Physical Oceanography Flashcards
True or false, warm fluid rises and cold sinks?
True
Does fluid move from a low pressure to high or high to low?
Higher pressure to lower pressure
What are the 3 main sources of water circulation?
Wind stress, density differences (temperature, salinity) and tidal movements
What is the Coriolis effect?
Fluid is not attached to the Earth and so does not move in a straight line. As the Earth rotates, fluid is DEFLECTED.
Which way is water deflected in the Northern and Southern Hemispheres?
Northern Hemisphere = deflection to righ
Southern Hemisphere = deflection to left
What are subtropical gyres?
Rotating systems of currents in ocean basins.
Elongated and intensified by Coriolis effect
Water ‘piles’ up at surface.
Why is deep water colder?
Cold currents are denser than warm so sink
What are estuaries?
The connection between freshwater river and marine ocean. Have daily alternations in fresh and seawater.
What are estuaries important for?
Very important habitat for juvenile marine species. Highly productive.
What is the thermocline?
Transition layer between the warmer mixed water at the surface and the cooler deep water below.
What does dimictic mean?
There are two periods during a year where there is full turnover of deep and surface water through vertical mixing and temperature differences are negligible.
When do the two periods of full turnover generally occur?
Spring and Autumn
What is stratification of water influenced by?
Temperature and salinity, resulting in pressure differences
When does stratification of the water column generally occur?
Summer and winter
Why does stratification occur in the summer?
Surface water is warmer than usual due to more sunlight and increased temperature, meaning that deeper waters are cooler
Why does stratification occur in the winter?
Ice forms on the surface of water, making the surface cooler than deeper waters.
What is stratification in estuaries mostly influenced by?
Salinity differences
Is seawater or freshwater more dense?
Seawater is more dense and will sink under freshwater
What affects the amount of mixing in an estuary?
Structure of channel and outflow
What is upwelling (surface water being pulled from coasts) caused by?
Parallel winds and Ekman transport
What is downwelling?
When water is pushed towards coasts
What is the El Nino Southern Oscillation (ENSO)?
When there is a relaxation in equatorial winds, resulting in less upwelling and warmer waters
Where does the El Nino Southern Oscillation (ENSO) occur?
In the central and eastern equatorial Pacific
What does the El Nino Southern Oscillation (ENSO) mean for animals?
Cold, deep water is more oxygen and nutrient-rich. A lack of this can have negative impacts on food source availability and a lack of oxygen may lead to hypoxic conditions.
