Researchers observed a “loose tooth” of ice dangle from the edge of the Antarctic ice sheet for 20 years, waiting to be detached. However, the wrong portion was observed as a nearby sheet of ice along with the same rift system, larger than its wobbling neighbor has broken off the Amery ice board according to the Australian Antarctic Division.
The massive iceberg known as D28 covering 1,636 square kilometers (632 square miles) with a depth of nearly 210 meters deep (689 feet) is approximately the size of urban Sydney. It is the largest iceberg weighing about 315 billion tonnes formed by the Amery ice shelf in more than fifty years.
Helen Fricker, a researcher from the Scripps Institution of Oceanography said that it is the molar compared to a baby tooth. Fricker says that the disintegration of the ice shelf from its edges is a natural phenomenon known as calving. It is to make space for new streams of ice and snow. Each individual ice sheet undergoes a different rate of calving which varies across seasons and takes more than decades to complete since it is an important way to balance masses of ice sheets around the world.
Researchers were unable to predict the location and timeline of calving in this case as all these parameters make it difficult to anticipate from beforehand. Fricker said that they anticipated a huge iceberg would break off between 2010 and 2015 when they first observed a split at the front of the ice board in the early 2000s. The event ultimately occurred after all these years however not at the location predicted by the researchers.
Amery ice shelf produced an iceberg like this covering an area of 9000 square kilometers in 1963. This ice shelf is normally expected to undergo one major calving event every six or seven decades, and so far two have been observed in the cycle. Hence this is not related to the global change of climate, although this is not the situation always.
For example, instead of every six years, the calving rate of Pine Glacier situated in Western Antarctica has accelerated, spreading deeper and shedding huge icebergs in 2013, 2015, 2017, and 2018 which is clearly not as per its normal timeline.
Sue Cook from the Institute of Marine and Antarctic Studies (IMAS) said that she expects the calving rate to increase because of climate change. She explained that icebergs will start becoming thinner as waters around Antarctica warm-up making them more vulnerable to breaking up.