BELISSIMA background

The Belgian government decided to construct a new scientific summer station in Antarctica. This station is located at the foot of the Sør Rondane Mountains in Dronning Maud Land.

A first reconnaissance expedition (joined by one of the ULBonIce members) was carried out to the Sør Rondane Mountains, Dronning Maud Land, Antarctica, November - December 2004 to select a potential site for the new Belgian research station on Antarctica (BELARE 2004). During this period we installed an automatic weather station, did D-GPS measurement of the site, ice radar sounding, and measured accumulation/ablation and ice velocity in the vicinity of the construction site. During a second expedition to the Sør Rondane Mountains, Dronning Maud Land, Antarctica in November - December 2005 (BELARE 2005), we collected the data from the weather station and did additional measurements on the site.

Glaciological research at ULB-GLACIOL (Université Libre de Bruxelles, Laboratoire de Glaciologie) essentially focuses on polar ice sheets, such as Antarctica. The 2008 expedition will concentrate on quantifying the mass loss/gain of the ice sheet in view of recent climate change.

There is currently a great lack of accuracy in the models that are used to predict the effect of climate change on the mass loss or gain of ice sheets. The major reason for this is that there is a lack of knowledge on the dynamic behaviour of grounding lines. The grounding line is the area where the ice sheet, as it flows towards the ocean, starts to float and forms an ice shelf.
While the carving off of icebergs further downstream constitutes the main cause for the mass loss of the Antarctic ice sheet, changes in the mass flux across the grounding line also has a direct impact on sea level. This is because as ice crosses the grounding line, it becomes part of the ocean system and positively contributes to sea level rise. It is therefore important to know the amount of mass loss that can be attributed to melting, but also the amount of mass loss that provokes an increased mass discharge across the grounding line. What we need to know, is whether these grounding lines are stable and how easily they migrate.

The last Antarctic expeditions we reported on this blog during the 2006-2007 winter were dealing with the Belgian research program ASPI (Antarctic Subglacial Processes and Interactions). This is now the BELISSIMA (BELgium Ice-Sheet/Shelf Ice Measurements in Antarctica) 2008 event, during which we will go to an ice rise situated 150 km away from the Princess Elisabeth Station, on the route to the station as you drive inland from the coast. This ice rise is a "pinning point" (an island of grounded ice sheet surrounded by floating ice shelves) that helps to stabilize the coastal ice sheet. From there, we can carry out ice radar and GPS measurements and drill an ice core. We are interested in studying the ice sheet's behaviour here over the last 10,000 years.

The purpose is not to extract a climate signal from the ice cores but to establish the deformation properties of the ice. The last glaciation terminated 10,000 years ago, as Earth entered the Holocene, a period of climate optimum. During this period of glaciation, the ice sheet expanded laterally over the continental shelf and reached areas that are now covered by ocean water. At the end of this glaciation, a major retreat of the ice sheet began, lasting until the beginning of the Holocene. The point of our research is to find out whether the ice sheet remained stable after this retreat or not. As such, we will be able to identify whether grounding lines migrate easily or not, a factor which has become important in view of recent global warming: further retreat of the grounding line drains more grounded ice into the ocean, making sea level rise. In some areas of the Antarctic ice sheet (Pine Island Glacier for instance), substantial grounding line retreat and ice sheet thinning have been observed over the last decade and have lead to a significant amount of ice loss.

With ice radar measurements, it is possible to map the internal layers and structure of the ice rise and, from there, see for how long the grounding line has been stable (by counting the layers). We also want to measure the ice flow and direction. It is possible to see from the radar data whether there was at a certain time a change in ice flow, a change in direction, etc. It is then possible to see how stable the grounding line was and when the grounding line was actually part of the big ice sheet had there remained a singular ice rise, etc.

Another point in the stability of grounding lines, and of ice rises in particular, is that when you go down to the coast itself to reach the grounding line, you find formation of marine ice: the ice sheet more or less breaks up to form bottom crevasses and, inside these open crevasses, ice of oceanic origin appears (ocean water that freezes in). Marine ice, however, can stabilize or destabilize the flow of the ice, depending on a varying number of parameters, and is therefore also an important aspect to study. In order to do so, you have to drill down, several hunderds of metres deep, and haul up an ice core with marine ice inclusions. It can then be analyzed in our lab in Brussels.