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stratification
water layers with different densities; densest water sinks to the bottom, least dense remains at the surface
water column
a vertical section of water extending from the surface down
temperature distribution
deep water: cold and dense
surface water: usually warm and less dense
profile
graph depicting temperature, salinity, or other characteristics at various depths
pynocline
zone of quick density increase with depth
thermocline
zone of rapid temperature drop with depth
halocline
zone of rapid salinity increase with depth
stability factors
low stability: more dense water over less dense water leads to easier mixing
high stability: increased density with depth limits mixing
downwelling
occurs when surface water becomes denser than deep water; happens typically in winter when cooling increases density
upwelling
winds blow across the ocean, pushing surface water away, causing deeper nutrient-rich water to rise
resulting water is colder and rich in nutrients
thermohaline circulation
“great ocean conveyor belt”
movement patterns of water masses influenced by temperature (thermo) and salinity (haline)
surface layer
mixed layer from surface down to 200 meters, influenced by wind, waves, and currents
intermediate layer
from 200 to 1,500 meters, characterized by thermocline with rapid temperature drop
deep/bottom layers
below 1,500 meters, uniformly cold
ocean motion
constant motion through waves, currents, and tides
coriolis effect
earth’s rotation causes moving objects to bend rather than travel in a straight line
deflects winds and currents: right (clockwise) in the northern hemisphere, left (counterclockwise) in southern
trade winds
known for being the steadiest winds on earth, moving from east to west in the tropics
winds bent 45 degrees towards the equator due to the Coriolis effect
westerlies
found at middle latitudes, moving from west to east
polar easterlies
at high latitudes, these winds are variable and move from east to west
ekman spiral
surface winds initiate surface current at a 45 degree angle due to the Coriolis effect; this movement propagates to layers below, creating an angled flow
equatorial currents
wind-driven surface currents moving parallel to the equator under trade winds’ influence
gyres
large, circular systems formed by the combination of equatorial currents, influenced by the Coriolis effect
crest
highest part of a wave
trough
lowest part of a wave
wavelength
distance between crests
wave height
vertical distance from trough to crest
period
time taken for two successive crests to pass a fixed point (in seconds)
generative forces
created primarily by wind; stronger and longer winds produce larger waves
fetch
distance over which the wind blows; longer fetch results in bigger waves
seas (wind waves)
formed during storms, sharp crests and flat troughs
swells
after the storm, waves smooth out into rounded crests and troughs, exhibiting ideal circular motion
tides
rhythmic rise and fall of sea levels, heavily impacting nearshore sea life
influenced by the gravitational forces of the moon and sun along with earth’s rotation
centrifugal force
causes water to bulge outward on the side away from the moon
gravitational force
pulls water toward the moon, creating tidal bulges
spring tides
occurs when the earth, moon, and sun align (full and new moons); leads to highest high tides and lowest low tides (twice monthly)
neap tides
result when the sun and moon are at right angles (quarter moons); leads to lower high tides and higher low tides (also twice monthly)
semidiurnal tides
two high and two low tides daily
mixed semidiurnal tides
successive high tides at different heights
diurnal tides
rare, characterized by one high and one low tide daily
what three factors affect wave height?
wind speed, wind duration, and fetch
tide table
a table indicating the times of high and low tides at a particular place
