Geoscience Reference
In-Depth Information
side. The nSCS is connected to the East China Sea through Taiwan Strait, and it is
connected to the open ocean through Luzon Strait, where a deep sill (>2,000 m) al-
lows effective water exchange with the western Pacifi c. The topography of the area is
characterized by the incline from the coast of mainland China towards the southeast,
with a gradient from the coastal zone (<50 m), continental shelf (<200 m), the slope
and open sea (>200 m), to the deep sea (>3,000 m) (Figure 1).
Figure 1.
Geographical locations of the transect and stations and the circulation in the northern
South China Sea (nSCS) (modified from Su, 1998; Xue et al., 2004). Transect N from the Pearl River
Estuary towards the southeastern nSCS is the main transect with six stations (full circle).
The runoff from 29 rivers, with different sized input into the nSCS with total drain-
age area of 5.5 × 10
5
km
2
, and an annual fresh water discharge of 3.8 × 10
11
m (Han et
al., 1998). Among them, the Pearl River is the largest with a drainage area of 4.3 × 10
5
km
2
and a discharge of 3.3 × 10
11
my
−1
(Han et al., 1998). It carries a large quantity of
suspended solids (8.3 × 10
7
ty
−1
, Han et al., 1998) and dissolved nutrients (N = 8.6 ×
10
4
ty
−1
; P = 1.2 × 10
4
ty
−1
; Si = 184.3 × 10
4
ty
−1
, before 1998, Wang and Peng, 1996;
and N = 19.14 × 10
4
ty
−1
, P = 0.8 × 10
4
ty
−1
after 1998, SOAC, 2000, 2001a, 2002,
2003, 2004) into the nSCS. The Pearl River plume extends offshore to cover a large
area of the nSCS (Yin et al., 2001). During the dry season in winter, the river plumes
extend westward along the coast of Guangdong. Due to the strong northeast monsoon;
during the fl ood season in summer, the river plume extends well into the nSCS, and
its southeastward and southward tongue can reach up to 17°00'N, 112°E, about 5°, in
latitude, away from the river mouth (Cai et al., 2007; Xue et al., 2001a, b).
The meteorological forcing over the nSCS is dominated by the East Asian Mon-
soon (Sadler et al., 1985). The upper ocean circulation follows closely the alternat-
ing monsoons (Wyrtki, 1961). During winter northeast monsoon, along the northern
boundary, the warm and saline Kuroshio Current water with oligotrophic properties
intrudes through Luzon Strait and fl ows westward along the continental margin of
China to become the deep-water mass of the nSCS (Nitani, 1972; Shaw, 1991). The
