OCEANOGRAPHY

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What is bathymetry?

Study of ocean depth/topography

What does single-beam sonar measure?

Narrow trackline of depth

What does multi-beam sonar measure?

Wide swath of depths

What does towed sonar provide?

High resolution measurements

What does satellite altimetry measure?

Sea surface gravity anomalies to infer seafloor topography

What is the continental shelf?

Shallow nearshore zone

What is the abyssal plain?

Flat deep seafloor

What is a mid-ocean ridge?

Spreading centers where new crust forms

What are island arcs?

Features formed from subduction of ocean crust beneath ocean crust

What are seamount chains?

Volcanic chains created by hot spots beneath moving plates

What is the lithosphere?

Tectonic plates that can contain oceanic or continental crust

What are the two types of crust?

Oceanic and continental

Describe oceanic crust

Thinner and denser; forms ocean basins

Describe continental crust

Thicker and less dense; forms land

What are four pieces of evidence for plate tectonics?

"Seafloor spreading

What is Pangaea?

Supercontinent that repeatedly assembled and broke apart (Wilson Cycle)

What happens at divergent boundaries?

Plates move apart

What do divergent boundaries create?

"Mid-ocean ridges

What happens at convergent boundaries?

Plates collide

What does ocean-continent convergence create?

Oceanic subduction → trenches and volcanic arcs

What does ocean-ocean convergence create?

Subduction → island arcs

What does continent-continent convergence create?

Collision → mountains (example: Himalayas)

What happens at transform boundaries?

Plates slide laterally (example: San Andreas Fault)

What are mantle hot spots?

Stationary plumes that create volcanic chains

How do hot spots create seamount chains?

Plate moves while plume stays stationary → creates chain (example: Hawaii)

What are terrigenous sediments?

Land-derived sediments from rivers and dust

What are biological sediments?

Calcareous (shells) and siliceous (diatoms) sediments

What are red clays?

Slow accumulation of dust in open ocean

Where is sediment accumulation thick?

Near coasts

Where is sediment accumulation very slow?

In the open ocean (cm per 1000 years)

What do deep-sea cores preserve?

Millions of years of Earth history

What are oxygen isotopes used for?

Temperature indicator (¹⁸O/¹⁶O ratio)

What are Ca/Mg ratios used for?

Additional temperature signal in paleoceanography

How many major mass extinctions occurred?

Five major extinctions in history

When did the asteroid kill the dinosaurs?

65 million years ago (mya)

What is the ongoing 6th extinction attributed to?

Humans

What are hydrothermal vents?

Circulating seawater extracts minerals and supports microbial ecosystems

What are the three major wind belts per hemisphere?

"0-30° (Trades)

Where is ocean surface temperature warmest?

At the equator (west)

Where is ocean surface temperature coldest?

At the poles

What causes the cold tongue at the eastern equator?

Upwelling

Where is salinity highest?

In subtropics (evaporation > precipitation)

Which ocean is saltier?

Atlantic is saltier than Pacific

What is the Coriolis force?

Apparent deflection due to Earth's rotation

Which direction does Coriolis deflect in Northern Hemisphere?

Right

Which direction does Coriolis deflect in Southern Hemisphere?

Left

What does Coriolis force explain?

Curved wind and ocean current paths

What is the Hadley Cell?

Warm air rises at equator → moves poleward → sinks at ~30° → returns as trade winds

What are sea level pressure patterns?

High at 30° latitude; low at equator and 60°

What causes pressure pattern differences?

Unequal heating of land vs ocean

Describe the vertical layers of the ocean

"Warm thin surface layer

What is the permanent thermocline depth?

~500 meters

How deep does light penetrate the ocean?

Only upper ~150 meters

What is stratification?

Less dense water over more dense water → stable

What is Ekman Transport?

Surface layer moves 90° to wind direction

What direction do gyres rotate in Northern Hemisphere?

Clockwise

What direction do gyres rotate in Southern Hemisphere?

Counterclockwise

Describe western boundary currents

Fast and warm (example: Gulf Stream)

What is equatorial upwelling?

Divergence from trade winds brings deep water up

What is coastal upwelling?

Winds push surface water offshore → deep water rises

What is downwelling?

Opposite of upwelling; surface water converges and sinks

What drives thermohaline circulation?

Density (temperature + salinity)

What is NADW?

North Atlantic Deep Water

What is AABW?

Antarctic Bottom Water

What is AAIW?

Antarctic Intermediate Water

Where does deep water form?

At high latitudes (cold and salty sinking)

How long does the global thermohaline journey take?

~2000 years

What does thermohaline circulation do?

Moves heat poleward and regulates climate

What is AMOC?

Atlantic Meridional Overturning Circulation

What is happening to AMOC?

Currently weakening; risk of collapse in decades-centuries

What would AMOC collapse do?

Drastically alter climate patterns

What was El Niño originally?

Warm current near Peru during Christmas

What does El Niño refer to now?

Intense warming events (every 3-7 years; lasts ~8 months)

What is the Southern Oscillation?

Pressure seesaw between Tahiti (high) and Darwin Australia (low); discovered by Sir Gilbert Walker in 1920s

What does ENSO stand for?

El Niño + Southern Oscillation

Describe normal ENSO conditions

Trade winds push warm water west → Western Pacific Warm Pool; cold upwelling off Peru (Eastern Pacific cold tongue)

Describe El Niño conditions

Weakening/reversal of trade winds; warm water spreads east → suppresses upwelling; Eastern Pacific warms

Describe La Niña conditions

Stronger-than-normal trade winds; cold tongue strengthens

What are direct impacts of ENSO?

Shifts rainfall patterns (droughts/floods); alters global wind circulation

What are indirect impacts of ENSO?

"Fisheries collapse (Peru

Name three other climate oscillations

"North Atlantic Oscillation (NAO)

What timescales do NAO/PDO/AO affect?

Seasonal to decadal timescales

What is wavelength (L)?

Distance between wave crests

What is wave speed (C)?

Distance traveled per unit time

What is wave period (T)?

Time for one wavelength to pass

What is wave frequency (f)?

Crests per unit time

What is constructive wave addition?

Waves combine to make bigger waves

What is destructive wave addition?

Waves cancel each other out

Do waves transfer mass or energy?

Energy (not mass); particles move in orbitals

When are waves deep-water waves?

When depth > L/2

What determines deep-water wave speed?

Wavelength only (longer = faster)

When are waves shallow-water waves?

When depth < L/20

What determines shallow-water wave speed?

Depth only (shallower = slower)

What is wave dispersion?

Long wavelengths outrun short ones after storms

What is wave refraction?

Waves bend when entering shallow water → focus energy on headlands and disperse in bays