Lecture 7a - Lake Structure Flashcards
Lakes Have a Vertical Structure Due to (3):
- Stratification
- Thermal Stratification
- Lake Mixing
What is Stratification:
Structuring of water body into ‘layers’ due to physical, chemical, and biological inputs and processes
What is Thermal Stratification:
Varies with latitude and climate due to different thermal inputs including wind fields
What is Lake Mixing:
is caused by energy inputs in a balance between buoyancy and inertia. There are seasonal mixing patters caused by a variety of energy inputs
Lake Structure is Based on (5):
- Morphometry
- Hydrology
- Light
- Heat
- Turbulence
Lake Structure - Morphometry:
Determines basin shape
Lake Structure - Hydrology
Retention time and chemical properties of the lake
Lake Structure - Light
Determines compensation depth
1. littoral
2. limnetic zones
3. profundal zones
Lake Structure - Heat
Determines the 1. Epilimnion, 2. Metalimnion, and 3. Hypolimnion zones in the lake
Lake Structure - Turbulence
Determines lake mixing, sediment stability/mobility in littoral
What Creates Stratification:
- Thermal inputs and lack of mixing
- Different layers with different densities and conditions
- less dense water has to rise above the other layers
- Different densities arises because of temperature but also due to chemistry
- Mixing occurs (no more stratification) when it overwhelms the buoyancy of different layers
Different Stratification/Mixing Patterns (7):
- Diel/episodic
- Dimictic
- Monomictic
- Amictic
- Polymictic
- Holomictic
- Meromictic
What is the Dimictic Mixing Pattern:
Spring and fall mixing
What is Monomictic Mixing Pattern:
Fall mixing
What is the Amictic Mixing Pattern:
No mixing
What is the Polymictic Mixing Pattern:
Pccurs in small, shallow lakes
What is the Holomictic Mixing Pattern:
Entire lake mixes
What is the Meromictic Mixing Pattern:
Deepl layer of non-mixing water
What Does Thermal Energy do For Lake Mixing:
- Heating
- Convection
- Precipitation
- Evaporation
What Does Wind Energy Do for Lake Mixing:
- Creates waves
- Stokes Drift
- Seiches
- Horizontal mixing
- Langmuir circulation
What Do Density Interactions Do for Lake Mixing:
- Stratification
- Instabilities
- Pumping
- cooling
- Morphometry
What are Seiches:
Typically caused by strong winds and rapid changes in atmospheric pressure push water from one end of a body of water to the other. THe water then rebounds when the wind stops
What are Internal Waves:
Propogation of a disturbance at the interface of two fluids of different density
What is Langmuir Circulation:
Are a powerful mechanism of vertical mixing in natural bodies of water, driven by wind and waves
