Future-proofing ice measurements from space

With diminishing ice one of many largest casualties of our warming world, it is crucial that correct measurements proceed to be made for scientific analysis and local weather coverage, in addition to for sensible purposes corresponding to ship routing.

To make sure that ESA and NASA are getting the perfect out of their ice-measuring satellites and to assist put together for Europe’s new CRISTAL satellite, the 2 space businesses together with the British Antarctic Survey and a crew of scientists teamed up lately 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 performed 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.

Realizing the peak of the ice permits scientists to calculate thickness—which, together with measurements of the extent of ice protection, is significant for understanding how the quantity of ice is altering, each ice on land and ice floating within the sea.

That is notably troublesome over sea ice as a result of snow can construct up on high 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 permits 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 laser and radar readings implies that estimates of snow depth will likely be extra dependable.

Nevertheless, currents and wind shift sea ice round. Below regular circumstances, the 2 satellites would take measurements over the identical location days aside, so it might be completely different ice below their regular orbital paths. Ice on land is, in fact, much less dynamic.

Till now, scientists haven’t been capable of absolutely 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 activity of elevating CryoSat’s orbital top by nearly 1 km to phase its floor tracks with these of ICESat-2. This orbital adjustment supplies a novel alternative to check coincident measurements from each satellite sensors.

Now that scientists are getting two several types of measurements of the identical sea ice, the current Antarctic marketing campaign served as a vital inter-satellite calibration step and paves the best way for the longer term use of the separate satellite 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 collect a set of high-resolution information over the identical sea ice. This can 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 radar altimetry file such from CryoSat, they are going to present a time collection of Antarctic sea-ice thickness stretching again many years and fill gaps within the information of sea ice within the polar areas.

The DASH-7 plane additionally carried a further set of sensors related to those who will likely be carried on the brand new Copernicus Polar Ice and Snow Topography Altimeter mission, or CRISTAL for brief.

As an alternative of counting on radar and laser measurements from completely different satellites, CRISTAL’s radar will use two completely 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 and different heritage missions.

These information will help secure 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 space.”

ESA’s CRISTAL mission scientist, Paolo Cipollini, added, “ESA is within the means of creating CRISTAL for the European Union’s Copernicus program. 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.”