Diathermal Heat Transport in a Global Ocean Model

Abstract

The rate at which the ocean moves heat from the tropics toward the poles, and from the surface into the interior, depends on diabatic surface forcing and diffusive mixing. These diabatic processes can be isolated by analyzing heat transport in a temperature coordinate (the diathermal heat transport). This framework is applied to a global ocean sea ice model at two horizontal resolutions (1/4° and 1/10°) to evaluate the partioning of the diathermal heat transport between different mixing processes and their spatial and seasonal structure. The diathermal heat transport peaks around 22°C at 1.6 PW, similar to the peak meridional heat transport. Diffusive mixing transfers this heat from waters above 22°C, where surface forcing warms the tropical ocean, to temperatures below 22°C where midlatitude waters are cooled. In the control 1/4° simulation, half of the parameterized vertical mixing is achieved by background diffusion, to which sensitivity is explored. The remainder is associated with parameterizations for surface boundary layer, shear instability, and tidal mixing. Nearly half of the seasonal cycle in the peak vertical mixing heat flux is associated with shear instability in the tropical Pacific cold tongue, highlighting this region’s global importance. The framework presented also allows for quantification of numerical mixing associated with the model’s advection scheme. Numerical mixing has a substantial seasonal cycle and increases to compensate for reduced explicit vertical mixing. Finally, applied to Argo observations the diathermal framework reveals a heat content seasonal cycle consistent with the simulations. These results highlight the utility of the diathermal framework for understanding the role of diabatic processes in ocean circulation and climate.

From Mixing to the Large Scale Circulation: How the Inverse Cascade Is Involved in the Formation of the Subsurface Currents in the Gulf of Guinea

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Atlantic Ocean Heat Transport Enabled by Indo‐Pacific Heat Uptake and Mixing

“…The volume (our study will be performed in the context of incompressible Boussinesq model simulations; if the fluid were instead compressible then it would be more appropriate to consider the mass rather than volume (Hochet & Tailleux, 2019;Holmes et al, 2019b)) of this region is…”

Climate Recorded in Seawater: A Workshop on Water-Mass Transformation Analysis for Ocean and Climate Studies

“…Implementing WMT diagnostics in numerical models allows for quantification and interpretation of key processes, aiding model intercomparison and evaluation. Modeling studies that embraced this approach have provided insights on the structure and drivers of ocean circulation, as well as information on model numerics and biases (e.g., Downes et al 2015;Holmes et al 2019). Models also fill spatiotemporal gaps in observed patterns of WMT (e.g., Cerovečki and Mazloff 2016) and to project future changes.…”