14. September 2018
Permafrost monitoring with latest radar technology in German-Canadian cooperation

Thaw­ing Arc­tic in radar view

Permafrost region Herschel Island
Per­mafrost re­gion Her­schel Is­land
Image 1/4, Credit: DLR (CC BY-NC-ND 3.0)

Permafrost region Herschel Island

Her­schel Is­land is lo­cat­ed on the north­west­ern tip of Cana­da and is char­ac­terised by con­tin­u­ous per­mafrost. The Per­mASAR radar im­age ac­quired in Au­gust 2018 re­veals veg­e­ta­tion in the L-band fre­quen­cy range (dark green colour) in the oth­er­wise tree­less tun­dra. The thaw­ing pro­cess is al­so ev­i­dent along the coasts: In the right part of the pic­ture, bro­ken ice floes float on the sea (vi­o­let). On the coast in the left part of the im­age are traces of mud­flows where the thawed soil breaks off and is washed away.
Havikpak Creek: L-band radar image
Havikpak Creek: L-band radar im­age
Image 2/4, Credit: DLR (CC BY-NC-ND 3.0)

Havikpak Creek: L-band radar image

Havikpak Creek is lo­cat­ed north of In­u­vik in north­west­ern Cana­da. The per­mafrost re­gion bor­ders the taiga and is oc­ca­sion­al­ly cov­ered by bo­re­al for­est. The radar sig­nal in the low-fre­quen­cy L-band pen­e­trates deep­er in­to the veg­e­ta­tion, down to the ground, and thus al­lows state­ments to be drawn about the vol­ume or the biomass of the veg­e­ta­tion. In the pic­ture area on the top right, the for­est ar­eas (light green) are clear­ly vis­i­ble.
Havikpak Creek: C-band radar image
Havikpak Creek: C-band radar im­age
Image 3/4, Credit: DLR (CC BY-NC-ND 3.0)

Havikpak Creek: C-band radar image

Havikpak Creek is lo­cat­ed north of In­u­vik in north­west­ern Cana­da. The per­mafrost re­gion bor­ders the taiga and is oc­ca­sion­al­ly cov­ered by bo­re­al for­est. The radar im­age in the C-band main­ly shows the dif­fer­ences in sur­face tex­ture (blue) and slope of the veg­e­ta­tion. The red­dish hues in­di­cate low veg­e­ta­tion near the shore.
Vegetation of the Mackenzie Deltas
Veg­e­ta­tion of the Macken­zie Deltas
Image 4/4, Credit: DLR (CC BY-NC-ND 3.0)

Vegetation of the Mackenzie Deltas

The aeri­al pho­to­graph was tak­en as part of the ‘Veg­e­ta­tion Tran­sect’ mea­sure­ments of the Per­mASAR cam­paign in Au­gust 2018. It shows a glimpse of the area north of In­u­vik, to­wards the Macken­zie Riv­er Delta. The Macken­zie Riv­er runs through the North­west Ter­ri­to­ries of Cana­da. The main branch of the riv­er is vis­i­ble at the top of the im­age.
  • Project PermASAR: succesfully completion of measurement flights over the permafrost region of Canada
  • Novel radar technologies and analytical methods enable monitoring of the Arctic with regard to climate change
  • Possible applications for current and future satellite missions such as Tandem-L
  • Focus: climate change, Tandem-L, aeronautics, space

Scientists from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Microwaves and Radar Institute are developing special radar technologies and analytical methods that enable the highly accurate observation of permafrost. As part of DLR's Permafrost Airborne SAR Experiment (PermASAR), they are carrying out extensive measurement flights over the permafrost region of Canada. The first measuring campaign, which surveyed 10 test sites along a 2000-kilometre-long North-South gradient – from boreal forests in Northern Saskatchewan up to the Canadian Arctic coastline – has now been successfully completed. DLR is cooperating with the Canada Centre for Mapping and Earth Observation (CCMEO).

For millennia, permafrost has been shaping the subsoil of the Arctic and subarctic latitudes, ranging from a few meters to more than one kilometer deep into the interior of the Earth. However, over the past decades global warming has caused the permanently frozen soil to thaw dramatically. The emission of the greenhouse gases methane and carbon dioxide is particularly critical. These gases are in the ice, bound up in huge quantities of dead plant remains, and are increasingly being released into the atmosphere.

In contrast to ground measurements, which are spatially limited and would be particularly difficult to conduct in remote regions such as the Canadian Arctic, Earth observation from space enables comprehensive and continuous observation of the permafrost. Radar satellites such as the current German TerraSAR-X and TanDEM-X satellites, the recently proposed future mission Tandem-L and the soon to be launched RADARSAT Constellation Mission of the Canadian Space Agency (CSA) are ideally suited for such operations, as their operation is independent of daylight and weather conditions.

"The international research community has a pressing need for a database in order to fully understand and predict the origins and effects of global climate change. DLR can make an important contribution towards this with radar remote sensing – particularly through highly innovative satellite missions such as Tandem-L. The findings from the PermASAR measurements are essential for preparing Tandem-L, which will in future make it possible to visualise the dynamic processes taking place in the Arctic on a weekly basis," explains Pascale Ehrenfreund, Chair of the DLR Executive Board.

Along the climate and vegetation gradients

From the Inuvik and Yellowknife stations in the Canadian Northwest Territories, the project team from the DLR Microwaves and Radar Institute investigated a total of 10 test sites. The measuring flights went from the northwestern tip of Canada, with its treeless tundra and continuous permafrost, to the south, over taiga regions with isolated forest areas and intermittent permafrost, all the way to the permafrost-free prairie of Saskatchewan, with its sweeping boreal forests and wetlands.

DLR deployed its Dornier Do 228-212 research aircraft, as it is ideally suited for remote sensing missions due to its robust design and numerous modifications, and is operated by DLR's Flight Experiments facility. The operations team is also responsible for flight planning and supports the scientists before and during the mission. The research aircraft was equipped with DLR's F-SAR radar system and recorded polarimetric and interferometric Synthetic Aperture Radar (SAR) data in four frequency ranges – X-, C-, S- and L–band – for the PermASAR measurements.

Together with innovative 3-D radar technologies – the so-called SAR tomography – the different frequency ranges allow the scientists from Oberpfaffenhohen to carry out comprehensive analysis of the vegetation and different environmental systems. Initial evaluations already show the diversity in the vegetation and soil of the test sites and the related information content of the image data from the different frequencies. For example, the measurements in L-band make it possible to detect differences between various soil conditions beneath the vegetation due to the long-wave radar signals.

Quantifying changes

The last four weeks of August were deliberately chosen to record the properties of the permafrost for the current PermASAR measuring campaign, as the soil has different thawing depths in summer. To gain insights into the state of the permafrost regions that are completely frozen up to the surface, the PermASAR team will carry out a second measuring campaign in spring 2019 and fly over the same Canadian test sites again using the F-SAR instrument. This will allow the radar experts from DLR, CCMEO and other research partners to observe and characterise the seasonal changes occurring in the Arctic.

The full set of PermASAR measurements will open up new applications for radar remote sensing and deepen our understanding of permafrost development. The comprehensive measurements form a unique database that now enable the scientists to develop new algorithms for optimal data analysis to determine biophysical and geophysical parameters. In addition to characterising the vegetation, obtaining information about the thawing depth and surface structure of the permafrost soil, areas of ground uplift or subsidence and the characteristics of thermokarst are also of interest for climate and environmental research.

This is particularly important in view of the current, newly concceived radar satellite mission Tandem-L. Despite today's new approach to Earth observation – towards special geo information for the end-user – only a few missions directly provide environmental and climate-related information with high temporal and spatial resolution. However, this is a prerequisite for understanding the dynamic processes of the Arctic and other ecosystems – which is at the core of Tandem-L.

Cooperation with Canada

PermASAR is already considered to be a flagship Earth observation project for the collaboration between DLR and Canada in the field of Earth Observation. The cornerstone for this is the successful cooperation for receiving satellite data via the Inuvik Satellite Station Facility (ISSF) in the Canadian Arctic. The Canada Centre for Mapping and Earth Observation (CCMEO) operates the station near the North Pole and is a founding partner together with DLR. The ISSF is crucial for the seamless data reception of the German radar satellite mission TanDEM-X and will celebrate its tenth anniversary next year. Additionally, in future, the ISSF will not only be prepared for future satellite missions such as the RADARSAT Constellation Mission and Tandem-L, but also provide additional services next to demanding data traffic.

The Canadian partners are planning on setting up a data evaluation centre in Inuvik, which, next to operational geo-information services, will also promote research and education locally. Among others, the Aurora Research Institute, which has been working closely with DLR for many years, is also involved in Inuvik. PermaSAR now complements the cooperation in the Arctic on both a scientific and on an application-oriented side. DLR and CCMEO are thus working on pioneering technologies and methods of radar remote sensing from space to better understand the fragile ecosystem of the Arctic to provide targeted protection against climate change.

  • Bernadette Jung
    Com­mu­ni­ca­tions Ober­paf­fen­hofen, Weil­heim, Augs­burg
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 8153 28-2251
    Fax: +49 8153 28-1243
    Münchener Straße 20
    82234 Weßling
  • Dr. Andreas Giez
    Ger­man Aerospace Cen­ter (DLR)

    Flight Ex­per­i­ments
    Telephone: +49 8153 28-2957
    Linder Höhe
    51147 Köln
  • Dr. Hannah Jörg
    Ger­man Aerospace Cen­ter (DLR)

    Mi­crowaves and Radar In­sti­tute
    Telephone: +49 8153 28-3759
    Linder Höhe
    51147 Köln

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