Reconcile climate and carbon cycle movements in the last 50 million years

Predicting future climate change requires a clear and positive understanding of the Earth’s climate. In a study published today in Advances in science, The University of Hawai’i (UH) at the Mānoa oceans has made a full settlement of climate trends and the carbon cycle of the past 50 million years – resolving a controversy that has been debated in the scientific literature for decades.

Throughout Earth’s history, global climate and the global carbon cycle have changed dramatically, some of which challenge current understanding of carbon cycle dynamics.

Less carbon dioxide in the atmosphere cools the Earth and reduces the weather of rocks and minerals on land over time. Less weather should lead to a deeper depth of calcite (CCD) compensation, i.e. the depth in the ocean where the rate of carbonate material precipitation is equal to the level of carbonate emissions (also known as “snow line”). The depth of the CCD can be traced over the geological period by studying the calcium carbonate content in seabed sediment corals.

Former marine science graduate Nemanja Komar and professor Richard Zeebe, both at the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), have presented the most complete computer model of ocean carbonate and CCD chemistry to date , making this the first study that verbally linked all important parts of the carbon cycle together across the Cenozoic (66 million years).

Contrary to expectations, the deep-sea carbonate records show that as atmospheric carbon dioxide (CO2) has decreased over the past 50 million years, the global CCD has deepened (without peeled), forming a carbon ring puzzle.

“The changing position of the paleo-CCD over time bears a sign of past carbon cycle dynamics,” said Komar, lead author of the study. “So monitoring CCD evolution across the Cenozoic and identifying mechanisms that are responsible for its variables is important in detecting past changes in it. the atmospheric CO2, weather and deep – sea carbonate burial. As CO2 and temperatures fell over the Cenozoic, the CCD should have shone but the records show that it has indeed deepened. “

Komar and Zeebe’s computer model allowed them to study mechanisms that may be responsible for the observed long-term trends and provide equipment to resolve all observations.

“Remarkably, we showed that the CCD response was separated from changes in silicate and carbonate weathering levels, challenging the long-term surge theory, which influences the CCD response to an increase in weather levels due to the formation of the Himalayas and which are contrary to our decisions, “Komar said.

Their research suggests that the decoupling developed in part as a result of the growing proportion of carbonate buried in the open ocean compared to the continental shelf due to depression. in sea level as the Earth cooled and continental ice sheets formed. In addition, the location of the ocean caused a massive growth of organisms that produced carbon production during that period.

“Our work gives us a fresh perspective on the basic processes and nutrients of the Earth’s system, which is crucial for predicting future predictions about climate change and carbon cycling,” Komar said. .

The researchers are currently working on new ways to reverse the chronology of climate change and the carbon cycle over the past 66 million years.

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