Their NASA-funded study used two separate satellite observation systems over the past 20 years and found that the melting is accelerating.
Writing in the journal Geophysical Research Letters, researcher Eric Rignot says the Greenland-Antarctica melt is overtaking ice loss from mountain glaciers and other ice caps as the dominant influence on sea level rise.
He adds that if the ice cap melting continues unabated, it could add an additional 5.9 inches to the average global sea level by 2050.
JPL scientist Isabella Velicogna says that while six more inches in sea level heights might not sound that much, the increase will be distributed unevenly around the world, with low-lying countries like Bangladesh being impacted the most.
And when added to the predicted sea level rise of 6.6 inches from glacial melt and thermal ocean expansion as the climate warms, the total sea level rise could reach almost 12.6 inches, the researchers warn.
Photo: Eric Rignot - NASA JPL