Predictability of Interannual Variability in the Kuroshio Transport South of Japan Based on Wind Stress Data over the North Pacific

It is expected that a roughly two-year forecast of the Kuroshio transport variation can be made from a past record of wind stress data over the ocean, since it takes nearly ten years for the first-mode baroclinic Rossby wave to traverse the entire basin in the midlatitude North Pacific (∼30°N). We therefore investigated the predictability using an ocean general circulation model driven by the wind stress data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. Referring to a hindcast experiment as the control run, we carried out fifteen forecast experiments, the initial conditions of which are taken from the hindcast experiment at intervals of two years during the period from the end of 1969 to the end of 1997. Each of the forecast experiments is driven only by wind stress in the year preceding each experiment. The forecasted Kuroshio transport anomaly south of Japan agrees better with the hindcasted one during the first two years of the forecast in most cases. In some cases, however, significant disagreements occur, most of which are likely due to larger unpredictable variations caused by wind stress anomalies near Japan. At the end of forecast year 2, the anomaly correlation coefficient is about 0.7, and rms of the forecast error is smaller than rms of the hindcasted anomaly. These results indicate that the prediction of the interannual variability in the Kuroshio transport could be made two years in advance at a statistically significant level. This revised version was published online in July 2006 with corrections to the Cover Date.     

关于南海暖水季节和年际变化的研究

阐述了研究南海暖水的意义 ,综述了关于南海暖水的现状 ,提出了关于南海暖水季节和年际变化方面应该研究的问题     

热带大西洋年际和年代际变率的时空结构模拟

使用美国夏威夷大学发展的中等复杂程度海洋模式(IOM)在给定表面强迫条件下模拟了热带大西洋上层海洋年际和年代际变率的时空结构.利用NCEP的41a(1958～1998年)逐月平均表面资料作为强迫场,积分海洋模式41a作为控制试验,并利用模式分别做动量(风应力)通量和热量通量无异常变化的平行试验,与控制试验作比较.对3组试验模拟上层海洋变率状况的比较,并按年际和年代际时间尺度分别分析,揭示表面风应力和热通量异常对海表面温度和温跃层深度变化的影响,并比较了其影响的相对重要性.结果表明模式成功地模拟出了热带大西洋上层海洋的变率.模式模拟的海表面温度年际变化主要表现为弱ENSO型,年代际变化表现为南、北大西洋变化相反的偶极子型.在年际时间尺度上,热力强迫和动力强迫对海表温度变化都有贡献,其中赤道外海表面温度异常(SSTA)变化主要由热通量异常引起,而近赤道SSTA的变化主要由动量异常强迫引起.在年代际时间尺度上,热通量强迫的作用远比动量强迫重要.模式不仅能够模拟SST在年际和年代际时间尺度上的变率,还能够模拟温跃层深度在年际和年代际时间尺度上的变率.年际和年代际时间尺度上,温跃层深度的变率主要由动量异常决定,热通量异常强迫的贡献很小.     

南海上层海洋热含量的年际和年代际变化

分析了1959—1988年南海表面至100m垂直平均温度（TAV）资料，结果表明：南海上层海洋热含量存在明显的准两年、4—5年和年代际振动。在E1Nino年，南海上层热含量显著增加。50年代末至70年代初，南海TAV为负距平，此后转为正距平。南海TAV的变化与ENSO事件、东亚冬季风和热带大气环流的变异密切相关。     

Variation in Water Masses on Shelf of Northern Bering Sea in September 2016-2018

Abstract

Based on hydrological data obtained during the 7th to 9th Chinese National Arctic Research Expeditions in the summers of 2016–2018, the main water structure on the shelf of the northern Bering Sea and the volume and heat fluxes of the Bering Strait throughflow were analyzed. Distinct variability was identified in the three Pacific water masses feeding the strait - Anadyr Water (AW), Bering Shelf Water (BSW) and Alaskan coastal water (ACW). Overall, the temperature and salinity of the entire section increased each year, with 2018 showing significant anomalies, i.e., a temperature anomaly of up to 1?°C and a maximum salinity anomaly of 2. From 2016 to 2018, the extent of the ACW gradually narrowed in the eastern part of this section, while the AW expanded eastward each year. The net volume transport through each of the three sections increased poleward from 1.65?Sv to 2.76?Sv, with the AW increasing from 0?Sv to 1.03?Sv, the BSW varying between 0.52–1.65?Sv, and the ACW gradually decreasing from 1.04?Sv to disappearing completely. The net heat fluxes were also poleward, varying between 25.77 TW and 61.50 TW, and showing a significant increase. Significant variations in magnitude and extent were observed in each water mass of the Bering Strait throughflow, which could produce widespread effects in the Arctic Ocean and the global ocean beyond.     

An Ecosystem Model Coupled with Nitrogen-Silicon-Carbon Cycles Applied to Station A7 in the Northwestern Pacific

A model based on that of Kishi et al. (2001) has been extended to 15 compartments including silicon and carbon cycles. This model was applied to Station A7 off Hokkaido, Japan, in the Northwestern Pacific. The model successfully simulated the observations of: 1. a spring bloom of diatoms; 2. large seasonal variations of nitrate and silicate concentrations in the surface water; and 3. large inter-annual variations in chlorophyll-a. It also reproduced the observed features of the seasonal variations of carbon dioxide partial pressure (pCO₂)—a peak in pCO₂ in winter resulting from deep winter convection, a rapid decrease in pCO₂ as a result of the spring bloom, and an almost constant pCO₂ from summer through fall (when the effect of increasing temperature cancels the effect of biological production). A comparison of cases with and without silicate limitation shows that including silicate limitation in the model results in: 1. decreased production by diatoms during summer; and 2. a transition in the dominant phytoplankton species, from diatoms to other species that do not take up silicate. Both of these phenomena are observed at Station A7, and our results support the hypothesis that they are caused by silicate limitation of diatom growth. This revised version was published online in July 2006 with corrections to the Cover Date.     

Numerical study of the summer temperature decrease induced by the enhancement of estuarine circulation in Fukuoka Bay

The Princeton Ocean Model with realistic bottom topography has been used to investigate the summer temperature decrease in the past 25 years in Fukuoka Bay. The vertical mixing of the model is expressed by a scheme that effectively includes the influences of interannual variations of tidal currents and wind. The results show that the historical temperature decrease in summer has been caused by tidal currents and wind weakening in the past 25 years in Fukuoka Bay. The weakening of tidal currents and wind gives rise to weakening of the vertical mixing, and to enhancement of the estuarine circulation in the bay. The enhancement of the estuarine circulation activates the inflow of open-ocean water toward Fukuoka Bay. Coastal water in summer has therefore tended to be colder and more saline in the past 25 years. This interannual variation in coastal waters is called “open-oceanization” in this study. On the basis of the numerical model, it is anticipated that the temperature will decrease by 0.2°C in the next 25 years in Fukuoka Bay if the tide and wind weaken persistently as in the present bay.     

大气环流模式的完全控制试验与模式大气的年际异常研究

对大气环流模式提出了完全控制试验（ＦＣ）的概念，对包括陆面下垫面在内的整个地球表面的热力强迫作了控制。在ＦＣ中，可以更好地分离出大气内动力过程对于模式大气短期气候异常的影响。利用ＩＡＰ２－ＬＡＧＣＭ（中国科学院大气物理所二层大气环流模式）实施了完全控制试验。结果表明，北半球夏半年ＦＣ的月平均海平面气压（ＳＬＰ）年际异常较Ｃ的小，而全球或南半球ＦＣ与Ｃ的ＳＬＰ无明显差别。东亚－西太平洋区域夏半年ＦＣ的月平均ＳＬＰ年际异常甚至高于Ｃ的，意味着该区域模式大气环流短期气候异常中大气内动力过程的作用不可忽视。