Jennifer McDowall reports on the increasing loss of lake ice in the northern hemisphere and explains the social and economic impacts.
Photo by Louis
A recent study of historical data has revealed that lakes in the northern hemisphere are becoming increasingly ice-free, a trend that is predicted to continue in coming years. Researchers discovered the ice loss was linked to rising air temperatures, meaning decreased ice cover is another symptom of climate change.
Due to its sensitivity to changes in the weather, lake ice formation is considered a good indicator of climate change. Many different factors can affect the formation of lake ice, such as varying weather conditions, but also physical lake characteristics like lake depth, elevation and shoreline features.
Around 117 million lakes are present in the non-glaciated regions of the world, covering nearly 4% of the world’s surface. Over 50 million of these are frozen during the winter months and, in the northern hemisphere, ice can be present on lakes for six months out of the year, normally with reliable freeze and thaw cycles. That’s beginning to change.
To investigate changes in lake ice coverage, a research team at York University in Canada studied eight decades of lake ice records, between 1939 and 2016, for 122 lakes in the northern hemisphere.
The data, provided by the National Snow and Ice Data Centre, contained freeze and thaw dates and allowed the authors to discover emerging patterns. Any year which had at least one day with 0% ice cover was classed as an ‘ice-free year’ for a particular lake. Almost 11% of lakes included experienced ice-free years within the time frame studied. In fact, by comparing the first forty years of the studied time period to the last forty, the researchers found that these extreme events now occur three times more frequently since 1978 and are becoming more severe in nature.
The team also determined that extreme temperatures are linked to respective extremes in lake ice cover and that local air temperature is the best predictor of ice cover, linking the ice loss directly to climate change. If temperatures increase to a relatively warm -4 degrees Celsius, then an ice-free year is more likely, with southern and coastal lakes being more prone to these events.
In addition, it was predicted that large-scale ice-loss would result from increasingly frequent ice-free years in years to come. Alessandro Filazzola, lead author of the research paper, emphasised that this is a growing problem, and a global one:
"This isn’t just happening in one lake in the northern United States, it’s happening in thousands of lakes around the world. Even in the last 40 years versus the last 80 years, there’s already an obvious pattern that’s occurring and it’s showing that we’re already experiencing a response from warming, which will likely get worse."
Social and Ecological Impacts
The authors of the study believe that unless measures are put in place to reduce carbon emissions substantially, the loss of lake ice could have significant socio-economic and ecological implications. This is because ice plays an important role in many cultures, ecosystems and lifestyles.
In Japan, for example, Shinto priests see the appearance of ice on Lake Suwa as a message from God and have celebrated the appearance of ice since 1443, with formal celebrations performed on the ice itself. Lake Suwa now only freezes over two out of every ten years, meaning this tradition is in danger.
Many northern areas rely on lakes and ice roads for transportation, which links communities and allows for trade of produce. In addition, winter festivals, involving ice fishing or ice sports for example, are hosted every year. Both festivals and transportation are economically important for many communities, and ice fishing can also be an important part of cultural identity and vital for food security.
It’s not only humans who will feel the loss of ice. Without it, more sunlight will be able to penetrate the water which will cause its temperature to rise. Higher temperatures can affect the life cycles of both plants and animals, increase water evaporation and also make it more likely for toxic algal blooms to form, which could affect wildlife and humans alike.
Currently, there is a global demand to reduce carbon emissions in an effort to slow climate change. However, the number of ice-free years is expected to increase even if carbon emissions are reduced, with a plateau predicted in 2050. If no action is taken, this loss will continue until at least 2100. It remains to be seen whether the world can rise to the challenge and prevent lasting damage.
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