As the climate warms, an unexpected river under the ice sheet could affect the flow and melting of ice, which could lead to faster ice loss.
A new study shows how water is collected at the base of the ice sheet from an area larger than Germany and France. It has been found that the base of the ice sheet has more active water flow than was thought.
The details of the discovery were published in the journal Nature Geoscience.
The lakes were thought to be isolated from each other when they were first discovered. If there weren't thousands of meters of ice on top of them, there would be a lot of systems down there.
There is enough ice in the region where this study is based to raise the sea level by 4.3m. The base of the ice is linked to how fast the ice is melting. This process could be influenced by the newly discovered river system.
There are two main ways in which water can appear beneath ice sheets, from surface meltwater running down through deep crevasses or from melting at the base.
The ice sheets in the north and south are different. During the summer months in Greenland, the surface experiences strong melting due to huge amounts of water channeling down through deep crevasses called moulins.
The summers are too cold for the surface to melt in enough quantities to make moulins. It was thought that there wasn't much water at the base of the ice sheets.
This idea has been turned on its head by the discovery that there is enough water from the melt to create a river system.
Airborne radar surveys allow researchers to look beneath the ice and model the ice sheet. The team focused on an area that includes ice from both the East and West Antarctic Ice Sheets, as well as reaching the Weddell Sea.
It's testament to how much we still need to know about the continent that such a large system could be undiscovered until now.
She said, "We know how much ice is being lost in certain areas, but we don't know why." There is a missing link in our models. The system will melt quickly if we don't account for the influence of the river systems.
By knowing why ice is being lost, we can make models and predictions of how the ice will react in the future under further global warming, and how much this could raise global sea levels.
A river emerges into the sea beneath a floating ice shelf where a glacier extends out from the land. Warming water from the river goes towards the bottom of the ice shelf.
Previous studies have looked at the interaction between the edges of ice sheets and ocean water to determine what melting looks like. The discovery of a river that reaches hundreds of kilometers inland shows that we can't fully understand the ice melt without taking into account the entire system.
Predicting the effects of climate change in the region needs to take into account the existence of large under-ice rivers. If summers warm enough to cause enough surface melt that the water reaches the base of the ice sheet, it could cause large effects on the river systems, potentially tipping Antarctica to a Greenland-like state.
Ice loss could be accelerated by feedback loops. If the ice starts to flow faster as water accumulates at the base, this will cause the ice to run over dry land, which will increase the amount of melt and water produced.
The team wants to gather more data from surveys to apply their models to other regions in order to better understand how a changing Antarctica could affect the planet.
More information: Christine Dow, Antarctic basal environment shaped by high-pressure flow through a subglacial river system, Nature Geoscience (2022). DOI: 10.1038/s41561-022-01059-1. www.nature.com/articles/s41561-022-01059-1 Journal information: Nature Geoscience
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