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Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations.

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]

The climate of the past 430 kyr is guided by large-amplitude 100-kyr glacial-interglacial cycles (5). Such cycles are triggered by the Earth's orbital changes and then amplified by various land-atmosphere [...], Sulphate aerosols, particularly micrometre-sized particles of sulphate salt and sulphate-adhered dust, can act as cloud condensation nuclei, leading to increased solar scattering that cools Earth's climate (1,2). Evidence for such a coupling may lie in the sulphate record from polar ice cores, but previous analyses of melted ice-core samples have provided only sulphate ion concentrations, which may be due to sulphuric acid (3). Here we present profiles of sulphate salt and sulphate-adhered dust fluxes over the past 300,000 years from the Dome Fuji ice core in inland Antarctica. Our results show a nearly constant flux of sulphate-adhered dust through glacial and interglacial periods despite the large increases in total dust flux during glacial maxima (4). The sulphate salt flux, however, correlates inversely with temperature, suggesting a climatic coupling between particulate sulphur and temperature. For example, the total sulphate salt flux during the Last Glacial Maximum averages 5.78 mg [m.sup.-2] [yr.sup.-1], which is almost twice the Holocene value. Although it is based on a modern analogue with considerable uncertainties when applied to the ice-core record, this analysis indicates that the glacial-to-interglacial decrease in sulphate would lessen the aerosol indirect effects on cloud lifetime and albedo, leading to an Antarctic warming of 0.1 to 5 kelvin.