Invisible Giant Waves Beneath the Ice

When massive icebergs break off from glacier fronts in Antarctica, they do not only generate visible waves at the surface. Beneath the water, tsunamis several meters high can be triggered, processes that have so far been little studied but that profoundly alter the ocean. An international research team led by the British Antarctic Survey (BAS) is now investigating how these underwater tsunamis form and what role they play for climate and ecosystems.

During so-called calving events, large masses of ice plunge into the sea, releasing enormous amounts of energy. The resulting underwater waves cause intense mixing of different water layers. Heat, oxygen, and nutrients are exchanged between depths, a mechanism that is crucial for life in the ocean and for climate regulation in the Southern Ocean. New calculations suggest that, in polar regions, this effect can locally be as significant as wind-driven mixing and in some cases even stronger than tides.

The phenomenon was discovered by chance during an Antarctic expedition aboard the former BAS research vessel RRS James Clark Ross. Since then, scientists at the Rothera Research Station on the Antarctic Peninsula, as well as aboard the British polar research ship RRS Sir David Attenborough, have been specifically investigating the formation and propagation of these underwater tsunamis.

The researchers use satellites, drones, remotely operated cameras, and autonomous underwater vehicles. The measurements are complemented by modern data analyses and computer models, which allow the team to estimate the impacts of the tsunamis on sea temperature, nutrient distribution, and marine productivity.

The findings could be significant far beyond Antarctica. Stronger mixing in the Southern Ocean could bring warm deep water closer to the surface and thus accelerate the melting of the Antarctic ice sheet, with consequences for global sea level. At the same time, changes in nutrient balances could affect the base of marine food webs. The aim of the project is to gain a better understanding of these previously hidden processes and to improve projections in future climate models.

Heiner Kubny, PolarJournal