Premium
Summer upwelling and thermal fronts in the northwestern S outh C hina S ea: O bservational analysis of two mesoscale mapping surveys
Author(s) -
Jing Zhiyou,
Qi Yiquan,
Du Yan,
Zhang Shuwen,
Xie Lingling
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2014jc010601
Subject(s) - upwelling , mesoscale meteorology , oceanography , submarine pipeline , monsoon , geology , wind stress , forcing (mathematics) , sea surface temperature , front (military) , climatology
Persistent coastal upwelling and upwelling‐induced thermal fronts in the northwestern South China Sea are investigated using satellite measurements, two intensive mesoscale mapping surveys and three bottom‐mounted ADCPs. The results indicate that pronounced surface cooling and upwelling‐related fronts with a width of 20–50 km occur around Hainan Island and persist through the summer upwelling season. Driven by the prevailing southwesterly monsoon, the subsurface cooling band is ∼6°C colder than the water offshore of the East Coast, where the thermal gradients are generally more than 0.1°C/km. The cold and nutrient‐rich coastal water is identified to be derived primarily from the deep water of the outer shelf. At the same time, the spatial structure of the upwelling and thermal front, as well as the upwelling‐related coastal currents, is significantly regulated by wind forcing. A prominent lagged correlation between the moored temperature records and alongshore wind stress is detected in the East Coast. The correlation coefficient is −0.8 with the temperature lagging behind wind stress by 2.2 days, indicating that the cooling band off the East Coast is dominated mostly by the alongshore southwesterly monsoon during the upwelling season.