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Thu January 31, 2013
Dr. Thomas Reichler, University of Utah – Stratospheric Winds and Ocean Currents
In today’s Academic Minute, Dr. Thomas Reichler of the University of Utah explains the connection between winds in the upper atmosphere and deep ocean currents.
Thomas Reichler is an associate professor of atmospheric sciences at the University of Utah where his research is focuses on climate change, large scale dynamics, and climate modeling. His Climate Research Group seeks to contribute to a better understanding of human impacts on the atmospheric environment and to improve predictions of natural and man-made climate variations.
Dr. Thomas Reichler – Stratospheric Winds and Ocean Currents
For decades, scientists around the world have been trying to improve the accuracy of predictions about weather and climate. One avenue of research suggests that the stratosphere, which is the layer of atmosphere between 6 miles and 30 miles above the Earth’s surface, is an important component of changes in climate and weather. Our recent study supports this idea.
From direct observations of the atmosphere and the oceans and also from computer simulations representing thousands of years , we found that periodic changes in winds in the stratosphere influence the ocean. By striking a vulnerable “Achilles’ heel” in the North Atlantic, these changes alter mile-deep ocean circulation patterns, which in turn affect Earth’s climate. Such a link between the stratosphere and the ocean is quite amazing because, compared with the dense ocean, the stratosphere has very little mass, making it hard to believe that the stratosphere could cause changes to the deep ocean. But our research finds that a chain of complicated natural events is responsible for making exactly this happen.
This is how it works:
During winter, winds in the stratosphere are usually strong and regular. However, sometimes catastrophic circulation events happen, abruptly interrupting the normal flow. These events are violent and they can affect the entire atmosphere. They can even be felt at the surface, in particular over a region of the North Atlantic to the south of Greenland. This is the so-called downwelling region, which is a crucial source of deep water that drives the circulation of worldwide ocean currents. There, small variations in temperature and thus density determine whether the sea water is heavy enough to sink or not. Through its impact on surface winds, the stratosphere creates tiny variations in evaporation and water temperature. Because of the high sensitivity of the ocean over this region, the variations are able to accelerate or delay the sinking of water into the abyss. Through this process, the stratosphere acts like a throttle, accelerating or slowing the engine that drives worldwide ocean currents and the climate of our planet.