Ice in motion: Satellites capture decades of change

New time-lapse videos of Earth's glaciers and ice sheets as seen from space -- some spanning nearly 50 years -- are providing scientists with new insights into how the planet's frozen regions are changing. At the annual meeting of the American Geophysical Union in San Francisco, scientists released new time series of images of Alaska, Greenland, and Antarctica using data from satellites including the NASA-U.S. Geological Survey Landsat missions. One series of images tells illustrates the dramatic changes of Alaska's glaciers and could warn of future retreat of the Hubbard Glacier. Over Greenland, different satellite records show a speed-up of glacial retreat starting in 2000, as well as meltwater ponds spreading to higher elevations in the last decade, which could potentially speed up ice flow. And in Antarctic ice shelves, the view from space could reveal lakes hidden beneath the winter snow.

Using images from the Landsat mission dating back to 1972 and continuing through 2019, glaciologist Mark Fahnestock of the University of Alaska Fairbanks, has stitched together six-second time-lapses of every glacier in Alaska and the Yukon.

"We now have this long, detailed record that allows us to look at what's happened in Alaska," Fahnestock said. "When you play these movies, you get a sense of how dynamic these systems are and how unsteady the ice flow is."

The videos clearly illustrate what's happening to Alaska's glaciers in a warming climate, he said, and highlight how different glaciers respond in varied ways. Some show surges that pause for a few years, or lakes forming where ice used to be, or even the debris from landslides making its way to the sea. Other glaciers show patterns that give scientists hints of what drives glacier changes.

The Columbia Glacier, for example, was relatively stable when the first Landsat satellite launched 1972. But starting in the mid-1980s, the glacier's front began retreating rapidly, and by 2019 was 12.4 miles (20 kilometers) upstream. In comparison, the Hubbard Glacier has advanced 3 miles (5 km) in the last 48 years. But Fahnestock's time-lapse ends with a 2019 image that shows a large indentation in the glacier, where ice has broken off.

"That calving embayment is the first sign of weakness from Hubbard Glacier in almost 50 years -- it's been advancing through the historical record," he said. If such embayments persist in the coming years, it could be a sign that change could be coming to Hubbard, he said: "The satellite images also show that these types of calving embayments were present in the decade before Columbia retreated."

The Landsat satellites have provided the longest continuous record of Earth from space. The USGS has reprocessed old Landsat images, which allowed Fahnestock to handpick the clearest Landsat scenes for each summer, over each glacier. With software and computing power from Google Earth Engine, he created the series of time-lapse videos.

Scientists are using long-term satellite records to look at Greenland glaciers as well. Michalea King of Ohio State University analyzed data from Landsat missions dating back to 1985 to study more than 200 of Greenland's large outlet glaciers. She examined how far the glacier fronts have retreated, how fast the ice flows, and how much ice glaciers are losing over this time span.

She found that Greenland's glaciers retreated an average of about 3 miles (5 km) between 1985 and 2018 -- and that the most rapid retreat occurred between 2000 and 2005. And when she looked at the amount of glacial ice entering the ocean, she found that it was relatively steady for the first 15 years of the record, but then started increasing around 2000.

"These glaciers are calving more ice into the ocean than they were in the past," King said. "There is a very clear relationship between the retreat and increasing ice mass losses from these glaciers during the 1985-through-present record. "While King is analyzing ice lost from the front of glacier, James Lea of the University of Liverpool in the United Kingdom is using satellites data to examine ice melting on top of Greenland's glaciers and ice sheets, which creates meltwater lakes.

These meltwater lakes can be up to 3 miles (5 km) across and can drain through the ice in a matter of hours, Lea said, which can impact how fast the ice flows. With the computing power of Google Earth Engine, Lea analyzed images of the Greenland ice sheet from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellites for every day of every melt seasons over last 20 years -- more than 18,000 images in all.

"We looked at how many lakes there are per year across the ice sheet and found an increasing trend over the last 20 years: a 27 percent increase in lakes," Lea said. "We're also getting more and more lakes at higher elevations -- areas that we weren't expecting to see lakes in until 2050 or 2060."

When these high-elevation meltwater ponds punch through the ice sheet and drain, it could cause the ice sheet to speed up, he said, thinning the ice and accelerating its demise.

It doesn't always take decades worth of data to study polar features -- sometimes just a year or two will provide insights. The Antarctic ice sheet experiences surface melt, but there are also lakes several meters below the surface, insulated by layers of snow. To see where these subsurface lakes are, Devon Dunmire of the University of Colorado, Boulder, used microwave radar images from the European Space Agency's Sentinel-1 satellite. Snow and ice are basically invisible to microwave radiation, but liquid water strongly absorbs it.

Dunmire's new study, presented at the AGU meeting, found lakes dotting the George VI and Wilkins ice shelves near the Antarctic Peninsula -- even a few that remained liquid throughout the winter months. These hidden lakes might be more common than scientists had thought, she said, noting that she is continuing to look for similar features across the continent's ice shelves.

Read more at Science Daily

See Six Months of Earth From Space: Timelapse

If you're a fan of epic ultra high definition time-lapse videos from space -- and really who isn't — then you'll be happy to know that Christmas arrived early and Hannukah is right on time. The European Space Agency has stiched together more than five months of astronaut Alexander Gerst's time-lapse photography from the International Space Station (ISS) and made it into a six-minute video.

Gerst spent 166 days in orbit starting in late May on the ISS as one of five flight engineers, all part of the European Space Agency's aptly named mission, Blue Dot. Luckily for us mere mortals, he also had an excellent photographic eye and captured some pretty spectacular views as the ISS hurtled around the planet at 17,200 mph, making more than 15 laps each day.

Lightning from space looks like daubs of electric paint atop of clouds. Large-scale weather patterns including spinning areas of low pressure look just like they do on weather maps. The aurora takes on the appearance of a shimmering green curtain draped around the high latitudes of Earth. And day and night on the horizon of Gerst and his fellow astronaut's view, the crystaline strip of the atmosphere -- the one we're filling with greenhouse gases -- is clearly visible, separating those of us back on planet Earth from the rest of the universe.

But lest you think it's all eye candy and fodder for philosophical musings, there are also a few hidden insights into how the various apparati that ensure the ISS can sustain the astronauts that call it home. Solar panels rotate to catch the most sun and keep all systems up and running. At the 1:35 mark, a robotic arm extends to pluck a Cygnus spacecraft -- one of the commercial spacecraft that help supply the ISS -- out of, well, space. After collecting its payload, the same arm releases it on its homeward journey at the 4:50 mark. It truly looks like science fiction.

So go ahead, ratchet the video up to ultra high definition and enjoy each one of the 12,500 images it took to create it. And let it not go unnoted that the European Space Agency also found some pretty futuristic background music for the video. Hope you're taking notes, NASA.

From Discovery News

Lightning, Stars, and Aurorae Shine in Epic Time-Lapse

When the sun sets, the show begins: night after night of incredible weather, shimmering aurorae, and stunning starry vistas over the rugged and rural landscapes of South Dakota, Utah, and Wyoming are captured in “Huelux,” the latest time-lapse film from photographer Randy Halverson.

Shot over seven months, Huelux presents the night sky in a way only time-lapse photography — and a skilled artist — can. Lightning storms flash, clouds speed by, the Northern Lights dance and, behind it all, the grand vista of the Milky Way makes its stately arc across the heavens. Human activity is reduced to mere flickers at these time scales, as the meteor-like flashes of commercial jet planes and communications satellites show.

“I came up with the title Huelux, which comes from hue (a color property), and lux which is Latin for light. Some of the aurora and Milky Way were difficult to color correct, so I spent a lot of time with the hue settings, white balance, etc. during the month and a half edit. The low aurora on the horizon were often yellow, while closer (higher in the sky) aurora were green. If I adjusted the yellow aurora on the horizon green, it threw the rest of the colors, such as grass, way off and made the whole image too blue.”

Fantastic work — truly a testament to the beauty of the night sky, as well as a haunting exhibition of a slightly more ponderous passage of time.

Taken from Discovery News