Physical and Chemical Oceanography
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Name and explain the difference in climate between the coastal regions east and west of the North-Atlantic Ocean.
• The gulf stream makes a strong and warm current on the west of the ocean • The canary current makes a colder current on the east of the ocean.
What is sonar and how does it work?
• SONAR is SOund Navigation And Ranging o Developed for hunting submarines o Sends a ‘ping’ and calculates how long it takes for the ‘ping’ to reverberate, and uses that time with the speed of sound in water to calculate the water depth.
What is the deepest point of the oceans? Approximately how deep is it?
• Challenger deep on the marinara trench. Its 10,935 meters deep.
What are convergent and divergent tectonic boundaries?
• They are boundaries in tectonic plates o At convergent, the sea floor is being destroyed and plates are coming together o At divergent, the sea floor is being created (undersea volcanic eruptions) and the plates are drifting apart.
Which sort of tectonic boundary are the Mid-Atlantic Ridge, the Marianas trench and the Scotia Sea Trench?
• The mid Atlantic ridge is divergent • The trenches are both convergent
What are hydrothermal vents? Are they typically found on divergent or Convergent boundaries? Explain why
• Hydrothermal vents are fissures on the sea floor that release superheated mineral-rich fluid and they are typically found on divergent plate boundaries because the separation of tectonic plates lets magma rise through the cracks in the ocean floors leading to the vents.
How is life able to survive around the deep-sea vents?
• A chemoautotrophic bacteria can use the chemicals and the hot water to get energy, and they’re eaten by shrimps and then by other animals.
What are the fastest-growing marine invertebrates?
• Giant tube worms (found near hydrothermal sea vents)
Why can hydrothermal vents be considered ephemeral habitats?
• Each community is unique, and vents can start and stop rapidly. When they stop, the inhabitants will die. • The vents can start and stop rapidly because of the underlying volcanic and tectonic activity.
What are the 4 most common ions (by mass) in seawater?
• Chloride • Sulfate • Hydrogen Bicarbonate • Bromide
If the ratio of the amounts of the ions of K+ to Cl− in the Atlantic Ocean was 0.02, what would be the ratio of the two ions in the Pacific Ocean?
• It would also be 0.02 because of the constancy of composition of seawater (always in the same relative proportions)
How is salinity measured?
• By comparing the conductivity of a water sample with that of a reference sample of “standard seawater” (ratio) (measured in practical salinity units ‘PSU’)
The salinity of seawater of average ocean density is 34.482. What does that mean?
• That means that there is 34.482 grams of dissolved salts in every kilogram of seawater of average ocean density
At what temperature is water at maximum density? What happens to the density if the water is cooled below this temperature or heated above this temperature? What causes these differences in density?
• 4°C is the maximum density for water o If water is heated ABOVE this temperature then the hydrogen bonds of water break quickly. o If water is below the 4°C then the kinetic energy of the water molecule falls below the energy of hydrogen bonds, making them form more frequently than break The hexagonal shape of water is less dense than when its loosely making bonds. Therefore < 4°C is lighter But also, therefore > 4° is lighter
What would happen if water would NOT have its maximum density in a fluid stage?
• Ice would SINK o Freeze bottom up, so eliminates most aquatic life o Colder waters o No ice caps to reflect sunlight.
What will happen to the water in the lake when all the water is cooled below to 3.98 °C?
• The water at the surface will cool down and become less dense, so cooler water on top and hotter water on bottom
Draw a cross section through a temperate lake in winter and summer, indicating the vertical profile of temperature and density
its easy, just 4°c on bottom and then it gets hotter on top for summer and colder on top for winter (density will always go down bc water is special)
What is the “density anomaly”? What is the typical density anomaly for seawater?
• How much denser seawater is to pure water (calculated the difference by subtracting 1000) • Value is sigma, or sigma-t at atmospheric pressure. • Typical density anomaly for seawater is 24-28 kg m-3
what does a CTD do?
measures the conductivity and temperature of the seawater and depth in pressure.
What are the 2 main factors determining seawater surface temperature?
• solar radiation levels • distribution of heat via surface currents
There are no coral reefs on the north west coast of Africa, whereas there are coral reefs at the Caribbean islands, which are located at the same latitude. Why?
• The northwest of Africa is bathed by the canary current which brings cold water down from higher latitudes, and therefore is too cold to host a coral reef- • The Caribbean is influenced by warm currents from the gulf stream which keep temperatures high.
What are the 2 factors determining sea surface salinity?
• Precipitation • Evaporation
What causes these differences in surface salinity?
• The Pacific Ocean has isohalines, which causes lines of equal salinity across latitudes. • In the Atlantic ocean there is so much circulation that it causes variation within the surface of salinity. • also when precipitation is higher then evaporation then salinity is lower i guess
would you expect surface salinity to be higher around the equator or in the subtropics? Why?
• yes, because near the equator / subtropics there are higher temperatures which lead to more evaporation, causing higher salinity.