Phytoplankton from Outer Space

UCSB Study Chronicles Global Warming’s Effect on Oceans

by Nick Welsh

UCSB professor David Siegel is the
scientific equivalent of the seasick sailor: He’s a
green-about-the-gills oceanographer. Twenty years after the fact,
Siegel — now 47 — still shudders to remember the horrors he
suffered during a five-week scientific ocean-faring expedition with
Scripps Institute back when he was a UC San Diego student. At the
time, Siegel was studying to become an engineer. But most of the
jobs in his field involved making bombs or working for the
Department of Defense, neither of which was acceptable to Siegel.
And despite the intense bodily distress inflicted by his early
oceanic research, he fell hopelessly in love. “You could say I was
hooked,” he recalled.

Siegel’s big challenge lay in figuring out how to study the
oceans without setting foot in a boat. For Siegel — a funny guy and
a self-described nerd — that salvation lay in the form of global
satellites. About 14 years ago, he began the first of his many
collaborations with NASA, the federal space agency whose numerous
satellites allow researchers to expand the scope of their inquiries
in ways previously unimaginable. Rather than traveling in
stomach-churning vessels whose top speed might equal a bicycle’s,
Siegel can now monitor the entire globe in two days, “moving” 100
kilometers almost in the blink of an eye.

For the past 15 years, Siegel has been involved with a research
effort, sponsored by NASA, to determine the effects of temperature
changes on the productivity of the oceans, or the extent to which
ocean life flourishes. Using photos taken during an eight-year
period from a global satellite built by Raytheon on Hollister
Avenue and launched from Vandenberg Air Force Base, Siegel and crew
examined the effect temperature changes had on phytoplankton, tiny
microscopic sea plants that serve as essential food for all oceanic
life. Two weeks ago, Siegel and his team went public, publishing
their findings for the first time in the pages of the prestigious
scientific journal Nature. Given the report’s significance in the
global warming debate, the group’s findings have been picked up by
most mainstream media outlets and given extensive airplay on
National Public Radio.

Boiled down to its bare bones, the report concludes that there
is almost certainly a direct and powerful connection between water
temperature and phytoplankton health. From sea to sea, Siegel found
that as the ocean waters warmed, phytoplankton populations dropped
and seas turned bluer; when the waters cooled, phytoplankton
populations increased and seas turned greener.

Siegel said that in some ways he was not surprised by the
results, terming them “almost obvious.” He noted, for example, that
in Santa Barbara, ocean water turns much greener and algae blooms
under the cooling influence of “June gloom.” But what stunned and
surprised Siegel was the extent to which that same trend held true
for all 14,000 data collection points located in every ocean across
the globe. “We could aggregate all the places of the ocean and show
numerically that there was a relationship between temperature and
the ocean’s productivity,” he said. “We saw that regularly and we
saw that glaringly.” For example, he said, due to the influence of
La Niña during the first two years of the study — 1996 and
1997 — oceans were generally cooling off and becoming greener. But
from 1998 to 2004 — the last year of data collection — oceans have
generally increased in temperature and blueness and decreased in
productivity.

Siegel said he was surprised not just by the universality of the
relationship between temperature and productivity, but by the
strength of the relationship. Of the many mysterious factors that
could influence oceanic productivity, Siegel said temperature
proved unusually powerful. “I had my suspicions beforehand what the
trend would be,” he said, “but I was astounded by how tight the
coupling was.”

What makes Siegel’s work so important in the global warming
discussion is not that he discovered the oceans were heating up at
a faster rate than anyone thought; he didn’t. In fact, Siegel said,
some parts of the ocean are still cooling off. Rather, the real
importance of his findings lies in the universality of the
temperature/productivity link, coupled with how vital phytoplankton
are to the web of life on planet Earth. “Obviously this is
speculative, but if we ratchet down on the fish food being
naturally produced, we might also be ratcheting down on the number
of fish out there to eat,” Siegel said.

And phytoplankton are not only the essential unit in the oceanic
food chain, but also account for roughly one-half of the planet’s
photosynthesis, the process by which plants convert sunlight into
energy. In that process, plants take in carbon dioxide and “exhale”
oxygen. If oceans absorb less carbon dioxide than they used to,
then presumably there will be more of it left in the atmosphere,
which could accelerate the pace of global warming. Experts estimate
that the planet’s oceans have warmed by about one degree Fahrenheit
in the past 100 years. “What happens in 2050 when ocean
temperatures might increase by two degrees?” Siegel asked. “Plant
life in the ocean will certainly suffer.” But if and when that
happens, Siegel will have provided future scientists a solid
baseline of reliable data from which to measure the decline.

Siegel is quick to stress that he was just one participant in a
broad multidisciplinary effort, working to increase the scientific
understanding “one brick at a time.” But his peers at UCSB, like
paleoclimatologist Professor David Lee (who was uninvolved in the
project), credited Siegel for figuring out the mathematical
algorithms necessary to accurately translate the green picked up
from the space satellite — indicating phytoplankton’s green
chlorophyll — into a reliable indicator of the plant’s health and
vitality. These calculations involved placing a delicate optical
instrument on the tip of a spacecraft and sending it hurtling into
space, then sifting through a tidal wave of visual information,
some of which had been distorted by radiation, particulate matter
in the atmosphere, and even clouds. “Dave’s been a real pioneer in
developing the methodology that lets the satellites detect these
changes in color,” said Lee. “It’s a very good study. It doesn’t
mean that the ocean’s ecosystem is about to crash, but it’s another
way of recognizing and quantifying how we’re messing with something
on a really grand scale.”

The scientific reason why a warming trend means trouble for
oceanic plant life is that it restricts the mixing of shallow
waters — where the phytoplankton live — with the colder, deeper
waters that contain nutrients necessary for phytoplankton to
thrive. The greater the difference in temperature between the two
layers, the less likely it is that hotter surface waters will make
the plunge down to where the nutrients are, and vice versa. Simply
put, global warming leads to a more stratified ocean.

The oceanic effects of global warming have been recognized by
some scientists and businesses, which are seeking to remedy it by
artificially reconnecting the upper and lower strata — thereby
jumpstarting the growth of phytoplankton. One company has proposed
doping the water with iron, one of the nutrients essential to
phytoplankton’s survival. In exchange, it hopes to lay claim to the
increased carbon dioxide that would be absorbed into the ocean as a
result of the thriving phytoplankton. Such “carbon offsets” are now
the subject of intense speculative interest. But given that
phytoplankton have a life span of only two days, it’s hard to know
how effective such a scheme would be — or to predict its possible
side effects.

Siegel for one was skeptical. “I go to meetings and I hear
people saying these things,” he said. “I know there’s venture
capital involved in such things, but I’m tempted to check their
reflexes to make sure they’re not stoned.”