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Physicochemical properties of bottom ice from Dome Fuji, inland East Antarctica
Author(s) -
Ohno Hiroshi,
Iizuka Yoshinori,
Hori Akira,
Miyamoto Atsushi,
Hirabayashi Motohiro,
Miyake Takayuki,
Kuramoto Takayuki,
Fujita Shuji,
Segawa Takahiro,
Uemura Ryu,
Sakurai Toshimitsu,
Suzuki Toshitaka,
Motoyama Hideaki
Publication year - 2016
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1002/2015jf003777
Subject(s) - ice core , geology , ice shelf , bottom water , ice sheet , sea ice , mineralogy , oceanography , geochemistry , chemistry , cryosphere
The deepest ice in inland Antarctica is expected to preserve the oldest ice records and to potentially contain microorganisms. However, little is known about the physicochemical conditions in the deepest part of ice sheets. This study investigates the physicochemical properties of the bottom section (3000–3035 m) of the Dome Fuji inland ice core, which is located immediately above unfrozen bedrock. The ubiquitous presence of air hydrates and the water isotope composition of ice comparable to the upper main ice core show that the bottom ice is meteoric. However, ion concentrations exhibit abnormal drops at the greatest depths (approximately below 3033 m). In the same depth range, microscopic investigations reveal that considerable relocation of air hydrates and microinclusions (water‐soluble impurities) occurs, suggesting that the observed reduction in ion concentration results from the segregation of inclusions to ice grain boundaries and the subsequent discharge of chemicals through liquid‐water veins. Principal component analysis of ion data supports the meteoric‐ice hypothesis, suggesting that the bottom ice had similar original chemistry through all depths. Statistical analyses of chemical data suggest that the water‐soluble impurities attached to hydrates or dust (water‐insoluble), the ice‐soluble chemical species (such as chlorine), and solid particles are less affected by this chemical displacement phenomenon. It is also noteworthy that in the bottom ice, impurity chemicals, which are limiting nutrients for ice‐dwelling microorganisms, are concentrated largely to ice‐hydrate interfaces, where oxygen, another vital matter for aerobic microorganisms, is also enriched.