普若岗日冰原及其小冰期以来的冰川变化

普若岗日是藏北高原最大的由数个冰帽型冰川组合成的大冰原.冰川覆盖面积422.58km²,冰储量为52.5153km³.冰川雪线海拔5620～5860m.冰原呈辐射状向周围微切割的宽浅山谷溢出50多条长短不等的冰舌,最大的可伸至山麓地带,形成宽尾状冰舌.在一些下伸较低的冰舌段,形成有许多冰塔林,以雄伟壮观的连座冰塔林和雏形冰塔林为主.在东南部一些冰舌段雏形冰塔林的上部,分布着奇特的新月型雪冰丘和链状排列有序的雪冰丘.小冰期以来,普若岗日的冰川呈退缩趋势.环绕冰舌分布的冰碛序列,在北部和东南部普遍可区分出3道.对比研究认为,分别属于小冰期3次寒冷期冰进的遗迹.而西部小冰期冰川作用的范围较小.按小冰期最盛时的规模量测当时的冰川面积,和现在相比该时段内冰川面积减少了24.20km²,当时冰川面积比现在大57%.由此引起的冰川资源的减少为3.6583km³,相当于36.583×10⁸m³的水量.在普若岗日西侧,小冰期后期至20世纪70年代,冰川退缩了20m;70年代至90年代末,冰川退缩了40～50m;平均1.5～1.9m·a^-1;1999年9月至2000年10月,退缩4～5m.明显反映出逐渐加剧的变化趋势.和其它地区相比较,普若岗日冰原变化比较小,表现出比较稳定的状。     

用树木年轮重建天山中部近350 a来的降水量

单相关普查表明，乌鲁木齐河谷树轮年表与上年7月至当年2月降水相关显著.西白杨沟及波尔钦沟两个树轮差值年表可较好地重建出天山中部近350 a来该时段的降水量，解释方差达62％.经用统计参数、独立降水资料、历史气候记载、冰川及其它资料多方面验证，表明近350 a的降水重建序列是可信的.降水特征分析指出：天山中部降水可划分出3个偏湿期(1671(?)一1692年，1716－1794年，1825－1866年)和3个偏干期(1693－1715年，1795－1824年，1867－1969年).其后两个偏湿期与乌鲁木齐河源1号冰川前的第二、第三道终碛垄相对应，经推算，相应年降水量比现今分别偏多约59 mm及30 mm.天山中部上年7月至当年2月的降水具有5、10、53～54、3.7及3.3 a的变化准周期，在1716－1969年间存在着明显的变干趋势，并在1831年发生过突变.重建降水序列对乌鲁木齐、昌吉州天山北坡一带的降水具有较好的代表性.     

Multi-proxy record of Holocene glacial history of the Spearhead and Fitzsimmons ranges,southern Coast Mountains,British Columbia

Evidence from glacier forefields and lakes is used to reconstruct Holocene glacier fluctuations in the Spearhead and Fitzsimmons ranges in southwest British Columbia. Radiocarbon ages on detrital wood and trees killed by advancing ice and changes in sediment delivery to downstream proglacial lakes indicate that glaciers expanded from minimum extents in the early Holocene to their maximum extents about two to three centuries ago during the Little Ice Age. The data indicate that glaciers advanced 8630–8020, 6950–6750, 3580–2990, and probably 4530–4090 cal yr BP, and repeatedly during the past millennium. Little Ice Age moraines dated using dendrochronology and lichenometry date to early in the 18th century and in the 1830s and 1890s. Limitations inherent in lacustrine and terrestrial-based methods of documenting Holocene glacier fluctuations are minimized by using the two records together.     

晚更新世以来我国北方沙漠地区的气候变化

本文通过地层沉积相等资料的分析,讨论了我国北方沙漠地区晚更新世以来的气候变化。     

The Features of Climate Variation and Glacier Response in Mt.Yulong,Southeastern Tibetan Plateau

The Features of climate change in Mt.Yulong, southeasten Tibetan Plateau were analyzed using linear regression, Mann Kendall abrupt test and Morlet wavelet analyses. In addition, the relationship between glacier retreating (Baishui Glacier No.1) and climate warming wasalso analyzed in this study. The main results are showedas follow: ① The annual mean temperature, precipitation have an increasing trend, withinclination rates being 0.15℃/10a and 9.0 mm/10a;annual temperaturedramatically ascend in 1998 with the change values 0.7 ℃; Morlet waveletsin annual temperature andtemperature in dry season mainly have a 10 to 15 year periods,while annual precipitation amount and the precipitation in rainy season presented a quasi 10 year periods. ②Prior to 1998, the important meteorological factor influencing the change of Baishui Glacier No.1 are temperature and precipitation, while in the following years, temperature plays a more important role in affecting its retreat and advance; The main characteristic ofvertical climate change in Mt. Yulong (1982/2009) is that the cold season shortens and temperature rises with elevation, and the maximal value of increased temperature in glacier zone is 2.2~2.5 ℃, resulting in greatly accelerated glacier ablation.     

The Medieval Warm Period and the Little Ice Age from a sediment record of Lake Ebinur,northwest China

Ma, L., Wu, J., Yu, H., Zeng, H. & Abuduwaili, J. 2011: The Medieval Warm Period and the Little Ice Age from a sediment record of Lake Ebinur, northwest China. Boreas, Vol. 40, pp. 518–524. 10.1111/j.1502‐3885.2010.00200.x. ISSN 0300‐9483. Lake Ebinur, Xinjiang, northwest China, is a closed‐basin, shallow lake that responds rapidly to changes in the ratio of precipitation to evaporation (P/E). A sediment record spanning the last 1500 years was obtained from the lake. We used δ¹⁸O and δ¹³C in bulk carbonate, and δ¹³C of organic matter in the lake sediments to infer environmental changes in the Ebinur region during the Medieval Warm Period (MWP) and the Little Ice Age (LIA). Decreased δ¹⁸O values of carbonate largely reflect an enhanced P/E ratio within the basin and a higher lake level. Bulk carbonates with higher δ¹³C values are deposited during periods when lake‐water pH is high, while lower δ¹³C values reflect a lower pH in the water column. δ¹³C in organic matter is associated with the amount of precipitation. The results indicate that the Ebinur region experienced a dry MWP and a wet LIA, although the MWP and LIA were warm and cold periods, respectively, as expected. Furthermore, the MWP and LIA were hydrologically complex and cannot be characterized as uniformly wet or dry. Peak wet periods are recorded in the sediment core around AD 1000, 1400 and 1700, and a dry event also occurred in the period of temperature change within the LIA (cold to warm around AD 1500). A comparison of the Lake Ebinur data with proxy records for the strength of the Siberian High and climate proxy indicators suggests that precipitation in the Ebinur region was a consequence, in part, of an enhanced Siberian High during the LIA.     

北半球50条山地冰川近期的物质平衡状况

近期北半球大多数山地冰川的物质平衡为负,冰川普遍退缩,表明北半球气候暖化的趋势.由于区域气候波动和变化的差异性以及冰川对气候变化的敏感性(响应程度)的不同,北半球山地冰川在普遍退缩的背景下具有鲜明的区域特征.     

1468-2001年新疆精河5～8月平均气温的重建

精河流域上游的3个树轮年表与精河5～8月的平均气温相关显著.考虑到气温对树木年轮生长的滞后效应,重建了精河1468-2001年的5～8月的平均气温,方差解释量为62.2%.在1468-2001年的534 a中精河共经历了7个偏暖和7个偏冷期,在不同阶段气温的变化周期不一致,气温在1541年、1684年、1855年和1969年前后出现突变.     

Holocene alpine glaciation inferred from lacustrine sediments on northeastern Baffin Island,Arctic Canada

With accelerated melting of alpine glaciers, understanding the future state of the cryosphere is critical. Because the observational record of glacier response to climate change is short, palaeo‐records of glacier change are needed. Using proglacial lake sediments, which contain continuous and datable records of past glacier activity, we investigate Holocene glacier fluctuations on northeastern Baffin Island. Basal radiocarbon ages from three lakes constrain Laurentide Ice Sheet retreat by ca. 10.5 ka. High sedimentation rates (0.03 cm a^?1) and continuous minerogenic sedimentation throughout the Holocene in proglacial lakes, in contrast to organic‐rich sediments and low sedimentation rates (0.005 cm a^?1) in neighbouring non‐glacial lakes, suggest that glaciers may have persisted in proglacial lake catchments since regional deglaciation. The presence of varves and relatively high magnetic susceptibility from 10 to 6 ka and since 2 ka in one proglacial lake suggest minimum Holocene glacier extent ca. 6–2 ka. Moraine evidence and proglacial and threshold lake sediments indicate that the maximum Holocene glacier extent occurred during the Little Ice Age. The finding that glaciers likely persisted through the Holocene is surprising, given that regional proxy records reveal summer temperatures several degrees warmer than today, and may be due to shorter ablation seasons and greater accumulation‐season precipitation. Copyright © 2009 John Wiley & Sons, Ltd.     

On Monsoon Precipitation Changes During the Medieval Warm Period and the Little Ice Age in Southeastern China

Periodic progresses have been made on monsoon precipitation changes during the past millennium in eastern China. However, trends of precipitation records reconstructed in the southern part of the region are inconsistent, especially for the relative humidity and dryness between the Medieval Warm Period and the Little Ice Age. In the present study, 17 published monsoon precipitation records, reconstructed from lake sediments, peat sediments, coastal muddy sediments and historical documents, for the past millennium from southeastern China were collected and compared. The results show that trends of various records are inconsistent. The inconsistencies could be partly attributed to age uncertainties and interpretation of the proxies; and the regional differences in precipitation changes might be another causation. To further explore the spatiotemporal patterns and driving mechanisms of monsoon precipitation during the past millennium in southeastern China, more records with accurate chronology and reliable proxies should be reconstructed.