An unexpected river found beneath the Antarctic ice sheet is affecting ice flow and melting, potentially accelerating ice loss as the climate warms.
The 460 km long river is revealed in a new study, which details how it collects water at the base of the Antarctic ice sheet in an area the size of Germany and France combined. His discovery shows that the base of the ice sheet has more active water flow than previously thought, which could make it more susceptible to climate change.
The discovery was made by researchers from Imperial College London, University of Waterloo, Canada, Universiti Malaysia Terengganu and Newcastle University, details of which were published today in nature geoscience.
Co-author Professor Martin Siegert, from the Grantham Institute at Imperial College London, said: “When we first discovered lakes under the ice of Antarctica a few decades ago, we thought that they were isolated from each other. are entire systems there, interconnected by vast river networks, as they might be if there were not thousands of meters of ice above them.
“The region where this study is based contains enough ice to raise global sea levels by 4.3m. How much of that ice melts, and how fast, is related to how the base of the ice is slippery. The recently discovered river system could strongly influence this process.”
Water can appear under the ice caps in two main ways: from surface meltwater flowing through deep crevices, or by melting at the base, caused by the Earth’s natural heat and friction. when the ice moves over the land.
However, the ice caps around the north and south poles have different characteristics. In Greenland, the surface experiences heavy melting during the summer months, where immense amounts of water flow through deep crevices called mills.
In Antarctica, however, the surface does not melt in sufficient quantity to create windmills, because the summers are still too cold. This was thought to mean that there was relatively little water at the base of the Antarctic ice sheets.
The new discovery turns that idea on its head, showing that there is enough water from basal melting alone to create huge river systems under ice several kilometers thick.
The discovery was made through a combination of airborne radar surveys that allow researchers to look under the ice and model the hydrology of the ice sheet. The team focused on a largely inaccessible and understudied area that includes ice from the East and West Antarctic Ice Sheets and reaches into the Weddell Sea.
The fact that such a large system has been discovered so far speaks to how much we still need to learn about the continent, says lead researcher Dr Christine Dow from the University of Waterloo.
She said: “Thanks to satellite measurements, we know which regions of Antarctica are losing ice, and how much, but we don’t necessarily know why. This discovery could be a missing link in our models. We could be underestimating enormously the speed with which the system will melt by not taking into account the influence of these river systems.
“Only by knowing why the ice is being lost can we make models and predictions of how the ice will react in the future under further global warming, and how much this might increase the global level of the sea.”
For example, the newly discovered river emerges into the sea under a floating ice shelf, where a glacier extending from land is buoyant enough to begin floating on ocean water. The fresh water from the river, however, lifts warmer water down from the ice shelf, melting it from below.
Co-author Dr Neil Ross, from the University of Newcastle, said: “Previous studies have looked at the interaction between the edges of ice caps and ocean water to determine what melting looks like. However, the discovery of a river that reaches hundreds of kilometers inland driving some of these processes shows that we cannot fully understand ice melt without considering the whole system: ice sheet, ocean and fresh water.”
The existence of large rivers under the ice must also be taken into account when predicting the possible consequences of climate change in the region. For example, if summers are hot enough to cause sufficient surface melting for water to reach the base of the ice sheet, this could have significant effects on river systems, potentially tipping Antarctica into a similar state. in Greenland, where ice loss is much faster.
There are also potential feedback loops that would accelerate ice loss. For example, if ice begins to sink faster as water accumulates at the base, this will increase friction where the ice is sinking on land, which could increase the amount of basal melting and produced water.
The team is now looking to gather more data on all of these mechanisms from surveys to apply their models to other regions and provide a better understanding of how a change in Antarctica could change the planet.
Antarctic ice sheets could be melting faster than we thought
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
Provided by Imperial College London
Quote: River Longer Than Thames Below Antarctic Ice Sheet May Affect Ice Loss (2022, October 27) Retrieved October 27, 2022 from https://phys.org/news/2022-10-river- longer-thames-beneath-antarctic.html
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