Lecture 4 Flashcards
Why is the ocean salty
- the ocean is salty because of dissolved chemicals eroded from the Earth’s crust and washed into the seas
- there are also ejections from volcanos, particles being swept to the ocean by winds, and materials dissolved from sediment deposited on the ocean floor
What is the biogeochemical cycle consist of
- weathering and erosion of continental rocks
- > these are then transported to the oceans
- > this is all part of a large, slow cycle
What is the definition of biogeochemical cycle
-pathways by which a chemical susbtrate moves through the biotic(biosphere) and abiotic(litrosphere, atmosphere, hydrosphere)
Do the compounds or solids dissolved in the ocean remain in the ocean
- no
- > they cycle into and out of the ocean by various processes
- > in by processes such as river discharge, volcanic eruption or hydrothermal activity
- > out by processes such as ocean precipitation and biological processes
Is the ocean in steady-state
- yes we assume the oceans are in steady state and the average amounts of various elements remain constant
- > quantity in= quantity out
What is the residence time
- the average length of time that a substance resides in the ocean
- > long residence time leads to higher concentrations of the dissolved substance
-residence time is essentially the time taken to replace all of the given substance in the ocean with new material of that substance from other sources
- R=M/I=M/O
- > no units because kilograms cancel out
What is the definition of salinity
- it is the total amount of dissolved material in grams in 1 kg of seawater
- > it is dimensionless and has no units
- salinity of seawater is about 3.5%
- > it is about 220 times saltier than freshwater
What is salinity expressed as
- it is expressed as: grams of dissolved salts/kilogram of seawater
- > can be expressed in parts per thousant
How do chemicals in seawater appear as
- they usually appear as compound ions rather than actual raw elements
- > so phosphate for example
-chemicals in seawater include most elements, a variety of radionuclides and numerous organic compounds
- they are designated as major, minor or trace
- > this just reflects their concentrations
How are dissolved chemicals in the ocean measured
- in parts per million
- > eg; 1 teaspoonfull in 5000 litres of water
- > parts per million is used for compounds that are designated as major
- in parts per billion
- > eg; 1 teaspoonfull in 5,000,000 litres of water
- > parts per billion is usually for compounds that are designated as trace or minor
What are the six major consitituents of seawater
- chlorine
- sodium
- sulfate
- magnesium
- calcium
- potassium
-these six make up together 99.28% of all salts in seawater
What are the minor constituents in seawater
- bromine
- carbon
- strontium
- boron
- silicon
- fluorine
- concentrations range from 1 to 100 parts per million
-note some are very important for biological processes
What is the major process to remove major constituents
- it is through the precipitation of salt deposits
- > which mainly occur in marginal seas with high evaporation
- the residence times for major constituents are very long
- > the associated river/erosion inputs are very slow
- > thus the concentrations of these ions vary little to little from time to place
- the concentrations of minor and trace elements are so low
- > the sources are also often localized
- > so the concentrations of trace elements can vary significantly in different parts of the ocean
Can minor and trace constituents change in distribution in a location over time
- yes
- >not something you would see in a major constituent
Describe the differences in freshwater from seawater
- since seawater is 96.5% water
- > many of its physical properties are shared with that of pure water
- > except that of freezing point, boiling point, pH and density
- the dissolved substances in sea water decrease the freezing point of sea water in comparison to pure water
- > while at the same time increase the boiling point of seawater
-seawater is more alkaline than pure water and has a higher pH
- seawater is slightly more dense than pure water
- > this is due to increasing salinity
How does salinity vary in terms of percentage in the open ocean
-in the opean ocean, far from land, salinity varies from 33%-38%
Is the salinity variance more extreme in the coastal areas
-yes
Baltic Sea
- > 10 parts per billion
- > because lots of freshwater inputs such as rivers produces brackish water
Red Sea
- > 42% salinity because of high evaporation
- > also there is limited open-ocean circulation producing a hypersaline environment
Why is sea surface salinity pattern more complex than temperature
-because evaporation and precipitation have a complex pattern
Describe the patterns in sea surface salinity
- SSS is generally highest in sub-tropical regions
- it is generally lower at the equator and in high-latitude regions
- > because of more precipitation
- SSS differences in some regions also heavily influenced due to runoff and or ice melt
- North Atlantic’s salinity is higher than the Pacific because of the circulation
- salinity is very high in marginal seas like the Red Sea where evaporation dominates
What are the six processes that affect the salinity by changing the amount of water
1) Evaporation
2) Precipitation
3) Runoff
4) Icebergs melting
5) Seaice melting
6) Sea ice forming
Is there more runoff in the northern latitudes
- yes
- >as a result, the salinity there is lower
Does Atlantic Ocean have higher SSS than the Pacific
- yes
- >because of the proximity to land
Describe the salinity in terms of depth between the low latitudes and the high latitudes
Low latitudes
->curve begins at the surface with high salinity
High-latitudes
->curve begins at surface with low saliniity
-at depths, curves converge since processes affecting salinity mainly occur at tthe surface
What is the halocline
- the region of rapidly changing salinity with depth
- >it separates the layers of different salinity in the ocean
What drives the atmosphere engine
- variations in solar radiation drive the global ocean-atmosphere engine
- > creating pressure and density differences that stirs currents and waves both in the atmosphere and the ocean
What is the composition of dry air
- it is almost entirely nitrogen and oxygen
- >with other gases like argon, carbon dioxide and water vapor in trace amounts
What is the triposphere
- it is the lowest layer of the atmosphere
- extends from surface to about 12 km up
- this is where all the weather occurs
- > note temperature decreases with altitude
- > at higher latitudes, air temperature is below freezing
Is warm air more dense than cold air or vice versa
- warm air is less dense than cold air
- > so warm air rises
- > cool air is more dense so it sinks
Is there a limit on how water vapor the atmosphere can hold
- yes
- > the atmosphere holds water vapor up to a certain amount
- > with the amount that can be held increasing with temperature
- > that is why warm air is typically moist and cold air is typically dry
Define the saturation water vapor pressure
- this is the maximum amount of water that can be held as vapor in air is the saturation vapor pressure
- > note amount of water vapor influences the density of air
What happens to water in the atmosphere during evaporation
-as water evaporates, water molecules which are lighter than air molecules are added to the atmosphere
- this means moist air is less dense than dry air
- > thus moist air tends to rise
- > if the water vapour is removed, the air gets more dense and sinks back
Does atmospheric pressure depend on the weight of the column of air above
- yes
- > thick column of air produces higher atmospheric pressure than a column of air
- this is why pressure decreases with altitude
- > higher up there is less air above you
- > so less weight/area pushing upon you
- > similar analogy to a swimming pool
How does a column of cool dense air compare to a column of warm air in terms of atmospheric pressure
Column of cool dense air
- > it is associated with high pressure at the surface
- > because of the fact that cooler air is sinking
Column of warm less dense air
- > it is associated with low pressure at the surface
- > because of the fact that warmer air is rising
- > rising is due to expansion
Does air flow in a pressure gradient
- yes it moves down the pressure gradient
- >from regions of high pressure to regions of low pressure
Connect the dots wit solar heating, density of air and the direction that wind would move
- solar heating causes air to rise at the equator
- > then this air spreads towards the poles
- rising air also creates low pressure at the surfface
- > so the surface winds flow towards the equator
- > rising air is moist but cools as it goes higher releasing it’s moisture as rain
- sinking air at the poles creates high pressure at the surface
- > sinking air is quite dry because cool air can’t hold much water vapor
- > poles experience clear and dry weather
What do the terms surface convergence and surface divergence mean in reference to the pressure at the equator and th epoles
Surface convergence
- > it occurs at the equator
- > this is resulting in low pressure
Surface divergence
- > it occurs at the poles
- > this is resulting in high pressure
