Atmospheric Circulation and Ocean Salinity

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Questions and Answers

What is the primary factor in determining the Force of Buoyancy according to Archimedes' Principle?

Weight of the object submerged

Volume of the medium displaced

Temperature of the displaced medium

Density of the displaced medium (correct)

Which process contributes to the decrease in seawater salinity by adding freshwater?

Evaporation

Sedimentation

Icebergs melting (correct)

Desalination

What is the salinity of the Dead Sea, as compared to the Great Salt Lake?

Irrelevant to the Great Salt Lake's salinity

Equal to the Great Salt Lake

Less than the Great Salt Lake

Greater than the Great Salt Lake (correct)

Which of the following processes adds salt to seawater?

Runoff from streams Signup and view all the answers

What is the value of gravitational acceleration (g) used in the calculation of buoyant force?

9.8 m/s² Signup and view all the answers

What characterizes the Hadley Cell in the Three-Cell Model of Atmospheric Circulation?

It exists from 0 to 30 degrees latitude. Signup and view all the answers

How does the Coriolis effect influence the movement of air in the atmosphere?

It deflects moving air strongly to the right in the Northern Hemisphere. Signup and view all the answers

Which circulation cell is the strongest according to the Three-Cell Model?

Hadley Cell Signup and view all the answers

At which latitudes do the Polar Cells primarily operate?

60-90 degrees Signup and view all the answers

What generates high and low pressure zones at the surface?

Rising and descending air from circulation cells. Signup and view all the answers

What is the primary wind direction associated with the trade winds?

Easterly Signup and view all the answers

Which latitudes are referred to as the horse latitudes?

0-30 degrees Signup and view all the answers

What impact do seasonal variations have on atmospheric circulation?

They create cancellations when averaging DJF and JJA. Signup and view all the answers

What describes the state of the ocean during anticyclonic conditions?

High sea surface height with warm core Signup and view all the answers

Which phenomenon causes the seasonal reversal of winds in the Indian Ocean?

Monsoon Signup and view all the answers

What effect does offshore Ekman transport have on coastal regions?

Drives coastal upwelling Signup and view all the answers

Which of the following occurs during El Nino conditions?

Weaker or reversed trade winds Signup and view all the answers

What is a characteristic of La Nina conditions?

Strengthened Walker cell circulation Signup and view all the answers

Which aspect of the Indian Ocean Monsoon significantly impacts phytoplankton productivity?

Seasonal land weather changes Signup and view all the answers

During a strong El Nino event, which of the following would occur?

Thermocline depression in the eastern Pacific Signup and view all the answers

What does the term 'heat capacity differential' refer to in the context of the Indian Ocean Monsoon?

Differences in temperature between land and sea Signup and view all the answers

How does sound propagate in water compared to its speed?

Sound tends to bend toward regions of lower sound speed. Signup and view all the answers

Which underwater sound source is categorized as a natural source?

Ice cracking Signup and view all the answers

What is a primary use of passive sonar?

Detection of natural sound sources Signup and view all the answers

What is a potential consequence of the spreading of underwater sound energy?

Weakening of sound intensity Signup and view all the answers

What does the phrase 'sound is lazy' imply about sound propagation?

Sound tends to follow paths of lower speed. Signup and view all the answers

Which regions are identified as sources of North Atlantic Deep Water?

Labrador Sea Signup and view all the answers

What is the main principle behind the conservation of volume in ocean currents?

Equal volumes of water must rise and sink. Signup and view all the answers

What drives the abrupt upwelling in the Antarctic Circumpolar Current?

Wind-driven pumping effect. Signup and view all the answers

Which mechanism is considered important for the turbulent mixing of ocean water?

Breaking internal waves Signup and view all the answers

What does the Atlantic Meridional Overturning Circulation (AMOC) involve?

Formation of both NADW and AABW. Signup and view all the answers

How are geostrophic currents inferred during AMOC observations?

From temperature and salinity measurements. Signup and view all the answers

What effect do winds have on North Atlantic Deep Water during AMOC circulation?

Winds play a role in the pumping of NADW to the surface. Signup and view all the answers

What significant variability can occur when observing the AMOC?

Year-to-year changes over 100%. Signup and view all the answers

What is a key outcome of adding freshwater to the surface ocean in a hosing experiment?

Decreases salinity and inhibits NADW formation Signup and view all the answers

What phenomenon describes the abrupt transition in system state due to small changes in forcing?

Threshold behavior Signup and view all the answers

What type of ice formation occurs before pancake ice is formed?

Slush from needle-like crystals Signup and view all the answers

What is a primary effect of crossing a threshold in the AMOC due to freshwater additions?

Possible irreversibility of the system Signup and view all the answers

Which of the following best describes a floe in the context of sea ice?

A large piece of floating ice over 20m across Signup and view all the answers

In the context of ocean modeling, what does an OGCM primarily simulate?

Global ocean flow using physics equations Signup and view all the answers

What is the primary driver of pressure ridges formed by sea ice?

The collision of large ice sheets/floes Signup and view all the answers

What occurs when icebergs break off from glaciers?

Release of freshwater into the ocean Signup and view all the answers

What is the primary result of the Coriolis effect on geostrophic currents in the Northern Hemisphere?

They veer to the right of their path. Signup and view all the answers

Which of the following statements most accurately describes coastal upwelling?

Cool, nutrient-rich water replaces displaced surface water. Signup and view all the answers

How does the Antarctic Circumpolar Current differ from other ocean currents?

It is the only current to completely encircle the Earth. Signup and view all the answers

What phenomenon occurs due to the meanders in the Gulf Stream?

Formation of warm-core and cold-core rings. Signup and view all the answers

What characteristic defines the term 'western intensification' in ocean currents?

Narrow, rapid currents develop along the western coasts. Signup and view all the answers

What is primarily responsible for the significant cooling in the eastern Pacific during La Niña conditions?

Enhanced Walker circulation Signup and view all the answers

What is a major characteristic of the deep-water formation process in both polar regions?

Cold and salty water is formed. Signup and view all the answers

What are the mechanisms suggested for the equatorial waves in relation to ENSO phenomena?

They are driven by planetary rotation and oceanic conditions. Signup and view all the answers

How long can it take for Antarctic Bottom Water (AABW) to return to the ocean's surface?

Up to 1000 years Signup and view all the answers

What characteristic distinguishes the sources of North Atlantic Deep Water (NADW)?

It flows south in the ocean interior. Signup and view all the answers

What is the salinity difference between the Great Salt Lake and the Dead Sea?

The Dead Sea is more saline by 50 ppt. Signup and view all the answers

Which process primarily results in a decrease in salinity due to the addition of freshwater?

Icebergs calving into the ocean. Signup and view all the answers

Based on Archimedes' Principle, what determines the buoyant force experienced by an object submerged in seawater?

The volume of seawater displaced. Signup and view all the answers

Which statement accurately reflects the impact of precipitation on seawater salinity?

It leads to a decrease in salt concentration. Signup and view all the answers

What role does runoff from streams play in salinity changes in seawater?

It decreases salinity due to the addition of freshwater. Signup and view all the answers

What condition leads to breaking waves in ocean waters?

Wave steepness greater than 1/7 Signup and view all the answers

In a deep water wave, what is the primary characteristic of wave motion beneath the surface?

Particles rotate in circular orbits Signup and view all the answers

What defines shallow-water waves compared to deep-water waves?

Water depth greater than L/20 Signup and view all the answers

How is the wave speed calculated for waves in deep water?

By using the formula c = L/T Signup and view all the answers

Which aspect of wave behavior is observed when the water depth is less than L/20?

Waves feel the sea floor strongly Signup and view all the answers

Study Notes

Introduction to Physical Oceanography - Midterm 1 Review

The Pacific Ocean is the largest and deepest ocean on Earth.
The Arctic Ocean is the smallest and shallowest ocean.
The Atlantic Ocean is the second largest ocean.
The Indian Ocean exists primarily in the Southern Hemisphere.
The Southern Ocean surrounds Antarctica, with its boundary defined by the Antarctic Convergence.

Earth's Oceans

Atlantic Ocean: Half the size of the Pacific, shallower
Indian Ocean: Smaller than Atlantic, similar depth, primarily in the Southern Hemisphere
Arctic Ocean: Smallest and shallowest

Earth's Oceans - Depths

Pacific Ocean: 3940 meters (12,927 feet)
Atlantic Ocean: 3844 meters (12,612 feet)
Indian Ocean: 3,840 meters (12,598 feet)
Arctic Ocean: 1117 meters (3,665 feet)

Arctic Ice Extent

Current extent: 4.4 x 10^6 km^2 (September 4, 2024)
Mean: 6.3 x 10^6 km^2 (1979-2024)
Minimum: 3.8 x 10^6 km^2 (2012)
Maximum: 8.2 x 10^6 km^2 (1980)

Nebular Hypothesis

Gravity concentrates material at the center of the cloud(the Sun).
Nebula evolves into a rotating disk, akin to a pizza dough.
Earth's equatorial bulge (40 km)
Protoplanets form from smaller concentrations of matter (aided by eddies).

Protoearth

Protoearth becomes hot due to:
Radioactive heat, spontaneous disintegration of atoms
Fusion reactions, contraction of the protoplanet and collisions
Protoearth partially melts
Enabling density stratification (layered Earth)

Density Stratification

High density = heavy for its size (mass per unit volume)
High-density materials (iron and nickel) settled in the core during early Earth's gravitational separation.
Less dense materials formed concentric spheres around the core.

Earth's Internal Structure

Crust: Low-density, mainly silicate minerals, 3-km thick (oceanic vs continental).
Mantle: Mainly iron (Fe) and magnesium (Mg) silicate minerals, extends to ~2,885 km depth.
Core: High-density, mainly iron (Fe) and nickel (Ni), from ~2,885 km to 6,371 km (Earth's radius).

Development of Earth's Oceans

Initially, water vapor and other gases were released from volcanic activity into the atmosphere.
Liquid water fell to Earth's surface, accumulating in low areas, forming oceans over time.

Evidence for Continental Drift

Wegener proposed Pangaea (one large continent) existed 200 million years ago.
Panthalassa—one large ocean, including the Tethys Sea.
modern continents fit together like a jigsaw puzzle.

Glacial Evidence

Evidence of glaciation in now tropical regions requires explanation (global climate change, snowball earth)
Direction of glacial flow and rock scouring provides evidence of continental movement.

Snowball Earth

Periods of extreme cold causing Earth's surface to be entirely frozen.
Occurred approximately 650 million years ago (mya).
Dropstones, rocks embedded in glacial deposits, offer observational evidence. Mechanism is the Ice-Albedo Feedback (More ice—more reflected radiation, leading to a cooler earth, leading to more ice—…)
Ways out of this state include high CO2 in the atmosphere and mudball (dust on ice surface reducing albedo/increasing absorption).

Plate Tectonic Processes

Continental crust is pushed away mid-ocean ridges, often forming volcanic arcs. A trench is the site of crust destruction.
Subduction zones are sites of oceanic trench destruction.
Subduction can generate deep ocean trenches and old rocks.

Age of Ocean Floor

Youngest oceanic rocks at mid-ocean ridges
Oldest rocks near subduction zones

Hydrogen Bonding

Polarity means a small negative charge at the O (oxygen) end and a small positive charge at the H (hydrogen) end.
Attraction occurs between positive and negative ends of water molecules.

Hydrogen Bonds in Three States of Water

Solid (ice): Three-dimensional crystalline structure with hydrogen bonds between all water molecules
Liquid: Some hydrogen bonds but less structured than ice
Gas: No hydrogen bonds, molecules move freely

Water's Heat Capacity

Heat Capacity: Amount of heat required to raise the temperature of 1 gram of any substance by 1° Celsius.
Water has a high heat capacity; it can take in or lose a relatively large amount of heat without changing temperature or hydrogen bonding.
Specific Heat: Heat capacity per unit mass.

Latent Heat

Latent heat is the amount of heat absorbed or released during a phase change (solid to liquid or liquid to gas) without changing the temperature, used for breaking intermolecular bonds in water

The Real Version: Evaporation-Precipitation

Global patterns of evaporation (E) and precipitation (P)
Subtropics generally have E>P, while mid-latitudes/polar regions usually have E<P

Water Density and Temperature

Fresh water reaches maximum density at 4°C.
Below 0°C , water expands as it solidifies into ice, decreasing its density.

Salinity

Total amount of dissolved solids in water. (Excluded dissolved gases)
Ratio of dissolved substance mass to water sample mass.
Typically expressed in parts per thousand (ppt)
Average ocean salinity is 35 ppt

Determining Salinity

Evaporation: Early method, not always accurate
Chemical analysis via titration (principle of constant proportions): Measures the amount of halogens to determine chlorinity; used to estimate salinity
Salinometer: Measures electrical conductivity. More dissolved substances will cause an increase in conductivity.

Salinity Variations

Open ocean salinity is ~33-38 ppt
Brackish water salinity: ~10 ppt, due to freshwater influx from rivers/rain
Hypersaline conditions: High evaporation conditions yield high salinity (exceed 35 ppt) like Great Salt Lake (280 ppt) and Dead Sea (330 ppt)

Archimedes' Principle

Force of Buoyancy = weight of the displaced medium in the same volume(e.g., water)
F = ρVg (ρ=density of displaced seawater, V=Volume of displaced seawater, g=9.8 m/s^2)

Processes Affecting Salinity

Precipitation: Adds water (H₂O) and lowers salinity
Runoff: Adds freshwater, lowers salinity
Icebergs melting: Adds water and lowers salinity
Sea ice formation: Removes water and increase salinity
Evaporation: Removes water and increases salinity
Sea ice melting: adds water and lowers salinity.

Earth's Hydrologic Cycle

Water is constantly recycled among the atmosphere, oceans, and continents.
Huge volumes of water (hundreds of thousands of cubic kilometers) are in motion throughout these pathways each year.

Cycling of Dissolved Seawater Components

Inputs into the ocean include river discharge, volcanic eruptions, hydrothermal activity (at mid-ocean ridges), chemical reactions, and sea spray.
Processes that remove ions from the ocean are adsorption, precipitation, ion entrapment in sea spray, and biological uptake.

Real Ocean Equation of State

Seawater EOS is simple conceptually: Using the relationships between temperature, salinity and density to determine the density of seawater.
“Official” Ocean EOS: TEOS-10 (Thermodynamic equation of seawater).

Approximate Oceanic EOS

The linearized EOS is used to determine the approximated density of seawater given temperature and salinity. (p(S,T) = fo − 2 (T − Tc) + B(S − S0)

Surface Salinity Variations

High latitudes tend to have low salinity due to sea ice melting and precipitation/runoff
Mid-latitudes/subtropics tend generally to have high salinity due to warm, dry air and enhanced evaporation from descending air from Hadley Cell.
Low latitudes (near equator): Local salinity minimum due to high precipitation/runoff

Salinity Variations with Depth

Mixed layer: Near surface mixing due to wind, surface cooling causing convection/turbulence.
Halocline: Region of abrupt salinity change with depth, typically a transition from varying salinity near the top, to a fairly consistent salinity in deep regions.
Low latitude: Salinity decreases with depth, higher at surface (high evaporation).
High latitude: Salinity increases with depth, lower at surface (runoff/precipitation).
Deep ocean: Salinity is fairly consistent globally.

Temperature and Density Variations with Depth

Mixed layer (0-100m): Homogeneous density and temperature from mixing from turbulence, convection, waves or wind.
Thermocline/Pycnocline (100-1000m): Rapid changes in temperature/density.
Low latitudes: Density primarily dictated by temperature, mirror images in top plots
High latitudes: Low temperatures and high densities, little structure vertically

Earth's Seasons

Earth's rotation axis is tilted 23.5° relative to the plane of its orbit around the sun.
Key times of year: winter solstice (Dec. 22), summer solstice (June 21), vernal equinox (Mar. 21), autumnal equinox (Sep. 23).
Equinoxes: Sun directly overhead at the equator.
Solstices: Sun directly overhead at the tropics of Cancer/Capricorn; no sunlight at the Arctic/Antarctic Circles during winter

Distribution of Solar Energy

Concentrated at equatorial regions compared to high latitudes and influenced by the thickness of the atmosphere
At higher latitudes, the angle of incoming solar radiation less direct and the area over which that solar radiation is distributed is greater, thereby decreasing the intensity of incoming radiation.

Heat Gained and Lost by Oceans

High latitudes lose more heat than gained.
Low latitudes gain more heat than lost — equatorial to pole temperature gradient
Circulation of ocean and atmosphere transfer heat to maintain equilibrium.

Physical Properties of the Atmosphere

Primarily nitrogen (N2) and oxygen (O2).
Important greenhouse gases (like methane and nitrous oxide) affect heat trapping.
Water vapor is also an important greenhouse gas.

Temperature Variation in the Atmosphere

Troposphere: Lowest layer, all weather occurs, temperature decreases with altitude.
Stratosphere: Above troposphere, temperature increases with altitude due to ozone heating.
Upper atmosphere: Very thin, low density.

Density Variations in the Atmosphere

Convection cell: Rising and sinking air.
Warm air rises due to being less dense, cooler air sinks due to being more dense.
Moist air is less dense than dry air due to a lower molar mass.

Forces on Air/Water Parcels

Pressure is a field that depends on location and time.
If pressure is higher on one side of a water parcel than the other, it experiences a push towards lower pressure.
Pressure and Coriolis forces are comparable and thus balance each other.

The Coriolis Effect

Force in east-west direction (flow in N-S direction): Fc = 2mΩV sin θ
Force in north-south direction (flow in E-W direction): Fc = −2mΩU sin θ
U: East-West velocity component
V: North-South velocity component
θ: Latitude

Vector Form of Coriolis Force

Mathematical representations for a velocity vector (U,V)
Mathematical representation for a Coriolis force vector(U,V).

Combining and Calculating Pressure and Coriolis Forces

Combining forces to determine motion and/or direction of parcels.

Three-Cell Model of Atmospheric Circulation

Hadley Cell (0-30 degrees latitude), Ferrel Cell (30-60 degrees latitude), Polar Cell (60-90 degrees latitude).
Rising and descending air from circulation cells create high and low-pressure zones at the surface.

Zonal Mean Zonal Surface Winds

Overview of global average wind patterns in the troposphere near the surface, including the trade winds, westerlies, horse latitudes, and doldrums.

Why is weather hard to predict?

The atmosphere has sensitive dependence on initial conditions (chaotic).

The "Climate" of the Lorenz Model

The state of convection (X,Y,Z) is a point in a 3D phase space
This trajectory, often represented as a "Lorenz butterfly," shows how initial conditions can lead to diverse outcomes; detailed predictions are impossible beyond a limited time.

Weather Systems

Cyclonic flow (counterclockwise NH, clockwise SH) around a low.
Anticyclonic flow (clockwise NH, counterclockwise SH) around a high.

Sea and Land Breezes

Land and sea warm differently under equal insolation due to differing heat capacities.
Sea breeze: Warm land air rises, cool ocean air moves in.
Land breeze: Cool land air sinks, warm ocean air rises.

Jet Stream

Narrow, fast-moving, eastward flow at middle latitudes just below the top of the troposphere.
Geostrophic balance applies. Patterns show pressure lines close together, indicating the jet stream.

Tropical Cyclones

Large rotating masses of low pressure that form in the tropics and migrate to extratropics.
Strength is classified based on sustained wind speed.
Typhoons are another name for tropical cyclones in the North Pacific, and Cyclones are used in the Indian Ocean

Hurricane Origins

Low pressure cell, winds gather moisture, air rises, low pressure deepens, latent heat accelerates ascent, warms, and deepens the low.
Winds circulate the low, capturing more water vapor. Cycle repeats to develop a storm.

Hurricane Facts

An average of 85 tropical storms form worldwide annually.
Requirements for hurricane formation: ocean waters warmer than 25°C, warm, moist air, Coriolis effect, initial low-level disturbance.
Hurricane season: June 1st to November 30th.
Warm surface waters, low wind shear, and presence of initial disturbances are additional requirements.

Historical Storm Tracks

Uses tracks of previous storms to study patterns of hurricane activity (pink shading depicts areas warm enough to support storms)
Saffir-Simpson hurricane intensity scale classifies hurricanes.

Hurricane Movement

Steering flow: High and low pressure areas influence hurricane movement in the North Atlantic Ocean.
Bermuda High; also identified as the subtropical high. Subtropical high pressure usually pushes hurricanes westward in the tropical Atlantic and then northward around the Bermuda High.

Hurricane Anatomy

Diameter typically less than 200 km, up to 800 km for larger hurricanes.
Eye of the hurricane is a low-pressure center.
Spiral rain bands: Areas with intense rainfall and thunderstorms are spiral-shaped bands.
Outflow of air at hurricane's top that merges with upper-level flows.

Other Factors Impacting Hurricane Formation

Warmer waters favor hurricane development; global warming might affect this.
El Niño: (warmer waters/more hurricanes in Pacific, enhanced wind shear in the equatorial Atlantic leads to fewer hurricanes in the Atlantic).
La Niña: (opposite of El Niño, enhanced wind shear in Pacific leads to fewer Pacific hurricanes, weaker wind shear in the Atlantic leading to more Atlantic hurricanes.)

Hurricane Destruction

High winds & intense rainfall during hurricanes.
Storm surge: an increase in shoreline sea level driven primarily by winds; low-pressure itself has a minimal effect.

Measuring Surface Currents

Direct methods: Floating devices tracked over time (Lagrangian) and fixed current meters (Eulerian) using measurement of speed/distance.
Indirect methods: Pressure gradients using sensors, Doppler flow meters, and acoustic Doppler current profilers (ADCP).
Using drifting objects (like shoes or sneakers).
Radar altimetry/ocean topographic measurements from satellites to infer current speeds

Measuring Deep Currents

Argo array: Free-drifting profiling floats measuring temperature, salinity.
Tracer methods: Particles/substances like tritium (from nuclear tests) Chlorofluorocarbons (CFCs), and salinity/temperatures track current movement.

Wind Belts and Surface Current Movement

Gyres: Large, circular loops of moving water.
Subtropical gyres are centered around 30 degrees latitude.
Gyres are bounded by equatorial, Western boundary, Northern/Southern boundary, and Eastern boundary currents.
Physics of gyres: Influences from continents and other current basins, gravity/pressure differences, friction/wind, Coriolis effect.
Rotation is clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.

Subtropical Gyres

North Atlantic, South Atlantic, North Pacific, South Pacific, Indian Ocean
Warm-core rings: Warmer Sargasso Sea water trapped by cool surrounding water.
Cold-core rings: Cold water trapped by warmer surrounding water.
Gulf Stream: Current flowing along the US coast, meanders and loops generate warm- and cold-core rings.
Loop Current: Warm ocean surface current in the Gulf of Mexico, generates warm loop current eddies and intensify hurricanes passing over warm cores

Coastal Upwelling and Downwelling

Ekman transport moves surface seawater away from shore.
Upwelling: Cool, nutrient-rich deep water rises to replace displaced surface water.
Downwelling: Surface water moves towards shore, piling up and moving downward.
Western United States has coastal upwelling; lack of marine life in downwelling zones.

Antarctic Circulation

Antarctic Circumpolar Current (ACC), also known as the West Wind Drift.
Completely encircles Earth, carrying more water than any other current.
East Wind Drift is due to polar easterlies.

Waves Approaching Shore

Deep water waves become shallow water waves, and the speed and wavelength change.
Wave speed decreases and height increases as waves approach the shore, and the wave steepness increases. The wave progressively flattens as it feels the floor with the wave base closer to the base/bottom of the floor.

Three Types of Breakers

Spilling breakers: Gentle slope sea floor, wave energy expended over longer distances, water slides down the front slope.
Plunging breakers: Moderately steep sea floor, wave energy expended over shorter distances; best for board surfers, curling wave crest.
Surging breakers: Steepest sea floor, waves break directly on the shore; best for body surfing.

Wave Refraction

Waves rarely approach the shore at a perfect 90-degree angle.
Wave speed is proportional to water depth.
Different segments of the wave crest travel at different speeds, causing the wave to bend as it nears the shore.

Tsunami

Seismic sea waves.
Originate from sudden sea floor topography change—earthquakes, landslides, underwater volcanic collapse, or meteorite impact.

Warning and Monitoring Systems

Pacific Tsunami Warning Center (PTWC): Uses seismic wave recordings to forecast tsunamis.
Deep Ocean Assessment and Reporting of Tsunamis (DART): System of buoys detects tsunami pulses.

Gravitational Forces

Force is derived from Newton's Law: Every object with mass attracts every other object in the universe in proportion to the product of their masses and inversely proportional to the square of the distances separating them.
Greatest force at zenith.
Least force at nadir.

Centrifugal and Net Tidal Forces

All points on the Earth experience a centrifugal force pointed away from the moon.

Tide-Generating Forces

Resultant force is significant to horizontal component (tangential or parallel to Earth's surface)

Earth's Rotation and Tides

Flood tide: water moves towards shore
Ebb tide: water moves away from the shore
Tidal bulges are fixed relative, so Earth's rotation moves different geographic locations into bulges.

Moon's Tidal Bulges

Tidal period = time between high tides.
Lunar day = time between successive overhead moons—24 hours, 50 minutes.
Solar day = 24 hours; high tides occur about 12 hours and 25 minutes apart.

Tidal Bulges: Sun's Effect

Solar bulges are similar to lunar bulges but about half the size.
Moon's closer proximity results in more control over Earth's tides.

Monthly Tidal Cycle

Syzygy: Earth, moon, and Sun aligned: Spring tides have greatest tidal ranges
Quadrature: Moon in first/third quarter; Neap tides have lowest tidal ranges.

Complicating Factors

Declination: Moon's or Sun's angular distance above or below the equator.
Unequal tides result from the combination of solar and lunar tides.
Slightly elliptical orbits affect the tides' timing & magnitude.

Tidal Patterns

Diurnal: One high tide/one low tide per day.
Semidiurnal: Two high tides/two low tides per day, tidal ranges are similar.
Mixed: Two high tides/two low tides per day, tidal ranges are different. Mostly common.

Tides in Coastal Waters

Bay of Fundy (Nova Scotia) has the world's largest tidal ranges (up to 17 meters).
Factors influencing large tides include narrowing & shoaling of the bay, tidal resonance, and natural frequency (close to tidal frequency).
Tidal bores can be formed with large spring tides and specific river characteristics, like a seaward river current, shallowing landward sea floor and narrowing of basin in upper reaches).

Coastal Tidal Currents

Flood current: Water rushes up a bay/river
Ebb current: Water drains from bay/river
High slack water: Peak of each high tide with no current motion.
Low slack water: Peak of each low tide with no current motion.

Tides and Marine Life

Grunion spawning: Small silvery fish come out of water to spawn in California only after higher high tide, during 3-4 nights following the highest spring high tide

What determines the average temperature of Earth?

Earth's energy balance—Energy gained from the sun must equal energy lost by thermal/black body radiation.

Geoengineering the Climate

CO2 is a significant greenhouse gas, absorbing and re-emitting infrared radiation and preventing heat loss to outer space.
Anthropogenic emissions have increased atmospheric CO2 concentrations.
Scientists are actively researching the implications of geoengineering to actively decrease atmospheric CO2 by introducing ways to actively remove CO2 from the atmosphere (like seeding iron into HNLC zones).

High Nutrient-Low Chlorophyll Regions

Phototrophs in the ocean need macro-nutrients (N, P), but many regions are high in essential nutrients, but still lack phytoplankton active in these regions (like the North Pacific, Equatorial Pacific, Southern Ocean) , due to lack of sufficient micronutrients (especially iron.)

Experiments in the Real Ocean

Between 1993 & 2005, a series of iron fertilization experiments were carried out in HNLC regions. Blooms of phototrophic microorganisms were observed.

Components of a climate model

GCM = Global Climate Model/General Circulation Model
Includes sub models for the Atmosphere, Ocean, Cryosphere, land use (albedo), Radiation code

How do these sub-models work

Concept of discretization: Breaks up continuous reality into discrete grid boxes.
Each climate variable (temp, salinity, pressure, velocity).
State vector/list of ALL values in the grid-boxes.

Coupling between sub-models

Atmosphere-ocean interaction (surface winds affect surface wind stress and surface layer of ocean flow): Tau = (constant)*u_(10 m)...
Atmosphere-ocean temperature difference (surface heat flux): Q = (constant)*(T_atm – T_ocean)

How many grid points do we need

Need a large number of grid points to model the Earth well, due to fine detail needed (down to the millimeter scale.)
Limits occur regarding the memory to run such a complex model.

Parameterizations

Simplified representation from small-scale processes like turbulence and clouds are necessary, otherwise computationally impossible.
Clouds, rain, snow, hail, and small-scale turbulence are examples of parameters.

Uncertainties in Climate Modelling

Model uncertainty: Inexact parameterizations, different models perform differently, coarse grid.
Uncertainties in chaos: Small differences in initial conditions can lead to dramatically different climate predictions, even with a perfect model.

The Butterfly Effect in Climate Trends

Small initial conditions perturbations can have significant impacts on longer-term climate trends.

Physics of Sound Propagation

Sound is a pressure wave that pushes its neighboring molecules (in air, water, or solids).
Sound travels much faster in water than in air.

Spreading of energy in space

Spreading of energy in space is an important process that weakens sound intensity.

Natural Sources of Underwater Sound

Natural sources: Wind, Rain, Earthquake, Ice cracking, Rainfall, Dolphins
Manmade sources: Sonar ping, Small ship, Large ship, Air gun

Fundamentals of Ocean Acoustics

Sound waves bend based on water speed.
Sound is "lazy" and bends toward where the sound speed is lower. (Slower surface wave speed causes waves to bend towards shallows).

Essential Ocean Acoustic Instruments

Active sonar: For precise mapping and ranging, but risks detection in military scenarios
Passive sonar: Used in stealth operations, detecting natural sound sources. Used in environmental studies and surveillance

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Description

Test your understanding of atmospheric circulation and the factors influencing ocean salinity. This quiz covers concepts such as Archimedes' Principle, the Hadley Cell, and the effects of seasonal variations on circulation patterns. Challenge yourself with questions about buoyancy, trade winds, and more!