations in multiple types of snow and ice samples were significantly different. Snowpit depths varied substantially from one profile to another during May and June 2016. The average concentrations of ILAIs in snowpits increase as snow melting progresses. Black carbon (BC) and dust cause snow albedo reduction more in snow with larger grain size Re. Based on a radiative transfer model calculation, the average albedo reduction induced by BC in the snowpack was 0.141 ± 0.02, and associated daily maximum radiative forcing (RF) was 72.97 ± 12.7 W m-2. BC is a controlling light-absorbing factor in snowpack and causes substantial albedo reduction and thus the associated daily maximum RF. The maximum reduction of snow cover duration was 4.56 ± 0.71 days caused by BC and dust in snowpack in southeastern TP. The average mass absorption cross-section (MAC) of BC from multiple snowpits was 3.26 ± 0.46 m2 g-1, which represents a typical value of MAC in snow on glaciers, but it is type-dependent of snow/ice samples. Tropospheric aerosols vertically extended up to 8 km over the TP and its surrounding areas, which indicates the transport of aerosols from remote sources through elevated pathways. A large amount of carbon stored in the brittle glaciers can be potentially released with meltwater runoff under a warming climate. This study provides a new insight for investigating carbonaceous and light-absorbing particles in glacierization areas.

Two new secolignan glycosides from the roots of Urtica triangularis Hand.-Mazz.

Two secolignan glycoside isomers, urticaside A (1) and urticaside B (2), were isolated from the roots of Urtica triangularis Hand.-Mazz. Their structures were elucidated by means of spectral analyses including 1D, 2D NMR and HR-EI-MS.

Lignan and flavonoid glycosides from Urtica laetevirens Maxim.

A new compound named pinoresinol 4-O-alpha-L-rhamnopyranosyl (1-->2)-beta-D-glucopyranoside (1) together with six known compounds, isolariciresinol 9-O-beta-D-glucopyranoside (2), apigenin 6,8-di-C-beta-D-glucopyranoside (3), luteolin 7-O-neohesperidoside (4), luteolin 7-O-beta-D-glucopyranoside (5), 5-methoxyluteolin 7-O-beta-D-glucopyranoside (6), and rutin (7), were isolated from the aerial parts of Urtica laetevirens Maxim. All of the above compounds were isolated from this plant for the first time.

New chemical constituents of roots of Urtica triangularis HAND-MASS.

Studies on the chemical constituents of roots of Urtica triangularis HAND-MASS have led to the isolation of four new compounds. The structures, including the absolute configurations, of these constituents have been elucidated through spectral studies including (1)H-NMR, (13)C-NMR, 2D-NMR experiments (heteronuclear single-quantum coherence, heteronuclear multiple bonding connectivity and nuclear Overhauser effect spectroscopy), high resolution mass spectroscopy (HR-MS) and circular dichroism as (-)-4-methoxy-8'-acetyl olivil, (-)-4-methoxy-8'-acetyl olivil-4-O-alpha-arabinopyronosyl-(1-->6)-beta-glucopyranoside, (-)-olivil-9-O-beta-glucopyranoside and cyclo-olivil-9-O-beta-glucopyranoside.