Oceanography Exam 3

Thermocline

water layer with a large decrease in temperature with depth

Pycnocline

water layer with a large increase in density with depth

Halocline

water layer with a large increase in salinity with depth

Temperature - Surface changes

air-sea heat exchange, solar energy, mixing waves

Temperature - Deep changes

Thermocline - decrease; below 1000m constant

Mid-latitude temperature profile

Seasonal & permanent

Equator temperature profile

permanent only

Pole temperature profile

0 degrees; little temperature variation at surface

Seasonal thermocline - bigger wave cause

more storms; winter

Seasonal thermocline - smaller wave cause

less storm; summer

Surface waves move due to

friction of wind on the water

Degree to which surface waves move

45

Degree to which deep waves move

90

Which winds drive surface currents?

Westerlies and Trade

Where does Ekman transport drive waves to

Gyre Centers

What are the five major ocean gyres?

North Atlantic, North Pacific, South Atlantic, South Pacific, Indian

Artic Ocean movement

Clockwise, driven by polar easterlies

Antarctic Circumpolar movement

Around Antarctica to the east

Western Intensification

Currents on the oceans’ western side are typically fast, narrow, deep

Eddies

Similar to oxbow lakes: warm pockets in cold water, cold pockets in warm water

Center of gyre due to

ekman transport

Center of gyre wind speed

little wind or current

Sea-level higher or lower in the center?

Higher

Upwelling: Surface convergence

surface waters driven together by wind/against a coast

Downwelling: Surface divergence

formed when wind blows surface waters away from a coast

Surface convergence can cause

windrows

Windrows

streaks of foam and debris

Sargasso Sea

Bermuda is here, algae grows due to the center rising up and having light

North Hemi Low Pressure System

cyclonic wind, counterclockwise, ekman transport produces surface divergence, upwelling

North Hemi High Pressure system

anticyclonic wind, clockwise, ekman produces surface convergence, downwelling

Seasonal changes in wind direction: U.S. NW - Summer

northerly wind, coastal upwelling

Seasonal changes in wind direction: U.S. NW - Summer

southerly wind, coastal downwelling

Waves represent what

transfer of energy

Swell waves movement direction

rise and fall as a wave passes

Most wind-waves are generated by

wind velocity, duration, and fetch

Fetch

area and distance of water over which the wind blows

Sea waves move particles in a ____ motion

orbital

Wave base

depth at which orbital motion is near zero

Wave that does not “feel bottom”

Deep-water wave

Wave that “feels bottom”

Shallow water wave

Wave Celerity

wave “speed” - wavelength/wave period (m/sec.)

As wavelength changes what can change?

Wave celerity

Do deep water waves usually break?

No

Rogue waves caused by

constructive wave interference

constructive wave interference

Wave + Wave = bigger waves

destructive wave interference

Wave + Wave = No wave

When a wave reaches shore

wave length decrease, wave height increase, celebrity decrease, wave period stays the same

Spilling breaker where?

gentle slope

plunging breaker

steep slope

Wave energy dissipation influenced by

angle of wave relative to shoreline and configuration of shoreline

Tsunami wave characteristics

very long wave length, small wave height, long period, high celerity

Wave height

Distance between crest and trough

Wave base calculation

½ * wavelength

Depth at which particles end in a deep water wave

Wave base

Fully developed seas

forms as waves reach the maximum height possible for a certain wind speed

Why do waves appear more irregular when they are close to the storm center

variability and intensity of wind energy

Whitecaps

small, unstable breaking waves, caused by increased wind, rough sea

How does deep-water waves turn into shallow-water?

Deep-water approaches shallow shore, enters intermediate, orbits flatten, wave compresses

Refaction/Bending of shallow water due to

one part of wave is in shallow, one is in deep

Plunging waves

on narrow beach slopes, breaks with a sudden loss of energy

Breaking waves

flatter beach, breaks gradually

Equilibrium Tidal Theory

mathematically ideal wave form behaving uniformly due to physics laws

Dynamic Tidal Analysis

considers that ocean responds to tides, Coriolis effect

Requirement to use tidal energy

10ft tidal range

Tidal range formula

difference between height of the high tide and the height of the low tide

Tidal Bore

“wave” of tidal forces rushing up into a narrow embayment/river mouth

Tidal day - diurnal

24hr, 50 min

Organism in intertidal zone speciality

they are exposed at low tide, they “understand” tides, strong enough to stand the tides

Sea level measurements

tide gauges (houses w/tube in water), satellite altimetry

Sea level rise is not the same everywhere, why?

glaciers put pressure and sunk some areas

Emergent coastlines

Rising land or falling sea, tectonic uplift, active volcanic coasts, formerly covered by ice, active margins

Submergent coastlines

sinking land or rising sea, passive margins

Evidence of former high sea level

coral reef exposed, knowledge of glaciers

Why is the West Antarctic Ice Sheet important to consider in future estimates of sea level rise?

it is mostly below sea level and can rapidly collapse, will cause sea level rise

Small rise in sea level on a flat coastline

more erosion

Groins

Shore stabilization, perpendicular to the shoreline, created in a group, deposition occurs where longshore drift deposits

Breakwater

protects a shore area from waves, parallel to the shore

Jetty

used to protect the entrance to a river, deposition occurs where longshore drift deposits and erodes on the opposite side

Beach renourishment Pros

absorbs wave energy, protects from flooding, slows erosions.

Beach renourishment Cons

not long-term, will need to be done again, repetitive ecosystem disturbance

How can a spit be used to tell the direction of longshore drift?

Longshore drift deposits the spit; longshore drift is towards the spit

Beach deposition during winter

erosion due to more storm

Beach deposition during summer

deposition due to less storm

Primary coast

formed by land processes; little time to change

Primary coast examples

estuary, deltas, fjords, volcanic coasts, uplifted coasts, tectonic (earthquake) coasts

Secondary coast

formed by oceanic processes; has been modified

Secondary coast examples

beaches, barrier islands, coral reef, mangrove swamps, saltwater marsh

Water refraction

focused on headland, not so much on bay

Berm

sand part of beach