Humankind is messing with the ocean in entirely new ways.
On top of rising sea levels, ocean acidification and
increasing temperatures, new research shows that we are changing the chemistry
of the seas by doubling the Pacific's nitrogen.
(Image: Scientists aboard the research vessel Ka'imikai-O-Kanaloa
study ocean chemistry as part of the Hawaii Ocean Time-series (HOT) Program in
the North Pacific Ocean. Credit: Paul Lethaby, UH SOEST.)
The changes are due to human-generated nitrogen compounds
that are changing the composition of the ocean from one that is short on
nitrogen to one that has lots of nitroen and is short of phosphous. What that does is change the
fertilization of the marine world.
What does it all mean?
“The possible impacts of this anthropogenic perturbation on
the open-ocean nitrogen cycle are numerous,” say the authors of a new paper, Increasing
anthropogenic nitrogen in the North Pacific Ocean.
University of Hawai`i researcher David Karl joins co-authors
Il-Nam Kim, Kitack Lee, Nicolas Gruber, John L. Bullister, Simon Yang and Tae-Wook
Kim from Korea, Switzerland and NOAA in writing the paper, which appeared in
the Nov. 28, 2014 issue of the journal Science.
The found that reactive nitrogen from fossil fuel burning and
fertilizer that flows off agricultural and urban areas has doubled in the
oceans during the past century.
"This is a sobering result, one that I would not have
predicted," said Karl. "The
North Pacific is so vast it is hard to imagine that humans could impact the
natural nitrogen cycle."
This is not the first paper to see increasing levels of
nitrogen, but is dramatic in part because it finds the increase is present
throughout the ocean. Previous studies have found similar results nearer
continents, and especially near Asia.
“The possible impacts of this anthropogenic perturbation on
the open-ocean nitrogen cycle are numerous,” the paper says.
While it might seem that fertilizing the ocean could improve
productivity, in fact it might change productivity in unanticipated ways—favoring
species that like a higher nitrogen and lower phosphorus environment—with potentially
unfavorable results.
“If similar trends are confirmed in the Atlantic and Indian
Oceans, it would constitute another example of a global-scale alteration of the
Earth system. Further, the findings of this study of the North Pacific
highlight the need for greater controls on the emission of nitrogen compounds
during combustion and agricultural processes.,” said a University of Hawai`ipress release on the research.
The Swiss university ETH Zurich issued a press release that
explains the results this way:
“When fossil fuels are burned at high temperatures, such as
in coal and gas-fired power stations, nitrogen oxide and other reactive nitrogen
compounds are formed and released into the atmosphere. Agricultural activities
also have the same effect, when a part of the nitrogen found in fertiliser is
lost into the atmosphere in the form of nitrogen oxide or ammonia. These
emissions have risen dramatically in the past decades, particularly in East
Asia where they have grown by 40 per cent in the past 10 years.”
How does the nitrogen get into the ocean? “The increase of
the nitrate concentration in the North Pacific is mostly attributable to
combustion processes in East Asia and to a lesser extent from agricultural
activities in that region. The prevailing westerly winds carry these substances
across the Pacific, where the rain flushes them from the air into the sea,” the
Swiss university said.
Citation: I-N Kim, K Lee, N Gruber, D M Karl, J L Bullister,
S Yang, T-W Kim (2014). Increasing anthropogenic nitrogen in the North Pacific
Ocean. Science, 27 November 2014.
© Jan TenBruggencate 2014
No comments:
Post a Comment