Ocean Atmosphere Interaction Questions and Answers

Answer: B

The amount of CO₂ that can be absorbed Increases.

Like other gases, CO₂ is more soluble in colder water. As seawater cools, its capacity to hold dissolved CO₂ rises, so it can take up more from the atmosphere. This 'solubility pump' is why cold high-latitude waters, such as the North Atlantic and Southern Ocean, are major sinks of atmospheric CO₂.

'Remains the same' ignores the temperature dependence, 'decreases' reverses it, and 'can either increase or decrease' suggests no consistent rule, when the effect of cooling on solubility is always in the same direction.

Answer: A

The correct identification is 1. Great Whirl, 2. East India Coastal Current, 3. East African Coastal Current, 4. Summer (Southwest) Monsoon Current, and 5. West India Coastal Current.

• 1, the closed clockwise eddy off Somalia at about 5-10°N, is the Great Whirl, which forms beside the Somali Current during the southwest monsoon.
• 2, along the east coast of India, is the East India Coastal Current.
• 3, flowing north along the African coast south of the equator, is the East African Coastal Current, which feeds the Somali Current.
• 4, the eastward flow across the Arabian Sea and round Sri Lanka into the Bay of Bengal, is the Summer (Southwest) Monsoon Current.
• 5, flowing south along India's west coast in summer, is the West India Coastal Current.

The other options misplace these; for example, a coastal current cannot be the eddy at 1, and the West India Coastal Current cannot be marker 3 off Africa.

Answer: C

The low-chlorophyll, low-nutrient region is Downwelling, anticyclonic eddy.

In an anticyclonic eddy (clockwise in the Northern Hemisphere), Ekman convergence piles warm surface water towards the centre and pushes it down. This downwelling deepens the thermocline and keeps nutrient-rich deep water away from the sunlit layer, so phytoplankton growth, and with it chlorophyll, stays low.

Cyclonic eddies do the opposite: divergence at the centre causes upwelling, lifting nutrients into the surface layer and raising chlorophyll. Pairing an anticyclonic eddy with upwelling, or a cyclonic eddy with downwelling, mixes up these two mechanisms.

Answer: B

Sensible heat flux is due to the difference in temperature between the upper surface of the ocean and the lower part of the atmosphere.

Sensible heat is exchanged by conduction and turbulent transfer whenever the sea surface and the air above it are at different temperatures; bulk formulas take it proportional to the wind speed times the air-sea temperature difference.

A difference in specific humidity drives the latent heat flux (evaporation), a difference in CO₂ partial pressure drives the gas flux, and a density difference does not drive heat exchange.

Answer: A

An upwelling region has low sea surface height.

Upwelling occurs where the wind-driven Ekman transport carries surface water away, for example along eastern boundary coasts or at the equator. The divergence of surface water lowers the sea surface, and the cold, dense water brought up from below further lowers the steric height, so upwelling zones appear as lows in satellite altimetry.

The upwelled water is rich in nutrients, which raises primary production; this is why upwelling regions such as the Peru and Benguela coasts support major fisheries. So 'decrease in primary production' and 'low nutrients' are wrong, as is high sea surface height.

Answer: D

Sea-water density does not directly depend on vorticity.

The equation of state of sea water gives density as a function of temperature, salinity and pressure only. Warmer water is lighter, saltier water is denser, and pressure compresses the water at depth.

Vorticity describes the rotation of the flow. It can affect the density field indirectly, for example by driving upwelling that brings dense water up, but it does not appear in the equation of state.

Answer: B

The directions are counter-clockwise; clockwise.

Subtropical gyres are driven by the trade winds on their equator side and the westerlies on their poleward side, and steered by the Coriolis effect. In the Northern Hemisphere the deflection is to the right and the gyres turn clockwise, so the North Atlantic gyre (Gulf Stream, North Atlantic Current, Canary Current, North Equatorial Current) is clockwise.

In the Southern Hemisphere the deflection is to the left and the gyres turn counter-clockwise, so the South Pacific gyre (including the East Australian Current and the Humboldt Current) is counter-clockwise. The other options give both gyres the same sense or reverse the hemispheres.

Answer: C

The order is (iii) \(\gt\) (i) \(\gt\) (ii).

The surface geostrophic current is proportional to the slope of the sea surface:

\[ u = \frac{g}{f}\frac{\Delta\eta}{\Delta x} \]

All three eddies are at the same latitude, so f is the same and only the slope matters:

• (i): (30 - 20) cm over 200 km, a slope of \(5 \times 10^{-7}\).
• (ii): (20 - 10) cm over 300 km, \(3.3 \times 10^{-7}\).
• (iii): (15 - 5) cm over 100 km, \(1 \times 10^{-6}\).

Each eddy has the same 10 cm height difference, so the shortest distance gives the steepest slope and the fastest current. The other orders rank the eddies by height or ignore the distance.

Answer: B

The parameters are P1: Nitrate; P2: Chlorophyll; P3: Dissolved Oxygen.

• P1 is near zero at the surface and increases steadily with depth. That is nitrate: phytoplankton use it up in the sunlit layer, and it is regenerated from sinking organic matter at depth.
• P2 has a sharp peak near 50 to 70 m and is low above and below. That is the deep chlorophyll maximum, where there is still enough light and the nitrate supply from below begins.
• P3 is highest at the surface and falls sharply to near zero below about 70 m. That is dissolved oxygen, high in the mixed layer through exchange with the air and photosynthesis. The northern Indian Ocean has an intense oxygen minimum zone just below it.

The other options give one of these shapes to the wrong variable, such as oxygen rising with depth or nitrate peaking below the surface.

Answer: D

North Atlantic Deep Water is associated with low temperature and high salinity.

It forms in the Nordic and Labrador seas, where warm, salty surface water carried north by the Gulf Stream and North Atlantic Current is cooled strongly in winter. Sea-ice formation adds salt as well. The water becomes cold (about 2 to 4 °C) and still salty (about 34.9 to 35), dense enough to sink and spread south at depth as part of the global overturning circulation.

High temperature would make the water too light to sink, and low salinity marks waters such as Antarctic Intermediate Water rather than NADW.