Hola amigos: A VUELO DE UN QUINDE EL BLOG., la Agencia Espacial NASA, nos informa del aumento de energía solar absorbida en el Ártico, los instrumentos designados en la investigación han observado un marcado incremento de la radiación solar absorbida en el Ártico desde el año 2,000, una tendencia que se alinea al mismo tiempo decrece el deshielo durante el mismo tiempo.
Mientras que el hielo marino es sobre todo blanco y refleja los rayos del sol, el agua del océano es oscura y absorbe la energía del sol a una velocidad superior. Una disminución en el albedo de la región - su reflectividad, en efecto - ha sido una de las principales preocupaciones entre los científicos ya que la cubierta de hielo marino del Ártico en verano comenzó disminuyendo en las últimas décadas. A medida que más de la energía del sol es absorbida por el sistema climático, mejora el calentamiento en curso en la región, que es más pronunciada que en cualquier otro lugar del planeta.
NASA satellite instruments have observed a marked increase in solar radiation
absorbed in the Arctic since the year 2000 – a trend that aligns with the steady
decrease in Arctic sea ice during the same period.
While sea ice is mostly white and reflects the sun’s rays, ocean water is
dark and absorbs the sun’s energy at a higher rate. A decline in the region’s
albedo – its reflectivity, in effect – has been a key concern among scientists
since the summer Arctic sea ice cover began shrinking in recent decades. As more
of the sun’s energy is absorbed by the climate system, it enhances ongoing
warming in the region, which is more pronounced than anywhere else on the
planet.
Since the year 2000, the rate of absorbed solar radiation in the Arctic in
June, July and August has increased by five percent, said Norman Loeb, of NASA’s
Langley Research Center, Hampton, Virginia. The measurement is made by NASA’s
Clouds and the Earth’s Radiant Energy System (CERES) instruments, which fly on
multiple satellites.
The Arctic Ocean is absorbing more of the sun's
energy in recent years as white, reflective sea ice melts and darker ocean
waters are exposed. The increased darker surface area during the Arctic summer
is responsible for a 5 percent increase in absorbed solar radiation since
2000.
Image Credit:
NASA Goddard's Scientific Visualization Studio/Lori
Perkins
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While a five percent increase may not seem like much, consider that the rate
globally has remained essentially flat during that same time. No other region on
Earth shows a trend of potential long-term change.
When averaged over the entire Arctic Ocean, the increase in the rate of
absorbed solar radiation is about 10 Watts per square meter. This is equivalent
to an extra 10-watt light bulb shining continuously over every 10.76 square feet
of Arctic Ocean for the entire summer.
Regionally, the increase is even greater, Loeb said. Areas such as the
Beaufort Sea, which has experienced the some of the most pronounced decreases in
sea-ice coverage, show a 50 watts per square meter increase in the rate of
absorbed solar radiation.
Five new NASA Earth science missions are launching
in 2014 to expand our understanding of Earth’s changing climate and
environment.
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“Advances in
our understanding of Arctic climate change and the underlying processes that
influence it will depend critically upon high quality observations like these
from CERES,” Loeb said.
As a region, the Arctic is showing more dramatic signs of climate change than
any other spot on the planet. These include a warming of air temperatures at a
rate two to three times greater than the rest of the planet and the loss of
September sea ice extent at a rate of 13 percent per decade.
While these CERES measurements could ultimately become another of those signs
of dramatic climate change, right now scientists say they have obtained the bare
minimum of a data record needed to discern what’s happening over the long
term.
Getting data beyond 15 years will allow scientists to better assess if recent
trend falls outside the realm of natural variability, said Jennifer Kay, an
atmospheric scientist at the Cooperative Institute for Research and
Environmental Science at the University of Colorado.
“We need long time series to detect climate change signals over the internal
variability. For example, observed sea ice loss over the last 30 years cannot
be explained by natural variability alone.” Kay said. “Fifteen years is long,
but climate is often defined as the average over 30 years – so we are only
half-way there with the CERES observations.”
Kay and colleagues have also analyzed satellite observations of Arctic clouds
during this same 15-year period. Kay’s research shows summer cloud amounts and
vertical structure are not being affected by summer sea ice loss. While
surprising, the observations show that the bright sea ice surface is not
automatically replaced by bright clouds. Indeed, sea ice loss, not clouds,
explain the increases in absorbed solar radiation measured by CERES.
Increasing absorbed solar radiation is causing multiple changes in the sea
ice cover, said Walt Meier, a sea ice scientist from NASA’s Goddard Space Flight
Center, Greenbelt, Maryland. Two of those changes include the timing of the
beginning of the melt season each year and the loss of older, thicker sea
ice.
The onset of the melt season in the high Arctic is now on average seven days
earlier than it was in 1982, Meier said. Earlier melting can lead to increased
solar radiation absorption. This is one step in a potential feedback cycle of
warming leading to melting, melting leading to increased solar radiation
absorption, and increased absorption leading to enhanced warming.
Since 2000, the Arctic has lost 1.4 million square kilometers (541,000 square
miles) of older ice that is more than 3 meters thick, which during winter has
essentially been replaced by ice that is less than 2 meters thick, according to
data provided by Mark Tschudi at the University of Colorado. Once again, Meier
said, this trend is a step in a feedback cycle.
“Having younger and thus thinner ice during winter makes the system more
vulnerable to ice loss during the summer melt season,” Meier said.
CERES instruments are currently flying on the Terra, Aqua and Suomi-NPP
satellites. The Terra satellite launched Dec. 18, 1999, and CERES first started
collecting Arctic data in 2000 so 2015 will mark 15 continuous years of CERES
measurements over the Arctic.
The instruments include three radiometers – one measuring solar radiation
reflected by Earth (shortwave), one measuring thermal infrared radiation emitted
by Earth (longwave), and one measuring all outgoing radiation, whether emitted
or reflected.
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Guillermo Gonzalo Sánchez Achutegui
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