There are twelve known isotopes of oxygen, including oxygen 13 to 24, of which oxygen 16, oxygen 17 and oxygen 18 are of the stable type. The other known isotopes are radioactive and all have half-lives of less than three minutes. USES: biological respiration, metallurgy and chemical engineering. But oxygen isotopes also play a role in Marine science, allowing scientists to calculate ocean temperatures numerically.

Three factors are known to influence the isotopes of oxygen in seawater. First, the glacial effect: when lighter oxygen isotopes enter high latitudes and fall as snow, the lighter water molecules are trapped in the glacier and cannot return to the ocean until they melt. Therefore, the average weight of oxygen isotopes in seawater was 1.0 ~ 1,7‰ heavier than that in the interglacial period. By contrast, if the glaciers were to melt completely today, the global average seawater oxygen isotope would change by -1.0‰. 2. Salinity and evaporation effects: when the regional seawater is affected by the injection of fresh water from tianshui or river, the seawater with lighter oxygen isotopes is mixed with the water, which makes the oxygen isotopes of seawater lighter, and the salinity effect becomes more obvious in the higher latitudes due to the lighter oxygen isotopes of the source water. At present, the oxygen isotopic value of Antarctic glacier is about -50 ~ -55‰, and the oxygen isotopic value of Greenland ice core is about -32 ~ -37‰, which is much lower than the current global average sea water oxygen isotope 0‰. Contrary to precipitation events, evaporation events will also affect the oxygen isotopic values of regional seawater. When vigorous evaporation takes place, water molecules with relatively light isotopic values will continue to leave the seawater and enter the atmosphere, making the oxygen isotopic values of regional seawater heavier than those of other seawater. 3. Lithospheric and hydrosphere exchange: It is an exchange process with a time scale of thousands of years, such as hydrothermal action and weathering near the mid-ocean ridge. O released from the lithosphere can change the value of seawater oxygen isotopes in the region.