Inferring dynamic height variations from acoustic travel time in the Pacific Ocean

James, Charles; Wimbush, Mark

doi:10.1007/bf02270524

Cited by 8 publications

(8 citation statements)

References 15 publications

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“…The SLACTS signal can be identified in the hydrographic data as 1‐year period oscillations, not necessarily sinusoidal, that are strongest in the surface layer and decay with increasing depth. The pressure level to which these seasonal effects penetrate is ∼150 dbar in the ASUKA region [ James and Wimbush , 1995]. By plotting CTD/XBT data from this region according to year‐day (regardless of year and location) and averaging in 1/8‐year bins, we calculated SLACTS signals for τ, T , and δ in this 0–150 dbar layer.…”

Section: Methodsmentioning

confidence: 99%

Kuroshio temporal and spatial variations south of Japan determined from inverted echo sounder measurements

et al. 2002

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[1] The Affiliated Surveys of the Kuroshio off Ashizuri-Misaki (ASUKA) project is a collaboration between scientists in Japan and the United States to improve our understanding of the structure and dynamics of the Kuroshio off the coast of southwest Japan. In this project an array of nine inverted echo sounders and nine current meter moorings were deployed for 2 years (1993)(1994)(1995) along a line extending 1000 km from Shikoku. Numerous hydrographic profiles along this section were used to determine the regional gravest empirical modes (GEMs), which relate vertical profiles of temperature and specific volume anomaly to vertical acoustic echo time. These GEMs were used in conjunction with the inverted echo sounder data to calculate 2-year time series of entire sections of relative geostrophic velocity and temperature. Current meter data provided absolute velocity references for the geostrophic velocity sections. In addition, a time series of Kuroshio position was determined from the GEM temperature sections. It shows three big (>80 km displacement) and three little offshore meanders of the Kuroshio occurring in February, May/June, and October of both years. This suggests a 4-month periodicity, possibly phase-locked to the annual cycle. The meanders may be caused by mesoscale eddies arriving from the east. The observed meanders were preceded by low Kuroshio volume transport and were followed by high Kuroshio volume transport. The Kuroshio volume and temperature transports were highly variable, with respective means of 65 ± 4 Sv and 3.7 ± 0.2 PW and standard deviations of 20 Sv and 0.9 PW.INDEX TERMS: 4576

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Section: Methodsmentioning

confidence: 99%

Kuroshio temporal and spatial variations south of Japan determined from inverted echo sounder measurements

et al. 2002

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“…Examples of the functional relationships between acoustic travel time and various standard dynamic variables may be found in Watts and Rossby (1977) (Sargasso Sea), Watts and Johns (1982) (Gulf Stream), Chiswell et al (1986) (eastern equatorial Pacific), Hallock (1987) (Gulf Stream and Sargasso Sea), Trivers and Wimbush (1994) James and Wimbush (1995) (North Pacific and Kuroshio Current), Garzoli and Bianchi (1987) (Malvinas and Brazil Currents), Garzoli and Gordon (1996) (Benguela Current), and Chiswell (1994) (Hawaii).…”

Section: Simulating An Ies Using Historical Hydrographic Datamentioning

confidence: 99%

Calibrating Inverted Echo Sounders Equipped with Pressure Sensors

Meinen

Watts

1998

J. Atmos. Oceanic Technol.

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The addition of an accurate pressure sensor to the inverted echo sounder (IES) has allowed for the development of a new method for calibrating the IES's acoustic travel-time record without the need for coincident conductivitytemperature-depth (CTD) or expendable bathythermograph profiles. Using this method, the round-trip traveltime measurement of the IES can be calibrated into various dynamic quantities with better accuracy than was possible with previous methods. For a set of four IES records from the Newfoundland Basin, the estimate of the accuracy of the geopotential height anomaly (integrated between 100 and 4000 db) calibrated from the IES measurements was reduced from 0.65 to 0.52 m 2 s Ϫ2 , which is a substantial reduction toward the intrinsic scatter of the geopotential height anomaly versus travel-time relationship for this region (0.42 m 2 s Ϫ2). The addition of the pressure sensor to the IES results in reduced errors and eliminates the need for coincident CTD measurements. Moreover, the pressure sensor provides a complementary dataset recording the changes of the barotropic pressure field.

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“…Oceanography | Vol.28, No.4 86 to 1992 (James and Wimbush, 1995) and the second from through 2004(Andres et al, 2008b. Most recently, two arrays were deployed by the OKMC/ OKTV programs.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, its connectivity (i.e., the degree to which Kuroshio structure and variability at one latitude is related to those at other latitudes) has been investigated in the joint Origins of the Kuroshio and Mindanao Currents and the Observations of Kuroshio Transport Variability (OKMC and OKTV) programs through a US-Taiwanese collaboration supported by the US Office of Naval Research (ONR) and the Ministry of Science and Technology of Taiwan, respectively (Rudnick et al, 2011;Jan et al, 2015). OKMC/OKTV builds on a series of in situ experiments conducted to 1992 (James and Wimbush, 1995) and the second from 2002 through 2004 (Andres et al, 2008b). Most recently, two arrays were deployed by the OKMC/ OKTV programs.…”

Section: Introductionmentioning

confidence: 99%

“…These regions correspond to the highlighted areas on the subsequent panels. (b)-(e) show the downstream evolution of mean Kuroshio properties as deduced from moored arrays (blue dots) and drifters (solid lines).Oceanography | Vol.28, No.4 86 to 1992 (James and Wimbush, 1995) and the second from through 2004(Andres et al, 2008b. Most recently, two arrays were deployed by the OKMC/ OKTV programs.…”

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confidence: 99%

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Mean Structure and Variability of the Kuroshio from Northeastern Taiwan to Southwestern Japan

Andres¹,

Jan²,

Sanford³

et al. 2015

Oceanog

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Mean Structure and Variability of the Kuroshio from Northeastern Taiwan to Southwestern JapanABSTRACT. In the subtropical western North Pacific Ocean, the Kuroshio delivers heat, salt, and momentum poleward, much like its North Atlantic analog, the Gulf Stream. Though the Kuroshio generally flows along the western boundary from Taiwan to southeastern Japan as an "attached" current, the Kuroshio's strength, vertical structure, and horizontal position undergo significant temporal and spatial variability along this entire route. Ubiquitous mesoscale eddies and complicated topography associated with a string of marginal seas combine to make the western North Pacific a region with complex circulation. Here, we synthesize results from the recent US Origins of the Kuroshio and Mindanao Currents and Taiwan Observations of Kuroshio Transport Variability observational programs with previous findings to build a comprehensive picture of the Kuroshio on its route from northeastern Taiwan to southeastern Japan, where the current finally transitions from a western boundary current into the Kuroshio Extension, a vigorously meandering free jet. in the western North Pacific over the past decades, many of them supported by ONR, that have focused on different sections along the Kuroshio (Table 1). Here, we summarize some of these earlier field programs and synthesize them with OKMC/OKTV results to describe the downstream evolution of the Kuroshio along its route from the western Philippine Basin through the East China Sea to south of Japan (Figure 1a). MEASURING THE KUROSHIODue to the rich eddy field in the western North Pacific (Figure 2a), individual synoptic sections across the Kuroshio from shipboard measurements are often not representative of the current's mean state. Longer duration measurements (or many crossings) are needed to estimate the current's mean transport and velocity structure. Since 1991, arrays of inverted echo sounders (IESs) have been deployed at various sections across the Kuroshio (e.g., Table 1 and the green lines in Figure 3a) to measure variability at hourly resolution for durations of one year or more. In most cases, the IESs were also equipped with pressure sensors (PIESs) and additional current sensors (CPIESs) or horizontal electric field sensors (HPIESs) to help establish the Kuroshio's time-varying position, absolute geostrophic transport, and velocity structure (see Meinen et al., 2002;Donohue et al., 2010;and Szuts, 2012, for reviews of the methodologies and the title page photo [opposite] for an image of a PIES). One of these experiments was along the Affiliated Surveys of the Kuroshio off Cape Ashizuri (ASUKA) Line, which extends 1,000 km southeastward from Shikoku, Japan, into the Philippine Basin (Figure 3a). A full array of instruments was deployed there from 1993 to 1995 (Book et al., 2002) with a reduced two-IES array maintained through (Kakinoki et al., 2008. Two IES arrays were also deployed along the PN Line, a repeat hydrographic line in the East China Sea northwest of Okinawa (labele...

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Inferring dynamic height variations from acoustic travel time in the Pacific Ocean

Cited by 8 publications

References 15 publications

Kuroshio temporal and spatial variations south of Japan determined from inverted echo sounder measurements

Kuroshio temporal and spatial variations south of Japan determined from inverted echo sounder measurements

Calibrating Inverted Echo Sounders Equipped with Pressure Sensors

Mean Structure and Variability of the Kuroshio from Northeastern Taiwan to Southwestern Japan

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