Hi all,
is there any information/paper if and possibly how the deltaO of the atmospheric oxygen has change in Earth's past?
Thanks,
Inga
Well,
the same mechanism controls the change in delta 18O in past or present, where,
the evaporation is a physical process in which energy-loaded water molecules move from the water phase to the vapor phase. Light water molecules evaporate more efficiently than heavy particles. Therefore, isotope differentiation occurs when partial evaporation of water. The vapor in light water molecules increases and is relatively reflected by negative δD and δ18O values. In contrast, the remaining water becomes relatively richer in heavy isotopes, and is reflected in positive δD and δ18O values. Isotope separation is more efficient if the vapor produced is constantly removed by the wind blowing over the evaporation water body.
Regards
Paleoclimatology Introduction Written in the Earth
A Record from the Deep The Ice Core Record Climate Close-up Explaining the Evidence
Understanding the Past to Predict the Future
As air cools by rising into the atmosphere or moving toward the poles, moisture begins to condense and fall as precipitation. At first, the rain contains a higher ratio of water made of heavy oxygen, since those molecules condense more easily than water vapor containing light oxygen. The concentration of 18O in precipitation decreases with temperature. The coldest sites, in locations such as Antartica and Greenland, have about 5 percent less 18O than ocean water. (Graph adapted from Jouzel et al., 1994) The remaining moisture in the air becomes depleted of heavy oxygen as the air continues to move poleward into colder regions. As the moisture reaches the upper latitudes, the falling rain or snow is made up of more and more water molecules containing light oxygen. Water vapor gradually loses 18O as it travels from the equator to the poles. Because water molecules with heavy 18O isotopes in them condense more easily than normal water molecules, air becomes progressively depleted in 18O as it travels to high latitudes and becomes colder and drier. In turn, the snow that forms most glacial ice is also depleted in 18O.
As glacial ice melts, it returns 16O-rich fresh water to the ocean. Therefore, oxygen isotopes preserved in ocean sediments provide evidence for past ice ages and records of salinity.
- Badges
- Science topic
- Similar topics
- Geoscience
- Atmospheric Sciences
- Atmosphere