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Tiny Gulf animals reveal past climate

Ancient plankton hold climate records

The new data will be used to develop better estimates of past conditions from analyses of microfossils in sediment cores.
The new data will be used to develop better estimates of past conditions from analyses of microfossils in sediment cores. (USGS)

St. Petersburg, FL – Sediment on the bottom of the Gulf's floor is unlocking climate secrets stretching back thousands of years and microfossils are holding the records.

Records of ancient temperatures can be deciphered by scientists looking at tree rings, ice cores, and microorganisms. These proxy sources of information show the climate has always changed over the eons on Earth. 

Most scientists agree the rate of global warming is unprecedented rising 170 times faster than natural forces since humans began emitting greenhouse gasses. 

Microfossils recovered from the northern Gulf of Mexico are used by the US Geological Society to assess what temperature and salinity had been before the industrial era.

The chemical composition left behind in the shells of tiny plankton animals is being used to develop better estimates of past conditions.

Plankton animals called foraminifera, or forams for short, live within the water and build a calcium-carbonate shell that chemically records the conditions of their ocean habitat.  

When ocean temperature increases, the foram will switch magnesium for calcium into its shell, thereby recording the change in temperature.  

So in effect, the higher the ocean temperature, the greater is the ratio between magnesium to calcium in its shell, and the lower the temperature, the smaller the ratio.

This archive of ocean temperature and past climate variability extends the record 2000 years in the past providing baseline data for present climate fluctuations. 


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