Journal of Tropical Oceanography >
The freshening trend of surface salinity in the South China Sea in recent two decades and its mechanism
Received date: 2016-10-19
Request revised date: 2017-01-02
Online published: 2017-07-26
Supported by
National Natural Science Foundation of China (41522601,41230962, 41276025, 41506019)
The Open Project Program of State Key Laboratory of Tropical Oceanography (LTOZZ1501)
The Pear River S&T Nova Program of Guangzhou (201506010036)
Copyright
In situ hydrographic data of sea surface salinity (SSS) revealed a freshening trend in the northern South China Sea (SCS) during 2004—2012, which was the freshest in 2012. Such freshening was also found in the UK Met Office EN4 objective analysis product and the ocean general circulation model for the Earth Simulator (OFES) output during 1993-2014, particularly west of Luzon Island and in the southeastern SCS. The salinity budget analysis in the upper layer indicated that the fresh water forcing and horizontal salinity advection contributed to the trends of SSS west of Luzon Island and in the western SCS, respectively. The excessive precipitation in summer accounted for the decrease of SSS to a great extent west of Luzon Island, which was associated with the strengthening trend of the Walker Circulation.
FU Yuanyuan , CHENG Xuhua , ZHANG Yuhong , YAN Youfang , DU Yan . The freshening trend of surface salinity in the South China Sea in recent two decades and its mechanism[J]. Journal of Tropical Oceanography, 2017 , 36(4) : 18 -24 . DOI: 10.11978/2016101
Tab. 1 Data used for the analysis of salinity trend and its mechanism表1 盐度变化和机制分析所用数据 |
序号 | 资料 | 水平分辨率 | 变量 |
---|---|---|---|
1 | 南海北部航次资料 | 盐度 | |
2 | EN4客观分析资料 | 1°×1° | 盐度 |
3 | Ishii资料 | 1°×1° | 盐度 |
4 | OFES资料 | 0.1°×0.1° | 盐度、流速 |
5 | GPCP资料 | 2.5°×2.5° | 降雨量 |
6 | ECMWF资料 | 1°×1° | 蒸发 |
7 | WOA13资料 | 1°×1° | 盐度 |
Fig. 1 Stations of conductivity-temperature-depth (CTD) during the open cruises in the northern South China Sea of 2004-2012 (symbols) and the spatial distribution of the averaged SSS during August and September in the SCS (South China Sea) from the WOA13 data (shading)图1 2004—2012年南海北部开放航次温盐站点位置(散点)和WOA13资料8、9月份表层(0~50m)盐度平均值的空间分布(填色) |
Fig. 2 Time series of SSS in the northern SCS based on the open cruises data, the Objectively Analysis EN4 data and the Ishii data图2 南海北部开放航次、客观分析数据EN4和Ishii数据的表层盐度时间序列 |
Fig. 3 Time series of basin-averaged SSS anomalies from 1993 to 2014 in the SCS (blue). The black curve is the basin-averaged SSS anomalies with trend removed图3 基于EN4数据1993—2014年期间南海海盆(5°—23°N, 110°—121°E)平均的海表盐度时间序列(蓝色实线)及去趋势后的海表盐度时间序列(黑色实线) |
Fig. 4 Linear trends of SSS during 1993-2014 in the SCS derived from the EN4 data图4 基于EN4数据的南海表层盐度在1993—2014年期间的变化趋势 |
Fig. 5 Linear trends of SSS during 1993-2014 in the SCS derived from the OFES output图5 基于OFES模式的南海表层盐度在1993—2014年期间的变化趋势 |
Fig. 6 Linear trends of surface salinity advection (shading) and surface current (vector) during 1993-2014 in the SCS图6 基于OFES数据南海表层盐度水平平流(填色)和海流(箭头)在1993—2014年的趋势 |
Fig. 7 Linear trends of surface (a) zonal and (b) meridional salinity advections during 1993-2014 in the SCS图7 南海纬向(a)和经向(b)盐度平流在1993—2014年的趋势 |
Fig. 8 Linear trends of fresh water forcing derived from GPCP and ECWMF datasets (a) and surface salinity flux derived from the OFES output (b) during 1993-2014 in the SCS图8 基于GPCP和ECWMF的淡水强迫(a)和OFES的盐度通量(b)在1993—2014年的趋势 |
Fig. 9 Linear trends of spring-winter SSS during 1993-2014 in the SCS derived from the EN4 data (a-d) and linear trends of spring-winter precipitation forcing during 1993-2014 in the SCS derived from GPCP (e-f)图9 基于EN4数据的春季—冬季的南海表层盐度在1993—2014年期间的变化趋势(a—d)和基于GPCP数据的春季—冬季南海降雨在1993—2014年期间的变化趋势(e—f) 白色等值线是趋势的零值线 |
The authors have declared that no competing interests exist.
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