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
Pleistocene Epoch 2.8 mya to 10,000 ya
Dansgaard-Oeschger
Events
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 nearinterglacial conditions that
occurred in a matter of
decades, and was followed by a
gradual cooling.
NOAA National Climatic Data Center
Blunier’s 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
Atlantic Meridional Overturning Circulation
(AMOC)
“The Great Ocean Conveyor”
Saundry, 2012
Blunier’s 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
(A) Isotope data from GISP2, Greenland
(C) Methane data from GISP2 and GRIP
(B) Isotope data from Byrd Station, Antarctica
(D) Methane data from Byrd Station
Blunier’s 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
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
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
Barker et al’s Hypothesis
The bipolar seesaw is a
key component not only
for millennial-scale
climate variability, but also
for changes on glacialinterglacial timescales.
1)
2)
3)
4)
5)
6)
GISP2
Marine core
Marine core
Marine core
Marine core TNO57-21 (this study)
Antarctic ice core
Matt’s time to shine
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.
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.
Barker et al’s 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.
Questions
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.noaa.gov/paleo/abrupt/data3.html (October 15, 2012)
Lowell, T., 2011, Chasing Greenland’s Melting Ice in Search of Climate Clues, Northwestern University,
http://news.medill.northwestern.edu/climatechange/page.aspx?id=189953 (October 14, 2012)
National Science Foundation, US Antarctic Program, 2005-2006,
https://www.nsf.gov/od/opp/antarct/treaty/opp06001/index.jsp#top (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_meridional_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-greenlandantarctica-climate-variability-3124/ (October 14, 2012)
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