Ice cores and climate Elisabeth Isaksson

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Ice cores and climateElisabeth Isaksson Dmitry
Divine
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What are ice cores good for?

• Temperature proxy
• Preserved air-bubbles
• Annual layers
• Rapid changes can be studied
• Specific events can be investigated and links to
  other climate systems established

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Ice cores as climatic indicators
d18O as an air temp. proxy
Trapped air bubbles in the ice can provide us
with information on the atmospheric greenhouse
content
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Dating - annual if accumulation is high
Example Core S100 from coastal
Antarctica. Seasonal peaks in the ?18O, DEP and
ECM records between 70-80 m depth used for
establishing an annual chronology.
Kaczmarska, M., Isaksson, E., Karlöf, K.,
Winther, J-G, Kohler, J., Godtliebsen, F.,
Ringstad Olsen, L., Hofstede, C M., van den
Broeke, M.R., Van De Wal, R. S.W., and
Gundestrup, N. 2004. Accumulation variability
derived from an ice core from coastal Dronning
Maud Land, Antarctica. Annals of Glaciology, 39,
339-345.
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Using specific events for dating ice
coresExamples from Svalbard ice cores
Volcanic eruptions Nuclear
weapon tests
Laki 1783
Kekonen and others, 2002
Pinglot and others, 2003
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Depth age relationship
Ice cores have layer thinning due to pure shear
which means that if sample size is consistant the
number per time unit will decrease with depth
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Lomonosovfonna drilled in April 1997 121 m deep,
about 800 yrs Project participants Norway, The
Netherlands, Sweden, Finland, Estonia
Svalbard drill sites
Austfonna drilled in 1998 and 1999 289 m deep,
about 800 yrs Project participants Japan, Norway
Holtedahlfonna (Snøfjellafonna) drilled in April
2005 125 m deep, about 400 yrs Project
participants Norway, The Netherlands, Sweden,
Finland, Estonia
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EPICA 1996-2004EPICA-MIS 2004-2007
EPICA DML 700S 407E 2890m asl mean temp.
-45C
NPI focus Recent Antarctic climate variability
Dome C 7506S 12323E 3233 m asl mean
temp. -55C
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• Climate parameters that we try to reconstruct in
  our group
• winter temperatures (d18O)
• precipitation (accumulation)
• sea ice (MSA, d18O)
• atmospheric circulation (ions)
• summer temperatures (melt index)

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Winter temperatures (d18O) Improve our
understanding the spatial variation of climate
Lomonosovfonna
Austfonna
Laki 1783
The d18O record from Lomonosovfonna suggests that
temperatures during the early part of the record
about 1100-1500 AD was at least as warm as the
1900s.
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Svalbard proxy-temperatures from ice cores
Smoothing window (years)
Smoothing window (years)
SiZer color coding purple no significant
trend blue significant increase red
significant decrease
Sizer of Lomonosovfonna and Austfonna d18O
1400-2000 AD . Upper panel dots - d18O samples,
lines - family of smooths obtained for various
versions of the bandwidth (h). Lower panel SiZer
significance test at 95 confidence level.
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Wavelet analysis reveals low frequency
oscillations on the 60-120 year scale on
Austfonna. This is similar to what has been found
in various climate records including instrumental
temperatures and tree-rings and has been proposed
as most important oscillation for the observed
trends in Arctic air temperatures.
Wavelet power spectra of the d18O records
Thick and dashed contours enclose the regions
where the wavelet power is above the red noise
background with the 95 and 90 confidence
levels, respectively. The cross-hatched areas
indicate the cone of influence where the edge
effects due to zero padding become important
Isaksson, E., Divine, D., Kohler, J., Martma, T.,
Pohjola, V., Motoyama, H., Watanabe, O. 2005.
Climate oscillations as recorded in Svalbard ice
core d 18O records between 1200-1997 AD.
Geografiska Annaler 87A(1), 203-214..
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Svalbard winter temperature variability - last
100 years
Analyses in progress
Correlation coefficent between Longyearbyen T and
d18O are about 0.5 for five year moving averages
(1911-1997) (Grinsted et al., JGR 2006)
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Pollution records from the ice cores
Nitrate records from two Svalbard ice cores
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Examples of problems that we have Comparing
several ice cores records from the same area -
is there a common signal i.e. regional
climate
Divine, Isaksson and others in prep.
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Comparing different proxiesWhat processes are
driving the variability we see in our time series?
d18O Temp. proxy
MSA biogenic productivity proxy
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Investigating if two time series have the same
variability
2. Wavelet coherence
1. Fourier analyses
Divine, Isaksson and others in prep.
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3. Then- investigating links to climate
indiciesSouthern Oscillation Index (SOI)
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• Ice core challanges
• Spatial variability needs to be understood and
  quantified
• Quantify climate variability on different
  time-scales
• Relate changes in the ice cores to atmospheric
  and meteorological conditions and improve our
  understanding of transfer functions

Zeppelin station Ny Ålesund