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To better understand the surface properties of the Antarctic ice sheet, we measured the specific surface area (SSA) of surface snow during two round-trip traverses between a coastal base near Syowa Station, located 15 km inland from the nearest coast, and Dome Fuji, located 1066 km inland, in East Antarctica from November 2021 to January 2022. Using a handheld integrating sphere snow grain sizer (HISSGraS), which directly measures the snow surface without sampling, we collected 215 sets of SSA data, with each set comprising measurements from 10 surfaces along a 20 m transect. The measured SSA shows no elevation or temperature dependence between 15 and 500 km from the coast (elevation: 615–3000 m), with a mean and standard deviation of 25 ± 9 m 2 kg -1. Beyond this range, SSA increases toward the interior, reaching 45 ± 11 m 2 kg -1 between 800 and 1066 km from the coast (3600–3800 m). SSA shows significant variability depending on surface morphologies and meteorological events. For example, (i) glazed surfaces formed by an accumulation hiatus in katabatic wind areas show low SSA (19 ± 4 m 2 kg -1), decreasing the mean SSA and increasing SSA variability. (ii) Freshly deposited snow shows high SSA (60–110 m 2 kg -1), but the snow deposition is inhibited by snow drifting at wind speeds above 5 m s -1. Our analyses clarified that temperature-dependent snow metamorphism, snowfall frequency, and wind-driven inhibition of snow deposition play crucial roles in the spatial variation of surface snow SSA in the Antarctic inland. The extensive dataset will enable the validation of satellite-derived and model-simulated SSA variations across Antarctica. [ABSTRACT FROM AUTHOR]

To better understand the surface properties of the Antarctic ice sheet, we measured the specific surface area (SSA) of surface snow during two round-trip traverses between a coastal base near Syowa Station, located 15 km inland from the nearest coast, and Dome Fuji, located 1066 km inland, in East Antarctica from November 2021 to January 2022. Using a handheld integrating sphere snow grain sizer (HISSGraS), which directly measures snow surface without sampling, we collected 215 sets of SSA data, each set comprising measurements from 10 surfaces along a 20 m transect. The measured SSA shows no elevation or temperature dependence between 15 and 500 km from the coast (elevation: 615–3000 m), with a mean and standard deviation of 25 ± 9 m2 kg−1. Beyond this range, SSA increases toward the interior, reaching 45 ± 11 m2 kg−1 between 800 and 1066 km from the coast (3600–3800 m). SSA shows significant variability depend ing on surface morphologies and short-term meteorological events. For example, (i) glazed surfaces formed by an accumulation hiatus in katabatic wind areas show low SSA (19 ± 4 m2 kg−1), decreasing the mean SSA and increasing SSA variability. (ii) Freshly deposited snow shows high SSA (60–110 m2 kg−1), but the snow deposition is inhibited by snow drifting at wind speeds above 5 m s−1. Our analyses clarified that temperature-dependent snow metamorphism, snowfall frequency, and wind-driven inhibition of snow deposition play crucial roles in the spatial variation of surface snow SSA in the Antarctic inland. The extensive dataset will enable the validation of satellite-derived and model-simulated SSA variations across Antarctica. [ABSTRACT FROM AUTHOR]

To better understand the near-surface evolution of polar firn in low-accumulation areas (<30 mm w.e. yr -1), we investigated the physical properties – density, microstructural anisotropy of ice matrix and pore space, and specific surface area (SSA) – of six firn cores collected within 60 km of Dome Fuji, East Antarctica. The physical properties were measured at intervals of ≤0.02 m over the top 10 m of the cores. The main findings are (i) a lack of significant density increase in the top ∼4 m, (ii) lower mean density near the dome summit (∼330 kg m -3) than in the surrounding slope area (∼355 kg m -3) in the top 1 m, (iii) developments of a vertically elongated microstructure and its contrast between layers within the top ∼3 m, (iv) more pronounced vertical elongation at sites and periods with lower accumulation rates than those with higher accumulation rates, (v) a rapid decrease in SSA in the top ∼3 m, and (vi) lower SSA at lower-accumulation sites, but this latter trend is less pronounced than that of microstructural anisotropy. These observations can be explained by a combination of the initial physical properties on the surface set by wind conditions and the metamorphism driven by water vapor transport through the firn column under a strong vertical temperature gradient (temperature gradient metamorphism, TGM). The magnitude of TGM depends on the duration of firn layers under the temperature gradient, determined by the accumulation rate; longer exposure causes a more vertically elongated microstructure and lower SSA. Overall, we highlight the significant spatial variability in the near-surface physical properties over the scale of ∼100 km around Dome Fuji. These findings will help us better understand the densification over the whole firn column and the gas-trapping process in deep firn and possible difference in them between existing deep ice cores and the upcoming "Oldest-Ice" cores collected tens of kilometers apart. [ABSTRACT FROM AUTHOR]

To better understand the near‐surface evolution of polar firn in low accumulation areas (<30 mm w.e. yr−1), we investigated the physical properties: density, microstructural anisotropy of ice matrix and pore space, and specific surface area (SSA), of six firn cores collected within 60 km around Dome Fuji, East Antarctica. The physical properties were measured at the intervals of ≤0.02 m over the top 10 m of the cores. The main findings are: (i) lack of significant density increase in the top ~4 m, (ii) lower density near the dome summit (~330 kg m−3) than the surrounding slope area (~355 kg m−3), (iii) developments of vertically elongated microstructure and its contrast between layers within the top ~3 m, (iv) more pronounced vertical elongation at sites and periods with lower accumulation rates than those with higher accumulation rates, (v) rapid decrease in SSA in the top ~3 m, and (vi) lower SSA at lower accumulation sites, but this trend is less pronounced than that of microstructural anisotropy. These observations can be explained by the combination of the initial physical properties on the surface set by wind conditions and the metamorphism driven by water vapor transport through the firn column under a strong vertical temperature gradient (temperature gradient metamorphism, TGM). The magnitude of TGM depends on the duration of firn layers under temperature gradient, determined by accumulation rate; longer exposure causes a more vertically elongated microstructure and lower SSA. Overall, we highlight the significant spatial variability in the near-surface physical properties over the scale of ~100 km around Dome Fuji. These findings will help better understand the densification over the whole firn column and the gas trapping process in deep firn, and possible difference in them between existing deep ice cores and the upcoming "Oldest-Ice" cores collected tens of kilometers apart. [ABSTRACT FROM AUTHOR]

To investigate regional and temporal variations in the sources and atmospheric transport processes for mineral dust deposited on the Greenland Ice Sheet, we analysed the morphology and mineral composition of dust in an ice core from northeastern Greenland (East Greenland Ice-Core Project, EGRIP), representing the period from 1910 to 2013, using scanning electron microscopy and energy-dispersive X-ray spectroscopy, and compared the results with those previously obtained for an ice core from northwestern Greenland (SIGMA-D). The composition of the SIGMA-D ice-core dust, comprising mostly silicate minerals, varied on a multi-decadal timescale due to an increased contribution of minerals originating from local ice-free areas during recent warming periods. In contrast, for the EGRIP ice-core dust, also consisting mostly of silicate minerals, there was relatively low compositional variation among the samples, suggesting that the mineral sources have not changed dramatically over the past 100 years. The subtle variation in the EGRIP ice-core mineral composition is likely due to a minor contribution of local dust. The type of silicate minerals differed significantly between the two ice cores; micas and chlorite, which form in cold dry regions, were abundant in the EGRIP ice core, whereas kaolinite, which forms in warm humid regions, was abundant in the SIGMA-D ice core. This indicates that the EGRIP ice-core dust likely originated from different geological sources than those for the SIGMA-D dust. A back-trajectory analysis indicated that the ice-core dust was transported from Northern Eurasia and North America to the EGRIP site, and that the contribution from each source was likely smaller and larger, respectively, than those for the SIGMA-D ice core. Furthermore, the higher illite content in the EGRIP ice core suggests dust transportation from Asian deserts. Although the back-trajectory analysis suggests that most of the air mass that arrived at the EGRIP site came from the Greenland coast, the mineral grain size and composition results showed that the local dust contribution was likely small. [ABSTRACT FROM AUTHOR]

We reconstructed surface mass balance (SMB) around Dome Fuji, Antarctica, over the last 5000 years using the data from 15 shallow ice cores and seven snow pits. The depth–age relationships for the ice cores were determined by synchronizing them with a layer-counted ice core from West Antarctica (WAIS Divide ice core) using volcanic signals. The reconstructed SMB records for the last 4000 years show spatial patterns that may be affected by their locations relative to the ice divides around Dome Fuji, proximity to the ocean, and wind direction. The SMB records from the individual ice cores and snow pits were stacked to reconstruct the SMB history in the Dome Fuji area. The stacked record exhibits a long-term decreasing trend at -0.037±0.005 kg m -2 per century over the last 5000 years in the preindustrial period. The decreasing trend may be the result of long-term surface cooling over East Antarctica and the Southern Ocean and sea ice expansion in the water vapor source areas. The multidecadal to centennial variations of the Dome Fuji SMB after detrending the record shows four distinct periods during the last millennium: a mostly negative period before 1300 CE, a slightly positive period from 1300 to 1450 CE, a slightly negative period from 1450 to 1850 CE with a weak maximum around 1600 CE, and a strong increase after 1850 CE. These variations are consistent with those of previously reconstructed SMB records in the East Antarctic plateau. The low accumulation rate periods tend to coincide with the combination of strong volcanic forcings and solar minima for the last 1000 years, but the correspondence is not clear for the older periods, possibly because of the lack of coincidence of volcanic and solar forcings or the deterioration of the SMB record due to a smaller number of stacked cores. [ABSTRACT FROM AUTHOR]

The retrieval of continuous ice core records of more than 1 Myr is an important challenge in palaeo-climatology. For identifying suitable sites for drilling such ice, knowledge of the subglacial topography and englacial layering is crucial. For this purpose, extensive ground-based ice radar surveys were carried out over Dome Fuji in the East Antarctic plateau during the 2017/18 and 2018/19 austral summers by the Japanese Antarctic Research Expedition, on the basis of ground-based radar surveys conducted over the previous ∼ 30 years. High-gain Yagi antennae were used to improve the antenna beam directivity, thereby significantly decreasing hyperbolic features of unfocused along-track diffraction hyperbolae in the echoes from mountainous ice–bedrock interfaces. We combined the new ice thickness data with the previous ground-based data, recorded since the 1980s, to generate an accurate high-spatial-resolution (up to 0.5 km between survey lines) ice thickness map. This map revealed a complex landscape composed of networks of subglacial valleys and highlands. Based on the new map, we examined the roughness of the ice–bed interface, the bed surface slope, the driving stress of ice and the subglacial hydrological condition. These new products and analyses set substantial constraints on identifying possible locations for new drilling. In addition, our map was compared with a few bed maps compiled by earlier independent efforts based on airborne radar data to examine the difference in features between datasets. Our analysis suggests that widely available bed topography products should be validated with in situ observations where possible. [ABSTRACT FROM AUTHOR]

Tiny samples of ancient atmosphere in air bubbles within ice cores contain argon (Ar), which can be used to reconstruct past temperature changes. At a sufficient depth, the air bubbles are compressed by the overburden pressure under low temperature and transform into air-hydrate crystals. While the oxygen (O2) and nitrogen (N2) molecules have indeed been identified in the air-hydrate crystals with Raman spectroscopy, direct observational knowledge of the distribution of Ar at depth within ice sheet and its enclathration has been lacking. In this study, we applied scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) to five air-hydrate crystals in the Greenland NEEM ice core, finding them to contain Ar and N. Given that Ar cannot be detected by Raman spectroscopy, the method commonly used for O2 and N2, the SEM-EDS measurement method may become increasingly useful for measuring inert gases in deep ice cores. [ABSTRACT FROM AUTHOR]

The long-term refrigerated storage of melted snow and/or ice samples for analyses of insoluble microparticles (hereafter, microparticles) may be limited by increases in the biological particle concentration caused by microbial growth after ~1–2 weeks. In this study, we examined an ultraviolet (UV) disinfection method for the storage of melted snow and/or ice samples and determined the effects of this method on microparticles. Surface snow obtained from Glacier No. 31 in the Suntar-Khayata Range, eastern Siberia, Russia was divided into two portions for UV treatment and untreated controls. Microparticle concentrations and size distributions (in the range of 0.52–12.0 μm) in the samples were measured using a Coulter counter. Whereas the microparticle concentration in untreated samples increased, no obvious increase was observed over 53 d in the samples subjected to UV treatment. Microbial growth was detected in only untreated samples using a viable particle counter. In addition, the original microparticle concentrations and size distributions were unaffected by UV treatment. Our results demonstrated that the microparticle size distribution in untreated melted water samples reflects the growth, decomposition and succession of microorganisms over time and further indicate that UV irradiation is effective for long-term storage for microparticle analysis. [ABSTRACT FROM AUTHOR]

The limited number of surface mass balance (SMB) observations in the Antarctic inland hampers estimates of ice‐sheet contribution to global sea level and locations with million‐year‐old ice. We present finely resolved SMB over the past three centuries in a low‐accumulation region with significant depth hoar formation on Dome Fuji derived from ∼1,100 km of microwave radar stratigraphy dated with a firn core. The regional‐mean SMB over the past 264 years is estimated to ∼22.5 ± 3.3 kg m−2 a−1, but with large local variability of up to 30%. We found that local SMB is negatively correlated with surface slope at scales of a few hundred meters, resulting in anomalous zones of low SMB which represent as much as 8–10% of the total SMB on the inland plateau if the SMB‐slope relationship is more widely valid. This impact should be investigated further to improve estimates of Antarctic mass balance and sea‐level contribution. Plain Language Summary: Sampling the world's Oldest Ice (more than 1 million years) is crucial for understanding why pacing of glacier‐interglacial cycles has changed in the past. Such ice will be preserved at the base of the Antarctic ice‐sheet interior, though its location depends on many factors, including snow accumulation rate. We mapped snow accumulation in the Dome Fuji region, using radar‐detected snow layers dated with volcanic signals in ice cores. Although climate models indicate a very low and nearly uniform snow accumulation in this region, the observations show large variations of up to about 30% which we found to be related to local surface slope at a scale of a kilometer or less. This new knowledge contributes to better locate Oldest Ice and to improve estimates of ice‐sheet mass changes and its contributions to global sea level. Key Points: Ultrawide band microwave radar reveals spatially highly variable surface mass balance (SMB) over the past three centuries in inland AntarcticaSMB anomalies resulting from local surface slopes may represent as much as 8–10% of the total SMB on the inland plateauThe new SMB data have direct implications for the search for million‐year‐old ice in the Dome Fuji area, East Antarctica [ABSTRACT FROM AUTHOR]

Atmospheric sea-salt and halogen cycles play important roles in atmospheric science and chemistry including cloud processes and oxidation capacity in the Antarctic troposphere. This paper presents a review and summarizes current knowledge related to sea-salt and halogen chemistry in the Antarctic. First, presented are the seasonal variations and size distribution of sea-salt aerosols (SSAs). Second, SSA origins and sea-salt fractionation on sea-ice and ice sheets on the Antarctic continent are presented and discussed. Third, we discuss SSA release from the cryosphere. Fourth, we present SSA dispersion in the Antarctic troposphere and transport into inland areas. Fifth, heterogeneous reactions on SSAs as a source of reactive halogen species and their relationship with atmospheric chemistry are shown and discussed. Finally, we attempt to propose an outlook for obtaining better knowledge related to sea-salt and halogen chemistry and their effects on the Antarctic and the Arctic. [ABSTRACT FROM AUTHOR]

This study analyzed pollen in snow pits dug in late summer (2008-2011) on the upstream side of Potanin Glacier, a summer accumulation-type glacier in the Mongolian Altai, to reconstruct the recent snow depositional environment, particularly melting conditions. Annual snow pit observations were performed at sites 0 and 4 (3752 and 3890 m a.s.l., respectively). Seasonal layers in the pits were identified according to the presence of pollen from three taxa (Betulaceae, Pinus, and Artemisia), which have different pollen seasons typically between May and early September. The pollen-dating method was successful in snow pits where conventional methods such as ice layer dating and use of δO records were unreliable due to significant melting. Depths of pollen concentration peaks for the three taxa differed annually at both sites. In some years, concentration peaks of the three pollen taxa were found at different depths, but in other years, peaks associated with each taxon were found at the same depth. This difference was explained by summer temperature. Snow melting during the relatively warm summers of 2007 and 2008 caused pollen grains to concentrate on the glacier surface, producing peaks at the same depth. In contrast, snow melting during the relatively cool summer of 2009 did not substantially alter pollen grain location, and each peak thus retained its original depth. The median temperatures in 2010 and 2011 corresponded to pollen concentrating on the glacier surface at site 0 but retaining their original position at site 4. [ABSTRACT FROM AUTHOR]

The article discusses a study which reported density profiles gathered at 46 survey sites, from coastal to inland plateau regions in East Antarctica. Research groups from Japan and Sweden carried out a traverse expedition in East Antarctica, between the Japanese inland base S16 and the Swedish Wasa station, from November 2007 to January 2008. Snow measurements were conducted on a side-wall of a snow pit excavated at each survey site. The snow structure was classified into fresh snow, compacted snow, faceted crystals or depth hoar, and a crust layer.

In this study, we used a 4.00-m pit on Belukha glacier in Russia's Altai region and attempted to establish the timing of chemical deposition events by analyzing pollen profiles. As the pollen deposition of each examined taxon on the glacier surfaces followed a distinct seasonal phenology, seasonal layers could be identified over a two-year period. The seasonal layer boundaries reconstructed from the pollen analyses were in close agreement with the in situ observations and indicated that the snow deposition on the glacier originates mainly from summer precipitation. The record of oxygen isotope ratios showed a relatively high mean value of -13.3‰, which was attributed to the absence of winter depositions. The formate (HCOO-) concentration records displayed seasonal variation with the highest emissions occurring in the spring, and a dust event in the spring of 2003 was detected from the Mg2+, Ca2+, and dust concentration profiles. Taken together, these results suggest the analysis of pollen profiles in combination with chemical data in snow pits and ice cores may lead to better reconstruction of seasonal variation. [ABSTRACT FROM AUTHOR]

As analog ICs are finding use in a higher frequency hand, a circuit simulator which is accurate in a high-frequency region beyond 100 MHz becomes necessary. In this paper, a 600-MHz wideband amplifier IC and its bipolar transistors and resistors are fabricated on an identical chip. By evaluating their S parameters, the accuracy of the device model was verified for simulation of analog IC at frequencies above 100 MHz. First, the parasitics of packages were modeled to verify the accuracy of the device model. It is shown that consideration of the resistance of pads is necessary. Next, the accuracy of the hybrid π model used widely as a high-frequency model of the bipolar transistor was verified with the S parameters. It is found that the present form has poor accuracy at frequencies above 100 MHz. It is shown also that the IC structure of the transistor must be considered to improve the accuracy. Significant improvement of accuracy can be obtained if an extended model is introduced in which the separations of the base- collector capacitance and the base-emitter capacitance and the introduction of substrate resistance are included. Finally, by means of this extended model, a good high-frequency simulation of a 600-MHz wideband amplifier IC is realized. [ABSTRACT FROM AUTHOR]

Pollen taxa in sediment samples can be identified based on morphology. However, closely related species do not differ substantially in pollen morphology, and accurate identification is generally limited to genera or families. Because many pollen grains in glaciers contain protoplasm, genetic information obtained from pollen grains should enable the identification of plant taxa at the species level. In the present study, species identification of Pinus pollen grains was attempted using whole-genome amplification (WGA). We used pollen grains extracted from surface snow (depth, 1.8–1.9 m) from the Belukha glacier in the summer of 2003. WGA was performed using a single pollen grain. Some regions of the chloroplast genome were amplified by PCR, and the DNA products were sequenced to identify the pollen grain. Pinus includes approximately 111 recognized species in two subgenera, four sections, and 11 subsections. The tree species Pinus sibirica and P. sylvestris are currently found at the periphery of the glacier. We identified the pollen grains from the Belukha glacier to the level of section or subsection to which P. sibirica and P. sylvestris belong. Moreover, we specifically identified two pollen grains as P. sibirica or P. cembra. Fifteen species, including P. sibirica, were candidates for the remaining pollen grain. [ABSTRACT FROM AUTHOR]