Observations of Volume Transport in the Taiwan Strait
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II 2.04 ) / ( 13.74 ) ( 2 + = m N Sv
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Abstract Several cruises of current measurements along various cross-taiwan Strait transects were conducted by using shipboard Acoustic Doppler Current Profiler (ADCP) during 2001-2003. The main purpose of these experiments is to obtain seasonal variations of flow structures and volume transport in the central and southern regions of the Taiwan Strait. In each cruise the semidiurnal tidal currents were eliminated from the ADCP currents by two different methods, i.e., the phase averaging method and the TSNOW calculation. The subtidal current in the Taiwan Strait generally flows in the parallel-strait direction. In summer when the southwest monsoon prevails, the water in the strait originates from the South China Sea (SCS) or the Kuroshio. This northward-flowing water is divided into two parts by the archipelago of Penghu; the majority keeps flowing northward along the Penghu Channel (PHC), the minority flows northwestward around the Penghu Island. The flows in the surface layer of the PHC reach a maximum speed of 60 cm/s or greater. In winter, strong NE winds push the fresh and cold China Coastal water southward, along the western part of the Taiwan Strait. The SCS or Kuroshio water still flows northward on the eastern part of the strait. The maximum northward current still occurs in the PHC and is around 20 cm/s or less in the winter. Our results from the phase averaging method of all six cruises indicate that the net transports along the Taiwan Strait are all flowing northward, with a maximum value of about 2.5 Sv in summer (August 2001) and a minimum value of about 0.5 Sv in winter (March 2003). The standard deviation of the volume transport is ± 0.3 Sv. Due to its greater depths and strong currents, the volume transport in the PHC amounts to approximately 75% of the total transport of the Taiwan Strait. Based on the phase averaging results, the transport is related to the along-strait 2 wind by a simple regression: Transport ( Sv) = 13.74 wind stress( N / m ) + 2. 42, the sign convention is positive for southwesterly wind and transport. Keywords: Taiwan Strait, phase average, shipboard ADCP IV
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S n ( t) = k = 1 2πt A k sin Tk θ k A1 A 2 θ1 θ 2 S( t) T1 T 2 14
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( Sv) = 0.12 ( m / s) + 2.42 ( Sv) = 0.14 ( m / s) + 2.03 33
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