基于遥感分析渤海湾冬季表层悬浮体浓度变化规律

渤海湾是三面环陆的半封闭浅水海湾,海底泥沙悬浮与输运对海洋工程与生态环境有重要影响。冬季是渤海泥沙输运、海床冲刷和海底灾害的主要发生季节,但冬季观测(特别是连续观测)难度大,观测资料相对缺乏,研究冬季悬浮体分布与输运规律对海洋生态环境保护和海洋工程维护等具有指导意义,对认识近海物质及能量循环有重要科学价值。本文基于海洋水色卫星GOCI(Geostationary Ocean Color Imager)遥感影像资料,对渤海湾冬季悬浮体浓度进行了长达8年监测,提取2011—2017年冬季(11、12、1、2月)悬浮体浓度(Total Suspended Sediment, TSS)月平均数据,对渤海湾冬季悬浮体分布情况及输运规律进行研究。结果表明,渤海湾冬季的表层悬浮体浓度分布呈现近岸高离岸低、南岸高北岸低的规律,悬浮体浓度的高值区主要分布于黄河口附近以及渤海湾南岸一带,该海域冬季TSS在80mg/L以上,最高可达200mg/L;海河口及辽东湾沿岸流区域各存在一个低值区,悬浮体浓度介于0—40mg/L。冬季大风天气对水体扰动剧烈,导致渤海湾海底泥沙再悬浮,风速与悬浮体浓度存在正相关性。同时,冬季渤海湾沿岸流等环流增强,使黄河口再悬浮的沉积物向渤海湾西部和北部扩散。

ANALYSIS OF SUSPENDED SEDIMENTS CONCENTRATION IN THE BOHAI BAY IN WINTER BASED ON REMOTE SENSING

Bohai Bay is a semi-enclosed shallow bay of the Bohai Sea, North China. Understanding the material and energy circulation in coastal areas at seabed is important for local marine engineering and ecological environment. Winter is the main season of sediment transportation, seabed erosion, and geologic hazards in the Bohai Sea. However, observation of the suspending sediment in winter (especially continuous observation) is difficult, and the observation data are relatively scarce. Based on the GOCI (Geostationary Ocean Color Imager) remote sensing image data, we conducted an 8-year observation to monitor the concentration of suspended sediments in Bohai Bay in winter (November, December, January, and February) from 2011 to 2017. The monthly averaged data of Total Suspended Sediments (TSS) concentration were obtained, with which distribution and transportation of suspended sediments in winter were analyzed. Results show that the TSS of near-shore areas was much higher than that of the offshore, and higher in the south coast than that of the north coast. The high-TSS areas distributed mainly near the Huanghe (Yellow) River estuary and on the southern coast of the Bohai Bay. In winter, TSS concentration was often above 80 mg/L, and the maximum could reach 200 mg/L occasionally. A low-TSS area was observed each in Haihe River estuary and Liaodong Bay coastal current area, where the TSS concentration was between 0 and 40mg/L. The strong wind in winter disturbed the water seriously, which resulted in the resuspension of sediment in the Bohai Bay. At the same time, circulation systems such as coastal current in Bohai Bay were strengthened in winter, making the sediments of the Huanghe River estuary re-suspended and diffused westward and northward in the Bohai Bay.