The circulation of water through the Atlantic Ocean during the last Ice Age was faster than previously assumed, and stronger than it currently is today, according to new research led by environmental physicists at Heidelberg University, Germany.
The “Atlantic heat pump” sees warm water from the Gulf of Mexico transported north and west where it affects the atmosphere over Europe, keeping it much warmer than it would otherwise be. At the same time cold water close to Europe sinks and is pulled back into the ocean, as part of a continuous circulation.
“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. Jörg Lippold, lead author of the study from Heidelberg University‘s Institute of Environmental Physics.
The scientists used ultra-precise measurements of natural radionuclides in ocean sediments to determine the strength of the ocean’s circulation.
“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,” Lippold explained.
Quoting the University of Heidelberg;
The two isotopes studied, protactinium-231 and thorium-230, are produced from the radioactive decay of uranium found naturally in sea water. While thorium is deposited directly in the sediment at the Ocean’s floor, the protactinium follows the circulation and is carried by the deep sea current from the North Atlantic. The proportion of the two elements in the sediment ergo reflects the strength of the circulation.
According to Dr. Lippold, at the time of the largest global ice coverage during the Ice Age some 20,000 years ago, there was less proctactinium-231, which points to an increase in the Atlantic circulation. This discovery is also backed up by model calculations.
Once again the question needs to be asked and answers, why do we care about what happened 20,000 years ago?
Understanding the climatic history of our planet helps us understand the climatic future. In particular is the need for climate models to correctly reflect the climate in the past if they are to be of any use to us in the future.
“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,” said Dr. Lippold. “With the Ocean circulating more quickly then, it could also extract and store more CO2 from the atmosphere.”
In particular, understanding the relationship the Atlantic Ocean has to its surrounding landmasses is critical for much of Europe.
““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,” explained Lippold.
Source: University of Heidelberg