250 Meter High Channel Hundreds of Kilometers Long Discovered Underneath Antarctic Ice Shelf

Credit: MODIS Mosaic of Antarctica (MOA) Image Map / Anne le Brocq.

An ice channel stretching hundreds of kilometers and reaching as high as 250 meters have been discovered under a floating ice shelf in Antarctica. The ice shelf was discovered using satellite image and radar measurements from the sky. Based on the data recorded, the channel is as tall as the Eiffel tower.

The image map from the MODIS Mosaic of Antarctica (see image above) shows the ice shelf channel as it aligns the flow route of the water under the ice sheet and the start of the ice shelf cannel. The dashed line marks the border where the ice leaves solid ground and starts to float on the ocean surface.

Ice shelves are thick platforms of ice 100 to 1000 meters thick that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface; similar to a pier or a dock. These can only be found in Antarctica, Greenland and Canada.

Around 44% of the ice shelves are connected to the Antarctic coastline covering an area of 1,541,700 km². In the image map above, the part of the ice sheet between the grounded ice (part of the ice shelf that rests on bedrock) and the floating shelf (on the ocean surface) is called the grounding line.

Greenland Ice Sheet Melting Faster Than Expected; Hits Record High

A supraglacial lake over the Greenland ice sheet in the Kangerlussuaq area at 1500 m elevation photographed on July 21, 2012. The lake feeds a stream that will deliver meltwater to the low elevations where it will either flow to the ocean on the surface or it will dive into the ice to contribute to the development of the englacial hydrological system.
Credit: Marco Tedesco

The Greenland Ice Sheet is the second largest body of ice in the world. It spans over 1,710,000 square kilometers (660,235 square miles) which is around 80% of the surface of Greenland. The ice sheet is generally more than 2 km (1.24 mi) thick and over 3 km (1.86 mi) at its thickest point.

The ice sheet is made up of layers of compressed snow from more than 100,000 years. It contains valuable climate data from years past. Scientists have drilled ice cores up to 4 kilometres (2.5 mi) deep. These ice cores provide information on past climate factors such as temperature, ocean volume, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, solar variability, sea-surface productivity, desert extent and forest fires.

During the summer (June to September), about 50% of the ice sheet's surface naturally melts. At high elevations, most of that melt water quickly refreezes in place. The melt water coming from the ice sheet that is near the coastal areas are retained by the sheet and the rest falls into the ocean.

Greenland melting breaks record 4 weeks before season's end

Melting over the Greenland ice sheet shattered the seasonal record on August 8 – a full four weeks before the close of the melting season, reports Marco Tedesco, assistant professor of Earth and atmospheric sciences at The City College of New York.

The melting season in Greenland usually lasts from June – when the first puddles of meltwater appear – to early-September, when temperatures cool. This year, cumulative melting in the first week in August had already exceeded the record of 2010, taken over a full season, according to Professor Tedesco's ongoing analysis.

"With more yet to come in August, this year's overall melting will fall way above the old records. That's a goliath year – the greatest melt since satellite recording began in 1979," said Professor Tedesco.

This spells a change for the face of southern Greenland, he added, with the ice sheet thinning at its edges and lakes on top of glaciers proliferating.

Professor Tedesco noted that these changes jibe with what most of the models predict – the difference is how quickly this seems to be happening.