27 août 2019
Seals are not naturally equipped with antennae. However, a scientific experiment has been carried out by an international team of researchers guided by the University of Washington, to investigate behind the conformation and history of the Antarctic and in particular, the origins of an enormous hole in the sea ice which has fascinated researchers for years.
A mysterious white chasm
The technical term for this type of abyss is “polynya”: an open stretch of salt water set in the ice cap. This one in particular is enormous: scientists explain that according to aerial photographs, it presents a surface area the size of South Carolina, that is to say 80 thousand square kilometres, in the area occupied by the Weddell Sea. A phenomenon which occasionally manifests itself, for no exact reason and of variable duration. For the sake of clarity, its presence is not linked to the rise in temperatures over certain periods, nor by the amount of precipitation.
So what does contribute towards its formation? Researchers have been trying to reconstruct evidently complex mechanisms which lead to the melting of ice in random points of the ice cap since the 70s. However they still have no answer.
Reconnaissance with cyborg seals
To shed some light on the mystery, a team of scientists led by the researcher Ethan Campbell from the University of Washington School of Oceanography has come up with an unprecedented method of exploration: enlisting a small team of sea elephants, large animals from the seal family which populate these cold areas of the planet. The animals were tracked along their journeys hundreds of metres below the sea surface, up to depths of over 2 thousand metres.
By equipping them with sensors, small antennae, the team was able to collect information on various layers of the ocean below the ice, to date unobtainable even by expert explorers and submarines. Selected specimens were fitted with small electronic helmets, specially designed not to interfere with the animal’s normal habits and programmed to automatically unhitch from their head a few weeks later, once the mission was completed.
What emerged from the study
The strange helmets, connected to satellite receivers, enabled scientists to access a place in the world which was previously impossible to reach, and to measure the chemical and physical properties of the environment beneath the mysterious “pool” set in the ice.
The results, recently published in the journal Nature, speak clear: veritable underwater storms cause the formation of these abysses, combined with variations in salinity and other extraordinary ocean conditions. Specifically, the mixing of waters at great depths shunts warmer streams of water towards the surface which in turn causes the melting of the ice “crust” and the formation of a hole.
Why always in the same place? In the case of the large polynya under investigation, the imbalance is likely to be attributable to the presence of an enormous underwater mountain at the bottom of the ocean, the Maud Rise. The impact of currents on this mountain causes a vortex which periodically results in the concentration of warmer waters under the ice cap, always in the same area.
It is still difficult to understand whether global warming plays a part in all of this. New data will need to be gathered, even more complex models will need to be developed and probably cyborg seals will need to be followed along new journeys in order to piece the puzzle together.