22. May 2015

Radar views of per­ma­nent ice for cli­mate re­search – DLR re­search flights over Green­land

DLR Do 228-212 re­search air­craft D-CF­FU
Image 1/3, Credit: DLR (CC-BY 3.0).

DLR Do 228-212 research aircraft D-CFFU

The DLR Do 228-212 re­search air­craft, D-CF­FU, with the Air­craft Sup­port­ed Syn­thet­ic Aper­ture Radar (Flugzeuggestütztes Radar mit Syn­thetis­ch­er Aper­tur; F-SAR) on board, dur­ing a stopover at Ilulis­sat, in Green­land. The radar an­ten­nas can be seen on the side of the air­craft fuse­lage.
In­stal­la­tion of radar re­flec­tor
Image 2/3, Credit: Silvan Leinss, ETH Zürich.

Installation of radar reflector

DLR re­searchers Mar­tin Keller and Georg Fis­ch­er an­chor two radar re­flec­tors on­to the Green­land ice sheet. In the fore­ground are two GPS sta­tions, which en­able the pre­cise mea­sure­ment of the lo­ca­tion of the re­flec­tors.
The long road to the next re­flec­tor in­stal­la­tion
Image 3/3, Credit: Silvan Leinss, ETH Zürich.

The long road to the next reflector installation

DLR re­searcher Georg Fis­ch­er makes his way to the next radar re­flec­tor. At the South Dome, the high­est test area, the favourable weath­er con­di­tions made it pos­si­ble to an­chor the radar re­flec­tors at just one kilo­me­tre from the air­craft.

The Greenland ice sheet is, in places, more than three kilometres thick and a crucial feature in climate modelling. Scientists of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), together with colleagues from ETH Zurich (Eidgenössische Technische Hochschule Zürich), are currently conducting tests of new radar imaging methods in a research flight campaign over Greenland initiated by the Microwaves and Radar Institute in cooperation with the Danish Defence Acquisition and Logistics Organization (DALO). These methods shall provide information about three-dimensional snow and ice conditions at depths of up to 50 metres. "In the long term, it should be possible to determine the impact of climate change on the internal stratification of snow, firn (partially compacted snow) and ice," explains Irena Hajnsek, Project Manager of the ARC­TIC15 campaign. This is interesting to, for example, investigate how much water from the snow that melts on the surface freezes again during infiltration and thus does not contribute to sea level rise. This effect is considered to be insufficiently addressed in current climate models, as stated in a recent report issued by the Intergovernmental Panel on Climate Change (IPCC).

Flights over crevasses and summits

The Aircraft Supported Synthetic Aperture Radar (Flugzeuggestütztes Radar mit Synthetischer Apertur; F-SAR) is installed on the DLR Do 228-212 research aircraft D-CFFU. The aircraft will fly over each of five study areas in southern Greenland several times during the approximately six-week campaign, which lasts until the end of May. "Flying over Greenland's permanent ice is something special," says DLR pilot Thomas van Marwick. "The vast distances between landing facilities and the sometimes extreme weather conditions must be carefully taken into account." The crew on board the DLR Flight Op­er­a­tions (FB) are flying, amongst other places, over areas along the coast where the ice sheet transforms into large glaciers and fissures as well as over the southern highlands, where the highest point, the South Dome, is found. The flights usually last between four and five hours; on the longer routes they sometimes include stopovers for refuelling.

Beneath the surface

"This new radar technology will enable us to, in the future, recognise the various types of ice and snow from the air or from space," says Campaign Manager Ralf Horn from the DLR Microwaves and Radar Institute. "Different types of ice reflect the radar signals differently and the DLR F-SAR is able to detect these differences – sometimes at depths of up to 50 metres." The ice covering Greenland reveals varying structures, depending on the region being examined. The central and high-altitude areas experience hardly any snowmelt in the summer, forming a firn layer tens of metres in thickness, which is converted to ice by the pressure of the overlying layers. In contrast, exposed ice is found near the coast; it has low snow cover only in the winter. An examination of the depth of the ice is, at the same time, a glimpse of the climate over the last few decades, because successive ice layers have formed over the years.

Hard fieldwork at the beginning

Before the flight campaign began, the remote areas on the ground were explored, radar reflectors were installed, and the snow, firn and ice were examined by hand. For this purpose, DLR researchers used a chartered aircraft capable of landing on snow. During the five- to six-hour stays, sometimes at temperatures below minus 25 degrees Celsius and strong winds, a ground radar system, on loan from the Alfred Wegener Institute, and a snow probe were used. "These were the toughest and most exciting working conditions that I have experienced in my career so far," says DLR researcher Georg Fischer, who organised the expedition and implemented it with two colleagues from DLR and ETH Zurich.

After returning from Greenland, on the basis of this research campaign, the researchers plan to develop new methods for snow and ice analysis, which will then be applied to the data gained from future satellite missions such as Tandem-L. This is expected to enable the use of a new method for examining variations in glaciers and ice sheets being observed from space, and will allow coverage information to be generated. At present, this can only be determined in select locations through complex expeditions.

All the research is being carried out as part of the Helmholtz Alliance 'Re­mote Sens­ing and Earth Sys­tem Dy­nam­ics' programme.

The researchers report on their adventurous scientific expedition in Greenland in the DLR Blog.

  • Falk Dambowsky
    Ger­man Aerospace Cen­ter (DLR)
    Me­dia Re­la­tions
    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-3959
    Fax: +49 2203 601-3249
    Linder Höhe
    51147 Cologne
  • Georg Fischer
    Ger­man Aerospace Cen­ter (DLR)

    Mi­crowaves and Radar In­sti­tute
    Telephone: +49 8153 28-3068
    Linder Höhe
    51147 Köln
  • Thomas van Marwick
    Ger­man Aerospace Cen­ter (DLR)

    Flight Ex­per­i­ments
    Telephone: +49 8153 28-1766
    Linder Höhe
    51147 Köln

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