Mission 1: The Gulf Stream carries more water than all the world's rivers combined. Is that why north-west Europe has mild winters?

Surface currents and gyres

• Wind, tides, and differences in temperature and salinity drive ocean currents.
• Earth's rotation deflects moving air and water to the right in the Northern Hemisphere and to the left in the Southern: the Coriolis effect.
• Surface currents form gyres, large rotating systems. There are five major gyres: the North and South Pacific, the North and South Atlantic, and the Indian Ocean subtropical gyres.

Warm and cold currents

• On the western side of each ocean basin, warm currents carry tropical water towards the poles (the Gulf Stream, the Kuroshio).
• The Gulf Stream's extension, the North Atlantic Drift, carries warm water on towards north-west Europe.
• On the eastern side, cold currents flow towards the equator (the Humboldt off Peru, the Canary, the Benguela).
• Warm currents warm and moisten the air above them; cold currents cool it and often bring fog and aridity to the coast.

The global conveyor belt

• Below the surface, the thermohaline circulation is driven by density, which depends on temperature (thermo) and salinity (haline).
• When sea ice forms, the remaining seawater gets saltier and denser, and starts to sink. Water that loses heat to the atmosphere also becomes denser and sinks.
• NOAA describes the global ocean conveyor belt as getting its "start" in the Norwegian Sea.
• The Atlantic part is the Atlantic Meridional Overturning Circulation (AMOC).

Nutrient transfers: upwelling

• Upwelling is a process in which deep, cold water rises towards the surface. Winds blowing along the shore push surface water away.
• Upwelled water is typically colder and rich in nutrients, so good fishing grounds are found where upwelling is common.
• Off Peru, upwelling in the Humboldt Current feeds the anchoveta fishery, which in recent years made up to 71% of catches in the South-east Pacific.

Energy transfers

• Currents move heat from the tropics towards the poles. NOAA calls the Gulf Stream "the main conveyor of heat from south to north in the Atlantic".
• This is an energy transfer: the ocean releases the heat to the air in higher latitudes.

Does the Gulf Stream warm Europe? (AO3)

• Seager et al. (2002) modelled Europe's mild winters. They found "the principal cause" of the winter contrast with eastern North America "is advection by the mean winds".
• Ocean heat transport warms winters on both sides of the North Atlantic "by a few degC", in an essentially uniform way, so it does not explain the contrast between them.
• Exam move: an influential model study is evidence, not proof. Say what it found, and weigh it against other explanations.

A changing conveyor

• IPCC (2021): the AMOC "is very likely to weaken over the 21st century for all emissions scenarios".
• It has "medium confidence that there will not be an abrupt collapse before 2100".
• If a collapse did occur, it would very likely bring abrupt shifts such as weaker African and Asian monsoons and drying in Europe.
• Synthesis: a change in one part of the ocean system has effects far away.

Mission 2: In December 2023 the Panama Canal let through 22 ships a day, against 36 in its "regular scenario". What did a patch of warm Pacific Ocean have to do with it?

Normal conditions in the tropical Pacific

• Trade winds blow west along the equator, taking warm water from South America towards Asia; cold water rises off South America to replace it.
• Warm water piles up in the west, as the Pacific Warm Pool. Air rises over it and sinks over the cooler east.
• This loop of rising air in the west and sinking air in the east is the Walker Circulation.

El Niño and La Niña

• El Niño: above-average sea surface temperatures in the central and eastern tropical Pacific. The easterly trade winds weaken or even reverse.
• Rising air and rain shift east with the warm water, beyond 180°: less rain over Indonesia, more over the central Pacific.
• The thermocline in the east-central Pacific deepens to typically 150–175 m, and upwelling weakens or stops.
• La Niña: below-average temperatures there, stronger trade winds, more upwelling, a thermocline of typically 50–100 m, and more rain over Indonesia.

A coupled system

• ENSO is coupled: ocean and atmosphere change together.
• The atmospheric half is the Southern Oscillation, a see-saw of air pressure between Tahiti and Darwin.
• A strongly negative Southern Oscillation Index (SOI) goes with El Niño, and a strongly positive one with La Niña.

How often, and how it is measured

• NOAA's Oceanic Niño Index (ONI) is the rolling 3-month average temperature anomaly in the east-central tropical Pacific. Values of +0.5 or higher indicate El Niño; −0.5 or lower, La Niña.
• Episodes typically occur every 3–5 years, though the interval has varied from 2 to 7 years. They typically last nine to 12 months.
• WMO: the 2023–24 El Niño peaked in December 2023 "as one of five strongest on record".

El Niño 2023–24: the Panama Canal

• The Gatun and Alhajuela lakes store water for the canal's operation and for Panama's population. October 2023 was the driest October on record in the Canal watershed, and 2023 its second-driest year.
• The Panama Canal Authority cut daily transits to 22, against 36 in what its table calls the "regular scenario", citing "the drought induced by the El Niño phenomenon". It called this "the first time the Canal has ever had to restrict transits".

El Niño 2023–24: southern Africa

• In large parts of central and southern Africa, February 2024 was the driest on record, with a severe heatwave.
• Seven countries declared national disasters (SADC's count; six of them for drought alone), including Malawi, Zambia and Zimbabwe. 71 million people were food insecure, 17.9% of the region's population.
• SADC: El Niño was "not the sole driver" of food insecurity, but was "the primary driver of the significant increase" in 2024.

El Niño and Peru's fishery

• In 2023, a coastal El Niño "disrupted the highly productive Humboldt Current upwelling system", and anchoveta catches were severely hit.
• As the anchoveta recovered, Peru's catches rose from 3.5 million tonnes in 2023 to 5.7 million tonnes in 2024.
• The chain: warmer water → weaker upwelling → fewer nutrients → fewer plankton → fewer fish.

La Niña 2020–23: the Horn of Africa

• The tropical Pacific was in a La Niña state, with short interruptions, from September 2020: WMO called it the first "triple-dip" La Niña of the 21st century.
• Southern Ethiopia, southern Somalia and eastern Kenya had five consecutive failed rainy seasons from October 2020.
• Kenya's drought early warning bulletin projected that 4.35 million people in its drought-affected counties would need humanitarian assistance by October 2022 (cited by WWA).

Weighing La Niña and climate change (AO3)

• Below-average short rains correlate highly with La Niña.
• World Weather Attribution found that climate change has made such droughts "about 100 times more likely", mainly through higher temperatures raising evaporation.
• Not all ENSO effects are harmful: El Niño "contributes to more eastern Pacific hurricanes and fewer Atlantic hurricanes", and La Niña's stronger upwelling supports more marine life off the Americas.
• Exam move: name the phase, place and date, and weigh ENSO against other drivers such as warming and vulnerability.

Mission 3: Hurricane Ian hit Florida with 130-knot winds in 2022. Why was water, not wind, its deadliest hazard?

What a tropical cyclone is

• A rapidly rotating storm that begins over tropical oceans; called a hurricane or typhoon, depending on the region.
• Structure: a calm eye, a ring of towering thunderstorms in the eyewall, and spiral rain bands.
• The Saffir–Simpson scale rates hurricanes 1 to 5 by maximum sustained wind: category 4 is 113–136 kt and category 5 is 137 kt or more. Categories 3–5 are major hurricanes.
• The scale "does not take into account" storm surge, rainfall flooding or tornadoes.

How they form

• Warm ocean water (about 80 °F, or 27 °C) at the surface, warm to a depth of about 150 ft (about 45 m).
• An atmosphere that cools quickly with height, with moist air in the middle troposphere.
• Enough spin from the Coriolis force, so at least 300 miles (about 480 km) from the equator, and low vertical wind shear.
• A pre-existing disturbance to start from: in the Atlantic, about 85% of intense hurricanes begin as African Easterly Waves. Many disturbances with favourable conditions still do not develop.

Where and when

• Tropical cyclones form over tropical waters, between 25°S and 25°N.
• Main seasons, "though there are differences from basin to basin": July–October in the Northern Hemisphere and December–March in the Southern. Globally, September is the most active month.
• The North-west Pacific has cyclones all year round. Cool water, as off the US west coast, quickly weakens storms.
• WMO counts, over "the past 50 years", 1,945 disasters attributed to tropical cyclones, with 779,324 deaths and US$1.4 trillion in losses.

Storm surge

• Storm surge: an abnormal rise of water generated by a storm, over and above the predicted astronomical tide. Storm surge plus tide gives the storm tide.
• It is caused mainly by strong onshore winds; in shallow water near the coast the water can only move up and inland.
• Surge is higher on a wide, gently sloping continental shelf, and on a concave coastline.

Case study: Hurricane Ian, 2022

• Ian intensified rapidly over waters of 30 °C and higher, with low wind shear.
• 27 September: landfall near La Coloma, Pinar del Río, Cuba, as a 110-kt category 3 hurricane.
• 28 September: peak of 140 kt (category 5), then landfall on Cayo Costa, Florida, at 130 kt (category 4).
• The NHC links the devastation to the exact track, strong winds and "large storm size".

Ian: impacts on coastal places

• Peak surge inundation was 10–15 ft (3–4.6 m) above ground at Fort Myers Beach. Portions of the Sanibel Causeway were washed away.
• Lee County: at least 52,514 structures impacted, 5,369 of them destroyed.
• On Florida's east coast, aerial imagery showed "extensive beach erosion and damage to piers" from large breaking waves.

Ian: deaths and damage

• In the US, at least 156 deaths, 66 of them directly caused by the storm. Storm surge killed 41, freshwater flooding 12 and wind 4.
• US damage: an estimated $112.9 billion (90% confidence interval $86.8–135.9 billion).
• Cuba: 5 deaths reported (3 directly caused by Ian); more than 100,000 homes damaged or destroyed; the whole island reportedly lost power for a few days.

Warnings and forecasts

• The storm surge watch and warning for Fort Myers Beach were issued 48 and 30 hours before tropical-storm-force winds arrived.
• The peak surge forecast there rose from 4–7 ft to 8–12 ft on 27 September, and to a final 12–18 ft. NHC's later analysis found 10–15 ft above ground.
• Intensity forecast errors were above average, largely because of the rapid intensification.

Recovery and evaluation (AO3)

• By September 2024, federal support topped $10.2 billion, including $1.15 billion for 387,139 households and $4.67 billion of flood-insurance claims paid to about 47,000 policyholders.
• The data are unequal too: the NHC gives no monetary damage estimate for Cuba, so losses in the two countries cannot be compared in dollars.
• Exam move: compare impacts and responses at different scales and levels of development, and say where data are missing.

Mission 4: The ocean took up 29% of the CO₂ humans emitted over the last decade. Why is that bad news for coral reefs?

The ocean as a carbon store

• The ocean holds about 50 times as much carbon as the atmosphere.
• Carbon moves quickly between surface water and the air, but may be stored for centuries in the deep ocean.
• A store holds carbon; a sink takes up more than it releases; a source releases more than it takes up.

The solubility pump

• CO₂ is more than twice as soluble in cold polar water as in warm equatorial water.
• Water cooled on its way poleward absorbs CO₂, becomes denser and sinks, taking the carbon to depth.

The biological pump

• Phytoplankton turn CO₂ into organic matter. Perhaps 30% of it sinks into deeper water, and only about 0.1% reaches the seafloor sediments.
• A 1995 model study (Sarmiento et al.), reported by Feely et al., estimated that the natural solubility pump causes about 20% of the vertical gradient in dissolved inorganic carbon, and the biological pump about 80%.

Sink and source

• 2015–2024: the ocean took up 3.2 ± 0.4 billion tonnes of carbon (GtC) a year, 29% of total CO₂ emissions; the land took up 21% and the atmosphere kept 50%.
• Natural CO₂ is released mostly in the tropics, especially where deep water upwells along the equator.
• During large El Niño events, less CO₂ escapes from the tropical Pacific, so the sink is stronger; it is weaker during La Niña. Synthesis with Mission 2.

A changing role

• The ocean sink has been "stagnant since 2016", partly because of climate variability and the ocean heatwave of 2023–24.
• Warmer water dissolves less CO₂ (screen 4.2), so warming works against the solubility pump.
• Models estimate that climate change cut the sink by 0.20 GtC a year in 2015–2024: 7.1% less than in a model run with rising CO₂ but no climate change.
• IPCC: the proportion of emissions taken up by land and ocean decreases as cumulative emissions rise.

Ocean acidification

• CO₂ dissolves in seawater to form carbonic acid, which releases hydrogen ions and bicarbonate. The ocean's average pH is now around 8.1.
• Extra hydrogen ions bond with carbonate ions, leaving fewer for corals and shellfish to build calcium carbonate skeletons. If pH falls far enough, shells and skeletons can begin to dissolve.
• IPCC: it is "virtually certain" that human CO₂ emissions are the main driver of current ocean acidification.

Coral reefs under two pressures

• Bleaching is caused by heat stress. From early 2023 to mid-2025, bleaching-level heat stress hit 84% of the world's coral reef area; mass bleaching was documented in at least 83 countries and territories.
• Acidification slows calcification and so reef growth. IPCC: acidification is projected to "amplify the adverse effects of warming".
• Coral reefs are projected to decline by a further 70–90% at 1.5 °C of warming, and by more than 99% at 2 °C.

The Great Barrier Reef: recent data

• Hard coral cover, northern GBR: 39.8% (2024) → 30.0% (2025), the largest annual decline recorded for the northern region since monitoring began. Southern GBR: 38.9% → 26.9%.
• AIMS: "the mass coral bleaching event was the primary source of coral mortality".
• 2026: northern cover recovered to 35.1%, helped by late-summer monsoon cloud and cooler water; southern cover was 26.4%.
• Exam move: separate heat (bleaching) from chemistry (acidification) when you explain reef decline.

Mission 5: Between 1951 and 2004 the cliffs at Aldbrough, on England's Holderness coast, retreated about 2 m a year. Why do they disappear so fast?

The coast as a system

• Inputs: energy from waves, tides and wind; sediment from rivers, cliffs and the seabed.
• Processes: erosion, transport, deposition and subaerial processes (weathering and mass movement on the cliff above the sea).
• Outputs: landforms, and sediment carried along or offshore.
• Coasts are divided into sediment cells: stretches within which sediment mostly circulates.

Waves

• Waves are made by wind. Their energy grows with wind speed, wind duration and fetch (the distance of open water the wind blows over).
• Destructive waves: high and steep, with a backwash stronger than the swash, so they remove material.
• Constructive waves: low, with a strong swash, so they build beaches.

Tides

• Tides: the rise and fall of sea level caused by the Moon and Sun. Britain has some of the largest tides in the world, with a range of up to 15 m.
• The tidal range decides where waves attack: a small range concentrates wave attack at one level of the cliff; a large range spreads it.

Erosion and transport

• Hydraulic action: the force of water, and air compressed into cracks, breaks rock apart.
• Abrasion: waves throw sand and pebbles against the cliff, wearing it away.
• Littoral (longshore) drift: waves arrive at an angle, so the swash moves sediment up the beach at that angle and the backwash drags it straight down; sediment zig-zags along the coast.
• Currents deposit the sediment where they slow down. A beach that loses its sand is left more exposed to waves.

Lithology: weak till and hard chalk

• Holderness cliffs are glacial till (boulder clay), mostly late Devensian (18,000–13,000 years old): the Skipsea Till and the overlying Withernsea Till.
• At Aldbrough the cliffs are about 20 m high. At high tide, waves erode their lower and sometimes middle sections.
• At Flamborough Head, to the north, the cliffs are chalk, capped by till. The chalk "is more resistant to erosion than the overlying till".

Subaerial processes and mass movement

• Above the waves, the till cliffs fail by rotational slumping, with smaller topples and falls, and short-lived mudflows.
• Increased rainfall could make the till more likely to fail.
• Waves remove the slumped material from the cliff foot, so the cycle repeats.

Sediment supply (synthesis)

• Holderness's erosion is also a sediment supply: estimates going back to 1786 put the loss from the cliffs at up to 2 million m³ a year.
• Spurn Point, to the south, formed from "deposits moving along the coast" (Mission 6).
• Exam move: one stretch of coast's loss is another's supply. Link erosion, transport and deposition.

Vegetation

• Vegetation traps and binds sediment: marram on dunes (Mission 6), and saltmarsh, which damps wave action and acts as a natural defence.
• Roots also bind cliff-top soil, but cannot stop slumping where the sea removes the cliff foot.

Mission 6: Spurn Point is over three miles long and in places only 50 m wide. How did a finger of sand form across the mouth of the Humber?

Cliffs and wave-cut platforms

• Waves erode a wave-cut notch at the base of a cliff by hydraulic action and abrasion.
• The overhang collapses, and the cliff retreats inland, leaving a gently sloping wave-cut platform, exposed at low tide.
• As the platform widens, waves break further out and lose energy before reaching the cliff, so retreat slows: negative feedback.

Headlands: cave, arch, stack, stump

• Waves exploit lines of weakness (joints and faults) in a headland: crack → cave → arch → stack → stump.
• At Flamborough Head, BGS warns that more wave activity could attack the chalk at wave level, "creating undercutting and cavities".
• Old Harry Rocks, Dorset: "towering sea stacks and cliffs topped by chalk downland".

Beaches and spits

• Beaches form where deposition exceeds removal: sand on gentle slopes, shingle on steeper ones.
• A spit forms where littoral drift carries sediment past a change in the direction of the coast; it grows out from the land, often with a recurved (hooked) end and saltmarsh behind it.
• Spurn formed "as a long, narrow spit from deposits moving along the coast carried by currents". It is over three miles long, but in places only 50 m wide.

Spurn: a changing landform

• Storms have breached Spurn many times. In December 2013 a tidal surge burst through its narrowest part and destroyed the road.
• A 1 km "washover" section is sometimes covered at high tide, cutting the end off from the mainland.
• BGS reports that sea-level rise "is predicted to completely cut off Spurn Head by 2050", according to modelled UKCP18 scenarios.

How sand dunes start

• Onshore winds blow dry sand inland from a wide beach; it collects behind obstacles such as the strandline.
• Embryonic dunes are the first, low dunes at the top of a beach, where pioneer plants such as sand couch and lyme-grass trap blowing sand. They are either replaced by marram-dominated dunes or washed away by storms.
• Dunes depend on a continued supply of sand from the beach.

Dune succession

• White (shifting) dunes, also called yellow dunes: sand-binding marram (Ammophila arenaria) usually dominates. The vegetation "will rapidly change and disappear if stability is imposed".
• Grey (fixed) dunes: grassland replaces marram as the dune stabilises and the sand gains organic matter.
• Dune slacks: low, seasonally flooded hollows with few nutrients.
• Succession on sand is a psammosere: each stage changes conditions for the next.

Studland and Sefton: dunes that move

• At Studland Dunes, Dorset, embryonic dunes "initiate the very clear successional sequence of dune communities".
• In the 2014 winter storms, Studland lost up to 10 m of dunes in a single storm. The National Trust is now focusing on adaptation and softer defences.
• The Sefton Coast, Merseyside, "displays both rapid erosion and active progradation": some parts retreat while others build seaward.

Mission 7: On the coast of the Gulf of Bothnia, the land rises out of the sea by about 0.9 m a century. Elsewhere, coasts are drowning. How can both be true?

Eustatic change: the sea moves

• Eustatic change is a worldwide change in sea level, as the volume of ocean water changes.
• Global mean sea level rose by 0.20 m between 1901 and 2018. The rate rose from 1.3 mm a year (1901–71) to 1.9 (1971–2006) and 3.7 (2006–18).
• Thermal expansion explained 50% of the rise in 1971–2018; glaciers 22%, ice sheets 20% and changes in water stored on land 8%.

Isostatic change: the land moves

• Isostatic change is a vertical movement of the land. The weight of an ice sheet presses the crust down; when the ice melts, the land slowly rises.
• On the High Coast (Sweden) and the Kvarken Archipelago (Finland), about 290 m of uplift has been recorded over the past 10,500 years.
• The land is still rising, by around 0.9 m a century, and new islands keep emerging. At today's rate, 10,500 years would give only about 95 m, so uplift was far faster at first.

Landforms of a falling relative sea level

• Raised beach: an old beach, with rounded pebbles and shells, now above the reach of the sea.
• Relict cliff: a former sea cliff behind a raised beach, no longer attacked by waves and weathering into a gentler slope.
• UNESCO's High Coast site includes "the full zonation of uplifted land and some of the highest shoreline": old shorelines now far inland and above the sea.

Fjords: valleys drowned by the sea

• A fjord forms by "submergence of a glaciated valley": a glacier carves a deep U-shaped trough, and the sea floods it when the ice melts.
• In the West Norwegian Fjords, walls rise up to 1,400 m from the sea and extend 500 m below sea level.
• Features include deep rock basins far below sea level and a shallower rock threshold near the mouth.

Advancing and retreating: future change (AO3)

• Relative sea-level change is sea-level change measured against the land: the eustatic change, minus any uplift of the land or plus any sinking (isostatic change).
• Coasts advance where the land rises faster than the sea, or where deposition builds out (Sefton); they retreat where the sea gains, or erosion wins (Holderness).
• IPCC likely global rise by 2100, relative to 1995–2014: 0.28–0.55 m under very low emissions and 0.63–1.01 m under very high emissions.
• Exam move: name the scale (global sea against local land) and the timescale (decades against millennia).

Mission 8: By 2014 the Environment Agency had built new banks inland at Medmerry, West Sussex, and let the sea flood the land between. Why give land to the sea?

The options

• Hold the line: maintain or raise the existing defences.
• Advance the line: build new defences seaward.
• Managed realignment (managed retreat): let the sea in behind a new, landward line of defence.
• No active intervention: stop maintaining defences and let nature take its course.
• England's coast is covered by Shoreline Management Plans, which set one of these policies for each stretch.

Hard and soft engineering

• Hard: sea walls, rock armour, and groynes, which trap littoral drift but can starve beaches further along the coast.
• Soft: beach nourishment, dune management and managed realignment, which work with natural processes.
• Exam move: weigh cost, lifespan, effects downdrift and effects on habitats, not just "does it work?".

Cliff line stabilisation: Ventnor

• Methods: drain water out of the cliff, regrade it to a gentler angle, and protect its toe from waves with a sea wall or rock armour.
• Ventnor, Isle of Wight, "sits at the bottom of the largest urbanised landslide complex in north-west Europe".
• Without the sea wall, erosion "would create instability to the landslide complex". In 2023 the Environment Agency began ground investigations to inform the repair and replacement of the defences, which would better protect about 3,000 homes and businesses.

Medmerry: the problem

• Medmerry lies west of Selsey, West Sussex. A shingle bank there protected 300 properties, large caravan sites and 650 hectares of land.
• Storms had breached the bank many times in the previous 15 years, and it needed extensive maintenance every winter.
• The B2145, the only road to Selsey, and essential utility services for the wider peninsula depended on the protection of this low-lying land.

The decision-making process

• The Environment Agency, with Chichester and Arun District Councils, completed a technical review in 2005, then consulted local communities in 2007.
• Options were judged over 100 years on flood and erosion risk, sea-level rise, cost and effects on the natural environment.
• The government had obligations to create new intertidal habitat to compensate for losses in protected (Natura 2000) sites elsewhere, and studies had identified Medmerry as a prime site.

Options and costs (2007 estimates)

• Present-value costs for Medmerry: no active intervention £8–10 million; hold the line £80 million; managed realignment £10 million.
• No active intervention cost about the same as realignment, but without winter repairs the bank was likely to breach within a year, and about 50 properties, sewage pumping stations and electricity sub-stations would flood.
• Holding the line was judged "not practical". Inland banks "will not need to be as large", but "a relatively large area of land" would flood.

Perspectives and outcome (AO3)

• Environment Agency: lower long-term risk and cost. Government: the wetland helps meet its habitat duty. RSPB: supported delivery.
• Selsey residents: road and key infrastructure protected. Farmland: "a relatively large area of land" floods.
• Completed in 2014, with 7 km of new embankments: at the time, the £28 million project was "the largest open-coast scheme in Europe".
• Evaluate: the £28 million reported for the completed scheme is not comparable with the £10 million present-value estimate of 2007.

Mission 9: 1,282 people and organisations sent formal comments on one plan for the Suffolk coast. Who were they, and who won?

Coastal land-use pressures

• Coasts attract commercial uses: tourism, industry and energy, ports, and housing.
• Conservation measures protect habitats and landscapes through designations (in the UK: SSSIs, Special Protection Areas, Ramsar sites, Areas of Outstanding Natural Beauty).
• Conflict arises when one stretch of coast is wanted for several uses at once.

Case study: Sizewell C, Suffolk

• A proposed nuclear power station of two reactors, about 1,670 MW each, about 3,340 MW in total.
• It includes an accommodation campus, sports facilities in Leiston, and compensation land for fen meadow and marsh harriers.
• Next to it: RSPB Minsmere, part of the Minsmere–Walberswick Special Protection Area and Ramsar site, and the Sizewell Marshes SSSI.

The process and the actors

• Application accepted June 2020; examined April–October 2021 by an Examining Authority (ExA) of planning inspectors; report to the Secretary of State in February 2022.
• 1,282 relevant representations were received.
• Actors included the developer, East Suffolk Council, Natural England, the RSPB and Suffolk Wildlife Trust, the National Trust, the water company, local action groups and residents.

Conservation, tourism and housing

• Conservation: harm to the Minsmere SSSI is "likely" (ExA), and the project takes land permanently from the Sizewell Marshes SSSI.
• Recreation: the developer agreed there would be significant adverse effects on the recreational benefits of the AONB, Minsmere and Dunwich.
• Tourism: effects likely negative during construction, neutral once operating; a Tourism Fund is the mitigation.
• Housing: a 2,400-bed accommodation campus and a 600-berth caravan site for workers, plus a Housing Fund.

The coast itself

• A hard coastal defence feature would reach 12.6 m above datum, adaptable to 16.4 m, fronted by a 5 m "sacrificial" sand dune that is recharged as it erodes.
• Without mitigation, the shore would erode enough to expose the hard defence by 2053–2087.
• The ExA found a breach of the Shoreline Management Plan's "hold the line" policy (MIN 13.1), but judged the defence was "as landward as possible".

The decision

• The ExA recommended that "unless the outstanding water supply strategy can be resolved and sufficient information provided to enable the Secretary of State carry out his obligations under the Habitats Regulations, the case for an Order granting development consent for the application is not made out".
• On 20 July 2022 the Secretary of State granted consent, concluding that "the very substantial and urgent need for the proposal outweighs the harms".
• A temporary desalination plant was added to the water supply plan. The government took its final investment decision on 22 July 2025.

Outcomes for stakeholders (AO3)

• Gains: the developer and government (consent), and local businesses ("substantial economic opportunities", acknowledged by the councils).
• Losses: wildlife sites (habitat and disturbance), recreation and tranquillity in the AONB, tourism during construction.
• Mitigated, not removed: funds, compensation land and adaptive sea defences.
• Exam move: the decision-maker weighs national need against local harms; say whose perspective each argument reflects.

Mission 10: A community on Kenya's coast earns money by not cutting down its mangroves. Who pays, and why?

Why mangroves matter

• Mangroves: salt-tolerant trees and shrubs of the intertidal zone on tropical and subtropical coasts.
• They store large amounts of carbon in their soils, protect coasts from storms and erosion, and support rich biodiversity.
• Global mangrove area was 14.8 million ha in 2020. Nearly 44% (6.48 million ha) is in South and South-east Asia; Indonesia alone has 21%.

Issues: losses and their drivers

• 2000–2020: 677,000 ha of mangroves were lost, and 393,000 ha of new mangrove grew.
• Drivers of loss: aquaculture 27%, natural retraction 26%, other agriculture 12%, oil palm 8%, rice 8%.
• The rate of net loss fell by 44%, from 18,200 ha a year (2000–10) to 10,200 ha a year (2010–20).

Example: Mikoko Pamoja, Gazi Bay, Kenya

• "The world's first community-led blue carbon project": mangroves are protected and replanted, and the carbon they store is sold as credits.
• 1,081 households take part; 22,169 credits had been issued by October 2026.
• Plan Vivo says it "has enabled community development such as provision of schoolbooks, construction of school buildings and the provision of clean drinking water"; it won the Equator Prize in 2017.
• Perspectives: the community gains income and services; buyers pay to offset emissions. Strength: local ownership. Limits: small scale, and income depends on the carbon market.

Example: the Great Barrier Reef

• The Marine Park covers 344,400 km², with some 3,000 coral reefs; it was inscribed as World Heritage in 1981.
• GBRMPA, citing a Deloitte study for the Great Barrier Reef Foundation, says the Reef contributes $9 billion a year to Australia's economy and supports 77,000 jobs; tourism generates $7.9 billion a year.
• More than 70 Traditional Owner groups have connections to the Reef.
• Other users: commercial and recreational fishers, shipping and ports, and farmers in the catchment.

The Reef's issues

• GBRMPA's 2024 Outlook Report: "the overall outlook for the Great Barrier Reef remains one of future deterioration due largely to climate change".
• Other threats it names: "crown-of-thorns starfish outbreaks, poor water quality and some fishing activities".
• It also found the Region "continues to be well-managed overall". Bleaching was the primary cause of coral loss in 2024–25 (Mission 4).

Managing reefs: evaluation (AO3)

• Zoning: each zone sets which activities are allowed, banned or need a permit. Fishers lose access to no-take zones; tourism and fish stocks can gain.
• Water quality: farm runoff is managed on land, outside the Marine Park.
• Scale: no local plan can stop the global heat stress that drives bleaching. Reef management works locally; the main threat is global.
• Exam move: "To what extent…" answers should separate what managers control (fishing, runoff) from what they cannot (ocean warming).

Mission 11: The world now farms more fish and shellfish than it catches. Does that solve overfishing?

Trends in fish use

• In 2022, for the first time, aquaculture overtook capture fisheries as the main producer of aquatic animals.
• 2024: production of aquatic animals reached 195 million tonnes: aquaculture 103 million tonnes (53%), capture 92 million tonnes (47%).
• Wild capture has stayed between 86 and 94 million tonnes since the late 1980s, apart from a peak of about 96 million in 2018, "as the biological and ecological limits of a number of wild fish stocks had been reached".

How many stocks are overfished?

• In 2023, 62.4% of assessed marine stocks were biologically sustainable, down from 64.5% in 2021; FAO says the fall reflects "both assessment revisions and the inclusion of new records".
• Weighted by catch, 72.6% of landings came from sustainable stocks: large stocks tend to be better managed.
• Regional range: 100% sustainable in the Antarctic areas and 89.3% in the North-east Pacific, but 45.7% in the Mediterranean and Black Sea and 47.1% in the Eastern Central Atlantic.

Marine mammals: whaling

• In 1982 the International Whaling Commission (IWC) agreed a pause in commercial whaling, effective from the 1985/86 season. It remains in place.
• Norway objected to the moratorium; Iceland rejoined the IWC in 2002 with a reservation to it; Japan left the IWC in 2019 and began commercial catches.

Alternatives: aquaculture and quotas

• Aquaculture now supplies most aquatic animals, but it was the largest single driver (27%) of mangrove loss in 2000–2020.
• Quotas limit the catch. Argentine red shrimp became sustainable through "strict quotas, seasonal/area closures and strong monitoring", but Argentine hake stayed overfished "despite partial recovery under quota-based management and spatial protection measures".
• 91.3% of assessed tuna stocks were sustainable in 2023; FAO credits precautionary management by regional tuna bodies.

The ocean as a global commons

• The guide frames this sub-section as "managing the oceans as a global commons": resources open to all and owned by no one, such as the high seas.
• Hardin's tragedy of the commons (1968): when a resource is open to all, each user gains from taking more while the cost of depletion is shared, so the resource is overused.
• Quotas, protected areas and treaties such as the High Seas Agreement are attempts to escape that tragedy.

Alternatives: conservation areas

• National waters are 39% of the ocean; 23.09% of them are in protected or conserved areas. The high seas (beyond national jurisdiction) are 61% of the ocean, and only 1.45% is protected.
• The High Seas (BBNJ) Agreement, adopted in 2023, entered into force on 17 January 2026, with 104 parties by October 2026. A central aim is a system of area-based management tools, including protected areas, beyond national jurisdiction.

Evaluating the alternatives (AO3)

• Protected areas need enforcement, especially far offshore.
• Quotas work where stocks are assessed and monitored, as with tuna; they fail where they are not.
• Aquaculture shifts pressure onto coasts (mangroves) and onto the fisheries that supply fish feed.
• Exam move: judge viability by scale (local, regional, high seas) and by who enforces the rules.

Mission 12: Tankers spilled about 95% less oil in the 2010s than in the 1970s. Why has plastic proved so much harder to stop?

Oil: a global strategy

• MARPOL, the International Convention for the Prevention of Pollution from Ships, was adopted in 1973; its 1978 Protocol followed a spate of tanker accidents, and it entered into force in 1983.
• 1992 amendments made double hulls mandatory for new oil tankers, with a phase-in for existing tankers.

What the record shows

• Quantity: about 164,000 tonnes were lost from tanker spills in the 2010s, a 95% reduction since the 1970s.
• Number: spills of more than 7 tonnes have fallen by over 90% since the 1970s; "there has however been little change in the last decade".
• 1990s: 358 spills, 1,134,000 tonnes lost. 2010s: 63 spills; a single spill caused about 70% of that decade's oil lost.

Oil: a national strategy

• On 24 March 1989 the tanker Exxon Valdez ran aground in Prince William Sound, Alaska, spilling nearly 11 million gallons of crude oil.
• "In the wake of the Exxon Valdez disaster", Congress passed the Oil Pollution Act of 1990 unanimously.
• It created a clean-up trust fund financed by a tax on oil, and requires facilities and vessels to submit plans for responding to spills.

The limits: Deepwater Horizon

• Tanker rules do not cover drilling. On 20 April 2010 an explosion on the Deepwater Horizon rig in the Gulf of Mexico killed 11 workers.
• About 134 million gallons of oil spilled before the well was capped three months later.

Plastic: global strategies

• Ships: MARPOL Annex V (in force 1988) imposes "the complete ban" on disposing of "all forms of plastics" into the sea from ships.
• All sources: in March 2022, the UN Environment Assembly agreed to negotiate "an international legally binding instrument on plastic pollution, including in the marine environment".
• Six negotiating sessions followed, the last substantive one in Geneva in August 2025. A one-day organisational session (INC-5.3) followed in February 2026, and a further session (INC-5.4) was being prepared.

Plastic: a national strategy

• Since 5 October 2015, large retailers in England have had to charge for single-use plastic carrier bags; since 21 May 2021 the charge is 10p and applies to all businesses.
• Main retailers issued 7.64 billion single-use bags in 2014 (WRAP; six of the seven main retailers); in 2025–26 the seven sold 126 million, and all reporting retailers 399 million.

Radioactive materials: a global ban

• The trigger: under the 1972 London Convention, low-level radioactive wastes could be dumped at sea under certain conditions.
• A voluntary moratorium followed in 1983, and in 1993 the Convention was amended to ban dumping radioactive wastes at sea.
• Under the 1996 London Protocol, in force since 2006, "all dumping is prohibited", except for possibly acceptable wastes on a "reverse list".

Regional and local strategies

• Regional: under the OSPAR Convention, North-east Atlantic states aim for concentrations "close to zero for artificial radioactive substances".
• Local: at Sellafield, Cumbria, an ion-exchange plant removes caesium and strontium from used water before discharge to the sea.

Has it worked? (AO3)

• OSPAR's fourth periodic evaluation (2016), as summarised in the UK's 2018 review, found that nuclear-sector discharges had fallen 2.5-fold for total alpha and 12-fold for total beta (excluding tritium) since the 1995–2001 baseline.
• Exam move: separate what a strategy aims for ("close to zero") from what the evidence shows.

Mission 13: Russia, Denmark and Canada have each asked a UN body to recognise their seabed rights in the Arctic Ocean. Who owns the ocean floor?

UNCLOS: the zones

• The UN Convention on the Law of the Sea (1982) entered into force in 1994; it has 172 parties.
• Territorial sea: up to 12 nautical miles (nm) from the baseline. Ships of all states have a right of innocent passage.
• Contiguous zone: up to 24 nm, for customs, fiscal, immigration and sanitary control.
• Exclusive economic zone (EEZ): up to 200 nm, with sovereign rights over living and non-living resources and energy.

The continental shelf and the Area

• A state's continental shelf can extend beyond 200 nm where its continental margin does. The limit is 350 nm or 100 nm beyond the 2,500 m depth line; on submarine ridges it is 350 nm.
• Rocks that cannot sustain human habitation or economic life of their own have no EEZ or continental shelf.
• The seabed beyond national limits is the Area, managed by the International Seabed Authority (ISA). UNCLOS calls the Area and its resources "the common heritage of mankind".

Abiotic demand: minerals

• Demand for battery metals is rising with electric vehicles and energy storage: lithium demand rose by nearly 30% in 2024, and nickel, cobalt and graphite by 6–8%.
• On the deep seabed, polymetallic nodules contain nickel, copper, cobalt and manganese; the richest deposits lie at 4,000–6,000 m, notably in the Clarion-Clipperton Zone, Pacific.
• The ISA has issued 17 exploration contracts for nodules there. Its exploitation regulations, in development since 2014, are still in draft.

Abiotic demand: Arctic oil and gas

• USGS estimated that 90 billion barrels of undiscovered oil and 1,669 trillion cubic feet of gas may lie north of the Arctic Circle, about 84% of it offshore (2008 estimate).
• Less sea ice makes these resources more accessible (screen 13.9).

Consequences: evidence from a 1979 test

• In 1979, a mining test in the Clarion-Clipperton Zone cut tracks across the seabed. Scientists revisited them in 2023.
• After 44 years, physical changes persisted and communities in the tracks were still altered, though some fauna had begun to re-establish.
• The authors conclude that mining impacts "will be persistent over at least decadal timeframes".
• Exam move: one small, old test is limited evidence for industrial-scale mining. Say so, and say why it still matters.

Case study: the contested Arctic seabed

• Arctic sea ice area in September fell by about 40% between 1979–88 and 2010–19. The Arctic is likely to be practically ice-free in September at least once before 2050.
• Less ice means more access to sea routes and resources, which raises the stakes.
• Submissions to the UN Commission on the Limits of the Continental Shelf (CLCS): Russia (2001; revised 2015), Denmark/Greenland (December 2014), Canada (May 2019).

Overlapping claims

• Denmark's submission states that Canada's outer limits "would overlap" those of Greenland's northern shelf, and that "there are potential overlaps of entitlement".
• The Lomonosov Ridge, "a sliver of continental crust that divides the Arctic Ocean into its two main basins", is central. Denmark argues that it and other ridges are "morphologically continuous with the land mass of Greenland".
• The CLCS adopted recommendations on Russia's revised submission in February 2023.

How the dispute is managed

• In the 2008 Ilulissat Declaration, the five Arctic Ocean coastal states committed to the law of the sea and to "orderly settlement of any possible overlapping claims".
• In 2014 Denmark/Greenland and Russia agreed by exchange of notes not to object to the CLCS considering each other's submissions, "without prejudice" to later delimitation.

Evaluating the process (AO3)

• The CLCS assesses the science of each claim; UNCLOS states that the shelf rules are "without prejudice to the question of delimitation" between states, so overlaps are settled by the states themselves.
• So far, the states have used scientific submissions and diplomatic notes.
• Uncertainties: resource estimates are old and probabilistic, and access depends on sea ice and costs.
• Exam move: separate the legal process (orderly so far) from the strategic stakes (rising as sea ice retreats).

Mission 14: In 2024, ships from Shenzhen to Rotterdam began sailing about 3,000 extra nautical miles around Africa. Why take the long way?

The strategic value of oceans

• UNCTAD: "Shipping is the backbone of globalized trade and smooth navigation through maritime chokepoints is crucial for trade".
• A choke point is a narrow passage, such as a strait or canal, that a large share of shipping must use.
• Islands matter too: they can generate a territorial sea, an EEZ and a continental shelf (Mission 13).

The Strait of Hormuz

• In 2024, oil flow through the Strait of Hormuz averaged 20 million barrels a day, about 20% of world petroleum liquids consumption.
• 84% of the crude oil and condensate passing through it went to Asian markets.
• Few alternative routes exist if it is closed.

The Red Sea and the Suez Canal

• The Suez Canal carries about 10% of global trade by tonnage.
• "Attacks on vessels in the Red Sea prompted most shipping lines to reroute around the Cape of Good Hope".
• By June 2024, transits through the Suez Canal were down 70% against mid-December 2023, and arrivals at the Cape of Good Hope had risen by 89%.

The Panama Canal (synthesis)

• Drought linked to El Niño (Mission 2) cut daily transits to 22 in December 2023, against the Canal Authority's "regular scenario" of 36. UNCTAD gives a long-term average of 38 ships a day.
• Over the first quarter of 2024, transits were about 20% lower than a year earlier.
• A climate event far out in the Pacific disrupted a canal that serves world trade.

A contested island: Hans Island (Tartupaluk)

• A 1.3 km², uninhabited island lying "midway" between Canada and Greenland.
• A 1973 treaty on the maritime border "deliberately left the border undefined" through the island.
• For decades, both countries' forces occasionally landed, raised their flags and left a bottle of whisky or aquavit: the "Whisky War".

Settled by negotiation

• On 14 June 2022, Canada and the Kingdom of Denmark, together with Greenland, signed an agreement that resolved the boundary over Tartupaluk (Hans Island).
• The island is "divided along a natural ridge", with roughly 60% to Denmark (Greenland) and the rest to Canada.
• It keeps "continued access to and freedom of movement on the entirety of the island"; Inuit of Nunavut and Greenland were consulted.
• The agreement also fixed the continental-shelf boundary within 200 nm in the Lincoln Sea.

Islands, canals and choke points (AO3)

• An island's value lies partly in the sea it generates: territorial sea, EEZ and shelf.
• Hans Island's dispute, like the Arctic seabed overlaps, was settled by negotiation; choke points such as the Red Sea show how insecurity at sea quickly reaches world trade.
• Exam move: compare disputes by what is at stake (resources, routes, symbols) and by how they are managed (law, negotiation, force).

How Option B is examined (Paper 1)

• Paper 1 is 35% of the grade at both SL and HL. SL answers two options in 1 hour 30 minutes; HL answers three in 2 hours 15 minutes: 45 minutes per option.
• Each option has a structured question and one extended-answer question from a choice of two: 10 + 10 = 20 marks.
• Questions may use topographic maps, which the guide flags as especially relevant to oceans and coastal margins.

Command terms for the extended answer

• Evaluate: "Make an appraisal by weighing up the strengths and limitations".
• To what extent: "Consider the merits or otherwise of an argument or concept", with conclusions "supported with empirical evidence and sound argument".
• Discuss: "Offer a considered and balanced review that includes a range of arguments, factors or hypotheses".

What the top band rewards (9–10 marks)

• "In-depth and question-specific (topic and command term)".
• Examples, statistics and details are integrated and explained: name the place, the date and the scale.
• Evaluation includes "cause and effect relations, other perspectives; strengths and weaknesses of evidence", as with Seager's model study or Medmerry's two cost figures.
• A balanced conclusion aligned with the evidence; maps and diagrams annotated and explained.

The big ideas

• Currents and the conveyor belt move heat and nutrients; ENSO shifts rainfall and fisheries across the globe (Panama, southern Africa, Peru, the Horn of Africa).
• Hurricanes need warm water, spin, low shear and a starting disturbance; storm surge is often the deadliest hazard (Ian).
• The ocean is a carbon sink, but its uptake acidifies seawater and adds to the heat stress on coral reefs.
• Lithology, waves and littoral drift shape coasts (Holderness, Spurn); dunes build by succession; isostatic and eustatic change make coasts advance or retreat.
• Management involves trade-offs between actors (Medmerry, Sizewell C, Mikoko Pamoja, the Great Barrier Reef).
• The oceans are a global commons: resources, pollution, sovereignty and choke points are managed from local to global scales (FAO, MARPOL, UNCLOS, the Arctic, Hans Island).

Final screen. Score, the mission list ticked, and "Next: test yourself in the Verify stage" (links to the Verify quiz).