Antarctica, the world’s southernmost landmass, is also the coldest, stormiest and most inhospitable of all the continents. Discovered in 1820 by a Russian expedition, Antarctica piques the scientific community, geologists and environmentalists, who find the ice covered desert to be an ideal place for conducting research and studying the effect of climate change, pollution, global warming and the ecology. There are dozens of base stations and scientific observation centers in Antarctica.
Global warming has taken a manifest toll on the polar caps of the earth and the glaciers and snow covered fields of Antarctica are also witnessing the drastic changes.
Hidden canyons in ice discovered
Antarctica’s ice is depleting and thick coats of snow are gradually thinning, but recently scientists have discovered huge canyons that pass through the ice, increasing its fragility manifold.
With the help of latest data from CryoSat and Sentinel-1, new light has been thrown on the hidden layers.
There are ice shelves — thick layers of ice that extend from the ice sheet and float on the coastal waters — that surround Antarctica. Ice shelves play a crucial role in bolstering the ice sheet on land, showing the sheet’s inward flow.
The ice sheet that covers Antarctica is dynamic and constantly on the move.
Recently, however, there has been alarming reports about its floating shelves thinning and even vanishing, allowing the grounded ice inland to flow faster to the ocean and lead to sea-level rise.
As scientists continue to study the different facets of Antarctica, observe cracks in the surface of the ice that might signal the destruction of a shelf and learn how these changes are impacting the biology of coastal waters, they are also aware of surprising changes taking place underneath the surface, shrouded from the human view.
There are huge inverted canyons in the underbelly of ice shelves, but very little is known about how they are formed and how they affect the stability of the ice sheet.
One type is assumed to be caused by subglacial water that drains from beneath the ice sheet and runs into the ocean. In this region, the ocean water is divided into different layers based on water temperature, with the warmer water at the bottom. However, as the colder meltwater pours down into the ocean it then raises because it is less dense than the seawater, but as it rises it drags up the warm bottom water which causes the underbelly of the floating ice shelf to melt.
Another type is caused by the way ocean water circulating under the shelf.
Doston Ice Shelf
Scientists have been using ESA’s CryoSat to analyze changes in the surface of the ice shelf and the Copernicus Sentinel-1 mission to observe how shelves flow to gain more insight about what’s going on that we are unable to see.
Their focus has been on the Dotson ice shelf in West Antarctica.
Noel Gourmelen from the University of Edinburgh said “We have found subtle changes in both surface elevation data from CryoSat and ice velocity from Sentinel-1 which shows that melting is not uniform, but has centred on a 5 km-wide channel that runs 60 km along the underside of the shelf. “Unlike most recent observations, we think that the channel under Dotson is eroded by warm water, about 1°C, as it circulates under the shelf, stirred clockwise and upward by Earth’s rotation.”
By re-analyzing old satellite data, it is estimated that melting changes have been taking place over the last 25 years.
In due course of time, the melt has splitted into a channel like feature that runs across the entire length, under the Doston ice shelf.
When Doston ice shelf melts each year, 40 billion tonnnes of fresh water is generated, and this canyon is solely responsible for the release of 4 billion tonnes.
Dr Gourmelen further adds “”The strength of an ice shelf depends on how thick it is. Since shelves are already suffering from thinning, these deepening canyons mean that fractures are likely to develop and the grounded ice upstream will flow faster than would be the case otherwise.
“It is the first time that we’ve been able to see this process in the making and we will now expand our area of interest to the shelves all around Antarctica to see how they are responding. We couldn’t do this without CryoSat and the European Commission’s Copernicus Sentinel missions,”