Technical University of Denmark: Reliable data paves the way for better climate models

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.