Holocene coastal environmental changes on the periphery of an area of glacio‐isostatic uplift: an example from Scapa Bay,Orkney, UK

The first detailed investigation of a deep, coastal, sedimentary basin in Orkney reveals a complex Holocene history of back‐barrier morphodynamics. At Scapa Bay, the sea flooded a freshwater marsh after ca. 9400 yr BP at ca. ?5.4 m OD. Before ca. 7800 BP, abundant sediment from nearby cliffs was mobilised inland into a series of gravel barriers across the valley mouth. By ca. 7500 BP, direct marine influence was restricted in the back‐barrier area, although saltmarsh persisted until ca. 5900 BP. By then, at least four gravel ridges had enclosed the backing lagoon, where freshwater inputs became dominant. As terrestrial sediments filled the basin, another freshwater marsh developed. The multiple barrier complex demonstrates progradation resulting from continuous sediment supply in a sheltered embayment. The progressively rising height of the barrier crests seawards probably resulted from a combination of factors such as barrier morphodynamics, increased storminess and long‐term rising relative sea levels. The dominant vegetation surrounding Scapa Bay changed from open grassland to scrub ca. 9400 BP, then to deciduous woodland ca. 7800 BP, and to dwarf‐shrub heath ca. 2600 BP, the latter probably a response to a combination of climate change and human activity. Copyright © 2007 John Wiley & Sons, Ltd.     

基于GAM模型分析夏秋季南奥克尼群岛南极磷虾渔场时空分布及与环境因子之间的关系

基于中国南极磷虾渔业科学观察员收集的数据,利用广义可加模型（GAM）,对2009—2010渔季和2010—2011渔季夏秋季南奥克尼群岛周边水域南极磷虾渔场时空分布及其与表温和海况之间的关系进行了研究。结果表明,GAM模型对单位捕捞努力量渔获量（CPUE）总偏差解释率为41.78%,其中贡献最大的为月份,贡献率为15.53%;奥克尼群岛水域CPUE分布模式均有明显的月份差异。1月份平均CPUE值最低,而4月份平均CPUE值最高,各月份平均CPUE存在显著性差异。渔场主要集中在60°12′—60°30′S,45°30′—47°30′W。南极磷虾作业渔场的适宜海水表温范围为0.1—1.8℃,最适表温范围为0.5—1.5℃。各海况等级间及不同渔船的平均CPUE均存在显著性差异。逐步GAM模型分析结果表明,影响CPUE的因子按重要性从大到小依次为月份、渔船、经度、海表温度、纬度和海况。     

A high-resolution tephrostratigraphy from Quoyloo Meadow,Orkney, Scotland: Implications for the tephrostratigraphy of NW Europe during the Last Glacial-Interglacial Transition

Macro- and crypto-tephra layers deposited in European climate archives during the Last Glacial-Interglacial Transition (LGIT ca. 16–8 ka) have become increasingly important as a means to robustly correlate palaeoclimate records, and to test the spatial and temporal synchronicity of climatic transitions. However, correlations between climate archives are currently limited by the number of tephra-linkages that can be made. This disparity in the observed distributions of tephras may lie with methodological limitations relating to the resolution of cryptotephra refinement within palaeoclimate records. Here we present new data from Quoyloo Meadow, Orkney Mainland, Scotland, where nine tephra horizons and ten chemically distinct tephra populations have been identified and correlated to known eruptions during the LGIT. Three of the tephras; the Hässeldalen, Hovsdalur and the Fosen are characterised and placed into a reliable tephrostratigraphy for the first time in the British Isles. The detection of new tephra layers in this case is thought to reflect modifications to the sampling approach applied here. The resulting tephrostratigraphy is used to produce an age model with centennial-scale precision, providing new age estimates for three poorly dated tephras. The chronology rivals the output of more traditionally dated radiocarbon chronologies, and illustrates the potential for tephra to develop robust age-depth models for carbonate sequences.     

Mid‐Holocene environmental changes in the Bay of Skaill,Mainland Orkney,Scotland: an integrated geomorphological,sedimentological and stratigraphical study

A detailed multidisciplinary investigation of intertidal freshwater sediments exposed in the north of the Bay of Skaill, Mainland Orkney, Scotland, have revealed a complex sedimentary sequence. This provided evidence for dynamic coastal environmental changes in the area since the mid‐Holocene. Freshwater ponds developed on glacial sediments ca. 6550 ± 80 yr BP (cal. bc 5590–5305). From ca. 6120 ± 70 yr BP (cal. bc 5040–4855), these were infilled by blown sand from the distal edge of a dune ridge located to the west. Thereafter, a series of sand‐blow events alternating with periods of quiescence occurred until ca. 4410 ± 60 yr BP (cal. bc 3325–2900). Between ca. 5240 ± 160 and 4660 ± 80 yr BP (cal. bc 4370–3115), pollen and charcoal records show evidence of anthropogenic activities, associated with the nearby Neolithic settlement of Skara Brae. Agriculture was probably affected by recurrent sand movement and widespread deposition of calcium carbonate in the hinterland of the bay. Machair development between ca. 6100 and 5000 yr BP (cal. bc 5235–3540) corresponds to a mid‐Holocene phase of dune formation recorded elsewhere in northwest Europe. The more recent and progressive formation of the bay has probably been related to increasing external forcing via storminess, long‐term relative sea‐level change and sediment starvation within this exposed environment. Copyright © 2000 John Wiley & Sons, Ltd.     

2011/2012年夏季南极半岛北端周边海域的水团与水交换

通过分析中国第28次南极考察队于2011年12月至2012年1月在南极半岛北端周边海域获得的5条断面CTD观测温盐剖面数据, 进一步认识了该海域的水团组成和水交换情况。观测区域南部的鲍威尔海盆及周边深海区, 可以观测到保持了较显著高温核心的威德尔深层水、密度大于28.27 kg·m^-3的威德尔海深层水以及温度低于－0.7 ℃的威德尔海底层水。周边陆坡上的威德尔海深层水则表现出因与周围水体发生混合而核心性质减弱的特征。在菲利普海岭、埃斯佩里兹海槽等复杂地形处, 观测到的对应于威德尔海深层水深度的混合与热盐入侵过程更为显著。威德尔海深层水能够到达南设得兰群岛以北的象岛东北面海域, 但是高盐核心加深至1 500 db, 并上覆温度基本不变但盐度随深度显著增大的较暖水体, 表明威德尔海深层水经历了不同的路径和变性过程。布兰斯菲尔德海峡中没有绕极深层水大规模侵入的迹象, 但是乔治王岛周边陆架上可能存在涡旋等中尺度过程, 会影响德雷克海峡与布兰斯菲尔德海峡之间的水交换。     

2009/2010—2011/2012年度夏秋季南奥克尼群岛水域南极磷虾捕捞群体年龄结构时空变化

利用南极磷虾渔业科学观察员收集的南极磷虾生物学数据,在将研究区域划分成60'×30'精细尺度单元的基础上,分析了南奥克尼群岛南极磷虾种群捕捞群体年龄结构的时空变化。结果表明,2009/2010年度,南极磷虾体长范围为33.2—69.0 mm,平均体长为51.8 mm,优势体长组为52—60 mm(52.3%),另在44—48 mm有一个次峰区;2010/2011年度,体长范围为22.9—59.3 mm,平均体长为44.5 mm,优势体长组为42—50 mm(56.8%);2011/2012年度,体长范围为18.5—59.4 mm,平均体长为41.7 mm,优势体长组为36—46 mm(67.3%)。三个年度间南极磷虾体长频次分布呈显著性差异(p0.001),且不具相似性(PSI=41.25—73.42)。2009/2010—2011/2012年度各旬别磷虾体长组可分成3个组,其中2011年2月上旬和2012年3月中旬可划分为一组,2010年1月下旬至2月中旬以及2011年2月中旬可归为一组,这几个体长组均呈双峰分布,其他的体长组划归为一组。1+和2+龄虾大多出现在离南奥克尼群岛最近的水域,而离南奥克尼群岛较远的单元中则多为4+龄以上的磷虾个体。     

南极南奥克尼群岛西部水域南极电灯鱼生物学

根据2010—2012年南半球夏季南极南奥克尼群岛西部水域开展的资源调查期间收集的数据,本研究对南极电灯鱼的基础生物学,包括体长（SL）、纯重（DW）、体长-体重关系、性成熟度和性腺指数及摄食强度进行了分析。结果表明：（1）南极电灯鱼体长范围为6.3—8.8cm,平均体长为7.51±0.03cm（平均值±95%置信区间）;体重范围为3.46—10.13g,平均体重为5.96±0.08g;纯重范围为3.11—8.69g,平均纯重为5.17±0.07g。（2）体重与纯重关系为DW=0.8497TW+0.1623（R2=0.9502）,体长与纯重关系为FL=0.0238DW2.6695。（3）调查期间,南极电灯鱼性成熟度处于Ⅰ—Ⅳ级,未发现有Ⅴ和Ⅵ级的个体出现。（4）摄食强度随体长的增加而有所加强,空胃与1级所占比例随体长增加而下降。