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8/13/2019 Diapositivas 2 Generalidades Del Oceano
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Ocean Basics: Seawater
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Learning objectives
Recall important properties of seawater that support life
Recognize variability in properties of seawater
Identify important ocean currents and how deep water
circulation works in the ocean
Recall some of the challenges of living in the ocean
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Seawater and life
One of the most important aspects of water is ability
to dissolve materials.
Makes the ocean salty - water balance
challenges
Dissolved nutrients that support growth of marine
plants - phytoplankton
Nitrogen, phosphorus, iron, carbon and others
Dissolved oxygen that supports metabolism of
much of life in the ocean
Dissolved ions that support chemosynthetic food
webs
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Seawater
Contains dissolved salts - e.g. sodium chloride
Average seawater ~ one kilogram (liter) has about 35 grams
(1.2oz) - 3.5% or 35 parts per thousand (ppt)
Seawater is denser than freshwater
Seawater freezes at lower temperatures than freshwater
(around -2 degrees Celsius)
Water is less dense when in solid form (ice)
Temperature and salinity define water masses, how they
move and their ecological effects
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The surface of the ocean
Ocean is not uniform in temperature, salinity,
currents etc
Vary greatly with latitude
Warm and saline near the tropics
Colder and less saline in polar regions
Surface currents driven by persistent winds
Deep currents driven by temperature and salinity
gradients - thermohaline circulation
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Global Average Sea Surface Temperatures Warm in the tropics, cold at the poles
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Surface currents of the world The ocean is not a homogenous place
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General ocean surfacecurrents
Warm, narrow western boundary
currents
Cool, broad eastern boundarycurrents
Central gyres in North/South
Pacific, North/South Atlantic, Indian
oceans
Antarctic circumpolar currents
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Large scale patterns in ocean salinity and
temperatureGlobal thermohaline circulation
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Pressure at depth
Assuming that the density of sea
water to be 1025 kg/m"(this
does vary slightly depending on
conditions), pressure increases
by about 1 atmosphere (14.7pounds per square inch) with
each 10 m of depth.
Pressure is a huge challenge for
marine organisms 0
250
500
750
1000
-10 -100 -1000 -10000
Increasing Depth
Increasing
Pressure
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Light at depth
Seawater scatters the cooler colors
(blue and green - known as short
wavelength light) and absorbs the
warmer colors (yellow and red)
Only small amounts of light penetrate
below 200m
Absence of light is a challenge for
marine organisms that live in the deep
ocean
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Sea ice and icebergs
Ice - the solid form of water - is less
dense than its liquid form.
Sea ice floats, substrate for life
Structures marine ecosystems
Incredible seasonal changes
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Seasonal changes in Arctic sea ice Rapid ecosystem change that supports life in the Arctic
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Summary
Seawater has special properties that
support life
Seawater also presents challenges for life
Oceans are not uniform but vary greatly in
time, space and depth
Seawater moves at surface and at depth,
driven by winds and temperature and
salinity gradients
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