Download Upwelling, Coastal Productivity, and El Nino

Upwelling, Coastal Productivity,
and El Nino Events
Content Objectives
• SWBAT explain the causes and consequences
of upwelling in coastal areas to marine
biomass and regional weather patterns.
• SWBAT explain El Nino events and their
impacts on regional weather patterns and
economies of the region.
Oxygen-levels, Nutrients, and Temperatures
Is the Bottom of the Ocean Best?
Where to Live; Bottom or Top?
• The surface waters contain most of the algae
because they can do photosynthesis in the
presence of light.
• But, sunlight also brings higher water temps and
thus lower O2/CO2 concentrations.
Where to Live; Bottom or Top?
• The ocean bottom is nutrient-rich since all of the
dead and decaying animals from the top sink
down and settle on the bottom.
• In addition, the waters at the bottom are much
colder, which means they can hold more
dissolved O2/CO2.
Bottom is the Dead Zone
• Despite the coldest water, that is where all the
bacteria are feeding on decaying matter.
• Thus, they consume all the available oxygen
without adequate mixing adding more at depth.
What a Conundrum…
• The answer?
• Upwelling…
Upwelling
• When winds blow across the surface, they move
surface waters away from land, causing deeper water
to rise up to fill the void.
• This draws up cold, nutrient-rich bottom waters to
the surface.
• This results in a boon for marine life nearshore.
Upwelling
• Upwelling tends to only occur where there is very
deep water close to shore.
• Upwelling is uncommon on the east coast, where
the water remains somewhat shallow for many
miles offshore.
Upwelling off the California Coast
• Notice the water is coldest right offshore. This
is the upwelling zone.
Influx of Nutrients Near Shore
• In addition to upwelling, nutrient levels are
higher near shore because rivers feed
nutrients into the ocean.
What About Coral Reefs?
• Coral reefs are always
found nearshore.
• Although warm
waters, they also have
nutrients from land
Wave Action
Brings Oxygen
El Niño Southern Oscillation
• Under normal conditions, the coast of South America,
especially near Peru contains very cold waters.
El Niño Southern Oscillation
• Under normal conditions, the coast of South America,
especially near Peru contains very cold waters.
• This is due to the Humboldt Current bringing up cold
waters from the Antarctic.
• In addition, there is significant upwelling off the coast
El Niño Southern Oscillation
• But, every 3-7 years, there is a sudden change
in wind direction off Peru that stops the
upwelling of cold waters.
• This causes a dramatic rise in sea surface
temperatures.
• The impacts of this are vast
El Niño Southern Oscillation
• Increase sea temperatures result in increased
evaporation and thus changes to the water
content of the air.
• This is transported by prevailing winds
resulting in some regions having wetter than
average weather and others drier.
El Nino is Bad for Peru
• The lack of upwelling means fewer nutrients in the
water and higher temps means less dissolved gases.
• The results are crashes in the marine life of the areas.
• This results in economic collapses as fishermen can not
catch fish to eat or sell and people starve.
• In the north of the country, warmer waters means
increased rainfall and flooding on land.
Peru Civil War of 1982
• The economic crisis caused by the particularly
strong El Nino of 1982 added to the tensions
that resulted in the Peruvian Civil War.
El Nino’s Effects on North America
• Warmer weather to
western Canada and
southern Alaska
• Drier weather to the Pacific
Northwest
• Wetter weather to southern
California
• Cooler and wetter weather
to the southern U.S.
El Nino 1997
• Biggest one ever recorded
• California was blasted by massive rains and
floods that went on all winter.
• Heavy snow fell in the Sierra Nevada
La Nina
• Often following an El Nino is a La Nina event
• La Nina’s bring unusually cold water to the Eastern
Pacific and major changes to world weather patterns.
• The Pacific Northwest gets usually cold
• The southern U.S. experiences extreme drought.
What About Now?
This will be an El Nino Winter!
• After the drought of the past two years, it is
expected that we will have a very snowy winter!