Historic climate data stored on the ocean floor in microscopic fossils

October 29, 2015 - 06:39

The climate is always changing. Mohamed Ezat has investigated climate changes in the Norwegian and North Atlantic seas that have occurred over the past 135 000 years.

In the picture above is an example of the the microfossils that Ezat used to conduct his research. To the left is a benthic foraminifera (single-cell organism with calcite shells that can only be found on or beneath the ocean floor) and to the right a planktonic foraminifera (microorganism that lives near the ocean surface). The calcite shell composition is affected by temperature, pH, and CO2 concentrations. (Photo: Rasmussen and Thomsen)

The sea is a very important regulator of the global climate. It circulates heat and affects the concentration of greenhouse gases in the atmosphere. 

The exchange of hot surface water from the sea area near the equator, and cold deep sea water from the Arctic is an important part of the global sea circulation. 

Mohamed Ezat has studied how this water exchange and how the carbon cycle in the ocean have been affected by the last ice ages, and whether they have influenced climate changes.

Sea circulation
Mohamed Ezat was born in Egypt and took a master's degree in the geology departmet at the University in Egypt, under the supervision of Beni-Suef. In 2011 he moved to Tromsø to persue a PhD in the field of polar climate. (Photo: Private)

"My PhD work has resulted in more information about exchange of heat and carbon between the North Sea and the North Atlantic over the last 135 000 years." 

"Our new data has given us the possibility to test earlier hypotheses that deal  with the sea's circulation in the North Atlantic, and how this is linked to historical regional climate changes, the marine carbon cycle and CO2 in the atmosphere" says Ezat.

He has also analyzed sediment samples from the ocean floor outside the Faeroe islands.  Calcite shells of dead microorganisms pile up on the ocean floor and become layered in the sediments like a climate archive. 

The map shows oceans currents in the Northern Atlantic Sea. Red arrows show the hot surface currents from south to north, including the Gulf stream. White dotted lines illustrates cold surface currents around the ice of Greenland and black arrows show cold deep water currents from the Arctic to the south. White dot next to the Faeroe islands marks the location of one the sediment samples Ezat has used in his work. (Map: Mohamed Ezat)

The calcite shell composition is also affected by temperature, pH and CO2 concentrations and will therefore be a product characteristic of its time period.

Researchers have reconstructed the sea temperature, salinity and carbonate chemistry (pH and CO2) thousands of years back in time and looked at the concentrations of greenhouse gases in the southern Norwegian Sea. They have compared the conditions to the North Atlantic and found that the Norwegian Sea physical environment and exchanges with the North Atlantic changed according to regional climate changes in the past.

"This suggests that the circulation of water masses we have looked at, and the carbon cycle in the sea played an important role as an amplifier of past climate changes" says Ezat.

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Translated by
Stephanie Hansen

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University of Tromsø – The Arctic University of Norway is the northernmost university of the world. Read more

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