Oceanography Flashcards
divergent plate boundry
2 plates drifting away from eachother
transform plate boundry
2 plates sliding past eachother (lateral sliding)
convergent plate boundry
1 plate goes underneath another
isostacy
gravity and bouyancy act on earths outer layers to bring them closer together
bathymetry
the measurement of ocean depths and the charting of the shape of the ocean floor
ring of fire
a string of volcanoes around edge of pacific ocean, substantial seismic activity and earthquakes caused by plate tectonics
ocean ridges
occupy 33% of total ocean floor area (continuosly spreading), sites of geological and biological importance due to deep sea thermal vents
abyssal plains
gradients less than 0.05 deg, flattest ocean feature (only interrupted by seamounts) and are covered in deep layers of sediments
sea mounts
most are ocean floor volcanoes (dont rise above sea level), slope angle as great as 25 deg
guyots
flat topped seamounts planed off by wave erosion
the hydrological cycle
the cycle of water through air/atmosphere, water and earth (water spends 7 days in clouds, 6.6 years in lakes and 3,060 years in the ocean)
key properties that determine the chemical structure of the oceans
temperature, salinity, depth/pressure determine the density of seawater
3 distinct zones of ocean temperature
1 - Surface zone (25-500m variable depth depends on mixing)
2 - Thermocline (200-1000m variable) rapid decrease in temp as surface heat diffuses down and advection of cool water
3 - Deep zone (below 1000m) stable temp around 1 deg C
Stratification
Temp and salinity determines the density of water, ocean therefore made of density layers. This stratification is key in determining nutrient supply to surface, and hence phytoplankton distributions and blooms.
warm tropical waters stratification
very stratified so nutrient depleted due to surface layers de-coupling from deep
Polar waters stratification
Cool at surface so easier to pull water down from surface (denser), so less stratified
important seawater nutrients for phytoplankton
- nitrogen as nitrate NO3- and ammonium NH4+
- phosphorus as phosphate (PO43-)
- silicon as silica SiO2).
Effects of salinity
As salinity increases
Density increases
Boiling point is higher
Freezing point is lower
what are ocean currents driven by
wind driven: generally surface currents.
Or can be part density driven: the global overturning circulation. Cold salty dense water produced at poles and sinks. There is a surface warm water flow. Most of the upwelling occurs in southern ocean. Thousand year timescale.
wind driven currents
major wind belts
The major surface loops: link closely to wind patternts with continential barriers
The gulf stream
The northerly loop of the north atlantic subtropical grye. About 4mph Carries warm water to the uk
Atlantic circumpolar current
It is the only current that circumscribes the whole earth. Connects all the other ocean basics. Driven by poweful westerly wind belt: ultimitaly drives upwelling of global deep waters back to surface. Stormiest ocean.
Pacific circulation
Two huge subtropical gryes dominate the pacific with a dominant equatorial countercurrent due to its size.
The plastic vortex
The convergent flow in the north pacific grye is also known as plastic vortex bc of collection over time of masses of debri non bio degradable
Equatorial flow
divergence and upwelling
Currents and winds drive vertical upwelling (as well as horiz flow) that replenishes surface nutrients to euphotic zone
