Ⅱ-7. Astrophysics and Astro-Glaciology

RIKEN Accel. Prog. Rep. 49 (2016)+
Overviewofofthe
thechemicalchemical composition
composition andcharacteristics
ofofNa+Overviewandcharacteristics
Na–– distributions
anddistributions inin samples
samples fromandClClfrom Antarctic
Antarcticice
icecorecoreDF01
DF01
in 2001
2001(Dome(DomeFuji)
Fuji) drilled inY. Motizuki,1 K. Takahashi,1 Y. Nakai,1 Y. Iizuka,2 K. Suzuki,3 and H. Motoyama4Ice core samples contain information about the geologicalhistory of Earth, including past climate changes. Dome Fuji,situated at the highest point of land in central Antarctica, isconsidered one of the best drilling locations for procuring
samples for reconstructing past climates and environments.
We present here fundamental data on the concentrations of
dissolved ions in shallow samples, between depths of 7.7 m
and 65.0 m, from the Dome Fuji ice core drilled in 2001. A
total of 1435 samples were obtained for analysis. The
measured anions were HCOO–, CH3COO–, CH3SO3–, F–,Cl–, NO2–, NO3–, SO42–, C2O42–, and PO43–, and the cationswere Na+, K+, Mg2+, Ca2+, and NH4+. The measurements
were carried out using ion chromatography. The temporal
resolution of the depth profiles of the ion concentrations
was less than one year. No significant correlations wereobserved among these ions except between Na+ and Cl–.
Figure 1 shows the ion balance in the core, based on theaveraged ion concentrations of the samples. As shown inthis figure, the ion balance in the ice core was far different
from that of sea salt, a result consistent with a finding ofprevious studies1),2). The previous studies and our data
imply the probability that precipitation around Dome Fuji
might reflect conditions in the stratosphere.
Mg

2+Ca2+SO42Mg-2+Na+

Average ion concentrations ofDF2001 samples(7.7m-65.0m)that climate conditions were such that precipitation
containing sea salt occurred in the Dome Fuji area. Theeffect of sea salt can hardly be recognized around DomeFuji thus far. This is a new finding by the analysis ofhigh-resolution depth profiles of Na+ and Cl– concentrations.
On the other hand, the Cl–/Na+ ratio of samples that did notexhibit Na+ and Cl– peaks in the depth profile differed fromthat previously reported for the covering snow3), 4). This
result implies that Cl–, but not Na+, was redistributed after
the snow had fallen. According to Fujita et al., (in press)5),
it is probable that high concentrations of sulphate made theCl- ion mobile in ice cores and the concentration of Cl- wassmoothed out. This might account for the alteration ofCl–/Na+ ratios and the distribution, exhibiting the dotted linein Fig. 2, has been achieved. To interpret these observations
and elucidate the climatic conditions that might account forthem, further studies to examine the transportation of water
into Antarctica and the metamorphism of ice, such as
isotopic analyses of δD and δ18O, will be required.

K+ClNa-+Sea salt

Fig. 1. Relative ion composition of the ice core (left) andsea salt (right).
In several samples, however, synchronous concentration
peaks of Cl– and Na+ were identified, and the Cl–/Na+ ratiosof the corresponding samples were close to the sea salt ratio.
Figure 2 shows a plot of Cl– vs. Na+ concentrations andseveral samples exhibit Cl–/Na+ ratios close to that of thesea salt (dashed line). This observation indicates thepossibility
1

RIKEN Nishina Center

2

Hokkaido University, Institute of Low Temperature

3

Shinshu University, Faculty of Science4

National Institute of Polar Research, Ice Core Cetnter- 133 -Fig. 2. Scatter plot of Na+ vs. Cl– concentrations in shallow
samples, between 7.7 m and 65.0 m depth, from the DomeFuji ice core drilled in 2001.
References1) K. Kamiyama et al.. J. Geophys. Res. 94, 18,519 (1998).
2) E. Fourré et al.. Earth Planet. Sci. Lett. 245, 56 (2006).
3) K. Hara et al. J. Geophys. Res. 109, D20208 (2004).
4) Y. Iizuka. et al.. J. Geophys. Res. 113, D07303 (2008).
5) S. Fujita et al.. J. Glaciology, in press.