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Greenland’s ice sheet mass loss rate has tripled since the mid-1950s in concert with sharply lowered albedo leading to increased absorption of solar radiation and enhanced surface melt. Snow and ice melt driven by solar absorption is enhanced by the presence of light absorbing particles (LAPs), such as black carbon (BC) and dust. Yet, the LAP impact on melt is poorly constrained, partly due to scarce availability of in-situ measurements. Here, we present a survey of snow properties and LAPs deposited in winter snow layers at five sites in southwest Greenland collected in May 2017. At these sites, BC and dust concentrations were 0.62 ± 0.35 ng g-1 and 2.09 ± 1.60 µg g-1, respectively. By applying the SNICAR model, we show the LAP influence on albedo through the combined effect of surface darkening and snow metamorphism. While the LAP concentrations are low, they result in a 1.7 % and 3.0 % reduction in albedo within the visible spectrum for spring and summer, respectively. Past studies have shown that even minor LAP induced albedo reductions, if widespread, can have a large impact on the overall surface mass balance. SNICAR simulations constrained by our measurements show that LAP-snow aging feedback reduce albedo reduction 4 to 10 times more than previously thought, therefore LAPs are likely a significant contributor to Greenland's accelerated mass loss. As far as we know, this is the first field study to consider the LAP impact on snow aging on the Greenland ice sheet.

Wildfires in the snow zone affect ablation by removing forest canopy, which enhances surface solar irradiance, and depositing light absorbing particles [LAPs, such as black carbon (BC)] on the snowpack, reducing snow albedo. How variations in BC deposition affects post-wildfire snowmelt timing is poorly known and highly relevant to water resources. We present a field-based analysis of BC variability across five sites of varying burn age and burn severity in the Cascade Range, Washington State, United States. Single particle soot photometer (SP2) analyses of BC snow concentrations were used to assess the impact of BC on snow albedo, and radiative transfer modeling was used to estimate the radiative effect of BC on snowmelt. Results were compared to Snowpack Telemetry (SNOTEL) data from one site that burned in 2012 and another in a proximal unburned forest. We show that post-wildfire forests provide a significant source of BC to the snowpack, and this effect increases by an order of magnitude in regions of high versus low burn severity, and decreased by two orders of magnitude over a decade. There is a shift in the timing of snowmelt, with snow disappearance occurring on average 19 ± 9 days earlier post-wildfire (2013–19) relative to pre-wildfire (1983–2012). This study improves understanding of the connection between wildfire activity and snowmelt, which is of high relevance as climate change models project further decreases in snowpack and increases in wildfire activity in the Washington Cascades.

Black carbon (BC) is an important climate-forcing agent that affects snow albedo. In this work, we present a record of refractory black carbon (rBC) variability, measured from a 20 m deep snow and firn core drilled in West Antarctica (79∘55′34.6′′ S, 94∘21′13.3′′ W, 2122 m above sea level) during the 2014–2015 austral summer. This is the highest elevation rBC record from West Antarctica. The core was analyzed using the Single Particle Soot Photometer (SP2) coupled to a CETAC Marin-5 nebulizer. Results show a well-defined seasonality with geometric mean concentrations of 0.015 µg L−1 for the wet season (austral summer–fall) and 0.057 µg L−1 for the dry season (austral winter–spring). The core was dated to 47 years (1968–2015) using rBC seasonality as the main parameter, along with sodium (Na), sulfur (S) and strontium (Sr) variations. The annual rBC concentration geometric mean was 0.03 µg L−1, the lowest of all rBC cores in Antarctica referenced in this work, while the annual rBC flux was 6.25 µg m−2 a−1, the lowest flux in West Antarctica rBC records. No long-term trend was observed. Snow albedo reductions at the site due to BC were simulated using SNICAR online and found to be insignificant (−0.48 %) compared to clean snow. Fire spot inventory and BC emission estimates from the Southern Hemisphere suggest Australia and Southern Hemisphere South America as the most probable emission sources of BC to the drilling site, whereas HYSPLIT model particle transport simulations from 1968 to 2015 support Australia and New Zealand as rBC sources, with limited contributions from South America. Spectral analysis (REDFIT method) of the BC record showed cycles related to the Antarctic Oscillation (AAO) and to El Niño–Southern Oscillation (ENSO), but cycles in common with the Amundsen Sea Low (ASL) were not detected. Correlation of rBC records in Antarctica with snow accumulation, elevation and distance to the sea suggests rBC transport to East Antarctica is different from transport to West Antarctica.

The Tibetan Plateau (TP) and its surroundings, known as the Third Pole, play an important role in the regional and global climate and hydrological cycle. Carbonaceous aerosols (CAs), including black carbon (BC) and organic carbon (OC), can directly/indirectly absorb and scatter solar radiation, and change the energy balance on Earth. CAs, along with other atmospheric pollutants (e.g., mercury), can frequently be transported over long distances into the inland TP. During the last decade, a coordinated monitoring network and research program on Atmospheric Pollution and Cryospheric Change (APCC) has been gradually setup and continuously operated within the Third Pole regions to investigate the linkage between atmospheric pollutants and cryospheric change. This paper presents a systematic dataset of BC, OC, water soluble organic carbon (WSOC), and water insoluble organic carbon (WIOC) from aerosols (19 stations), glaciers (17 glaciers, including samples from surface snow/ice, snowpit, and two ice cores), snow cover (2 stations continuous observed, and 138 sites surveyed), precipitation (6 stations), and lake sediment cores (7 lakes) collected across the TP and its surroundings, as the first dataset released from this APCC program. These data were created based on online (in-situ) and laboratory measurements. High-resolution (daily scale) atmospheric equivalent BC (eBC) concentrations were obtained by using an aethalometer (AE-33) in the Mt. Everest (Qomolangma) region, which can provide a new insight into the mechanism of BC transportation over the Himalayas. Spatial distributions of BC, OC, WSOC and WIOC from aerosols, glaciers, snow cover, and precipitation indicated different features among the different regions of the TP, which were mostly influenced by emission sources, transport, and deposition processes. Several hundred years of refractory BC (rBC) records from ice cores and BC from lake sediment cores revealed the strength of human activities since the industrial revolution. BC isotopes from glaciers and aerosols identified the relative contributions of biomass and fossil fuel combustion to BC deposition on the Himalayas and TP. Mass absorption cross section of BC and WSOC from aerosol, glaciers, snow cover, and precipitation samples were also provided. This updated dataset is released to the scientific communities focusing on atmospheric science, cryospheric science, hydrology, climatology and environmental science. The related datasets are presented in the form of excel files. These files are available to download from the State Key Laboratory of Cryosphere Sciences, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences at Lanzhou (https://doi.org/10.12072/ncdc.NIEER.db0114.2021, Kang and Zhang, 2021). In the future, datasets of mercury, heavy metals, and POPs will be reported.

This case study provides a framework for future monitoring and evidence for human source pollution in the Khumbu region, Nepal. We analyzed the chemical composition (major ions, major/trace elements, black carbon, and stable water isotopes) of pre-monsoon stream water (4300-5250 m) and snow (5200-6665 m) samples collected from Mt. Everest, Mt. Lobuche, and the Imja Valley during the 2019 pre-monsoon season, in addition to a shallow ice core recovered from the Khumbu Glacier (5300 m). In agreement with previous work, pre-monsoon aerosol deposition is dominated by dust originating from western sources and less frequently by transport from southerly air mass sources as demonstrated by evidence of one of the strongest recorded pre-monsoon events emanating from the Bay of Bengal, Cyclone Fani. Elevated concentrations of human-sourced metals (e.g., Pb, Bi, As) are found in surface snow and stream chemistry collected in the Khumbu region. As the most comprehensive case study of environmental chemistry in the Khumbu region, this research offers sufficient evidence for increased monitoring in this watershed and surrounding areas.

Carbonaceous matter, including organic carbon (OC) and black carbon (BC), is an important climate forcing agent and contributes to glacier retreat in the Himalayas and the Tibetan Plateau (HTP). The HTP – the so-called “Third Pole” – contains the most extensive glacial area outside of the polar regions. Considerable research on carbonaceous matter in the HTP has been conducted, although this research has been challenging due to the complex terrain and strong spatiotemporal heterogeneity of carbonaceous matter in the HTP. A comprehensive investigation of published atmospheric and snow data for HTP carbonaceous matter concentration, deposition and light absorption is presented, including how these factors vary with time and other parameters. Carbonaceous matter concentrations in the atmosphere and glaciers of the HTP are found to be low. Analysis of water-insoluable organic carbon and BC from snowpits reveals that concentrations of OC and BC in the atmosphere and glacier samples in arid regions of the HTP may be overestimated due to contributions from inorganic carbon in mineral dust. Due to the remote nature of the HTP, carbonaceous matter found in the HTP has generally been transported from outside the HTP (e.g., South Asia), although local HTP emissions may also be important at some sites. This review provides essential data and a synthesis of current thinking for studies on atmospheric transport modeling and radiative forcing of carbonaceous matter in the HTP.

An extended‐range Single Particle Soot Photometer (SP2) coupled to a Marin‐5 nebulizer was used to measure the refractory black carbon (rBC) mass and number size distributions in 1,004 samples from a West Antarctica snow/firn core. The SP2 was calibrated using Aquadag and a Centrifugal Particle Mass Analyzer for BC particles ranging from 0.5 to 800 fg. Our results indicate a significant contribution of rare, large particles of mass‐equivalent diameter (DBC) > 500 nm to the total rBC mass (36%), while small particles (DBC 1,810 nm (uncontained mode). We compared two sets of samples from different seasons (wet vs. dry) and observed that dry season concentrations are 3.4 and 2 times that of the wet season in the ranges of 80 nm

Sulfur aerosols, mainly composed of sulfate and methanesulfonic acid (MSA), significantly affect the Earth’s radiation balance, biogeochemical cycles and ecosystems, especially in the polar regions with vulnerable environments. To better understand the relationship between anthropogenic activities and climate change, a comprehensive review is presented, covering sulfate and MSA concentrations and isotope composition from 18 sites in the Arctic, 22 sites in the Antarctic and 25 sites in the Tibetan Plateau. The spatio-temporal variability of sulfur aerosols and the potential factors controlling their concentrations are summarized, sulfur isotopes are used to identify the importance of anthropogenic vs. natural inputs, and ice cores are employed to reconstruct the paleo-evolution of atmospheric sulfates. Finally, this review discusses the need for future research on organosulfur aerosols, the mixing state of sulfur aerosols, their deposition fluxes and velocities, potential emissions by biomass burning, and the anticipated trends in sulfur aerosol concentrations in the Arctic, Antarctic, and Tibetan Plateau.

Remote sensing of light-absorbing particles (LAPs), or dark colored impurities, such as black carbon (BC) and dust on snow, is a key remaining challenge in cryospheric surface characterization and application to snow, ice, and climate models. We present a quantitative data set of in situ snow reflectance, measured and modeled albedo, and BC and trace element concentrations from clean to heavily fossil fuel emission contaminated snow near South Pole, Antarctica. Over 380 snow reflectance spectra (350-2500 nm) and 28 surface snow samples were collected at seven distinct sites in the austral summer season of 2014-2015. Snow samples were analyzed for BC concentration via a single particle soot photometer and for trace element concentration via an inductively coupled plasma mass spectrometer. Snow impurity concentrations ranged from 0.14 to 7000 part per billion (ppb) BC, 9.5 to 1200 ppb sulfur, 0.19 to 660 ppb iron, 0.013 to 1.9 ppb chromium, 0.13 to 120 ppb copper, 0.63 to 6.3 ppb zinc, 0.45 to 82 parts per trillion (ppt) arsenic, 0.0028 to 6.1 ppb cadmium, 0.062 to 22 ppb barium, and 0.0044 to 6.2 ppb lead. Broadband visible to shortwave infrared albedo ranged from 0.85 in pristine snow to 0.62 in contaminated snow. LAP radiative forcing, the enhanced surface absorption due to BC and trace elements, spanned from less than 1 W m(exp. -2) for clean snow to approximately 70 W m(exp. -2) for snow with high BC and trace element content. Measured snow reflectance differed from modeled snow albedo due to specific impurity-dependent absorption features, which we recommend be further studied and improved in snow albedo models.

The Yakima Air Wintertime Nitrate Study (YAWNS) was conducted in January 2013 to investigate the drivers of elevated levels of fine particulate matter (PM 2.5 ) frequently present in the region during winter stagnation periods. An extended stagnation period occurred during the study. For the first four days of the event, skies were clear and the strong diel variation in air pollution patterns were consistent with the expected effects of strong low-level nighttime temperature inversions with moderate mixing during daylight hours. Later in the event a low-level cloud layer formed that persisted over the Yakima Valley for the next seven days while regional conditions remained stagnant. Coincident with the onset of cloud, the levels of all measured primary pollutants, including CO 2 , CO, NO x , particle number concentration, and black carbon, dropped dramatically and remained low with negligible diel variation for as long as the cloud layer was present. The observed patterns for these air pollutants are consistent with decreased stability and enhanced mixing associated with the cloud-topped boundary layer. Interestingly, levels of secondary pollutants, most notably particulate ammonium nitrate, did not exhibit the same decline. This difference may be due to shifts in the chemical production of secondary pollutants during cloudy conditions, or may merely reflect a further influence of mixing. The results imply that the best strategies for managing wintertime air quality during episodes of persistent cloud are likely different from those needed during clear-sky stagnation events.

An extended-range Single-Particle Soot Photometer (SP2) coupled to a Marin-5 nebulizer was used to measure the refractory black carbon (rBC) mass and number size distributions in 1004 samples from ...

A multiple linear regression (MLR) chemical mass balance model was applied to data collected during an air quality field experiment in Yakima, WA during January, 2013to determine the relative contribution of residential wood combustion (RWC) and vehicle emissions to ambient pollutant levels. Acetonitrile was used as a chemical tracer for wood burning and nitrogen oxides (NOx) as a chemical tracer for mobile sources. RWC was found to be a substantial source of gas phase air toxics in winter time. The MLR model found RWC primarily responsible for emissions of formaldehyde (73%), acetaldehyde (69%), and black carbon (55%) and mobile sources primarily responsible for emissions of carbon monoxide (CO) (83%), toluene (81%), C2 – alkylbenzenes (81%), and benzene (64%). When compared with the EPA's 2011 winter emissions inventory, the MLR results suggest that the contribution of RWC to CO emissions was underestimated in the inventory by a factor of 2. Emission ratios to NOx from the MLR model agreed to within 25% with wintertime emission ratios predicted from the Motor Vehicle Emissions Simulator (MOVES) 2010b emission model for Yakima County for all pollutants modeled except for CO, C2 – alkylbenzenes, and black carbon. The MLR model results suggest that MOVES was over predicting mobile source emissions of CO relative to NOx by a factor of 1.33 and black carbon relative to NOx by about a factor of 3.

High-resolution δ18O records from a Geladaindong mountain ice core spanning the period 1477-1982 were used to investigate past temperature variations in the Yangtze River source region of the central Tibetan Plateau (TP). Annual ice-core δ18O records were positively correlated with temperature data from nearby meteorological stations, suggesting that the δ18O record represented the air temperature in the region. A generally increasing temperature trend over the past 500 years was identified, with amplified warming during the 20th century. A colder stage, spanning before the 1850s, was found to represent the Little Ice Age with colder periods occurring during the 1470s–1500s, 1580s–1660s, 1700s–20s and 1770s–1840s. Compared with other temperature records from the TP and the Northern Hemisphere, the Geladaindong ice-core record suggested that the regional climate of the central TP experienced a stronger warming trend during the 20th century than other regions. In addition, a positive relationship between the Geladaindong δ18 O values and the North Atlantic Oscillation index, combined with a wavelet analysis of δ18 O records, indicated that there was a potential atmospheric teleconnection between the North Atlantic and the central TP.

A 147-m ice core was retrieved from Guoqu Glacier (33.58°N, 91.18°E, 5750 m a.s.l.) during the Sino–US cooperation expedition on Mt. Geladaindong in the central Tibetan Plateau (TP). In this study, we investigated the high-resolution of atmospheric dust records by using the insoluble particles and crustal ions (Ca 2 + and Mg 2 + ) from the upper 109.93 m segments, covering the period of 1477 to 1982 AD. There existed positive correlations among the ice core dust records themselves and with the dust days from the nearby meteorological stations during the recent decades, indicating that the insoluble particles and crustal ions in the ice core can be used to reconstruct the past atmospheric dust variability. During the past 500 years, the insoluble particles and crustal ions showed high concentrations in the 18th to 19th centuries and low concentrations in the 20th century, corresponding to low and high precipitation in the potential dust source regions. The ice core dust records were positively correlated with the zonal wind and the winter North Atlantic Oscillation (NAO) index, suggesting that NAO may be teleconnected to dust entrainment over the inland TP. This long-term ice core provided an approach to understand the atmospheric dust variability in the central TP during the last 500 years.

Characterizing black carbon (BC) concentrations in the seasonal snowpack is of interest because BC deposition on snow can reduce albedo and accelerate melt. In Washington State, USA snowmelt from the seasonal snowpack provides an important source of water resources, but minimal work has been done characterizing BC concentrations in snow in this region. BC concentrations in snow were monitored over two winters (2012 and 2013) at Tronsen Meadow, located near Blewett Pass in the eastern Cascade Mountains in Central Washington, to characterize spatial and temporal variations in BC concentrations, and the processes affecting BC concentrations in the snowpack. BC concentrations were measured using a Single Particle Soot Photometer. Snowpit BC concentrations at spatial scales ranging from centimeter to 100 m scales were fairly homogenous during the accumulation season, with greater spatial variability during the melt season due to variable melt patterns. BC concentrations in snow increased in late winter-spring due to an increase in atmospheric BC concentrations and trapping of BC on the snow surface during melt. However, during a period of intense melt in 2013 BC concentrations decreased, likely caused by meltwater scavenging. In summer 2012 the Table Mountain forest fire burned adjacent to the study site, and BC concentrations in the snowpack in 2013 were far higher than in previous years, with charred trees postfire the likely source of the elevated BC.

Two ice cores were retrieved from high elevations (~5800 m a.s.l.) at Mt. Nyainqêntanglha and Mt. Geladaindong in the southern and central Tibetan Plateau region. The combined tracer analysis of tritium (3H), 210Pb and mercury, along with other chemical records, provided multiple lines of evidence supporting that the two coring sites had not received net ice accumulation since at least the 1950s and 1980s, respectively. These results implied an annual ice loss rate of more than several hundred millimeter water equivalent over the past 30–60 years. Both mass balance modeling at the sites and in situ data from the nearby glaciers confirmed a continuously negative mass balance (or mass loss) in the region due to dramatic warming in recent decades. Along with a recent report on Naimona'nyi Glacier in the Himalayas, the findings suggest that the loss of accumulation area of glacier is a possibility from the southern to central Tibetan Plateau at high elevations, probably up to about 5800 m a.s.l. This mass loss raises concerns over the rapid rate of glacier ice loss and associated changes in surface glacier runoff, water availability, and sea levels.

Understanding past atmospheric dust variability is necessary to put modern atmospheric dust into historical context and assess the impacts of dust on the climate. In Asia, meteorological data of atmospheric dust is temporally limited, beginning only in the 1950s. High-resolution ice cores provide the ideal archive for reconstructing preinstrumental atmospheric dust concentrations. Using a ~500 year (1477–1982 A.D.) annually resolved calcium (Ca) dust proxy from a Tibetan Plateau (TP) ice core, we demonstrate the lowest atmospheric dust concentrations in the past ~500 years during the latter twentieth century. Declines in late nineteenth to twentieth century Ca concentrations significantly correspond with regional zonal wind trends from two reanalysis models, suggesting that the Ca record provides a proxy for the westerlies. Twentieth century warming and attendant atmospheric pressure reductions over northern Asia have potentially reduced temperature/pressure gradients resulting in lower zonal wind velocities and associated dust entrainment/transport in the past ~500 years over the TP.

In this study we attempt to optimize the method for measuring black carbon (BC) in snow and ice using a single particle soot photometer (SP2). Beside the previously applied ultrasonic (CETAC) and Collison-type nebulizers we introduce a jet (APEX-Q) nebulizer to aerosolize the aqueous sample for SP2 analysis. Both CETAC and APEX-Q require small sample volumes (few milliliters) which makes them suitable for ice core analysis. The APEX-Q shows the least size-dependent nebulizing efficiency in the BC particle diameter range of 100–1000 nm. The CETAC has the advantage that air and liquid flows can be monitored continuously. All nebulizer-types require a calibration with BC standards for the determination of the BC mass concentration in unknown aqueous samples. We found Aquadag to be a suitable material for preparing calibration standards. Further, we studied the influence of different treatments for fresh discrete snow and ice samples as well as the effect of storage. The results show that samples are best kept frozen until analysis. Once melted, they should be sonicated for 25 min, immediately analyzed while being stirred and not be refrozen.

A Mt. Geladaindong (GL) ice core was recovered from the central Tibetan Plateau (TP) spanning the period 1940–2005 AD. High-resolution major ion (Na+, K+, Ca2+, Mg2+, Cl−, SO42−, NO3−) time-series are used to investigate variations in atmospheric dust loading through time. The crustal source ions vary seasonally with peaks in dust concentrations occurring during the winter and spring which are consistent with atmospheric dust observations at local meteorological stations. However, both similarities and dissimilarities are displayed between the decadal variation of atmospheric dust in the GL core and dust observation records from meteorological stations, which can be attributed to local environmental effects at the stations. This paper compares the 1980s and 1970s as case periods for low and high atmospheric dust loading, respectively, two periods reflecting shifts in spring atmospheric circulation (a weakening of zonal and meridional winds) from the 1970s (a period of enhanced dust aerosol transportation to central TP) to the 1980s (a period of diminished dust aerosol transportation to central TP), especially a significant decrease of meridional wind speeds in the 1980s. GL ice core dust proxies (Ca2+ and K+) are correlated with Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) data in spring over the TP and in the northwestern China (especially for K+). Thus variability of crustal ions in central TP ice core provides a proxy for reconstructing a history of atmospheric dust loading not only on the TP, but also in northwestern China.

A Mount Everest ice core analyzed at high resolution for major and trace elements (Sr, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi, U, Tl, Al, S, Ca, Ti, V, Cr, Mn, Fe, Co) and spanning the period a.d. 1650–2002 is used to investigate the sources of and variations in atmospheric dust through time. The chemical composition of dust varies seasonally, and peak dust concentrations occur during the winter–spring months. Significant correlations between the Everest dust record and dust observations at stations suggest that the Everest record is representative of regional variations in atmospheric dust loading. Back-trajectory analysis in addition to a significant correlation of Everest dust concentrations and the Total Ozone Mapping Spectrometer (TOMS) aerosol index indicates that the dominant winter sources of dust are the Arabian Peninsula, Thar Desert, and northern Sahara. Factors that contribute to dust generation at the surface include soil moisture and temperature, and the long-range transport of dust aerosols appears to be sensitive to the strength of 500-mb zonal winds. There are periods of high dust concentration throughout the 350-yr Mount Everest dust record; however, there is an increase in these periods since the early 1800s. The record was examined for recent increases in dust emissions associated with anthropogenic activities, but no recent dust variations can be conclusively attributed to anthropogenic inputs of dust.

Continuous Bi profile of the East Rongbuk (ER) ice core near Mt. Qomolangma reveals nine major volcanic events since AD 1800. Compared with Volcanic Explosivity Index (VEI), it shows that the concentrations of Bi in the ER ice core can reflect the major volcanic events within the key areas. This provides a good horizon layer for ice core dating, as well as a basis for reconstructing a long sequence of volcanic records from the Qinghai-Xizang (Tibet) Plateau ice cores.

In summer 2005, two pilot snow/firn cores were obtained at 5365 and 5206 m a.s.l. on Fedchenko glacier, Pamirs, Tajikistan, the world’s longest and deepest alpine glacier. The well-defined seasonal layering appearing in stable-isotope and trace element distribution identified the physical links controlling the climate and aerosol concentration signals. Air temperature and humidity/precipitation were the primary determinants of stable-isotope ratios. Most precipitation over the Pamirs originated in the Atlantic. In summer, water vapor was re-evaporated from semi-arid regions in central Eurasia. The semi-arid regions contribute to non-soluble aerosol loading in snow accumulated on Fedchenko glacier. In the Pamir core, concentrations of rare earth elements, major and other elements were less than those in the Tien Shan but greater than those in Antarctica, Greenland, the Alps and the Altai. The content of heavy metals in the Fedchenko cores is 2–14 times lower than in the Altai glaciers. Loess from Afghan–Tajik deposits is the predominant lithogenic material transported to the Pamirs. Trace elements generally showed that aerosol concentration tended to increase on the windward slopes during dust storms but tended to decrease with altitude under clear conditions. The trace element profile documented one of the most severe droughts in the 20th century. ‘There is no culture without glaciers. Without the mountain ranges where the snow is accumulated over winter and eventually packed to become ice, the flat lands would be desert lands’W. Rickmer Rickmers (1929); after his expedition to the Pamirs with R. Finsterwalder

Annual-layer thickness data, spanning AD 1534–2001, from an ice core from East Rongbuk Col on Qomolangma (Mount Everest, Himalaya) yield an age–depth profile that deviates systematically from a constant accumulation-rate analytical model. The profile clearly shows that the mean accumulation rate has changed every 50–100 years. A numerical model was developed to determine the magnitude of these multi-decadal-scale rates. The model was used to obtain a time series of annual accumulation. The mean annual accumulation rate decreased from ∼0.8 m ice equivalent in the 1500s to ∼0.3 m in the mid-1800s. From ∼1880 to ∼1970 the rate increased. However, it has decreased since ∼1970. Comparison with six other records from the Himalaya and the Tibetan Plateau shows that the changes in accumulation in East Rongbuk Col are broadly consistent with a regional pattern over much of the Plateau. This suggests that there may be an overarching mechanism controlling precipitation and mass balance over this area. However, a record from Dasuopu, only 125 km northwest of Qomolangma and 700 m higher than East Rongbuk Col, shows a maximum in accumulation during the 1800s, a time during which the East Rongbuk Col and Tibetan Plateau ice-core and tree-ring records show a minimum. This asynchroneity may be due to altitudinal or seasonal differences in monsoon versus westerly moisture sources or complex mountain meteorology.

Annual accumulation records covering the period A.D. 1952–1998 were reconstructed using a 29.5-m ice core from the col of the Lanong Glacier (5850 m a.s.l.) on the eastern saddle of Mt. Nyainqentanglha, southern Tibetan Plateau. Using NCEP/NCAR Reanalysis data, we explore the relationships between this ice-core accumulation record and primary components of the climate system. Linear correlation analysis between annual accumulation and climate components for the 47-yr overlap period indicates that annual accumulation variations are closely correlated with sea-surface and 500-mb air temperature over the North Indian Ocean and atmospheric circulation (surface pressure and geopotential height) over Asia (r > 0.34, P < 0.01). An intensification of atmospheric circulation and increase of sea-surface and air temperatures, resulting in intensified moisture availability and moisture transport, have been a major cause for the increase of ice-core accumulation over the Mt. Nyainquentanglha region since the ...

In May 2005, a total of 14 surface snow (0–10 cm) samples were collected along the climbing route from the advanced base camp to the summit (6500–8844 m a.s.l.) on the northern slope of Mt. Everest (Qomolangma). A 108 m firn/ice core was retrieved from the col of the East Rongbuk Glacier (28.031N, 86.961E, 6518 m a.s.l.) on the north eastern saddle of Mt. Everest in September 2002. Surface snow and the upper 3.5 m firn samples from the core were analyzed for major and trace elements by inductively coupled plasma mass spectroscopy (ICP-MS). Measurements show that crustal elements dominated both surface snow and the firn core, suggesting that Everest snow chemistry is mainly influenced by crustal aerosols from local rock or prevalent spring dust storms over southern/central Asia. There are no clear trends for element variations with elevation due to local crustal aerosol inputs or redistribution of surface snow by strong winds during the spring. Seasonal variability in snow/firn elements show that high elemental concentrations occur during the non-monsoon season and low values during the monsoon season. Ca, Cr, Cs, and Sr display the most distinct seasonal variations. Elemental concentrations (especially for heavy metals) at Mt. Everest are comparable with polar sites, generally lower than in suburban areas, and far lower than in large cities. This indicates that anthropogenic activities and heavy metal pollution have little effect on the Mt. Everest atmospheric environment. Everest firn core REE concentrations are the first reported in the region and seem to be comparable with those measured in modern and Last Glacial Maximum snow/ice samples from Greenland and Antarctica, and with precipitation samples from Japan and the East China Sea. This suggests that REE concentrations measured at Everest are representative of the background atmospheric environment. r 2007 Elsevier Ltd. All rights reserved.

A total of 48 precipitation samples have been collected from individual precipitation events at the Nam Co Monitoring and Research Station for Multisphere Interactions (Nam Co Station, 30°47′N, 90°58′E; 4730 m a.s.l) located in the central Tibetan Plateau from August 2005 to August 2006. All samples were analyzed for major cations (NH4 ,N a + ,K + ,C a 2+ and Mg 2+ ) and anions (Cl − ,N O3 and SO4− ), conductivity and pH. Precipitation pH values ranged from 6.03 to 7.38 with an average value of 6.59. The high pH is due to large inputs of crustal aerosols in the atmosphere, which contain a large fraction of carbonate. Ca 2+ is the dominant cation in precipitation with an average value of 65.58 μeq L −1 (4.91–301.41 μeq L −1 ), accounting for 54% of the total cations in precipitation. HCO3 is the predominant anion, accounting for 62% of the total anions. When compared with data from a snow pit in the Zhadang Glacier 50 km away (5800 m a.s.l), major ion concentration in precipitation at the Nam Co Station is much higher due to local aerosol inputs. Correlation and empirical orthogonal function (EOF) analysis indicate that regional crustal aerosols and species from combustion emissions of residents are the major sources for these ions, lake salt aerosols from the Nam Co nearby and regional mineral aerosols from dry lake sediments are secondary sources, and sea salt contribution is the least due to the long distance transport. © 2007 Elsevier B.V. All rights reserved.

International audience; Time series of west-Antarctic (WA) annual surface mass balance (SMB) from ITASE firn/ice cores are compared with the ECMWF 1958-2001 ERA40 reanalysis-based model forecasts. The ITASE series partially confirm the spatial structure of the signature of El Nino Southern Oscillation (ENSO) in WA precipitation as previously identified in ERA40 and other models. However, an improvement of ERA40's ability to reproduce the west-Antarctic SMB since the 1970s is evidenced and is probably related to the onset and increasing use of satellite data in late 1972 and 1978. Restricting the analysis to the 1973-2000 (satellite) period, interannual correlations between ITASE cores and ERA40 SMB series are generally significant (95% confidence level) but weak. The fraction of common variability increases when the series are spatially averaged, suggesting that small-scale perturbation (SSP) of the large-scale SMB variability significantly contributes to year-to-year variability in single core series. A comparison of stake network and core data from the South Pole suggests that SSP can almost fully obscure the large-scale component of the SMB variability as recorded in a single core. Because of SSP, the 1973-2000 period is too brief to verify whether all aspects of the WA large-scale signatures of ENSO and of the Antarctic Oscillation suggested by ERA40 are confirmed in the core series. More annually resolved field data from cores and stakes, spatially extended using high-resolution ground penetrating radar, are necessary to fully assess the relationship between the Antarctic SMB and the large-scale climate as currently suggested by meteorological and climate models.

Shallow ice cores were obtained from widely distributed sites across the West Antarctic ice sheet, as part of the United States portion of the International Trans-Antarctic Scientific Expedition (US ITASE) program. The US ITASE cores have been dated by annual-layer counting, primarily through the identification of summer peaks in non-sea-salt sulfate (nssSO42–) concentration. Absolute dating accuracy of better than 2 years and relative dating accuracy better than 1 year is demonstrated by the identification of multiple volcanic marker horizons in each of the cores, Tambora, Indonesia (1815), being the most prominent. Independent validation is provided by the tracing of isochronal layers from site to site using high-frequency ice-penetrating radar observations, and by the timing of mid-winter warming events in stable-isotope ratios, which demonstrate significantly better than 1 year accuracy in the last 20 years. Dating precision to ±1 month is demonstrated by the occurrence of summer nitrate peaks and stable-isotope ratios in phase with nssSO42–, and winter-time sea-salt peaks out of phase, with phase variation of

We present highly resolved, annually dated, calibrated proxies for atmospheric circulation from several Antarctic ice cores (ITASE (International Trans-Antarctic Scientific Expedition), Siple Dome, Law Dome) that reveal decadal-scale associations with a South Pole ice-core 10Be proxy for solar variability over the last 600 years and annual-scale associations with solar variability since AD 1720. We show that increased (decreased) solar irradiance is associated with increased (decreased) zonal wind strength near the edge of the Antarctic polar vortex. The association is particularly strong in the Indian and Pacific Oceans and as such may contribute to understanding climate forcing that controls drought in Australia and other Southern Hemisphere climate events. We also include evidence suggestive of solar forcing of atmospheric circulation near the edge of the Arctic polar vortex based on ice-core records from Mount Logan, Yukon Territory, Canada, and both central and south Greenland as enticement for future investigations. Our identification of solar forcing of the polar atmosphere and its impact on lower latitudes offers a mechanism for better understanding modern climate variability and potentially the initiation of abrupt climate-change events that operate on decadal and faster scales.

Sixteen high-resolution marine aerosol (Na+, SO42–) records from spatially distributed International Trans-Antarctic Scientific Expedition (ITASE) ice cores spanning the last ~200 years from the Pine Island–Thwaites and Ross drainage systems and the South Pole are used to examine sources (sea spray and frost flowers) and transport pathways of marine aerosols into West Antarctica. Factors contributing to the amount of marine aerosols transported inland include sea-ice extent, the presence of open-water features (polynyas, leads), wind strength and direction, and the strength and positioning of low-pressure systems. Analysis of SO42–/Na+ ratios indicates that frost flowers can contribute significantly (40%) to the Na+ budget of Antarctic ice cores. Higher Na+ concentrations in the Ross drainage system may result from greater production of marine aerosols related to frost flowers in the Ross Sea region in association with greater sea-ice extent and larger open-water areas. Significant positive correlations of sea-ice extent and the Na+ time series exist in some regions of West Antarctica. Higher wind speeds in winter and higher Na+ concentrations when sea-level pressure is lower indicate that intensified atmospheric circulation enhances transport and production of marine aerosols.

Chemistry data from 16, 50–115m deep, sub-annually dated ice cores are used to investigate spatial and temporal concentration variability of sea-salt (ss) SO42– and excess (xs) SO42– over West Antarctica and the South Pole for the last 200 years. Low-elevation ice-core sites in western West Antarctica contain higher concentrations of SO42– as a result of cyclogenesis over the Ross Ice Shelf and proximity to the Ross Sea Polynya. Linear correlation analysis of 15 West Antarctic ice-core SO42– time series demonstrates that at several sites concentrations of ssSO42– are higher when sea-ice extent (SIE) is greater, and the inverse for xsSO42–. Concentrations of xsSO42– from the South Pole site (East Antarctica) are associated with SIE from the Weddell region, and West Antarctic xsSO42– concentrations are associated with SIE from the Bellingshausen–Amundsen–Ross region. The only notable rise of the last 200 years in xsSO42–, around 1940, is not related to SIE fluctuations and is most likely a result of increased xsSO42– production in the mid–low latitudes and/or an increase in transport efficiency from the mid–low latitudes to central West Antarctica. These high-resolution records show that the source types and source areas of ssSO42– and xsSO42– delivered to eastern and western West Antarctica and the South Pole differ from site to site but can best be resolved using records from spatial ice-core arrays such as the International Trans-Antarctic Scientific Expedition (ITASE).

Sixteen high-resolution ice-core records from West Antarctica and South Pole are used to examine the spatial and temporal distribution of sulfate for the last 200 years. The preservation of seasonal layers throughout the length of each record results in a dating accuracy of better than 1 year based on known global-scale volcanic events. A dual transport source for West Antarctic sea-salt (ss) SO42– and excess (xs) SO42– is observed: lower-tropospheric for areas below 1000m elevation and mid-/upper-tropospheric/stratospheric for areas located above 1000 m. Our xsSO42– records with volcanic peaks removed do not display any evidence of an anthropogenic impact on West Antarctic SO42– concentrations but do reveal that a major climate transition takes place over West Antarctica at ∼1940. Global-scale volcanic eruptions appear as significant peaks in the robust-spline residual xsSO42– records from sites located above 1000m elevation but do not appear in the residual records from sites located below 1000 m.

Isochronal layers in firn detected with ground-penetrating radar (GPR) and dated using results from ice-core analyses are used to calculate accumulation rates along a 100 km across-flow profile in West Antarctica. Accumulation rates are shown to be highly variable over short distances. Elevation measurements from global positioning system surveys show that accumulation rates derived from shallow horizons correlate well with surface undulations, which implies that wind redistribution of snow is the leading cause of this variability. Temporal changes in accumulation rate over 25–185 year intervals are smoothed to along-track length scales comparable to surface undulations in order to identify trends in accumulation that are likely related to changes in climate. Results show that accumulation rates along this profile have decreased in recent decades, which is consistent with core-derived time series of annual accumulation rates measured at the two ends of the radar profile. These results suggest that temporal variability observed in accumulation-rate records from ice cores and GPR profiles can be obscured by spatial influences, although it is possible to resolve temporal signals if the effects of local topography and ice flow are quantified and removed.

Thirteen annually resolved accumulation-rate records covering the last ~200 years from the Pine Island–Thwaites and Ross drainage systems and the South Pole are used to examine climate variability over West Antarctica. Accumulation is controlled spatially by the topography of the ice sheet, and temporally by changes in moisture transport and cyclonic activity. A comparison of mean accumulation since 1970 at each site to the long-term mean indicates an increase in accumulation for sites located in the western sector of the Pine Island–Thwaites drainage system. Accumulation is negatively associated with the Southern Oscillation Index (SOI) for sites near the ice divide, and periods of sustained negative SOI (1940–42, 1991–95) correspond to above-mean accumulation at most sites. Correlations of the accumulation-rate records with sea-level pressure (SLP) and the SOI suggest that accumulation near the ice divide and in the Ross drainage system may be associated with the mid-latitudes. The post-1970 increase in accumulation coupled with strong SLP–accumulation-rate correlations near the coast suggests recent intensification of cyclonic activity in the Pine Island– Thwaites drainage system.

Two ice cores were retrieved from high elevations (~ 5800 m a.s.l.) at Mt. Nyainqentanglha and Mt. Geladaindong in the southern to inland Tibetan Plateau. The combined analysis of tritium (3H), 210Pb, mercury tracers, along with other chemical records, revealed that the two coring sites had not received net ice accumulation since at least the 1950s and 1980s, respectively, implying an annual ice loss rate of more than several hundred millimeter water equivalent over these periods. Both mass balance modeling at the sites and in situ data from nearby glaciers confirmed a continuously negative mass balance (or mass loss) in the region due to the dramatic warming in the last decades. Along with a recent report on Naimona'nyi Glacier in the Himalaya, the findings suggest that glacier decapitation (i.e., the loss of the accumulation zone) is a wide-spread phenomenon from the southern to inland Tibetan Plateau even at the summit regions. This raises concerns over the rapid rate of glacier ice loss and associated changes in surface glacier runoff, water availability, and sea levels.

We analyzed refractory black carbon (rBC) in an ice core spanning 1875–2000 AD from Mt. Muztagh Ata, the Eastern Pamirs, using a Single Particle Soot Photometer (SP2). Additionally a pre-existing levoglucosan record from the same ice core was used to differentiate rBC that originated from open fires, energy-related combustion of biomass, and fossil fuel combustion. Mean rBC concentrations increased four-fold since the mid-1970s and reached maximum values at end of the 1980s. The observed decrease of the rBC concentrations during the 1990s was likely driven by the economic recession of former USSR countries in Central Asia. Levoglucosan concentrations showed a similar temporal trend to rBC concentrations, exhibiting a large increase around 1980 AD followed by a decrease in the 1990s that was likely due to a decrease in energy-related biomass combustion. The time evolution of levoglucosan/rBC ratios indicated stronger emissions from open fires during the 1940s–1950s, while the increase in rBC during the 1980s–1990s was caused from an increase in energy-related combustion of biomass and fossil fuels.

Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snow pits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal during spring and fall 2009, providing the first observational data of BC concentrations in snow and ice from the southern slope of the Himalaya. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). Measured BC concentrations underestimate actual BC concentrations due to changes to the sample during storage and loss of BC particles in the ultrasonic nebulizer; thus, we correct for the underestimated BC mass. BC and Fe concentrations are substantially higher at elevations < 6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations < 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter–spring snow/ice horizons are sufficient to reduce albedo by 6–10% relative to clean snow, corresponding to localized instantaneous radiative forcings of 75–120 W m−2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40–42% relative to clean snow and give localized instantaneous radiative forcings of 488 to 525 W m−2. Adding the BC absorption to the other impurities results in additional radiative forcings of 3 W m−2. The BC and Fe concentrations were used to further examine relative absorption of BC and dust. When dust concentrations are high, dust dominates absorption, snow albedo reduction, and radiative forcing, and the impact of BC may be negligible, confirming the radiative transfer modeling. When impurity concentrations are low, the absorption by BC and dust may be comparable; however, due to the low impurity concentrations, albedo reductions are small. While these results suggest that the snow albedo and radiative forcing effect of dust is considerably greater than BC, there are several sources of uncertainty. Further observational studies are needed to address the contribution of BC, dust, and colored organics to albedo reductions and snow and ice melt, and to characterize the time variation of radiative forcing., Atmospheric Chemistry and Physics, 14 (15), ISSN:1680-7375, ISSN:1680-7367

Black carbon (BC) deposited on snow and glacier surfaces can reduce albedo and lead to accelerated melt. An ice core recovered from Guoqu glacier on Mt. Geladaindong and analyzed using a Single Particle Soot Photometer provides the first long-term (1843–1982) record of BC concentrations from the Central Tibetan Plateau. The highest concentrations are observed from 1975–1982, which corresponds to a 2.0-fold and 2.4-fold increase in average and median values, respectively, relative to 1843–1940. BC concentrations post-1940 are also elevated relative to the earlier portion of the record. Causes for the higher BC concentrations include increased regional BC emissions and subsequent deposition, and melt induced enrichment of BC, with the melt potentially accelerated due to the presence of BC at the glacier surface. A qualitative comparison of the BC and Fe (used as a dust proxy) records suggests that if changes in the concentrations of absorbing impurities at the glacier surface have influenced recent glacial melt, the melt may be due to the presence of BC rather than dust. Guoqu glacier has received no net ice accumulation since the 1980s, and is a potential example of a glacier where an increase in the equilibrium line altitude is exposing buried high impurity layers. That BC concentrations in the uppermost layers of the Geladaindong ice core are not substantially higher relative to deeper in the ice core suggests that some of the BC that must have been deposited on Guoqu glacier via wet or dry deposition between 1983 and 2005 has been removed from the surface of the glacier, potentially via supraglacial or englacial meltwater.