Melt water drips from the ice of the Jakobshavn Isbræ glacier
Photo: Paul Souders / Getty Images
Greenland's ice sheet is melting.
This has an impact on the rise in sea level, but apparently also on the groundwater below the Greenland land mass - and thus possibly on the complex interplay of the water masses in the ocean.
In an article that appeared in the journal Nature Geoscience, the researchers describe the direct effect the melting ice sheet has on the groundwater.
"The mass loss of the Greenland ice sheet has an impact on the associated terrestrial and marine hydrological systems with global consequences," it says.
The groundwater is a key component in the water cycle in the Arctic.
Despite its enormous extent, it is not yet known how the Greenland groundwater reservoir reacts to the ongoing changes in the ice sheet.
The international research team claims to have taken samples of the deep groundwater through a 651 meter long borehole through ice and bedrock.
In 32 additional holes at the top of the glacier, the scientists measured the water conditions at the boundary between ice and rock.
Even there, the ice was at least one kilometer thick.
After two hours, the drill holes froze over
After drilling, the team will install sensors in the ice column and at the bottom of the ice sheet to monitor ice dynamics and water conditions as the water flows under the ice to the edge.
The prevailing temperatures made the work difficult: within two hours, the holes were repeatedly frozen over.
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The group noted that "ongoing and future ice thinning" is likely to reduce groundwater runoff rates. This in turn could have an impact on submarine freshwater runoff, but also on the supply of freshwater to the fjords and rivers in the Arctic. "Our latest results show that the changes in the ice sheet have real effects on Arctic hydrology," said Joel Harper of the University of Montana, who was involved in the study, summarizing the study.
The shrinking ice surface could reduce the speed of the groundwater flow into the ocean and thus significantly alter the balance of water temperature and salinity.
However, this intact balance is critical to the ocean's circulation patterns.
Because: Salty water has a higher density than fresh water, warm water has a higher density than cold water - these factors bring movement into the water masses of the oceans and are decisive for the system of ocean currents on the globe.
The groundwater is important for the entire Arctic
"In our considerations on the complex feedbacks that result from the ongoing changes in Greenland, we have neglected the groundwater component," said the scientist Harper.
"But now we see that the groundwater system is actually changing quite quickly, and there are some compelling reasons why this could be of concern to the Arctic in general."
The aim of further research must be to quantify the effects of changes in the groundwater on the ocean.
This is the only way to correctly assess the consequences.