The Dynamics of the Atmosphere and the Hydrosphere
On the beach in Mazatlán, the sand burns under your feet, but the sea water is cool. That simple difference is actually the engine that starts the wind you feel on your face every afternoon along the boardwalk. How can a simple "hot here, cold there" move the air?
The Sun, Engine of Air and Water
In summer, the ground around a pool can burn your bare feet while the water stays cool, even though both receive the same solar radiation. Why do land and water react so differently to the Sun's heat?
Wind and ocean currents get their energy from the Sun. Using an everyday example (air moving when a radiator is turned on, or water in a heated pot), explain what…
Wind and ocean currents get their energy from the Sun. Using an everyday example (air moving when a radiator is turned on, or water in a heated pot), explain what happens to air or water when heated and how this movement gives rise to winds or currents.
The Sea Breeze
The diagram shows what happens on a summer morning at the coast, with four numbered steps. Explain what happens in each of the steps labelled 1 to 4 and reason why warm…
The diagram shows what happens on a summer morning at the coast, with four numbered steps. Explain what happens in each of the steps labelled 1 to 4 and reason why warm air rises over the land and a sea breeze forms, blowing from the sea towards the coast.
Order the following steps in the formation of a sea breeze during the day: the cool air over the sea moves towards the coast, forming the breeze; the Sun heats the land…
Order the following steps in the formation of a sea breeze during the day: the cool air over the sea moves towards the coast, forming the breeze; the Sun heats the land faster than the sea; the air over the land warms up and rises; higher up, the air moves towards the sea and descends over it.
Ocean Currents
In 1992, thousands of plastic ducks fell from a cargo ship in the middle of the Pacific Ocean and, years later, turned up on beaches in Alaska, Hawaii, and even the Arctic. What invisible conveyor belts run through the planet's waters?
In Mexico something similar happens. The California Current, which is cold, flows along the western coast of Baja California and makes its beaches cooler than others at the same latitude. In contrast, the Gulf of Mexico and the Caribbean receive warm waters: the Gulf Stream starts from there. In the Caribbean, currents also carry sargassum seaweed to the beaches of Quintana Roo.
Currents and winds are energy in motion: wind turns wind turbines (wind power) and the rise and fall of the sea is harnessed in tidal power plants. Both are ultimately fed by the uneven heating caused by the Sun.
The simplified map shows two ocean currents bordering two coastlines located at the same latitude. a) State where each current originates and where it is headed. b)…
The simplified map shows two ocean currents bordering two coastlines located at the same latitude.
- a) State where each current originates and where it is headed.
- b) Reason which of the two locations, A or B, will have a milder and wetter climate and explain why.
The Sea Softens the Coastal Climate
Two locations situated at the same latitude, one on the coast and another inland, have different climates: the coastal town has milder winters and cooler summers.…
Two locations situated at the same latitude, one on the coast and another inland, have different climates: the coastal town has milder winters and cooler summers. Explain why, taking into account that seawater heats up and cools down more slowly than land.
Look at the temperature data for three locations situated at the same latitude (43° N) and at a similar altitude: Location 1: Average temp. in January: 9.2 °C; Average…
Look at the temperature data for three locations situated at the same latitude (43° N) and at a similar altitude:
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Location 1: Average temp. in January: 9.2 °C; Average temp. in August: 21.1 °C.
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Location 2: Average temp. in January: 2.5 °C; Average temp. in August: 28.0 °C.
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Location 3: Average temp. in January: 12.0 °C; Average temp. in August: 17.5 °C.
- a) Calculate the thermal amplitude (temperature range) of each one and deduce, with reasoned arguments, which corresponds to a small oceanic island, which to a continental coastal city, and which to the interior of a large continental landmass.
- b) A classmate claims that seawater warms the coast in summer and cools it in winter. Refute their claim by explaining the thermal property of water (specific heat capacity) that turns the hydrosphere into a thermal regulator for the atmosphere.
London (United Kingdom) and Calgary (Canada) are located at virtually the same latitude (around 51° N). However, the average January temperature in London is 5.5 °C…
London (United Kingdom) and Calgary (Canada) are located at virtually the same latitude (around 51° N). However, the average January temperature in London is 5.5 °C (with very rare snowfall), while in Calgary it is -7.5 °C (with continuous snow for months).
- a) Justify this marked climatic difference by analysing how general atmospheric circulation and surface ocean currents interact in the North Atlantic.
- b) A model predicts that global warming will trigger accelerated melting in Greenland, pouring huge volumes of freshwater into the ocean. Predict and justify what effect this input would have on ocean density, the North Atlantic thermohaline circulation (AMOC), and winter temperatures in north-western Europe.
Water, Wind, and Landforms
The Sun does not only move the air and the currents: it also starts the water cycle. Solar energy evaporates water from the sea, and winds carry that vapor toward the interior of the continents, where it condenses and falls as rain.
That water and air also wear down rocks: rain, wind, and temperature changes break the rock apart (weathering), and runoff, wind, and waves carry the fragments away (erosion). That is why a structure at the shoreline does not stop the wearing down of a cliff.
The water cycle and winds are connected. Explain where the energy that evaporates seawater comes from, and what role winds play in transporting water vapour from the…
The water cycle and winds are connected. Explain where the energy that evaporates seawater comes from, and what role winds play in transporting water vapour from the ocean to the interior of continents.
Along a stretch of coast with limestone cliffs, a town council plans to build a large concrete sea wall at the base of the cliff to stop wave action, claiming that this…
Along a stretch of coast with limestone cliffs, a town council plans to build a large concrete sea wall at the base of the cliff to stop wave action, claiming that this single project will completely stop cliff retreat.
- a) Critically evaluate this claim: justify why it is insufficient by analysing the weathering and erosion processes that the atmosphere (precipitation, wind, and thermal changes) and the continental hydrosphere (runoff and infiltration) will continue to exert on the upper and middle sections of the cliff.
- b) Predict what medium-term consequences the installation of the sea wall will have on the adjacent beach, relating coastal transport and sedimentation dynamics.
Extreme Events and What We Can Do
When the uneven heating of air and water intensifies, extreme events appear. Warm seas feed tropical cyclones (hurricanes in the Atlantic and the northeastern Pacific). In Mexico, the season runs from May or June to November and is measured with the Saffir-Simpson scale, from category 1 to 5. Other events are heat waves, droughts, and torrential rains.
Where do they occur around the world?
They are not distributed at random: they depend on latitude, sea temperature, and whether the place is near the coast or in the interior of a continent. The figure shows, approximately, in which latitude bands each event is most frequent.
| Event | Where it is most frequent | Examples |
|---|---|---|
| Tropical cyclones | Warm seas, at about 5° to 30° latitude, on both sides of the equator | Atlantic, Caribbean, Gulf of Mexico, northeastern Pacific (Mexican coasts) |
| Droughts | Subtropical bands and continental areas far from the sea | Northern Mexico, African Sahel, Australia |
| Torrential rains | Humid tropics and monsoon regions, where warm, moist air rises strongly | South Asia, Amazon, southeastern Mexico |
| Heat waves | Continental interiors, far from the softening influence of the sea | Northern Mexico, central North America, southern Europe |
Mexico lies between 15° and 30° north latitude, with two warm oceans on its sides. That is why it receives cyclones from both the Pacific and the Atlantic, and has dry regions in the north and very rainy areas in the south.
What does global warming have to do with it? A warmer ocean provides more energy and more water vapor, and a warmer atmosphere can hold more moisture. Scientific studies indicate that this favors more intense cyclones, heavier rains when it rains, and more frequent or prolonged heat waves and droughts in many regions.
There are two types of actions in response: mitigation (reducing the causes, for example using less energy from fossil fuels) and adaptation (preparing ourselves). In a school or community these can be: collecting rainwater, using water responsibly, planting trees to provide shade, and having a civil protection plan.
Summary
Back to the beginning: the afternoon wind on the boardwalk is produced because the hot sand makes the air rise and draws the cooler air over the sea toward the shore.