The Ocean Circulation of Chatham Sound,British Columbia,Canada: Results From Numerical Modelling Studies Using Historical Datasets

Chatham Sound, a semi-enclosed inland sea located off northern British Columbia, is an important waterway due to many proposed industrial activities related to the Port of Prince Rupert, along with its high levels of marine productivity. The oceanographic forcing in Chatham Sound is complex due to a combination of large tides, seasonally strong winds, and large freshwater discharges. Although much oceanographic data have been collected over the past six decades, past studies of the oceanographic regime of the full Chatham Sound area have been very limited. Using these extensive forcing datasets, high-resolution three-dimensional numerical modelling using the Coastal Circulation model for Sediment transport was conducted to investigate the tidal and wind-driven currents in the stratified waters of Chatham Sound. The numerical study shows the progression of the river-dominated lower salinity near-surface waters being advected northward, especially on the eastern side of Chatham Sound, with more saline waters on the western side of the Sound, especially in areas of exchanges with the waters of Hecate Strait through side channels. These surface circulation results are in good agreement with the large-scale representation of the outer diffuse Skeena River plume as seen in high-resolution Landsat satellite imagery. The model was operated over a representative year with four seasonal model runs. Southern Chatham Sound was found to be dominated by large tidal currents. Seasonal variations of residual flow were also investigated. Significant correlation between non-tidal current speeds and Skeena River discharges was found in the Skeena River delta area and through narrow tidal channels in southern Chatham Sound. In other offshore areas, non-tidal currents were found to be constrained near the surface and driven mainly by winds.     

North Indian Ocean warming and sea level rise in an OGCM

The variability in the long-term temperature and sea level over the north Indian Ocean during the period 1958–2000 has been investigated using an Ocean General Circulation Model, Modular Ocean Model version 4. The model simulated fields are compared with the sea level observations from tide-gauges, Topex/Poseidon (T/P) satellite, in situ temperature profile observations from WHOI moored buoy and sea surface temperature (SST) observations from DS1, DS3 and DS4 moored buoys. It is seen that the long (6–8 years) warming episodes in the SST over the north Indian Ocean are followed by short episodes (2–3 years) of cooling. The model temperature and sea level anomaly over the north Indian Ocean show an increasing trend in the study period. The model thermocline heat content per unit area shows a linear increasing trend (from 1958–2000) at the rate of 0.0018 × 10¹¹ J/m² per year for north Indian Ocean. North Indian Ocean sea level anomaly (thermosteric component) also shows a linear increasing trend of 0.31 mm/year during 1958–2000.     

北太平洋经向翻转环流年际变化的数值模拟

北太平洋经向翻转环流(NPMOC)是北太平洋所有经向翻转环流圈的总称,拥有5个环流圈结构.其中,热带环流圈(TC)、副热带环流圈(STC)和深层热带环流圈(DTC)位于北太平洋热带-副热带海域,是该海域间经向物质和能量交换的重要通道.主要运用NEMO模式对这3个经向翻转环流圈的年际变化特征和机理进行了研究.结果表明,TC、STC和DTC的经向流量都具有显著的年际变化特征:在El Nio期间,TC的南、北向流量均减弱,STC的北向流量增强、南向流量减弱,DTC的南向流量减弱;而在La Nia期间则相反.敏感性试验表明,在风应力强迫下得到的TC、STC南、北向流量和DTC南向流量的年际变化特征都很显著,并与在风应力、热通量和淡水通量共同强迫下得到的结果非常一致;而仅在热通量和淡水通量的强迫下,各分支流量的年际变化均较小.由此可见,风场驱动是引起北太平洋经向翻转环流年际变化的主要驱动因素,而热通量和淡水通量的影响却较小.     

基于FVCOM的台湾海峡三维潮汐与潮流数值模拟研究

基于FVCOM海洋数值模式,采用非结构三角形网格较好地刻画了台湾海峡复杂的岸线边界及海底地形,建立了台湾海峡的三维潮汐潮流数值模型.模拟结果同长期观测资料符合良好,较好地反映出台湾海峡内潮汐、潮流运动的变化状况和分布特征,利用T_tide工具包进行水位潮流调和分析给出了M2、S2、K1、O1四个主要分潮的同潮图、表层潮流椭圆分布.分析表明,M2分潮由台湾岛南北两端传入台湾海峡,两支潮波在澎湖—台湾浅滩南缘相遇,呈NE—SW向倾斜,振幅最大值为2.45m,出现在福建省湄洲湾、兴化湾一带.K1分潮潮波由东北向西南传入,并向南海传播,传播方向上右侧振幅较左侧大0.05m.台湾海峡存在一条分潮潮流椭圆率为0的分隔线,该分隔线大致呈NE—SW走向,分隔线上半部分潮流椭圆旋转方向为逆时针方向,下半部分为顺时针方向.四个主要分潮潮流椭圆长轴基本呈NE—SW走向,但在台湾浅滩表层潮流椭圆长轴方向为NW—SE向,澎湖水道呈N—S向.台湾浅滩处四个分潮的潮流椭圆均较大,对应的潮流也强,可能受当地水深较浅的影响.     

Decadal Climatic Anomalies in the Northern Adriatic Sea Inferred from a New Oceanographic Data Set

Abstract. In 1997, Artegiani et al. depicted for the first time the seasonal climatology of the Adriatic Sea; they used the ATOS data set, formed by 5540 oceanographic stations sampled over this continental basin from 1911 to 1980. Lately, two Italian institutes working on the Adriatic Sea for long time, IBM and IRPEM, merged their recent data sets for the northernmost part of the basin. This yielded 3600 new oceanographic stations, concentrated in an area where 809 ATOS stations were located. The new data were quality checked, and then a seasonal climatology was drawn up as a first analysis step. The new climatology differed significantly from the ATOS results; this could be explained, at least partially, by the climatic changes that have occurred on this area. For example, air temperature increased significantly over northern Italy starting from 1988. Variations of the observed air temperature and Po River runoff qualitatively agree with sea surface temperature and salinity variations. A preliminary computation of heat fluxes based on ECMWF reanalysis confirms an increased heat flux to the Northern Adriatic Sea starting from 1988.     

Atmospheric input of anthropogenic phosphorus to the northwest mediterranean under oligotrophic conditions

Phosphorus (P) concentration in the atmospheric aerosol was measured at a northwestern Mediterranean coastal site. Airborne P ranged between 25 and 85 ng m(-3) (geometric mean: 51 ng m(-3)). Due to a significant contribution (about 90%) of anthropogenic land-based source emissions, dry deposition velocities of 0.1-0.5 cm s(-1) were used to estimate a dry flux of 0.15-0.7 micromol P m(-2) day(-1). The theoretical impact of the dry flux on primary production (0.1-0.4 mg C m(-2) day(-1)) is 50-200-fold lower than that of a single significant wet event. The incineration plant of the Nice district is identified as a possible major source of airborne anthropogenic P. As the implementation of waste plants is currently expanding along the western European shores, the importance of the P atmospheric source to the western Mediterranean is likely to increase with time.     

Seasonal dynamics, environmental preferences and habitat selection of John Dory (Zeus faber)

Spatial distribution patterns of John Dory (Zeus faber, L.) were examined in relation to sea bottom temperature, bathymetry, locational covariates and season. Data were collected during a 2-year period (1996–1997) of seasonal sampling using demersal trawl surveys in the Aegean Sea (eastern Mediterranean). The ecological preferences of the species throughout four seasons were elucidated and the degree in which these environmental relationships might be modulated by the different hydrographic and topographic regime was also considered. Key determinants of the species' spatial aggregation in all four seasons were the water depth, the sea bottom temperature and the latitude. The sea bottom temperature had a significant effect on seasonal John Dory abundance both directly, as a main effect, and indirectly, through its interactive effect with the water depth. John Dory seasonal abundance was consistently greater in the shallower regions of the area having warmer bottom waters. Results indicated a distinct southward shift as progressing through the year, with peak abundances being observed in gradually lower latitudes of shallow areas as seasons evolved. John Dory appeared to avoid the deeper waters regardless of their bottom temperature and geographic position. The present results also suggested a seasonal pattern of habitat associations for specific locations characterised by weak hydrographic activity. John Dory preferences for certain water depth zones, sea bottom temperatures and substrate types are hypothesized to modulate the seasonal spatial aggregation of the species to preferred grounds.