Abstract
Quasi-two-dimensional visualizations of microstructure in the
thermocline are created by processing χpod signals in a non-standard
way. As the moored instrument is pumped by surface waves, the fast
thermistors at each end trace out vertically overlapping paths, from
which we produce 2–3 m tall swaths. A swath capturing the unmistakable
form of Kelvin–Helmholtz billows provides a proof of concept—albeit
by relying on what is a rare event in our dataset. More commonly, swaths
exhibit steppy temperature fields during weaker turbulence, an abundance
of small overturns during stronger turbulence, or some combination
thereof. To examine this continuum statistically, we take a 13-month
dataset from an equatorial χpod at 120 m deep and divide it into 53 000
swaths, each 10 minutes long. Swaths are ordered based on their
associated buoyancy Reynolds number (Reb) inferred from our standard
χpod processing. Clear visual differences in swath characteristics arise
when comparing across an order of magnitude or more (e.g., Reb
< 10 vs Reb = 10–100 vs Reb > 100). With the
help of a convolutional neural network to semi-objectively pick
representative swaths, we present our best estimates of what
microstructure looks like in two dimensions as a function of Reb.