Density of Seawater calculations

[Laurie211098]

Seawater density is often reported in σ. Densities reported this way show the deviation from pure water in kg/m³. Therefore a seawater density of 25 σ indicates an actual density of 1025 kg/m³. This is done so the important density changes are easier to visualise.

The general form of the density equation is
σ = a +bT + cS +dT² +eST + fS² + gT³ + hST² + iS²T + jS³
Where σ is the density, S is salinity (in psu) and T is temperature (in °C).
The polynomial coefficients ‘a to j’ are given below as calculated by Cox et al. (1970).
a = 8.00969062 x 10^-2
b = 5.88194023 x 10^-2
c = 7.97018644 x 10^-1
d = -8.11465413 x 10^-3
e = -3.25310441 x 10^-3
f = 1.31710842 x 10^-4
g = 4.76600414 x 10^-5
h = 3.89187483 x 10^-5
i = 2.87971530 x 10^-6
j = -6.11831499 x 10^-8

Table 1

Location	Water Temperature (°C)	Water Salinity (psu)
Gulf Stream	27.94	35.89
North Atlantic Drift	17.83	35.27
Greenland Sea	8.24	34.78
NADW	4.34	34.88
AABW	0.17	34.77

What is the density of water in the Gulf Stream (in σ)?

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Question 12

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What is the density of water in the North Atlantic Drift (in σ)?

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Question 13

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What is the density of water in the Greenland Sea (in σ)?

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Question 14

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What is the density of AABW (in σ)?

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Question 15

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What is the density of NADW in σ ?

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Question 16

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There is observational error on the temperatures and salinities shown above - so the densities you have computed may not be physically plausible. Does your knowledge of physical geography mean that dense water formed in the North Atlantic must flow above that of dense water formed around Antarctic.

True or false?




Question 17

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Heat Capacity (Cp) is the thermal energy it takes to raise 1 kilogram of a substance by 1°C. Seawater has a very high Heat Capacity of 3.993 kJ kg⁻¹ K⁻¹. Assume the Gulf Stream is 80 Sv (10⁶ m³/s) and as it travel across the North Atlantic Ocean to the Greenland Sea the surface 10% cools by 10˚C. Calculate to three significant figures how much energy the Gulf Stream releases per day as it cools (in kJ). Assume that one litre of seawater weighs one kg and remember there are a 1000 litres in one m³.

Select one:
a. 1.15e12
b. 7.67e13
c. 2.76e7
d. 3.19e11
e. 2.76e16





Question 18

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Estimate to two significant figures how many coal fire stations generate the same amount of heat released over Europe by the cooling of the Gulf Stream. Assume a standard 500 MW coal fire power station generates 4.32 x 10¹⁰ KJ per day.

Answer:

 

[Laurie211098]

Seawater Density Questions Help Please!!!

[FONT=&quot]Seawater density is often reported in σ. Densities reported this way show the deviation from pure water in kg/m³. Therefore a seawater density of 25 σ indicates an actual density of 1025 kg/m³. This is done so the important density changes are easier to visualise.

The general form of the density equation is
σ = a +bT + cS +dT² +eST + fS² + gT³ + hST² + iS²T + jS³
Where σ is the density, S is salinity (in psu) and T is temperature (in °C).
The polynomial coefficients ‘a to j’ are given below as calculated by Cox et al. (1970).
a = 8.00969062 x 10^-2
b = 5.88194023 x 10^-2
c = 7.97018644 x 10^-1
d = -8.11465413 x 10^-3
e = -3.25310441 x 10^-3
f = 1.31710842 x 10^-4
g = 4.76600414 x 10^-5
h = 3.89187483 x 10^-5
i = 2.87971530 x 10^-6
j = -6.11831499 x 10^-8

Table 1

Location	Water Temperature (°C)	Water Salinity (psu)
Gulf Stream	27.94	35.89
North Atlantic Drift	17.83	35.27
Greenland Sea	8.24	34.78
NADW	4.34	34.88
AABW	0.17	34.77

What is the density of water in the Gulf Stream (in σ)?

Answer:


[/FONT]
[FONT=&quot][h=3]Question 12[/h]Answer saved
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[h=4]Question text[/h]What is the density of water in the North Atlantic Drift (in σ)?

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[FONT=&quot][h=3]Question 13[/h]Answer saved
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[h=4]Question text[/h]What is the density of water in the Greenland Sea (in σ)?

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[FONT=&quot][h=3]Question 14[/h]Answer saved
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[h=4]Question text[/h]What is the density of AABW (in σ)?

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[FONT=&quot][h=3]Question 15[/h]Answer saved
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[h=4]Question text[/h]What is the density of NADW in σ ?

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[FONT=&quot][h=3]Question 16[/h]Answer saved
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[h=4]Question text[/h]There is observational error on the temperatures and salinities shown above - so the densities you have computed may not be physically plausible. Does your knowledge of physical geography mean that dense water formed in the North Atlantic must flow above that of dense water formed around Antarctic.

Select one:
True
​False




[/FONT]
[FONT=&quot][h=3]Question 17[/h]Answer saved
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[h=4]Question text[/h]Heat Capacity (Cp) is the thermal energy it takes to raise 1 kilogram of a substance by 1°C. Seawater has a very high Heat Capacity of 3.993 kJ kg⁻¹ K⁻¹. Assume the Gulf Stream is 80 Sv (10⁶ m³/s) and as it travel across the North Atlantic Ocean to the Greenland Sea the surface 10% cools by 10˚C. Calculate to three significant figures how much energy the Gulf Stream releases per day as it cools (in kJ). Assume that one litre of seawater weighs one kg and remember there are a 1000 litres in one m³.

Select one:
a. 1.15e12
b. 7.67e13
c. 2.76e7
d. 3.19e11
e. 2.76e16




[/FONT]
[FONT=&quot][h=3]Question 18[/h]Not yet answered
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[h=4]Question text[/h]Estimate to two significant figures how many coal fire stations generate the same amount of heat released over Europe by the cooling of the Gulf Stream. Assume a standard 500 MW coal fire power station generates 4.32 x 10¹⁰ KJ per day.

Answer:


[/FONT]

 

[frank789]

Did you try plugging in your information? After a quick glance it seems you have all the information you need and it is just a matter of substituting the information provided in the table in the equation provided.

 

[frank789]

With regards to question 17, you have to calculate the amount of energy released. How did you try approaching it? Question 18 should be relatively straightforward after answering 17 as that is where you get the amount of energy you can equate to.

 

[mmm4444bot]

As noted in the forum's guidelines, there is no need to submit duplicate posts.