During many years of satellite and airborne survey campaigns over Greenland and the Arctic, researchers have observed how Greenland's glaciers melt and shrink. Among them is the Zachariae Glacier. (Photo: DTU Space)

Reliable data paves the way for better climate models

Monday 13 Jun 22

Contact

Sine Munk Hvidegaard
Senior Advisor
DTU Space
+45 45 25 97 72

Contact

Henriette Skourup
Senior Researcher
DTU Space
+45 45 25 97 66

DTU Space Arctic climate research

Researchers and experts from DTU Space are often on missions in Greenland to conduct research related to climate change. In this way, we help to provide the basic knowledge that is the starting point for green transition and mitigating climate change.

 

In addition to the measurement campaigns, DTU Space makes a number of other contributions to climate research in the Arctic:

 

DTU Space operates GNSS stations distributed over Greenland on behalf of SDFI, which is part of the Danish Ministry of Energy, Utilities and Climate. The stations are used, among other things, to register melting of land ice.

 

The operation of DTU's campus in Sisimiut in Greenland is also anchored at DTU Space, which contributes to teaching in areas such as Earth observation and engineering in Arctic conditions.

DTU experts have carried out surveys of sea and land ice in the Arctic to test methods to improve data for UN climate models.

Over three weeks this spring, researchers and other experts from DTU Space have carried out detailed measurements of the ice in the Arctic. It has been done using planes, drones and in situ measurements by experts on the ice. The researchers have covered over 16,000 km across Greenland and the adjacent sea areas.

It is a successful campaign where a lot of data has been obtained and a new type of test has been carried out. The results were presented to other scientists and experts at ESA’ Living Planet Symposium 2022 in Bonn in May.

"The main purpose of the measurements is to validate the data obtained with climate satellites from ESA and NASA over very large areas in the Arctic," says senior advisor at DTU Space, Sine Munk Hvidegaard. She has led the recent validation campaign together with senior researcher at DTU Space Henriette Skourup.

"Ultimately, this work is about ensuring the quality of the data that forms the basis of the climate reports from the UN's Climate Panel IPCC, so decision makers can act on climate change on as accurate a basis as possible."

Detailed data is collected from smaller areas about the quantity, volume, of the ice, which is then compared with the satellite measurements. In this way, it is validated that the data on land ice and sea ice collected over large areas with the satellites match the 'reality on earth' and live up to the required accuracy. 

International cooperation led by DTU 

The measurement campaign is called CryoVEx 2022 and is led by DTU Space, which for 30 years has developed expertise in the field in terms of technology and science as well as handling the logistical challenges in the harsh environments of the Arctic and Antarctic.

The campaign is carried out in an international collaboration with experts from ESA and researchers from several European countries and the US.

“We measure the thickness of the sea ice and the height of the glaciers, both from the surface of the ice itself, using drones and aircraft. It provides large amounts of data over relatively small areas, which are then used to compare with data from the satellites, which cover very large areas. In this way, we validate that the data from the satellites are as accurate as we expect,” says Sine Munk Hvidegaard.

“The satellites provide a great overview of climate change. How much ice is melting in the Arctic and how fast. Therefore, validation of the data is important”.

Test of new methods to improve climate models

This year, a new method has been tested. An ESA satellite called Cryosat-2 and a NASA satellite called Icesat-2 have been flying coordinated over the same area in the Arctic, while at the same time measurements have taken place on the same tracks with aircraft, drones and directly on the ice. This allows for a direct comparison of data from the two satellites with the data collected by the measurement campaign.

In addition, a new system has been tested that can make future measurements more accurate.

Often there is snow on top of the ice. And it can be difficult for satellites' radar systems to determine exactly where the transition between snow and ice is.

By measuring the surface on two frequencies at the same time, a more accurate picture of the conditions can be obtained.

“This year we have flown with an instrument that measures two frequencies and tested a concept for future satellite missions. This method can eliminate some of the uncertainties that exist on the datasets today. In this way, we can get better measurements of the climate changes we see now and thus become better at predicting what will happen in the future,” says Sine Munk Hvidegaard. 

Less ice in the Arctic year by year

During the campaigns the researchers fly long distances over the ice, are down on ice floes at sea and get far into the ice sheet in Greenland to be able to get accurate measurements. The many hours in the Arctic also give the scientists an overview of climate change.

"We can see that there is less ice year after year. There is more open water now, and some of the large glaciers on land that were previously contiguous are now disintegrating. This applies, for example, to the Zachariae Glacier in north-eastern Greenland,” says Sine Munk Hvidegaard.

Approximately every other year an extensive validation campaign is carried out. They typically involve several small aircraft, a helicopter and drones as well as a team of approximately 20 Danish and international experts.

Organizing the campaigns is a huge task.

"Apart from the fact that the equipment must of course function properly in cold conditions, there is a huge logistics task in planning the routes so that we can get down on the ice, ensure that there are airports nearby and that the weather, which can change quickly in the Arctic, are taken into account,” says the DTU expert.

This is how the measurements in the mission 'ESA CryoSat-2 Validation Experiment' (CryoVEx) take place:

  • CryoVEx takes place in an international collaboration. Among the partners are the University of Leeds, the British Center for Polar Observation and Modeling (CPOM) as well as French Vortex.io and LOcean.

    Through measurements by aircraft, drones and on the ice in the Arctic, data is collected over smaller areas that are used to validate data retrieved via Earth observation satellites over very large areas in the same region. In this way, it is ensured that climate data from satellites on the melting of sea ice and land ice provide as accurate a picture of the actual conditions as possible. This is important as the data that scientists use in climate models today come largely from ESA's and NASA's satellite monitoring programs.

    This is obtained by measuring very precisely in the same tracks the satellites fly. This is done by aircraft over larger areas, with drones on a smaller scale and on the ice itself with measurements in small areas.

    DTU Space is a leader in Europe within satellite validation campaigns in the Arctic area around Greenland. Campaigns for ESA like CryoVEx as well as related campaigns for the EU, among others, have provided great insight into the properties of the ice and snow, which helps to make the satellite measurements and thus the climate models for which data is retrieved, much more accurate.

 

  • The measurements take place at different frequencies with Ku and Ka-band radar height measurements as well as by scanning with NIR laser. It is supplemented with position and direction data determined with GNSS and inertial navigation, as well as visual images of the surface.

    As something new, the use of Ku and Ka is being tested at the same time. This gives a more accurate picture of the snow and ice. One of the challenges with measurements from satellites is that it can be difficult for the systems to determine exactly where the ice begins if, as is often the case, there is snow on top. By measuring on two frequencies at the same time, some of this uncertainty can be eliminated. This methodology will help enable ESA's future climate mission CRISTAL to deliver unprecedented accurate measurements, thereby improving our knowledge of the climate.

    Find more information and data from previous campaigns here on the DTU Space project data page and here at ESA.