The Kuroshio East of Taiwan: Modes of Variability and Relationship to Interior Ocean Mesoscale Eddies

Dongxiao Zhang Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

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Thomas N. Lee Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

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William E. Johns Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

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Cho-Teng Liu Institute of Oceanography, National Taiwan University, Taipei, Taiwan

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Rainer Zantopp Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida

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Abstract

Observations from the World Ocean Circulation Experiment PCM-1 moored current meter array in the East Taiwan Channel are analyzed and combined with TOPEX/Poseidon altimetry data and the Parallel Ocean Climate Model simulation to study Kuroshio variability and relationships to westward propagating sea surface height anomalies in the Philippine Sea.

Approximately 60% of the total subinertial velocity and temperature variance in the Kuroshio east of Taiwan is associated with so-called “transport” and “meandering” modes revealed from empirical orthogonal function analysis. The transport mode is dominated by a 100-day peak, while the most coherent energetic meandering signals are found in three limited frequency bands centered near periods of 100 days, 40 days, and 18 days. The detailed structure of the meanders is studied by frequency domain EOF analysis, which also reveals a higher frequency meander centered near 10 days confined to the western side of the channel.

On the 100-day timescale, the Kuroshio transport entering the East China Sea is strongly related to meandering of the Kuroshio, which in turn is caused by westward propagating anticyclonic eddies from the interior ocean. During low transport events, the Kuroshio meanders offshore and partly bypasses the East Taiwan Channel to flow northward along the eastern side of the Ryukyu islands. The interior eddy features that lead to the meandering can be identified as far east as 134°E, propagating westward to the coast of Taiwan at about 10 km day−1. The 100-day variability that is so dominant in the Kuroshio is virtually absent in the Florida Current but is strongly present east of Bahamas in the Antilles Current and deep western boundary current, presumably being blocked from entering the Straits of Florida by the Bahamas Island chain.

* Current affiliation: NOAA Pacific Marine Environmental Laboratory, Seattle, Washington.

Corresponding author address: Dr. Dongxiao Zhang, NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

Email: zhang@pmel.noaa.gov

Abstract

Observations from the World Ocean Circulation Experiment PCM-1 moored current meter array in the East Taiwan Channel are analyzed and combined with TOPEX/Poseidon altimetry data and the Parallel Ocean Climate Model simulation to study Kuroshio variability and relationships to westward propagating sea surface height anomalies in the Philippine Sea.

Approximately 60% of the total subinertial velocity and temperature variance in the Kuroshio east of Taiwan is associated with so-called “transport” and “meandering” modes revealed from empirical orthogonal function analysis. The transport mode is dominated by a 100-day peak, while the most coherent energetic meandering signals are found in three limited frequency bands centered near periods of 100 days, 40 days, and 18 days. The detailed structure of the meanders is studied by frequency domain EOF analysis, which also reveals a higher frequency meander centered near 10 days confined to the western side of the channel.

On the 100-day timescale, the Kuroshio transport entering the East China Sea is strongly related to meandering of the Kuroshio, which in turn is caused by westward propagating anticyclonic eddies from the interior ocean. During low transport events, the Kuroshio meanders offshore and partly bypasses the East Taiwan Channel to flow northward along the eastern side of the Ryukyu islands. The interior eddy features that lead to the meandering can be identified as far east as 134°E, propagating westward to the coast of Taiwan at about 10 km day−1. The 100-day variability that is so dominant in the Kuroshio is virtually absent in the Florida Current but is strongly present east of Bahamas in the Antilles Current and deep western boundary current, presumably being blocked from entering the Straits of Florida by the Bahamas Island chain.

* Current affiliation: NOAA Pacific Marine Environmental Laboratory, Seattle, Washington.

Corresponding author address: Dr. Dongxiao Zhang, NOAA/Pacific Marine Environmental Laboratory, 7600 Sand Point Way NE, Seattle, WA 98115.

Email: zhang@pmel.noaa.gov

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