Early citizen scientists collected rare ice data, confirm warming since industrial revolution
In 1442, Shinto priests in Japan began keeping records of the freeze dates of a nearby lake, while in 1693 Finnish merchants started recording breakup dates on a local river. Together they create the oldest inland water ice records in human history and mark the first inklings of climate change, says a new report published today out of York University and the University of Wisconsin.
|Torne River, spring 2003 in Tornio |
[Credit: Terhi Korhonen]
Sapna Sharma, a York University biologist, and John J. Magnuson, a University of Wisconsin limnologist, co-led an international team of scientists from Canada, United States, Finland, and Japan looking at this early data. Their findings are published in Nature Scientific Reports.
"These data are unique," says Sharma. "They were collected by humans viewing and recording the ice event year after year for centuries, well before climate change was even a topic of discussion."
|Lake Suwi's Omiwatari when the ice heaves in a line across the lake|
[Credit: York University]
Ice seasonality, or when a lake or river freezes over in winter or thaws again in spring, are a variable strongly related to climate, says Magnuson. And while such a long-term, human-collected dataset is remarkable in and of itself, the climate trends they reveal are equally notable. "Even though the two waters are half a world apart and differ greatly from one another," he says, "the general patterns of ice seasonality are similar for both systems."
|Postcard from 1906 taken in Happaranda |
[Credit: York University]
In recent years, says Magnuson, both waters have also exhibited more extreme ice dates corresponding with increased warming. For Lake Suwa, that means more years without full ice cover even occurring. Before the Industrial Revolution, Lake Suwa froze over 99 per cent of the time. More recently, it does so only half the time. A similar trend is seen with extremely early ice breakup on Torne River. Extreme cases once occurred in early May or later 95 per cent of the time, but they are now primarily in late April and early May.
|The Priest Mr. Kiyoshi Miyasaki pointing out some of the records on lake ice and the omiwatari. His data sheet|
summarizing the records are on the table [Credit: JJ Magnuson]
The team of researchers say they are planning follow-up studies to better understand the ecological consequences of the big changes in these two water bodies.
Source: York University [April 26, 2016]