Southern Ocean winds open window to the deep sea

Mar 15, 2010

Australian and US scientists have discovered how changes in winds blowing on the Southern Ocean drive variations in the depth of the surface layer of sea water responsible for regulating exchanges of heat and carbon dioxide between the ocean and the atmosphere.

The researchers' findings - published on-line today in Nature Geoscience - provide new insights into natural processes which have a major influence on the rate of .

The surface-mixed layer is a crucial pathway between the atmosphere and the deeper layers of the ocean. Changes in the depth of the mixed layer can affect air-sea exchange, carbon and heat storage in the ocean, and the rate at which water sinks from the surface ocean into the deep ocean.

Changes in the mixed layer also affect , by altering how much light and nutrients are available to support growth of at the base of the food chain.

The paper's lead author, CSIRO Wealth from Oceans Flagship oceanographer Dr Jean-Baptiste Sallée, said the winds over the had increased in strength and shifted closer to Antarctica in recent decades.

"The shift in winds is one of the strongest trends in southern hemisphere climate over the last 30 years," Dr Sallée said. "The key question is; 'How does the wind change affect the ocean?'

"Our knowledge of how the Southern Ocean changes in time is poor because of the lack of ship-based observations in this remote region. But we now have seven years of year-round observations from a fleet of profiling floats known as Argo, which allow us to see for the first time how the Southern Ocean changes with the seasons and from year-to-year."

The researchers, including Dr Steve Rintoul from the Antarctic Climate and Ecosystems CRC and CSIRO and Professor Kevin Speer from Florida State University, examined the relationship between changes in wind and changes in the surface-mixed layer.

"We found that the depth of the mixed layer was more sensitive than we expected to a pattern known as the Southern Annular Mode, the major mode of variability of the southern hemisphere atmosphere," Dr Sallée said. "Even more surprising was the fact that the response is very different in different regions."

When the winds strengthen and contract closer to Antarctica, the surface-mixed layer deepens in the eastern Indian and central Pacific oceans, and shallows in the western part of these basins. The reverse is seen when the winds weaken and migrate north.

The asymmetry can be explained by small deviations in the generally west-to-east winds and their effect on the heat exchange between ocean and atmosphere: when cold winds blow from the south, this causes heat loss from the ocean and deeper mixed layers.

"These changes in mixed layer depth affect how much light is available to support the growth of phytoplankton. We found that changes in the mixed layer depth driven by the winds are associated with changes in the amount of phytoplankton biomass," Dr Sallée said.

Explore further: Clean air: Fewer sources for self-cleaning

Related Stories

Human-generated aerosols affect our weather

Jan 22, 2008

The rise of human-generated pollution in the global atmosphere is forcing a change in ocean circulation in the Southern Hemisphere, in turn affecting our region’s weather systems.

Hurricanes' effects on ocean temperature revisited

Mar 04, 2010

(PhysOrg.com) -- The role of hurricanes in the global climate system has gained interest ever since scientists suggested that strong hurricanes have become more frequent in recent decades and might continue ...

Southern Ocean seals dive deep for climate data

Aug 11, 2008

(PhysOrg.com) -- Elephant seals are helping scientists overcome a critical blind-spot in their ability to detect change in Southern Ocean circulation and sea ice production and its influence on global climate.

Recommended for you

Clean air: Fewer sources for self-cleaning

52 minutes ago

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

There's something ancient in the icebox

52 minutes ago

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Image: Grand Canyon geology lessons on view

7 hours ago

The Grand Canyon in northern Arizona is a favorite for astronauts shooting photos from the International Space Station, as well as one of the best-known tourist attractions in the world. The steep walls of ...

First radar vision for Copernicus

8 hours ago

Launched on 3 April, ESA's Sentinel-1A satellite has already delivered its first radar images of Earth. They offer a tantalising glimpse of the kind of operational imagery that this new mission will provide ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

CouchP
not rated yet Mar 15, 2010
If true, is this evidence that massive wind farms could cause disruptions or changes in weather patterns or what level could begin to affect same?

More news stories

There's something ancient in the icebox

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

Clean air: Fewer sources for self-cleaning

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

Turning off depression in the brain

Scientists have traced vulnerability to depression-like behaviors in mice to out-of-balance electrical activity inside neurons of the brain's reward circuit and experimentally reversed it – but there's ...

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...