At high latitudes, such as near Antarctica and the Arctic Circle, the ocean’s surface waters are cooled by frigid temperatures and become so dense that they sink a few thousand meters into the ocean’s abyss. Ocean waters are thought to flow along a sort of conveyor belt that transports them between the surface and the deep in a never-ending loop. However, it remains unclear where the deep waters rise to the surface, as they ultimately must. This information would help researchers estimate how long the ocean may store carbon in its deepest regions before returning it to the surface.
(From MIT News/by Jennifer Chu) — Now scientists from MIT, Woods Hole Oceanographic Institution (WHOI), and the University of Southampton in the U.K. have identified a mechanism by which waters may rise from the ocean’s depths to its uppermost layers. Their results are published today in the journal Nature Communications.
Through numerical modeling and observations in the Southern Ocean, the team found that topographic features such as seamounts, ridges, and continental margins can trap deep waters from migrating to flatter, calmer parts of the ocean. The underwater chasms and cliffs generate turbulent flows, similar to wind that whips between a city’s skyscrapers. The longer water is trapped among these topographic features, the more it mixes with upper layers of the ocean, swirling its way back toward the surface.
“In the abyssal ocean, you have 4,000-meter sea mountains and very deep troughs, up and down, and these topographic features help create turbulence,” says Raffaele Ferrari, the Cecil and Ida Green Professor of Oceanography in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “What seems to be emerging is that water comes back up from the abyss by spending a lot of time in these places where turbulence is really strong.”
Knowing there are hotspots where deep waters return to the surface may help scientists identify regions where carbon, once absorbed from the atmosphere and stored deep in the ocean, rises and is released back to the atmosphere.
Read the full article here: http://news.mit.edu/2017/underwater-mountains-turbulence-ocean-circulation-0306