2001-2020年南海周边河流入海沉积物通量时空变化特征研究

Spatial and temporal variations of sediment flux entering into the South China Sea from 2001 to 2020

在人类活动和快速气候变化的影响下,南海周边河流入海沉积物通量发生巨大变化。本文基于2001-2020年间南海周边河流数据及海表悬浮沉积物浓度数据,探究南海周边河流入海沉积物通量的时空变化特征。研究结果表明:2001-2020年南海周边河流入海沉积物通量超过345 Mt/a,人类活动导致珠江、红河、湄公河入海沉积物通量减少约300 Mt/a。南海周边河流入海沉积物通量还受台风和气候变化的影响:台风是影响南海周边河流入海沉积物通量的重要因素,尤其是台风期间台湾地区的高屏溪入海沉积物通量可达全年总量的89%。在东亚季风系统影响下,南海周边河流入海沉积物通量表现出雨季高、旱季低的变化特征,雨季期间入海沉积物通量占全年总量的80%以上,相应地,河流表层羽流在雨季具有浓度高和扩散范围大的典型特征。受厄尔尼诺-南方涛动的影响,南海周边河流流量和入海沉积物通量也存在不同周期变化,南海周边大型河流入海沉积物通量表现出2.5~3.0 a的变化周期,并与NI?O3.4指数存在相关性。本文利用20年的河流数据系统论证了台风、气候变化和大坝建设对21世纪以来南海周边河流入海沉积物通量的影响,在源汇过程研究及流域治理方面具有重要意义。

Under the influence of human activities and rapid climate change,the fluvial sediments flux entering in-to the South China Sea(SCS)has changed greatly.Based on the hydrological data of rivers around the SCS and sea surface Suspended Sediment Concentration data from 2001 to 2020,this study investigated spatial and temporal variation of sediment flux entering into the SCS.The results show that the sediment flux entering into the SCS ex-ceeds 345 Mt/a during 2001-2020.Human activities result in a reduction of 300 Mt/a in sediment flux from the Zhujiang River,Red River and Mekong River.The sediment flux is also affected by typhoons and climate change:typhoons are the most important factor affecting the sediment flux of small rivers,and the sediment flux of the Gaoping River during the typhoon can reach 89%of total.Under the influence of the East Asian monsoon system,the sediment flux entering into the SCS characterized by significant seasonal variations,the sediment flux is high in wet season and low in dry season.During the wet season,the sediment flux entering into the SCS accounted for more than 80%of total,accordingly,the river plume has the typical characteristics of high concentration and large diffusion range in the wet season.Under the influence of El Niño-Southern Oscillation,the discharge and sediment flux into the sea around the South China Sea also have different periodic changes.The river discharge and sediment flux of large rivers around the South China Sea show a 2.5-3.0 a period,and are correlated with the NIÑO3.4 index,while the sediment flux Taiwan rivers has no obvious period on the interannual scale.Based on data of the 20 a,this study systematically demonstrates the influences of extreme weather,climate change and dam construction on the sediment flux entering into SCS since the 21st century,which is of great significance in the study of source-to-sink processes and watershed management.