“Even when it’s likely that we won’t have a record low, the sea ice is not showing any kind of recovery. It’s still in a continued decline over the long term,” said Walt Meier, a sea ice scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s just not going to be as extreme as other years because the weather conditions in the Arctic were not as extreme as in other years.”
Credits: NASA Goddard's Scientific Visualization Studio/Cindy Starr
The rate of ice loss picked up again during the first two weeks of August, and is now greater than average for this time of the year. A strong cyclone is moving through the Arctic, similar to one that occurred in early August 2012. Four years ago, the storm caused an accelerated loss of ice during a period when the decline in sea ice is normally slowing because the sun is setting in the Arctic. However, the current storm doesn’t appear to be as strong as the 2012 cyclone and ice conditions are less vulnerable than four years ago, Meier said.
“This year is a great case study in showing how important the weather conditions are during the summer, especially in June and July, when you have 24 hours of sunlight and the sun is high in the sky in the Arctic,” Meier said. “If you get the right atmospheric conditions during those two months, they can really accelerate the ice loss. If you don’t, they can slow down any melting momentum you had. So our predictive ability in May of the September minimum is limited, because the sea ice cover is so sensitive to the early-to-mid-summer atmospheric conditions, and you can’t foresee summer weather.”
Credits: NASA/Kate Ramsayer
As scientists are keeping an eye on the Arctic sea ice cover, NASA is also preparing for a new method to measure the thickness of sea ice – a difficult but key characteristic to track from orbit.
"We have a good handle on the sea ice area change," said Thorsten Markus, Goddard’s cryosphere lab chief. "We have very limited knowledge how thick it is."
The Ice, Cloud and land Elevation Satellite-2, or ICESat-2, will use lasers to try to get more complete answers of sea ice thickness. The satellite, slated to launch by 2018, will use a laser altimeter to measure the heights of Earth’s surface.
In the Arctic, it will measure the elevation of the ice floes, compared to the water level. However, only about one-tenth of sea ice is above the water surface; the other nine-tenths lie below.
To estimate the entire thickness of the ice floe, researchers will need to go beyond the above-water height measurements, and perform calculations to account for factors like the snow on top of the ice and the densities of the frozen layers. Scientists are eager to see the measurements turned into data on sea ice thickness, Markus said.
"If we want to estimate mass changes of sea ice, or increased melting, we need the sea ice thickness," he said. "It’s critically important to understanding the changes in the Arctic."
Contacts and sources:
By Maria-José Viñas and Kate Ramsayer
NASA's Goddard Space Flight Center