Iceberg A68a, one of the largest ever recorded icebergs, floating near South Georgia Island Image credit: Cpl Phil Dye RAF/Crown copyright
A new cause of iceberg breakup has been revealed by simulations of one of the largest icebergs on record. Giant tabular iceberg A68a exceeded 100 miles long and 30 miles wide when it calved from an ice shelf on the Antarctic Peninsula in 2017. Initially famous for its size, the iceberg received further media attention in 2020 when it showed potential for getting stuck in shallow water near South Georgia Island and cutting off penguins and seals from their feeding grounds. However, the iceberg instead diverted into the deep ocean, where unknown forces caused it to fragment into several pieces.
In a new study published in Science Advances and led by AOS Postdoc Alex Huth (now affiliated with GFDL), Princeton researchers simulated this breakup event using new methods to represent giant icebergs within climate models. The simulations showed that breakup was triggered when part of the iceberg became positioned within stronger ocean currents than the rest of the iceberg, causing enough tension along the iceberg body to break it into pieces. Identifying this breakup mechanism and developing the methods to simulate it will improve the fidelity of climate simulations. Iceberg breakup influences the location and rate at which icebergs deposit freshwater into the ocean as they melt, which can significantly impact ocean circulation, sea-ice formation, and the marine biosphere. Huth co-authored the paper with AOS Research Oceanographer Alistair Adcroft, AOS Research Glaciologist Olga Sergienko, and Princeton CIMES 2021 summer intern Nuzhat Khan.