TIM eMagazine Vol.3 Issue 11
A new MIT study finds that over
the coming decades climate
change will affect the ocean’s
color, intensifying its blue
regions and its green ones
Credit: NASA Earth Observatory
This time around, the researchers added a new element to
the model, that has not been included in other ocean modeling
techniques: the ability to estimate the specific wavelengths of light
that are absorbed and reflected by the ocean, depending on the
amount and type of organisms in a given region.
“Sunlight will come into the ocean, and anything that’s in the
ocean will absorb it, like chlorophyll,” Dutkiewicz says. “Other things
will absorb or scatter it, like something with a hard shell. So it’s a
complicated process, how light is reflected back out of the ocean to
give it its color.”
When the group compared results of their model to actual
measurements of reflected light that satellites had taken in the
past, they found the two agreed well enough that the model could
be used to predict the ocean’s color as environmental conditions
change in the future.
“The nice thing about this model is, we can use it as a laboratory,
a place where we can experiment, to see how our planet is going to
change,” Dutkiewicz says.
A signal in blues and greens
As the researchers cranked up global temperatures in the model,
by up to 3 degrees Celsius by 2100 — what most scientists predict
will occur under a business-as-usual scenario of relatively no action
to reduce greenhouse gases — they found that wavelengths of light
in the blue/green waveband responded the fastest.
What’s more, Dutkiewicz observed that this blue/green waveband
showed a very clear signal, or shift, due specifically to climate
change, taking place much earlier than what scientists have
previously found when they looked to chlorophyll, which they
projected would exhibit a climate-driven change by 2055.
“Chlorophyll is changing, but you can’t really see it because of its
incredible natural variability,” Dutkiewicz says. “But you can see a
significant, climate-related shift in some of these wavebands, in the
signal being sent out to the satellites. So that’s where we should be
looking in satellite measurements, for a real signal of change.”
According to their model, climate change is already changing
the makeup of phytoplankton, and by extension, the color of the
oceans. By the end of the century, our blue planet may look visibly
altered.
“There will be a noticeable difference in the color of 50 percent
of the ocean by the end of the 21st century,” Dutkiewicz says. “It
could be potentially quite serious. Different types of phytoplankton
absorb light differently, and if climate change shifts one community
of phytoplankton to another, that will also change the types of food
webs they can support. “
This research was supported, in part, by NASA and the
Department of Energy. http://news.mit.edu
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