Lo5 waves,currents,coasts

Earth’s Atmosphere Earth’s Atmosphere and Oceansand Oceans

Currents, Waves and Currents, Waves and CoastlinesCoastlines

Ocean Currents: Ocean Currents: the motions of oceans the motions of oceans (sorry, couldn’t resist the bad rhyme!)(sorry, couldn’t resist the bad rhyme!)

• Causes:Causes:– Tides – gravitational pull from moon and Tides – gravitational pull from moon and

sun causes predictable tidal currentssun causes predictable tidal currents

– Wind – Surface CurrentsWind – Surface Currents

– Thermohaline Circulation (density Thermohaline Circulation (density differences) = Deep Currentsdifferences) = Deep Currents

Surface CurrentsSurface Currents

• Rotate due to CoriolisRotate due to Coriolis

• Create Gyres –circles of moving Create Gyres –circles of moving water within the oceanswater within the oceans– Clockwise – Northern HemisphereClockwise – Northern Hemisphere– Counterclockwise – Southern Counterclockwise – Southern

HemisphereHemisphere

GyresGyres

•Gyres

Gyres and Surface CurrentsGyres and Surface Currents

UpwellingUpwelling

• formation of upwellingformation of upwelling

What is upwelling?What is upwelling?

• Subsurface water rises to surfaceSubsurface water rises to surface

• Characteristics:Characteristics:– ColderColder– Rich in nutrientsRich in nutrients– Biologically productive = Good fishingBiologically productive = Good fishing

Major Areas of UpwellingMajor Areas of Upwelling

Global Conveyor beltGlobal Conveyor beltThermohaline Circulation Thermohaline Circulation BeginsBegins

• Surface and Deep Ocean CurrentsSurface and Deep Ocean Currents

Idealized “conveyor Idealized “conveyor belt” model of ocean belt” model of ocean circulationcirculation

Ocean WavesOcean Waves• What makes big waves?What makes big waves?

– Wind – speed and durationWind – speed and duration– Fetch – distance that a wave has to growFetch – distance that a wave has to grow

Breaking WavesBreaking Waves

• Friction between sea floor and waterFriction between sea floor and water

• Waves become too steepWaves become too steep

• Breakers formBreakers form

The basic parts and The basic parts and movement of a non-movement of a non-breaking wavebreaking wave

Changes that occur Changes that occur when a wave moves when a wave moves onto shoreonto shore

Beach Beach Construction/DestructionConstruction/Destruction• Swash and Swash and

BackwashBackwash

Wave refraction along Wave refraction along an irregular coastlinean irregular coastline

Beach drift and Beach drift and longshore currentslongshore currents

Example of Longshore Drift Example of Longshore Drift Shoreline ErosionShoreline Erosion

– Tucker Island Lighthouse, NJ, 1927Tucker Island Lighthouse, NJ, 1927

Rip CurrentsRip Currents

• Rip CurrentsRip Currents

Coastal Erosion CausesCoastal Erosion Causes

• Storm wavesStorm waves

• Long shore driftLong shore drift

• Storm surgeStorm surge

• Winter stormsWinter storms

• Human-Induced CausesHuman-Induced Causes

Human-Induced Coastal Human-Induced Coastal ErosionErosion

• Removing vegetation and protective Removing vegetation and protective dunesdunes

• Building “protective” structuresBuilding “protective” structures

• River modification and dredgingRiver modification and dredging

JettiesJetties

Which direction is longshore Which direction is longshore drift?drift?

Which direction is the longshore Which direction is the longshore drift?drift?

SummerSummer – – The lower waves of summer build The lower waves of summer build sand onshore and widen the sand onshore and widen the beach.beach.

WinterWinter - - Higher winter waves Higher winter waves move sand offshore and narrow move sand offshore and narrow the beach.the beach.

Dune StabilizationDune Stabilization

COASTAL EROSIONCOASTAL EROSION

Marine TerracesMarine Terraces

Sea archSea arch

Sea stackSea stack

Coastal DepositionCoastal Deposition

SpitSpit

Baymouth BarBaymouth Bar

Aerial view of a spit Aerial view of a spit and baymouth bar and baymouth bar along the along the Massachusetts Massachusetts coastlinecoastline

Barrier IslandsBarrier Islands

• Long, narrow islands paralleling Long, narrow islands paralleling shorelineshoreline

• Protected salt water bays behindProtected salt water bays behind

• Protect mainland Protect mainland

• Naturally transientNaturally transient

Fire Island migrationFire Island migration

Miami Beach before Miami Beach before beach nourishmentbeach nourishment

Miami Beach after Miami Beach after beach nourishmentbeach nourishment

EstuariesEstuaries

Major Major estuaries estuaries along the along the East Coast East Coast of the of the United United StatesStates

The EndThe End

TomboloTombolo