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

Elizabeth K. Thomas  Jason Szymanski  Jason P. Briner 《第四纪科学杂志》2010,25(2):146-161

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.  相似文献   

Introducing a transferable fishing day management regime for Pacific Island countries     

Steven Shanks 《Marine Policy》2010

On 1 December 2007, eight ‘Small Island Developing States’ in the Western and Central Pacific Ocean implemented a management regime restricting the total number of days fished by tuna purse seine vessels within their waters, commonly referred to as the Vessel Day Scheme (VDS). The VDS is seen as one component of management arrangements to reduce fishing mortality on bigeye and yellowfin tuna, constrain fishing effort, and increase the rate of return from access fees by Distant Water Fishing Nations.  相似文献   

磁尾宽频带静电噪声的一种新的激发机制          下载免费PDF全文

沐建林  濮祖荫  方正知 《地球物理学报》1988,31(6):613-621

本文提出了磁尾宽频带静电噪声强谱段的一种新的激发机制。在等离子体片边界层中存在着瞬时的局域性的晨昏电场。电子和离子对该电场的响应不同:在电场存在的区域内,电子作回旋漂移运动,而离子轨道在的时间尺度内可视为直线。由于等离子体片边界层中等离子体是非均匀的,这就导致了电荷分离的产生,从而可激发静电不稳定性。本文通过求解含电场的Vlasov方程,计算了由此产生的不稳定波的频率和增长率,考察了波矢方向。上述计算结果均与强谱段静电噪声的观测特征一致。  相似文献   

层状含水系统R—C电网络模拟方法     

谢剑飞 《水文地质工程地质》1993,20(2):42-43,57

本文论述了R-C电网络模型的基本原理及模拟装置,分析了不同类型的层状含水系统。根据榴似性原理,建立了不同类型的电网络模型。在此基础上,预测了内蒙古某露天煤矿的矿坑疏干涌水量,取得了比较满意的结果。  相似文献   

电偶源频率电磁测深中比值视电阻率和阻抗相位的联合反演   总被引：1，自引：0，他引：1  

林长佑  罗东山  吕福林  武玉霞 《物探与化探》1993,17(4):288-295

本文论述了电偶源频率电磁测深中,利用比值视电阻率和相应阻抗相位进行联合反演的必要性和可能的应用前景及具体实施方法。理论模型和实际观测资料的反演试验表明这一联合反演是可行和有效的,且明显地优于视电阻率和阻抗相位的单参量反演。  相似文献   

电偶源瞬变电磁测深一维全区视电阻率解释方法研究   总被引：4，自引：0，他引：4  

黄力军 《物探与化探》1995,19(5):391-397

本文从理论计算和野外实测资料处理两方面讨论了电偶源瞬变电磁测深─维全区视电阻率解释方法以及与之相关的实测数据预处理、磁场计算及─维磁场数值反演方法.  相似文献   

方差—协方差分量极大似然估计的通用公式   总被引：6，自引：1，他引：6  

於宗俦 《测绘学报》1994,23(1):6-13

本文由概括平差函数模型出发，按极大似然做估计原则导出了适用于所有平差函数模型的方差分量估计的通用公式，由Ｋ．Ｋｕｂｉｋ和Ｃ．Ｒ．Ｋｏｃｈ所导出的两个公式都是它的特例。  相似文献   

线性规划在徐州地下水资源开发中的应用   总被引：1，自引：0，他引：1  

陈爱光  陈国富 《地球科学》1985,(1)

本文从地下水系统的观点出发,对徐州地区中寒武统—中奥陶统碳酸盐岩地下水系统进行了分析。并应用线性规划的原理和方法对徐州市西郊四个水源地地下水进行了水文地质计算。在规定水位允许降深的约束条件下,求得至2000年,该区地下水最大开采量为14万米~3/天及各水源地相应取水量的最佳分配。文中采用特定条件图解法计算多边界、多主井抽水干扰影响的方法,具有通用意义。  相似文献   

Orographic effect on potential gradient     

Syed Nizamuddin 《Pure and Applied Geophysics》1984,122(1):86-88

Potential gradients were measured in the valley of the Simhachalam hills and near the top. They were found to be higher at the top than in the valley, where they increased in the forenoon. It was the reverse at the top of the hills. The valley winds were found to play an important role in the variation of potential gradient.  相似文献   

Preliminary　inquiry　into　the　causes　of　anomaly　increase　of　air　temperature　by　an　impending　earthquake   总被引：3，自引：0，他引：3  

徐秀登  徐向民  马升灯  骆高远 《地震学报(英文版)》1995,8(1):149-154

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