Antarctica's 'Doomsday Glacier'

 "Doomsday Glacier" is on the brink of losing its ice shelf          

The Thwaites Glacier has the world’s widest glacial interface with the ocean, extending roughly 75 miles (120 km), and the collapse of this glacier could cause a catastrophic rise in sea levels worldwide. Some 30 miles (50 km) of the glacier’s ocean front terminates in an ice shelf which floats above Pine Island Bay. The grounding line of the ice shelf extends downward from the sea surface to depths between about 2,600 and 3,940 feet (roughly 800 and 1,200 meters). The glacier covers approximately 74,100 square miles (192,000 square km). West Antarctica's "Doomsday Glacier" is further compromising the already melting ice mass and threatening to unleash devastating sea-level rises. The Thwaites Glacier is nicknamed the "Doomsday Glacier" because its collapse would send so much ice into the Southern Ocean that global sea levels would rise by 2.1 feet (65 cm's or 26 inches), flooding coastal communities worldwide. This collapse could take centuries, but there is an imminent threat to Thwaites' eastern ice shelf, which will likely accelerate the glacier's demise.

Antarctica landmass is almost wholly covered by a vast ice sheet. Often described as a continent of superlatives, Antarctica is not only the world’s southernmost continent. It is also the world’s highest, driest, windiest, coldest and iciest continent. Antarctica is about 5.5 million square miles (14.2 million square km) in size, and thick ice covers about 98% of the land. The continent is divided into East Antarctica and West Antarctica. Researchers say that satellite images reveal that the Thwaites eastern ice shelf is about to detach from the glacier. While the glacier sits on land, the ice shelf is a floating body of ice which is attached to the glacier's mouth. Researchers still have a lot to learn about the glacier, but this shelf acts as a buttress, restraining the flow of ice from the glacier into the sea. The ice shelf is very likely to break up in the near future. The last bit of ice shelf in front of the glacier is poised to disintegrate as per researcher's. We don't know quite how this ice shelf is going to break up, but it's definitely going to go. 

The continental ice sheet contains approximately 7 million cubic miles (about 29 million cubic km) of ice, representing about 90% of the world’s ice and 80% of its fresh water. Its average thickness is about 5,900 feet (1,800 metres). Ice shelves, or ice sheets floating on the sea, cover many parts of the Ross and Weddell seas. These shelves together with other shelves around the continental margins, fringe about 45% of Antarctica. Around the Antarctic coast, shelves, glaciers, and ice sheets continually “calve,” or discharge, icebergs into the seas. The continent is a cold dry desert where access to water determines the abundance of life. While the terrestrial ecosystem contains more than a thousand known species of organisms, most of these are microorganisms. Maritime Antarctica supports more life than inland Antarctica, and the surrounding ocean is as rich in life as the land is barren. Around the size of Florida, Thwaites Glacier is the largest glacier in West Antarctica. The gigantic river of ice is more than 6,500 feet (2,000 meters) thick in some parts and 75 miles (120 km's) across. The glacier has been melting rapidly since the 1980s, losing hundreds of billions of tons of ice. It's due to relatively warm ocean water flowing underneath the ice shelf and melting the glacier at its base, where ice sits on ground that's below sea level. The glacier has retreated around 12.4 miles (20 km) since 1992.

Governments mandated many early expeditions, whether ostensibly economic, scientific or exploratory in character, to make territorial claims. The ice-choked and stormy seas around Antarctica long hindered exploration by wooden-hulled ships. No lands break the relentless force of the prevailing west winds as they race clockwise around the continent, dragging westerly ocean currents along beneath. The southernmost parts of the Atlantic, Pacific, and Indian oceans meet the Southern (or Antarctic) Ocean, the cold oceanic water mass with unique biological and physical characteristics. Icebreakers and aircraft now make access relatively easy, although still not without hazard in inclement conditions. In addition, many tourists have visited Antarctica, which has underscored the value of scenic resources in the continent’s economic development. Modeling the demise of massive glaciers is a complex task, making it hard to put an exact date on when Thwaites Glacier will finally collapse. However, a latest study found that the glacier could be losing 180 billion to 200 billion tons of ice/year by 2067. The Thwaites eastern ice shelf is fracturing where the shelf is held in place by a ridge on the ocean floor, and at the mouth of the glacier. Movement on the western side of the shelf, where the ice is breaking away, has approximately doubled over the last eight months.

As per new expeditions, each range in ever-increasing detail, concepts of the geologic structure are continually modified. Antarctica’s structural record is now known to be more complex than that implied in the past. The average thickness of the terrestrial crust for both East and West Antarctica approximates that of other continents. Although it has been postulated that West Antarctica might be an oceanic island archipelago if the ice were to melt, its crustal thickness of about 20 miles indicates an absence of oceanic structure. This thickness is similar to that of coastal parts of other continents. The crust thickens sharply along the Transantarctic Mountains front, possibly a deep crustal fault system, and averages about 25 miles thick in East Antarctica. Significant earthquakes are not recorded along this or other known faults in Antarctica, the most seismically quiet of all continents, in which mostly minor activity is associated with surrounding oceanic ridges or volcanoes. However, the occurrence of one unusually large earthquake of magnitude 6.4 in the Bellingshausen Sea in 1977 suggests that the Antarctic Plate may have greater seismicity than generally believed. Thwaites Glacier's slow collapse is part of a wider concern among scientists for the future of the West Antarctic ice sheet. 

Thwaites is a key pillar of the ice sheet, protecting other ice from slipping into the ocean. If the whole ice sheet were to go, sea levels would rise by 10.8 feet (3.3 m), according to the British Antarctic Survey. The collapse of ice sheets like this one are considered tipping points, or "points of no return," in the fight against climate change, meaning that once they are crossed, they bring about permanent changes which cannot be reversed for many thousands of years. "Much like other Antarctic sea ice, and the glacier itself, this shelf is undermined by warmer, saltier water being forced up from deep below the surface of the Southern Ocean. Larter noted that it's more about the circulation of water than warming, but indications are that human-driven climate change is ultimately to blame. There is an active scientific debate about exactly how this works, but it seems pretty clear that in some way, the changes to the Southern Hemisphere westerly winds are what is driving warm water onto the continent and wind changes are part of the wider pattern of climate change that we're seeing. The ancient crust of Antarctica must have been highly mobile and the configuration of the continent many hundreds of millions of years ago in the Precambrian far different from today’s situation. 

There are two faces of the present-day continent of Antarctica. One, seen visually, consists of the exposed rock and ice-surface terrain. The other, seen only indirectly by seismic or other remote-sensing techniques, consists of the ice-buried bedrock surface. Both evolved through long and slow geologic processes. Effects of glacial erosion and deposition dominate everywhere in Antarctica, and erosional effects of running water are relatively minor. Yet, on warm summer days, rare and short-lived streams of glacial melt water do locally exist. Antarctica, with an average elevation of about 7,200 feet (2,200 metres) above sea level, is the world’s highest continent. International concern is increasing over the possibility of global warming. The glaciers and ice sheets of Antarctica may document such change, especially in West Antarctica. Average winter temperatures on the Antarctic Peninsula have increased by 10.8 °F (6 °C) since 1960, and the disintegration of much of the Larsen Ice Shelf  was largely attributed to climatic changes resulting from rising average air temperatures. Many factors determine Antarctica’s climate, but the primary one is the geometry of the Sun-Earth relationship. The 23.5° axial tilt of Earth to its annual plane of orbit, or ecliptic, around the Sun results in long winter nights and long summer days alternating between both polar regions and causing seasonal variations in climate.