October 16, 2012
Atlantic Heat Pump Was Once Faster, New Insights For Climate Models
April Flowers for redOrbit.com - Your Universe Online
A new study from an international team of scientists led by environmental physicists at Heidleberg University in Germany suggests that the circulation of the Atlantic Ocean was faster during the last Ice Age than today.
The team used ultra-precise measurements of natural radionuclides — atoms that have an unstable nucleus — in sediments on the ocean's floor to study the ocean's strength of circulation. What they uncovered was new information about the Atlantic "heat pump," which is significant for correctly predicting climate models.
“Thanks to the Gulf Stream and its northern branches, it is much warmer here than at the same latitudes in North America. Without the ocean´s heat transport, which is comparable to that of a million large power plants, temperatures in Northern and Western Europe would be considerably cooler,” explained Dr. JÃ¶rg Lippold, from Heidelberg University℠s Institute of Environmental Physics.
The waters of the Atlantic warm and flow in a northeasterly direction from the Gulf of Mexico due to wind and the Earth´s rotation, providing the origin of Europe's natural heating system. The surface water cools and grows denser, causing it to sink in the North Atlantic before flowing south again in the ocean's depths.
“Using two exotic representatives of the periodic table from core samples of Atlantic deep sea sediment, we were able to quantitatively determine this return flow for the first time,” said the Heidelberg researchers.
The team studied two isotopes, protactinium-231 and thorium-230, both of which are produced during the radioactive decay of uranium found naturally in seawater. Thorium is deposited directly into the sediment on the ocean floor, while protactinium follows the water circulation and is carried by the deep-sea current from the North Atlantic. The strength of the circulation is reflected in the proportions of the two elements in the sediment.
The researchers found that levels of proctactinium-231 during the time of the largest global ice coverage approximately 20,000 years ago was lower than expected. This points to an increase in the Atlantic circulation, according to Dr. Lippold.
This new knowledge is important for climate models that are used to calculate future global climate change. The way scientists assess the accuracy of the model's predictions is largely based on whether they correctly reflect known historical climate trends.
“The oceans are the key to the Earth´s climate system. There is approximately 50 times more CO2 bound in the Earth´s Oceans than in the atmosphere, with 1,000 times more heat storage capacity,” explained Lippold.
“With the Ocean circulating more quickly then, it could also extract and store more CO2 from the atmosphere. If the Ocean warms in the course of climate change and the density of the waters of the North Atlantic drops due to melt water or increased precipitation, the heat pump could weaken. Paradoxically, this could cause cooling in Europe while the rest of the world heats up,” he continued.
The data used in the large scale study was based on measurements obtained from mass spectrometers and particle accelerators that are able to detect the variations in the concentrations of the two elements within a few picograms.
The team´s findings are published in the journal Nature Geoscience.