Return after a successful field trip

The IceCon team is back at PEA after a successful trip to the Derwael Ice Rise. So here is a brief update of the activities that took place during that two-weeks period.

Morgane proudly showing a piece of core

It took 22 hours to get to Derwael Ice Rise, driving all day and all night. Once camp established, the ice core drilling operations started. This went quite smooth for the first tens of meters, but a series of problems occurred, especially near a depth of 60m, where further drilling became seemingly impossible. Nevertheless, thanks to the continuous efforts of everyone around camp (drillers, support people from BELARE such as Kristof and even an inventive approach from the field guide Raphy), they finally got through that difficult bit and succeeded in drilling up to 120 m of core. At that depth, the ice seemed rather hard to go through and it is not clear for the moment what the origin of this could be. The site is on an ice rise, influenced by the Raymond effect and therefore different from other areas where a similar drill has been used. In the end, the televiewer was lowered down in the borehole to completely image the internal structure, which will make it possible to count internal layers within the firn part and maybe beyond.

ROB1 power station and receiver

From the beginning of the field activities we also started on erecting the ROB1 cGPS point. This takes a bit more time than the ULX1 point on Seal. It consists of digging a large snow pit to lower down the power plant (batteries, solar panels and wind turbines). Digging was also the key word for mounting the GPS antenna and securing the whole thing for winter. After a couple of days, ROB1 was operational and setup as a base station for all other GPS activities that were carried out in the area.

Coffee-can marker: a steel cable goes via two
pulleys through a hole in the firn where it is
held tight with an anchor. 

Digging continued to make water for hot water drilling. Since ROB1 is on the ice and prone to vertical ice movements, we need to have an insight into the processes that govern that motion (compression and strain). Therefore, we set up a series of markers at different depths in the firn, ranging from 10 to 50m of depth. These markers are a steel cable anchored at depth and connected to the surface. Every year, the length of the cable will be measured, leading to a series of relative displacements. The hot water drilling required 2500 liters of liquid snow, which implied digging, melting and hosing. This took a day and a half to do and in nice weather was quite a leisurely job. Drilling in itself took less than an hour (it is like cooking a meal for hours and finishing dinner in 10 minutes). The so-called coffee-can markers (designed by Kristof and Greg at PEA and field proven afterwards) were thus easily installed.

Denis and his high-frequency radar: whenever it goes well,
it is a boring job to do!

On and around the Derwael ice rise, an intensive network of high- and low-frequency radar lines have been surveyed, revealing not one Raymond bump, but two. Moreover, the quality of the data is superior to the data gathered two years ago during the BELISSIMA programme, so that we are sure to have a complete 3D view of the dome area. Besides a strain network was established around the dome so that we can monitor the horizontal deformation precisely.

Besides the IceCon project, the Be:Wise project was also very successful. They established camp on the Roi Baudouin ice shelf and surveyed near to 180 km of radar data (both high and low frequency) and monitored 20 stakes on horizontal and vertical displacement using precise GPS. The markers will be re-surveyed next year.

Be:Wise: don't fool with us, because we are professionals!

In short, more than expected has been done in relatively little time. The spirits in camp were always high and it was a fun thing to do. We could rely on a professional support team and surely, the good and balmy weather made us work every day. It is Antarctica, but also the coast, and recorded temperatures were regularly positive.

The return trip was more of a burden with poor visibility, bad and soft snow conditions and too high temperatures on the ice shelf so that the hydraulic system of the Prinoths went to high so that we had to stop at regular times. It took us a bit less than 30 hours to return to the station.

Operations at derwael ice rise

It took 22 hours of travel with two Prinoth trains to Derwael ice rise. Departure was delayed due to a few mechanical problems and we arrived by 7 am on Monday at the camp spot. It didn’t take long to get everything into place which meant that the science activities started later on the day (December 3, 2012). The weather has been very nice, warm and mostly cloudy with light snow fall. Ideal weather to pursue the activities. After three days, ROB1 was installed on the snow (or better dug in into the snow), which involved a lot of digging and snow removal. The GNSS antenna pole was put at a depth of 2m below the snow surface.

Drilling operations went rather smoothly, thanks to extensive testing at PEA. After three days, a depth of almost 60m was reached. Only few melt layers were detected in the upper firn part.

All radar profiles around Derwael were swiftly run. The first day (4 December), 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.

Today, December 7, the Be:Wise team is ready to move their advance camp to the Roi Baudouin ice shelf.

Departure

Group picture on the day of the departure to the field.

Final preparations

Planned field work operations at Derwal ice rise (right) and on the ice shelf (Be:Wise project)

All equipment has been thoroughly tested and the Eclipse drill is working. Final preparations for the cargo train towards the coast are on their way. Yesterday the weather deteriorated and the whole morning until mid afternoon there was a lot of wind, making operations difficult. The plan is to depart early morning on Sunday, if everything goes well. In the meantime there is plenty of work for everyone in getting the final planning together, checking and double checking cargo and requirements or resting before embarking on a very long trip towards Derwael ice rise.

A presentation of the science of IceCon, given last night at the station for all station personnel and other vistors can be downloaded on the Publication page of this website.

 

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Field training

View from within the crevasse

Field training is part of Antarctic research activities. The ice sheet is not a safe place: as the ice slowly moves from the center towards the edge, it cracks and opens up at the surface due to tension, especailly when the ice moves across an obstacle (subglacial bump or mountain). Those cracks, called crevasses, are usually covered by snow, which means that they are hidden. Most of the areas we will visit are safe, meaning that crevasses are not present, but one should be prepared.

We went to a crevassed area 9 km from PEA to do crevasse training and rescue. Each of us was lowered safely in the crevasse, 20m down and then pulled up by two simple techniques, one involving a pully system anchored on a skidoo, another technique using two skidoos, in which the pully was done by the second skidoo. The latter goes fast of course :-)

The crevasse itself was very impressive, with beautiful snow crystals inside, as well as very silent (compared to the buzz at the surface). The field training ended with the immobilization and transport of a person that was injured (fictively of course, and perfectly mis-en-scène by Bryn) to PEA.

 

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ULX1 installed

Installing the antenna on the ULX1 mast.

On Tuesday 27 November, the geodetic continuous GPS system was successfully installed on Seal Nunatak, a small rock outcrop next to the former Japanese Asuka station, approximately 60 km from PEA. The area is particularly known to be windy, which is very nice from the point of view of energy supply via our wind turbines, but less interesting if one needs to install the GPS mast and the power supply box at the top of the nunatak. Fortunately for us (Alain, Raphy, Nicolas and Frank), the conditions were quite balmy, with only a 20cm high wind drift around the rock (while at PEA there was no wind at all!). The reason why it is so windy is that the site is further to the east, hence less protected by the mountains from catabatic winds. (Catabatic winds are gravitationally driven winds coming from the polar plateau and picking up speed while making there descent towards the coast)

The fixing and drilling of the mast and the battery box was done by Alain and Raphy, while Nicolas and Frank installed the solar panels, wind turbines and powered up the whole system. Luckily it was all tested at PEA before, because the windy conditions do not leave much room for quiet analysis of what to do next and reading the manual at ease. All systems seem to work, the solar panels produce the bulk energy and wind power is only used during absence of sunshine. However, the latter could not be checked completely, unless we decoupled the solar panels from the system.

Instalation on Seal Nunatak of the GPS mast ULX1, the battery box and receiver, solar panels and wind turbines.

The system will now run continuously for several years. The consumption of energy is rather low, and the batteries are charged via solar panels (summer) and wind (winter). Once they are charged above 13V, they will charge the internal battery of the receiver, which in view of the low consumption should be sufficient to get us through this whole period without major maintenance.

The cGPS is meant to measure tiny horizontal and vertical motions of the Earth's crust due to tectonics as well as uplift due to changes in ice mass (in response to a bigger ice sheet during the Last Glacial period). This information will be extremely useful to constrain GIA models (see the IceCon project page for more information on the subject).

 

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Instrument testing and calibration

Setting up the Eclipse ice corer

Weather is nice and warm (at least during the day) with very low wind speeds. This allowed for extensive testing and assembling of the equipment. The drill team (Jean-Louis, Bryn and Morgane) are in the process of assembling the Eclipse corer that will be employed for drilling an ice core at the ice divide of Derwael ice rise.

The radar/GPS team (Kenny, Reinhard and Denis) is then quite happily busy with testing the 5 GPS systems that will be deployed to measure a strain network on Derwael ice rise and several continuous measurements on the Roi Baudouin ice shelf with the purpose of establishing the effect of tides on the ice shelf at different places across so-called shear margins on the ice shelf (weaker zones where ice acceleration is expected). The latter is within the framework of the Be:Wise project.

Nicolas testing the cGPS data at PEA

Finally, the geodetic GPS team (Nicolas and Frank) set up and tested two cGPS systems. The first one to be set at Seal nunatak (near the former Japanese Asuka station), and one one the Derwael ice rise (shown here). Both systems are different in the setup and power. They will run autonomously during several years. The battery box contains 10 batteries (more than 400kg!), which are powered up by both solar panels and wind turbines.

 

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