Researchers have been using NASA data to calculate how much Earth's melting land ice is adding to the rise in sea levels worldwide.

Earlier this year, NASA said ice loss from Greenland, Antarctica, and their peripheral ice caps and glaciers averaged 385 billion tons a year.

For several days this July, Greenland's surface ice melted over a larger area than at any time in more than 30 years of observations. Nearly the entire ice cover of Greenland, from its thin coastal edges to its two-mile-thick center, experienced some degree of surface melting, according to NASA.

The melting spread quickly. Melt maps derived from the three satellites showed that on July 8, about 40 percent of the ice sheet's surface had melted. By July 12, 97 percent had melted.

In addition, a 12.5-mile swath of ice broke off this month and headed out to sea. Click through to see images and video of what's happening in Greeland and Antarctica.