Experimental study of strong reflection of regular water waves over submerged breakwaters in tandem

A series of laboratory experiments was carried out to investigate the strong reflection of regular water waves over a train of submerged breakwaters. Rectangular and trapezoidal shapes of submerged breakwaters are employed and compared for reflecting capability of incident waves. Measured reflection coefficients of regular waves over impermeable submerged breakwaters are verified by comparing with those of the eigenfunction expansion method. A very good agreement is observed. Reflection coefficients of permeable submerged breakwaters are less than those of impermeable breakwaters. The trapezoidal shape is recommended for a submerged breakwater in terms of reflecting capability and practical application.     

Subsurface Water Masses in the Central North Pacific Transition Region: The Repeat Section along the 18° Meridian

A repeat hydrographic section has been maintained over two decades along the 180° meridian across the subarctic-subtropical transition region. The section is naturally divided into at least three distinct zones. In the Subarctic Zone north of 46°N, the permanent halocline dominates the density stratification, supporting a subsurface temperature minimum (STM). The Subarctic Frontal Zone (SFZ) between 42°–46°N is the region where the subarctic halocline outcrops. To the south is the Subtropical Zone, where the permanent thermocline dominates the density stratification, containing a pycnostad of North Pacific Central Mode Water (CMW). The STM water colder than 4°C in the Subarctic Zone is originated in the winter mixed layer of the Bering Sea. The temporal variation of its core temperature lags 12–16 months behind the variations of both the winter sea surface temperature (SST) and the summer STM temperature in the Bering Sea, suggesting that the thermal anomalies imposed on the STM water by wintertime air-sea interaction in the Bering Sea spread over the western subarctic gyre, reaching the 180° meridian within a year or so. The CMW in this section originates in the winter mixed layer near the northern edge of the Subtropical Zone between 160°E and 180°. The CMW properties changed abruptly from 1988 to 1989; its temperature and salinity increased and its potential density decreased. It is argued that these changes were caused by the climate regime shift in 1988/1989 characterized by weakening of the Aleutian Low and the westerlies and increase in the SST in the subarctic-subtropical transition region. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Zonal Pathway for NADW in the South Atlantic

Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate (AAIW), North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW) of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well. Here we use the spatially and temporally averaged velocities measured by these floats, combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays, to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S. We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates. In support of this notion, we find that a net of about 5 Sv. of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the Mid-Atlantic Ridge. Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin. The data suggest that the NADW then continues on into the Indian Ocean. This scheme is discussed in the context of distributions of dissolved oxygen, silicate and salinity. In spite of the many float-years of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest. Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers.     

水面皮层破坏-复原过程的实验室模拟研究

依据水面红外发射和红外遥感测温原理，采用HDG－高灵敏度红外测温仪和常规测量仪器相结合的方法，在实验室空气稳定条件下，模拟测得了水面皮层破坏－复原（重建）的热力过程和气－水温差对水面皮层复原过程的影响，获得了大量的测量数据。数据分析表明，当气－水温差从3．0℃变为11．5℃时，水面皮层破坏可导致皮温增量从气－水温差3．0℃时的0．15℃变到11．5℃时的0．45℃，并发现恢复时间与气－水温差呈负线性关系。     

前颌间银鱼资源变动原因的初步探讨

于1985—1988年对前额间银鱼生物学特性、资源变动状况及其原因进行了现场和社会调查。调查表明,前颌间银鱼资源变动的原因是南、西区和吴淞口三大污染源对其生态环境严重污染;同时还有多年持续过捕超过其再增殖能力。为此,提出治理污染,恢复前颌间银鱼的生活环境及保护繁殖亲体的对策和建议。     

Northward transport of pacific summer water along the Northwind Ridge in the Western Arctic Ocean

The recent sea-ice reduction in the Arctic Ocean is not spatially uniform, but is disproportionally large around the Northwind Ridge and Chukchi Plateau compared to elsewhere in the Canada Basin. In the Northwind Ridge region, Pacific Summer Water (PSW) delivered from the Bering Sea occupies the subsurface layer. The spatial distribution of warm PSW shows a quite similar pattern to the recent ice retreat, suggesting the influence of PSW on the sea-ice reduction. To understand the regionality of the recent ice retreat, we examine the dynamics and timing of the delivery of the PSW into this region. Here, we adopt a two-layer linearized potential vorticity equation to investigate the behavior of Rossby waves in the presence of a topographic discontinuity in the high latitude ocean. The analytical results show a quite different structure from those of mid-latitude basins due to the small value of β. Incident barotropic waves excited by the sea-ice motion with large annual variation can be scattered into both barotropic and baroclinic modes at the discontinuity. Since the scattered baroclinic Rossby wave with annual frequency cannot propagate freely, a strong baroclinic current near the topographic discontinuity is established. The seasonal variation of current near the topographic discontinuity would cause a kind of selective switching system for shelf water transport into the basin. In our simple analytical model, the enhanced northward transport of summer water and reduced northward transport of winter water are well demonstrated. The present study indicates that these basic dynamics imply that a strengthening of the surface forcing during winter in the Canada Basin could cause sea-ice reduction in the Western Arctic through the changes of underlying Pacific Summer Water.     

胶州湾异养细菌及大肠菌群的分布及对陆源污染的指示

2002年2月—2004年11月对胶州湾异养细菌和大肠菌群进行长期调查发现,胶州湾异养细菌丰度在105—106cells/ml之间,其中河口区域和近岸区域数量较高,其它区域相对较低。从季节上来看,夏季、秋季细菌丰度较高(分别为7.4×105、7.2×105cells/ml),冬季和春季丰度较低(分别为4.1×105cells/ml、5.9×105cells/ml),且在一年内呈现出一定的规律性波动。从季节尺度上看异养细菌丰度与温度呈现很好的正相关性(R=0.54)。对大肠菌群的研究表明,河口区域的大肠菌群数量显著高于其它区域,并且河口区域大肠菌群常年处于严重超标状态(最高为1.1×106cells/L,超过国家前三类水质标准的100倍)。根据大肠菌群的数量状况可以将胶州湾分为三个区域,即严重污染区、中度污染区和轻度污染区。该区域划分与通过营养盐对胶州湾区域的划分(富营养区、中度营养区、贫营养区)结果一致。     

Atlas of Japan (East) Sea hydrographic properties in summer, 1999

Hydrographic properties from CTD and discrete bottle sample profiles covering the Japan (East) Sea in summer, 1999, are presented in vertical sections, maps at standard depths, maps on isopycnal surfaces, and as property–property distributions. This data set covers most of the Sea with the exception of the western boundary region and northern Tatar Strait, and includes nutrients, pH, alkalinity, and chlorofluorocarbons, as well as the usual temperature, salinity, and oxygen observations.     

Preliminary optical classification of lakes and coastal waters in Estonia and south Finland

A preliminary optical classification of lakes in Estonia and south Finland which can also be used for small bays of the Baltic Sea is elaborated. The classification is based on the optical properties of water (diffuse attenuation coefficient, diffuse reflectance) and parameters that are routinely monitored in water bodies (Secchi depth, concentration of chlorophyll-a, total suspended matter and yellow substance). The data complex used for our classification covers different types of water ecosystems (ranging from oligotrophic to hypertrophic) and the variability of water constituent concentrations in the ice-free period in Estonia and south Finland. Using cluster analysis, we found 5 optical classes of waters: clear (C), moderate (M), turbid (T), very turbid (V) and brown (B). There is satisfactory correspondence between class of water, shape of diffuse attenuation coefficient and diffuse reflectance spectra and trophic state of the lakes.     

Outflow of the Intermediate Oyashio Water from Sagami Bay to the Shikoku Basin

Since the Intermediate Oyashio Water (IOW) gradually accumulates in Sagami Bay, it can reasonably be supposed that the IOW also flows out from Sagami Bay, even though it may be altered by mixing with other waters. We have occasionally observed a water less than 34.2 psu with a potential density of 26.8 at the southeastern area off Izu Peninsula in July 1993 by the training vessel Seisui-maru of Mie University. Observational data supplied by the Japan Meteorological Agency and the Kanagawa Prefectural Fisheries Experimental Station show that the IOW of less than 34.1 psu was observed at northern stations of the line PT (KJ) off the Boso Peninsula and to the east of Oshima in the late spring 1993. Based upon these observations, it is concluded that the IOW flows out from Sagami Bay into the Shikoku Basin along southeastern area off the Izu Peninsula. The less saline water (<34.2 psu) was also observed to the west of Miyake-jima during the same cruise, and the westward intrusion of IOW from south of the Boso Peninsula to the Shikoku Basin through the gate area of the Kuroshio path over the Izu Ridge was detected. This event indicated that the IOW branched south of the Boso Peninsula and flowed into Sagami Bay and/or into the gate area over the Izu Ridge. The southward intrusion of IOW into the south of the Boso Peninsula is discussed in relation to the latitudinal location of the main axes of the Kuroshio and the Oyashio. This revised version was published online in July 2006 with corrections to the Cover Date.