Status of the Recent Declining of Arctic Sea Ice Studies

In the past 30 years, a large-scale change occurred in the Arctic climatic system, which had never been observed before 1980s. At the same time, the Arctic sea ice experienced a special evolution with more and more rapidly dramatic declining. In this circumstance, the Arctic sea ice became a new focus of the Arctic research. The recent advancements about abrupt change of the Arctic sea ice are reviewed in this paper .The previous analyses have demonstrated the accelerated declining trend of Arctic sea ice extent in the past 30 years, based on in-situ and satellite-based observations of atmosphere, as well as the results of global and regional climate simulations. Especially in summer, the rate of decrease for the ice extents was above 10% per decade. In present paper, the evolution characteristics of the arctic sea ice and its possible cause are discussed in three aspects, i.e. the sea ice physical properties, the interaction process of sea ice, ocean and atmosphere and its response and feedback mechanism to global and arctic climate system.     

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Presolar grains in the CM2 chondrite Sutter's Mill

The Sutter's Mill (SM) carbonaceous chondrite is a regolith breccia, composed predominantly of CM2 clasts with varying degrees of aqueous alteration and thermal metamorphism. An investigation of presolar grains in four Sutter's Mill sections, SM43, SM51, SM2‐4, and SM18, was carried out using NanoSIMS ion mapping technique. A total of 37 C‐anomalous grains and one O‐anomalous grain have been identified, indicating an abundance of 63 ppm for presolar C‐anomalous grains and 2 ppm for presolar oxides. Thirty‐one silicon carbide (SiC), five carbonaceous grains, and one Al‐oxide (Al₂O₃) were confirmed based on their elemental compositions determined by C‐N‐Si and O‐Si‐Mg‐Al isotopic measurements. The overall abundance of SiC grains in Sutter's Mill (55 ppm) is consistent with those in other CM chondrites. The absence of presolar silicates in Sutter's Mill suggests that they were destroyed by aqueous alteration on the parent asteroid. Furthermore, SM2‐4 shows heterogeneous distributions of presolar SiC grains (12–54 ppm) in different matrix areas, indicating that the fine‐grained matrix clasts come from different sources, with various thermal histories, in the solar nebula.     

南极乔治王岛长城湾沿岸固定冰中有色层生态观察

自1988年11月至1989年3月,对南极乔治王岛的长城湾沿岸水域中的海洋生物和环境因子进行了调查,1988年11月20日在2号站采得的冰芯中部有一层约5cm的棕色层,而1988年11月17日、20日和26日在5号站采得的冰芯样中有二层棕色层。固定冰中叶绿素a浓度范围在2.55～56.8mg/m~3之间,而且大部分含量集中在海冰的中间层中,而不象其它海区如昭和、戴维斯、凯西和麦克默多等站,大部分叶绿素a集中在海冰的底部,造成这种差别的原因、可能是由于海冰的结构和形成过程不同所致。     

宁夏盐池县相对资源承载力

采用相对资源承载力的理论与研究方法,定量分析了盐池县8个乡镇相对资源承载力时空变化及差异特征,并对承载力匹配特征进行空间表达。结果表明：盐池县辖各乡镇相对于盐池县的综合人口承载力表现出严重超载、超载和富余3种不同的状态;相对自然资源经济承载力时空变化稳定,自然资源的经济潜力不断增大;相对草地资源牲畜承载力随时间推移不断递增且空间差异明显;依据3种承载力状态组合划分了不同的承载力匹配类型,并提出不同类型的可持续发展策略。本研究可为盐池县禁牧10年后各乡镇发展提供建议,并为“退牧还草”政策的继续实施提供理论支持。     

Winter Temperature Variability During Warming and Cooling Periods in the Conterminous United States, 1947–1992

Summary  Much literature has reported on the concept of increased surface temperature variability during cool periods, although analyses on temperature records have rendered inconsistent results. In addition, temperature variability during transition periods has been rarely investigated. This study examines temperature variability during wintertime cooling (1947–1977) and warming (1978–1992) periods for the conterminous United States to determine both whether temperature variability is different during warming or cooling periods, and whether the change in variability is supported by midtropospheric circulation conditions. Our results indicate that regions with high temperature variability are mostly found below the troughs in the midtropospheric pressure fields. The direction of change in temperature variability corresponding to cooling or warming conditions, however, varied spatially. For the southeastern and northeastern United States, winter temperatures were more variable during the cooling period than during the warming period, while the northern and central Great Plains had greater temperature variability during the warming period than the cooling period. Similar spatial patterns are also found for the changes in the variability of geopotential height fields. Such spatial patterns in the temperature and height variability during warming and cooling periods may be related to the dominant midtropospheric circulation patterns, such as the different phases of the Pacific-North American teleconnection pattern, and the El Ni?o/Southern Oscillation events. It is concluded that the response of interannual temperature variability to climatic changes is determined by the variation in circulation patterns, and therefore, not spatially uniform. Received September 26, 1996 Revised April 2, 1998     

城镇增长下的收缩：以武汉为例

首先从人口、经济、用地3个维度综合考察武汉市增长与收缩的全貌,并采用县区及街道2个尺度的数据定量描述了武汉市增长与收缩的特征与空间格局,发现武汉市下辖青山区、硚口区、汉阳区和蔡甸区存在局部较严重的收缩现象,空间上形成集聚,形态上呈“穿孔式”。进一步以青山区为案例,着重从资本视角探讨发生局部收缩的内在机制,发现其存在老龄化、少子化趋势,但局部收缩的主因是资本从产业部门的“逃逸”。     

塔里木河下游河岸带地下水埋深对生态输水的响应过程

为了解塔里木河下游生态输水量与地下水埋深多年响应变化过程,得出地下水埋深对生态输水的响应变化规律,以塔里木河下游英苏断面为研究区,运用定性与定量分析方法,综合考虑不同输水差异（包括零输水年即2008年、输水极少年即2009年、输水较多年2011年等）,对2000-2015年英苏断面1 050 m范围内地下水埋深数据进行了分析。结果表明：研究断面内地下水埋深在各年份总体呈现比较平稳的递减趋势,年内个别月具有较大的增幅,另外由于冻土消融等因素影响,地下水埋深在2~3月有一定的增幅;离河较近区域的地下水埋深变化对生态输水的响应具有时间同步性,而离河道较远地区的地下水埋深在响应时间上存在滞后性,本研究断面1 050 m范围内地下水埋深响应时间维持在1 a内;经过多年生态输水过程,英苏监测断面距离河道约750 m范围内地下水平均埋深维持在2~6 m范围内,基本达到植物生长所需地下水埋深水平;另外,综合分析研究断面多年输水引起的地下水位响应过程,为获得生态输水过程所带来的最大生态效益,生态输水不仅要保持一定的输水量,还要保持输水年周期的连续性。     

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