Glacier melt provides an important source of freshwater, particularly during dry years and late in the summer, after most of the seasonal snow has melted. Glaciers are losing mass in most of the world’s mountain regions, which leads to uncertainties around the availability of freshwater to the downstream catchments. While contributions of glacial meltwater to rivers can be quantified through hydrograph separation methods, changes in the chemical characteristics of glacial meltwater may impact these calculations. We collected samples of supraglacial snow and ice and proglacial stream water over the course of a melt season at Haig Glacier in the Canadian Rocky Mountains and analyzed these samples for stable water isotopes (oxygen-18 and deuterium) and dissolved major ions to assess their seasonal variability. We identify isotopic enrichment in stable water isotopes on the surface of Haig Glacier as dry snow turns to wet snow and eventually in the bare ice that remains. This enrichment is reflected in isotopic ratios in the proglacial stream. Two possible explanations include: 1) isotopic enrichment through sublimation or liquid water evaporation on the glacier surface, 2) isotopic fractionation during diurnal freeze-thaw cycles, with the heavier isotopes preferentially refreezing. We evaluate both of these scenarios and conclude that both processes are likely active, with evaporation effects sufficient to explain much of the observed isotopic enrichment in the glacial runoff.

Tapado Glacier is a subtropical mountain glacier in the Coquimbo region of Chile that has been continuously retreating during the last 60 years due to diminishing precipitation rates and rising temperatures and likely due to a currently unknown influence from atmospheric pollutant deposition. Climatic and meteorological impacts on this, and other, Andean glacier have been previously studied; however, cryosphere changes driven by aerosols are still largely unknown. To contribute to the understanding of the origin of aerosols and their dispersion, this study aims to identify natural and anthropogenic sources of air pollution deposited on the Tapado Glacier (4500–5536 m a.s.l.) and their transport by using a receptor model (positive matrix factorization) together with the concentration of major ions as proxies of air pollution deposited on this glacier. This model’s outcomes were complemented with daily wind backward trajectories computed for a whole year using the HYSPLYT meteorological model. Four sources were identified as the main contributors to major soluble ions in the Tapado surface snow. These sources are natural Aeolian dust (38%) from the Atacama Desert (including mining sites), natural weathered sulphates (27%), anthropogenic nitrates (25%), and coastal aerosols (10%). Coastal nitrate emissions and coastal aerosols are both sources with an important anthropogenic component, coming from La Serena and Coquimbo’s coastal cities. The crustal components and sulphate profiles are similar to detritus dispersed from the glacier after wind erosion. Although the glacier is located over 4000 m above sea level, anthropogenic pollutants reached this location. However, their contributions were smaller compared to natural contaminants. Our findings can likely be extended to the nearest glaciers in Northern Chile, which have similar potential contaminant sources from cities, ports, and thriving mining activity. However, these findings may not be suitable for southern Chilean glaciers, which are closer to bigger cities and to smoke from residential heating prevalent in winter months and wildfires during the summer.

Matlab data file containing the GraphEM- infilled version of HadCRUT4.2

PAGES, a core project of Future Earth, is supported by the U.S. and Swiss National Science Foundations. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Some of this work was conducted as part of the North America 2k Working Group supported by the John Wesley Powell Center for Analysis and Synthesis, funded by the U.S. Geological Survey. B. Bauer, W. Gross, and E. Gille (NOAA National Centers for Environmental Information) are gratefully acknowledged for helping assemble the data citations and creating the NCEI versions of the PAGES 2k data records. We thank all the investigators whose commitment to data sharing enables the open science ethos embodied by this project.

This study uses stable isotopes and major ions to examine the seasonal evolution of penitentes on the surface of Tapado Glacier, in the Norte Chico region of the Chilean Andes. A snow pit was sampled in November 2011, and penitentes were sampled during the summer (December 2011 and January 2012). The major ion load of the winter snowpack is dominated by Ca2+ (60%), SO42- (16%) and NO3- (13%), and there is little influence from marine air masses at the site, with most SO42-, Mg2+, Ca2+ and Na+, derived from non-sea salt sources. During the early ablation season we observe increases in stable isotope ratios and major ion concentrations (particularly lithic ions Na+, Mg2+ and Ca2+) in the upper reaches of penitentes, which is attributed to sublimation and the aeolian deposition of dust particles. In the late-summer, melt replaces sublimation as the dominant ablation process and results in smoothing of the stable isotope profile and the elution of major ions within the penitente snow and ice matrix. Copyright (C) 2015 John Wiley & Sons, Ltd.

We present the first proxy record of sea-ice area (SIA) in the Ross Sea, Antarctica, from a 130year coastal ice-core record. High-resolution deuterium excess data show prevailing stable SIA from the 1880s until the 1950s, a 2-5% reduction from the mid-1950s to the early-1990s, and a 5% increase after 1993. Additional support for this reconstruction is derived from ice-core methanesulphonic acid concentrations and whaling records. While SIA has continued to decline around much of the West Antarctic coastline since the 1950s, concurrent with increasing air and ocean temperatures, the underlying trend is masked in the Ross Sea by a switch to positive SIA anomalies since the early-1990s. This increase is associated with a strengthening of southerly winds and the enhanced northward advection of sea ice.

Understanding airmass pathways is critical for ice core interpretation, and the ability to determine the broadscale characteristics and seasonality of synoptic-scale flow using paleoclimate records offers great potential to improve the understanding of past atmospheric circulation. The dominant airmass pathways to a coastal Antarctic ice core site at the Whitehall Glacier in the Ross Sea are modeled using snowfall and high-resolution stable isotope data between 1979 and 2006, combined with back trajectories produced from both NCEP-NCAR and ECMWF Interim Re-Analysis (ERA-Interim) data. Back trajectories generated from both datasets produce comparable results. They show that high snowfall is associated with cyclonic airflow in the Ross Sea with a strong meridional component along the western Ross Sea coast. Over a 28-yr time frame, trajectories also reveal a clear distinction between flow paths associated with above-and below-average annual temperatures (high and low delta D) in the ice core record. In cold months (low delta D), when there is a strengthened trough of low pressure around the continent, synoptically driven incursions of marine air across West Antarctica and trajectories originating from coastal East Antarctica are dominant. Conversely, in warmer months (high delta D), airmass pathways are centered over the Ross Sea and the adjacent Southern Ocean. These trajectories are slower moving and are expected to draw marine moisture from high-latitude seasonally open oceans.

Synoptic variability in the Ross Sea region, Antarctica over the last thirty years is investigated using back‐trajectory modeling and cluster analysis. We identify two dominant air‐mass trajectory clusters: oceanic/West Antarctic and continental/East Antarctic. Our analysis shows that the oceanic/West Antarctic trajectories have an annual cycle similar to the Semiannual Oscillation and on average peak in frequency during April, while continental/East Antarctic trajectories reach their annual maximum during December. We demonstrate a causal association between the El Niño Southern Oscillation (ENSO) and the frequency of oceanic/West Antarctic trajectories originating from the Ross Sea and Amundsen Sea regions. In contrast, we find that the Southern Annular Mode (SAM) has little influence on the trajectory cluster frequencies. We then develop proxy records for synoptic variability using a shallow firn core from Gawn Ice Piedmont in Southern Victoria Land. Continental/East Antarctic trajectory frequency correlates with concentrations of nitrate (NO3), which is sourced from stratospheric air‐masses descending over the Antarctic interior. At seasonal to inter‐annual scales, the frequency of oceanic/West Antarctic trajectory clusters strongly correlate with deuterium excess, which is sensitive to changes in relative humidity and sea surface temperature in the Ross and Amundsen Seas. Inter‐annual variability in the frequency of oceanic/West Antarctic trajectories is discussed with respect to ENSO and changes in SST and sea ice extent.

A 125-yr ice core record of climate from the Whitehall Glacier ice divide provides exceptionally highresolution stable isotope data from the northwest margin of the Ross Sea, Antarctica. This is the only proxy data available to extend the instrumental record of temperature in this region, where little is known about climate variability over the past two centuries. Using ECMWF Interim Re-Analysis (ERA-Interim) data, this study develops a precipitation-weighted d 18 O-temperature transfer function of 0.62& 8C 21 ,w hich is comparable toother proximal icecores, such as Taylor, Talos, andLaw Domes. Reconstructedmean annual temperatures show no significant change between 1882 and 2006. However, a decrease in cold season [April‐September (AMJJAS)] temperatures of 21.59 86 0.848 Cd ecade 21 (at 90% confidence) is observed since 1979. This cooling trend is in contrast to a surface temperature record from Ross Island (Scott Base) where significant spring warming is observed. It is also coincident with a positive trend in the southern annular mode, which is linked to stronger southerly winds and increased sea ice extent and duration in the western Ross Sea.

This study presents a first quantitative study of inorganic ion concentrations and loading in precipitation in the Canadian Rocky Mountains. The 2005/2006 winter snowpack and July 2006 rainfall are examined to define the magnitude, and altitudinal and seasonal variability of atmospheric deposition at high altitude sites. Little is currently known about the sources and concentrations of inorganic ions in watersheds in this region, and careful measurement of snowpack and rainfall chemistry are required to accurately assess the total annual deposition and the potential environmental effects of atmospheric pollution on high elevation ecosystems and snowmelt-dominated catchments on both sides of the continental divide. Snowpit profiles from three sites between 2100 and 2750 m above sea level (masl) show little variation in ion concentrations with altitude, but all sites show strong seasonal variations. Air-mass back trajectories and the identification of storms in snowpits using high-resolution oxygen isotope (00) data show that the increases in acid anions in the surface (spring) layers and early-winter snow layers are associated with southwesterly storm systems that swept moisture across the northwestern US into western Canada. July rainfall ion concentrations were 1.5-3.0 times higher than winter snowpack concentrations and were also primarily associated with southwesterly storms. The chemical composition of precipitation in this region, and the relative contribution of snow and rain to annual precipitation, suggest that rates of nitrogen (N) deposition in the Canadian Rocky Mountains may be comparable to the US Rocky Mountains where N deposition is altering ecosystem function. These results lend support to increased monitoring of precipitation chemistry in this environmentally sensitive region. (C) 2011 Elsevier B.V. All rights reserved.

A Lagrangian (Rayleigh) distillation model is used to track the evolution of stable isotopes in precipitation over mountainous terrain from the Pacific Coast of Canada to two alpine field sites in the Canadian Rocky Mountains. Precipitation δ18O at Vancouver constrains the model and air–mass back trajectories provide the water vapour pathway for 10 winter storm events. Isotopic values along storm pathways are modelled with a classical Rayleigh model that prescribes a linear decrease in temperature and pressure from initial to final conditions, and two models that account directly for orographic precipitation processes by: (i) applying an orographic rainfall model and (ii) using North American Regional Reanalysis data to calculate the change in vapour content along storm pathways. All models are significant predictors of snowpack δ18O, but the orographic model provides the best fit to precipitation‐weighted δ18O for each storm. The improvement in modelled δ18O by accounting for terrain along storm trajectories illustrates the need to account for orographically driven moisture loss when modelling vapour transport to ice core sites with mountainous upwind terrain. This finding is also applicable to isotopic studies of paleoaltimetry and source areas of groundwater recharge. Copyright © 2011 John Wiley & Sons, Ltd.

Dominant storm tracks to two ice core sites on the western margin of the Ross Sea, Antarctica (Skinner Saddle (SKS) and Evans Piedmont Glacier), are investigated to establish key synoptic controls on snow accumulation. This is critical in terms of understanding the seasonality, source regions, and transport pathways of precipitation delivered to these sites. In situ snow depth and meteorological observations are used to identify major accumulation events in 2007–2008, which differ considerably between sites in terms of their magnitude and seasonal distribution. While snowfall at Evans Piedmont Glacier occurs almost exclusively during summer and spring, Skinner Saddle receives precipitation year round with a lull during the months of April and May. Cluster analysis of daily back trajectories reveals that the highest‐accumulation days at both sites result from fast‐moving air masses, associated with synoptic‐scale low‐pressure systems. There is evidence that short‐duration pulses of snowfall at SKS also originate from mesocyclone development over the Ross Ice Shelf and local moisture sources. Changes in the frequency and seasonal distribution of these mechanisms of precipitation delivery will have a marked impact on annual accumulation over time and will therefore need careful consideration during the interpretation of stable isotope and geochemical records from these ice cores.

Five high schools in British Columbia, Canada, participated in an atmospheric sciences project during the winter of 2006-07 established by researchers at the University of Calgary. Precipitation gauges and temperature and relative humidity probes were installed at each school and students were asked to collect a water sample each day that precipitation accumulated. These samples were used to trace the evolution of stable water isotopes across southwestern Canada. Researchers visited schools to talk about water resources and climate change, and data were collated and given to teachers to use in an atmospheric science project. The participatory nature of this project gave students exposure to data collection and basic analytical techniques used in atmospheric sciences. This was a first attempt at collaboration between our research group and secondary schools, and we point out a number of issues that arose in our study with respect to a successful two-way engagement between researchers and students. These include school engagement, the geographic distribution of the participating schools, the time span of the project, and the time available to schools. There are also a number of data quality considerations, but we were successful overall in acquiring a unique, high-quality dataset that satisfies our research objectives.

The effects of temperature and seasonal air-mass trajectories on stable water isotopes in alpine snowpacks are investigated using meteorological and snow-pit data at two alpine field sites in the Canadian Rocky Mountains: Haig Glacier, Alberta, and Opabin Glacier, British Columbia. Snow pits were sampled through three accumulation seasons (October-June, 2004/05, 2005/06 and 2006/07) for delta O-18, delta D, temperature and density. The isotopic characteristics of precipitation over these time periods, including the local meteoric waterline and average delta O-18, delta D and deuterium excess, were defined using this dataset. Individual snowfall events over the three seasons were identified in the accumulation records from both sites and then fit to snow-pit stratigraphies to determine their mean isotopic characteristics. A trajectory classification was produced for all events, and the key meteorological characteristics of each trajectory class were investigated using data from alpine field sites and a suite of meteorological records from the region. An analysis of the relative influences of temperature and air-mass trajectory on snow isotope ratios reveals some separation in mean delta O-18 between storm classes. However, the separation appears to be driven primarily by the mean temperature of each class rather then being a direct effect of vapour pathway.

To assess the seasonal stability of the delta O-18 stratigraphy in winter snowpacks in the Canadian Rocky Mountains, snow pits were sampled over three accumulation seasons at two field sites. These sites, Opabin and Haig Glaciers, are similar to 160 km apart at similar elevations and represent windward and lee-slope environments respectively. At both sites, snow pits were sampled at one glacier and one forefield location throughout each accumulation season. Intra-seasonal changes in delta O-18 at each site were examined to determine the extent of post-depositional modification of isotope stratigraphies. At both glacier sites, there was minimal temporal change before the onset of spring melt in all years. in addition, the similar structure of delta O-18 profiles from both glacier sites suggests that regional controls govern the isotopic composition of solid-phase precipitation across the study area. At forefield locations, the absence of an insulating layer of ice at the base of the snowpack allowed for vapour transport and post-depositional modification of the seasonal delta O-18 signal. This did not result in consistent changes to the mean delta O-18 deuterium excess and delta D-delta O-18 regression line slopes in the lower layers of snow, and the observed smoothing of delta O-18 profiles was less than that simulated by applying a diffusion model to these snowpacks.

Fresh snow samples were collected following seven snow accumulation events along an altitudinal transect of the Robertson Valley. This glacierized valley is on the eastern slopes of the Canadian Rockies at the Continental Divide and receives precipitation from both westerly (Pacific) air masses and from easterly (upslope) systems. Snow samples were collected over two winter seasons and were analyzed for delta O-18, revealing altitudinal gradients that ranged from -0.3 parts per thousand/100 m to +1.8 parts per thousand/100 m. Five of seven snow events had positive (inverse) isotopic gradients with altitude: 180 enrichment at higher altitudes. Surface and upper-air meteorological data were analyzed to classify the type of weather systems bringing precipitation to the area for each accumulation event. Three storm classifications were developed: westerly, upslope, and mixed/northwesterly systems. Positive delta O-18-elevation gradients were found under strong westerly and northwesterly flow, when the Robertson Valley acts as a leeward slope, while more conventional negative gradients correspond with upslope flow, when easterly winds make the Robertson Valley a windward snow deposition environment. We interpret the inverse isotopic gradients as evidence of ongoing Rayleigh distillation as westerly systems cross the Continental Divide. Position on the Rayleigh distillation curve had a strong influence on the magnitude of delta O-18-elevation gradients.