A coherent structure found in the upper ocean that has been observed in both stable and unstable conditions. These are found in the upper few meters, are aligned with the wind, and marked by horizontal temperature changes of 0.1 K over 0.1 m. They indicate the upward transport of cool/warm fluid during stable/unstable conditions, and are driven by an instability triggered by the wind thought to be similar to the Kelvin–Helmholtzinstability. These are as yet not well understood.