Download Oceans and Climate

Oceans and Climate
Margaret Mayer, Diné College
How the Sacred Element of Air
Impacts the Oceans
• Winds and Surface Currents (friction)
• Moving Water influenced by the Coriolis
Effect (Earth’s Rotation)
• Atmospheric Circulation
How the Sacred Element of Earth
Impacts the Oceans
• Trade winds produce westward flowing
currents in the tropics that deflect north
and south when they hit the western
continents
• Westerlies cause currents to flow eastward
in the midlatitudes until they hit the
eastern land masses where they deflect
toward the poles or toward the equator.
• The overall effect is a gyre.
Coriolis Effect
How the Sacred Element of Water
Impacts the Oceans
• Heat capacity – energy required to heat
water (extremely high due to H-bonding)
• Solid state of water is less dense than
liquid water (ice floats)
• Salt water is more dense than fresh water
• Water remains a liquid over an extremely
wide range of temperatures
• Vertical composition of the ocean is driven
by differences in salinity.
How the Sacred Element of Fire
Impacts the Oceans
Oceans absorb and store large amounts of
energy as heat.
Oceans change temperature much more slowly
than the atmosphere or land.
SST – Sea Surface Temperature
Vertical composition of the ocean is also driven
by temperature
Overall effect is called thermohaline circulation
Hydrologic Cycle and Oceans
• Oceans contain 97% of the water on Earth
• Oceans receive 78% of all precipitation
• Oceans evaporate 86% of all water to the
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atmosphere (salt remains behind)
Oceans are key to transporting water (and heat)
in large gyres from the equator to the poles and
back to the equator
Note: all wind and current patterns observed on
the surface of the planet is the direct result of the
uneven heating and uneven heat distribution of
the earth’s surface by the sun.
Global Warming and an Accelerated
Hydrological Cycle
• Evaporation rates increase with surface
temperature
– Loss of fresh water in equatorial areas
• Precipitation increases as temperatures
decrease (cold air holds less water)
– Gain of fresh water in polar regions
Natural Sources of Warming
• Changes in solar output (our sun)
• Volcanic activity(complex)
• El Niño-Southern Oscillation (ENSO)
– "It is scientifically inconceivable that - after changing
forest into cities, putting dust and soot into the
atmosphere, putting millions of acres of desert into
irrigated agriculture, and putting greenhouse gases
into the atmosphere - humans have not altered the
natural course of the climate system." American
Geophysical Union
Shifts in Southern Oscillation (SO)
El Nino vs La Nina Ocean Temps
The Role of the Ocean in Climate
• Stores most of the solar energy from the sun
as heat (1000 times more than air but moves
energy slower so air-ocean impacts similar)
• Stores CO2
– (50% of carbon emissions)
• Stores fresh water
• Stores salt
Great Ocean Conveyor Belt (GOC)
a Heat Pump Driven by Thermohaline
circulation
What has or can stop the Heat Pump?
• If surface waters in the north are no
longer dense enough to sink
– SST too warm to sink
– Too much fresh water from
• Melting ice
• Increased precipitation
• Little Ice Age – 700 years ago
(1300 – 1800 AD)
• Greenland Ice Sheet melts
Changes in Salinity
The record of recent climate changes
Abrupt Climate Change Events
The Younger Dryas—about 12,700 years ago, average temperatures in
the North Atlantic region abruptly plummeted nearly 5°C and remained
that way for 1,300 years before rapidly warming again. Believed to be
caused by a huge influx of fresh water to the ocean.
The Medieval Period—An abrupt warming took place about 1,000 years
ago. It was not nearly so dramatic as past events, but it nevertheless
allowed the Norse to establish settlements in Greenland.
The Little Ice Age—The Norse abandoned their Greenland settlements
when the climate turned abruptly colder 700 years ago. Between 1300 and
1850, severe winters had profound agricultural, economic, and political
impacts in Europe. (R.B. Alley, from The Two-Mile Time Machine, 2000)
Thought to be caused by sulfates from coal burning.
Ocean/Air Temperature
• Sea surface temperatures(SSTs) have risen during the
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last twenty years by 1-2 o F. As water has a much higher
specific heat/heat capacity than air, this represents a
major amount of heat added into the ocean when one
also takes into account the surface area of the ocean
versus the surface area of the continents.
– Corals extremely temperature sensitive
Air temperatures have risen on average 3-4 o F during
the same period and are expected to rise even more up
to 7 o F over the next century.
Changes in jet stream patterns, weather patterns.
Acidity of Oceans
• When CO2 dissolves it forms a weak acid
– CO2 + H2O  H2CO3 carbonic acid
• CaCO3 + Acid  dissolves (demo)
• pH scale as acidity increases, pH
decreases
• Lower pH is causing the shells of many
marine organisms to dissolve including coral
reefs.
Oceanic Inverted Biopyramid
• Most organisms are in the bottom phyla
• Most organisms are endemic
• Phytoplankton generate large amounts of
oxygen
• Phytos are eaten almost as soon as they
add biomass to the system, hence the
inverted biopyramid.
Changes in Flora/Fauna
• Overall – observed changes in species
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distribution.
Seeing species typically found at temperate or
tropical latitudes being found in subarctic
latitudes – be it land or sea.
Changes in phytoplankton distribution – Bering
Sea and Gulf of Alaska – diatoms (cold water
phytos) are being replaced by coccolithophorids
(warm water phytos). This changes the entire
dynamics of the Arctic oceanic food web.
”Belch from the deep”
• Methane hydrates (solid, ice-like
formations at the bottom of the oceans)
• Methane is produced by bacteria in the
ocean
• Powerful greenhouse gas
• If temperatures increase or pressure
decreases this gas could be released in
large quantities
The Great Paradox
• Could global warming lead to an ice age?
• Added surface fresh water which reduces salinity
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(and thus density) can shut down the “Conveyor
Belt” which is a major heat distribution
mechanism for the planet.
This change can occur (and has occurred) on
the order of decades if not years.
There is some indication this may have begun as
researchers from Dalhousie University in Halifax,
Nova Scotia have documented a slow down in
the vertical sinking rate in the GINSEA.
Assignment:
• Draw the major ocean currents
– Label cold and warm currents
• Next, draw a 2nd sketch showing how
those currents might be affected by
climate change
• One-page paper: discuss your sketches,
and how the change in ocean currents
might affect life on our planet.