Oceanic Processes Flashcards
Why is the ocean important?
Absorbs CO2 Regulates stabilises earths temp Contains most earths volcanoes Drives weather and climate Shape earths chemistry Abundance of living things Produces 70% oxygen
How much of earths surface is covered by the ocean?
70%
What is latent heat?
The amount of heat energy absorbed or released when 1kg of the substance changes phase/state
Waters properties
High specific heat capacity
Water has lower density than solid
Melting and boiling points unusually high
Good solvent
Three zones of the ocean
Euphotic (sunlight) zone
Disphotic (twilight) zone
Aphotic (midnight) zone
Euphotic zone
Layer nearest surface
Extends from the surface to 200m
Photosynthesis occurs because enough sunlight
90% all marine life lives in this zone
Disphotic zone
Minuscule amount of light
Extends from a depth of 200m-1000m
Plants do not grow, only animals with adaptations
Aphotic zone
Extends beyond 1000m, completely dark
90% of the ocean in this zone
What is a thermocline
A layer of water where temp changes rapidly with depth, separating warm surface water from cool, deeper waters
Thermoclines and latitude
Vary with latitude, high latitudes and equator no thermocline as water isothermal
Mid-latitudes coastal water warmed during summer cooled during winter developing a thermocline
Thermoclines and seasonal changes
Thermoclines are seasonal in mid-latitudes forming during spring and autumn
Mixing distributes heat energy, amount of mixing determines how quickly temp changes
Winter: no thermocline-water well mixed stormy conditions
Spring: thermocline starts- less mixing less wind, surface warmer
Summer: strong thermocline- no mixing very little wind, water warm
Autumn: thermocline decays- surface water cooling, winds increase mixing
Factors that increase salinity at the surface
Evaporation, sea-ice formation
Factors that decrease salinity at the surface
Precipitation (rainfall), river runoff, melting icebergs, melting sea ice
Haloclines and latitude
Salinity varies with latitude, high latitudes water less saline as melting icebergs, precipitation, runoff. Temperate regions warm dry air descends because of circulation increases evaporation, water more saline.
Equator temp higher evaporation is greater increase salinity but greater precipitation and runoff offset evaporation
What is a halocline
A layer of water where salinity rapidly changes with depth
Halocline and depth
Salinity varies with depth, at equator halocline not as prominent as tropics and poles
What is density
How much mass is contained in a given volume (density=mass/volume)
Density of pure water at 4 degrees
1 g cm-3
Density of seawater
1.022 g cm-3 to 1.030 g cm-3
Salinity of the ocean
Between 32 and 37 ppt
How does temp, salinity, pressure determine water density
Temperature increases, density decreases due to thermal expansion
Salinity increases, density increases due to dissolved material
Pressure increases, density increases due to compression effects of pressure
Three layers of ocean water on density
Surface mixed layer
Pycnocline/transition layer
Deep layer/bottom layer
Surface mixed layer
Top layer (2%), less dense water Temp changes with weather (higher temp) Salinity changes evaporation or dilution of water (lower salinity)
What is a pycnocline
The layer in water where density changes rapidly with depth due to either change in temp or salinity
Transition layer/pycnocline
Occurs 300 to 1000m below surface. Forms strong barrier that prevents mixing of low density and high density water between surface layer and deep layer
Deep layer/bottom layer
(80%) cold dense water
Temp does not change much as depth increases and becomes nearly constant at about 0 to 3 degrees Celsius
What is pressure
The ratio of force to the area over which that force is distributed
Two types of ocean currents
Surface currents
Deep water currents (thermohaline)
Surface currents driven by:
Winds
Deep water currents/thermohaline driven by:
Density
What generates ocean currents
Solar radiation
Gravity
Winds (westerlies and easterly trade winds)
What is the coriolis effect
The apparent deflection of objects (aircraft, wind, missiles and ocean currents) moving in a straight path relative to the earths surface. Rotates clockwise NH and anticlockwise in SH
What is a gyre
A large system of rotating ocean currents
How much of the earths surface is covered by the ocean?
75% or three quarters
West boundary currents
Large deep fast ocean currents moving warm water/heat from equator to poles
Eastern boundary currents
Shallower broader slower currents that transport cool water from poles to equator
3 factors that affect wind wave growth
Wind strength
Wind duration
Fetch
4 factors that affect wave speed and direction
Wave refraction, defraction, reflection, interference
Ekman transport in NH
Moves water 90 degrees to the right
Ekman transport in SH
Moves water 90 degrees to the left
What is Ekman transport
Surface water moved by winds drags deeper layers below. Each layer moved by friction of upper layer. Deeper layers slower as energy lost, tend to twist. Layers deflected by Coriolis effect, each successively deeper layer moves to right or left.
Coastal upwelling in SH
Southerly wind causes upwelling
Coastal downwelling in SH
Northerly wind causes downwelling
What is a wave
A cycle that travels through water transferring energy through its motion
Types of waves
Capillary waves (gentle breezes)
Wind waves (wind)
Tsunamis (landslides, earthquakes, volcanoes)
Tides (gravitational attraction)
Tides
Regularly rising and falling sea levels caused by combined effects of earths rotation and gravitational forces of moon and sun
Spring and king tides
Sun earth and moon in line (new and full moons) combined gravities exert greatest pull on oceans causing highest highs and lowest lows.
Moon closest to earth causes king tides.
Neap tide
Sun and moon at right angles to each other (1/4 and 3/4 moons) gravitational pulls on ocean in two ways gives low high and a high low tide.
Thermohaline circulation
Deep ocean currents carry warm and cold water at a speed of a few cm’s per second around the globe by density differences. A mixture of temp and salinity determine density.
Physical pump
CO2 dissolved into oceans –> transported down to deep ocean stored in currents and sediments –> upwelling CO2 released back to atmosphere
Biological pump
CO2 used by marine organisms to synthesise other C compounds –> die or eaten drift down as marine snow –> buried on sea floor, bacteria assist decomposition, CO2 back into water from respiration
