NASA’s ICESat-2 Measures Arctic Ocean’s Sea Ice Thickness, Snow Cowl

From NASA

Might 14, 2020

Arctic sea ice helps preserve Earth cool, as its vibrant floor displays the Solar’s power again into area. Every year scientists use a number of satellites and information units to trace how a lot of the Arctic Ocean is roofed in sea ice, however its thickness is tougher to gauge. Preliminary outcomes from NASA’s new Ice Cloud and land Elevation Satellite tv for pc-2 (ICESat-2) recommend that the ocean ice has thinned by as a lot as 20% because the finish of the primary ICESat mission (2003-2009), opposite to present research that discover sea ice thickness has remained comparatively fixed within the final decade.

ICESat-2 has a laser altimeter, which makes use of pulses of sunshine to exactly measure top right down to about an inch. Every second, the instrument sends out 10,000 pulses of sunshine that bounce off the floor of Earth and return to the satellite tv for pc and data the size of time it takes to make that spherical journey. The sunshine displays off the primary substance it hits, whether or not that’s open water, naked sea ice or snow that has amassed on high of the ice, so scientists use a mixture of ICESat-2 measurements and different information to calculate sea ice thickness. 

By evaluating ICESat-2 information with measurements from one other satellite tv for pc, researchers have additionally created the primary satellite-based maps of the quantity of snow that has amassed on high of Arctic sea ice, monitoring this insulating materials.

“The Arctic sea ice pack has modified dramatically since monitoring from satellites started greater than 4 many years in the past,” stated Nathan Kurtz, ICESat-2 deputy undertaking scientist at NASA’s Goddard Area Flight Heart in Greenbelt, Maryland. “The extraordinary accuracy and year-round measurement functionality of ICESat-2 gives an thrilling new software to permit us to raised perceive the mechanisms main to those adjustments, and what this implies for the long run.”

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Arctic sea ice, with ridges and cracks

Scientists have used NASA’s ICESat-2 to measure the thickness of Arctic sea ice, in addition to the depth of snow on the ice. Right here, ridges and cracks have fashioned in sea ice within the Arctic Ocean. Credit: NASA / Jeremy Harbeck

Arctic sea ice thickness dropped drastically within the first decade of the 21st Century, as measured by the primary ICESat mission from 2003 to 2009 and different strategies. The European Area Company’s CryoSat-2, launched in 2010, has measured a comparatively constant thickness in Arctic sea ice since then. With the launch of ICESat-2 in 2018, researchers appeared to this new method of measuring sea ice thickness to advance the examine of this information file.

“We are able to’t get thickness simply from ICESat-2 itself, however we will use different information to derive the measurement,” stated Petty. For instance, the researchers subtract out the peak of snow on high of the ocean ice by utilizing laptop fashions that estimate snowfall. “The primary outcomes have been very encouraging.”

Of their examine, printed just lately within the Journal of Geophysical Analysis: Oceans, Petty and his colleagues generated maps of Arctic sea ice thickness from October 2018 to April 2019 and noticed the ice thickening by means of the winter as anticipated.

Total, nevertheless, calculations utilizing ICESat-2 discovered that the ice was thinner throughout that point interval than what researchers have discovered utilizing CryoSat-2 information. Petty’s group additionally discovered that small however vital 20% decline in sea ice thickness by evaluating February/March 2019 ICESat-2 measurements with these calculated utilizing ICESat in February/March 2008 – a decline that the CryoSat-2 researchers don’t see of their information.

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These are two very completely different approaches to measuring sea ice, Petty stated, every with its personal limitations and advantages. CryoSat-2 carries a radar to measure top, versus ICESat-2’s lidar, and radar largely passes by means of snow to measure the highest of the ice. Radar measurements like those from CryoSat-2 might be thrown off by seawater flooding the ice, he famous. As well as, ICESat-2 remains to be a younger mission and the pc algorithms are nonetheless being refined, he stated, which might finally change the thickness findings.

“I feel we’re going to study so much from having these two approaches to measuring ice thickness. They is perhaps giving us an higher and decrease certain on the ocean ice thickness, and the best reply might be someplace in between,” Petty stated. “There are the explanation why ICESat-2 estimates might be low, and the explanation why CryoSat-2 might be excessive, and we have to do extra work to know and produce these measurements in keeping with one another.”

A view of the Arctic Ocean with month-to-month common sea ice thickness spanning November 2018 to March 2019. Low values are depicted in mild blue, and better values (5 meters) are depicted in magenta. Credit: NASA’s Scientific Visualization Studio Measuring Sea Ice Thickness with ICESat-2

With ICESat-2 and CryoSat-2 utilizing two completely different strategies to measure ice thickness – one measuring the highest of the snow, the opposite the boundary between the underside of the snow layer and the highest of the ice layer – however researchers realized they may mix the 2 to calculate the snow depth.

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“That is the primary time ever that we will get snow depth throughout your entire Arctic Ocean’s sea ice cowl,” stated Ron Kwok, a sea ice scientist at NASA’s Jet Propulsion Laboratory in Southern California and creator of one other examine in JGR Oceans. “The Arctic area is a desert – however what snow we do get is essential when it comes to the local weather and insulating sea ice.”

The examine discovered that snow begins build up slowly in October, when newly fashioned ice has a mean of about 2 inches (5 centimeters) of snow on it and multiyear ice has a mean of 5.5 inches (14 cm) of snow. Snowfall picks up later within the winter in December and January and reaches its most depth in April, when the comparatively new ice has a mean of 6.7 inches (17 cm) and the older ice has a mean of 10.6 inches (27 cm) of snow.

When the snow melts within the spring, it might pool up on the ocean ice – these soften ponds take up warmth from the Solar and may heat up the ice sooner, simply one of many impacts of snow on ice.

For extra info on ICESat-2, go to www.nasa.gov/icesat-2 or icesat-2.gsfc.nasa.gov

By Kate Ramsayer

NASA’s Goddard Area Flight Heart, Greenbelt, Maryland Final Up to date: Might 14, 2020 Editor: Kate Ramsayer

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