This satellite map shows dangerous arctic warming feedback loop (Wired UK)


Nasa


One of the ways our planet manages its heat budget is by storing
solar energy in the oceans. In recent years, the Arctic has been
taking in more than its usual share of heat energy, which could be
bad news for our steadily warming planet.

This latest dire climate update was presented by NASA
scientists here at American Geophysical Union meeting on
Dec. 17. The map above was made using heat-sensing, satellite-borne
instruments that measure the rate of solar radiation change. In the
Arctic, the rate of heat absorption has increased by more than 10
Watts of energy per square meter since 2000. In some areas — like
the big red blob representing the Beaufort Sea north of Alaska –
this rate has increased as much as 45 Watts per square meter.

Not all of the sun’s energy sticks around on Earth. Different
land surface types bounce it off back into space, while others
absorb it. Ice, snow and clouds are really reflective. Water
varies, depending on the angle of the sun. For the past
15 years, NASA has been using a satellite sensor called CERES
(on three different satellites, TerraAqua and 
Suomi-NPP) to calculate how much solar energy is being absorbed
versus bounced back into space.

Every summer, the Arctic ice cap partially melts away, and
freezes again in the winter, covering more or less (OK, mostly
less) the same area it has in the past. But, because recent
years have had record levels of sea ice loss, a lot of that winter
ice is barely a year or two old, and less than 6 feet thick. When
summer comes back around, this thin ice melts quickly, exposing the
ocean below to solar radiation. Since 1982, the average onset of
the annual summer melt season has moved up by seven days.

This creates a solar radiation feedback loop. The thin ice melts
earlier in the summer when the sun is higher in the sky,
which exposes the heat-sinking ocean surface to collect even
more solar radiation. This causes a feedback loop, as more heat is
absorbed into the ocean, which in turn causes more melting.
Currently, the average temperatures in the Arctic are rising twice
as fast as the rest of the globe.

In addition, the researchers originally thought the loss of sea
ice would result in more clouds forming over the Arctic, which
would make up for some of the lost sea ice by reflecting back
sunlight (the rest of the world’s oceans are covered by clouds much
of the time). However, the cloud cover isn’t filling in, and is in
fact being quite unpredictable. This is contributing to the overall
rate of solar energy absorption.

Atmospheric scientist Jennifer Kay of the University of
Colorado, a collaborator on this research, says it’s too soon to
use CERES data to confirm any long term climate trends. “Climate is
usually considered to be a 30 year average,” she said at a
press conference. As CERES has been collecting Arctic solar energy
data since 2000, this research is only about halfway done.

This article originally appeared on Wired.com

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19 December 2014 | 10:16 am – Source: wired.co.uk

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