How NASA measures the death of a glacier from space
Editor’s note: This story is part of a series, The Wild Side of Sea Level Rise, which explores the basic research behind ocean expansion and its impacts on coastal ecology.
My photos from last summer capture a beauty that is disappearing faster and faster each year. But the images don’t do the experience justice. Standing on frozen ground, tasting air heavy with huckleberries, I had to perch on a lofty boulder in order to focus the whole ice mass in my smartphone screen. Only 25 glaciers remain inside Glacier National Park — down from 150 in the mid-19th century — and scientists estimate that these peaceful giants that sculpt the homes of grizzly bears and wildflowers will be gone by 2050.
It’s long been known that much of the Earth’s ice is melting. But we don’t know how fast that melt is occurring, or how soon the corresponding sea level rise could mean coastal cities and crops will be under the water. We need data to establish an effective plan against climate change, said Dan Fagre, an ecologist at the Northern Rocky Mountain Science Center of the US Geological Survey.
“We [Glacier National Park] will be a story about what happened when climate change started,” Fagre said.
Glaciers are made from snowfall that turns into ice that is large enough to last through the warm months. People call them “living” glaciers because the bottom layer isn’t solid. They move and ooze, dragging rocks and sediment with them, Fagre said. Glaciers move under the pressure of their own weight and gravity, carving any earth that’s in the way, and they must be roughly 25 acres large to do so. But when their rate of melting outpaces the rate of freezing, they shrink and lose the necessary weight to slide and sculpt the surrounding earth. As they lose mass and weight, they slow down, losing the ability to push forward, until they eventually stop and melt away — like a snowbank at the end of winter.
The size of a glacier is a direct indicator of climate change, Fagre said. Glaciers can’t adapt to warmer weather with behavior the way that animals or insects might. So any changes you see are a direct result of the weather.
In 1850, Glacier National Park had 150 living glaciers — that’s six times more than it has now. Since at least that time, glaciers there have been declining. But 50 years ago, the rate of decline jumped and the number of glaciers in the park took a nosedive. The situation has become increasingly bleak with time. The snow is melting faster, forcing bears and birds to adapt to new food patterns. Less snow through July and August means warmer waters, which hurts endangered species like the bull trout and the meltwater stonefly. The hotter climate means less water in the forest, which can lead to an increase in the number of fires and a depleted water supply.
Fagre’s team does most of its glacier monitoring on the ground, using photography, tree ring studies and snow measurements. Tracking all 1,583 square miles of the park would be easier from space; but the technology to zoom in on the national park’s glaciers — which are “crumbs” compared to large ice masses in the north and south pole — isn’t in space… yet.
Meet ICESat-2. NASA’s new Ice Cloud and Land Elevation satellite is designed to provide a more detailed picture of the state of global ice melt than we’ve ever had. It will measure ice both big and small, in sea and on land. How, you ask? With a really cool laser.
Almost everything at NASA Goddard Space Flight Center in southern Maryland is big – big ideas, big 40-foot-high chambers for prepping the space satellites and a big love of ice from guys like Tom Neumann, the deputy project scientist for NASA’s ICESat-2.
“I’m a land ice guy” said Neumann, who looks like the world-saving physicist you might see in an apocalyptic blockbuster movie. His hair flows like a young Einstein around black-rimmed glasses and a warm smile.
NASA Goddard is ICESat-2’s birthplace. The satellite lives in a three-story, dust-free “clean room” with slatted doors that resemble a garage from the outside. Black tape covered the panels to keep light from the satellite’s laser from seeping out during testing. The laser was off on the day of my visit, and I got to peek inside through a viewing window. A half dozen scientists in full body protective gear, or “bunny suits,” were darting around the satellite. The room is kept so pristine that the team must print all of their checklists on a special flake-free paper.
Using a laser to survey the globe isn’t new. The satellite’s predecessor — ICESat-1 — used Lidar (think radar, but with a laser) to measure ice from 2003 to 2009. But ICESat-2’s laser, referred to as Advanced Topographic Laser Altimeter System or ATLAS, is designed to capture much more detail.
“It’s so powerful that it can tell if you mowed your front lawn last weekend,” said project scientist Thorsten Markus.
Here’s how it works. Light particles, or photons from the laser will continuously beam down to Earth with 10,000 emitted per second. These photons will reflect off water, snow, grass and rock — and then bounce back into space. A receiver on ATLAS will detect returning photons. (Note: The photons from ICESat-2 are harmless — an infinitesimally small fraction when compared to the photons in daily sunlight.)
Scientists will determine distance by measuring how long it takes each photon to depart the satellite, bounce off the earth and return to the satellite. Clocks on ATLAS are extremely precise — they measure time within “a billionth of a second,” Neumann said.
So what does all this tell us about ice? Imagine a floating piece of ice in the Arctic Ocean. To measure this piece of ice, the photons bounce off the ice itself and the water that surrounds it. Now imagine one ATLAS photon bouncing off the frigid water and returning back to the satellite. As the satellite moves forward in space, another photon will strike adjacent to where the last photon landed, on top of the floating ice. The laser keeps moving until it covers the entire piece of ice and surrounding water. Then scientists can calculate the difference between the distance traveled by the photon that made contact with water and the photon that made contact with ice. That difference is how much the ice sticks out of the water, which can be used to calculate total ice thickness.
But wait, it gets better. Onboard ICESat-2, the laser snakes through a seven-foot obstacle course before leaving the satellite. Bouncing off mirrors and passing through optics, it breaks into three pairs, for a total of six beams. This setup allows ICESat-2 to take a measurement on the ground around every two feet. Not bad for a satellite 300 miles from Earth.
Measuring the thickness of the ice is important, but scientists also need to know the rate of change. “ICESat-2 will take the same measurements over the same track every 90 days,” Neumann said. “So if you compare the data today with data 90 days from now, and then 90 days later, you can see how the ice is changing through time.”
Before it launches in 2017, ICESat-2 must pass a series of tests. Inside a huge vacuum chamber, ICESat-2 will have to face both frigid and hot temperatures, simulating what it will experience as it passes in and out of the sun’s rays. Because the satellite will hitch a ride into space on the NASA Delta II rocket, scientist will also put the satellite on a giant vibrating platform, as they do with all satellites, to see if it can withstand the vigorous shaking experienced during a launch.
Many are rooting for ICESat-2 to pass these tests. Just like ICESat-1, ICESat-2 data will be made available to the public. “I hope everyone uses this data; it’s going to be fabulous data. It’s going to change everything,” Neumann said.
ICESat-2’s smaller footprint will be important for Sinead Farrell, a scientist at the University of Maryland that used ICESat data in the past. She studies sea ice or floating chunks of ocean ice that are much smaller than a glacier. Only one-eighth of sea ice is above water, and LIDAR can only measure ice above the water, which makes sea ice tough to quantify with accuracy.
Since ICESat-1 completed its mission, her team has turned to data from an interim NASA project called Operation IceBridge – a lidar-equipped plane designed to monitor the most problematic areas until ICESat-2 is launched. But IceBridge is only a temporary solution, as it would cost at least a billion dollars more to have a plane cover all the ground that ICESat-2 will cover.
NASA video outlining the results from ICESat-1 and IceBridge
ICESat-2’s range will be bigger, and its use will extend beyond ice. In fact, Amy Neuenschwander, an engineer at University of Texas’ Center for Space Research, plans on using the data to measure tree height.
“What might take months and months to measure ten trees in a plot in Africa, you can do with one pass from a satellite,” Neuenschwander said.
Farrell said sea ice influences climate change by acting like a baseball cap, a blanket and a conveyor belt. The white surface of sea ice reflects light better than liquid ocean water. So the presence of sea ice keeps sun rays from warming the seas, much like a baseball cap keeps your face cool. Sea ice behaves like a blanket by preventing water molecules from easily escaping into the atmosphere via evaporation. Water vapor in the atmosphere leads to further heating, worsening ice melt, Farrell said. Finally, ocean particles — water molecules, silt, salts — from the surface to the sea floor are constantly in motion. They slowly move along a conveyer belt — pivoting from top to bottom as they reach the edge of the sea. This is called Thermohaline circulation, and it is driven by how salty and warm the ocean becomes in warmer season. Melting sea ice has the potential to slow or halt this natural churning of the ocean.
“We know that sea ice plays an important role in the thermohaline circulation, but it remains unclear exactly what influence a diminishing sea ice pack would have on the global ocean circulation. Through new measurements, such as those expected from ICESat-2, we hope to learn more about these processes,” Farrell said.
Between 2003 and 2012, the Arctic Ocean lost about 1,500 cubic kilometers of winter sea ice. That’s equivalent to the volume of water in 600 million Olympic-size swimming pools. With less sea ice, we can expect warmer waters, more evaporation and altered currents. All of this is happening at an accelerated rate, Farrell said.
Ice melt is the primary contributor to sea level rise, which is increasing three to four millimeters per year, said Ted Scambos, a glaciologist at University of Colorado’s National Snow and Ice Data Center. Scambos used ICESat data to monitor Antarctic ice shelves – floating sheets of ice attached to the earthy mainland. Ice shelves can act as gatekeepers to larger glaciers. But when an ice shelf collapses, humongous glaciers move rapidly into open warmer waters and start to shrink. This event can cause an abrupt rise in sea level. Scambos will use ICESat-2 data to help predict how long these weakening ice shelves will hold.
To Scambos, ICESat-2 is the next step in combating climate change. “We need to transition from a science of discovery about climate change to a science of monitoring – how does this happen and how is it progressing?”
In the meantime, David Greene, an environmental policy expert at the University of Tennessee suggests that everyone take a hard look at their energy consumption. Walk and bike more, he said, reserve your air conditioner for freeway driving, and brake and accelerate less. A lighter car with “less drag” is a greener car.
But that will only take us so far. Even if we were to drastically change our behavior, Glacier National Park would be glacier-less within this century, Neumann said. If all of Greenland melted away, he said, it would raise sea-level by 21 feet. But if the rate of sea-level rise stays constant, that will take 20,000 years. So there is still time to save the large masses of land ice.