Describe the pattern of ocean salinity shown on the map.

Explain what is meant by the La Niña phenomenon.

Using examples, analyse two economic impacts associated with La Niña.

Examine the role of oceans as a store and source of carbon dioxide.

Highest salinity levels are found towards the tropics [1 mark] with higher levels in the Atlantic than the Pacific [1 mark]. Salinity levels generally decrease towards polar areas [1 mark]. Award [1 mark] for accurate quantification.

La Niña refers to an intensification of “normal” ocean temperature conditions [1 mark], bringing colder temperatures in the eastern Pacific and warmer in the west [1 mark]. Alternatively, there is high pressure in the eastern Pacific, low pressure in the western Pacific [1 mark], a high altitude flow from west to east, and a surface flow from east to west [1 mark].

• Loss of crops due to droughts and floods
• Cost of re-building damaged infrastructure (Australia, Brisbane floods, 2011)
• Costs of securing safe water supplies
• Benefits of increased fish stocks (Peru).

Award [1 mark] for an outlined impact and [1 mark] for use of examples.

The oceans account for an important share of the world’s carbon dioxide (fossil fuels 10 000 × 1012 kg, atmosphere 750 × 1012 kg, and oceans 38 000 × 1012 kg). They also play an important role in the carbon cycle. Photosynthesis by phytoplankton forms
organic compounds of carbon dioxide. Some of this passes through the food chain and sinks to the ocean floor where it accumulates in sediment. Eventually it is destroyed at subduction zones and later released during volcanic activity. It is a very long time-scale. Oceans also absorb and then store in solution carbon dioxide derived from the air.

Candidates may look at spatial variations in oceans as a source (more in warmer, nutrient rich water) and stores.

To access band D candidates must explain both store and source (balance not necessary). At bands E and F, a structured examination of both store and source begins to address the role/importance of the oceans.

Marks should be allocated according to the markbands.

Many found it difficult to describe the pattern of ocean salinity, although the best answers made effective use of quantitative information shown on the map.

There were some very good, detailed responses to this question. Unfortunately, a minority confused La Niña with El Niño and the impacts were assigned to the wrong locations.

There were some very good, detailed responses to this question. Unfortunately, a minority confused La Niña with El Niño and the impacts were assigned to the wrong locations.

Some good answers on oceans and carbon dioxide, and the better answers were well-structured. However, in general, this topic was not well understood.