Research Suggests
Dynamic Forces At Work in Arctic Ice
Despite its image as a static, frozen wasteland, the dynamic ice pack above
the Arctic Circle plays an important role in regulating the Earth's climate.
That's the focus of research conducted at NASA's Laboratory for Hydrospheric
Processes at the Goddard Space Flight Center. Unlike Antarctica, the ice
covered continent capping the South Pole, there is no land covering the
North Pole. But study of the northern pack ice shows that it's not only
more complex than initially thought, but also highly influential in the
health of the planet.
Microwave Analysis
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| Winter |
Summer |
View High Resolution Winter Image
View High Resolution Summer Image
Research and data collection of Arctic Ocean ice isn't easy. But using
data collected by a number of different satellites from 1978 to 1998, scientists
have been able to stitch together a quality controlled record of sea ice in that
part of the world. The data used to create this visualization comes from
different instruments onboard a group of satellites: the scanning multichannel
microwave radiometer attached to the Nimbus 7 satellite, and the special sensor
microwave imagers attached to the Defense Meteorological Satellite Program's
F8, F11, and F13 satellites. Part of the challenge for researchers was in the
elimination of bad data, from atmospheric interference to instrument
calibration issues and more. The following two visualizations present average
annual polar ice concentrations for the nineteen-year period studied. The first
visualization displays average ice concentrations in March, the seasonal maximum;
the second visualization shows the seasonal minimum, with measurements taken in
September.
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| March 1979 |
September 1979 |
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| March 1998 |
September 1998 |
View High Resolution March, 1979, Image
View High Resolution September, 1979, Image
View High Resolution March, 1998, Image
View High Resolution September, 1998, Image
The Dynamic Ice Pack
As part of their research into polar ice trends, scientists collected
data on the annual spread and recession of ice around the North Pole. One of
the features made most clear by their efforts is how the northern ice pack
is a dynamic and complex environment, showing seasons much like the rest of
the world. In spring and summer, the northern ice pack shrinks and in autumn
and winter, it grows. The scientists on this project used observations
of seasonal changes in the ice to determine if biannual averages were changing
over time. In this visualization, 365 daily measurements of ice concentration are shown for the year 1998.
Ice Concentrations-Changes over Time
View High Resolution Image
Over a nineteen-year period, the total concentration of ice over the
northern part of the globe has decreased, but just slightly. At first glance
this visualization appears to be a simple quantitative comparison of North Pole
ice over time. In fact it is more subtle. This visualization shows comparative
concentration, that is, how much area is covered by ice. It does not compare
total amount of ice, nor thickness, nor density. Concentration in this case
refers to amount of open water visible from space. In these images, blue
represents ice concentrations in 1979 and red represents ice concentrations
in 1998.
Charting Change in a Computer
View High Resolution 1940 Image
View High Resolution 2000 Image
View High Resolution 2060 Image
Part of the ongoing research into polar ice trends encompasses evaluation
from sophisticated computer models. At the Geophysical Fluid Dynamics Laboratory
at Princeton University, run by NASA's sibling agency NOAA, researchers modeled
a 5,000 year period to see how polar ice might behave over time depending
on several different variables. This visualization shows a 120-year slice
of that complete model, essentially offering a research window on to experimental
processes that require longer time frames than human lifetimes. According
to the model shown here, projecting a period from 1940 to 2060, there is evidence
to suggest human factors have had a measurable effect on Arctic ice decreases.
Reflectivity and Heating-The
Global Role of the Polar Caps
Click here to View QuickTime
Click here to View High Resolution Image
The polar caps not only hold much of the planet's total fresh water, but also
play an important role in regulating the Earth's temperature. The relevant
characteristic is called albedo. It's a measure of how much radiation, or
light, is reflected from a body. Similar to how a white shirt helps keep a
person cooler in the summer than a black shirt, the vast stretches of polar
ice covering much of the planet's top and bottom reflect large amounts of
solar radiation falling on the planet's surface. Were the ice caps to appreciably
recede, sunlight that otherwise would have been reflected back into space
would get absorbed by the darker, denser mass of ocean and land beneath. As
light is absorbed, the environment is heated, thus intensifying a feedback
loop: a warmer planet yields more ice melting thus an even warmer planet.
Is the Ocean Rising?
Click here to View QuickTime
Click here to View High Resolution Image
This animation provides a more close-up perspective of the relationship between
ice and solar reflectivity. As glaciers, the polar caps, and in this case,
icebergs melt, less sunlight gets reflected into space. It is instead absorbed
into the oceans and land, thus raising the overall temperature, and adding
energy to a vicious circle. Of the many concerns voiced by scientists who
study global warming trends, rising ocean levels is one of the most dramatic.
An average rise in global ocean levels of just a few inches could have devastating
effects on coastal towns, cities, and ecosystems. Why then is even the slightest
risk of a shrinking polar cap not sounding alarms all across the world's lowland
regions?
It comes down to a simple principal proved thousands of years ago by the
Greek philosopher and scientist Archimedes. He showed that a body, in this case
the floating ice of the North Pole, immersed in a fluid is buoyed up by a force
equal to the weight of the displaced fluid. In other words, since the northern
pack ice is already floating its melting would not independently cause ocean
levels to rise. However, the attending planetary conditions necessary to
facilitate polar melting would likely have other enormous effects on the
environment, including the likely melting of the southern polar cap. As the ice
over Antarctica is NOT floating, a corresponding rise in the world's sea level
would almost certainly result if it melted.
This multimedia project is the work of a dedicated team of researchers,
animators, and media specialists. A companion video to this web site is
available from NASA-TV. Below are a list of agencies, departments, and
researchers who provided expertise and data for this production:
Please give credit for these images to:
NASA - Goddard Space Flight Center
Scientific Visualization Studio
Television Production NASA-TV/GSFC
Arctic Sea Ice Changes
Laboratory for Hydrospheric Processes
Senior Scientist in GSFC's Oceans and Ice Branch:
Dr Claire Parkinson
Content Preparation and Project Production:
Michael Starobin
Click here to read the Press Release.
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