Thursday, December 18, 2014

On travel, storms and science


Back at the station!! And here a very short overview of the accomplishments of the IceCon project. Over the next couple of days, more in-depth accounts will be given here.

We left PEA on 27 November in the evening for a night and a day travel to Derwael ice rise. Camp installment went smoothly, but after one day we got caught in a storm, and not a nice one. Atmospheric pressure dropped very quickly, winds picked up and snow drift was amazing. Furthermore, it was quite warm, meaning that snow melted in contact with persons and goods. We had to leave are tents and sleep in the containers for 2 days. The storm lasted for more than two days and it took another day to clean up camp. For science, this meant a delay, but it is amazing how quickly we picked up after that.
 
Getting the contents out of the tents during the storm at Derwael ice rise

 
The drill hole of 2012 was retrieved (under three meters of snow) and was again televiewed: this is an instrument that images the interior of the borehole. It was done in 2012 and we hope to see changes in the internal structure when comparing with the 2014 data. The cGPS station was again covered under a lot of snow (as usual), but also here the system worked perfectly through the Antarctic winter and all data were retrieved. In a couple of days Nico managed with the help of Kristof, Raphie, Cristophe and Jan to get also this station installed again for another (third) winter. Another task was to drill two 30 meter firn cores at either side of the ice divide of Derwael. While it would normally take 2 days for each of them, it was remarkably done in less time, including the installation of the drill equipment at either site (4 kilometers apart). We noticed from the drilling in 2012 and subsequent radar surveys that the accumulation variability across the ice divide is very large, with one side having an accumulation rate that is twice as high as the other, due to a so-called foehn effect, leading to more precipitation at one side and erosion due to sublimation and wind scouring at the lee side of the ice rise. If you are in the field, you have the impression that the ice rise is a gently sloping, hardly noticeable rise in the surface elevation, but its effect on mass balance is quite impressive. All boreholes were subsequently linked through radar profiles with our snow radar. Finally, we installed also a whole network of pRES measurements. This new type of radar enables us to measure directly change in the internal structure of the ice, which is necessary to identify the effects of snow compaction and strain to interpret the cGPS data. We already identified that the surface of Derwael ice rise is thinning, but we wish to reveal by how much exactly and what the processes are behind. The pRES data will complement the results from our coffee-cans we installed two years ago and have been functioning for the last two years. Unfortunately, only two of them were still operational (again under three meters of snow!) and we had to abandon them this time. However, the pRES will hopefully give more detailed insight in the dynamics of the ice. Our work at Derwael ended again with a storm, this time less forceful (we could stay in the tents), but it was again a two-day delay (storm + getting the camp cleaned up).
 
pRES measurements at Derwael ice rise
Digging out the cGPS station

 
In the morning of 8 December we moved the camp to the Roi Baudouin ice shelf (RBIS) for another series of exciting measurements. One of them was the third drilling through the ice shelf. Although such a floating ice shelf looks relatively flat with a constant ice thickness between 250 and 300 m, some areas are significantly thinner. These are elongated depressions hardly a couple of hundred meters in width, but stretching from the grounding line (contact of the Antarctic ice sheet with the ocean) to the edge of the ice shelf (more than hundred kilometer). We already found out that these depressions are formed by deeply incised channels at the bottom of the ice shelf so that ice thickness is around 150 m. These features are presumably formed at the grounding line and transported (advected) with the ice flow, but they may also indicate melting at the bottom of the shelf. Therefore we carried out deep drilling through the ice shelf and complemented this with shallow radar surveys as well as pRES measurements that directly can measure bottom melting (if present). The shallow radar was also used to link the borehole in the shelf with shallow cores as part of the BENEMELT project of Jan Lenaerts. The drilling went not so smoothly, but after some interventions, we were capable to drill to 107m. Several pRES measurements were carried out across the channels and the instrument was then finally buried in the snow and left for the winter. It will record every hour the vertical change in the ice shelf. Together with 2 other GPS instruments at the side of the channel to witness the flow, they will send their position every day. The latter is part of the @TweetinIceShelf project (more later).
 
Drilling through the ice shelf with the Eclipse drill
 

 
In short, and despite the bad weather at Derwael, the scientific programme was carried out completely. The drill didn't make it all the way to the bottom of the shelf, but what has been recovered is already a wealth of information that will be extremely useful in understanding ice-shelf dynamics. We wish to express our gratitude to the support at PEA, because it was quite something to make the different projects (IceCon, BENEMELT, SISMO) work together and change the plans according to the unpredictability of the weather. 

Thursday, November 27, 2014

It’s time to go to the field …


Yesterday, thanks to the hard work of Jean-Louis and Morgane, the Eclipse Drill passed the test and was installed on the sledge:  everything is now ready to go to the field. The schedule of the next weeks is the following: after crossing the Roi Baudouin Ice Shelf for about 200 km, which should pass slightly more than 20 hours, we will arrive on Derwael Ice Rise, where we will set up the first Camp! Brice and Frank will first of all deploy the radar to make the first measurements of ice thickness and ice layers, which will facilitate exact positioning of the first drill site. We will spend 1 week at this camp (we plan to drill two holes and cover the area with pRES measurements). The next two weeks will be dedicated to the setup of the 2 GPSs (follow @tweetiniceshelf, funded by “les 10Km de l’ULB”) on the Roi Baudouin Ice Shelf. On the same site, we will also perform many radar measurements, drill a deep ice core (155 meters), and conduct CTD (conductivity-temperature-depth) measurements under the ice shelf. Finally, we will revisit the GPS points that were installed by Reinhard and Nicolas last year.  

Sunday, November 23, 2014

Preparations

Saturday morning was spent to the second and the last part of the field training around Utsteinen. Only Nicolas dropped out on this one because he had to revisit the cGPS station at Asuka. Frank dropped out as well ... because of not enough skidoos around. On the program: handling the skidoo ! Now, everyone is ready to get into the field in a secure way.

 

The remainder of the day was spent on verifying and testing different instruments: Frank and Brice took care of the pRES, GSSI, and several GPS systems (assembly of antennas, material checking, matlab code verifications, …). A novel part of the field trip is the use of a phase-sensitive radar (or pRES). As any other radar we commonly use in polar regions, the pRES enables to determine the thickness of the ice by sending out an electromagnetic signal that bounces off when it reaches the bottom of the ice and is received back at the instrument. The wave speed through ice is known, so that the ice thickness can be inferred. However, any radar is also capable of detecting internal structures in the ice. The pRES is capable of seeing changes in the position of these structures over time. So, if you send out at exact the same place an electromagnetic signal a year later, you may detect the change in position of these structures, from which the vertical flow of the ice can be inferred. This is quite unique, because we normally don't have any direct measurement of how ice moves at it interior. At the surface, horizontal flow speeds are easily detected through a GPS measurement, but not inside the ice mass. These parameters are essential in the IceCon project, because the ice dynamics need to be taken into account to interpret our geodetic GPS signals.

During this time, Morgane et Jean-Louis finished the assembly of the last parts of the drill. It is no easy task as some connections need to be welded, inside a very crucial section, called "the anti-torque". This fancy device aims at decoupling the movement of the drill motor, from the movement of the cable to which it is attached. Having done that, we assembled the winch that lifts up the drill from the horizontal to the vertical position. We are almost ready for the first test borehole. This one will be used to test another instrument, a borehole camera that produces a virtual image of the ice core. Another borehole will be drilled in blue ice, in order to test the efficiency of the new cutting head for drilling into stiff ice.

 

Once in the field, we will drill two 30 m deep ice cores on Derwael Ice Rise, 2 km on each side of the divide, to investigate the spatial variability of snow accumulation induced by this 300 m high topographic feature. We will then move the base camp on the "Roi Baudouin Ice Shelf", where we will drill all the way down the ice shelf to reach the ocean water (about 150 meters) and investigate the presence of marine ice. This ice is in fact refrozen meltwater that accumulates under the ice shelf, influencing its stability.


 

 

 

 

 

Friday, November 21, 2014

Welcome to the Princess Elisabeth Station

21 Novembre, l’ensemble de l’équipe est maintenant à PES. Le survol et l’immensité de l’Antarctique, l’arrivée à la station avec les montagnes en arrière-plan ne peuvent laisser personne indifférent. L’équipe de la station nous attendait pour décharger le matériel et nous faire un premier tour de la base ; perchée sur une arrête rocheuse, elle domine le paysage aux alentours.
Vous pouvez voir sur le t-shirt ci-dessus l’indication 10 Belare. Comme expliqué hier, on fête cette année les 10 ans du début du projet de construction de la station. Mais, c’est également pour Frank le dixième anniversaire de son premier pas sur Utsteinen puisqu’il faisait partie de l’équipe chargée de faire les premières mesures scientifiques avant la construction de la station.

L’après-midi de notre Saint V fut consacré à la planification des différentes missions. Vers 15h, direction une zone de crevasse pour notre premier entrainement de terrain. Mise en conditions réelles et parfois très réelles étaient au programme : comment sortir d’une crevasse, secourir un blessé, … ça laissera de très bons souvenirs notamment lorsque l’un des harnais a cédé … . Ce matin nous terminerons notre entrainement de terrain et nous commencerons à vérifier l’ensemble du matériel (radars, GPS, drill, …).


Thursday, November 20, 2014

20 November 2014: the long haul to Princess Elisabeth.

BELARE, the Belgian Antarctic Research Expedition, exists 10 years. The first expedition, back in 2004, was meant to find a suitable spot to construct the Princess Elisabeth Station. The station was supposed to be build on rock (to make it longer lasting - or at least technically more simpler as it would not be covered in the ever accumulating snow. At that time we visited several potential sites that were selected according to access, rock strength and flatness of the terrain. The Utsteinen rim was far out the best place. But there was something more interesting about that place. Since it is situated at the Western side of the Sor Rondane Mountains, it is also more protected from severe winds (especially katabatic ones) which makes it so nicec to work. I mention this, because going to Princess Elisabeth demands several stopovers. The first one in Cape Town, but no-one is going to complain about that, the second one is Novo airstrip on the Antarctic coast just off South Africa. It is a less protected side and when we arrived yesterday morning at 3AM GMT in fairly good weather conditions, we had to offload the plane in a fierce wind. Most of us are familiar with those uncomfortable conditions, but it is even more strenuous for the newly arrived who are immediately confronted with the harsh conditions of field work.

Offloading the plane at Novo and separating the cargo for the different feeder flights

 

The weather conditions gradually improved, the wind got down by 6AM, the time we went for breakfast and when the plane was offloaded. We had quite a lot of material to unpack and pack and to shift it in two heaps, each heap for a feeder flight that would take us to Princess Elisabeth station. After a nap in the barracks at Novo, the first group and cargo left at 4PM and a group of 6 stayed behind at Novo (Jean-Louis, Denis, Jan, Nico, Raffi and Frank) waiting for the next flight, that, ..., was rescheduled for the following day. A night at Novo for part of the group and hopefully by noon in at PES.

 

 

Monday, November 17, 2014

Départ imminent pour l’Antarctique

Bonne nouvelle, les conditions météorologiques s’étant améliorées à Novo, le vol pour l’Antarctique qui avait initialement été postposé partira bien demain (18/11) à 23h15.

Après un vol sans encombre, nous avons retrouvé Morgane pour un premier briefing avec l’ensemble des équipes scientifiques participant à la saison Belare 2014-2015. Ensuite, repos et boulot pour certains, montée du Lion’s head avec une vue impressionnante sur Cape Town pour d’autres.

Ce matin direction l’aéroport pour une vérification complète du matériel pour Brice et Jean-Louis (tout est bien arrivé) avant un briefing sur le déroulement du vol  avec les responsables d’alci (Antarctic Logistics Centre International). Nous partirons donc tous ensemble demain soir pour 6h de vol vers Novo avant de séparer en deux groupes pour le second vol vers PES.


Friday, November 14, 2014

J-1 avant le départ

Dernier jour de préparatifs au Laboratoire de Glaciologie avant de rejoindre l’Antarctique ; tout le monde est prêt à partir, et bonne nouvelle la station Princesse Elisabeth est opérationnelle ! Les radars attendent avec impatience de pouvoir émettre des ondes, les GPS de signaler leur position et le carotteur d’atteindre la base de l’iceshelf.
Profiles radars effectués en 2012/13 sur le Roi Baudouin iceshelf et localisation du futur forage de 155 m
Pour certains ce sera la 18e mission en Antarctique pour d’autres la première ; les différentes teams seront donc composées de gens très expérimentés et d’autres plein d’énergie ! Nous arriverons à Cape Town dimanche pour une première vérification du matériel. Ensuite, direction Novolazarevskaya  (station russe) et arrivée à la station Princesse Elisabeth le 18. Après un entrainement de terrain et une seconde vérification du matériel, nous nous dirigerons le 23 novembre vers les différentes zones d’analyses. Les mesures se feront à partir de 2 camps de base différents : un sur le Derwael ice rise que nous quitterons le 29 novembre et un sur le Roi Baudouin Iceshelf avec un retour prévu à la station le 16 décembre !

Ouverture de la station et localisation des différents camps de base