Tandong Yao

Black soot and the survival of Tibetan glaciers

We find evidence that black soot aerosols deposited on Tibetan glaciers have been a significant contributing factor to observed rapid glacier retreat. Reduced black soot emissions, in addition to reduced greenhouse gases, may be required to avoid demise of Himalayan glaciers and retain the benefits of glaciers for seasonal fresh water supplies.

Review of climate and cryospheric change in the Tibetan Plateau.

The Tibetan Plateau (TP), with an average elevation of over 4000 m asl and an area of approximately 2.5 × 10 6 km 2 , is the highest and most extensive highland in the world and has been called the ‘Third Pole’. The TP exerts a huge influence on regional and global climate through thermal and mechanical forcing mechanisms. Because the TP has the largest cryospheric extent outside the polar region and is the source region of all the large rivers in Asia, it is widely recognized to be the driving force for both regional environmental change and amplification of environmental changes on a global scale. Within China it is recognized as the ‘Asian water tower’. In this letter, we summarize the recent changes observed in climate elements and cryospheric indicators on the plateau before discussing current unresolved issues concerning climate change in the TP, including the temporal and spatial components of this change, and the consistency of change as represented by different data sources. Based on meteorological station data, reanalyses and remote sensing, the TP has shown significant warming during the last decades and will continue to warm in the future. While the warming is predominantly caused by increased greenhouse gas emissions, changes in cloud amount, snow-albedo feedback, the Asian brown clouds and land use changes also partly contribute. The cryosphere in the TP is undergoing rapid change, including glacier retreat, inconsistent snow cover change, increasing permafrost temperatures and degradation, and thickening of the active layer. Hydrological processes impacted by glacial retreat have received much attention in recent years. Future attention should be paid to additional perspectives on climate change in the TP, such as the variations of climate extremes, the reliability of reanalyses and more detailed comparisons of reanalyses with surface observations. Spatial issues include the identification of whether an elevational dependency and weekend effect exist, and the identification of spatial contrasts in temperature change, along with their causes. These issues are uncertain because of a lack of reliable data above 5000 m asl.

Tibetan Plateau summer monsoon northward extent revealed by measurements of water stable isotopes

A program of individual precipitation events and river water sampling and of water isotopic measurements (δD, δ18O) was carried out during summer 1996 along a northeast/southwest transect of the Tibetan Plateau. The spatial distribution of both δ18O and deuterium excess (d = δD-8*δ18O) of the precipitation reveals three distinct regions. Simulations with a simple isotopic model and seasonal isotopic variations measured at two extreme south and north locations support our interpretation in terms of different summer moisture origins: (1) South of the Himalayan mountains, the moisture provided by the Indian monsoon has been recycled over the Indian peninsula. (2) Between the Himalayas and the Tanggula mountains the oceanic moisture is directly transported from the Bay of Bengal along the Brahmaptra River valley. (3) North of the Tanggula mountains, the moisture is not provided by the monsoon anymore but by continental water recycling.

Recent Glacial Retreat and Its Impact on Hydrological Processes on the Tibetan Plateau, China, and Surrounding Regions

ABSTRACT Glacial retreat on the Tibetan Plateau and surrounding regions is characteristic since the 1960s and has intensified in the past 10 yr. The magnitude of glacial retreat is relatively small in the interior of the Tibetan Plateau and increases to the margins of the plateau, with the greatest retreat around the edges. Glacial retreat in this region is impacting the hydrological processes in the Tibetan Plateau and surrounding regions. The glacial retreat has caused an increase of more than 5.5% in river runoff from the plateau. In some areas, such as the Tarim River basin, the increase in river runoff is greater. Glacial retreat has also caused rising lake levels in the areas with large coverage of glaciers, such as the Nam Co Lake and Selin Co Lake areas. Rising lake levels are devastating grasslands and villages near the lakes.

Geographic distance and pH drive bacterial distribution in alkaline lake sediments across Tibetan Plateau.

Continent-scale biogeography has been extensively studied in soils and marine systems, but little is known about biogeographical patterns in non-marine sediments. We used barcode pyrosequencing to quantify the effects of local geochemical properties and geographic distance for bacterial community structure and membership, using sediment samples from 15 lakes on the Tibetan Plateau (4–1670 km apart). Bacterial communities were surprisingly diverse, and distinct from soil communities. Four of 26 phyla detected were dominant: Proteobacteria, Bacteroidetes, Firmicutes and Actinobacteria, albeit 20.2% of sequences were unclassified at the phylum level. As previously observed in acidic soil, pH was the dominant factor influencing alkaline sediment community structure, phylotype richness and phylogenetic diversity. In contrast, archaeal communities were less affected by pH. More geographically distant sites had more dissimilar communities (r = 0.443, P = 0.030). Variance partitioning analysis showed that geographic distance (historical contingencies) contributed more to bacterial community variation (12.2%) than any other factor, although the environmental factors explained more variance when combined (28.9%). Together, our results show that pH is the best predictor of bacterial community structure in alkaline sediments, and confirm that both geographic distance and chemical factors govern bacterial biogeography in lake sediments.

Climatological significance of δ18O in north Tibetan ice cores

Oxygen isotopic ratios (δ18O) of precipitation samples collected over several years at three meteorological stations on the northern Tibetan Plateau were used to conduct the first investigation of the relationship between δ18O and contemporaneous air temperatures (Ta). Inferring past temperatures from δ18O measured in recently acquired Tibetan ice cores necessitates establishing whether a δ18O-Ta relationship exists. For each station a strong temporal relationship is found between δ18O and Ta, particularly for monthly averages which remove synoptic-scale influences such as changes in condensation level, condensation temperature, and moisture sources. Moisture source is identified as a major factor in the spatial distribution of δ18O, but air temperature determines the temporal fluctuations of δ18O at individual sites on the northern Tibetan Plateau. The 30-year records of annually averaged δ18O from three different ice coring sites are not correlated significantly with contemporaneous air temperature records from their closest meteorological station (150 to 200 km). However, since 1960 the three air temperature records reveal a modest warming trend, while the three contemporaneous δ18O records show a modest 18O enrichment.

Passive Air Sampling of Organochlorine Pesticides, Polychlorinated Biphenyls, and Polybrominated Diphenyl Ethers Across the Tibetan Plateau

So far there are limited data on persistent organic pollutants (POPs) in the atmosphere of the Tibetan Plateau. XAD 2-resin based passive air samplers were therefore deployed for 1 year (between July 2007-June 2008) at 16 locations across the Tibetan Plateau. Based on previously reported sampling rates (R) derived in the north and south America, and their correlations with atmospheric temperature and pressure, R values in the present study were in the range of 2.2-3.3 m(3) d(-1) (average = 2.7 +/- 0.3). Derived air concentrations (pg/m(3)) ranged as follows: DDTs, 5-75; HCHs, 0.1-36; alpha-endosulfan, 0.1-10; HCB, 2.8-80; sum of 15 PCBs, 1.8-8.2; and sum of 9 PBDEs, 0.1-8.3. The highest DDTs occurred at Qamdo, where the sampling site is near to farm land, indicating the spatial distribution of DDTs across the plateau may be influenced by scattered local usage of DDT. Higher levels of HCHs were observed at sites with high elevation (>4000 m) and close to the China-India border, indicating possible long-range atmospheric transport. The highest levels of HCB, PCBs, and PBDEs were found at a site impacted by forest fire during the sampling campaign.

Climate variation since the Last Interglaciation recorded in the Guliya ice core

The climatic and environmental variations since the Last Interglaciation are reconstructed based on the study of the upper 268 m of the 309-m-long Guliya ice core. Five stages can be distinguished since the Last Interglaciation from the δ18O record in the Guliya ice core: Stage 1 (Deglaciation), Stage2 (the Last Glacial Maximum), Stage 3 (interstadial), Stage 4 (interstadial in the early glacial maximum) and Stage 5 (the Last Interglaciation). Stage 5 can be divided further into 5 substages; a, b, c, d, e. The δ18O record in the Guliya ice core indicates clearly the close correlation between the temperature variation on the Tibetan Plateau and the solar activities. The study indicates that the solar activity is a main forcing to the climatic variation on the Tibetan Plateau. Through a comparison of the ice core record in Guliya with that in the Greenland and the Antarctic, it can be found that the variation of large temperature variation events in different parts of the world is generally the same, but the variation amplitude of temperature is different.

Amplitude of climatic changes in Qinghai-Tibetan Plateau

On the basis of ice core and meteorological data from the Qinghai-Tibetan (Q-T) Plateau, this article focuses on the discussion of the problems related to the sensitivity of temporal and spatial changes of the climate in high-altitude regions, particularly in the Q-T Plateau. The features of abrupt climatic changes of the past 100 ka, 2 000 a and recent years indicate that the amplitude of these changes in the Q-T Plateau was obviously larger than that in low-altitude regions. The scope of temperature change above 6 000 m in the Q-T Plateau between glacial and interglacial stages could reach over 10°C, but only about 4°C in low-elevation regions close to sea level. During the last 2 000 a, the amplitude of temperature changes at Guliya (over 6 000 m a.s.l.) in the Q-T Plateau reached 7°C, in comparison with 2°C in eastern China at low altitude. In the present age, apparent differences of climatic warming have been observed in the Q-T Plateau, indicating that the warming in high-elevation regions is much higher than that in low-elevation regions. The temperature in over 3 500 m regions of the Q-T Plateau have been increasing at a rate of 0.25×101/a in recent 30 years, but almost no change has taken place in the regions below 500 m. Thus, we concluded that high-altitude regions are more sensitive to climatic changes than the low-altitude regions.

Evaporative cooling over the Tibetan Plateau induced by vegetation growth

Significance Understanding land-surface biophysical feedbacks to the atmosphere is needed if we are to simulate regional climate accurately. In the Arctic, previous studies have shown that enhanced vegetation growth decreases albedo and amplifies warming. In contrast, on the Tibetan Plateau, a statistical model based on in situ observations and decomposition of the surface energy budget suggests that increased vegetation activity may attenuate daytime warming by enhancing evapotranspiration (ET), a cooling process. A regional climate model also simulates daytime cooling when prescribed with increased vegetation activity, but with a magnitude smaller than observed, likely because this model simulates weaker ET enhancement in response to increased vegetation growth. In the Arctic, climate warming enhances vegetation activity by extending the length of the growing season and intensifying maximum rates of productivity. In turn, increased vegetation productivity reduces albedo, which causes a positive feedback on temperature. Over the Tibetan Plateau (TP), regional vegetation greening has also been observed in response to recent warming. Here, we show that in contrast to arctic regions, increased growing season vegetation activity over the TP may have attenuated surface warming. This negative feedback on growing season vegetation temperature is attributed to enhanced evapotranspiration (ET). The extra energy available at the surface, which results from lower albedo, is efficiently dissipated by evaporative cooling. The net effect is a decrease in daily maximum temperature and the diurnal temperature range, which is supported by statistical analyses of in situ observations and by decomposition of the surface energy budget. A daytime cooling effect from increased vegetation activity is also modeled from a set of regional weather research and forecasting (WRF) mesoscale model simulations, but with a magnitude smaller than observed, likely because the WRF model simulates a weaker ET enhancement. Our results suggest that actions to restore native grasslands in degraded areas, roughly one-third of the plateau, will both facilitate a sustainable ecological development in this region and have local climate cobenefits. More accurate simulations of the biophysical coupling between the land surface and the atmosphere are needed to help understand regional climate change over the TP, and possible larger scale feedbacks between climate in the TP and the Asian monsoon system.