Measurements of sea ice thickness and its subice morphology analysis using ice-penetration radar in the Arctic Ocean

Based on radar penetrating measurements and analysis of sea ice in the Arctic Ocean, The potential of radar wave to measure sea ice thickness and map the morphology of the underside of sea ice is investigated. The results indicate that the radar wave can penetrate Arctic summer sea ice of over 6 meters thick; and the propagation velocity of the radar wave in sea ice is in the range of 0.142 m·ns -1 to 0.154 m·ns -1 . The radar images display the roughness and micro-relief variation of sea ice bottom surface. These features are closely related to sea ice types, which show that radar survey may be used to identify and classify ice types. Since radar images can simultaneously display the linear profile features of both the upper surface and the underside of sea ice, we use these images to quantify their actual linear length discrepancy. A new length factor is suggested in relation to the actual linear length discrepancy in linear profiles of sea ice, which may be useful in further study of the area difference between the upper surface and bottom surface of sea ice.

Determination of ice thickness,subice topography and ice vol-ume at Glacier No.1 in Tien Shan,China by ground penetrating radar

We describe a radio-echo sounding (RES) survey for the determination of ice thickness, subglacial topography and ice volume of Glacier No. 1 , in Tien Shan, China, using ground-penetrating radar (GPR). Radar data were collected with 100-MHz antennas that were spaced at 4 m with a step size of 8 m. The images produced from radar survey clearly show the continuity of bedrock echoes and the undulation features of the bedrock surface. Radar results show that the maximum ice thickness of Glacier No. 1 is 133 m, the thickness of the east branch of Glacier No. 1 averages at 58. 77 m while that of the west branch of Glacier No. 1 averages at 44. 84 m. Calculation on ice volume indicates that the ice volume of the east branch of Glacier No. 1 is 51. 87 × 106 m3 and that of the west branch of Glacier No. 1 is 20. 21 × 106 m3. The amplitude of the undulation of the bedrock surface topography revealed by radar profiles is larger than that of the glacier surface topography, indicating that the surface relief does not directly depend on that of the bedrock undulation in Glacier No. 1 , in Tien Shan.

The transport of chemical components in homogeneous snowpacks on Urumqi Glacier No.1, eastern Tianshan Mountains, Central Asia

Chemical records from alpine ice cores provide an invaluable source of paleoclimatic and environ- mental information. Not only the atmospheric chemical composition but also depositional and post-depositional processes are recorded within snow/tim strata. To interpret the environmental and climatic significance of ice core records, we studied the variability of glacier snowpack chemistry by investigating homogeneous snowpacks from October 2003 to September 2006 on Urumqi Glacier No. 1 in eastern Tianshan Mountains, Central Asia. Principle Component Analysis of ionic species in dry and wet seasons revealed the impact of meltwater in redistributing ions in the snowpacks. The 1st, 2nd and 3rd principle components for dry seasons differ significantly, reflecting complex associations between depositional or/and post-depositional processes. The variability trend of ionic concentrations during the wet seasons was found to fit a Gauss Function with significant parameters. The elution factor revealed that more than half of ions are leached out during the wet seasons. Differences with respect to ion snowpack mo- bility were found. Of the ions studied SO42- was the most mobile and Mg2＋ the least mobile. A threshold relationship between air temperatures and the elution process was investigated over the study period. The results indicate that the strong melt/ablation processes and iconic redistribution occur at a threshold air temperature of 0℃. The study found that surface melt on the snowpacks is the main factor causing the alteration of the snowpack chemistry. Rainfall also has an impact on the chemistry but plays a less significant role than the surface melt.

Tropospheric pyruvate changes in the remote area of northwestern China

Pyruvate is a light carboxylate in the troposphere and can act as potential cloud condensation nuclei. Due to its low concentrations, however, little work has been done on the species in precipitation. Past 43-year record of pyruvate was recovered from an ice core of Glacier 1 at 43°06′N and 86°49′E in the remote East Tianshan, northwestern China. It was revealed that pyruvate varied over a relatively large range with some below the detection limit, while part of it is so high as to be up to 70 ng·g{-1}. With an average concentration of {4.1} ± {8.1} ng·g{-1} (mean ± 1σ, N=543), pyruvate is a minor species in comparison with other carboxylates. It is also low as compared with its precipitation in other parts of the world, suggesting a difference in its major source flux. The record revealed high pyruvate concentrations in the late halves of the 1950s and 1980s, but low in the late 1950s, late 1970s, and middle 1990s. The variation trend in the past 43 years is closely correlated with that of acetate, a major carboxylate from anthropogenic pollution to the atmosphere, indicating that tropospheric pyruvate in the remote area of northwestern China is probably a by-product in acetate formation.

Evidence for cold events in the early Holocene from the Guliya ice core, Tibetan Plateau,China

Evidence for the '8.2 ka cold event' has been provided mostly from the circum-North Atlantic area. However, whether this cold event occurred in other places is a key to understanding its cause. Here, we provide the evidence for the '8.2 ka cold event' from the Guliya ice core in the northwest Tibetan Plateau, and it was found that the peak cooling (-8.3-8.2 ka) in this ice core was about 7.8-10°C, which was larger than the cooling in the North Atlantic region. The primary causes for this episode were diminished solar activity and weakened thermohaline circulation. Moreover, another weak cold event, centered about 9.4 ka, was also recorded in the Guliya ice core record. These two cold events were concurrent with the ice-rafting episodes in the North Atlantic during the early Holocene, which implies that the millennial-scale climatic cyclicity might exist in the Tibetan Plateau as well as in the North Atlantic.

Sea ice thickness measurement and its underside morphol-ogy analysis using radar penetration in the Arctic Ocean

Based on radar penetrating measurements and analysis of sea ice in the Arctic Ocean, the potential of radar wave to measure sea ice thickness and map the morphology of the under-side of sea ice is investigated. The results indicate that the radar wave can penetrate Arctic sum-mer sea ice of over 6 m in thickness; and the propagation velocity of the radar wave in sea ice is in the range of 0.142 m·ns-1 to 0.154 m·ns-1. The radar images display the roughness and mi-cro-relief variation of sea ice bottom surface. These features are closely related to sea ice types, which show that radar survey may be used to identify and classify ice types. Since radar images can simultaneously display the linear profile features of both the upper surface and the underside of sea ice, we use these images to quantify their actual linear length discrepancy. A new length factor is suggested in relation to the actual linear length discrepancy in linear profiles of sea ice, which may be useful in the further study of the area difference between the upper surface and bottom surface of sea ice.

中纬度地区混合云中稳定同位素分馏的数学模拟—以乌鲁木齐降水为例(英)

The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model, the temperature effect of stable isotopes in precipitation is simulated under different cooling conditions. The rate of change of δ18O against temperature in the process of wet adiabatic cooling is smaller than in the process of isobaric cooling under the same humidity. The increasing supersaturation ratio at the ice surface, Si, leads to the strengthening of the kinetic fractionation effect. The kinetic fractionation function makes the synthesis fractionation factor decreased and the change of δ18O with temperature flatted, compared with that in the equilibrium state. The simulated results show that the slope parameter b and the intercept d of the meteoric water line (MWL), 6D = bδ18O+d, in wet adiabatic cooling are both greater than those in isobaric cooling. The global MWL lies between the two MWLs simulated under wet adiabatic and isobaric cooling processes, respectively. The magnitudes of 6 and d are directly proportional to Si. The greater the Si, the stronger the kinetic fractionation effect, and thus the greater the 6 and d, and vice versa. However, 6 and d have low sensitivity to the liquid-water contents in the cloud. Using the kinetic fractionation model, the variation of stable isotopes in precipitation at Uriimqi is simulated. The simulated stable isotopic ratio vs temperature and the SD vs δ18O curves are very consistent with the actual regressions and MWL at Uriimqi, respectively.

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

从极的冰表恢复的冰核心从爆炸暴烈的爆发收到了并且保存硫磺的酸放射性尘埃， DT263 冰核心从东方 Antarcticlocation 被检索。冰核心用年度层作为 780 年(1215-1996 A.D ) 数和暴烈的 timestratigraphic 地平线的联合被标明日期。冰核心记录在约 1460 的时期期间表明那 - 1800 A.D，累积是比层次在以前并且在这个时期以后严厉地低的。这个时期与最近的 neoglacial 与气候的事件一致，“很少冰川期(LIA ) ”，那在众多的北半球代理和历史性的记录被发现了。non-sea-salt SO_2 集中在 DT263ice 核心显示十七个暴烈的事件。与那些相比从以前的南极冰核心，重要差异在几个著名事件的相对暴烈的流动在这些记录之间被发现。在这些记录之中的差异可以被差别在在冰核心上加亮本地冰河学的潜在的影响的表面地形学，累积率，雪飘移和分发解释暴烈的记录，分析技术为硫酸盐测量使用了，等等。在中间、高的南部的纬度的暴烈的爆发在低纬度比那些更强烈地在南极雪中影响暴烈的记录。

Paleosandstorm characteristics and lake evolution history deduced from investigation on lacustrine sediments——The case of Hongjiannao Lake, Shaanxi Province

Sediment cores from desert lakes serve as good records of the frequency and intensity of sandstorms in his- tory. By multi-proxy analysis of grain-size, magnetic suscep- tibility, TOC and Rb/Sr ratio, the paleosandstorm character- istics and lake evolution history in Yulin Area for the past 80 years. are discussed in this article. It is revealed that Hong- jiannao Lake formed in about 1928 A.D. and in its initial stage sandstorms were prevalent with three extremes taking place in 1936 A.D., 1939 A.D. and 1941 A.D.. During the ex- pansion period of 1952―1960 A.D., inflow waters to the lake increased sharply and a lot more weathered materials were carried into the lake. The frequency and intensity of sand- storms have reduced a lot since 1960s and the “double peaks” feature of the grain-size frequency curve has changed into the “single peak” feature. Study on the catchment ecol- ogy of the lake shows that the occurrence of sandstorms has been effectively restrained by the forest plantation and water and soil conservation.

On the magnitude of temperature decrease in the equatorial regions during the Last Glacial Maximum

Based on the data of temperature changes revealed by means of various palaeothermometric proxy indices,it is found that the magnitude of temperature decrease became large with altitude in the equatorial regions during the Last Glacial Maximum. The direct cause of this phenomenon was the change in temperature lapse rate, which was about(0.1±0.05)℃/100 m larger in the equator during the Last Glacial Maximum than at present. Moreover, the analyses show that CLIMAP possibly underestimated the sea surface temperature decrease in the equatorial regions during the Last Glacial Maximum.

中国冰川研究进展

Glacier inventory compilation during the past 20 years and modifications ofthat for the Eastern Pamir and Banggong Lake indicate that there are 46,342 modern glaciers with atotal area and volume of 59415 km^2 and 5601 km^3 respectively in China. These glaciers can beclassified into maritime and continental (including sub-continental and extremely continental)types. Researches show that glaciers in China have been retreating since the Little Ice Age and themass wastage was accelerated during the past 30 to 40 years. Being an important part ofglaciological studies in China, ice core climatic and environmental studies on Tibetan Plateau andin the Antarctica have provided abundant, high resolution information about past climatic andenvironmental evolution over the Tibetan Plateau and Antarctica. Except for different parametersrecorded in ice cores relating to climate and environment changes on Tibetan Plateau, records fromice cores extracted from different glaciers show that the discrepancies in climatic andenvironmental changes on the north and south parts of the plateau may be the consequence ofdifferent influencing effects from terrestrial and solar sources. Glaciological and meteorologicalphenomena imply that Lambert Glacier valley is an important boundary of climate in the eastAntarctica, which is thought to be connected with cyclonic activities and Circum-polar Waves overthe Antarctica.

Ecological Environment Change in North Slope of Qilianshan Mountains

Based on meteorological,hydrological, forest,and grassland data collected by location observation,remote sensing,field surveys and relevant literature during 1956 to 2009,the ecological environment change in northern slope of the Qilianshan Mountains was analyzed synthetically using regression and correlation analyses.The results showed that the temperature had an annual variation rate of 0.033 4℃·a-1 in northern slope of the Qilianshan Mountains since 1960,and exhibited a raising trend,especially since 1987.The annual variation rate of annual precipitation was 0.570 2 mm·a-1,indicating that the precipitation tended to increase.The climate had changed from arid to humid in this region since 1976.From 1956 to 2006,the glacier area of six inland river basin（Shiyanghe river,Heihe river, Beidahe river,Shulehe river,Danghe river and Halternhe river） and Datonghe river basin in northern slope of Qilianshan mountains decreased by 17.7%. Thickness of the glacier reduced about 5-20 m,and the snow line rose about 100-140 m.The Glacier ice reserves in inland river basin of Hexi decreased by 11.4%.From 1972 to 2007,27 glaciers in the eastern section of the Qilianshan Mountains disappeared.From 1956 to 2009,the runoff change in the northern slope of the Qilianshan Mountains was different in different regions.The runoff was reduced significantly in Shiyanghe river basin, increased slightly in Heihe river basin,and increased obviously in Shulehe river basin.From 1958 to 1988, the area of deforestation and farming was more than 10.0 million ha,and the forest area was reduced 0.6 million ha.Since the Qilianshan Mountain Nature Reserve was established in 1989, the forest was restoring gradually because of continual protection and cultivating,and the forest area was increased 9.4 million ha from 1989 to 2008. Due to human interference,especially over-grazing impact,the quality of the wood-land,shrub-land and grass-land in northern slope of the Qilianshan Mountains were in a degraded condition,which resulted in serious harm of forest pests,decrease of shrubbery snow and water-retention capacity and exacerbation of soil erosion.The ecological environment in northern slope of the Qilianshan Mountains was improved in certain regions,but deteriorated in overall region,and the protection and management are needed to be strengthened.

CLIMATE ANOMALY RECORDED IN GULIYA ICE CORE AND ENSO EVENTS

Examination of ENSO events and the accumulated precipitation and δ^(18)O values recorded in the Guliya ice core,China,shows that the relationship between the occurrence of ENSO events and the precipitation anomaly in Guliya is significant.In the years of El Nino events,the anomalies of precipitation and δ^(18)O values in the Guliya ice core were negative anomalies,that is,the ENSO events are related to the deficit of precipitation as well as low temperature in the western China.

Climatic variations since the Little Ice Age recorded in the Guliya Ice Core

The climatic variations since the Little Ice Age recorded in the Guliya Ice Core are discussed based on glacial δ18O and accumulation records in the Guliya Ice Core. Several obvious climate fluctuation events since 1570 can be observed according to the records. In the past 400 years, the 17th and 19th centuries are relatively cool periods with less precipitation, and the 18th and 20th centuries are relatively warm periods with high precipitation. The study has also revealed the close relationship between temperature and precipitation on the plateau. Warming corresponds to high precipitation and cooling corresponds to less precipitation, which is related with the influence of monsoon on this region.

Mass balance of the Lambert Glacier basin,East Antarctica

Since it is the largest glacier system in Antarctica, the Lambert Glacier basin plays an important role in the mass balance of the overall Antarctic ice sheet. The observed data and shallow core studies from the inland traverse investigations in recent years show that there are noticeable differences in the distribution and variability of the snow accumulation rate between east and west sides. On the east side, the accumulation is higher on the average and has increased in the past decades, while on the west side it is contrary. The ice movement measurement and the ice flux calculation indicate that the ice velocity and the flux are larger in east than in west, meaning that the major part of mass supply for the glacier is from the east side. The mass budget estimate with the latest data gives that the integrated accumulation over the upstream area of the investigation traverse route is larger than the outflow ice flux by 13%, suggesting that the glacier basin is in a positive mass balance state and the ice thickness will increase if the present climate is keeping.