Fridtjof Nilsen, who led the first expedition to cross Greenland's Arctic, once called the Arctic "the great adventure in the ice, deep, and pure as infinite." Nansen's 1888 journey was not possible without knowing the secrets beneath the icy landscape below his skis.
Today, thanks to radar and other technologies, the part of Greenland that sits below its 9,800-foot-thick(3,000 meters) ice sheet is coming into focus. These tools show a complex landscape hidden from view that provides clues to the Arctic's past and future.
The longest canyon in the world
3D view of subglacial canyon looking northwest from central Greenland. Image credit: J. Bamber University Bristol
The longest canyon is hidden by the Greenland Ice Sheet.
The canyon was discovered in 2013. It stretches 460 mile (740 km) from Petermann Glacier, on the northwest coast, to the highest point of central Greenland. This canyon is significantly longer than China's Yarlung Tsangpo Grand Canyon which measures 308 miles (496 km). It is the longest canyon you can actually see on Earth.
It plunges to 2,600 feet (800m) in some places, and it is 6 miles (10km) wide. The Grand Canyon, Arizona is about 1 mile (16 km) deep and approximately 10 miles (16 km) wide.
Some parts of the canyon could route meltwater beneath the ice sheets to the sea. It was probably formed before the ice sheets and was once the channel for a great river.
Invisible mountains
Greenland's ice melts at the surface. Water then carves fissures until it reaches the base. This is where the ice meets the land. Sub-glacial glacier ice can be used to lubricate glaciers, which causes them to flow faster to the ocean and deplete more quickly. Image credit: Ashley Cooper via Getty Images
Greenland's sub-ice landscape isn't just rugged. The island has been mapped by ice-penetrating radar for decades. This radar is typically mounted on an airplane and can be used to map rugged mountain ranges as well as plunging fjords below the ice.
A 2017 map of Greenland shows a depression-like area in the middle of the island. This depression is surrounded by a circle of mountain ranges along the coast. This map showed the topography of Greenland's flowing glaciers. Scientists can use this information to predict how fast they will move under warmer conditions and how quickly they will calve the ocean.
A primeval lake
Humboldt Glacier, northwest Greenland seems like ice will never cease. (Image credit: VWPics/Universal Images Group via Getty Images
It was home to a lake that was twice the size of Rhode Island or Delaware a few hundred thousand years ago.
The lake today is a depression that's stuffed with sediment. It was once 800 feet deep (250 m) in places. It covers 2,700 sq. miles (7.100 km2) and was fed by at most 18 streams.
Although the lake bed may contain valuable clues about the Arctic's climate in the distant past it would be necessary to drill through the 1.1 mile (1.8 km) of ice that covers the site.
Hidden gems
Greenland's surface meltwaters are the blue rivers and splotches that you see. (Image credit to Andrew Sole/University of Sheffield).
Greenland's glaciers also conceal a vast landscape of lakes shaped like jewels and filled with crystallized meltwater. These small lakes are found in Greenland's northern and eastern regions. Stephen Livingstone, who is a senior lecturer and researcher in physical geography at Sheffield, in the United Kingdom, previously reported that there are at least 60 of them.
These lakes can range in size from 656 feet (220 m) to 3.7 miles (5.9km) across. These lakes could be fed by meltwater from the ice sheet or may melt due to friction caused by the movement of ice and geothermal energy below.
Evidence of meteor impacts
Crater below the Greenland ice sheet. (Image credit NASA's Goddard Space Flight Center/ Cynthia Starr).
Some of the topography beneath the ice sheets may not be from Earth. Scientists have discovered at least two possible meteor craters beneath the ice. Both are located in northwest Greenland. One is below Hiawatha Glacier while the other is 114 mi (183 km) away. Hiawatha crater lies under approximately a mile (930 m) of glacier, while the second crater lies under 1.2 miles (2km) of ice. It is the 22-mile (36 km) wide second crater, making it 22 miles (36km) in size. The first crater is slightly smaller at 19 mi (31 km).
Beautifully preserved fossil plants
Greenland's Ice Sheet may have vanished far quicker than previously thought. This has allowed trees and plants to flourish. (Image credit: Joshua Brown/UVM)
A Cold War-era attempt to build a nuclear weapons station was made from an ice core. It was found in a freezer and contained perfectly preserved fossils of plants that date back to one million years ago.
Andrew Christ, lead author of the study and postdoctoral fellow in the Department of Geology at The University of Vermont, Burlington told Live Science that freeze-drying is the best way to describe them. They looked almost like they had died just a few hours ago when we took them out and gave them some water.
The core was found in northwestern Greenland. It is possible that the plants contained within were grown in a boreal forest. This forest could only thrive in conditions that are largely free from ice, which suggests that some parts of Greenland's Ice Sheet may be older than previously thought.
Original publication on Live Science
