Abstract

The influence of seasonal, monsoonal winds on the temporal and spatial variability of chlorophyll-a (chl-a) in the Beibu Gulf is studied based on long-term satellite data of sea surface winds, chl-a concentration and sea surface temperature (SST) and in-situ observations for the years from 2002 to 2014. The analysis results indicated that under northeasterly monsoonal winds, chl-a concentrations were substantially elevated in most area of the Beibu Gulf, with a high chl-a concentration (>2 mg m-3) patch extending southwestward from the coastal water of the northeastern Gulf, consistent with the winter wind pattern. Meanwhile, the spatial distribution of high chl-a concentration is correlated with low SST in the northeastern Gulf. In the southern Gulf, there was generally low chl-a, except in the coastal waters southwest of Hainan Island. Here, the upwelling cold water prevails outside the mouth of the Beibu Gulf, driven by the southwesterly monsoonal winds and the runoff from the Changhua River, as implied by low observed SST. Correlation analysis indicated the chl-a concentration was strongly modulated by wind speed (r = 0.63, p<0.001), particularly in the middle of the northern Gulf and southern Hainan Island (r>0.7, p<0.001). Integrated analysis also showed that stratification is weak and mixing is strong in winter as affected by the high wind speed, which suggests that the wind-induced mixing is a dominant mechanism for entrainment of nutrients and the spatial distribution of chl-a in winter.

Highlights

  • Annual atmospheric and upper ocean variability in the South China Sea (SCS) region are primarily controlled by the East Asian monsoon, with strong northeasterly monsoonal winds prevailing from September to April, and weak southwesterly monsoonal winds present from July to August [1,2,3]

  • We evaluate Moderate Resolution Imaging Spectrometer (MODIS)-derived chl-a data in combination with in-situ observations in the Beibu Gulf

  • The results indicate a high correlation (r = 0.84, p

Read more

Summary

Introduction

Annual atmospheric and upper ocean variability in the SCS region are primarily controlled by the East Asian monsoon, with strong northeasterly monsoonal winds prevailing from September to April, and weak southwesterly monsoonal winds present from July to August [1,2,3]. Previous studies have confirmed that the East Asian monsoon plays an important role in regulating the spatial distribution of chl-a in the SCS [1, 4,5,6]. Open Foundation of State Key Laboratory of Tropical Oceanography, South China Sea Institute o fOceanology, Chinese Academy of Sciences.

Methods
Results
Discussion
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call