Climate Change and Lakes

ice cover

• ice cover is decreasing

• lakes are freezing later and breaking up earlier

• less ice - more solar warming - longer growing season

lake temperature

• lakes are warming

• most lakes show increasing surface water temperatures

stratification

• stratification lasts longer

• earlier onset and later breakdown of thermal stratification

• leads to less frequent mixing

longer stratification causes…

• reduced oxygen replenishment

• bottom waters become hypoxic or anoxic

phosphorus loading

• internal phosphorus loading increases

• anoxic sediments release phosphorus

• fuels algal blooms

• eutrophication can increase without more external nutrients

productivity

• generally increases - but not everywhere

• many lakes show higher productivity and more blooms

• some deep lakes (L. Tanganyika) show decreased productivity due to reduced nutrient mixing