Meltwater is accelerating the movement of Greenland ice Today’s Video of the Day from NASA Goddard reveals that bottomless sinkholes are funneling meltwater to the base of the Greenland Ice Sheet. This results in increased water pressure that slightly detaches the ice and speeds up the rate at which it flows into the ocean.
With a surface area that is about as big as the size of Mexico, Greenland’s ice is the largest contributor to global sea level rise.
For one particular sliding glacier in southwest Greenland, researchers concluded that the main contributor to its speed was how quickly the water pressure changed within cavities at the base of the ice where meltwater met bedrock.
“Even if the cavities are small, as long as the pressure is ramping up very fast, they will make the ice slide faster,” said Dr. Laurence C. Smith of Brown University. Therefore the Meltwater is accelerating the movement of Greenland ice.
This is the first time that direct observations have revealed how changes in the volume of water under the Greenland Ice Sheet drive the flow velocities of a glacier. The presence of ice-rafted sediments in deep-sea cores recovered from northwest Greenland, in the Fram Strait, and south of Greenland indicated the more or less continuous presence of either an ice sheet or ice sheets covering significant parts of Greenland for the last 18 million years. From about 11 million years ago to 10 million years ago, the Greenland Ice Sheet was greatly reduced in size.
The Greenland Ice Sheet formed in the middle Miocene by coalescence of ice caps and glaciers. There was an intensification of glaciation during the Late Pliocene. Ice sheet formed in connection to the uplift of the West Greenland and East Greenland uplands. Also the western and eastern side of the mountains constitute passive continental margins that were uplifted in two phases, 10 and 5 million years ago, in the Miocene epoch. Computer modelling shows that the uplift would have enabled glaciation by producing increased orographic precipitation and cooling the surface temperatures. The oldest known ice in the current ice sheet is as much as 1,000,000 years old. The ice cores also record human impact, such as lead from the Roman Empire.
The study is published in the journal Geophysical Research Letters.
Video Credit: NASA Goddard
By Chrissy Sexton, Earth.com Staff Writer