Credit: Unsplash/CC0 Public Domain

Climate change undoubtedly affects lakes and the functioning of their ecosystems, but seasonal impacts are not always straightforward. An international team of researchers from York University in Canada, the Finnish Environment Institute and the University of Eastern Finland in Joensuu investigated how lake autumn surface warming is associated with winter under-ice temperatures and ice phenology.

The results were published in Water Resources Research . The study synthesized 37–50 years of data since 1971 from dozens of Finnish lake sites that are located across the country.

Warm autumns delay lake freezing, but overall water temperatures in winter can become lower

There was a negative relationship between the timing of ice-on and under-ice bottom water temperatures. In warmer autumns, when lakes freeze later, bottom water temperatures are colder in winter compared to years with cooler autumns and earlier freeze-up.…