When it comes to the ocean's response to global warming, we're not in entirely uncharted waters. A new study shows that episodes of extreme heat in Earth's past caused the exchange of waters from the surface to the deep ocean to decline.
demonstrates how the conveyor belt responded around 50 million years ago. At that time, Earth's climate resembled conditions predicted by the end of this century, if significant action is not taken to reduce carbon emissions. "Today, the oceans contain nearly 40,000 billion tons of carbon -- more than 40 times the amount of carbon in the atmosphere. Oceans also take up about a quarter of anthropogenic COemissions," Kirtland Turner said.
By analyzing tiny fossil shells from different sea floor locations around the globe, the researchers reconstructed patterns of deep ocean circulation during these hyperthermal events. The shells are from microorganisms called foraminifera, which can be found living throughout the world's oceans, both on the surface and on the sea floor. They are about the size of a period at the end of a sentence.
The researchers also examined carbon isotopes in the shells, which reflect the age of the water where the shells were collected, or how long water has been isolated from the ocean surface. In this way, they can reconstruct patterns of deep ocean water movement. Scientists often make predictions about ocean circulation today using computer climate models. They use these models to answer the question: 'how is the ocean going to change as the planet keeps warming?' This team similarly used models to simulate the ancient ocean's response to warming. They then used the foraminifera shell analysis to help test results from their climate models.