ocean Flashcards
how much of the earth’s surface does the ocean cover
70%
how many oceans are there and how many basics
1 ocean with 5 basins (atlantic, pacific, indian, southern, arctic)
what light penetrates deepest into the ocean
blue light penetrates deeper than red light
the 3 ocean layers
sunlight zone, twilight zone, midnight zone
sunlight zone
is the surface layer also known as the euphotic or epipelagic zon, or the mixed layer. the upper 200 meters of the ocean. important layer for photosynthesis with enough sunlight and 90% of all marine life live here.
twilight zone
also known as the mesopelagic or dysphotic zone. little light penetration, 200-1000m. little photosynthesis occurs here
midnight zone
also known as the bathpelagic or aphotic zone. receives no sunlight, little light penetration from bioluminescent organisms. unusual organisms can survive in this, dark, harsh and high pressure environment
what are of the earth gets the most sunlight
the sun shines directly at the equator and tropics where most of the solar energy gets absorbed.
3 temperature layers
mixed layer, transition layer, deep layer
mixed layer
the temperature varies according to season and latitude. wind, waves, tides and convection mix this layer. the sun warms up this layer
transition layer
the temperature rapidly changes. also known as pycnocline, thermocline, or halocline.
deep layer
temperature is cool and about the same temp all the time
sunlight zone (surface of ocean) temp at high lats (polar)
as cold as -2, ocean water freezes at -194 so sea ice forms at high lats
sunlight zone temp at low latitudes (tropics)
as warm as 36
thermocline
layer of water where temperature changes rapidly with depth, also known as the transition layer (twilight zone area). separates warm surface water with the cool deep water. depth and strength of thermocline varies with season and lat. strongest at the tropics and nonexistent at the poles. found in low lats
thermocline seasonal variations in winter
weather/climate cold and stormy, no thermocline and layers well mixed
thermocline seasonal variations in spring
weather/climate is warming, reduced wind. reducsed mixing and thermocline is growing
thermocline seasonal variations in summer
weather/climate warmest and low wind. no mixing and a strong thermocline
thermocline seasonal variations in autumn
weather/climate cooling, increasing wind. thermocline decays and mixing begins
the densest water
cold, salty water
thermocline changes with latitude
the closer to the equator the more pronounced the thermocline is.
composition of seawater
96.5% water. 3.5% salt (made up of chloride, sodium, sulfate, magnesium, calcium, potassium and other minor constituents)
salinity
the mass of dissolved salt in water. most salt in the ocean comes from water running over rocks containing salt carrying it to sea
salinity reduced by
rainfall (tropics and mid lats) and river runoff adding large amounts of water changing the concentration
salinity increased by
evaporation (in tropics) and ice formation (polar) cause they remove large amounts of water while leaving salt behind.
why is polar water the densest
when seawater freezes salt is left behing in the ocean forming very dense water that sinks. cold and salty
halocline
layer of water where salinity rapidly changes with depth. varies around the earth prominent at the poles. found in high lats
halocline in high lats
water is less dense at the surface cause ice has formed and the cold salty dense water sinks. with depth salinity increases
halocline at low lats
salinity is high at the surface because of evaporation but because the water is warm it stays on the surface, halocline to the left as with depth salinity decreases
density
mass/volume.
density in the ocean
- the saltier the water the denser it is
- the colder the water the denser it is
-the least dense water is warm fresh water - densest is cold salty water
ocean is divided into 3 laters
surface layer, pycnocline layer, deep layer
pycnocline
layer where density changes rapidly. 18% of ocean. density changes due to temperature or vertical changes in salinity. its the barrier between surface and deep zones.
does salinity increase or decrease with water depth
increases with water depth
does temperature increase or decrease with water depth
decreases
does density increase or decrease with water depth
increases
the 3 density layers
the surface layer, pyncocline, deep ocean
surface mixed zone in density
(2% of the ocean) least dense water, mixed by wind, waves, tides and ocean currents. same salinity and temp throughout whole layer. temp changes due to sun and local weather. salinity varies due to evaporation, ice formation, run off and precipitation. non-existent in high lats.
deep zone density
80% of ocean, the bottom layer. the water is always cold and dense. cold dense water sinks at poles carrying o2, co2 and nutrients downward
ocean pressure
the deeper you go the greater the pressure of water
what determines density
pressure, salinity, and temperature
the thermohaline circulation (thc)
also known as the ocean’s conveyer belt is a global scale circulation that occurs over 100-1000 years. a giant convection current with many branches transports energy (heat), matter (nutrients, oxygen and co2) deep into the ocean and around the globe
what is the thc’s impact on the climate
it moves warmer waters towards the poles and cold water to the equator. the cold waters are nutrient rich with lots of dissolved co2 while warm waters are oxygenated less nutrients
how is the thc connected
the southern ocean connects all other oceans, it links major surface and deep water currents in atlatnic, indian, pacific and southern oceans
downwelling
occures when surface currents converge, the water has no where to go but down and surface water sinks. leading to low productivity zones as surface waters are low in nutrients
upwelling
process which deep, cold, nutrient rich water rises towards the surface replacing diverging surface water
how thermohaline circulation happens
- warm tropical water travels on the surface of the ocean towards the arctic and antartica (replacing cold water that has sunk)
- very cold winds blow off the ice and cool and freeze warm water
- latent heat released into atmoshere and lost in ocean
- as sea water freezes water immediately below ice becomes cold and dense. this dense water is called brine and sinks (downwells) to the ocean bottom driving the thc
- some of the deep water rises up to the surface in pacific and indian ocean after 1600-2000 years
- deep water eventually makes its way to the surface in the tropics (upwelling)
what is AABW
antartic bottom water, the densest water layer produced in antarctica (extreme south). this water is so dense it creeps along the ocean floor