General Marine - Oceanography Unit 1

How are land and sea breezes formed?

They are caused by the differential heating of land and water. During the day, land heats faster than water, creating low pressure over land and drawing cool air from the sea (sea breeze). At night, land cools faster, creating high pressure over land and pushing air toward the sea (land breeze).

What causes ocean tides and what are their cycles?

Tides are primarily caused by the gravitational pull of the Moon and the Sun on Earth's oceans. They follow cycles typically resulting in two high tides and two low tides per lunar day (semi-diurnal) or one of each (diurnal).

What are the main factors that create ocean currents?

Ocean currents are driven by wind patterns, the Coriolis force (Earth's rotation), differences in water temperature, and variations in water density (thermohaline circulation).

What is the Leeuwin Current?

A warm, southward-flowing ocean current that runs along the Western Australian coastline, which significantly influences the local climate and marine biodiversity by transporting warm tropical water toward cooler southern regions.

What is the West Australian Current?

A cold, northward-flowing current that forms the eastern part of the Indian Ocean gyre, moving along the coast of Western Australia and helping to regulate water temperatures.

What is the South Equatorial Current?

A significant westward-flowing current in the Indian Ocean, driven by the trade winds, which acts as a primary source of water for the Leeuwin Current.

What methods are used to measure surface current speed and direction?

Common methods include using satellite altimetry, drifting buoys (drifters), moored current meters, and acoustic Doppler current profilers (ADCPs).

What are the 5 designated oceans of the world?

Pacific, Atlantic, Indian, Southern, and Arctic Oceans.

What percentage of the Earth's surface is covered by oceans?

Approximately 71 percent.

What is the deepest part of the ocean?

The Challenger Deep in the Mariana Trench, which is approximately 10,935 meters deep.

What are the four main branches of oceanography?

Physical, Chemical, Biological, and Geological Oceanography.

What is Physical Oceanography?

The study of the physical attributes of the ocean, including waves, tides, currents, and the interaction between the ocean and the atmosphere.

What is Chemical Oceanography?

The study of the chemical composition of seawater and its properties, including how chemicals interact with the marine environment.

What is Biological Oceanography?

The study of marine organisms and their relationship to the ocean environment.

What is Geological Oceanography?

The study of the ocean floor, including plate tectonics, sediment, and the history of the Earth's crust beneath the sea.

What is air pressure?

The force exerted by the weight of air molecules bumping into each other in the atmosphere.

What instrument is used to measure air pressure?

A barometer.

What weather is associated with high-pressure systems?

Clear skies, cool temperatures, and dry conditions.

What weather is associated with low-pressure systems?

Warmer weather, clouds, rain, and potential storms.

How does air pressure change during a hurricane or tornado?

It drops dramatically, signaling the approach of intense storms.

What is wind?

The movement of air masses from areas of high pressure to areas of low pressure.

What instrument is used to measure wind speed?

An anemometer.

What does the closeness of isobars on a weather map indicate?

The closer the isobars, the steeper the pressure gradient and the stronger the wind speed.

What is the Coriolis force?

The effect of the Earth's rotation that causes moving air and water to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Name three major ocean currents surrounding Australia.

The Leeuwin Current, the West Australian Current, and the South Equatorial Current.

What is a 'straight' in a nautical context?

A narrow passage of water connecting two larger areas of water.

What is a gulf?

A deep inlet of the sea almost surrounded by land, with a narrow mouth.

What happens to air in a low-pressure system?

The air is lighter and rises, which causes it to cool and form clouds and precipitation.

What happens to air in a high-pressure system?

The air is heavier and sinks, creating a downward motion that clears the skies.

What is the primary cause of ocean currents?

Factors include wind, the Earth's rotation (Coriolis force), water temperature differences, and water density.

What is the role of the Leeuwin Current?

It is a warm ocean current that flows southward along the Western Australian coastline.

What causes wind?

Differences in atmospheric pressure; air moves from high-pressure areas to low-pressure areas to rebalance the atmosphere.

What increases wind speed?

A greater difference in pressure between high and low-pressure areas, or a steeper pressure gradient (isobars closer together).

How are winds named?

Winds are named based on the direction from which they originate (e.g., a westerly wind blows from the west).

What is the Beaufort Wind Scale?

An empirical measure that relates wind speed to observed conditions on land or sea (e.g., Force 0 is calm, Force 12 is a hurricane).

What is a gust of wind?

A brief, sudden increase in the speed of the wind.

How does wind influence the ocean?

Wind forms waves through fetch zones, controls the direction of ocean swells, and influences the size and direction of ocean currents.

How is a sea breeze formed?

During the day, land heats up faster than the sea, causing air over land to rise. Cooler, denser air from the sea is drawn in to replace it, creating a convection current.

What is the difference between onshore and offshore winds?

Onshore winds blow from the sea toward the land, while offshore winds blow from the land toward the sea.

What are isobars?

Lines on a synoptic weather chart that connect points of equal atmospheric pressure.

What is a trough in meteorology?

An elongated area of relatively low pressure extending from the center of a low-pressure system.

What happens to air pressure as a high moves out of an area?

The air pressure in that area will decrease as the high-pressure system moves away.

What happens to air pressure as a low moves out of an area?

The air pressure in that area will increase as the low-pressure system moves away.

In which direction does air spiral in a Southern Hemisphere low-pressure region?

Air spirals in a clockwise direction.

In which direction does air spiral in a Southern Hemisphere high-pressure region?

Air spirals in an anti-clockwise direction.

What are three features of a synoptic chart besides isobars?

Cold fronts, warm fronts, and pressure system centers (H or L).

What causes ocean tides?

The gravitational pull exerted by the Moon and the Sun on the Earth's oceans.

What is a spring tide?

A spring tide occurs when the Sun and Moon align, causing their gravitational pull to combine, resulting in the highest high tides and lowest low tides.

What is a neap tide?

A neap tide occurs when the Sun, Earth, and Moon are positioned such that their gravitational effects partially cancel each other out, resulting in the lowest high and low tides.

How does coastline shape affect tides?

Irregular coastlines, headlands, and varying ocean depths create friction and obstacles that slow down the tidal bulge, causing variations in tide times.

What is a King tide?

A non-scientific term for an exceptionally high tide that occurs when the orbits of the Earth, Moon, and Sun align to create maximum gravitational pull.

What causes most ocean waves?

Most ocean waves are caused by wind blowing over the surface of the water, which pushes the water and causes it to pile up.

What is a wave crest?

The highest point of a wave.

What is a wave trough?

The low point between two waves.

What causes a tsunami?

Tsunamis are caused by the release of massive amounts of energy from underwater volcanic eruptions or earthquakes.

How does wind speed affect wave height?

Generally, stronger winds result in higher waves because more energy is transferred to the water surface.

Frequency (Ocean Waves)

The number of wave crests that pass a fixed point per unit of time.

Wave Period

The time it takes for two successive wave crests to pass a specific point.

Fetch

The distance over open water that the wind blows in a single direction to generate waves.

Five factors influencing wave formation

1. Wind speed, 2. Wind duration, 3. Fetch, 4. Water depth, 5. Bottom topography.

What causes ocean currents?

Ocean currents are primarily caused by wind patterns (trade winds), differences in water density (temperature and salinity), and the rotation of the Earth.

Surface Currents vs. Deep Currents

Surface currents are warm, low-density, and wind-driven; deep currents are cold, high-density, and driven by thermohaline circulation.

Coriolis Effect

The deflection of moving objects (like water or air) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere due to Earth's rotation.

Leeuwin Current

A warm ocean current flowing south along the western coast of Australia, which influences local rainfall and supports tropical marine life.

West Australian Current

A cool surface current of the Southern Ocean that flows north parallel to the western coast of Australia.

How does temperature affect ocean currents?

Warmer water is less dense and tends to stay at the surface, while colder water is denser and sinks, driving deep-ocean circulation.

Upwelling

The process where deep, cold, nutrient-rich water rises to the surface, often occurring when surface currents are forced away from a coastline.

Thermohaline circulation

Large-scale ocean circulation driven by global density gradients created by surface heat and freshwater fluxes.

Seas vs. Swell

Seas are waves currently being generated by local winds; swell refers to waves that have traveled away from their area of origin.