Clastic sediment flux to tropical Andean lakes: records of glaciation and soil erosion

NASA Astrophysics Data System (ADS)

Rodbell, Donald T.; Seltzer, Geoffrey O.; Mark, Bryan G.; Smith, Jacqueline A.; Abbott, Mark B.

2008-08-01

We developed records of clastic sediment flux to 13 alpine lakes in Peru, Ecuador, and Bolivia, and compared these with independently dated records of regional glaciation. Our objectives are to determine whether a strong relationship exists between the extent of ice cover in the region and the rate of clastic sediment delivery to alpine lakes, and thus whether clastic sediment records serve as reliable proxies for glaciation during the late Pleistocene. We isolated the clastic component in lake sediment cores by removing the majority of the biogenic and authigenic components from the bulk sediment record, and we dated cores by a combination of radiocarbon and tephrochronology. In order to partially account for intra-basin differences in sediment focusing, bedrock erosivity, and sediment availability, we normalized each record to the weighted mean value of clastic sediment flux for each respective core. This enabled the stacking of all 13 lake records to produce a composite record that is generally representative of the tropical Andes. There is a striking similarity between the composite record of clastic sediment flux and the distribution of ˜100 cosmogenic radionuclide (CRN) exposure ages for erratics on moraine crests in the central Peruvian and northern Bolivian Andes. The extent of ice cover thus appears to be the primary variable controlling the delivery of clastic sediment to alpine lakes in the region, which bolsters the increasing use of clastic sediment flux as a proxy for the extent of ice cover in the region. The CRN moraine record and the stacked lake core composite record together indicate that the expansion of ice cover and concomitant increase in clastic sediment flux began at least 40 ka, and the local last glacial maximum (LLGM) culminated between 30 and 20 ka. A decline in clastic sediment flux that began ˜20 ka appears to mark the onset of deglaciation from the LLGM, at least one millennium prior to significant warming in high latitude regions. The interval between 20 and 18 ka was marked by near-Holocene levels of clastic sediment flux, and appears to have been an interval of much reduced ice extent. An abrupt increase in clastic sediment flux 18 ka heralded the onset of an interval of expanded ice cover that lasted until ˜14 ka. Clastic sediment flux declined thereafter to reach the lowest levels of the entire length of record during the early-middle Holocene. A middle Holocene climatic transition is apparent in nearly all records and likely reflects the onset of Neoglaciation and/or enhanced soil erosion in the tropical Andes.

Late Pleistocene and Holocene paleoclimate and alpine glacier fluctuations recorded by high-resolution grain-size data from an alpine lake sediment core, Wind River Range, Wyoming, USA

NASA Astrophysics Data System (ADS)

Thompson Davis, P.; Machalett, Björn; Gosse, John

2013-04-01

Varved lake sediments, which provide ideal high-resolution climate proxies, are not commonly available in many geographic areas over long time scales. This paper utilizes high-resolution grain-size analyses (n = 1040) from a 520-cm long sediment core from Lower Titcomb Lake (LTL), which lies just outside the type Titcomb Basin (TTB) moraines in the Wind River Range, Wyoming. The TTB moraines lie between Lower Titcomb Lake and Upper Titcomb Lake (UTL), about 3 km beyond, and 200 m lower than the modern glacier margin and Gannett Peak (Little Ice Age) moraines in the basin. Based on cosmogenic exposure dating, the TTB moraines are believed to be Younger Dryas (YD) age (Gosse et al., 1995) and lie in a geomorphic position similar to several other outer cirque moraines throughout the western American Cordillera. Until recently, many of these outer cirque moraines were believed to be Neoglacial age. The sediment core discussed here is one of five obtained from the two Titcomb Lakes, but is by the far the longest with the oldest sediment depositional record. Two AMS radiocarbon ages from the 445- and 455-cm core depths (about 2% loss on ignition, LOI) suggest that the lake basin may have been ice-free as early as 16.1 or even 16.8 cal 14C kyr, consistent with 10Be and 26Al exposure ages from boulders and bedrock surfaces outside the TTB moraines. The 257-cm depth in the core marks an abrupt transition from inorganic, sticky gray silt below (<1% LOI) to more organic, less sticky, light brown silt above (4-10% LOI). Eight AMS radiocarbon ages on bulk sediment and macrofossils date the transition to about 11.6 cal 14C kyr. Thus, sampling resolution above the transition is about 22.57 yr and below the transition is about 12.56 yr, consistent with a decreased sediment accumulation rate in LTL when Younger Dryas ice pulled back from the TTB moraines opening up UTL as a sediment depositional basin. The presented high-resolution grain size record reveals amplitudes and other structural features similar to delta 18O records from deep-lake ostracods in southern Germany, the Greenland ice core record, and speleothems in China. Major increases in the 2 - 8 µm grain size fraction indicative of increased glacier rock flour production between the 257 and 466 cm core depths appear to be roughly correlative with the YD-Alleröd-Bölling-Meiendorf-Heinrich 1 climate events recognized in other terrestrial records and Northern Atlantic Ocean marine cores, but provide much higher resolution than most of those records from a climate-sensitive alpine region in North America.

A Storm-by-Storm Analysis of Alpine and Regional Precipitation Dynamics at the Mount Hunter Ice Core Site, Denali National Park, Central Alaska Range

NASA Astrophysics Data System (ADS)

Saylor, P. L.; Osterberg, E. C.; Kreutz, K. J.; Wake, C. P.; Winski, D.

2014-12-01

In May-June 2013, an NSF-funded team from Dartmouth College and the Universities of Maine and New Hampshire collected two 1000-year ice cores to bedrock from the summit plateau of Mount Hunter in Denali National Park, Alaska (62.940291, -151.087616, 3912 m). The snow accumulation record from these ice cores will provide key insight into late Holocene precipitation variability in central Alaska, and compliment existing precipitation paleorecords from the Mt. Logan and Eclipse ice cores in coastal SE Alaska. However, correct interpretation of the Mt. Hunter accumulation record requires an understanding of the relationships between regional meteorological events and micrometeorological conditions at the Mt. Hunter ice core collection site. Here we analyze a three-month window of snow accumulation and meteorological conditions recorded by an Automatic Weather Station (AWS) at the Mt. Hunter site during the summer of 2013. Snow accumulation events are identified in the Mt. Hunter AWS dataset, and compared on a storm-by-storm basis to AWS data collected from the adjacent Kahiltna glacier 2000 m lower in elevation, and to regional National Weather Service (NWS) station data. We also evaluate the synoptic conditions associated with each Mt. Hunter accumulation event using NWS surface maps, NCEP-NCAR Reanalysis data, and the NOAA HYSPLIT back trajectory model. We categorize each Mt. Hunter accumulation event as pure snow accumulation, drifting, or blowing snow events based on snow accumulation, wind speed and temperature data using the method of Knuth et al (2009). We analyze the frequency and duration of events within each accumulation regime, in addition to the overall contribution of each event to the snowpack. Preliminary findings indicate that a majority of Mt. Hunter accumulation events are of pure accumulation nature (55.5%) whereas drifting (28.6%) and blowing (15.4%) snow events play a secondary role. Our results will characterize the local accumulation dynamics on Mt. Hunter and quantify the relationship between alpine micrometeorological and regional precipitation dynamics, providing key insights into the interpretation of the Mt. Hunter paleoprecipitation record.

Groundwater Storage and Flow Pathways in a Rock Glacier Complex in the Canadian Rockies

NASA Astrophysics Data System (ADS)

Hayashi, M.; Mozil, A.; Harrington, J.; Bentley, L. R.

2015-12-01

Hydrological functions of alpine glaciers and their responses to the warming climate have received much attention by hydrologists working in alpine catchments around the world. As alpine glaciers retreat, they commonly leave debris-covered ice or ice-cored moraine behind, which can remain frozen in ground for many decades or centuries. In many alpine catchments, characteristic landforms indicating rock glaciers or their relicts are found in locations where glaciers do not exist under the current climate. These landscape features associated with mountain permafrost are ubiquitous in alpine catchments, but their hydrological functions have not received much attention. Do rock glaciers and other mountain-permafrost features contribute significantly to storage of snowmelt water and its delayed release to sustain baseflow in the critical alpine stream habitats? How are these storage functions responding to the climate warming? In order to answer these questions, we initiated a hydrological study of rock glaciers in an alpine catchment in the Canadian Rockies in 2014. We will present preliminary results of our study using geophysical imaging techniques, hydro-meteorological monitoring, and groundwater tracing using various environmental tracers. Key findings are: 1) substantial amount of permafrost exists in the rock glacier which is inactive (i.e. no active motion) under the present climate, 2) spatial distribution of permafrost is controlled by both meteorological and geological factors, 3) the rock glacier complex contributes 30-50 % of summer stream flow even though they occupy less than 5% of the catchment area, and 4) the low temperature (< 2 C) of groundwater discharging at the toe of rock glacier plays a significant role in regulating the temperature of stream, which hosts a population of trout species that is listed as "threatened" in the list of the status of endangered wildlife in Canada.

Quantification of dissolved organic carbon at very low levels in natural ice samples by a UV-induced oxidation method.

PubMed

Preunkert, S; Legrand, M; Stricker, P; Bulat, S; Alekhina, I; Petit, J R; Hoffmann, H; May, B; Jourdain, B

2011-01-15

The study of chemical impurities trapped in solid precipitation and accumulated in polar ice sheets and high-elevation, midlatitude cold glaciers over the last several hundreds of years provides a unique way to reconstruct our changing atmosphere from the preindustrial era to the present day. Numerous ice core studies of inorganic species have already evaluated the effects of growing anthropogenic emissions of SO(2) or NO(x) on the chemical composition of the atmosphere in various regions of the world. While it was recently shown that organic species dominate the atmospheric aerosol mass, the contribution of anthropogenic emissions to their budget remains poorly understood. The study of organics in ice is at the infancy stage, and it still is difficult to draw a consistent picture of the organic content of polar ice from sparse available data. A UV oxidation method and IR quantification of CO(2) was optimized to obtain measurements of dissolved organic carbon content as low as a few ppbC. Stringent working conditions were defined to prevent contamination during the cleaning of ice. Measurements in various ice cores corresponding to preindustrial times revealed dissolved organic carbon content of less than 10 ppbC in Antarctica and up to 75 ppbC in alpine ice.

Historic records of organic compounds from a high Alpine glacier: influences of biomass burning, anthropogenic emissions, and dust transport

NASA Astrophysics Data System (ADS)

Müller-Tautges, C.; Eichler, A.; Schwikowski, M.; Pezzatti, G. B.; Conedera, M.; Hoffmann, T.

2016-01-01

Historic records of α-dicarbonyls (glyoxal, methylglyoxal), carboxylic acids (C6-C12 dicarboxylic acids, pinic acid, p-hydroxybenzoic acid, phthalic acid, 4-methylphthalic acid), and ions (oxalate, formate, calcium) were determined with annual resolution in an ice core from Grenzgletscher in the southern Swiss Alps, covering the time period from 1942 to 1993. Chemical analysis of the organic compounds was conducted using ultra-high-performance liquid chromatography (UHPLC) coupled to electrospray ionization high-resolution mass spectrometry (ESI-HRMS) for dicarbonyls and long-chain carboxylic acids and ion chromatography for short-chain carboxylates. Long-term records of the carboxylic acids and dicarbonyls, as well as their source apportionment, are reported for western Europe. This is the first study comprising long-term trends of dicarbonyls and long-chain dicarboxylic acids (C6-C12) in Alpine precipitation. Source assignment of the organic species present in the ice core was performed using principal component analysis. Our results suggest biomass burning, anthropogenic emissions, and transport of mineral dust to be the main parameters influencing the concentration of organic compounds. Ice core records of several highly correlated compounds (e.g., p-hydroxybenzoic acid, pinic acid, pimelic, and suberic acids) can be related to the forest fire history in southern Switzerland. P-hydroxybenzoic acid was found to be the best organic fire tracer in the study area, revealing the highest correlation with the burned area from fires. Historical records of methylglyoxal, phthalic acid, and dicarboxylic acids adipic acid, sebacic acid, and dodecanedioic acid are comparable with that of anthropogenic emissions of volatile organic compounds (VOCs). The small organic acids, oxalic acid and formic acid, are both highly correlated with calcium, suggesting their records to be affected by changing mineral dust transport to the drilling site.

Wisconsinan and early Holocene glacial dynamics of Cumberland Peninsula, Baffin Island, Arctic Canada

NASA Astrophysics Data System (ADS)

Margreth, Annina; Gosse, John C.; Dyke, Arthur S.

2017-07-01

Three glacier systems-an ice sheet with a large marine-based ice stream, an ice cap, and an alpine glacier complex-coalesced on Cumberland Peninsula during the Late Wisconsinan. We combine high-resolution mapping of glacial deposits with new cosmogenic nuclide and radiocarbon age determinations to constrain the history and dynamics of each system. During the Middle Wisconsinan (Oxygen Isotope Stage 3, OIS-3) the Cumberland Sound Ice Stream of the Laurentide Ice Sheet retreated well back into Cumberland Sound and the alpine ice retreated at least to fiord-head positions, a more significant recession than previously documented. The advance to maximal OIS-2 ice positions beyond the mouth of Cumberland Sound and beyond most stretches of coastline remains undated. Partial preservation of an over-ridden OIS-3 glaciomarine delta in a fiord-side position suggests that even fiord ice was weakly erosive in places. Moraines formed during deglaciation represent stillstands and re-advances during three major cold events: H-1 (14.6 ka), Younger Dryas (12.9-11.7 ka), and Cockburn (9.5 ka). Distinctly different responses of the three glacial systems are evident, with the alpine system responding most sensitively to Bølling-Allerød warming whereas the larger systems retreated mainly during Pre-Boreal warming. While the larger ice masses were mainly influenced by internal dynamics, the smaller alpine glacier system responded sensitively to local climate effects. Asymmetrical recession of the alpine glacier complex indicates topoclimatic control on deglaciation and perhaps migration of the accumulation area toward moisture source.

Performance and Safety Characteristics in Ice-Climbing Equipment Selection.

ERIC Educational Resources Information Center

Wells, W. Tom

This study sought to determine whether Alaskan ice climbers place more emphasis on performance characteristics or on safety characteristics when selecting their various ice-climbing equipment. A survey distributed to members of the Alaska Alpine Club and the Alaska Alpine Rescue Group was developed to contain responses related to both safety and…

Historical record of European emissions of heavy metals to the atmosphere since the 1650s from alpine snow/ice cores drilled near Monte Rosa.

PubMed

Barbante, Carlo; Schwikowski, Margit; Döring, Thomas; Gäggeler, Heinz W; Schotterer, Ulrich; Tobler, Leo; van de Velde, Katja; Ferrari, Christophe; Cozzi, Giulio; Turetta, Andrea; Rosman, Kevin; Bolshov, Michael; Capodaglio, Gabriele; Cescon, Paolo; Boutron, Claude

2004-08-01

Cr, Cu, Zn, Co, Ni, Mo, Rh, Pd, Ag, Cd, Sb, Pt, Au, and U have been determined in clean room conditions by inductively coupled plasma sector field mass spectrometry and other analytical techniques, in various sections of two dated snow/ice cores from the high-altitude (4450 m asl) glacier saddle Colle Gnifetti, Monte Rosa massif, located in the Swiss-Italian Alps. These cores cover a 350-year time period, from 1650 to 1994. The results show highly enhanced concentrations for most metals in snow/ice dated from the second half of the 20th century, compared with concentrations in ancient ice dated from the 17th and 18th centuries. The highest increase factors from the pre-1700 period to the post-1970 period are observed for Cd (36), Zn (19), Bi (15), Cu (11), and Ni (9), confirming the importance of atmospheric pollution by heavy metals in Europe. Metal concentrations observed in Colle Gnifetti snow around 1980 appear to be quantitatively related to metal emissions from Italy, Switzerland, Germany, France, Belgium, and Austria at that time, making it possible to reconstruct past changes in metal emission in these countries during the last centuries.

Alpine Skiing in the Classroom

ERIC Educational Resources Information Center

Mendez-Gimenez, Antonio; Fernandez-Rio, Javier

2012-01-01

Many students settle indoors in the winter. However, this does not mean that winter should be a period of time with no physical activity. Several snow activities could be practiced during those months, such as ice-skating, ice-hockey, snowshoeing, cross-country skiing, alpine skiing, or snowboarding. In order to counteract the tendency for…

Glaciation of alpine valleys: The glacier - debris-covered glacier - rock glacier continuum

NASA Astrophysics Data System (ADS)

Anderson, Robert S.; Anderson, Leif S.; Armstrong, William H.; Rossi, Matthew W.; Crump, Sarah E.

2018-06-01

Alpine ice varies from pure ice glaciers to partially debris-covered glaciers to rock glaciers, as defined by the degree of debris cover. In many low- to mid-latitude mountain ranges, the few bare ice glaciers that do exist in the present climate are small and are found where snow is focused by avalanches and where direct exposure to radiation is minimized. Instead, valley heads are more likely to be populated by rock glaciers, which can number in the hundreds. These rock-cloaked glaciers represent some of the most identifiable components of the cryosphere today in low- to mid-latitude settings, and the over-steepened snouts pose an often overlooked hazard to travel in alpine terrain. Geomorphically, rock glaciers serve as conveyor belts atop which rock is pulled away from the base of cliffs. In this work, we show how rock glaciers can be treated as an end-member case that is captured in numerical models of glaciers that include ice dynamics, debris dynamics, and the feedbacks between them. Specifically, we focus on the transition from debris-covered glaciers, where the modern equilibrium line altitude (ELA) intersects the topography, to rock glaciers, where the modern ELA lies above the topography. On debris-covered glaciers (i.e., glaciers with a partial rock mantle), rock delivered to the glacier from its headwall, or from sidewall debris swept into the glacier at tributary junctions, travels englacially to emerge below the ELA. There it accumulates on the surface and damps the rate of melt of underlying ice. This allows the termini of debris-covered glaciers to extend beyond debris-free counterparts, thereby decreasing the ratio of accumulation area to total area of the glacier (AAR). In contrast, rock glaciers (i.e., glaciers with a full rock mantle) occur where and when the environmental ELA rises above the topography. They require avalanches and rockfall from steep headwalls. The occurrence of rock glaciers reflects this dependence on avalanche sources because they are most common on lee sides of ridges and peaks where wind-blown snow enhances the strength of the avalanche source. To maintain positive mass balance, the avalanche cone developed in the winter must be sufficiently thick not to melt entirely in the summer, thus providing an ice accumulation area for the rock glacier. In the absence of rockfall, this would support a short cirque glacier. The presence of debris, however, facilitates the development of rock glaciers with lengths of hundreds of meters, thicknesses of tens of meters, and speeds of meters per year that are well described by numerical models. Numerical models are used to explore the alpine glacier response to its climate history. In warming climates, a debris-covered glacier can transform into a much shorter rock glacier, leaving in its wake a thinning ice-cored moraine. Rock glaciers will persist in landscapes well beyond debris-free counterparts because they have much longer response times to climate change. The headwaters of alpine basins with steep headwalls will therefore oscillate between glacier and rock glacier occupation over glacial-interglacial cycles, maintaining a means by which rock from the headwall can be conveyed away. This enhances the asymmetry of alpine ridgelines, with downwind valleys biting deeply into the range crests, as originally noted by G.K. Gilbert.

CALICE: Calibrating Plant Biodiversity in Glacier Ice

NASA Astrophysics Data System (ADS)

Festi, Daniela; Cristofori, Antonella; Vernesi, Cristiano; Zerbe, Stefan; Wellstein, Camilla; Maggi, Valter; Oeggl, Klaus

2017-04-01

The objective of the project is to reconstruct plant biodiversity and its trend archived in Alpine glacier ice by pollen and eDNA (environmental DNA) during the last five decades by analyzing a 40 m ice core. For our study we chose the Adamello glacier (Trentino - Südtirol, Lombardia) because of i) the good preservation conditions for pollen and eDNA in ice, ii) the thickness of the ice cap (270m) and iii) the expected high time resolution. The biodiversity estimates gained by pollen analysis and eDNA will be validated by historical biodiversity assessments mainly based on vegetation maps, aerial photos and vegetation surveys in the catchment area of the Adamello glacier for the last five decades. This historical reconstruction of biodiversity trends will be performed on a micro-, meso- and macro-scale (5, 20-50 and 50-100 Km radius, respectively). The results will serve as a calibration data set on biodiversity for future studies, such as the second step of the coring by the POLLiCE research consortium (pollice.fmach.it). In fact, arrangements are currently been made to drill the complete ice cap and retrieve a 270 m thick core which has the potential to cover a time span of minimum 400 years up to several millennia. This second stage will extend the time scale and enable the evaluation of dissimilarity/similarity of modern biodiversity in relation to Late Holocene trends. Finally, we believe this case study has the potential to be applied in other glaciated areas to evaluate biodiversity for large regions (e.g. central Asian mountain ranges, Tibet and Tian Shan or the Andes).

Linking two thousand years of European historical records with environmental change recorded in a high Alpine ice core

NASA Astrophysics Data System (ADS)

Bohleber, Pascal; Spaulding, Nicole; Mayewski, Paul; Kurbatov, Andrei; Hoffmann, Helene; Erhardt, Tobias; Fischer, Hubertus; More, Alexander; Loveluck, Christopher; Luongo, Matthew; Kabala, Jakub; McCormick, Michael

2016-04-01

Its extraordinary network of historical and archaeological records makes Europe exceptionally promising for investigating environmental change and human response over the last two thousand years. Among natural proxy archives, ice core records offer a wide range of environmental reconstructions including natural and human source histories of the chemistry of the atmosphere. To link these robust environmental records with historical evidence of past civilizations remains a great challenge, however. In central Europe the unique target for a comparison for environmental change recorded in ice cores and human activity is the small firn saddle of Colle Gnifetti (4550 m above sea level on the Italian-Swiss border). Its exceptionally low net accumulation make Colle Gnifetti (CG) the only feasible site in the Alps for retrieving a long-term ice core record beyond the last century. However, at CG rapid annual layer thinning eventually limits conventional cm-resolution analysis to multi-annual signals and hampers dating by annual layer counting beyond a few hundred years. Thereby, a crucial gap is introduced to the sub-seasonal time scale of events typically recorded in written archives. In our ongoing project we pioneer correlating the CG environmental ice core archive with a unique compilation of European historical records provided through the Harvard Initiative for the Science of the Human Past and the Digital Atlas of Roman and Medieval Civilization. For this purpose, state-of-the-art glacio-chemical analysis was performed on a newly recovered CG ice core, including continuous flow analysis chemistry and stable isotopes. A crucial contribution comes from the application of LA-ICP-MS (laser ablation ion coupled plasma mass spectrometry) to meter long sections of frozen ice samples, developed and operated by the University of Maine's Climate Change Institute, offering glacio-chemical records up to 100 μm in resolution. The new methods significantly improves sampling resolution and allows detection of annual layers even in highly compressed old sections of CG ice cores: A breakthrough not only for extending the ice core dating over the last two millennia but also for bridging the gap in time scales to historical records. Here we present first results from our ongoing efforts in bringing together ice core time series with historical evidence, focusing on the time period from 1 to 1400 C.E. Based on a thorough consideration of the glaciological constraints at CG we explore various ice core proxy signals for their significance to correlate with events recorded in human writing, such as dust storms, volcanic events, climate-induced crop failures and starvation as well as metal production levels. Distinct dust layers are frequently found in CG ice cores, representative for meteorological conditions that transported sand from the Sahara to Europe. At the same time, Saharan dust events were also frequently recorded by ancient and medieval observers as "blood rain". Ultimately we work towards using past extreme climate events from medieval Europe recorded as written evidence to constrain the ice core age scale and, vice versa, to investigate the response of human societies to environmental change recorded in the CG glacier archive.

Temperature and mineral dust variability recorded in two low-accumulation Alpine ice cores over the last millennium

NASA Astrophysics Data System (ADS)

Bohleber, Pascal; Erhardt, Tobias; Spaulding, Nicole; Hoffmann, Helene; Fischer, Hubertus; Mayewski, Paul

2018-01-01

Among ice core drilling sites in the European Alps, Colle Gnifetti (CG) is the only non-temperate glacier to offer climate records dating back at least 1000 years. This unique long-term archive is the result of an exceptionally low net accumulation driven by wind erosion and rapid annual layer thinning. However, the full exploitation of the CG time series has been hampered by considerable dating uncertainties and the seasonal summer bias in snow preservation. Using a new core drilled in 2013 we extend annual layer counting, for the first time at CG, over the last 1000 years and add additional constraints to the resulting age scale from radiocarbon dating. Based on this improved age scale, and using a multi-core approach with a neighbouring ice core, we explore the time series of stable water isotopes and the mineral dust proxies Ca2+ and insoluble particles. Also in our latest ice core we face the already known limitation to the quantitative use of the stable isotope variability based on a high and potentially non-stationary isotope/temperature sensitivity at CG. Decadal trends in Ca2+ reveal substantial agreement with instrumental temperature and are explored here as a potential site-specific supplement to the isotope-based temperature reconstruction. The observed coupling between temperature and Ca2+ trends likely results from snow preservation effects and the advection of dust-rich air masses coinciding with warm temperatures. We find that if calibrated against instrumental data, the Ca2+-based temperature reconstruction is in robust agreement with the latest proxy-based summer temperature reconstruction, including a Little Ice Age cold period as well as a medieval climate anomaly. Part of the medieval climate period around AD 1100-1200 clearly stands out through an increased occurrence of dust events, potentially resulting from a relative increase in meridional flow and/or dry conditions over the Mediterranean.

Glaciochemical investigation of an ice core from Belukha Glacier,Siberian Altai

NASA Astrophysics Data System (ADS)

Olivier, S.; Schwikowski, S.; Gäggeler, H. W.; Lüthi, M.; Eyrik, S.; Blaser, C.; Saurer, M.; Schotterer, U.

2003-04-01

Little is known about climatic change and paleo-atmospheric composition in Siberia. The Altai is the only alpine region in this area covered by glaciers that might serve as archives for such studies. Moreover, it is located close to air pollution sources in East Kazakhstan and South Siberia (heavy metal mining, metallurgy) as well as to the nuclear test site of Semipalatinsk (release of radionuclides into the atmosphere). In order to reconstruct air pollution levels in the Altai region, a 140-meter ice core down to bedrock was recovered from the Belukha glacier (N49^o48'26", E86^o34'43", 4062 m asl) in July 2001. This site was selected based on the results of an exploratory study conducted in 2000. So far, the concentrations of major ionic species and the stable isotope ratio δ18O were determined in the approx. 90 topmost meters of the ice core covering about 200 years. Dating of the upper part of the ice core was performed by a combination of methods that include e.g. nuclear techniques and annual-layer counting. The annual net accumulation amounts to about 0.53 m weq. and indicates that snow at the Belukha glacier might be partly eroded by wind, a situation that is often observed for a glacier saddle. The borehole temperature (-16 ^oC at 80 m depth), the discernible fluctuations of the stable isotope and chemistry records as well as the linearity of the decrease of the log. 210Pb activities with depth indicate that the glaciochemical record is well preserved and not significantly altered by melting processes. In pre-industrial ice concentrations of carboxylic acids and ammonium are high, suggesting the surrounding forest as source of biogenic emissions.

Ice barriers promote supercooling and prevent frost injury in reproductive buds, flowers and fruits of alpine dwarf shrubs throughout the summer.

PubMed

Kuprian, Edith; Briceño, Verónica F; Wagner, Johanna; Neuner, Gilbert

2014-10-01

Over-wintering reproductive buds of many woody plants survive frost by supercooling. The bud tissues are isolated from acropetally advancing ice by the presence of ice barriers that restrict ice growth. Plants living in alpine environments also face the risk of ice formation in summer months. Little knowledge exists, how reproductive structures of woody alpine plants are protected from frost injury during episodic summer frosts. In order to address this question, frost resistance of three common dwarf shrubs, Calluna vulgaris , Empetrum hermaphroditum and Loiseleuria procumbens was measured and ice formation and propagation were monitored in twigs bearing reproductive shoots during various stages of reproductive development (bud, anthesis, and fruit) throughout the alpine summer. Results indicated that, in the investigated species, ice barriers were present at all reproductive stages, isolating the reproductive shoots from ice advancing from the subtending vegetative shoot. Additionally, in the reproductive stems ice nucleating agents that are active at warm, sub-zero temperatures, were absent. The ice barriers were 100% effective, with the exception of L. procumbens , where in 13% of the total observations, the ice barrier failed. The ice barriers were localized at the base of the pedicel, at the anatomical junction of the vegetative and reproductive shoot. There, structural aspects of the tissue impede or prevent ice from advancing from the frozen stem into the pedicel of the reproductive shoot. Under the experimental conditions used in this study, ice nucleation initially occurred in the stem of the vegetative shoot at species-specific mean temperatures in the range of -4.7 to -5.8 °C. Reproductive shoots, however, remained supercooled and ice free down to a range of -7.2 to -18.2 °C or even below -22 °C, the lowest temperature applied in the study. This level of supercooling is sufficient to prevent freezing of reproductive structures at the lowest air temperature occurring at the altitude of the upper distribution boundary of the natural habitat of the investigated species which is between -8 and -10 °C in summer. Frost resistance assays indicated that reproductive shoots are much less frost resistant than vegetative stems, and in contrast to vegetative shoots, are not ice tolerant. Supercooling of reproductive shoots in alpine, woody plant species is an effective mechanism that protects developing offspring from potential frost damage resulting from episodic summer freezing events.

Ice barriers promote supercooling and prevent frost injury in reproductive buds, flowers and fruits of alpine dwarf shrubs throughout the summer☆

PubMed Central

Kuprian, Edith; Briceño, Verónica F.; Wagner, Johanna; Neuner, Gilbert

2014-01-01

Over-wintering reproductive buds of many woody plants survive frost by supercooling. The bud tissues are isolated from acropetally advancing ice by the presence of ice barriers that restrict ice growth. Plants living in alpine environments also face the risk of ice formation in summer months. Little knowledge exists, how reproductive structures of woody alpine plants are protected from frost injury during episodic summer frosts. In order to address this question, frost resistance of three common dwarf shrubs, Calluna vulgaris, Empetrum hermaphroditum and Loiseleuria procumbens was measured and ice formation and propagation were monitored in twigs bearing reproductive shoots during various stages of reproductive development (bud, anthesis, and fruit) throughout the alpine summer. Results indicated that, in the investigated species, ice barriers were present at all reproductive stages, isolating the reproductive shoots from ice advancing from the subtending vegetative shoot. Additionally, in the reproductive stems ice nucleating agents that are active at warm, sub-zero temperatures, were absent. The ice barriers were 100% effective, with the exception of L. procumbens, where in 13% of the total observations, the ice barrier failed. The ice barriers were localized at the base of the pedicel, at the anatomical junction of the vegetative and reproductive shoot. There, structural aspects of the tissue impede or prevent ice from advancing from the frozen stem into the pedicel of the reproductive shoot. Under the experimental conditions used in this study, ice nucleation initially occurred in the stem of the vegetative shoot at species-specific mean temperatures in the range of −4.7 to −5.8 °C. Reproductive shoots, however, remained supercooled and ice free down to a range of −7.2 to −18.2 °C or even below −22 °C, the lowest temperature applied in the study. This level of supercooling is sufficient to prevent freezing of reproductive structures at the lowest air temperature occurring at the altitude of the upper distribution boundary of the natural habitat of the investigated species which is between −8 and −10 °C in summer. Frost resistance assays indicated that reproductive shoots are much less frost resistant than vegetative stems, and in contrast to vegetative shoots, are not ice tolerant. Supercooling of reproductive shoots in alpine, woody plant species is an effective mechanism that protects developing offspring from potential frost damage resulting from episodic summer freezing events. PMID:25284910

Towards a quasi-complete reconstruction of past atmospheric aerosol load and composition (organic and inorganic) over Europe since 1920 inferred from Alpine ice cores

NASA Astrophysics Data System (ADS)

Preunkert, S.; Legrand, M.

2013-07-01

Seasonally resolved chemical ice core records available from the Col du Dôme glacier (4250 m elevation, French Alps), are here used to reconstruct past aerosol load and composition of the free European troposphere from before World War II to present. Available ice core records include inorganic (Na+, Ca2+, NH4+, Cl-, NO3-, and SO42-) and organic (carboxylates, HCHO, humic-like substances, dissolved organic carbon, water-insoluble organic carbon, and black carbon) compounds and fractions that permit reconstructing the key aerosol components and their changes over the past. It is shown that the atmospheric load of submicron aerosol has been increased by a factor of 3 from the 1921-1951 to 1971-1988 years, mainly as a result of a large increase of sulfate (a factor of 5), ammonium and water-soluble organic aerosol (a factor of 3). Thus, not only growing anthropogenic emissions of sulfur dioxide and ammonia have caused the enhancement of the atmospheric aerosol load but also biogenic emissions producing water-soluble organic aerosol. This unexpected change of biospheric source of organic aerosol after 1950 needs to be considered and further investigated in scenarios dealing with climate forcing by atmospheric aerosol.

Climate regulates alpine lake ice cover phenology and aquatic ecosystem structure

USGS Publications Warehouse

Preston, Daniel L.; Caine, Nel; McKnight, Diane M.; Williams, Mark W.; Hell, Katherina; Miller, Matthew P.; Hart, Sarah J.; Johnson, Pieter T.J.

2016-01-01

High-elevation aquatic ecosystems are highly vulnerable to climate change, yet relatively few records are available to characterize shifts in ecosystem structure or their underlying mechanisms. Using a long-term dataset on seven alpine lakes (3126 to 3620 m) in Colorado, USA, we show that ice-off dates have shifted seven days earlier over the past 33 years and that spring weather conditions – especially snowfall – drive yearly variation in ice-off timing. In the most well-studied lake, earlier ice-off associated with increases in water residence times, thermal stratification, ion concentrations, dissolved nitrogen, pH, and chlorophyll-a. Mechanistically, low spring snowfall and warm temperatures reduce summer stream flow (increasing lake residence times) but enhance melting of glacial and permafrost ice (increasing lake solute inputs). The observed links among hydrological, chemical, and biological responses to climate factors highlight the potential for major shifts in the functioning of alpine lakes due to forecasted climate change.

Geologic and hydrologic hazards in glacierized basins in North America resulting from 19th and 20th century global warming

USGS Publications Warehouse

O'Connor, J. E.; Costa, J.E.

1993-01-01

Alpine glacier retreat resulting from global warming since the close of the Little Ice Age in the 19th and 20th centuries has increased the risk and incidence of some geologic and hydrologic hazards in mountainous alpine regions of North America. Abundant loose debris in recently deglaciated areas at the toe of alpine glaciers provides a ready source of sediment during rainstorms or outburst floods. This sediment can cause debris flows and sedimentation problems in downstream areas. Moraines built during the Little Ice Age can trap and store large volumes of water. These natural dams have no controlled outlets and can fail without warning. Many glacier-dammed lakes have grown in size, while ice dams have shrunk, resulting in greater risks of ice-dam failure. The retreat and thinning of glacier ice has left oversteepened, unstable valley walls and has led to increased incidence of rock and debris avalanches. ?? 1993 Kluwer Academic Publishers.

A high altitude paleoclimate record from an ice core retrieved at the northern margin of the Mediterranean basin

NASA Astrophysics Data System (ADS)

Gabrielli, P.; Barbante, C.; Carturan, L.; Davis, M. E.; Dalla Fontana, G.; Dreossi, G.; Dinale, R.; Draga, G.; Gabrieli, J.; Kehrwald, N. M.; Mair, V.; Mikhalenko, V.; Oeggl, K.; Schotterer, U.; Seppi, R.; Spolaor, A.; Stenni, B.; Thompson, L. G.; Tonidandel, D.

2013-12-01

Atmospheric temperatures in the Alps are increasing at twice the global rate and this change may be amplified at the highest elevations. There is a scarcity of paleo-climate information from high altitudes to place this current rapid climate change in a paleo-perspective. The 'Ortles Project' is an international scientific effort gathering institutes from six nations with the primary goal of obtaining a high altitude paleo-climate record in the Mediterranean area. In 2011 four ice cores were extracted from Alto dell'Ortles (3859 m, South Tyrol, Italy) the highest glacier in the eastern Alps. This site is located ~30 km away from where the famous ~5.2 kyr old Tyrolean Ice Man was discovered emerging from an ablating ice field (Hauslabjoch, 3210 m) in 1991. The good state of conservation of this mummy suggested that the current warming trend is unprecedented in South Tyrol during the late Holocene and that unique prehistoric ice was still present in this region. During the ice core drilling operations we found that the glacier Alto dell'Ortles shows a very unusual thermic behavior as it is transitioning from a cold to a temperate state. In fact, below a 30 meter thick temperate firn portion, we observed cold ice layers sitting on a frozen bedrock (-2.8 C). These represent remnants of the colder climate before ~1980 AD, when an instrumental record indicates a ~2 C lower temperature in this area during the period 1864-1980 AD. By analyzing one of the Ortles cores for stable isotopes, dust and major ions, we found an annually preserved climatic signal embedded in the deep cold ice of this glacier. Alto dell'Ortles is therefore the first low-accumulation (850 mm w.e. per year) alpine drilling site where both winter and summer layers can be identified. Preliminary annual layer counting and two absolute time markers suggest that the time period covered by the Ortles ice cores spans from several centuries to a few millennia. In particular, a Larix (larch) leaf discovered at 74 m depth suggests a 14C bottom ice age of 2664 ×166 years (early European Iron Age) supporting the idea that exceptional prehistoric ice is still present at the highest elevations of South Tyrol. Here we present the records of the first Ortles core analyzed in terms of δ18O (proxy of mid-tropospheric temperature), major ions and dust. We found that δ18O measured in the shallowest layers of this glacier exceeds the average deeper values indicating that the Ortles cores capture the recent increase in atmospheric temperatures at high elevation and that this is anomalous over a time scale that extends from hundreds to thousands of years.

Metric remote sensing experiments in preparation for Spacelab flights. [alpine geomorphology and ice and/or snow cover

NASA Technical Reports Server (NTRS)

Galibert, G.

1978-01-01

Aerial and ground photographs of Wallis mountains and of Dolomiti di Cortina d'Ampezzo in Italy were made using spectrozonal emulsions and optical multichannel filters. A metric camera was used in the perspective of the first Spacelab flight aboard the space shuttle. Elementary forms of alpine geomorphology and ice or snow phenomena are detectable on these metric scenes.

Inflorescences of alpine cushion plants freeze autonomously and may survive subzero temperatures by supercooling

PubMed Central

Hacker, Jürgen; Ladinig, Ursula; Wagner, Johanna; Neuner, Gilbert

2011-01-01

Freezing patterns in the high alpine cushion plants Saxifraga bryoides, Saxifraga caesia, Saxifraga moschata and Silene acaulis were studied by infrared thermography at three reproductive stages (bud, anthesis, fruit development). The single reproductive shoots of a cushion froze independently in all four species at every reproductive stage. Ice formation caused lethal damage to the respective inflorescence. After ice nucleation, which occurred mainly in the stalk or the base of the reproductive shoot, ice propagated throughout that entire shoot, but not into neighboring shoots. However, anatomical ice barriers within cushions were not detected. The naturally occurring temperature gradient within the cushion appeared to interrupt ice propagation thermally. Consequently, every reproductive shoot needed an autonomous ice nucleation event to initiate freezing. Ice nucleation was not only influenced by minimum temperatures but also by the duration of exposure. At moderate subzero exposure temperatures (−4.3 to −7.7 °C) the number of frozen inflorescences increased exponentially. Due to efficient supercooling, single reproductive shoots remained unfrozen down to −17.4 °C (cooling rate 6 K h−1). Hence, the observed freezing pattern may be advantageous for frost survival of individual inflorescences and reproductive success of high alpine cushion plants, when during episodic summer frosts damage can be avoided by supercooling. PMID:21151351

A fast semi-quantitative method for Plutonium determination in an alpine firn/ice core

NASA Astrophysics Data System (ADS)

Gabrieli, J.; Cozzi, G.; Vallelonga, P.; Schwikowski, M.; Sigl, M.; Boutron, C.; Barbante, C.

2009-04-01

Plutonium is present in the environment as a consequence of atmospheric nuclear tests carried out in the 1960s, nuclear weapons production and releases by the nuclear industry over the past 50 years. Plutonium, unlike uranium, is essentially anthropogenic and it was first produced and isolated in 1940 by deuteron bombardment of uranium in the cyclotron of Berkeley University. It exists in five main isotopes, 238Pu, 239Pu, 240Pu, 241Pu, 242Pu, derived from civilian and military sources (weapons production and detonation, nuclear reactors, nuclear accidents). In the environment, 239Pu is the most abundant isotope. Approximately 6 tons of 239Pu have been released into the environment as a result of 541 atmospheric weapon tests Nuclear Pu fallout has been studied in various environmental archives, such as sediments, soil and herbarium grass. Mid-latitude ice cores have been studied as well, on Mont Blanc, the Western Alps and on Belukha Glacier, Siberian Altai. We present a Pu record obtained by analyzing 52 discrete samples of an alpine firn/ice core from Colle Gnifetti (M. Rosa, 4450 m a.s.l.), dating from 1945 to 1991. The239Pu signal was recorded directly, without preliminary cleaning or preconcentration steps, using an ICP-SFMS (Thermo Element2) equipped with a desolvation system (APEX). 238UH+ interferences were negligible for U concentrations lower than 50 ppt as verified both in spiked fresh snow and pre-1940 ice samples. The shape of 239Pu profile reflects the three main periods of atmospheric nuclear weapons testing: the earliest peak starts in 1954/55 to 1958 and includes the first testing period which reached a maximum in 1958. Despite a temporary halt in testing in 1959/60, the Pu concentration decreased only by half with respect to the 1958 peak. In 1961/62 Pu concentrations rapidly increased reaching a maximum in 1963, which was about 40% more intense than the 1958 peak. After the sign of the "Limited Test Ban Treaty" between USA and URSS in 1964, Pu deposition decreased very sharply reaching a minimum in 1967. The third period (1967-1975) is characterized by irregular Pu profiles with smaller peaks (about 20-30% compared to the 1964 peak) which could be due to French and Chinese tests. Comparison with the Pu profiles obtained from the Col du Dome and Belukha ice cores by AMS (Accelerator Mass Spectrometry) shows very good agreement. Considering the semi-quantitative method and the analytical uncertainty, the results are also quantitatively comparable. However, the Pu concentrations at Colle Gnifetti are normally 2-3 times greater than in Col du Dome. This could be explained by different air mass transport or, more likely, different accumulation rates at each site.

Glacial refugia, recolonization patterns and diversification forces in Alpine-endemic Megabunus harvestmen.

PubMed

Wachter, Gregor A; Papadopoulou, Anna; Muster, Christoph; Arthofer, Wolfgang; Knowles, L Lacey; Steiner, Florian M; Schlick-Steiner, Birgit C

2016-06-01

The Pleistocene climatic fluctuations had a huge impact on all life forms, and various hypotheses regarding the survival of organisms during glacial periods have been postulated. In the European Alps, evidence has been found in support of refugia outside the ice shield (massifs de refuge) acting as sources for postglacial recolonization of inner-Alpine areas. In contrast, evidence for survival on nunataks, ice-free areas above the glacier, remains scarce. Here, we combine multivariate genetic analyses with ecological niche models (ENMs) through multiple timescales to elucidate the history of Alpine Megabunus harvestmen throughout the ice ages, a genus that comprises eight high-altitude endemics. ENMs suggest two types of refugia throughout the last glacial maximum, inner-Alpine survival on nunataks for four species and peripheral refugia for further four species. In some geographic regions, the patterns of genetic variation are consistent with long-distance dispersal out of massifs de refuge, repeatedly coupled with geographic parthenogenesis. In other regions, long-term persistence in nunataks may dominate the patterns of genetic divergence. Overall, our results suggest that glacial cycles contributed to allopatric diversification in Alpine Megabunus, both within and at the margins of the ice shield. These findings exemplify the power of ENM projections coupled with genetic analyses to identify hypotheses about the position and the number of glacial refugia and thus to evaluate the role of Pleistocene glaciations in driving species-specific responses of recolonization or persistence that may have contributed to observed patterns of biodiversity. © 2016 John Wiley & Sons Ltd.

Potential sources of bacteria colonizing the cryoconite of an Alpine glacier

PubMed Central

Franzetti, Andrea; Navarra, Federico; Tagliaferri, Ilario; Gandolfi, Isabella; Bestetti, Giuseppina; Minora, Umberto; Azzoni, Roberto Sergio; Diolaiuti, Guglielmina; Smiraglia, Claudio

2017-01-01

We investigated the potential contribution of ice-marginal environments to the microbial communities of cryoconite holes, small depressions filled with meltwater that form on the surface of Forni Glacier (Italian Alps). Cryoconite holes are considered the most biologically active environments on glaciers. Bacteria can colonize these environments by short-range transport from ice-marginal environments or by long-range transport from distant areas. We used high throughput DNA sequencing to identify Operational Taxonomic Units (OTUs) present in cryoconite holes and three ice-marginal environments, the moraines, the glacier forefield, and a large (> 3 m high) ice-cored dirt cone occurring on the glacier surface. Bacterial communities of cryoconite holes were different from those of ice-marginal environments and hosted fewer OTUs. However, a network analysis revealed that the cryoconite holes shared more OTUs with the moraines and the dirt cone than with the glacier forefield. Ice-marginal environments may therefore act as sources of bacteria for cryoconite holes, but differences in environmental conditions limit the number of bacterial strains that may survive in them. At the same time, cryoconite holes host a few OTUs that were not found in any ice-marginal environment we sampled, thus suggesting that some bacterial populations are positively selected by the specific environmental conditions of the cryoconite holes. PMID:28358872

Potential sources of bacteria colonizing the cryoconite of an Alpine glacier.

PubMed

Franzetti, Andrea; Navarra, Federico; Tagliaferri, Ilario; Gandolfi, Isabella; Bestetti, Giuseppina; Minora, Umberto; Azzoni, Roberto Sergio; Diolaiuti, Guglielmina; Smiraglia, Claudio; Ambrosini, Roberto

2017-01-01

We investigated the potential contribution of ice-marginal environments to the microbial communities of cryoconite holes, small depressions filled with meltwater that form on the surface of Forni Glacier (Italian Alps). Cryoconite holes are considered the most biologically active environments on glaciers. Bacteria can colonize these environments by short-range transport from ice-marginal environments or by long-range transport from distant areas. We used high throughput DNA sequencing to identify Operational Taxonomic Units (OTUs) present in cryoconite holes and three ice-marginal environments, the moraines, the glacier forefield, and a large (> 3 m high) ice-cored dirt cone occurring on the glacier surface. Bacterial communities of cryoconite holes were different from those of ice-marginal environments and hosted fewer OTUs. However, a network analysis revealed that the cryoconite holes shared more OTUs with the moraines and the dirt cone than with the glacier forefield. Ice-marginal environments may therefore act as sources of bacteria for cryoconite holes, but differences in environmental conditions limit the number of bacterial strains that may survive in them. At the same time, cryoconite holes host a few OTUs that were not found in any ice-marginal environment we sampled, thus suggesting that some bacterial populations are positively selected by the specific environmental conditions of the cryoconite holes.

Catchment-mediated atmospheric nitrogen deposition drives ecological change in two alpine lakes in SE Tibet.

PubMed

Hu, Zhujun; Anderson, Nicholas John; Yang, Xiangdong; McGowan, Suzanne

2014-05-01

The south-east margin of Tibet is highly sensitive to global environmental change pressures, in particular, high contemporary reactive nitrogen (Nr) deposition rates (ca. 40 kg ha(-1)  yr(-1) ), but the extent and timescale of recent ecological change is not well prescribed. Multiproxy analyses (diatoms, pigments and geochemistry) of (210) Pb-dated sediment cores from two alpine lakes in Sichuan were used to assess whether they have undergone ecological change comparable to those in Europe and North America over the last two centuries. The study lakes have contrasting catchment-to-lake ratios and vegetation cover: Shade Co has a relatively larger catchment and denser alpine shrub than Moon Lake. Both lakes exhibited unambiguous increasing production since the late 19th to early 20th. Principle component analysis was used to summarize the trends of diatom and pigment data after the little ice age (LIA). There was strong linear change in biological proxies at both lakes, which were not consistent with regional temperature, suggesting that climate is not the primary driver of ecological change. The multiproxy analysis indicated an indirect ecological response to Nr deposition at Shade Co mediated through catchment processes since ca. 1930, while ecological change at Moon Lake started earlier (ca. 1880) and was more directly related to Nr deposition (depleted δ(15) N). The only pronounced climate effect was evidenced by changes during the LIA when photoautotrophic groups shifted dramatically at Shade Co (a 4-fold increase in lutein concentration) and planktonic diatom abundance declined at both sites because of longer ice cover. The substantial increases in aquatic production over the last ca. 100 years required a substantial nutrient subsidy and the geochemical data point to a major role for Nr deposition although dust cannot be excluded. The study also highlights the importance of lake and catchment morphology for determining the response of alpine lakes to recent global environmental forcing. © 2013 John Wiley & Sons Ltd.

Ice Core Reconnaissance in Siberian Altai for Mid-Latitudes Paleo-Climatic and Environmental Reconstruction

NASA Astrophysics Data System (ADS)

Aizen, V.; Aizen, E.; Kreutz, K.; Nikitin, S.; Fujita, K.; Cecil, D.

2001-12-01

Investigations in Siberian Altai permits to expand our scope from Tibet, Himalayas, Tien Shan and Pamir to the area located at the northeastern edge of the Central Asia Mountain System. Altai forms a natural barrier to the northern and western air masses and therefore affords an opportunity to develop modern paleo-climate records relating to the westerly jet stream, the Siberian High and Pacific monsoon. Moreover, Altai alpine snowice accumulation areas are appropriative for studying air pollution dynamics at the center of Eurasia, eastward from the major Former USSR air pollutants in Kazakhstan, South Siberia and Ural Mountains. During the last century Altai Mountains became extremely contaminated region by heavy metal mining, metallurgy, nuclear test in Semipalatinsk polygon and Baikonur rocket site. Our first field reconnaissance on the West Belukha snow/firn plateau at the Central Altai was carried out in July 2001. Dispute of the large Alatai Mountains glaciation, the West Belukha Plateau (49o48' N, 86o32'E, 4000-4100 m a.s.l.) is only one suitable snow accumulation site in Altai to recover ice-core paleo-climatic and environmental records that is not affected by meltwater percolation. The objective of our first reconnaissance was to find an appropriate deep drilling site by radio-echo sounding survey, to recover shallow ice-core, to identify the annual snow accumulation rate, major ions, heavy metals, radio nuclides and oxygen isotopes level distribution. During 6 days of work on the Plateau, a 22 m shallow firn/ice core has been recovered by PICO hand auger at elevation 4050 m where the results of radio-echo sounding suggests about 150 m ice thickness. In addition to the firn/ice core recovery, five 2.5 meter snow pits were sampled for physical statigraphy, major ions, trace element, and heavy metals analysis to assess spatial variability of the environmental impact in this region. Four automatic snow gauges were installed near proposed deep ice coring site for year around records. The seasonal accumulation at the drilling site was ranged from 250 to 300 ?? with density of 0.34 - 0.40 g cm-3. The ice-core stratigraphy analysis has shown that accumulation area seems to lie in the cold infiltration-recrystallization zone. Geochemical analysis of the shallow ice core, snow pit samples collecting during the 2001 field research will be discussed along with meteorological and synoptic data collected at the nearest to Belukha Plateau Akkem, (2050 m) and Kara -Tyurek (3600 ?) stations. A preliminary result has revealed that variability of elementary synoptic processes over the region impact on the amount of precipitation. North Atlantic Oscillation and West Pacific Oscillation indices have inverse associations with average amount of precipitation in Siberia where Altai is located. >http://www.icess.ucsb.edu/%7eaizen/aizen.html

Minimal erosion of Arctic alpine topography during late Quaternary glaciation

NASA Astrophysics Data System (ADS)

Gjermundsen, Endre F.; Briner, Jason P.; Akçar, Naki; Foros, Jørn; Kubik, Peter W.; Salvigsen, Otto; Hormes, Anne

2015-10-01

The alpine topography observed in many mountainous regions is thought to have formed during repeated glaciations of the Quaternary period. Before this time, landscapes had much less relief. However, the spatial patterns and rates of Quaternary exhumation at high latitudes--where cold-based glaciers may protect rather than erode landscapes--are not fully quantified. Here we determine the exposure and burial histories of rock samples from eight summits of steep alpine peaks in northwestern Svalbard (79.5° N) using analyses of 10Be and 26Al concentrations. We find that the summits have been preserved for at least the past one million years. The antiquity of Svalbard’s alpine landscape is supported by the preservation of sediments older than one million years along a fjord valley, which suggests that both mountain summits and low-elevation landscapes experienced very low erosion rates over the past million years. Our findings support the establishment of northwestern Svalbard’s alpine topography during the early Quaternary. We suggest that, as the Quaternary ice age progressed, glacial erosion in the Arctic became inefficient and confined to ice streams, and high-relief alpine landscapes were preserved by minimally erosive glacier armour.

Differences in dissolved organic matter lability between alpine glaciers and alpine rock glaciers of the American West

NASA Astrophysics Data System (ADS)

Hall, E.; Fegel, T. S., II; Baron, J.; Boot, C. M.

2015-12-01

While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.

Promise and Pitfalls of Using Grain Size Analysis to Identify Glacial Sediments in Alpine Lake Cores.

NASA Astrophysics Data System (ADS)

Clark, D. H.

2011-12-01

Lakes fed by glacier outwash should have a clastic particle-size record distinct from non-glacial lakes in the same area, but do they? The unique turquoise color of alpine glacial lakes reflects the flux of suspended clastic glacial rock flour to those lakes; conversely, lakes not fed by outwash are generally clear with sediments dominated by organics or slope-wash from nearby hillslopes. This contrast in sediment types and sources should produce a distinct and measureable different in grain sizes between the two settings. Results from a variety of lakes suggest the actual situation is often more subtle and complex. I compare grain size results to other proxies to assess the value of grain size analysis for paleoglacier studies. Over the past 10 years, my colleagues and I have collected and analyzed sediment cores from a wide variety of lakes below small alpine glaciers in an attempt to constrain the timing and magnitude of alpine glaciation in those basins. The basic concept is that these lakes act as continuous catchments for any rock flour produced upstream by glacier abrasion; as a glacier grows, the flux of rock flour to the lake will also increase. If the glacier disappears entirely, rock flour deposition will also cease in short order. We have focused our research in basins with simple sedimentologic settings: mostly small, high-altitude, stripped granitic or metamorphic cirques in which the cirque glaciers are the primary source of clastic sediments. In most cases, the lakes are fed by meltwater from a modern glacier, but were ice free during the earlier Holocene. In such cases, the lake cores should record formation of and changes in activity of the glacier upstream. We used a Malvern Mastersizer 2000 laser particle size analyzer for our grain size analyses, as well as recording magnetic susceptibility, color, and organics for the same cores. The results indicate that although lakes often experience increases in silt and clay-size (<0.63 mm) clastic particles when a glacier is present upstream, the signal can be highly variable and complex, most likely the result of stochastic processes in the basin. Our analyses indicate that although particle size reflects glacier activity upstream, it is rarely the best record of glacier change and is most useful in combination with other proxies, most notably MS, color, and organic content.

Recent accumulation rates of an Alpine glacier derived from repeated airborne GPR and firn cores

NASA Astrophysics Data System (ADS)

Sold, Leo; Huss, Matthias; Eichler, Anja; Schwikowski, Margit; Hoelzle, Martin

2014-05-01

The topmost areas of glaciers contain a valuable record of their past accumulation rates. The water equivalent of annual firn layers can be used to initiate or extend existing time series of local mass balance and, ultimately, to consolidate the knowledge on the response of glaciers to changing climatic conditions. Measurements of the thickness and density of firn layers typically involve drilling in remote areas and core analysis and are thus expensive in terms of time and effort. Here, we discuss measurements from 2012 on Findelengletscher, Switzerland, a large Alpine valley glacier, using two in-situ firn cores and airborne Ground-Penetrating Radar (GPR). The firn cores were analysed regarding their density, major ions and deuterium concentration. The ammonium (NH4+) concentration is known to show seasonality due to a higher source activity and pronounced vertical transportation in the atmosphere in summer. The deuterium concentration serves as a proxy for air temperature during precipitation formation. Together, they provide depth and dating of annual summer surfaces. GPR has previously been used for a non-destructive assessment of internal layers in snow, firn and ice. Signal reflections indicate changes in the dielectric properties of the material, e.g. density changes at former summer surfaces. Airborne surveys allow measurements to be taken in remote and inaccessible areas. However, to transfer information from the GPR pulse travel time to the depth domain, the dielectric permittivity of the material is required, that changes with density of the firn. We observed a good agreement of the GPR signal with pronounced changes in the density profile, ice layers and peak contents of major ions. This underlines the high potential of GPR for detecting firn layers. However, not all peak-densities and thick ice layers represent a former glacier summer surface but can also be due to melting and refreezing during winter. We show that up to four years of annual accumulation on Findelengletscher can be reconstructed from repeated GPR measurements alone. A simple transient spatial model for firn compaction is calibrated based on a comparison with GPR data of 2013 at positions were profiles intersect. Density and water equivalent of firn layers can then be extracted along the measured GPR profiles. However, if no in-situ information from firn cores is available, the dating of reflectors as former annual summer surfaces must be verified by external information such as modelled mass balance to avoid misinterpretations. We show that helicopter-borne GPR is an effective method to derive several years of past accumulation rates of mountain glaciers. It benefits but does not depend exclusively on the time-matched availability of firn cores when overlapping profiles are mapped in subsequent years.

Atmospheric depositions of black carbon, inorganic pollutants and mineral dust from the Ortles, Eastern European Alps ice cores during the last 3000 years

NASA Astrophysics Data System (ADS)

Bertò, Michele; Barbante, Carlo; Gabrielli, Paolo; Gabrieli, Jacopo; Spolaor, Andrea; Dreossi, Giuliano; Laj, Paolo; Zanatta, Marco; Stenni, Barbara

2017-04-01

Reconstructions of the atmospheric content of black carbon, heavy metals and mineral dust covering millennial time scales are rare, particularly in the European region. Evaluating the human impact on the environment through mining and industrial activities, road traffic, biomass and coal burning, and the naturally emitted aerosols atmospheric load, is important to know the degree of contaminations and the quality of melting water, the radiative effect on the glacier's radiative balance, the atmospheric aerosols' climatic impacts and the recent decades pollutions emissions policies' efficiencies. Four ice cores were drilled in 2011 from the "Alto dell'Ortles" (3859 m), the highest glacier of the Mt. Ortles massif (South Tirol, Italy). Three 74 m long ice cores were dated by mean of 210Pb, tritium, beta emissions and 14C analyses following also the new dating technique based on filtering the ice for extracting the carbonaceous component of the deposited aerosols. The depth-age curve was obtained by using a Monte Carlo based empirical fitting model (COPRA). The basal ice of core#2 and #3 was dated back to about 7000 years b.p., whereas that of core#1, about one meter shorter, to 3000 years before present. Below the firn-ice transition, at a depth of about 24 m, the borehole temperature revealed the presence of well-preserved cold ice (Gabrielli et al, 2012). The O and H stable isotopes profiles describe well the atmospheric warming as well as the low temperatures recorded during the Little Ice Age (LIA). The proximity of the "Alto dell'Ortles" to densely industrialized areas (Po Valley) makes these ice cores specifically suited for reconstructing the anthropogenic impacts in the Eastern European Alpine region over the last 3 millennia. The ice core#1 was analyzed with a "Continuous Flow Analysis" system (CFA). The separation between internal and external parts of the core prevents any kind of contamination. The core was melted at about 2.5 cm min-1 and simultaneous analyses of conductivity, dust concentration and size distribution (from 0.8 to 80 μm), trace elements with Inductive Coupled Plasma Mass Spectrometer (ICP-MS, Agilent 7500) and refractory black carbon (rBC) with the Single Particle Soot Photometer (SP2, Droplet Measurement Technologies) were performed. A fraction of the melt water was collected by an auto-sampler. More than 1000 samples were analyzed discreetly with a CRC-ICP-MS (with the highest resolution of about 3 cm). The rBC shows significant variability over the last century peaking in concentrations of about 10 ng g-1 from the 1920s to the 1970s, whereas very low values characterized the period from 1000 BC to 1850 AD. The seasonality appears to be preserved even in the firn temperate part of the core as argued from the comparison with the water stable isotopes ratios (δO18). The overall determined trace elements are Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Sr, Ag, Cd, Sb, Te, I, Cs, Ba, Hg, Tl, Pb, Bi, U. The Enrichment Factors (EF) for the crustal elements didn't show any particular trend. While mining and smelting activities appeared to be the most significant heavy metals sources before the 19th century, other anthropogenic heavy metals strongly increased from the onset of the Industrial Revolutions.

Glacial isostatic uplift of the European Alps

PubMed Central

Mey, Jürgen; Scherler, Dirk; Wickert, Andrew D.; Egholm, David L.; Tesauro, Magdala; Schildgen, Taylor F.; Strecker, Manfred R.

2016-01-01

Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ∼90% of the geodetically measured rock uplift in the Alps can be explained by the Earth’s viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions. PMID:27830704

Glacial isostatic uplift of the European Alps.

PubMed

Mey, Jürgen; Scherler, Dirk; Wickert, Andrew D; Egholm, David L; Tesauro, Magdala; Schildgen, Taylor F; Strecker, Manfred R

2016-11-10

Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ∼90% of the geodetically measured rock uplift in the Alps can be explained by the Earth's viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions.

Glacier advance during Marine Isotope Stage 11 in the McMurdo Dry Valleys of Antarctica

PubMed Central

Swanger, Kate M.; Lamp, Jennifer L.; Winckler, Gisela; Schaefer, Joerg M.; Marchant, David R.

2017-01-01

We mapped six distinct glacial moraines alongside Stocking Glacier in the McMurdo Dry Valleys, Antarctica. Stocking Glacier is one of several alpine glaciers in the Dry Valleys fringed by multiple cold-based drop moraines. To determine the age of the outermost moraine, we collected 10 boulders of Ferrar Dolerite along the crest of the moraine and analyzed mineral separates of pyroxene for cosmogenic 3He. On the basis of these measurements, the exposure age for the outermost moraine is 391 ± 35 ka. This represents the first documented advance of alpine glacier ice in the Dry Valleys during Marine Isotope Stage (MIS) 11. At this time, Stocking Glacier was ~20–30% larger than today. The cause of ice expansion is uncertain, but most likely it is related to increased atmospheric temperature and precipitation, associated with reduced ice extent in the nearby Ross Embayment. The data suggest complex local environmental response to warm climates in Antarctica and have implications for glacial response to Holocene warming. The study also demonstrates the potential for using alpine glacier chronologies in the Transantarctic Mountains as proxies for retreat of grounded glacier ice in the Ross Embayment. PMID:28139676

Geosphere - Cryosphere Interactions in the Saint Elias orogen, Alaska and Yukon (Invited)

NASA Astrophysics Data System (ADS)

Bruhn, R. L.; Sauber, J. M.; Forster, R. R.; Cotton, M. M.

2009-12-01

North America's largest alpine and piedmont glaciers occur in the Saint Elias orogen, where microplate collision together with the transition from transform faulting to subduction along the North American plate boundary, create extreme topographic relief, unusually high annual precipitation by orographic lift, and crustal displacements induced by both tectonic and glacio-isostatic deformation. Lithosphere-scale structure dominates the spatial pattern of glaciation; the piedmont Bering and Agassiz-Malaspina glaciers lay along deeply eroded troughs where reverse faults rise from the underlying Aleutian megathrust. The alpine Seward and Bagley Ice Valley glaciers flow along an early Tertiary plate boundary that has been reactivated by reverse faulting, and also by dextral shearing at the NW end of the Fairweather transform fault. Folding above a crustal-scale fault ramp near Icy Bay localizes orographic uplift of air masses, creating alpine glaciers that spill off the highlands into large ice falls, and rapidly dissect evolving structure by erosion. The rate and orientation of ice surface velocities, and the location of crevassing and folding partly reflect changes in basal topography of the glaciers caused by differential erosion of strata, and juxtaposition of variably oriented structures across faults. The effects of basal topography on ice flow are investigated using remote sensing measurements and analog models of glacier flow over uneven topography. Deformation of the ice in turn affects englacial hydrology and sub-ice fluvial systems, potentially impacting ice mass balance, on-set of surging, and loci of glacier quakes. The glaciers impact tectonics by localizing uplift and exhumation within the orogen, and modulating tectonic stress fields as ice masses wax and wane. This is particularly evident in crustal seismicity rates at annual to decadal time scales, while stratigraphy of coastal terraces record both earthquake deformation and glacial isostasy over millennia.

Post-17th-century changes of European lead emissions recorded in high-altitude alpine snow and ice.

PubMed

Schwikowski, Margit; Barbante, Carlo; Doering, Thomas; Gaeggeler, Heinz W; Boutron, Claude; Schotterer, Ulrich; Tobler, Leo; van de Velde, Katja; Ferrari, Christophe; Cozzi, Giulio; Rosman, Kevin; Cescon, Paolo

2004-02-15

Lead concentrations and lead isotope ratios were analyzed in two firn/ice cores covering the period from 1650 to 1994, which were obtained from the 4450 m high glacier saddle Colle Gnifetti located in the Monte Rosa massif at the Swiss-Italian border. This study presents the first glaciochemical time series with annual resolution, spanning several centuries of lead concentrations and lead isotopic compositions in precipitation in Europe. Lead concentrations in firn dated from the 1970s are approximately 25 times higher than in ice dated from the 17th century, confirming the massive rise in lead pollution in Europe during the last few centuries. A decline of the lead concentration is then observed during the last two decades, i.e., from 1975 to 1994. The lead isotope ratio 206Pb/207Pb decreased from about 1.18 in the 17th and 18th centuries to about 1.12 in the 1970s. These variations are in good agreement with available information on variations in anthropogenic lead emissions from West European countries, especially from the use of lead additives in gasoline.

New radiocarbon ages from cirques in Colorado Front Range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, P.T.; Birkeland, P.W.; Caine, N.

The authors recovered sediment cores 3.1 m long from Blue Lake ([approximately]37m water depth, [approximately]3,445m a.s.l., 40[degree]5 minutes 20 seconds N, 105[degree]37 minutes 08 seconds W) and 2.7m long from Lake Dorothy ([approximately]35m water depth, [approximately]3,675m a.s.l., 40[degree]00 minutes 46 seconds N, 105[degree]41 minutes 11 seconds W). A light-weight percussion coring system suspended from perlon ropes was used because of sediment thicknesses, water depths, and ski-backpacking requirements. Lake ice provided a stable coring platform. One purpose of the project is provision of a high-resolution record of environmental change in the subalpine/alpine ecotone during the Holocene, under the auspices of themore » Niwot Ridge Long-Term Ecological Research program. The sediment cores also provide minimum-limiting radiocarbon ages for deglaciation of cirques and the deposits that impound their tarns. Here the authors report on this second purpose. The Blue Lake core bottomed in sandy, gray, inorganic sediment, presumably glacial diamict. A bulk sample from 2.8--2.9m depth yielded a conventional radiocarbon age of 12,275[+-]345 yrs BP. Thus, ice retreated from the site by 12 ka. Since 12 ka both glacial and rock-glacial sediments have been deposited upvalley; some of these events may be recognized in the core. In contrast, the Lake Dorothy core did not penetrate gray inorganic diamict and is entirely organic-rich. A bulk sample from 2.65--2.7m depth yielded a conventional radiocarbon age of 10,910 [+-] 320 yrs BP. Thus, the moraines impounding the lake are 2--3 times older than suggested by a combination of relative-age methods and one radiocarbon age from surface sediments.« less

Pattern and forcing of Northern Hemisphere glacier variations during the last millennium

NASA Astrophysics Data System (ADS)

Porter, Stephen C.

1986-07-01

Time series depicting mountain glacier fluctuations in the Alps display generally similar patterns over the last two centuries, as do chronologies of glacier variations for the same interval from elsewhere in the Northern Hemisphere. Episodes of glacier advance consistently are associated with intervals of high average volcanic aerosol production, as inferred from acidity variations in a Greenland ice core. Advances occur whenever acidity levels rise sharply from background values to reach concentrations ≥1.2 μequiv H +/kg above background. A phase lag of about 10-15 yr, equivalent to reported response lags of Alpine glacier termini, separates the beginning of acidity increases from the beginning of subsequent ice advances. A similar relationship, but based on limited and less-reliable historical data and on lichenometric ages, is found for the preceding 2 centuries. Calibrated radiocarbon dates related to advances of non-calving and non-surging glaciers during the earlier part of the Little Ice Age display a comparable consistent pattern. An interval of reduced acidity values between about 1090 and 1230 A.D. correlates with a time of inferred glacier contraction during the Medieval Optimum. The observed close relation between Noothern Hemisphere glacier fluctuations and variations in Greenland ice-core acidity suggests that sulfur-rich aerosols generated by volcanic eruptions are a primary forcing mechanism of glacier fluctuations, and therefore of climate, on a decadal scale. The amount of surface cooling attributable to individual large eruptions or to episodes of eruptions is simlar to the probable average temperature reduction during culminations of Little Ice Age alacier advances (ca. 0.5°-1.2°C), as inferred from depression of equilibrium-line altitudes.

Hypsometry and the distribution of high-alpine lakes in the European Alps

NASA Astrophysics Data System (ADS)

Prasicek, Günther; Otto, Jan-Christoph; Buckel, Johannes; Keuschnig, Markus

2017-04-01

Climate change strongly affects alpine landscapes. Cold-climate processes shape the terrain in a typical way and ice-free overdeepenings in cirques and glacial valleys as well as different types of moraines favor the formation of lakes. These water bodies act as sediment sinks and high-alpine water storage but may also favor outburst and flooding events. Glacier retreat worldwide is associated with an increasing number and size of high-alpine lakes which implies a concurrent expansion of sediment retention and natural hazard potential. Rising temperatures are regarded to be the major cause for this development, but other factors such as the distribution of area over elevation and glacier erosional and depositional dynamics may play an important role as well. While models of ice flow and glacial erosion are employed to understand the impact of glaciers on mountain landscapes, comprehensive datasets and analyses on the distribution of existing high-alpine lakes are lacking. In this study we present an exhaustive database of natural lakes in the European Alps and analyze lake distribution with respect to hypsometry. We find that the distribution of lake number and lake area over elevation only weakly coincides with hypsometry. Unsurprisingly, largest lakes are often tectonically influenced and located at the fringe of the mountain range and in prominent inter-montane basins. With increasing elevation, however, the number of lakes, lake area and total area decrease until a local minimum is reached around the equilibrium line latitude (ELA) of the last glacial maximum (LGM). Above the LGM ELA, total area further decreases, but lake number and area increase again. A local maximum in lake area coincides with an absolute maximum in lake number between the ELAs of the LGM and the little ice age around 2500 m. We conclude that glacial erosional and depositional dynamics control the distribution and size of high-alpine lakes and thus demand for exceptional attention when predicting future lake development.

Exploring the ground ice recharge near permafrost table on the central Qinghai-Tibet Plateau using chemical and isotopic data

NASA Astrophysics Data System (ADS)

Wang, Weihua; Wu, Tonghua; Zhao, Lin; Li, Ren; Zhu, Xiaofan; Wang, Wanrui; Yang, Shuhua; Qin, Yanhui; Hao, Junmin

2018-05-01

Thawing permafrost on the Qinghai-Tibet Plateau (QTP) has great impacts on the local hydrological process by way of causing ground ice to thaw. Until now there is little knowledge on ground ice hydrology near permafrost table under a warming climate. This study applied stable tracers (isotopes and chloride) and hydrograph separation model to quantify the sources of ground ice near permafrost table in continuous permafrost regions of the central QTP. The results indicated that the ground ice near permafrost table was mainly supplied by active layer water and permafrost water, accounting for 58.9 to 87.0% and 13.0 to 41.1%, respectively, which implying that the active layer was the dominant source. The contribution rates from the active layer to the ground ice in alpine meadow (59 to 69%) was less than that in alpine steppe (70 to 87%). It showed well-developed hydrogeochemical depth gradients, presenting depleted isotopes and positive chemical gradients with depth within the soil layer. The effects of evaporation and freeze-out fractionation on the soil water and ground ice were evident. The results provide additional insights into ground ice sources and cycling near permafrost table in permafrost terrain, and would be helpful for improving process-based detailed hydrologic models under the occurring global warming.

Friis Hills glacial history: an international collaboration to examine Miocene climate in Antarctica

NASA Astrophysics Data System (ADS)

Halberstadt, A. R. W.; Kowalewski, D. E.

2016-12-01

The Friis Hills, Antarctica (western McMurdo Dry Valleys) contain unique, well-preserved records of Miocene climate. These terrestrial deposits hold geomorphic clues for deciphering the glacial history in a region directly adjacent to the East Antarctic Ice Sheet. Stacked till sheets, interbedded with lake sediments and non-glacial deposits, reveal a complex history of ice flow and erosion throughout multiple glacial-interglacial cycles (Lewis and Ashworth, 2015). Fossiliferous beds containing Nothofagus, diatoms, algal cells, pollen, insects, and mosses provide past climatological constraints. The Friis Hills sustained multiple alpine glaciations as well as full ice-sheet development, recording glacial drainage reorganization and evidence of previous ice configurations that possibly overrode the Transantarctic Mountains (Lewis and Ashworth, 2015) exposing only scattered nunataks (i.e. a portion of Friis Hills). Lack of chronological control has previously hindered efforts to link the Friis Hills glacial history with regional context; a tephra deposit at the base of the glacial drifts currently provides a single age constraint within the drift deposits. To build upon previous studies, an international collaboration between the USAP, Antarctic New Zealand, and the Italian Antarctic community proposes to core a paleo-lake in the center of the Friis Hills in November 2016, thereby acquiring one of the oldest continuous sedimentological records within the McMurdo Dry Valleys. Here we report discoveries from this year's fieldwork, and reconstruct paleoenvironment at the periphery of the East Antarctic Ice Sheet for the mid-early Miocene, a critical time when marine isotopic records indicate dramatic ice fluctuations. Ash within the sediment core stratigraphy will provide a more robust chronology for the region, and will also suggest possible outcrop locations of corresponding ash deposits to pursue while in the field. We anticipate that the Friis Hills stratigraphy will have the necessary chronological control for correlation with offshore marine records from the Ross Embayment, including the ANDRILL project.

Slip localization on the southern Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Barth, N. C.; Boulton, C.; Carpenter, B. M.; Batt, G. E.; Toy, V. G.

2013-06-01

of a detailed field study of the southern onshore portion of New Zealand's Alpine Fault reveal that for 75 km along-strike, dextral-normal slip on this long-lived structure is highly localized in phyllosilicate-rich fault core gouges and along their contact with more competent rocks. At three localities (Martyr River, McKenzie Creek, and Hokuri Creek), we document complete cross sections through the fault. New 40Ar/39Ar dates on mylonites, combined with microstructural and mechanical data on phyllosilicate-rich fault core gouges show that modern slip is localized onto a single, steeply dipping 1 to 12 m-thick fault core composed of impermeable (k = 10-20 to 10-22 m2), frictionally weak (μs = 0.12-0.37), velocity-strengthening, illite-chlorite, and saponite-chlorite-lizardite fault gouges. Fault core materials are (1) comparable to those of other major weak-cored faults (e.g., San Andreas Fault) and (2) most compatible with fault creep, despite paleoseismic evidence of quasiperiodic large magnitude earthquakes (Mw > 7) on this portion of the Alpine Fault. We conclude that frictional properties of gouges at the surface do not characterize the overall seismogenic behavior of the southern Alpine Fault.

Erosion by an Alpine glacier.

PubMed

Herman, Frédéric; Beyssac, Olivier; Brughelli, Mattia; Lane, Stuart N; Leprince, Sébastien; Adatte, Thierry; Lin, Jiao Y Y; Avouac, Jean-Philippe; Cox, Simon C

2015-10-09

Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years. Copyright © 2015, American Association for the Advancement of Science.

Sudden disintegration of ice in the glacial-proglacial transition zone of the largest glacier in Austria

NASA Astrophysics Data System (ADS)

Kellerer-Pirklbauer, Andreas; Avian, Michael; Hirschmann, Simon; Lieb, Gerhard Karl; Seier, Gernot; Sulzer, Wolfgang; Wakonigg, Herwig

2017-04-01

Rapid deglaciation does not only reveal a landscape which is prone to rapid geomorphic changes and sediment reworking but also the glacier ice itself might be in a state of disintegration by ice melting, pressure relief, crevasse formation, ice collapse or changes in the glacier's hydrology. In this study we considered the sudden disintegration of glacier ice in the glacial-proglacial transition zone of Pasterze Glacier. Pasterze Glacier is a typical alpine valley glacier and covers currently some 16.5 km2 making it to the largest glacier in Austria. This glacier is an important site for alpine mass tourism in Austria related to a public high alpine road and a cable car which enable access to the glacier rather easily also for unexperienced mountaineers. Spatial focus in our research is given on two particular study areas where several ice-mass movement events occurred during the 2015- and 2016-melting seasons. The first study area is a crevasse field at the lower third of the glacier tongue. This lateral crevasse field has been substantially modified during the last two melting seasons particularly because of thermo-erosional effects of a glacial stream which changed at this site from subglacial (until 2015) to glacier-lateral revealing a several tens of meters high unstable ice cliff prone to ice falls of different magnitudes. The second study area is located at the proglacial area. At Pasterze Glacier the proglacial area is widely influenced by dead-ice bodies of various dimensions making this area prone to slow to sudden geomorphic changes caused by ice mass changes. A particular ice-mass movement event took place on 20.09.2016. Within less than one hour the surface of the proglacial area changed substantially by tilting, lateral shifting, and subsidence of the ground accompanied by complete ice disintegration of once-debris covered ice. To understand acting processes at both areas of interest and to quantify mass changes we used field observations, terrain analysis (based on multi-temporal DEM generation derived from terrestrial laser scanning/TLS and unmanned aerial systems/UAS), electrical resistivity tomography (ERT), ground climate monitoring, and data from an automatic remote camera (RDC) system. Results for both areas of interest are presented and discussed regarding its relevance for the glacier itself but also the potential risks for mountaineers.

The vegetation and climate history of the last glacial cycle in a new pollen record from Lake Fimon (southern Alpine foreland, N-Italy)

NASA Astrophysics Data System (ADS)

Pini, R.; Ravazzi, C.; Reimer, P. J.

2010-11-01

The sediments of Lake Fimon, N-Italy, contain the first continuous archive of the Late Pleistocene environmental and climate history of the southern Alpine foreland. We present here the detailed palynological record of the interval between Termination II and the Last Glacial Maximum. The age-depth model is obtained by radiocarbon dating in the uppermost part of the record. Downward, we correlated major forest expansion and contraction events to isotopic events in the Greenland Ice core records, via a stepping-stone approach involving intermediate correlation to isotopic events dated by TIMS U/Th in Alpine and Apennine stalagmites, and to pollen records from marine cores of the Iberian margin. Modelled ages obtained by Bayesian analysis of deposition are thoroughly consistent with actual ages, with maximum offset of ±1700 years. Sharp expansion of broad-leaved temperate forest and of sudden water table rise mark the onset of the Last Interglacial after a treeless steppe phase at the end of penultimate glaciation. This event is actually a two-step process which matches the two-step rise observed in the isotopic record of the nearby Antro del Corchia stalagmite, respectively dated to 132.5 ± 2.5 and 129 ± 1.5 ka. At the interglacial decline mixed oak forests were replaced by oceanic mixed forests, the latter persisting further for 7 ka till the end of the Eemian succession. Warm-temperate woody species are still abundant at the Eemian end, corroborating a steep gradient between central Europe and the Alpine divide at the inception of the last glacial. After a stadial phase marked by moderate forest decline, a new expansion of warm broad-leaved forests, interrupted by minor events and followed by mixed oceanic forests, can be identified with the north-alpine Saint Germain I. The spread of beech during the oceanic phase is a valuable circumalpine marker. The subsequent stadial-interstadial succession, lacking the telocratic oceanic phase, is also consistent with the evidence at the north-alpine foreland. The Middle Würmian (full glacial) is marked by persistence of mixed forests dominated by conifers but with significant lime and other broad-leaved species. A major Arboreal Pollen decrease is observed at modelled age of 38.7 ± 0.5 ka (larch expansion and last occurrence of lime), which has been related to Heinrich Event 4. The evidence of afforestation persisting south of the Alps throughout most of MIS 3 contrasts with a boreal and continental landscape known for the northern alpine foreland, pointing to a sharp rainfall boundary at the Alpine divide and to southern air circulation. This is in agreement with the Alpine paleoglaciological record and is supported by the pressure and rainfall patterns designed by mesoscale paleoclimate simulations. Strenghtening the continental high pressure during the full glacial triggered cyclogenesis in the middle latitude eastern Europe and orographic rainfall in the eastern Alps and the Balkanic mountains, thus allowing forests development at current sea-level altitudes.

The gut morphology of the African ice rat, Otomys sloggetti robertsi, shows adaptations to cold environments and sex-specific seasonal variation.

PubMed

Schwaibold, U; Pillay, N

2003-11-01

We studied the gut morphology of the ice rat Otomys sloggetti robertsi, a non-hibernating murid rodent endemic to the sub-alpine and alpine regions of the southern African Drakensberg and Maluti mountains. The gut structure of O. s. robertsi is well adapted for a high fibre, herbivorous diet, as is the case with other members of its subfamily Otomyinae. Despite the broad similarity in gross gut morphology with mesic- and arid-occurring otomyines, O. s. robertsi has a larger small intestine, caecum, stomach volume and parts of the colon, which we suggest are adaptations for increased energy uptake and/or poor diet quality in alpine environments. However, O. s. robertsi has a smaller larger intestine than other otomyines, perhaps because it occupies a mesic habitat. Seasonal sexual differences occurred, with females increasing dimensions of the stomach, small intestine length, caecum, and large intestine in summer. Sexual asymmetry in gut morphology may be related to increased energy requirements of females during pregnancy and lactation, indicating phenotypic plasticity in response to poor quality vegetation and a shorter growing season in alpine habitats.

Towards a quasi-complete reconstruction of past atmospheric aerosol load and composition (organic and inorganic) over Europe since 1920 inferred from Alpine ice cores

NASA Astrophysics Data System (ADS)

Preunkert, S.; Legrand, M.

2013-02-01

Seasonally resolved chemical ice core records available from the Col du Dôme glacier (4250 m elevation, French Alps) are here revisited in view to reconstruct past aerosol load of the free European troposphere from prior World War II to present. The extended array of inorganic (Na+, Ca2+, NH4+, Cl-, NO3-, and SO42-) and organic (carboxylates, HCHO, HUmic LIke Substances, dissolved organic carbon, water insoluble organic carbon, and black carbon) compounds and fractions already investigated permit to examine the overall aerosol composition and its change over the past. It is shown that the atmospheric load of submicron aerosol has been increased by a factor of 3 from the 1921-1951 to 1971-1988 years, mainly as a result of a large increase of sulfate (a factor of 5), ammonium and water-soluble organic aerosol (a factor of 3). It is shown that not only growing anthropogenic emissions of sulfur dioxide and ammonia have caused the enhancement of the atmospheric aerosol load but also biogenic emissions producing water soluble organic aerosol. This unexpected change of biospheric source of organic aerosol after 1950 needs to be considered and further investigated in scenarii dealing with climate forcing by atmospheric aerosol.

Catchment nitrogen saturation drives ecological change in an alpine lake in SW China (eastern margin of Tibet)

NASA Astrophysics Data System (ADS)

Anderson, N. J.; Hu, Z.; Yang, X.; Zhang, E.

2011-12-01

There is substantial evidence for recent (last ca. 120 years) ecological change in remote arctic and alpine lakes (increased productivity, altered biological structure). Initially, these changes were attributed to global warming which has altered the heat budgets of these lakes (stronger stratification, longer ice free periods). The emphasis on temperature, however, ignores that global environmental change is driven by a range of multiple stressors (e.g. altered biogeochemical cycles, land cover change). One of the characteristics of the observed change in remote lakes is the expansion of small species of the planktonic diatom genus Cyclotella. It is increasingly obvious that the recent success of this diatom genus is driven by other factors (nutrients, light, mixing depth) as much as temperature. SE Asia is a major hotspot for the emission of reactive nitrogen as a result of intensive agriculture and fossil fuel combustion. In this study we report recent ecological change in a small, oligotrophic alpine lake (ShadeCo; altitude 4423 m) located in Sichuan Province (SW China), one of many relatively unstudied alpine lakes on the eastern margin of Tibet. The lake is located above the tree-line and there is no cultural land-use; the catchment vegetation is dominated by alpine shrub (predominantly Rhododendron). We used a multi-proxy palaeolimnological approach (diatom, geochemical and stable isotope analyses of a 210-Pb dated core) coupled with regional long-term climate data to understand the pronounced 20th century changes in the diatom record, notably an expansion of Cyclotella spp from around 1920. This initial increase is coincident with warming in SW China but the maximum Cyclotella abundance occurs in in the 1970s and 1980s, a period of regional cooling and major changes in catchment-lake biogeochemistry as indicated by geochemical analyses. The possible drivers of the observed changes (nitrogen deposition, temperature) at this site are discussed in the context of regional water chemistry surveys.

In Review (Geology): Alpine Landscape Evolution Dominated by Cirque Retreat

NASA Technical Reports Server (NTRS)

Oskin, Michael; Burbank, Doug

2005-01-01

Despite the abundance in alpine terrain of glacially dissected landscapes, the magnitude and geometry of glacial erosion can rarely be defined. In the eastern Kyrgyz Range, a widespread unconformity exhumed as a geomorphic surface provides a regional datum with which to calibrate erosion. As tectonically driven surface uplift has progressively pushed this surface into the zone of ice accumulation, glacial erosion has overprinted the landscape. With as little as 500 m of incision into rocks underlying the unconformity, distinctive glacial valleys display their deepest incision adjacent to cirque headwalls. The expansion of north-facing glacial cirques at the expense of south-facing valleys has driven the drainage divide southwards at rates up to 2 to 3 times the rate of valley incision. Existing ice-flux-based glacial erosion rules incompletely model expansion of glacial valleys via cirque retreat into the low-gradient unconformity remnants. Local processes that either directly sap cirque headwalls or inhibit erosion down-glacier appear to control, at least initially, alpine landscape evolution.

Multi Source Remote Sensing for Monitoring Light-Absorbing Impurities on Snow and Ice in the European Alps

NASA Astrophysics Data System (ADS)

Colombo, R.; Baccolo, G.; Garzonio, R.; Massabò, D.; Julitta, T.; Rossini, M.; Ferrero, L.; Delmonte, B.; Maggi, V.; Mattavelli, M.; Panigada, C.; Cogliati, S.; Cremonese, E.; Di Mauro, B.

2016-12-01

The European Alps are located close to one of the most industrialized areas of the planet and they are 3.000 km from the largest desert of the Earth. Light-absorbing impurities (LAI) emitted from these sources can reach the Alpine chain and deposit on snow covered areas and mountain glaciers. Although several studies show that LAI have important impacts on the optical properties of snow and ice, reducing the albedo and promoting the melt, this impact has been poorly characterized in the Alps. In this contribution, we present the results of a multisource remote sensing approach aimed to study the LAI impact on snow and ice properties in the Alpine area. This process has been observed by means of remote and proximal sensing methods, using satellite (Landsat 8, Hyperion and MODIS data), field spectroscopy (ASD measurements), Automatic Weather Stations, aerial surveys (Unmanned Aerial Vehicle), radiative transfer modeling (SNICAR and TARTES) and laboratory analysis (hyperspectral imaging system). Furthermore, particle size (Coulter Counter), geochemical (Instrumental Neutron Activation Analysis, INAA) and optical (Multi-Wavelength Absorbance Analyzer, MWAA) analyses have been applied to determine the nature and radiative properties of particulate material deposited on snow and ice or aggregated into cryoconite holes. Our results demonstrate that LAI can be monitored from remote sensing at different scale. LAI showed to have a strong impact on the Alpine cryosphere, paving the way for the assessment of their role in melting processes.

Multi-resolution Changes in the Spatial Extent of Perennial Arctic Alpine Snow and Ice Fields with Potential Archaeological Significance in the Central Brooks Range, Alaska

NASA Astrophysics Data System (ADS)

Tedesche, M. E.; Freeburg, A. K.; Rasic, J. T.; Ciancibelli, C.; Fassnacht, S. R.

2015-12-01

Perennial snow and ice fields could be an important archaeological and paleoecological resource for Gates of the Arctic National Park and Preserve in the central Brooks Range mountains of Arctic Alaska. These features may have cultural significance, as prehistoric artifacts may be frozen within the snow and ice. Globally significant discoveries have been made recently as ancient artifacts and animal dung have been found in melting alpine snow and ice patches in the Southern Yukon and Northwest Territories in Canada, the Wrangell mountains in Alaska, as well as in other areas. These sites are melting rapidly, which results in quick decay of biological materials. The summer of 2015 saw historic lows in year round snow cover extent for most of Alaska. Twenty mid to high elevation sites, including eighteen perennial snow and ice fields, and two glaciers, were surveyed in July 2015 to quantify their areal extent. This survey was accomplished by using both low flying aircraft (helicopter), as well as with on the ground in-situ (by foot) measurements. By helicopter, visual surveys were conducted within tens of meters of the surface. Sites visited by foot were surveyed for extent of snow and ice coverage, melt water hydrologic parameters and chemistry, and initial estimates of depths and delineations between snow, firn, and ice. Imagery from both historic aerial photography and from 5m resolution IKONOS satellite information were correlated with the field data. Initial results indicate good agreement in permanent snow and ice cover between field surveyed data and the 1985 to 2011 Landsat imagery-based Northwest Alaska snow persistence map created by Macander et al. (2015). The most deviation between the Macander et al. model and the field surveyed results typically occurred as an overestimate of perennial extent on the steepest aspects. These differences are either a function of image classification or due to accelerated ablation rates in perennial snow and ice coverage between 2011 and 2015. Further work is ongoing to develop a model to guide archaeological and paleoecological snow and ice field surveys. This will entail a fine scale, empirically based model of accumulation and ablation to estimate changes in three dimensional geometries of historically perennial arctic alpine snow and ice fields in the study area.

Constraining Quaternary ice covers and erosion rates using cosmogenic 26Al/10Be nuclide concentrations

NASA Astrophysics Data System (ADS)

Knudsen, Mads Faurschou; Egholm, David Lundbek

2018-02-01

Paired cosmogenic nuclides are often used to constrain the exposure/burial history of landforms repeatedly covered by ice during the Quaternary, including tors, high-elevation surfaces, and steep alpine summits in the circum-Arctic regions. The approach generally exploits the different production rates and half-lives of 10Be and 26Al to infer past exposure/burial histories. However, the two-stage minimum-limiting exposure and burial model regularly used to interpret the nuclides ignores the effect of variable erosion rates, which potentially may bias the interpretation. In this study, we use a Monte Carlo model approach to investigate systematically how the exposure/burial and erosion history, including variable erosion and the timing of erosion events, influence concentrations of 10Be and 26Al. The results show that low 26Al/10Be ratios are not uniquely associated with prolonged burial under ice, but may as well reflect ice covers that were limited to the coldest part of the late Pleistocene combined with recent exhumation of the sample, e.g. due to glacial plucking during the last glacial period. As an example, we simulate published 26Al/10Be data from Svalbard and show that it is possible that the steep alpine summits experienced ice-free conditions during large parts of the late Pleistocene and varying amounts of glacial erosion. This scenario, which contrasts with the original interpretation of more-or-less continuous burial under non-erosive ice over the last ∼1 Myr, thus challenge the conventional interpretation of such data. On the other hand, high 26Al/10Be ratios do not necessarily reflect limited burial under ice, which is the common interpretation of high ratios. In fact, high 26Al/10Be ratios may also reflect extensive burial under ice, combined with a change from burial under erosive ice, which brought the sample close to the surface, to burial under non-erosive ice at some point during the mid-Pleistocene. Importantly, by allowing for variable erosion rates, the model results may reconcile spatially varying 26Al/10Be data from bedrock surfaces preserved over multiple glacial cycles, suggesting that samples from the same high-elevation surface or neighbouring alpine summits may have experienced similar long-term burial under ice, but varying amounts of glacial erosion.

Transient Fluvial Response to Alpine Deglaciation, Mount Rainier, WA: Geomorphic Process Domains and Proglacial Flux Controls on Channel Evolution.

NASA Astrophysics Data System (ADS)

Beyeler, J. D.; Montgomery, D.; Kennard, P. M.

2016-12-01

Downwasting of all glaciers on the flanks of Mount Rainier, WA, in recent decades has debuttressed Little Ice Age glaciogenic sediments driving proglacial responses to regionally warming climate. Rivers draining the deglaciating edifice are responding to paraglacial sedimentation processes through transient storage of retreat-liberated sediments in aggrading (e.g., >5m) fluvial networks with widening channel corridors (i.e., 50-150%) post-LIA (ca., 1880-1910 locally). We hypothesize that the downstream transmission of proglacial fluxes (i.e., sediment and water) through deglaciating alpine terrain is a two-step geomorphic process. The ice-proximal portion of the proglacial system is dominated by the delivery of high sediment-to-water ratio flows (i.e., hyperconcentrated and debris slurries) and sediment retention by in-channel accumulation (e.g., confined debris fans within channel margins of valley segments) exacerbated by recruitment and accumulation of large wood (e.g., late seral stage conifers), whereas ice-distal fluvial reworking of transient sediment accumulations generates downstream aggradation. Historical Carbon River observations show restricted ice-proximal proglacial aggradation until a mainstem avulsion in 2009 initiated incision into sediment accumulations formed in recent decades, which is translating into aggradation farther down the network. Surficial morphology mapped with GPS, exposed subsurface sedimentology, and preliminary dating of buried trees suggest a transitional geomorphic process zone has persisted along the proglacial Carbon River through recent centuries and prior to the ultimate LIA glaciation. Structure-from-motion DEM differencing through the 2016 water year shows discrete zones of proglacial evolution through channel-spanning bed aggradation forced by interactions between large wood and sediment-rich flows that transition to fluvial process dominance as sediment is transported downstream. Long-term DEM differencing suggests these are persistent geomorphic processes as rivers respond to alpine deglaciation. This process-based study implies downstream river flooding in deglaciating alpine terrain globally is driven by glaciogenic sediment release and downstream channel aggradation irrespective of changes in discharge.

Varied records of early Wisconsinan alpine glaciation in the western United States derived from weathering-rind thicknesses

USGS Publications Warehouse

Clark, Peter U.; Lea, P.D.

1992-01-01

Weathering-rind thicknesses were measured on volcanic clasts in sequences of glacial deposits in seven mountain ranges in the western United States and in the Puget lowland. Because the rate of rind development decreases with time, ratios of rind thicknesses provide limits on corresponding age ratios. In all areas studied, deposits of late Wisconsinan age are obvious; deposits of late Illinoian age (ca. 140 ka) also seem to be present in each area, although independent evidence for their numerical age is circumstantial. The weathering-rind data indicate that deposits that have intermediate ages between these two are common, and ratios of rind thicknesses suggest an early Wisconsinan age (about 60 to 70 ka) for some of the intermediate deposits. Three of the seven studied alpine areas (McCall, Idaho; Yakima Valley, Washington; and Lassen Peak, California) appear to have early Wisconsinan drift beyond the extent of late Wisconsinan ice. In addition, Mount Rainier and the Puget lowland, Washington, have outwash terraces but no moraines of early Wisconsinan age. The sequences near West Yellowstone, Montana; Truckee, California; and in the southern Olympic Mountains have no recognized moraines or outwash of this age. Many of the areas have deposits that may be of middle Wisconsinan age.Differences in the relative extents of early Wisconsinan alpine glaciers are not expected from the marine oxygen-isotope record and are not explained by any simple trend in climatic variables or proximity to oceanic moisture sources. However, alpine glaciers could have responded more quickly and more variably than continental ice sheets to intense, short-lived climatic events, and they may have been influenced by local climatic or hypsometric effects. The relative sizes of early and late Wisconsinan alpine glaciers could also reflect differences between early and late Wisconsinan continental ice sheets and their regional climatic effects.

Girls on Ice: Using Immersion to Teach Fluency in Science

NASA Astrophysics Data System (ADS)

Pettit, E. C.; Mortenson, C.; Stiles, K.; Coryell-Martin, M.; Long, L.

2010-12-01

Young women choose not to pursue science careers for several reasons; two important ones are that they more often lack the confidence in their own ability to succeed or they perceive many science jobs as isolated (working alone in a lab) or lacking in altruistic values of helping other people or communities. We developed an immersion-science program, Girls on Ice, to provide young women with strong, female role models; with an opportunity to see what a career in the Earth sciences is like; with one-on-one interactions with scientists; with facilitated discussions on the value of Earth science in societal issues such as climate change; and with challenges that will build their self-confidence in multiple ways. Girls on Ice is field-based program for teenage young women with the theme of Glaciers, Climate, and the Alpine Landscape. The concepts we cover range from glacier dynamics to alpine plant ecology to mountain weather. The educational goals are 1. to increase young women's self-efficacy and interest in pursuing science as a career, 2. to create life-long advocates for the scientific process and its role in public policy 3. to teach critical thinking skills which will be important for all of their future pursuits 4. to enhance their leadership self-confidence so that they have a higher likelihood of becoming community leaders in the future. The educational philosophy of Girls on Ice consists of three core values: that teaching the whole process of science gives students ownership of the science; that teaching to the whole student puts the science in context; and that diversity inspires new ideas, new approaches, and better science in the end. We use a field-based immersion format -- the science equivalent of language-immersion course - in order to achieve the goals listed above in a setting that emphasizes this educational philosophy. The immersion-style course creates a deep connection between science and daily life for these young women. Combined with climate change content, this style of teaching guides these young women toward becoming scientifically-literate leaders and decision makers and strengthens the connection between scientists and decision makers, educators, and communicators in regard to modern society-science issues.

Vanishing Ice: Art as a Tool for Documenting Climate Change

ERIC Educational Resources Information Center

Kothe, Elsa Lenz; Maute, Mary Jo; Brewer, Chris

2015-01-01

The work of artists as naturalists, scientists, documentarians, and explorers has long been part of an interdisciplinary approach to scientific studies. As museum educators, this group of authors has gained inspiration from the exhibition Vanishing Ice: Alpine and Polar Landscapes in Art, 1775-2012 (Matilsky, 2013) and discovered how historical…

Hydrological role of large icings within glacierized Sub-Arctic watershed: case study in Upper Duke River valley, Yukon, Canada.

NASA Astrophysics Data System (ADS)

Chesnokova, Anna; Baraer, Michel

2017-04-01

Sub-Arctic glacierized catchments are complex hydrological systems of paramount importance for water resources management as well as for various ecosystem services. Such systems host many climate-sensitive water sources. Among those, icing is an important component as they provide substantial amount of water during the melt season. Moreover, collecting water of different origins during their formation, icings can be seen as an indicator for different water sources and water pathways that remain active during the freezing period. The present study focuses on genesis and dynamics of large icings within both proglacial field and neighboring alpine meadow in Upper Duke River valley, Yukon, in order to i) provide new insights on water sources and pathways within Sub-Arctic glacierized watersheds, and ii) to quantify contribution of icings to the total runoff of those hydrological systems. A multi-approach technique was applied to cope with the high hydrological complexity met in Sub-Arctic mountainous environments. Time series of positions of large river icings within the study area were obtained using Landsat images for the period 1980-2016. Four time-lapse cameras (TLC) were installed in the watershed targeting two proglacial fields and two alpine meadows in order to monitor icing dynamics all year long. Meteorological data was measured by an Automatic Weather Station in the main valley. In addition air temperature and relative humidity were measured at the location of each TLC. Finally, four icings along the Duke River valley, as well as 2 icings in its main tributary were sampled for stable water isotopes, solutes concentrations and total organic carbon. In addition, samples of freezing exclusion precipitates from icing surfaces were taken. Remote sensing data shows the persistence of large icing complexes in the area during last 30 years: icing within proglacial field appear with almost constant position relative to main glacier tongue on the 30 years long period. Absolute position of icings limits is changing however, and is shifting upstream following glacier retreat. TLC show that appearance and growth of icing is correlated with occurrence of milder but still negative temperature episodes. Hydrochemical analysis suggests that main source of water for icing formation within alpine meadow is groundwater, whereas icing formed within proglacial field are fed by both glacier and possibly buried ice water. Thus the multi-technic approach reveals a tight connection of proglacial and river icing formation in Upper Duke River valley with current and past glacier systems: sub-glacial drainage water as well as water from buried ice are collected in a form of icing during mild winter episodes and then are being redistributed to total runoff during ablation season contributing substantially. Moreover, observed relation between icing formation and air temperature regime in the valley suggests that hydrological role of icings in Sub-Arctic glacierized watershed will be subject to changes under changing climate.

Seasonal inorganic nitrogen release in alpine lakes on the Colorado western slope

USGS Publications Warehouse

Inyan, B.I.; Williams, M.W.; Tonnessen, K.; Turk, J.T.; Campbell, D.H.

1998-01-01

In the Rocky Mountains, the association of increases in acidic deposition with increased atmospheric loading of sulfate and direct changes in surface water chemistry has been well established. The importance, though, of increased nitrogen (N) deposition in the episodic acidification of alpine lakes and N saturation in alpine ecosystems is only beginning to be documented. In alpine areas of the Colorado Front Range, modest loadings of N in deposition have been associated with leakage of N to surface waters. On the Colorado western slope, however, no leakage of N to surface waters has been reported. A 1995 study that included early season under-ice water samples that were not available in earlier studies showed that there is, in fact, N leakage to surface waters in some western slope basins. Under-ice nitrate (NO3-) concentrations were as high as 10.5 ??q L-1, and only decreased to detection limits in September. Landscape type appears to be important in leakage of N to surface waters, which is associated with basins having steep slopes, thin soils, and large amounts of exposed bedrock. NO3- leakage compounds the existing sensitivity to episodic acidification from low acid neutralizing capacity (ANC), which is less than 40 ??eq L-1 in those basins.

Modeling the Rock Glacier Cycle

NASA Astrophysics Data System (ADS)

Anderson, R. S.; Anderson, L. S.

2016-12-01

Rock glaciers are common in many mountain ranges in which the ELA lies above the peaks. They represent some of the most identifiable components of today's cryosphere in these settings. Their oversteepened snouts pose often-overlooked hazards to travel in alpine terrain. Rock glaciers are supported by avalanches and by rockfall from steep headwalls. The winter's avalanche cone must be sufficiently thick not to melt entirely in the summer. The spatial distribution of rock glaciers reflects this dependence on avalanche sources; they are most common on lee sides of ridges where wind-blown snow augments the avalanche source. In the absence of rockfall, this would support a short, cirque glacier. Depending on the relationship between rockfall and avalanche patterns, "talus-derived" and "glacier-derived" rock glaciers are possible. Talus-derived: If the spatial distribution of rock delivery is similar to the avalanche pattern, the rock-ice mixture will travel an englacial path that is downward through the short accumulation zone before turning upward in the ablation zone. Advected debris is then delivered to the base of a growing surface debris layer that reduces the ice melt rate. The physics is identical to the debris-covered glacier case. Glacier-derived: If on the other hand rockfall from the headwall rolls beyond the avalanche cone, it is added directly to the ablation zone of the glacier. The avalanche accumulation zone then supports a pure ice core to the rock glacier. We have developed numerical models designed to capture the full range of glacier to debris-covered glacier to rock glacier behavior. The hundreds of meter lengths, tens of meters thicknesses, and meter per year speeds of rock glaciers are well described by the models. The model can capture both "talus-derived" and "glacier-derived" rock glaciers. We explore the dependence of glacier behavior on climate histories. As climate warms, a pure ice debris-covered glacier can transform to a much shorter rock glacier, leaving in its wake a thinning ice-cored moraine. Rock glaciers have much longer response times to climate change than their pure ice cousins.

First measurement of ice-bedrock interface of alpine glaciers by cosmic muon radiography

NASA Astrophysics Data System (ADS)

Nishiyama, R.; Ariga, A.; Ariga, T.; Käser, S.; Lechmann, A.; Mair, D.; Scampoli, P.; Vladymyrov, M.; Ereditato, A.; Schlunegger, F.

2017-06-01

The shape of the bedrock underneath alpine glaciers bears vital information on the erosional mechanism related to the flow of ice. So far, several geophysical exploration methods have been proposed to map the bedrock topography though with limited accuracy. Here we illustrate the first results from a technology, called cosmic ray muon radiography, newly applied in glacial geology to investigate the bedrock geometry beneath the Aletsch Glacier situated in the Central Swiss Alps. For this purpose we installed new cosmic muon detectors made of emulsion films at three sites along the Jungfrau railway tunnel and measured the shape of the bedrock under the uppermost part of Aletsch Glacier (Jungfraufirn). Our results constrain the continuation of the bedrock-ice interface up to a depth of 50 m below the surface, where the bedrock underneath the glacier strikes NE-SW and dips at 45° ± 5°. This documents the first successful application of this technology to a glaciated environment.

Rapid response of alpine timberline vegetation to the Younger Dryas climate oscillation in the Colorado Rocky Mountains, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reasoner, M.A.; Jodry, M.A.

2000-01-01

Paleobotanical records from two high-altitude (>3,300 m) sites in Colorado show a clear and immediate response to the Younger Dryas climate oscillation. The Black Mountain Lake and Sky Pond records indicate that alpine timberline migrated upslope to near-modern elevations during the late Bolling-Allerod (13.6--12.9 ka). Subsequent declines in arboreal pollen percentages and accumulation rates during the Younger Dryas interval (12.9--11.7 ka) reflect a downslope displacement of the alpine timberline ecotone of 60--120 m in elevation. This change translates to a cooling of summer temperature by {approximately}0.4--0.9 C and is consistent with proposed Younger Dryas advances of alpine glaciers in themore » Rocky Mountains to positions close to Little Ice Age maxima. Alpine timberline readvanced upslope to elevations above both sites between 11.7 and 11.4 ka. The concomitant response of temperature-sensitive alpine timberline vegetation in Colorado and late-glacial changes in North Atlantic thermohaline circulating implicates a rapid, widespread atmospheric transmission of the Younger Dryas climate oscillation.« less

Late Pleistocene leopards across Europe - northernmost European German population, highest elevated records in the Swiss Alps, complete skeletons in the Bosnia Herzegowina Dinarids and comparison to the Ice Age cave art

NASA Astrophysics Data System (ADS)

Diedrich, Cajus G.

2013-09-01

European leopard sites in Europe demonstrate Early/Middle Pleistocene out of Africa lowland, and Late Pleistocene Asian alpine migrations being driven by climatic changes. Four different European Pleistocene subspecies are known. The final European Late Pleistocene “Ice Age leopard” Panthera pardus spelaea (Bächler, 1936) is validated taxonomically. The skull shows heavy signs of sexual dimorphism with closest cranial characters to the Caucasian Panthera pardus ciscaucasica (Persian leopard). Late Pleistocene leopards were distributed northernmost, up to S-England with the youngest stratigraphic records by skeletons and cave art in the MIS 2/3 (about 32,000-26,000 BP). The oldest leopard painting left by Late Palaeolithics (Aurignacians/Gravettians) in the Chauvet Cave (S-France) allows the reconstruction of the Ice Age leopard fur spot pattern being close to the snow or Caucasian leopards. The last Ice Age glacial leopard habitat was the mountain/alpine boreal forest (not mammoth steppe lowland), where those hunted even larger prey such as alpine game (Ibex, Chamois). Into some lairs, those imported their prey by short-term cave dwelling (e.g. Baumann's Cave, Harz Mountains, Germany). Only Eurasian Ice Age leopards specialized, similar as other Late Pleistocene large felids (steppe lions), on cave bear predation/scavenging partly very deep in caves. In Vjetrenica Cave (Dinarid Mountains, Bosnia Herzegovina), four adult leopards (two males/two females) of the MIS 3 were found about two km deep from the entrance in a cave bear den, near to one cave bear skeleton, that remained articulated in its nest. Leopards died there, partly being trapped by raising water levels of an active ponor stream, but seem to have been killed possibly either, similar as for lions known, in battles with cave bears in several cave bear den sites of Europe (e.g. Baumann's Cave, Wildkirchli Cave, Vjetrenica Cave). At other large cave sites, with overlap of hyena, wolf and dhole dens at the cave entrances, leopard bones with bite damages indicate their remains to have been imported and consumed by predators in alpine regions due to reduced prey availability. The best models for the competition/taphonomy of large predators - felids, hyenids, canids - within large cave bear dens of Europe is represented in combination of the Zoolithen Cave and Vjetrenica Cave taphonomy.

Spatio-temporal patterns of major bacterial groups in alpine waters.

PubMed

Freimann, Remo; Bürgmann, Helmut; Findlay, Stuart E G; Robinson, Christopher T

2014-01-01

Glacial alpine landscapes are undergoing rapid transformation due to changes in climate. The loss of glacial ice mass has directly influenced hydrologic characteristics of alpine floodplains. Consequently, hyporheic sediment conditions are likely to change in the future as surface waters fed by glacial water (kryal) become groundwater dominated (krenal). Such environmental shifts may subsequently change bacterial community structure and thus potential ecosystem functioning. We quantitatively investigated the structure of major bacterial groups in glacial and groundwater-fed streams in three alpine floodplains during different hydrologic periods. Our results show the importance of several physico-chemical variables that reflect local geological characteristics as well as water source in structuring bacterial groups. For instance, Alpha-, Betaproteobacteria and Cytophaga-Flavobacteria were influenced by pH, conductivity and temperature as well as by inorganic and organic carbon compounds, whereas phosphorous compounds and nitrate showed specific influence on single bacterial groups. These results can be used to predict future bacterial group shifts, and potential ecosystem functioning, in alpine landscapes under environmental transformation.

Speculations on the spatial setting and temporal evolution of a fjord-style lake

NASA Astrophysics Data System (ADS)

Sarnthein, M.; Spötl, C.

2012-04-01

The Inn Valley, a classical region of Quaternary research in the Alps, is bordered by terraces that extend over almost 70 km and record an ancient lake with a lake level near 750-830 m above sea level (a.s.l.), about 250-300 m above the modern valley floor. Over large distances, the terrace sediments consist mainly of laminated "Banded Clays", above ~750 m a.s.l. overlain by glaciofluvial gravel and finally, by tills that record the Upper Würmian ice advance of Marine Isotope Stage (MIS) 2. In the (former) clay pit of Baumkirchen this boundary forms the Alpine type locality for the onset of the Upper Würmian, well supported by 14C-based age control first established by Fliri (1971). On the basis of a recently cored sediment section at Baumkirchen, the >200 m thick "Banded Clays" store a continuous, largely undisturbed, highly resolved, and widely varved climatic archive of MIS 3. Major unknowns concern the location and origin of dams that may have barred the vast and deep Inn Valley lake. We discuss potential linkages to the pattern of moraines and ice advance of MIS 4 glaciers, which was less prominent than during MIS 2, thus leading to a distinct east-west segment¬ation of the run-off systems in Tyrol. East of Imst, for example, the lake was possibly barred by both a rock sill reaching up to 830 m a.s.l. and a lateral moraine deposited by an Ötz Valley glacier. 80 km further east, a lateral moraine of a glacier advancing from the Ziller Valley may have barred the ancient Inn Valley lake to the east. The final rapid coarsening of clastic lake sediments at the end of MIS 3 is widely ascribed to major climatic deter¬ioration. However, the MIS 3-2 boundary was linked to an only modest change of global climates and accordingly, different forcings may be considered. In turn, the rapid coarsening may document a date, when the Central Alpine glaciers had already filled the basin of Imst to the west of the Inn Valley lake. This ice mass may have forced the melt waters to flow across the rock sill toward east into the lake basin, with a sediment load that already records an advanced state of Alpine glaciation during the onset of MIS 2. Fliri, F. (1971): Veröff. Museum Ferdinandeum Innsbruck, 51, 5-21.

Sub-alpine amphibian distributions related to species palatability to non-native salmonids in the Klamath mountains of northern California

Treesearch

Hartwell H. Welsh Jr; Karen L. Pope; Daniel Boiano

2006-01-01

The goal of this study was to examine how introduced trout influence the distributions and abundances of a sub-alpine amphibian assemblage whose members display a variety of different life-history and defence strategies. Our study was conducted in the sub-alpine lentic habitats of three wilderness areas that form the core of the Klamath-Siskiyou Bioregion of northern...

Quaternary geology of the DFDP-2 drill holes, Alpine Fault, New Zealand

NASA Astrophysics Data System (ADS)

Upton, P.; Cox, S.; Howarth, J. D.; Sutherland, R.; Langridge, R.; Barth, N. C.; Atkins, C.

2015-12-01

A 240 m-thick Quaternary sediment sequence in Whataroa Valley was much thicker than predicted before drilling. DFDP-2A and DFDP-2B were mostly drilled through the sequence by dual-rotary method using air or water circulation, returning cuttings bagged at 1 or 2 m sample intervals. Some sorting/bias and contamination occurred. Core was retrieved in DFDP-2A from 125-160 m, with highly variable recovery (0-100%) and mixed preservation/quality. The sequence is interpreted to comprise: fluvial-glacial gravels (0-58 m); grading downward into sandy lake delta sediments (59-77 m); overlying a monotonous sequence of lake mud and silts, with rare pebble-cobble diamictite (77-206 m); with a basal unit (206-240 m) containing coarse cobbles and boulders that may represent a distinct till/diamictite. Evidence has yet to be found for any marine influence in lowermost sediments, despite deposition at least 120 m below present day sea level, and potentially 200 m bsl if uplift has occurred on the Alpine Fault. When corrected for uplift the lacustrine sequence broadly correlates to those in present Lakes Rotokina and Wahapo, suggesting a substantial (~100 km2) pro-glacial lake once covered the area. Radiocarbon dating of plant fragments indicate 70 m of upper lacustrine and deltaic sediments (129-59 m) were deposited rapidly between 16350-15800 Cal BP. Overlying alluvial gravels are much younger (<1 ka), but potentially also involved pulses of rapid aggradation. The sequence provides a record of sedimentation on the Alpine Fault hanging wall following late-glacial ice retreat up Whataroa Valley, with uplift and erosion followed by Holocene alluvial gravel deposition. Future work will address: (1) the nature and history of sedimentation, including the lithology and origin of sediments; (2) what, if any, geological record of tectonics (movement) or Alpine Fault earthquakes (shaking) the sediments contain.

The current evolution of complex high mountain debris-covered glacier systems and its relation with ground ice nature and distribution: the case of Rognes and Pierre Ronde area (Mont-Blanc range, France).

NASA Astrophysics Data System (ADS)

Bosson, Jean-Baptiste; Lambiel, Christophe

2014-05-01

The current climate forcing, through negative glacier mass balance and rockfall intensification, is leading to the rapid burring of many small glacier systems. When the debris mantle exceeds some centimeters of thickness, the climate control on ice melt is mitigated and delayed. As well, debris-covered glaciers respond to climate forcing in a complex way. This situation is emphasised in high mountain environments, where topo-climatic conditions, such as cold temperatures, amount of solid precipitation, duration of snow cover, nebulosity or shadow effect of rockwalls, limit the influence of rising air temperatures in the ground. Beside, due to Holocene climate history, glacier-permafrost interactions are not rare within the periglacial belt. Glacier recurrence may have removed and assimilated former ice-cemented sediments, the negative mass balance may have led to the formation of ice-cored rock glaciers and neopermafrost may have formed recently under cold climate conditions. Hence, in addition to sedimentary ice, high mountain debris-covered glacier systems can contain interstitial magmatic ice. Especially because of their position at the top of alpine cascade systems and of the amount of water and (unconsolidated) sediment involved, it is important to understand and anticipate the evolution of these complex landforms. Due to the continuous and thick debris mantle and to the common existence of dead ice in deglaciated areas, the current extent of debris-covered glacier can be difficult to point out. Thus, the whole system, according to Little Ice Age (LIA) extent, has sometimes to be investigated to understand the current response of glacier systems to the climate warming. In this context, two neighbouring sites, Rognes and Pierre Ronde systems (45°51'38''N, 6°48'40''E; 2600-3100m a.s.l), have been studied since 2011. These sites are almost completely debris-covered and only few ice outcrops in the upper slopes still witness the existence of former glaciers. Electrical resistivity tomographies, kinematic data and ground surface temperature show that heterogeneous responses to climate forcing are occurring despites their small areas (> 0.3 km2). This complex situation is related to Holocene climate history and especially to glacier systems evolution since LIA. The current dynamics depend of ground ice nature and distribution. Five main behaviours can be highlighted: - Debris covered glacier areas are the most active. Their responses to climate forcing are relatively fast, especially through massive ice melt-out each summer. - Ice-cored rock glacier areas are quite active. The existence of massive glacier ice under few meters of debris explain the important surface lowering during the snow free period . - Ice-cemented rock glacier areas are characterised by winter and summer subhorizontal downslope creeping. - Moraine areas containing dead ice have heterogeneous activities (directions and values of detected movements) related to the ice vanishing. - Deglaciated moraine areas are almost inactive, except modest superficial paraglacial rebalancing.

Organochlorine compounds in ice melt water from Italian Alpine rivers.

PubMed

Villa, Sara; Negrelli, Christian; Finizio, Antonio; Flora, Onelio; Vighi, Marco

2006-01-01

Organochlorine chemicals (OCs) (dichlorodiphenyltrichloroethanes, hexachlorocyclohexanes, and hexachlorobenzene) were measured in ice melt water from five glaciers in the Italian Alps. Even though the data collected may not be sufficient for a precise description of persistent organic pollutant release patterns from glacier melting, they have, however, highlighted the potential for surface water contamination. Concentrations were of the same order of magnitude in all glacial streams, indicating comparable contamination levels in different glaciers of the alpine region. OC levels in nonglacial springs sampled in the same areas are usually lower. Even if differences during the melting season (from spring to autumn) have been identified, a regular seasonal pattern in OC concentrations was not observed. Risk for the aquatic environment is excluded through direct water exposure, but it is likely to occur through biomagnification and secondary poisoning exposure.

New Aerogeophysical exploration of the Gamburtsev Province (East Antarctica)

NASA Astrophysics Data System (ADS)

Ferraccioli, F.; Bell, R. E.; Studinger, M.; Damaske, D.; Jordan, T. A.; Corr, H.; Braaten, D. A.; Gogineni, P. S.; Fahnestock, M. A.; Finn, C.; Rose, K.

2009-12-01

The enigmatic Gamburstev Subglacial Mountains (GSM) in the interior of East Antarctica, have remained the least understood mountain range on earth, since their discovery some 50 years ago. An improved knowledge of the GSM region is however essential to underpin reconstructions of the Antarctic cryosphere and climate evolution. The GSM are a key nucleation site for the inception of the East Antarctic Ice Sheet approximately 34 Ma ago, and the adjacent Lambert Glacier played a pivotal role for ice sheet dynamics throughout the Neogene (23-0 Ma). The GSM province may also provide tectonic controls for major subglacial lakes flanking the range. In addition, the ice encasing the GSM province has been inferred to contain the oldest detailed climate record of the planet, a prime target for future deep ice core drilling. With the overarching aim of accomplishing the first systematic study of the cryosphere and lithosphere of the GSM province we launched a new geophysical exploration effort- AGAP (Antarctica’s Gamburtsev Province)-, a flagship programme of the International Polar Year. The aerogeophysical and seismology components of AGAP were accomplished by pooling resources from 7 nations. We deployed 2 Twin Otters, equipped with state-of-the art geophysical instrumentation and operating from two remote field camps on either side of Dome A. Over 120,000 line-km of new airborne radar, laser, aerogravity and aeromagnetic data survey were collected during the 2008/09 field campaign. Our grids of ice surface, ice thickness, subglacial topography, and gravity and magnetic anomalies provide a new geophysical foundation to analyse the GSM province, from the surface of the East Antarctic Ice Sheet down to mantle depths beneath the Precambrian shield. The anomalously high-elevation, alpine-type landscape of the GSM is now mapped with unprecedented detail. Two distinct branches of a subglacial rift system are imaged along the north-western and north-eastern margins of the Gamburtsev’s and provide geological controls for ice flow in the Lambert Glacier region.

Metagenomic and satellite analyses of red snow in the Russian Arctic.

PubMed

Hisakawa, Nao; Quistad, Steven D; Hester, Eric R; Martynova, Daria; Maughan, Heather; Sala, Enric; Gavrilo, Maria V; Rohwer, Forest

2015-01-01

Cryophilic algae thrive in liquid water within snow and ice in alpine and polar regions worldwide. Blooms of these algae lower albedo (reflection of sunlight), thereby altering melting patterns (Kohshima, Seko & Yoshimura, 1993; Lutz et al., 2014; Thomas & Duval, 1995). Here metagenomic DNA analysis and satellite imaging were used to investigate red snow in Franz Josef Land in the Russian Arctic. Franz Josef Land red snow metagenomes confirmed that the communities are composed of the autotroph Chlamydomonas nivalis that is supporting a complex viral and heterotrophic bacterial community. Comparisons with white snow communities from other sites suggest that white snow and ice are initially colonized by fungal-dominated communities and then succeeded by the more complex C. nivalis-heterotroph red snow. Satellite image analysis showed that red snow covers up to 80% of the surface of snow and ice fields in Franz Josef Land and globally. Together these results show that C. nivalis supports a local food web that is on the rise as temperatures warm, with potential widespread impacts on alpine and polar environments worldwide.

MABEL Photon-Counting Laser Altimetry Data in Alaska for ICESat-2 Simulations and Development

NASA Technical Reports Server (NTRS)

Brunt, Kelly; Neumann, T. A.; Amundson, M.; Kavanaugh, J. L.; Moussavi, M. S.; Walsh, K. M.; Cook, W. B.; Markus, T.

2016-01-01

Multiple Altimeter Beam Experimental Lidar (MABEL) maps Alaskan crevasses in detail, using 50 of the expected along-track Advanced Topographic Laser Altimeter System (ATLAS) signal-photon densities over summer ice sheets. Ice, Cloud, and Land Elevation Satellite 2 (ICESat-2) along-track data density, and spatial data density due to the multiple-beam strategy, will provide a new dataset to mid-latitude alpine glacier researchers.

Glacier Dynamics Within a Small Alpine Cirque

NASA Astrophysics Data System (ADS)

Sanders, J. W.; Cuffey, K. M.; MacGregor, K. R.; Kavanaugh, J. L.; Dow, C. F.

2008-12-01

Cirques, with their steep walls and overdeepened basins, have captivated the imagination of scientists since the mid-1800s. Glaciers in cirques, by generating these spectacular amphitheater-shaped landforms, contribute significantly to erosion in the core of mountain ranges and are one of the principal agents responsible for the relief structure at high elevations. Yet comprehensive studies of the dynamics of cirque glaciers, and their link to erosional processes, have never been undertaken. To this end, we acquired an extensive new set of measurements at the West Washmawapta Glacier, which sits in a cirque on the east side of Helmet Mountain in the Vermillion Range of the Canadian Rockies. Ice thickness surveys with ground penetrating radar revealed that the glacier occupies a classic bowl-shaped depression complete with a nearly continuous riegel. Using GPS-derived surface velocities of a glacier-wide grid network and the tilt of one borehole, we calculated the complete force balance of the glacier. This analysis also produced a map of basal sliding velocity and a value for the viscosity of temperate ice. We will discuss the implications of these findings for the problem of how cirques are formed by glacial erosion.

Late Pleistocene climate change and landscape dynamics in the Eastern Alps: the inner-alpine Unterangerberg record (Austria)

PubMed Central

Starnberger, Reinhard; Drescher-Schneider, Ruth; Reitner, Jürgen M.; Rodnight, Helena; Reimer, Paula J.; Spötl, Christoph

2013-01-01

Drill cores from the inner-alpine valley terrace of Unterangerberg, located in the Eastern Alps of Austria, offer first insights into a Pleistocene sedimentary record that was not accessible so far. The succession comprises diamict, gravel, sand, lignite and thick, fine grained sediments. Additionally, cataclastic deposits originating from two paleo-landslide events are present. Multi-proxy analyses including sedimentological and palynological investigations as well as radiocarbon and luminescence data record the onset of the last glacial period (Würmian) at Unterangerberg at ∼120–110 ka. This first time period, correlated to the MIS 5d, was characterised by strong fluvial aggradation under cold climatic conditions, with only sparse vegetation cover. Furthermore, two large and quasi-synchronous landslide events occurred during this time interval. No record of the first Early Würmian interstadial (MIS 5c) is preserved. During the second Early Würmian interstadial (MIS 5a), the local vegetation was characterised by a boreal forest dominated by Picea, with few thermophilous elements. The subsequent collapse of the vegetation is recorded by sediments dated to ∼70–60 ka (i.e. MIS 4), with very low pollen concentrations and the potential presence of permafrost. Climatic conditions improved again between ∼55 and 45 ka (MIS 3) and cold-adapted trees re-appeared during interstadials, forming an open forest vegetation. MIS 3 stadials were shorter and less severe than the MIS 4 at Unterangerberg, and vegetation during these cold phases was mainly composed of shrubs, herbs and grasses, similar to what is known from today's alpine timberline. The Unterangerberg record ended at ∼45 ka and/or was truncated by ice during the Last Glacial Maximum. PMID:23805019

Spatial Variability of Climate Signatures Recorded in an Array of Shallow Firn Cores from the Western Greenland Percolation Zone

NASA Astrophysics Data System (ADS)

Thundercloud, Z. R.; Osterberg, E. C.; Ferris, D. G.; Graeter, K.; Lewis, G.; Hawley, R. L.; Marshall, H. P.

2016-12-01

Greenland ice cores provide seasonally to annually resolved proxy records of past temperature, accumulation and atmospheric circulation. Most Greenland ice cores have been collected from the dry snow zone at elevations greater than 2500 m to produce records of North Atlantic paleoclimate over the last full glacial cycle. Ice cores collected from more costal regions, however, provide the opportunity to develop regional-scale records of climate conditions along ice sheet margins where recent temperature and precipitation changes have been larger than those in the ice sheet interior. These cores are more readily comparable to lake sediment and landscape (i.e. moraine) records from the ice sheet margin, and are potentially more sensitive to sea-ice variability due to the proximity to the coast. Here we present major ion and stable isotope records from an array of firn cores (40-55 year records) collected in the western Greenland percolation zone, and assess the spatial variability of ice core statistical relationships with the North Atlantic Oscillation (NAO) and Baffin Bay sea ice extent. Seven cores were collected from elevations of 2100-2500 m along a 400-km segment of the ice sheet from Dye-2 to Milcent as part of the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) project from May-June 2016. They were sampled by a continuous melter system at Dartmouth College, and analyzed using Dionex ion chromatographs and a Picarro L2130-i laser ring-down spectrometer. We focus on the signature of the NAO and Baffin Bay sea ice extent in the sea-salt, dust, deuterium excess (d-excess), and methanesulfonic acid (MSA) firn core records, and assess the special variability of these climate-ice core relationships across the study area. Climate reanalysis data indicate that NAO-ice core correlations should be stronger at lower elevation in the percolation zone than high in the dry snow zone. Our results will provide valuable insight into the sensitivity of Greenland ice core paleoclimate reconstructions to the specific ice core location, and thereby aid in site selection for deeper ice cores that could span the Holocene.

Numerical simualtions and implications of air inclusions on the microdynamics of ice and firn

NASA Astrophysics Data System (ADS)

Steinbach, Florian; Weikusat, Ilka; Bons, Paul; Griera, Albert; Kerch, Johanna; Kuiper, Ernst-Jan; Llorens-Verde, Maria-Gema

2016-04-01

Although ice sheets are valuable paleo-climate archives, they can loose their integrity by ice flow (Faria et al. 2010). Consequently, understanding the dynamic processes that control the flow of ice is essential when investigating the past and future climate. While recent research successfully modelled the microdynamics of pure ice (e.g. Montagnat et al., 2014; Llorens et al., 2015), work taking into account second phases is scarce. Only a few studies also show the microstructural influence of air inclusions (Azuma et al., 2012, Roessiger et al., 2014). Therefore, modelling was performed focussing on the implications of the presence of bubbles on the microdynamical mechanisms and microstructure evolution. The full-field theory crystal plasticity code (FFT) of Lebensohn (2001), was coupled to the 2D multi-process modelling platform Elle (Bons et al., 2008), following the approach by Griera et al. (2013). FFT calculates the viscoplastic response of polycrystalline materials deforming by dislocation glide, taking into account mechanical anisotropy. The models further incorporate surface- and stored strain energy driven grain boundary migration (GBM) and intracrystalline recovery simulating annihilation and rearrangement of dislocations by reduction of internal misorientations. GBM was refined for polyphase materials following Becker et al. (2008) and Roessiger et al. (2014). Additionally, the formation of new high angle grain boundaries by nucleation and polygonisation based on critical internal misorientations has been implemented. Successively running the codes for different processes in very short numerical timesteps effectively enables multi-process modelling of deformation and concurrent recrystallisation. Results show how air inclusions control and increase strain localisation, leading to locally enhanced dynamic recrystallisation. This is in compliance with Faria et al. (2014), who theoretically predicted these localizations based on firn data from EPICA Dronning Maud Land (EDML) ice core. We propose that strain localisation has a strong control on the dominating recrystallisation mechanisms and can account for microstructural observations from alpine and polar ice cores. Our results confirm dynamic recrystallisation occurring in the uppermost levels of ice sheets as observed by Kipfstuhl et al. (2009) and Weikusat et al. (2009) in EDML core. References Azuma, N., et al. (2012) Journal of Structural Geology, 42, 184-193 Becker, J.K., et al. (2008) Computers & Geosciences, 34, 201-212 Bons, P.D., et al. (2008) Lecture Notes in Earth Sciences, 106 Faria, S.H., et al. (2010) Quaternary Science Reviews, 29, 338-351 Faria, S.H., et al. (2014) Journal of Structural Geology, 61, 21-49 Griera, A., et al. (2013) Tectonophysics, 587, 4-29 Kipfstuhl, S., et al. (2009) Journal of Geophysical Research, 114, B05204 Lebensohn, R.A. (2001) Acta Materialia, 49, 2723-2737 Llorens, M.G., et al. (2015) Journal of Glaciology, in press, doi:10.1017/jog.2016.28 Montagnat, M., et al. (2014) Journal of Structural Geology, 61, 78-108 Roessiger, J., et al. (2014) Journal of Structural Geology, 61, 123-132 Weikusat, I., et al. (2009) Journal of Glaciology, 55, 461-472

Modelled Growth and Decay of the Cordilleran Ice Sheet Through the Last Glacial Cycle

NASA Astrophysics Data System (ADS)

Marshall, S. J.; Banwell, A.

2015-12-01

The Cordilleran Ice Sheet in western North America had an enigmatic evolution during the last glacial cycle, developing out of sync with the larger Laurentide and global glaciation. The geological record suggests that the ice sheet emerged late, ca. 45 ka, growing to be a fully-established ice sheet in isotope stages 3 and 2 and deglaciating late in the glacial cycle. This has been a challenge to model, and is a paleoclimatic curiosity, because the western Cordillera of North America is heavily glacierized today, and one would intuitively expect it to act as an inception centre for the Pleistocene ice sheets. The region receives heavy precipitation, and modest cooling should induce large-scale glacier expansion. Indeed, a Cordilleran Ice Sheet quickly nucleates in isotope substage 5d in most ice sheet modeling studies to date, and is a resilient feature throughout the glaciation. The fact that a full-scale Cordilleran Ice Sheet did not develop until relatively late argues for either: (a) ice sheet models that have been inadequate in resolving the process of alpine-style glaciation, i.e., the coalescence of alpine icefields, or (b) a climatic history in western North America that deviated strongly from the hemispheric-scale cooling which drove the growth of the Laurentide and Scandinavian Ice Sheets, as recorded in Greenland. We argue that reasonable reconstructions of Cordilleran Ice Sheet growth and decay implicate a combination of these two considerations. Sufficient model resolution is required to capture the valley-bottom melt that suppresses icefield coalescence, while early-glacial cooling must have been modest in the Pacific sector of North America. We argue for a persistent warm, dry climate relative to that in eastern North America and the Atlantic sector, likely associated with positive feedbacks between atmospheric circulation and the nascent Laurentide Ice Sheet (i.e., peristent circulation patterns similar to those of 2014-2015). This must have been disrupted as the Laurentide thickened and advanced southward, allowing the Cordilleran Ice Sheet to emerge from numerous isolated icefield complexes.

Inferring the colonization of a mountain range--refugia vs. nunatak survival in high alpine ground beetles.

PubMed

Lohse, Konrad; Nicholls, James A; Stone, Graham N

2011-01-01

It has long been debated whether high alpine specialists survived ice ages in situ on small ice-free islands of habitat, so-called nunataks, or whether glacial survival was restricted to larger massifs de refuge at the periphery. We evaluate these alternative hypotheses in a local radiation of high alpine carabid beetles (genus Trechus) in the Orobian Alps, Northern Italy. While summits along the northern ridge of this mountain range were surrounded by the icesheet as nunataks during the last glacial maximum, southern areas remained unglaciated. We analyse a total of 1366 bp of mitochondrial (Cox1 and Cox2) data sampled from 150 individuals from twelve populations and 530 bp of nuclear (PEPCK) sequence sampled for a subset of 30 individuals. Using Bayesian inference, we estimate ancestral location states in the gene trees, which in turn are used to infer the most likely order of recolonization under a model of sequential founder events from a massif de refuge from the mitochondrial data. We test for the paraphyly expected under this model and for reciprocal monophyly predicted by a contrasting model of prolonged persistence of nunatak populations. We find that (i) only three populations are incompatible with the paraphyly of the massif de refuge model, (ii) both mitochondrial and nuclear data support separate refugial origins for populations on the western and eastern ends of the northern ridge, and (iii) mitochondrial node ages suggest persistence on the northern ridge for part of the last ice age. © 2010 Blackwell Publishing Ltd.

Five millennia of frozen vegetation and fire dynamics from an ice core in the Mongolian Altai

NASA Astrophysics Data System (ADS)

Brügger, S. O.; Gobet, E.; Sigl, M.; Osmont, D.; Papina, T.; Rudaya, N.; Schwikowski, M.; Tinner, W.

2017-12-01

The steppes of the Altai region in Central Asia are highly vulnerable to e.g. drought and overgrazing. Degradation during the past decades may undermine their resilience under global change conditions. Knowledge about past vegetation and fire dynamics in Mongolian Altai may contribute to a better understanding of future climate and human impact responses, however, paleo records are scarce in the area. Our novel high-alpine ice record from Tsambagarav glacier (48°39.338'N, 90°50.826'E, 4130m asl) in the Mongolian Altai provides unique paleoenvironmental informations at the landscape scale. The site is surrounded by dry steppes with scattered boreal tree stands. We assume that the site collects pollen and spores within several hundred km. The archive provides an exceptional temporal resolution with a sound chronology covering the past 5500 years (Herren et al. 2013). Microfossil analysis allows to reconstruct large-scale fire and vegetation dynamics to gain a better understanding of the timing and causes of late Holocene response variability. We use pollen as proxies for vegetation composition and structure, microscopic charcoal as a proxy for fire activity (Eichler et al. 2011), and spheroidal carbonaceous particles (SCPs or soots) as a proxy for fossil fuel combustion. Here we present the first microscopic charcoal record from Mongolia and link it to vegetation dynamics of the past. The reconstructed mid to late Holocene forest collapses likely in response to climate change underscore the vulnerability of relict forest ecosystems in the Mongolian Altai. Our multiproxy-study suggests that moisture is more important than temperature for forest preservation. The lacking resilience of vegetation to moisture changes in the past emphasizes the vulnerability of large forests in neighboring dry areas such as the Russian Altai, if global warming is associated to moisture declines as future projections forecast (IPCC; Climate Change 2013). References: Eichler et al. (2011). An ice-core based history of Siberian forest fires since AD 1250. Quat Sci Rev 30(9) Herren et al. (2013). The onset of Neoglaciation 6000 years ago in western Mongolia revealed by an ice core from the Tsambagarav mountain range. Quat Sci Rev 69 IPCC; Climate Change (2013): The Physical Science Basis. IPCC Working Group I Contribution to AR5

A common and optimized age scale for Antarctic ice cores

NASA Astrophysics Data System (ADS)

Parrenin, F.; Veres, D.; Landais, A.; Bazin, L.; Lemieux-Dudon, B.; Toye Mahamadou Kele, H.; Wolff, E.; Martinerie, P.

2012-04-01

Dating ice cores is a complex problem because 1) there is a age shift between the gas bubbles and the surrounding ice 2) there are many different ice cores which can be synchronized with various proxies and 3) there are many methods to date the ice and the gas bubbles, each with advantages and drawbacks. These methods fall into the following categories: 1) Ice flow (for the ice) and firn densification modelling (for the gas bubbles); 2) Comparison of ice core proxies with insolation variations (so-called orbital tuning methods); 3) Comparison of ice core proxies with other well dated archives; 4) Identification of well-dated horizons, such as tephra layers or geomagnetic anomalies. Recently, an new dating tool has been developped (DATICE, Lemieux-Dudon et al., 2010), to take into account all the different dating information into account and produce a common and optimal chronology for ice cores with estimated confidence intervals. In this talk we will review the different dating information for Antarctic ice cores and show how the DATICE tool can be applied.

In-situ carbon and nitrogen turnover dynamics and the role of soil functional biodiversity therein; a climate warming simulation study in Alpine ecosystems

NASA Astrophysics Data System (ADS)

Djukic, Ika

2010-05-01

Climate change affects a variety of soil properties and processes. Alpine soils take an extraordinary position in this context because of the vulnerability of mountain regions to climatic changes. We used altitudinal soil translocation to simulate the combined effects of changing climatic conditions and shifting vegetation zones in order to study short- to medium-term soil changes in the Austrian Limestone Alps. We translocated 160 soil cores from an alpine grassland site (1900 m asl) down to a sub-alpine spruce forest (1300 m asl) and a montane beech forest site (900m asl), including reference soil cores at each site to estimate artifacts arising from the method. 15N-labeled maize straw was added (1 kg/m2) to translocated and control soil cores and sampled over a period of 2 years for the analysis of δ13C and δ15N in the bulk soil and extracted phospholipid fatty acids (PLFAs). Additionally, 20 litter bags (at each of the three climatic zones) containing Fagus sylvatica or Pinus nigra litter were inserted into the soil, and decomposition was studied over a two-year period. The basic soil parameters (organic C, total N and pH) were unaffected by translocation within the observation time. Overall, decomposition of Pinus nigra litter was significantly slower compared to Fagus sylvatica, and the decomposition rate of both litter types was inversely related to elevation. The decomposition of the maize straw carbon was significantly faster in the translocated soil cores (sites at 900 and 1300 m asl) than at the original site (1900 m asl). The labelled nitrogen contents in the translocated soil cores showed just marginal differences to the soil cores at the original site. The maize straw application promptly increased the amount of bacterial and fungal PLFAs at all studied sites. Downslope translocated soil cores showed an increase in total microbial biomass and sum of bacteria. The fungal PLFA biomarker 18:2ω6,9 was slightly lower at the new (host) sites compared to the original site. The bacterial to fungal ratio of the translocated soil cores showed a rapid acclimatization to the new (host) soil conditions. Our study demonstrates that rising temperatures in Alpine ecosystems will accelerate decomposition of fresh C pools but also lead to rapid adaptation of the microbial community to the new conditions.

Evaluation of permafrost conditions in non-alpine scree slopes in Central Europe by geophysical methods

NASA Astrophysics Data System (ADS)

Gude, M.; Hauck, C.; Kneisel, C.; Krause, S.; Molenda, R.; Ruzicka, V.; Zacharda, M.

2003-04-01

Many slope sections covered with blocky material situated in Central European highlands display special microclimatic conditions that resemble those of high latitude or high altitude periglacial areas. In some of these screes even permafrost-like conditions are detected although they are located on elevations fairly below 1000 m a.s.l. These conditions are accompanied by a circulation of air through the open void system, which effects a formation of an ice body during winter by re-sublimation of air humidity, supported by refreezing water from snow melt and precipitation. This ice body is assumed to prevail during the entire summer. Population genetic investigations on alpine and polar beetle species that inhabit the screes proof the continuous existence of the extraordinary cool conditions with probable permafrost throughout the Holocene - i.e. these periglacial-like condition are relatively stable despite all Holocene climatic variations. Observations of summer ice and numerous temperature measurements lead to the assumption of permafrost with enduring ice in the open voids as an integral factor of the microclimatic system. To evaluate its existence the underground was investigated in seven European screes by means of DC resistivity and refraction seismic in early summer. In order to solve the multi-phase subsurface structures, tomographic survey and inversion techniques are necessary, as 1-dimensional plane layer approximations are usually invalid. The results clearly reveal seismic and resistivity anomalies e.g. in the Klic scree (50°49'N, 14°04'E, base at 524 m a.s.l.) in Northern Bohemia. Within a blocky layer of about 10 m high thickness velocity anomalies (2000-3000 m/s) indicate the existence of a small ground ice body, which is confirmed by the synchronous detection of resistivity anomalies in the same place. These conditions are confined to steep scree slopes in regions with thin winter snow cover to enable air circulation. It is probable, that these effects are also found in alpine regions, where they cause a significant depression of the current lower permafrost limit.

The impact of Pleistocene climate change on an ancient arctic–alpine plant: multiple lineages of disparate history in Oxyria digyna

PubMed Central

Allen, Geraldine A; Marr, Kendrick L; McCormick, Laurie J; Hebda, Richard J

2012-01-01

The ranges of arctic–alpine species have shifted extensively with Pleistocene climate changes and glaciations. Using sequence data from the trnH-psbA and trnT-trnL chloroplast DNA spacer regions, we investigated the phylogeography of the widespread, ancient (>3 million years) arctic–alpine plant Oxyria digyna (Polygonaceae). We identified 45 haplotypes and six highly divergent major lineages; estimated ages of these lineages (time to most recent common ancestor, TMRCA) ranged from ∼0.5 to 2.5 million years. One lineage is widespread in the arctic, a second is restricted to the southern Rocky Mountains of the western United States, and a third was found only in the Himalayan and Altai regions of Asia. Three other lineages are widespread in western North America, where they overlap extensively. The high genetic diversity and the presence of divergent major cpDNA lineages within Oxyria digyna reflect its age and suggest that it was widespread during much of its history. The distributions of individual lineages indicate repeated spread of Oxyria digyna through North America over multiple glacial cycles. During the Last Glacial Maximum it persisted in multiple refugia in western North America, including Beringia, south of the continental ice, and within the northern limits of the Cordilleran ice sheet. Our data contribute to a growing body of evidence that arctic–alpine species have migrated from different source regions over multiple glacial cycles and that cryptic refugia contributed to persistence through the Last Glacial Maximum. PMID:22822441

Seismic and gravity investigations of the shallow (upper 1 km) hanging wall of the Alpine Fault in the vicinity of the Whataroa River, New Zealand

NASA Astrophysics Data System (ADS)

Kovacs, A.; Gorman, A. R.; Lay, V.; Buske, S.

2013-12-01

Paleoseismic evidence from the vicinity of the plate-bounding Alpine Fault on New Zealand's South Island suggests that earthquakes of magnitude 7.9 occur every 200-400 years, with the last earthquake occurring in AD 1717. No human observations of this event are recorded. Therefore, the Deep Fault Drilling Project 2 (DFDP-2) drill hole, which is planned for 2014 on the hanging wall of the Alpine Fault in the Whataroa Valley, provides a critical opportunity to study the behavior of this transpressive plate boundary late in its seismogenic cycle. New seismic and gravity data collected since 2011 have been analyzed to assist with the positioning of the drill hole in this glacial valley that provides rare low-elevation access to the hanging wall of the Alpine Fault. The WhataDUSIE controlled-source seismic project, led by researchers from the University of Otago (New Zealand), TU Bergakademie Freiberg (Germany) and the University of Alberta (Canada), provided relatively high-resolution coverage (4-8 m geophone spacing, 25-100 m shot spacing) along a 5-km-long profile across the Alpine Fault in the Whataroa Valley. This work has been supplemented by focused hammer-seismic studies and gravity data collection in the valley. The former targets surface layer properties, whereas the latter targets the depth to the base of the glacially carved paleovalley. In positioning DFDP-2, an understanding of the nature of overburden and valley-fill sediments is critical for drilling design. A velocity model has been developed for the valley based on refraction analysis of the WhataDUSIE and hammer-seismic data combined with a ray-theoretical travel-time tomography (RAYINVR) image of the shallow (uppermost 1 km or so) part of the hanging wall of the Alpine Fault. The model shows that the glacial valley, which presumably was last scoured by ice at the Last Glacial Maximum, has been filled with 200-350 m of post-glacial sediments and outwash gravels. The hanging-wall rocks into which the valley was cut are presumed to be mylonitized Alpine Schist. Considering uplift rates of 6-10 mm/a on the hanging wall of the fault and a glacial withdrawal date of 10,000 years before present (i.e., 60-100 m of uplift since the ice vacated the valley), the floor of the valley would have been as deep as about 350 m below sea level at the time that the ice withdrew (given the current elevation of ~100 m on the valley floor). Basal sediments in the valley could therefore be either marine (if the valley was open to the ocean) or lacustrine (if the valley was isolated from the open ocean by elevated footwall rocks along the west coast of the South Island). Once the original water body in the valley was filled, sediments would accumulate as outwash gravels above sea level.

The potential for retreating alpine glaciers to alter alpine ecosystems in the Colorado Front Range

NASA Astrophysics Data System (ADS)

Hall, E.; Baron, J.

2013-12-01

Glaciers are retreating at an unprecedented rate. In mid-latitude alpine ecosystems the presence of glaciers and rock glaciers govern rates and ecology of alpine and sub-alpine ecosystems. Changes in the thermal environment due to the loss of isothermal habitat and inputs from glacier melt chemistry are altering alpine ecosystems in unpredictable ways. In particular, glacier may be a source of nitrogen that is altering alpine ecosystem dynamics. Loch Vale Watershed (LVWS) located within Rocky Mountain National Park. LVWS contains a surface glacier (Andrew's glacier) and a rock glacier (Taylor's glacier) at the headwater of each of the two drainages within the watershed. We collected precipitation from a National Atmospheric Deposition Site and surface water from multiple alpine lakes and streams during a particularly high and low snow year in the Colorado Front Range. We also sampled stream and lake sediments at each site to analyze the associated microbial community. Concentrations of nitrate and ammonium, relative abundance of amoA (the gene responsible for a key step in the microbial nitrification pathway), and the dual isotope signal to nitrate all point to snow melt as a key deliverer of nitrogen to ecosystems along the Colorado Front Range. However, late summer surface water chemistry is isotopically similar to the chemistry of glacial ice. This suggests that retreating glacier may be an additional source of N to alpine ecosystems and have the potential to alter microbial community composition, biogeochemical rate processes, and ecosystem function. These dynamics are most likely not unique to the Colorado Front Range and should be globally distributed as glaciers continue to retreat in high altitude ecosystems around the world.

IceChrono1: a probabilistic model to compute a common and optimal chronology for several ice cores

NASA Astrophysics Data System (ADS)

Parrenin, F.; Bazin, L.; Capron, E.; Landais, A.; Lemieux-Dudon, B.; Masson-Delmotte, V.

2015-05-01

Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores and the estimation of the age-scale uncertainty are essential to interpret the climate and environmental records that they contain. It is, however, a complex problem which involves different methods. Here, we present IceChrono1, a new probabilistic model integrating various sources of chronological information to produce a common and optimized chronology for several ice cores, as well as its uncertainty. IceChrono1 is based on the inversion of three quantities: the surface accumulation rate, the lock-in depth (LID) of air bubbles and the thinning function. The chronological information integrated into the model are models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice- and air-dated horizons, ice and air depth intervals with known durations, depth observations (depth shift between synchronous events recorded in the ice and in the air) and finally air and ice stratigraphic links in between ice cores. The optimization is formulated as a least squares problem, implying that all densities of probabilities are assumed to be Gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono follows an approach similar to that of the Datice model which was recently used to produce the AICC2012 (Antarctic ice core chronology) for four Antarctic ice cores and one Greenland ice core. IceChrono1 provides improvements and simplifications with respect to Datice from the mathematical, numerical and programming point of views. The capabilities of IceChrono1 are demonstrated on a case study similar to the AICC2012 dating experiment. We find results similar to those of Datice, within a few centuries, which is a confirmation of both IceChrono1 and Datice codes. We also test new functionalities with respect to the original version of Datice: observations as ice intervals with known durations, correlated observations, observations as air intervals with known durations and observations as mixed ice-air stratigraphic links. IceChrono1 is freely available under the General Public License v3 open source license.

Deeply subducted continental fragments - Part 1: Fracturing, dissolution-precipitation, and diffusion processes recorded by garnet textures of the central Sesia Zone (western Italian Alps)

NASA Astrophysics Data System (ADS)

Giuntoli, Francesco; Lanari, Pierre; Engi, Martin

2018-02-01

Contiguous continental high-pressure terranes in orogens offer insight into deep recycling and transformation processes that occur in subduction zones. These remain poorly understood, and currently debated ideas need testing. The approach we chose is to investigate, in detail, the record in suitable rock samples that preserve textures and robust mineral assemblages that withstood overprinting during exhumation. We document complex garnet zoning in eclogitic mica schists from the Sesia Zone (western Italian Alps). These retain evidence of two orogenic cycles and provide detailed insight into resorption, growth, and diffusion processes induced by fluid pulses in high-pressure conditions. We analysed local textures and garnet compositional patterns, which turned out remarkably complex. By combining these with thermodynamic modelling, we could unravel and quantify repeated fluid-rock interaction processes. Garnet shows low-Ca porphyroclastic cores that were stable under (Permian) granulite facies conditions. The series of rims that surround these cores provide insight into the subsequent evolution: the first garnet rim that surrounds the pre-Alpine granulite facies core in one sample indicates that pre-Alpine amphibolite facies metamorphism followed the granulite facies event. In all samples documented, cores show lobate edges and preserve inner fractures, which are sealed by high-Ca garnet that reflects high-pressure Alpine conditions. These observations suggest that during early stages of subduction, before hydration of the granulites, brittle failure of garnet occurred, indicating high strain rates that may be due to seismic failure. Several Alpine rims show conspicuous textures indicative of interaction with hydrous fluid: (a) resorption-dominated textures produced lobate edges, at the expense of the outer part of the granulite core; (b) peninsulas and atoll garnet are the result of replacement reactions; and (c) spatially limited resorption and enhanced transport of elements due to the fluid phase are evident along brittle fractures and in their immediate proximity. Thermodynamic modelling shows that all of these Alpine rims formed under eclogite facies conditions. Structurally controlled samples allow these fluid-garnet interaction phenomena to be traced across a portion of the Sesia Zone, with a general decrease in fluid-garnet interaction observed towards the external, structurally lower parts of the terrane. Replacement of the Permian HT assemblages by hydrate-rich Alpine assemblages can reach nearly 100 % of the rock volume. Since we found no clear relationship between discrete deformation structures (e.g. shear zones) observed in the field and the fluid pulses that triggered the transformation to eclogite facies assemblages, we conclude that disperse fluid flow was responsible for the hydration.

Deep Radiostratigraphy of the East Antarctic Plateau: Connecting the Dome C and Vostok Ice Core Sites

NASA Technical Reports Server (NTRS)

Cavitte, Marie G. P.; Blankenship, Donald D.; Young, Duncan A.; Schroeder, Dustin M.; Parrenin, Frederic; Lemeur, Emmanuel; Macgregor, Joseph A.; Siegert, Martin J.

2016-01-01

Several airborne radar-sounding surveys are used to trace internal reflections around the European Project for Ice Coring in Antarctica Dome C and Vostok ice core sites. Thirteen reflections, spanning the last two glacial cycles, are traced within 200 km of Dome C, a promising region for million-year-old ice, using the University of Texas Institute for Geophysics High-Capacity Radar Sounder. This provides a dated stratigraphy to 2318 m depth at Dome C. Reflection age uncertainties are calculated from the radar range precision and signal-to-noise ratio of the internal reflections. The radar stratigraphy matches well with the Multichannel Coherent Radar Depth Sounder (MCoRDS) radar stratigraphy obtained independently. We show that radar sounding enables the extension of ice core ages through the ice sheet with an additional radar-related age uncertainty of approximately 1/3-1/2 that of the ice cores. Reflections are extended along the Byrd-Totten Glacier divide, using University of Texas/Technical University of Denmark and MCoRDS surveys. However, core-to-core connection is impeded by pervasive aeolian terranes, and Lake Vostok's influence on reflection geometry. Poor radar connection of the two ice cores is attributed to these effects and suboptimal survey design in affected areas. We demonstrate that, while ice sheet internal radar reflections are generally isochronal and can be mapped over large distances, careful survey planning is necessary to extend ice core chronologies to distant regions of the East Antarctic ice sheet.

Toward an integrated ice core chronology using relative and orbital tie-points

NASA Astrophysics Data System (ADS)

Bazin, L.; Landais, A.; Lemieux-Dudon, B.; Toyé Mahamadou Kele, H.; Blunier, T.; Capron, E.; Chappellaz, J.; Fischer, H.; Leuenberger, M.; Lipenkov, V.; Loutre, M.-F.; Martinerie, P.; Parrenin, F.; Prié, F.; Raynaud, D.; Veres, D.; Wolff, E.

2012-04-01

Precise ice cores chronologies are essential to better understand the mechanisms linking climate change to orbital and greenhouse gases concentration forcing. A tool for ice core dating (DATICE [developed by Lemieux-Dudon et al., 2010] permits to generate a common time-scale integrating relative and absolute dating constraints on different ice cores, using an inverse method. Nevertheless, this method has only been applied for a 4-ice cores scenario and for the 0-50 kyr time period. Here, we present the bases for an extension of this work back to 800 ka using (1) a compilation of published and new relative and orbital tie-points obtained from measurements of air trapped in ice cores and (2) an adaptation of the DATICE inputs to 5 ice cores for the last 800 ka. We first present new measurements of δ18Oatm and δO2/N2 on the Talos Dome and EPICA Dome C (EDC) ice cores with a particular focus on Marine Isotopic Stages (MIS) 5, and 11. Then, we show two tie-points compilations. The first one is based on new and published CH4 and δ18Oatm measurements on 5 ice cores (NorthGRIP, EPICA Dronning Maud Land, EDC, Talos Dome and Vostok) in order to produce a table of relative gas tie-points over the last 400 ka. The second one is based on new and published records of δO2/N2, δ18Oatm and air content to provide a table of orbital tie-points over the last 800 ka. Finally, we integrate the different dating constraints presented above in the DATICE tool adapted to 5 ice cores to cover the last 800 ka and show how these constraints compare with the established gas chronologies of each ice core.

Historical Isotopic Temperature Record from the Vostok Ice Core (420,000 years BP-present)

DOE Data Explorer

Petit, J. R. [Laboratoire de Glaciogie et Geophysique de l'Environnement; Raynaud, D. [Laboratoire de Glaciogie et Geophysique de l'Environnement; Lorius, C. [Laboratoire de Glaciogie et Geophysique de l'Environnement; Jouzel, J. [Laboratoire des Sciences du Climat et de l'Environnement; Delaygue, G. [Laboratoire des Sciences du Climat et de l'Environnement; Barkov, N. I. [Arctic and Antarctic Research Inst. (AARI), St. Petersburg (Russian Federation); Kotlyakov, V. M. [Institute of Geography, Russia

2000-01-01

Because isotopic fractions of the heavier oxygen-18 (18O) and deuterium (D) in snowfall are temperature-dependent and a strong spatial correlation exists between the annual mean temperature and the mean isotopic ratio (18O or δD) of precipitation, it is possible to derive ice-core climate records. The record presented by Jouzel et al. (1987) was the first ice core record to span a full glacial-interglacial cycle. That record was based on an ice core drilled at the Russian Vostok station in central east Antarctica. The 2083-m ice core was obtained during a series of drillings in the early 1970s and 1980s and was the result of collaboration between French and former-Soviet scientists. Drilling continued at Vostok and was completed in January 1998, reaching a depth of 3623 m, the deepest ice core ever recovered (Petit et al. 1997, 1999). The resulting core allows the ice core record of climate properties at Vostok to be extended to ~420 kyr BP.

A review of sea ice proxy information from polar ice cores

NASA Astrophysics Data System (ADS)

Abram, Nerilie J.; Wolff, Eric W.; Curran, Mark A. J.

2013-11-01

Sea ice plays an important role in Earth's climate system. The lack of direct indications of past sea ice coverage, however, means that there is limited knowledge of the sensitivity and rate at which sea ice dynamics are involved in amplifying climate changes. As such, there is a need to develop new proxy records for reconstructing past sea ice conditions. Here we review the advances that have been made in using chemical tracers preserved in ice cores to determine past changes in sea ice cover around Antarctica. Ice core records of sea salt concentration show promise for revealing patterns of sea ice extent particularly over glacial-interglacial time scales. In the coldest climates, however, the sea salt signal appears to lose sensitivity and further work is required to determine how this proxy can be developed into a quantitative sea ice indicator. Methane sulphonic acid (MSA) in near-coastal ice cores has been used to reconstruct quantified changes and interannual variability in sea ice extent over shorter time scales spanning the last ˜160 years, and has potential to be extended to produce records of Antarctic sea ice changes throughout the Holocene. However the MSA ice core proxy also requires careful site assessment and interpretation alongside other palaeoclimate indicators to ensure reconstructions are not biased by non-sea ice factors, and we summarise some recommended strategies for the further development of sea ice histories from ice core MSA. For both proxies the limited information about the production and transfer of chemical markers from the sea ice zone to the Antarctic ice sheets remains an issue that requires further multidisciplinary study. Despite some exploratory and statistical work, the application of either proxy as an indicator of sea ice change in the Arctic also remains largely unknown. As information about these new ice core proxies builds, so too does the potential to develop a more comprehensive understanding of past changes in sea ice and its role in both long and short-term climate changes.

Geomorphic consequences of rapid deglaciation at Pasterze Glacier, Hohe Tauern Range, Austria, between 2010 and 2013 based on repeated terrestrial laser scanning data

NASA Astrophysics Data System (ADS)

Avian, M.; Kellerer-Pirklbauer, A.; Lieb, G. K.

2018-06-01

Since the end of the Little Ice Age around 1850 CE glaciers in the Alps have been receding dramatically. This study aimed to quantify and characterize the geomorphic and landform changes of a 0.9 km2 large proglacial area at the largest glacier in Austria (Pasterze Glacier, Austria, N 47°04‧, E 12°44‧). Point clouds from multiple terrestrial laserscanning (TLS) and different image data were used to quantify surface elevation changes and distinguish different types of erosional and depositional landforms during the period 2010-2013. Results indicate that the study area is characterized by a total volume loss of 1,309,000 m3. Excluding the area which was deglaciated, the volume loss equals 275,000 m3 in the period 2010-13. The decrease is related to sediment transfer out of study area and due to sediment-buried glacier ice which is slowly melting. The landform classification reveals that drift mantled slopes are most frequent (20.9% of the study area in 2013) next to ice contact terrace landforms (19.7%). In terms of vertical surface elevation changes, our results suggest distinguishing between 3 distinct domains within the study area: (i) a flat valley bottom area consisting of water/sandur areas and ice-cored landforms dominated by widespread subsurface ice melting and lateral fluvial (and thermal) erosion; (ii) a gently-sloping footslope area consisting of ice-contact sediments, former ice marginal channels and deep incised gullies with corresponding debris cones dominated by linear erosion and corresponding deposition; and (iii) a steep lateral slope area mainly built up of consolidated drift material with incised gullies dominated by linear erosion. Our results not only confirm the previously revealed high geomorphic activity for proglacial areas of alpine glaciers in terms of surface elevation variations, they also highlight that landforms might change substantially from one year to the next not only because of erosional/depositional processes, but also because of the melting of buried dead-ice bodies.

Rapid Access Ice Drill: A New Tool for Exploration of the Deep Antarctic Ice Sheets and Subglacial Geology

NASA Astrophysics Data System (ADS)

Goodge, J. W.; Severinghaus, J. P.

2014-12-01

The Rapid Access Ice Drill (RAID) will penetrate the Antarctic ice sheets in order to core through deep ice, the glacial bed, and into bedrock below. This new technology will provide a critical first look at the interface between major ice caps and their subglacial geology. Currently in construction, RAID is a mobile drilling system capable of making several long boreholes in a single field season in Antarctica. RAID is interdisciplinary and will allow access to polar paleoclimate records in ice >1 Ma, direct observation at the base of the ice sheets, and recovery of rock cores from the ice-covered East Antarctic craton. RAID uses a diamond rock-coring system as in mineral exploration. Threaded drill-pipe with hardened metal bits will cut through ice using reverse circulation of Estisol for pressure-compensation, maintenance of temperature, and removal of ice cuttings. Near the bottom of the ice sheet, a wireline bottom-hole assembly will enable diamond coring of ice, the glacial bed, and bedrock below. Once complete, boreholes will be kept open with fluid, capped, and made available for future down-hole measurement of thermal gradient, heat flow, ice chronology, and ice deformation. RAID will also sample for extremophile microorganisms. RAID is designed to penetrate up to 3,300 meters of ice and take sample cores in less than 200 hours. This rapid performance will allow completion of a borehole in about 10 days before moving to the next drilling site. RAID is unique because it can provide fast borehole access through thick ice; take short ice cores for paleoclimate study; sample the glacial bed to determine ice-flow conditions; take cores of subglacial bedrock for age dating and crustal history; and create boreholes for use as an observatory in the ice sheets. Together, the rapid drilling capability and mobility of the drilling system, along with ice-penetrating imaging methods, will provide a unique 3D picture of the interior Antarctic ice sheets.

Ice residual properties in mixed-phase clouds at the high-alpine Jungfraujoch site.

PubMed

Kupiszewski, Piotr; Zanatta, Marco; Mertes, Stephan; Vochezer, Paul; Lloyd, Gary; Schneider, Johannes; Schenk, Ludwig; Schnaiter, Martin; Baltensperger, Urs; Weingartner, Ernest; Gysel, Martin

2016-10-27

Ice residual (IR) and total aerosol properties were measured in mixed-phase clouds (MPCs) at the high-alpine Jungfraujoch research station. Black carbon (BC) content and coating thickness of BC-containing particles were determined using single-particle soot photometers. The ice activated fraction (IAF), derived from a comparison of IR and total aerosol particle size distributions, showed an enrichment of large particles in the IR, with an increase in the IAF from values on the order of 10 -4 to 10 -3 for 100 nm (diameter) particles to 0.2 to 0.3 for 1 μm (diameter) particles. Nonetheless, due to the high number fraction of submicrometer particles with respect to total particle number, IR size distributions were still dominated by the submicrometer aerosol. A comparison of simultaneously measured number size distributions of BC-free and BC-containing IR and total aerosol particles showed depletion of BC by number in the IR, suggesting that BC does not play a significant role in ice nucleation in MPCs at the Jungfraujoch. The potential anthropogenic climate impact of BC via the glaciation effect in MPCs is therefore likely to be negligible at this site and in environments with similar meteorological conditions and a similar aerosol population. The IAF of the BC-containing particles also increased with total particle size, in a similar manner as for the BC-free particles, but on a level 1 order of magnitude lower. Furthermore, BC-containing IR were found to have a thicker coating than the BC-containing total aerosol, suggesting the importance of atmospheric aging for ice nucleation.

Outlook for Improved Numerical Weather Prediction Using Satellite Data with a Special Emphasis on the Hydrological Variables,

DTIC Science & Technology

1983-11-18

Prediction, June 6-9, 1983, Omaha, Nebr., AMS, pp. 269-274. (5) Bellon, A., S. Lovejoy , and G. L. Austin, 1980: Combining satellite and radar data...1979: Global sea-ice limits. In Inventory of Snow Cover and Sea Ice Data. Rep. GD-7, Institute of Arctic and Alpine Research, edited by R. G. Crane... parent organization in parentheses and location or current name in square brackets follow the acronym definition. AFCRL Air Force Cambridge Research

Heating up relations between cold fish: competition modifies responses to climate change.

PubMed

Urban, Mark C; Holt, Robert D; Gilman, Sarah E; Tewksbury, Joshua

2011-05-01

Most predictions about species responses to climate change ignore species interactions. Helland and colleagues (2011) test whether this assumption is valid by evaluating whether ice cover affects competition between brown trout [Salmo trutta (L.)] and Arctic charr [Salvelinus alpines (L.)]. They show that increasing ice cover correlates with lower trout biomass when Arctic charr co-occur, but not in charr's absence. In experiments, charr grew better in the cold, dark environments that typify ice-covered lakes. Decreasing ice cover with warmer winters could mean more trout and fewer charr. More generally, their results provide an excellent example, suggesting that species interactions can strongly modify responses to climate change. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society.

Latest Pleistocene advance and collapse of the Matanuska - Knik glacier system, Anchorage Lowland, southern Alaska

NASA Astrophysics Data System (ADS)

Kopczynski, Sarah E.; Kelley, Samuel E.; Lowell, Thomas V.; Evenson, Edward B.; Applegate, Patrick J.

2017-01-01

At the end of the last ice age, glacier systems worldwide underwent dramatic retreat. Here, we document the advance and retreat of a glacier system with adjacent marine- and land-based components during the latter part of the Termination. We utilize three lines of evidence: lithologic provenance, geomorphic mapping, and radiocarbon ages derived from lake cores to reconstruct glacier extent and timing of advance and retreat within our study area centered at N 61.50°, W 149.50°, just north of Anchorage, Alaska. Two glaciers, sourced in the Talkeetna and Chugach Mountains, flowed down the Matanuska and Knik Valleys forming a coalesced lobe that advanced onto the Anchorage Lowlands and terminated at Elmendorf Moraine. We use the presence of lithologies unique to the Matanuska catchment in glacial drift to delineate the paleoflow lines and to estimate the suture line of the two glacier systems. The eastern side of the lobe, attributed to ice flow from the Knik Valley, was in contact with elevated marine waters within the Knik Arm fjord, and thus retreat was likely dominated by calving. Geomorphic evidence suggests the western side of the lobe, attributed to ice flow from Matanuska Valley, retreated due to stagnation. We constrain retreat of the combined Matanuska and Knik lobe with thirteen new radiocarbon ages, in addition to previously published radiocarbon ages, and with geomorphic evidence suggesting the retreat occurred in two phases. Retreat from the Elmendorf Moraine began between 16.8 and 16.4 ka BP. A second, faster retreat phase occurred later and was completed by 13.7 ka BP. With the 140 km of total retreat occurring over ∼3000 years or less. This pattern of glacial advance and retreats agrees well with the deglacial histories from the southern sectors of the Cordilleran Ice Sheet, as well as many other alpine glacier systems in the western U.S. and northern Alaska. This consistent behavior of glacier systems may indicate that climate oscillated over western North America early in deglaciation before it was recorded in other proxies such as ice cores. Furthermore, the period in which we note mountain glacier collapse in northwestern North America is synchronous with the worldwide glacial termination raising questions about intrahemispheric linkages.

Past and future demographic dynamics of alpine species: limited genetic consequences despite dramatic range contraction in a plant from the Spanish Sierra Nevada.

PubMed

Blanco-Pastor, J L; Fernández-Mazuecos, M; Vargas, P

2013-08-01

Anthropogenic global climate change is expected to cause severe range contractions among alpine plants. Alpine areas in the Mediterranean region are of special concern because of the high abundance of endemic species with narrow ranges. This study combined species distribution models, population structure analyses and Bayesian skyline plots to trace the past and future distribution and diversity of Linaria glacialis, an endangered narrow endemic species that inhabits summits of Sierra Nevada (Spain). The results showed that: (i) the habitat of this alpine-Mediterranean species in Sierra Nevada suffered little changes during glacial and interglacial stages of late Quaternary; (ii) climatic oscillations in the last millennium (Medieval Warm Period and Little Ice Age) moderately affected the demographic trends of L. glacialis; (iii) future warming conditions will cause severe range contractions; and (iv) genetic diversity will not diminish at the same pace as the distribution range. As a consequence of the low population structure of this species, genetic impoverishment in the alpine zones of Sierra Nevada should be limited during range contraction. We conclude that maintenance of large effective population sizes via high mutation rates and high levels of gene flow may promote the resilience of alpine plant species when confronted with global warming. © 2013 John Wiley & Sons Ltd.

Paleo ice-cap surfaces and extents

NASA Astrophysics Data System (ADS)

Gillespie, A.; Pieri, D.

2008-12-01

The distribution, equilibrium-line altitude (ELA) and timing of Pleistocene alpine glaciers are used to constrain paleoclimatic reconstructions. Attention has largely focused on the geomorphic evidence for the former presence of simple valley glaciers; paleo alpine ice caps and their outlet glaciers have proven to be more problematical. This is especially so in the remote continental interior of Asia, where the research invested in the Alps or Rocky Mountains has yet to be duplicated. Even the putative existence and size of paleo ice caps in Tibet and the Kyrgyz Tien Shan is controversial. Remote sensing offers the opportunity to assess vast tracts of land quickly, with images and co-registered digital elevation models (DEMs) offering the most information for studies of paleoglaciers. We pose several questions: (1) With what confidence can nunataks be identified remotely? (2) What insights do their physiographic characteristics offer? (3) What characteristics of the bed of a paleo ice cap can be used to identify its former presence remotely? and (4) Can the geomorphic signatures of the edges of paleo ice caps be recognized and mapped? Reconstruction of the top surface of a paleo ice cap depends on the recognition of nunataks, typically rougher at 1 m to 100 m scales than their surroundings. Nunataks in southern Siberia are commonly notched by multiple sub- horizontal bedrock terraces. These step terraces appear to originate from freeze-thaw action on the rock-ice interface during periods of stability, and presence of multiple terraces suggests stepwise lowering of ice surfaces during deglaciation. An older generation of step-terraced nunataks, distinguished by degraded and eroded terraces, delineates a larger paleo ice cap in the Sayan Range (Siberian - Mongolian border) that significantly pre-dates the last glacial maximum (LGM). Large ice caps can experience pressure melting at their base and can manifest ice streams within the ice cap. Valleys left behind differ from fluvial valleys in their width/depth profiles: the channels maintain width but get shallower near their sources. Link junction angle distributions within superimposed drainage networks are broader and distinct from those of evolved fluvial networks, and their character and statistics can be used to identify the perimeters of large paleo ice caps. (This work was carried out in part at the Jet Propulsion Laboratory of the California Institute of Technology under contract to NASA.)

10Be evidence for the Matuyama-Brunhes geomagnetic reversal in the EPICA Dome C ice core.

PubMed

Raisbeck, G M; Yiou, F; Cattani, O; Jouzel, J

2006-11-02

An ice core drilled at Dome C, Antarctica, is the oldest ice core so far retrieved. On the basis of ice flow modelling and a comparison between the deuterium signal in the ice with climate records from marine sediment cores, the ice at a depth of 3,190 m in the Dome C core is believed to have been deposited around 800,000 years ago, offering a rare opportunity to study climatic and environmental conditions over this time period. However, an independent determination of this age is important because the deuterium profile below a depth of 3,190 m depth does not show the expected correlation with the marine record. Here we present evidence for enhanced 10Be deposition in the ice at 3,160-3,170 m, which we interpret as a result of the low dipole field strength during the Matuyama-Brunhes geomagnetic reversal, which occurred about 780,000 years ago. If correct, this provides a crucial tie point between ice cores, marine cores and a radiometric timescale.

Dansgaard-Oeschger cycles observed in the Greenland ReCAP ice core project

NASA Astrophysics Data System (ADS)

Kjær, Helle Astrid; Vallelonga, Paul; Vinther, Bo; Simonsen, Marius; Maffezzoli, Niccoló; Gkinis, Vasileios; Svensson, Anders; Jensen, Camilla Marie; Dallmayr, Remi; Spolaor, Andrea; Edwards, Ross

2017-04-01

The new REnland ice CAP (RECAP) ice core was drilled in summer 2015 in Greenland and measured by means of Continuous flow analysis (CFA) during the last 3 months of 2015. The Renland ice core was obtained as part of the ReCAP project, extending 584.11 meters to the bottom of the Renland ice cap located in east Greenland. The unique position on a mountain saddle above 2000 meters altitude, but close to the coast, ensures that the Renland ice core offers high accumulation, but also reaches far back in time. Results show that despite the short length the RECAP ice core holds ice all the way back to the past warm interglacial period, the Eemian. The glacial section is strongly thinned and covers on 20 meters of the ReCAP core, but nonetheless due to the high resolution of the measurements all 25 expected DO events could be identified. The record was analyzed for multiple elements including the water isotopes, forest fire tracers NH4+ and black carbon, insoluble dust particles by means of Abakus laser particle counter and the dust ion Ca2+, sea salt Na+, and sea ice proxies as well as acidity useful for finding volcanic layers to date the core. Below the glacial section another 20 meters of warm Eemian ice have been analysed. Here we present the chemistry results as obtained by continuous flow analysis (CFA) and compare the glacial section with the chemistry profile from other Greenland ice cores.

Ice cores and SeaRISE: What we do (and don't) know

NASA Technical Reports Server (NTRS)

Alley, Richard B.

1991-01-01

Ice core analyses are needed in SeaRISE to learn what the West Antarctic ice sheet and other marine ice sheets were like in the past, what climate changes led to their present states, and how they behave. The major results of interest to SeaRISE from previous ice core analyses in West Antarctic are that the end of the last ice age caused temperature and accumulation rate increases in inland regions, leading to ice sheet thickening followed by thinning to the present.

The 1500m South Pole Ice Core: Recovering a 40 Ka Environmental Record

NASA Technical Reports Server (NTRS)

Casey, Kimberly Ann; Neumann, Thomas Allen; Fudge, T. J.; Neumann, T. A.; Steig, E. J.; Cavitte, M. G. P.; Blankenship, D. D.

2014-01-01

Supported by the US National Science Foundation, a new 1500 m, approximately 40 ka old ice core will be recovered from South Pole during the 2014/15 and 2015/16 austral summer seasons using the new US Intermediate Depth Drill. The combination of low temperatures, relatively high accumulation rates and low impurity concentrations at South Pole will yield detailed records of ice chemistry and trace atmospheric gases. The South Pole ice core will provide a climate history record of a unique area of the East Antarctic plateau that is partly influenced by weather systems that cross the West Antarctic ice sheet. The ice at South Pole flows at approximately 10m a(exp-1) and the South Pole ice-core site is a significant distance from an ice divide. Therefore, ice recovered at depth originated progressively farther upstream of the coring site. New ground-penetrating radar collected over the drill site location shows no anthropogenic influence over the past approximately 50 years or upper 15 m. Depth-age scale modeling results show consistent and plausible annual-layer thicknesses and accumulation rate histories, indicating that no significant stratigraphic disturbances exist in the upper 1500m near the ice-core drill site.

Holocene climate dynamics in the Eastern Italian Alps: a multi-proxy study from ice and peat bogs

NASA Astrophysics Data System (ADS)

Poto, Luisa; Gabrieli, Jacopo; Segnana, Michela; Festi, Daniela; Oeggl, Klaus; Barbante, Carlo

2014-05-01

The Eastern Italian Alps are located near one of the areas in the world with some of the longest records of extreme environmental use by human activity. In this area, paleo-climate studies are hampered by the lack of high-resolution multi-proxy records with adequate chronological control. With this project, we propose to reconstruct Holocene climatic and environmental variations in the Eastern Italian Alps using terrestrial and glaciological archives. We aim to study the characteristics of different climate stages in this sector of the Alps using an ice core drilled on the top of the Ortles glacier (46°30' N, 10°32 E, 3850 m a.s.l.) and ombrotrophic peat bog records from the Dolomites (Danta di Cadore, 46°34' N, 12°33 E, 1400 m a.s.l. and Coltrondo 46°39'28.37''N 12°26'59.17''E, 1800 m a.s.l., Belluno province). The study of global climatic change require a holistic and multi-proxy approach to better understand several complex and often non-linear relationships. In the Italian Alps our study on peat cores represents the first attempt where a multi-proxy approach is applied, and here we report our first results. A 7.0 m peat sequence was extracted in Danta di Cadore. The depth-age scale, based upon independent 14C and 210Pb dates and modeled with the Clam method (Blaauw, 2010), demonstrates that the archive covers more than 13,200 years (cal BP). We determined physical proprieties, Ca and Ti trends, pore water pH, conductivity, and Ca/Mg ratios to identify changes in trophic conditions. The results confirm that the uppermost 400 cm are composed of ombrotrophic peat representing the longest Eastern Alpine ombrotrophic record yet obtained, covering the last 7,000 years. The oldest radiocarbon age (13,200 years cal BP) provides evidence that, during the Bölling-Alleröd interstadial, the upper part of the Piave Glacier was ice-free up to 1400 m a.s.l.. At that time pollen assemblages show that a conifer forest characterized the local vegetation. This forest was then affected by the climatic cooling of the Younger Dryas, which caused an opening of the vegetation. The climatic amelioration occurring at the onset of the Holocene favored the local expansion of warmth-demanding species. X-ray Fluorescence Core Scanner (XRF-CS) analysis was applied for the first time on Eastern Alpine peat sequences. XRF-CS signals were calibrated with ICP-MS, showing very high correlation and demonstrating that the XRF-CS technique provides reliable quantitative data. Results provide information about geochemical processes occurring in the bog. The impact of mining activity was also evaluated. Concentration levels and enrichment factors (EFs) of several trace elements such as Pb, Ag and Cd correspond to the historical data about mining activities in the Cadore region. Lead isotopes ratios were measured to identify natural and anthropogenic sources of Pb emissions. Results show an increase of Pb deriving from fuel combustion over the last decades that gradually overlie the impacts of mining activity. The decreasing 206Pb/207Pb trend reached its minimum value of 1.153 in the 1990s and then increased again. In these years, Italy started to follow EU rules to limit global pollutants in the atmosphere, and finally banned leaded fuels in 2002. Both 206Pb/207Pb ratio and Pb fluxes show a particular event between 1975 and 1980: this behavior is characteristic of the ILE (Isotopic Lead Experiment), a large-scale isotopic tracer experiment which was carried out in the Piedmont region (N-W Italy). This multi-proxy approach that integrates, using new chronological insights, chemical physical and biological features of the core, improves our understanding of Eastern Alpine Holocene climate, helping to delineate biotic and abiotic responses to climate dynamics during the present interglacial. Blaauw, M. 2010. Methods and code for 'classical' age modeling of radiocarbon sequences. Quarternary Geochronology, 5: 512-518.

IceChrono1: a probabilistic model to compute a common and optimal chronology for several ice cores

NASA Astrophysics Data System (ADS)

Parrenin, Frédéric; Bazin, Lucie; Capron, Emilie; Landais, Amaëlle; Lemieux-Dudon, Bénédicte; Masson-Delmotte, Valérie

2016-04-01

Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores and the estimation of the age scale uncertainty are essential to interpret the climate and environmental records that they contain. It is however a complex problem which involves different methods. Here, we present IceChrono1, a new probabilistic model integrating various sources of chronological information to produce a common and optimized chronology for several ice cores, as well as its uncertainty. IceChrono1 is based on the inversion of three quantities: the surface accumulation rate, the Lock-In Depth (LID) of air bubbles and the thinning function. The chronological information integrated into the model are: models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice and air dated horizons, ice and air depth intervals with known durations, Δdepth observations (depth shift between synchronous events recorded in the ice and in the air) and finally air and ice stratigraphic links in between ice cores. The optimization is formulated as a least squares problem, implying that all densities of probabilities are assumed to be Gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono follows an approach similar to that of the Datice model which was recently used to produce the AICC2012 chronology for 4 Antarctic ice cores and 1 Greenland ice core. IceChrono1 provides improvements and simplifications with respect to Datice from the mathematical, numerical and programming point of views. The capabilities of IceChrono is demonstrated on a case study similar to the AICC2012 dating experiment. We find results similar to those of Datice, within a few centuries, which is a confirmation of both IceChrono and Datice codes. We also test new functionalities with respect to the original version of Datice: observations as ice intervals with known durations, correlated observations, observations as gas intervals with known durations and observations as mixed ice-air stratigraphic links. IceChrono1 is freely available under the GPL v3 open source license.

Rise in central west Greenland surface melt unprecedented over the last three centuries

NASA Astrophysics Data System (ADS)

Trusel, Luke; Das, Sarah; Osman, Matthew; Evans, Matthew; Smith, Ben; McConnell, Joe; Noël, Brice; van den Broeke, Michiel

2017-04-01

Greenland Ice Sheet surface melting has intensified and expanded over the last several decades and is now a leading component of ice sheet mass loss. Here, we constrain the multi-century temporal evolution of surface melt across central west Greenland by quantifying layers of refrozen melt within well-dated firn and ice cores collected in 2014 and 2015, as well as from a core collected in 2004. We find significant agreement among ice core, satellite, and regional climate model melt datasets over recent decades, confirming the fidelity of the ice core melt stratigraphy as a reliable record of past variability in the magnitude of surface melt. We also find a significant correlation between the melt records derived from our new 100-m GC-2015 core (2436 m.a.s.l.) and the older (2004) 150-m D5 core (2472 m.a.s.l.) located 50 km to the southeast. This agreement demonstrates the robustness of the ice core-derived melt histories and the potential for reconstructing regional melt evolution from a single site, despite local variability in melt percolation and refreeze processes. Our array of upper percolation zone cores reveals that although the overall frequency of melt at these sites has not increased, the intensification of melt over the last three decades is unprecedented within at least the last 365 years. Utilizing the regional climate model RACMO 2.3, we show that this melt intensification is a nonlinear response to warming summer air temperatures, thus underscoring the heightened sensitivity of this sector of Greenland to further climate warming. Finally, we examine spatial correlations between the ice core melt records and modeled melt fields across the ice sheet to assess the broader representation of each ice core record. This analysis reveals wide-ranging significant correlations, including to modeled meltwater runoff. As such, our ice core melt records may furthermore offer unique, observationally-constrained insights into past variability in ice sheet mass loss.

Changes of the Bacterial Abundance and Communities in Shallow Ice Cores from Dunde and Muztagata Glaciers, Western China

PubMed Central

Chen, Yong; Li, Xiang-Kai; Si, Jing; Wu, Guang-Jian; Tian, Li-De; Xiang, Shu-Rong

2016-01-01

In this study, six bacterial community structures were analyzed from the Dunde ice core (9.5-m-long) using 16S rRNA gene cloning library technology. Compared to the Muztagata mountain ice core (37-m-long), the Dunde ice core has different dominant community structures, with five genus-related groups Blastococcus sp./Propionibacterium, Cryobacterium-related., Flavobacterium sp., Pedobacter sp., and Polaromas sp. that are frequently found in the six tested ice layers from 1990 to 2000. Live and total microbial density patterns were examined and related to the dynamics of physical-chemical parameters, mineral particle concentrations, and stable isotopic ratios in the precipitations collected from both Muztagata and Dunde ice cores. The Muztagata ice core revealed seasonal response patterns for both live and total cell density, with high cell density occurring in the warming spring and summer months indicated by the proxy value of the stable isotopic ratios. Seasonal analysis of live cell density for the Dunde ice core was not successful due to the limitations of sampling resolution. Both ice cores showed that the cell density peaks were frequently associated with high concentrations of particles. A comparison of microbial communities in the Dunde and Muztagata glaciers showed that similar taxonomic members exist in the related ice cores, but the composition of the prevalent genus-related groups is largely different between the two geographically different glaciers. This indicates that the micro-biogeography associated with geographic differences was mainly influenced by a few dominant taxonomic groups. PMID:27847503

Allostratigraphic approach on the Alpine Lateglacial

NASA Astrophysics Data System (ADS)

Monegato, Giovanni; Reitner, Jürgen M.

2017-04-01

The reconstruction of the Alpine deglaciation after the Last Glacial Maximum is the one-of-a-kind chance of understanding glaciers dynamics in a period of climate warming. Long-lasting studies beginning in the 19th Century resulted in the definition of five major phases established on the base of Δ ELA values. However, they have been recently re-discussed on the base of dating results and field evidence. Field based reconstructions in some areas of the Alps (Tyrol, Julian Alps) utilizing allostratigraphy i.e. the use of unconformity-bounded units, provide pinpoint in total to a plausible tripartite subdivision of Lateglacial deposits (Colucci et al., 2014; Bichler et al., 2016; Reitner et al., 2016). From the chronological point no consensus on the start of the Alpine Lateglacial exists: The major Garda and Ticino glaciers persisted until about 17.5 ka (e.g. Ravazzi et al., 2014), whereas the tongue basins and, moreover, even major valleys inside the Alps where ice-free already around 18.5 ka (e.g., Schmidt et al., 2012). For the short phase of ice-decay, as the first expression of activity of rather small local glaciers in contact to dead ice, only luminescence datings are available so far centered around 19 ka. The Gschnitz stadial, at about 16-17 ka, and the Egesen stadial corresponding to the Younger Dryas, are the only two remarkable phases of advance of glacier tongues into the valleys, which stabilized for considerable time. The reconstructions suggest that more effort is needed, in term of sedimentological and (allo-)stratigraphic investigations together with geochronology to understand if this tripartite stratigraphic scheme can be exported in the whole Alpine area, or if stabilization of glacier fronts could have taken place somewhere also due to local mechanisms. References Bichler, M. G., Reindl, M., Reitner, J. M., Drescher-Schneider, R., Wirsig, C., Christl, M., Hajdas, I. & Ivy-Ochs, S., 2016: Landslide deposits as stratigraphical markers for a sequence-based glacial stratigraphy: a case study of a Younger Dryas system in the Eastern Alps. Boreas, 45: 537-551. Colucci, R. R., Monegato, G., Žebre, M. (2014). Glacial and proglacial deposits of the Resia Valley (NE Italy): New insights on the onset and decay of the last alpine glacial maximum in the Julian Alps. Alpine and Mediterranean Quaternary, 27: 85-104. Ravazzi, C., Pini, R., Badino, F., De Amicis, M., Londeix, L., Reimer, P.J. (2014). The latest LGM culmination of the Garda Glacier (Italian Alps) and the onset of glacial termination. Age of glacial collapse and vegetation chronosequence. Quaternary Science Reviews, 105: 26-47. Reitner, J.M., Ivy-Ochs, S., Drescher-Schneider, R., Hajdas, I., Linner, M. (2016). Reconsidering the current stratigraphy of the Alpine Lateglacial: Implications of the sedimentary and morphological record of the Lienz area (Tyrol/Austria). E&G Quaternary Science Journal, 65: 113-144. Schmidt, R., Weckström, K., Lauterbach, S., Tessadri, R., Huber, K. (2012). North Atlantic climate impact on early late-glacial climate oscillations in the south-eastern Alps inferred from a multi-proxy lake sediment record. Journal of Quaternary Science, 27: 40-50.

An Optical Dye Method for Continuous Determination of Acidity in Ice Cores.

PubMed

Kjær, Helle Astrid; Vallelonga, Paul; Svensson, Anders; Elleskov L Kristensen, Magnus; Tibuleac, Catalin; Winstrup, Mai; Kipfstuhl, Sepp

2016-10-04

The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on spectroscopically determined color changes of two common pH-indicator dyes, bromophenol blue, and chlorophenol red. The sealed-system method described here is not equilibrated with CO 2 , making it simpler than existing methods for pH determination in ice cores and offering a 10-90% peak response time of 45 s and a combined uncertainty of 9%. The method is applied to Holocene ice core sections from Greenland and Antarctica and compared to standard techniques such as electrical conductivity measurement (ECM) conducted on the solid ice, and electrolytic meltwater conductivity, EMWC. Acidity measured in the Greenland NGRIP ice core shows good agreement with acidity calculated from ion chromatography. Conductivity and dye-based acidity H dye + are found to be highly correlated in the Greenland NEGIS firn core (75.38° N, 35.56° W), with all signals greater than 3σ variability coinciding with either volcanic eruptions or possible wild fire activity. In contrast, the Antarctic Roosevelt Island ice core (79.36° S, 161.71° W) features an anticorrelation between conductivity and H dye + , likely due to strong influence of marine salts.

Sea ice and pollution-modulated changes in Greenland ice core methanesulfonate and bromine

NASA Astrophysics Data System (ADS)

Maselli, Olivia J.; Chellman, Nathan J.; Grieman, Mackenzie; Layman, Lawrence; McConnell, Joseph R.; Pasteris, Daniel; Rhodes, Rachael H.; Saltzman, Eric; Sigl, Michael

2017-01-01

Reconstruction of past changes in Arctic sea ice extent may be critical for understanding its future evolution. Methanesulfonate (MSA) and bromine concentrations preserved in ice cores have both been proposed as indicators of past sea ice conditions. In this study, two ice cores from central and north-eastern Greenland were analysed at sub-annual resolution for MSA (CH3SO3H) and bromine, covering the time period 1750-2010. We examine correlations between ice core MSA and the HadISST1 ICE sea ice dataset and consult back trajectories to infer the likely source regions. A strong correlation between the low-frequency MSA and bromine records during pre-industrial times indicates that both chemical species are likely linked to processes occurring on or near sea ice in the same source regions. The positive correlation between ice core MSA and bromine persists until the mid-20th century, when the acidity of Greenland ice begins to increase markedly due to increased fossil fuel emissions. After that time, MSA levels decrease as a result of declining sea ice extent but bromine levels increase. We consider several possible explanations and ultimately suggest that increased acidity, specifically nitric acid, of snow on sea ice stimulates the release of reactive Br from sea ice, resulting in increased transport and deposition on the Greenland ice sheet.

Early to mid-Miocene palaeoclimate of Antarctica based on terrestrial records

NASA Astrophysics Data System (ADS)

Ashworth, Allan; Lewis, Adam

2017-04-01

Paleontological and stratigraphic studies of sites in the Transantarctic Mountains (TAM) are advancing knowledge of the landscape, vegetation and climate that existed immediately before the growth of the modern East Antarctic Ice Sheet. The sites are located in the Friis Hills and the western Olympus Range in the McMurdo Dry Valleys. In both localities, parts of ancient landscapes are preserved on upland surfaces high above modern valley floors. The early to mid-Miocene interval is bracketed by 40Ar/39Ar ages on volcanic ashes of 19.76 ± 0.11 Ma to 13.85 ± 0.03 Ma. Like all glacial records it is discontinuous but even so several trends can be detected. The record is one of an evolving glacial system during which ice caps coalesced to form an ice sheet. Initially, small alpine glaciers flowed southwestward toward the continental interior eroding shallow troughs into granitic bedrock. By the close of the interval, large glaciers flowed eastward from the continental interior to the Ross Sea. The interval was marked by numerous glacial advances and retreats. Tills are matrix-rich, and outwash sands and gravels ripple-laminated and cross-bedded, typical of those associated with wet-based glaciation. The vegetation during the interval was in a dynamic flux retreating downslope during glacial advances and recolonizing valleys after retreats. Fossils accumulated in peat beds and organic silts representing lacustrine, fluvial and paludal environments. Fossils include diatoms, fungal ascomycetes, pollen and spores, lycopod megaspores, mosses, wood and leaves of Nothofagus (southern beech), fruits of vascular plants, and insect skeletal parts of Diptera (flies) and Coleoptera (beetles). The vegetation was a tundra, initially shrub- and later moss-dominated. During the interval there was a marked decline in biodiversity. Initially, there were 4 species of Nothofagus represented by different leaf types and at least 9 species of vascular plants by their seeds. At the close of the interval neither Nothofagus fossils nor seeds of vascular plants occur in the fossil assemblages which are bryophyte- and lycopod- dominated. During the interval, mean summer temperatures (Nov. - Jan.) are estimated to have declined from about 8° to 4° C. Precipitation during the interval was also likely over 1000 mm. In general, the terrestrial record is in agreement with the dynamic record of glacial advances and retreats described from the ANDRILL 2A shallow marine core. In the larger picture of Antarctic glaciation, however, it is difficult to reconcile the terrestrial record from the McMurdo Dry Valleys with interpretations from Oligocene and early Miocene marine isotopic and modeling studies which indicate Antarctic ice volumes 125% of those of modern values. Interpretations show the Oligocene and early Miocene ice sheet overriding the TAM. To the contrary, the early Miocene glacial record in the TAM indicates no large ice sheet in the interior. Instead, the record begins with alpine glaciers flowing towards the interior. This suggests that the Oligocene ice sheet had a lower profile and different aerial configuration than modeling currently suggests. Research supported by NSF grant no. 0739693.

Rapid Loss of Andean Alpine Glaciers: A Reflection on Cotopaxi´s Long-Distance Historical Lahars and Future Lahar Scenarios

NASA Astrophysics Data System (ADS)

Mothes, P. A.; Hall, M. L.; Samaniego, P.; Francou, B.; Castro, M.; Hidalgo, X.

2007-05-01

Andean alpine glaciers are in rapid retreat, as witnessed by actual measurements, comparative imagery and popular memory. Overall glacier losses will diminish future water availability for human consumption as well as for lahar generation, the product of mixing incandescent eruptive materials with glacial ice and snow. The field study and modeling of long-distance historical lahars from Cotopaxi volcano, Ecuador has shown them to be some of the most voluminous and longest reported. Based on back calculations, peak discharges were commonly between 45,000-60,000 m3/sec, velocities reached 70 km/hr, and run outs attained 325 km. The last "super" debris flow was produced at Cotopaxi in 1877. Observations made after the 1877 eruption reported that the glacier had suffered about 10 meters of ice stripped off the top and the incision of deep gullies from melting and erosion by the scoria block-rich pyroclastic flows. Average reductions of 45% and 60%, respectively, of the area and volume of Cotopaxi´s 19 alpine glaciers during the last 30 years have left an ice cap of only 13 km2 and a volume of 0.60 km3. Descriptions by astute 18th and 19th century observers lead us to conclude that Cotopaxi glaciers were much more robust then, surpassing a total area of about 30 km2, a fact which contributed to generating large volume lahars and high discharges, during the waning "Little Ice Age". If an eruption similar to that of 1877 occurs at Cotopaxi in the future, reduced glacier sizes and the glaciers´ preferential distribution upon the cone will likely attenuate volcano-ice interactions and will lower the probability of "super" lahars being produced during eruptive periods. However, in the last 2000 years of eruptive activity, explosive eruptions display a large size span-- from weakly explosive events (VEI= 2) to highly explosive eruptive cycles (VEI= 4-5). Given the uncertainty of the size of the next explosive eruption of Cotopaxi, several scenarios for lahar generation must be envisioned, which include the magnitude of the explosive event as well as the retreat of the glacier. These scenarios all have implications for the populations living in adjacent valleys, where future lahars may pass.

Ice Core Records of Recent Northwest Greenland Climate

NASA Astrophysics Data System (ADS)

Osterberg, E. C.; Wong, G. J.; Ferris, D.; Lutz, E.; Howley, J. A.; Kelly, M. A.; Axford, Y.; Hawley, R. L.

2014-12-01

Meteorological station data from NW Greenland indicate a 3oC temperature rise since 1990, with most of the warming occurring in fall and winter. According to remote sensing data, the NW Greenland ice sheet (GIS) and coastal ice caps are responding with ice mass loss and margin retreat, but the cryosphere's response to previous climate variability is poorly constrained in this region. We are developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate change and cryospheric response in NW Greenland to improve projections of future ice loss and sea level rise in a warming climate. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 21 m) from the coastal region of the GIS (2Barrel site; 76.9317o N, 63.1467o W, 1685 m el.) and the summit of North Ice Cap (76.938o N, 67.671o W, 1273 m el.) in 2011, 2012 and 2014. The 2Barrel ice core record has statistically significant relationships with regional spring and fall Baffin Bay sea ice extent, summertime temperature, and annual precipitation. Here we evaluate relationships between the 2014 North Ice Cap firn core glaciochemical record and climate variability from regional instrumental stations and reanalysis datasets. We compare the coastal North Ice Cap record to more inland records from 2Barrel, Camp Century and NEEM to evaluate spatial and elevational gradients in recent NW Greenland climate change.

Glaciers and ice sheets as a biome.

PubMed

Anesio, Alexandre M; Laybourn-Parry, Johanna

2012-04-01

The tundra is the coldest biome described in typical geography and biology textbooks. Within the cryosphere, there are large expanses of ice in the Antarctic, Arctic and alpine regions that are not regarded as being part of any biome. During the summer, there is significant melt on the surface of glaciers, ice caps and ice shelves, at which point microbial communities become active and play an important role in the cycling of carbon and other elements within the cryosphere. In this review, we suggest that it is time to recognise the cryosphere as one of the biomes of Earth. The cryospheric biome encompasses extreme environments and is typified by truncated food webs dominated by viruses, bacteria, protozoa and algae with distinct biogeographical structures. Copyright © 2011 Elsevier Ltd. All rights reserved.

Paleo-Ice flow and overdeepenings in an Alpine setting: Examples from the Tyrolian Alps (Austria)

NASA Astrophysics Data System (ADS)

Reitner, J. M.; Gruber, W.

2009-04-01

Overdeepened valleys and basins are the most interesting features of former glacial action in Alpine areas. Understanding the formation of such phenomena are not only a scientific task but also an important challenge for a society increasingly exploiting sustainable natural resources even in remote areas. The feasibility of hydrogeological or geothermal projects, for instance, depends on the bedrock depth and the sedimentary infill of such valleys. Generally, overdeepened valleys are formed in areas where the ice discharge was high, such as near the equilibrium line, at valley junctions, or at narrowings of the valley profile. The long known overdeepened tongue basins in the Eastern Alps are regarded as typical examples of the impact of high ice flow velocities combined with increased debris load and running water under hydrostatic pressure around the former (LGM, and older glaciations) equilibrium lines (e.g. van Husen, 2000). However, within a highly dissected mountain topography like that of the Eastern Alps the existence of overdeepened valleys-parts supposedly also reflects changes in ice flow direction and velocity during glacial history within one glacial event (like the LGM) as well as during the Pleistocene. For example, ice flow in the phase of ice build-up at the beginning of major glaciations is controlled by the topography and trend of the valleys whereas during the climax of the big glaciations a mountain ice cap exists with a continuous discharge across water divides. Thus, the onsets of ice transfluences as well as the valley orientation in relation to the changing ice flow direction are regarded as major conditions for overdeepenings in an inneralpine setting. Such a complex and changing pattern of ice flow will be shown by the example of the Inn valley and its tributary valleys in the S and E (valley of the Wildschönauer Ache and of the Brixentaler Ache). Based on extensive geological mapping and lithostratigraphy in combination with geophysical surveys, a model of the LGM ice flow, its variation and its effect on glacial erosion is developed. On the one hand the effect of topography on ice dynamics in terms of promoting ice build-up as well as restricting erosion is evident. For the tributary valleys, on the other hand, the biggest amount of glacial erosion most probably occurred during the phase of ice build-up. However, seismic data, especially seismic stratigraphy (Reitner et al., 2007), shows the limitations of paleo-glaciological models derived from the youngest sequence, in this case the LGM sequence, for explaining sedimentary remnants of older glaciations. According to our example shifts of, and changes in, the amount of glacial erosion in tributary valleys may best be explained by changes in the onset of ice transfluences during ice build-up. Hence, a step-by-step lowering of passes and cols (water divides) during pleniglacial conditions had a profound impact on the ice dynamics of the following glaciation and, thus, on the occurrence of overdeepenings. Our model for a dynamic evolution of morphology presents an inverse relationship between the shaping of the surface and the subsurface and may only hold for a restricted area. However, this non-static view on glacier constellation and its change through time can explain the occurrence of unexpected overdeepenings or changes in erratic clast content elsewhere in dissected, formerly glaciated, Alpine landscapes. References: Husen, D. van, 2000. Geological Processes during the Quaternary.- Mitteilungen der Österreichischen Geologischen Gesellschaft, 92 (1999), 135-156, Wien. Reitner, J.M., Gruber, W., Römer, A., Bieber, G., Schmid, C., 2007. Complex Pleistocene stratigraphy and structure within an inneralpine setting: The basin of Hopfgarten (Northern Tyrol/Austria).- Geophysical Research Abstracts, Vol. 9, 09369, 2007, SRef-ID: 1607-7962/gra/EGU2007-A-09369, European Geosciences Union.

Establishing a Reliable Depth-Age Relationship for the Denali Ice Core

NASA Astrophysics Data System (ADS)

Wake, C. P.; Osterberg, E. C.; Winski, D.; Ferris, D.; Kreutz, K. J.; Introne, D.; Dalton, M.

2015-12-01

Reliable climate reconstruction from ice core records requires the development of a reliable depth-age relationship. We have established a sub-annual resolution depth-age relationship for the upper 198 meters of a 208 m ice core recovered in 2013 from Mt. Hunter (3,900 m asl), Denali National Park, central Alaska. The dating of the ice core was accomplished via annual layer counting of glaciochemical time-series combined with identification of reference horizons from volcanic eruptions and atmospheric nuclear weapons testing. Using the continuous ice core melter system at Dartmouth College, sub-seasonal samples have been collected and analyzed for major ions, liquid conductivity, particle size and concentration, and stable isotope ratios. Annual signals are apparent in several of the chemical species measured in the ice core samples. Calcium and magnesium peak in the spring, ammonium peaks in the summer, methanesulfonic acid (MSA) peaks in the autumn, and stable isotopes display a strong seasonal cycle with the most depleted values occurring during the winter. Thin ice layers representing infrequent summertime melt were also used to identify summer layers in the core. Analysis of approximately one meter sections of the core via nondestructive gamma spectrometry over depths from 84 to 124 m identified a strong radioactive cesium-137 peak at 89 m which corresponds to the 1963 layer deposited during extensive atmospheric nuclear weapons testing. Peaks in the sulfate and chloride record have been used for the preliminary identification of volcanic signals preserved in the ice core, including ten events since 1883. We are confident that the combination of robust annual layers combined with reference horizons provides a timescale for the 20th century that has an error of less than 0.5 years, making calibrations between ice core records and the instrumental climate data particularly robust. Initial annual layer counting through the entire 198 m suggests the Denali Ice Core record will span the past 1000 years.

Laser Induced Fluorescence Emission (L.I.F.E.): In Situ Non-Destructive Detection of Microbial Life on Supraglacial Environments

NASA Astrophysics Data System (ADS)

Sattler, B.; Tilg, M.; Storrie-Lombardi, M.; Remias, D.; Psenner, R.

2012-04-01

Laser-induced fluorescence emission (L.I.F.E.) is an in situ laser scanning technique to detect photoautotrophic pigments such as phycoerythrin of an ice ecosystem such as supraglacial environments without contamination. The sensitivity of many psychrophiles to even moderate changes in temperature, and the logistical difficulties associated with either in situ analysis or sampling makes it difficult to study microbial metabolism in ice ecosystems in a high resolution. Surface communities of cold ecosystems are highly autotrophic and therefor ideal systems for L.I.F.E examinations. 532nm green lasers excite photopigments in cyanobacteria and produce multiple fluorescence signatures between 550nm and 750nm including carotenoids, phycobiliproteins which would enable a non-invasive in-situ measurement. The sensitivity of many psychrophiles to even moderate changes in temperature, and the logistical difficulties associated with either in situ analysis or sampling makes it difficult to study these cryosphere ecosystems. In general, the ice habitat has to be disrupted using techniques that usually include coring, sawing, and melting. Samples are also often chosen blindly, with little indication of probable biomass. The need for an in situ non-invasive, non-destructive technique to detect, localize, and sample cryosphere biomass in the field is therefore of considerable importance. L.I.F.E has already been tested in remote ecosystems like Antarctica (Lake Untersee, Lake Fryxell), supraglacial environments in the Kongsfjord region in the High Arctic and High Alpine glaciers but until now no calibration was set to convert the L.I.F.E. signal into pigment concentration. Here we describe the standardization for detection of Phycobiliproteins (Phycoerythrine) which are found in red algae, cyanobacteria, and cryptomonads. Similar methods are already used for detection of phytoplankton in liquid systems like oceans and lakes by NASÁs Airborne Oceanographic LIDAR since 1979. The possibility to use L.I.F.E. in ice though is a novelty and provides a promising tool to monitor vanishing ice systems like retreating glaciers.

Bipolar volcanic events in ice cores and the Toba eruption at 74 ka BP (Invited)

NASA Astrophysics Data System (ADS)

Svensson, A.

2013-12-01

Acidity spikes in Greenland and Antarctic ice cores are applied as tracers of past volcanic activity. Besides providing information on the timing and magnitude of past eruptions, the acidity spikes are also widely used for synchronization of ice cores. All of the deep Greenland ice cores are thus synchronized throughout the last glacial cycle based on volcanic markers. Volcanic matching of ice cores from the two Hemispheres is much more challenging but it is feasible in periods of favourable conditions. Over the last two millennia, where ice cores are precisely dated, some 50 bipolar volcanic events have thus been identified. In order for an eruption to express a bipolar fingerprint it generally needs to be a low latitude eruption with stratospheric injection. Sometimes tephra is associated with the ice-core acidity spikes, but most often there is no tephra present in the ice. As yet, an unknown eruption occurring in 1259 AD is the only event reported to have deposited tephra in both Greenland and Antarctica. During the last glacial period bipolar volcanic matching is very challenging and very little work has been done, but recent high-resolution ice core records have the potential to provide bipolar ice core matching for some periods. Recently, Greenland and Antarctic ice cores have been linked by acidity spikes in the time window of the most recent eruption (the YTT eruption) of the Indonesian Toba volcano that is situated close to equator in Sumatra. Ash from this Toba event is widespread over large areas in Asia and has been identified as far west as Africa, but no corresponding tephra has been found in polar ice cores despite several attempts. The age of the YTT eruption is well constrained by recent Ar-Ar dating to have occurred some 74 ka ago close to the Marine Isotope Stage 4/5 boundary and close to the onset of the cold Greenland Stadial 20 and the corresponding mild Antarctic Isotopic Maxima 19 and 20. Surprisingly, no single outstanding acidity spike can be associated with the YTT Toba eruption in Greenland or Antarctica. Instead, several large bipolar ice cores acidity spikes are occurring within a couple of centuries at the time of the YTT eruption. To complicate matters, the intensity of those acidity spikes varies greatly from ice core to ice core. At this point, it is therefore impossible to relate the Toba eruption to a single event in the ice cores. Probably there have been several large low-latitude eruptions occurring close to the time of the YTT or the Toba volcano itself had multiple large eruptions within centuries. Bipolar volcanic matching allows for an estimation of the climatic impact of eruptions on a global scale. In the case of Toba, there must have been a global cooling following the enormous eruption, but unfortunately at this depth the resolution of the ice core temperature proxies does not allow for an identification of short term events (<100 yr). A significant warming event in Antarctica following the period associated with the YTT shows, however, that Toba did not initiate a long-term global cooling (>100 yr). At the time of YTT it appears that the inter-hemispheric climate variability is governed by the bipolar seesaw pattern that is active throughout most of the last glacial period. Still, it is intriguing that Toba occurs right at the time when Greenland and much of the northern Hemisphere enters its most extreme cold stadial of the last glacial period.

Initial Continuous Chemistry Results From The Roosevelt Island Ice Core (RICE)

NASA Astrophysics Data System (ADS)

Kjær, H. A.; Vallelonga, P. T.; Simonsen, M. F.; Neff, P. D.; Bertler, N. A. N.; Svensson, A.; Dahl-Jensen, D.

2014-12-01

The Roosevelt Island ice core (79.36° S, -161.71° W) was drilled in 2011-13 at the top of the Roosevelt Island ice dome, a location surrounded by the Ross ice shelf. The RICE ice core provides a unique opportunity to look into the past evolution of the West Antarctic Ice sheet. Further the site has high accumulation; 0.26 m of ice equivalent is deposited annually allowing annual layer determination for many chemical parameters. The RICE core was drilled to bedrock and has a total length of 763 metres. Preliminary results derived from water isotopes suggest that the oldest ice reaches back to the Eemian, with the last glacial being compressed in the bottom 60 metres. We present preliminary results from the RICE ice core including continuous measurements of acidity using an optical dye method, insoluble dust particles, conductivity and calcium. The core was analyzed at the New Zealand National Ice Core Research Facility at GNS Science in Wellington. The analytical set up used to determine climate proxies in the ice core was a modified version of the Copenhagen CFA system (Bigler et al., 2011). Key volcanic layers have been matched to those from the WAIS record (Sigl et al., 2013). A significant anti-correlation between acidity and calcium was seen in the Holocene part of the record. Due to the proximity to the ocean a large fraction of the calcium originates from sea salt and is in phase with total conductivity and sodium. In combination with the insoluble dust record, calcium has been apportioned into ocean-related and dust-related sources. Variability over the Holocene is presented and attributed to changing inputs of marine and dust aerosols.

Dry calving processes at the ice cliff of an antarctic local glacier: the study case of Strandline Glacier (Northern Victoria Land, Antarctica)

NASA Astrophysics Data System (ADS)

Smiraglia, C.; Motta, M.; Vassena, G.; Diolaiuti, G.

2003-04-01

In Antartic coastal area, where the ice sheet and the large outlet glaciers do not reach the sea and where some rugged mountain chains are often present, many small glaciers can be found. They are the so called local or alpine type glaciers, which have their terminus ground-based such as the real alpine glaciers and rarely reach the main valley floors. They are practically isolated and independent from the supply flowing down from the plateau and their mass balance is mainly controlled by sublimation and aeolic erosion and accumulation. The glaciers closer to the coast are submitted to the melting as well, and when the terminus is cliff-shaped they are also affected by dry calving. The most known and studied Antarctic local glaciers are placed in the Dry Valleys region (Chinn, 1985), but this kind of glaciers is also diffused all along the Northern Victoria Land coastal region (Chinn and others, 1989). Since the first Italian Antarctic expedition (1985), many studies have been carried out on this type of glaciers, which can be usefull for detailed mass balance evaluations and for obtaining information about the effects of the present climatic dynamics on the Antarctic coastal environment (Baroni and Orombelli, 1987; Baroni and others, 1995; Meneghel, 1999; Vassena and others., 2001). The Strandline Glacier (74 41 S; 164 07 E), in particular is a small alpine glacier (0,79 kmq) on the coast of Terra Nova Bay, Northern Victoria Land; it is a cold glacier where accumulation and ablation basins are mainly controlled by wind processes. Its terminus forms in the central part a grounded ice cliff about 30 m high, about 130 m far from the sea. On that glacier mass balance, surface velocity and calving rate were measured. During the southern summer season 2000-2001 many topographycal profiles of the ice cliff were surveyed by using both classical topographical and glaciological methods (total station and stakes) and GPS technique. It was so possible to detect the short term changes in ice cliff position (a retreat of 10 m in the central part of the front on 15 days) caused by crack propagation from the glacier surface and calving of ice flakes from the cliff face; during the warmest days also melting occurred along glacier surface and on the cliff. In the same period of 15 days ice thickness near the cliff boundary decreased about 30 cm. The collected measures regard also surface velocities and meteorological data . This work was carried out within the framework of the Project on Glaciology and Palaeoclimatology of the Programma Nazionale Ricerche in Antartide (PNRA), national co-ordinator Prof. G. Orombelli.

Response of alpine vegetation growth dynamics to snow cover phenology on the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wang, X.; Wu, C.

2017-12-01

Alpine vegetation plays a crucial role in global energy cycles with snow cover, an essential component of alpine land cover showing high sensitivity to climate change. The Tibetan Plateau (TP) has a typical alpine vegetation ecosystem and is rich of snow resources. With global warming, the snow of the TP has undergone significant changes that will inevitably affect the growth of alpine vegetation, but observed evidence of such interaction is limited. In particular, a comprehensive understanding of the responses of alpine vegetation growth to snow cover variability is still not well characterized on TP region. To investigate this, we calculated three indicators, the start (SOS) and length (LOS) of growing season, and the maximum of normalized difference vegetation index (NDVImax) as proxies of vegetation growth dynamics from the Moderate Resolution Imaging Spectroradiometer (MODIS) data for 2000-2015. Snow cover duration (SCD) and melt (SCM) dates were also extracted during the same time frame from the combination of MODIS and the Interactive Multi-sensor Snow and Ice Mapping System (IMS) data. We found that the snow cover phenology had a strong control on alpine vegetation growth dynamics. Furthermore, the responses of SOS, LOS and NDVImax to snow cover phenology varied among plant functional types, eco-geographical zones, and temperature and precipitation gradients. The alpine steppes showed a much stronger negative correlation between SOS and SCD, and also a more evidently positive relationship between LOS and SCD than other types, indicating a longer SCD would lead to an earlier SOS and longer LOS. Most areas showed positive correlation between SOS and SCM, while a contrary response was also found in the warm but drier areas. Both SCD and SCM showed positive correlations with NDVImax, but the relationship became weaker with the increase of precipitation. Our findings provided strong evidences between vegetation growth and snow cover phenology, and changes in snow cover should be also considered when analyzing alpine vegetation growth dynamics in future.

Visual-Stratigraphic Dating of the GISP2 Ice Core: Basis, Reproducibility, and Application

NASA Technical Reports Server (NTRS)

Alley, R. B.; Shuman, C. A.; Meese, D. A.; Gow, A. J.; Taylor, K. C.; Cuffey, K. M.; Fitzpatrick, J. J.; Grootes, P. M.; Zielinski, G. A.; Ram, M.;

Visual-stratigraphic dating of the GISP2 ice core: Basis, reproducibility, and application

NASA Astrophysics Data System (ADS)

Alley, R. B.; Shuman, C. A.; Meese, D. A.; Gow, A. J.; Taylor, K. C.; Cuffey, K. M.; Fitzpatrick, J. J.; Grootes, P. M.; Zielinski, G. A.; Ram, M.; Spinelli, G.; Elder, B.

1997-11-01

Annual layers are visible in the Greenland Ice Sheet Project 2 ice core from central Greenland, allowing rapid dating of the core. Changes in bubble and grain structure caused by near-surface, primarily summertime formation of hoar complexes provide the main visible annual marker in the Holocene, and changes in "cloudiness" of the ice correlated with dustiness mark Wisconsinan annual cycles; both markers are evident and have been intercalibrated in early Holocene ice. Layer counts are reproducible between different workers and for one worker at different times, with 1% error over century-length times in the Holocene. Reproducibility is typically 5% in Wisconsinan ice-age ice and decreases with increasing age and depth. Cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50,000 years. Visible observations are not greatly degraded by "brittle ice" or many other core-quality problems, allowing construction of long, consistently sampled time series. High accuracy requires careful study of the core by dedicated observers.

The design and performance of IceCube DeepCore

NASA Astrophysics Data System (ADS)

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Allen, M. M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brown, A. M.; Buitink, S.; Caballero-Mora, K. S.; Carson, M.; Chirkin, D.; Christy, B.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; Cruz Silva, A. H.; D'Agostino, M. V.; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; Degner, T.; Demirörs, L.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Dunkman, M.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Góra, D.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, B.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kroll, G.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lünemann, J.; Madsen, J.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Panknin, S.; Paul, L.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Rodrigues, J. P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schmidt, T.; Schönwald, A.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Stüer, M.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Zoll, M.

2012-05-01

The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

The Design and Performance of IceCube DeepCore

NASA Technical Reports Server (NTRS)

Stamatikos, M.

2012-01-01

The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking pbysics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

Recent Increases in Snow Accumulation and Decreases in Sea-Ice Concentration Recorded in a Coastal NW Greenland Ice Core

NASA Astrophysics Data System (ADS)

Osterberg, E. C.; Thompson, J. T.; Wong, G. J.; Hawley, R. L.; Kelly, M. A.; Lutz, E.; Howley, J.; Ferris, D. G.

2013-12-01

A significant rise in summer temperatures over the past several decades has led to widespread retreat of the Greenland Ice Sheet (GIS) margin and surrounding sea ice. Recent observations from geodetic stations and GRACE show that ice mass loss progressed from South Greenland up to Northwest Greenland by 2005 (Khan et al., 2010). Observations from meteorological stations at the U.S. Thule Air Force Base, remote sensing platforms, and climate reanalyses indicate a 3.5C mean annual warming in the Thule region and a 44% decrease in summer (JJAS) sea-ice concentrations in Baffin Bay from 1980-2010. Mean annual precipitation near Thule increased by 12% over this interval, with the majority of the increase occurring in fall (SON). To improve projections of future ice loss and sea-level rise in a warming climate, we are currently developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate variability and cryospheric response in NW Greenland, with a focus on past warm periods. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 20 m) from the coastal region of the GIS (2Barrel site; 76.9317 N, 63.1467 W) and the summit of North Ice Cap (76.938 N, 67.671 W) in 2011 and 2012, respectively. The 2Barrel ice core was sampled using a continuous ice core melting system at Dartmouth, and subsequently analyzed for major anion and trace element concentrations and stable water isotope ratios. Here we show that the 2Barrel ice core spanning 1990-2010 records a 25% increase in mean annual snow accumulation, and is positively correlated (r = 0.52, p<0.01) with ERA-Interim precipitation. The 2Barrel annual sea-salt Na concentration is strongly correlated (r = 0.5-0.8, p<0.05) with summer and fall sea-ice concentrations in northern Baffin Bay near Thule (Figure 1). We hypothesize that the positive correlation represents a significant Na contribution from frost flowers growing on fall frazil ice. Ongoing analyses will evaluate the relationship between MSA concentrations and sea ice extent. Our results show that a deep ice core collected from this dynamic and climate-sensitive region of NW Greenland would produce a valuable record of late Holocene climate and sea ice extent.

Rapid changes in ice core gas records - Part 1: On the accuracy of methane synchronisation of ice cores

NASA Astrophysics Data System (ADS)

Köhler, P.

2010-08-01

Methane synchronisation is a concept to align ice core records during rapid climate changes of the Dansgaard/Oeschger (D/O) events onto a common age scale. However, atmospheric gases are recorded in ice cores with a log-normal-shaped age distribution probability density function, whose exact shape depends mainly on the accumulation rate on the drilling site. This age distribution effectively shifts the mid-transition points of rapid changes in CH4 measured in situ in ice by about 58% of the width of the age distribution with respect to the atmospheric signal. A minimum dating uncertainty, or artefact, in the CH4 synchronisation is therefore embedded in the concept itself, which was not accounted for in previous error estimates. This synchronisation artefact between Greenland and Antarctic ice cores is for GRIP and Byrd less than 40 years, well within the dating uncertainty of CH4, and therefore does not calls the overall concept of the bipolar seesaw into question. However, if the EPICA Dome C ice core is aligned via CH4 to NGRIP this synchronisation artefact is in the most recent unified ice core age scale (Lemieux-Dudon et al., 2010) for LGM climate conditions of the order of three centuries and might need consideration in future gas chronologies.

IceChrono v1: a probabilistic model to compute a common and optimal chronology for several ice cores

NASA Astrophysics Data System (ADS)

Parrenin, Frédéric

2015-04-01

Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores is essential to interpret the paleo records that they contain, but it is a complicated problem since it involves different dating methods. Here I present IceChrono v1, a new probabilistic model to combine different kinds of chronological information to obtain a common and optimized chronology for several ice cores, as well as its uncertainty. It is based on the inversion of three quantities: the surface accumulation rate, the Lock-In Depth (LID) of air bubbles and the vertical thinning function. The chronological information used are: models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice and gas dated horizons, ice and gas dated depth intervals, Δdepth observations (depth shift between synchronous events recorded in the ice and in the air), stratigraphic links in between ice cores (ice-ice, air-air or mix ice-air and air-ice links). The optimization problem is formulated as a least squares problems, that is, all densities of probabilities are assumed gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono is similar in scope to the Datice model, but has differences from the mathematical, numerical and programming point of views. I apply IceChrono on an AICC2012-like experiment and I find similar results than Datice within a few centuries, which is a confirmation of both IceChrono and Datice codes. IceChrono v1 is freely available under the GPL v3 open source license.

BrGDGT-based quantitative temperature reconstruction over the past 2000 years from an alpine lake in subtropical southwestern China

NASA Astrophysics Data System (ADS)

Zhao, C.; Feng, X.

2017-12-01

BrGDGTs have been proposed as a proxy for quantitative paleotemperature reconstructions in terrestrial environment, and numerous transfer functions have been framed based on modern soils and lake sediments. However, these spatial-based functions have been seldom successful for paleotemperature reconstructions in lake sediments. In this study, we report a quantitative temperature record over the past 2000 years, using a temporal-based transfer function inferred from branched GDGTs from a sediment core collected at a small alpine lake (Tiancai lake, 26°38'E, 99°43'N, 3898 m asl) in a remote location in subtropical southwestern China. The chronology is established by both 210Pb and AMS-14C dating methods. We find a significant correlation between brGDGT distributions and instrumental mean annual air temperature (MAAT) (R2=0.902, p<0.0001) over the past 60 years. We then establish a local instrumental calibration and apply it to the entire core for MAAT reconstruction over the past 2000 years. Our preliminary results show the reconstructed MAAT varies between -0.77 and 4.13° over the past 2000 years. Our data indicate four warm intervals at 20-142AD, 321-578AD, 796-1215AD and after 1940AD, and four cold intervals at 158-321AD, 550-657AD, 1500-1727AD, 1810-1912AD. The warm period at 796-1215AD and the cold period at 1500-1727AD are likely corresponding with the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA), respectively, which is consistent with published data in northern China and the northern Hemisphere. Our preliminary result indicates that this temporal-based calibration could be more practical in some environmental-stable open lakes, and also suggests coherent temperature changes in the subtropical and high-latitude northern hemisphere over the past 2000 years.

Determination of lead isotopes in a new Greenland deep ice core at the sub-picogram per gram level by thermal ionization mass spectrometry using an improved decontamination method.

PubMed

Han, Changhee; Burn-Nunes, Laurie J; Lee, Khanghyun; Chang, Chaewon; Kang, Jung-Ho; Han, Yeongcheol; Hur, Soon Do; Hong, Sungmin

2015-08-01

An improved decontamination method and ultraclean analytical procedures have been developed to minimize Pb contamination of processed glacial ice cores and to achieve reliable determination of Pb isotopes in North Greenland Eemian Ice Drilling (NEEM) deep ice core sections with concentrations at the sub-picogram per gram level. A PL-7 (Fuso Chemical) silica-gel activator has replaced the previously used colloidal silica activator produced by Merck and has been shown to provide sufficiently enhanced ion beam intensity for Pb isotope analysis for a few tens of picograms of Pb. Considering the quantities of Pb contained in the NEEM Greenland ice core and a sample weight of 10 g used for the analysis, the blank contribution from the sample treatment was observed to be negligible. The decontamination and analysis of the artificial ice cores and selected NEEM Greenland ice core sections confirmed the cleanliness and effectiveness of the overall analytical process. Copyright © 2015 Elsevier B.V. All rights reserved.

On the use of δ18Oatm for ice core dating

NASA Astrophysics Data System (ADS)

Extier, Thomas; Landais, Amaelle; Bréant, Camille; Prié, Frédéric; Bazin, Lucie; Dreyfus, Gabrielle; Roche, Didier M.; Leuenberger, Markus

2018-04-01

Deep ice core chronologies have been improved over the past years through the addition of new age constraints. However, dating methods are still associated with large uncertainties for ice cores from the East Antarctic plateau where layer counting is not possible. Indeed, an uncertainty up to 6 ka is associated with AICC2012 chronology of EPICA Dome C (EDC) ice core, which mostly arises from uncertainty on the delay between changes recorded in δ18Oatm and in June 21st insolation variations at 65°N used for ice core orbital dating. Consequently, we need to enhance the knowledge of this delay to improve ice core chronologies. We present new high-resolution EDC δ18Oatm record (153-374 ka) and δO2/N2 measurements (163-332 ka) performed on well-stored ice to provide continuous records of δ18Oatm and δO2/N2 between 100 and 800 ka. The comparison of δ18Oatm with the δ18Ocalcite from East Asian speleothems shows that both signals present similar orbital and millennial variabilities, which may represent shifts in the InterTropical Convergence Zone position, themselves associated with Heinrich events. We thus propose to use the δ18Ocalcite as target for δ18Oatm orbital dating. Such a tuning method improves the ice core chronology of the last glacial inception compared to AICC2012 by reconciling NGRIP and mid-latitude climatic records. It is especially marked during Dansgaard-Oeschger 25 where the proposed chronology is 2.2 ka older than AICC2012. This δ18Oatm - δ18Ocalcite alignment method applied between 100 and 640 ka improves the EDC ice core chronology, especially over MIS 11, and leads to lower ice age uncertainties compared to AICC2012.

Dust Records in Ice Cores from the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wang, N.; Yao, T.; Thompson, L. G.

2014-12-01

Dust plays an important role in the Earth system, and it usually displays largely spatial and temporal variations. It is necessary for us to reconstruct the past variations of dust in different regions to better understand the interactions between dust and environments. Ice core records can reveal the history of dust variations. In this paper, we used the Guliya, Dunde, Malan and Dasuopu ice cores from the Tibetan Plateau to study the spatial distribution, the seasonal variations and the secular trends of dust. It was found that the mean dust concentration was higher by one or two order of magnitudes in the Guliya and Dunde ice cores from the northern Tibetan Plateau than in the Dasuopu ice core from the southern Tibetan Plateau. During the year, the highest dust concentration occurs in the springtime in the northern Tibetan Plateau while in the non-monsoon season in the southern Tibetan Plateau. Over the last millennium, the Dasuopu ice core record shows that the 1270s~1380s and 1870s~1990s were the two epochs with high dust concentration. However, the Malan ice core from the northern Tibetan Plateau indicates that high dust concentration occurred in the 1130s~1550s and 1770s~1940s. Interestingly, climatic and environmental records of the ice cores from the Tibetan Plateau reflected that the correlation between dust concentration and air temperature was strongly positive in the southern Plateau while negative in the northern Plateau over the last millennium. This implies that climatic and environmental changes existed considerable differences in the different parts of the Plateau. Moreover, four Asian megadroughts occurred in 1638~1641, 1756~1758, 1790~1796 and 1876~1878, which caused more than tens millions people died, were revealed clearly by dust record in the Dasuopu ice core.

Experimental simulation of frost wedging-induced crack propagation in alpine rockwall

NASA Astrophysics Data System (ADS)

Jia, Hailiang; Leith, Kerry; Krautblatter, Michael

2016-04-01

Frost wedging is widely presumed to be the principal mechanism responsible for shattering jointed low-porosity rocks in high alpine rockwalls. The interaction of ice and rock physics regulates the efficacy of frost wedging. In order to better understand temporal aspects of this interaction, we present results of a series of laboratory experiments monitoring crack widening as a result of ice formation in an artificial crack (4mm wide, 80mm deep) cut 20 mm from the end of a rectangular granite block. Our results indicate that i) freezing direction plays a key role in determining the magnitude of crack widening; in short-term (1 day) experiments, maximum crack widening during top-down freezing (associated with 'autumn' conditions) was around 0.11mm, while inside-out freezing (resulting from 'spring' conditions) produced only 0.02 mm of deformation; ii) neither ice, nor water pressure (direct tension and hydraulic fracturing respectively) caused measurable irreversible crack widening during short-term tests, as the calculated maximum stress intensity at the crack tip was less than the fracture toughness of our granite sample; iii) development of ice pressure is closely related to the mechanical properties of the fracture in which it forms, and as such, the interaction of ice and rock is intrinsically dynamic; iv) irreversible crack widening (about 0.03mm) was only observed following a long-term (53 day) experiment representing a simplified transition from autumn to winter conditions. We suggest this is the result of stress corrosion aided by strong opening during freezing, and to a lesser degree by ice segregation up to one week after the initial freezing period, and downward migration of liquid water during the remainder of the test. Our results suggest the fundamental assumption of frost wedging, that rapid freezing from open ends of cracks can seal water inside the crack and thus cause damage through excessive stresses induced by volumetric expansion seems questionable.

WISDOM GPR Investigations of Ice Thickness, Stratigraphy, Structure, and Basal Topography in an Alpine Ice Cave in Dachstein, Austria

NASA Astrophysics Data System (ADS)

Clifford, S. M.; Plettemeier, D.; Dorizon, S.; Lustrement, B.; Humeau, O.; Hassen-Khodja, R.; Galic, A.; Ciarletti, V.

2012-12-01

The WISDOM GPR is one of the instruments that have been selected as part of the Pasteur payload of ESA's 2018 ExoMars Rover mission. WISDOM will remotely characterize the shallow subsurface (top ~2-3 m) of Mars, with a vertical resolution of several centimeters, providing information essential to understanding the local geological context and identifying the best locations for obtaining subsurface samples with the Rover's onboard drill. The geoelectrical properties of H2O make WISDOM a particularly powerful tool for investigating the local distribution and state of subsurface H2O, including the potential presence of segregated ground ice and the persistent or transient occurrence of liquid water/brine. WISDOM prototypes, representative of the final flight model, are currently being field tested in various Mars analogue and cold-climate environments. In April of this year, members of the WISDOM team brought two development prototypes to an Alpine ice cave in Dachstein, Austria, to field test the instrument and participate in the Mars Simulation organized by the Austrian Space Forum. 2- and 3-D profiles were obtained of the icy interior of the cave utilizing the radars mounted on three different platforms: a manually operated cart, the radio-controlled 'Magma White' rover (developed and operated by a Polish team from ABM Space Education), and a cliffbot (developed and operated by the French Planète Mars Association). Radar investigations were conducted in four different cave environments, measuring ice thickness, stratigraphy, fracture geometry, and basal topography. Because of variations in fracture width, density and orientation, determining fracture geometry proved to be the most challenging of these four tasks. Radar-derived 2- and 3-D reconstructions of the internal characteristics of the ice deposits and cave floor were in agreement with those determined by direct observation and previously obtained with commercial GPRs.

Initial results from geophysical surveys and shallow coring of the Northeast Greenland Ice Stream (NEGIS)

NASA Astrophysics Data System (ADS)

Vallelonga, P.; Christianson, K.; Alley, R. B.; Anandakrishnan, S.; Christian, J. E. M.; Dahl-Jensen, D.; Gkinis, V.; Holme, C.; Jacobel, R. W.; Karlsson, N. B.; Keisling, B. A.; Kipfstuhl, S.; Kjær, H. A.; Kristensen, M. E. L.; Muto, A.; Peters, L. E.; Popp, T.; Riverman, K. L.; Svensson, A. M.; Tibuleac, C.; Vinther, B. M.; Weng, Y.; Winstrup, M.

2014-07-01

The Northeast Greenland Ice Stream (NEGIS) is the sole interior Greenlandic ice stream. Fast flow initiates near the summit dome, and the ice stream terminates approximately 1000 km downstream in three large outlet glaciers that calve into the Greenland Sea. To better understand this important system, in the summer of 2012 we drilled a 67 m firn core and conducted ground-based radio-echo sounding (RES) and active-source seismic surveys at a site approximately 150 km downstream from the onset of streaming flow (NEGIS firn core, 75°37.61' N, 35°56.49' W). The site is representative of the upper part of the ice stream, while also being in a crevasse-free area for safe surface operations. Annual cycles were observed for insoluble dust, sodium and ammonium concentrations and for electrolytic conductivity, allowing a seasonally resolved chronology covering the past 400 yr. Annual layer thicknesses averaged 0.11 m ice equivalent (i.e.) for the period 1607-2011, although accumulation varied between 0.08 and 0.14 m i.e., likely due to flow-related changes in surface topography. Tracing of RES layers from the NGRIP (North Greenland Ice Core Project) ice core site shows that the ice at NEGIS preserves a climatic record of at least the past 51 kyr. We demonstrate that deep ice core drilling in this location can provide a reliable Holocene and late-glacial climate record, as well as helping to constrain the past dynamics and ice-lithosphere interactions of the Greenland Ice Sheet.

1500 Years of Annual Climate and Environmental Variability as Recorded in Bona-Churchill (Alaska) Ice Cores

NASA Astrophysics Data System (ADS)

Thompson, L. G.; Mosley-Thompson, E. S.; Zagorodnov, V.; Davis, M. E.; Mashiotta, T. A.; Lin, P.

2004-12-01

In 2003, six ice cores measuring 10.5, 11.5, 11.8, 12.4, 114 and 460 meters were recovered from the col between Mount Bona and Mount Churchill (61° 24'N; 141° 42'W; 4420 m asl). These cores have been analyzed for stable isotopic ratios, insoluble dust content and concentrations of major chemical species. Total Beta radioactivity was measured in the upper sections. The 460-meter core, extending to bedrock, captured the entire depositional record at this site where ice temperatures ranged from -24° C at 10 meters to -19.8° C at the ice/bedrock contact. The shallow cores allow assessment of surface processes under modern meteorological conditions while the deep core offers a ˜1500-year climate and environmental perspective. The average annual net balance is ˜~1000 mm of water equivalent and distinct annual signals in dust and calcium concentrations along with δ 18O allow annual resolution over most of the core. The excess sulfate record reflects many known large volcanic eruptions such as Katmai, Krakatau, Tambora, and Laki which allow validation of the time scale in the upper part of the core. The lower part of the core yields a history of earlier volcanic events. The 460-m Bona-Churchill ice core provides a detailed history of the `Little Ice Age' and medieval warm periods for southeastern Alaska. The source of the White River Ash will be discussed in light of the evidence from this core. The 460-m core also provides a long-term history of the dust fall that originates in north-central China. The annual ice core-derived climate records from southeastern Alaska will facilitate an investigation of the likelihood that the high resolution 1500-year record from the tropical Quelccaya Ice Cap (Peru) preserves a history of the variability of both the PDO and the Aleutian Low.

Dating of 30m ice cores drilled by Japanese Antarctic Research Expedition and environmental change study

NASA Astrophysics Data System (ADS)

Motoyama, H.; Suzuki, T.; Fukui, K.; Ohno, H.; Hoshina, Y.; Hirabayashi, M.; Fujita, S.

2017-12-01

1. Introduction It is possible to reveal the past climate and environmental change from the ice core drilled in polar ice sheet and glaciers. The 54th Japanese Antarctic Research Expedition conducted several shallow core drillings up to 30 m depth in the inland and coastal areas of the East Antarctic ice sheet. Ice core sample was cut out at a thickness of about 5 cm in the cold room of the National Institute of Polar Research, and analyzed ion, water isotope, dust and so one. We also conducted dielectric profile measurement (DEP measurement). The age as a key layer of large-scale volcanic explosion was based on Sigl et al. (Nature Climate Change, 2014). 2. Inland ice core Ice cores were collected at the NDF site (77°47'14"S, 39°03'34"E, 3754 m.a.s.l.) and S80 site (80°00'00"S, 40°30'04"E, 3622 m.a.s.l.). Dating of ice core was done as follows. Calculate water equivalent from core density. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. We determined the key layer with nssSO42 - peak corresponding to several large volcanic explosions. The accumulation rate was kept constant between the key layers. As a result, NDF was estimated to be around 1360 AD and S80 was estimated to be around 1400 AD in the deepest ice core. 3. Coastal ice core An ice core was collected at coastal H15 sites (69°04'10"S, 40°44'51"E, 1030 m.a.s.l.). Dating of ice core was done as follows. Calculate water equivalent from ice core density. Accumulate water equivalent from the surface. Approximate the relation of depth - cumulative water equivalent by a quartic equation. Basically we decided to summer (December) and winter (June) due to the seasonal change of the water isotope (δD or δ18O). In addition to the seasonal change of isotope, confirm the following. Maximum of SO42- / Na +, which is earlier in time than the maximum of water isotope. Maximum of MSA at about the same time as the maximum of the water isotope. Na+ is maximal immediately after the local maximum of the water isotope. The deepest age was estimated to be around 1940 AD. 4. Example of results In the inland area, the annual average surface mass balance decreased from 1450 to 1850 AD, but it has increased since 1850 AD. The annual mass balance of coastal H15 is consistent with the result of snow stake measurement.

Chemistry of microparticles trapped in last glacial period ice of EPICA-DML deep ice core

NASA Astrophysics Data System (ADS)

Nedelcu, Aneta F.; Faria, Sérgio H.; Kipfstuhl, Sepp; Kuhs, Werner F.

2010-05-01

The EDML ice core, drilled within the framework of the European project for Ice Coring in Antarctica, (EPICA), in the interior of Dronning Maud Land, DML, Antarctica (at 75°S, 0°E), is the first deep ice core in the Atlantic sector of the Southern Ocean region that provides higher-resolution atmosphere and climate records for the last glacial period, when compared with other ice cores retrieved from the East Antarctic plateau [1]. The chemical impurities embedded in the ice matrix of an ice sheet are basic proxies for climate reconstruction, and their concentration and composition usually determine the occurrence of distinct (cloudy or clear) strata in the ice sheet structure. The easiest observable impurities in polar ice are air bubbles. But a considerable amount of the impurities trapped inside ice layers are observed as microscopic deposits of solid (soluble or insoluble) particles, not bigger than a few micra in size, called microinclusions. Layers of ice with a high content of (micro)inclusions are in general called cloudy bands and are considered to have been formed from the precipitations deposited during colder periods. Roughly, we expect that the colder the climate during the time the snow accumulated, the cloudier the ice stratum that forms afterwards [2]. Mainly by means of in-situ micro-Raman spectroscopy, it has been shown that in Antarctic glacial ice the soluble microinclusions occur mostly as sulphate and nitrate salts [3], while in Arctic ice more commonly as carbonate salts [4]. These findings could be explained in terms of different aerosol compositions determined by the specific regional environments and climatic conditions [5]. Regarding the insoluble particles that might exist in natural ice, with higher frequency in ice layers formed during glacial type stages, the general findings classify them in the (alumino)silicate mineralogical class [6]. Microinclusions existent in solid samples taken from clear and cloudy ice layers, corresponding to the Marine Isotope Stage 2 of the EDML deep ice core, were subjected to in-situ Raman scattering measurements. The overall results [7] resemble the observations [8] that a high content of sulphate anions could characterize the chemical composition of the aerosols arriving at the EDML ice core drilling site. Many microparticles provided a Raman signal different from what would be expected if only simple compounds were forming them (and dissimilar with those in [3]). For example, it resulted that in the same microinclusion nonequivalent sulphate groups are present (20% of all), or that sulphate and silicate anions coexist (10% of all). On the one hand, this can be explained by a simple post-depositional aggregation of very small inclusions of simple sulphate salts into microclusters. On the other hand the results might be interpreted in terms of aerosol chemistry, when a mixture of sulphate salts could have been already formed prior to deposition. This work will offer answers for questions related with the existence of a post-depositional alteration of the initial impurities deposited in the LGP ice at the EDML ice core drilling site. [1] EPICA community members (2006). One-to-one coupling of glacial climate variability in Greenland and Antarctica, Nature, 444, 195-198. [2] Faria, S.H., Freitag, J., Kipfstuhl, S. (2010) Polar ice structure and the integrity of ice-core paleoclimate records, Quaternary Sci. Rev., 29, 1-2, 338-351. [3] Ohno H., M. Igarashi, T. Hondoh. 2005. Salt inclusions in polar ice core: Location and chemical form of water-soluble impurities, Earth Planet.Sci. Lett., 232, 171-178. [4] Sakurai T., Iizuka Y., Horikawa S., Johnsen S., Dahl-Jensen D., Steffensen J.P., Hondoh T. (2009). Direct observation of salts as micro-inclusions in the Greenland GRIP ice core. J. Glaciol., 55, 193, 777-783. [5] Iizuka Y., Horikawa S., Sakurai T., Johnson S, Dahl-Jensen D., Steffensen J.P., Hondoh T. (2008). A relationship between ion balance and the chemical compounds of salt inclusions found in the Greenland Ice Core Project and Dome Fuji ice cores. J. Geophys. Res., 113, D7, D07303. [6] Iizuka, Y., Miyake T., Hirabayashi M., Suzuki T., Matoba S., Motoyama H., Fujii Y., Hondoh T. (2009). Constituent elements of insoluble and non-volatile particles during the Last Glacial Maximum exhibited in the Dome Fuji (Antarctica) ice core. J. Glaciol., 55, 191, 552-562. [7] Nedelcu A.F., Kipfstuhl S., Faria S.H., Kuhs W.F. Microinclusions in clear and cloudy (MIS2) EDML ice revealed by Raman spectroscopy. In preparation for J. Glaciol. [8] Weller R., Wagenbach D. (2007) Year-round chemical aerosol records in continental Antarctica obtained by automatic samplings. Tellus 59, 755-765.

Cool Science Explains a Warming World: Using Ice Core Science to Bridge the Gap Between Researchers and the K-12 Classroom

NASA Astrophysics Data System (ADS)

Huffman, L. T.

2017-12-01

Changing ice has urgent implications for people around the world. The Ice Drilling Program Office (IDPO) provides scientific leadership and oversight of ice coring and drilling activities funded by the US National Science Foundation and also has goals to enhance education and communication of current research information. In a time when misinformation is rampant and climate change science is suspect, it is essential that students receive accurate scientific information and engage in learning activities that model complex ideas through engaging and age appropriate ways, while also learning to validate and recognize reliable sources. The IDPO Education and Outreach (EO) office works to create resources, activities and professional development that bridge the gap between ice core science research and educators and their students. Ice core science is on the cutting edge of new discoveries about climate change and understanding better the past to predict the future. Hands-on inquiry activities based on ice core data allow teachers to lead their students to new discoveries about climate secrets hidden deep in the ice. Capitalizing on the inherent interest in the extremes of the Polar Regions, IDPO materials engage students in activities aligned with NGSS standards. Ice drilling technologies make an ideal platform for intertwining engineering concepts and practices with science research to meet the SEP (Science and Engineering Practices) in the NGSS. This session will highlight how the IDPO EO office has built a community of ice core scientists willing to take part in education and outreach projects and events and share some of the resources available to K-12 educators. We will highlight some of the successes and lessons learned as we continually evolve our work toward more effective science education and communication highlighting ice core and climate change science.

Isotopic Composition of the Neolithic Alpine Iceman's Tooth Enamel and Clues to his Origin

NASA Astrophysics Data System (ADS)

Muller, W.; Muller, W.; Halliday, A. N.

2001-12-01

Five small enamel fragments from three teeth of the upper right jaw from the mummy of the Neolithic Alpine Iceman have been investigated for their isotopic composition in order to shed light on his geographic origins. Soils from approximately contemporaneous sites were sampled for comparison. Tooth enamel forms ontogenetically very early and is not re-mineralized during later lifetime (unlike with bone material). Therefore, unique insights into the Iceman's childhood can be acquired. Enamel also is the densest tissue of a human body and is thus less susceptible to post-mortem alteration. Both radiogenic (Sr, Pb, Nd) and stable isotopes (O, C) are investigated. Radiogenic isotopes allow reconstruction of the local geological background, because humans incorporate Sr, Pb and Nd from their local environment by eating local food. Stable isotopes provide information about altitude and/or position relative to the main Alpine watershed. High spatial-resolution laser-ablation ICPMS profiles reveal that most elements are distributed in a manner that is essentially similar to modern human teeth except of that La, Ce, Nd (LREE) show up to a 100-fold enrichment towards the outer enamel surface. These uptake-profiles may reflect interaction with melt water, consistent with data for the composition of samples of the Iceman's skin. Biogenic apatites (enamel, bone) have very low in-vivo LREE concentrations, but take up LREEs post-mortem from the burial environment. Ice core samples from the finding site show concentrations up to 400 ppt Ce. Such high uptake of the LREEs precludes the derivation of an in-vivo Nd isotopic signal, but both other radiogenic tracers, Sr and Pb, show pristine (in-vivo) concentrations of 87 ppm and 0.1 ppm, respectively. Strontium isotopic compositions were determined on fragments from the canine, the first and second premolar (1 - 9 mg) and two hip bone samples, utilizing three sequential leaching steps for each sample to detect possible alteration-related disturbance. Enamel fragments from three teeth are characterized by virtually similar and high 87Sr/^{86}Sr ratios of 0.7203-0.7206, consistent with the compositions of crystalline gneisses and schists close to the finding site. Sites overlying bedrock built up by limestone from further south or north can clearly be excluded as the Iceman's childhood area. Among the three teeth, enamel mineralized approximately during a 2-3 year interval starting with the canine at the age of ~2 years. Hence, during this period, the food source for the Iceman must have remained essentially constant. Two compact bone samples from the damaged hip region have 87Sr/^{86}Sr ratios of 0.7175 and 0.7181, significantly lower than that of the enamel. The internal variation in the Iceman's bone Sr isotopic composition argues for somewhat different Sr turnover times within the skeleton, but it is evident that during the last 1-3 decades of his life, food from a different region was utilized. The 87Sr/^{86}Sr ratios of the initial bone leachates point towards post-mortem alteration with water having 87Sr/^{86}Sr ratios higher than ~0.718, consistent with that measured for contemporaneous ice samples (0.720-0.723). These Sr isotopic variations among ice samples may have implications for the post depositional (climate) history of the Iceman's finding site, since it appears unlikely that substantial compositional differences among adjacent ice samples would be preserved if the site had thawed near completely during e.g. the Roman warm period.

Technical Note: Seasonality in alpine water resources management - a regional assessment

NASA Astrophysics Data System (ADS)

Vanham, D.; Fleischhacker, E.; Rauch, W.

2008-01-01

Alpine regions are particularly affected by seasonal variations in water demand and water availability. Especially the winter period is critical from an operational point of view, as being characterised by high water demands due to tourism and low water availability due to the temporal storage of precipitation as snow and ice. The clear definition of summer and winter periods is thus an essential prerequisite for water resource management in alpine regions. This paper presents a GIS-based multi criteria method to determine the winter season. A snow cover duration dataset serves as basis for this analysis. Different water demand stakeholders, the alpine hydrology and the present day water supply infrastructure are taken into account. Technical snow-making and (winter) tourism were identified as the two major seasonal water demand stakeholders in the study area, which is the Kitzbueheler region in the Austrian Alps. Based upon different geographical datasets winter was defined as the period from December to March, and summer as the period from April to November. By determining potential regional water balance deficits or surpluses in the present day situation and in future, important management decisions such as water storage and allocation can be made and transposed to the local level.

Towards multi-decadal to multi-millennial ice core records from coastal west Greenland ice caps

NASA Astrophysics Data System (ADS)

Das, Sarah B.; Osman, Matthew B.; Trusel, Luke D.; McConnell, Joseph R.; Smith, Ben E.; Evans, Matthew J.; Frey, Karen E.; Arienzo, Monica; Chellman, Nathan

2017-04-01

The Arctic region, and Greenland in particular, is undergoing dramatic change as characterized by atmospheric warming, decreasing sea ice, shifting ocean circulation patterns, and rapid ice sheet mass loss, but longer records are needed to put these changes into context. Ice core records from the Greenland ice sheet have yielded invaluable insight into past climate change both regionally and globally, and provided important constraints on past surface mass balance more directly, but these ice cores are most often from the interior ice sheet accumulation zone, at high altitude and hundreds of kilometers from the coast. Coastal ice caps, situated around the margins of Greenland, have the potential to provide novel high-resolution records of local and regional maritime climate and sea surface conditions, as well as contemporaneous glaciological changes (such as accumulation and surface melt history). But obtaining these records is extremely challenging. Most of these ice caps are unexplored, and thus their thickness, age, stratigraphy, and utility as sites of new and unique paleoclimate records is largely unknown. Access is severely limited due to their high altitude, steep relief, small surface area, and inclement weather. Furthermore, their relatively low elevation and marine moderated climate can contribute to significant surface melting and degradation of the ice stratigraphy. We recently targeted areas near the Disko Bay region of central west Greenland where maritime ice caps are prevalent but unsampled, as potential sites for new multi-decadal to multi-millennial ice core records. In 2014 & 2015 we identified two promising ice caps, one on Disko Island (1250 m. asl) and one on Nuussuaq Peninsula (1980 m. asl) based on airborne and ground-based geophysical observations and physical and glaciochemical stratigraphy from shallow firn cores. In spring 2015 we collected ice cores at both sites using the Badger-Eclipse electromechanical drill, transported by a medley of small fixed wing and helicopter aircraft, and working out of small tent camps. On Disko Island, despite high accumulation rates and ice thickness of 250 meters, drilling was halted twice due to the encounter of liquid water at depths ranging from 18-20 meters, limiting the depth of the final core to 21 m, providing a multi-decadal record (1980-2015.) On Nuussuaq Peninsula, we collected a 138 m ice core, almost to bedrock, representing a 2500 year record. The ice cores were subsequently analyzed using a continuous flow analysis system (CFA). Age-depth profiles and accumulation histories were determined by combining annual layer counting and an ice flow thinning model, both constrained by glaciochemical tie points to other well-dated Greenland ice core records (e.g. volcanic horizons and continuous heavy metal records). Here we will briefly provide an overview of the project and the new sites, and the novel dating methodology, and describe the latest stratigraphic, isotopic and glaciochemical results. We will also provide a particular focus on new regional climatological insight gained from our records during three climatically sensitive time periods: the late 20th & early 21st centuries; the Little Ice Age; and the Medieval Climate Anomaly.

Ice Core Investigations

ERIC Educational Resources Information Center

Krim, Jessica; Brody, Michael

2008-01-01

What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

Microshear in the deep EDML ice core analyzed using cryogenic EBSD

NASA Astrophysics Data System (ADS)

Kuiper, Ernst-Jan; Pennock, Gill; Drury, Martyn; Kipfstuhl, Sepp; Faria, Sérgio; Weikusat, Ilka

2017-04-01

Ice sheets play an important role in sea level evolution by storing large amounts of fresh water on land. The ice in an ice sheet flows from the interior of the ice sheet to the edges where it either melts or calves into the ocean. This flow of ice results from internal deformation of the ice aggregate. Dislocation creep is assumed to be the dominant deformation mechanism for polar ice and is grain size insensitive. Recently, a different deformation mechanism was identified in the deeper part of the EDML ice core (Antarctica) where, at a depth of 2385 meters, the grain size strongly decreases, the grain aspect ratio increase and, the inclination of the grain elongation changes (Faria et al., 2006; Weikusat et al., 2017). At this depth the borehole displacement increases strongly (Weikusat et al., 2017), which indicates a relatively high strain rate. Part of this EDML ice core section was studied using cryogenic electron backscattered diffraction (cryo-EBSD) (Weikusat et al, 2011). EBSD produces high resolution, full crystallographic (a-axis and c-axis) maps of the ice core samples. EBSD samples were taken from an ice core section at 2392.2 meter depth. This section was chosen for its very small grain size and the strongly aligned grain boundaries. The EBSD maps show a very low orientation gradient of <0.3° per millimetre inside the grains, which is 5-10 times lower than the orientation gradients found in other parts of the ice core. Furthermore, close to some grain boundaries, a relatively strong orientation gradient of 1°-2° per millimetre was found. The subgrain boundaries developed such that they elongate the sliding boundaries in order to accommodate the incompatibilities and maintain the strongly aligned grain boundary network. We identify the dominant deformation mechanism in this part of the ice core as grain boundary sliding accommodated by localized dislocation creep, which is a process similar to microshear (Drury and Humpreys, 1988). The existence of layers of soft ice has serious implications for ice core dating, related paleoclimate studies and ice flow modelling with respect to ice sheet mass balance and sea level predictions. References: - Drury and Humphreys, 1988. Microstructural shear criteria associated with grain boundary sliding during ductile deformation. J. of Struc. Geol. 10, 1, 83-89. - Faria et al., 2006. Is Antarctica like a birthday cake?, Max Planck Institute of Mathematics and the Sciences - Weikusat et al., 2011. Cryogenic EBSD on ice: preserving a stable surface in a low pressure SEM. J. Micros. 242, 3, 295-310. (doi: 10.1111/j.1365-2818.2010.03471.x) - Weikusat et al., 2017. Physical analysis of an Antarctic ice core-towards an integration of micro- and macrodynamics of polar ice. Phil. Trans. R. Soc. A 375, 2015347. (doi:10.1098/rsta.2015.0347)

A multi-proxy paleolimnological reconstruction of Holocene climate conditions in the Great Basin, United States

NASA Astrophysics Data System (ADS)

Reinemann, Scott A.; Porinchu, David F.; Bloom, Amy M.; Mark, Bryan G.; Box, Jason E.

2009-11-01

A sediment core spanning ˜ 7000 cal yr BP recovered from Stella Lake, a small sub-alpine lake located in Great Basin National Park, Nevada, was analyzed for subfossil chironomids (non-biting midges), diatoms, and organic content (estimated by loss-on-ignition (LOI)). Subfossil chironomid analysis indicates that Stella Lake was characterized by a warm, middle Holocene, followed by a cool "Neoglacial" period, with the last two millennia characterized by a return to warmer conditions. Throughout the majority of the core the Stella Lake diatom-community composition is dominated by small, periphytic taxa which are suggestive of shallow, cool, alkaline, oligotrophic waters with extensive seasonal ice cover. A reconstruction of mean July air temperature (MJAT) was developed by applying a midge-based inference model for MJAT (two-component WA-PLS) consisting of 79 lakes and 54 midge taxa ( rjack2 = 0.55, RMSEP = 0.9°C). Comparison of the chironomid-inferred temperature record to existing regional paleoclimate reconstructions suggests that the midge-inferred temperatures correspond well to regional patterns. This multi-proxy record provides valuable insight into regional Holocene climate and environmental conditions by providing a quantitative reconstruction of peak Holocene warmth and aquatic ecosystem response to these changes in the Great Basin, a region projected to experience increased aridity and higher temperatures.

Snow contribution to first-year and second-year Arctic sea ice mass balance north of Svalbard

NASA Astrophysics Data System (ADS)

Granskog, Mats A.; Rösel, Anja; Dodd, Paul A.; Divine, Dmitry; Gerland, Sebastian; Martma, Tõnu; Leng, Melanie J.

2017-03-01

The salinity and water oxygen isotope composition (δ18O) of 29 first-year (FYI) and second-year (SYI) Arctic sea ice cores (total length 32.0 m) from the drifting ice pack north of Svalbard were examined to quantify the contribution of snow to sea ice mass. Five cores (total length 6.4 m) were analyzed for their structural composition, showing variable contribution of 10-30% by granular ice. In these cores, snow had been entrained in 6-28% of the total ice thickness. We found evidence of snow contribution in about three quarters of the sea ice cores, when surface granular layers had very low δ18O values. Snow contributed 7.5-9.7% to sea ice mass balance on average (including also cores with no snow) based on δ18O mass balance calculations. In SYI cores, snow fraction by mass (12.7-16.3%) was much higher than in FYI cores (3.3-4.4%), while the bulk salinity of FYI (4.9) was distinctively higher than for SYI (2.7). We conclude that oxygen isotopes and salinity profiles can give information on the age of the ice and enables distinction between FYI and SYI (or older) ice in the area north of Svalbard.