Kokichi Kamiyama

Evidence for the loss of snow‐deposited MSA to the interstitial gaseous phase in central Antarctic firn

We have examined several MSA (methanesulfonic acid) records from the upper 200 m of the Antarcticice sheet and in particular the new Dome F profile. At all the four sites studied, concentration profilesexhibit similar patterns as a function of depth. They suggest that snow metamorphism and solid phasemigration are responsible for a marked release of gaseous MSA to interstitial firn air as well as probablyto the free atmosphere, in particular at extremely low accumulation sites. Snow acidity can also modifyMSA concentration. It is proposed that, below the upper few metres where the communication withthe free atmosphere is possible, gaseous MSA may remain in the firn layers and be entrapped later inair bubbles at pore close-off, i.e. when firn is transformed into ice. Chemical measurements on the firncore do not take into account the MSA released to the gaseous phase, but this fraction is measurable inice samples. In spite of these alterations occurring in the firn layers, relative changes of the atmosphericMSA concentration in the past are probably still there deep within the Antarctic ice sheet. However, for glacial periods, different processes have to be considered in relation to modified aerosol properties.

Ratios of Mg2+/Na+ in snowpack and an ice core at Austfonna ice cap, Svalbard, as an indicator of seasonal melting

Snowpack and ice-core samples were collected from the dome of Austfonna ice cap, Svalbard, in the spring of both 1998 and 1999. The samples were analyzed for anions, cations, pH, liquid electrical conductivity and oxygen isotopes. Concentrations of chemical components in snowpack with a history of melting were much lower than those in unmelted snowpack. There was a clear difference between Mg 2+ /Na + ratios previously in melted snowpack (0.011 ± 0.02) and in unmelted snowpack (0.11 ± 0.02). We propose that the Mg 2+ /Na + ratio can be used as an indicator of whether or not firn or bubbly ice in the Austfonna ice core has experienced melt percolation. The Mg 2+ /Na + ratio indicates that firn or bubbly ice prior to AD 1920 was much less affected by melt percolation than firn or bubbly ice formed after 1920.

Ice cores from Arctic sub-polar glaciers: chronology and post-depositional processes deduced from radioactivity measurements

The response of Arctic ice masses to climate change is studied using ice cores containing information on past climatic and environmental features. Interpretation of this information requires accurate chronological data. Absolute dating of ice cores from sub-polar Arctic glaciers is possible using well-known radioactive layers deposited by atmospheric nuclear tests (maximum fallout in 1963) and the Chernobyl accident (1986). Analysis of several isotopes (H-3, Cs-137) shows that H-3 provides the most accurate dating of the 1963 maximum as indicated also in comparison with results from total-beta measurements (Sr-90 and Cs-137). Mean annual net mass balances are derived from the dated ice cores from 1963 up to the date of the drillings. The Cs-137 and H-3 deposited by nuclear tests, after decay correction, are used to define a melt index for all 13 ice cores studied. The relative strength of melting and percolation post-depositional processes is studied on the basis of these Cs-137 and H-3 deposits.

Distribution of sea salt components in snow cover along the traverse route from the coast to Dome Fuji station 1000 km inland at east Dronning Maud Land, Antarctica

Abstract We show and discuss the results of the regional distribution of Cl− and Na+ concentrations in snow cover along the study route from the coast to Dome Fuji station, 1000 km inland, in east Dronning Maud Land, Antarctica. The concentrations of Cl− and Na+ at the coast exponentially decreased with distance from the coast up to 200 km inland. Between 200–1000 km inland, the concentrations of Na+ were nearly constant. On the other hand, the concentrations of Cl− increased with distance beyond 750 km inland. Furthermore, the contribution factors between Cl− and Na+ decreased and the Cl−/Na+ ratio and the nssCl−/Cl− ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl− other than sea salt exists in the inland plateau of Antarctica.

Distribution of hydrogen peroxide in surface snow over antarctic ice sheet

Abstract The concentration of hydrogen peroxide (H2O2) in surface snow samples obtained in East Queen Maud Land, Antarctica, from summer 1991 to late summer 1993, is discussed. Surface snow samples were obtained in various locations and seasons during five traverses with snow vehicles. Gradual distributions were observed, depending upon the season and the location. The concentration of H2O2 is higher in summer than in winter, and is also higher in the inland region at higher altitude than in the coastal region lower altitude. A sudden increase in early summer snow was observed, suggesting the sudden change in atmospheric environments, affecting the concentration of H2O2 in the snow. Snow chemistry will possibly make the atmospheric environment more clear for us in near future.

Lead-210 profile in firn layer over Antarctic ice sheet and its relation to the snow accumulation environment

Vertical distributions of 210Pb in surface firn were obtained at five locations in east Dronning Maud Land, Antarctica. The distributions obtained in the inland high-plateau region are well described by the theoretical radioactive decay curve. On the other hand, the distributions obtained in the katabatic wind region have significant fluctuations including intervals where higher activity is found below layers with lower activity. We examined the relationship between the fluctuation of the 210Pb profile and the temporal variation of the snow accumulation rate obtained by the snow stake method, and found a clear negative correlation between them. This result suggests that the fluctuation of the 210Pb profile in the firn layer is closely related to the environment in the ice sheet surface, i.e. the extent of erosion—redistribution of snow. The measurement of the 210Pb distribution in the ice sheet will be useful as an indicator of the surface stability in the Antarctic ice sheet.

Distribution of chemical constituents in superimposed ice from austre brøggerbreen, spitsbergen

10 m and 2.3 m ice cores were obtained on Austre Brøggerbreen, Spitsbergen in Svalbard (78°53′N, 11°56′E, 450 m a.s.l.) in September 1994 and in March 1995, respectively. Stratigraphy, bulk density, pH, electrical conductivity, and major ions were obtained from the core samples. The chemical effect of meltwater percolation through snow/ice is examined. Good correlation between Cl− and Na+ was obtained. The ratio of Cl− to Na+ was 1.14 which was nearly the same value as in bulk sea water. However, the variation of Cl−/Na+ shows that higher ratio occured in the bubble‐free ice. Furthermore the Cl− ions remain in higher concentration than SO 4 2− or Na+ ions.