Mapping climatic temperature changes in the ocean with acoustictomography: navigational requirements

In eddy-resolving hydrodynamic models, first-mode baroclinic Rossby waves linked to El Nino/Southern Oscillation are the dominant features which change basin-wide temperatures below the seasonal thermocline in the northeast Pacific at periods less than a decade. Simulations are carried out in which Rossby waves are mapped using acoustic tomography. Based on the model which propagated these waves, a Kalman filter is used to map temperature signals for a year. The modeled data are taken from a dense network of acoustic tomography sections. At 300-m depth, where the temperature perturbations associated with Rossby waves are about ±1°C, 80% to 90% of the model variance is accounted for with tomographic estimates. The corresponding standard deviations of the estimates are less than 0.1°C at 400-km resolution. About 80% of the model variance is accounted for with tomography when the navigational errors of the sources and receivers are as poor as one kilometer. Consequently, it may be unnecessary to accurately navigate actual tomographic instruments to map climate change. Modeling results are insensitive to: 1) a reduction in data due to a significant number of instruments which fail; 2) whether the instruments are mobile or fixed; 3) the detailed trajectories of mobile receivers; 4) the shape of the a priori spectrum of ocean fluctuations; 5) the corrections to the acoustic travel-time biases; and 6) the errors in the sound-speed algorithm. In basin-scale arrays, the modeled variance of acoustic travel time depends on the horizontal wavenumber of temperature as k^-5.5. Because sound has little sensitivity to small wavelengths, modeled Rossby waves can be mapped in a day from a few sources and of order ten receivers. The results only depend on the model having large scales in space and time     

Estimating the potential of ocean wave power resources

The realistic assessment of an ocean wave energy resource that can be converted to an electrical power at various offshore sites depends upon many factors, and these include estimating the resource recognizing the random nature of the site-specific wave field, and optimizing the power conversion from particular wave energy conversion devices. In order to better account for the uncertainty in wave power resource estimates, conditional probability distribution functions of wave power in a given sea-state are derived. Theoretical expressions for the deep and shallow water limits are derived and the role of spectral width is studied. The theoretical model estimates were compared with the statistics obtained from the wave-by-wave analysis of JONSWAP based ocean wave time-series. It was shown that the narrow-band approximation is appropriate when the variability due to wave period is negligible. The application of the short-term models in evaluating the long-term wave power resource at a site was illustrated using wave data measured off the California coast. The final example illustrates the procedure for incorporating the local wave data and the sea-state model together with a wave energy device to obtain an estimate of the potential wave energy that could be converted into a usable energy resource.     

Deep ocean temperature profile measurements

Temperature is one of the most frequently measured parameters of the ocean because of its importance to the understanding and prediction of oceanic and meteorological events, and also because the measurement is required for the determination of salinity and density. The ocean temperature range is narrow,-2degto35degC, but measurement is complicated by the harsh ocean environment, the necessity of remote hands off readings, power limitations due to the cable, and the fast response required to obtain a profile in a reasonable length of time. Platinum and copper thermometers are used for most precision measurements with thermistors or thermocouples used in some cases to improve speed of response and for lesser accuracy. A number of very different circuits have been used successfully in salinity, temperature, and depth profiling systems and achieve millidegree accuracies in laboratory measurements. However, very careful precautions and many checks are required to achieve that accuracy in the field, and to achieve the correlation of conductivity, pressure, and temperature readings required for equivalent accuracy in the salinity and density measurements.     

Estimating the underwater light field from remote sensing of ocean color

We present a new approach that incorporates two models to estimate the underwater light field from remote sensing of ocean color. The first employs a series of analytical, semi-analytical, and empirical algorithms to retrieve the spectrum of inherent optical properties (IOPs), including the absorption and the backscatter coefficients, from the spectrum of remote sensing reflectance. The second model computes the profile of photosynthetically available radiation E _0,PAR (z) for a vertically homogeneous water column using the information of the retrieved IOPs and the ambient optical environment. This computation is based on an improved look-up table technology that possesses high accuracy, comparable with the full solution of the radiative transfer equation, and meets the computational requirement of remote sensing application. This new approach was validated by in situ measurements and an extensive model-to-model comparison with a wide range of IOPs. We successfully mapped the compensation depth by applying this new approach to process the SeaWiFS imagery. This research suggests that E _0,PAR (z) can be obtained routinely from ocean-color data and may have significant implications for the estimation of global heat and carbon budget.     

Estimating photosynthetically available radiation at the ocean surface from GOCI data

A technique is presented to estimate photosynthetically available radiation (PAR) at the ocean surface from Geostationary Ocean Color Imager (GOCI) data. The sensor is adapted to the problem, since it measures at visible wavelengths and does not saturate over clouds, and the hourly data provides adequate temporal sampling to describe diurnal variability of clouds. Instantaneous surface PAR is computed as the difference between the solar irradiance incident at the top of the atmosphere (known) and the solar irradiance reflected back to space (derived from GOCI radiance), taking into account absorption and scattering by the clear atmosphere (modeled). Knowledge of pixel composition is not required. Apart from planetary albedo and sun zenith angle, the model parameters are fixed at their climatological values. The instantaneous PAR estimates at hourly intervals are integrated over time to provide daily values. The technique is applied to GOCI imagery acquired on 5 April 2011, and the GOCI daily PAR estimates are compared with those obtained from MODerate Resolution Imaging Spectrometer (MODIS) data. Agreement is good between the two types of estimates, with a coefficient of determination (r ²) of 0.778, a bias of 0.23 Em^?2d^?1 (0.5% with higher GOCI values), and a root-mean-squared difference of 5.00 Em^?2d^?1 (11.2%). Differences in cloudy conditions are attributed to daily cloudiness changes not captured by the MODIS observations. The comparison statistics indicate that GOCI PAR estimates have acceptable accuracy for regional studies of aquatic photosynthesis.     

阿拉伯海上层海温的双峰特征

利用全球海洋Argo网格数据集、SODA月平均海洋数据集和CCMP风场数据,通过EOF分析,揭示了阿拉伯海5、50、100、200 m层海温全年2次增温、2次降温的双峰变化特征.结果表明,5 m层温度变化双峰信号出现在第一模态,其方差贡献率为75.79%,该信号主要受风场、太阳辐射及风生环流影响;50 m层温度变化双峰信号出现在第三模态,其方差贡献率为11.95%,该信号主要受风生环流影响;100 m层温度变化双峰信号出现在第一模态和第三模态,其中第一模态方差贡献率为52.03%,第三模态方差贡献率为9.55%.由100 m层第一模态可知,100 m层温度变化幅度最大、变化范围最广,是由于100 m层处于海洋温度变化最为剧烈的温跃层中.100 m层海温变化主要受风应力旋度(方向:向上为正)影响,风应力旋度为负时,大气对海洋的强迫导致局地海水辐合,温跃层加深,100 m层部分海域温度升高;风应力旋度为正时,大气对海洋的抽吸导致局地海水辐散,海洋深处的冷水上升,100 m层部分海域温度降低.     

Securing ocean benefits for society in the face of climate change

Benefits humans rely on from the ocean – marine ecosystem services – are increasingly vulnerable under future climate. This paper reviews how three valued services have, and will continue to, shift under climate change: (1) capture fisheries, (2) food from aquaculture, and (3) protection from coastal hazards such as storms and sea-level rise. Climate adaptation planning is just beginning for fisheries, aquaculture production, and risk mitigation for coastal erosion and inundation. A few examples are highlighted, showing the promise of considering multiple ecosystem services in developing approaches to adapt to sea-level rise, ocean acidification, and rising sea temperatures.Ecosystem-based adaptation in fisheries and along coastlines and changes in aquaculture practices can improve resilience of species and habitats to future environmental challenges. Opportunities to use market incentives – such as compensation for services or nutrient trading schemes – are relatively untested in marine systems. Relocation of communities in response to rising sea levels illustrates the urgent need to manage human activities and investments in ecosystems to provide a sustainable flow of benefits in the face of future climate change.     

Recreational fishing in a time of rapid ocean change

Fishing is an important recreational activity for many Australians, with one in every four people participating every year. There are however many different pressures exerted on Australian fish stocks, including climate-related changes that drive changes in local fish abundances. It is inevitable that recreational fishers will need to adapt to these changes. When resource abundance alters substantially, user adaptation to the new situation is required and policies and incentives may need to be developed to encourage behaviour change. It is important to correctly anticipate fisher's response to these policies and incentives as much as possible. Improved understanding of recreational fisher's likely adaptation decisions and the nature and timing of these decisions can help avoid unintended consequences of management decisions. Based on a survey of recreational fishers in the south-east Australian climate hotspot, we identify 4 relevant dimensions to recreational fisher's behavioural adaptation. There are differences in adaptation timing (early, late, and non-adaptors). Non-adaptors are characterised by greater cultural attachment to fishing and stronger perceptions of the factors that influence abundance change. The fisher's preferred adaptation responses and the timing of the behavioural response differs between decreasing versus increasing fish abundance. Insight into perspectives and expectations on how recreational fishers might adapt to changes is useful to develop a set of behavioural incentives that appeal to different groups but remain efficient and effective in their implementation. Such knowledge can create new pathways to achieve meaningful and targeted adaptation responses for different types of recreational fishers.     

A description of short period temperature fluctuations in the upper ocean

Dynamical properties of short-period temperature fluctuations are studied. Water temperature was measured continuously at several depths at the following stations: at 38°29.5′N, 141°35.8′E (100 m depth) on the continental shelf off Miyagi Prefecture in the summer of 1967, at 35°01.8′N, 139°0.8.5′E (100 m depth) in Sagami Bay in the summer of 1968, and at 32°32.2′N, 129°53.7′E (74 m depth) in Tachibana Bay in the summer of 1970. These measurements were made with a thermistor array laid down from the R. V.Tanseimaru (Ocean Research Institute, University of Tokyo) which was fixed with bow and stern anchors. Significant temperature fluctuations found at the first and the third stations are thought to be due to first mode internal waves having amplitude 3 to 5 m and period 5 to 20 minutes. The wave length of the waves is estimated to be 25 m to 400 m from the observed density structure. At the second station, we found second-mode internal waves. The period, amplitude and wave length of the waves are about 30 minutes, 1.3 m and 600 m, respectively. In all cases, the spectral density of the temperature fluctuations decreases with increase in frequency. However, the decrease obey neither the ?3 power law nor the ?5/3 power law. Coherences in the temperature fluctuations between two depths of measurement in the seasonal thermocline are significantly high in the range of frequencies lower than the local Brunt-Väisälä frequency, but are low in the higher frequency range. At the first and the third stations, the difference in the level of coherences between the lower frequencies and the higher frequencies are large. Phase differences between two depths in the thermocline are small in the lower frequency range. This suggests that the first-mode internal waves are predominant over higher-mode internal waves and over other disturbances.     

Climate change projections for the surface ocean around New Zealand

The future status of the surface ocean around New Zealand was projected using two Earth System Models and four emission scenarios. By 2100 mean changes are largest under Representative Concentration Pathway 8.5 (RCP8.5), with a +2.5°C increase in sea surface temperature, and decreases in surface mixed layer depth (15%), macronutrients (7.5–20%), primary production (4.5%) and particle flux (12%). Largest macronutrient declines occur in the eastern Chatham Rise and subantarctic waters to the south, whereas dissolved iron increases in subtropical waters. Surface pH projections, validated against subantarctic time-series data, indicate a 0.335 decline to ～7.77 by 2100. However, projected pH is sensitive to future CO₂ emissions, remaining within the current range under RCP2.6, but decreasing below it by 2040 with all other scenarios. Sub-regions vulnerable to climate change include the Chatham Rise, polar waters south of 50°S, and subtropical waters north of New Zealand, whereas the central Tasman Sea is least affected.     

Estimating photosynthetically available radiation at the ocean surface from ADEOS-II global imager data

A simple, yet efficient and fairly accurate algorithm is presented to estimate photosynthetically available radiation (PAR) at the ocean surface from Global Imager (GLI) data. The algorithm utilizes plane-parallel radiation-transfer theory and separates the effects of the clear atmosphere and clouds, i.e., the planetary atmosphere is modeled as a clear atmosphere positioned above a cloud layer. PAR is computed as the difference between the incident 400–700 nm solar flux at the top of the atmosphere (known) and the solar flux reflected back to space by the atmosphere and surface (derived from GLI radiance), taking atmospheric absorption into account. Knowledge of pixel composition is not required, eliminating the need for cloud screening and arbitrary assumptions about sub-pixel cloudiness. For each GLI pixel, clear or cloudy, a daily PAR estimate is obtained. Diurnal changes in cloudiness are taken into account statistically, using a regional diurnal albedo climatology based on 5 years of Earth Radiation Budget Satellite (ERBS) data. The algorithm results are verified against other satellite estimates of PAR, the National Centers for Environmental Prediction (NCEP) reanalysis product, and in-situ measurements from fixed buoys. Agreement is generally good between GLI and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) estimates, with root-mean-squared (rms) differences of 7.9 (22%), 4.6 (13%), and 2.7 (8%) Einstein/m²/day on daily, weekly, and monthly time scales, and a bias of only 0.8–0.9 (about 2%) Einstein/m²/day. The rms differences between GLI and Visible and Infrared Spin Scan Radiometer (VISSR) estimates and between GLI and NCEP estimates are smaller and larger, respectively, on monthly time scales, i.e., 3.0 (7%) and 5.0 (14%) Einstein/m²/day, and biases are 1.1 (2%) and −0.2 (−1%) Einstein/m²/day. The comparison with buoy data also shows good agreement, with rms inaccuracies of 10.2 (23%), 6.3 (14%), and 4.5 (10%) Einstein/m²/day on daily, weekly, and monthly time scales, and slightly higher GLI values by about 1.0 (2%) Einstein/m²/day. The good statistical performance makes the algorithm suitable for large-scale studies of aquatic photosynthesis.     

海洋表层温度剖面数值模拟

遥感测量海水表面温度(SST)需用海表面以下实测温度资料加以校正,由于长时间大范围进行海洋表层海水垂向温度剖面野外观测非常困难,建立经有限资料验证的数值模型十分重要。文章基于美国加利福尼亚湾3组船载光学实验的气象及海温资料,考虑太阳热辐射作用与海表面冷温层效应,建立了一个海表下20m深度范围内水温剖面演变的数值模型。通过冷温层计算合理加密了表层网格,使数值模型更准确地估计海表散热作用。计算结果与野外实测海温资料对比显示,海表剖面测试仪(SkinDeEP)未能准确定位和捕捉海表冷温层,实验方法有待改进。整合模型能准确描述海温剖面的演变趋势,在近海表20cm深度内,特别是与遥感SST相关的近海表1cm深度内,模拟结果优于无本皮肤层模型的计算结果。     

包含温度因子的海水地球物理模型函数建模研究

以SeaWinds散射计为例,利用其L2A卫星测量数据和相应的海面浮标测量数据,以温度作为独立变量,借助人工神经网络首次尝试建立了包含温度因子的海水地球物理模型函数。建模实验结果表明,在3—15m.s-1风速范围内,对于两种极化方式,后向散射系数先随温度的升高而增大,当风速大于某一数值后,又随温度的升高而减小,但两种极化方式的转折风速存在差异。该研究结果为海面微波散射机理认识的进一步深入和模型函数精度的进一步提高展示了潜在的可能途径。     

Dominant sea-surface temperature anomaly patterns in summer over the North Pacific ocean

We investigated the structure and persistency of the dominant sea-surface temperature (SST) anomaly pattern in summer over the North Pacific from 1960 to 2004, which has been attracting less attention than those in winter. The leading empirical orthogonal functions (EOFs) for August and September, which can be treated as the summer patterns, rather resemble each other in both spatial structure and time variations but are quite different from those of the other months. A lag correlation analysis indicates that the summer patterns do not show significant persistency in the following winter and the summer of the next year. An inappropriate definition of the summer season might obscure the characteristics of the dominant summer SST anomaly pattern in the North Pacific.     

Non-uniqueness of the ocean thermohaline circulation,discontinuous auto-oscillations,and internal variability of the climatic system

Stable and unstable stationary thermohaline circulations provided by a box model comprising three ventilated masses—surface, intermediate, and deep—are discussed. The most likely states have been determined. It is shown that jump-like variations of the thermocline circulation are likely. An inference is made that long-term (10 000 years) climatic oscillations may be caused by the internal variability of the climatic system rather than by astronomical factors.     

利用卫星观测海面信息反演三维温度场

基于历史观测的温盐剖面资料,采用回归分析方法统计出海面温度异常、海面动力高度异常与温度剖面异常之间的相关关系;然后利用高分辨率的卫星遥感海表面温度(SST)和卫星观测海面高度(SSH)信息重构了三维海洋温度场。在台湾岛周边海域建立了时间分辨率为天、空间分辨率为0.25°×0.25°的三维温度分析场。通过与实测资料的比较分析,文章所构建的分析场能够较好地描述海洋三维温度场的结构特征,能够较为真实地反映海洋的中尺度变化过程。该分析场可以作为海洋数值模式的初始场,也可以作为伪观测同化到海洋数值再分析和预报系统中,进而改善三维温、盐、流的数值再分析和预报。     

气候变化背景下江苏省水稻气候适宜性区划研究

综合利用前人研究结果与江苏地区水稻生长所需的光、温、水特性,提出了江苏水稻气候适宜性评价指标为适宜生长期、5—10月降水量、t≥10℃活动积温、日照时数;依据现有稻麦(油)两熟的耕作制度,确立了江苏水稻气候适宜性区划因子和分级阈值。基于1961—2019年江苏省及周边共85个站(市、区)的气象数据,采用模糊综合评判法建立水稻气候适宜性评估模型,并确定综合评估指数,利用ArcGIS的自然断点法,将江苏中熟中粳、迟熟中粳、早熟晚粳、中熟晚粳种植适宜区进行区划。通过30 a尺度下的年代际分析发现,由于适宜生长期延长和活动积温增加,使得四个品种特性的水稻适宜种植区域均有所调整,其中晚熟粳稻的种植范围北扩到淮河以南地区。     

基于遥感数据的温度剖面预报研究

为了提高温度剖面的预报精度,提出了一种基于遥感数据的温度剖面预报方法.文中使用27个实测温度剖面和遥感SST、SSHA数据实现了对温度剖面的预报,并用该点的ARGO数据进行了检验.实验结果表明,将遥感数据同化到温度剖面的预报中是可行的,并能有效的提高温度剖面的预报精度.     

Estimating the compensation irradiance in the ocean: The importance of accounting for non-photosynthetic uptake of inorganic carbon

The compensation irradiance, the irradiance at which net photosynthesis is zero over a 24-h period, was estimated at station ALOHA (22°45′N, 158°W) from analysis of ¹⁴C uptake rates measured from 8 January 1989 to 13 June 1990 at depths ranging from 5 to 175 m. The estimates were made on the basis of linear regressions of the difference between light bottle and dark bottle ¹⁴C uptake in the light-limited region of the euphotic zone and determination of the depth at which the difference between the uptake rates was zero. About half of the non-photosynthetic ¹⁴C uptake at the compensation irradiance could be attributed to chemolithoautotrophy; the remainder was presumably due to anaplerotic processes. Deriving the compensation irradiance by extrapolating dawn-to-dawn light-bottle uptake above the compensation irradiance to zero resulted in underestimation of the compensation irradiance by a factor of 2. We estimated the compensation irradiance at station ALOHA to be 0.054 mol-photons m⁻² d⁻¹, about 0.11% of surface 400–700 nm radiation and 1% of surface 475-nm (blue) light.     

On transformation of the near-surface atmospheric boundary layer in the ocean temperature front area

A two-dimensional, quasi-analytical model for the formation of the internal atmospheric boundary layer in the ocean temperature front area is described, developed on the basis of integral relations for motion and thermal conductivity equations. The computed data are matched with wind speed observations, as well as with direct and indirect dynamic velocity measurements in the air, obtained across the Gulf Stream frontal zone.Translated by V. Puchkin.