Greenland's Ice Conveyor Belt
The Greenland ice sheet loses the majority of its ice into the Arctic Ocean through ice streams. An international team of researchers, including staff from the Alfred Wegener Institute, is now working to better understand these flows and ice loss so as to better predict future sea-level rises. To do so, they travelled to northeast Greenland, where they will drill through an ice stream for the first time – with the aid of a pioneering ice camp and methods.
Greenland is covered by a massive sheet of ice – one that is roughly five times the size of Germany and up to three kilometres thick. Yet these ice masses don’t just lie there; in fact, they’re almost constantly in motion. Like a giant conveyor belt system, several streams transport ice from the interior of the country to the Arctic Ocean. Their flow speed is several times higher than the remainder of the ice sheet, which is why the majority of the ice lost is due to these streams.
“Ice streams into the Arctic Ocean account for half of the Greenland ice sheet’s mass loss. And many of these streams have doubled their speed over the past few years,” explains AWI glaciologist Dr Sepp Kipfstuhl. “We need to understand how this flow works so that we can fully integrate it into climate models. In turn, we hope to use the models to predict future mass loss and corresponding sea-ice rise. But we still know very little about the ice streams in the Greenland ice sheet.”
To gain new insights, researchers from the Alfred Wegener Institute and international partners launched EGRIP (East Greenland Ice-core Project) in 2015. As the name implies, the team will collect ice cores from the ice stream in northeast Greenland – marking the first-ever core drilled out of an ice stream
Traditionally, researchers have always sought to find the oldest-possible ice, which requires clearly defined structures. Accordingly, they normally collected ice-bore samples by drilling down from the uppermost point in the ice sheet – because the ice flows down from this point in all directions, but there is very little lateral movement at the ice-boring point itself. This approach normally produces a clear cross-section, with the oldest ice at the bottom.
Now the scientists are drilling through the middle of the ice stream – essentially on its slope – for the first time. Doing so will finally give them the chance to investigate that ice that quickly flows out toward the ocean. We know that the upper layers of the ice flow faster, while friction slows the movement of the lower layers. But how great is the difference? In the context of EGRIP, this aspect will be measured on an ice stream for the first time.
In addition to helping answer the question of how much the melting glacial ice will contribute to rising sea levels, ice cores always offer new insights into the past.
Ice cores offer unique archives of climate information over incredibly long periods of time – up to several hundred thousand years. According to Kipfstuhl, “The Greenland ice sheet essentially consists of several thousand individual snowfalls that are stacked one on top of the other in chronological order. And for each layer, we can determine the temperature at the time the snow fell using the mass relations of the water molecules trapped in the ice. In addition, aerosols – tiny particles, including dust particles, from the air – are stored in the ice. The amount of aerosols we find in the ice is an indirect indicator of their atmospheric concentration, which has changed with the climatic conditions.”
The drilling in northeast Greenland will delve down as far as 2,550 metres. The resulting cores will then be analysed at the onsite camp and several laboratories around the globe, including the AWI’s ice core laboratories.
But getting to that point will take plenty of work: ice-drilling camps require substantial equipment and extensive logistical planning. The expedition team had to first transport several hundred tonnes of material to the camp. They then set up tents for their sleeping quarters and wooden igloos where they can meet, work and eat together, not to mention the massive “science trench” – cut out of the ice and carefully buttressed to prevent its collapse, it offers the perfect setting for storing the ice cores at stable temperatures of more than 20 degrees below zero, and for slicing them into segments for subsequent analysis. In turn, a number of different testing rooms are connected to this “underground lab”.
Construction of the EGRIP camp began in 2015, and the site was fully equipped by the following summer season, allowing drilling to commence in 2017. “The first major challenge is always to get the equipment we need to the planned site, and to set up the camp there. Plus, we have to make sure the camp is adequately protected from storms and the extreme cold,” explains Kipfstuhl.
And the participating scientists aren’t simply working to refine their established techniques: the EGRIP team has introduced a completely new method that requires fewer resources, significantly simplifying logistics. Using an innovative new approach, they were able to set up the underground research laboratory, located several metres below the surface, much more efficiently.
For the first time, the science trench was made using snow alone: with the help of a snow blower, the team first created chambers measuring up to 50 metres long. In each chamber, they then inflated an enormous balloon with a diameter of up to five metres and blew the excavated snow back on top of the balloon to form the roof. Once the snow had become sufficiently packed, they then deflated the balloons. The result: “We were able to create giant vaults in the snow, without using a single piece of wood,” reports Sepp Kipfstuhl. The scientists will be using the vaults to drill and process the ice cores until 2020.
The Innovative Construction
Images: Sepp Kipfstuhl; edited by: Nadine Michel