Ocean Mixing in Drake Passage Linked to Climate
The Drake Passage, also known as the Mar de Hoces, or sea of Hoces is the channel of water located between the southern tip of South America and the Antarctic continent. Known for its powerful waves and stormy weather, this area has been the focus for research concerning how deep and mid-depth ocean waters are mixed.
Because of undersea mountains that are located under these icy waters, new research has shown that sea water mixes dramatically when it rushes over these landforms. This consequently plays an important role in regulating the Earth's climate and ocean currents.
As part of the study, researchers measured mixing in the Southern Ocean by releasing tiny quantities of an inert chemical tracer into the Southeast Pacific. They tracked the tracer for several years as it went through Drake Passage to observe how quickly the ocean mixed.
The tracer showed almost no vertical mixing in the Pacific but as the water passed over the mountainous ocean floor in the relatively narrow continental gap that forms the Drake Passage it began to mix dramatically.
Professor Andrew Watson from the University of Exeter (previously at the University of East Anglia) says:
"A thorough understanding of the process of ocean mixing is crucial to our understanding of the overall climate system. Our study indicates that virtually all the mixing in the Southern Ocean occurs in Drake Passage and at a few other undersea mountain locations. Our study will provide climate scientists with the detailed information about the oceans that they currently lack."
Ocean mixing transfers carbon dioxide from the atmosphere to the deep sea, and ultimately controls the rate at which the ocean takes up carbon dioxide. Over several hundred years this process will remove much of the carbon dioxide that we release into the atmosphere, storing it in the deep ocean. Ocean mixing also affects climate, for example an increase in the rate of deep sea mixing would enable the ocean to transfer more heat towards the poles.
Scientists believe that the lower concentrations of atmospheric carbon dioxide present during the ice ages may have been the result of slower ocean mixing between the surface and the deep sea. Although the reasons for this are not yet clear, this further emphasizes the link between ocean mixing and climate.
The study was carried out by the universities of Exeter, East Anglia and Southampton, the Woods Hole Oceanographic Institution, the British Antarctic Survey and the Scottish Association for Marine Science and is published in the journal Nature.
Read more at the British Antarctic Survey.
Drake Passage via Shutterstock.