IB Geography Option B: Oceans and coastal margins

What Option B covers

Option B starts with ocean–atmosphere interactions: surface currents, gyres and the Coriolis effect, upwelling, thermohaline circulation, the Walker circulation, El Niño and La Niña, and tropical cyclones. Interactions between oceans and coastal places: waves and fetch, swash, backwash and longshore drift, sediment cells, coastal landforms such as spits, tombolos and wave-cut platforms, and eustatic and isostatic changes in sea level. Then managing coastal margins and the oceans themselves: hard engineering such as groynes and rip-rap, soft approaches such as beach nourishment and managed retreat, and integrated coastal zone management; and how ocean resources are shared and protected, through UNCLOS and its maritime zones, from the territorial sea to the exclusive economic zone and the high seas, maximum sustainable yield, bycatch and marine protected areas.

Where students slip

• A eustatic change is a worldwide rise or fall in sea level, as the volume of ocean water changes. An isostatic change is the land itself rising or sinking, as when land rebounds after an ice sheet melts, and it changes sea level only locally.
• A coastal state's sovereignty reaches only to the edge of its territorial sea, 12 nautical miles out, and even there foreign ships keep a right of innocent passage. In its exclusive economic zone, out to 200 nautical miles, it controls fishing and seabed resources, but other states' ships are free to sail through.
• Groynes protect the beach they are built on by trapping sediment moving along the coast by longshore drift. The same sediment no longer reaches the beaches further along, so erosion there can get worse.