, 60 ,2016 2

`

SEASONAL VARIABILITY OF LAND-DERIVED PASSIVE TRACER DISPERSAL IN THE SETO INLAND SEA AND THE ENSHU-NADA COAST

1 2 2 Yusuke UCHIYAMA, Yota SUZUE and Taichi KOSAKO

1 657-8501 1-1

2 657-8501 1-1

Coastal marginal seas and estuaries are generally dumpsites for wastewater from sewage and power plants. For an urgent assessment of dilution and dispersal of toxic materials due to accidental leakage, we develop an offline passive tracer model by exploiting oceanic reanalysis products and analyze differences in spatiotemporal variability of the leaked tracers in an estuary and a continental shelf margin on the Pacific side of Japan. In the estuary, the northeastward through flow affects the dispersal, while the month-long transport is dominated rather by inter-seasonal variability of wind-driven Ekman flow and counter-clockwise local circulations associated with the cold-dome density structure. On the marginal coast, the Kuroshio and resultant secondary recirculation readily entrain the tracer, leading to immediate transport mostly in the alongshore direction. The seasonal difference in the tracer dispersal is apparent such as sporadic offshore tracer eruption episodes, depending on the locations of the Kuroshio path.

Key Words : ROMS, coastal dispersal, offline Eulerian passive tracer model, Kuroshio, Seto Inland Sea

1.

)1)

2)

(

)

traceroffline passive tracer 3)

offline offline

) tracer

tracer online

offline

)

tracer

2)

2)

2.

JCOPE2 4)

10 km )

ROMS 1-way offline 25-7)

5-7) 5, 6)

2 km ROMS−L1 600 m ROMS-L2 -1-1 7) ROMS−L1

3 km L2 1 km-2 -2 ROMS−L2

20132 5 8 11 1 0 UTC 31

tracer2)

(

) 112.2 1014 Bq/day 2.42 PBq

( 31 tracer) offline ROMS−L2

offline(

offline) online tracer 2

) 531 -3 offline

-5 3 offline online5 NE

tracer2 SW tracer

online offline)

offline online

offline tracer

offline

3. tracer

8)

)

-4

2 ) tracer(

offline 2 5 8

-1 2

L1 L2 m .

-2 2 L1

L2 m -10

-1 ROMS-L2

2012 1 1 2014 1 31 800 × 480 × 32 Δx = 600 m

JMA GPV−MSM 1 COAMPS 6)

TPXO7 10 DB ( )

-2 ROMS-L2

2012 1 1 2014 2 14 800 × 672 × 40 Δx = 1 km

JMA GPV-MSM 1 COADS NOAA,

-3 online 2013 2 5

31 tracer

11 ) 1 31) tracer

-5 ) 1 tracer70 km

NE SWtracer

NE 8)

SW-4 SW

)

11 ) NE30 km NE SW

)

2 NE) curl τs τs

[Pa]11

-6

11)

(

tracer NE -4

)

20 m -7 5 8

SW tracer

)

SW-7 )

) -8)

)9) cold dome

) -8

-6 2 11

N/m3

-4 GPV-MSM 10 m

m/s 2 5 8 11

-5 -4 31 tracer Bq/m3

0.2 m/s 0.2 m/s

10 15 km Etracer NE

4. tracer

(1) -9

tracer31 )

3

33 35oN

tracer EENE 300 km

tracer

tracer 2 58 11

58 tracer

tracer)

) tracer)

-1050 m )

20131 6

-7 -4 m/s

20m -8

-8 -3 5 8

E .

)

2 58 11

-9 )

-11tracer

tracer(

(2) tracer

tracer -9137.44oE )

138.84oE 233.0 oN 1 3

tracer

3 )

tracertracer

-3 )

31

2, 5 ) 8

1/2 1/3 5

-9 31 tracer Bq/m3

2 ( ) 5 ( ) 8 ( ) 11 ( )

-10 ROMS-L2

2013

-11 2013 10 km

4 GPV-MSMROMS-L2

E N m/s

-3 tracer TBq, ), ND: 0.01TBq , monthly:

31 , max, mean:

Transect) flux) Feb.) May) Aug.) Nov.)

West)137.44oE)

monthly) 768) 1263) 1214) 54.6)max) 908) 1310) 1820) 63.9)mean) 264) 312) 717) 10.7)

East)138.84oE)

monthly) 313) 39.3) 411) 734)max) 313) 39.3) 411) 755)mean) 31.4) 9.21) 28.6) 184)

South)33.0)oN)

monthly) ND) ND) 445) 662)max) ND) ND) 640) 662)mean) ND) ND) 48.4) 191)

Suruga)Bay)

monthly) 372) 222) 57.0) 1291)max) 1258) 2029) 108) 1831)mean) 367) 666) 27.3) 1159)

Ise/)Mikawa)

monthly) 0.15) 43.9) 56.4) ND)max) 0.15) 43.9) 56.4) ND)mean) 0.02) 5.45) 14.0) ND)

Sagami/)Tokyo)

monthly) 0.02) 4.41) 4.38) 13.4)max) 0.02) 4.41) 4.38) 13.7)mean) ND) 0.24) 0.68) 3.01)

residual)in)the)box)

monthly) 1339) 1118) 350) 969)rate)(%)) 55.3%) 46.2%) 14.5%) 40.0%)

8, 11-9

) 31

1

3× 11

2.42 PBq 1.29 PBq

31 2 9

tracer

tracer

(

5, 8 44 56 TBq

11 14 TBq2.42 PBq 0.6 2.3%

-3 31)

tracer8 1 40 55

tracer 8

tracer14.5%

5.

tracer

2013 1tracer

) 2

tracer 70 [km/ ] 8)

9)

tracer4

tracer

JAMSTEC

25110508, 24560622, 15H04049, 15H00977

)

1) Uchiyama, Y., Idica, E., McWilliams, J.C. and Stolzenbach, K.D.: Wastewater effluent dispersal in Southern California Bays, Cont. Shelf Res., No. 76, pp. 36-52, 2014.

2) 137

B2 Vol.68, No. 2, pp. I_931-I_935, 2012.

3) Idica, E. Y.: Contaminant Transport in the Southern California Bight, Ph.D. Dissertation, UCLA, 154 p., 2010.

4) Miyazawa, Y. and coauthors: Water mass variability in the western North Pacific detected in a 15-year eddy resolving ocean reanalysis. J. Oceanogr., Vol. 65, pp. 737-756, 2009.

5)

B2 , No. 68, Vol. 2, pp. I_441-I_445, 2012.

6) B3

, Vol. 71, No. 2, pp. I_383-I_388, 2015. 7)

) Argo 3,

B3 , Vol.71, No.2, pp. I_365-I_370, 2015. 8)

, B2 , Vol.71, No.2, pp. I_1231-

I_1236, 2015. 9) Chang, P.-H., Guo, X., and Takeoka, H.: A numerical study on

the seasonal circulation in the Seto Inland Sea, Japan. J. Oceanogr., Vol. 65, pp. 721-736, 2009.

2015.9.30