Diapositivas 2 Generalidades Del Oceano

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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Diapositivas 2 Generalidades Del Oceano