National Aeronautics and Space Administration (NASA) of the US estimates that an Antarctic iceberg measuring 5,800 sq km in area broke off from the mainland Antarctic continent between July 10 and 12, 2017 (NASA, 2017). The Antarctic iceberg has broken off from the Larsen C ice shelf, which is the fourth-largest ice shelf around Antarctica. The Larsen C ice shelf is located at the eastern side of the tip of the Western Antarctic Peninsula. An ice shelf is a floating sheet of ice that is permanently locked onto a land mass.
Fig: The Larsen C ice shelf in Western Antarctica
A crack in this Antarctic iceberg, comprising 10 per cent of the area of the Larsen C shelf, developed slowly. Its progress was observed by the scientific community and its development covered by the international media. Satellite data using technologies such as thermal imaging and radar altimeters that measure sea surface height were deployed throughout the ice shelves that flank 75 per cent of the ice sheet in Antarctica.
The data for Larsen C revealed in 2014 that a crack in progress for decades in the ice shelf had hastened to develop northwards. By June-July in 2017, the outer end of the rift had begun to drift apart with the greatest speed ever recorded for the development of the Antarctic iceberg. Scientists working with a UK-based research project in the Antarctic, Project MIDAS, report that between June 24 to 27, 2017, the progress of the crack sped to more than 10 m a day (PTI, 2017), finally breaking off by July 12, 2017 to form the massive free floating Antarctic iceberg.
According to NASA, the health of ice sheets that form an Antarctic iceberg can be assessed by looking at their balance. Balance in an ice sheet is the balance between the ice added through snowfall and the ice that is lost due to melting and formation of icebergs. Ice sheets can destabilize sometimes due to the formation of a particularly big iceberg or thorough the disintegration of an ice shelf. A significant effect of this phenomenon is that Antarctic glaciers that were previously grounded due to resistance from the ice shelf now can flow freely into the ocean, thereby contributing to raising overall sea levels (NASA, 2017). In a study published
in 2011 by the National Centre for Antarctic and Ocean Research (NCAOR), Goa on the fluctuating climate system in Antarctica, significant climatic changes were reported in Antarctica in recent decades. The study revealed that atmospheric temperatures had increased in most parts of Antarctica, with the largest annual warming trends recorded for Western Antarctica, with significant warming in the Antarctic Peninsula in particular (NCAOR, 2011), where the Larsen C ice shelf is located.
There is a lack of an adequate number of recoded breaks of large Antarctic icebergs out of ice shelves such as the one off Larsen C, and such large calving events are extremely rare. It cannot be said cumulatively whether such natural events are due to human intervention or whether they are natural. Among the possible reasons that scientists are debating, one contributory cause could be human-induced global warming, which could lead to melting of ice both from above due to the Sun and from below due to the action of warmer waters (Guardian, UK, 2017).
Dan McGrath, a glaciologist at Colorado State University studying the Larsen C ice shelf since 2008 is reported to have told NASA that â€œThe Antarctic Peninsula has been one of the fastest warming places on the planet throughout the latter half of the 20thcentury. This warming has driven really profound environmental changes, including the collapse of Larsen A and Bâ€ (NASA, 2017).
There is significant evidence to suggest that global warming might be a concomitant cause of the breaking off of the Larsen C ice shelf. However, in a historic deficiency of studied breaks of extremely large Antarctic icebergs out of the landmass, only time will tell whether this is an isolated case or something indicative of a larger trend.