Scientiﬁc paper
General tendencies of stable isotopes and major chemical constituentsof the Dome Fuji deep ice core
Okitsugu Watanabe1, Kokichi Kamiyama1, Hideaki Motoyama1, Yoshiyuki Fujii1,Makoto Igarashi1, Teruo Furukawa1, Kumiko Goto-Azuma1, Takashi Saito2,Satoru Kanamori1, Nobuko Kanamori1, Naohiro Yoshida3 and Ryu Uemura3
1National Institute of Polar Research, Kaga 1-chome, Itabashi-ku, Tokyo 173-8515
2Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji 611-0011
3Tokyo Institute of Technology, Nagatsuda, Midori-ku, Yokohama 226-8502
Abstract: Stable isotope compositions of water and major chemical constituents of theDome Fuji ice core are analyzed and the data sets over the entire depth of the 2503-m coreare presented in appropriate time resolution as consecutive series of average value in deﬁniteterms.  These results based on the ﬁrst stage analyses allow a temporal climatic dividing ofthe three glacial-interglacial cycles present in the records.  A comparison of the climatic andenvironmental characteristics of these climate stages is presented.
key words: Dome Fuji, ice core, stable isotope, chemical constituent, Antarctica
1. Introduction
The ﬁrst successful deep ice core drilling at Camp Century, Greenland in 1966 had astrong impact on earth science.  It was followed by another successful ice core drilling atByrd station, west Antarctica in 1968.  Deep ice core studies started in several places on theAntarctic and Greenland ice sheets after these successes.The Antarctic ice sheet preserves past global scale climate and environment signals inthe snow and ice.  These signals are linked to local temperature and precipitation rate, mois-ture source conditions by stable isotope ratios of oxygen and hydrogen in water molecules,and earth surface condition and general circulation strength by the ﬂux and composition ofprimary and secondary aerosols from marine, terrestrial, cosmic and anthropogenic origins.Entrapped air inclusions provide direct records of past changes in atmospheric trace gas com-position.To construct a long term paleoclimate record, deep ice core drilling has been carried outat Byrd, Vostok, Dome C, and Law Dome in Antarctica.The Vostok ice core data show that the atmospheric concentrations of greenhouse gasesoscillated in close harmony with global temperature changes during the past several hundredthousand years (Barnola et al., 1987; Petit et al., 1999).  In the Arctic, the GRIP (GreenlandIce-core Project; 1990–1992) core reveals 22 interstadial (warm) events during the lastglacial period with very rapid warming and moderate cooling (Johnsen et al., 1992).A deep ice core drilling project was carried out during 1993–1998 at Dome Fuji,
Mem. Natl Inst. Polar Res., Spec. Issue, 57, 1–24, 2003©2003 National Institute of Polar Research
Antarctica, as a part of a comprehensive glaciological study to clarify the present and pastglaciological and climate condition of the Antarctic Ice Sheet in East Dronning Maud Land(Watanabe et al., 1997a, b).Deep ice core drilling was carried out to a depth of 2503.52 m in 1996 at Dome Fuji,which is one of the principal summits of the ice sheet in East Antarctica (Fig. 1).This paper is a result of basic analysis of the Dome Fuji deep ice core.  We present aseries of detailed Dome Fuji records covering more than 320-kyr.  In a full-depth core, themean values of oxygen isotope content and main chemical concentration were obtained inuniform intervals (corresponding to equal numbers of years).Climatic division in three glacial cycles has been determined from the proﬁles of oxy-gen isotope composition, of concentrations of the principal chemicals components and ofatmospheric gas composition.  The environmental characteristics of each climatic divisionare described in terms of concentrations of the principal chemical constituents and atmo-spheric trace gases.
2. Geographic and climatic conditions of the Dome Fuji area
Dome Fuji is the second highest summit area of the Antarctic ice sheet (excludingcoastal mountains).  A JARE inland traverse party found the location of the top in 1985
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Fig. 1.Location of Dome Fuji drilling site in East Dronning Maud Land, Antarctica. S: Shirase drainage basin,R: Ragnhild drainage basin. Contour lines are drawn every 100 m.Dome Fuji Station; Location: 77°19'01"S, 39°42'12"E; Altitude: 3810 m a.s.l.; Ice thickness: 3028±15 m.
(Ageta et al., 1989).The surface topography of the Dome Fuji area is very smooth and ﬂat as shown in Fig.2; surface elevations around 30 km from the dome summit are only 7 m to 30 m lower thanat the summit, with a mean of some 20 m at that distance.  The mean surface slope in the cir-cle of radius 30 km is estimated at about 1/1500.  A topographical map of the bedrock aroundDome Fuji is shown in Fig. 3.The location of Dome Fuji Station (drilling site) was decided on the basis of both sur-face and bedrock topographies.  The station is situated above relatively ﬂat bedrock about800 m in altitude.  The bedrock topography around the dome exhibits what appears to be asaddle point.  Bedrock hills higher than 1000 m a.s.l. are located to the southeast and north-west, and lowlands lower than 600 m a.s.l. are located to the west.The ice thickness at the Dome summit was measured by detailed radar echo soundingsto be 3028±15 m in 1996 (Watanabe et al., 1999).Atmospheric pressure, air temperature, wind direction, wind speed and global solarradiation were observed by the JARE wintering teams from 1995 to 1997 (JapanMeteorological Agency, 1996, 1997, 1998).  These data except global solar radiation areshown in Fig. 4.  From March 1995 to December 1997, an annual mean air temperature of–54.3°C at 1.5 m height was recorded.  The lowest recorded temperature for this period,–79.7°C, occurred on 14 May 1996 and 8 July 1997.  Annual mean atmospheric pressure was598.4 hPa, and annual mean wind speed at 10 m height was 5.8 m s-1.  The most frequentwind direction was northeasterly, but this accounted for only 15% of the total.
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Fig. 2.Surface topography of Dome Fuji area (S.Fujita, unpublished).• : Location of Dome Fuji Station. Numerals:Altitude, m a.s.l
Fig. 3.Bedrock topography of Dome Fuji area (S.Fujita, unpublished).• : Location of Dome Fuji Station. Numerals:Altitude, m a.s.l.
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Fig. 4.Meteorological data at Dome Fuji Station during 1995–98.  From top, daily mean atmospheric pressure(hPa), air temperature (°C), wind direction (1-16) and wind speed (m s–1).
3. Glaciological conditions of the Shirase drainage basin and Dome Fuji area
Dome Fuji is upstream of the Shirase drainage basin (Fig. 1) where glaciologicalresearch has been conducted by JARE inland traverse teams in the last 10 years.Glaciological data such as surface elevation, ice thickness, surface ice ﬂow velocity, snowaccumulation, snow temperature vs. depth proﬁle, surface snow stratigraphy, isotopic andchemical characteristics of surface snow cover have been observed along the traverse routefrom the coast to the Dome Fuji area.The spatial distribution of oxygen isotopic composition and major chemical constituentsof the snow cover along the traverse route from the coast to the Dome area are shown in theFolio series (National Institute of Polar Research, 2001).Observations of snow depositional characteristics at Dome Fuji have been conducted inthe period 1995–1997 as well.  The average surface mass balance (3.2 g cm-2 a-1) in this areawas estimated in 1989 using the 1963 tritium peak horizon (Kamiyama et al., 1989).  Anannual surface mass balance of 2.5±1.0 g cm-2 a-1 was found for the measurement period 25January 1995 to 31 January 1996.  More than 95% of the surface mass balance (2.4 g cm-2)was accounted for by the period February to mid-October.  The surface mass balance for therest of the year was reduced (0.1 g cm-2 for the period mid-October–January) due to strongsublimation during the summer months.  In total during 1995, the sublimation process sub-tracted ~6% (0.16 g cm-2 a-1) from the surface mass balance.  Measurements of the verticaldistribution of snow temperature through 1995 revealed an average 10 m-depth temperatureof –57.3°C.The seasonal distribution of δ18O in the surface snow at Dome Fuji is in the range –45‰to –75‰, increasing in summer and decreasing in winter, as shown in Fig. 5.  Judging fromFig. 5, concentrations of Na+ and Cl– in surface snow increased in spring-early summer.Those of MSA– and SO42– attained maximum values in spring and late autumn, thendecreased in late summer and winter.  NO3– showed increasing trends in early summer andlate winter.  Cl–/Na+ increased in summer.  Stratigraphic observations, density measurementsand snow sampling for chemical analyses were conducted in 2–3 m deep snow pits in eachyear during 1995–2000.  A distinct structure consisting of stratiﬁed layers composed of alter-nately hard packed and loose snow is observed in the deposited snow at Dome Fuji Station.The hard layers are composed of a mixture of compacted snow and hard-type depth hoar.The loose layer is skeleton-type depth hoar.  Vertical proﬁles of major chemical concentra-tions in the surface layers are shown in Fig. 6.  These proﬁles suggest the occurrence ofchemical migration processes in the surface snow layer.  Na+, Cl– and SO42– show no remark-able change with depth.  An abrupt decrease of NO3– and MSA– concentration is present near30 cm in depth from the surface.
4. In-situ procedure
The in-situ core analyses consist of electrical conductivity measurements (ECM), strati-graphic observations and bulk density measurements were carried out.  ECMs include bothDC and AC measurements.  Stratigraphic observations include careful examination of tephralayers, cloudy bands and air bubbles/clathrate hydrates.
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Fig. 5.Seasonal variation of oxygenisotope composition, major chemicalconcentrations (Cl–, Na+, NO3–, SO42–,MSA–) and Cl–/Na+ at Dome FujiStation during 1995–98.  Daily meanair temperature is shown at the top ofthe ﬁgure.
After ice core retrieval, the cores were ﬁrst stored in a storage trench for 1 to 4 months.Then they were processed.  In the processing line, ﬁrst the core sections were logged and bulkdensity measurements were made.  Then the cores were cut parallel to the core axis into partsof 60% and 40%.  The cut surfaces of the 60% parts were used for AC-, DC-ECM, and strati-graphic observations.  At the end of the core processing line, cores were ﬁnally cut into threepieces along the core axis: 60% (A core); 25% (B core) and 15% (C core) (Fig. 7), and cut atevery 50 cm for packing.  Room temperature was normally kept at around –20°C for theECM measurements.Twenty-ﬁve tephra layers were observed in the core down to 2503 m (Fujii et al., 1999).Two of these layers were found between 500 m and 600 m, and the remaining 23 were locat-ed below 1000 m, down to 2503 m.  The layer thickness is in the range from 1 to 22 mm.The cores were brittle at depths between some 500 m to 840 m.  The starting depth ofthe brittle zone was roughly the same as the depth at which the ﬁrst cloudy bands andclathrate hydrate crystals appeared.  More than 700 distinct cloudy bands were found as wellas many ambiguous layers.  Most of the layers were located at three depth ranges, around 550 m, 1000 m and 2000 m and visible layer were rare at other depth ranges.  Visible air bub-bles have not been observed at depths below about 1100 m.
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Fig. 6.Vertical proﬁle of major chemical concentrations (Cl–, SO42–, Na+, NO3– and MSA–) in the surface layerat Dome Fuji Station on December 26, 1997. Snow layer from the surface to 2.5-m deep contains about25 annual layers.
5. Oxygen isotope analyses
5.1. Oxygen measurementsThe stable isotope composition of water (d18O and dD) is the most important element ofthe ice core study.  The isotope composition is a function of the condensation temperature ofvapor in the atmosphere, and the averaged d 18O of the surface snow cover can be indicated interms of the annual mean temperature which is approximately equal to the 10 m-depth snowtemperature.Systematic surface glaciological research has revealed a relationship between 10 m-depth snow temperature (T; °C), and d18O (denoted by d ‰) value.  This relation isdescribed as follows (Satow et al., 1999).
d = 0.852 ◊ (T + 57.3) – 56.7.
The core dating (Watanabe et al., 2003) is estimated using a ﬂow model, whichdescribes the thinning rate of the annual layer thickness.  The annual layer thickness at thesurface (accumulation rate) is estimated from d 18O by an empirical equation using the presentrelationship between the accumulation rate (l 0; cm of ice equivalent a–1) and d 18O from theDome Fuji area higher than 3200 m a.s.l.:
l 0 = 3.88 exp (0.146 (d + 55) ).
To obtain a primary working time scale for the Dome Fuji core, continuous oxygen iso-tope measurements have been made on 25 or 50 cm-long samples (so called half or full bagsamples) over the entire core depth.  The measurements were performed on a Mat Delta Emass-spectrometer and the 18O/16O ratio obtained from each sample have been converted tod 18O, the relative deviation from that in standard mean ocean water.  The total number ofsamples analyzed is about 8000.After establishing an age-depth relation, 50-year averages of d 18O data were calculatedover the whole depth of the Dome Fuji core.
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Fig. 7.Core cutting plan and item of core analyses.A core (60%): Preservation part for future analyses; Analysis ofatmospheric components.B core (25%): Non destructive analyses; Stratigraphic analyses,physical properties, mechanical properties.C core (15%): Melting and consumption analysis; Stable isotopeanalyses, chemical analyses, micro-particle analy-ses.
5.2. Oxygen isotope proﬁleThe oxygen isotope proﬁle from the surface to 110 m-depth was measured using a ﬁrncore drilled by shallow drilling.  The measurement procedure was different from that used forthe ice core: surface contamination was scrapped off the ﬁrn surface.The results of the analyses are shown in Figs. 8 and 9, as proﬁles from the surface to 10m-depth and a proﬁle from the surface to 110 m-depth, respectively.  The surface to 10 m-depth d proﬁle is composed of data obtained during 1993–1999 campaigns.  In theupper part of the 1993 shallow core, the d values cover the range –62~–45‰ with a tenden-cy toward to higher d near the surface (warmer temperature).  To examine this tendency,closer sampling from the shallow cores and pit walls were performed near the station.  Figure8 shows that the surface proﬁle obtained from the 1993 shallow core can be said to supportthis tendency.  Also Fig. 8 indicates that the scattered d distribution at the near surface is con-verging with depth due to depth hoar process caused by the intensive temperature gradientand mechanical packing in the surface snow cover.Figure 9 shows d 18O scattering in range of –58~–50‰.  The thick line in Fig. 9 is theaverage value over 50 years with a mean of the value of –54.9‰ and this value has beenapplied as the present mean value of the Dome Fuji surface snow.The Dome Fuji deep ice core record of oxygen isotopes from the surface to the depth of2500 m is shown in Fig. 10.  This ﬁgure is a combination of the 50-year d 18O averages and aproﬁle of the 1000-year running means (see Fig. 11).This proﬁle clearly shows three glacial interglacial cycles in a similar pattern to the
General tendencies of Dome Fuji deep ice core9
Fig. 8.Vertical proﬁle of oxygen isotope com-position from the surface to 10 m-depth (about110 year before accumulation) at Dome FujiStation.  0 m in depth means the snow surfacein December 1993.  Four sampling pointswere settled in a range of 200 m.
Vostok dD proﬁle.  Petit et al. (1999) noted that all four climate cycles show the same “saw-tooth” sequence of a warm interglacial (Marine Isotope Stage: MIS:11, 3, 9.3, 7.5 and 5.5),followed by increasingly colder interstadial events, ending with a rapid return toward thenext interglacial.  Also the Dome Fuji d 18O proﬁle exhibits similar features.
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Fig. 9.Proﬁles of oxygen isotope compositionof Dome Fuji shallow ice core from the sur-face to 110 m in depth.  Solid circles mean thedata of 10–20 cm long samples.  The solid linemeans the 50-year average value.
Fig. 10. Proﬁle of oxygen isotope composition of Dome Fuji deep ice core from surface to 2503 m depth. Red thinline is 50-year averages. Black solid thin line means the 1000-year running mean value.
The temperature difference between glacial minima and inter-glacial maxima is 6–8°Cusing the relation between annual air temperature and average d18O in surface snow cover.The maximum temperatures in the inter-glacial phases are different in each cycle.
6. Deuterium analysis
6.1. Deuterium measurementThe sampling intervals are about 2 m from the snow surface to 400 m depth (the aver-age time resolution is about 70 years), about 3 m to 2000 m depth (300 years resolution), andabout 1 m to 2503 m-depth (300 years resolution).In order to obtain the Dome Fuji d-excess record, dD measurement has been performed.Hydrogen isotope ratios of ice core samples are determined by the isotope equilibriummethod at Tokyo Institute of Technology.  Equilibration time is more than one hour withthree platinum catalyst beads (Hokko beads, Shoko Co., Ltd.).  The d-excess value is signiﬁ-cantly altered by the subtle dD change.  Two reference waters has been used as working stan-dards with values similar to the internationally accepted reference (VSMOW and SLAP), andresults were corrected to accepted values by using these waters.In order to estimate the long term standard uncertainty of the dD measurements in thelaboratory, a laboratory standard (distilled tap water with dD=–62.3‰) was constantly mea-sured.  The standard deviation (1s, n=330) from results of the repeated analyses of the labo-ratory water standard over a year is ±0.43‰.
6.2. Deuterium excess recordThe deuterium excess (d-excess) that is deﬁned as d-excess=dD–8d 18O (Dansgaard,1964) indicates conditions of evaporation from the ocean surface.  This deﬁnition is derivedfrom a global scale linear relationship between deuterium and oxygen-18 composition ofwater (expressed as “dD=8d 18O+10”, Craig, 1961).  Although the global average d-excess isabout 10, the d-excess of individual precipitation value shows signiﬁcant variations.  Thevariations of d-excess of each precipitation value are mainly caused by changes in evapora-tion conditions such as SST (sea surface temperature), humidity, and wind speed above thevapor source, ocean surface (Merlivat and Jouzel, 1979).  Therefore, a d-excess record recov-ered from an ice core potentially has unique information on the sea surface condition of thewater vapor source areas.Figure 11 shows the Dome Fuji ice core records of dD and d-excess with the d 18O pro-ﬁle.  The dD values of the Dome Fuji core range from –390‰ to –470‰.  Although the d-excess record oscillates, most of the record ranges from 8‰ to 16‰.  The δD and d-excessrecords are clearly distinct in the short-period oscillation, but the δD record is smoother.  Thismay partly be attributed to the larger analytical error of the d-excess.The d-excess record shows three periodic glacial-interglacial changes, which differfrom the dD and d 18O records.  For instance, d-excess value is high (from 13 to 16) duringthe ﬁrst half of the last glacial period (from about 110 kyr BP to 70 kyr BP), and low (from10 to 14) during the latter half of the period (from about 70 kyr BP to 20 kyr BP).  A similar d-excess trend has been observed in the Vostok ice core (Vimeux et al., 2001), and detailedcomparison of the d-excess record of Dome Fuji and Vostok will provide additional infor-mation about changes in the origin of precipitation (Watanabe et al., 2003)
General tendencies of Dome Fuji deep ice core11
7. Chemical analyses
7.1. Sample preparation and data processingBasic analyses of major chemical species were carried out using 7–10 cm ice samplescut out of the 50 cm-long “bag samples” spaced from 0.5 to 2.5 m.  Then data with 200-yearresolution were established by the depth-age relationship for the entire depth of the DomeFuji ice core.  The total number of samples analyzed was about 3550.  For comparison of thechemical data to the d 18O data, both data set were transformed to the same time-scale.The 7–10 cm long chemical samples were prepared in a cold room.  Three mm of thesurface part was scraped off to remove contamination by a ceramic knife in a clean-bench ina cold laboratory.  The ice samples were stored in a plastic bag, and just before the meltingand measurements they are rinsed with ultra-pure water (with an electrical resistance higherthan 18.3 MΩ).The ﬁrn samples were stored in a Teﬂon bottle and melted just before the measurementsas reported by Watanabe et al. (1997).The chemical analysis of the melted ice sample was done by ion-chromatograph DionexDX-500 (isocratic system for cations and gradient system for anions).The measured ions were Na+, NH4+, K+, Mg2+, Ca2+, F–, Cl–, SO42–, NO2–, NO3–, HCOO–,CH3COO–, C2O42–, PO43– and CH3SO3–.The vertical proﬁles of major chemical constituents are shown in Fig. 12.  Remarkablyhigh values were checked for possible contamination and/or improper sample treatment, andeither excluded from the general plot, or measured again if possible.
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Fig. 11. Stable isotope composition (d 18O and dD) and d-excess proﬁle of Dome Fuji core.  The d 18O proﬁleshows the 1000-year running mean.  Intervals of dD and d-excess are described in the text.
7.2. Distribution and behavior of chemical constituents7.2.1. Correlations of the major chemical constituentsCorrelation analysis among eleven anions as well as non-sea-salt (nss) SO42– and ﬁvecations was carried out.  The correlation matrix is given in Table 1.Correlation coefficients higher than 0.8 are found in 8 sets, and values higher than 0.7 inanother 11 sets.  Among the major chemical constituents of sea-salt related species (Cl–,
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Fig. 12. Proﬁles of the concentration of d 18O and major chemical species (Cl– Ca2+, MSA–, nssSO42– and NO3–) inthe Dome Fuji core. Data intervals are 200 years.
SO42–, Na+, Mg2+, Ca2+, K+), higher correlations are found in the following 6 sets: Na+-Cl–
(0.90), Na+-SO42– (0.83), Na+-Mg2+ (0.89), Cl–-Ca2+ (0.86), Cl–-Mg2+ (0.82), and Mg2+-SO42-
(0.81).  These high coefficients indicate a signiﬁcant contribution of the sea-salt to glacierice, and at the same time, suggest an important effect of non-sea-salt deposition.  Amongthese sea salt components, SO42– in Antarctic snow and ice is mainly of biogenic sulfur ori-gin and a part of the Mg2+, Ca2+, and K+ is of terrestrial origin.  In this report, the sea-saltderived part is temporarily evaluated referring to Na+, assuming all Na+ is of sea-salt origin.Legrand and Delmas (1988) report that Na+ partly derives from terrestrial dust (Legrandand Delmas, 1988).The extent of the non-sea-salt contribution can be evaluated from Fig. 13.  The biggerthe gap between clusters of plotted points and the sea-salt ratio line, the higher the contribu-
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Table 1.Correlation matrix of the major chemical concentrations of the Dome Fuji deep ice core.
Fig. 13. Relation between Na+ and some chemical species (SO42–, Cl–, Mg2+, Ca2+).  Solid lines are relations insea water.
tion from other sources.  The contribution from SO42– is most evident, signiﬁcant parts ofMg2+ and Ca2+ are of non-sea-salt origin and Cl– shows complex behavior against Na+.7.2.2. Relation between chemical concentrations and oxygen isotopic compositionProﬁles of major chemical constituents (Na+, Cl–, Ca2+, MSA, nssSO42– and NO3–) alongthe Dome Fuji core are shown in Fig. 12.  These concentration proﬁles conﬁrm that deposi-tion of chemical constituents of marine and terrestrial origin are higher during cold climaticconditions than during the warm interglacials.  The higher deposition is probably linked tohigher meridional atmospheric circulation, more extensive arid areas and greater exposure ofcontinental shelves under cold climate condition (Legrand et al., 1988), which is exhibited aslow d 18O in the d-records.In the present paper, chemical concentrations are plotted against d 18O value to disclosethe direct relationship between distribution of chemical constituents and atmospheric tem-perature.  The relation between major chemical constituents and oxygen isotope compositioncan be classiﬁed into three groups (1)–(3), as seen in Fig. 14.(1) Na+, Mg2+ and Cl– groupThe data plot of Na+, like that of Mg2+ (not shown), converges to a concaved curve asseen in Fig. 14a and the concentration increases with decreasing d 18O value, and thus with
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Fig. 14.Relation between oxygen isotopecomposition and chemical elements (Na+,Cl–, NO3– and MSA–).  They are divided intothree patterns.
decreasing temperature.  This can be attributed to enhanced transportation by strengthenedwind during the glacial cold period.  The same plot of Cl–, given in Fig. 14b, shows the sametrend, but with some complex behavior, also Cl– increases with decreasing d 18O as Na+.On the other hand, nssCl– keeps constant low level in periods of higher δ18O anddecreases to negative values in periods of lower d 18O, with a minimum at about –57‰ (asseen in Fig. 15a).  The presence of negative nssCl– is also reported in the Vostok core and wasascribed to the formation of HCl gas from sea salt particles by reaction with H2SO42–
(Legrand et al., 1988).Further information is obtained from the Cl–/Na+ ratio plotted in Fig. 15b.  The Cl–/Na+
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Fig. 15a.   Relation between oxygen isotope composition (d 18O), Cl– and nssCl–.
Fig. 15b.   Relation between oxygen isotope composition (d 18O), Cl– and Cl–/Na+.
ratio increases with increasing d 18O at range higher than –57‰ and indicates the formationof HCl from sea salt particles.  In the lower range, on the contrary, the Cl–/Na+ ratio decreas-es to a minimum value at 1.0 or less and then increases to about 1.2, which is the Cl–/Na+ ratioin sea water.  This points at a higher transportation and deposition rate of sea salt particlesdue to high wind speed without reaction with nssSO42– (Legrand et al., 1988).According to the above considerations, the Cl– concentration is mainly controlled by achemical reaction process which is more active at warmer climate condition, whereas Cl– atcolder climate condition is controlled by physical processes with a switching point for thetwo processes around a d 18O value of –57‰.(2) NO3–, SO42– and Ca2+ groupThe plot of concentration of these constituents against d 18O can be treated as a combi-nation of two different curves: the upper one, which leads to higher concentration withincreasing temperature, and the lower one, which leads to progressively higher concentrationtoward the coldest climate.  The latter is the same process as mentioned in (1); both combineat a d 18O value about –57‰.  The case of NO3– is a typical one as shown in Fig. 14c.  Theincrease in NO3– concentration with increasing temperature may due to higher activity oforganisms on the earth surface, higher solar radiation and other causes.  SO42– and Ca2+ showsimilar behavior to NO3– but without the distinctive increase at higher temperature.(3) MSA–, NO2–, NH4+ and F– groupThese chemical constituents show broadly scattered proﬁle patterns against d 18O asshown in Figs. 14d.  Low correlation coefficients are found.  Most elements belonging to thisgroup are derived through processes including gaseous reactions during transportation to theAntarctic inland region from their source area.7.2.3. The relation between micro-particles and oxygen isotope compositionThe numbers and volume concentrations of micro-particles are measured by setting themeasurement range 10 to 0.52–5.04 mm.  The number concentration of micro-particles inDome Fuji core increases in the coldest phase during the glacial period as described inWatanabe et al. (1999).  A detailed discussion of the measurement and the proﬁle are pre-sented by Fujii et al. (2003).
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Fig. 16a. Relation between oxygen isotope composition (d 18O) and volume concentration of micro-particlesranges.
The relation between the total volume concentration and d 18O is shown in Fig. 16a.  Asseen in this ﬁgure, the plot pattern resembles the pattern of most chemical constituents (1) inFig. 14.  The distribution pattern is a combination of a warmer climate pattern and a colderclimate pattern.The volume number of three particle size fractions (0.52–0.63, 1.00–1.26, and4.00–5.05 µm) plotted versus d18O is shown in Fig. 16b.  The sharp increase in particle vol-ume in the coldest period is most evident with the largest size fraction and clearly indicatesincreased exposed area of continental shelf due to sea surface lowering and transportation ofparticles by high wind speed.  This conﬁrms that the process, which is active in a colder cli-mate and induces a high load of impurity on the ice sheet, is supported by enhanced trans-portation of terrestrial aerosols.
8. Climatic and environmental division during the glacial–interglacial cycles
8.1. Climatic division of the glacial-interglacial cycleIn the previous section we examined the characteristics of climatic and environmentalvariation based on the proﬁles of continuous 50-year bulk averaged oxygen isotopic compo-sition and major chemical concentration in 200-year resolution.The entrapped air component in the core has been analyzed by a Tohoku Universitygroup, and the results are reported by Kawamura (2000) and Kawamura et al. (2003).The 320 kyr d 18O variation of the Dome Fuji deep ice core reveals three glacial-inter-glacial cycles.  These cycles show similarities in general tendency and also differences ifexamined in detail.  For detailed comparison of each climatic stage and its characteristics, cli-mate dividing is essential.Lorius et al. (1985) designated the successive warm and cold stages as A–H for the 160kyr Vostok core.  Starting from the top, the warm periods are designate by A, C, E and G andthe cold periods by B, D, F and H.  In their designation, stage A corresponds to the presentHolocene period and Stage G is the last interglacial and stage H is the last part of the previ-ous glacial.  Though the deﬁnition of the stage boundary is not clear, it exhibit the interme-
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Fig. 16b. Relation between oxygen isotope composition (d 18O) and volume concentration of micro-particles clas-siﬁed into three particle sizes.
diate between the highest and lowest temperatures in adjacent stages.To do our climate dividing, we deﬁne the stage boundaries by comparison with theVostok δD record.  In our application, Stage A corresponds to the interglacial stage and themark B-F corresponds to stadial and interstadial stages during a glacial period.Petit et al. (1999) examined all glacial terminations and commencements using the dataset of the past 420 kyr from Vostok core.  The proﬁles of dDice, δ18Oatm, CO2 ,CH4 and dusthave been analyzed.  According to their ﬁgure, which indicated time series of the elementsduring glacial terminations, the terminations of the past four glacial periods coincide withlarge decreases in dust concentration including a case of much earlier occurrence.The climate events during the transition phases in the Dome Fuji core exhibit variationsof d 18Oice, d 18Oair and CH4 as shown in Fig. 17.  Also the variations of major chemical con-centrations, Na+, Ca2+ and SO42–, as environmental signals, are shown in the ﬁgure.In these glacial–interglacial cycles, similar trends of variation are found and amongthem remarkable stadial and interstadial stages show distinctive climate events.  It is obvious
General tendencies of Dome Fuji deep ice core19
Fig. 17. Variation of climatic signals in the transition phase (Termination I–III). d 18Oice, d 18Oatm, CH4, Na+ Ca2+
and SO42– are shown in this ﬁgure.
from these ﬁgures, that concentration of Ca2+, mainly from originated mainly from terrestri-al areas, d 18Oice and SO42– reached minimum levels about the same time.  The minimum lev-els of Ca2+ and SO42– indicate the completion of intense aerosol transportation from marineand land through highly developed air circulation during the glacial period.  As to theAntarctic ice sheet, the completion of intense general circulation means the termination of aglacial period.Using the termination timing estimated from comparison of the climatic and environ-mental signals as indicated in Fig. 17, a tentative climatic dividing of the glacial-interglacialcycles is proposed.  Scheme of this dividing is indicated in Fig. 18a.  In this ﬁgure, the cli-mate division is designated by A–G; A and G are interglacial periods so that G is A' and G'is A".  Warm periods (interstadial) are A, C and E, and cold periods (stadial) are the same asin the usage of Lorius et al. (1985).  Marine isotope stage numbers in this ﬁgure are tentative.Average concentration value of the major chemical components in each stadial-intersta-dial stage are indicated as the line graph in Fig. 18b.
8.2. Comparison of environmental characteristics between the glacial-interglacial cyclesThe Antarctic ice sheet preserves signals relating to global paleo-environmental and cli-matic changes in form of emission of substances and gases from various sources during thelast some hundred thousand years.  Those substances and gases were transported to theAntarctic ice sheet through general circulation of the troposphere and the stratosphere.Substances originate from the ocean surface and marine bioactivities are transported tothe Antarctic ice sheets through the lower troposphere by cyclonic disturbances.  Dust fromarid regions and exposed continental shelves is the most probable source for micro-particles
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Fig. 18a.  Temporal climatic division in the three glacial-interglacial cycle.  Notations are described in this text.
in polar core.  The concentration decreases with distance from the coast.Transportation of trace gases and gas derived aerosols differs much from that of partic-ulate matters; they are spread to the upper troposphere and the stratosphere.  Subsidence ofair masses of the upper troposphere and stratosphere is an important process at the inlandplateau of the Antarctic ice sheet for gas derived aerosols and stratospheric substances suchas nitrate and tritium (Kamiyama et al., 1989).The isotopic composition, major chemical concentrations and entrapped air constituentsin the Dome Fuji deep ice core are examined to characterize variations during glacial andinterglacial cycles.  In particular, similarities and differences in the variation during stadialand interstadial stages are compared in detail.As results from these studies, some of interesting phenomena are found and described;(1) In general, a good correlation is found between concentrations of atmospheric gases,ions and d 18O (temperature proxy).  Typical examples are Na+ and Cl– (may be SO42– also) asgood indicators of wind velocity over the sea surface.  In the ﬁrst cold phase (F in a glacialclimatic stage; stadial), increasing of Na+ concentration occurred clearly, like in other fol-
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Fig. 18b. Variation in the averaged concentration of some chemical species in the stadial-interstadial stages.(a) Cl–, Na+ and SO42–, (b) NO3–, Ca2+ and MSA–.
lowing cold stage (stadials), but the concentration increase of aerosol materials such as Ca2+,Mg2+ and NO3– did not occur, as seen in Fig. 18b.  The reason is not completely clear but itcan be imagined that the source areas for these chemical materials are not yet completelyactive at this early stage of the ice sheet formation in the glacial period, although the trans-portation process are operating(2) The two peaks pattern of NO3– in two glacial period is predominant but it is not seen inthe oldest glacial period represented in the records (Figs. 18b and 19).  Is this missing peakin the oldest glacial period, due to some climatic or orbital reason or the occurrence of miss-
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Fig. 19. Occurrence characteristics of concentration proﬁle of NO3– during the three glacial-interglacial cycles.Concentrations of NO3– are increased in climate stages B and D marked by arrows.  d 18O is also plottedin this ﬁgure.
Fig. 20.  Mg2+–d 18O relation in three glacial-interglacial cycles.
ing layer (long term hiatus) due to lack of sedimentation or decrease of accumulation undera peculiar climatic condition?  According to the relation between NO3– and d18O, the patternindicate that for the NO3–, SO42–, Ca2+ group, as described before, the NO3– concentrationincreased intensively at a δ18O value of –57‰ or lower.  This means that insufficient coolingmay be an appropriate reason.(3) Characteristics of the relation between the chemical concentrations and d 18O in each“glacial period” of Mg2+ and other constituents are shown in Fig. 20.  A tendency towardhigher concentration in the oldest glacial period is found.  It is not clear if this tendencydepends on climatic characteristics or/and on physical processes under glacial dynamic con-dition.  This is an important problem for future study.
Acknowledgments
This work is a contribution of the Dome Fuji deep drilling project.  We thank all of thecolleagues of the glaciological program in the Japanese Antarctic Research Expedition.  Wealso extend our thanks to Mrs. T. Kobayashi, Mrs. Y. Nagamoto, Mrs. M. Naka and Miss M.Nakata for their efforts on the core sample measurements.  This work was supported by aGrant-in-Aid for Science Research (No. 10204101) from the Ministry of Education, Culture,Sports, Science and Technology, Japan.
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(Received December 12, 2002; Revised manuscript accepted February 3, 2003)
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