Ice loss, toxic algae blooms: Canadian study looks at Northern Hemisphere's warming lakes
Lakes in the Northern Hemisphere have been warming six times faster since 1992 than they were at any other time period in the past 100 years, a Canadian study suggests.
The study, entitled “Loss of Ice Cover, Shifting Phenology and More Extreme Events in Northern Hemisphere Lakes,” was published in the October issue of the Journal of Geophysical Research: Biogeosciences and led by York University in Ontario.
The most northern of the Great Lakes, Lake Superior, which spans the Canada-U.S. border was one of the fastest warming lakes, the study found, losing more than two months of ice cover since conditions started being recorded in 1857. Grand Traverse Bay in Lake Michigan had one of the fastest melting trends recorded, with the ice melting about 16 days earlier per century.
“We found that lakes are losing on average 17 days of ice cover per century. Alarmingly, what we found is that warming in the past 25 years, from 1992 to 2016, was six times faster than any other period in the last 100 years,” said study author and associate professor at York University Sapna Sharma in a release.
Some of the lakes studied in Canada were Lake Michigan, Lake Superior, Lake Simcoe, Lake Nipissing and Lake of Bays.
Researchers studied 40 lakes in North America, 18 lakes in Europe and two in Asia, Lake Baikal in Siberia and Lake Suwa in Japan.
Researchers analyzed ice trends for 60 lakes for the first time since 2004 by studying ice phenology records ranging from 107 to 204 years-old, prior to the industrial revolution.
Phenology refers to the study of periodic events in biological life cycles and how they are affected by seasonal changes and variations in climate – like when the first leaves and buds appear in the spring.
The timing of ice formation and ice melting has been observed for centuries because of its importance to refrigeration, transportation (ice roads), recreation and spiritual and cultural traditions, the study says.
Sharma said many of the lakes “may be approaching a tipping point to ice-free conditions which will have vast cultural and ecological implications.”
The study found that on average, the lakes being studied were freezing 11 days later and thawing approximately 6.8 days earlier, something researchers posit was due to extremely warm winters over the last decades contributing to the increasing rate of ice loss.
“We found that the duration of winter ice cover has decreased, particularly since 1995, to the point where some lakes are beginning to have more winters with minimal or even no ice cover,” said study co-author David Richardson in the release. “For example, some deep lakes in Switzerland and Germany, which historically used to freeze each winter, have permanently lost their ice cover in the past few decades.”
Lake ice phenology is considered an important signifier of climate change, and a reduction in greenhouse gas emissions is necessary if the loss of ice is to be mitigated, the study says. Ice loss contributes to increased evaporation rates, warmer water temperatures, worse water quality and aids in the formation of toxic algae blooms.