Even more bad global warming news
While everyone (but seemingly the media) is on basically the same page with the fact that global warming is a human caused problem — and one we need to fix the effects of this change are still coming to light. Human-induced changes to Earth’s carbon cycle – for example, rising atmospheric carbon dioxide and ocean acidification – have been observed for decades. However, a new study showed human activities, in particular industrial and agricultural processes, have also had significant impacts on the upper ocean nitrogen cycle.
The rate of deposition of reactive nitrogen (i.e., nitrogen oxides from fossil fuel burning and ammonia compounds from fertilizer use) from the atmosphere to the open ocean has more than doubled globally over the last 100 years. This anthropogenic addition of nitrogen has reached a magnitude comparable to about half of global ocean nitrogen fixation (the natural process by which atmospheric nitrogen gas becomes a useful nutrient for organisms).
The multi-international team worked to assess changes in nitrate concentration between the 1960s and 2000s across the open North Pacific Ocean.
Their analysis, which could discern human-derived nitrogen from natural nitrogen fixation, revealed that the oceanic nitrate concentration increased significantly over the last 30 years in surface waters of the North Pacific due largely to the enhanced deposition of nitrogen from the atmosphere.
“This is a sobering result, one that I would not have predicted,” said David Karl, Professor of Oceanography. “The North Pacific is so vast it is hard to imagine that humans could impact the natural nitrogen cycle.”
The researchers used ocean data in conjunction with the state-of-the-art Earth System Model to reconstruct the history of the oceanic nitrate concentration and make predictions about the future state of the North Pacific Ocean. Their assessment revealed a consistent picture of increasing nitrate concentrations, the magnitude and pattern of which can only be explained by the observed increase in atmospheric nitrogen deposition.
Enhanced nitrogen deposition has several potential ecological ramifications. Because biological activity is limited by nitrate availability in the North Pacific Ocean, the input of new nitrogen from the atmosphere may increase photosysnthesis in the sunlit layers and export of carbon-rich organic material out of the surface ocean into the deep.
“The burgeoning human population needs energy and food – unfortunately, nitrogen pollution is an unintended consequence and not even the open ocean is immune from our daily industrial activities,” said Karl.
Given the likelihood that the magnitude of atmospheric nitrogen deposition will continue to increase in the future, the North Pacific Ocean could rapidly switch to having surplus nitrate. Thus, past and future increases in atmospheric nitrogen deposition have the potential to alter the base of the marine food web; and, in the long term, the structure of the ecosystem.
In particular, the shift in nutrient availability could favor marine organisms that thrive under the high nitrate and low phosphorus conditions. 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.
While the media makes it sound like there is some “controversy” about this issue, the fact of the matter is that science is clear on the facts. Roughly 97% of scientific papers show that we are the problem (and lets face it the other 3% aren’t even necessarily against the idea, they are mostly inconclusive results).
To put it another way, if 97 out of 100 doctors said you have cancer and need life saving treatment now — while the other three say you’re just fine — who would you trust?
Kim IN, Lee K, Gruber N, Karl DM, Bullister JL, Yang S, & Kim TW (2014). Chemical oceanography. Increasing anthropogenic nitrogen in the North Pacific Ocean. Science (New York, N.Y.), 346 (6213), 1102-6 PMID: 25430767