Variability in the air-sea interaction patterns and timescales within the south-eastern Bay of Biscay, as observed by HF radar data

Two high-frequency (HF) radar stations were installed on the coast of the south-eastern Bay of Biscay in 2009, providing high spatial and temporal resolution and large spatial coverage of currents in the area for the first time. This has made it possible to quantitatively assess the air-sea interaction patterns and timescales for the period 2009-2010. The analysis was conducted using the Barnett-Preisendorfer approach to canonical correlation analysis (CCA) of reanalysis surface winds and HF radar-derived surface currents. The CCA yields two canonical patterns: the first wind-current interaction pattern corresponds to the classical Ekman drift at the sea surface, whilst the second describes an anticyclonic/cyclonic surface circulation. The results obtained demonstrate that local winds play an important role in driving the upper water circulation. The wind-current interaction timescales are mainly related to diurnal breezes and synoptic variability. In particular, the breezes force diurnal currents in waters of the continental shelf and slope of the south-eastern Bay. It is concluded that the breezes may force diurnal currents over considerably wider areas than that covered by the HF radar, considering that the northern and southern continental shelves of the Bay exhibit stronger diurnal than annual wind amplitudes.

Stationary Eddies and Zonal Variations of the Global Hydrological Cycle in a Changing Climate

This thesis advances our physical understanding of the sensitivity of the hydrological cycle to global warming. Specifically, it focuses on changes in the longitudinal (zonal) variation of precipitation minus evaporation (P - E), which is predominantly controlled by planetary-scale stationary eddies. By studying idealized general circulation model (GCM) experiments with zonally varying boundary conditions, this thesis examines the mechanisms controlling the strength of stationary-eddy circulations and their role in the hydrological cycle. The overarching goal of this research is to understand the cause of changes in regional P - E with global warming. An understanding of such changes can be useful for impact studies focusing on water availability, ecosystem management, and flood risk.

Based on a moisture-budget analysis of ERA-Interim data, we establish an approximation for zonally anomalous P - E in terms of surface moisture content and stationary-eddy vertical motion in the lower troposphere. Part of the success of this approximation comes from our finding that transient-eddy moisture fluxes partially cancel the effect of stationary-eddy moisture advection, allowing divergent circulations to dominate the moisture budget. The lower-tropospheric vertical motion is related to horizontal motion in stationary eddies by Sverdrup and Ekman balance. These moisture- and vorticity-budget balances also hold in idealized and comprehensive GCM simulations across a range of climates.

By examining climate changes in the idealized and comprehensive GCM simulations, we are able to show the utility of the vertical motion P - E approximation for splitting changes in zonally anomalous P - E into thermodynamic and dynamic components. Shifts in divergent stationary-eddy circulations dominate changes in zonally anomalous P - E. This limits the local utility of the "wet gets wetter, dry gets drier” idea, where existing P - E patterns are amplified with warming by the increase in atmospheric moisture content, with atmospheric circulations held fixed. The increase in atmospheric moisture content manifests instead in an increase in the amplitude of the zonally anomalous hydrological cycle as measured by the zonal variance of P - E. However, dynamic changes, particularly the slowdown of divergent stationary-eddy circulations, limit the strengthening of the zonally anomalous hydrological cycle. In certain idealized cases, dynamic changes are even strong enough to reverse the tendency towards "wet gets wetter, dry gets drier” with warming.

Motivated by the importance of stationary-eddy vertical velocities in the moisture budget analysis, we examine controls on the amplitude of stationary eddies across a wide range of climates in an idealized GCM with simple topographic and ocean-heating zonal asymmetries. An analysis of the thermodynamic equation in the vicinity of topographic forcing reveals the importance of on-slope surface winds, the midlatitude isentropic slope, and latent heating in setting the amplitude of stationary waves. The response of stationary eddies to climate change is determined primarily by the strength of zonal surface winds hitting the mountain. The sensitivity of stationary-eddies to this surface forcing increases with climate change as the slope of midlatitude isentropes decreases. However, latent heating also plays an important role in damping the stationary-eddy response, and this damping becomes stronger with warming as the atmospheric moisture content increases. We find that the response of tropical overturning circulations forced by ocean heat-flux convergence is described by changes in the vertical structure of moist static energy and deep convection. This is used to derive simple scalings for the Walker circulation strength that capture the monotonic decrease with warming found in our idealized simulations.

Through the work of this thesis, the advances made in understanding the amplitude of stationary-waves in a changing climate can be directly applied to better understand and predict changes in the zonally anomalous hydrological cycle.

Relationship between abundance of juvenile rockfishes (Sebastes spp.) and environmental variables documented off northern California and potential mechanisms for the covariation

We estimated annual abundance of juvenile blue (Sebastes mystinus), yellowtail (S. f lavidus), and black (S. melanops) rockfish off northern California over 21 years and evaluated the relationship of abundance to oceanographic variables (sea level anomaly, nearshore temperature, and offshore Ekman transport). Although mean annual abundance was highly variable (0.01−181 fish/minute), trends were similar for the three species. Sea level anomaly and nearshore temperature had the strongest relationship with interannual variation in rockfish abundance, and offshore Ekman transport did not correlate with abundance. Oceanographic events occurring in February and March (i.e., during the larval stage) had the strongest relationship with juvenile abundance, which indicates that year-class strength is determined during the larval stage. Also of note, the annual abundance of juvenile yellowtail rockfish was positively correlated with year-class strength of adult yellowtail rockfish; this finding would indicate the importance of studying juvenile abundance surveys for management purposes.

Upwelling, offshore transport, and the availability of rockfish in central California

EXTRACT (SEE PDF FOR FULL ABSTRACT): We used the diet of a seabird, the common murre (Uria aalge), nesting on Southeast Farallon Island and feeding in the Gulf of the Farallones, California, as an index to abundance of juvenile rockfish, then related fish abundance to indices of turbulence and upwelling over an 18-year period, 1973-1990. Strong, persistent upwelling or downwelling led to reduced availability of fish in the study area, in contrast to great abundance when upwelling was mild or pulsed. ... On the basis of our study, one effect might be that fishes thought strong enough to resist Ekman transport could be transported out of normal areas of recruitment.

Effect of low-frequency Rossby wave on thermal structure of the upper southwestern tropical Indian Ocean

We investigate the influence of low-frequency Rossby waves on the thermal structure of the upper southwestern tropical Indian Ocean (SWTIO) using Argo profiles, satellite altimetric data, sea surface temperature, wind field data and the theory of linear vertical normal mode decomposition. Our results show that the SWTIO is generally dominated by the first baroclinic mode motion. As strong downwelling Rossby waves reach the SWTIO, the contribution of the second baroclinic mode motion in this region can be increased mainly because of the reduction in the vertical stratification of the upper layer above thermocline, and the enhancement in the vertical stratification of the lower layer under thermocline also contributes to it. The vertical displacement of each isothermal is enlarged and the thermal structure of the upper level is modulated, which is indicative of strong vertical mixing. However, the cold Rossby waves increase the vertical stratification of the upper level, restricting the variability related to the second baroclinic mode. On the other hand, during decaying phase of warm Rossby waves, Ekman upwelling and advection processes associated with the surface cyclonic wind circulation can restrain the downwelling processes, carrying the relatively colder water to the near-surface, which results in an out-of-phase phenomenon between sea surface temperature anomaly (SSTA) and sea surface height anomaly (SSHA) in the SWTIO.

Observations of Kuroshio intrusion into the South China Sea

To discuss the intrusion of the Kuroshio into the SCS, we examined the mixing between the North Pacific and South China Sea (SCS) waters based on in-situ CTD data collected in August and September 2008 and the moored ADCP data taken from mid September 2008 to early July 2009. The CTD survey included four meridional sections from 119A degrees E to 122A degrees E around the Luzon Strait, during which pressure, temperature, and salinity were measured. The CTD data show that the isopycnal surface tilted from the SCS to the North Pacific; and it was steeper in the lower layers than in the upper ones. Meanwhile, we found strong vertical mixing taken place in the areas near 121A degrees E. The Kuroshio in high temperature and salinity intruded westward through Luzon Strait. The frequency of buoyancy was one order of magnitude greater than that of the common ones in the ocean, suggesting stronger stratification in the northeastern SCS. On the other hand, the long-term ADCP data show that before late October 2008, the direction of water flow in the SCS was eastward, and from November 2008 to late February 2009, it turned northwestward in the layers shallower than 150 m, while remained unchanged in deep layers from 200 to 450 m. From March to June 2009, the direction shifted with increasing depth from northward to southward, akin to the Ekman spiral. EOF analysis of the current time series revealed dominant empirical modes: the first mode corresponded to the mean current and showed that the Kuroshio intrusion occurred in the upper layers only from late December to early March. The temporal coefficient of the first and the second mode indicated clearly a dominant signal in a quasi-seasonal cycle.

Evolution of freshwater plumes and salinity fronts in the northern Bay of Bengal

[1] The evolution of freshwater plumes and the associated salinity fronts in the northern Bay of Bengal ( henceforth the bay) is studied using rotated empirical orthogonal function (REOF) analysis and extended associate pattern analysis (EAPA). The results show that sea surface salinity distribution is featured by eastern-bay and western-bay plumes in the northern bay during different seasons. The western-bay plume begins in early July, peaks in late August, and then turns into a bay-shaped plume with the two plumes in either side of the bay, which peaks in late October. The southward extension of the western-bay plume can be explained by the southwestward geostrophic flow associated with the cyclonic gyre in the northern bay, which counters the northeastward Ekman drift driven by wind stress. The offshore expansion of the western-bay plume is induced by the offshore Ekman drift which also produces a salinity front near the east coast of India. The bay-shaped plume appears when the cyclonic gyre shifts westward and a weak anticyclonic gyre occupies the northeastern bay. As the season advances, the western part of the bay-shaped plume decays while the eastern part persists until the following June, which is believed to be associated with the anticyclonic gyre in the northern bay. The evolution of the plumes except the eastern part of the bay-shaped plume in fall can be partly explained by the seasonal variation of mass transport associated with the Sverdrup balance. The fact that the western-bay (eastern-bay) plume appears when surface freshwater flux in the northeastern bay increases ( decreases) dramatically suggests that the plumes are not produced directly by surface freshwater flux. River discharge seems to be the freshwater source for the plumes and has little to do with the evolution of the plumes.

南海暖流形成机制的探计

收集、补充和强调指出的观测事实。南海暖流是一支沿岸流亦将它和付热带逆流进行了比较，发现有两点不同，（1）南海受报风控制，而付热带逆流流域受太平洋的大洋风系控制。（2）付热带逆流位于大洋中部，它的形成与边界没有直接关系。认为，对于海洋动力学，侧边界的意义无论怎么强调都不过份！它正是使海洋动力学区别于大气动力学的主要特征之一。南海上空的报风场基本是冬夏对称的。无论是季风还是太阳加热，都有着约为 1 年的周期。由于陆架上水浅（小于 100 米），涡动混合和自然对流在冬季将那里的海水基本搅均匀了，尽管由于大陆冷却及由于渐渐变浅，单位面积水柱的热量向岸递减，使等温线密集且平等于岸，但那里已经几乎没有斜压效应了。那里的流场将主要是 Ekman 飘流和次生的沿岸正压梯度流。南海北部处于付热带，这是一个从热带向中纬度过渡的纬度范围，这里的海水，作为地球流体，应兼有低纬和中纬的特征。分析了 1975 年 4 月～1976 年 12 月国家海洋局在海南岛东南海域两个 NW －SE 向断面的温度资料。从文献 [10] 的图 1a 可见，只有 4 个断面的大面图上似乎有些直径为百公里量级的漩涡存在。除了前面谈到的规模较大的带状结构上，在不同时间和不同断面上都可以见到它。

中国东部近海温度锋面的分布特征和变化规律

海洋锋面既是各种物理过程，如环流、上升流、混合等的结果，也是这些物理过程的指标，还是影响流场结构、海洋热量和动量交换、海气相互作用以及生物化学过程的重要因素。同时，海洋锋面研究还与海洋产业活动，如海洋渔业、环境保护、海洋倾废等密切相关，也是军事海洋学必须考虑的问题。所以，海洋锋面的研究也成为物理海洋学和海洋交叉学科研究中的一个重要内容。 本研究以中国东部近海（渤海、黄海、东海及南海北部）锋面的分布特征、变化规律、动力机制及对相应过程的影响为研究对象，以1985~2002年AVHRR Pathfinder的卫星海表面温度数据为基础，辅以POM模式，通过数据分析、模式验证和动力机制分析相结合的方法，既全面描述了中国东部近海锋面分布和变化的总体特征，又深入研究了三个典型锋面，即南黄海西部沿岸锋面、黄海暖流源区陆架锋面和东海黑潮陆坡锋面的具体特点，结果如下： 1，中国东部近海温度锋面分布状况的季节变化明显。冬季，锋面丰富，形状规则，位置稳定，可以明确区分出14条沿岸流锋面和暖流锋面。春季及夏初，锋区分布范围广，没有规则的锋面形态，也没有固定的发生区域，不能明确分辨出具体锋面，锋区大体按黑潮流域—长江河口沿岸区域—南黄海区域的方向和渤海—北黄海—南黄海的方向转移。夏季在沿岸区域产生潮汐锋，秋季则很少有锋面出现。对于冬季锋面的位置来讲，沿岸锋面的年际变化小，暖流锋面的年际变化大；受地形限制的锋面年际变化小，脱离地形控制的锋面年际变化大。 2，冬季山东半岛南部（即南黄海西部）温度锋面的完整形态为“N”形，东、西两部分平行岸线和等深线，中间部分跨越等深线。表层以下的黄海沿岸流和黄海暖流及分支是此锋面生成和维持的直接原因：南下沿岸流与北上的黄海暖流形成了锋面的东部部分，反气旋性回流的沿岸流与被沿岸流挟入南黄海西部的黄海暖流暖水及进入南黄海西部的黄海暖流分支形成了锋面的中部和西部部分。通过强烈的垂直混合，此锋面形态特征从表层以下传播到表层。沿岸流和暖流的强弱会影响此锋面的位置，锋面的形成会反过来影响上述流态。冬季风是维持相关环流和锋面结构的间接原因。 3，暖舌西移和双暖舌温度结构是冬季南黄海温度分布的主要特征，黄海暖流源区暖舌南北两侧形成的双锋面是南黄海锋面结构的主要特征，这两条锋面有时也可在西端连为一体，形成环绕黄海暖水舌前锋区的弧形锋面。南侧锋面大致沿长江浅滩边缘，北侧锋面大致呈东西走向，横跨黄海海槽入口，在此锋面的阻挡下，黄海暖舌无法沿海槽中央北上，在两锋面之间沿着黄海海槽西侧进入黄海。统计结果表明，北侧锋面的位置、强度变化，是驱使暖舌沿海槽西侧进入黄海、并控制其西移程度的主要因素。当北侧锋面偏南或强度大时，暖舌西移程度大，当两条锋面间隔距离大时，暖舌的西移程度弱，暖舌主体北侵的程度就越大，双暖舌结构越不明显。源区黄海暖流的东西向质量和热量输运，黄海内部的风应力等通过影响锋面的位置和强度而间接影响暖舌西移程度。黄海暖舌甚至黄海暖流的起源值得进一步探讨。 4，东海黑潮锋在台湾岛东北部和九州岛西南部的平均经向位置之间存在着反位相的年际变化规律。长期观测资料和数值试验结果都表明，进入东海的黑潮流量的改变能够导致黑潮锋面位置在两地反位相的变化：当黑潮流量增大时，黑潮在台湾岛东北部的向陆架入侵减小，锋面向南偏移，而同时黑潮在九州岛西南部的向陆架入侵增大，锋面向北偏移；冬季风应力在台湾岛东北部以东北风为主，在九州岛西南部以西北风为主。当风应力增大时，黑潮锋面在台湾岛东北部向西北偏移，在九州岛西南部向西南方向偏移。黑潮流轴位置的改变也可能是导致反位相变化的原因。位涡输运方程中的地形和斜压联合效应项以及风应力项（主要是Ekman输运）在两地的不同表现可能是控制这种变化的机制。

孟加拉湾表层盐度季节变化和ENSO循环的拓展伴随模态分析

本文采用旋转经验正交函数分析和拓展伴随模态分析方法研究孟加拉湾表层盐度的季节变化，结果表明其主要特征是西北淡水羽（位于湾的西北部）和东北淡水羽（位于湾的东北部）的季节性演变。西北淡水羽始于7月初，8月底达到峰值，10月底转变为湾形淡水羽；湾形淡水羽集中分布在孟加拉湾的西北和东北沿岸附近，并在第2年1月转变为东北淡水羽。 孟加拉湾北部的环流（地转流+Ekman漂流）对淡水羽的形成和演变起重要作用。Sverdrup环流，代表对风应力的正压响应，能部分解释除了秋季湾形淡水羽的东支之外淡水羽的形成机制和演变过程。海表淡水通量与淡水羽在空间上分布不一致：当孟加拉湾东北部的海表淡水通量急剧增加（减少）时，西北淡水羽（湾形淡水羽的东支）产生，所以海表淡水通量不是淡水羽的形成和演变的主要原因。此外，孟加拉湾周边河流的径流量可能只是淡水羽的主要淡水来源，而与淡水羽的形成和演变关系不大。 初步研究了孟加拉湾北部盐度对海面高度异常的影响，结果表明Ekman 抽吸对孟加拉湾的海面高度异常起着主要作用，热量通量和淡水通量起次要作用。7－12月，孟加拉湾北部的淡水通量决定北部的海面比容高度异常；1－3月，热量通量对海面比容高度异常起主要作用；4－6 月，热量通量和淡水通量在不同时空对孟加拉湾北部的海面比容高度异常起不同的作用。 同样，采用拓展伴随模态分析方法研究ENSO循环的暖位相——El Niño，表明必须将中低纬度印度洋和太平洋海气系统作为一个整体来研究El Niño；证实了正是直接来自南北中纬度太平洋的异常西风爆发和海面风辐聚所驱动的近赤道异常表层海水东移和经向辐聚，而不是Kelvin波，造就了El Niño现象的增温信号。El Niño事件中海洋和大气具有明显不同的性态：气候系统中并不存在一个相对独立的热带太平洋大气变异，但是的确存在一个相对独立的热带太平洋海洋变异。总体上而言：El Niño事件早期主要是大气驱动海洋，晚期主要是海洋驱动大气。 研究结果显示拓展伴随模态分析方法是研究ENSO循环和海洋水文特征形成机制的有力工具。

台湾东北部及吕宋海峡黑潮的水文动力学分析

本论文应用一种流函数投影方法对台湾东北部黑潮近二十年的历史水文数据进行了诊断分析。 结果表明，苏澳海脊北部位于冲绳海槽西南角的黑潮中层水的盐度明显高于周围海区；而位于1000m以下的冲绳海槽黑潮深层水相对于苏澳海脊以南的黑潮深层水具有高温低盐的特征，反映了苏澳海脊对黑潮水团的阻挡作用；位于300m 以浅的冲绳海槽黑潮热带水相对于苏澳海脊以南的黑潮热带水具有低温低盐的特征。针对冲绳海槽西南角黑潮中层水高盐中心的成因，分析表明除了苏澳海脊的阻挡作用外，台湾东北部的气旋式冷涡与黑潮主体在陆架坡折交汇区的垂直混合过程是需要考虑的关键因素。另外，针对吕宋海峡黑潮表层水入侵南海的现象，本文结合卫星高度计数据对Argos漂流浮标轨迹进行了初步分析，结果显示除了风生Ekman流之外黑潮地转流也起着重要的平流作用。

夏季长江口外海区域上升流现象的数值研究

中国沿岸海域是上升流的多发区. 渤、黄海域，东海陆架区，台湾海峡，以及南海沿岸都存在众多的上升流区. 上升流有利于穿越陆架的物质输运，可以把下层海水中的营养物质带至真光层，促进浮游植物生长，为赤潮爆发提供有利条件. 长江口外和浙江沿岸上升流区连续几年爆发大规模赤潮，该海域已成为我国近海赤潮严重的区域之一. 同时上升流也是该海域海洋渔场形成的重要动力因子. 因此，对长江口外及浙江沿岸上升流的研究具有重要的意义. 本文基于Blumberg等（1996）的ECOMSED模式，对长江口外海区域夏季的上升流现象进行了数值模拟研究. 为了提高对长江口外海区域上升流模拟的准确性和可靠性，模式综合考虑了径流，风应力，环流，热通量和M2，S2，K1，O1四个主要分潮的作用. 本文首先进行控制实验，综合考虑各种动力因子，模拟长江口外南部冷水区的上升流现象，再单独考虑各个动力因子做数值实验，并对各种数值实验结果进行分析对比来研究产生该区域上升流现象的主要原因. 我们设计了3个数值实验：不考虑风应力和热通量、不考虑环流、仅考虑温盐和潮因子. 方便起见，将综合考虑各种动力因子的数值模拟称作控制实验. 各种实验结果的分析表明，长江口外水下河谷的南边（杭州湾口门中心东侧），上升流主要是由向北流动的台湾暖流通过底Ekman效应和陆坡的抬升共同作用产生的. 夏季偏南风对长江口外水下河谷西侧上升流的产生有一定影响，但作用不大. 此外，潮汐潮流对上升流的产生也起着一定的作用，但在本文关注的上升流区潮作用影响不大.

Workshop summary: Hormonal suppression in the neoadjuvant setting and advanced disease

SCOPUS: cp.j

Physical controls on the seasonal migration of the North Pacific transition zone chlorophyll front

The large seasonal migration of the transition zone chlorophyll front (TZCF) is of interest because a number of marine fauna, both commercial and endangered, appear to track it. Herein we examine the physical dynamics driving this seasonal migration of the TZCF. Vertical processes, traditionally viewed as controlling the dynamical supply of nutrients to surface waters, prove insufficient to explain seasonal variations in nutrient supply to the transition zone. Instead, we find that the horizontal Ekman transport of nutrients from higher latitudes drives the TZCF's southward migration. The estimated horizontal transport of nitrate supports up to 40% of new primary productivity in the region annually and nearly all of new primary productivity in the winter. The significance of horizontal advection to the North Pacific transition zone supports revising the paradigm that nutrients are supplied to surface waters from below. © 2010 by the American Geophysical Union.

Contribution to the knowledge of the genus "Cladonia" in Macaronesia

Sixteen species of the genus Cladonia are reported from Macaronesia from the Canary Islands. Three species are new to canarian flora and, two of them new to Macaronesia. The chemical variation of the taxa is reported. A phytogeographic distribution of the taxa with data on their habitat and ecology are presented.