Arctic
sea ice was at a record low wintertime maximum extent for the second straight
year. At 5.607 million square miles, it is the lowest maximum extent in the
satellite record, and 431,000 square miles below the 1981 to 2010 average
maximum extent.
Credit: NASA Goddard's Scientific
Visualization Studio/C. Starr
Arctic
sea ice appears to have reached a record low wintertime maximum extent for the
second year in a row, according to scientists at the NASA-supported National
Snow and Ice Data Center (NSIDC) and NASA.
Every year, the cap of frozen seawater floating on top of the Arctic Ocean and its neighboring seas melts during the spring and summer and grows back in the fall and winter months, reaching its maximum yearly extent between February and April. On March 24, Arctic sea ice extent peaked at 5.607 million square miles (14.52 million square kilometers), a new record low winter maximum extent in the satellite record that started in 1979. It is slightly smaller than the previous record low maximum extent of 5.612 million square miles (14.54 million square kilometers) that occurred last year. The 13 smallest maximum extents on the satellite record have happened in the last 13 years.
The
new record low follows record high temperatures in December, January and
February around the globe and in the Arctic. The atmospheric warmth probably
contributed to this lowest maximum extent, with air temperatures up to 10
degrees Fahrenheit above average at the edges of the ice pack where sea ice is
thin, said Walt Meier, a sea ice scientist at NASA's Goddard Space Flight
Center in Greenbelt, Maryland.
The
wind patterns in the Arctic during January and February were also unfavorable
to ice growth because they brought warm air from the south and prevented
expansion of the ice cover. But ultimately, what will likely play a bigger role
in the future trend of Arctic maximum extents is warming ocean waters, Meier
said.
"It
is likely that we're going to keep seeing smaller wintertime maximums in the
future because in addition to a warmer atmosphere, the ocean has also warmed
up. That warmer ocean will not let the ice edge expand as far south as it used
to," Meier said. "Although the maximum reach of the sea ice can vary
a lot each year depending on winter weather conditions, we're seeing a
significant downward trend, and that's ultimately related to the warming
atmosphere and oceans." Since 1979, that trend has led to a loss of
620,000 square miles of winter sea ice cover, an area more than twice the size
of Texas.
This
year's record low sea ice maximum extent will not necessarily result in a
subsequent record low summertime minimum extent, Meier said. Summer weather
conditions have a larger impact than the extent of the winter maximum in the
outcome of each year's melt season; warm temperatures and summer storms make
the ice melt fast, while if a summer is cool, the melt slows down.
Arctic
sea ice plays an important role in maintaining Earth's temperature--its bright
white surface reflects solar energy that the ocean would otherwise absorb. But
this effect is more relevant in the summer, when the sun is high in the sky in
the Arctic, than in the winter, when the sun doesn't rise for months within the
Arctic Circle. In the winter, the impact of missing sea ice is mostly felt in
the atmosphere, said Jennifer Francis, a climate scientist at Rutgers
University in New Brunswick, New Jersey.
"In
places where sea ice has been lost, those areas of open water will put more
heat into the atmosphere because the air is much colder than unfrozen sea
water," Francis said. "As winter sea ice disappears, areas of
unusually warm air temperatures in the Arctic will expand. These are also areas
of increased evaporation, and the resulting water vapor will contribute to increased
cloudiness, which in winter, further warms the surface."
https://www.sciencedaily.com/releases/2016/03/160328195126.htm
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