Bi‐Directional Energy Cascades in the Pacific Ocean From Equator to Subarctic Gyre

Qiu, Bo; Nakano, Toshiya; Chen, Shuiming; Klein, Patrice

doi:10.1029/2022gl097713

Cited by 19 publications

(13 citation statements)

References 56 publications

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“…3 ). A similar result showing negative values of SF3 at smaller scales had been observed in the atmosphere about two decades earlier ( 44 ) and was recently observed in the eastern Pacific Ocean ( 45 ).…”

Section: Resultssupporting

confidence: 87%

Direct observational evidence of an oceanic dual kinetic energy cascade and its seasonality

et al. 2022

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The ocean’s turbulent energy cycle has a paradox; large-scale eddies under the control of Earth’s rotation transfer kinetic energy (KE) to larger scales via an inverse cascade, while a transfer to smaller scales is needed for dissipation. It has been hypothesized, using simulations, that fronts, waves, and other turbulent structures can produce a forward cascade of KE toward dissipation scales. However, this forward cascade and its coexistence with the inverse cascade have never been observed. Here, we present the first evidence of a dual KE cascade in the ocean by analyzing in situ velocity measurements from surface drifters. Our results show that KE is injected at two dominant scales and transferred to both large and small scales, with the downscale flux dominating at scales smaller than ∼1 to 10 km. The cascade rates are modulated seasonally, with stronger KE injection and downscale transfer during winter.

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Section: Resultssupporting

confidence: 87%

Direct observational evidence of an oceanic dual kinetic energy cascade and its seasonality

et al. 2022

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“…(2022) and Qiu et al. (2022) have also verified the existence of a bi‐directional energy cascade by using velocity structure function to analyze regional observational data. The co‐existence of positive and negative energy transfer suggests that NIWs play an important role in the energy cascade across different scales.…”

Section: Resultsmentioning

confidence: 96%

Energy Transfer Between Mesoscale Eddies and Near‐Inertial Waves From Surface Drifter Observations

Liu,

Chen,

et al. 2023

Geophysical Research Letters

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Hourly satellite‐tracked surface drifter data are utilized to study energy transfer from eddies to Near‐Inertial Waves (NIWs). Spatial velocity gradients are computed from two consecutive velocity estimates derived from the same drifter, providing variable spatial resolutions of O(1 km). The eddy‐to‐NIW energy transfer can be positive or negative, with the positive transfer (forward energy cascade) dominant. The global integrated energy transfer rate (ε) is 0.025 TW, with the anticyclonic eddy contribution dominant over the cyclonic eddy contribution. Given that the global near‐inertial wind work (W) is 0.2 TW, the eddy‐to‐NIW energy transfer efficiency (ε/W) is about 13%, which is one order of magnitude larger than that in low resolution simulations. This result may still underestimate the Eulerian energy transfer by a factor of 2. To our knowledge, this is the first time that this energy transfer is calculated from global drifter observations, providing a baseline for comparison in future studies.

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“…It remains unclear whether the oceanic energy cascades are multi-stage processes (Davidson, 2015) and how many stages may occur, such as the electronic energy levels. It is certain that multi-scale interactions and cross-scale energy transfers exist (Qiu et al, 2022). For the large/basin-scale ocean general circulations, equilibrium is the result of energy conservation.…”

Section: Introductionmentioning

confidence: 99%

Submesoscale dynamics accompanying the Kuroshio in the East China Sea

Chen

Zhu²,

Zheng³

et al. 2023

Front. Mar. Sci.

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Submesoscale processes in the ocean are vital for sustaining energy balance across scales. Taking advantage of the high resolution and wide coverage of numerical simulations, which are currently lacking for field observations, we investigated the basic patterns of submesoscale dynamics and mechanisms of corresponding variabilities along with the Kuroshio in the East China Sea. The large-scale western boundary jet serves as a remarkable submesoscale energy reservoir, promoted by steep topographic features. In the discovered hotspots, that is, the continental slope and lee area of the Tokara Strait, long-lasting submesoscale footprints arose in the form of linear patterns of strongly skewed Rossby numbers with maximum values of ~O(1). Their origin may be derived from the high topographically induced strain rate, which shows a consistent distribution and high correlation with the Rossby number. Corresponding to the characteristics of such active submesoscale processes, kinetic energy wavenumber spectra were visibly flatter than previous estimations of typical two-dimensional geostrophic turbulence and were not temporally fixed under the combined effects of multiple factors. The annual cycle of stratification induces seasonality by affecting mixed-layer instabilities, which control the kinetic and potential energy conversion rates. The tidal periods may be due to tides generating inertia-gravity waves that partially overlap in submesoscale ranges. Various other intermediate periods of variability were probably related to the eddy-caused Kuroshio path meander, which implied a closely coupled dynamical system across scales. Uncertainties come from the ascertainment of the specific contribution ratios of each part, which will be studied in the future.

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Bi‐Directional Energy Cascades in the Pacific Ocean From Equator to Subarctic Gyre

Cited by 19 publications

References 56 publications

Direct observational evidence of an oceanic dual kinetic energy cascade and its seasonality

Direct observational evidence of an oceanic dual kinetic energy cascade and its seasonality

Energy Transfer Between Mesoscale Eddies and Near‐Inertial Waves From Surface Drifter Observations

Submesoscale dynamics accompanying the Kuroshio in the East China Sea

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