Lecture 15: Oceans 1 Flashcards
What is the Global distribution of the ocean?
Most of the southern hemisphere is ocean and most of the northern hemisphere is land
How much of the earth’s surface does ocean cover?
71%
What is the maximum depth of the ocean?
11km
What is the average depth of the ocean?
4.5km
What is Salinity?
The measure of the proportion of dissolved ions in ocean water
What are the primary ions dissolved in water?
Chloride, Sodium, Sulfate, Magnesium, Calcium, Potassium, Bicarbonate
What are the main dissolved ions in oceans?
Chloride and Sodium
What is the Source of Ions in the ocean?
Ions enter into the ocean primarily from the dissolved loads of rivers and from submarine volcanic activity at mid ocean ridges
What are Ocean Sinks?
When ions are removed from sea water by precipitation of minerals, sequestration by living organisms to produce shells, sorption to clay minerals, in sea spray and reactions with basaltic seafloor rocks
What does the Residence time of ions mean?
The average time an ion spends in seawater
What does the residence time of ions in water depend on?
The flux of an ion into sea water (sources) and the rate at which the ions is removed from sea water as well as the solubility of the ion
Why do Organisms remove ions from the ocean?
The remove ions in order to build their shells with calcium carbonate and silica
How do Mid-ocean ridges affect ions in the ocean?
They at Calcium and Potassium to the water and remove Magnesium and Sulfate
Which ions have to longest residence times in oceans?
Sodium, Potassium and Calcium
Why do Manganese, Iron and Aluminium how lower residence times in oceans?
Because they are less soluble in water
Where in oceans is Salinity high?
In regions of high evaporation and/or low precipitation
Where in is salinity of oceans low?
Where river water enter into the ocean
What was the composition of ocean water back in history?
Salinity was probably lower early in earth history and iron concentrations were higher as banded iron formation were deposited as atmospheric oxygen increased and iron oxidized
What is the distribution of temperature in the ocean?
Temperatures are hotter near the equator and temperature decreases poleward
What causes the distribution of ocean surface temperature on earth?
Ocean circulation patterns and amount of sunlight
How is ocean temperature affected by depth?
Temperature decreases with depth and the cold water is denser and sinks
What is the Thermocline?
The zone of rapid temperature change in the ocean
How does depth affect the salinity of water?
Salinity increases with depth because saline water is denser and sinks
What is the Halocline?
The region of rapid salinity change in the ocean
What are the causes of ocean density increasing with depth?
Decreasing temperature, increasing salinity, and compression of liquid water
What is the Pycnocline?
The zone of rapid density change in the water
What are ocean surface Currents caused by?
- Air currents interacting with the surface of the oceans
- The sinking of denser (colder or saline) water
- Effects resulting from rotation of the earth
What are Deep Ocean currents caused by?
Dense, cold, high salinity water that descends at the poles
What occurs is the Conveyer belt in the Atlantic Ocean?
Water freezes and loses salt at the antartic and the remaining water is more dense and becomes bottom water under the north atlantic deep water. As the north atlantic deep water approaches antarctica it interacts with warmer water to become intermediate water
What is the Thermohaline circulation a result of?
Density driven movement of water in the oceans
What does the Thermohaline Circulation play a critical role in?
Controlling global climate
What causes Surface currents?
The sun unevenly heating the planet causing different wind directions that pass over the water and cause currents
What is Surface circulation dominated by?
Gyres driven by the Coriolis effect
What are Gyres?
Circular patterns of surface water movement
Where is the surface of earth not rotating?
Its rotating everywhere but the equator
Which direction is the surface of earth rotating in each hemisphere?
- CCW in the northern hemisphere
* CW in the southern hemisphere
What direction do objects that are going straight appear to be going in each hemisphere?
- Right (CW) in N. hemisphere
* Left (CCW) in S. Hemisphere
How does the Coriolis effect affect wind drive currents in the northern hemisphere?
It causes them to be 90º clockwise
What occurs in Ekman transport?
Wind causes the surface water to be blown away but instead of going straight it goes clockwise. As that water gets blown away, water from underneath comes and fills the spot and also gets rotated clockwise in 90º
What does Ekman transport cause?
Upwelling of deep nutrient rich water to the surface where transport direction is offshore
When do areas of Downwelling occur?
Where Ekman transport is onshore
What is El Nino?
When the circulation system of the oceans change and upwelling declines, reducing fish and bird populations and trade winds reverse in the west specific
What occurs in a normal year and not an El nino year?
Surface currents off the coast of South america move northward and Ekman transport (CCW in the southern hemisphere) cause upwelling and movement offshore
What causes El Nino?
Atmospheric pressure changes that cause trade winds to reverse which stops upwelling
How does El Nino affect fisheries?
The top 100 meters of ocean water in the intertropical convergence zone warm up, lowering oxygen concentration causing fish to go deeper to survive or die off due to red algae
How often does El Nino occur?
Every 4 years with variable severity
