Human Influences

Global Geochemical Experiments

Over the past 200 years or so, humans have altered the chemical composition of the atmosphere and oceans. Growing levels of carbon dioxide, methane, and nitrous oxides are present in the environment.

Meanwhile, industrial gases such as chlorofluorocarbons (CFCs) injected into the atmosphere have spread around the globe, altering chemical processes in the stratosphere. These gases, along with nuclear bomb test and reactor radionuclides, have dissolved into the surface ocean and have been carried into the interior of the ocean by currents.

Some chemical elements, like mercury and lead from gasoline, have been mobilized by humans multifold above their natural geochemical cycles and carried by the atmosphere and ocean currents to places far from their emission sources.

Three of the largest anthropogenic effects on ocean chemistry are acidification, loss of oxygen (hypoxia) in coastal oceans, and pollution. At MIT, our researchers are taking advantage of these “global geochemical experiments” to gain a better understanding of how the chemistry of our oceans works and the ways in which human activities may be changing the natural balance.