Robotic gliders show undersea topography may generate hot spots of ocean mixing

2017-12-04 03:24:20 GMT2017-12-04 11:24:20(Beijing Time) Xinhua English

LOS ANGELES, Dec. 1 (Xinhua) -- Using underwater robots inwaters surrounding Antarctica, scientists have shown that theintersection of strong currents with the slope of landmasses risingfrom the ocean floor makes a significant contribution to the mixingof different waters in the Southern Ocean.

The finding, detailed in a paper recently published online inthe journal Nature Geoscience, has bearing on models of heattransport toward Antarctica and the ocean's role in the carboncycle. According to the study, in the ocean, global waterproperties may depend on very localized mixing processes.

"Most global ocean observations acquire measurements in the openocean or in the top layers of the water, while our research showsthat important mixing processes may be occurring in the deep oceanin thin layers over sloping topography," senior author AndrewThompson, professor at California Institute of Technology(Caltech), was quoted as saying in a news release on Friday.

The research team from Caltech deployed two autonomousunderwater drones, or "gliders," for a period of eight months overthe course of a year and a half in the Southern Ocean, whichencircles Antarctica.

They concentrated on the region around Drake Passage, the1,000-kilometer-wide waterway between Antarctica and SouthAmerica.

The gliders were able to reach depths of 1,000 meters, nearlyscraping the bottom at times. When they come to the surface, theyregularly relay this data back to Thompson and his colleagues.

The data were collected by the instruments, which the gliderscarry to measure temperature, salinity, the quantity of variousnutrients like nitrogen and iron, and other variables.

"There is growing evidence that topography plays a bigger rolein oceanographic mixing than we had previously suspected," sayslead author Xiaozhou Ruan, a Caltech graduate student. "While thisboundary region represents a small fraction of the ocean, theinteraction between water and continental topography plays anoutsized role in mixing."

Such mixing has been predicted by high-resolution oceancirculation models, but this is the first time it has been observeddirectly over a period of many months, according to Caltech.

Documenting these physical processes and improving ourunderstanding of where and how they arise may improve our abilityto simulate the changes in ocean circulation and in Earth's climatein the past and in the future, researchers say.