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There will be a gap of several years in our ability to measure the thickness of ice at the top and bottom of the world, scientists warn.
Scientists fear satellites that have tracked ice loss in Antarctica and the Arctic will die before replacements are shipped.
Photo: BRUSINI Aurélien / hemis.fr / AFP
The only two satellites dedicated to observing the poles will almost certainly die before the replacements are made.
This could blind us to some major changes in the Arctic and Antarctica as the climate warms.
Researchers have raised their concerns with the European Commission (EC) and the European Space Agency (Esa).
This week a letter detailing the problem and possible solutions was sent to the main officials of EC and Esa; and although the US space agency (NASA) has not been formally approached, it has been informed of the correspondence.
The issue is the longevity of the European CryoSat-2 and American IceSat-2 missions.
These ships carry instruments called altimeters that measure the shape and elevation of ice surfaces.
They have been fundamental in the recording of the loss of sea ice volume and the decrease in the mass of glaciers.
The only thing about satellites is their orbits around the Earth. They fly 88 degrees north and south from the equator, which means they see all of the Arctic and Antarctic regions except for a small circle about 430 km in diameter at the poles themselves.
Artistic conception of ICESat-2.
Photo: NASA Goddard Space Flight Center
In contrast, most other satellites typically do not exceed 83 degrees. As a result, they lose, for example, a large swath of the central Arctic Ocean and its frozen icebergs.
The concern is that CryoSat-2 and IceSat-2 will have been decommissioned long before any follow-up is released.
CryoSat-2 is already well beyond its design life. It was put into space in 2010 with the expectation that it would operate for at least 3.5 years. Engineers believe they can keep it running until maybe 2024, but battery degradation and a fuel leak suggest not for much longer.
IceSat-2 was launched in 2018 with a three-year design life and fuel to 2025. Its altimeter also uses lasers, which are a complex technology to maintain in space.
“Without successful mitigation, there will be a gap of between two and five years in the altimetric capacity of our polar satellite,” says the scientists’ letter.
“This gap will introduce a decisive break in the long-term records of sea ice and ice sheet thickness change and polar oceanography, and this in turn will degrade our ability to assess and improve climate model projections.” .
The only satellite replacement currently in the offing is the EC / Esa mission codenamed Cristal. It will be like Cryosat, although with much greater capacity thanks to a dual-frequency radar altimeter.
The industry has started work on the spacecraft, but it won’t launch until 2027/28, perhaps even later because the full funding to make this date a reality is not yet available.
Visitors and members of the CryoSat-2 project view the satellite in a clean room at the space technology company IABG in Germany, 2009.
Photo: Tobias Hase / AFP
Dr. Josef Aschbacher, director of Earth observation at Esa, said his agency was working as quickly as possible to close the gap.
“This is a concern; we recognize it,” he told the BBC. “We have put plans in place to build Cristal as quickly as possible. Despite Covid, despite heavy workloads and everyone’s video conferencing, we have gone through the assessment … and Cristal was launched in early September.” .
Just over 10 percent of the nearly 600 signatories to the letter are American scientists.
To Dr. Thomas Zurbuchen, NASA’s science director, the letter is not being sent because it is addressed primarily to European funders, and most of the signatories are European. However, Dr. Zurbuchen knows the letter and its content.
He said he was hopeful that any polar gaps could be plugged or minimized.
“I think there are multiple options right now that we can implement to that end, in partnership or otherwise,” he said.
One such solution in Europe would be to run a version of NASA’s IceBridge project.
This was an aerial platform that the US agency operated during the eight years between the end of the first IceSat mission in 2010 and the launch of IceSat-2 in 2018.
A plane flew a laser altimeter over the Arctic and Antarctica to collect some limited data sets that could eventually be used to bridge the two IceSat missions.
There are many who think that a European “CryoBridge” is the most affordable and short term option to mitigate the gap years between CryoSat-2 and Cristal.
The airborne radar altimeter could cost perhaps € 5 million ($ NZ8.5m) to manufacture, scientists believe, but it would likely take two years to design and manufacture. Therefore, a project of this type would have to be launched relatively soon. Of course, you would also need an operating budget.
Signatories to the letter sent to the EC and Esa include leading scientists using data from CryoSat and IceSat, the president of the International Society of Glaciology, and lead authors of the United Nations Intergovernmental Panel on Climate Change, which prepares the status of climate reports for world governments.
-BBC
