Oceanography Midterm 2 (Shortened info only no numbers)

USC Oceanography Spring 2026

What are the two main global wind patterns that drive ocean currents

Trade winds and westerlies

Where is low and high pressure on Earth

Low pressure at the equator and high pressure at the poles

What is the Coriolis effect

The deflection of moving air or water due to Earth's rotation

In the Northern Hemisphere which direction does Coriolis deflect movement

To the right

In the Southern Hemisphere which direction does Coriolis deflect movement

To the left

What direction does the surface ocean current move relative to wind

At an angle away from wind due to Coriolis and friction

What is Ekman transport

The net movement of surface ocean water at 90 degrees to wind direction

What direction is Ekman transport in the Northern Hemisphere

To the right of the wind

What direction is Ekman transport in the Southern Hemisphere

To the left of the wind

Why does Ekman transport occur

Wind drags water and Coriolis deflects each layer creating a net movement

What happens to water movement with depth in the Ekman spiral

It slows down and changes direction more

What is a gyre

A large circular system of ocean currents

What causes gyres to form

Wind patterns Coriolis effect and continents redirecting flow

Why do gyres rotate clockwise in the Northern Hemisphere

Coriolis deflects currents to the right

Why do gyres rotate counterclockwise in the Southern Hemisphere

Coriolis deflects currents to the left

What role do continents play in gyres

They block and redirect currents into circular patterns

What are eddies

Small rotating currents within larger current systems

Why are eddies important

They transport heat nutrients and energy

What is a warm current

A current that carries warm water toward higher latitudes

Where are warm currents typically located

Along western boundary currents on eastern coasts of continents

How do warm currents affect climate

They warm nearby coastal regions

What creates wind generated waves

Friction between wind and ocean surface

What three main factors control wave size

Wind speed duration and fetch

What is fetch

The distance wind blows across water

What is duration

How long wind blows over water

What happens to waves when wind blows longer or over greater distance

They grow larger and more energetic

What is a fully developed sea

When wave growth stops because energy input equals energy loss

Do ocean waves move water across the ocean

No water mostly moves in circular orbits

What type of motion do water particles follow in waves

Orbital circular motion

What happens to a water particle after a wave passes

It returns near its original position

What happens to orbital motion with depth

It decreases with depth

What is wave base

The depth where wave motion becomes negligible

When do waves begin to interact with the seafloor

When water depth becomes shallow relative to wave size

Why do waves break near shore

The bottom slows the wave base causing the crest to topple forward

What happens to a wave as it approaches shallow water

It slows down steepens and breaks

How is wave energy related to wave height

Energy increases rapidly as height increases

What is wave period

The time between successive wave crests

What is wavelength

The distance between wave crests

What is wave refraction

The bending of waves as they approach shore

Why does wave refraction occur

Parts of the wave slow down at different times in shallow water

What happens to wave direction after refraction

Waves become more parallel to the shoreline

Where is wave energy concentrated after refraction

On headlands

Where is wave energy weaker after refraction

In bays

What is a tsunami

A long wavelength wave caused by sudden displacement of ocean water

What causes tsunamis

Earthquakes landslides or volcanic eruptions

How do tsunamis behave in deep water

They are low in height but carry large amounts of energy

What happens to tsunamis near shore

They slow down and increase dramatically in height

Why can tsunamis be destructive near shore

Energy is compressed into a smaller space increasing wave height

What are tides

Long period waves caused by gravitational pull of the Moon and Sun

What causes the two tidal bulges

Gravitational pull and inertia of the Earth Moon system

How many tides occur per day in most places

Two high tides and two low tides

What are spring tides

Tides with the greatest range when Sun Moon and Earth align

What are neap tides

Tides with the smallest range when Sun and Moon are at right angles

Why does the Moon have a stronger effect on tides than the Sun

Because it is much closer to Earth

What is a coastline

A boundary where land and ocean interact

What determines whether a coast erodes or builds

The balance between ocean energy and sediment supply

What happens when sediment supply is high

The coastline builds outward

What happens when wave energy is high

The coastline erodes

Why are coasts vulnerable to hazards

They are exposed to storms flooding and erosion

What is the source of most beach sand

Erosion of land carried by rivers and waves

What is a longshore current

A current that flows parallel to the shoreline

What causes a longshore current

Waves hitting the shore at an angle

What is longshore drift

The movement of sediment along the shore in a zigzag pattern

How does swash move sediment

Up the beach at an angle

How does backwash move sediment

Straight down due to gravity

What is the net effect of longshore drift

Sediment moves along the coastline

What is a rip current

A fast narrow current flowing away from shore

How do rip currents form

Water piled near shore escapes through gaps in waves

Why are rip currents dangerous

They quickly carry swimmers offshore

What is a groin

A structure that traps sand and interrupts longshore drift

What happens to sand on the updrift side of a groin

It accumulates

What happens to sand on the downdrift side of a groin

It decreases

What is a jetty

A structure that keeps channels open by blocking sediment

What is a wave cut platform

A flat surface formed by wave erosion at the base of cliffs

What are sea caves

Openings formed by wave erosion in rock

What are sea arches

Formed when caves erode through a headland

What are sea stacks

Isolated rock pillars formed after arches collapse

What is a barrier island

A long narrow island parallel to the coast made of sand

Why are barrier islands unstable

They constantly shift due to waves and storms

What is a lagoon

A shallow water body separated from the ocean

What is an estuary

A place where freshwater and seawater mix

What is brackish water

Water with mixed salinity

How does water move in an estuary

Freshwater flows out on top saltwater flows in below

What is a delta

A landform formed by sediment deposited at a river mouth

Why do deltas form

Rivers slow down and drop sediment

What controls phytoplankton growth

Availability of light nutrients and carbon dioxide

What are phytoplankton

Microscopic organisms that perform photosynthesis

Why are phytoplankton important

They form the base of the marine food web

What nutrients are most important for phytoplankton

Nitrogen phosphorus and carbon

What nutrient usually limits phytoplankton growth if they cant get it

Nitrogen phosphorus or iron not carbon dioxide

What is upwelling

The movement of deep nutrient rich water to the surface

Why does upwelling increase productivity

It brings nutrients to surface waters

What is remineralization

The breakdown of organic matter releasing nutrients

Why are nutrients low at the surface

They are used by phytoplankton

Why are nutrients high at depth

Decomposition releases nutrients

How does oxygen vary with depth

High at surface low at depth

What is plankton

Drifting organisms in the ocean

What is phytoplankton

Photosynthetic plankton

What is zooplankton

Animal plankton that consume other organisms

What is a heterotroph

An organism that consumes organic matter for energy