Li Zhongqin

Regional Distribution of Monsoon and Desert Dust Signals Recorded in Asian Glaciers

Short-term (6 months to 17 years) glaciochemical records have been collected from glacier basins throughout the mountains of central Asia. The spatial distribution of snow chemistry in central Asia is controlled predominantly by the influx of dust from the arid and semi-arid regions in central Asia. The glaciochemical data suggests that glaciers which are removed from large source areas of mineral aerosol, such as those in the Himalaya, the Karakoram, and the southeastern Tibetan Plateau, are the ones most likely to contain longer-term glaciochemical records which detail annual to decadal variation in the strength of the Asian monsoon and long-range transport of Asian dust.

The chemical composition of aerosols over the Eastern Himalayas and Tibetan plateau during low dust periods

Aerosol samples were collected at four high elevation sites (>5000 m a.s.l.) in the mountains of central Asia. The sites extend from the southern slopes of the Himalayas to the northern margin of the Tibetan Plateau and are representative of the natural landscape variations in the highlands of central Asia. Daily samples were collected over periods of four days to two weeks in late summer or early autumn. This period is typically one of relatively low levels of dust in the Asian troposphere. Here we discuss the water soluble chemical composition of the aerosol samples. Tropospheric aerosols from the south slope of the Himalayas and the southern/central portions of the eastern Tibetan plateau are dominated (in order of importance) by NH4+, SO42−, NO3− and Ca2+. Concentrations of these species are comparable to previously reported measurements in the remote troposphere. Tropospheric aerosol from the northeastern region of the Tibetan Plateau shows very high levels of Ca2+, SO42−, Cl−, and Mg2+ due to the influx of evaporite mineral rich dust derived from the Qaidam Basin and/or Taklamakan Desert. Our results confirm that high-elevation mountain sites in the Himalayas and southern/central regions of the eastern Tibetan Plateau provide isolated platforms above the planetary boundary layer from which to investigate the composition of the remote continental troposphere. Fresh and surface snow samples were also collected. The results show that the general composition and spatial pattern in summer snow chemistry is similar to that for aerosols.

Mass balance and recession of Urumqi glacier No. 1, Tien Shan, China, over the last 45 years

Abstract Observations of Ürümqi glacier No. 1 at the headwaters of the Ürümqi river, Tien Shan, show remarkable changes between 1959 and 2003. The cumulative mass balance of the glacier is –10 032 mm, equivalent to 11.1 m of glacier ice, or 20% of the glacier volume, showing particular sensitivity to temperature change. The speed of glacier flow has gradually declined, especially since the 1980s. From 1980 to 2003, the flow speed of the east and west branches of the glacier decreased by about 21% and 43%, respectively. The glacier continuously retreated from 1962 to 2003. Its length has decreased by about 180 m (7.5%) and its area has diminished by 0.23 km2 (11.8%). Analyses show that summer precipitation is negatively correlated with mass balance and positively associated with runoff. These relationships are reasonable, as higher precipitation leads to higher runoff and lower glacier melt. On the other hand, summer temperature is negatively correlated with mass balance and positively associated with runoff, as higher temperatures lead to higher glacier melt and thus higher runoff, with summer temperatures controlling mass-balance variation. Over the past 45 years the negative mass balance, caused by higher ablation than accumulation, is associated with precipitation increase and temperature warming over the study area.

Observed changes of cryosphere in China over the second half of the 20th century: an overview

During approximately the past five decades, changes in snow cover, mountain glaciers, frozen ground (including permafrost), sea ice and river ice have been observed in China. However, most data were published in Chinese and thus unknown to the international communities. Here we review these published results to show an overview of cryospheric changes in China for the last � 50 years. Long-term variability of snow cover over the Qinghai-Xizang (Tibetan) Plateau (QXP) is characterized by large interannual variability superimposed on a continuously increasing trend. Glacier changes in western China vary remarkably in different regions. Although in most mountains the glaciers display a retreating trend (� 80%) or have even vanished, some glaciers (� 20%) are still advancing. Frozen ground (including permafrost) has experienced a rapid decay since the 1980s, and these changes are occurring both in the QXP and in the cold regions of north China. Sea-ice areas in the Bohai and north Yellow Seas have been shrinking since the 1970s. Interannual variations possibly relate to the solar cyles, and sea-ice extent extremes relate to El Nino-Southern Oscillation (ENSO) events. The freeze-up and break-up dates of river ice in north China in the 1990s are, on average, 1-6 days later and 1-3 days earlier, respectively, than the 1950s-1990 mean. Frozen duration and the maximum thickness of river ice are, respectively, 4-10 days shorter and 0.06-0.21 cm thinner in the 1990s than the average. cryosphere. The cryosphere in China is mainly located in the Qinghai-Xizang (Tibetan) Plateau (hereafter QXP), the eastern Tien Shan, the Altai Shan, the east Pamirs and northeast China. The total number of glaciers in China is 46 298, with a total area of 59 406 km 2 and an ice volume of 5590 km 3 . The permafrost and the seasonally frozen ground (SFG) cover an area of 1.49 � 10 6 and 5.28 � 10 6 km 2 , accounting for 11.5% and 55% of Chinese land territory, respectively. The snow-covered area in China is around 9.0 � 10 6 km 2 , and of this an area over 4.8 � 10 6 km 2 consists of unstable snow cover (duration 60 days) is mainly located in the QXP, north Xinjiang (including the Tien Shan) and the Inner Mongolia-northeast China (hereafter IM-NEC) regions. The mean snow-cover areas of these three regions are 2.3 � 10 6 , 0.5 � 10 6 and 1.4 � 10 6 km 2 , respectively. Seasonal sea ice forms in the Bohai Sea and in the northern Yellow Sea of China. Sea ice forms in mid- to late November, reaches itsAbstract During approximately the past five decades, changes in snow cover, mountain glaciers, frozen ground (including permafrost), sea ice and river ice have been observed in China. However, most data were published in Chinese and thus unknown to the international communities. Here we review these published results to show an overview of cryospheric changes in China for the last ~50 years. Long-term variability of snow cover over the Qinghai–Xizang (Tibetan) Plateau (QXP) is characterized by large interannual variability superimposed on a continuously increasing trend. Glacier changes in western China vary remarkably in different regions. Although in most mountains the glaciers display a retreating trend (~80%) or have even vanished, some glaciers (~20%) are still advancing. Frozen ground (including permafrost) has experienced a rapid decay since the 1980s, and these changes are occurring both in the QXP and in the cold regions of north China. Sea-ice areas in the Bohai and north Yellow Seas have been shrinking since the 1970s. Interannual variations possibly relate to the solar cyles, and sea-ice extent extremes relate to El Niño–Southern Oscillation (ENSO) events. The freeze-up and break-up dates of river ice in north China in the 1990s are, on average, 1–6 days later and 1–3 days earlier, respectively, than the 1950s–1990 mean. Frozen duration and the maximum thickness of river ice are, respectively, 4–10 days shorter and 0.06–0.21cm thinner in the 1990s than the average.

Primary results of glaciological studies along an 1100 km transect from Zhongshan station to Dome A, East Antarctic ice sheet

Abstract The Chinese National Antarctic Research Expedition (GHINARE) carried out three traverses from Zhongshan station to Dome A, Princess Elizabeth Land and Inaccessible Area, East Antarctic ice sheet, during the 1996/97 to 1998/99 Antarctic field seasons. The expeditions are part of the Chinese International Trans-Antarctic Scientific Expedition program. In this project, glaciological investigations of mass balance, ice temperature, ice flow, stratigraphy in snow pits and snow/firn ice cores, as well as the glaciochemical study of surface snow and shallow ice cores, have been carried out. In the 1998/99 field season, CHINARE extended the traverse route to 1128 km inland from Zhongshan station. The density profiles show that firnification over Princess Elizabeth Land and Inaccessible Area (290–1100 km along the route) is fairly slow, and the accumulation rate recovered from snow pits along the initial 460 km of the route is 4.6–21 cm (46–210 kg m–2a–1 ) water equivalent. The initial 460 km of the route can be divided into four sections based on the differences of accumulation rate. This pattern approximately coincides with the study on the Lambert Glacier basin (LGB) by Australian scientists. During the past 50 years, the trends of both air temperature and accumulation rate show a slight increase in this area, in contrast to the west side of the LGB. Data on surface accumulation rates and their spatial and temporal variability over ice-drainage areas such as the LGB are essential for precise mass-balance calculation of the whole ice sheet, and are important for driving ice-sheet models and testing atmospheric models.

Climatological Significance of δ 18 O in Precipitation and Ice Cores: a Case Study at the Head of the Ürütnqi River, Tien Shan, China

Stable-oxygen-isotope ratios (δ 18 O) of precipitation and ice-core samples collected from the headwaters of the Urumqi river, Tien Shan, China, were used to test the relationship between δ 18 O and contemporaneous surface air temperature (T a ). A strong temporal relationship is found between δ 18 O in precipitation and T a , particularly for the monthly averages which remove synoptic-scale influences such as changes in condensation level, condensation temperature and moisture sources (Yao and others, 1996). Linear fits as high as 0.95‰ °C for precipitation events and 1.23‰ °C for monthly averages are found. Although the δ 18 O amplitude in ice cores drilled at the nearby Urumqi glacier No. 1 (∼2 km from the precipitation sampling site decreased dramatically compared to the precipitation samples, the ice-core records of annually averaged δ 18 O are still positively correlated with contemporaneous air temperature, especially summer air temperature, at the nearby Daxigou meteorological station. Nevertheless, the relationship between the ice-core δ 18 O records and contemporaneous air temperature is less significant than that for the precipitation samples due to depositional and post-depositional modification processes, which are highlighted by the successive snow-pit δ 18 O profiles from the Urumqi glacier No. 1. Our results might extend the application of high-altitude and subtropical ice-core δ 18 O-T a records for palcoclimate reconstruction.

Meteorological and glaciological evidence for different climatic variations on the east and west sides of the Lambert Glacier basin, Antarctica

Abstract Surface mass-balance studies and climatic records from firn cores show remarkable differences between the east and west sides of the Lambert Glacier basin (LGB). The spatial distribution of the surface accumulation is influenced by the atmospheric moisture flux, and by the surface wind field, which is largely determined by topography. Atmospheric water-vapor budget data for the ice-sheet sector covering the basin (45–90˚ E) show that on the east side of the LGB the moisture flux is poleward, averaging 18 kgm–1 s–1 in 1988, while for the west side it is Equatorward, averaging 5 kgm–1 s–1. A similar pattern, but with much lower transport of vapor flux, is seen across 70˚ S. Two firn cores from the east side of the basin and two from the west side were analyzed to determine accumulation-rate and temperature-proxy variations for the past 50 years. The trends were opposite on the different sides of the basin. Similar opposing trends are seen in meteorological records from Davis and Mawson coastal stations, situated on the east and west sides of the LGB respectively. There is a good correlation between the accumulation/18O record in ice cores from the eastern LGB and the sea-level pressure (obtained from the US National Centers for Environmental Prediction/US National Center for Atmospheric Research (NCEP/NCAR) re-analyses) of a Southern Indian Ocean low (SIOL), but not between the SIOL and the records from the western LGB. This study reveals that variations in local circulation could alter at least the annual to decadal time-scale climate records, and may result in completely different climate histories between adjacent areas.

250 years of accumulation, oxygen isotope and chemical records in a firn core from Princess Elizabeth Land, East Antarctica

A 51.85-m firn core collected from site DT001 (accumulation rate 127 kgm−2a−1, mean annual temperature −33.1 °C) on Princess Elizabeth Land, East Antarctica, during the 1996–97 Chinese First Antarctic Inland Expedition has been analyzed for chemical composition and oxygen isotope ratio. A comparison between the seasonal variations of major ions was carried out in order to reduce the dating uncertainty, using the volcanic markers as time constrains. A deposition period of 251 years was determined. The calculated accumulation rates display an increasing trend before 1820, while after 1820, the trend of the accumulation is not obvious. Overall, temperature change in the region shows a slight increasing trend over the past 250 years. But, notably, a temperature decline of −2 °C is observed from 1860 to the present. This feature, at odds with the warming trend over the past century recorded in both hemispheres, likely reflects a regional characteristic related to the lack of a high latitude/low latitude link in the Southern Hemisphere circulation patterns. The results of the glaciochemical records of the firn core show that the mean concentrations of Cl−, Na+ and Mg2+ are similar to those reported from other sites in East Antarctica. However, the mean concentration of Ca2+ is much higher than that reported from other regions, suggesting the influence of the strong local terrestrial sources in Princess Elizabeth Land. There is no evidence of a positive correlation between NO3− concentrations and solar activity (11-year solar cycle and solar cycle length), although solar proton events may account for some of the NO3− peak values in the record.

The climatic and environmental features on both sides of the Lambert Glacier Basin

During the 1992–1993 joint Australian-Chinese over-snow traverse of the western Lambert Glacier Basin (LGB), two firn cores were drilled respectively at MGA and LGB16. During the 1996–1997 and 1997–1998 austral summers, two firn cores were drilled respectively at DT001 and DT085 on the eastern LGB. Based on the measurements made during the expeditions, the climatic and environmental features on both sides of the LGB have been studied. Results show that during the past 50 years, the trends of both air temperature and accumulation rate show a slight increase on the east side of the LGB, in contrast to the west side of the LGB. The spatial trends of the accumulation rate measured by accumulation canes at 2 km intervals along the nearly 500 km of the traverse lines on both sides of the LGB are different. Moreover, correlations of δ18O vsT10along the two sides of the LGB are also different. In addition, the variations of sea salt ion concentrations show different trends in the past 50 years. All the evidence shows that the Lambert Glacier is a dividing region for the different climatic regimes over the East Antarctic ice sheet, which may be due to different moisture resources resulting from special local circumfluence such as cyclone activities, local terrain influences.

Depositional characteristics of NH4+ on Ürümqi glacier No. 1, eastern Tien Shan, China

Abstract Investigation into the depositional and post-depositional processes of atmospheric NH4 + on Ürümqi glacier No. 1 (UG1), China, was implemented within the Program for Glacier Processes Investigation (PGPI) campaign. Aerosol and surface snow samples were collected concurrently on a weekly basis from March 2004 to March 2005 in the UG1 accumulation zone at the headwaters of the Ürümqi river, eastern Tien Shan. All samples were analyzed for NH4 + and other chemical species. This paper investigates the seasonal variations of NH4 +. A significant linear relationship (R 2 = 0.70, N = 21, P < 0.01) between NH4 + concentrations in surface snow and aerosol was found during spring and summer, indicating that the warm–wet condition facilitates the air–snow exchange of NH4 +. Humidity was found to be a significant meteorological factor influencing NH4 + in deposition in autumn and winter. The NH4 + concentration in aerosol clearly shows a trend similar to that in surface snow, suggesting that the variation of atmospheric NH4 + might have been preserved in the surface snow. The possible source of NH4 + is discussed in this paper.