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Monday, March 27, 2023

How Freshwater Mixes in a Winter Lake

• Physics 16, s1

An inflow of hotter water mixing with a colder ambient quantity can create a dense parcel that drives backside currents and determines the ensuing circulation patterns.

In late winter within the mountains of British Columbia, water from the Thompson River enters Kamloops Lake and flows like an avalanche alongside the floor. Upon mixing with the lake water, the inflow can improve in density, plunging it to the lake’s backside, the place it flows downslope. Simulations by Andrew Grace of the College of Waterloo, Canada, and his colleagues now describe how the evolution of those currents will depend on the temperature distinction between the 2 our bodies of water [1].

Whereas most fluids get denser as they strategy their freezing level, freshwater reaches its most density at 4 °C. If two freshwater parcels are, respectively, above and beneath this temperature, their mixing creates a fluid parcel that’s denser than the typical of the 2. When this mixing happens due to comparatively heat river water coming into a chilly lake—corresponding to at Kamloops Lake—the ensuing dense water sinks, warming the lake from the underside up. This will end in a dense, warm-water mass that impacts the circulation of the lake water.

Grace and his colleagues modeled the dynamics of such a state of affairs, figuring out how far an intruding stream might attain earlier than it generated denser water through mixing. In some instances, its density elevated sufficiently to sink and, in the end, type a second present alongside the lake backside. The group developed a framework that described the underside present’s conduct.

The researchers say that a greater understanding of circulation patterns in river–lake methods might assist to foretell how vitamins and pollution unfold and the way power-plant wastewater impacts the native atmosphere.

–Rachel Berkowitz

Rachel Berkowitz is a Corresponding Editor for Physics Journal based mostly in Vancouver, Canada.


  1. A. P. Grace et al., “Gravity currents within the cabbeling regime,” Phys. Rev. Fluids 8, 014502 (2023).

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