Ren Jiawen

Foliar δ 13C and δ 15N values of C3 plants in the Ethiopia Rift Valley and their environmental controls

The foliar C and N stable isotopic compositions (δ13C and δ15N) and the relationships between these compositions and environmental factors of C3 plants in the Ethiopia Rift Valley were investigated. There were three distribution patterns for foliar δ13C with mean values of −26.7‰±0.4‰, −29.7‰ ± 0.6‰, and −26.9‰ ± 1.2‰ in cold-moist, temperate-moist, and arid-hot environments, respectively. The δ15N values ranged from −1.4‰ ± 1.7‰ to 14.3‰ ± 0.1‰, with higher values under arid-hot conditions and the lowest values in plants growing at higher altitudes under cold-moist conditions. A strong negative relationship between mean annual precipitation and δ15N explained more than half of the observed variation in the δ15N values (r2 = 0.54, P < 0.001); a modest positive relationship was also found between δ15N and temperature (r2 = 0.32, P < 0.01). A weakly positive relationship existed between δ13C and temperature, and changes in δ13C values with precipitation and altitude followed quadratic curves. This suggests a shift in the effects of water and heat conditions caused by altitude on carbon isotopic discrimination.

A 780-year record of explosive volcanism from DT263 ice core in east Antarctica

Ice cores recovered from polar ice sheet received and preserved sulfuric acid fallout from explosive volcanic eruptions. DT263 ice core was retrieved from an east Antarctic location. The ice core is dated using a combination of annual layer counting and volcanic time stratigraphic horizon as 780 years (1215–1996 A.D.). The ice core record demonstrates that during the period of approximately 1460–1800 A.D., the accumulation is sharply lower than the levels prior to and after this period. This period coincides with the most recent neoglacial climatic episode, the “Little Ice Age (LIA)”, that has been found in numerous Northern Hemisphere proxy and historic records. The non-sea-salt SO42− concentrations indicate seventeen volcanic events in DT263 ice core. Compared with those from previous Antarctic ice cores, significant discrepancies are found between these records in relative volcanic flux of several well-known events. The discrepancies among these records may be explained by the differences in surface topography, accumulation rate, snow drift and distribution which highlight the potential impact of local glaciology on ice core volcanic records, analytical techniques used for sulfate measurement, etc. Volcanic eruptions in middle and high southern latitudes affect volcanic records in Antarctic snow more intensively than those in the low latitudes.

Meteorological Features at 6523 m of Mt. Qomolangma (Everest) between 1 May and 22 July 2005

Mt. Qomolangma (Everest), the highest mountain peak in the world, has little been studied extensively from a meteorological perspective, mostly because of the remoteness of the region and the resultant lack of meteorological data. An automatic weather station (AWS), the highest in the world, was set up on 27 April 2005 at the Ruopula Pass (6523 m asl) on the northern slope of Mt. Qomolangma by the team of integrated scientific expedition to Mt. Qomolangma. Here its meteorological characteristics were analyzed according to the 10-minute-averaged and 24-hour records of air temperature, relative humidity, air pressure and wind from 1 May to 22 July 2005. It is shown that at 6523 m of Mt. Qomolangma, these meteorological elements display very obvious diurnal variations, and the character of averaged diurnal variation is one-peak-and-one-value for air temperature, one-vale for relative humidity, two-eak-and-two-vale for air pressure, and one-peak with day-night asymmetry for wind speed. In the 83 days, all the air temperature, relative humidity and air pressure increased with some different fluctuations, while wind speed decreased gradually and wind direction turned from north to south. The variations of relative humidity had great fluctuations and obvious local differences. Then the paper discusses the reason for the characters of diurnal and daily variations.Compared with the corresponding records in May 1960, 5-day-averaged maximums, minimums and diurnal variations of air temperature in May 2005 were apparently lower.

Modification of three ice-core d 18 O records from an area of high melt

Abstract Stable oxygen isotope ratios (δ18O) of three shallow ice cores (extending back to 1963) from Urümqi glacier No. 1 at the headwater of Urümqi river, Tien Shan, northwest China, were used to test the relationship between δ18O and contemporaneous surface air temperature (T a). The ice cores were dated using the seasonal stable-isotopic signals, and seven insoluble particulate β-activity horizons associated with known nuclear tests. Although a strong positive relationship exists between δ18O in precipitation and Ta at our study site, this relationship is not preserved between the annually averaged ice-core δ18O records and the local temperature due to post-depositional modification. These results indicate that the processes forming the ice-core chemical records in areas of high melt must be understood before the δ18O record can be confidently interpreted as a climatic indicator.

Assessment of perception and adaptation to climate-related glacier changes in the arid Rivers Basin in northwestern China

In many mountainous areas of the world, glaciers serve as a source of fresh water that is of critical importance and contributes to the sustainability of agriculture and other socio-economic activities. An enhanced understanding of socio-economic consequences of the climate-related glacier changes is essential to the identification of vulnerable entities and the development of well-targeted environmental adaptation policies. A questionnaire and interviews of farmers in the Heihe River Basin were used to analyze their perception of cryospheric changes, attitudes towards mitigation of cryospheric changes, and the ways in which they perceived their responsibility. Preferred responses and interventions for cryospheric change and views on responsible parties were also collected and evaluated. Our investigation revealed that most rural residents were concerned about glacier changes and believed they would bring harm to present society, individuals, and families, as well as to future generations. The respondents’ perceptions were mainly influenced by the mass media. Most respondents tended to favor adaptation measures implemented by the government and other policy-making departments. An integrated approach will be needed to deal with the challenges to tackling climate-related glacier change.

The features of sea-ice cover, snow distribution and its densification in the central arctic ocean

Based on the observation of sea-ice cover and measurement of snow depths and stratigraphy during China’s First North Pole Scientific Expedition, three types of surface topography of sea ice and correspondingly three categories of snow distribution in the central Arctic are classified. It is considered that the classification will help to determine the sites for snow depth measurement, stratigraphy observation and snowpits sampling. The snow cover is slowly accumulated during the long Arctic winter, approximately from September to early May next year, while its ablation shows abrupt from south to north. By the end of August, the snow cover is almost totally removed. The spatial distribution of snow depth is characterized by a northwardly decreasing trend, which is proposed to result from the remote vapour sources, i.e., the major vapour over the Arctic regions is transported from mid-latitudes. The stratigraphy of the snowpits are characterized by the extensively existed depth hoar at the deeper part of the pits, which is probably a signal of the beginning of the long Arctic winter. The present of infiltration-congelation ice adhering to sea ice surface at the end of the ablation season indicates that the annual accumulation is approximately equals to the annual ablation near north pole.