There are about 400 subglacial lakes around the world, but these are the first scientists believe to be salty.
The glaciers have been shrinking since the 1960s.
A new technique compiled hundreds of thousands of images over seven years.
“This is sort of a dark archaeology, where we benefit from climate change that's making this ice melt."
This heat source is found all over the planet and is extremely difficult to measure.
The worst scenario would flood lands that are home to 236 million people.
The glacier has long been receding.
Fierce volcanic activity near the Vatnajökull glacier between 2014 and 2015 created huge calderas.
Imja Tsho has been rapidly expanding due to climate change.
Rising temperatures have caused an environmental disaster, according to the IOM.