Consequently any processes that affect the ocean uptake of CO2 can have an effect on global warming.
Various nitrogen compounds, especially nitrates and ammonium, play an important role in oceans photosynthesis by acting as fertilizers that stimulate the growth of marine organisms. Because of human activities, the emission rates of these compounds have increased greatly over the last 100 years. The transport of these compounds to the oceans, mostly through the atmosphere, have acted to increase the draw-down of CO2 from the atmosphere.
The paper in Science compares emissions of nitrogen compounds in the year 1860, before humans had a great impact on pollution emissions, with current emissions. Today pollutant nitrogen deposition to the oceans accounts for about ten percent of the draw-down of CO2 from the atmosphere to the ocean. However, the deposition of these pollutants also results in the increased emissions of nitrous oxide, N2O, which is also a potent greenhouse gas. The net effect is that the N2O emissions offset about one-third of the effects of the increased drawdown of CO2 due to pollution deposition.
The team who wrote the paper appearing in Science also estimates emissions for the year 2020 using scenarios from the IPCC report. All of us are concerned that the amount of anthropogenic nitrogen transported to the oceans will to continue to rise in the future, commented Prospero.
|Contact: Barbra Gonzalez|
University of Miami Rosenstiel School of Marine & Atmospheric Science