Wednesday, December 31, 2014

Yet another way humans are messing with the oceans: doubling nitrogen.

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

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