German-American Satellites Tracing Water and Melting Ice

A PhD student in her research is examining the seasonal changes of the hydrosphere and the related mass distribution. The results are different from what would be expected.

Annamária Kiss, PhD student of the Department of Geodesy and Surveying is researching a special and unique topic. She has been analysing the GRACE satellites’ measurement results and their various areas of application and she finds that climate changes in the Arctic are much less serious and alarming than they appear in public perception.

GRACE satellites were launched by NASA and the German Space Agency in 2002. Originally they were due to operate for 5 years but according to the current plans they will stay in orbit for a few more years and in 2016-17 their “successors” will also be launched. The satellite pair orbit the Earth in one month on average. From their positions and the distance between them a global geoid model is set up reflecting the changes of the Earth’s surface: water levels of oceans and rivers, melting of ice. 

"When preparing for my BSc thesis I asked my consultant, Lóránt Földváry, to find a topic for me, which I can research in the long term,” said Annamária Kiss. Therefore at that time she was studying the mass redistribution of water in the South-American La Plata sub-basin's catchment area through the changes of water levels of the rivers. “Earth’s gravitation is determined by the distribution of mass, therefore where mass is bigger the gravitational force is stronger,” she explained. “Very few researchers compare GRACE satellites’ results with the water levels. The satellites take records of the total mass below them so their data reflect the complex water balance of the area,” highlighted the young researcher adding that “changes in the water levels of the river cannot be determined from the measurement results, but the differences during the year and the annual highest levels can well be analysed and compared.”

Annamária Kiss made a poster presentation at the Conference held on the 150th Anniversary of the International Association of Geodesy

Annamária was supported by Argentinean specialist consultants as well; therefore she prepared her thesis in English language. Her leading consultant asked a researcher of the Technical University of Munich to support her during her research work for her MSc thesis. Martin Horwath, who has Hungarian origins and whose scientific areas include GRACE satellites and the arctic found this request a great opportunity to practice his mother’s language, therefore on his request this thesis was written in Hungarian language. In her MSc thesis Annamária Kiss was researching redistribution of masses of ice in Greenland and the Antarctica, as according to her judgement these issues “can have more practical applications and are currently more problematic”.

Data from GRACE satellites substitute measurements that are impossible to carry out directly due to the extremely difficult conditions (huge remote lands) in the area. At the same time the researcher had to face an unexpected obstacle during the examinations: “the raw, uninterpretable measurement data is analysed and “translated” in Texas, USA and Potsdam, Germany. In practice it means that they set up spherical harmonics coefficients on the basis of tide, atmospheric and other models, but results from the two research centres are not identical due to differences in measurement methods and corrections. “With my leading consultant, Lóránt Földváry, we examined that if we reproduce the calculations of the two research centres the same way we find a few millimetres/year differences in the results,” explained Annamária Kiss. Eventually – with consideration to the findings of international scientific literature as well - she decided to use the data from the American institution for her research.

Mm/year measurement unit expresses how many millimetres of ice is affected by mass changes in the given area

After one year of researching and analysing the topic the young scientist highlights that “ice is shrinking in the whole area of Greenland but on the Antarctica growing and melting of ice occurs at the same time.” On the Antarctica west from the Greenwich Meridian line “measurement data from the past 10 years show intensive shrinking of ice.” There is a general opinion that the greenhouse effect is responsible for this phenomenon, but it has to be added that “on this area there are two ice shelves about the size of Spain; these platforms of ice are not on the solid ground but they are floating in the ocean. Their characteristic is enhanced bottom melting due to warmer ocean water circulating under the floating ice, therefore they may separate easier,” she explains. Easter side of the Antarctica is grounded: it rests on bedrock. “Measurement results showed that there are areas where ice is continually growing,” she emphasized.

The young researcher states that “it is impossible to get absolutely accurate results as besides the previously mentioned differences in the calculations they are also influenced by the smoothing radius of the applied noise reduction method (with the so-called Gaussian filter the satellite measurements’ noise can be reduced) and the model used to determine movements after the ice-age. It is obvious that more ice is melting than growing but the situation is not as bad as it is often reported and considered in Hungary and internationally as well,” she emphasized.

Annamária is much less determined when speaking about her plans for the future. “Originally I wanted to teach but my consultant has given me excellent research topics so presently research looks much more appealing. In my PhD studies I will summarize all fields of application of the data provided by the satellite-pair. I am also considering to spend a term or an academic year abroad as in the GRACE centres more accurate and current data would be available for my research” she says.

Annamária Kiss feels positive about her position in the mostly male-dominated world of scientific research. “In the field of engineering there are few women therefore me and my results get more attention. This means a kind of advantage for me because as a man I would be just one of the majority but as a women I am more acknowledged” she says with a smile on her face.

- MA -

Photos: János Philip