Kang Shichang

Monsoon and Dust Signals Recorded in Dasuopu Glacier, Tibetan Plateau

During summer 1997, a 15 m firn core was recovered from Dasuopu glacier (28°23′ N, 85°44′ E; 7000 m a.s.l.) on the northwest margin of Xixabarngma Feng in the central Himalaya. Oxygen isotope values and concentrations of Ca 2+ , Mg 2+ , NH 4 + , SO 4 2− and NO 3 − were measured over the 10 years of snow accumulation captured in the firn core. The seasonal variations of δ 18 O values and major-ion concentrations in the Dasuopu core indicate that summer monsoon and dust signals are clearly recorded in Dasuopu glacier. Annual variations in δ 18 O values are controlled by the amount effect, with more negative (i.e. lighter) δ 18 O values representing summer monsoon precipitation characteristic of tropical regions. Higher concentrations of Ca 2+ , Mg 2+ and SO 4 2− reflect the influx of mineral aerosols from the vast arid and semi-arid desert regions to the north and west during the spring dust-storm period. High spring concentrations of NH 4 + and NO 3 − appear to reflect changes in regional biogenic-source strength.

Evidence for Recent Climate Change from Ice Cores in the Central Himalaya

Abstract Comparison of the terminus locations of Rongbuk Glacier, Mount Everest, measured in 1966 and 1997 shows that in the past 30 years the glacier has retreated 170–270 m equivalent to a retreat speed of 5.5–8.7 m a–1 . During summer 1997, a 15 m firn core was recovered from Dasuopu glacier (28°23’ N, 85°44’ E; 7000 m a.s.D on the northwest margin of Xixabangma Feng, Xizang (Tibet). The seasonal variations of δ 18O values in the core indicate that monsoon signals are clearly recorded in the glacier. δ18O values are controlled by the amount effect in the monsoon season; more negative δ18O is representative of the monsoon season in snow layers. Analysis of the relationship between ice-core δ18O, sampled from 6500 m a.s.l. on the north side of Mount Everest, and instrumental series representing regional-scale precipitation, atmospheric circulation and temperature suggests a change in the relative influence of these parameters on δ18O since the 1940s. The results of the comparison add to and lengthen the sparse array of instrument data available for the Tibetan (Qinghai-Xizang) Plateau and demonstrate a recent decline in moisture flux for at least the southern part of the plateau. Glacier retreat, associated with a recent increase in temperature in the region, is coincident with this period of decreased moisture flux.

Climate change over the Yarlung Zangbo River Basin during 1961-2005

The Yarlung Zangbo River (YR) is the highest great river in the world, and its basin is one of the centers of human economic activity in Tibet. Using 10 meteorological stations over the YR basin in 1961–2005, the spatial and temporal characteristics of temperature and precipitation as well as potential evapotranspiration are analyzed. The results are as follows. (1) The annual and four seasonal mean air temperature shows statistically significant increasing trend, the tendency is more significant in winter and fall. The warming in Lhasa river basin is most significant. (2) The precipitation is decreasing from the 1960s to the 1980s and increasing since the 1980s. From 1961 to 2005, the annual and four seasonal mean precipitation is increasing but not statistically significant, especially in fall and spring. The increasing precipitation rates are more pronounced in Niyangqu and Palong Zangbo river basins, the closer to the upper YR is, the less precipitation increasing rate would be. (3) The annual and four seasonal mean potential evapotranspiration has decreased, especially after the 1980s, and most of it happens in winter and spring. The decreasing trend is most significant in the middle YR and Nianchu river basin. (4) Compared with the Mt. Qomolangma region, Tibetan Plateau, China and global average, the magnitudes of warming trend over the YR basin since the 1970s exceed those areas in the same period, and compared with the Tibetan Plateau, the magnitudes of precipitation increasing and potential evapotranspiration decreasing are larger, suggesting that the YR basin is one of the most sensitive areas to global warming.

Temperature and methane changes over the past 1000 years recorded in Dasuopu glacier (central Himalaya) ice core

Abstract In 1997, three ice cores were recovered from Dasuopu glacier on the northern slope of the central Himalaya. the first core, 159.9 m long, was drilled at 7000ma.s.l. down the flowline from the top of the col. the second core, 149.2m long, was drilled on the col at 7200ma.s.l. the third core, 167.7 m long, was also drilled on the col at 7200ma.s.l., 100 maway from the second core. the present paper discusses the δ18O and methane results reconstructed for the past 1000 years based on the second core. the δ18O can be interpreted as an air-temperature signal. the methane concentration is mainly representative of atmospheric methane concentration. Both δ18O and methane records show an obvious increasing trend in the past 1000 years. Methane concentration in the record is similar to the fluctuations of δ18O, decreasing during cold periods and increasing during warm periods. the Little Ice Age was well recorded in the core by both δ18O and methane. the coldest period appeared in the late 18th century, accompanied by a decrease in methane concentration. the abrupt methane-concentration increase starting after the 18th century is no doubt due to anthropogenic input. the observed methane-concentration decrease during World Wars I and II clearly demonstrates the importance of the anthropogenic input to atmospheric methane concentration if further measurements prove that it is a true atmospheric signal.

Response of Glacier and Lake Covariations to Climate Change in Mapam Yumco Basin on Tibetan Plateau during 1974–2003

The study of spatial and temporal covariances of glaciers and lakes would help us to understand the impact of climate change within a basin in Tibet. This study focuses on glacier and lake variations in the Mapam Yumco basin (covering 7 786.44 km2) by integrating series of spatial data from topographic maps and digital satellite images at four different times: 1974, 1990, 1999, and 2003. The results indicate that: (1) decreased lakes, retreated glaciers, enlarged lakes and advanced glaciers co-exist in the basin during the last 30 years; (2) glacier recession was accelerated in recent years due to the warmer climate; (3) lake areas in the basin are both reduced and enlarged by an accelerated speed with more water supplies from speeding melt glaciers or frozen ground in the last three decades.

Organochlorine pesticides in fresh-fallen snow on East Rongbuk Glacier of Mt. Qomolangma (Everest)

During a field campaign in April 2005, fresh-fallen snow samples were collected on the East Rongbuk Glacier of the Mt. Qomolangma at four altitudes (6500 m, 6300 m, 6100 m and 5900 m), to study the role of Mt. Qomolangma as “cold-traps” for Persistent Organic Pollutants. From these snow samples collected at the highest-altitude, organochlorine pesticides (OCPs):HCB, p, p′-DDT and p, p′-DDD were detected, with the concentrations in the ranges of 44–72 pg/L, 401–1560 pg/L, and 20–80 pg/L, respectively. The concentration of o, p′-DDT was around the method detection limit. Analysis of backward trajectories showed that the detected compounds came from the north of India, suggesting that DDTs detected in the snow were possibly originated from new emissions in this area. Relationships between the concentrations of OCPs in snow samples and the sampling altitudes were discussed. The altitudes had no obvious effect on HCB concentrations in the fresh-fallen snow, while increases in the concentrations of p, p′-DDT and p, p′-DDD with increasing altitude were found, which was reversed compared to the trends observed in North America. Three factors likely resulted in this trend: (1) the properties of the target compounds; (2) the low temperatures at high altitudes; and (3) the location of the mountain sampling sites relative to their sources.

Microbial community structure in major habitats above 6000 m on Mount Everest

Bacterial abundance in surface snow between 6600 and 8000 m a.s.l. on the northern slope of Mt. Everest was investigated by flow cytometry. Bacterial diversity in serac ice at 6000 m a.s.l., glacier meltwater at 6350 m, and surface snow at 6600 m a.s.l. was examined by constructing a 16S rRNA gene clone library. Bacterial abundance in snow was higher than that in the Antarctic but similar to other mountain regions in the world. Bacterial abundance in surface snow increased with altitude but showed no correlation with chemical parameters. Bacteria in the cryosphere on Mt. Everest were closely related to those isolated from soil, aquatic environments, plants, animals, humans and other frozen environments. Bacterial community structures in major habitats above 6000 m were variable. The Cytophaga-Flavobacterium-Bacteroides (CFB) group absolutely dominated in glacial meltwater, while β-Proteobacteria and the CFB group dominated in serac ice, and β-Proteobacteria and Actinobacteria dominated in surface snow. The remarkable differences among the habitats were most likely due to the bacterial post-deposition changes during acclimation processes.

Reliability of NCEP/NCAR reanalysis data in the Himalayas/Tibetan Plateau

Due to the difficult logistics in the extreme high elevation regions over the Himalayas and Tibetan Plateau, the observational meteorological data are very few. In 2003, an automatic weather station was deployed at the northeastern saddle of Mt. Nyainqentanglha (NQ) (30°24′44.3″N, 90°34′13.1″E, 5850 m a.s.l.), the southern Tibetan Plateau. In 2005, another station was operated at the East Rongbuk Glacier Col (28°01′0.95″N, 86°57′48.4″E, 6523 m a.s.l.) of Mt. Qomolangma. Observational data from the two sites have been compared with the reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), reliability of NCEP/NCAR reanalysis data has been investigated in the Himalayas/Tibetan Plateau region. The reanalysis data can capture much of the synoptic-scale variability in temperature and pressure, although the reanalysis values are systematically lower than the observation. Furthermore, most of the variability magnitude is, to some degree, underestimated. In addition, the weather event extracted from the NCEP/NCAR reanalyzed pressure and temperature prominently appears one day ahead of the observational data on Mt. Qomolangma, while on Mt. NQ it occurs basically in the same day.

Fresh snow chemistry from high mountain regions in central himalayas

During 1997 summer, fresh snow samples were collected from the high elevation region (5400–7000 m) of Dasuopu Galcier on the northern slope of Mt. Xixabangma (28°33′ N, 85°44′ E). Compared with other remote regions in the world, major ion concentrations in fresh snow are very low during summer in Mt. Xixabangma, suggesting that the atmosphere is very clean and may represent background value for the middle/upper troposphere in the middle/low latitude area. During summer at Mt. Xixabangma the fresh snow chemistry is minimally influenced by anthropogenic pollutants as revealed by the snow pH (mean value of 6.0). Conductivity of fresh snow are low and constant. A multi-regression curve of pH vs conductivity shows a strong correlation; snow pH is negatively correlated with conductivity when pH<6.0, and positively correlated when pH> 6.0. This suggests that the dominant chemical species of snow are interchanging between acid anions (e.g. SO42−, NO3−) and crustal cations.

Research progress of light-absorbing impurities in glaciers of the Tibetan Plateau and its surroundings

Light-absorbing impurities (LAIs, including black carbon, organic carbon, and dust) deposited on glacier surface can have strong effects on mass and energy balance of the cryosphere. Widespread with amount of glaciers, the Tibetan Plateau (TP) is considered to be an ideal region to study the impact of LAIs to glacier melt. Based on recent studies of LAIs in glacial snow of the TP, we summarized the research progress of LAIs in glacial snow, including their concentrations and spatial distributions, especially focusing on discussion of sources of black carbon, and documenting the albedo reduction and radiative forcing caused by LAIs. Additionally, we identified research gaps and suggested future research directions. At present, spatial distribution of LAIs in glacial snow and ice from TP and its surroundings exist a significant difference due to natural/anthropogenic emission sources, local topography, atmospheric transportation, and different glacial surface (e.g., fresh snow, aged snow, granular ice, bare ice). In general, higher concentrations of BC occurred in the northern and southern regions; LAIs in aged snow or granular ice were higher by 1–2 order of magnitude than that in the fresh snow or snowpit. Characteristics of LAIs from different glacial surfaces were still limited especially in Tienshan regions, which need to be further studies. Since Industrial Revolution, BC in ice cores increased in recent decades which may be likely caused by increasing emissions of fossil fuel combustion and biomass burning in the South Asia and Central Asia. The process of snowmelt can enrich the BC concentrations in surface and change the mixture of BC with snow grains, which will further enhance the albedo reduction. Studies on post-deposition processes of other LAIs and their effects on snow surface albedo are urgent to be strengthened. Simulation results indicated that BC aerosol of the southern TP mainly originated from the South Asia, which can contributed to approximately 50% in non-monsoon season and 30% in monsoon season; anthropogenic sourced BC can contributed to 30%–70%. However, studies on enrichment and transport processes of LAIs in glacial surface snow still should be emphasized. Although LAIs initiated powerful snow albedo feedbacks and glacier melt, estimation of this effect was associated with a large uncertainty. Based snow ice and aerosol radiation (SNICAR) model, effects of BC and dust on albedo reduction were estimated to be less than 10% in the southern TP and more than 25% in the central and northern TP influencing by snow types. Simulation of BC on albedo effects were affected by mixture of BC, coatings with other components, and snow grains, which lead to different radiative forcing in different regions. For aged snow or granular ice, effects of BC and dust can give localized instantaneous radiative forcing to about near or more than 100 W m−2; for fresh or snowpit, BC and dust can result in a minor radiative forcing (mostly less than 10 W m−2). These effects of LAIs on albedo reduction and radiative forcing enhanced glacier melt, which will further affect the hydrological processes. Estimation represented that LAIs in snow can lead to approximately 15% of the total glacier melt in the southeast TP and 6.3% increasing glacier melt in the Pamir regions. However, there still existed differences between the observations and simulations of LAIs in snow, which was mostly related to the different deposition flux and snow accumulation. In the future, mixing state of LAIs in snow, and their synergistic effects of biogeochemical process and climate change will be a new research direction.