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Abstract Sea ice is regarded as a temporal sink and carrier of microplastics (MPs). Nevertheless, knowledge and understanding of MPs in sea ice remain sparse. This study investigated the abundance, composition, size (> 30 μm), and shape of MPs in four sea-ice cores retrieved at the southern end of the Sea of Okhotsk. Nine microplastic (MP) types, mostly with fragmentary shapes, were detected among ice-core sections. Most fragmentary MPs were smaller than 120 μm, but all fiber MPs were in the largest size class (> 210 μm). MP concentrations were 0–60 particles/L, with an average of 21 particles/L. Higher occurrences of MPs observed in the lower ice layers are attributable to heavier MP contamination in the southern part of the sea and/or relocation of MPs in the ice matrix. No significant correlation was found between the distributions of MP and inorganic particle (sediment) abundances, implying difference in their kinetics of suspension freezing. Taken together, these findings suggest important implications for elucidating the nature and distribution of MPs in sea ice.

Abstract Ice nucleating particles (INPs) affect the cloud radiative budget in the rapidly warming Arctic by changing the cloud liquid/ice phase balance. Dust emitted in the Arctic (Arctic dust) has been suggested to be a major contributor to INPs in the Arctic lower troposphere. However, how Arctic dust and its impacts on ice nucleation change with Arctic warming has not been explored. Here we find that the simulated dust emission flux in the Arctic (>60°N) in global model simulations increases by 20% from 1981–1990 to 2011–2020. This increase weakens the sensitivity of ice nucleation in Arctic lower tropospheric clouds to warming by 40% compared to the case without considering Arctic dust emission increases. Our results demonstrate a better understanding of the counterbalancing feedbacks of Arctic dust (i.e., increasing emissions and decreasing ice nucleation efficiency) is needed for more accurate estimates of changes in ice nucleation in the rapidly changing Arctic climate.

Abstract While the short-term relationship between clouds and aerosols is well known, no adequate data is available to verify the longer-term, annual to decadal, relationship. It is important to quantify the aerosol–cloud interaction (ACI) for mitigating uncertainty in climate prediction. Here the long-term ACI over the mid-to-high latitudes of the Northern Hemisphere was analyzed by using seasonally-resolved ion fluxes reconstructed from a southeastern Greenland ice core (SE-Dome ice core) as aerosol proxies, and satellite-based summer cloud amount between 1982 and 2014. As a result, SO4 2− flux in the ice core shows significant positive correlation with total cloud amounts ( $${CC}_{T}$$ CC T ) and cloud droplet concentration ( $${N}_{d}$$ N d ) in the summer over the southeastern Greenland Sea, implying that the sulfate aerosols may contribute to the variability of $${CC}_{T}$$ CC T via microphysical cloud processes. Significant positive correlations are persistent even under the constrained conditions when cloud formation factors such as relative humidity, air temperature at cloud height, and summer North Atlantic Oscillation are limited within ± 1σ variability. Hence sulfate aerosols should control the interannual variability of summer $${CC}_{T}$$ CC T In terms of decadal changes, $${CC}_{T}$$ CC T was approximately 3–5% higher in the 1960s–1970s than in the 1990s–2000s, which can be explained by changes in the, $${{{\text{SO}}}_{4}}^{2-}$$ SO 4 2 - flux preserved in the SE-Dome ice core.

In recent decades, surface melting on the inland Greenland ice sheet has increased, leading to significant meltwater-refreezing in the snow and firn. Increased knowledge of the physical and chemical characteristics of these melt features (i.e., ice layers) is needed to help estimate future global sea-level rise. Here, using a combination of microscopy and spectroscopy, we investigate the size, shape, location, and chemical compositions of inclusions in 12 ice layers of the SIGMA-A ice core in the northwestern Greenland ice sheet (78°03′06″N, 67°37′42″W, 1490 m a.s.l.). In the ice layers, we found inclusions exceeding 30 μm diameter that could only be formed by melting–refreezing, which we classify into columnar-, particle-, and rod-like inclusions. We propose that the smaller columnar- and particle-like inclusions of solid Na2SO4⋅10H2O and CaSO4⋅2H2O form first, within the ice grains, followed by the larger rod-like inclusions of brines with mainly Na+ and Cl− in grain boundaries. Our results suggest a new proxy that may help identify past warm climates in deeper ice cores in Greenland and for studying future ice sheet melting behavior.

Abstract Snowfall is regarded as a carrier of airborne microplastics (MPs). Deposited snow can function as a temporary reservoir for atmospheric MPs. Nevertheless, knowledge and understanding of MPs in snow remain sparse. This study investigates the abundance, composition, size (> 30 µm), and shape of MPs in snow specimens from various nature preservation areas and also from urban sites in Hokkaido. Various polymeric-type MPs with mostly fragmentary shapes were detected among the specimens. More than half of MPs were in the smallest size class (30–60 µm), implying the presence of more MPs below the limit (

Summer sea ice retreat in the high latitude North Atlantic since 2000 is associated with increases in oceanic emissions of dimethyl sulfide, according to a record of methane sulfonic acid fluxes from an ice core in southeast Greenland.

Earlier gas measurements of firn air (atmosphere in open pore channels) at polar sites have revealed the occurrence of gas fractionation phenomena during bubble close-off, in addition to well-known thermal and gravitational gas separation. Nevertheless, because of difficulties posed by measurement, little is known about the distribution of air constituents in already closed pores (bubbles) in firn. Herein, we describe the application of high-sensitivity pure rotational Raman spectroscopy, combined with sample immersion in the fluorocarbon-based inert fluid for removing the optical disturbance by diffused reflection. That application efficiently elicits information about nitrogen and oxygen composition ratios (N2/O2 or O2/N2) for each air bubble in firn. The developed methodology presents important implications for elucidating how gas records are formed and modified in the course of pore close-off in polar firn.

Abstract Previous reconstructions of summer temperatures from ice cores have relied on a statistical relationship between a melt layer and temperature observed at nearby stations. This study presents a novel method for reconstructing summer temperatures from melt layers in ice cores using an energy balance model that incorporates heat conduction and meltwater refreezing in the firn. We use the seasonal patterns in the ERA‐Interim reanalysis data set for an ice core site to calculate the amounts of refreezing water within the firn under various summer mean temperature (SMT) and annual precipitation conditions, and prepared calibration tables containing these three variables. We then estimate the SMTs from the refreezing amount and annual accumulation, both of which can be obtained from an ice core. We apply this method to four ice cores that were recovered from sites with different climates: two sites on the Greenland Ice Sheet, one in Alaska, and one in Russian Altai. The reconstructed SMTs show comparable variations with those of observed temperatures at nearby stations. The nonlinear relationship between SMT and melt layer thickness differs between sites, indicating that a single linear approximation cannot be employed to estimate SMT. Sensitivity analyses suggest that the annual temperature range, amount of annual precipitation, and firn albedo (which is a time‐invariant value in the model) significantly affect the relationship between SMT and melt layer thickness. This new method provides an alternative to existing approaches and yields an independent estimate of SMT from ice cores that have been affected by melting.

The Antarctic temperature record displays a puzzling asynchrony with changes in CO2 through glacial cycles. Here, the authors show that a 720,000-year Antarctic temperature record is affected by variations in obliquity-induced local insolation that are associated with phase modulation of eccentricity cycle.

An in-depth examination of rheology within the deep sections of polar ice sheets is essential for enhancing our understanding of glacial flow. In this study, we investigate the crystalline textural properties of the 3035-m-long Antarctic deep ice core, with a particular emphasis on its lowermost 20%. We examine the crystal orientation fabric (COF) and compare it with various other properties from the ice core. In the uppermost approximately 80% thickness zone (UP80%), the clustering strength of single pole COF steadily increased, reaching its possible maximum at the bottom of the UP80%. Below 1800 m in the UP80%, layers with more or fewer dusty impurities exhibit slower or faster growth of cluster strength. This situation continued until 2650 m. In the remaining lowermost approximately 20% thickness zone (LO20%), the trend of the COF clustering strength changed around 2650 m and exhibited substantial fluctuations below this depth. In more impurity-rich layers, stronger clustering is maintained. In impurity-poor layers, relaxation of the COF clustering occurred due to the emergence of new crystal grains with c-axis orientation distinctly offset from the existing cluster, and dynamic recrystallization related to this emergence. The less impure layers show apparent features of bulging and migrating grain boundaries. We argue that the substantial deformational regime of polar ice sheets involves dislocation creep in both UP80% and LO20%, with dynamic recrystallization playing a critical role in the LO20%, particularly in impurity-poor layers, to recover a potential of COF available for the continuation of dislocation-creep-based deformation. Furthermore, we observe that layers and cluster axes of COF rotate meridionally due to rigid-body rotation caused by simple shear strain above subglacial slopes. These features provide vital clues for the development of the 3D structure of polar ice sheets in the deeper part, leading to inhomogeneous deformation between layers in various thickness scales, and the formation of folds, faults and mixing depending on the layers. [ABSTRACT FROM AUTHOR]

To better understand how sea salt reacts in surface snow of Antarctica, we collected and identified non-volatile particles in surface snow along a traverse in East Antarctica. Samples were obtained during summer 2012/2013 from coastal to inland regions within 69°S to 80°S and 39°E to 45°E, a total distance exceeding 800 km. The spatial resolution of samples is about one sample per latitude between 1500 and 3800 m altitude. Here, we obtain the atomic ratios of Na, S and Cl, and calculate the masses of sodium sulphate and sodium chloride. The results show that, even in the coast snow sample (69°S), sea salt is highly modified by acid (HNO3 or H2SO4). The fraction of sea salt that reacts with acid increases in the region from 70°S to 74°S below 3000 m a.s.l., where some NaCl remains. At the higher altitudes (above 3300 m a.s.l.) in the inland region (74°S to 80°S), the reaction uses almost all of the available NaCl.

In the seventh five-year plan of the Japanese Antarctic Research Expedition, a group of Japanese scientists (led by the National Institute of Polar Research) together with a group of Swedish scientists, conducted field surveys to better understand the glaciology of the ice sheet in Dronning Maud Land, East Antarctica, during the 2007/2008 austral summer season. This paper reports on the planning and field preparations, and outlines the scientific achievements of the field expedition. We have gained numerous new scientific insights on the spatio-temporal distribution of the ice sheet environment in the inland plateau. Here, we provide an overview of the new knowledge gained.

Antarctic ice cores preserve the record of past aerosols, an important proxy of past atmospheric chemistry. Here we present the aerosol compositions of sulphate and chloride particles in the Talos Dome (TD) ice core from the Holocene and Last Glacial Period. We find that the main salt types of both periods are NaCl, Na2SO4 and CaSO4, indicating that TD ice contains relatively abundant sea salt (NaCl) from marine primary particles. By evaluating the molar ratio of NaCl to Na2SO4, we show that about half of the sea salt does not undergo sulphatisation during late Holocene. Compared to in inland Antarctica, the lower sulphatisation rate at TD is probably due to relatively little contact between sea salt and sulphuric acid. This low contact rate can be related to a reduced time of reaction for marine-sourced aerosol before reaching TD and/or to a reduced post-depositional effect from the higher accumulation rate at TD. Many sulphate and chloride salts are adhered to silicate minerals. The ratio of sulphate-adhered mineral to particle mass and the corresponding ratio of chloride-adhered mineral both increase with increasing dust concentration. Also, the TD ice appears to contain Ca(NO3)2 or CaCO3 particles, thus differing from aerosol compositions in inland Antarctica, and indicating the proximity of peripheral regions to marine aerosols.

Ice core analyses start with the processing of ice cores. Especially for chemical analyses, pre-treatments for introducing the samples to the measuring instruments without contamination is essential. Part of processing can be carried out under a normal laboratory instead of the cold one to improve the efficiency of processing the core samples. The ice core cutting was carried out in a small chamber, with temperature control, installed in a normal laboratory. The ice core sample was cut with a small instrument in the chamber and melted after the determination of solid bulk density. The melted samples were stored after labeling for the planned measurements, such as HTO measurements. The core processing including cutting in the chamber, measurement of bulk density and electrical conductivity before the storage of melted samples with labeling, were carried out at the rate of 5m/(6 hours・person). The continuous melting and sampling procedures for the ice core sample toward the depth direction are also discussed. Continuous melting with continuous sampling for measurement of ion chromatography was carried out on 10 samples/(15cm・30min・person). The processing was efficient for the delicate sampling, and the data obtained in the procedure was supported by those obtained with normal procedure.

The establishment of a system for providing appropriate long-term care services for older people is a national issue in Japan, and it will likely become a worldwide issue in the years to come. Under Japanese Long-term Care Insurance System, long-term care is provided based on long-term care programs, which were designed by care providers on the basis of long-term care service plans, which were designed by care managers. However, defined methodology for designing long-term care service plans and care programs has not been established yet. In this paper, we propose models for designing long-term care service plans and care programs for older people, both by incorporating the technical issues from previous studies and by redesigning the total methodology according to these studies. Our implementation model consists of “Function,” “Knowledge Structure,” and “Action Flow.” In addition, we developed the concrete knowledgebases based on the Knowledge Structure by visualizing, summarizing, and structuring the inherent knowledge of healthcare/welfare professionals. As the results of the workshop and retrospective verification, the adequacy of the models was suggested, while some further issues were pointed. Our models, knowledgebases, and application make it possible to ensure the quality of long-term care for older people.