Role of wind forcing and eddy activity in the intraseasonal variability of the barrier layer in the South China Sea     

Zhanlin Liang  Qiang Xie  Lili Zeng  Dongxiao Wang 《Ocean Dynamics》2018,68(3):363-375

In addition to widely discussed seasonal variability, the barrier layer (BL) of the South China Sea (SCS) also exhibits significant intraseasonal variability (ISV) and plays an important role in the upper heat and salt balances. The characteristics and mechanisms of spatiotemporal variations in the BL are investigated using an eddy-resolving ocean model OFES (OGCM For the Earth Simulator) ouput and related atmospheric and oceanic processes. The active intraseasonal BL variability in the SCS occurs mainly during the late summer/autumn and winter and exhibits remarkable differences between these two periods. The BL ISV in late summer/autumn occurs in the southern basin, while in winter, it is limited to the northwestern basin. To further discuss the evolution and driving thermodynamic mechanisms, we quantify the processes that control the variability of intraseasonal BL. Different mechanisms for the intraseasonal BL variability for these two active periods are investigated based on the case study and composite analysis. During late summer/autumn, the active BL in the southern basin is generated by advected and local freshwater, and then decays rapidly with the enhanced wind. In winter, anticyclonic eddy activity is associated with the evolution of the BL by affecting the thermocline and halocline variations, while wind stress and wind stress curl have no obvious influence on BL.  相似文献   

黄茅海浮游生物及其粒径结构的潮汐变化特征研究     

刘子嘉  李芊  陈寅超  帅义萍  马梦真 《海洋与湖沼》2021,52(6):1408-1417

河口区浮游生物作为食物链的重要组成部分,在海洋生物地球化学循环中起到重要作用。为了解黄茅海河口浮游生物及其粒径结构的时空分布特征,于2017年8月17日至21日对黄茅海河口区域微微型浮游生物（pico-,<2 μm）,微型浮游生物（nano-,2-20 μm）及小型浮游生物（micro-,20-200 μm）及其粒径结构进行观测。结果显示,河口外侧总叶绿素a浓度最高,为19.34μg/L,且大粒径浮游生物占比最高。底层水体受上溯海水影响较为明显,表现出盐度及营养盐浓度随潮汐呈现显著的周期性变化。潮汐过程对不同粒径的浮游生物影响不同,对微微型浮游生物影响较小,对大粒径浮游生物影响较大。涨潮时,表层标准化浮游生物粒径谱（NBSS）斜率增大,大粒径浮游生物占比增多。落潮时,NBSS斜率减小,小粒径浮游生物占比增多。潮汐过程及由其引起的营养盐、温度和可利用光强的改变是影响黄茅海河口浮游生物分布的主要因素。研究可为河口区浮游生态系统以及海洋生物地球化学循环过程等的研究提供重要依据。  相似文献   

The impact of climate change and human activities on streamflow and sediment load in the Pearl River basin   总被引：2，自引：0，他引：2  

Chuangshou Wu  Changchen Ji  Benwei Shi  Yaping Wang  Jianhua Gao  Yang Yang  Jinbin Mu 《国际泥沙研究》2019,34(4):307-321

This paper uses monthly streamflow, suspended sediment concentration, and meteorological data to examine the impact of human activity and climate change on streamflow and sediment load in the Pearl River basin from the 1950s to the 2000s. The influences of climate change and human activities on hydrological processes were quantitatively evaluated using the Mann–Kendall abrupt change test and power rating curves. The results showed that:(1) abrupt changes and turning points in streamflow occurred in 1963, 1983, and 1991 which were found to be consistent with global ENSO events and volcanic eruptions. However, abrupt changes in sediment load showed significant spatial differences across the Pearl River basin. For the Xijiang River, an abrupt change in sediment load occurred in 2002, and after 2007 the change becomes significant at the 95% confidence level. At Beijiang and Dongjiang, abrupt changes in sediment load occurred in 1998 and 1988, respectively.(2) The time series of sediment load data was divided into four periods according to abrupt changes. The contribution of climate change and human activities is different in the different rivers. For the Xijiang River, compared with the first period, climate change and human activities contributed 83% and 17%, respectively, to the increasing sediment load during the second period. In the third period, the variation of sediment load followed a decreasing trend. The contribution from climate change and human activities also changed to t236% and -136%, respectively. In the fourth period, climate change and human activities contributed -32% and t132%, respectively. Meanwhile, For the Beijiang River, climate change and human activities contributed 90% and 10% in the second period, the contribution of climate change increased to t115% and human activities decreased to -15% in the third period. In the fourth period, the value for climate change decreased to t36% and human activities increased to t64%. For the Dongjiang River, the contribution of human activities was from 74.5% to 90%, and the values for climate change were from 11% to 25%. Therefore, the effect of human activity showed both spatial and temporal differences, and it seems likely that the decreased sediment load will continue to be controlled mainly by human activities in the future.  相似文献