The Oceans Exam 2

Water vapor _____ the density of air, because water molecules displace _____ nitrogen and oxygen molecules

decreases, heavier

Warm, ____ air is less dense than ___ air, causing it to rise through the atmosphere until it hits its equilibrium level.

moist, dry

As warm, moist air ____, it expands and cools causing water vapor to condense into clouds and rain.

rises

Atmospheric and oceanic circulations balance Earth’s heat budget by ___________________

transferring heat from low latitudes (equator) to high latitudes (poles).

The equator experiences a net ________ because solar rays strike at a high angle, while the poles experience a net _______ because rays hit at a low angle over a spread-out area.

heat gain, heat loss

More water ________________ than returns as rain, whereas more rain _________ than evaporates from it.

evaporates over the oceans, falls over land

There are exactly 3 atmospheric convection cells in each hemisphere.

• Hadley cell: Extends from the equator to roughly 30 degrees latitude.

• Ferrel cell: The temperate mid-latitude cell located between 30 and 60 degrees.

• Polar cell: The high-latitude cell capping the polar regions.

High-pressure zones: Regions where air masses descend vertically feature _____________ (e.g., the subtropical horse latitudes and polar deserts).

clear skies and light winds

Surface ocean salinity patterns are primarily driven by ________________.

large-scale precipitation and evaporation balances

Sea surface salinity is highest in ______________ because evaporation rates are high and rainfall is scarce.

subtropical regions far from land

An El Niño event officially begins when the ___________________

Pacific trade winds weaken or completely reverse

The collapse of Pacific trade winds allows warm surface water to slide eastward toward Peru, capping off and _____________ of cold, nutrient-rich deep water.

stopping the normal coastal upwelling

Oceans ___________________________ due to water's high heat capacity.

warm up more slowly and cool down more slowly

Rain shadows form on the leeward sides of coastal mountains because moist ocean air is forced to _______________ before descending as dry air.

rise, cool, and drop its water content on the windward slope

Hurricanes extract their immense energy from the ___________________ over warm tropical ocean waters.

latent heat released by the condensation of water vapor

Hurricanes ___________________ because the Coriolis effect is zero there, preventing the storm from developing its essential cyclonic rotation.

cannot form directly at the equator (0 degrees)

Steady winds drag surface ocean water via friction, creating currents moving at about ______________.

1% to 3% of the wind's speed.

The direction of Ekman transport is explicitly determined by _____________.

wind direction and the Coriolis effect.

Moving objects and fluids are deflected to the right in the ____________ and to the left in the ___________.

Northern Hemisphere, Southern Hemisphere

Descending down the water column inside an Ekman current, the flow velocity drops and the direction spirals progressively to the right in the ____________.

Northern Hemisphere

Ocean surface currents form giant closed loops called subtropical gyres which rotate clockwise in the ____________ and counterclockwise in the ___________.

Northern Hemisphere, Southern Hemisphere

Major gyres dominate the North/South Atlantic, North/South Pacific, and Indian Oceans; however, the _______ does not contain a major subtropical gyre.

Arctic Ocean

Gyres are maintained by a balance between the Coriolis effect pulling water inward and the ___________ pulling water down the slope of the piled-up center.

horizontal pressure gradient

Gyre development and movements are steered by winds, continents, and the Coriolis effect, but ______ do not influence gyre formation.

tidal cycles

When converging horizontal ocean currents pile up water near a shoreline or open ocean convergence, _________ occurs.

downwelling

Within a subsurface pressure gradient, vertical water replacement _______ occurs explicitly on the low-pressure end where surface waters diverge.

upwelling

Strong, steady winds create shallow, alternating corkscrew vortices aligned with the wind; floating debris and foam collect in the linear downwelling lines, or _______ formed between these cells.

windrows

Eddies are defined as _______________ spun off from larger main currents.

circular, swirling currents of ocean water

The rings and swirls of eddies are produced by ___________________ along the margins of fast boundary currents like the Gulf Stream.

intense turbulence and meandering fronts

The word "thermohaline" translates directly to temperature ("thermo") and salinity ("haline").

temperature ("thermo"), salinity ("haline")

Thermohaline circulation is driven entirely by ____________________.

density differences in water masses

The immense global conveyor belt circulation is driven by dense deep-water formation that sinks from the surface in the ________________________.

North Atlantic near Greenland and Iceland

The MOC acts as a massive thermal regulator, heavily influencing and __________________ by conveying equatorial heat to northern Europe.

stabilizing global climate patterns

How do convection cells form?

Surface heating or evaporation makes air rise; it cools and loses water by condensation, then eventually cools, becomes denser, and sinks.

What is the latitudinal heat imbalance?

The tropics receive more solar energy than they radiate away, while high latitudes lose more energy than they receive.

How is the latitudinal heat imbalance reduced?

Atmospheric and ocean circulation transport heat from the tropics toward the poles.

What is the Coriolis effect?

The apparent deflection of moving air and water caused by Earth's rotation: to the right in the Northern Hemisphere and left in the Southern Hemisphere.

What are the trade winds?

Easterly surface winds that flow from subtropical highs toward the equatorial low-pressure belt, deflected westward by the Coriolis effect.

Why do climatic wind belts shift seasonally?

The zone of maximum solar heating and associated pressure belts migrate north and south with the seasons.

What is a monsoon?

A seasonal reversal or major shift in regional winds, commonly caused by contrasting seasonal heating of land and ocean.

Why do many Asian summer monsoons bring heavy rain?

Land heats strongly in summer, drawing moist ocean air inland; that air rises and produces extensive rainfall.

What is ENSO?

The El Niño-Southern Oscillation, a coupled Pacific Ocean-atmosphere pattern with El Niño, neutral, and La Niña phases.

What is El Niño?

The warm ENSO phase, when unusually warm surface water spreads into the central or eastern equatorial Pacific and trade winds weaken.

What is La Niña?

The cool ENSO phase, typically with stronger trade winds and unusually cool surface water in the central and eastern equatorial Pacific.

What happens to Pacific trade winds during a typical El Niño?

They weaken, allowing warm western Pacific surface water to move eastward.

How can El Niño affect rainfall near the equatorial Pacific?

Rainfall shifts toward the unusually warm central or eastern Pacific, while regions such as Indonesia and Australia may become drier.

What is the Madden-Julian Oscillation (MJO)?

A roughly 30-day eastward-moving tropical pattern of clouds and associated wind bursts that can influence weather and sometimes ENSO development.

What is the North Atlantic Oscillation (NAO)?

A variation in the pressure difference between the Icelandic low and the subtropical high near the Azores, affecting North Atlantic winds and European winter weather.

What is the Pacific Decadal Oscillation (PDO)?

A long-term pattern of Pacific sea-surface-temperature variability with contrasting warm and cool regions that shifts over years to decades.

What is a climate regime shift?

A relatively abrupt change between periods with different ranges of average environmental conditions.

Why can precise long-range climate and weather prediction be difficult?

The atmosphere-ocean system is complex and chaotic; small changes can grow, and some patterns shift unpredictably.

Why do climate-zone boundaries represent approximations?

Climate factors vary gradually with latitude, topography, land-ocean position, and year-to-year variability, so zones merge into one another.

What shapes ocean climate zones?

They generally form latitudinal bands related to average ocean-surface temperature and circulation.

Why can polar and subpolar ocean surface waters have low salinity despite low precipitation?

Sea-ice melt and, especially in the Arctic, freshwater runoff dilute the surface layer.

What characterizes temperate ocean zones?

Strong westerlies, high precipitation, and frequent winter extratropical cyclones.

What characterizes subtropical ocean zones?

Light winds, clear skies, and low precipitation near the divergence between Hadley and Ferrel cells.

What characterizes trade-wind ocean zones?

Persistent winds, generally limited cloud cover and dryness, and high evaporation and salinity; the equatorial region is warmer, cloudier, and rainier.

What is a maritime climate?

A climate moderated by nearby ocean water, usually with smaller daily and seasonal temperature ranges.

What is a continental climate?

A climate farther from ocean influence, usually with larger daily and seasonal temperature ranges.

How do onshore climatic winds affect coastal climate?

They carry marine air inland, moderating temperatures and often increasing precipitation.

How do offshore climatic winds affect coastal climate?

They limit the ocean's moderating influence because air flows from land toward the sea.

How can ocean currents affect coastal climate?

Warm currents can warm nearby air and moderate winters; cold currents can cool coastal air and contribute to fog.

What are two ways landmasses affect atmospheric circulation?

They physically block or steer air, and their low heat capacity makes them heat and cool faster than oceans.

What causes a sea breeze?

Daytime land heats faster than ocean; warm air rises over land and cooler marine air flows inland to replace it.

What causes a land breeze?

At night land cools faster than ocean; denser air flows from land toward the relatively warmer ocean.

What causes coastal fog associated with sea breezes?

Moist air is drawn over cold nearshore water, cools to saturation, and condenses into tiny droplets.

What is the mountain (rain-shadow) effect?

Moist air rises over a mountain, cools and loses moisture as rain or snow on the windward side; descending air warms and dries on the leeward side.

Why is a mountain's leeward side often dry?

Air has lost much of its water on the windward slope and warms as it descends, increasing its capacity to hold vapor.

What is the island effect?

The mountain effect on an island: prevailing moist winds produce a wet windward side and a drier leeward side.

What pressure pattern is associated with a surface high?

Dense air sinks, creating higher surface pressure, then spreads outward near the surface.

What pressure pattern is associated with a surface low?

Warm, moist air rises, creating lower surface pressure; surrounding air flows inward near the surface.

How do winds circulate around pressure systems near the surface in the Northern Hemisphere?

Counterclockwise and inward around lows; clockwise and outward around highs.

How do winds circulate around pressure systems near the surface in the Southern Hemisphere?

Clockwise and inward around lows; counterclockwise and outward around highs.

What is geostrophic flow?

Wind flow in which the pressure-gradient force and Coriolis effect are balanced, making winds flow roughly parallel to isobars.

How does surface friction affect winds around highs and lows?

It weakens Coriolis deflection, so surface winds spiral outward from highs and inward toward lows.

What is a tropical cyclone?

A rotating low-pressure storm that develops over warm tropical ocean water; regional names include hurricane, typhoon, and cyclone.

What conditions favor tropical-cyclone formation?

Sea-surface temperatures above about 26°C, sufficient Coriolis effect (usually more than 5° from the equator), moisture, and a developing low-pressure disturbance.

Why are tropical cyclones rare within about 5° of the equator?

The Coriolis effect is too weak there to produce the needed rotation.

How does a tropical cyclone gain energy?

Air takes up heat and moisture over warm water; condensation releases latent heat that sustains rising air and intensifies the storm.

What is the eyewall?

The ring of intense thunderstorms around the eye, where the strongest winds and heaviest rainfall occur.

How do tropical cyclones rotate?

Counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

What is storm surge?

A rise of seawater pushed toward shore by a storm's winds and low pressure, capable of flooding low-lying coasts.

What is an extratropical cyclone?

A large midlatitude storm that develops along the polar front where cold polar air meets warmer midlatitude air.

How do extratropical cyclones form?

A wave develops along the polar front; warm air rises over denser cold air, and Coriolis deflection helps create a rotating low.

How do extratropical cyclones differ from tropical cyclones?

They form along fronts in midlatitudes, can be larger, generally move eastward, and are powered by temperature contrasts rather than only warm tropical water.

What is a cold front?

The boundary where advancing cold air pushes beneath warm air, forcing it to rise and often producing clouds and precipitation.

What is a warm front?

The boundary where advancing warm air rises over retreating cold air, often producing widespread clouds and precipitation.

What is an occluded front?

The boundary formed when a cold front catches up to a warm front and lifts the warm air off the ground.

How can the Gulf Stream intensify nor'easters?

The warm current supplies heat and moisture to passing storms, sometimes causing rapid intensification.

What is the Main energy source driving horizontal ocean currents in the upper 100–200 meters.

Winds (Atmospheric circulation).

Main energy source driving deep ocean circulation below the wind-driven layer.

Variations in water density (Thermohaline circulation) driven by differences in temperature and salinity.

Why do ocean currents continue to flow for long periods after the wind stops blowing?

Water mass momentum (dissipated very slowly because internal friction between water layers is small).

Where on Earth is the Coriolis effect at its maximum, and where is it zero?

Maximum at the poles; decreases at lower latitudes; zero at the equator.

Definition of the oceanographic term cum sole.

"With the sun"—meaning to the right in the Northern Hemisphere and to the left in the Southern Hemisphere

Describe the behavior of wind-driven water velocity and direction as depth increases.

Current speed decreases while the direction spirals progressively cum sole (to the right in the NH, left in the SH).

Under ideal conditions (constant wind, uniform density), what is the angle of the surface current relative to the wind?

45° cum sole to the wind direction

What is the net direction of total water movement (Ekman transport) over the entire depth of the wind-driven layer

90° cum sole to the wind direction

How does a steep pycnocline alter the Ekman spiral

It causes frictional decoupling. Water layers slide over each other too easily, restricting wind transport to the shallow layer above the pycnocline

How do shallow coastal waters affect wind-driven transport

Bottom friction with the seafloor reduces deflection. In very shallow water, transport moves directly in the wind direction and is steered by bottom contours

What is geostrophic flow

A horizontal current where the Coriolis deflection is perfectly balanced by the horizontal pressure gradient force