Human induced industrial and agricultural processes have significantly caused the Ocean acidification. This fact was revealed in a study titled Increasing anthropogenic nitrogen in the North Pacific Ocean published in latest issue of Science Magazine on 28 November 2014.
The study claimed that, recent increase in anthropogenic emissions of reactive nitrogen from northeastern Asia and the subsequent enhanced deposition over the extensive regions of the North Pacific Ocean (NPO) have led to a detectable increase in the nitrate (n) concentration of the upper ocean.
Main findings of the study
• The rate of increase of excess N relative to phosphate (P) was found to be highest (∼0.24 micromoles per kilogram per year) in the vicinity of the Asian source continent, with rates decreasing eastward across the NPO, consistent with the magnitude and distribution of atmospheric nitrogen deposition.
• This anthropogenically driven increase in the N content of the upper NPO may enhance primary production in this N-limited region, potentially leading to a long-term change of the NPO from being N-limited to P-limited.
• The rate of deposition of reactive nitrogen from the atmosphere to the open ocean has more than doubled globally over the last 100 years. This anthropogenic addition of nitrogen has reached magnitude comparable to about half of global ocean nitrogen.
In the study, 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.
The change in nitrate concentration between the 1960s and 2000s across the open North Pacific Ocean was assessed by David Karl, at the University of Hawaii, along with researchers from Korea, Switzerland and the U.S. National Oceanic and Atmospheric Administration.
When: 28 November 2014