A new sensitive method for the quantification of glyoxal and methylglyoxal in snow and ice by stir bar sorptive extraction and liquid desorption-HPLC-ESI-MS

In this study, the development of a new sensitive method for the analysis of alpha-dicarbonyls glyoxal (G) and methylglyoxal (MG) in environmental ice and snow is presented. Stir bar sorptive extraction with in situ derivatization and liquid desorption (SBSE-LD) was used for sample extraction, enrichment, and derivatization. Measurements were carried out using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). As part of the method development, SBSE-LD parameters such as extraction time, derivatization reagent, desorption time and solvent, and the effect of NaCl addition on the SBSE efficiency as well as measurement parameters of HPLC-ESI-MS/MS were evaluated. Calibration was performed in the range of 1–60 ng/mL using spiked ultrapure water samples, thus incorporating the complete SBSE and derivatization process. 4-Fluorobenzaldehyde was applied as internal standard. Inter-batch precision was <12 % RSD. Recoveries were determined by means of spiked snow samples and were 78.9 ± 5.6 % for G and 82.7 ± 7.5 % for MG, respectively. Instrumental detection limits of 0.242 and 0.213 ng/mL for G and MG were achieved using the multiple reaction monitoring mode. Relative detection limits referred to a sample volume of 15 mL were 0.016 ng/mL for G and 0.014 ng/mL for MG. The optimized method was applied for the analysis of snow samples from Mount Hohenpeissenberg (close to the Meteorological Observatory Hohenpeissenberg, Germany) and samples from an ice core from Upper Grenzgletscher (Monte Rosa massif, Switzerland). Resulting concentrations were 0.085–16.3 ng/mL for G and 0.126–3.6 ng/mL for MG. Concentrations of G and MG in snow were 1–2 orders of magnitude higher than in ice core samples. The described method represents a simple, green, and sensitive analytical approach to measure G and MG in aqueous environmental samples.

Eemian interglacial reconstructed from a Greenland folded ice core

Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8±4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400±250 metres, reaching surface elevations 122,000 years ago of 130±300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.

Microstructural, chemical and isotopic evidence for the origin of late neolithic leather recovered from an ice field in the Swiss Alps

Archaeological leather samples recovered from the ice field at the Schnidejoch Pass (altitude 2756 m amsl) in the western Swiss Alps were studied using optical, chemical molecular and isotopic (δ13C and δ15N of the bulk leather, and compound-specific δ13C analyses of the organic-solvent extracted fatty acids) methods to obtain insight into the origin of the leather and ancient tanning procedures. For comparison, leathers from modern native animals in alpine environment (red deer, goat, sheep, chamois, and calf/cow) were analyzed using the same approach. Optical and electron microscopically comparisons of Schnidejoch and modern leathers showed that the gross structure (pattern of collagen fibrils and intra-fibrils material) of archaeological leather had survived essentially intact for five millennia. The SEM studies of the hairs from the most important archaeological find, a Neolithic leather legging, show a wave structure of the hair cuticle, which is a diagnostic feature for goatskins. The variations of the bulk δ13C and δ15N values, and δ13C values of the main fatty acids are within the range expected for pre-industrial temperate C3 environment. The archaeological leather samples contain a mixture of indigenous (from the animal) and exogenous plant/animal lipids. An important amount of waxy n-alkanes, n-alkan-1-ols and phytosterols (β-sitosterol, sitostanol) in all samples, and abundant biomarker of conifers (nonacosan-10-ol) in the legging leathers clearly indicate that the Neolithic people were active in a subalpine coniferous forest, and that they used an aqueous extract of diverse plant material for tanning leather.

210Pb dating of the Miaoergou ice core from the eastern Tien Shan, China

In 2005, two ice cores with lengths of 58.7 and 57.6 m respectively to bedrock were recovered from the Miaoergou flat-topped glacier (43 degrees 03 ' 19 '' N, 94 degrees 19 ' 21 '' E; 4512 m a.s.l.), eastern Tien Shan. Pb-210 dating of one of the ice cores (57.6 m) was performed, and an age of AD 1851 +/- 6 at a depth of 35.2 m w.e. was determined. For the period AD 1851-2005, a mean annual net accumulation of 229 +/- 7 mm w.e. a(-1) was calculated. At the nearby oasis city of Hami (similar to 80 km from the Miaoergou flat-topped glacier) the annual precipitation rate is 38 mm w.e. a(-1), hence glacial meltwater is a major water supply for local residents. The surface activity concentration of Pb-210(ex) was found to be similar to 400 mBq kg(-1), which is higher than observed at other continental sites such as Belukha, Russia, and Tsambagarav, Mongolia, which have surface activity concentrations of 280 mBq kg(-1). The Pb-210 dating agrees well with the chronological sequence deduced from the annual-layer counting resulting from the seasonalities of delta O-18 and trace metals for the period AD 1953-2005, and beta-activity horizons resulting from atmospheric nuclear testing during the period AD 1962-63. We conclude that Pb-210 analysis is a suitable method for obtaining a continuous dating of the Miaoergou ice core for similar to 160 years, which can also be applied to other ice cores recovered from the mountains of western China.

Fire in ice: two millennia of boreal forest fire history from the Greenland NEEM ice core

Biomass burning is a major source of greenhouse gases and influences regional to global climate. Pre-industrial fire-history records from black carbon, charcoal and other proxies provide baseline estimates of biomass burning at local to global scales spanning millennia, and are thus useful to examine the role of fire in the carbon cycle and climate system. Here we use the specific biomarker levoglucosan together with black carbon and ammonium concentrations from the North Greenland Eemian (NEEM) ice cores (77.49° N, 51.2° W; 2480 m a.s.l) over the past 2000 years to infer changes in boreal fire activity. Increases in boreal fire activity over the periods 1000–1300 CE and decreases during 700–900 CE coincide with high-latitude NH temperature changes. Levoglucosan concentrations in the NEEM ice cores peak between 1500 and 1700 CE, and most levoglucosan spikes coincide with the most extensive central and northern Asian droughts of the past millennium. Many of these multi-annual droughts are caused by Asian monsoon failures, thus suggesting a connection between low- and high-latitude climate processes. North America is a primary source of biomass burning aerosols due to its relative proximity to the Greenland Ice Cap. During major fire events, however, isotopic analyses of dust, back trajectories and links with levoglucosan peaks and regional drought reconstructions suggest that Siberia is also an important source of pyrogenic aerosols to Greenland.

A community-based geological reconstruction of Antarctic Ice Sheet deglaciation since the Last Glacial Maximum

A robust understanding of Antarctic Ice Sheet deglacial history since the Last Glacial Maximum is important in order to constrain ice sheet and glacial-isostatic adjustment models, and to explore the forcing mechanisms responsible for ice sheet retreat. Such understanding can be derived from a broad range of geological and glaciological datasets and recent decades have seen an upsurge in such data gathering around the continent and Sub-Antarctic islands. Here, we report a new synthesis of those datasets, based on an accompanying series of reviews of the geological data, organised by sector. We present a series of timeslice maps for 20 ka, 15 ka, 10 ka and 5 ka, including grounding line position and ice sheet thickness changes, along with a clear assessment of levels of confidence. The reconstruction shows that the Antarctic Ice sheet did not everywhere reach the continental shelf edge at its maximum, that initial retreat was asynchronous, and that the spatial pattern of deglaciation was highly variable, particularly on the inner shelf. The deglacial reconstruction is consistent with a moderate overall excess ice volume and with a relatively small Antarctic contribution to meltwater pulse 1a. We discuss key areas of uncertainty both around the continent and by time interval, and we highlight potential priorities for future work. The synthesis is intended to be a resource for the modelling and glacial geological community.

Sea surface temperature and sea ice variability in the subpolar North Atlantic from explosive volcanism of the late thirteenth century

In this study, we use IP and alkenone biomarker proxies to document the subdecadal variations of sea ice and sea surface temperature in the subpolar North Atlantic induced by the decadally paced explosive tropical volcanic eruptions of the second half of the thirteenth century. The short- and long-term evolutions of both variables were investigated by cross analysis with a simulation of the IPSL-CM5A LR model. Our results show short-term ocean cooling and sea ice expansion in response to each volcanic eruption. They also highlight that the long response time of the ocean leads to cumulative surface cooling and subsurface heat buildup due to sea ice capping. As volcanic forcing relaxes, the surface ocean rapidly warms, likely amplified by subsurface heat, and remains almost ice free for several decades

A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three synchronized Greenland ice-core records: refining and extending the INTIMATE event stratigraphy

Due to their outstanding resolution and well-constrained chronologies, Greenland ice-core records provide a master record of past climatic changes throughout the Last Interglacial–Glacial cycle in the North Atlantic region. As part of the INTIMATE (INTegration of Ice-core, MArine and TErrestrial records) project, protocols have been proposed to ensure consistent and robust correlation between different records of past climate. A key element of these protocols has been the formal definition and ordinal numbering of the sequence of Greenland Stadials (GS) and Greenland Interstadials (GI) within the most recent glacial period. The GS and GI periods are the Greenland expressions of the characteristic Dansgaard–Oeschger events that represent cold and warm phases of the North Atlantic region, respectively. We present here a more detailed and extended GS/GI template for the whole of the Last Glacial period. It is based on a synchronization of the NGRIP, GRIP, and GISP2 ice-core records that allows the parallel analysis of all three records on a common time scale. The boundaries of the GS and GI periods are defined based on a combination of stable-oxygen isotope ratios of the ice (δ18O, reflecting mainly local temperature) and calcium ion concentrations (reflecting mainly atmospheric dust loading) measured in the ice. The data not only resolve the well-known sequence of Dansgaard–Oeschger events that were first defined and numbered in the ice-core records more than two decades ago, but also better resolve a number of short-lived climatic oscillations, some defined here for the first time. Using this revised scheme, we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the Last Glacial period that are represented in the Greenland ice records. The final product constitutes an extended and better resolved Greenland stratotype sequence, against which other proxy records can be compared and correlated. It also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations.