New NASA satellite will track ice melt on Earth

ICESat-2 will study seasonal changes using lasers to measure ice height worldwide.

NASA is launching a new laser satellite that will study Earth’s ice sheets and changes they undergo over the next three years.

Titled the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), the satellite will measure and track changes in ice levels across the globe from one season to another. It will be capable of detecting thickness changes as small as one-fifth of an inch.

Two previous NASA probes, the original ICESat, launched in 2003 and Operation IceBridge, begun in 2009, previously monitored changes in ice thickness worldwide.

ICESat measured ice thickness by bouncing a single laser off the surface of ice in each area it studied. Operation IceBridge, which used an airplane rather than a satellite, focused on specific regions of ice deemed crucial and was largely a stopgap mission until the current satellite was ready for launch.

Unlike the previous missions, ICESat-2 will measure the world’s ice in 3D.

“The areas that we’re talking about are vast–think the size of the continental US or larger–and the changes that are occurring over them can be very small,” explained NASA scientist Tom Wagner at an August 22 press conference. “They benefit from an instrument that can make repeat measurements in a very precise way over a large area and that’s why satellites are an ideal way to study them.”

The first ICESat mission confirmed the planet’s sea ice is becoming thinner, Wagner said. “We’ve probably lost over two-thirds of the ice that used to be there back in the ’80s.”

Capable of monitoring ice levels on both land and sea, ICESat-2 will orbit 300 miles (500 km) above Earth’s surface. ItsĀ  Advanced Topographic Laser Altimeter System (ATLAS) will emit single laser beams of green light, each of which will be split into six separate beams, which will be bounced off ice surfaces in a grid-like pattern. The satellite will then measure the exact time it takes for these photons to bounce off the ice and return to ATLAS. Only a small number of the photons will return.

Mission scientists will use the amount of time the photons take to return to calculate the height of the surface from which the laser was bounced.

In order for ICESat-2 to observe the same locations during each season, “The orbit is designed so that after 91 days, which is 1,387 individual orbits of the Earth, it exactly repeats itself. This allows the mission to look at the same piece of Earth in each of the four seasons,” said ICESat-2 project manager Doug McLennan.

Launch of ICESat-2 from Vandenberg Air Force Base in California is scheduled for September 15.


Satellite data shows acceleration of Arctic carbon cycle

Region is behaving more like a boreal forest than a tundra.

Satellite data collected under NASA’s Arctic Boreal Vulnerability Experiment (ABoVE) confirms the Arctic carbon cycle is speeding up due to warming temperatures, causing the region to act more like a North American boreal forest than like icy tundra.

Boreal forests are those found in regions south of the Arctic, specifically cold, temperate regions.

A NASA research team analyzed over 40 years of carbon dioxide surface measurements acquired by the National Oceanic and Atmospheric Administration’s (NOAA) observatory in Barrow, Alaska, using a standard computer model geared toward ecosystem carbon balance in a study to determine the rate at which carbon is moving into and out of Alaska’s North Slope.

While computer models used in earlier studies indicated an acceleration in the region’s carbon cycle, satellite data, along with information collected from the area’s air and surface, show that acceleration to be greater than any of the models predicted.

Carbon in the North Slope’s tundra regions now spends 13 percent less time trapped in frozen soil than it did four decades ago, the researchers determined.

“Warming temperatures mean that essentially we have one ecosystem–the tundra–developing some of the characteristics of a different ecosystem–a boreal forest,” said Anthony Bloom of NASA’s Jet Propulsion Laboratory (JPL) in California. “While various factors regulate how fast this transformation will continue to occur, studies using Landsat and MODIS satellite imagery with field measurements over the past decades have observed a northward migration of shrubs and trees.”

Landsat is a joint program between NASA and the United States Geological Survey (USGS) of Earth-observing satellites that provide the longest continuous space-based Earth observations. The Moderate Resolution Imaging Spectroradiometer (MODIS) is a satellite that observes every point on Earth in discrete spectral bands every one to two days.

The Arctic carbon cycle involves the release of carbon dioxide during Arctic summers, when warmer temperatures melt the top layers of permafrost, allowing microbes to break down organic matter that had been frozen in colder weather. This triggers plant growth, with plants removing the carbon dioxide as they conduct photosynthesis.

Overall warmer temperatures mean the carbon dioxide spends less time frozen in the soil and more time in the atmosphere, a phenomenon that could have global consequences.

“The balance between these two dynamics will determine whether Arctic ecosystems will ultimately remove or add atmospheric carbon dioxide in the future climate. Our study finds the latter is more likely. We anticipate that residence time of Arctic carbon will lead to faster and more pronounced seasonal and long-term changes in global atmospheric carbon dioxide,” said former JPL researcher Sujong Jeong of Seoul National University.

A paper on the study has been published in the journal Science Advances.