They discover a new way in which the largest icebergs break up

Ice melting and iceberg calving are the two mechanisms that decrease the frozen mass of Antarctica and increase the volume of the Southern Ocean. Icebergs come in different sizes. The so-called ‘tabular’ (table-shaped) are some of the largest and most abundant. When they break off, they move through the sea as they melt, and they can also break if they collide with the seabed. What was not known, until now, is that strong ocean currents can also break them into pieces.

This has been discovered by a team of researchers from Princeton University, New Jersey (United States). In their study, published in the journal Science Advances, they took as reference the evolution of the 4,200 km2 tabular iceberg A68a, which experienced two crack rupture events in December 2020. The first was triggered when the iceberg briefly collided with the bottom Marine. The second, surprisingly, occurred in deep water. To find out what could have caused this second partition, the scientists developed a new research model, called Kinematic Iceberg Dynamics (iKID), which led them to the conclusion that the ocean current could induce horizontal stresses in the iceberg that generated the breakup, a cause that until then had not been taken into account.

Understanding the evolution of tabular icebergs, like A68a, is important because their size and breakup determine where they deposit meltwater in the ocean as they move, which has effects on the climate. “This meltwater can substantially influence ocean circulation, sea ice formation, the state of the marine biosphere, and potentially produce changes in climate,” said Alexander Huth, a researcher at Princeton University and lead author of the paper. study.

For example, ocean currents are what allow Europe to have a relatively warm climate, even warmer than the East Coast of the United States which, despite being at a similar latitude, suffers from a much colder climate. On the other hand, the area where icebergs melt influences the formation of deep waters and the release or accumulation of CO2 in the oceans.

Improve climate models

However, current climate models only represent those icebergs with areas smaller than ~3.5 km2, and not the largest ones, such as A68a, even though giant icebergs with lengths greater than 18.5 km represent 98% of the volume. total of all Antarctic icebergs. “This is because, in these models, an iceberg is usually represented as a ‘point particle’ that moves and melts without regard to fracture and breakup, but this approach is not suitable for modeling tabular icebergs,” explains Alex Huth, author of the study and postdoctoral research associate at Princeton University.

The omission of information on large icebergs makes models of meltwater distribution inaccurate, as the size of these frozen blocks influences their trajectory and decomposition. For example, small icebergs melt faster than large icebergs. ‘Our new model is suitable for modeling icebergs of any size, even the largest on record, which had an area greater than 10,000 km2. Therefore, we hope that implementing our method within climate models will advance our understanding of the role of these icebergs in the Earth system and how they may interact with the changing climate,” Huth states.

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