12. June 2019
South America

Tan­DEM-X re­veals glaciers in de­tail

TerraSAR-X image
Ter­raSAR-X im­age – the Up­sala Glacier in Patag­o­nia
Image 1/3, Credit: DLR (CC BY-NC-ND 3.0)

TerraSAR-X image – the Upsala Glacier in Patagonia

Ar­ti­fi­cial­ly coloured Ter­raSAR-X im­age (strip mode) of the Up­sala Glacier in Patag­o­nia, Ar­genti­na, cre­at­ed us­ing da­ta ac­quired on 7 Jan­uary 2008. The colours pro­vide in­for­ma­tion about the rough­ness of the ter­rain. Ar­eas that ap­pear pre­dom­i­nant­ly smooth to the radar are tint­ed in dark­er shades of blue and grey. Ar­eas with a coars­er sur­face tex­ture are shown in yel­low.      
Mass changes in the Southern Patagonian Ice Field
Mass changes in the South­ern Patag­o­ni­an Ice Field re­vealed by radar
Image 2/3, Credit: Malz et. al. 2018 doi:10.3390/rs10020188

Mass changes in the Southern Patagonian Ice Field revealed by radar

De­tail from a map show­ing the changes in height of the South­ern Patag­o­ni­an Ice Field; the names on the map in­di­cate the most im­por­tant out­let glaciers. (a) Pix­el-based es­ti­ma­tion of the mass change over the pe­ri­od 2000 to 2015; (b) es­ti­mat­ed av­er­age mass change for the area of the glacier catch­ment area. El­e­va­tion mod­els from the Shut­tle Radar To­pog­ra­phy Mis­sion in 2000 and from the Tan­DEM-X mis­sion con­duct­ed from 2011 to 2015 were used for the anal­y­sis.      
Grey Glacier in Argentina
On-site glacier mea­sure­ments
Image 3/3, Credit: FAU/Matthias Braun

On-site glacier measurements

Glacio­log­i­cal ground mea­sure­ments on the Grey Glacier in Ar­genti­na. Poles are drilled in­to the glacier to mea­sure the rate of melt­ing. Such mea­sure­ments serve as ref­er­ences for anal­y­sis us­ing satel­lite da­ta.      

Focus: Earth observation, space, global change

A precise understanding of glacier evolution requires knowledge of a glacier's exact mass. This is important in South America, in the tropical regions between Bolivia and Venezuela, where meltwater from glaciers provides drinking water during the dry season. However, basic data about mass changes in glaciers are not easy to obtain. Mass losses are also contributing to rising sea levels on a global scale. As a new analysis method using TanDEM-X data shows, this is particularly true for Patagonia.

Prior to the availability of this method, scientists had to measure changes in glacier mass on site, which is difficult for large and inaccessible areas. An example is the Patagonian Ice Fields, which lie in the Andes – on the border between Chile and Argentina – and cover an area of almost 18,000 square kilometres. Alternatively, satellite-based gravitational field measurements can provide information about the mass balance. However, this method is not suitable for glaciers in tropical regions with low ice cover. TanDEM-X now offers the possibility of determining the mass balance of glaciers using radar remote sensing. This has the advantages of being a uniform measuring method and offering a higher degree of precision than ever before. Scientists from the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have developed a special processing method, which they have used to obtain a detailed picture of the mass changes in all of South America's glaciers from radar data for the first time.

Entire glaciers have disappeared

The FAU study shows that the Patagonian Ice Fields have suffered the biggest losses – in addition to the mass losses in the large ice sheets, entire glaciers have already disappeared. Between 2000 and 2015, Patagonia's Ice Fields shrank by around 17.4 gigatonnes. This equates to a decrease of 19.3 cubic kilometres per year and exceeds even the mass losses of glaciers located in the tropics. Analysis of the TanDEM-X data confirms previous investigations and reveals a dramatic change, which was previously only confirmed for areas in Bolivia and Peru.

The TanDEM-X terrain models record height differences with an accuracy of one metre, allowing even individual glaciers to be accurately measured. Geographers working with Matthias Braun and Tobias Sauter in the fields of remote sensing, geoinformation and physical climatology at FAU are using these data from the 2011–2015 period and comparing them with data acquired by the Shuttle Radar Topography Mission, which took place in 2000. Using a complex procedure, they used the differences to calculate the height changes for the glaciers and hence the changes in their mass. By using the high-resolution TanDEM-X data and the new processing method, the FAU researchers were thus able to analyse the large Patagonian inland ice sheets separately from the surrounding glaciers for the first time. The results of the extensive study were published in the journal Nature Climate Change and may be included in the next report of the Intergovernmental Panel on Climate Change.

Continuation of TanDEM-X and Tandem-L

The global terrain model derived from data acquired by the TanDEM-X mission is currently being updated, with the researchers from the FAU hoping to benefit even more from these data in future. They are looking to extend their analysis to other regions and update it over time. The geographers are also excited about Tandem-L, the follow-up mission to TanDEM-X. Tandem-L aims to map Earth's landmass on a weekly basis. In the L-band frequency range, at a wavelength of 23.6 centimetres, the radar signals of the new satellites would be able to penetrate through the vegetation and into the ground. Radar tomographic images will form part of the Tandem-L mission, thus ensuring even more accurate coverage of glacier masses. In future, FAU scientists will be able to observe the glacier regions of South America with high temporal and spatial precision and thus gain further valuable insights.

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

    DLR Cor­po­rate Com­mu­ni­ca­tions
    Telephone: +49 8153 28-2251
    Fax: +49 8153 28-1243
    Münchener Straße 20
    82234 Weßling
  • Prof. Irena Hajnsek
    Ger­man Aerospace Cen­ter (DLR)
    Mi­crowaves and Radar In­sti­tute
    Sci­ence Co­or­di­na­tion
    Telephone: +49 8153 28-2362
    Münchener Straße 20
    82234 Oberpfaffenhofen-Weßling
  • Prof. Dr. Matthias Braun Braun
    Friedrich-Alexan­der-Uni­ver­sität Er­lan­gen-Nürn­berg

    In­sti­tute of Ge­og­ra­phy
    Telephone: +49 9131 85-22015
    Wetterkreuz 15
    91058 ErlangenErlangen

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