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June 17, 2004
NASA Data Shows Hurricanes Help Plants
Bloom in “Ocean Deserts”
Whenever a hurricane races across the
Atlantic Ocean, chances are phytoplankton will
bloom behind it. According to a new study using
NASA satellite data, these phytoplankton blooms
may also affect the Earth’s climate and
carbon cycle.
Dr. Steven Babin, a researcher at the Johns
Hopkins University Applied Physics Laboratory in
Laurel, Md., studied 13 North Atlantic hurricanes
between 1998 and 2001. Ocean color data from the
SeaWiFS instrument on the SeaStar satellite were
used to analyze levels of chlorophyll, the green
pigment in plants. The satellite images showed
tiny microscopic ocean plants, called
phytoplankton, bloomed following the storms.
“Some parts of the ocean are like
deserts, because there isn’t enough food
for many plants to grow. A hurricane’s high
winds stir up the ocean waters and help bring
nutrients and phytoplankton to the surface, where
they get more sunlight, allowing the plants to
bloom,” Babin said.
Previous research has relied largely on
sporadic, incomplete data from ships to
understand how and when near-surface
phytoplankton bloom. “This effect of
hurricanes in ocean deserts has not been seen
before. We believe it is the first documented
satellite observation of this phenomenon in the
wake of hurricanes,” Babin noted.
“Because 1998 was the first complete
Atlantic hurricane season observed by this
instrument, we first noticed this effect in late
1998 after looking at hurricane Bonnie,”
Babin said.
The study found the physical make-up of a
storm, including its size, strength and forward
speed, is directly related to the amount of
phytoplankton that blooms. Bigger storms appear
to cause larger phytoplankton blooms. An
increased amount of phytoplankton should have
more chlorophyll, which satellite sensors can
see.
Hurricane-induced upwelling, the rising of
cooler nutrient-rich water to the ocean surface,
is also critical in phytoplankton growth. For two
to three weeks following almost every storm, the
satellite data showed phytoplankton growth. Babin
and his colleagues believe it was stimulated by
the addition of nutrients brought up to the
surface.
Whenever the quantity of plants increases or
decreases, it affects the amount of carbon
dioxide in the atmosphere. As phytoplankton grow,
they absorb carbon dioxide, a heat-trapping
greenhouse gas. The gas is carried to the ocean
floor as a carbon form when the tiny plants die.
This enables atmospheric carbon to get into the
deep ocean. It is one of several natural
processes that contribute to Earth’s carbon
cycle.
By stimulating these phytoplankton blooms,
hurricanes can affect the ecology of the upper
ocean. Phytoplankton is at the bottom of the food
chain. The factors that influence their growth
also directly affect the animals and organisms
that feed on them. In addition, since
climate-related phenomena like El Niño may
change the frequency and intensity of hurricanes,
storm-induced biological activity may have even
greater contributions to future climate
change.
Scientists are still trying to determine how
much carbon dioxide might be removed from such a
process. “Better knowledge of the carbon
cycle will improve our understanding of global
ecology and how climate change might affect
us,” Babin said.
The research appeared as a paper in a recent
issue of the Journal of Geophysical
Research-Oceans. Study co-authors include J.A.
Carton, University of Maryland, College Park,
Md.; T.D. Dickey, Ocean Physics Laboratory,
University of California, Santa Barbara, Calif.;
and J.D. Wiggert, Center for Coastal Physical
Oceanography, Old Dominion University, Norfolk,
Va.
NASA’s Earth Science Enterprise funded
part of the research. The Enterprise is dedicated
to understanding the Earth as an integrated
system and applying Earth System Science to
improve climate, weather, and natural hazard
prediction using the unique vantage point of
space.
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Contacts:
Gretchen Cook-Anderson
Headquarters, Washington
Phone: 202/358-0836
Rob Gutro/Mike Bettwy
Goddard Space Flight Center, Greenbelt, Md.
Phone: 301/286-4044
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Hurricanes Leave Plankton in Their
Wake
For two to three weeks following almost every
storm, the SeaWiFS data showed
greater-than-normal phytoplankton growth,
stimulated by the additional nutrients brought up
to the surface. SeaWiFS took the following images
of Hurricane Isabel on September 13th
and 18th of 2003. As the hurricane
passes, it leaves behind it a trail of plankton
blooms, evident by the rapid change in
chlorophyll amounts. The lighter blue areas in
the hurricane’s wake represent higher
amounts of chlorophyll. Credit: NASA/Orbimage
Ocean’s Overall Health Influenced
by Hurricanes
As a hurricane passes over the Atlantic, cooler
water brings phytoplankton and nutrients to the
surface. Bigger storms cause larger plankton
blooms and more plankton absorb a greater amount
of carbon from our atmosphere. As phytoplankton
die, a major portion sink to the bottom of the
ocean, becoming what oceanographers call
“marine snow.” Credit: NASA
Colder Water Left in Hurricane
Isabel’s Wake
In this visualization, red and orange indicate
water at 82 F or warmer. As Hurricane Fabian
drives through a large patch of warm water, it
leaves a colder water trail behind (seen in
blue). Hurricane Isabel hits the same area and
takes a different path, leaving another cold
trail behind. The AMSR-E instrument on board the
Aqua satellite provided data for this animation
from August 22 to September 17, 2003. Credit:
NASDA/NASA
Planet-Wide Plankton
Blooms
Using five years of data from the SeaWiFS
instrument, scientists have taken the
Earth’s pulse. Every spring, phytoplankton
spread across the North Atlantic in one of the
largest “blooms” on the planet. In
this visualization, the phytoplankton colony
shown in green covers an area larger than the
Amazon rainforest in South America.
Credit: NASA/Orbimage
Small-sized Friends, Super-sized
Effects
Phytoplankton may be humankind’s smallest
friend. These microscopic single-celled organisms
are the foundation for the oceanic food chain.
Our oceans teem with them. Despite their size,
they play a major role in the carbon cycle
affecting every form of life on Earth. Right now,
tiny phytoplankton produce almost half the oxygen
you breathe. Credit: NASA
Before and After Bonnie
NASA’s SeaWiFS instrument took the data
for these before-and-after Hurricane Bonnie
images. The excess chlorophyll is evident off the
coast as a bright green patch. These two images
developed by Dr. Babin in August 1998 first
alerted his team to the phytoplankton blooms left
in a hurricane’s wake. Credit: JHUAPL
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