Of The biggest lake ecosystem of the world blows
WISCONSIN, on November 16. In canadian-American shore of lake superior, the largest area of freshwater lake in the world, over the last 20 years have seen major changes. Professor of Ankur Desai from the University of Wisconsin and his colleagues came to an unexpected conclusion: the increase in the temperature of atmospheric air in the summer has led to the fact that the speed of the winds blowing over the lake, has increased, reports Infox .
According to scientists, for the same reason, the increased speed and currents. Naturally, such changes could not but affect the inhabitants of the water.
While in sight of limnologen (Ostrovidov) managed to get only the phytoplankton. The scientists conducted their research since 1985. Based on data collected using three hydrological buoys and satellite imagery, Professor Desai and his colleagues have figured out what is going on with the Top.
According to scientists, the temperature in the surface layers of the lake during the summer period increased at a rate of 1.2°C in one decade. And the water heats up 15% faster than the air over the lake. “The fact that the temperature regime of a lake depends largely on the amount of ice and the time of its melting. That is, the earlier occurs the melting of the ice on the lake, the faster heats the water itself,” explain the authors.
The difference in the growth temperature leads to a stronger wind. The fact that the wind speed on any body of water is determined by the interaction between the surface water and the lower layers of the atmosphere. The greater the difference between air and water temperature, the more stable the atmosphere is formed with a predominance of weak winds. When the difference decreases, the atmosphere becomes hectic – there begins to form many vortices. Professor Desai has calculated that the wind speed over the lake is increased by 5% per decade, and the speed of currents, affected by all these changes, increases by 10% per decade.
Theoretically, if the speed of the currents increases, then the mixing of layers of water of different temperature and different properties should happen faster, and these conditions are just very favorable for phytoplankton. This means that it should grow. But the research by Professor Desai show that this is not happening. The content of chlorophyll in the lake (according to this index one can judge about the well-being and the amount of phytoplankton) is reduced.
Professor Desai and his colleagues believe that the heating of the surface of the water, increasing speed of wind and currents has led to the fact that the period of temperature stratification when warm layers near the surface and colder at depth clearly separated from each other, was longer than a few days. So, the water no longer mixed, and phytoplankton are created for adverse conditions.
Another trouble that has befallen lake superior, – the diffusion of pollutants. Because with increasing wind speed, the pollutants easily and quickly moved above the lake.
In the future, the researchers plan to see what happens to the carbon cycle in the lake and how the phytoplankton, if all of these changes will continue.
Earlier, the food and agriculture organization of the United Nations (FAO) drew attention to the humanitarian crisis associated with the drying of lake Chad. Over the past decades due to droughts, climate change, inefficient water management and over-consumption of water area of this lake has decreased by 90%. If you do not take decisive action, then within 20 years the lake Chad will die and disappear from the map of the earth. Resources from this lake in Central Africa affects the lives of approximately 30 million people in Cameroon, Chad, Nigeria and Niger.