Simulating the Global Ocean's Submesoscale and Its Kinetics with
Kilometer-Resolution Configurations of High-Resolution Earth System
Model on Sunway Supercomputer
Abstract
Simulating the ocean’s submesoscale is key to understand the mass and
energy cycles of the ocean and the global climate system. Contrast to
the ocean’s mesoscale, submesoscale processes are usually highly
ageostrophic and manifest at the scales within 10km. Ocean general
circulation models with kilometer-resolution are capable to resolve key
submesoscale processes, hence indispensable for both process and climate
studies. We construct a grid hierarchy for the ocean-sea ice model in
the High-Resolution Earth System Model on Sunway supercomputer
(SW-HRESM), which is based on Community Earth System Model (CESM2) with
deep optimizations on the Chinese home-brew supercomputing architecture
of Sunway. The highest grid resolution is 0.03o (2.4km globally). In
this study we evaluate the ocean-sea ice coupled simulations by
SW-HRESM, focusing on the submesoscale and the kinetic energy (KE)
cycles. In particular, highly ageostrophic submesoscale turbulence is
simulated, dominated by deepened mixed layers (ML) during winter and the
ensuing instabilities. KE and its transition between scales are further
evaluated for major western boundary current systems. During winter,
submesoscale is shown to dominate inverse cascading which energizes
large-scale flows, as well as forward cascading to dissipation scales.
The mesoscale-submesoscale continuum and the associated inverse KE
cascading is further complemented by the forward KE cascading from the
large-scale due to flow instabilities. In order to fully resolve the
submesoscale spectrum, including frontal processes and wind-wave
interactions, models finer than 1km are needed. Besides the model
resolution, improvements for both the ocean and the fully coupled model
of SW-HRESM are also discussed.