Middepth Recipes
Name
phoc-JPO-D-22-0225.1.pdf
Description
Published version
Size
1.85 MB
Format
Adobe PDF
Checksum (MD5)
cf6913282971038237000d2c7cb8b446
Author(s)
Rogers, Mason
Ferrari, Raffaele
Nadeau, Louis-Philippe
Date Issued
July 17, 2023
Journal
Journal of Physical Oceanography
Publisher
American Meteorological Society
Citation
Rogers, M., R. Ferrari, and L. Nadeau, 2023: Middepth Recipes. J. Phys. Oceanogr., 53, 1753–1766.
Version
Final published version
Abstract
The Indo-Pacific Ocean appears exponentially stratified between 1- and 3-km depth with a decay scale on the order of 1 km. In his celebrated paper “Abyssal recipes,” W. Munk proposed a theoretical explanation of these observations by suggesting a pointwise buoyancy balance between the upwelling of cold water and the downward diffusion of heat. Assuming a constant upwelling velocity w and turbulent diffusivity κ, the model yields an exponential stratification whose decay scale is consistent with observations if κ ∼ 10−4 m2 s−1. Over time, much effort has been made to reconcile Munk’s ideas with evidence of vertical variability in κ, but comparably little emphasis has been placed on the even stronger evidence that w decays toward the surface. In particular, the basin-averaged w nearly vanishes at 1-km depth in the Indo-Pacific. In light of this evidence, we consider a variable-coefficient, basin-averaged analog of Munk’s budget, which we verify against a hierarchy of numerical models ranging from an idealized basin-and-channel configuration to a coarse global ocean simulation. Study of the budget reveals that the decay of basin-averaged w requires a concurrent decay in basin-averaged κ to produce an exponential-like stratification. As such, the frequently cited value of 10−4 m2 s−1 is representative only of the bottom of the middepths, whereas κ must be much smaller above. The decay of mixing in the vertical is as important to the stratification as its magnitude.
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DOI of Published Version
https://doi.org/10.1175/JPO-D-22-0225.1
