Coherence of internal tide modulations along the Hawaiian Ridge

Mitchum, Gary T.; Chiswell, Stephen M.

doi:10.1029/2000jc900140

Cited by 47 publications

(55 citation statements)

References 15 publications

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“…Changes in the internal tide with corresponding small changes in its surface expression (e.g. Ray and Mitchum, 1997;Mitchum and Chiswell, 2000;Colosi and Munk, 2006). Such changes can occur even though the barotropic tide is invariant.…”

Section: Discussionmentioning

confidence: 99%

A survey of recent changes in the main components of the ocean tide

Woodworth

2010

Continental Shelf Research

154

148

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Changes in the ocean tide during the 20 th century have been reported for several parts of the world by different authors. However, it has not always been clear whether the observed changes have been local or regional in scale. This paper reports on a survey of tidal changes in recent decades using a quasi-global data set of tide gauge information. Little evidence has been found in Europe or the Far East (including Australasia and Asia) for the extensive regional changes to the main tidal constituents reported recently for N America. However, evidence for change in smaller regions can be identified wherever the density of tide gauge information allows. Therefore, it seems that tidal changes may be commonplace around the world, although not necessarily with large spatial scales.All of the reported changes have been difficult to explain. However, it is hoped that quasi-global surveys such as the present one may eventually provide further insights.

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Section: Discussionmentioning

confidence: 99%

A survey of recent changes in the main components of the ocean tide

Woodworth

2010

Continental Shelf Research

154

148

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“…For both Honolulu and Hilo high amplitude correlates with high sea level, and the upper sign in Eq. (77) applies 8 ( is negative); for Kahului, Maui, the correlation is negative (Table 1 of Mitchum and Chiswell 2000). Whatever the sign, unless is near 0 or , any perturbation in sea level is accompanied by an instantaneous perturbation in amplitude, thus accounting for the near-zero phase difference in Figs.…”

Section: Fitting the Correlationmentioning

confidence: 99%

“…A surprising result discovered by Mitchum and Chiswell (2000) is that the two time series are correlated. This correlation plays a major role in our attempt to disentangle the record.…”

Section: The Mitchum and Chiswell Correlationmentioning

confidence: 99%

“…They found that M 2 amplitudes measured at the offshore site of the Hawaii Ocean Time-Series (HOT) 1991-94 with inverted echo sounders could be correlated with amplitudes measured by coastal tide gauges along the north side of the Hawaiian Ridge. Further, Mitchum and Chiswell (2000) demonstrated that the large M 2 amplitudes occurred at times of a relatively deep thermocline (high sea level). The authors envision a barotropic-baroclinic mode conversion at a nearby shelf break and modulated by the variable depth of the thermocline.…”

Section: Introductionmentioning

confidence: 99%

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Tales of the Venerable Honolulu Tide Gauge*

Colosi

Munk

2006

Journal of Physical Oceanography

108

100

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Surface expressions of internal tides constitute a significant component of the total recorded tide. The internal component is strongly modulated by the time-variable density structure, and the resulting perturbation of the recorded tide gives a welcome look at twentieth-century interannual and secular variability. Time series of mean sea level h SL (t) and total recorded M 2 vector a TT (t) are extracted from the Honolulu 1905-2000 and Hilo 1947-2000 tide records. Internal tide parameters are derived from the intertidal continuum surrounding the M 2 frequency line and from a Cartesian display of a TT (t), yielding a ST ϭ 16.6 and 22.1 cm, a IT ϭ 1.8 and 1.0 cm for surface and internal tides at Honolulu and Hilo, respectively. The proposed model a TT (t) ϭ a ST ϩ a IT cos IT (t) is of a phase-modulated internal tide generated by the surface tide at some remote point and traveling to the tide gauge with velocity modulated by the underlying variable density structure. Mean sea level h SL (t) [a surrogate for the density structure and hence for IT (t)] is coherent with a IT (t) within the decadal band 0.2-0.5 cycles per year. For both the decadal band and the century drift the recorded M 2 amplitude is high when sea level is high, according to ␦a TT ϭ O(0.1␦h SL ). The authors attribute the recorded secular increase in the Honolulu M 2 amplitude from a TT ϭ 16.1 to 16.9 cm between 1915 and 2000 to a 28°rotation of the internal tide vector in response to ocean warming.

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“…They attributed this to an overflow event of cold Arctic Intermediate Water which enhanced the local stratification. Mitchum and Chiswell [2000] used tide gauges around the Hawaiian Islands to find significant correlations between seasonal to interannual sea level variations and amplitude modulations of the semidiurnal internal tides.…”

Section: Introductionmentioning

confidence: 99%

Variability of the semidiurnal internal tides observed on the Timor Shelf

et al. 2010

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[1] Semidiurnal internal tides drive strong flow variations on the shelf between Timor Island and Australia. The variability of the internal tide over seasonal to interannual time scales is studied using temperature and velocity measurements from 11 moorings, a first attempt for an observational regional synthesis of internal tide behavior. The energy density and flux carried by the semidiurnal tides were calculated from the full water column profile estimated by the Gauss-Markov fit of the vertical modes incorporating the effects of sloping bottom topography. The estimated energy flux can be interpreted either as generated at and propagating from nearby forcing sites where strong barotropic tides flow over steep topography or as trapped by and circulating around an island topography. The relevant horizontal length scale of the topography is several tens of kilometers, which is the wavelength of the vertical first-mode internal tides. At some of the moorings with sufficiently long records, seasonal variations of energy density and flux are found with maxima in late summer to winter, which is the same phase as the seasonal variation of the temperature stratification between 100 and 200 m depths. The relationship between the temperature stratification and the internal tide energy density is not linear. For the energy density, the amplitude of the seasonal variation as well as the standard deviation correlates well with the mean value with a correlation coefficient >0.8 and a p value <0.03, but the correlation between the energy density and area-integrated barotropic tidal forcing is not significant.

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Coherence of internal tide modulations along the Hawaiian Ridge

Cited by 47 publications

References 15 publications

A survey of recent changes in the main components of the ocean tide

A survey of recent changes in the main components of the ocean tide

Tales of the Venerable Honolulu Tide Gauge*

Variability of the semidiurnal internal tides observed on the Timor Shelf

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