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| © Joshua Stevens/NASA Earth Observatory |
By Jen Christensen, CNN
The ocean will not look the same color in the future. It won't turn
pink or anything radically different; the change will be more apparent
through optic sensors than though the human eye. But it serves as
anearly warning sign that global warming is significantly altering the
planet's ecosystems, according to a new study.
Essentially, climate change will make the blues of the ocean bluer
and the greens greener. Scientists figured this out by creating a global
model that simulates the growth of a tiny creature that lives in the
oceans and affects the color we see. Their research was published Monday
in the journal Nature Communications.
The ocean looks blue or
green to us because of a combination of how sunlight interacts with
water molecules and with whatever else lives in that water.
The molecules in water absorb all but the blue part of the spectrum of
sunlight, and the water reflects that blue color back. That's the color
we see.
The water looks greener when it has more phytoplankton,
tiny, microscopic organisms that, like plants, can use chlorophyll to
capture mostly the blue portions of the spectrum of sunlight. They then
use photosynthesis to create the chemical energy they need to live. When
there are more of these creatures in the water absorbing sunlight, they
make the water look greener. Conversely, if there are fewer
phytoplankton, the water looks bluer.
The creatures' growth is
dependent on how much sunlight, carbon dioxide and nutrients are around.
Climate change is altering the ocean currents, meaning there will be
fewer nutrients for phytoplankton to feed on in some areas, so there
will be a decline in their number in those regions.
Since the 1990s, satellites have taken regular measurements
of how much chlorophyll is in the ocean. Those levels can change
because of weather events or because of climate change. But using those
images to look at reflected light alone, the researchers in the new
study could distinguish what is specifically due to climate change. And
they noticed that there will be a significant shift in the color of the
oceans much earlier than was previously predicted, just looking at
chlorophyll changes.
The study predicts that the blues will
intensify, most likely in subtropical regions where phytoplankton will
decrease. These are areas near the equator like Bermuda and the Bahamas
that are already quite low in phytoplankton.
Regions where there
are a lot of nutrients, like in the Southern Ocean or parts of the
North Atlantic, will see even faster-growing phytoplankton because those
waters are warming with climate change. Those waters will look greener.
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| © Joshua Stevens/NASA Earth Observatory |
Climate change will bring a color change to half of the world's oceans by the end of the21st century, the
study says. That's bad for climate change on several levels: For one,
phytoplankton remove about as much carbon dioxide from the air as plants
and help regulate our climate, research shows. They are also key to other animals' survival.
"The change is not a good thing, since it will definitely impact the rest of the food web," said study co-author Stephanie Dutkiewicz, a principal research scientist in MIT's Department of Earth, Atmospheric, and Planetary Sciences.
"Phytoplankton are at the base, and if the base changes, it endangers
everything else along the food web, going far enough to the polar bears
or tuna or just about anything that you want to eat or love to see in
pictures."
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