Barnes Ice Cap sits on the central plateau of Baffin Island, in the Canadian Arctic. It is the last surviving fragment of the Laurentide Ice Sheet, the largest of the Pleistocene ice sheets, which at its peak buried most of Canada under two miles of ice and locked away around 80 meters of sea level. That remnant has now yielded direct physical evidence that ice sheets might have reversed their retreat and started to grow again thousands of years ago.
In a recent Science study, researchers show that the Laurentide reached its smallest size about 3,600 years ago, then started re-expanding roughly 2,000 years ago, which the team interprets as the opening move of the next glaciation. Apparently, this brand-new ice age was on its way until about 1960, when human-caused climate warming reversed it.
Frozen to the bed
“Barnes is the last remaining piece of one of the domes of the Laurentide Ice Sheet,” says Nicolás Young, a geologist at Columbia University's Lamont-Doherty Earth Observatory and lead author of the study. As that enormous dome thinned through the Holocene, its margin withdrew up onto Baffin Island, and what's left today is the deflated core of something that was once two miles thick. The reason Barnes can testify about its own history, Young explains, comes down to the temperature at its base.
From orbit, today’s space-based laser instruments measure Earth’s forests and terrain one narrow line at a time. Between those lines are enormous gaps that include millions of acres of land scientists never directly measure. NASA’s CASALS instrument will blend machine learning with an ultra-compact lidar instrument to adaptively ‘sweep’ large swaths of Earth’s surface. This new capability for space-based remote sensors allows CASALS to create truly three-dimensional (3D) topographical renderings.
Video from a CASALS flight over the Great Cypress Swamp in Delaware on Nov. 12, 2024, showing tree canopy tops in green, the ground in purple, and near-ground vegetation in blue.
Credit: NASA
A team of researchers at NASA’s Goddard Space Flight Center (GSFC) has developed a new instrument designed to eliminate blind spots between lines of lidar data on the Earth’s surface. Built with support from NASA’s Earth Science Technology Office (ESTO), the Concurrent Artificially-intelligent Spectrometry Lidar System (CASALS) could help researchers map the features of Earth’s surface with unprecedented detail. Rather than mechanically steering a laser with moving mirrors, CASALS steers light using wavelength itself, generating a continuous, 3D swath of the ground below.
John Yorks, a physical research scientist at GSFC and Principal Investigator for CASALS, explained that the instrument features a novel transmitter and optical grating system that manipulates laser pulses without heavy, failure-prone motorized mirrors.
Instead, CASALS uses a fast-pulsing, tunable “seed” laser centered at 1040 nanometers, rapidly cycling through 256 unique wavelengths as it pulses through an optical component with a microscopic pattern of ridges called a transmission grating.
At this point, the physics of diffraction takes over. Because light bends at slightly different angles depending on its exact wavelength, the grating naturally “steers” each of the 256 pulses into a distinct position across the flight path.
This non-mechanical approach paints a continuous 3D swath of the ground. Not only does this eliminate the large unmapped gaps left between the isolated tracks of legacy spaceborne lidars, but stripping away moving parts drastically reduces the instrument’s size, weight, and power (SWaP) requirements. This makes it more reliable for the harsh environment of space.
Another key innovation within CASALS is its detector array. This component features a uniquely high Quantum Efficiency (QE), a variable that describes how effectively a detector converts incoming light (photons) into an electrical signal. CASALS operates at 80% QE. This means CASALS wastes almost none of the light that makes it back to the sensor.
With QE that high, CASALS can detect much weaker return signals, allowing it to collect useful measurements from darker surfaces or through denser vegetation.
This technology isn’t limited to a laboratory environment. In November 2024, an airborne CASALS prototype flew aboard NASA’s B200 King Air aircraft. The instrument produced science-quality datasets on its first campaign, exceeding the team’s expectations.
“I’m very impressed with Guang Yang, Jeffrey Chen, and all our engineers, and how well CASALS performed. This worked really well from the first time we flew it, which is pretty impressive,” said Yorks.
Flying at an altitude of roughly five kilometers, CASALS can distinguish individual tree branches and subtle changes in ground elevation, thanks to its 22-centimeter horizontal resolution.
“We’re able to see really fine details of vegetation structure and changes in the topography of the surface,” Yorks said.
But there’s more work to do to prepare the technology for space. The team plans to make several improvements to CASALS before creating a space-ready prototype. Specifically, they’re widening the instrument’s swath and adding onboard data processing software.
Transitioning from a successful airborne prototype to a fully realized space mission is a challenge, but the CASALS team is up to the task.
“The team’s really done a great job of sticking together and keeping on task and on schedule. We are being funded to optimize and improve the performance, and we’re also then looking at ways to take the technologies used in the airborne instrument and mature them and prepare them for a spaceborne version in the future,” said Yorks.
If successful, CASALS could become the first spaceborne lidar capable of mapping Earth’s forests and terrain as continuous three-dimensional swaths rather than isolated profiles, giving scientists a dramatically more complete picture of our changing planet.
For additional details, see the entry for this project on NASA TechPort.
Project Lead(s): John Yorks, NASA’s Goddard Space Flight Center
Sponsoring Organization(s): NASA’s Decadal Survey Incubation (DSI) program; NASA’s Instrument Incubation Program (IIP); NASA’s Goddard Space Flight Center; University of California, Santa Barbara; Virginia Polytechnic Institute and State University
In most cases, hotspot-driven volcanism is relatively sedate, with lava flowing down mountainsides slowly enough that people can walk out of its way. But in a number of locations—Mount Etna, Hawaii, Iceland—lava gets expelled in dramatic fountains that can reach several hundred meters in height.
Right now, we're not sure what powers them. However, thanks to a recent set of eruptions at the Kilauea volcano, we have some of the best documentation yet of erupting lava fountains. In a recent edition of Science, researchers from the US Geological Survey describe what we've seen and compare it with what we might expect based on our best ideas about what powers these fountains of molten rock.
Years of fountains
With three active volcanic regions that engage in fountaining, there has been a steady flow of dramatic videos of red-hot molten rock spouting from the Earth. But Kilauea has had only three fountaining episodes since 1823, even though it's the youngest and most active volcano in Hawaii. That activity has led to intensive study, and we have a good idea of the volcano's structure. Previous work has identified a couple of lava residues within a few kilometers of the surface, and the volcano had 35 separate data-gathering stations set up on Kilauea, including "seismic, infrasound, geodetic, gas, and visual and thermal cameras."
Login
