Horizontal diffusivity in a small, ice‐covered lake1

Abstract

A horizontal eddy diffusivity ( K x ) value of 0.47 cm 2 · s ‒1 was calculated from tracer cloud expansion data from a previous experiment in which a 24 Na solution was introduced as a point source under ice cover in Tub Lake, Wisconsin. This K x value, the first from a lake where surface wind stress was not a factor, is lower than any lake K x previously reported. The constancy of K x found for the 48‐h period of monitoring implied mixing eddy lengths <1.6 m, the diffusion cloud size found at first monitoring. Surface seiches or convective flows appeared to be probable sources of mixing energy.