A multi-dimensional spectral description of ocean variability with applications

Wortham, Cimarron

doi:10.1575/1912/5662

Cited by 13 publications

(26 citation statements)

References 63 publications

(148 reference statements)

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“…The characteristics of surface momentum fluxes at the Kuroshio and Gulf Stream Extension regions estimated using a 5-year altimetric data are similar to those estimated from the 13-year data (Greatbatch et al, 2010). Our analysis also shows that the spatial pattern and mag- (Wortham, 2012), as a result of eddy-eddy interaction, instability, and the wide-range of spatial scales in external forcing, topography, coastlines, etc. Consequently, small-scale features should exist in the time-mean eddy fluxes.…”

Section: On the Length Of The Recordsupporting

confidence: 77%

“…The bottom drag dissipation (τ b ·u b ) in the ECCO2 model may be underestimated to some extent (Table 3.2). Consistently, Wortham (2012) found that the total kinetic energy in the ECCO2 state estimate below 2000 m at the mooring sites is approximately half of the kinetic energy observed from the current meters. On the other Table 3.2: The 16-year average of the globally integrated energy terms from the ECCO2 state estimate and previous estimates (T W ).…”

Section: On the Globally Integrated Valuessupporting

confidence: 57%

“…Forget and Wunsch, 2007), the hydrographic variability in To conclude, the variability in the model is overall consistent with the observed variability, especially in the upper ocean of mid-and low latitudes. The comparison of the modeled total kinetic energy with those from moorings also suggests that the ECCO2 model has better performance at low latitudes than high latitudes (Wortham, 2012). There are several possible reasons why the relative misfit is smaller in the upper ocean of these latitudes.…”

Section: Comparison Between Modeled and Observed Eddiesmentioning

confidence: 90%

“…Though the ocean system is nonlinear in most mid-and high latitude regions (Tulloch et al, 2009;Wortham, 2012), linear theories are still useful in interpreting many ocean features, such as eddy length scales and time-mean circulation (Tulloch et al, 2011;Wunsch, 2011). Thus, here we explore both the weakly-forced and strongly- (Figure 4-11).…”

Section: Experiments Setupmentioning

confidence: 99%

“…Arbic et al, 2012) and the spectra in the ocean tend to be red (e.g. Wortham, 2012); therefore it is probably reasonable to assume that the model spectrum for the non-propagating case (Eq. …”

Section: Model Spectrum and Eddy-propagation Mechanismmentioning

confidence: 99%

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Energy pathways and structures of oceanic eddies from the ECCO2 state estimate and simplified models

Chen¹

2013

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Studying oceanic eddies is important for understanding and predicting ocean circulation and climate variability. The central focus of this dissertation is the energy exchange between eddies and mean flow and banded structures in the low-frequency component of the eddy field. A combination of a realistic eddy-permitting ocean state estimate and simplified theoretical models is used to address the following specific questions. (1) What are the major spatial characteristics of eddy-mean flow interaction from an energy perspective? Is eddy-mean flow interaction a local process in most ocean regions? (2) The banded structures in the low-frequency eddy field are termed striations. How much oceanic variability is associated with striations? How does the time-mean circulation, for example a subtropical gyre or constant mean flow, influence the origin and characteristics of striations? How much do striations contribute to the energy budget and tracer mixing?

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Section: On the Length Of The Recordsupporting

confidence: 77%

Section: On the Globally Integrated Valuessupporting

confidence: 57%

Section: Comparison Between Modeled and Observed Eddiesmentioning

confidence: 90%

Section: Experiments Setupmentioning

confidence: 99%

Section: Model Spectrum and Eddy-propagation Mechanismmentioning

confidence: 99%

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Energy pathways and structures of oceanic eddies from the ECCO2 state estimate and simplified models

Chen¹

2013

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Eddy stirring and horizontal diffusivity from Argo float observations: Geographic and depth variability

Cole

Wortham

Kunze

et al. 2015

Geophysical Research Letters

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Stirring along isopycnals is a significant factor in determining the distribution of tracers within the ocean. Salinity anomalies on density surfaces from Argo float profiles are used to investigate horizontal stirring and estimate eddy mixing lengths. Eddy mixing length and velocity fluctuations from the ECCO2 global state estimate are used to estimate horizontal diffusivity at a 300 km scale in the upper 2000 m with near‐global coverage. Diffusivity varies by over two orders of magnitude with latitude, longitude, and depth. In all basins, diffusivity is elevated in zonal bands corresponding to strong current regions, including western boundary current extension regions, the Antarctic Circumpolar Current, and equatorial current systems. The estimated mixing lengths and diffusivities provide an observationally based data set that can be used to test and constrain predictions and parameterizations of eddy stirring.

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Diagnostic Characteristics of Submesoscale Coastal Surface Currents

Soh

Kim

2018

JGR Oceans

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Submesoscale kinetic energy (KE) spectra and fluxes at the length scales ranging from 2 to 25 km are estimated from hourly and O(1) km‐scale coastal surface current maps observed from shore‐based high‐frequency radars off southern San Diego. The one‐dimensional wave number‐domain KE spectra of the surface currents have decay slopes between k−2 and k−3 at a wave number (k) of 0.5 km−1. The KE spectra exhibit anisotropy associated with anisotropic circulation, which is constrained by the shoreline and bottom bathymetry. Moreover, the KE spectra exhibit weak seasonality related to the regional submesoscale eddies and low‐frequency circulation with weak seasonal variability. The estimated KE fluxes are categorized into four cases of purely forward cascades and inverse cascades at all wave numbers, inverse‐then‐forward cascades with a single zero‐crossing within the range of wave numbers (0.04 to 0.5 km−1), and residuals, which account for approximately 33%, 39%, 19%, and 9% of the total number of realizations, respectively. An injection scale where forward enstrophy cascade and inverse energy cascade occur is estimated to be 5 to 10 km from the cases of the inverse‐then‐forward cascade, which is consistent with the length scales of the regional submesoscale eddies. Thus, the regional submesoscale processes are initiated by surface frontogenesis due to the weak seasonal low‐frequency surface circulation and topography‐related currents, then maintained by baroclinic instabilities associated with the seasonal mixed layer and O(10) km‐scale submesoscale eddies with weak seasonal variability.

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A multi-dimensional spectral description of ocean variability with applications

Cited by 13 publications

References 63 publications

Energy pathways and structures of oceanic eddies from the ECCO2 state estimate and simplified models

Energy pathways and structures of oceanic eddies from the ECCO2 state estimate and simplified models

Eddy stirring and horizontal diffusivity from Argo float observations: Geographic and depth variability

Diagnostic Characteristics of Submesoscale Coastal Surface Currents

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