From the rapid melting of Arctic ice sheets to an increase in severe weather around the world, the effects of the rising global temperature have been documented for decades. But a recent study took a closer look at the relationship between early ice-out in freshwater lakes and its effect on air temperatures.    

What's happening?

Ice-out is when the winter ice cover on a lake breaks up and melts away for the remainder of the year. This eventually leads to a process where the lake's water column mixes, redistributing oxygen and nutrients throughout the body of water, which can affect water quality as well as marine life in the lake.

In an effort to better understand the significance of "ice-out timing and lake thermal and biogeochemical structure," a team of climate scientists compiled data from 13 lakes in West Greenland. According to the researchers, during examples of early ice-out, lakes were able to reach higher temperatures across the water column and have deeper epilimnia, or the top layer of the lake most affected by the sun.

Despite this, air temperatures in the spring had a higher probability of being cooler following the early ice-out. The research team also discovered that a later ice-out period would lead to an increased probability of warmer temperatures.

Why are ice-out timetables important?

Beneath the surface of each lake, the results of the study baffled the researchers. They not only recorded higher epilimnetic temperatures following early ice-out periods but also increased hypolimnetic temperatures. This means that the deepest parts of each early ice-out lake saw unexpected warmth.

The study suggests that if cooler air temperatures arrive after that early melt, the lake can fully mix from top to bottom, referred to as lake turnover. "Hypolimnion temperatures are on average higher in early ice-out years, but the increase is amplified when early ice-out is coupled with lower post-ice-out air temperatures," the study reads.

While deeper mixing caused by early ice-out was able to lead to warmer bottom waters, the warmer hypolimnion was associated with higher dissolved oxygen concentrations. In most cases, warmer temperatures in mild climates have been primarily linked to lower dissolved oxygen.

Dissolved oxygen can be a critical indicator of water quality, as it's essential for the survival of marine life. The higher the dissolved oxygen, the more it may improve water quality by reducing the release of harmful substances and aiding in nutrient cycling.

As noted in the study, a warming climate can result in earlier lake ice-out in many temperate and higher-latitude regions. But with the Arctic region warming up to five times faster than the rest of the world, it can lead to continued early ice-out in lakes. 

What's being done about Arctic lake ice-outs?

The team of researchers indicates that being able to link "thermal structure metrics to specific seasonal climate signals will allow us to better disentangle long-term trends in lake responses to climate change." This can go a long way toward understanding long-term trends in our evolving climate and how it impacts various regions.

The only long-term solution is to stop the heat-trapping air pollution that is warming up our planet.

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