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Frank Pattyn |
IceCube is a cubic kilometre large neutrino observatory at the Amundsen-Scott South Pole Station. Like its predecessor, the Antarctic Muon And Neutrino Detector Array (AMANDA), IceCube is being constructed in deep Antarctic ice by deploying thousands of spherical optical sensors (photomultiplier tubes, or PMTs) at depths between 1,450 and 2,450 meters. The sensors are deployed on "strings" of sixty modules each, into holes melted in the ice using a hot water drill. The IIHE laboratory of the ULB is strongly involved in this project.
The IceCube setup offers also a unique opportunity to investigate ice sheet dynamics at high resolution, which has never been done before. Deep drillings have been carried out in central parts of the ice sheet, but always on an ice divide (where horizontal ice flow is minimal) and at one specific point. IceCube surveys one cubic kilometer of ice to depths of more than 2500m, way from the ice divide where ice deformation and flow matter. Moreover, IceCube is close to a subglacial lake, emphasising the importance of the interaction with subglacial processes.
The recent IPCC report (2008) gives a rather conservative estimate when it comes to predicting future sea-level rise due to melting of the large ice sheets of Greenland and Antarctica, as the influence of ice dynamical acceleration is neglected in the models. The main reason is that the rpesent suite of models is NOT capable of simulating the present-day observed acceleration of major outlet glaciers. Representing correct ice physics into these models thus becomes an essential task for the coming years.
Within IceCube we will install additional inclinometers at depth to measure ice deformation. The neutrino detectors that are currently installed will be employed as well to infer ice deformation. We will establish new constitutive equations for ice flow (accurately determining Glen's index), and verify high-resolution higher-order and full Stokes models with the measured deformation rates in IceCube.
Frank Pattyn developed 2D and 3D higher-order models (approximations to the full Stokes force balance) that are applicable to complex ice flow prevalent in ice sheets, ice shelves and transitions zones in between (also called LMLa models). Applications are made to ice streams and subglacial lake dynamics. He is the lead coordinator of benchmark experiments for such experiments (ISMIP-HOM), co-convener of marine ice sheet model intercomparisons (MISMIP) and a member of SCAR-SALE (Scientific Committee on Antarctic Research: Subglacial Antarctic Lake Environments).
Daniel Bertrand developed his experimental research in the framework of the weak interactions. He first determined the branching fraction of rare K decays. He then participated to the experimental discovery of the neutral currents looking to neutrino interactions in bubble chambers. Joining the DELPHI experiment at the LEP at CERN he participated to the experimental verification of the predictions of the Standard Model. More recently he joined the project AMANDA/IceCube aiming to identify cosmic neutrino sources. Such a discovery could confirm the hadronic models of cosmic acceleration of ultra high energy cosmic rays. The observation of neutrinos of different savors will also bring informations on the oscillation mechanism of these particles.
Jean-Louis Tison has developed his expertise in the glaciology of temperate and polar regions (with a special emphasis on “interface ice”: basal ice, marine ice and sea ice). He has developed several analytical techniques in the Laboratory such as the measure of textural and crystallographic properties of ice, the cutting and thin-sectioning of fragile or debris-loaded ice sample with an original technique using diamond wire saws, the extraction and measurement of total gas content and gas composition in ice samples. He is now the Belgian representative in the Steering Group of the International Research Programme ASPeCt (Antarctic Sea ice Processes and Climate), a sub-program of GLOCHANT (Global Change in the Antarctic) within SCAR (Scientific Committee for Antarctic Research).