With the melting of unstable glaciers on the edges of West Antarctica, international projects have resorted to new methods to investigate the most unstable region of the continent. The idea is to seek answers to the uncertainties about the pace and causes of this process and to estimate when they may collapse.
These glaciers hold the mass of ice within the continent, preventing it from sliding into the sea. If they melt and collapse, rising sea levels are likely to be the main consequence, which would impact around 800 million people in coastal regions.
Professor Ilana Wainer, from the Oceanographic Institute at USP, told Sheet that today there are no general models that make projections of melting or collapse. They are experimental models, specific to each type of environment in Antarctica.
The British Alex Brisbourne, from the British Antarctic Survey, in turn, said that the latest IPCC report (UN Intergovernmental Panel on Climate Change) recognized the instability of glaciers and the possibility of collapse, but in the category of “low probability” and “high impact” capability.
Antarctica accumulates 90% of Earth’s ice. Satellites have detected a significant reduction of this ice in the last 20 years, especially in Pine Island and Thwaites glaciers, in West Antarctica. An annual average of 150 gigatons of ice was drained into the sea, raising its level by 0.4 millimeters per year.
A newly published study showed that Pine and Thwaites glaciers are shrinking faster than in the last 5000 years. Scientists used carbon-14 dating to estimate the age of ancient penguin shells and bones found on beaches near glaciers, in order to estimate past sea variations.
Theodore Scambos leads the Thwaites Glacier International Collaboration, the most advanced and expensive project (R$ 200 million) that monitors Thwaites, dubbed the “glacier of the end of the world” (doomsday glacier).
Thwaites is the size of Britain and has the potential to raise sea level — alone — by up to 65 cm if it collapses. Since the industrial revolution, the sea has risen by about 18 cm.
Scambos considers that “we may already be at the beginning of an eventual collapse of the ice sheet”. The Thwaites collapse would take a few hundred years, he reckons. The problem is that as this develops, sea level rise could more than double, forcing coastal cities to build defenses against the water.
Jefferson Simões, lead glaciologist at the National Institute of Science and Technology of the Cryosphere, told Sheet who plans to go to Pine Island Glacier in December to study its climate variability. The team will be isolated for two months at the site. For any emergencies, the next station is hundreds of kilometers away.
In the IPCC’s (Intergovernmental Panel on Climate Change’s) highest risk scenario, without taking the collapse into account, the predicted sea level rise for 2100 for the Brazilian coast is 90 cm to 1 meter.
Brenda Hall, a paleoclimatologist at the University of Maine (USA), told the report that the main difficulty in predicting glacier melt is the short observation period (70 years) in relation to the large temporal scales of changes in the ice sheet, which are of the order of thousands or millions of years.
“We need to look into the past, find out how the ice behaved and try to predict its behavior in the future,” Hall said.
It is suspected that the last collapse of West Antarctica was 120,000 years ago, according to Heitor Evangelista, a paleoclimatologist at the University of the State of Rio de Janeiro.
There was another collapse in the Pliocene, about 4 million years ago, when the concentration of COâ‚‚ atmospheric pressure reached 400 parts per million (ppm). In the last decade, this mark has been surpassed, and currently the global average is at 418 ppm, according to data released by the Global Monitoring Laboratory, USA.
Evangelista warns that “under these conditions, the collapse is a possible scenario, as it has historically occurred, when the sea level was between six and nine meters higher than today”.
To infer the atmospheric composition of the past, scientists drilled through the ice and reached deep soil samples up to 20 million years ago. The international project Andrill (Antarctic Drilling Project) led the investigations.
Scambos said that the most relevant melts occur at the bases of glaciers, where they are washed by warm ocean waters, and slowly erode and destabilize.
Scientists use autonomous underwater robots, such as Icefin, developed at the Georgia Institute of Technology (USA) to explore the bases of glaciers. The vehicle dives up to 1 km deep and is equipped with HD cameras, sonar, altimeter and other powerful sensors.
Geothermal heat, produced inside the Earth, also warms the glaciers of West Antarctica. The region has intense seismic activity, dozens of volcanoes under the ice, some even active.
A recent phenomenon is the formation of lakes of melt water on the surfaces of glaciers during “melting days”. This water infiltrates the glaciers, feeding the subglacial waters, and “works” like soap, increasing the slide of the glaciers towards the sea”, according to Heitor Evangelista.
The scientist goes to the interior of Antarctica in December to try to identify the phenomenon using equipment from the Brazilian research module Criosphere 1.
