In the sediments under the Antarctic glaciers, scientists have found a powerful system of water circulation to a depth of 2 km. It may be important for the movement of glaciers towards the sea and the release of carbon dioxide, and thus for the climate.
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According to many experts, understanding the liquid water regime of glaciers is the key to understanding their behavior.
Scientists have discovered in recent years Hundreds of interconnected lakes and rivers are hidden within the ice of Antarctica. They also made maps of deep reservoirs with sediments beneath them – under the ice, suspecting that there may also be water systems in these sediments. So far, however, no one has discovered such a thing.
A team from Columbia University has just provided a map of a powerful system of this type with circulating water in West Antarctica.
A team from Columbia University has just provided a map of a powerful system of this type with circulating water in West Antarctica. “Hypotheses that deep water might be hiding in these sediments have existed before, but until now no one has studied such structures,” says Chloe Gustafson, lead author of the study published in Science.
The water systems described now have not yet been found despite decades of research, incl. with the use of radars. Only in one case, with the help of the instrument placed in the helicopter, in 2019, it was possible to detect a tank of several hundred meters under ice 350 meters thick.
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However, most sediment reservoirs are much deeper and the ice is much thicker. Therefore, wells are also proven to be poor in this type of research.
The Columbia University team used a different technique based on measuring the Earth’s magnetic field.
Ice, freshwater, and rock deposits block the magnetic field with varying degrees of intensity. method So it looks like an MRI technology It allows you to “see” deeply hidden structures. In addition, scientists used the analysis of the propagation of seismic waves.
They conducted their research in the area of \u200b\u200bthe Whillans Glacier, which extends for more than 100 kilometers and feeds the well-known great Ross Shelf glacier, among other things. From the subglacial lake and sediment accumulated under it.
Previous wells showed the presence of water and microorganisms in the shallow layers of these sediments, but what went deeper was not known.
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Meanwhile, the authors of the new work have discovered layers of glacial sediment located between ice and hard rock, reaching a depth of 500 m to 2 km.
They also emphasized that it contains water at its best. At the same time it turns out that the salinity of the water increases with depth. Perhaps this is because sediments formed long ago in the marine environment.
According to researchers, about 5-7 thousand sea water reached this place. Since years. On the other hand, when a glacier occupied the area, fresh water displaced salt water from above.
The influx of this fresh water into the sediment can also prevent its accumulation at the base of the glacier, which in turn slows down its movement.
Moreover, measurements made at the interface between a land glacier and a floating glacier indicate that the water here is slightly less saline than sea water. This indicates that the icy water that flows into the sediment travels all the way to the sea, creating space for more water and keeping the system stable.
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However, scientists believe that if the surface of the ice becomes thinner, which can happen due to climate change, the movement of water in the sediments may be reversed.
Water will begin to accumulate in larger quantities just under the ice, and this will reduce friction and accelerate the movement of the glacier (the ice here is already moving towards the sea at a speed of one meter per day).
And if water moves up from the deeper layers, it will carry geothermal energy and heat the ice. This will increase the speed of its base melting and increase its speed.
However, these are just theories so far – whether and to what extent this will actually happen is unknown.
In the end, we do not have good data on the permeability of sediments and how quickly water passes through them. We do not know whether the described phenomenon will lead to a waterfall without return, or whether the groundwater is of secondary importance to the movement of the glacier,” emphasizes Dr. Gustafson.
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The presence of previously detected microbes in the shallow sediment layers raises further questions.
Scientists believe that the existing system and similar systems are likely to be inhabited by life to the bottom.
If the water flows in the opposite direction to it, it will release all the carbon stored by the microbes. This means that Antarctica, hitherto ignored, could also become a carbon source.
However, in this case also, it is not known to what extent this effect will be significant.
In conclusion, the researchers conclude: “Confirmation of the existence of dynamic and deeply hidden water systems has changed our understanding of the behavior of glacial currents and will force us to change our models of subglacial water.”
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