Thermohaline Circulation and the

1
Thermohaline Circulation and the Effects of
Global Warming
Global warming is causing significant changes in
ocean currents which will in turn alter global
climate, biodiversity, and human civilizations.
http//seawifs.gsfc.nasa.gov/OCEAN_PLANET/MOVIES/T
opex_Dynamic_Ocean_Topography.mpg
Lauren Eaton, Sarah Cook, and Alice Rice Section
2, Group 2
2
Outline

• What are ocean currents?
• How global warming is a factor
• How global warming and currents are interacting
• Why we care
• How this is affecting Biodiversity
• Phytoplankton Graph
• Case Study The ACC
• Take Home Message
• Bibliography

3
Ocean Currents

• What
• Keep oceans in constant motion
• Contribute to heat transport
• How
• Driven by wind, tides, gravity, Coriolis Force
• Create gyres
• Surface current driven by wind
• Deep ocean currents driven by density and
  temperature
• Where
• Entire world!
• Major currents North and South Equatorial
  Currents, Gulf Stream, Kuroshio Current,
  Antarctic Circumpolar Current, East Australia
  Current

4
Global Warming

• Combination of temperature and salinity determine
  density
• Warming of the planet will cause an influx of
  freshwater from melting glaciers.
• Fresh water is less saline than salt water, wont
  be as dense and sink, the density gradient that
  determines currents will be lower.
• Currents slow down
• Northern latitudes become less salty
• As the currents slow down the water will be less
  mixed, fewer nutrients cycling, release of CO2
  sinks
• Not currently shown because the top few meters of
  the ocean hold as much heat energy as the entire
  atmosphere

Adkins, Jess F., McIntyre, Katherine, and Daniel
p. Schrang.
5
Our Changing Ocean Currents

• Possible slowing of Conveyor Belt
• Temperature and rising waters
• As Oceans and world warms the world will also
  start to cool
• no heat exchange
• could produce winters 2x as harsh as the worst
  winter on record
• Melting Glaciers
• Salinity and density fluxes, will only intensify
  problem

Yin, J., Schlesinger, M., Adronova, N., Malyshev,
S., Li, B
6
Why we care.

• Climate
• Temperature
• As currents slow the exchange of water will slow
  and climate change will intensify
• Weather
• When glacial melting increases as a result of
  global warming there will be more ocean surface
  area, resulting in more precipitation in some
  areas and drought in others.
• Slowing currents result from more rain falling in
  polar regions, further melting glaciers
• Ecosystems
• Biodiversity
• Plankton
• As a result of changing temperature habitats
  change, both aquatic and terrestrial
• Social
• Population vs. Space
• as oceans get warmer and rise there will be a
  fight for available land
• Adaptation
• Humans and other animals will be living in a
  warmer world

Department of Earth Sciences, University of
Southern California Faculty. 2006.
7
Changing Biodiversity

• Changes in phytoplankton concentrations over the
  last 20 years. Deep blues show the greatest loss
  of phytoplankton. Yellow represents almost no
  change. Browns, reds, and oranges show
  phytoplankton increases. Black indicates that no
  data is available.
• Without Ocean currents 1/50 of nutrients would be
  lost automatically each year as a result of
  sinking nutrients that arent redistributed.
• Ocean currents mix up layers and spread nutrients
  throughout the ocean, with the slowing of
  currents there will be less mixing, phytoplankton
  will receive fewer nutrients
• Also nutrients are not spread as much by the ACC

• Roach, John. 2005.

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How temperature and phytoplankton are correlated
(2001)

• NOAA. World ocean database 2001

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Antarctic Circumpolar Current

• The Antarctic is an indicator
• Where oceans converge
• Largest current
• Further warming melts more glaciers
• Controls circulation throughout world
• Density

Baer, Andrea. Antarctic Current circles the
World. 2002.
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What Will Our World Look Like?

• Complete failure of the conveyor belt possible
• Could be restarted with a drastic change
• Mini ice age possible
• Younger dryas
• Increased CO2
• Sink lost
• Earth processes
• Drought
• Precipitation
• Cloud cover
• Increased ocean surface area

• Pearce, Fred. 2005

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Take Home Message

• Ocean Currents are changing and will cause
  significant changes on the Earth but worry not,
  there is still hope.

12
Bibliography

• Adkins, Jess F., McIntyre, Katherine, and Daniel
  p. Schrang. The salinity, temperature and ?18
  of the glacial deep ocean. 2006.
  lthttp//www.sciencemag.org/cgi/reprint/298/5599/17
  69.pdfgt (20 November 2006)
• Baer, Andrea. Antarctic Current circles the
  World. 2002. lthttp//antarcticsun.usap.gov/oldi
  ssues2002-2003/Sun121502/current.htmlgt
• (22 October 2006) The last revision was 15
  December 2002. I visited the site on 22 October
  2006.
• CSIRO Marine Research. Southern Ocean and
  Antarctic Circumpolar Current. 2005.
  lthttp//www.marine.csiro.au/LeafletsFolder/10ocean
  /10.htmlgt (24 October 2006)
• Department of Earth Sciences, University of
  Southern California Faculty. Ocean Currents and
  Climate. 2006. lthttp//earth.usc.edu/stott/Catal
  ina/Oceans.htmlgt (30 November 2006)
• Gagosian, Robert B. Abrupt climate change
  should we be worried?. Jan 27 2003.
• lthttp//www.whoi.edu/institutes/occi/viewArticle.d
  o?id9986gt (1 December 2006)
• Gille, S. T. Warming of the Southern Ocean since
  the 1950s. 2002 lthttp//www.sciencemag.org/cgi/co
  ntent/full/295/5558/1275gt (1 December 2006)
• NOAA. World ocean database 2001 - plankton
  abundance 2001 lthttp//www.nodc.noaa.gov/OC5/WOA0
  1/abundance.htmIgt (1 December 2006)
• Pearce, Fred. Failing ocean current raises fear
  of mini ice age. 30 November 2005.
  lthttp//www.newscientist.com/article.ns?iddn8398gt
  (20 November 2006)