The turbidity maxima of the northern Jiangsu Shoal-water in the Yellow Sea, China

Xiao Hua Wang1, Fangli Qiao2, Jing Lu2 and Fang Gong3

1School of Physical, Environmental and Mathematical Sciences, University of New South Wales atAustralian Defence Force Academy, Canberra, ACT 2600, Australia

2First Institute of Oceanography, State Oceanic Administration, Qingdao, China

3State Key Laboratory of Satellite Ocean Environment Dynamic, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China

32 ～33.5 N，120.40 ～122.10E;200 km longitudinally and 140 km latitudinally;The water depth less than 10m;Total area: 22470 km2;More than 70 sand ridges extending from Jianggang offshore;Tidal flat area: 3700 km2.

From Song et al., 2006

MODIS-Aqua 2008

MODIS (mg l-1)

Exp 1 (mg l-1)

Exp 2 (mg l-1)

2006 March 50.1 36.2 9.7

April 50.9 36.4 9.3

2007 March 42.9 48.1 10.2

April 32.7 35.8 9.4

2008 March 42.0 31.5 9.6

April 22.9 34.6 9.4

Average March 45.0 38.6 9.8

April 35.5 35.6 9.4

Monthly averaged surface suspended sediment concentration for March and April 2006-2008

)531(/)551()]667()551([991.0385.5)ln( nmRnmRnmRnmRC rsrsrsrs ×+×+=

Mar

April

Wind stress (N/m2)

Jan06 Apr06 Jul06 Oct06 Jan07 Apr07 Jul07 Oct07 Jul08 Apr08 Jul08 Oct08-0.7-0.6-0.5-0.4-0.3-0.2-0.1

00.10.20.30.4

Wind stress (N/m2)

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Heat flux (W/m2)

0.03 N/m2

W/m2

2008

0.08m/s

2008Jiangsu coast, Yellow Sea

m/s

N/m2

N/m2

Exp 1: the SWAN simulated wave fields were used for wave-current interaction in the BBL;

Exp 2: the wave effects on the bottom stress were not considered

mg/l

Exp 1-Exp 2 Exp 1-Exp 2

g/(m2s)Spring 2008

Winter 2008

Exp 1 Exp 2

Cross section N

(kg s-1)

March -1 -1

April 1 0

Cross section J

(kg s-1)

March 6269 2959

April 12042 3947

Cross section S

(kg s-1)

March -2390 -1581

April -4037 -1146

Cross section E

(kg s-1)

March 40 41

April 131 139

The model predicted monthly averaged sediment flux at the cross sections N, J, S and E  for March and April 2008 (Positive flux is in northward or eastward direction)

MODIS (mg l-1) Exp 1 (mg l-1) Exp 2 (mg l-1)

2006 March 50.1 36.2 9.7

April 50.9 36.4 9.3

2007 March 42.9 48.1 10.2

April 32.7 35.8 9.4

2008 March 42.0 31.5 9.6

April 22.9 34.6 9.4

Average March 45.0 38.6 9.8

April 35.5 35.6 9.4

Wind speed

(m s-1)

Wave

amplitude (m)

2006 March 6.03 0.78

April 6.06 0.82

2007 March 6.68 0.90

April 5.88 0.66

2008 March 5.65 0.64

April 5.50 0.65

Monthly averaged surface suspended sediment concentration for March and April 2006-2008

Direct Economic Cost:87.3 million US$(Wang et al, 2009, EOS)

6月22日－回推至4月23日

Summary and conclusions

-- Surface waves played a dominant role over the tides to form the turbidity maxima in the NJSW region: surface SSC value increased by a factor of 4, and sediment flux by a factor of 3;

-- As March and April 2008 was a wind anomalous year with a decreased wind speed over last three years, the wind generated waves in the region were also reduced, leading to lower sediment resuspension and SSC in that year: possible cause of the algae bloom in Summer 2008;

-- In March and April, sediment flux is northward along the northern Jiangsu coast; while during winter months (December – January) sediment flux is southward due to the dominantly northerly wind.

The wave-current couplingBottom stress:

Where hs is the wave height, k the wavenumber, ω=2π/Ts and fcw is the wave-current friction factor as from Grant-Madson (1986).

We have now allowed the mean current acted at any angle with the direction of the wave propagation

2u wu+= bcwb f ρ21τ

uw = 0.5hsω / sinh(kH)ω 2 = gk tanh(kH )