Earth's oceans found to be a much greater source of greenhouse gas than previously believed
A new study by MIT hasrevealed that the quantities of nitrous oxide (N2O),otherwise known as laughing gas, being released by the world's oceanshas been dramatically underestimated. Heightened levels of N2Ohave the potential to seriously influence the health of our planet'sozone layer, as the gas is around 300 times more potent than the moreprevalent menace of carbon dioxide emissions.
N2O iscreated, and subsequently largely destroyed, in the boundary betweenthe oxygen saturated layer of water near an ocean's surface, and theanoxic waters that lie beneath. Nitrogen is initiallyintroduced to the marine environment from a number of sources,including as a runoff from agricultural fertilizer in the form ofammonia. The nitrogen is then consumed by bacteria and marinemicrobes that produce N2O as a byproduct.
“The denitrifying bacteria that produce N2O also consume it, andit was thought that these two processes are pretty tightly coupled,”states Andrew Babbin, MIT postdoc at the Department of Civil andEnvironmental Engineering and lead author of a paper on the study. "But that’s not the case in the suboxiclayer, resulting in leftover N2O that leaksaway to the surface."
Prior to the study, itwas not well understood just how much of the gas was escaping theocean and entering the environment above, and the potential harm thatthis could be inflicting on our planet's fragile atmosphere.
Babbinand his team were able to gain a better understanding by making acomputer analysis of water samples from various depths at threedifferent locations in the eastern tropical North Pacific, in orderto determine denitrification rates for the region.
Results appear to showthat previous estimates on the quantities of N2O escapingthe oceans may have been off by as much as a factor of 10. By makinguse of recent climate models, Babbin and his team estimate that ourworld's oceans could be producing as much as 4 million metric tons ofN2O per year
This output of theharmful gas has the potential to seriously harm Earth's ozone layer,and it is predicted that production will rise as agricultural growthcontinues, introducing ever more nitrogen into Earth's oceans.