According to a new study by Columbia University, a huge aquifer discovered beneath a fast-flowing glacier stream in West Antarctica could contain seawater thousands of years ago. The presence of groundwater on the continent was already known, but this is the first time that scientists have collected direct observations of this formation.
The discovery provides new insights into how Antarctica’s glaciers behave with climate change, as well as whether these groundwaters are affecting the melting of the ice above, and what types of microbial life inhabit these environments.
Geophysicist Chloe de Gustafson, lead author of the discovery, explained that the existing groundwater system can be understood as a giant sponge. According to them, the thickness of the aquifer is from 0.5 to 2 kilometers – that is, it is very deep.
The aquifer is located below the ice stream that feeds subglacial Lake Whillans, which lies 800 meters below the ice sheet. The newly discovered aquifer contains more than 10 times the volume of water found in other known systems.
Scientists have long talked about the possibility of huge hidden aquifers, but the available technologies have not allowed them to collect good evidence of deep hydrological systems. So Gustafson and his team focused on shallow lakes and rivers near the glacier.
ice magnetic resonance
To understand what was happening in the depths, the researchers used the magneto method, which uses electromagnetic fields formed by the interaction of the solar wind with the ionosphere – the upper atmospheric layer of the Earth’s atmosphere, which is filled with electrically charged particles and particles. When the solar wind hits these particles, they are stirred up.
The magnetospheric method uses electromagnetic fields formed by the interaction of the solar wind with the ionosphere – the upper atmosphere of the Earth that is filled with electrically charged particles and particles. When the solar wind hits these particles, they are stirred up.
These particles generate moving electromagnetic fields capable of penetrating the surface. These fields then stimulate secondary fields in ice, snow, and even sediment. From these secondary fields magnetic devices are read.
The researchers buried these devices at 68 different points in the ice stream. “It’s like doing an MRI of the Earth,” Gustafson added. Previous work had used the method of magnetism in Antarctica, but only to examine the crust and upper mantle just below.
In addition, they measured the flow of the Whillans Ice Stream, a belt of ice up to 0.8 kilometers thick and moving at a rate of 1.8 meters per day — toward the Ross Ice Shelf.
The researchers focus on a depth ranging from the base of the ice flow to 5 kilometers below. In this area, they discovered in the depths a thick layer of sediments with rather saline sea water, while fresh water is located at the top.
Signs of discovery
The difference between fresh water and salt water in the aquifer indicates that shallow subglacial systems are associated with it and that both can influence ice flow directly above. But at the moment, it is not clear whether they periodically change their water or whether only one of them receives the water that flows from the ice stream.
The aquifer could be lubricating the ice stream, by injecting water from time to time into the subglacial system, or alternatively, removing water from these systems. Both scenarios will directly affect the ice flow above. Moreover, this difference can affect the microbial life that lives there.
The flow of water from the aquifer and interconnected rivers and lakes provides nutrients for these microorganisms. Another point is that the salt water at the bottom of the aquifer, and the fresh water in the shallow part, also affects the types of microbes that can live in each environment.
As for the nature of salt water, researchers believe that ocean water flowed into the groundwater system between 5,000 and 7,000 years ago, in the warm period of the Holocene when the Antarctic ice sheet retreated. As the ice reconstituted, the water became trapped in the aquifer.
The researchers have now collected evidence in other systems like this one and will compare the data to see if there are any patterns or differences. This will also help improve models that study glacier melting, which do not take these hydrodynamics into account.
The work was featured in the magazine Science.
Source: Science, Via Live Science