Scientists carried out a "very hands-on" study in Canada to arrive at their conclusion.
This is the first time researchers have attempted to map out the number of lakes lying on the surface of the ice sheet during peak melt season.
With temperatures reaching 20 degrees below zero and colder, the National Weather Service was urging people not to go outside.
The permafrost beneath certain lakes is thawing rapidly, which will release a significant amount of methane into the atmosphere.
There are about 400 subglacial lakes around the world, but these are the first scientists believe to be salty.
Centuries ago, Indian princes would bathe in the lake. In modern times, even the poorest villagers going anywhere near it.