Antarctic Ice Core Results to Date Amanda Solomon Geology

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Antarctic Ice Core Results to Date

• Amanda Solomon
• Geology 495
• February 15, 2006

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Outline

• Introduction
• What is an ice core?
• Why study ice cores?
• Previous Studies
• Antarctic Ice Core Results
• Vostok
• Dome C
• Conclusions

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Introduction

• What is an ice core?
• Similar to other core samples, but made of ice
  not rock.

http//www.homepage.montana.edu/lkbonney/IMAGES/A
ntarctic images/Ice Microbes/Ice core.JPG
Photo credit Chelsey Ebel
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Introduction

• Why study ice cores?
• Provide useful climatic data

• Layers of snow and ice
• Debris such as ash and dust
• Temperature from MSA and NSSS
• Ocean Volume from 18O/16O isotopes
• Composition of the atm. from inclusions
• Mean accumulation rate from Deuterium isotopes

http//earthobservatory.nasa.gov/Library/UVB/Image
s/antarctica.jpg
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Tison, J. L. et. al., 1993

• Used ice core samples to study D/18O K/Mg
  isotope ratios
• Did a crystallographic and structural study of
  the ice core
• Reconstructed the salinity of the host H2O
  developed a model for marine ice accretion

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Warwick, F. et. al., 1994

• Looked at ice cores taken by Mayewski Legrande
  (1990) which showed a near-surface increase of
  nitrate concentration
• Took new surficial samples and analysed them to
  conclude that the nitrate ppt was stratospheric
  i.e. snow

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deMora, S. J. et. al., 1997

• Took samples from aerosols, surficial snow, and
  ice cores
• Studied the methanesulphonate (MSA) non-sea
  salt sulphate (NSSS) for changes in the
  dimethylsulphide (DMS) derived species
• DMS from oceans enters atm. and oxidizes to form
  MSA NSSS
• Forms clouds in the marine trophosphere which
  affects the earths albedo and causes a cooling
  effect
• Found that the aerosols were consistent with
  transport from the mid-latitudes

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Jeffries, M., et. al., 1997

• Studied ice core and stable isotope data
• Ice core data showed a trend of an upper granular
  ice layer and a lower columnar ice layer
• 18O Stable isotope data showed the difference
  between snow ice and frazil ice
• Obtained the first understanding of the main
  physical characteristics, conditions and
  processes in a first year ice pack.
• Ice growth occurs in stages of frazil ice growth
  and pancake ice formation, followed by
  thermodynamic thickening

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Seigert, M., et. al., 2001

• Used airborne radar data to map the 3D structure
  of the ice sheet around Dome C
• Studied data to determine the past and present
  flow of ice
• Determined that above 2km the ice layers
  submerge and diverge from each other in vertical
  section as a result of accumulation.
• Below 2km, ice layers are controlled by
  subglacial topography and former ice flow

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Narcisi, B., et. al., 2001

• Studied layer of Tephra (particles few to 200
  micrometers) in ice core from Talus Dome
• NSSS data allowed dating of layer to 1254 /- 2 a
  A.D.
• Determined area ash covered, looked at prevailing
  wind directions, and compared composition of
  nearby volcanoes to the ash sample
• Concluded that nearby volcanoes The Pleiades or
  Mt. Rittmann were responsible

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Orelemans, J., 2005

• Used deuterium record from EPICA Dome C to
  determine mean accumulation rate, and the
  composite deep sea 18O record to determine the
  total ice volume on earth
• Used this data in a simple ice sheet model to
  determine the volume history of the Antarctic Ice
  Sheet

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Antarctic Ice Core Results
Map of Antarctica showing main study areas. From
DeMora et. al., 1997.
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Vostok

• Shows evidence of 4 past glaciations
• Analyzed to determine a history of atmospheric
  CO2, temperature, and the composition of wind
  blown dust
• Can be correlated with the upper part of the
  EPICA Dome C ice core

http//www.ldeo.columbia.edu/mstuding/new_vostok_
cartoon_high.gif
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Dome C

• Drilled to a depth of 3270.2m
• Oldest ice at depth is around 720 000 a
• Shows evidence of eight past glaciations
• Spot was picked using radar data so that ice
  layers are horizontal.

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http//upload.wikimedia.org/wikipedia/en/f/f2/Epic
a_do18_plot.png
Comparision of the Vostok and EPICA (Dome C) ice
cores.
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Further Study

• Why is further study of Antarctica important?
• - large area (14 million km2)
• - 98 covered in ice
• - desert environment
• - stable for many years
• virtually pristine climate record that has been
  largely unstudied

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Conclusions

• Ice cores are a valuable tool to reconstruct the
  past environment, and can be applied in many
  different studies
• Antarctica has been glaciated for many years, and
  has been largely untouched by human civilization
  or biogenic activity
• Ice cores that have been studied give climate
  data going back 720 000 years, and show evidence
  of at least 8 glaciations
• Ice cores have correlated across fairly large
  areas and can be correlated to previous marine
  isotope data