"Dead zone of the ocean" due to climate change of the earth turned out to be expanding

The impact on the environment caused by global warming is called out,Global warming and humanity have nothing to do with itVarious arguments are being made on the cause including the theory to be. However, it is true that various changes are occurring on the earth in reality. In the wide area of ​​the Pacific Coast, sea creatures can not inhabit "Dead zone"Has been announced as a result of the survey that it is expanding.

PLOS ONE: Paleoceanographic Insights on Recent Oxygen Minimum Zone Expansion: Lessons for Modern Oceanography
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0115246


Climate change could mean massive ocean dead zones | The Verge
http://www.theverge.com/2015/1/28/7930047/climate-change-could-mean-massive-ocean-dead-zones

◆ Ocean of Death to Expand "Dead Zone"
From around 2002, on the fishing ground in the state of Oregon located on the west coast of the Americas, it has become very common that dead fish take over on the net. This incident was received with shock as local fishermen "have never experienced", but now the occurrence area "Dead zoneIt is said that it is steadily increasing.

The cause of this mass death has been found to be "suffocation death" due to the reduced amount of oxygen contained in the seawater. Mr. Sara Mofitt, a researcher at the University of California, Davis, Bodega, Marine Laboratory, investigated the actual situation and announced that the dead zone spread throughout the West Coast of the United States. The following map shows the oxygen deficient area (yellow) spreading along the terrain of the American West Coast, and the area where oxygen deficiency is in crisis (red).


Furthermore, it is confirmed that this "dead zone" has spread to a wide area on the coast of the Pacific Ocean. Some can be seen from the situation of Japan extending from Hokkaido to the Tohoku region. This phenomenon is thought to have occurred due to a change in the state of convection of seawater.


◆ Earth's ocean current system and climate change
The convection of sea water is affected by the environment inside and outside the earth. In the area around Oregon, for example, the wind from the continent blows into the sea in the summer, so that warm, oxygen-rich seawater is driven off the coast. Ocean current from the deep ocean occurs when sea water on the surface is flowed off the coast. This flowRise and fall(Yuushyuryuu) is called, has the function of pushing up the seawater containing a lot of nutrients from the deep sea to the surface layer.

Seawater containing nutrients generates a lot of phytoplankton and sea ecosystem is built by fish, crabs and the like using that plankton as a food. The dead phytoplankton sinks to the bottom of the ocean and forms an oxygen deficient area, that is, a dead zone along the ground. The situation occurring in recent years is that this dead zone where oxygen is deficient is spreading out with rapid momentum.


Climate change and the occurrence of the dead zone are complicatedly intertwined. As the seawater is warmed, the amount of oxygen that can be contained in the ocean decreases. In addition, the seawater 's "layer" due to the temperature difference becomes stronger, and the surface ocean water containing a lot of oxygen will be difficult to mix with the deep sea water. In addition, global warming raises the temperature of the Earth's polar regions, creating a global ocean currentDeep ocean currentWeakens the movement of the sea affects the entire sea. In addition, the movement of the atmosphere affects the movement of the wind flowing on the surface of the earth, which will affect the occurrence of upwelling.

The rough mechanism of the deep ocean current can be seen in the image which NHK has published on the net.

Deep ocean currents flowing through the ocean floor


The detailed reasons the dead zone is expanding are not yet clarified yet, but it is undeniable that the scale is actually expanding and that the trend shows acceleration trend.One studyAccording to prediction by the end of this century, the result that 50% of the low oxygen area expands is also clarified. Expansion of the hypoxic area means a decrease in viable marine organisms, which means that the amount of marine products we produce will decrease.

Mr. Mofit's research tells us how these problems occur at a fast pace. In the discussion on current climate changeThe sea level rises 1 meterYaOcean water acid value increases by 170%Although mainstreaming is mainstream, Mohitt pointed out that the problem we should address now is to understand the complex interlocking system that triggers the turning point of the environment and the impact caused by it. Regarding its importance "This is not only a matter of temperature, which means that the planetary system of the earth that we misunderstood that mankind is" very stable "is being destroyed Earth The system is not stable, it includes the possibility that if we blow the climate system a brief storm will become unstable. "