Spatial and temporal variability of coastal storms in the North Atlantic Basin

Over the past three to four decades, there has been a growing awareness of the important controls exerted by large-scale meteorological events on coastal systems. For example, definitive links are being established between short-term (timescales of 5–10 years) beach dynamics and storm frequency. This paper assesses temporal variability of coastal storms (both tropical and extratropical) and the wave climatology in the North Atlantic Basin (NAB), including the Gulf of Mexico. With both storm types, the empirical record shows decadal scale variability, but neither demonstrates highly significant trends that can be linked conclusively to natural or anthropogenic factors. Tropical storm frequencies have declined over the past two or three decades, which is perhaps related to recent intense and prolonged El Niños. Some forecasts predict higher frequencies of tropical storms like that experienced from the 1920s to the 1960s to occur in coming decades. Results from general circulation models (GCMs) suggest that overall frequencies of tropical storms could decrease slightly, but that there is potential for the generation of more intense hurricanes. These data have important implications for the short-term evolution of coastal systems.

There is strong suggestion that extratropical systems have declined overall over the past 50–100 years, but that there is an increase in frequency of very powerful storms, especially at higher latitudes. Both ENSO and the North Atlantic Oscillation (NAO) are shown to have associations with frequencies and tracking of these systems. These empirical results are in general agreement with GCM forecasts under global warming scenarios. Analyses of wave climatology in the NAB show that the last two to three decades have been rougher at high latitudes than several decades prior, but this more recent sea state is similar to conditions from about 100 years ago. The recent roughness at sea seems to be related to high NAO index values, which are also expected to increase with global warming. Thus, when coupled to an anticipated continued rise in global sea level, this trend will likely result in increasing loss of sediment from the beach-nearshore system resulting in widespread coastal erosion.     

北极海冰变率的独特模式及其与大气强迫的关系

The spatial structure of the Arctic sea ice concentration(SIC) variability and the connection to atmospheric as well as radiative forcing during winter and summer for the 1979–2017 period are investigated. The interannual variability with different spatial characteristics of SIC in summer and winter is extracted using the empirical orthogonal function(EOF) analysis. The present study confirms that the atmospheric circulation has a strong influence on the SIC through both dynamic and thermodynamic processes, as the heat flux anomalies in summer are radiatively forced while those in winter contain both radiative and "circulation-induced" components. Thus,atmospheric fluctuations have an explicit and extensive influence to the SIC through complex mechanisms during both seasons. Moreover, analysis of a variety of atmospheric variables indicates that the primary mechanism about specific regional SIC patterns in Arctic marginal seas are different with special characteristics.     

Flow of Canadian basin deep water in the Western Eurasian Basin of the Arctic Ocean

The LOMROG 2007 expedition targeted the previously unexplored southern part of the Lomonosov Ridge north of Greenland together with a section from the Morris Jesup Rise to Gakkel Ridge. The oceanographic data show that Canadian Basin Deep Water (CBDW) passes the Lomonosov Ridge in the area of the Intra Basin close to the North Pole and then continues along the ridge towards Greenland and further along its northernmost continental slope. The CBDW is clearly evident as a salinity maximum and oxygen minimum at a depth of about 2000 m. The cross-slope sections at the Amundsen Basin side of the Lomonosov Ridge and further south at the Morris Jesup Rise show a sharp frontal structure higher up in the water column between Makarov Basin water and Amundsen Basin water. The frontal structure continues upward into the Atlantic Water up to a depth of about 300 m. The observed water mass division at levels well above the ridge crest indicates a strong topographic steering of the flow and that different water masses tend to pass the ridge guided by ridge-crossing isobaths at local topographic heights and depressions. A rough scaling analysis shows that the extremely steep and sharply turning bathymetry of the Morris Jesup Rise may force the boundary current to separate and generate deep eddies.     

Dominant climate factors influencing the Arctic runoff and association between the Arctic runoff and sea ice

By using the Arctic runoff data from R-ArcticNET V4.0 and ArcticRIMS, trends of four major rivers flowing into the Arctic Ocean, whose climate factor plays an important role in determining the variability of the Arctic runoff, are investigated. The results show that for the past 30 years, the trend of the Arctic runoff is seasonally dependent. There is a significant trend in spring and winter and a significant decreasing trend in summer, leading to the reduced seasonal cycle. In spring, surface air temperature is the dominant factor influencing the four rivers. In summer, precipitation is the most important factor for Lena and Mackenzie, while snow cover is the most important factor for Yenisei and Ob. For Mackenzie, atmospheric circulation does play an important role for all the seasons, which is not the case for the Eurasian rivers. The authors further discuss the relationships between the Arctic runoff and sea ice. Significant negative correlation is found at the mouth of the rivers into the Arctic Ocean in spring, while significant positive correlation is observed just at the north of the mouths of the rivers into the Arctic in summer. In addition, each river has different relationship with sea ice in the eastern Greenland Sea.     

Dominant climate factors influencing the Arctic runoff and association between the Arctic runoff and sea ice

介绍了星载雷达波谱仪的观测原理及误差分析模型,并在Hauser等提出的SWIM(sea wave investigation and monitoring by satellite)的基础上分析了波谱仪反演海浪谱的波长分辨率和角度分辨率。为了减小反演调制谱的波动,在数据处理过程中时域和波数域相邻单元的平均个数分别为10和8个。系统在不同的模式下工作,为了获取20°的角度分辨率,对调制谱平均次数分别取3次(模式1)、7次(模式2)、10次(模式3)。使用解析法和仿真法分析了SWIM工作在模式2时海浪谱观测的能量误差,两种方法的结果一致。对于给定的海浪条件,能量误差小于20%。     

黄海、渤海铅-210沉积速率的分布特征及其影响因素

对黄海、渤海17个箱式柱样进行了210Pb放射性活度测定,计算了近百年来210Pb沉积速率,并结合前人资料对黄海、渤海区210Pb沉积速率的空间分布特征及其影响因素进行探讨,结果表明,黄河口附近站位沉积速率最高(＞2 cm/a),而在渤海中部、渤海湾以及山东半岛沿岸的站位沉积速率较小(≈0.5 cm/a),部分站位沉积...     

Photogrammetric Bathymetry for the Canadian Arctic

Abstract

Remote sensing is becoming common in the estimation of bathymetry for navigational charting through a process known as Satellite Derived Bathymetry (SDB). Most SDB techniques currently used by hydrographic offices employ an empirical approach, requiring the use of in-situ data to calibrate a relationship between spectral information and coincident depths. This article reports on a multi-site test of an alternative SDB method which uses photogrammetry to extract depths from stereo WorldView-2 imagery. In areas with heterogeneous seafloors, the empirical approach faces difficulties in establishing the relationship between colour and depth, while the photogrammetric approach uses the contrasting seafloor features for triangulation. Additionally, the photogrammetric method may be applied in areas lacking previous survey data. Five study areas in Nunavut, Canada were selected to test the robustness of the method in different environments and under different imaging conditions. Study areas were (with resulting RMSE/Bias given in metres) Coral Harbour (0.84/?0.47), Cambridge Bay (1.16/?0.15), Queen Maud Gulf (0.97/0.06), Arviat (0.99/?0.009), and Frobisher Bay, where extraction largely failed due to environmental conditions. Accuracies demonstrated here are similar to those seen using the empirical approach, suggesting that these two methods may be used in conjunction, each applied to regions where they are better suited.     

北极王湾2010年夏季水体营养盐分布及影响因素

王湾海域位于北极斯瓦尔巴群岛西北侧,其水体特征主要受到北极冰川与大西洋的共同影响。为了研究冰川融水与大西洋水对王湾营养盐分布以及生态系统的影响,在2010年夏季黄河站考察期间,对王湾海水与地表径流进行采样分析,并测定了营养盐和叶绿素a。结果表明:2010年夏季王湾是大西洋水影响较弱的年份,以低温低盐高营养盐的本地变异水为主导。2010年7月王湾水体可以划分为4个水团,表层水(SW)、中层变异水(TIW)、本地变异水(TLW)和大西洋变异水(TAW),其中,表层水与中层变异水营养盐浓度较低,随着深度增加,本地变异水与大西洋变异水营养盐浓度都较高。大西洋变异水主要影响200m以深水柱,其营养盐浓度低于本地变异水影响的底部值,本地变异水中营养盐浓度的增加主要来自于颗粒物中营养盐的再生。表层水主要来源于地表径流与冰川融水,这些淡水输入与浮游植物的初级生产作用共同决定了表层水的营养盐浓度水平及结构。本地变异水中在水深100m上下出现的铵盐高值可能与浮游动物和/或微生物的代谢过程有关。     

Morphogenetic classification of the Arctic coastal zone

Arctic coastal evolution is the result of interactions between exogenic and endogenic processes. In the arctic region, this evolution differs from that in other areas of the worlds oceans as a result of interactions between modern wave and ice factors, and the influences of glaciations and large-scale sea level changes in the past. Geologic structure, origin and development determine contemporary relief morphology. Morphology appears to be the most significant relief characteristic, but it is controlled by a set of interactive processes active over long periods. Our approach, in which a multitude of interacting factors are simultaneously analyzed and determined, could be called morphogenetic. We consider marine coasts and offshore zones (shelf) as a unit, and providing a general explanation for their evolution. The classification presented here is based upon the general approach given in the Science and Implementation Plan of Arctic Coastal Dynamics (ACD), a project of the International Arctic Science Committee and the International Permafrost Association. Our classification extends beyond the morphological ACD classification to include a morphogenetic classification.     

Modelling coastal connectivity in a Western Boundary Current: Seasonal and inter-annual variability

Understanding the transport and distribution of marine larvae by ocean currents is one of the key goals of population ecology. Here we investigate circulation in the East Australian Current (EAC) and its impact on the transport of larvae and coastal connectivity. A series of Lagrangian particle trajectory experiments are conducted in summer and winter from 1992-2006 which enables us to investigate seasonal and inter-annual variability. We also estimate a mean connectivity state from the average of each of the individual realisations. Connectivity patterns are related to the movement of five individual larval species (two tropical, two temperate and one invasive species) and are found to be in qualitative agreement with historical distribution patterns found along the coast of SE Australia.We use a configuration of the Princeton Ocean Model to investigate physical processes in the ocean along the coast of SE Australia where the circulation is dominated by the EAC, a vigorous western boundary current. We assimilate hydrographic fields from a ∼10?\km global analysis into a ∼3?\km resolution continental shelf model to create a high-resolution hindcast of ocean state for each summer and winter from 1992-2006. Particles are released along the coast of SE Australia, and at various isobaths across the shelf (25-1000 m) over timescales ranging from 10-90 days. Upstream of the EAC separation point across-shelf release location dominates the particle trajectory length scales, whereas seasonality dominates in the southern half of the domain, downstream of the separation point.Lagrangian probability density functions show dispersion pathways vary with release latitude, distance offshore and the timescale of dispersion. Northern (southern) release sites are typified by maximum (minimum) dispersal pathways. Offshore release distance also plays a role having the greatest impact at the mid-latitude release sites. Maximum alongshore dispersion occurs at the mid-latitude release sites such as Sydney. Seasonal variability is also greatest at mid-latitudes, associated with variations in the separation point of the EAC. Climatic variations such as El Niño and La Niña are also shown to play a role in dictating the connectivity patterns. La Niña periods have a tendency to increase summer time connectivity (particularly with offshore release sites) while El Niño periods are shown to increase winter connectivity.The EAC acts as a barrier to the onshore movement of particles offshore, which impacts on the connectivity of offshore release sites. Consequentially particles released inshore of the EAC jet exhibit a greater coastal connectivity than those released offshore of the EAC front. The separation point of the EAC also dictates connectivity with more sites being connected (with lower concentration) downstream of the separation point of the EAC. These results can provide a useful guide to the potential connectivity of marine populations, or the spread of invasive pests (via ballast water or release of propagules from established populations).     

Late Holocene paleoceanography and climate variability over the Mackenzie Slope (Beaufort Sea,Canadian Arctic)

Late Holocene paleoceanography and climate variability of the Southeastern Beaufort Sea (Canadian Arctic) have been investigated on the basis of sedimentary cores collected over the Mackenzie Slope. Piston, trigger and box cores were sampled at station 803 in 2004 aboard the CCGS Amundsen at 218 m water depth. The chronology of the piston core is constrained by 4 AMS-¹⁴C dates, as the sedimentation rate in the box core is assessed from ²¹⁰Pb data. We obtain a continuous composite sequence covering the last 4600 years, with a sedimentation rate of ~ 140 cm.kyr^? 1. Transfer functions (modern analogue technique) based on dinoflagellate cyst (dinocyst) assemblages were used to reconstruct the evolution of sea-surface conditions over the time period covered by the cores.Palynological data reveal that dinocyst assemblages are dominated by Operculodinium centrocarpum sensu lato (mean of 43.3%) throughout the core, with the accompanying taxa Brigantedinium spp. (19.6%), Islandinium minutum (15.6%) and cysts of Pentapharsodinium dalei (13.7%). Four zones have been established on the basis of dinocyst relative abundances. Dinocyst assemblage zone 1 (D1), from 4600 to 2700 cal years BP, is dominated by O. centrocarpum (mean of 49.0%). In zone D2 (2700–1500 cal years BP), the relative abundances of O. centrocarpum decrease (34.4%) in favour of the opportunistic, heterotrophic taxa Brigantedinium spp. (28.8%) and cysts of Polykrikos sp. var. arctic/quadratus (2.8%). Dinocyst zone D3 (1500–30 cal years BP or 450–1920 AD) is characterised by the high relative abundance of the peridinioid taxa I. minutum (19.9%). The last zone (D4), spanning from 1920 to 2004 AD, is again dominated by O. centrocarpum (44.5%), and shows low relative abundances of Brigantedinium spp. and cf. Echinidinium karaense.Quantitative reconstructions of past sea-surface parameters (August sea-surface temperature: SST, August sea-surface salinity: SSS, and duration of sea-ice cover) indicate relatively stable conditions over the last 4.6 kyr, with episodic cooling events (SST of ~ 1.5 °C below the modern value of 6 °C) that took place between 700 and 1820 AD. We associate the last and the longest of these cooling events (1560–1820 AD) with the Little Ice Age. Reconstructed SSS shows decadal oscillations since 1920 AD that we tentatively associate with the accumulation of freshwater by the Beaufort Gyre and the subsequent Great Salinity Anomalies. Our data suggest that similar salinity anomalies could have occurred ca. 1860 and 1790 AD.Stable isotopic data show a slight increase in δ¹³C values (from ~?27.1‰ at the base to ~?25.8‰ at the top) over the last 4.6 kyr that we associate with the gradual increase in atmospheric CO₂ concentration as recorded by Antarctic ice cores. Variations in the δ¹⁵N profile suggest variations in Pacific water influence from 4600 to ~ 1300 cal years BP, associated with centennial scale shifts of the Arctic Oscillation phases.     

Spatial patterns of primary production on the shelf, slope and basin of the Western Arctic in 2002

In the spring and summer of 2002 primary production in the Chukchi Sea was measured, using ¹⁴C uptake experiments. Our cruise track encompassed the shelf and continental slope area of the Chukchi and Beaufort Seas progressing into deep water over the Canada Basin. The study area experienced upwards of 90% ice cover during the spring, with ice retreating into the basin during the summer. Production in the spring was light-limited due to ice cover, with average euphotic zone production rates of <0.3 g C m⁻² d⁻¹. Values of 8 g C m⁻² d⁻¹ were observed in association with surface bloom conditions during the initial ice breakup. Considerable nutrient reduction in the surface waters took place between the spring and summer cruise, and although not observed, this was attributed to a spring bloom. Decreased ice cover and increased clarity of surface waters in the summer allowed greater light penetration. The highest rates of production during the second cruise were found at 25–30 m, coincident with the top of the nutricline. Daily euphotic zone productivity in the summer averaged 0.78 g C m⁻² d⁻¹ on the shelf and 0.32 g C m⁻² d⁻¹ on the edge of the Canada basin. These data provide an estimated annual production of 90 g C m⁻² yr⁻¹ in the study area.     

Electronic atlas of the Russian Arctic coastal zone

A set of digital maps including geology, Quaternary sediments, landscapes, engineering-geological, vegetation, geocryological and the series of regional sources have been selected to characterize the Russian Arctic coast. Based on this data, new maps of engineering geocryological zoning and zoning of the coast with respect to the intensity of exogenous geological processes and risk of technogenic impacts have been generated at the scales of 1:4,000,000–1:8,000,000. These maps are a tool to assess the impact of industry on the Arctic coast of the country.     

闽台海岸带生境质量时空演变及其影响因素

快速城镇化、工业化背景下对海岸带生境质量进行评估,揭示影响生境变化的关键驱动因子,对于海岸带生态可持续发展具有重要意义。本研究以福建东海岸和台湾西海岸（以下合称闽台海岸带）为研究对象,借助1990年、2000年、2010年、2020年的土地利用以及社会经济数据,运用InVEST模型及地理探测器分析土地利用变化下生境质量的时空演变特征及其影响因素,为城市生态空间优化提供可靠的理论依据。结果表明：（1）1990—2020年两岸土地利用变化以建设用地的增长及耕地的减少为主要特征。建设用地2000—2010年面积增长最多,年均增长5.66%。耕地作为建设用地面积最大转入来源,面积共减少1781?km2,年均减少2.55%。土地变化福建东海岸大于台湾西海岸。（2）1990—2020年闽台海岸带生境质量均值为0.82,总体生态质量良好,但呈下降趋势。2000—2010年两岸低等级生境面积增长最快,2010年后增长速度趋缓。生态用地向非生态用地的转移对生境退化的贡献率超过70%。（3）夜间灯光指数、人口密度、GDP、高程、坡度为影响生境质量变化的主要因素,30年间主导因素由地形因素变为社会经济因素。研究为闽台沿海地区陆海土地资源管理提供科学依据,对区域协同发展具有重要意义。     

Limits and barriers to adaptation to climate variability and change in Bangladeshi coastal fishing communities

Limits and barriers to adaptation restrict people’s ability to address the negative impacts of climate change or manage risks in a way that maximises their wellbeing. There is a lack of evidence of this on small-scale fishing communities in developing countries. This study identifies and characterises limits and barriers to adaptation of fishing activities to cyclones and examines interactions between them in two fishing communities in Bangladesh, using household questionnaires, oral history interviews, vulnerability matrices and focus group discussions. The limits include physical characteristics of climate and sea like higher frequency and duration of cyclones, and hidden sandbars. Barriers include technologically poor boats, inaccurate weather forecast, poor radio signal, lack of access to credit, low incomes, underestimation of cyclone occurrence, coercion of fishermen by the boat owners and captains, lack of education, skills and livelihood alternatives, unfavourable credit schemes, lack of enforcement of fishing regulations and maritime laws, and lack of access to fish markets. These local and wider scale factors interact in complex ways and constrain completion of fishing trips, coping with cyclones at sea, safe return of boats from sea, timely responses to cyclones and livelihood diversification. The findings indicate a need for further detailed research into the determinants and implications of such limits and barriers, in order to move towards an improved characterisation of adaptation and to identify most suitable means to overcome the limits and barriers.     

Microzooplankton grazing impact in the Western Arctic Ocean

Microzooplankton grazing impact on phytoplankton was assessed using the Landry–Hassett dilution technique in the Western Arctic Ocean during spring and summer 2002 and 2004. Forty experiments were completed in a region encompassing productive shelf regions of the Chukchi Sea, mesotrophic slope regions of the Beaufort Sea off the North Slope of Alaska, and oligotrophic deep-water sites in the Canada Basin. A variety of conditions were encountered, from heavy sea-ice cover during both spring cruises, moderate sea-ice cover during summer of 2002, and light to no sea ice during summer of 2004, with a concomitant range of trophic conditions, from low chlorophyll-a (Chl-a; <0.5 μg L⁻¹) during heavy ice cover in spring and in the open basin, to late spring and summer shelf and slope open-water diatom blooms with Chl-a >5 μg L⁻¹. The microzooplankton community was dominated by large naked ciliates and heterotrophic gymnodinoid dinoflagellates. Significant, but low, rates of microzooplankton herbivory were found in half of the experiments. The maximum grazing rate was 0.16 d⁻¹ and average grazing rate, including experiments with no significant grazing, was 0.04±0.06 d⁻¹. Phytoplankton intrinsic growth rates varied from the highest values of about 0.4 d⁻¹ to the lowest values of zero to slightly negative growth, on average 0.16±0.15 d⁻¹. Light limitation in spring and post-bloom senescence during summer were likely explanations of observed low phytoplankton growth rates. Microzooplankton grazing consumed 0–120% (average 22±26%) of phytoplankton daily growth. Grazing and growth rates found in this study were low compared to rates reported in another Arctic system, the Barents Sea, and in major geographic regions of the world ocean.     

Spatial and temporal variability of shoreline change in the Beaufort-Mackenzie region, northwest territories, Canada

Aerial photographs from 1972, 1985 and 2000 were analyzed to obtain measurements of coastal change in the Mackenzie Delta region of the Beaufort Sea. Changes from 1972 to 2000 are dominated by retreat of the shoreline with average annual retreat rates of –0.6 m a^–1, but ranging as high as –22.5 m a^–1. Rates vary significantly both between and within zones of similar exposure, morphology and coastal geology with the highest average rates located in areas that are most exposed to northwest winds. In general, decadal-scale rates of change have remained constant during the 28 years encompassed by this study.     

海南西岛珊瑚群落变化及其影响因素 *

在2018年的海南三亚西岛珊瑚群落分布和水质环境因子调查中, 共记录到造礁石珊瑚68种, 多孔螅2种。基于珊瑚礁底质类型的非度量多维标度分析, 可将西岛站位划分为区域1(东-南侧)和区域2(西侧)。全岛活珊瑚覆盖率为13.6%, 区域1和区域2分别为4.2%和27.7%, 区域2珊瑚多样性高于区域1。区域1珊瑚礁处在显著退化状态, 而区域2相对健康, 但是优势种类单一。与历史资料对比分析, 东侧站位造礁石珊瑚覆盖率从2011年的近40%降至2018年不足4%, 退化显著, 而西侧站位珊瑚礁无明显退化; 丛生盔形珊瑚(Galaxea fascicularis)逐渐取代分枝状的鹿角珊瑚成为绝对优势种类; 珊瑚礁区浊度、溶解无机氮(dissolved inorganic nitrogen, DIN)和喇叭藻的δ¹⁵N均值分别为2.54NTU、9.63μmol·L^-1和5.09‰, 均处在较高水平。相关性分析表明, 环境因子的空间变化并不能解释珊瑚群落的空间分布。因此, 推测人类活动引起的极端扰动事件可能是导致西岛珊瑚群落空间分布和东侧站位珊瑚近几年显著退化的主要原因, 如三亚河清淤在三亚湾随意倾倒引起的浑浊事件。应加强对三亚湾清淤和西岛人类活动的管控, 减轻颗粒物沉积和营养盐富集的影响, 促进西岛珊瑚礁逐渐恢复。