Thanks to rising temperatures, glaciers in Greenland are melting faster than scientists previously thought — and a new NASA video shows how researchers are tracking the magnitude of the changes (in feet per day).

NASA's aptly titled Oceans Melting Greenland (OMG) project studies the extent to which warm ocean waters are melting glaciers from below — and it's much faster than anyone expected. According to a new video from the "Science at NASA" YouTube channel, several feet of the ice melts every day during the summer.

Warm ocean currents sweep across the glaciers' surfaces, eroding them from below, according to the video. [Unstoppable Antarctic Glacier Melt: How Scientists Figured It Out (Video)]

For a few weeks each year, a NASA aircraft flies around Greenland to map the elevations along the glaciers using the Glacier and Land Ice Surface Topography Interferometer (GLISTIN). High-resolution maps of the ice show how quickly the glaciers are losing ice at their edges.

The aircraft also drops about 250 ocean probes each year and will continue to do so until 2020, to measure changes in temperature and the concentration of salt in the water between the ocean's surface and the seafloor, according to OMG's website. Surface water is usually colder and contains less salt than water at the seafloor, the video said, because it is made primarily of the water melting from the glaciers. The probes should help scientists learn how changes in the ocean affect the ice, according to the video.

OMG also uses sonar to measure the seafloor's shape and depth, which affects where warm ocean waters erode the ice and the extent to which they do so, according to the video. The project also conducts airborne measurements of gravity to help determine ocean depth.

The whole project aims to improve scientific estimates of increasing sea levels, according to OMG's website.

Scientists combine OMG's data with that of a second NASA project, Operation IceBridge, which measures how much polar ice melts from above, to get the most accurate measure of Greenland's changes in glacial ice.

Ala Khazendar, a glaciologist with OMG, said in the video that IceBridge's high-resolution topographic mapper is the "gold standard of measuring surface elevation changes of the ice sheet." The two projects in combination help scientists better determine if more ice is being lost due to temperatures of the ocean water or of the atmosphere, the video says.

If all of the ice in Greenland were to melt, it could raise global sea levels by 20 feet (6 meters), Josh Willis, the principal investigator on OMG, said in the video. Right now, scientists working with OMG expect that to take several hundred years.

Follow Kasandra Brabaw on Twitter @KassieBrabaw. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.