基于高频地波雷达观测的粤西近海潮流潮能分析

利用粤西海域高频地波雷达观测得到的表层海流资料进行潮流调和分析。结果表明:粤西近海主要属于不正规半日分潮,浅水分潮较强。以M_2分潮为例,潮流运动形式主要为逆时针的往复流为主,方向沿西北—东南方向。粤西近海的潮能主要由东部陆架输送进来,潮能自东向西传播,在大潮期间,粤西的潮能出现向岸方向分量,表现为从东南向西北方向传播,在近岸区域潮能通量传播的方向会发生一个向岸的偏转。通过潮能收支方程计算潮能耗散,发现粤西近海潮能耗散的高值区在西部岛屿密集区域,与琼州海峡的存在和琼州海峡东北处地形变化存在明显的相关关系。

南海北部夏季叶绿素a分布规律及影响因素

采用2002—2016年6—9月Aqua/MODIS叶绿素a产品分析珠江冲淡水在南海北部生态效应的季节及年际变化特征。6月来自陆源的营养物质在西南季风作用下向河口以东陆架区输运,浮游植物增殖,叶绿素a含量增大;7月河口以东高浓度叶绿素a覆盖面积达到最大;8月在减弱的珠江径流和环境风场共同影响下,口门外海高浓度叶绿素a覆盖面积明显减小;9月北部陆架区处于东北季风影响之下,河口以西覆盖面积逐渐增大。通过线性回归分析可知,珠江径流量是口门外海高浓度叶绿素a覆盖面积的主要影响因素,且这种影响有一个月左右的滞后效应。显著大于(小于)多年平均的珠江径流量和环境风场等因素共同作用,导致2008(2004)年表现为高浓度叶绿素a覆盖面积的极大值(极小值)年份。叶绿素a在南海北部陆架区的时空变化特征主要受冲淡水过程影响,订正过的卫星叶绿素a产品可以用来讨论珠江冲淡水的季节及年际变化。

The Origin,Historical Variations,and Distribution of Heavy Metals in the Qiongzhou Strait and Nearby Marine Areas

We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas.The areas of high concentrations are primarily outside the eastern mouth of the Qiongzhou Strait and on the west side of the Leizhou Peninsula,whereas the areas of low concentrations are located primarily in the eastern Qiongzhou Strait.The maximum Cd,Pb and Zn concentrations in the samples collected in our study do not exceed the official standards for marine sediments,whereas the concentrations of Cr and Cu slightly exceed the standards.Correlations exist between the concentrations of Cu,Pb,Zn,Cr and Cd,and the concentrations of these metals are positively correlated with the mean particle size(φ value),indicating that the finer sediments have adsorbed greater amounts of heavy metal elements than the coarser sediments.An evaluation of the potential environmental risks demonstrates that certain indices of heavy metal pollution and environmental risks are relatively low and may be assigned low risk levels,thereby indicating that,in terms of heavy metals,the marine sedimentary environment in this region is only mildly impacted.Our analysis of the contaminant origins shows that the heavy metals in this region primarily originate in the Pearl River Estuary and that a small amount of them is derived from local runoff.The elevated heavy metal concentrations from the upper sections of the cores started 130 years ago,which indicats that heavy metals in the surface sediments are primarily due to human activities associated with industrialization.

Comparison of summer chlorophyll a concentration in the South China Sea and the Arabian Sea using remote sensing data

The South China Sea（SCS） and the Arabian Sea（AS） are both located roughly in the north tropical zone with a range of similar latitude（0°–24°N）. Monsoon winds play similar roles in the upper oceanic circulations of the both seas. But the distinct patterns of chlorophyll a（Chl a） concentration are observed between the SCS and the AS.The Chl a concentration in the SCS is generally lower than that in the AS in summer（June–August）; the summer Chl a concentration in the AS shows stronger interannual variation, compared with that in the SCS; Moderate resolution imaging spectroradiometer（MODIS）-derived data present higher atmospheric aerosol deposition and stronger wind speed in the AS. And it has also been found that good correlations exist between the index of the dust precipitation indicated by aerosol optical thickness（AOT） and the Chl a concentration, or between wind and Chl a concentration. These imply that the wind and the dust precipitation bring more nutrients into the AS from the sky, the sub-layer or coast regions, inducing higher Chl a concentration. The results indicate that the wind velocity and the dust precipitation can play important roles in the Chl a concentration for the AS and the SCS in summer. However aerosol impact is weak on the biological productivity in the west SCS and wind-induced upwelling is the main source.