Journal of Tropical Oceanography ›› 2021, Vol. 40 ›› Issue (6): 63-75.doi: 10.11978/2020151CSTR: 32234.14.2020151

• Marine Environmental Science • Previous Articles     Next Articles

Interannual variation of subsurface chlorophyll maximum in the northern South China Sea

WANG Renzheng1,2(), SHAN Zhengduo1, MENG Siyu2, GONG Xiang1()   

  1. 1. School of Mathematics and Physics, Qingdao University of Science and Technology, Qingdao 266061, China
    2. College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
  • Received:2020-12-24 Revised:2021-03-09 Online:2021-11-10 Published:2021-03-15
  • Contact: GONG Xiang E-mail:2818622577@qq.com;gongxiang@qust.edu.cn
  • Supported by:
    National Natural Science Foundation(U1906215)

Abstract:

Subsurface chlorophyll maxima (SCMs) are widely found in the global oceans. The layer of SCM accounts for a great proportion of marine primary productivity and new productivity. Studying the interannual variation of SCMs can deepen our understanding of marine ecosystems under climatic change. In this study, a one-dimensional physical-biological coupled model (MEM-1D) was used to simulate the vertical distribution of ocean temperature, salinity, nutrients, and chlorophyll in the northern South China Sea from 1994 to 2019. Based on numerical modeling results, we analyzed the interannual variations of SCM characteristics (intensity, depth and thickness) using three statistical methods from different aspects, i.e., overall trend, different time scales and significant changes. In general, the intensity of SCMs from 1994 to 2019 shows a slightly decreasing trend (the trend slope S<0). Specifically, the SCM intensity decreased from 1994 to 2004 ( decreased significantly from 1999 to 2004), while it increased from 2005 to 2012 and then decreased until 2019. The depth of SCMs showed a deepening tendency between 1994 and 2019 (the trend slope S>0), gradually becoming deeper from 1994 to 2011, and then shoaling; but the changing trend was not significant. The thickness of SCMs increased as a whole, and it had increased significantly since 1999. Correlation analysis showed no relationship between annually averaged sea-surface temperature (SST) and the characteristics of SCMs (P>0.05). The influence of SST on SCMs was mainly on the seasonal scale, and the depth and intensity of SCMs changed consistently with SST. The seasonal, autoregressively integrated moving average model has a good fit for the three characteristics of SCMs, with the mean absolute percentage errors of 5.33% for intensity, 0.62% for depth and 2.49% for thickness, indicating that the model can be used to predict the trend of SCM characteristics.

Key words: subsurface chlorophyll maximum, trend statistical analysis, time series model, numerical simulation, northern South China Sea

CLC Number: 

  • X145