Deglaciation

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Deglaciation

• Timing of Millennial-Scale Climate Change in
  Antarctica and Greenland During the Last Glacial
  Period
• Thomas Blunier and Edward Brook, 2001
• Interhemispheric Atlantic Seesaw Response During
• the Last Deglaciation
• Stephen Barker et al, 2009
• Jesse Senzer

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Pleistocene Epoch 2.8 mya to 10,000 ya
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Dansgaard-OeschgerEvents

• Dansgaard-Oeschger (D-O) events were first
  reported in Greenland ice cores by scientists
  Willi Dansgaard and Hans Oeschger. Each of the 25
  observed D-O events consist of an abrupt warming
  to near-interglacial conditions that occurred in
  a matter of decades, and was followed by a
  gradual cooling.
• NOAA National Climatic Data Center

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Bluniers Hypothesis

• Millennial-scale temperature variability is
  characterized by abrupt changes in Greenland, and
  more gradual fluctuations in Antarctica. This
  offset pattern is thought to be a direct result
  of oceanic thermohaline circulation patterns, and
  results in the bipolar seesaw phenomenon.

• Schuttenhelm, 2011

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Atlantic Meridional Overturning Circulation
(AMOC)The Great Ocean Conveyor

• Saundry, 2012

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Bluniers Evidence

• Contrasted the timing of climate events using
  isotopic data in the Greenland Ice Sheet Project
  2 (GRISP2) ice core from Summit, Greenland with
  the Byrd ice core from Byrd Station, Antarctica.
  Used atmospheric methane from GRIP in Greenland
  and Byrd and Vostok in Antarctica as a
  correlation.

Lowell, 2011

• National Science Foundation

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(A) Isotope data from GISP2, Greenland (B)
Isotope data from Byrd Station, Antarctica(C)
Methane data from GISP2 and GRIP (D) Methane data
from Byrd Station
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Bluniers Take Home Message
Understanding climate dynamics and forcing is an
evolving science. The bipolar seesaw has been a
persistent feature of glacial climate. As seen
in the Richard Kerr article, North Atlantic deep
water and the AMOC are part of a continuous,
interrelated system that is not fully understood.
Saundry, 2011
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Heinrich Stadials HS1-6

• Related to some of the coldest intervals between
  D-O events were six distinctive periods, named
  after paleoclimatologist Hartmut Heinrich. They
  represent an increase in icebergs discharged from
  the Laurentide ice sheet in North America and a
  southward extension of cold, polar waters.

NOAA National Climatic Data Center
10
Younger Dryas (YD)

• The Younger Dryas occurred during the transition
  from the last glacial period into the present
  interglacial (the Holocene).
• About 14,500 years ago, the Earth's climate began
  to shift from a cold glacial world to a warmer
  interglacial state. Partway through this
  transition, temperatures in the Northern
  Hemisphere suddenly returned to near-glacial
  conditions. This near-glacial period is called
  the Younger Dryas, named after a flower (Dryas
  octopetala) that grows in cold conditions and
  became common in Europe during this time.
• NOAA National Climatic Data Center

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Barker et als Hypothesis

• The bipolar seesaw is a key component not only
  for millennial-scale climate variability, but
  also for changes on glacial-interglacial
  timescales.

• 1) GISP2
• Marine core
• Marine core
• Marine core
• Marine core TNO57-21 (this study)
• Antarctic ice core

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Matts time to shine
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Key Fig 2. Concepts

• Polar species decline mirrors Antarctic
  temperature increase and N. Atlantic SST
  decrease.
• Direct link between abrupt changes at high
  northern latitudes and similarly abrupt
  variations in the geometry of the ACC.
• Mg/Ca ratios in planktonic forams show warming
  generally occurs during intervals of reduced
  polar species.

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Key Fig 3. Concepts

• Surface ocean productivity associated with warmer
  SST found by analyzing abundance of benthic
  forams.
• Intensification of the ACC during HS1 might have
  promoted the release of carbon dioxide by
  increasing the rate of vertical mixing within the
  Southern Ocean.

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Barker et als Take Home Message

• Increasing our understanding of the physical
  links between north and south at millennial
  timescales is critical for understanding the
  potential role of such variability as a feedback
  on global climate change.

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Questions
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Works Cited

• Barker, S. et al, 2009, Interhemispheric Atlantic
  Seesaw Response During the Last Deglaciation,
  Nature, v. 457, p. 1097-1102.
• Blunier, T. and Brook, E.J., 2001, Timing of
  Millennial-Scale Climate Change in Antarctica and
  Greenland During the Last Glacial Period,
  Science, v. 291, p. 109-112.
• Heinrich and Dansgaard-Oeschger Events, NOAA
  National Climatic Data Center, http//www.ncdc.noa
  a.gov/paleo/abrupt/data3.html (October 15, 2012)
• Lowell, T., 2011, Chasing Greenlands Melting Ice
  in Search of Climate Clues, Northwestern
  University, http//news.medill.northwestern.edu/cl
  imatechange/page.aspx?id189953 (October 14,
  2012)
• National Science Foundation, US Antarctic
  Program, 2005-2006, https//www.nsf.gov/od/opp/ant
  arct/treaty/opp06001/index.jsptop (October 14,
  2012)
• Raymo, M. and Huybers, P., 2008, Unlocking the
  Mysteries of the Ice Ages, Nature, v. 451, p.
  284-285.
• Saundry, P., 2012, Atlantic Meridional
  Overturning Circulation, The Encyclopedia of
  Earth, http//www.eoearth.org/article/Atlantic_mer
  idional_overturning_circulation (October 16,
  2012)
• Schuttenhelm, R., 2011, New Evidence for Bipolar
  Seesaw Link Between Greenland and Antarctica- and
  Abrupt Climate Variability, Bits of Science,
  http//www.bitsofscience.org/bipolar-seesaw-greenl
  and-antarctica-climate-variability-3124/ (October
  14, 2012)