LATE‐GLACIAL GLACIER EVENTS IN SOUTHERNMOST SOUTH AMERICA: A BLEND OF ‘NORTHERN’ AND 'SOUTHERN’ HEMISPHERIC CLIMATIC SIGNALS?

ABSTRACT. This paper examines new geomorphological, chronological and modelling data on glacier fluctuations in southernmost South America in latitudes 46–55°S during the last glacial–interglacial transition. Establishing leads and lags between the northern and southern hemispheres and between southern mid‐latitudes and Antarctica is key to an appreciation of the mechanisms and resilience of global climate. This is particularly important in the southern hemisphere where there is a paucity of empirical data. The overall structure of the last glacial cycle in Patagonia has a northern hemisphere signal. Glaciers reached or approached their Last Glacial Maxima on two or more occasions at 25–23 ka (calendar) and there was a third less extensive advance at 17.5 ka. Deglaciation occurred in two steps at 17.5 ka and at 11.4 ka. This structure is the same as that recognized in the northern hemisphere and taking place in spite of glacier advances occurring at a time of high southern hemisphere summer insolation and deglaciation at a time of decreasing summer insolation. The implication is that at orbital time scales the‘northern’ signal dominates any southern hemisphere signal. During deglaciation, at a millennial scale, the glacier fluctuations mirror an antiphase 'southern’ climatic signal as revealed in Antarctic ice cores. There is a glacier advance coincident with the Antarctic Cold Reversal at 15.3–12.2 ka. Furthermore, deglaciation begins in the middle of the Younger Dryas. The implication is that, during the last glacial–interglacial transition, southernmost South America was under the influence of sea surface temperatures, sea ice and southern westerlies responding to conditions in the 'southern’ Antarctic domain. Such asynchrony may reflect a situation whereby, during deglaciation, the world is more sensitized to fluctuations in the oceanic thermohaline circulation, perhaps related to the bipolar seesaw, than at orbital timescales.     

基于理想分形规则扩展的地图曲线模拟方法研究

针对地图目标中许多线状要素具有典型统计分形特征的性质,探讨了在理想分形规则基础上通过增加随机因子,从而根据分维数反过来模拟构建地图曲线的方法.     

福建中亚热带天然阔叶林理想结构探讨

根据典型林分结构的分析，以“近自然林业”理论为指导，提出福建中亚热带天然阔叶林理想结构的指标与标准，包括林层结构、乔木层物种多样性、灌木层中乔木幼树、林分基本蓄积量、材积按径阶分布、林分密度、株数按径阶分布、商品材树种结构等8个指标和各指标的具体标准，旨在为福建中亚热带天然阔叶林可持续经营提供基础依据，为异龄林理想结构的研究提供实例。     

Some thermodynamic criteria for river channel changes

Ｉ.ＩｎｔｒｏｄｕｃｔｉｏｎＡｒｉｖｅｒｃｈａｎｎｅｌｉｎｎａｔｕｒａｌｇｅｏｇｒａｐｈｉｃａｌｅｎｖｉｒｏｎｍｅｎｔｃｏｕｌｄｂｅｒｅｇａｒｄｅｄａｓａｎｏｐｅｎｇｅｏｇｒａｐｈｉｃａｌｓｙｓｔｅｍｂｅｃａｕｓｅｏｆｔｈｅｆｌｏｗｉｎｇｏｆｗａｔｅｒ.Ｔｈｅｒｅｗｉｌｌｃｏｎｔｉｎｕｅｔｏｏｃｃｕｒｅｘｃｈａｎｇｅｓｂｅｔｗｅｅｎｗａｔｅｒ,ｓｅｄｉｍｅｎｔ(ｍａｔｅｒｉａｌ)ａｎｄｔｈｅｉｒｋｉｎｅｔｉｃｅｎｅｒｇｙ,ｇｒａｖｉｔａｔｉｏｎａｌｐｏｔｅｎｔｉａｌｅｎｅｒｇｙ(ｅｎｅｒｇｙ),ａｎｄｔ…     

A PRELIMINARY STUDY ON QUATERNARY GLACIAL LANDFORMS IN MT.MA'AN

ＡＰＲＥＬＩＭＩＮＡＲＹＳＴＵＤＹＯＮＱＵＡＴＥＲＮＡＲＹＧＬＡＣＩＡＬＬＡＮＤＦＯＲＭＳＩＮＭＴ．ＭＡ’ＡＮＬｕｏＣｈｅｎｇｄｅ（罗成德）ＤｅｐａｒｔｍｅｎｔｏｆＧｅｏｇｒａｐｈｙ,ＬｅｓｈａｎＴｅａｃｈｅｒｓＣｏｌｅｇｅ,Ｌｅｓｈａｎ６１４００４...     

气候变暖使珠穆朗玛峰地区冰川处于退缩状态

９９７年中美联合考察队对珠穆朗玛峰绒布冰川考察期间,采用ＧＰＳ技术对冰川末端位置进行了测量．将其结果与１９６６年考察测量的位置对比得出,过去３０ａ间该冰川末端后退了１７０～２７０ｍ,平均年退缩量为５５～８７ｍ．由于目前气候仍在变暖,该冰川将继续保持退缩状态．     

水环境质量综合评价的多目标决策-理想区间法

对水环境质量综合评价中应用的多目标决策-理想点法进行了分析,认为实际上水环境质量评价标准是区间概念而非点的概念,因而传统的多目标决策-理想点法把评价标准处理成理想点存在一定缺陷。为了克服这种缺陷,提出了一种多目标决策-理想区间法(MODMIIM)。介绍了MODMIIM的原理,给出了它的构成方法,并把它应用到水环境质量综合评价中。MODMIIM与PP模型和神经网络法相比,简单、有效;与多目标决策理想点法相比,具有更大的适用性。MODMIIM可广泛应用于各种环境质量综合评价中。     

Remote sensing detection of glacier changes in Tianshan Mountains for the past 40 years

Both marginal fluctuation and areal change were used to detect the accurate dynamics of glacier change in the study area using Landsat MSS, ETM, SPOT HRV and topographic maps based on GIS. From 1963 to 1977, four of eight glaciers advanced, two of them retreated and another two kept stable, the glacier advanced generally. From 1977 to 1986, four of eight glaciers retreated and the others kept stable, but the retreated glaciers were those which advanced from 1963 to 1977. From 1986 to 2000, seven of eight glaciers retreated and only one glacier kept stable, the retreating velocity was 10-15 m/a. Glacier recession in this period became very fast and universal. From 1963 to 2000, the area of glaciers decreased from 5479.0 ha to 4795.4 ha, up to 12.5%. It is alarming that most of glacier retreats happened from 1986 to 2000. This was very consistent with change process of summer mean temperature in this region and global warming beginning in the 1980s.     

An analysis of short-term albedo variations at Haut Glacier d'Arolla, Switzerland

Abstract An analysis of ten‐minute albedo variations, recorded on Haut Glacier d'Arolla, Switzerland, over an 11 day period in the 1999 ablation season is presented. Most of the short‐term (<1 day) albedo variability is caused by variations in cloud cover, while solar zenith angle variations in the range 25° to 75° are of minor importance, probably due to the predominantly cloudy conditions during the measurement period. A new method to calculate albedo variation as a function of cloud cover is developed. Short‐term albedo variations are expressed by the ratio of the measured albedo to the daily albedo ‘minimum’, defined as the albedo under cloud‐free conditions when the solar zenith angle is <50°. Variations in cloud cover are quantified by the ratio of the measured incoming shortwave radiation flux to the theoretical direct‐beam shortwave radiation flux. The resulting relationships are successful, explaining 83% and 87–90% of short‐term albedo variation on snow and ice respectively, and may be incorporated into albedo parameterizations already used in numerical energy balance melt models, without the need for additional data. Simulations with a glacier energy balance model suggest that melt rates are overestimated by between 1 and 3 mm water equivalent per day if a correction is not made for the increase in albedo under cloudy conditions. Other causes of albedo variation are identified and evidence is found for the removal of fine debris from the glacier surface by intense rainfall, leading to an albedo increase. The implications for energy balance models and satellite‐derived albedo measurements are discussed.     

Recurring Jökulhlaups in Sälka, Northern Sweden

An ice‐dammed lake at the margin of the glacier Sälkaglaciären, in the Kebnekaise Mountains in northern Sweden, drained suddenly in July 2003 producing a flood with a measured peak discharge of 9.5±0.25 m³s^‐1. The total lake volume of 4.55×10⁵ million³ drained within two days. The hydrograph of this event is characteristic of a jökulhlaup controlled by a single basal ice tunnel that enlarges due to melting. The jökulhlaup had an exponential rise to a peak discharge, and following the peak, a very steep fall in discharge as the water supply to the drainage system ceased. A similar jökulhlaup was observed in August 1990 with an estimated release of 8.05×10⁵ m³ water. Jökulhlaups at Sälkaglaciären are recurring events and have been indirectly observed since the 1950s.