EARTHSS 60B Lecture Notes - Lecture 6: Thermohaline Circulation, Conveyor Belt, Global Warming
LECTURE 6:
What controls ocean circulations patterns?
● Thermohaline circulation (ran by densities)
○ Causes layers to not mix but move past each other
○ d=m/v, in high salinity mass goes up
○ Temperature changes volume (hot water expands)
● Ocean circulation and nutrient distributions
○ Nutrients increase productivity
○ Nutrient concentrations are lower at the surface and higher at depth
■ No algae deep in the ocean, nutrients sink to the bottom
○ Center of the ocean gyres, low nutrients
○ Margins have upwelling, more nutrients
● Stratification experiment
○ Salt water prevents mixing from happening
○ The cold water surrounds the ice and allows it to not melt as quickly
○ Global warming can cause stratification to increase in some areas
■ Land ice sheets melting and flowing into the ocean
● Conveyor belt slows or shuts down
● Upwelling now and in the future
○ Coastal upwelling, nutrients surface from below
○ With enhanced stratification→ 50% more nutrients
■ How will phytoplankton respond to increase in nitrate?
● Decrease in number of toxin producers
● Decline in number of chains forming in phytoplankton
○ With added N, more single shells
○ How would this affect C export?
■ Smaller cells don;t weigh as much, less sinking
exports
● How would food webs be affected?
○ More energy foraging for food, less energy for other things
● El Nino and La Nina years
■ Typical trade winds
● Warm nutrient poor waters
■ La Nina:Intensified trade winds
● Warmer water on one side, colder water on the other
● More fish production
■ El nino: weakening trade winds
● Upwelling is prevented
● Less fish production
● More rain→ more moisture from warm waters
● When do we have an El Nino
○ 0.5 degrees celsius avg. increase sea surface temperature for 3 month
Document Summary
Causes layers to not mix but move past each other. D=m/v, in high salinity mass goes up. Nutrient concentrations are lower at the surface and higher at depth. No algae deep in the ocean, nutrients sink to the bottom. Center of the ocean gyres, low nutrients. The cold water surrounds the ice and allows it to not melt as quickly. Global warming can cause stratification to increase in some areas. Land ice sheets melting and flowing into the ocean. Decline in number of chains forming in phytoplankton. Smaller cells don;t weigh as much, less sinking exports. More energy foraging for food, less energy for other things. Warmer water on one side, colder water on the other. More rain more moisture from warm waters. When do we have an el nino. 0. 5 degrees celsius avg. increase sea surface temperature for 3 month. Rise in air pressure over indian ocean, fall in air pressure over tahiti and.