lec 7 Flashcards
what is the effect of stratification on oxygen profiles?
while water is mixing in spring/fall, the oxygen profile looks relatively uniform
in summer, as stratification lengthens, oxygen depletes in the hypolimnion (epilim is largely unaffected and metalim as well to some extent)
what conditions allow for faster diffusion (2 factors)
higher temp + smaller particles
coriolis effect ekman transport etc
bc the earth rotates nothing goes right –> ekman transport in water
how does wind work considering the boundary layer stifles interaction between air/water?
kinetic energy by wind leads to circular motion that moves downward –> causes waves
consider water is sticky: when the layer above it moves, the lower layer is dragged along
what is langmuir circulation?
wind waves push against gravity waves, causing spirals that spin perpendicular to direction of the wind
how do daytime currents occur? where are they more likely to occur?
heating in surface waters creates a density gradient against the cooler waters below –> rather than mixing, they spread out - denser water fills its place
in the evening when the water cools, the denser cooler water that didn’t warm up sinks back down while the warmed water cools a bit, sinking as well
most likely to occur in shallower lakes
out of wind induced currents, langmuir circulation, and daytime currents, which is most influential on the epilimnion?
wind induced + langmuir are important for epilim, daytime currents are not
how do seiches work? what is an internal seiche, and what implications does it have for lake mixing?
strong winds push water so that it builds up –> big big wave, even when winds stop (internal motion persists)
internal seiches occur when the motion persists, and it has big implications for mixing between the epi- and hypolimnion (advective transport that transports nutrients/oxygen up and down)
