Salt-fingering in seasonally ice-covered lakes

TL;DR

This study investigates salt-finger formation beneath ice-covered lakes through laboratory experiments, revealing their presence, quantifying their dynamics, and suggesting they are common in such environments.

Contribution

The paper provides the first visual evidence and quantitative analysis of salt-fingering in seasonally ice-covered lakes, highlighting its potential significance.

Findings

Salt-fingers are detectable via visual recordings but not temperature signals.

Salt plumes have measurable velocities and increase bottom salinity.

Salt-fingering conditions are likely common in seasonally ice-covered lakes.

Abstract

When ice forms on lakes, dissolved salts are rejected, which can lead to under-ice salt-finger formation. We performed a series of laboratory experiments to visualize these fingers. While we detected salt-fingers in our camera recordings, the signal of these fingers is nearly absent in the temperature record. We quantify the velocity of the salt plumes and measure the bottom salinity increase from these fingers. Further, we estimate that the salinity is often distributed evenly with depth. Comparing the salt fluxes in our experiments with a typical salt flux in lakes, we suggest that conditions are favorable for salt-fingering in most seasonally ice-covered lakes.