Black carbon (BC) aerosol is one of the most important factor in global warming. BC radiative forcing remains unconstrained, mainly because of the uncertain parameterizations of its absorption and scattering properties in the atmosphere. The single sphere model is widely used in current climate assessment of BC aerosols due to its computational convenience, however, their complex morphologies in particle level are excessively simplified which leads to computed inaccuracy. In this study, we present a dynamic model for optical calculations of BC aerosol ensembles considering their complex fractal aggregate morphologies with the constraint of max monomer numbers (N s, max) and radius (a max). We show that the simulation accuracy of the dynamic model with suitable values of N s, max and a max may achieve similar to 95% while the computation time may reduce to similar to 6%. We find that optical properties of BC aerosol ensembles can be simulated for higher accuracy or faster calculation by performing different selections of monomer numbers and radius in their size distributions. This method enables extensive and accurate optical calculations of BC particles with complex morphologies, which would be useful for the remote sensing inversion and the assessment of climate.

The areas covered by permafrost in the polar regions are vulnerable to rapid changes in the current climate. The well-studied near-surface active layer and permafrost zone are in contrast to the unknown exact shape of the bottom permafrost boundary. Therefore, the entire shape of permafrost between the upper and lower boundaries is not identified with sufficient accuracy. Since most of the factors affecting deep cryotic structures are subsurface in nature, their evolution in deeper layers is also relatively unclear. Here, we propose a hypothesis based on the results of geophysical studies regarding the shape of the permafrost in the coastal area of Svalbard, Southern Spitsbergen. In the article, we emphasize the importance of recognizing not only the uppermost active layer but also the bottom boundary of permafrost along with its transition zone, due to the underestimated potential role of its continuity in observing climate change. The lower permafrost boundary is estimated to range from 70 m below the surface in areas close to the shore to 180 m inland, while a continuous layer of an entirely frozen matrix can be identified with a thickness between 40 m and 100 m. We also hypothesized the presence of the possible subsea permafrost in the Hornsund. The influence of seawater intrusions, isostatic uplift of deglaciated areas, and surface-related processes that affect permafrost evolution may lead to extensive changes in the hy-drology and geology of the polar regions in the future. For all these reasons, monitoring, geophysical imaging and understanding the characteristics and evolution of deep permafrost structures requires global attention and scientific efforts.

Ground ice distribution and abundance have wide-ranging effects on periglacial environments and possible impacts on climate change scenarios. In contrast, very few studies measure ground ice in the High Arctic, especially in polar deserts and where coarse surficial material complicates coring operations. Ground ice volumes and cryostructures were determined for eight sites in a polar desert, near Resolute Bay, Nunavut, chosen for their hydrogeomorphic classification. Dry, unvegetated polar desert sites exhibited ice content close to soil porosity, with a <45 cm thick ice-enriched transition zone. In wetland sites, suspended cryostructures and ice dominated cryofacies (ice content at least 2x soil porosity values) were prevalent in the upper similar to 2 m of permafrost. Average ground ice saturation at those locations exceeded porosity values by a factor between 1.8 and 20.1 and by up to two orders of magnitude at the similar to 10 cm vertical scale. Sites with the highest ice contents were historically submerged wetlands with a history of sediment supply, sustained water availability, and syngenetic and quasi-syngenetic permafrost aggradation. Ice enrichment in those environments were mainly caused by the strong upward freezing potential beneath the thaw front, which, combined with abundant water supply, caused ice aggradation and frost heaving to form lithalsa plateaus. Most of the sites already expressed cryostratigraphic evidence of permafrost degradation. Permafrost degradation carries important ecological ramifications, as wetland locations are the most productive, life-supporting oases in the otherwise relatively barren landscape, carrying essential functions linked with hydrological processes and nutrient and contaminant cycling.

Arctic permafrost is degrading and is thus releasing nutrients, solutes, sediment and water into soils and freshwater ecosystems. The impacts of this degradation depends on the geochemical characteristics and in large part on the spatial distribution of ground ice and solutes, which is not well-known in the High Arctic polar desert ecosystems. This research links ground ice and solute concentrations, to establish a framework for identifying locations vulnerable to permafrost degradation. It builds on landscape classifications and cryostratigraphic interpretations of permafrost history. Well-vegetated wetland sites with syngenetic permafrost aggradation show a different geochemical signature from polar desert and epigenetic sites. In wetlands, where ground ice contents were high (<97% volume), total dissolved solute concentrations were relatively low (mean 283.0 +/- 327.8 ppm), reflecting a carbonate terrestrial/freshwater setting. In drier sites with epigenetic origin, such as polar deserts, ice contents are low (<47% volume), solute concentrations were high (mean 3248.5 +/- 1907.0 ppm, max 12055 ppm) and dominated by Na+ and Cl- ions, reflecting a post-glacial marine inundation during permafrost formation. Dissolved organic carbon and total dissolved nitrogen concentrations usually increased at the top of permafrost and could not be as clearly associated with permafrost history. The research shows that the geochemistry of polar desert permafrost is highly dependent on permafrost history, and it can be estimated using hydrogeomorphological terrain classifications. The lower ice content of polar desert sites indicates that these areas are more vulnerable to thaw relative to the ice-rich wetland sites, and the elevated solute concentrations indicate that these areas could mobilise substantial solutes to downstream environments, should they become hydrologically connected with future warming.

Effective density (peff) is an important property describing particle transportation in the atmosphere and in the human respiratory tract. In this study, the particle size dependency of peff was determined for fresh and photochemically aged particles from residential combustion of wood logs and brown coal, as well as from an aerosol standard (CAST) burner. peff increased considerably due to photochemical aging, especially for soot agglomerates larger than 100 nm in mobility diameter. The increase depends on the presence of condensable vapors and agglomerate size and can be explained by collapsing of chain-like agglomerates and filling of their voids and formation of secondary coating. The measured and modeled particle optical properties suggest that while light absorption, scattering, and the single-scattering albedo of soot particle increase during photochemical processing, their radiative forcing remains positive until the amount of nonabsorbing coating exceeds approximately 90% of the particle mass.

Anthropogenic climate change threatens water storage and supply in the periglacial critical zone. Rock glaciers are widely distributed alpine aquifers with slower response to temperature increases, that provide the summer water flow of many alpine streams. Knowing the extent and makeup of rock glaciers is necessary to evaluate their potential for water supply. We used non-invasive methods, integrating geological, geomorphological, meteoro-logical, and geophysical information to characterize the internal structure and hydrology of the Upper Camp Bird rock glacier (UCBRG) located on level 3 of Camp Bird Mine in Ouray, Colorado, and assessed the applicability of two electromagnetic induction systems in this highly heterogeneous landform with a history of anthropogenic activity. The time-domain (G-TEMTM) system achieved deep subsurface penetration (similar to 100 m) and realistic modeling of the internal structure of the UCBRG: a shell of volcanic rock fragments (< 3 m thick; 1-100 Ohm-m), a meltwater component (10(2)-10(3) Ohm-m), located between 50 and 100 m near the toe (subpermafrost flow), and 1-30 m in the soundings farthest from the toe (suprapermafrost flow within the active layer), and a frozen component (permafrost 50-80 m thick; 10(3)-10(6) Ohm-m). The frequency-domain system, however, was highly susceptible to local environmental conditions, including anthropogenic objects (i.e., mine carts, lamp posts, tunnel tracks, etc.) and was unable to resolve UCBRG's internal makeup. The non-invasive methodology and general conceptual framework presented here can be used to characterize other alpine aquifers, contributing to the quantification of global water resources, and highlighting the importance of preserving rock glaciers as storage for critical water supply in the future.

Black carbon (BC) is an important aerosol species due to its strong heating of the atmosphere accompanied by cooling of the Earth's surface, but its radiative forcing is poorly constrained by different regional size distributions due to uncertain reproductions of a morphologically simplified model. Here, we quantify the BC morphological effect on measuring the particle size using an aggregate model. We show that the size distributions of loose BC particles could account for up to 45% underestimation by morphological simplification, leading to up to 25% differences, by relying on a simplified model to estimate radiative forcing. We find that the BC particle size is remarkably amplified for looser and larger BC aggregates by angular scattering observations. We suggest that the BC morphological diversity can be neglected in forward scattering angles (<30 degrees), which is a useful supplement to reduce the uncertainty of radiative forcing assessment.

Accurate estimates of regional and global glacier mass require many field-based sample measurements that are widely distributed across an area of interest. The Sawir Mountains are an isolated mountain system in Central Asia and changes in glacier mass balance from this region have rarely been reported. In this study, we provide a comprehensive analysis of mass changes of the Muz Taw Glacier in the Sawir Mountains based on glaciological and geodetic measurements. The glaciological mass balance exhibited a strong variability during the period 2016-2020, with a range of values between - 1.29 and - 0.31 m water equivalent (w.e.) and a mean value of - 0.86 +/- 0.16 m w.e. Differences in the surface elevation of the Muz Taw Glacier were determined from analysis of a topographic map (1:100,000 scale) and terrestrial laser scanning (TLS) point-cloud data, with these data sources indicating an average surface elevation change of approximately - 33.36 +/- 9.39 m or - 0.54 +/- 0.15 m a(-1) during 1959-2021. This thickness is roughly equivalent to half of the mean thickness of the glacier terminus, which has contributed to the negative geodetic mass balance of - 28.36 +/- 8.23 m w.e. or - 0.46 +/- 0.13 m w.e. a(-1). Approximately twice as much mass has been lost from the Muz Taw Glacier during the past 5 years (2016-2020) than estimated by geodetic data, indicating that the mass loss of Muz Taw Glacier has continued unabated.

The radiative forcing of soot is dependent on the morphology, mixing state and structure. Cloud processing has been predicted to affect their mixing properties but little is known about the resulting light absorption properties. We collected ambient particles in the pre-cloud period, the cloud residues and interstitials in the in-cloud period at Mt. Tianjing (southern China). The morphology parameters of soot aggregates with varying mixing materials [sulfate (S) and organics (OM)] and mixing structures were investigated by a transmission electron microscope, and their absorption cross were calculated based on discrete dipole approximation. We found that the number contribution of soot-S decreased from 45% in the pre-cloud period to 32% in the in-cloud period, and that of soot-OM increased from 44% to 60%. Moreover, the number proportion of soot-OM with fully embedded structure increased remarkably in the in-cloud period (29%), compared with that in the pre-cloud period (3%). In addition, the soot-S aggregates became denser after in-cloud aqueous process. However, for soot-OM aggregates, the morphology remained relatively constant. The distinctly different change of soot-S and soot-OM in morphology highlights the chemically resolved reconstruction of soot morphology. Theoretical calculation further shows that the changes of soot particles in the mixing state and morphological characteristics by the cloud process resulted in the light absorption enhancement increase from 1.57 to 2.01. This study highlights that the evolution of microphysical properties upon cloud processing should also be considered in climate models to more accurately evaluate the impacts of soot particles.

The role of snow is underrated in the dendrogeomorphic research in terms of the interpretation of the climate factors responsible for the geomorphic activity. We analysed snow parameters and the combined effect of spring and summer climate variables to interpret their role in debris flow/flood and flow-like landslide initiation in two Central European mid-mountain regions. We revisited the tree-ring based chronologies based on a total of 1043 trees for four debris flow/flood catchments and four flow-like landslide bodies. Three approaches were used to determine the event year, including a floating event-response index and different weighted index thresholds. In addition, data from precipitation and streamflow gauges were used to identify the best indicators of rapid snow melting and find the best explanatory climate factors during event years using logistic regression. We identified 24-40 event years with hydrogeomorphic activity and 10-29 years with flow-like landslide reactivations during 1961-2017. The amount of melted snowpack and rain-on-snow during spring were considered the best rapid snowmelt parameters obtained from the precipitation gauges due to highest correlations with the stream gauge data (R = 0.69-0.70). We identified very likely rapid snowmelt in seven debris flow/flood event years and six landslide event years since 1981. Furthermore, high maximum snowpack in spring combined with extreme oneday rainfall in summer were the best explanatory factors for hydrogeomorphic activity, but probably not during the high-magnitude debris flows, which were more dependent on the extreme summer rainfall alone. Landslide reactivations were most likely to occur during years with extreme one-day rainfall events in May to September preceded by a wet period since the last day of continuous snow cover. This study defines a step-by-step procedure to reveal the role of snowmelt and antecedent precipitation in dendrogeomorphic research and shows likely scenarios of geomorphic activity typical of the study area.