Exploring Oceans

What Exploring Oceans covers

Exploring Oceans is examined in Component 03, Geographical debates. It covers the size of the oceans and the shape of the sea floor; salinity and temperature through the water column; surface currents, the great gyres and the North Atlantic conveyor; the light, warmth and nutrients that limit ocean life, and food webs from the inter-tidal zone to the deep sea; and the resources the oceans offer, from Southern Ocean krill and whales to oil, gas, wave and tidal energy and deep-sea metals. It also covers the global commons and ocean governance; marine pollution, the Deepwater Horizon spill and the North Pacific garbage patch; ocean acidification, coral bleaching, rising sea level in the Maldives and the loss of Arctic sea ice; the changing Arctic and its new sea routes; and shipping lanes, naval power, piracy and migration by sea.

The 22 subtopics

Each one has its own page.

• The size and spread of the world's oceansRecall questions on the share of the Earth covered by ocean, its area, volume and share of Earth's water, the five named oceans, the Pacific as largest and the Arctic as smallest and shallowest, mean ocean depth, the Challenger Deep, the Southern Ocean boundary, the water hemisphere, and why ocean volume matters for climate.Open →
• The shape of the sea floor, from shelf to trenchRecall questions on the continental shelf and its importance to fishing, the continental slope and submarine canyons, the abyssal plain, ocean ridges and their rift valleys on the Mid-Atlantic Ridge and East Pacific Rise, ocean trenches in the Pacific, and how seamounts and flat-topped guyots form and support marine life.Open →
• Salinity and temperature through the water columnRecall questions on salinity and its average value, the dissolved salts and their origin, why surface salinity varies from the subtropics to the equator and poles, the Red Sea and Baltic Sea, haloclines and brine rejection, the thermocline in tropical and mid-latitude seas, the freezing point of sea water, and how temperature and salinity set density.Open →
• Surface currents and the great ocean gyresRecall questions on what drives surface currents, the five subtropical gyres and the Coriolis effect, warm currents such as the Gulf Stream and Kuroshio, cold currents such as the Peru and Benguela, arid coasts and upwelling fisheries, the Antarctic Circumpolar Current, western and eastern boundary currents, and heat transfer.Open →
• The North Atlantic conveyor, from Gulf Stream to deep return flowRecall questions on surface circulation in the North Atlantic, the Gulf Stream and North Atlantic Drift, mild British winters and ice-free Norwegian ports, the Labrador Current and Newfoundland fog, how North Atlantic Deep Water forms and flows, thermohaline circulation, and how Greenland meltwater could weaken the overturning.Open →
• Light, warmth and nutrients as limits on ocean lifeRecall questions on the photic zone and light penetration, red deep-sea animals, phytoplankton and limiting nutrients, nutrient-poor open oceans and gyre deserts, seasonal and polar plankton blooms, upwelling and its share of the fish catch, latitude and species richness, chemosynthesis, and the diversity of coral reefs.Open →
• Food webs in the inter-tidal zone and the deep seaRecall questions on inter-tidal producers, rocky shore food chains and zonation, the stresses and limpet adaptations of the shore, inter-tidal productivity, the absence of photosynthesis in the deep sea, marine snow, deep-sea conditions and fish adaptations, contrasting food chains, biomass and diversity, hydrothermal vents, and slow deep-sea recovery.Open →
• Harvesting Southern Ocean krillRecall questions on Antarctic krill as a keystone species, its stock size and dependence on sea ice, the products it is harvested for, Norway and other fishing nations, the CCAMLR ecosystem approach and trigger level, fishing in the Scotia Sea, continuous pumping, local pressure on penguins and seals, and the threats of warming and ocean acidification.Open →
• Whaling, stakeholder conflict and resource thresholdsRecall questions on the International Whaling Commission and the moratorium, the collapse of blue whales, legal exceptions and whaling by Norway and Iceland, arguments for and against whaling, whale watching, how wealth and IWC voting shape the debate, K-strategists and krill resilience, maximum sustainable yield, recruitment overfishing, thresholds, and the Southern Ocean Whale Sanctuary.Open →
• Ocean energy: oil, gas, waves and tidesRecall questions on offshore oil and gas as non-renewable resources, the conditions for an oil field, the North Sea, Gulf of Mexico and Brazil's pre-salt fields, costs, environmental risks and decommissioning, wave power and oscillating water columns, tidal range and tidal stream technology, La Rance and Sihwa Lake, the Severn Estuary, and barrage impacts.Open →
• Mining the deep sea bed for metalsRecall questions on ferrous and non-ferrous minerals, polymetallic nodules in the Clarion-Clipperton Zone, seafloor massive sulfides and cobalt-rich crusts, rising demand for battery metals and cobalt from the Democratic Republic of the Congo, the International Seabed Authority and the common heritage of mankind, ecological impacts, slow recovery, and calls for a pause.Open →
• The global commons, maritime zones and ocean governanceRecall questions on the global commons and Hardin's tragedy of the commons, its ocean examples and proposed solutions, free riders, baselines, territorial seas, contiguous zones and exclusive economic zones, the high seas, the UN Convention on the Law of the Sea and its weaknesses, marine protected areas such as the Ross Sea, paper parks, and the 2023 high seas treaty.Open →
• The major sources of marine pollutionRecall questions on land-based marine pollution, point and diffuse sources, carbon dioxide as an ocean pollutant, plastic inputs, primary and secondary microplastics, ghost gear, mercury poisoning at Minamata, bioaccumulation and biomagnification in orcas, radioactive waste, fertiliser dead zones in the Gulf of Mexico, and routine oil pollution.Open →
• The Deepwater Horizon oil spill and its aftermathRecall questions on the 2010 Deepwater Horizon blowout at the Macondo well, the deaths and the scale of the spill, booms, skimmers and burning, deep dispersant injection and its controversy, oiled coastline, harm to dolphins, deep corals, birds and turtles, effects on fishing and tourism, the compensation fund, penalty spending, and regulatory change.Open →
• Drifting plastic and the North Pacific garbage patchRecall questions on why debris gathers in gyres and crosses oceans, the location, size and nature of the North Pacific garbage patch, fishing gear and microplastics in its make-up, its sources, deaths of sea turtles and albatross chicks, false satiation, toxic chemicals and rafting species, clean-up systems, and tackling plastic at source.Open →
• Ocean acidification, warming seas and coral bleachingRecall questions on the chemistry of ocean acidification and the fall in pH, shell-building organisms and pteropods, impacts on shellfish farms, fish stocks and seafood-dependent people, ocean heat uptake, zooxanthellae and coral bleaching, recovery and the rising frequency of bleaching, the value of reefs, and the Great Barrier Reef.Open →
• Rising sea level and low-lying island communitiesRecall questions on thermal expansion and ice sheet melt, groundwater pumping, the rise since 1900 and local variation, consequences for low coasts, the geography, economy and fresh water lenses of the Maldives, the 2004 tsunami and coral loss, short-term adaptations, Hulhumalé and population consolidation, and island diplomacy.Open →
• Sea ice, the albedo feedback and irreversible thresholdsRecall questions on sea ice and icebergs, the seasonal cycle and decline of Arctic sea ice extent and volume, albedo and the positive ice-albedo feedback, Arctic amplification, an opposing negative feedback, climate tipping points in Greenland, West Antarctica and ocean circulation, and hysteresis.Open →
• The changing Arctic: peoples, politics and new sea routesRecall questions on the Arctic Council and its indigenous Permanent Participants, competing sea bed claims, Arctic gas reserves and Russia's 2007 flag, the Northern Sea Route and slow growth of shipping, the disputed Northwest Passage, effects on Inuit livelihoods, the relocation of Shishmaref, new opportunities, heavy fuel oil rules, the central Arctic fishing moratorium, and the Council's weaknesses.Open →
• Shipping lanes, container ships and seaborne tradeRecall questions on seaborne trade, the busiest liner routes, chokepoints such as Hormuz, Malacca, Suez and Panama, the 2021 Suez blockage, containerisation and TEUs, ever-larger ships and their drawbacks, transhipment hubs, flows of manufactured goods and bulk raw materials, the backhaul problem, and shipping's environmental effects.Open →
• Naval power and contested seasRecall questions on sea power and overseas bases, United States Navy home ports, overseas bases and aircraft carriers, China's base at Djibouti and the string of pearls, the four Russian fleets and warm-water ports, the South China Sea, the nine-dash line, Spratly island building and the 2016 ruling, the status of reefs, freedom of navigation operations, and other contested seas.Open →
• Piracy and migration by seaRecall questions on the legal definition of piracy, its control in the Strait of Malacca, Somali piracy and its causes, the Gulf of Guinea, shipboard defences, naval operations and prosecution, why piracy must be ended on land, the deadly Mediterranean routes to Europe, why people risk the crossing, rescue duties, Australia's boat turnbacks, the Rohingya in the Andaman Sea, and non-refoulement.Open →

What you need to know

Answer each one before you reveal it.

Take Exploring Oceans further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Sea ice vs Iceberg

  Sea ice: frozen salt water that forms and floats on the ocean surface, so its melting adds nothing to global ocean level. Iceberg: A floating mass of frozen fresh water that has broken away from a glacier flowing off the land, so its melting does raise global ocean level.

• Ocean ridge vs Ocean trench

  Ocean ridge: an undersea mountain chain marking a constructive margin, where magma rises between separating plates and new crust is created. Ocean trench: A long, narrow deep marking a destructive margin, where one plate is forced down beneath another and crust is destroyed.

• Thermocline vs Halocline

  Thermocline: the layer of the water column across which temperature falls sharply with increasing depth. Halocline: The layer of the water column across which salinity changes rapidly with increasing depth.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Roughly what proportion of the Earth's surface is covered by ocean?

   Model answer

   About 71% of the Earth's surface is ocean, leaving roughly 29% as land.

2. 2

   State the approximate total surface area of the world's oceans.

   Model answer

   The oceans cover an area of about 361 million km².

3. 3

   Approximately what volume of water do the oceans hold?

   Model answer

   The oceans hold roughly 1.34 billion km³ of water.

4. 4

   What share of all the water on Earth is held in the oceans?

   Model answer

   About 97% of the Earth's water is held in the oceans as saline water.

5. 5

   Name the five named oceans recognised today.

   Model answer

   They are the Pacific, Atlantic, Indian, Southern and Arctic Oceans.

6. 6

   Which ocean is the largest, and roughly how much of the ocean surface does it occupy?

   Model answer

   The Pacific is the largest, covering about 165 million km², which is close to half of all ocean area.

What is inside Levo

Six ways to work the same material.

Exploring Oceans revision questions

What does Exploring Oceans cover in OCR A-Level Geography?

22 subtopics: the size and spread of the world's oceans, the shape of the sea floor, from shelf to trench, salinity and temperature through the water column, surface currents and the great ocean gyres, the north atlantic conveyor, from gulf stream to deep return flow, light, warmth and nutrients as limits on ocean life, food webs in the inter-tidal zone and the deep sea, harvesting southern ocean krill, whaling, stakeholder conflict and resource thresholds, ocean energy: oil, gas, waves and tides, mining the deep sea bed for metals, the global commons, maritime zones and ocean governance, the major sources of marine pollution, the deepwater horizon oil spill and its aftermath, drifting plastic and the north pacific garbage patch, ocean acidification, warming seas and coral bleaching, rising sea level and low-lying island communities, sea ice, the albedo feedback and irreversible thresholds, the changing arctic: peoples, politics and new sea routes, shipping lanes, container ships and seaborne trade, naval power and contested seas and piracy and migration by sea. Each one has its own page with questions and model answers.

How is Exploring Oceans organised?

By the OCR H481 specification, subtopic by subtopic, so it matches the order you are taught it in.