The Camp at Derwael Ice Rise - © International Polar Foundation/Alain Hubert

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At Derwael Ice Rise

Following up Alain's blog - The World's Most Southerly Anthill, the team have now moved a couple of hundred kilometres to the Derwael ice rise, to start work on the IceCon and Be:Wise projects, both of which are investigating the behaviour of Antarctica's ice cap. Here's a report from the International Polar Foundation's Alain Hubert and IceCon's Frank Pattyn: 

It took 25 hours of travel with two trains of Prinoth tractors to reach Derwael ice rise. The team’s departure was delayed due to a few mechanical problems, but we arrived by early on Monday at the camping spot.

En route, at 2AM, the convoy dropped off Alain and Reinhard – the glaciologist in charge of the Be:Wise project - to install two GPS measurement points that will stay in place during the expedition on Baudouin ice shelf. They reached the new base camp at 5.30AM, and had enough time to sketch out the base camp before the convoy’s arrival. So when they arrived, it took just one hour to get every thing ready: electricity, water and all containers aligned according to our drawing: a nice and efficient base camp conceived to protect us from storms.

At Derwael camp, the science team is supported by the Princess Elisabeth Antarctica technical team; Alain – expedition leader, Kristof – chief mechanic and Raphy – field guide. It didn’t take long to get everything into place, which meant that the science activities could start later on in the day. The weather has been very nice, warm and mostly cloudy with light snow fall. Ideal weather for pursuing our activities. After three days, ROB1 was installed, which involved a lot of digging and snow removal. The GNSS (Global Navigation Satellite System) antenna pole was put at a depth of 2m below the snow surface.

Drilling operations went rather smoothly, thanks to extensive testing at Princess Elisabeth Antarctica. After three days, and thanks to the very professional logistics and technical assistance provided by the station’s team, a depth of almost 60m was reached. Only few melt layers were detected in the upper first part.

All radar profiles around Derwael were swiftly run. The first day December 4th, 70 km of low-frequency radar data were collected, clearly showing the different aspects of the Raymond bump, as well as a side bump to the south of the ice divide (the highest point on the ice rise where the major bump is situated.

The origin of these bumps are due to the ice rheology. Ice deformation underneath an ice divide is essentially due to longitudinal stretching of the ice layers, while away from the divide, vertical shearing becomes more important. Due to the nonlinear nature of the flow law for ice, this leads to a higher effective viscosity under the divide, making the ice less easy to deform under the divide compared to the flanks. The result is that ice layers on the flanks are at greater depth on the flanks compared to the divide, leading to an upwarping of layers under the divide. This effect has been theoretically put forward by Charlie Raymond in the 1980s, but only observed for the first time with radar almost 20 years later. It is therefore commonly known as the Raymond effect. As a result of this effect, the ice core will reveal ice of an older age at depth compared to a position situated on the flanks.

On December 7, the Be:Wise team is making itself ready to move its advance camp to the Roi Baudouin ice shelf.

"IceCon’s main hypothesis is that the LGM ice sheet volume in Dronning Maud Land was not as big as previously predicted by large-scale ice sheet models, although it advances further towards the coast. Less grounded ice during the LGM implies less ice loss during deglaciation (the process of mass loss between LGM and now), making it difficult to associate a historical event – “meltwater pulse 1A” to the Antarctic ice sheet. Meltwater pulse 1A was rise of around 20m in sea levels that took place during a 500-year period, some 14,200 years ago."

Read more about IceCon: IceCon: Constraining Ice Mass Change in Antarctica

"The Be:Wise project aims to improve understanding of ice-shelf flow dynamics by focusing on the buttressing role of ice rises and pinning points – small offshore mountains which support Antarctic ice shelves from underneath."

Read more about Be:Wise: The Buttressing Effect: Why ice shelves are essential

Author: Alain Hubert and Frank Pattyn

Picture: The Camp at Derwael Ice Rise - © International Polar Foundation/Alain Hubert

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