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Coarse-grained local available potential energy
Authors:
Jacob O. Wenegrat,
Tomas Chor,
Roy Barkan
Abstract:
The available potential energy (APE) of a fluid can be defined locally in space, providing useful insights into both the energetics and dynamics of stratified flows ranging from three-dimensional turbulence to planetary scale circulations. Here we develop a framework for considering the multi-scale evolution of the local APE using a spatial filtering, or coarse-graining, approach. Evolution equati…
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The available potential energy (APE) of a fluid can be defined locally in space, providing useful insights into both the energetics and dynamics of stratified flows ranging from three-dimensional turbulence to planetary scale circulations. Here we develop a framework for considering the multi-scale evolution of the local APE using a spatial filtering, or coarse-graining, approach. Evolution equations for the APE at scales larger, and smaller, than the filtering scale are derived -- including the cross-scale APE flux term. These results can be paired with existing frameworks for coarse-grained kinetic energy, offering the potential for examining a complete energy cycle that accounts for conversions between both spatial scales and energy reservoirs. An illustrative example of the application of this approach to a simulation of two-dimensional Kelvin-Helmholtz instability is provided.
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Submitted 15 May, 2026;
originally announced May 2026.
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Direct Numerical Simulations of Ice-Ocean Boundary Turbulence
Authors:
Ken X. Zhao,
Tomas Chor,
Eric Skyllingstad,
Jonathan Nash,
Madelaine Rosevear,
Craig McConnochie
Abstract:
Turbulent heat and freshwater transport at ice-ocean interfaces controls glacier and iceberg melt rates, yet the underlying physics remains poorly constrained. Parameterizations that assume shear boundary layer scaling are commonly used, which neglects meltwater buoyancy-driven convective processes. Using Direct Numerical Simulations with realistic salt diffusivity, which is critical for represent…
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Turbulent heat and freshwater transport at ice-ocean interfaces controls glacier and iceberg melt rates, yet the underlying physics remains poorly constrained. Parameterizations that assume shear boundary layer scaling are commonly used, which neglects meltwater buoyancy-driven convective processes. Using Direct Numerical Simulations with realistic salt diffusivity, which is critical for representing the thin solutal boundary layer (deltaS ~ 0.4 mm) and resulting convective instabilities, we investigate ice-ocean boundary layer turbulence across varying temperature, salinity, stratification, external velocity, and interfacial slope angles. Our simulations agree with laboratory measurements of melt rate and interfacial temperature. In the absence of external flows, we find no transition from buoyancy-controlled to shear-controlled regimes and convection is important even at near-horizontal slopes. External shear becomes significant only when it is strong enough to thin the thermal and solutal boundary layers, which starts influence melting substantially above background flow speeds of 5 cm/s. Understanding how shear and convection compete to determine the ice-ocean diffusive boundary layer enables accurate melt rate predictions across the parameter space relevant to ice shelves and marine-terminating glaciers.
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Submitted 19 March, 2026;
originally announced March 2026.
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High-level, high-resolution ocean modeling at all scales with Oceananigans
Authors:
Gregory L. Wagner,
Simone Silvestri,
Navid C. Constantinou,
Ali Ramadhan,
Jean-Michel Campin,
Chris Hill,
Tomas Chor,
Jago Strong-Wright,
Xin Kai Lee,
Francis Poulin,
Andre Souza,
Keaton J. Burns,
Siddhartha Bishnu,
John Marshall,
Raffaele Ferrari
Abstract:
We describe the user interface, governing equations, and numerical methods underpinning the community ocean modeling software called "Oceananigans". Oceananigans development has been lead by the Climate Modeling Alliance to build a trainable climate model with quantifiable uncertainty. Oceananigans is written in the Julia programming language, which, like similar recent efforts based on modern pro…
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We describe the user interface, governing equations, and numerical methods underpinning the community ocean modeling software called "Oceananigans". Oceananigans development has been lead by the Climate Modeling Alliance to build a trainable climate model with quantifiable uncertainty. Oceananigans is written in the Julia programming language, which, like similar recent efforts based on modern programming languages, distinguishes it from usual software based on Fortran. Oceananigans can efficiently simulate all scales of ocean motion, ranging from millimeter-scale turbulence in a small box to planetary-scale ocean circulation. Oceananigans design combines (i) a basic structured finite volume algorithm (ii) optimized for high-resolution simulations on GPUs which is (iii) exposed behind a high-level, programmable user interface. This design negotiates a dual mandate for highest-possible performance (to support state-of-the-art applications) and enhanced accessibility (to facilitate adoption and development). The dual mandate aims ultimately to accelerate the progress of Earth system science. Achieving this aim, however, requires a substantial and sustained increase in the collective effort of Oceananigans development.
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Submitted 13 November, 2025; v1 submitted 19 February, 2025;
originally announced February 2025.