How physical forces influence marine biota

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How physical forces influence marine biota

• Factors that affect physical oceanographic
  processes
• ll. Very large scale currents
• III. Large-Scale currents- Gyres
• lV. Upwelling
• IV. Coastal eddies
• IV. El Nino

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Sun glint in the Mediterranean Sea
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What drives all this motion?
1) Solar Radiation
2) Rotation of the Earth
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Rotation of the earth produces
Coriolis Force
(gravitational, pressure gradient, frictional,
Coriolis)
Earth spins west to east (eastward)
Eastward velocity is greatest at equator and
decreases poleward
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Coriolis Force causes path of a moving object
to be deflected to the right in the NH and to the
left in SH relative to the surface of the earth
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Solar Radiation
1) Sun drives ocean circulation through the
circulation of the Atmosphere- winds

• Energy transferred from winds to the upper layers
  of the ocean

2) Sun drives circulation by causing variation in
Temp. salinity, which changes density

• Changes in Temp. are caused by fluxes of heat
  across sea-air interface

• Changes in salinity caused by addition or removal
  of FW- evaporation or precipitation

• If surface water becomes more dense than
  underlying water, it sinks

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Which factors create oceanic currents?
1) Solar Radiation
Wind
2) Rotation of the Earth
Coriolis Force
Moving bodies (e.g. water masses) to be deflected
from their initial trajectory
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World Surface Currents
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Part II Very large-scale current generation
Thermohaline circulation
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Part III Large-scale current generation
What processes create gyres?
Gyres force coastal currents and related
processes
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Wind moves clockwise in the Atlantic Ocean
Ekman transport causes water to pile up in the
center of the Atlantic
Body of water moves 90? to the right of wind
direction
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Forcing of cold, more nutrient rich water to the
surface leads to an increase in primary
production.
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Water movement creates differences in Sea Surface
Height
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Geostrophic Flow

• Flow driven by density differences
• Density of seawater controlled by temperature and
  salinity
• Temperature ? density ?
• Salinity ? density ?

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Specific Volume of Seawater

• S.V. 1/density 1/(g cm-3) cm3/g
• volume occupied by one gram
• When density is high specific volume is low

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Specific volume affect sea surface height and
therefore currents
1 cm
100 cm
100g of 1 cm3/g
100g of 2 cm3/g
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Geostrophic Flow(water flows around hills)
Warm, low salinity
Cold, high salinity
Sea Floor
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Density Driven Flow
Geostrophic Flow caused by sloping sea
surfaces Pressure Gradient Force (PGF) The
force associated with the tendency for water to
flow downhill due to gravity. The PGF goes from
tall to short water columns. Increasing
temperature or decreasing salinity lowers the
density of seawater. For the same mass of water,
the less dense water column will be taller. The
net transport of water is 90 to the RIGHT of the
PGF in the northern hemisphere. The net transport
of water is 90 to the LEFT of the PGF in the
southern hemisphere. OR use the light on the
right rule. Place your right arm (left arm) in
the direction of the lighter, taller, water
column and you are looking down current in the
northern hemisphere (southern hemisphere).
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Gyre Circulation
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Implication Measuring Sea Surface Height (SSH)
can tell you the speed and direction of current
flow Satellites can measure accurately variation
in SSH at a 1-cm scale
Web Page SSH http//www-ccar.colorado.edu/real
time/gsfc_global-real-time_ssh/
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Western Boundary Currents
Why?
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Western Boundary currents
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Part IV Upwelling
1) Organisms in photic zone die and sink-
worldwide
2) Deep, cold water is relatively rich in
nutrients
3) Upwelling Movement of cold, nutrient rich
water towards the surface
4) Areas of high primary production and
biomass-rich food webs
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Equatorial upwelling
equator
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coastal upwelling northern hemisphere
wind from north
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World Surface Currents
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Upwelling California Current
http//www.montereybay.noaa.gov/sitechar/icons/phy
fi3.gif
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upwelling variations
downwelling
upwelling
bottom currents
surface currents
Grantham et al., 2004, Nature
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coastal downwelling northern hemisphere
wind from south
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Marine Food Chains/Webs

• Energy from primary production is transferred up
  the trophic chain
• Each step is inefficient (90 energy is lost)
• Shorter chains are more efficient at producing
  apex predators

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Bottom Up Control on the Marine Food Webs
hn
CO2
O2
Phytoplankton
Food Web
Plants
NUTS
Primary Secondary Production
Production
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Primary Production by Biome
Ryther (1969) Science
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Marine Food Chains/Webs

• Open ocean 90 area most of the NPP but
  little fish production
• Coastal ocean 9.9 area 20 of the global NPP
  but ½ of the fish production
• Upwelling systems 0.1 area little NPP but ½
  fish production

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CalCoFI Zooplankton Sampling
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CalCoFIZooplankton
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Seasonal Zooplankton
Zoo Winds
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Seasonal Zooplankton
Zoo Winds
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CalCoFI Zooplankton
Highest in the tongue of CA Current
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The Upwelling Conveyor Belt
High Zoo
Low Zoo
Lower Zoo
High Chl
Low Chl
Lower Chl
High NUTS
Low NUTS
Sinking POM
Highest NUTS
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CalCoFIZooplankton
Hi Zoos Low Temp ENSO connection All in
pre-1977
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CalCoFI Zooplankton
70 Decline in 1970s
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SURFACE WATERS HAVE WARMED IN Southern
California (Decadal Climate Regime Shift)
Scripps
gt 1o C Increase in Mean Annual Sea Water
Temperature 1975-2000
MEAN ANNUAL SURFACE TEMPERATURE
Santa Barbara
1960
1980
1990
YEAR
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Temporal Changes in Biomass of Zooplankton
in So. Ca. Bight
80 Decline in Warming Event
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Temporal Changes in Abundance of Reef
Fishes in So. Ca. Bight (data from 2
locations)
70 Decline in Warming Event
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Pacific Decadal Oscillation

• Evidence for just two full PDO cycles in the past
  century
• "cool" PDO regimes prevailed from 1890-1924 and
  again from 1947-1976
• "warm" PDO regimes dominated from 1925-1946 and
  from 1977 through (at least) the mid-1990s

• Causes for the PDO are not currently known
• Potential predictability for this climate
  oscillation are not known.
• Some climate simulation models produce PDO-like
  oscillations, although often for different
  reasons.

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The Upwelling Conveyor Belt/Climate change
High Zoo
Low Zoo
Lower Zoo
High Chl
Low Chl
Lower Chl
High NUTS
Low NUTS
Sinking POM
Highest NUTS
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Oregon coastal upwelling
Grantham et al., 2004, Nature
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• Ocean dynamics directly and indirectly affect the
  spatial and temporal variability of organisms and
  the performance of organisms (especially egg and
  larval mortality)
• Storms, for example, disperse larvae and destroy
  food patches and persistent wind-induced
  upwelling or anomalous currents along a coast can
  advect larvae to unsuitable
• areas where growth and survivorship can be low or
  where returning to nearshore settlement habitat
  is impossible

• At greater temporal and spatial scales, climatic
  events alter water mass distributions, water
  column structure, current patterns, and coastal
  upwelling of nutrient-rich water
• These environmental perturbations affect
  movement, spawning, and recruitment patterns of
  fish populations

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• Large-scale physical processes producing
  mortality in the early pelagic phase of fishes
  and other marine organisms can be offset by
  smallerscale mechanisms
• For example, coastal eddies, mesoscale features
  inherent in temporally and spatially variable
  current fields, can retain fishes during their
  pelagic phase and may enhance recruitment

• Mary Nishimoto and Libe Washburn (UCSB)

• Sampled with mid-water trawls California
  smoothtongue, northern
• lampfish, Mexican lampfish, Pacific hake, and
  rockfishes
• Latter 2 taxa were represented by late-stage
  larvae and pelagic juveniles.
• Small fishes of about 15 to 100 mm standard
  length (SL) important
• forage for seabirds, marine mammals, piscivorous
  fishes including salmon

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• California Current System (CCS) is the eastern
  boundary current system of the North Pacific
• Eddies, filaments, and meanders driven by
  variable winds and pressure gradients
  characterize the flow field over the shelf and
  offshore in the equatorward-flowing jet of the
  CCS
• Mesoscale features result in part from headlands
  and bathymetry along the coast
• Santa Barbara Channel is a transition region
  between the strong coastal upwelling regime
  extending northward from Point Conception to
  Washington and the warmer waters of the Southern
  California Bight.

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• A poleward, temperature-dependent pressure
  gradient tends to drive strong westward currents
  in the Channel
• Opposing the pressure gradient are winds that
  tend to induce upwelling and drive eastward flow,
  especially in the southern Channel
• When effects of wind and pressure gradients
  balance, the flow is cyclonic with westward flow
  along the northern boundary of the Channel and
  eastward flow along the Channel Islands, the
  southern boundary

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• Currents in the upper layers carry a diversity of
  fish species into the Santa Barbara Channel where
  many recruit to adult habitats

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Part V El Nino - Southern Oscillation

• El Niño events are linked to
• delayed and reduced phytoplankton productivity
• reduced zooplankton biomass
• increased mortality of coastal fishes during
  their planktonic larval phase

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Normal Conditions
Warm, moist air rises in Indonesia
Air moves poleward towards South America
High pressure over S. America, Low over Indonesia
Creates SE Trade Winds
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Normal Conditions
S-E Trade winds cause warm water to pile up in
the western Pacific
warm water
Indonesia/ Australia
S. America
cool water
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El Nino Conditions
High/Low Pressure system weakens
Area that is normally dry
SE Trades stop or even reverse
warm water
Gradient in Sea Surface Height degenerates
Warm, nutrient-poor water moves east
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