Salinity, Temperature & Density Flashcards
Define salinity.
The total amount of solid material contained in a unit mass of seawater.
How does salinity occur?
The buildup of solutes over time in the hydrological cycle.
What are the units of salinity?
g/kg, ppt but now psu or nothing.
How is salinity measured?
Used to be titration with silver nitrate - now use electrical conductivity.
Define the term ‘Haline’.
To do with salt/salinity.
Define isohaline.
A line joining up all points of the same salinity.
Define the halocline.
A strong change in the gradient of salinity. Most common in estuaries. Density dominated by temperature in vertical (open ocean) so either high or low possible in upper layers.
What is the distribution of salinity like?
Zonal in distribution - surface salinity with close correlation to evaporation and rainfall.
What is the seasonal variation in the halocline?
It’s very slight - ice zones due to melting, Bay of Bengal + N.E. Pacific (strong monsoonal range).
What is the diurnal variation in salinity?
None, other than tides.
What does ‘T’ stand for? What are its units?
T = temperature of the ocean. Measured in degrees C or in Kelvin (deg. C +273).
What is the range of temperatures from pole to equator and from surface to deep?
Typically -1.9 to 30 deg.C from pole to equator, and 2 deg.C from 1000m+.
What is the annual change in temperature
20 deg.C in estuaries/Sea of Japan.
How is temperature measured?
+Thermometers (glass/mercury).
+Conductance of metal or semi-conductor (now).
+Remote sensing (surface skin layer only).
How does the conductance of metal/semi-conductors measure temperature?
When metals are heated, they become more resistant.
When semi-conductors are heated, they become less resistant.
What is the isotherm?
A line of equal temperature.
What is the thermocline?
An area of strong temperature gradient.
How does the temperature of the oceans shift during winter and summer?
In summer it shifts north, in winter it shifts south.
What is the main thermocline?
The thermocline that is present at all temperatures apart from at high latitudes.
Why is there no thermocline at higher latitudes?
It’s a result of water circulation patterns and low levels of sunlight. The solar energy is not enough to raise the surface temperature significantly, and without a warm top layer, the thermocline cannot form. The strong circumpolar currents also disrupt thermocline circulation.
Where is the majority of the heat diffusion?
At the poles, though it’s still very slow.
What causes the thin layer of mixed water at the surface of the ocean?
Surface wind and Ekman transport.
Why does water make a good solvent?
Its polar nature makes dissolving things very easy.
