(CNN) Arctic sinkholes are appearing across the Canadian High Arctic as permafrost -- ice expected to be frozen year-round -- thaws and collapses due to climate change, according to research published Monday.

Researchers found maximum thaw depths had already exceeded what they had expected to occur by 2090, according to the report published in Geophysical Research Letters journal.

At one site, Mould Bay, the level of thawing was 240% higher than historic norms.

Between 2003 and 2016, the scientists found there had been between 150% and 240% more thawing of permafrost on average in the Canadian High Arctic, compared with the period between 1979 and 2000.

In this aerial image, thermokarst lakes are seen on June 21, 2017 in Alaska, United States.

Scientists blamed a series of warm summers for damaging the "very cold permafrost," noting that there was little soil or vegetation to buffer the permafrost from the temperature changes.

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