![]() ![]() The deep water contains an abundance of decaying matter and sulfurous gases when it reaches the surface, it produces a telltale odor that indicates the process has begun. ![]() Now, storms and sustained high winds can begin to perform the task of overturning and mixing all of the water in the lake - referred to as fall turnover. At some point, the majority of the water in the lake reaches an approximately uniform temperature. At about 500, the cooler water (with a higher oxygen content) at the surface begins to sink into and through the thermocline, forcing warmer and less dense water to the surface, eventually erasing the temperature stratification built up over the summer. Meanwhile, this site claims fall turnover happens at about 50 degrees ()ĭid some more digging and found this interesting paragraph.Īs the days get shorter and cooler, and energy is transported away from/out of the lake, mixing becomes easier. A more detailed description of the physical characteristics of lakes, including temporal and density interactions, can be found at the Water on the Web site, sponsored by the University of Minnesota - Duluth and funded by the National Science Foundation. This describes the general principle however, other factors (including climate and lake depth variations) can cause certain lakes to act differently.The sinking combined with wind mixing causes spring "turnover." This time ice melts, and surface waters warm and sink until the water temperature at all depths reaches approximately 39º F. During spring, the process reverses itself.The sinking action and mixing of the water by the wind results in the exchange of surface and bottom waters which is called "turnover." Because there is very little difference in density at this stage, the waters are easily mixed by the wind. This continues until the water temperature at all depths reaches approximately 39º F. The heavier water sinks, forcing the lighter, less dense water to the surface. During late summer and autumn, air temperatures cool the surface water causing its density to increase.Less dense water is at the surface and more dense water is near the bottom. In summer and winter, lakes are maintained by climate in what is called a stratified condition. Water is most dense (heaviest) at 39º F (4º C) and as temperature increases or decreases from 39º F, it becomes increasingly less dense (lighter). The key to this question is how water density varies with water temperature.What is meant by "lake turnover"? How and why do lakes do this in autumn and spring? I was intrigued by your question, and google helped me find this. ![]()
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