Salinity, Temperature & Density

Question 1

Define salinity.

Answer 1

The total amount of solid material contained in a unit mass of seawater.

Question 2

How does salinity occur?

Answer 2

The buildup of solutes over time in the hydrological cycle.

Question 3

What are the units of salinity?

Answer 3

g/kg, ppt but now psu or nothing.

Question 4

How is salinity measured?

Answer 4

Used to be titration with silver nitrate - now use electrical conductivity.

Question 5

Define the term ‘Haline’.

Answer 5

To do with salt/salinity.

Question 6

Define isohaline.

Answer 6

A line joining up all points of the same salinity.

Question 7

Define the halocline.

Answer 7

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.

Question 8

What is the distribution of salinity like?

Answer 8

Zonal in distribution - surface salinity with close correlation to evaporation and rainfall.

Question 9

What is the seasonal variation in the halocline?

Answer 9

It’s very slight - ice zones due to melting, Bay of Bengal + N.E. Pacific (strong monsoonal range).

Question 10

What is the diurnal variation in salinity?

Answer 10

None, other than tides.

Question 11

What does ‘T’ stand for? What are its units?

Answer 11

T = temperature of the ocean. Measured in degrees C or in Kelvin (deg. C +273).

Question 12

What is the range of temperatures from pole to equator and from surface to deep?

Answer 12

Typically -1.9 to 30 deg.C from pole to equator, and 2 deg.C from 1000m+.

Question 13

What is the annual change in temperature

Answer 13

20 deg.C in estuaries/Sea of Japan.

Question 14

How is temperature measured?

Answer 14

+Thermometers (glass/mercury).
+Conductance of metal or semi-conductor (now).
+Remote sensing (surface skin layer only).

Question 15

How does the conductance of metal/semi-conductors measure temperature?

Answer 15

When metals are heated, they become more resistant.

When semi-conductors are heated, they become less resistant.

Question 16

What is the isotherm?

Answer 16

A line of equal temperature.

Question 17

What is the thermocline?

Answer 17

An area of strong temperature gradient.

Question 18

How does the temperature of the oceans shift during winter and summer?

Answer 18

In summer it shifts north, in winter it shifts south.

Question 19

What is the main thermocline?

Answer 19

The thermocline that is present at all temperatures apart from at high latitudes.

Question 20

Why is there no thermocline at higher latitudes?

Answer 20

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.

Question 21

Where is the majority of the heat diffusion?

Answer 21

At the poles, though it’s still very slow.

Question 22

What causes the thin layer of mixed water at the surface of the ocean?

Answer 22

Surface wind and Ekman transport.

Question 23

Why does water make a good solvent?

Answer 23

Its polar nature makes dissolving things very easy.