19/01/2023
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With diminishing ice one of many largest casualties of our warming world, it’s crucial that correct measurements proceed to be made for scientific analysis and local weather coverage, in addition to for sensible purposes similar to ship routing. To make sure that ESA and NASA are getting the very best out of their ice-measuring satellites and to assist put together for Europe’s new CRISTAL satellite tv for pc, the 2 area businesses together with the British Antarctic Survey and a crew of scientists teamed up not too long ago to hold out an bold marketing campaign in Antarctica.
The marketing campaign concerned taking simultaneous measurements of sea ice from ESA’s CryoSat and NASA’s ICESat-2 satellites, and from an plane flying immediately beneath the 2 satellites.
It’s the first time that this has ever been completed within the Antarctic.
CryoSat carries a radar altimeter and ICESat-2 carries a laser. Each devices measure the peak of ice by emitting a sign and timing how lengthy it takes for the sign to bounce off the ice floor and return to the satellite tv for pc.
Realizing the peak of the ice permits scientists to calculate thickness – which, together with measurements of the extent of ice protection, is important for understanding how the quantity of ice is altering, each ice on land and that floating within the sea.
That is notably troublesome over sea ice as a result of snow can construct up on prime of the ice.
Figuring out the thickness of sea ice includes measuring the ‘freeboard’ of ice floes – the peak protruding from the water. Nevertheless, snow can push the floe down into the water, hiding the ice’s true thickness. A snow-loading correction due to this fact must be utilized to the information.
Combining measurements from the 2 satellites permit scientists to right for this snow-loading impact.
Whereas CryoSat’s radar penetrates via the snow layer and displays carefully off the ice under, ICESat-2’s laser displays off the highest of the snow layer. Mixing simultaneous satellite tv for pc laser and radar readings implies that estimates of snow depth will likely be extra dependable.
Nevertheless, currents and wind shift sea ice round. Beneath regular circumstances, the 2 satellites would take measurements over the identical location days aside, so it could possibly be totally different ice underneath their regular orbital paths. Ice on land is, in fact, much less dynamic.
Till now, scientists haven’t been capable of totally exploit coincident measurements recorded by every mission to observe sea ice within the Southern Ocean.
A few years in the past, ESA carried out the tough job of elevating CryoSat’s orbital top by nearly 1 km to part its floor tracks with these of ICESat-2. This orbital adjustment offers a novel alternative to match coincident measurements from each satellite tv for pc sensors.
Now that scientists are getting two various kinds of measurement of the identical sea ice, the latest Antarctic marketing campaign served as an important inter-satellite calibration step and paves the best way for the longer term use of the separate satellite tv for pc measurement information.
For the marketing campaign, the British Antarctic Survey’s DASH-7 plane was fitted with cutting-end sensors that mimic the radar altimeter on CryoSat and the laser on ICESat-2. It was additionally fitted with devices that measure snow depth, floor albedo, and roughness.
Flights from the Survey’s Rothera Analysis Station had been timed to happen precisely because the satellites orbited above, permitting the crew to assemble a collection of high-resolution knowledge over the identical sea ice. It will assist the crew develop extra correct algorithms to enhance satellite-derived sea-ice thickness estimates.
By making use of these algorithms to the historic satellite tv for pc radar altimetry file such from CryoSat, they may present a time collection of Antarctic sea-ice thickness stretching again a long time and fill gaps within the data of sea ice within the polar areas.
The DASH-7 plane additionally carried a further set of sensors comparable to those who will likely be carried on the brand new Copernicus Polar Ice and Snow Topography Altimeter mission, or CRISTAL for brief.
As a substitute of counting on radar and laser measurements from totally different satellites, CRISTAL’s radar will use two totally different frequencies to measure and monitor sea-ice thickness, overlying snow depth and ice-sheet elevations.
CRISTAL will make sure the long-term continuation of radar altimetry ice-elevation and topographic-change information, following on from CryoSat mission and different heritage missions.
These knowledge will help protected maritime operations within the polar oceans and contribute to a greater understanding of local weather processes. CRISTAL can even help purposes associated to coastal and inland waters, in addition to offering observations of ocean topography.
Andrew Shepherd, from the College of Leeds and principal scientific advisor to the CryoSat and CRISTAL missions, famous, “Flying the DASH-7 is an thrilling alternative because it reveals that we will bridge the hole that may come up between CryoSat and CRISTAL.”
ESA Analysis Fellow, Isobel Lawrence, famous, “The marketing campaign in Antarctica has been important in future-proofing sea-ice thickness measurements from area.”
ESA’s CRISTAL mission scientist, Paolo Cipollini, added, “ESA is within the technique of creating CRISTAL for the European Union’s Copernicus programme. This mission will present the sustained, long-term observations crucially wanted for polar local weather monitoring, local weather analysis and marine providers. And additionally it is anticipated to allow thrilling new science, by advantage of its enhanced and expanded set of devices”.
