Earlier this week, NASA revealed to members of the press that it would initiate an “intensive research effort” to determine the exact the rate at which global sea levels are currently rising due to the accelerated melting of glaciers near the world’s poles.

According to a report from the Washington Post, the space agency revealed details about data measuring the rise of the world’s oceans, which are currently rising at a rate of 3.21 millimeters per year. NASA climate scientists have made a particularly shocking discovery as they combed through the data; out of all the world’s ice sheets, the one on Greenland is disappearing the fastest.

Antarctica has significantly thicker ice cover than Greenland, and it melts into the Southern Ocean at a slower pace. The climate is more stable at the South Pole, and the Arctic has seen a much more rapid rate of warming over the last few decades. Greenland has lost several gigatons of ice per year for multiple years now.

A gigaton is the same as one billion metric tons of ice. If it were distributed evenly throughout the oceans of the Earth, it would lead to an average of .74 millimeters of sea-level rise per year. Taking into account the additional water from Antarctica and other melting glaciers in the Arctic circle, as well as thermal expansion of the ocean’s water molecules, the modeled rate of global sea level rise agrees with the data.

If all the ice on Greenland melted, the world’s oceans would rise 20 feet, while if all the ice on Antarctica melted, the sea level would increase by 200 feet. Glacial cover is at risk from atmospheric heat and the warming of the oceans below. Warm ocean chips away at the edges of glaciers as streams of melted fresh water pour into the sea from above.

NASA’s predictions don’t see the rate of melting slowing down anytime soon. They are rolling out extensive programs to track meltwater added to the ocean at a number of locations, but there appears to be little they can do in the way of stopping it.