Dahe Qin

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.

Glacier variations and climate warming and drying in the central Himalayas

Repeat measurements of glacier terminus positions show that glaciers in the central Himalayas have been in a continuous retreat situation in the past decades. The average retreat rate is 5.5–8.7 m/a in Mt. Qomolangma (Everest) since the 1960s and 6.4 m/a in Mt. Xixiabangma since the 1980s. In recent years, the retreat rate is increasing. Ice core studies revealed that the accumulation rate of glaciers has a fluctuating decrease trend in the last century with a rapid decrease in the 1960s and a relatively steady low value afterwards. Meteorological station record indicates that the annual mean temperature has a slow increase trend but summer temperature had a larger increase in the past 30 a. All these suggest that the glacier retreat results from precipitation decrease in combination with temperature increase, and hence glacier shrinkage in this region will speed up if the climatic warming and drying continues.

Sources of black carbon to the Himalayan–Tibetan Plateau glaciers

Combustion-derived black carbon (BC) aerosols accelerate glacier melting in the Himalayas and in Tibet (the Third Pole (TP)), thereby limiting the sustainable freshwater supplies for billions of people. However, the sources of BC reaching the TP remain uncertain, hindering both process understanding and efficient mitigation. Here we present the source-diagnostic Δ14C/δ13C compositions of BC isolated from aerosol and snowpit samples in the TP. For the Himalayas, we found equal contributions from fossil fuel (46±11%) and biomass (54±11%) combustion, consistent with BC source fingerprints from the Indo-Gangetic Plain, whereas BC in the remote northern TP predominantly derives from fossil fuel combustion (66±16%), consistent with Chinese sources. The fossil fuel contributions to BC in the snowpits of the inner TP are lower (30±10%), implying contributions from internal Tibetan sources (for example, yak dung combustion). Constraints on BC sources facilitate improved modelling of climatic patterns, hydrological effects and provide guidance for effective mitigation actions.

Storage, patterns, and control of soil organic carbon and nitrogen in the northeastern margin of the Qinghai?Tibetan Plateau

This study tested the hypothesis that soil organic carbon (SOC) and total nitrogen (TN) spatial distributions show clear relationships with soil properties and vegetation composition as well as climatic conditions. Further, this study aimed to find the corresponding controlling parameters of SOC and TN storage in high-altitude ecosystems. The study was based on soil, vegetation and climate data from 42 soil pits taken from 14 plots. The plots were investigated during the summers of 2009 and 2010 at the northeastern margin of the Qinghai-Tibetan Plateau. Relationships of SOC density with soil moisture, soil texture, biomass and climatic variables were analyzed. Further, storage and vertical patterns of SOC and TN of seven representative vegetation types were estimated. The results show that significant relationships of SOC density with belowground biomass (BGB) and soil moisture (SM) can be observed. BGB and SM may be the dominant factors influencing SOC density in the topsoil of the study area. The average densities of SOC and TN at a depth of 1 m were about 7.72 kg C m(2) and 0.93 kg N m 2. Both SOC and TN densities were concentrated in the topsoil (0-20 cm) and fell exponentially as soil depth increased. Additionally, the four typical vegetation types located in the northwest of the study area were selected to examine the relationship between SOC and environmental factors (temperature and precipitation). The results indicate that SOC density has a negative relationship with temperature and a positive relationship with precipitation diminishing with soil depth. It was concluded that SOC was concentrated in the topsoil, and that SOC density correlates well with BGB. SOC was predominantly influenced by SM, and to a much lower extent by temperature and precipitation. This study provided a new insight in understanding the control of SOC and TN density in the northeastern margin of the Qinghai-Tibetan Plateau.

Twentieth century increase of atmospheric ammonia recorded in Mount Everest ice core

An NH + 4 record covering the period A.D. 1845-1997 was reconstructed using an 80.4 m ice core from East Rongbuk Glacier at an elevation of 6450 m on the northern slope of Mount Everest. Variations in NH4 are characterized by a dramatic increase since the 1950s. The highest NH + 4 concentrations occur in the 1980s. They are about twofold more than those in the first half of twentieth century. Empirical orthogonal function (EOF) analysis on the eight major ion (Na + , K + , Mg 2+ , NH + 4 , Ca 2+ , NO - 3 , SO 2- 4 and Cl - ) series from this core indicates that NH + 4 is loaded mainly on EOF3 (60% of NH + 4 variance), suggesting that NH + 4 has a unique signature. Instrumental sea level pressure (SLP) and regional temperatures are used to explore the relationship between NH + 4 variations and both atmospheric circulation and natural source strength over Asia. Higher NH + 4 concentrations are associated with an enhanced winter Mongolian High and a deepened summer Mongolian Low. A positive relationship also exists between NH4 concentrations and regional temperature changes of the GIS Box 36 (Indian subcontinent), indicating that an increase in temperature may contribute to the strengthening of natural ammonia emissions (e.g., from plants and soils). A close positive correlation between NH + 4 and acidic species (SO 2- 4 plus NO - 3 ) concentrations suggests that a portion of the increase in NH + 4 concentrations could be contributed by enhanced atmospheric acidification. Anthropogenic ammonia emissions from enhanced agricultural activities and energy consumption over Asia in concert with population increase since the 1950s appear also to be a significant factor in the dramatic increase of NH + 4 concentrations during the last few decades.

Dendroclimatic temperature record derived from tree-ring width and stable carbon isotope chronologies in the middle qilian mountains, China

ABSTRACT Using long-lived Qilian juniper (Sabina przewalskii Kom.) in the middle Qilian Mountains, the temperature variations in the last 1000 yr were reconstructed. We find that the annual growth ring width and δ13C series mainly reflect variations in regional temperature. Except in May, warmer temperatures indicate greater growth over the period from December to April, and δ13C values in tree-rings are higher for years with higher temperature. The notable features in the temperature reconstruction are the occurrence of the Little Ice Age from A.D. 1600 to 1880 and the abrupt warming over the end of past millennia. The comparison of our chronology to a Northern Hemispheric temperature proxy shows that our tree-ring data will facilitate intercontinental differentiation of large-scale synoptic climate variability.

Snow Accumulation Rate on Qomolangma (Mount Everest), Himalaya: Synchroneity With Sites Across the Tibetan Plateau on 50-100 Year Timescales

Annual-layer thickness data, spanning AD 1534-2001, from an ice core from East Rongbuk Col on Qomolangma (Mount Everest, Himalaya) yield an age-depth profile that deviates systematically from a constant accumulation-rate analytical model. The profile clearly shows that the mean accumulation rate has changed every 50-100 years. A numerical model was developed to determine the magnitude of these multi-decadal-scale rates. The model was used to obtain a time series of annual accumulation. The mean annual accumulation rate decreased from ∼0.8m ice equivalent in the 1500s to ∼0.3m in the mid-1800s. From ∼1880 to ∼1970 the rate increased. However, it has decreased since ∼1970. Comparison with six other records from the Himalaya and the Tibetan Plateau shows that the changes in accumulation in East Rongbuk Col are broadly consistent with a regional pattern over much of the Plateau. This suggests that there may be an overarching mechanism controlling precipitation and mass balance over this area. However, a record from Dasuopu, only 125 km northwest of Qomolangma and 700 m higher than East Rongbuk Col, shows a maximum in accumulation during the 1800s, a time during which the East Rongbuk Col and Tibetan Plateau ice-core and tree-ring records show a minimum. This asynchroneity may be due to altitudinal or seasonal differences in monsoon versus westerly moisture sources or complex mountain meteorology.

Stable-isotopic composition of precipitation over the northern slope of the central Himalaya

Stable-water-isotope data (6D and δ 18 O) from three groups of samples (fresh-snow and snow-pit samples collected on Qomolangma (Mount Everest) and Xixabangma during field seasons 1997, 1998 and 2001, and precipitation samples collected at Tingri station during summer 2000) are presented and used to survey the isotopic composition of precipitation over the northern slope of the central Himalaya. Multi-year snow-pit samples on Qomolangma have a local meteoric water-line (slope = 8) close to the global value. Deuterium excess (d = δD-8δ -18 O) values at Tingri are much lower than those in fresh snow from Qomolangma, probably due to differences in moisture source and air-mass trajectories as well as local weather conditions. There is no obvious seasonal trend for d values in the Qomolangma region. A negative relationship exists between δ 18 O and d values in both fresh snow on Qomolangma and precipitation at Tingri. Fresh-snow samples collected from different altitudes on Xixabangma allow us to investigate the altitude effect on δ 18 O values in snow. Of four storm events, only one has an obvious altitude effect on δ 18 O variation and a very low gradient of -0.1% per 100 m elevation.

The International Trans-Antarctic Scientific Expedition (ITASE): an overview

Abstract From its original formulation in 1990 the International Trans-Antarctic Scientific Expedition (ITASE) has had as its primary aim the collection and interpretation of a continent-wide array of environmental parameters assembled through the coordinated efforts of scientists from several nations. ITASE offers the ground-based opportunities of traditional-style traverse travel coupled with the modern technology of GPS, crevasse detecting radar, satellite communications and multidisciplinary research. By operating predominantly in the mode of an oversnow traverse, ITASE offers scientists the opportunity to experience the dynamic range of the Antarctic environment. ITASE also offers an important interactive venue for research similar to that afforded by oceanographic research vessels and large polar field camps, without the cost of the former or the lack of mobility of the latter. More importantly, the combination of disciplines represented by ITASE provides a unique, multidimensional (space and time) view of the ice sheet and its history. ITASE has now collected >20 000km of snow radar, recovered more than 240 firn/ice cores (total length 7000 m), remotely penetrated to ~4000m into the ice sheet, and sampled the atmosphere to heights of >20 km.

Soluble species in aerosol and snow and their relationship at Glacier 1, Tien Shan, China

Simultaneous sampling of aerosol (n = 20) and snow (n = 114) was made at Glacier 1, Tien Shan, between May 19 and June 29, 1996. Similar temporal patterns of some major ion (calcium, magnesium, potassium, sodium, chloride, and sulfate) concentrations between snow and aerosol show that snow chemistry basically reflects changes in the chemistry of the atmosphere. This gives us confidence in the reconstruction of past atmospheric change using some snow data. There are no significant correlations between aerosol and snow samples for ammonium and nitrate. This suggests that postdepositional and/or postcollection processes may alter ammonium and nitrate concentrations in snow. The fact that the measured cations in aerosol and snow always exceed the measured anions suggests that the atmosphere is alkaline over Glacier 1, Tien Shan. In aerosol and snow samples, calcium is the dominant cationic species, with sulfate and presumed carbonate being the dominant anions. There is a very good inverse relationship (r = 0.96) between the equivalence ratio of calcium to sulfate and the ratio of ammonium to sulfate in aerosols, but this relationship does not hold for snow. This further suggests that postdepositional and/or postcollection processes exert important controls on ammonium concentrations in snow. Although melt-freeze cycles might increase the concentration of all crustal species through progressive dissolution of dust, these cycles seem most important for magnesium and carbonate.