Exam in GEF 2610 - Physical Oceanography
Day of exam:
Exam hours:
Monday 3 June, 2013
14:30 - 17:30
This examination paper consists of 5 pages.
Appendices: 1 map (2 copies)
Permitted materials: Calculator
Make sure that your copy of this examination paper is complete before answering.
a) A map of the Arctic Sea and the Nordic Seas, including a part of the North Atlantic, is enclosed. Draw the arrows for the surface currents and name the currents. (If there is too little space on the map, represent the names of the currents with numbers, and add a list of the numbers with corresponding names.) b) Where are the deep and bottom waters of this region formed? Mark the areas on the map with crosses. c) There are three main water types recognized in the Arctic Sea; Arctic Water, Atlantic
Water and Deep or Bottom Water. What are the differences in hydrographic properties
(salinity, temperature, density) between these water types? d) Describe briefly how the Atlantic Water enters the Arctic Sea, how it circulates, and what happens to it. e) What is the name of the ridge that separates the Arctic Sea into two basins, and what are the names of these basins?
a) The figure below shows isohalines in a vertical section of the Atlantic Ocean, in the northsouth direction (south to the left, north to the right). Four characteristic water types can be identified below the surface layer. Which ones are these water types, and where are they formed?
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b) The mentioned water types constitute parts of a vertical circulation. What is the name (or names) of this circulation? Which forces are driving this circulation? c) What are typical horizontal velocities of this circulation in the surface layer and in the deeper layers? d) What are typical vertical velocities in the downward direction and in the upward direction of this circulation? e) Describe briefly the circulation pattern in an estuarine circulation. What is usually setting up an estuarine circulation, and which forces are driving it? What is a typical vertical scale in an estuarine circulation? f) Describe briefly the circulation pattern in an upwelling. What is usually creating an upwelling, and which forces are driving it? What is a typical vertical scale?
a) The south-going transport of deep water in Question 2 (a) has been estimated to be 18 Sv.
If we assume that the transport of this water back up to the surface layer takes place in an area between 40°S-60°S and 20°E-60°W in the Atlantic, corresponding to about 12·10 12
m
2
, what will be the average vertical velocity, and how many days will a water particle need to travel 1 m in the upward direction? b) We assume that the velocities at the surface of the California Current (30 °N) and the East
Greenland Current (70 °N) both have average values of around 0.2 m s -1
. If these currents are geostrophically balanced, what will be the slopes of the surface across the currents at the two latitudes? c) At the station Malmøykalven the following energy irradiances were recorded on April 19,
2013:
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Depth (m) Irradiance (W m
-2
)
0
1
2
102
31
19
5
10
15
20
8.6
2.2
0.74
0.29
At which depth (make a crude estimate) has 99 % of the irradiance at 0 m (just beneath the surface) been absorbed? d) We shall assume that the irradiance at two depths z
1
and z
2 can be related to each other by
E ( z
2
)

E ( z
1
) e

K ( z
2
 z
1
) where K is the average vertical attenuation coefficient of irradiance between z
1
and z
2
. Based on the data in (c), what is the value of K between 10 and 20 m? e) Densities ρ recorded by the CTD instrument on April 19, 2013, are
Depth (m)
ρ
(kg m
-3
)
0
1
Malmøykalven
1022.80
1022.84
Geitholmen
ρ
(kg m
-3
1020.62
1022.26
)
2
3
1022.89
1022.92
1022.51
1022.63
Provided the surface is horizontal, what is the hydrostatic pressure at 3 m depth, at the stations Mamøykalven and Geitholmen, respectively? f) If the difference in hydrostatic pressure at 3 m depth at the two stations shall be compensated for by a difference ∆ z of the surface level, what will be the value of ∆ z ? g) Global warming may affect sea level by melting of land-based ice and by thermal expansion of seawater. The latter process may crudely be expressed as ∆
V =
γ
V ∆ T , where V is the original volume, γ the thermal expansion coefficient, and ∆ V the change of volume caused by the change ∆
T of temperature. We assume that
γ
≈ 0.0001 K
-1
, that the average depth of the world ocean is 3700 m, and that the surface area of the ocean remains constant. If
∆
T = 1 K, how much will the average rise of sea level be?
END
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ENCLOSURE Question 1 - GEF2610-2013
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ENCLOSURE Question 1 - GEF2610-2013
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