Subpolar marginal seas play a key role in making the subarctic Pacific nutrient-rich

August 07, 2020

A group of researchers from three Japanese universities has discovered why the western subarctic Pacific Ocean, which accounts for only 6 percent of the world's oceans, produces an estimated 26 percent of the world's marine resources.

Japan neighbors this ocean area, known for rich marine resources including salmon and trout. The area, located at the termination of the global ocean circulation called the ocean conveyor belt, has one of the largest biological carbon dioxide draw-downs of the world's oceans.

The study, led by Hokkaido University, the University of Tokyo and Nagasaki University, showed that water rich in nitrate, phosphate and silicate - essential chemicals for producing phytoplankton - is pooled in the intermediate water (from several hundred meters to a thousand meters deep) in the western subarctic area, especially in the Bering Sea basin. Nutrients are uplifted from the deep ocean through the intermediate water to the surface, and then return to the intermediate nutrient pool as sinking particles through the biological production and microbial degradation of organic substances.

The intermediate water mixes with dissolved iron that originates in the Okhotsk Sea and is uplifted to the surface - pivotal processes linking the intermediate water and the surface and that maintain high surface biological productivity. This finding defies the conventional view that nutrients are simply uplifted from the deep ocean to the surface.

The study relied on ocean data obtained by a research vessel that surveyed the marginal seas (the Okhotsk Sea and the Bering Sea) where, the group believed, large-scale mixture of seawater occurs due to the interaction of tidal currents with the rough topography. This voyage was made in collaboration with a Russian research team because many of the areas surveyed fall inside Russia's exclusive economic zone. The obtained data was then combined with data collected by Japanese research vessels.

Analysis of the data showed that nitrate and phosphate re-produced through microbial degradation of organic substances accumulate in high concentrations in intermediate water in the entire subpolar Pacific region.

The researchers also found that the vertical mixing magnitude near the Kuril Islands and the Aleutian Islands is far stronger than that in the surrounding open seas. This study demonstrated that large-scale vertical mixing in the marginal seas breaks the density stratification to mix ocean water, transporting nutrients from the intermediate water to the surface.

"Our findings should help deepen understanding about the circulation of carbon and nutrients in the ocean and ecological changes caused by climate change," says Associate Professor Jun Nishioka of Hokkaido University, who led the study.
The results of this study were published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Hokkaido University

Related Deep Ocean Articles from Brightsurf:

DNA in seawater can reveal fish diversity in the deep ocean
A new study demonstrates the effectiveness of a novel method for using DNA in seawater samples to determine which fish species are present in a given part of the deep sea.

Ocean acidification puts deep-sea coral reefs at risk of collapse
Deep-sea coral reefs face challenges as changes to ocean chemistry triggered by climate change may cause their foundations to become brittle, a study suggests.

Can pumping up cold water from deep within the ocean halt coral bleaching?
Rising ocean temperatures cause marine heat waves, which place stress on living coral animals, as well as the photosynthetic algae on which they depend for energy.

Deep channels link ocean to Antarctic glacier
Newly discovered deep seabed channels beneath Thwaites Glacier in West Antarctica may be the pathway for warm ocean water to melt the underside of the ice.

New study reveals strength of the deep ocean circulation in the South Atlantic
A new study from oceanographers at NOAA and the University of Miami Rosenstiel School's Cooperative Institute for Marine and Atmospheric Studies (CIMAS) has for the first time described the daily variability of the circulation of key deep currents in the South Atlantic Ocean.

New current that transports water to major 'waterfall' discovered in deep ocean
An international team discovered a previously unrecognized ocean current that transports water to one of the world's largest 'waterfalls' in the North Atlantic Ocean: the Faroe Bank Channel Overflow into the deep North Atlantic

The deep ocean is warming slowly -- but dramatic changes are ahead
The world's deep oceans are warming at a slower rate than the surface, but it's still not good news for deep-sea creatures according to an international study.

How stable is deep ocean circulation in warmer climate?
If circulation of deep waters in the Atlantic stops or slows due to climate change, it could cause cooling in northern North America and Europe - a scenario that has occurred during past cold glacial periods.

New sediment record reveals instability of North Atlantic deep ocean circulation
In the future's warmer climate, large, abrupt and frequent changes in ocean ventilation may be more likely than currently assumed, according to a new study.

Microplastics from ocean fishing can 'hide' in deep sediments
Microplastic pollution in the world's oceans is a growing problem, and most studies of the issue have focused on land-based sources, such as discarded plastic bags or water bottles.

Read More: Deep Ocean News and Deep Ocean Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to