Oceanography Notes Midterm Corrections

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  unaffected by human activity
  

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  -increase by 1.2ppm/yr
  

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  -higher sea-surface temp [more tropical storms, alteration in deep water currents]
  
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  -most severe drought, more intense precip
  
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  -water contamination [larger outbreaks disesase]
  
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  -longer/more intense heat waves
  
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  -shift in distribution of life
  
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  -melting ice caps [rising sea lvl]
  

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  most of this CO2 incorporated into organisms ->photosynthesis
  

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  fear of oxygen depletion in these areas. some companies filed patents
  

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  Low pres; CCW rot
  
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  high pres ; CW rot
  
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  more evaporation over low pressure
  
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  most weather generated at seas
  
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  hurricane wind speed: at least 74mph
  
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  air exiting eye of hurricane comes out at left, but then once free, curves right
  
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  Coriolis affect ocean and atmosphere:
  
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    causes Hadley cells
    
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    causes W ocean basin current intensity [Gulf Stream]
    
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    causes CCW; tornadoes, hurricanes
    
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  “Fixed Reference Frame” -> “intertial frame”
  
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  gravity does not affect direction
  

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  Air rises at 60 degrees latitude and falls at 30 and 90.
  
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  Sun is directly over equator at both vernal and autumnal equinox
  
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  Water vapor contributes the most to greenhouse warming
  
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  Land breeze flows from land to sea
  
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  Wind belts created by lowermost portion of circulation cell
  
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  Surface winds of anticyclone in S hemis go CCW
  
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  most abundant gas in atmos is nitrogen
  
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  least abundant gas is carbon dioxide
  
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  polar easterlies between 60-90 degrees
  
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  polar front at about 60 degrees
  
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  increase earths tilt; warmer summers, cooler winters
  
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  Coriolis; CW rot around high, CCW rot around lows
  
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  air moves in and up in low pressure areas
  
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  surface winds in tropics [trade] blow W and toward equator
  
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  midlat storms: contrasting air masses, jet stream, westerlies, polar front
  
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  cause hurricanes: trade winds, warm ocean, water vapor rich warm air, jet stream
  
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  more intense storms maybe with global warming
  

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  ocean current: masses of ocean water from one place to another. Any mass, Any depth, simple or complex.
  
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  huge current system dominates surfaces, transfer heat from warmer to cooler areas.
  
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  transfer 1/3 of heat, wind belts transfer 2/3
  
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  sun drives surface currents
  
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  closely follow windbelt patterns
  
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  cold currents flowing toward equator on W sides of continents produce arid conditions
  

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  warm currents flowing poleward on E sides of continents produce warm, humid conditions
  
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  ocean currents contribute to mild climate of N Europe and Iceland; conditions at similar lats along Atlantic coast of N America much colder.
  
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  currents deliver ocygen in cold, dense water, and they helped prehistoric peoples travel
  
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  currents either wind or density driven
  
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  surface currents: caused by wind belts parallel to the surface. Horizontal
  
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  deep currents: caused by cold, dense water sinking. vertical
  
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  surface currents rarely flow in same direction at same rate
  
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    -measuring is difficult: can be measured directly or indirectly
    
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    -some consistency exists in overall surface current pattern
    
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  Direct measurement:
  
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    1]floating device placed into current; tracked through time
    
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    2]place device in current from fixed position
    
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  Indirect measurement:
  
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    1]determine the internal distribution of density and the corresponding pressure gradient across an area of the ocean
    
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    2] radar altimeters [TOPEX/Poseidon satellite 1992]: determine bulge’s in sea surface which are results of the shape of the underlying sea floor and current flow. dynamic topographic maps produced from this data that show speed/direction of surface currents
    

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  3]Doppler flow meter to transmit low-frequency sound signals through the water. measures shift in frequency between the sounds water emitted and those backscattered by particles in the watter to determine current movement.
  
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  deep current measurement:
  
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    -more difficult to measure because of depth
    
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    -mapped by:
    
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      -device carried with current
      
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      -tracking telltale chemical tracers
      
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      -some traces absorb into seawater, other intentionally added
      
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      -useful tracers [tritium from atom bomb tests][chlorofluorocarbons freons and other gases]
      
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      -measure temp/salin characteristics of deep ocean currents
      
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  surface currents occur within/above pycnocline to a depth of 1km
  
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  surface currents only affect 10% of ocean water
  
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  due to friction with wind
  
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  2% of winds energy transferred to ocean surface. 50-knot wind produces a 1-knot current
  
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  if not continents, surface currents would follow major wind belts.
  
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    -interaction between trade winds and prevailing westerlies creates circularmoving loops of water in Atlantic ocean
    

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  gyre: large, circular-moving loops of water driven by major windbelts.
  
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  subtropical gyres: 1]North Atlantic 2]South Atlantic 3]North Pacific 4]South Pacific 5]Indian Ocean [mostly S]
  
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    -coincide with subtropics at 30 N, S lats
    
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    -CCW in S hemis. CW in N hemis
    
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  Each composed of 4 mains currents that flow into one another:
  
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    equatorial currents: motion trade winds b/w tropics. From SE in S hemis, NE in N hemis.
    
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      -travel westward along equator: form equatorial boundary current of subtropical gyre.
      
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    western boundary currents: caused by coriolis effect deflecting the equatorial currents that have reached a continent away from the equator.
    
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      -Western boundary of subtrop gyres
      
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    Northern/Southern boundary currents: B/w 30 and 60 lat: caused by prevailing westerlies from NW in S hemis and SW in N hemis. Direct currents easterly.
    

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  -comprise Northern for N subtrop gyres, visa verse for S
  
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  eastern boundary currents: Coriolis effect and continental barriers turn currents toward equator when they flow back across the ocean basins
  
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    -eastern boundaries of subtrop gyres
    
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  equatorial countercurrents: water on western margins flowing downhill under influence of gravity due to avg sea lvl at westward margins being as much as 2m higher than on eastern side.
  
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    -flow east
    
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    -apparent in pacific
    
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    -affected by shape of continents in Atlantic
    
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    -strongly influenced by monsoons in Indian ocean.
    
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  subpolar gyres: currents [of prevailing westerlies] moving westerly by polar easterlies
  
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    -at 60 lat
    
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    -rotate opposite the adjacent subtrop gyre
    
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    -smaller and fewer than subtrop gyres
    
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  Fridtjof Nansen: 1861-1930; Norwegian explorer; voyage in unexplored Arctic
  
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  Fram: his ship. 39m. wooden; designed to be pushed to surface by freezing water
  
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  nansen bottle: for collecting water samples at depth
  
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  Arctic ocean ice moves 20-40 to the right of wind blowing across its surface
  
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    -in S hemis, surface currents move to the left of wind direction
    
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    V. Walfrid Ekman: [1874-1954]; Swedish physicist; developed:
    

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  Ekman Sprial: explains Nansen’s observations in accordance with Coriolis effectl describes speed/direction of flow of surface waters at various depths
  

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  -assumes a uniform column of water set in motion by wind blowing across surface
  

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  -N hemis: immediate surface water flow 45 to right of wind [S hemis left]
  

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  -as surface water moves, it sets in motion other “layers” beneath it
  

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  current speed decreases with incrasing depth, and coriolis effect increase curvature to right
  

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  at same depth, water may move exactly opposite the direction the wind that started it is going.
  

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  deep enough water, friction consumes energy of wind and there’s no motion: normally occurs at 100meters.
  

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  Ekman Transport: All layers combine to create new water movement that is 90 from the direction of the wind. 90 right of wind in N hemis, left in S hemis
  
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    -nothing is ideal: Ekman Transport in open ocean is typically 70, nearly same direction as wind in shallow coastal waters
    
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  subtropical convergence: water in middle of a gyre, causing water to literally pile up in center of subtrop gyre. caused by Ekman transport causing CW rotation within ocean basin
  
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    -resulting in all subtrop gyres having a 2meter high hill
    
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  geostrophic current: when coriolis effect and gravity balance, causing the water wanting to fall down the hill to move around it.
  
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    -path of the ideal geostrophic flow
    
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    -hill has a steeper westward slope
    
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    -path of actual geostrophic flow: friction results in this current eventually downhill
    

S Pacific less intense than other gyres, because large area, many islands.

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  there is a narrow and strong flow to north on western side of subtrop gyres in N hemis.
  
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  narrow strong flow to South in S hemis [still on W boundary of gyre]
  
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  general: western boundaries of subtrop gyres faster, narrower, deeper
  
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    -due to apex being closer to W side
    
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    -Kuroshio 15x faster, 20x narrower, 5x as deep as Cali current
    
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    western intensificiation: this phenomenon: currents affected by this are western intensified
    

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  -ALL W boundaries of subtrop gyres are western intensified
  
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  -Coriolis effects eastward, high lat water, making it turn toward equator more strongly;
  
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    -causes wide, slow, shallow flow of water toward equator across subtrop gyres [picture a funnel]
    
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  -surface currents directly influence climate of adjoining landmasses
  
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    -warm current; warm air; rain over continent
    
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    -continental margins with warm offshore currents typically have humid climate [E coast]
    
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    -temperature migrate N-S with seasons
    
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    -continental margins with cold offshore currents typically have drier climate [W coast]
    

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  Downwelling: surface water -> deeper
  
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  productivity: presence of microscopic algae
  
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    -cold water= better productivity supports larger marine life
    
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  downwelling less productivity, but carries oxygen dissolved to deep-ocean life
  
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  current divergence: surface water away from an area on ocean’s surface: equator
  
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  geographical equator: 0 lat
  
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  meteorlogical equator: ~5lat N
  
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  equatorial upwelling: caused by trade winds causing current divergence -> Ekman transport causes surface water N of equator to veer right [Northward] and water south of equator to veer left [southward]: divergence of surface current along geographical equator
  
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    -high productivity
    
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  current convergence caused by currents movement toward each other
  
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    ex] N Atlantic; Gulf Stream, Labrado, E Greenland currents come together
    
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  water piles, sinks
  
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  coastal winds can cause either welling due to Ekman transport
  
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  coastal upwelling: caused by coastal wind from the S [in S hemis] causing Ekman transport to move coastal water to the left, away from coast [on a western coast of continent] Water from below rises to replace this water
  
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    -W coast US experience this. Natural air conditioner in the summer
    
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  coastal downwelling: just the opposite.
  
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  both upwelling and downwelling common in high latitudes
  
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  absence of pycnocline allows lots of vertical mixing
  
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  upwelling also caused by: offshore winds, seafloor obstructions, sharp bend in coast.
  

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  Most productivity in coastal areas
  
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  summer in Arabian sea, wind blows SW->NW with respect to India
  
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  eastern boundary currents greatly affected by coriolis effect
  
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  ice dam cold water into oceans would hinder N Atlantic circulation
  

Antarctic circulation dominated by movement of water mass South of 50 S lat

ACC powered by prevailing westerly wind belt “Roaring Forties, Furious Fifties, Screaming Sixties”

-most developed in Wedell and Ross seas.

-directed toward Antarctica. closer to cont than ACC

Antarctic divergence: around Antarctica where East wind drift scrapes ACC

-much marine life during S hemis summer b.c of upwelling created here

transport off Chespeak bay 100 sverdrups [ more than 100x great than combined flow of all world rivers]: water from Sargossa sea combining with Florida current

-this water from Sargossa sea returns at Newfoundland.

meanders: snaked-like bends in current which often disconnect from gulf Stream and form large rotating masses of water called vortexes, eddies, or rings.

-mechanisms that produce the dramatic water loss as Gulf S moves N yet to be determined

-both rings: unique temp chars, biological pops; warm-water organism in cold ocean and visa versa; can survive as long as ring does, 2yrs sometimes.Coldcore rings last longer, and have more life.

Ben Franklin postmaster discovered Gulf Stream.

Labrador current: with the gulf stream form much fog in N atl, then break into Irminger current along Iceland’s W coast and Norweigan current moving N on Norway’s coast

North Atlantic Current: crosses N atlantic. turns south to become canary current.

Gulf Stream moderates E coast temp and N Europe temp, so temps across atlantic in Europe much higher even though on same lat, b/c of heat transfer from GS to Europe. Spain, Portugal at same lat as NE states.

-as much as 20F warmer

-the difference b/w S and N temp on E coast much greater than b/w N and S coasts of Europe.

equatorial counter current of pacific better developed in pacific

Walker Circulation Cell: in equatorial S pac: caused by pressure difference between W and E pacific. SE trade winds blow across pacific.

-1920 effect first describe; Sir Gilbert Walker.

Normal conditions: walker cell rotates CW. Low pressure in the West, high pressure in the E

pacific warm pool: warm water flowing in equatorial regions creating a wedge of warm water on the western pacific. Thermocline below 100m

-thermocline in E is generally within 30m of surface

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  El Nino; low pressure along equatorial regions in S America. SE trade winds diminish, sometimes reverse. CCW air rotation
  
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    -warm pool flows back from west
    
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    -begins to move in sept: at S American in dec/jan
    
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    -water off S American coast up to 18F warmer than normal
    
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    -sea lvl increase as much as 8in [thermal expansion along coast]
    
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    -increases number of tropical storms
    
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    -thermocline flattens; more horizontal
    
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    -downwelling sometimes occurs
    
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    -productivity diminishes, life reduced
    
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    -high pressure replace Indonesian low; dry conditions
    

-closer to normal conditions

-stronger walker cell instead of reverse one

-stronger trade winds

-more upwelling

-shallower thermocline in e pac

-band of cooler than norm water stretch across equatorial S pac

-commonly occur right after Nino

-Calculated by atmospheric pressure, winds, sea surface temp

-possitive numbers=Nino negative numbers=Nina zero=normal conds

El Nino occurs avg every 2-10 years. Irregular pattern

-lasts 12-18 months

-some can last for years

-more El Ninos in early 22^nd century

-most severe in 20^th: 1982-1983

-pac in warm stage of PDO from 1977-1999, just having entered cool phase

[Marine Galapagos Iguanas shrink]

-mild nino affect only S pac ocean. severe affect world temp

-difficult to predict

-can result in: flooding, erosion, droughts, fires, tropical storms, and effect marine life.

La Nina sea surface temp and weather opposite of Nino

El Nino events do occur in ocean basins

Indian counter current flow between 2 and 8 S of equator instead of N b/c Indian ocean is mostly in S hemis.

because of low heat capacity of land, continent heats faster than ocean in summer, creating low pressure area, resulting in the winds reversing: southwest monsoon: thought of as continuation of SE trade winds across equator.

North equatorial current gone during summer, replaced by southwest monsoon current W to E

Agulhas current: S along African coast, joins ACC

Aghulas Retroflection: abrupt turn as current collide [ACC]

deep ocean current affect 90% of ocean water. moves more water slower 6-12 miles per year.

take 1 year for 1 hr travel of surface current for deep current

thermohaline circulation: deep ocean circulation because differences in temperature and salinity cause dense differences