南海北部近岸海域5～6月微型硅藻

本文对南海北部近岸的南澳、海门、湛江、北海、海口、三亚等6个系样点的水样进行微型浮游植物（＜20μm)的叶绿素a含量测定,并对其微型硅藻（＜20μm)和小型硅藻（＞20μm)作计数、鉴定。结果表明,该区微型硅藻有50多种,其数量以海口最多。为84000个／dm^3;海门和江最少（500个／dm^2),文中描述了我国首次记录的8种双眉藻（Amphora).它们是Amphora castellata,A.coputata,A.cymbelloides,A.margaritifera,A.minima,A.mueeleri,A.reichardtiana和A.subacutiuscula。     

Assessment Methods for Sea-RelatedHazards in Coastal Areas

Italian legislation provides for hazardcontingency plans to be prepared by the regional,provincial and local authorities. Despite the extentof damage often caused on the Italian coasts by theaction of the sea, sea related hazards have so farbeen usually ignored; only recently a limited budgetin some provinces was allocated for the analysis ofrisks related to storm damage.The present paper reports on the proceduresand the techniques employed and tested within theframework of the provincial contingency plan onthe coast of the Salerno province in Italy (Figure 1).The work was mainly oriented to the evaluation ofthe potential damage that can be caused by the directaction of waves on coastal areas and on thepreparation of hazard maps. The methods and the datathat can be used to evaluate the risks are reviewed here,first by rapid examination of the wave fieldformation offshore and its transformation on shallowwater and then by considering the run-up on beachesand infrastructures; the paper is focussed inparticular on these latter problems, which – formsome point of view – are original and specific tocivil protection problems.     

苏北滨海平原全新世沉积物物源研究--元素地球化学与重矿物方法比较

运用元素地球化学与重矿物方法对苏北滨海平原全新世沉积物物源进行的比较研究表明,沉积物形成主要由长江与黄河提供物质来源,且又以黄河物源为主。全新世早期长江物质对本区影响范围大于黄河,黄河供给泥沙量较少,对本区影响主要在北部、中部地区。全新世最大海侵之后,黄河曾由苏北入海并携带了大量泥沙,其影响范围明显大于长江,长江仅由狭窄的汊道提供有限的物质而影响范围较小。最近２０００ 年来本区沉积物物源主要由黄河提供。分析表明元素地球化学方法在沉积物物源判别时,可有效的避免水动力因素影响,而相对重矿物方法取得较好的效果。     

浙闽沿海地区I型-A型复合花岗岩体的地球化学及成因

以鼓山－魁岐、青田和普陀山－桃花岛三个典型岩体为例,系统研究了浙闽沿海Ｉ型－Ａ型复合花岗岩体的地质和地球化学特征。研究结果表明：复合岩体中Ｉ型与Ａ型花岗岩在主量、微量和稀土元素特征上均存在明显变异。总体而言,Ａ型花岗岩较之Ｉ型花岗岩富硅、富碱、贫钙、镁、铝,并具偏高的Ｒｂ／Ｓｒ、Ｒｂ／Ｂａ、Ｇａ／Ａｌ和偏低的ＬＲＥＥ／ＨＲＥＥ比值及显著的铕负异常。两类花岗岩的Ｎｄ、Ｓｒ同位素组成均具有壳幔混熔岩浆的特点,但仍存在一定的变异。上述变异既有岩浆分异演化的影响,又有幔源岩浆卷入的贡献,在不同的复合岩体中起主导作用的因素各不相同。通过对岩石产出动力地质背景的全面分析,结合本区不同复合岩体中二类花岗岩具不同地球化学变异特点的地质事实,提出浙闽沿海Ｉ型－Ａ型复合花岗岩是区域构造应力、断裂构造、幔源岩浆卷入和岩浆分异演化多种因素综合作用的结果     

A STUDY ON LOW－LEVEL ATMOSPHERIC STRUCTURE ON THE SEASIDE BORDERS TO THE WEST OF HAIKOU

In this paper, the observed data of low-level wind and temperature collected from western outskirts of Haikou city, Hainan Island, are analysed. Mean boundary layer structure, generation and development of ground-level inversion and inner boundary layer on the coastal area of interest, which is in China,s northern tropical area, are analysed. It is found that an inner thermal boundary layer can be produced under intense insolation in both dry and rainy seasons, and the mixing layer on the coast is remarkably deeper than that of inland.     

夏季烟台—威海北部近海溶解氧浓度垂向分布的最小值

基于2020年夏季的大面航次观测数据,分析了烟台—威海北部海洋牧场及邻近海域海水溶解氧浓度垂向分布最小值（氧最小值层）的空间分布特征,并探讨了影响因素。从6月至8月,海水溶解氧浓度不断减小,垂向结构亦存在显著变化。海水溶解氧浓度垂向分布的最小值主要集中于7月的近岸海域,最小值大致从外海向近岸方向减小,其距离海底高度及与底层溶解氧浓度之差的绝对值均于双岛湾邻近海域为最大。海水溶解氧浓度垂向分布的最小值位于最强密度层结以下。但是海水溶解氧浓度垂向分布最小值的强度向北减小,而密度层结向北增大,两者的空间分布基本相反,说明密度层结抑制垂向湍流扩散可极大减少深层海水溶解氧的来源,是海水溶解氧浓度垂向分布最小值形成的必要条件,但不是主导因素。在海水溶解氧浓度垂向分布的最小值层,表观耗氧量存在垂向分布的最大值,大部分站点的pH存在垂向分布的最小值,说明局地增强、持续的生物地球化学耗氧是控制海水溶解氧浓度垂向分布最小值形成和空间分布的一个重要过程。研究结果表明氧最小值层是夏季烟台—威海北部近岸海水溶解氧垂向结构的典型特征之一。     

Sediment accumulation in embayments controlled by bathymetric slope and wave energy: Implications for beach formation and persistence

High energy, rocky coastlines often feature sandy beaches within headland‐bound embayments. Not all such embayments have beaches however, and beaches in embayments can be removed by storms and may subsequently reform. What dictates the presence or absence of an embayed beach and its resilience to storms? In this paper, we explore the effect of offshore slope and wind conditions on nearshore sediment transport within idealised embayments to give insight into nearshore sediment supplies. We use numerical simulations to show that sand can accumulate near shore if the offshore slope is >0.025 m/m, but only under persistent calm conditions. Our modelling also suggests that if sediment in an embayment with an offshore gradient steeper than 0.025 m/m is removed during a period of persistent stormy conditions, it will be unlikely to return in sub‐decadal timescales. In contrast, sediment located in embayments with shallower gradients can reform swiftly in both calm and stormy conditions. Our findings have wide implications for contemporary coastal engineering in the face of future global climate change, but also for Quaternary environmental reconstruction. Our simple method to predict beach stability based on slope can be used to interpret differing responses of embayments to periods of changing coastal storminess such as the medieval climate anomaly‐little ice age (MCA‐LIA) transition. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

On the exploration of a marine aquifer offshore Israel by long-offset transient electromagnetics

The existence of aquifers extending from land beneath the sea floor up to a distance of several kilometres has been observed and examined all over the world. The coastal aquifer of Israel is a heavily used groundwater reservoir which has to be constantly monitored to ensure the drinking water supply. Former land-based electromagnetic measurements show that it is, in several places, blocked to seawater intrusion and is consequently a candidate for submarine extension. Multicomponent long-offset transient electromagnetic measurements were carried out offshore on the coast of Israel. We deployed a 400-m-long grounded dipole as transmitter and several electric and magnetic receivers on the sea floor up to a distance of 4.8 km from the coast. Altogether, we deployed 8 transmitter positions and received data sets at 14 receiver stations onshore and offshore, with offsets of mostly 400 and 800 m. In this paper, we present the survey and 1D Occam and Marquardt inversions of the offshore horizontal electric components in the broadside and inline configuration. In addition, the vertical magnetic component in the broadside position is also considered. Only single inversions, both single offset and single component, were used to detect the aquifer under sea sediments. We prove the submarine existence of the Israeli coastal aquifer up to a distance to the coast of approximately 3.2 to 3.6 km using all measured long-offset transient electromagnetic components. In addition, we present modelling studies with synthetic data derived from a subsurface model adjusted to our survey area with very shallow water from 10 to 50 m. As part of the planning before the survey, a parameter study of the expected subsurface, the examination of the airwave phenomenon and the justification for our 1D inversion strategy are shown. More detailed eigen parameter analyses are added to explain the measured data.     

Insights of long-term geomorphological evolution of coastal landscapes in hot-spot oceanic islands

The Canary Islands form a volcanic archipelago in which a west–east (W–E) chain of progressively older and less active islands can be observed. In the Canary Islands, unlike most hot-spot archipelagos, certain geodynamic peculiarities have promoted longer periods of island survival, exceeding 20 Myr. This factor makes these islands a suitable context for this work, which aims to analyze extensively the coastal geomorphic structure on islands with different development states. For this, three islands in different volcanic phases were selected: La Palma (1.8 Myr), Gran Canaria (14.5 Myr) and Fuerteventura (22.6 Myr). An ad hoc landform-based hierarchical taxonomy was designed to analyze the coastal geomorphic structure of the three islands. Based on a multi-sourced analysis in geographic information system (GIS) and field recognition, a comprehensive cartographic database was collected using the coastline data-storing (CDS) method as a feature abundance proxy. Three different aspects of the geomorphological structure were compared and related between the islands: (i) composition, (ii) abundance and (iii) diversity. Through their comparison, we attempt to explore geomorphological aspects of coastal evolution over geological spatiotemporal scales. Composition was explored analyzing the distribution of the feature's longshore frequencies (p). Abundance, by metrics of local abundance (N_∩) and whole density (N_U). Diversity, through four indices: normalized richness (S) and Margalef index (M) to estimate richness; Simpson index (D) and Shannon index (H’) to estimate evenness. We identified a systematic transformation in the dominant landform composition and a systematic trend in increasing geomorphological abundance and diversity from younger to older islands. The results show a long-term structural pattern defined by the increase in coastal geomorphic complexity (abundance and diversity) over geological time, as the coasts evolve from predominantly rocky-erosive to increasingly clastic-depositional environments. This long-term geomorphological pattern may be a general aspect of hot-spot island archipelagos, which can bring a new perspective to the knowledge of their coastal evolution. © 2018 John Wiley & Sons, Ltd.     

High-resolution optical dating of Late Holocene storm surge deposits – a showcase from Schokland (Noordoostpolder,the Netherlands)

Storm surges have a major impact on land use and human habitation in coastal regions. Our knowledge of this impact can be improved by correlating long-term historical storm records with sedimentary evidence of storm surges, but so far few studies have applied such an approach. Here we apply, for the first time, state-of-the-art optically stimulating luminescence (OSL) methods to obtain high-resolution age information on a sequence of Late Holocene storm surge deposits. By combining this chronological framework of storm surges with other reconstruction methods, we investigate the storm surge impact on the former island Schokland, located in a former inlet of the North Sea (central Netherlands).During the Late Holocene, Schokland transformed from a peat area that gradually inundated (~800 CE) via an island in a marginal marine environment (~1600 CE) to a land-locked island in the reclaimed Province of Flevoland (1942 CE). These transitions are recorded in the sediment archive of the island, consisting of silty clay with sandy intervals deposited during storm surges. A series of ten quartz OSL ages, obtained using best-practice methods to deal with incomplete resetting of the OSL signal and dose rate heterogeneity, reveal two periods of storm surge deposition, around 1600 CE and between 1742 and 1822 CE. Historical sources indicate that major storm surges hit Schokland during these periods. Laboratory analyses (thermogravimetry, grain-size, foraminifera, bivalves and ostracods) corroborates the existence of the two sets of storm surge deposits within the clay sequence. Our study sets a benchmark for obtaining robust depositional age constraints from storm surge sediments, and demonstrates the great potential of modern OSL methods to contribute to improved assessment of storm surge risk. © 2018 John Wiley & Sons, Ltd.