Oceanography

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Oceanography

• Montgomery Ch 7, pg 225-8
• Oceanography handout (web) and this power point

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typical groundwater flow rate 15 m per
day compared to a river velocity of 1 m s-1
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key point fresh water is less dense than
saltfresh water floats on salt water
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Aberjona R Watershed Woburn Ma
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Back to Woburn

• Best policy is to prevent such tragedies

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Back to Woburn

• Best policy is to prevent such tragedies
• Both industry and government failed at Woburn

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Back to Woburn

• Best policy is to prevent such tragedies
• Both industry and government failed at Woburn
• Environmental Protection Agency (EPA) 1970
  charged with protecting environment and human
  health

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Back to Woburn

• Best policy is to prevent such tragedies
• Both industry and government failed at Woburn
• Environmental Protection Agency (EPA) 1970
  charged with protecting enviroment and human
  health
• Two key water-resource laws enforced by EPA
  Safe Drinking Water Act establishes Maximum
  Contamination Levels (MCL) of pollutants in
  public drinking supplies this would have
  prevented the Woburn tragedy the MCL for TCE is
  0

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Back to Woburn

• Best policy is to prevent such tragedies
• Both industry and government failed at Woburn
• Environmental Protection Agency (EPA) 1970
  charged with protecting enviroment and human
  health
• Two key water-resource laws enforced by EPA
  Clean Water Act (1972) complex legislation
  designed to control discharge of pollutants into
  navigable waters

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Oceanography Handout on web

• Oceanography Handout
• The oceans cover 71 of the earths surface and
  are home to our fisheries, and perhaps more
  importantly are essential in the maintenance of
  our climate. This document is a brief review of
  key facets of oceanography.

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Oceanography Handout on web

• Oceanography Handout
• The oceans cover 71 of the earths surface and
  are home to our fisheries, and perhaps more
  importantly are essential in the maintenance of
  our climate. This document is a brief review of
  key facets of oceanography.
• One of the most important aspects of the oceans
  is that they moderate our climate through (1) the
  heat required (or evolved) when water evaporates,
  precipitates, freezes or melts, and
• H2O liq H2O vap heat is absorbed when
  reaction goes to the right (150 j/gm) heat is
  evolved when it goes to
• left

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Oceanography Handout on web

• Oceanography Handout
• The oceans cover 71 of the earths surface and
  are home to our fisheries, and perhaps more
  importantly are essential in the maintenance of
  our climate. This document is a brief review of
  key facets of oceanography.
• One of the most important aspects of the oceans
  is that they moderate our climate through (1) the
  heat required (or evolved) when water evaporates,
  precipitates, freezes or melts, and (2) ocean
  currents which transport warm water to high
  latitudes (see below).
• H2O liq H2O vap heat is absorbed when
  reaction goes to the right (150 j/gm)

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Key point sea level is rising at a rate of 2
mm per year (average Of last 100 years)
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East coast shorelines vulnerable to sea level rise
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Sea level rise or fall is a common Occurrence in
Earth HIstory
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20,000 years ago during The last glacial
maximum Or Ice Age
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Sea level was 130 m lower than today
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Sea level was 130 m lower than today during last
glacial maximum Sea level rose rapidly before
6000 Years ago
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Sea level rose rapidly before 6000 Years ago
(17 mm per year between 14,000 and 8000 years
ago) 0.1 to 0.2 mm per year thereafter Until
the last 100 to 150 years When it rose at a rate
of 1 to 2 mm Per year.
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Here are raised beaches On Baffin Island,
Canadian Arctic
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Here are raised beaches On Baffin Island,
Canadian Arctic These reflect apparent Sea
level drop due to
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Here are raised beaches On Baffin Island,
Canadian Arctic These reflect apparent Sea
level drop due to Crust rebounddue to
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These reflect apparent Sea level drop due
to Crust rebounddue To melting of the ice
sheet Following the Ice Age note contours of ice
thickness
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Sea level rise is a particularly Critical problem
for Lousiana
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In Lousiana, beach Erosion is bad not only
Because of sea level Rise but because the
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The Mississippi Delta which Additional
mass Causes the Land to sink Moreover
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Flood control Measures Have Decreased Sediment De
livery to delta
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And the delta Continues to sink
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Coastal processes processes Important from the
wetlands Behind the beach to the Edge of the
continental Shelf
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Coastal processes processes Important from the
wetlands Behind the beach to the Edge of the
continental Shelf Note the line of beach Dunes
which act as a Barrier to the ocean And protect
the land behin The dunes
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Coastal processes processes Important from the
wetlands Behind the beach to the Edge of the
continental Shelf Note the wide continental
Shelf in this cartoonwhere is This the case in
North Amer. East or west coast?
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The tectonically passive margin Of eastern North
Am. Has a wide Continental shelfbut the active
Western margin of South America Has a very
narrow shelf
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Typical beach Note Wetlands Dunes beachface
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Outer Banks of North Carolina Note expanse of
Shallow water And wetlands Behind the Barrier
island
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Wetlands are nurseries for fish and Crustaceans,
beach is a rather narrow Ephemeral structure
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Coasts are dynamic Sand, silt, cobbles are
driven Along the coast By long shore currents
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Waves are transmitted through medium but the
water remains in placebreakers form when the sea
floor becomes shallow enough to interfere with
wave movement
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Remember Coasts are dynamic Sand, silt, cobbles
are driven Along the coast By long
shore Currents Note how the Waves hit the Beach
at an Angle this Creates the longshore current
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Rip tides, consequence of water piling up on the
beachthese are currents Not tidesswim parallel
to beach to get out of them
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Wave Energyhere Focused on a Headlandcan Breaku
p rocks Into sand grains but
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Wave erosion can have considerable effects over
short Time periods
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A characteristic landform Is a wave-cut platform
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But a critical sand supply Comes from rivers
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Sediment very much Controlled by Geology Black
Sand beach, Hawaii
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Grayton Beach, FL panhandle to the right Pure
quartz sand from Appalachian Igneous and
metamorphic rocks
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Dynamic on a yearly basis Summer beach
(top) Winter beach (bottom) At which times are
the Waves more energetic?
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Cape Cod
Growth of Cape Cods southern tip from 1884-1958
via long shore currents
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Sapelo Island Georgia Note narrow beach marshes
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Sapelo Island Georgia Note narrow
beach Marshes Sand is being transferred From
north (left) to south End of island
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Developed beaches wetlands Destroyed, commonly
filled in and Built upon
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Supply of sediment Diminished because Of dams
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Beach groins rock jetties Built
perpendicular To beach used to trap
Sediment What is the common Longshore
current Direction here?
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Beach groins rock jetties Built
perpendicular To beach used to trap
Sediment What is the common Longshore
current Direction here? Left to right
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Artificial channel with Jetties blocking
transfer Of sand across channel
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Miamis approachbrute forcetruck in
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The 60 million dollar Project makes sense
here Because of tourist dollars But not many
places elsewhere
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Major damage is associated With hurricanes
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Katrina
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In northern hemisphere Worst damage will Be to
the Northeast of the eye
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Biloxi MS which took brunt of wind
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While New Orleans was flooded
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Houses are commonly built on top of The dunes
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Lake Michigan results
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Dauphin Island AL July 2001 before Hurricane
Lilli Sept 2004, after Ivan Aug 2005,
after Katrina
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What happens of interest in the Deepoceanremember
the mean depth Of the oceans is about 4.5 kmso
the Open ocean is by far the most Important
domain in terms of volume
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Seawater compositionnote difference in residence
time and river concentration for Na compared to
HCO3- and Ca2

• Species Concentration Concentration Mean
  Residence
• In seawater in avg. river water time
  (million years)
• (mg/kg) (mg/kg)
  in oceans
• Chloride, Cl- 19350 5.75 120
• Sodium, Na 10760 5.15 75
• Sulfate, SO4- 2712 8.25 12
• Magnesium, Mg2 1294 3.35 14
• Calcium, Ca2 412 13.4 1.1
• Potassium, K 399 1.3 11
• Bicarbonate, HCO3- 145 52 0.10
• Bromide Br- 67 0.02 100
• Boron B3 4.6 0.01 10
• Strontium, Sr2 7.9 0.03 12
• Fluoride, F- 4.6 0.10 0.5
• Total 35150 89
• Source Schlesinger (1991) Biogeochemistry

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Seawater compositionnote difference in residence
time and river concentration for Na compared to
HCO3- and Ca2

• Species Concentration Concentration Mean
  Residence
• In seawater in avg. river water time
  (million years)
• (mg/kg) (mg/kg)
  in oceans
• Chloride, Cl- 19350 5.75 120
• Sodium, Na 10760 5.15 75
• Sulfate, SO4- 2712 8.25 12
• Magnesium, Mg2 1294 3.35 14
• Calcium, Ca2 412 13.4 1.1
• Potassium, K 399 1.3 11
• Bicarbonate, HCO3- 145 52 0.10
• Bromide Br- 67 0.02 100
• Boron B3 4.6 0.01 10
• Strontium, Sr2 7.9 0.03 12
• Fluoride, F- 4.6 0.10 0.5
• Total 35150 89
• Source Schlesinger (1991) Biogeochemistry

Major input is river water
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The heat associated with mid-ocean ridge
volcanism leads To creation of hot springs,
black smokers
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Note Source of water seawater Which picks up
various Ion as it circulates through The crust
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Note Source of water seawater Which picks up
various Ion as it circulates through The crust
Volume of water volume Of oceans
circulates Through the crust every 10 million
years or so
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Note Source of water seawater Which picks up
various Ion as it circulates through The crust
Volume of water volume Of oceans
circulates Through the crust every 10 million
years or so So this is a major influence on
seawater composition as well
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Seawater compositionnote difference in residence
time and river concentration for Na compared to
HCO3- and Ca2

• Species Concentration Concentration Mean
  Residence
• In seawater in avg. river water time
  (million years)
• (mg/kg) (mg/kg)
  in oceans
• Chloride, Cl- 19350 5.75 120
• Sodium, Na 10760 5.15 75
• Sulfate, SO4- 2712 8.25 12
• Magnesium, Mg2 1294 3.35 14
• Calcium, Ca2 412 13.4 1.1
• Potassium, K 399 1.3 11
• Bicarbonate, HCO3- 145 52 0.10
• Bromide Br- 67 0.02 100
• Boron B3 4.6 0.01 10
• Strontium, Sr2 7.9 0.03 12
• Fluoride, F- 4.6 0.10 0.5
• Total 35150 89
• Source Schlesinger (1991) Biogeochemistry

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• Ca2 2 HCO3- CaCO3 CO2 H2O
• represents sequestration of CO2 in carbonates

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• Ca2 2 HCO3- CaCO3 CO2 H2O
• represents sequestration of CO2 in carbonates
• shells
• limestones
• corals
• etc.

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Salinityif you evaporate seawater you get
calcite then gypsum (CaSO4), then salt, then
sylvite, KCl
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Surface seawater Temperatures range From about
30oC To about 0oC Orange yellows warm Blues
cold Note various Temperature bulges
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One of the bulges Gulf Stream false color
image Orange, red warm Green, blue
cold What about density?
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Surface Currents driven by prevailing winds and
influenced by the Coriolis Effectnote direction
of movement in gyres north of equatorclockwise
or Counter clockwise?...how about south of the
equator?
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Water parcels moving north from equator have
high angular velocities (due to Earths
rotation) and bend to the right (east)just the
opposite effect when They head south to the
equatorhence the clockwise rotation of the gyres
north Of the equatordoes the same reasoning
work in the south?
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Ocean is vertically Stratified with Respect to
T, density, salinity Note T at bottom of ocean
in the Deep oceans is near Freezing
everywhere Thermocline etc. are where there are
large rapid changes in T etc. Note thin surface
zone is well mixed due to wind action
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What happens to Gulf Stream waters as they Move
north? Orange, red warm Grenn, blue
cold What about density?
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Warm Salty water becomes cold and denseand sinks
to bottom of ocean
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This is the start of The oceanic
conveyor Belta an ocean wide Current that
includes currents In the deep ocean Note warm
water Carried into N. Atlantic Make Greenland,
Iceland And northern Europe habitable
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This is the start of The oceanic
conveyor Belta an ocean wide Current that
includes currents In the deep ocean Note
vulnerability of Conveyer belt to influx
of Freshwater from Greenland ice cap
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Cross sectional view of what happens in the
Atlantic
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Global Warming Uncertainty What happens if The
Greenland Ice Sheet melts (which It is doing)
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Relatively Cold, fresh water At surface will
not Sinkand the Conveyor belt may Shut down
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Global Warming Uncertainty What happens if The
Greenland Ice Sheet melts (which It is
doing)Gulf Stream blocked by Cold, light,
fresh Water at the surface??