Impact of atmospheric pressure variations on methane ebullition and lake turbidity during ice-cover

TL;DR

This study reveals that atmospheric pressure drops trigger methane bubbling from ice-covered lake sediments and links ebullition to increased turbidity, highlighting factors influencing methane release during winter.

Contribution

It provides the first high-frequency acoustic record of methane ebullition during ice-cover and identifies atmospheric pressure drops as a key control.

Findings

Ebullition occurs mainly when atmospheric pressure drops below a certain threshold.

Ebullition intensity correlates with the magnitude of pressure drops.

Ebullition contributes to elevated turbidity levels during ice-cover.

Abstract

Methane ebullition (bubbling) from lake sediments is an important methane flux into the atmosphere. Previous studies have focused on the open-water season, showing that temperature variations, pressure fluctuations and wind-induced currents can affect ebullition. However, ebullition surveys during the ice-cover are rare despite the prevalence of seasonally ice-covered lakes, and the factors controlling ebullition are poorly understood. Here, we present a month-long, high frequency record of acoustic ebullition data from an ice-covered lake. The record shows that ebullition occurs almost exclusively when atmospheric pressure drops below a threshold that is approximately equal to the long-term average pressure. The intensity of ebullition is proportional to the amount by which the pressure drops below this threshold. In addition, field measurements of turbidity, in conjunction with laboratory experiments, provide evidence that ebullition is responsible for previously unexplained elevated levels of turbidity during ice-cover.