“Greatest lake period” and its palaeo-environment on the Tibetan Plateau

The “greatest lake period” means that the lakes are in the stage of their maximum areas. As the paleo lake shorelines are widely distributed in the lake basins on the Tibetan Plateau, the lake areas during the “greatest lake period” may be inferred by the last highest lake shorelines. They are several, even tens times larger than that at present. According to the analyses of tens of lakes on the Plateau, most dating data fell into the range of 40-25 ka BP, some lasted to 20 ka BP. It was corresponded to the stage 3 of marine isotope and interstitial of last glaciation. The occurrence of maximum areas of lakes marked the very humid period on the Plateau and was also related to the stronger summer monsoon during that period.     

An abrupt cooling event early in the last interglacial in the northern South China Sea

The high-resolution quantitative analysis of the planktonic foraminifera and the δ¹⁸O records of the section between 96.49– 137.6 mcd at ODP Site 1144 on the continental slope of northern South China Sea reveals an abrupt cooling event of sea surface temperature (SST) during the last interglacial (MIS 5.5, i.e. 5e). The dropping range of the winter SST may come to 7.5°C corresponding to 1.2‰ of the δ¹⁸O value of sea surface water. This event is comparable with those discovered in the west Europe and the northern Atlantic Ocean, but expressed in a more intensive way. It is inferred that this event may have been induced by middle- to low-latitude processes rather than by polar ice sheet change. Since the Kuroshio-index speciesPulleniatina obliquiloculata displayed the most distinct change at the event, it may also be related to the paleoceanographic change of the low-latitude area in the western Pacific Ocean. This event can be considered as one of “Younger Dryas-style coolings” and is indicative of climate variability of the last interglacial stage.     

Research on Autonomous Orbit Determination of Navigation Satellite Based on Crosslink Range and Orientation Parameters Constraining

Introduction Thepotentialvulnerabilityofsatellitenaviga tionsystemthatreliesongroundstationsisthat thesystemwouldbreakdownifgroundstations weredestroyed,whichcannotmeettherequire mentofnavigationwarfare[1].Withthedevelop mentofsuchspace basedsystemsasgrou…     

Change of Gas Hydrate Reservoir and Its Effect on the Environment in Xisha Trough since the Last Glacial Maximum

In this article, Milkov and Sassen’s model is selected to calculate the thickness of the gas hydrate stable zone (GHSZ) and the amount of gas hydrate in the Xisha (西沙) Trough at present and at the last glacial maximum (LGM), respectively, and the effects of the changes in the bottom water temperature and the sea level on these were also discussed. The average thickness of the GHSZ in Xisha Trough is estimated to be 287 m and 299 m based on the relationship between the GHSZ thickness and the water depth established in this study at present and at LGM, respectively. Then, by assuming that the distributed area of gas hydrates is 8 000 km2 and that the gas hydrate saturation is 1.2% of the sediment volume, the amounts of gas hydrate are estimated to be ~2.76×1010 m3 and ~2.87×1010 m3, and the volumes of hydrate-bound gases are ~4.52×1012 m3 and ~4.71×1012 m3 at present and at LGM, re- spectively. The above results show that the thickness of GHSZ decreases with the bottom water tem- perature increase and increases with the sea level increase, wherein the effect of the former is larger than that of the latter, that the average thickness of GHSZ in Xisha Trough had been reduced by ~12 m, and that 1.9×1011 m3 of methane is released from approximately 1.1×109 m3 of gas hydrate since LGM. The released methane should have greatly affected the environment.     

Instability characteristics of the East Asian Monsoon recorded by high-resolution loess sections from the last interglacial (MIS5)

The selection of high-resolution loess sections is needed in order to determine the climatic variability of the East Asian Monsoon during the last interglacial. Two sequences of S1 on the eastern and west-ern sides of the Liupan Mountain were both composed of five paleosol layers and four loess layers,indicating that there were five strong summer monsoon events and four strong winter monsoon events in MIS5. This corresponds with other records of the East Asian Monsoon,along with NGRIP and the North Atlantic records,implying that the climate of the Northern Hemisphere was very instable during the last interglacial. Two layers of paleosols and one layer of loess had developed during MIS5a and MIS5c. Compared with MIS5e,the climate in MIS5a and MIS5c fluctuated more intensively on a millen-nial scale,whereas the climate was relatively stable in MIS5e.     

Glacier fluctuations in the southern Peruvian Andes during the late‐glacial period,constrained with cosmogenic 3He

The occurrence of pronounced climate reversals during the last glacial termination has long been recognised in palaeoclimate records from both hemispheres and from high to low latitudes. Accurate constraint of both the timing and magnitude of events, such as the Younger Dryas and Antarctic Cold Reversal, is vital in order to test different hypotheses for the causes and propagation of abrupt climate change. However, in contrast to higher‐latitude regions, well‐dated records from the Tropics are rare and the structure of late‐glacial tropical climate remains uncertain. As a step toward addressing this problem, we present an in situ cosmogenic ³He surface exposure chronology from Nevado Coropuna, southern Peru, documenting a significant fluctuation of the ice margin during the late‐glacial period. Ten tightly clustered ages from a pair of moraines located halfway between the modern glacier and the Last Glacial Maximum terminus range from 11.9 to 13.9 ka and give an arithmetic mean age of 12.8 ± 0.7 ka (1σ). These data constitute direct evidence for a readvance, or prolonged stillstand, of glaciers in the arid Andes of southwestern Peru. Copyright © 2011 John Wiley & Sons, Ltd.     

EVIDENCE FOR ABRUPT CLIMATIC CHANGES ONNORTHWESTERN MARGIN OF EAST ASIAN MONSOON REGION DURING LAST DEGLACIATION

Based on investigations of the Zhongwei Nanshan aeolian section situated in the southeastern margin of Tengger Dcsert, carbon-14 and TL (thermoluminescence) dating results and paleoclimatic proxies such as magnetic susceptibility and grain size, we inferred that the northwestern margin of East Asian monsoon region experienced abrupt climatic changes during the last deglaciation. Six oscillation events were identified: Oldest Dryas, Belling, Older Dryas, AllerФd, lntra-AllerФd Cold Period (1ACP) and Younger Dryas (YD). The summer monsoon was weaker during Oldest Dryas and Younger Dryas when the winter monsoon was stronger. However, during the B/A (BФlling/AllerФd) period, the summer monsoon strengthened, reflected by magnetic susceptibility, when the winter monsoon also became strong, which is different from the paleoclimatic pattern established in the East Asian monsoon region. Furthermore,the summer monsoon was nearly in phase with the climate changes inferred from the oxygen isotopic records of Greenland ice cores. It could be speculated that the variations of the sea ice cover in the high latitudes of the North Hemisphere affected the high pressure of Asian continent and the changes of the winter monsoon inland. On the other hand,the sea ice cover variations might have indirectly caused the occurrence of ENSO events that has tightly been related to the summer monsoon in northwest margin of East Asian monsoon region.     

Interannual Climate Variability of the Past Millennium from Simulations

The interannual variability of global temperature and precipitation during the last millennium is analyzed using the results of ten coupled climate models participating in the Paleoclimate Modelling Intercomparison Project Phase 3. It is found that large temperature(precipitation) variability is most dominant at high latitudes(tropical monsoon regions), and the seasonal magnitudes are greater than the annual mean. Significant multi-decadal-scale changes exist throughout the whole period for the zonal mean of both temperature and precipitation variability, while their long-term trends are indistinctive. The volcanic forcings correlate well with the temperature variability at midlatitudes, indicating possible leading drivers for the interannual time scale climate change.     

九江市蓼花剖面末次冰期中晚期沉积的粒度端元特征与气候变化

鄱阳湖湖滨地区广泛分布着晚第四纪风沙沉积序列。在星子县沙岭沙山进行野外调查后选择蓼花剖面开展工作,测试了地质时代和粒度,对粒度结果使用端元分析模型进行研究,探讨该区域末次冰期中晚期的气候变化规律。结果显示：该剖面由湖相-古土壤-沙丘砂等沉积相叠覆堆积组成,形成于末次冰期中晚期（48.8—17.1 ka）。端元分析模型将粒度数据分解出3个不同的粒度端元,不同端元组分在垂向上呈峰谷交替的旋回变化,EM1代表粉砂端元组分,峰值对应湖相和古土壤发育时期;EM2和EM3代表中砂—粗砂端元组分,峰值对应沙丘砂发育期,这些峰谷交替变化的规律指示了末次冰期的季风演变以及气候波动变化,万年尺度上表现为LH10 (48.8—39.9 ka)和LH3～LH5 (28.1—17.1 ka)的冬季风强盛期,分别对应深海氧同位素的MIS3b和MIS2阶段。LH6～LH9 (39.9—28.1 ka)为温暖的夏季风时期,对应深海氧同位素的MIS3a阶段。这些变化与YZ洞石笋氧同位素以及格陵兰冰心有良好的对应,与全球气候变化基本一致。     

Impact of the Kuroshio Current on the South China Sea based on a 115 000 year diatom record

We used the tropical oceanic planktonic diatom species Nitzschia marina, Rhizosolenia bergonii and Azpeitia africana/Azpeitia neocrenulata, most commonly found in the surface sediments of the northeasternmost South China Sea (SCS) where the Kuroshio Current enters the SCS through the Bashi Strait north of Luzon, to analyse the influence of the the Kuroshio Current on the SCS. The impact of the Kuroshio Current seems to be relatively strong during major warm periods and, to a lesser degree, in minor warm periods during the last 115 000 years. The strongest influence took place during the main part of the Holocene and during the very late phase of Marine Isotope Stage (MIS) 5e. It is possible to distinguish two magnitudes of change in the impact of the Kuroshio Current on the SCS: large changes occurred at shifts between glacial and interglacial conditions, while smaller changes seem to have recurred in both glacial and interglacial episodes as well as during the Holocene. Climatic/oceanographic changes and sea‐level variations were possibly the two most important mechanisms for the varying influences of the Kuroshio Current on the SCS. The interaction between the Kuroshio Current and monsoon‐related processes may also have played a role. However, because of restricted knowledge of the present‐day Kuroshio Current and the absence of a modern analogue to the ancient SCS due to the marked changes in palaeogeography, this relationship is difficult to establish. Copyright © 2006 John Wiley & Sons, Ltd.