Publication

Tracing the origins of metalimnetic methane in a stratified large lake: Insights from high‐resolution mapping and three‐dimensional hydrodynamic modeling

2026

Abstract

Methane (CH 4 ) accumulation in the oxic metalimnion is a common yet poorly resolved feature of deep stratified lakes. In Lake Geneva, lateral transport from the Rhône delta has been suggested but lacks spatial validation. Here, we quantify the role of lateral advection in shaping metalimnetic CH 4 using high‐resolution in situ CH 4 measurements, δ 13 C‐CH 4 analyses, and a three‐dimensional Lagrangian particle‐tracking model. Elevated metalimnetic CH 4 (up to 1143 nM) near the Rhône delta becomes isotopically enriched, likely from prolonged residence and partial oxidation during summer stratification. While additional sources may contribute, comparisons of in situ measurements with particle‐tracking simulations suggest circulation gyres may distribute deltaic CH 4 . Moreover, isotope‐ and transport‐based indicators suggest more coherent coupling in the epilimnion than in the metalimnion. These results demonstrate that horizontal advection can be an important driver of metalimnetic CH 4 and highlight the importance of circulation‐driven lateral transport for assessing CH 4 fluxes from large, stratified lakes.

Official source

https://infoscience.epfl.ch/entities/publication/edd5e712-4860-4bb4-aa55-30aafd6118e5

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2026

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/edd5e712-4860-4bb4-aa55-30aafd6118e5

About this result

Related concepts (32)

Lake stratification

Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers: the epilimnion, comprising the top warm layer; the thermocline (or metalimnion), the middle layer, whose depth may change throughout the day; and the colder hypolimnion, extending to the floor of the lake. Every lake has a set mixing regime that is influenced by lake morphometry and environmental conditions.

Hypolimnion

The hypolimnion or under lake is the dense, bottom layer of water in a thermally-stratified lake. The word "hypolimnion" is derived from λιμνίον. It is the layer that lies below the thermocline. Typically the hypolimnion is the coldest layer of a lake in summer, and the warmest layer during winter. In deep, temperate lakes, the bottom-most waters of the hypolimnion are typically close to 4 °C throughout the year. The hypolimnion may be much warmer in lakes at warmer latitudes.

Dimictic lake

A dimictic lake is a body of freshwater whose difference in temperature between surface and bottom layers becomes negligible twice per year, allowing all strata of the lake's water to circulate vertically. All dimictic lakes are also considered holomictic, a category which includes all lakes which mix one or more times per year. During winter, dimictic lakes are covered by a layer of ice, creating a cold layer at the surface, a slightly warmer layer beneath the ice, and a still-warmer unfrozen bottom layer, while during summer, the same temperature-derived density differences separate the warm surface waters (the epilimnion), from the colder bottom waters (the hypolimnion).