Surface heating steers planetary-scale ocean circulation

Gyres are central features of large-scale ocean circulation and are involved in transporting tracers such as heat, nutrients, and carbon-dioxide within and across ocean basins. Traditionally, the gyre circulation is thought to be driven by surface winds and quantified via Sverdrup balance, but it has been proposed that surface buoyancy fluxes may also contribute to gyre forcing. Through a series of eddy-permitting global ocean model simulations with perturbed surface forcing, the relative contribution of wind stress and surface heat flux forcing to the large-scale ocean circulation is investigated, focusing on the subtropical gyres. In addition to gyre strength being linearly proportional to wind stress, it is shown that the gyre circulation is strongly impacted by variations in the surface heat flux (specifically, its meridional gradient) through a rearrangement of the ocean's buoyancy structure. On shorter timescales ($\sim$ decade), the gyre circulation anomalies are proportional to the magnitude of the surface heat flux gradient perturbation, with up to $\sim 0.15\,\mathrm{Sv}$ anomaly induced per $\mathrm{W}\,\mathrm{m}^{-2}$ change in the surface heat flux. On timescales longer than a decade, the gyre response to surface buoyancy flux gradient perturbations becomes non-linear as ocean circulation anomalies feed back onto the buoyancy structure induced by the surface buoyancy fluxes. These interactions complicate the development of a buoyancy-driven theory for the gyres to complement the Sverdrup relation. The flux-forced simulations underscore the importance of surface buoyancy forcing in steering the large-scale ocean circulation.Comment: Submitted to the Journal of Physical Oceanograph

CliMA/Oceananigans.jl: v0.87.4

Oceananigans v0.87.4 Diff since v0.87.3 Merged pull requests: Deal with x ⇆ y, λ ⇆ φ, etc when filling halos for metrics/coords in ConformalCubedSphereGrid (#3256) (@navidcy) Rename return_metrics -> coordinates (#3257) (@navidcy) Update dependencies and use Julia 1.9.3 for CI (#3258) (@navidcy) (0.87.4) Add missing with_advective_forcing method (#3259) (@glwagner) Closed issues: Evolving perturbations vs total fields in Nonhydrostatic model (#3251) Rename return_metrics since it returns coordinates, not metrics (#3253) Metrics across ConformalCubedSphereGrid panels (#3254

CliMA/Oceananigans.jl: v0.88.0

Oceananigans v0.88.0 Diff since v0.87.4 Merged pull requests: (0.88.0) MPI communication and computation overlap in the HydrostaticFreeSurfaceModel and NonhydrostaticModel (#3125) (@simone-silvestri) Linear time interpolation in FieldTimeSeries (#3236) (@simone-silvestri) Fill metrics for halo regions for OrthogonalSphericalShellGrid (#3239) (@navidcy) Fix docstring for RectilinearGrid grid metrics (#3255) (@navidcy) Cubed sphere tracer advection script (#3266) (@glwagner) Remove some type instabilities (#3271) (@navidcy) Closed issues: Overlapping computation and MPI halo communication (#615) Abstraction for configuring kernels (#3067) Offsetting kernel indices (#3068) Velocity profile of channel flow case has difference with log-law (#3195) OrthogonalSphericalShellGrid metrics and coordinates are missing values in halo points (#3198) Advection of tracer with prescribed or constant velocities over a ConformalCubedSphereGrid (#3204) Should grid be a positional argument to model constructors? (#3250) RectilinearGrid metrics are described wrong in the docstring (#3252) GPU illegal memory access (#3267) Does Oceananigans support coastal modelling? (#3269