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Sample records for glacial lake outburst

  1. Simulations of cataclysmic outburst floods from Pleistocene Glacial Lake Missoula

    USGS Publications Warehouse

    Denlinger, Roger P.; O'Connell, D. R. H.

    2009-01-01

    Using a flow domain that we constructed from 30 m digital-elevation model data of western United States and Canada and a two-dimensional numerical model for shallow-water flow over rugged terrain, we simulated outburst floods from Pleistocene Glacial Lake Missoula. We modeled a large, but not the largest, flood, using initial lake elevation at 1250 m instead of 1285 m. Rupture of the ice dam, centered on modern Lake Pend Oreille, catastrophically floods eastern Washington and rapidly fills the broad Pasco, Yakima, and Umatilla Basins. Maximum flood stage is reached in Pasco and Yakima Basins 38 h after the dam break, whereas maximum flood stage in Umatilla Basin occurs 17 h later. Drainage of these basins through narrow Columbia gorge takes an additional 445 h. For this modeled flood, peak discharges in eastern Washington range from 10 to 20 × 106 m3/s. However, constrictions in Columbia gorge limit peak discharges to 6 m3/s and greatly extend the duration of flooding. We compare these model results with field observations of scabland distribution and high-water indicators. Our model predictions of the locations of maximum scour (product of bed shear stress and average flow velocity) match the distribution of existing scablands. We compare model peak stages to high-water indicators from the Rathdrum-Spokane valley, Walulla Gap, and along Columbia gorge. Though peak stages from this less-than-maximal flood model attain or exceed peak-stage indicators along Rathdrum-Spokane valley and along Columbia gorge, simulated peak stages near Walulla Gap are 10–40 m below observed peak-stage indicators. Despite this discrepancy, our match to field observations in most of the region indicates that additional sources of water other than Glacial Lake Missoula are not required to explain the Missoula floods.

  2. Hazard and Risk of Glacial Lake Outburst Floods in the Nepal Himalayas

    NASA Astrophysics Data System (ADS)

    Rounce, David; McKinney, Daene

    2016-04-01

    As the climate changes and glaciers continue to melt, the number of glacial lakes and the size of these lakes is rapidly increasing. These glacial lakes are contained by terminal moraines composed of debris, soil, and sometimes ice, which are susceptible to fail catastrophically and cause a glacial lake outburst flood (GLOF). Understanding the hazard and risk associated with these lakes is important for downstream communities and other stakeholders, e.g., hydroelectric companies. Unfortunately, existing methods that are used to assess GLOF hazards yield conflicting classifications, which leads to confusion amongst the stakeholders who these studies are meant to assist. This study assesses existing methods on potentially dangerous glacial lakes in Nepal and uses these methods to develop an objective and holistic risk & action framework that may be used to assist and prioritize risk-mitigation actions.

  3. Changing glacial lakes and associated outburst floods risks in Nanda Devi Biosphere Reserve, Indian Himalaya

    NASA Astrophysics Data System (ADS)

    Mal, S.; Singh, R. B.

    2014-09-01

    Glacial lakes and associated outburst floods (GLOFs) have increased in the Himalayan region due to climate change during the last century that has led to huge losses to society. Therefore, the present study was undertaken to map glacial lakes, their increasing extent, and associated damage potential in Nanda Devi Biosphere Reserve (NDBR), Indian Himalaya. The glacial lakes were mapped on Landsat TM (3 November, 2009 and 6 November 2010) and Landsat MSS satellite images (15 November 1976 and 26 October 1979) to assess their changing area. Potential GLOFs sites have been identified and studied for their damage potentials using site characteristics and past occurrence of GLOFs. A total of 35 lakes were mapped, of which 14 lakes are located at more than 4500 m. The size and damage potentials of lakes have increased. Some lakes grew so much that they merged to form a big lake. All of these are potential GLOFs and can cause severe damage to society.

  4. Climate Change Adaptation Decision Making for Glacial Lake Outburst Floods From Palcacocha Lake in Peru

    NASA Astrophysics Data System (ADS)

    Cuellar, A. D.; McKinney, D. C.

    2014-12-01

    Climate change has accelerated glacial retreat in high altitude glaciated regions of Peru leading to the growth and formation of glacier lakes. Glacial lake outburst floods (GLOF) are sudden events triggered by an earthquake, avalanche into the lake or other shock that causes a sudden outflow of water. These floods are catastrophic because of their sudden onset, the difficulty predicting them, and enormous quantity of water and debris rapidly flooding downstream areas. Palcacocha Lake in the Peruvian Andes has experienced accelerated growth since it burst in 1941 and threatens the major city of Huaraz and surrounding communities. Since the 1941 flood stakeholders have advocated for projects to adapt to the increasing threat posed by Palcacocha Lake. Nonetheless, discussions surrounding projects for Palcacocha have not included a rigorous analysis of the potential consequences of a flood, probability of an event, or costs of mitigation projects. This work presents the first step to rationally analyze the risks posed by Palcacocha Lake and the various adaptation projects proposed. In this work the authors use decision analysis to asses proposed adaptation measures that would mitigate damage in downstream communities from a GLOF. We use an existing hydrodynamic model of the at-risk area to determine how adaptation projects will affect downstream flooding. Flood characteristics are used in the HEC-FIA software to estimate fatalities and injuries from an outburst flood, which we convert to monetary units using the value of a statistical life. We combine the monetary consequences of a GLOF with the cost of the proposed projects and a diffuse probability distribution for the likelihood of an event to estimate the expected cost of the adaptation plans. From this analysis we found that lowering the lake level by 15 meters has the least expected cost of any proposal despite uncertainty in the effect of lake lowering on flooding downstream.

  5. Monitoring of a recurring glacial lake outburst flood in north-western Nepal

    NASA Astrophysics Data System (ADS)

    Neckel, Niklas; Kropacek, Jan; Schröter, Benjamin; Tyrna, Bernd; Buchroithner, Manfred

    2014-05-01

    Since 2004 an almost annual recurring glacial lake outburst flood threatens Halji Village, located in Limi valley in one of the most remote regions of north-western Nepal. So far a considerable extent of rare fields and several houses have been destroyed. A cultural heritage site, the Halji Monastery which is the oldest Buddhist monastery in western Nepal is located only 30 m from the flood path. A supra-glacial lake at an altitude of 5300 m a.s.l. located approximately 6 km away from the village was identified as the source of the flood from recent satellite imagery. In November/December 2013 we carried out a field survey in this region in order to understand the drainage paths of the lake, to measure the volume of the glacial lake and to set up an Automatic Weather Station (AWS). To assess both the filling and draining of the glacial lake a terrestrial time-lapse camera was installed taking six photographs every day. These show the glacial lake and parts of the feeding water channels. The images combined with the AWS data will help us to understand the dependency of magnitude and timing of the outburst event to the temperature, snow conditions and glacier movements. The collected data will also help us to learn more about the flooding event and serve as the input for a two dimensional hydrodynamic model which simulates the flood extent under different flooding scenarios.

  6. Towards an improved inventory of Glacial Lake Outburst Floods in the Himalayas

    NASA Astrophysics Data System (ADS)

    Veh, Georg; Walz, Ariane; Korup, Oliver; Roessner, Sigrid

    2016-04-01

    The retreat of glaciers in the Himalayas and the associated release of meltwater have prompted the formation and growth of thousands of glacial lakes in the last decades. More than 2,200 of these lakes have developed in unconsolidated moraine material. These lakes can drain in a single event, producing potentially destructive glacial lake outburst floods (GLOFs). Only 44 GLOFs in the Himalayas have been documented in more detail since the 1930s, and evidence for a change, let alone an increase, in the frequency of these flood events remains elusive. The rare occurrence of GLOFs is counterintuitive to our hypothesis that an increasing amount of glacial lakes has to be consistent with a rising amount of outburst floods. Censoring bias affects the GLOF record, such that mostly larger floods with commensurate impact have been registered. Existing glacial lake inventories are also of limited help for the identification of GLOFs, as they were created in irregular time steps using different methodological approach and covering different regional extents. We discuss the key requirements for generating a more continuous, close to yearly time series of glacial lake evolution for the Himalayan mountain range using remote sensing data. To this end, we use sudden changes in glacial lake areas as the key diagnostic of dam breaks and outburst floods, employing the full archive of cloud-free Landsat data (L5, L7 and L8) from 1988 to 2015. SRTM and ALOS World 3D topographic data further improve the automatic detection of glacial lakes in an alpine landscape that is often difficult to access otherwise. Our workflow comprises expert-based classification of water bodies using thresholds and masks from different spectral indices and band ratios. A first evaluation of our mapping approach suggests that GLOFs reported during the study period could be tracked independently by a significant reduction of lake size between two subsequent Landsat scenes. This finding supports the feasibility

  7. Modeling a Glacial Lake Outburst Flood Process Chain: The Case of Lake Palcacocha and Huaraz, Peru

    NASA Astrophysics Data System (ADS)

    Chisolm, Rachel; Somos-Valenzuela, Marcelo; Rivas Gomez, Denny; McKinney, Daene C.; Portocarrero Rodriguez, Cesar

    2016-04-01

    One of the consequences of recent glacier recession in the Cordillera Blanca, Peru, is the risk of Glacial Lake Outburst Floods (GLOFs) from lakes that have formed at the base of retreating glaciers. GLOFs are often triggered by avalanches falling into glacial lakes, initiating a chain of processes that may culminate in significant inundation and destruction downstream. This paper presents simulations of all of the processes involved in a potential GLOF originating from Lake Palcacocha, the source of a previously catastrophic GLOF on December 13, 1941, 1800 people in the city of Huaraz, Peru. The chain of processes simulated here includes: (1) avalanches above the lake; (2) lake dynamics resulting from the avalanche impact, including wave generation, propagation, and run-up across lakes; (3) terminal moraine overtopping and dynamic moraine erosion simulations to determine the possibility of breaching; (4) flood propagation along downstream valleys; and (5) inundation of populated areas. The results of each process feed into simulations of subsequent processes in the chain, finally resulting in estimates of inundation in the city of Huaraz. The results of the inundation simulations were converted into flood intensity and hazard maps (based on an intensity-likelihood matrix) that may be useful for city planning and regulation. Three avalanche events with volumes ranging from 0.5-3 x 106 m3 were simulated, and two scenarios of 15 m and 30 m lake lowering were simulated to assess the potential of mitigating the hazard level in Huaraz. For all three avalanche events, three-dimensional hydrodynamic models show large waves generated in the lake from the impact resulting in overtopping of the damming-moraine. Despite very high discharge rates (up to 63.4 x 103 m3/s), the erosion from the overtopping wave did not result in failure of the damming-moraine when simulated with a hydro-morphodynamic model using excessively conservative soil characteristics that provide very

  8. Modeling a glacial lake outburst flood process chain: the case of Lake Palcacocha and Huaraz, Peru

    NASA Astrophysics Data System (ADS)

    Somos-Valenzuela, Marcelo A.; Chisolm, Rachel E.; Rivas, Denny S.; Portocarrero, Cesar; McKinney, Daene C.

    2016-07-01

    One of the consequences of recent glacier recession in the Cordillera Blanca, Peru, is the risk of glacial lake outburst floods (GLOFs) from lakes that have formed at the base of retreating glaciers. GLOFs are often triggered by avalanches falling into glacial lakes, initiating a chain of processes that may culminate in significant inundation and destruction downstream. This paper presents simulations of all of the processes involved in a potential GLOF originating from Lake Palcacocha, the source of a previously catastrophic GLOF on 13 December 1941, killing about 1800 people in the city of Huaraz, Peru. The chain of processes simulated here includes (1) avalanches above the lake; (2) lake dynamics resulting from the avalanche impact, including wave generation, propagation, and run-up across lakes; (3) terminal moraine overtopping and dynamic moraine erosion simulations to determine the possibility of breaching; (4) flood propagation along downstream valleys; and (5) inundation of populated areas. The results of each process feed into simulations of subsequent processes in the chain, finally resulting in estimates of inundation in the city of Huaraz. The results of the inundation simulations were converted into flood intensity and preliminary hazard maps (based on an intensity-likelihood matrix) that may be useful for city planning and regulation. Three avalanche events with volumes ranging from 0.5 to 3 × 106 m3 were simulated, and two scenarios of 15 and 30 m lake lowering were simulated to assess the potential of mitigating the hazard level in Huaraz. For all three avalanche events, three-dimensional hydrodynamic models show large waves generated in the lake from the impact resulting in overtopping of the damming moraine. Despite very high discharge rates (up to 63.4 × 103 m3 s-1), the erosion from the overtopping wave did not result in failure of the damming moraine when simulated with a hydro-morphodynamic model using excessively conservative soil

  9. Decision Making Methodology to Mitigate Damage From Glacial Lake Outburst Floods From Imja Lake in Nepal

    NASA Astrophysics Data System (ADS)

    McKinney, D. C.; Cuellar, A. D.

    2015-12-01

    Climate change has accelerated glacial retreat in high altitude glaciated regions of Nepal leading to the growth and formation of glacier lakes. Glacial lake outburst floods (GLOF) are sudden events triggered by an earthquake, moraine failure or other shock that causes a sudden outflow of water. These floods are catastrophic because of their sudden onset, the difficulty predicting them, and enormous quantity of water and debris rapidly flooding downstream areas. Imja Lake in the Himalaya of Nepal has experienced accelerated growth since it first appeared in the 1960s. Communities threatened by a flood from Imja Lake have advocated for projects to adapt to the increasing threat of a GLOF. Nonetheless, discussions surrounding projects for Imja have not included a rigorous analysis of the potential consequences of a flood, probability of an event, or costs of mitigation projects in part because this information is unknown or uncertain. This work presents a demonstration of a decision making methodology developed to rationally analyze the risks posed by Imja Lake and the various adaptation projects proposed using available information. In this work the authors use decision analysis, data envelopement analysis (DEA), and sensitivity analysis to assess proposed adaptation measures that would mitigate damage in downstream communities from a GLOF. We use an existing hydrodynamic model of the at-risk area to determine how adaptation projects will affect downstream flooding and estimate fatalities using an empirical method developed for dam failures. The DEA methodology allows us to estimate the value of a statistical life implied by each project given the cost of the project and number of lives saved to determine which project is the most efficient. In contrast the decision analysis methodology requires fatalities to be assigned a cost but allows the inclusion of uncertainty in the decision making process. We compare the output of these two methodologies and determine the

  10. Monitoring of Bashkara glacial lakes (the Central Caucasus) and modelling of their potential outburst.

    NASA Astrophysics Data System (ADS)

    Krylenko, I.; Norin, S.; Petrakov, D.; Tutubalina, O.; Chernomorets, S.

    2009-04-01

    In recent decades due to glacier retreat the glacial lakes in the Central Caucasus, as well as in other high-mountainous areas of the world, have expanded intensively. As result the risk of lake outbursts and destructive floods is raising. In this paper we present one of the most potentially hazardous lakes of this region - a group of glacial lakes near the Bashkara glacier in the upper Adylsu river valley, to the southeast of Mt. Elbrus. Total area of these lakes is about 100,000m2, and a total volume exceeds 1,000,000 m3. The biggest of them - the Bashkara lake has formed in late 1930s - early 1940s and the small Lapa lake has appeared in the end of 1980s. The Bashkara lake outburst occurred twice in the end of 1950s and produced devastating debris flows of ca. 2 million m3. We have monitored these lakes since 1999. Our work includes detailed field research: constant measurements of water level during warm period, annually repeated bathymetric surveys, geodetic surveys, observations on dam condition and some special measurements (i.e. water temperature distribution, current velocity). Also we use aerial and satellite images to obtain data about dynamic of areas for the lakes. From 2001 to 2006 years volume of the Lapa lake has increased 5 times (from 30,000 m3 to 140,000 m3), the Bashkara lake in this period was quasi-stable. In 2006-2008 volume of the Lapa lake has decreased due to sedimentation, however, rapid growth of water level in Bashkara lake (more than 20 sm. per day) has suddenly begun. As a result, volume of the Bashkara lake exceeded 1,000000 m3 in July 2008 whereas in 2001 -2007 year it was about 800,000 m3. Previous maximum of water level was exceeded on 3,5 m, moraine dam with ice core was overtopped and overflow has started. Thus, Bashkara glacier lakes are unstable and risk of outburst is increasing. To assess parameters and zones of potential outburst flood in the Adylsu River valley we have carried out hydrodynamic simulation. Two computer

  11. Hazard Map in Huaraz-Peru due to a Glacial Lake Outburst Flood from Palcacocha Lake

    NASA Astrophysics Data System (ADS)

    Somos-Valenzuela, M. A.; Chisolm, R. E.; McKinney, D. C.; Rivas, D.

    2013-12-01

    Palcacocha lake is located in the Ancash Region in the Cordillera Blanca at an elevation of 4,567 m in the Quilcay sub-basin, province of Huaraz, Peru. The lake drains into the Quebrada Cojup, which subsequently drains into the Quilcay River. The Quilcay River passes through the City of Huaraz emptying its water into the Santa River, which is the primary river of the basin. This location has a special interest since the city of Huaraz, which is located at the bottom of the Quilcay sub-basin, was devastated by a glacial lake outburst flood (GLOF) released from Lake Palcacocha on December 13, 1941. In that event, many lost their lives. In recent years Palcacocha has grown to the point where the lake is once again dangerous. Ice/rock avalanches from the steep surrounding slopes can now directly reach the lake. A process chain of debris flow and hyper-concentrated flow from Lake Palcacocha could easily reach the city of Huaraz with the current lake volume. Local authorities and people living in Huaraz are concerned about the threat posed by Lake Palcacocha, and consequently they have requested technical support in order to investigate the impacts that a GLOF could have in the city of Huaraz. To assess the hazard for the city of Huaraz a holistic approach is used that considers a chain of processes that could interact in a GLOF event from Lake Palcacocha. We assume that an avalanche from Palcaraju glacier, located directly above the lake, could be a GLOF trigger, followed by the formation of waves in the lake that can overtop the damming moraine starting an erosive process. The wave and avalanche simulations are described in another work, and here we use those results to simulate the propagation of the inundation downstream using FLO-2D, a model that allows us to include debris flow. GLOF hydrographs are generated using a dam break module in Mike 11. Empirical equations are used to calculate the hydrograph peaks and calibrate the inundation model. In order to quantify

  12. Uncertainty in the Himalayan energy–water nexus: estimating regional exposure to glacial lake outburst floods

    NASA Astrophysics Data System (ADS)

    Schwanghart, Wolfgang; Worni, Raphael; Huggel, Christian; Stoffel, Markus; Korup, Oliver

    2016-07-01

    Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia’s soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.

  13. Uncertainty in the Himalayan energy-water nexus: estimating regional exposure to glacial lake outburst floods

    NASA Astrophysics Data System (ADS)

    Schwanghart, Wolfgang; Worni, Raphael; Huggel, Christian; Stoffel, Markus; Korup, Oliver

    2016-07-01

    Himalayan water resources attract a rapidly growing number of hydroelectric power projects (HPP) to satisfy Asia’s soaring energy demands. Yet HPP operating or planned in steep, glacier-fed mountain rivers face hazards of glacial lake outburst floods (GLOFs) that can damage hydropower infrastructure, alter water and sediment yields, and compromise livelihoods downstream. Detailed appraisals of such GLOF hazards are limited to case studies, however, and a more comprehensive, systematic analysis remains elusive. To this end we estimate the regional exposure of 257 Himalayan HPP to GLOFs, using a flood-wave propagation model fed by Monte Carlo-derived outburst volumes of >2300 glacial lakes. We interpret the spread of thus modeled peak discharges as a predictive uncertainty that arises mainly from outburst volumes and dam-breach rates that are difficult to assess before dams fail. With 66% of sampled HPP are on potential GLOF tracks, up to one third of these HPP could experience GLOF discharges well above local design floods, as hydropower development continues to seek higher sites closer to glacial lakes. We compute that this systematic push of HPP into headwaters effectively doubles the uncertainty about GLOF peak discharge in these locations. Peak discharges farther downstream, in contrast, are easier to predict because GLOF waves attenuate rapidly. Considering this systematic pattern of regional GLOF exposure might aid the site selection of future Himalayan HPP. Our method can augment, and help to regularly update, current hazard assessments, given that global warming is likely changing the number and size of Himalayan meltwater lakes.

  14. Periodic Glacial Lake Outburst Floods threatening the oldest Buddhist monastery in north-west Nepal

    NASA Astrophysics Data System (ADS)

    Kropáček, J.; Neckel, N.; Tyrna, B.; Holzer, N.; Hovden, A.; Gourmelen, N.; Schneider, C.; Buchroithner, M.; Hochschild, V.

    2014-11-01

    Since 2004 Halji Village, home of the oldest Buddhist Monastery in north-west Nepal has suffered from recurrent Glacial Lake Outburst Floods (GLOFs). Studies of recent satellite images identified a supra-glacial lake, located at a distance of 6.5 km from the village, as a possible source of the flood. During a field survey in 2013, the finding was confirmed and several entrances to en-glacial conduits which are draining the lake were found. The topography of the lake basin was then mapped by combining Differential Global Positioning System (DGPS) measurements with a Structure From Motion (SFM) approach from terrestrial photographs. From this model the maximum filling capacity of the lake has been estimated as 1.06 × 106 m3 with a maximum discharge of 77.8 m3 s-1 calculated using an empirical relation. The flooded area in the valley has been estimated by employing a raster-based hydraulic model considering six scenarios of discharge volume and surface roughness. To understand the changes in glacier geometry in the last decade the thinning and retreat of Halji Glacier have been analysed by geodetic mass balance measurements and a time series of satellite images respectively. The GLOF occurrences have further been correlated with cumulative temperature and cumulative liquid precipitation calculated from the High Asia Reanalysis (HAR) dataset. Finally, effective mitigation measures and adaption strategies for Halji village have been discussed.

  15. Repeated Glacial-Lake Outburst Floods in Patagonia: An Increasing Hazard?

    NASA Astrophysics Data System (ADS)

    Dussaillant, A.; Benito, G.; Buytaert, W.; Carling, P.; Gonzalez, F.; Link, O.; Meier, C.

    2009-04-01

    Patagonian glaciers are recording one of the fastest glacial retreats on Earth, inferred to be a direct response to recorded climate change in South America. The dynamic response of the region's glaciers to climate change was evident when two self-similar glacial-lake outburst floods occurred in April and October 2008, the largest floods from this glacier on record. On each occasion, the lake Cachet 2, in the Northern Patagonia Ice-Field, dammed by the Colonia glacier, released about 200 million m3 water into the Colonia river. The lake is refilling rapidly, such that further outbreak floods can be expected. This paper anticipates future events, by providing an assessment of the hydraulic properties of the 2008 events. Pipeflow calculations of the subglacial tunnel drainage and hydraulic models of the river flood give consistent results, with an estimated peak discharge of between 2500 and 3000 m3s-1. However, geomorphological analysis of the Colonia valley shows evidence of former catastrophic outburst floods, with flood discharges possibly as high as 16,000 m3s-1. Given the impacts of climate change on glacier dynamics in the area, the frequency and high magnitude jökulhlaups may increase future flood risks for infrastructure and population, particularly relevant in view of the current development of hydropower projects in Chilean Patagonia.

  16. Outburst floods of glacial lakes in Patagonia: is there an increasing trend?

    NASA Astrophysics Data System (ADS)

    Casassa, Gino; Wendt, Jens; Wendt, Anja; López, Paulina; Schuler, Thomas; Maas, Hans-Gerd; Carrasco, Jorge; Rivera, Andrés.

    2010-05-01

    Glaciers in Patagonia are temperate and many of them are receding at an accelerated rate, with a consequent enlargement of glacial lakes. We will review the occurrence of Glacial Lake Outburst Floods (GLOFs) recorded during the last century in Patagonia (Northern and Southern Patagonia icefields), and analyse them in view of the general warming of 0.5°C affecting the region during the last 40 years. Special attention will be devoted to Lake Cachet 2 (47°12' S, 73°15' W, 422 m a.s.l.) which has experienced 6 GLOF events during the last 2 years: April 6-7 2008, October 7-8 2008, 21-22 December 2008, 5 March 2009, 16 September 2009 and 5-6 January 2010. Lake Cachet 2 has an area of 4 km2, located on the eastern margin of the Northern Patagonia Icefield, being dammed on its southern margin by Colonia Glacier. Prior to the April 2008 event there had been no historical record of catastrophic flooding of this lake. Each event resulted in a flood wave of which travelled down Colonia River to the confluence with Baker River in a period of less than 48 hours, where it reached peak flows of approximately 2,000 m3/s. Here we present airborne and ground explorations carried out in the period 2008-2009 which confirm that the Lake Cachet 2 floods drain through an englacial tunnel under Colonia Glacier for a distance of 8 km, emerging at the front of the glacier. We propose that the lake started draining in 2008 as a result of the weakening of the ice dam produced by long-term thinning of Colonia Glacier. Measurements of the empty lake bed were performed with the CECS airborne laser scanner onboard a helicopter, which show that the maximum water volume of the lake is 200 x 106 m3. Modelling of the flood events has been carried out based on the subglacial flood model of Clarke (2003), showing that a semi-circular subglacial tunnel attaining a maximum dimension of 15 m can evacuate Lake Cachet 2 in approximately 48 hours, with peak flows on the order of 4000 m3/s. Preliminary

  17. Repeated glacial lake outburst flood threatening the oldest Buddhist monastery in north-western Nepal

    NASA Astrophysics Data System (ADS)

    Kropáček, J.; Neckel, N.; Tyrna, B.; Holzer, N.; Hovden, A.; Gourmelen, N.; Schneider, C.; Buchroithner, M.; Hochschild, V.

    2015-10-01

    Since 2004, Halji village, home of the oldest Buddhist Monastery in north-western Nepal, has suffered from recurrent glacial lake outburst floods (GLOFs). A sudden englacial drainage of a supraglacial lake, located at a distance of 6.5 km from the village, was identified as the source of the flood. The topography of the lake basin was mapped by combining differential Global Positioning System (DGPS) measurements with a structure-from-motion (SFM) approach using terrestrial photographs. From this model the maximum filling capacity of the lake has been estimated as 1.06 ×106 m3 with a maximum discharge of 77.8 m3 s-1, calculated using the empiric Clague-Mathews formula. A simulation of the flooded area employing a raster-based hydraulic model considering six scenarios of discharge volume and surface roughness did not result in a flooding of the village. However, both the village and the monastery are threatened by undercutting of the river bank formed by unconsolidated sediments, as it already happened in 2011. Further, the comparison of the GLOF occurrences with temperature and precipitation from the High Asia Reanalysis (HAR) data set for the period 2001-2011 suggests that the GLOF is climate-driven rather than generated by an extreme precipitation event. The calculation of geodetic mass balance and the analysis of satellite images showed a rapid thinning and retreat of Halji Glacier which will eventually lead to a decline of the lake basin. As the basin will persist for at least several years, effective mitigation measures should be considered. A further reinforcement of the gabion walls was suggested as an artificial lake drainage is not feasible given the difficult accessibility of the glacier.

  18. Glacial lake outburst floods from Kyagar Glacier, Karakoram, P. R. China

    NASA Astrophysics Data System (ADS)

    Haemmig, Christoph; Huss, Matthias; Keusen, Hansrudolf; Hess, Josef; Wegmüller, Urs; Ao, Zhigang; Kulubayi, Wubuli

    2013-04-01

    Kyagar Glacier is located in the Karakoram Mountains in the southwest of Xinjiang Uygur Autonomous Region, P.R. China. The glacier tongue entirely blocks the riverbed of the upper Shaksgam Valley and impounds a glacial lake at 4750 m a.s.l., which was the source of several violent and disastrous Glacial Lake Outburst Floods (GLOF) over the past decades. The spontaneous floods are a threat to over 1 mio. inhabitants in the floodplains of the Yarkant River. A GLOF early warning system, combining satellite remote sensing and two terrestrial observation and warning stations at Kyagar Lake and 200 km downstream, was implemented in 2011 and 2012. The stations provide daily images based on automatic cameras, water level measurements, and are equipped with weather sensors to monitor local climate. We discuss the GLOF early warning system and present first measurement series of melt-water runoff and meteorological conditions from one of the remotest regions of the Karakoram mountains. The ongoing project also elaborates scenario-based forecasts of future glacier lake developments, considering the ice-flow dynamics of Kyagar Glacier as well as surface mass-balance response to climate change. Comparison of two high-resolution Digital Elevation Models (DEMs) for the ice dam show surface lowering rates of more than 4 m a-1 between 2002 and 2011 leading to a significant reduction in lake volume and hence, a decreasing GLOF hazard potential. Glacier melt modelling using climate scenarios indicates a rapid retreat of the glacier tongue over the next decades. However, two DEMs covering the entire glacier for 2000-2008 show small elevation changes in the accumulation area and even a slight mass gain in the central part. This is supported by the observation of a moderate ice-flow speed-up in this region. This pattern is typical for surge-type glaciers and is consistent with the numerous documented glacier surges in the Karakoram. Furthermore, the displacement rate of the glacier

  19. Debris flows resulting from glacial-lake outburst floods in tibet, China

    USGS Publications Warehouse

    Cui, P.; Dang, C.; Cheng, Z.; Scott, K.

    2010-01-01

    During the last 70 years of general climatic amelioration, 18 glacial-lake outburst floods (GLOFs) and related debris flows have occurred from 15 moraine-dammed lakes in Tibet, China. Catastrophic loss of life and property has occurred because of the following factors: the large volumes of water discharged, the steep gradients of the U-shaped channels, and the amount and texture of the downstream channel bed and bank material. The peak discharge of each GLOF exceeded 1000 m3/s. These flood discharges transformed to non-cohesive debris flows if the channels contained sufficient loose sediment for entrainment (bulking) and if their gradients were >1%. We focus on this key element, transformation, and suggest that it be included in evaluating future GLOF-related risk, the probability of transformation to debris flow and hyperconcentrated flow. The general, sequential evolution of the flows can be described as from proximal GLOFs, to sedimentladen streamflow, to hyperconcentrated flow, to non-cohesive debris flow (viscous or cohesive debris flow only if sufficient fine sediment is present), and then, distally, back to hyperconcentrated flow and sediment-laden streamflow as sediment is progressively deposited. Most of the Tibet examples transformed only to non-cohesive debris flows. The important lesson for future hazard assessment and mitigation planning is that, as a GLOF entrains (bulks) enough sediment to become a debris flow, the flow volume must increase by at least three times (the "bulking factor"). In fact, the transforming flow waves overrun and mix with downstream streamflow, in addition to adding the entrained sediment (and thus enabling addition of yet more sediment and a bulking factor in excess of three times). To effectively reduce the risk of GLOF debris flows, reducing the level of a potentially dangerous lake with a siphon or excavated spillway or installing gabions in combination with a downstream debris dam are the primary approaches.

  20. 21st century Himalayan hydropower: Growing exposure to glacial lake outburst floods?

    NASA Astrophysics Data System (ADS)

    Schwanghart, Wolfgang; Worni, Raphael; Huggel, Christian; Stoffel, Markus; Korup, Oliver

    2014-05-01

    Primary energy demand in China and India has increased fivefold since 1980. To avoid power shortages and blackouts, the hydropower infrastructure in the Hindu Kush-Himalaya region is seeing massive development, a strategy supported by the policy of the World Bank and in harmony with the framework of the Kyoto Protocol. The targeted investments in clean energy from water resources, however, may trigger far-reaching impacts to downstream communities given that hydropower projects are planned and constructed in close vicinity to glaciated areas. We hypothesize that the location of these new schemes may be subject to higher exposure to a broad portfolio of natural hazards that proliferate in the steep, dissected, and tectonically active topography of the Himalayas. Here we focus on the hazard from glacial lake outburst floods (GLOF), and offer an unprecedented regional analysis for the Hindu Kush-Himalaya orogen. We compiled a database of nearly 4,000 proglacial lakes that we mapped from satellite imagery; and focus on those as potential GLOF sources that are situated above several dozen planned and existing hydropower plants. We implemented a scenario-based flood-wave propagation model of hypothetic GLOFs, and compared thus simulated peak discharges with those of the local design floods at the power plants. Multiple model runs confirm earlier notions that GLOF discharge may exceed meteorological, i.e. monsoon-fed, flood peaks by at least an order of magnitude throughout the Hindu Kush-Himalaya. We further show that the current trend in hydropower development near glaciated areas may lead to a >15% increase of projects that may be impacted by future GLOFs. At the same time, the majority of the projects are to be sited where outburst flood modelling produces its maximum uncertainty, highlighting the problem of locating minimum risk sites for hydropower. Exposure to GLOFs is not uniformly distributed in the Himalayas, and is particularly high in rivers draining the Mt

  1. Vulnerability assessment of Glacial Lake Outburst Floods using Remote Sensing and GIS in North Sikkim (India), Eastern Himalaya

    NASA Astrophysics Data System (ADS)

    Aggarwal, Suruchi; Probha Devi, Juna; Thakur, Praveen Kumar; Rai, Suresh Chand

    2016-04-01

    Glacial lake outburst floods (GLOFs) occur when glacier melt water dammed by a moraine is released in short time. Such floods may lead to disastrous events posing, therefore, a huge threat to human lives and infrastructure. A devastating GLOF in Uttarakhand, India, on 17 July 2013 has led to the loss of all villages in a stretch of 18 km downstream the lake and the loss of more than 5000 lives. The present study evaluates all 16 glacial lakes (with an area >0.1 km²) in the Thangu valley, northern Sikkim (India), eastern Himalaya, with respect to potential threats for the downstream areas. The hazard criteria for the study include slope, aspect and distance of the respective parent glacier, change in the lake area, dam characteristics and lake depth. For the most hazardous lakes, the socio-economic conditions in the downstream areas (settlements and infrastructure) are analysed regarding the impact of potential GLOFs. For the vulnerability analysis, we used various satellite products including LANDSAT, RESOUCESAT-1 and 2, RISAT-1 imageries and ASTER GDEM covering the period from 1977 to 2014. For lake mapping, we applied the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Snow Index (NDSI). A Land Use Land Cover (LULC) map of the study area showing in-situ observations is serving as driving factor for the vulnerability analysis. The results of the study show that almost all evaluated glacial lakes were expanding during the study period (1977-2014). Combining the hazard criteria for the lakes, 5 of the 16 studied glacial lakes are identified as highly hazardous. In the downstream area, there are two villages with 200 inhabitants and an army camp within the zone of highest vulnerability. The identified vulnerability zones may be used by the local authorities to take caution of the threatened villages and infrastructure and for risk analysis for planned future hydropower plants.

  2. Surface exposure dating of glacial lake shorelines: implications for constraining ice margin positions and meltwater outbursts during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Dube-Loubert, Hugo; Roy, Martin; Schaefer, Joerg

    2016-04-01

    The Laurentide ice sheet (LIS) played an important role in the climate variability of the last deglaciation, notably through large discharges of meltwater to the North Atlantic that disturbed the ocean's circulation and heat transport. Deglaciation of the northeastern sector of the LIS was complex and included the development of large ice-dammed lakes that were confined within the main river valleys draining northward into Ungava Bay. The history of these lakes is closely related to the temporal evolution of the Labrador ice dome, but large uncertainties regarding the position and dynamic of the ice margin through time currently limit our understanding of these glacial lakes. In the Ungava lowlands, glacial lake Naskaupi invaded the George River valley, leaving a series of well-developed shorelines and deltas. These spectacular raised shorelines are 10 to 20 meters wide and can be followed for several kilometers. Our field investigations and remote sensing analysis indicate that Lake Naskaupi experienced a complex history, as shown by the succession of shorelines that likely reflect the opening of new topographic outlets during ice retreat. Constraining the timing of the different phases of the lake and its drainage has traditionally been challenging, as organic material suitable for radiocarbon dating is scarce or lacking. Recent progress in Surface Exposure Dating (SED) by cosmogenic nuclides now inspires novel approaches to glacial and deglacial geomorphology. Here we apply 10Be SED to boulders that form part of these shorelines and mark the main (high-level) stage of Lake Naskaupi. We sampled 4-6 multi-meter size boulders at 4 different sites. Preliminary results show high internal consistency and, indicate that the main lake phase developed very late in the regional deglaciation, which extends from about 8500 to 6800 cal. yr BP (Dyke and Prest, 1987). We also present SED results from boulders deposited by a substantial outburst flood presumably associated with

  3. Hazard Assessment of Glacial Lake Outburst Flood and Potential of ICTs for Coping: A Case of Eastern Himalaya of Nepal

    NASA Astrophysics Data System (ADS)

    Bhattarai, D. R.; Pradhananga, D.

    2014-12-01

    Alarming rate of retreat of glaciers and formation of glacial lakes in higher elevation of Nepal Himalaya has been reported to be related with the pronounced atmospheric temperature rise in the region. Glacier Lake Outburst Floods (GLOF) are the growing climate induced hazards in the Himalaya increasing the vulnerability of community living in the mountain valley, and the fragile ecosystem. This study tried to come up with the potential impacts from glacial lake outburst flood (GLOF) in highland of eastern region of Nepal and potential role of Information Communication Technologies (ICT) in coping. I analyzed the trend of climatic pattern (temperature and precipitation) of the Eastern Himalaya Region of Nepal available from Department of Hydrology and Meteorology (DHM), Government of Nepal, and also prepared the latest location map of the glacial lakes using google earth and ArcGIS application in the highland of the Kanchanjungha Conservation Area of the region. Tiptala glacial lake, located at an elevation of 4950 masl, within the conservation area, was selected for the GLOF hazard assessment. I used semi-structured questioner survey and key informants interviews in the community living below the lake in the highland of the study area in order to assess the potential hazard of GLOF. Analysis shows the increasing trend of atmospheric temperature in the region. With the varying sizes, 46 glacial lakes were located in the region, which covers over 2.57 sq. km in total. Though the larger portion of the downstream area of the Tiptala glacial lake fall in the remote location away from major residential area, few villages, major pasture lands for Yaks, foot trails, and several bridges across the Tamor River below the lake are in risk of GLOF. Poor access due to extreme geographical remoteness and capacity to afford the modern technologies in the community is seen as the major limiting factor to the knowledge and information about the climate change and related impacts

  4. An improved method to represent DEM uncertainty in glacial lake outburst flood propagation using stochastic simulations

    NASA Astrophysics Data System (ADS)

    Watson, Cameron S.; Carrivick, Jonathan; Quincey, Duncan

    2015-10-01

    Modelling glacial lake outburst floods (GLOFs) or 'jökulhlaups', necessarily involves the propagation of large and often stochastic uncertainties throughout the source to impact process chain. Since flood routing is primarily a function of underlying topography, communication of digital elevation model (DEM) uncertainty should accompany such modelling efforts. Here, a new stochastic first-pass assessment technique was evaluated against an existing GIS-based model and an existing 1D hydrodynamic model, using three DEMs with different spatial resolution. The analysis revealed the effect of DEM uncertainty and model choice on several flood parameters and on the prediction of socio-economic impacts. Our new model, which we call MC-LCP (Monte Carlo Least Cost Path) and which is distributed in the supplementary information, demonstrated enhanced 'stability' when compared to the two existing methods, and this 'stability' was independent of DEM choice. The MC-LCP model outputs an uncertainty continuum within its extent, from which relative socio-economic risk can be evaluated. In a comparison of all DEM and model combinations, the Shuttle Radar Topography Mission (SRTM) DEM exhibited fewer artefacts compared to those with the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM), and were comparable to those with a finer resolution Advanced Land Observing Satellite Panchromatic Remote-sensing Instrument for Stereo Mapping (ALOS PRISM) derived DEM. Overall, we contend that the variability we find between flood routing model results suggests that consideration of DEM uncertainty and pre-processing methods is important when assessing flow routing and when evaluating potential socio-economic implications of a GLOF event. Incorporation of a stochastic variable provides an illustration of uncertainty that is important when modelling and communicating assessments of an inherently complex process.

  5. Hazard Assessment of Glacial Lake Outburst Flood and Potential of ICTs for Coping: A Case of Eastern Himalaya of Nepal

    NASA Astrophysics Data System (ADS)

    Bhattarai, D. R.

    2015-12-01

    Retreat of glaciers and formation of glacial lakes in Nepal Himalaya have been reported to be related with the temperature rise in the region. Glacier Lake Outburst Floods (GLOF) are the growing climate induced hazards in the Himalaya. GLOF has increased the vulnerability of community and fragile ecosystem in the mountain valleys. This study has analyzed the potential impacts from GLOF in the highland of eastern Nepal and the potential role of Information Communication Technologies (ICT) to cope with such impacts. I analyzed the trend of climatic pattern (temperature and precipitation) of the Eastern Himalaya Region of Nepal available from the Department of Hydrology and Meteorology, Government of Nepal, and prepared the latest location map of the glacial lakes using google earth and ArcGIS applications in the highland of the Kanchanjungha Conservation Area of the region. Tiptala glacial lake, located at an elevation of 4950 m, within the conservation area, was selected for the GLOF hazard assessment. I used semi-structured questionnaire survey and key informants' interviews in the community in order to assess the potential hazard of GLOF. With the varying sizes, 46 glacial lakes were located in the region, which covers over 2.57 sq. km in total. Though the larger portion of the downstream area of the Tiptala glacial lake fall in the remote location away from major residential area, few villages, major pasture lands for Yaks, foot trails, and several bridges across the Tamor River below the lake are in risk of GLOF. Poor access due to extreme geographical remoteness and capacity to afford the modern technologies in the community are the major limiting factor to the knowledge and information about the climate change and related impacts. Modern ICTs has high potential to reduce the risk of climate related hazards in the remote area by information dissemination and awareness.

  6. Rainfall and snow-melt triggered glacial lake outbursts: a systematic analysis of the Kedarnath (Uttarakhand, India), June 2013 disaster

    NASA Astrophysics Data System (ADS)

    Allen, Simon; Rastner, Philipp; Arora, Manohar; Huggel, Christian; Stoffel, Markus

    2015-04-01

    Heavy rainfall in early June 2013 triggered flash flooding and landslides throughout the Indian Himalayan state of Uttarakhand, killing more than 6000 people. The destruction of roads and trekking routes left around 100,000 pilgrims and tourists stranded. Most fatalities and damages resulted directly from a lake outburst and debris flow disaster originating from above the village of Kedarnath on June 16 and 17. Here we provide a first systematic analysis of the contributing factors leading to the Kedarnath disaster, both in terms of hydro-meteorological triggering (rainfall, snowmelt, and temperature) and topographic predisposition. Specifically, the topographic characteristics of the Charobari lake watershed above Kedarnath are compared with other glacial lakes across the northwestern Indian Himalayan states of Uttarakhand and Himachal Pradesh, and implications for glacier lake outburst hazard assessment in a changing climate are discussed. Our analysis suggests that the early onset of heavy monsoon rainfall (390 mm, June 10 - 17) immediately following a prolonged four week period of unusually rapid snow cover depletion and elevated streamflow is the crucial hydro-meteorological factor, resulting in slope saturation and significant runoff into the small seasonal glacial lake. Over a four week period the MODIS-derived snow covered area above Kedarnath decreased nearly 50%, from above average coverage in mid-May to well below average coverage by the second week of June. Such a rapid decrease has not been observed in the previous 13-year record, where the average decrease in snow covered area over the same four week window is only 15%. The unusual situation of the lake being dammed in a steep, unstable paraglacial environment, but fed entirely from snow-melt and rainfall within a fluvial dominated watershed is important in the context of this disaster. A simple scheme enabling large-scale recognition of such an unfavorable topographic setting is presented, and on the

  7. Modelling cascading and erosional processes for glacial lake outburst floods in the Quillcay catchment, Huaraz, Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Baer, Patrick; Huggel, Christian; Frey, Holger; Chisolm, Rachel; McKinney, Daene; McArdell, Brian; Portocarrero, Cesar; Cochachin, Alejo

    2016-04-01

    Huaraz as the largest city in Cordillera Blanca has faced a major disaster in 1941, when an outburst flood from Lake Palcacocha killed several thousand people and caused widespread destruction. Recent studies on glacial lake outburst flood (GLOF) modelling and early warning systems focussed on Lake Palcacocha which has regrown after the 1941 event, from a volume of half a million m3 in 1974 to a total volume of more than 17 million m3 today. However, little research has been conducted so far concerning the situation of other lakes in the Quillcay catchment, namely Lake Tullparaju (12 mill. m3) and Cuchillacocha (2.5 mill. m3), which both also pose a threat to the city of Huaraz. In this study, we modelled the cascading processes at Lake Tullparaju and Lake Cuchillacocha including rock/ice avalanches, flood wave propagation in the lake and the resulting outburst flood and debris flows. We used the 2D model RAMMS to simulate ice avalanches. Model output was used as input for analytical 2D and 3D calculations of impact waves in the lakes that allowed us to estimate dam overtopping wave height. Since the dimension of the hanging glaciers above all three lakes is comparable, the scenarios in this study have been defined similar to the previous study at Lake Palcacocha. The flow propagation model included sediment entrainment in the steeper parts of the catchment, adding up to 50% to the initial flow volume. The results for total travel time as well as for inundated areas and flow depth and velocity in the city of Huaraz are comparable to the previous studies at Lake Palcacocha. This underlines the importance of considering also these lakes within an integral hazard analysis for the city of Huaraz. A main challenge for modelling GLOFs in the Quillcay catchment using RAMMS is the long runout distance of over 22 km combined with the very low slope gradient of the river. Further studies could improve the process understanding and could focus on more detailed investigations

  8. Evaluation of an early warning system for glacial lake outburst flood (GLOF) events in Huaraz, Peru

    NASA Astrophysics Data System (ADS)

    McKinney, D. C.; Somos-Valenzuela, M. A.

    2014-12-01

    People in Cordillera Blanca range in Peru have a long history dealing with natural disasters associated to high mountains; particularly Glacier Lakes Outburst Flood (GLOF). Examples in the Cordillera Blanca vary from a GLOF that occurred in 1941 that killed more than 5000 people in the city of Huaraz to recent events from Lake Artison Baja in 2012 and Lake 513 on 2010, which were not devastating thanks to safety systems previously installed in those lakes. However, glaciers continue melting leaving new lakes or changing the characteristics of lakes that were previously controlled making safety systems obsolete that worked successfully in the past protecting communities downstream. Lake Palcacocha has evolved from being safe after the installation of a safety system in 1970 to an imminent source of GLOF risk due to the expansion that has occurred during the last 40 years increasing from a volume of 500,000 to 17 million m3. In response to this risk the community in Huaraz is planning an Early Warning System (EWS) that will allow the population to mobilize to a safe area in case a GLOF occurs. In this work we present an adaptation of the LifeSIM model to calculate the benefits from such an EWS using 2007 census data and a FLO-2D flood simulation model. The outputs are the number of people in Huaraz that could lose their life due to a GLOF. Our results indicate that without an EWS around 19,773 people could lose their life; whereas, if an EWS is installed the number of victims reduces to 7344. Finally, if mobilization of the affected population is improved the value reduces to 2865. The results show the importance of the EWS as well as informing and training the population to how to react if a GLOF occurs.

  9. Reconstruction of glacial lake outburst floods in northern Tien Shan: Implications for hazard assessment

    NASA Astrophysics Data System (ADS)

    Zaginaev, V.; Ballesteros-Cánovas, J. A.; Erokhin, S.; Matov, E.; Petrakov, D.; Stoffel, M.

    2016-09-01

    Glacier lake outburst floods (GLOFs) and related debris flows are among the most significant natural threats in the Tien Shan Mountains of Kyrgyzstan and have even caused the loss of life and damage to infrastructure in its capital Bishkek. An improved understanding of the occurrence of this process is essential so as to be able to design reliable disaster risk reduction strategies, even more so in view of ongoing climate change and scenarios of future evolutions. Here, we apply a dendrogeomorphic approach to reconstruct past debris-flow activity on the Aksay cone (Ala-Archa valley, Kyrgyz range), where outbursting glacier lakes and intense rainfalls have triggered huge debris flows over the past decades. A total of 96 Picea abies (L.) Karst. trees growing on the cone and along the main channel have been selected based on the evidence of past debris-flow damage in their trunks; these trees were then sampled using increment borers. The dating of past events was based on the assessment of growth disturbances (GD) in the tree-ring records and included the detection of injuries, tangential rows of traumatic resin ducts, reaction wood, and abrupt growth changes. In total, 320 GD were identified in the tree-ring samples. In combination with aerial imagery and geomorphic recognition in the field, reactions in trees and their position on the cone have allowed reconstruction of the main spatial patterns of past events on the Aksay cone. Our findings suggest that at least 27 debris flows have occurred on the site between 1877 and 2015 and point to the occurrence of at least 17 events that were not documented prior to this study. We also observe high process activity during the 1950s and 1960s, with major events on the cone in 1950, 1966, and 1968, coinciding with phases of slight glacier advance. The spatial analyses of events also point to two different spatial patterns, suggesting that quite dissimilar magnitudes probably occurred during glacier lake outburst floods and

  10. A procedure for objective preliminary assessments of outburst flood hazard from glacial lakes in Aosta Valley

    NASA Astrophysics Data System (ADS)

    Bal, Germain; Godio, Alberto; Theodule, Alex

    2010-05-01

    GLOFs represent a major natural hazards in glaciated mountain regions, because of their fair-reaching capacity and of the difficulty in detecting source areas (especially in case of internal water pockets) and in forecasting the breakdown moment. GLOFs hazard is probably increasing because of the current glaciers retreat, and its prevention and management requires a multi-disciplinary approach, in order to (i) detect dangerous sites, (ii) assess danger, (iii) define and measure triggering factors and parameters and (iv) assess potential reaching areas so to define risk. Such a study was carried out in Aosta Valley, a mountainous territory with more than 200 glaciers covering an area of about 130 km2 (about 5% of the whole territory). The aim was double: to inventory and analyse all existing glacial lakes focusing on the newborn lakes and on potentially dangerous sites; to test surveying and modeling methods to be applied for hazard mapping and prevention. First, an inventory was compiled by means of GIS analysis of ortophotos (taken in 2005). The images were compared with previous ones to detect morphological evolution. Ground-based and helicopter surveys were also carried out. Historical data have been analyzed in order to recognize most dangerous sites and situations and to classify most recurrent phenomena. In case of recognized dangerous situations, some parameters are needed in order to evaluate the potential water volume and runout distance. Ground-penetrating radar (GPR) technique was tested to detect the presence of glacial internal cavities and water pockets on a well known situation (a glacier with well known collapse cavities). The same technique was also used to measure the bathymetry of a glacial lake. The technique was carried out successfully, allowing to estimate with a good resolution the lake depth and bottom morphology; encouraging results were also obtained in detecting glacial cavities and drainage channels. To perform the downstream runoff

  11. An autonomous image based approach for detecting glacial lake outburst floods

    NASA Astrophysics Data System (ADS)

    Koschitzki, R.; Schwalbe, E.; Maas, H.-G.

    2014-06-01

    The potential danger caused by glacier margin lakes and the related risk of glacier lake outburst floods (GLOF) increases constantly due to glaciers retreating in many parts of the world. Reasons for this development are on the one hand the new formation and enlargement of glacier margin lakes due to melt water. On the other hand, retreating and thinning glacier tongues lead to a decrease of the back pressure against the dammed glacier lakes. The paper describes the design of a photogrammetric GLOF monitoring system, based on monoscopic image sequence analysis for automatic detection of water level changes. The presented approach for measuring the water line in an image sequence is based on directional edge detection in LoG-filtered image data. After that, the water level is determined by a transformation of image measurements into object space based on orientation parameters of the camera and a geo-referenced lake basin model. The model can for instance be determined by photogrammetric methods after a GLOF; it may also be determined portion-wise by analysing shore lines at various water levels. Camera orientation parameters are determined by a local GPS-supported photogrammetric network. Comparing the determined water level changes with reference data provided by a water gauge, the precision is estimated in the order of one decimetre. A major challenge is the automatic detection of the water line in image sequences under varying light and visibility conditions. The paper will also discuss promising approaches such as multispectral images as well as a statistical analysis of grey value changes over short image sequences to eliminate disturbing reflections on the rough water surface.

  12. Multi-sensor detection of glacial lake outburst floods in Greenland from space

    NASA Astrophysics Data System (ADS)

    Citterio, M.

    2015-12-01

    GLOFs cause substantial erosion, transport and delivery of sediment along the river system from the glaciated parts of the hydrologic catchment to the sea, and have been found to control the riverine export dynamics of some pollutants like mercury in NE Greenland. GLOFs also pose a risk to human presence and infrastracture. Ice-dammed lakes at the margin of the ice sheet and of local glaciers and ice caps are common features of Greenland's landscape. The occasional or periodic emptying of some of these lakes have been described as early as the 18thcentury. Thinning glaciers in a warming climate are already changing the behaviour of some of these lakes. However, little is known of the frequency and seasonality of glacier lake outburst floods (GLOF) outside of the relatively more densely populated parts of West and South Greenland. This contribution demonstrates automatic multi-sensor detection of ice-dammed lake emptying events from space for three test regions in West, South and Northeast Greenland, using visible imagery from Landsat, ASTER, PROBA-V and MODIS. The current detection algorithm relies on prior knowledge of lakes location and approximate shape from a topographic map at the scale of 1:250.000, and it is meant as a prototype for a future operational product. For the well documented case of the glacier-dammed lake of A.P. Olsen Ice Cap (NE Greenland), where GLOF's observations at Zackenberg Research Station started in 1996, the remote sensing and in situ records are compared, showing good agreement. ICESat altimetry, MODIS and AVHRR thermal imagery, and the ENVISAR ASAR signature of two detected GLOFs that took place late autumn and winter are also discussed to demonstrate the potential for successful retrievals during the polar night. The upcoming Sentinel-3 missions will alleviate what is currently the major drawback of implementing this prototype into an operational service, namely the limited availability of high resolution imagery. This is of special

  13. Analysis and mitigation of remote geohazards in high mountain areas of Tajikistan with special emphasis on glacial lake outburst floods

    NASA Astrophysics Data System (ADS)

    Schneider, Jean F.; Mergili, Martin; Schneider, Demian

    2010-05-01

    Remote geohazard events in the mountains of Tajikistan have repeatedly caused disasters during the past decades. The rock avalanche of Khait in1949 and the glacial lake outburst flood (GLOF) in Dasht in 2002 are only two examples. However, the awareness among stakeholders and the local people is limited since the source areas are far away and the frequency of events is low. The major objective of the research outlined here is to identify and to highlight potential source areas and pathways of remote geohazard events, particularly of GLOFs, in order to allow for well-designed mitigation procedures. The geohazard assessment was carried out in a four-step procedure: • Pre-assessment: GIS and remote sensing techniques were employed for detecting potential source areas and pathways of remote geohazard processes. Relevant features were mapped from medium-resolution datasets and specific areas of interest were deducted from the mapping results. • Helicopter survey: the areas of interest identified during the Pre-assessment were screened from the helicopter. The knowledge gained this way was used to select the areas for the field assessment. • Field assessment: the areas of specific interest were visited in the field by international groups of 4 researchers. These areas were analyzed and mapped in detail and the level of hazard emanating from the lakes or slopes was estimated. • Post-assessment. Based on the field assessment, areas of particular hazard were selected for further analysis. Scenarios of dam breaks and flood waves were built and the possible impact farther down the valley was assessed using computer models. Based on that, recommendations how to mitigate the hazard will be given to the relevant agencies and stakeholders as well as to the local population. In the Southern Pamir, a number of growing glacial lakes was identified. Resulting flood waves could trigger process chains with catastrophic consequences for the population dozens of kilometres

  14. Glacial Lake Outburst Flood Risk in Himachal Pradesh, India: An Integrative and Anticipatory Approach to Inform Adaptation Planning

    NASA Astrophysics Data System (ADS)

    Allen, Simon; Linsbauer, Andreas; Huggel, Christian; Singh Randhawa, Surjeet

    2016-04-01

    Most research concerning the hazard from glacial lake outburst floods (GLOFs) has focused on the threat from lakes that have formed over the past century, and which continue to expand rapidly in response to recent warming of the climate system. However, attention is shifting towards the anticipation of future hazard and risk associated with new lakes that will develop as glaciers continue to retreat and dramatically different landscapes are uncovered. Nowhere will this threat be more pronounced than in the Himalaya, where the majority of the world's glaciers are found, and where the dynamics of nature interact closely with livelihoods and anthropogenic resources. Using the Indian Himalayan state of Himachal Pradesh (HP) as a case study, we combine a suite of GIS-based approaches to: 1)Implement a large-scale automated GLOF risk assessment within an integrative climate risk framework that recognizes both physical and socio-economic determining factors. 2)Expand the assessment beyond the current situation, to provide early anticipation of emerging GLOF hazard as new lakes form in response to further retreat of the Himalayan glaciers. Results clearly demonstrate a significant future increase in relative GLOF hazard levels across most Thesils of HP (administrative units), as the overall potential for GLOFs being triggered from mass movement of ice and rock avalanches increases, and as new GLOF paths affect additional land areas. Across most Thesils, the simulated increase in GLOF frequency is an order of magnitude larger than the simulated increase in GLOF affected area, as paths from newly formed glacial lakes generally tend to converge downstream within existing flood channels. In the Thesil of Kullu for example, we demonstrate a 7-fold increase in the probability of GLOF occurrence, and a 3-fold increase in the area affected by potential GLOF paths. In those situations where potential GLOFs from new lakes will flow primarily along existing flood paths, any

  15. Extensive deposits on the Pacific plate from Late Pleistocene North American glacial lake outbursts

    USGS Publications Warehouse

    Normark, W.R.; Reid, J.A.

    2003-01-01

    One of the major unresolved issues of the Late Pleistocene catastrophic-flood events in the northwestern United States (e.g., from glacial Lake Missoula) has been what happened when the flood discharge reached the ocean. This study compiles available 3.5-kHz high-resolution and airgun seismic reflection data, long-range sidescan sonar images, and sediment core data to define the distribution of flood sediment in deepwater areas of the Pacific Ocean. Upon reaching the ocean at the mouth of the Columbia River near the present-day upper continental slope, sediment from the catastrophic floods continued flowing downslope as hyperpycnally generated turbidity currents. The turbidity currents resulting from the Lake Missoula and other latest Pleistocene floods followed the Cascadia Channel into and through the Blanco Fracture Zone and then flowed west to the Tufts Abyssal Plain. A small part of the flood sediment, which was stripped off the main flow at a bend in the Cascadia Channel at its exit point from the Blanco Fracture Zone, continued flowing more than 400 km to the south and reached the Escanaba Trough, a rift valley of the southern Gorda Ridge. Understanding the development of the pathway for the Late Pleistocene flood sediment reaching Escanaba Trough provides insight for understanding the extent of catastrophic flood deposits on the Pacific plate.

  16. Hydrologic and Geomorphic Changes Resulting from the Onset of Episodic Glacial Lake Outburst Floods: Colonia River, Chile

    NASA Astrophysics Data System (ADS)

    Jacquet, J.; McCoy, S. W.; McGrath, D.; Nimick, D.; Friesen, B.; Fahey, M. J.; Leidich, J.; Okuinghttons, J.

    2015-12-01

    The Colonia river system, draining the eastern edge of the Northern Patagonia Icefield, Chile, has experienced a dramatic shift in flow regime from one characterized by seasonal discharge variability to one dominated by episodic glacial lake outburst floods (GLOFs). We use multi-temporal visible satellite images, high-resolution digital elevation models (DEMs) derived from stereo image pairs, and in situ observations to quantify sediment and water fluxes out of the dammed glacial lake, Lago Cachet Dos (LC2), as well as the concomitant downstream environmental change. GLOFs initiated in April 2008 and have since occurred, on average, two to three times a year. Differencing concurrent gage measurements made on the Baker River upstream and downstream of the confluence with the Colonia river finds peak GLOF discharges of ~ 3,000 m3s-1, which is ~ 4 times the median discharge of the Baker River and over 20 times the median discharge of the Colonia river. During each GLOF, ~ 200,000,000 m3 of water evacuates from the LC2, resulting in erosion of valley-fill sediments and the delta on the upstream end of LC2. Differencing DEMs between April 2008 and February 2014 revealed that ~ 2.5 x 107 m3 of sediment was eroded. Multi-temporal DEM differencing shows that erosion rates were highest initially, with > 20 vertical m of sediment removed between 2008 and 2012, and generally less than 5 m between 2012 and 2014. The downstream Colonia River Sandur also experienced geomorphic changes due to GLOFs. Using Landsat imagery to calculate the normalized difference water index (NDWI), we demonstrate that the Colonia River was in a stable configuration between 1984 and 2008. At the onset of GLOFs in April 2008, a change in channel location began and continued with each subsequent GLOF. Quantification of sediment and water fluxes due to GLOFs in the Colonia river valley provides insight on the geomorphic and environmental changes in river systems experiencing dramatic shifts in flow

  17. Record of glacial Lake Missoula floods in glacial Lake Columbia, Washington

    NASA Astrophysics Data System (ADS)

    Hanson, Michelle A.; Clague, John J.

    2016-02-01

    During the last glaciation (marine oxygen isotope stage 2), outburst floods from glacial Lake Missoula deposited diagnostic sediments within glacial Lake Columbia. Two dominant outburst flood lithofacies are present within glacial Lake Columbia deposits: a flood expansion bar facies and a finer-grained hyperpycnite facies. We conclude that the flood sediments have a glacial Lake Missoula source because: (1) current indicators indicate westward flow through the lake, and upvalley flow followed by downvalley flow in tributary valleys; (2) no flood sediments are found north of a certain point; (3) there is a dominance of Belt-Purcell Supergroup clasts in a flood expansion bar; and (4) some of the finer-grained beds have a pink colour, reflective of glacial Lake Missoula lake-bottom sediments. A new radiocarbon age of 13,400 ± 100 14C BP on plant detritus found below 37 flood beds helps constrain the timing of outburst flooding from glacial Lake Missoula.

  18. Using satellite images to monitor glacial-lake outburst floods: Lago Cachet Dos drainage, Chile

    USGS Publications Warehouse

    Friesen, Beverly A.; Cole, Christopher J.; Nimick, David A.; Wilson, Earl M.; Fahey, Mark J.; McGrath, Daniel J.; Leidich, Jonathan

    2015-01-01

    During 2008–2013, 14 GLOFs were released from Lago Cachet Dos and created environmental and safety concerns for downstream residents and to infrastructure. If GLOFs and the consequent headward erosion continue, the moraine that creates Lago Cachet Uno could be destabilized and breached, and the two lakes could merge. If the two lakes become connected, the volume of future GLOFs likely would be greater and thus cause longer and (or) more extensive flooding downstream. Additional GLOFs from Lago Cachet Dos are expected in the future, and continued environmental monitoring could provide an early warning system as well as scientific information that could increase our understanding of GLOFs and their consequences. GLOFs occur in glaciated areas around the world and remote sensing technologies can allow researchers to better understand—and potentially predict—future GLOF events.

  19. Reconstruction of a glacial lake outburst flood (GLOF) in the Engaño Valley, Chilean Patagonia: Lessons for GLOF risk management.

    PubMed

    Anacona, Pablo Iribarren; Mackintosh, Andrew; Norton, Kevin

    2015-09-15

    Floods from moraine-dammed lake failures can have long standing effects not only on riverine landscapes but also on mountain communities due to the high intensity (i.e. great depth and high velocities) and damaging capacity of glacial lake outburst floods (GLOFs). GLOFs may increase in frequency as glaciers retreat and new lakes develop and there is an urgent need to better understand GLOF dynamics and the measures required to reduce their negative outcomes. In Patagonia at least 16 moraine-dammed lakes have failed in historic time, however, data about GLOF dynamics and impacts in this region are limited. We reconstruct a GLOF that affected a small village in Chilean Patagonia in March 1977, by semi structured interviews, interpretation of satellite images and 2D hydraulic modelling. This provides insight into the GLOF dynamics and the planning issues that led to socioeconomic consequences, which included village relocation. Modelling shows that the water released by the GLOF was in the order of 12-13 × 10(6)m(3) and the flood lasted for about 10h, reaching a maximum depth of ~1.5m in Bahía Murta Viejo, ~ 26 km from the failed lake. The lake had characteristics in common with failed lakes worldwide (e.g. the lake was in contact with a retreating glacier and was dammed by a narrow-steep moraine). The absence of land-use planning and the unawareness of the GLOF hazard contributed to the village flooding. The Río Engaño GLOF illustrates how small-scale and short-distance migration is a reasonable coping strategy in response to a natural hazard that may increase in frequency as atmospheric temperature rises and glaciers retreat.

  20. Mercury exports from a High-Arctic river basin in Northeast Greenland (74°N) largely controlled by glacial lake outburst floods.

    PubMed

    Søndergaard, Jens; Tamstorf, Mikkel; Elberling, Bo; Larsen, Martin M; Mylius, Maria Rask; Lund, Magnus; Abermann, Jakob; Rigét, Frank

    2015-05-01

    Riverine mercury (Hg) export dynamics from the Zackenberg River Basin (ZRB) in Northeast Greenland were studied for the period 2009-2013. Dissolved and sediment-bound Hg was measured regularly in the Zackenberg River throughout the periods with running water (June-October) and coupled to water discharge measurements. Also, a few samples of snow, soil, and permafrost were analysed for Hg. Mean concentrations of dissolved and sediment-bound Hg in the river water (±SD) were 0.39 ± 0.13 and 5.5 ± 1.4 ngL(-1), respectively, and mean concentrations of Hg in the river sediment were 0.033 ± 0.025 mg kg(-1). Temporal variations in river Hg were mainly associated with snowmelt, sudden erosion events, and outburst floods from a glacier-dammed lake in the upper part of the ZRB. Annual Hg exports from the 514 km(2) ZRB varied from 0.71 to >1.57 kg and the majority (86-96%) was associated with sediment-bound Hg. Hg yields from the ZRB varied from 1.4-3.1 gH gk m(-2)yr(-1) and were among the highest yields reported from Arctic river basins. River exports of Hg from ZRB were found to be largely controlled by the frequency, magnitude and timing of the glacial lake outburst floods, which occurred in four of the five years in July-August. Floods accounted for 5 to >10% of the annual water discharge, and up to >31% of the annual Hg export. Also, the winter snowfall and the summer temperatures were found to be important indirect controls on the annual Hg export. The occurrence and timing of glacial lake outburst floods in the ZRB in late summer at the time of maximum soil thaw depth, the location of the glacier in the upper ZRB, and increased thawing of the permafrost in Zackenberg in recent years leading to destabilisation of river banks are considered central factors explaining the high fraction of flood-controlled Hg export in this area.

  1. Potential flood volume of Himalayan glacial lakes

    NASA Astrophysics Data System (ADS)

    Fujita, K.; Sakai, A.; Takenaka, S.; Nuimura, T.; Surazakov, A. B.; Sawagaki, T.; Yamanokuchi, T.

    2013-07-01

    Glacial lakes are potentially dangerous sources of glacial lake outburst floods (GLOFs), and represent a serious natural hazard in Himalayan countries. Despite the development of various indices aimed at determining the outburst probability, an objective evaluation of the thousands of Himalayan glacial lakes has yet to be completed. In this study we propose a single index, based on the depression angle from the lakeshore, which allows the lakes to be assessed using remotely sensed digital elevation models (DEMs). We test our approach on five lakes in Nepal, Bhutan, and Tibet using images taken by the declassified Hexagon KH-9 satellite before these lakes experienced an outburst flood. All five lakes had a steep lakefront area (SLA), on which a depression angle was steeper than our proposed threshold of 10° before the GLOF event, but the SLA was no longer evident after the events. We further calculated the potential flood volume (PFV); i.e., the maximum volume of floodwater that could be released if the lake surface was lowered sufficiently to eradicate the SLA. This approach guarantees repeatability to assess the possibility of GLOF hazards because it requires no particular expertise to carry out, though the PFV does not quantify the GLOF risk. We calculated PFVs for more than 2000 Himalayan glacial lakes using visible band images and DEMs of ASTER data. The PFV distribution follows a power-law function. We found that 794 lakes did not have an SLA, and consequently had a PFV of zero, while we also identified 49 lakes with PFVs of over 10 million m3, which is a comparable volume to that of recorded major GLOFs. This PFV approach allows us to preliminarily identify and prioritize those Himalayan glacial lakes that require further detailed investigation on GLOF hazards and risk.

  2. Glacial lakes in the Indian Himalayas--from an area-wide glacial lake inventory to on-site and modeling based risk assessment of critical glacial lakes.

    PubMed

    Worni, Raphael; Huggel, Christian; Stoffel, Markus

    2013-12-01

    Glacial lake hazards and glacial lake distributions are investigated in many glaciated regions of the world, but comparably little attention has been given to these topics in the Indian Himalayas. In this study we present a first area-wide glacial lake inventory, including a qualitative classification at 251 glacial lakes >0.01 km(2). Lakes were detected in the five states spanning the Indian Himalayas, and lake distribution pattern and lake characteristics were found to differ significantly between regions. Three glacial lakes, from different geographic and climatic regions within the Indian Himalayas were then selected for a detailed risk assessment. Lake outburst probability, potential outburst magnitudes and associated damage were evaluated on the basis of high-resolution satellite imagery, field assessments and through the use of a dynamic model. The glacial lakes analyzed in the states of Jammu and Kashmir and Himachal Pradesh were found to present moderate risks to downstream villages, whereas the lake in Sikkim severely threatens downstream locations. At the study site in Sikkim, a dam breach could trigger drainage of ca. 16×10(6)m(3) water and generate maximum lake discharge of nearly 7000 m(3) s(-). The identification of critical glacial lakes in the Indian Himalayas and the detailed risk assessments at three specific sites allow prioritizing further investigations and help in the definition of risk reduction actions. PMID:23218457

  3. Glacial lakes in the Indian Himalayas--from an area-wide glacial lake inventory to on-site and modeling based risk assessment of critical glacial lakes.

    PubMed

    Worni, Raphael; Huggel, Christian; Stoffel, Markus

    2013-12-01

    Glacial lake hazards and glacial lake distributions are investigated in many glaciated regions of the world, but comparably little attention has been given to these topics in the Indian Himalayas. In this study we present a first area-wide glacial lake inventory, including a qualitative classification at 251 glacial lakes >0.01 km(2). Lakes were detected in the five states spanning the Indian Himalayas, and lake distribution pattern and lake characteristics were found to differ significantly between regions. Three glacial lakes, from different geographic and climatic regions within the Indian Himalayas were then selected for a detailed risk assessment. Lake outburst probability, potential outburst magnitudes and associated damage were evaluated on the basis of high-resolution satellite imagery, field assessments and through the use of a dynamic model. The glacial lakes analyzed in the states of Jammu and Kashmir and Himachal Pradesh were found to present moderate risks to downstream villages, whereas the lake in Sikkim severely threatens downstream locations. At the study site in Sikkim, a dam breach could trigger drainage of ca. 16×10(6)m(3) water and generate maximum lake discharge of nearly 7000 m(3) s(-). The identification of critical glacial lakes in the Indian Himalayas and the detailed risk assessments at three specific sites allow prioritizing further investigations and help in the definition of risk reduction actions.

  4. Potential flood volume of Himalayan glacial lakes

    NASA Astrophysics Data System (ADS)

    Fujita, K.; Sakai, A.; Takenaka, S.; Nuimura, T.; Surazakov, A. B.; Sawagaki, T.; Yamanokuchi, T.

    2013-01-01

    Glacial lakes are potentially dangerous sources of glacial lake outburst floods (GLOFs), and represent a serious natural hazard in Himalayan countries. Despite the development of various indices aimed at determining the risk of such flooding, an objective evaluation of the thousands of Himalayan glacial lakes has yet to be completed. In this study we propose a single index, based on the depression angle from the lakeshore, which allows the lakes to be assessed using remotely sensed digital elevation models (DEMs). We test our approach on five lakes in Nepal, Bhutan, and Tibet using images taken by the declassified Hexagon KH-9 satellite before these lakes flooded. All five lakes had a steep lakefront area (SLA), on which a depression angle was steeper than our proposed threshold of 10° before the GLOF event, but the SLA was no longer evident after the events. We further calculated the potential flood volume (PFV); i.e. the maximum volume of floodwater that could be released if the lake surface was lowered sufficiently to eradicate the SLA. This approach guarantees repeatability because it requires no particular expertise to carry out. We calculated PFVs for more than 2000 Himalayan glacial lakes using the ASTER data. The distribution follows a power-law function, and we identified 49 lakes with PFVs of over 10 million m3 that require further detailed field investigations.

  5. Assessment of Potentially Dangerous Glacial Lakes in Chinese Himalayas

    NASA Astrophysics Data System (ADS)

    Xiaojun, Yao; Shiyin, Liu; Xin, Wang

    2010-05-01

    Glacial lake outburst floods (GLOFs) are catastrophic discharges of water resulting primarily from melting glaciers. In the face of global warming, most Himalayan glaciers have been retreating at a rate that ranges from a few meters to several tens of meters per year, resulting in an increase in the number and size and size of glacial lakes and a concomitant increase in the threat of GLOFs. In the past 50 years, 16 GLOF events which were reported in Tibet had caused the loss of human lives as well as severe damage to local infrastructure. Based on the combination of temperature and precipitation of these 14 failed moraine-dammed lakes, the climatic background could be classified into 4 types, that is, warm-wet, warm-arid, cold-wet and near common weather condition. Under different climatic background types, the outburst mechanisms can be further divided into 5 types and 21 modes based on the analysis of 31 failed moraine-dammed lakes documented all over the world. As to a potentially dangerous moraine-dammed lake, all possible breach modes under each climatic background are firstly described and its qualitative possibilities are given by experts, then the decision-making trees are formed and the breach probability of the potentially dangerous moraine-dammed lake can be calculate. The breaching probabilities of the 143 potentially dangerous moraine-dammed lakes were calculated one by one using the decision-making trees model in Chinese Himalayas. The calculating results show that there are 44 lakes with very high breaching probability, 47 lakes with high breaching probability, 24 lakes with median breaching probability, 24 lakes with low breaching probability, 4 lakes with very low breaching probability. The 91 lakes with very high and high breaching probability rate should be requested in the next steps of detailed assessment and should be took into account in local infrastructure construction, such as road, hydropower station and residential plan, etc. Key words

  6. Identification and monitoring of potentially dangerous glacial lakes in northern Tien Shan (Kazakhstan/Kyrgyzstan) using geoinformation techniques

    NASA Astrophysics Data System (ADS)

    Bolch, Tobias; Pradhan, Biswajeet; Peters, Juliane; Buchroithner, Manfred

    2010-05-01

    Like in many other parts of the world, the glaciers in northern Tien Shan are receding and the permafrost is thawing and concomitant glacial lakes are developing. Outbursts of these glacial lakes pose severe hazards for the society. Over the last decade, several outbursts in this seismically active region are documented. Multi-temporal space imageries are an ideal means to study and monitor glaciers and glacial lakes over larger areas. Morphometric analyses and modelling approaches allow the estimation of the potential danger of glacial lake outburst floods (GLOFs). In this paper, we present a comprehensive approach to identify glaciers and the potentially dangerous glacial lakes based on multi-temporal space imagery from 1972 (Corona KH-4B), 1973 (Landsat MSS), 1991 (Landsat TM), 1999 (Landsat ETM+), 2000/2001/ (ASTER) 2005, and 2008 (Landsat TM) as well as morphometric analysis and modelling. The identification and monitoring of glacial lakes were carried out automatically using image ratioing and the Normalized Difference Water Index (except for the panchromatic Corona images). The results were evaluated and, if necessary, manually edited. The probability of the growth of a glacial lake was estimated by analysing glacier changes, glacier motion, and slope analysis. A permafrost model based on morphometric parameters, solar radiation and regionalised temperature conditions aided us to asses the effect of probable permafrost thawing. A GIS-based model was applied in order to simulate the possible downstream impact of a lake outburst. The findings of our studies indicate a continuous glacier recession with an increasing number and area of glacial lakes. This possibly leads into a higher risk of a glacial lake outburst. Finally, the lakes are classified according to their outburst probability and their downstream impact.

  7. Development stages of hazardous mountain lakes and simulation of their outbursts (Central Caucasus, Russia; Sichuan mountain region, China).

    NASA Astrophysics Data System (ADS)

    Kidyaeva, Vera; Krylenko, Inna; Chernomorets, Sergey; Petrakov, Dmitry

    2013-04-01

    The importance of mountain lakes studies is related to the increasing threat of natural disasters, associated with lake outbursts and debris flows formation, because of population growth on exposed areas. The outburst hazard has not been sufficiently researched, there is a lack of data because of the lakes inaccessibility and remote sensing data is usually not detailed enough. The main scientific topics include assessment of outburst possibility and further simulation of possible outbursts scenarios. There are two types of mountain lakes: glacial (cirque, cirque-moraine, barrier-moraine, glacial-barrier, etc.) lakes and barrier (landslide, rockfall, debris flow, etc.) lakes. The first type was studied in the Central Caucasus (Russia), and the second type - in the Sichuan mountain region (China). The group of scientists, including authors, has been monitoring glacial lakes in the Mnt. Elbrus area for more than ten years. The unique data were collected, including detailed hydrological characteristics of more than ten lakes (water level dynamics, temperature, morphometrical characteristics, water balance components, etc.). Outbursts of at least three glacial lakes were observed. Hydrological characteristics of landslide Tangjiashan Lake were collected with Chinese colleagues during field studies in 2010 and 2011 years. Analysis of the collected data was used to understand the outburst mechanisms, formation factors, dam breaking factors, development stages of mountain lakes. Statistical methods of analysis in this case can be applied with some limitations because of the lack of sufficient monitoring objects, and therefore the results has been verified by experts. All types of possible outbursts mechanisms were divided by the authors into five groups: geomorphologic (caused by changes in lake dams), seismic, or geodynamic (caused by seiches, waves from rockfalls, landslides), glacial (caused by breaks in impounding glaciers, ice floating and melting), water

  8. Glacier lake outburst floods - modelling process chains

    NASA Astrophysics Data System (ADS)

    Schaub, Yvonne; Huggel, Christian; Haeberli, Wilfried

    2013-04-01

    New lakes are forming in high-mountain areas all over the world due to glacier recession. Often they will be located below steep, destabilized flanks and are therefore exposed to impacts from rock-/ice-avalanches. Several events worldwide are known, where an outburst flood has been triggered by such an impact. In regions such as in the European Alps or in the Cordillera Blanca in Peru, where valley bottoms are densely populated, these far-travelling, high-magnitude events can result in major disasters. For appropriate integral risk management it is crucial to gain knowledge on how the processes (rock-/ice-avalanches - impact waves in lake - impact on dam - outburst flood) interact and how the hazard potential related to corresponding process chains can be assessed. Research in natural hazards so far has mainly concentrated on describing, understanding, modeling or assessing single hazardous processes. Some of the above mentioned individual processes are quite well understood in their physical behavior and some of the process interfaces have also been investigated in detail. Multi-hazard assessments of the entire process chain, however, have only recently become subjects of investigations. Our study aims at closing this gap and providing suggestions on how to assess the hazard potential of the entire process chain in order to generate hazard maps and support risk assessments. We analyzed different types of models (empirical, analytical, physically based) for each process regarding their suitability for application in hazard assessments of the entire process chain based on literature. Results show that for rock-/ice-avalanches, dam breach and outburst floods, only numerical, physically based models are able to provide the required information, whereas the impact wave can be estimated by means of physically based or empirical assessments. We demonstrate how the findings could be applied with the help of a case study of a recent glacier lake outburst event at Laguna

  9. The state and their implication of Himalayan glacial lake changes from satellite observations

    NASA Astrophysics Data System (ADS)

    Nie, Y.; Sheng, Y.; Liu, Q.; Liu, L.; Liu, S.; Zhang, Y.; Song, C.

    2015-12-01

    Glacial lake outburst floods (GLOFs)generally result in catastrophic damages and fatalities. The Himalayas, the world's highest mountains hosting large number of glaciers, have frequently suffered from GLOFs events in the past decades. Climatic warming-induced melting and retreating glaciers make glacial lakes expand obviously and urge the potential risk of GLOFs in Himalayas. However, our knowledge on the state of glacial lakes in the entire Himalayas is still limited. This study conducts a systematically satellite-based inventory to firstly reveal the evolution complex, regional difference and causes of Himalayan glacial lake changes in the whole Himalayas. Hundreds of Landsat images and Google Earth high resolution imagery were employed to extract the extents of glacial lakes at four epochs (circa1990, circa 2000, circa 2005 and circa 2010). Object-oriented mapping method was used to automatically map the lakes. In association with published glacier data (e.g., China Glacier Inventory, Randolph and GLIMS Glacier data), visual inspections and iterative checks for individual lake guarantee the accuracy of our results. This study demonstrates the spatial and topographic distributions, differences, heterogeneity of glacial lake changes and their causes. Our results show that Himalayan glacial lakes present a rapidly expanding state in general. Both disappeared lakes and new-formed lakes were observed, however, pre-existing glacial lakes contributed most to the total areal expansion. Himalayan glacial lakes appeared a clear altitudinal difference between north side and south side of main range. Evolutions of glacial lakes between eastern, western and central Himalaya were different, and the most rapidly expanding areas need to be more concerned. Climatic and geomorphic controls result in the heterogeneity of glacial lake changes. This study will help assess the potential risk of GLOFs and promote the public awareness of glacial disasters in high mountain areas.

  10. Challenges in understanding, modelling, and mitigating Lake Outburst Flood Hazard: experiences from Central Asia

    NASA Astrophysics Data System (ADS)

    Mergili, Martin; Schneider, Demian; Andres, Norina; Worni, Raphael; Gruber, Fabian; Schneider, Jean F.

    2010-05-01

    Lake Outburst Floods can evolve from complex process chains like avalanches of rock or ice that produce flood waves in a lake which may overtop and eventually breach glacial, morainic, landslide, or artificial dams. Rising lake levels can lead to progressive incision and destabilization of a dam, to enhanced ground water flow (piping), or even to hydrostatic failure of ice dams which can cause sudden outflow of accumulated water. These events often have a highly destructive potential because a large amount of water is released in a short time, with a high capacity to erode loose debris, leading to a powerful debris flow with a long travel distance. The best-known example of a lake outburst flood is the Vajont event (Northern Italy, 1963), where a landslide rushed into an artificial lake which spilled over and caused a flood leading to almost 2000 fatalities. Hazards from the failure of landslide dams are often (not always) fairly manageable: most breaches occur in the first few days or weeks after the landslide event and the rapid construction of a spillway - though problematic - has solved some hazardous situations (e.g. in the case of Hattian landslide in 2005 in Pakistan). Older dams, like Usoi dam (Lake Sarez) in Tajikistan, are usually fairly stable, though landsildes into the lakes may create floodwaves overtopping and eventually weakening the dams. The analysis and the mitigation of glacial lake outburst flood (GLOF) hazard remains a challenge. A number of GLOFs resulting in fatalities and severe damage have occurred during the previous decades, particularly in the Himalayas and in the mountains of Central Asia (Pamir, Tien Shan). The source area is usually far away from the area of impact and events occur at very long intervals or as singularities, so that the population at risk is usually not prepared. Even though potentially hazardous lakes can be identified relatively easily with remote sensing and field work, modeling and predicting of GLOFs (and also

  11. Glacial Lake Expansion in the Central Himalayas by Landsat Images, 1990–2010

    PubMed Central

    Nie, Yong; Liu, Qiao; Liu, Shiyin

    2013-01-01

    Glacial lake outburst flood (GLOF) is a serious hazard in high, mountainous regions. In the Himalayas, catastrophic risks of GLOFs have increased in recent years because most Himalayan glaciers have experienced remarkable downwasting under a warming climate. However, current knowledge about the distribution and recent changes in glacial lakes within the central Himalaya mountain range is still limited. Here, we conducted a systematic investigation of the glacial lakes within the entire central Himalaya range by using an object-oriented image processing method based on the Landsat Thematic Mapper (TM) or Enhanced Thematic Mapper (ETM) images from 1990 to 2010. We extracted the lake boundaries for four time points (1990, 2000, 2005 and 2010) and used a time series inspection method combined with a consistent spatial resolution of Landsat images that consistently revealed lake expansion. Our results show that the glacial lakes expanded rapidly by 17.11% from 1990 to 2010. The pre-existing, larger glacial lakes, rather than the newly formed lakes, contributed most to the areal expansion. The greatest expansions occurred at the altitudinal zones between 4800 m and 5600 m at the north side of the main Himalayan range and between 4500 m and 5600 m at the south side, respectively. Based on the expansion rate, area and type of glacial lakes, we identified 67 rapidly expanding glacial lakes in the central Himalayan region that need to be closely monitored in the future. The warming and increasing amounts of light-absorbing constituents of snow and ice could have accelerated the melting that directly affected the glacial lake expansion. Across the main central Himalayas, glacial lakes at the north side show more remarkable expansion than those at the south side. An effective monitoring and warning system for critical glacial lakes is urgently needed. PMID:24376778

  12. Glacial Retreat and Associated Glacial Lake Hazards in the High Tien Shan

    NASA Astrophysics Data System (ADS)

    Smith, T. T.

    2013-12-01

    A number of studies have identified glacial retreat throughout the greater Himalayan region over the past few decades, but the Karakorum region remains an anomaly with large stagnating or advancing glaciers. The glacial behavior in the Tien Shan is still unclear, as few studies have investigated mass balances in the region. This study focuses on the highest peaks of the Tien Shan mountain range, in the region of Jengish Chokusu along the Kyrgyzstan-China-Kazakhstan border. In a first step, a 30-year time series of Landsat imagery (n=27) and ASTER imagery (n=10) was developed to track glacial growth and retreat in the region. Using a combination of spectral and topographic information, glacial outlines are automatically delineated. As several important glaciers in the study region contain medium to high levels of debris cover, our algorithm also improves upon current methods of detecting debris-covered glaciers by using topography, distance weighting methods, river networks, and additional spectral data. Linked to glacial retreat are glacial lake outburst floods (GLOFs) that have become increasingly common in High Mountain Asia over the last few decades. As glaciers retreat, their melt water is often trapped by weakly bonded moraines. These moraines have been known to fail due to overtopping caused by surge waves created by avalanches, rockslides, or glacial calving. A suite of studies throughout High Mountain Asia have used remotely-sensed data to monitor the formation and growth of glacial lakes. In a second step of the work, lake-area changes over the past 15 years were tracked monthly and seasonally using dense Landsat/ASTER coverage (n=30) with an automatic procedure based on spectral and topographic information. Previous work has identified GLOFs as a significant process for infrastructural damage in the southern Tien Shan/northern Pamir, as well as in the better studied Himalaya region. Lake identification and quantification of lake-growth rates is a valuable

  13. The 24 July 2008 outburst flood of Zyndan glacier lake, Ysyk-Köl region, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Narama, C.; Duishonakonov, M.; Kääb, A.; Abdrakhmatov, K.

    2009-04-01

    On 24 July 2008, a glacial lake outburst flood (GLOF) occurred in the Zyndan River, the Ysyk-Köl region, Kyrgyzstan. The flood killed three people and many livestock (horse, sheep, fish), and caused heavy damage destroying a bridge, road, two homes, and crops of agriculture fields. We researched the damege after two days of the GLOF. Using kinematic GPS we measured the decrease of the glacier lake area, and the according drop of the water level through the outburst. Glacier lake area of about 0.03 km2 reduced after the collapse, more than 400,000 m3 of water were discharged. While the initial flood discharge was relatively small, it increased substantially and was carrying large boulders after 30 minutes. When spreading further downstream, the dirty waters trapped eight people on islands between the stream branches. The flood discharge continued to rise until midnight and began to decrease again around 3 AM the next morning. The lake at 3771 m asl is located in front of the west Zyndan glacier at the head of the Zyndan River basin. The glacier lake had developed rapidly due to glacier shrinkage caused by recent atmospheric warming. Reasons for the outburst included melting of dead ice inside the moraine that dammed the lake. The villages downstream escaped heavy damage, because the main flood changed its direction, away from the water reservoir along the village and towards another river.

  14. Identification of glacier motion and potentially dangerous glacial lakes in the Mt. Everest region/Nepal using spaceborne imagery

    NASA Astrophysics Data System (ADS)

    Bolch, T.; Buchroithner, M. F.; Peters, J.; Baessler, M.; Bajracharya, S.

    2008-12-01

    Failures of glacial lake dams can cause outburst floods and represents a serious hazard. The potential danger of outburst floods depends on various factors like the lake's area and volume, glacier change, morphometry of the glacier and its surrounding moraines and valley, and glacier velocity. Remote sensing offers an efficient tool for displacement calculations and risk assessment of the identification of potentially dangerous glacial lakes (PDGLs) and is especially helpful for remote mountainous areas. Not all important parameters can, however, be obtained using spaceborne imagery. Additional interpretation by an expert is required. ASTER data has a suitable accuracy to calculate surface velocity. Ikonos data offers more detail but requires more effort for rectification. All investigated debris-covered glacier tongues show areas with no or very slow movement rates. From 1962 to 2003 the number and area of glacial lakes increased, dominated by the occurrence and almost linear areal expansion of the moraine-dammed lakes, like the Imja Lake. Although the Imja Lake will probably still grow in the near future, the risk of an outburst flood (GLOF) is considered not higher than for other glacial lakes in the area. Potentially dangerous lakes and areas of lake development are identified. There is a high probability of further lake development at Khumbu Glacier, but a low one at Lhotse Glacier.

  15. Evolution and outburst risk analysis of moraine-dammed lakes in the central Chinese Himalaya

    NASA Astrophysics Data System (ADS)

    Shijin, Wang; Shitai, Jiao

    2015-04-01

    The recent evolution and outburst risk of two typical moraine-dammed lakes, Galong and Gangxi, central Chinese Himalaya, are analyzed using topographic maps from 1974 and Landsat satellite imagery acquired in 1988, 2000 and 2014. The datasets show the areas of Galong and Gangxi lakes increasing at rates of 0.45 and 0.34 km2/year during the period 1974-2014, an expansion of 501% and 107%, respectively, in the past 41 years, while the areas of the parent glaciers, Reqiang and Jipucong decreased by 44.22% and 37.76%, respectively. The accelerating retreat of the glaciers not only reflects their generally negative mass balance but is consistent with the rapid expansion of the moraine-dammed lakes. When acted upon by external forces such as earthquakes, heavy rainfall, rapid melting of glaciers and dead ice, and snow/ice/rock avalanches, these lakes can become extremely dangerous, easily forming outburst mudslides, which can potentially spread to the Poiqu river basin and develop into cross-border (China and Nepal) GLOF disasters. Therefore, there is an urgent need to strengthen integrated risk management of glacial lake outburst disasters with multiple objectives and modes.

  16. Mapping Glacial Lakes on the Tibetan Plateau with Landsat TM/ETM+ Imagery

    NASA Astrophysics Data System (ADS)

    Li, J.; Sheng, Y.

    2009-12-01

    With a pronounced temperature rise of 0.16oC per decade, the Tibetan plateau is one of the world’s most vulnerable areas responding to global change. Glaciers and glacial lakes serve as sensitive indicators to these regional climate and water cycle variations. Recent study shows that glaciers on the plateau have retreated dramatically, leading to the expansion of the existing glacial lakes and the emergence ofnew glacial lakes. The existence of these lakes increases the possibility of outburst floods to the downstream areas during the ice melting season. Mapping and monitoring these glacial lakes will facilitate our understanding of the glacier-related hazards and regional climate changes. However, rigorous field surveys of glacial lake dynamics are prohibitive in high-mountainous areas on the plateau due to their low accessibility. Satellite remote sensing provides an efficient and objective tool to analyze the status and variations of glacial lakes. Theoretically, lakes and other surface open water bodies are readily identified in satellite images owing to their very low reflectance in near-infrared (NIR) channels of Landsat sensors. In the mountain regions where glacial lakes are located, cloud shadows, mountain shadows, melting glaciers or even lakes under different conditions (e.g., ice lakes, salt lakes, turbid lakes) could become disturbing factors and create problems to glacial lake delineation. We use normalized difference water index (NDWI), the normalized ratio index between the green and near infrared spectral bands, to differentiate water bodies from other land features. As lake features are on the relatively flat areas, topographic features such as terrain slope and hill shades derived from digital elevation model (DEM) are also used to remove the shadows from lakes. Based on NDWI and topographic characteristics, We have developed an automated hierarchical method to monitor glacial lakes using Landsat TM/ETM+ imagery. Firstly, lakes are roughly

  17. A new remote hazard and risk assessment framework for glacial lakes in the Nepal Himalaya

    NASA Astrophysics Data System (ADS)

    Rounce, David R.; McKinney, Daene C.; Lala, Jonathan M.; Byers, Alton C.; Watson, C. Scott

    2016-08-01

    Glacial lake outburst floods (GLOFs) pose a significant threat to downstream communities and infrastructure due to their potential to rapidly unleash stored lake water. The most common triggers of these GLOFs are mass movement entering the lake and/or the self-destruction of the terminal moraine due to hydrostatic pressures or a buried ice core. This study initially uses previous qualitative and quantitative assessments to understand the hazards associated with eight glacial lakes in the Nepal Himalaya that are widely considered to be highly dangerous. The previous assessments yield conflicting classifications with respect to each glacial lake, which spurred the development of a new holistic, reproducible, and objective approach based solely on remotely sensed data. This remote hazard assessment analyzes mass movement entering the lake, the stability of the moraine, and lake growth in conjunction with a geometric GLOF to determine the downstream impacts such that the present and future risk associated with each glacial lake may be quantified. The new approach is developed within a hazard, risk, and management action framework with the aim that this remote assessment may guide future field campaigns, modeling efforts, and ultimately risk-mitigation strategies. The remote assessment was found to provide valuable information regarding the hazards faced by each glacial lake and results were discussed within the context of the current state of knowledge to help guide future efforts.

  18. A lake detection algorithm (LDA) using Landsat 8 data: A comparative approach in glacial environment

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Anshuman; Singh, Mritunjay Kumar; Joshi, P. K.; Snehmani; Singh, Shaktiman; Sam, Lydia; Gupta, R. D.; Kumar, Rajesh

    2015-06-01

    Glacial lakes show a wide range of turbidity. Owing to this, the normalized difference water indices (NDWIs) as proposed by many researchers, do not give appropriate results in case of glacial lakes. In addition, the sub-pixel proportion of water and use of different optical band combinations are also reported to produce varying results. In the wake of the changing climate and increasing GLOFs (glacial lake outburst floods), there is a need to utilize wide optical and thermal capabilities of Landsat 8 data for the automated detection of glacial lakes. In the present study, the optical and thermal bandwidths of Landsat 8 data were explored along with the terrain slope parameter derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model Version2 (ASTER GDEM V2), for detecting and mapping glacial lakes. The validation of the algorithm was performed using manually digitized and subsequently field corrected lake boundaries. The pre-existing NDWIs were also evaluated to determine the supremacy and the stability of the proposed algorithm for glacial lake detection. Two new parameters, LDI (lake detection index) and LF (lake fraction) were proposed to comment on the performances of the indices. The lake detection algorithm (LDA) performed best in case of both, mixed lake pixels and pure lake pixels with no false detections (LDI = 0.98) and very less areal underestimation (LF = 0.73). The coefficient of determination (R2) between areal extents of lake pixels, extracted using the LDA and the actual lake area, was very high (0.99). With understanding of the terrain conditions and slight threshold adjustments, this work can be replicated for any mountainous region of the world.

  19. Glacial lake evolution in the southeastern Tibetan Plateau and the cause of rapid expansion of proglacial lakes linked to glacial-hydrogeomorphic processes

    NASA Astrophysics Data System (ADS)

    Song, Chunqiao; Sheng, Yongwei; Ke, Linghong; Nie, Yong; Wang, Jida

    2016-09-01

    Glacial lakes, as an important component of the cryosphere in the southeastern Tibetan Plateau (SETP) in response to climate change, pose significant threats to the downstream lives and properties of people, engineering construction, and ecological environment via outburst floods, yet we currently have limited knowledge of their distribution, evolution, and the driving mechanism of rapid expansions due to the low accessibility and harsh natural conditions. By integrating optical imagery, satellite altimetry and digital elevation model (DEM), this study presents a regional-scale investigation of glacial lake dynamics across two river basins of the SETP during 1988-2013 and further explores the glacial-hydrogeomorphic process of rapidly expanding lakes. In total 1278 and 1396 glacial lakes were inventoried in 1988 and 2013, respectively. Approximately 92.4% of the lakes in 2013 are not in contact with modern glaciers, and the remaining 7.6% includes 27 (1.9%) debris-contact lakes (in contact with debris-covered ice) and 80 (5.7%) cirque lakes. In categorizing lake variations, we found that debris-contact proglacial lakes experienced much more rapid expansions (∼75%) than cirque lakes (∼7%) and non-glacier-contact lakes (∼3%). To explore the cause of rapid expansion for these debris-contact lakes, we further investigated the mass balance of parent glaciers and elevation changes in lake surfaces and debris-covered glacier tongues using time-series Landsat images, ICESat altimetry, and DEM. Results reveal that the upstream expansion of debris-contact proglacial lakes was not directly associated with rising water levels but with a geomorphological alternation of upstream lake basins caused by melting-induced debris subsidence at glacier termini. This suggests that the hydrogeomorphic process of glacier thinning and retreat, in comparison with direct glacial meltwater alone, may have played a dominant role in the recent glacial lake expansion observed across the

  20. Provenance of Palouse Loess and Relation to Late Pleistocene Glacial Outburst Flooding, Washington State

    NASA Astrophysics Data System (ADS)

    Sweeney, M. R.; Busacca, A. J.; Gaylord, D. R.; Zender, C. S.

    2002-12-01

    The eolian system of the Pacific Northwest is a product of long-term deflation of expansive sedimentary units by prevailing winds throughout the Quaternary. The Palouse loess is a deposit of wind-blown silt that covers approximately 10,000 sqare km up to 75 m thick. Late Quaternary units of the loess become finer texturally and thinner to the northeast, suggesting that they were derived from sedimentary basins south and west. The source of the loess has been inferred and hypothesized but never directly determined. A geochemical study of the late-Pleistocene to Holocene L1 unit of the Palouse loess and its possible sources was conducted to determine its provenance. There are two sedimentary units that lie upwind of the loess that may have contributed sediment via eolian deflation: 1) sand- and silt-rich slackwater sediment derived from late-Pleistocene outburst flooding of glacial Lake Missoula, and 2) sand- and silt-rich sediment from the Miocene-Pliocene Ringold Formation. Both are very similar in mineral composition, being derived from plutonic, metamorphic, and volcanic rocks of the western United States and southern British Columbia. Major and trace element data determined by x-ray fluorescence (XRF) of silt to very fine sand from loess and potential source sediments was used to pinpoint the exact source of the loess. A one-to-one relationship of major and trace elements exists between eolian and flood sediments, whereas Ringold Formation sediments have elevated Ti, P, Mg, and Ca oxides and lower K oxide values as well as scattered trace element values relative to Palouse loess. These trends may be due to the presence of basalt lithic grains in flood sediment that have been broken down and distributed throughout the loess. The Ringold Formation lacks appreciable amounts of basalt. The geochemical data from this study demonstrates that flood sediment is the dominant source of eolian material for the Palouse loess. The spatial distribution of the possible source

  1. Emergency satellite observation and assessment of a glacier lake outburst flood in Bhutan

    NASA Astrophysics Data System (ADS)

    Nagai, Hiroto; Tadono, Takeo; Suzuki, Shinichi

    2016-04-01

    Following a glacial lake outburst flood (GLOF) on Jun. 28, 2015, in western Bhutan, the Japan Aerospace Exploration Agency performed an emergency observation on Jul. 2, 2015 using the Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2) onboard the Advanced Land Observing Satellite-2 (ALOS-2, "DAICHI-2"). Based on a dataset generated from the Advanced Land Observing Satellite (ALOS) imagery, "The Glacial Lake Inventory of Bhutan using ALOS Data", the glacier lake that potentially contributed to this GLOF were identified at 28°4'7.7"N, 89°34'50.0"E, in a headwater of the Mo Chu river basin, western Bhutan. A post-event lake outline was delineated manually using the acquired PALSAR-2 image. Pre-event outlines were delineated from previously acquired PALSAR-2 images (Apr. 23, 2015), Landsat 8 (Mar. 8, 2015), and ALOS (Dec. 22, 2010). The differences between these outlines reveal a remarkable expansion (+48.0%) from Mar. 8 to Apr. 23, 2015, followed by a remarkable shrinkage (‑52.9%) from Apr. 23 to Jul. 2, 2015. This result indicates the lake to be a highly likely source of the flood. Topographically, it is located at a glacier terminus, surrounded by a moraine. Differing backscatter patterns between successive PALSAR-2 images in a certain part of the moraine suggest that it underwent some collapse, possibly as a result of the GLOF. More detailed investigations, including field surveys, are necessary to fully reveal and understand this event.

  2. Late Glacial lakes - uniform or contrasting ecosystems?

    NASA Astrophysics Data System (ADS)

    Zawiska, Izabela; Rzodkiewicz, Monika; Noryśkiewicz, Agnieszka M.; Obremska, Milena; Ott, Florian; Kramkowski, Mateusz; Słowiński, Michał; Błaszkiewicz, Mirosław; Brauer, Achim

    2015-04-01

    Climate changes are one of the most investigated topic in paleolimnology. The Late Glacial and Early Holocene time are specially interesting as than most abrupt changes happened. Lake sediments are known to be great source of information of the past environments. They are functioning as natural archives because in them preserve animal and plants remains. In this study we investigated three cores of the biogenic sediments from the lakes located in close vicinity in Tuchola Forest (Northern Poland): paleolake Trzechowskie, Lake Czechowskie-deepest part and Lake Czechowskie-bay. We made Cladocera, diatom and pollen analysis, the chronology was determined by varve counting, Laacher See Tephra (12,880 yrs BP) and 14C dating. The aim of our research was to find out the response of zooplankton, phytoplankton, lake and catchment vegetation to abrupt climate changes. We were interested in similarities and differences between those three locations in response of entire communities but also species composition. The preliminary results revealed that the Cladocera, diatoms and plants communities were sensitive to climatic shifts and it is well shown in the results of ordination method (PCA). However in the Cladocera and diatoms assemblages, which reflect well lake environment conditions, the dominant species and total number of species present, were different in all three locations. Especially great difference was noted between paleolake Trzechowskie and Lake Czechowskie (core from the deepest part). The results of our research shows that in Late Glacial time landscape in Lake Czechowskie region (Tuchola Forest, Northern Poland) had mosaic character. Local factors such as relief, edaphic conditions strongly modified type of vegetation and in close vicinity existed lakes that had very diverse environments.

  3. Status of glacial Lake Columbia during the last floods from glacial Lake Missoula

    USGS Publications Warehouse

    Atwater, B.F.

    1987-01-01

    The last floods from glacial Lake Missoula, Montana, probably ran into glacial Lake Columbia, in northeastern Washington. In or near Lake Columbia's Sanpoil arm, Lake Missoula floods dating from late in the Fraser glaciation produced normally graded silt beds that become thinner upsection and which alternate with intervals of progressively fewer varves. The highest three interflood intervals each contain only one or two varves, and about 200-400 successive varves conformably overlie the highest flood bed. This sequence suggests that jo??kulhlaup frequency progressively increased until Lake Missoula ended, and that Lake Columbia outlasted Lake Missoula. The upper Grand Coulee, Lake Columbia's late Fraser-age outlet, contains a section of 13 graded beds, most of them sandy and separated by varves, that may correlate with the highest Missoula-flood beds of the Sanpoil River valley. The upper Grand Coulee also contains probable correlatives of many of the approximately 200-400 succeeding varves, as do nearby parts of the Columbia River valley. This collective evidence casts doubt on a prevailing hypothesis according to which one or more late Fraser-age floods from Lake Missoula descended the Columbia River valley with little or no interference from Lake Columbia's Okanogan-lobe dam. ?? 1987.

  4. Potentially dangerous glacial lakes in Kyrgyzstan - Research overview of 2004-2015

    NASA Astrophysics Data System (ADS)

    Jansky, Bohumir; Yerokhin, Sergey; Sobr, Miroslav; Engel, Zbynek; Cerny, Michal; Falatkova, Kristyna; Kocum, Jan; Benes, Vojtech

    2016-04-01

    Global warming causes intensive melting and retreat of glaciers in most of high mountains all over the world. This process is also evident in the mountain regions of central Tien Shan. Glacier melt water affects changes in hydrological regime of water streams and causes overfilling of high mountain lake basins. The dams of many lakes are very unstable and can burst open. To determine the degree of such risk, it is necessary to analyse the genesis of lakes, to characterize the morphology of the lake basins and to know the particularities of their hydrological regime. According to the latest inventory within territory of Kyrgyzstan, a total of 1328 lakes have been identified as potentially dangerous, 12 lakes are considered as currently dangerous, other 25 feature high potential hazard. Since 1952 more than 70 disastrous cases of lake outburst have been registered. The hazardous alpine lakes are studied in Kyrgyzstan systematically since 1966. Since 2004, Czech-Kyrgyz research team has been operating in Kyrgyzstan in the field of dangerous glacial lakes. Projects were focused primarily on high-mountain glacial lakes risk assessment, propositions of risk mitigation measures, establishment of permanent research station near one of the studied glacier complexes, preparation of risk analysis for selected endangered valleys, evaluation of climatic and hydrological data and glacier development within observed regions. The most significant portion of data and information has been gathered during field work, complemented by satellite image analysis and surveillance flights over the monitored sites.

  5. A subtropical fate awaited freshwater discharged from glacial Lake Agassiz

    SciTech Connect

    Condron, Alan; Winsor, Peter

    2011-02-10

    The 8.2 kyr event is the largest abrupt climatic change recorded in the last 10,000 years, and is widely hypothesized to have been triggered by the release of thousands of kilometers cubed of freshwater into the North Atlantic Ocean. Using a high-resolution (1/6°) global, ocean-ice circulation model we present an alternative view that freshwater discharged from glacial Lake Agassiz would have remained on the continental shelf as a narrow, buoyant, coastal current, and would have been transported south into the subtropical North Atlantic. The pathway we describe is in contrast to the conceptual idea that freshwater from this lake outburst spread over most of the sub-polar North Atlantic, and covered the deep, open-ocean, convection regions. This coastally confined freshwater pathway is consistent with the present-day routing of freshwater from Hudson Bay, as well as paleoceanographic evidence of this event. In this study, using a coarse-resolution (2.6°) version of the same model, we demonstrate that the previously reported spreading of freshwater across the sub-polar North Atlantic results from the inability of numerical models of this resolution to accurately resolve narrow coastal flows, producing instead a diffuse circulation that advects freshwater away from the boundaries. To understand the climatic impact of freshwater released in the past or future (e.g. Greenland and Antarctica), the ocean needs to be modeled at a resolution sufficient to resolve the dynamics of narrow, coastal buoyant flows.

  6. Evolution of supra-glacial ponds on a debris-covered Chamlang South Glacier, Nepal Himalaya to a potentially dangerous glacial lake

    NASA Astrophysics Data System (ADS)

    Lamsal, D.; Sawagaki, T.; Watanabe, T.; Sakai, A.

    2013-12-01

    A number of moraine dammed glacial lakes have been developed in the Himalayan region since 1950s as a result of melting and retreat of debris-covered glaciers. Such glacial lakes sometimes produce devastating glacier lake outburst floods (GLOFs) which are often several times bigger than normal climatic floods. In Nepal Himalaya, about a score glacial lakes have been identified as ';potentially dangerous' largely relying on remote sensing image analyses. Chamlang South Glacier Lake in the Eastern Nepal Himalaya, which evolved from few tiny supra-glacial ponds in 1960s on debris-covered Chamlang South Glacier into a large glacial lake is one among them. Moreover, the lake has been repeatedly cited as a potentially dangerous lake for a glacial lake outburst flood (GLOF) and also regarded as one of the most highly prioritized critical lakes in Nepal Himalaya. However, detailed investigation of the lake either by field survey or remote sensing has not been carried out on Chamlang South Glacier/Glacier Lake hitherto. We carried out surface area and bathymetric mappings of the lake, detailed topographic mappings of moraine dam complex and surrounding of the glacial lake, and field assessment to examine the development of Chamlang South Glacier Lake, and to assess its prospect of GLOF and potential volume of water to be released from the lake in the event of dam breach. High-resolution Corona KH-4A and Advanced Land Observing Satellite (ALOS) PRISM stereo-data taken in 1964 and 2006 respectively were processed to generate digital terrain models (DTMs). Surface area of supra-glacial ponds in 1964 was 0.040 km2 which grew to 0.636 km2 by 1992 and reached 0.864 km2 by 2000 and virtually stopped expanding thereafter. Produced bathymetric map revealed the lake to be 87 m deep (maximum) and volume of water contained in the lake was calculated to be ~35.6 × 106 m3. Extensive surface lowering as high as 156.9 m, and average surface lowering by 2.2 m/year is found. All topographic

  7. Regional Analysis of the Hazard Level of Glacial Lakes in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Chisolm, Rachel E.; Jhon Sanchez Leon, Walter; McKinney, Daene C.; Cochachin Rapre, Alejo

    2016-04-01

    The Cordillera Blanca mountain range is the highest in Peru and contains many of the world's tropical glaciers. This region is severely impacted by climate change causing accelerated glacier retreat. Secondary impacts of climate change on glacier retreat include stress on water resources and the risk of glacial lake outburst floods (GLOFs) from the many lakes that are forming and growing at the base of glaciers. A number of GLOFs originating from lakes in the Cordillera Blanca have occurred over the last century, several of which have had catastrophic impacts on cities and communities downstream. Glaciologists and engineers in Peru have been studying the lakes of the Cordillera Blanca for many years and have identified several lakes that are considered dangerous. However, a systematic analysis of all the lakes in the Cordillera Blanca has never before been attempted. Some methodologies for this type of systematic analysis have been proposed (eg. Emmer and Vilimek 2014; Wang, et al. 2011), but as yet they have only been applied to a few select lakes in the Cordillera Blanca. This study uses remotely sensed data to study all of the lakes of the Glacial Lake Inventory published by the Glaciology and Water Resources Unit of Peru's National Water Authority (UGRH 2011). The objective of this study is to assign a level of potential hazard to each glacial lake in the Cordillera Blanca and to ascertain if any of the lakes beyond those that have already been studied might pose a danger to nearby populations. A number of parameters of analysis, both quantitative and qualitative, have been selected to assess the hazard level of each glacial lake in the Cordillera Blanca using digital elevation models, satellite imagery, and glacier outlines. These parameters are then combined to come up with a preliminary assessment of the hazard level of each lake; the equation weighting each parameter draws on previously published methodologies but is tailored to the regional characteristics

  8. The sequence and timing of large late Pleistocene floods from glacial Lake Missoula

    NASA Astrophysics Data System (ADS)

    Hanson, Michelle A.; Lian, Olav B.; Clague, John J.

    2012-01-01

    through the rail line exposure. The sediment at the two sections was deposited during later stages of glacial Lake Missoula, after the largest outburst events.

  9. Light attenuation characteristics of glacially-fed lakes

    NASA Astrophysics Data System (ADS)

    Rose, Kevin C.; Hamilton, David P.; Williamson, Craig E.; McBride, Chris G.; Fischer, Janet M.; Olson, Mark H.; Saros, Jasmine E.; Allan, Mathew G.; Cabrol, Nathalie

    2014-07-01

    Transparency is a fundamental characteristic of aquatic ecosystems and is highly responsive to changes in climate and land use. The transparency of glacially-fed lakes may be a particularly sensitive sentinel characteristic of these changes. However, little is known about the relative contributions of glacial flour versus other factors affecting light attenuation in these lakes. We sampled 18 glacially-fed lakes in Chile, New Zealand, and the U.S. and Canadian Rocky Mountains to characterize how dissolved absorption, algal biomass (approximated by chlorophyll a), water, and glacial flour contributed to attenuation of ultraviolet radiation (UVR) and photosynthetically active radiation (PAR, 400-700 nm). Variation in attenuation across lakes was related to turbidity, which we used as a proxy for the concentration of glacial flour. Turbidity-specific diffuse attenuation coefficients increased with decreasing wavelength and distance from glaciers. Regional differences in turbidity-specific diffuse attenuation coefficients were observed in short UVR wavelengths (305 and 320 nm) but not at longer UVR wavelengths (380 nm) or PAR. Dissolved absorption coefficients, which are closely correlated with diffuse attenuation coefficients in most non-glacially-fed lakes, represented only about one quarter of diffuse attenuation coefficients in study lakes here, whereas glacial flour contributed about two thirds across UVR and PAR. Understanding the optical characteristics of substances that regulate light attenuation in glacially-fed lakes will help elucidate the signals that these systems provide of broader environmental changes and forecast the effects of climate change on these aquatic ecosystems.

  10. A rapidly growing moraine-dammed glacial lake on Ngozumpa Glacier, Nepal

    NASA Astrophysics Data System (ADS)

    Thompson, Sarah S.; Benn, Douglas I.; Dennis, Kathryn; Luckman, Adrian

    2012-04-01

    Moraine-dammed glacial lakes are becoming increasingly common in the Himalaya as a result of glacier mass loss, causing concern about glacier lake outburst flood risk. In addition to extant lakes, the potential exists for many more to form, as more glaciers ablate down to the level of potential moraine dams. In this paper, we document the recent rapid growth of, a moraine-dammed lake on Ngozumpa Glacier, Nepal. Using a combination of ground-based mapping and sonar surveys, aerial photographs (< 1 m resolution), and ASTER imagery (15 m resolution), processes and rates of lake expansion have been determined. The lake first formed between 1984 and 1992 when collapse of an englacial conduit allowed water to accumulate at the level of a gap in the lateral moraine, ~km from the glacier terminus. Lake growth was initially slow, but since 2001 it has undergone exponential growth at an average rate of 10% y-1. In 2009, the lake area was 300,000 m2, and its volume was at least 2.2 million m3. Calving, subaqueous melting, and melting of subaerial ice faces all contribute to the expansion of the lake; but large-scale, full-height slab calving is now the dominant contributor to growth. Comparison with other lakes in the region indicate that lake growth will likely continue unchecked whilst the spillway remains at its current level and may attain a volume of hundreds of millions of cubic metres within the next few decades.

  11. Case for periodic, colossal jokulhlaups from Pleistocene glacial Lake Missoula.

    USGS Publications Warehouse

    Waitt, R.B., Jr.

    1985-01-01

    Lake Missoula (2500 km3) remained sealed as long as any segment of the glacial dam remained grounded; when the lake rose to a critical level c.600 m in depth, the glacier bed at the seal became buoyant, initiating underflow from the lake. Subglacial tunnels then grew exponentially, leading to catastrophic discharge. Calculations of the water budget for the lake basin (including input from the Cordilleran ice sheet) suggest that the lake filled every three to seven decades. -from Author

  12. Emerging Glacial Lakes in the Cordillera Blanca, Peru: A Case Study at Arteson Glacier

    NASA Astrophysics Data System (ADS)

    Chisolm, R. E.; Mckinney, D. C.; Gomez, J.; Voss, K.

    2012-12-01

    Tropical glaciers are an essential component of the water resources systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean glaciers in recent decades. The shrinkage of Andean glaciers influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some glaciers. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical glaciers in Peru and how climate change is likely to impact glacial melt and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to glaciers in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect glacier mass balance. This study presents GPR data taken in July 2012 at the Arteson glacier in the Cordillera Blanca, Peru. A new lake has begun to form at the terminus of the Arteson glacier, and this lake has key features, including overhanging ice and loose rock likely to create landslides, that could trigger a catastrophic GLOF if the lake continues to grow. This new lake is part of a series of three lakes that have formed below the Arteson glacier. The two lower lakes, Artesonraju and Paron, are much larger so that if there were an avalanche or landslide into the new lake below Arteson glacier, the impact could potentially be more catastrophic than a GLOF from one single lake. Estimates of how the lake mass balance is likely to evolve due to the retreating glacier are key to assessing the flood risk from this dynamic three-lake system. Because the glacier mass balance and lake mass balance are closely linked, the ice thickness measurements and measurements of the bed slope of the Arteson glacier and underlying bedrock give us a clue to how the lake is likely to evolve. GPR measurements of

  13. Sedimentary record of sub-glacial outburst floods at Laurentian Fan

    NASA Astrophysics Data System (ADS)

    Leng, Wei; von Dobeneck, Tilo

    2016-04-01

    Large-scale glacial meltwater discharge could be widely recognized off the eastern Canadian continental margin. At Laurentian Fan, sub-glacial outburst floods eroded Permian-Carboniferous redbeds at Gulf of St. Lawrence and then delivered the reddish sediments by Laurentian Channel. Sedimentary record from four gravity cores (GeoB18514-2, 18515-1, 18516-2 and 18517-1) at the SW slope of the Grand Banks of Newfoundland revealed the major depositional processes since Heinrich event 2 (ca. 22 ka). In the cores, the upper thick Holocene olive-grey silty mud units overly IRD-rich Heinrich 1 layer, five reddish units are distinguished in the lower part. Reddish units get proportionally thinner along the SW slope at higher and more distal positions; instead, separating olive-grey layers get thicker with height and distance. Reddish and olive grey units have sharp boundaries and no signs of erosion. Mean grain size changes abruptly from coarse in grey layers to fine in reddish layers, terrigenous elements (as Al, K, Ti, Fe) and clays (Al/Si) are highly elevated in reddish layers and low in Heinrich layers, which are instead enriched in detrital continental carbonates. Both Heinrich layers and reddish layers have enhanced magnetic susceptibility, but Heinrich layer have higher ferromagnetic (SIRM) content (mafic rocks), while reddish layers have more hematite (HIRM). These five reddish layers differ from event to event, which seems to reflect different mixing ratios of event-related and background sedimentation. This mixing will allow estimating event-specific sedimentation rates. Using mixing ratio combined with 14C dating data could contribute to estimate the sedimentation rate and duration of outburst floods, which could help to build ice sheet retreat history and find the connection with paleoclimate changes.

  14. Numerical simulation of the paleohydrology of glacial Lake Oshkosh, eastern Wisconsin, USA

    USGS Publications Warehouse

    Clark, J.A.; Befus, K.M.; Hooyer, T.S.; Stewart, P.W.; Shipman, T.D.; Gregory, C.T.; Zylstra, D.J.

    2008-01-01

    Proglacial lakes, formed during retreat of the Laurentide ice sheet, evolved quickly as outlets became ice-free and the earth deformed through glacial isostatic adjustment. With high-resolution digital elevation models (DEMs) and GIS methods, it is possible to reconstruct the evolution of surface hydrology. When a DEM deforms through time as predicted by our model of viscoelastic earth relaxation, the entire surface hydrologic system with its lakes, outlets, shorelines and rivers also evolves without requiring assumptions of outlet position. The method is applied to proglacial Lake Oshkosh in Wisconsin (13,600 to 12,900??cal yr BP). Comparison of predicted to observed shoreline tilt indicates the ice sheet was about 400??m thick over the Great Lakes region. During ice sheet recession, each of the five outlets are predicted to uplift more than 100??m and then subside approximately 30??m. At its maximum extent, Lake Oshkosh covered 6600??km2 with a volume of 111??km3. Using the Hydrologic Engineering Center-River Analysis System model, flow velocities during glacial outburst floods up to 9??m/s and peak discharge of 140,000??m3/s are predicted, which could drain 33.5??km3 of lake water in 10??days and transport boulders up to 3??m in diameter. ?? 2007 University of Washington.

  15. Why did the Nepal Gorkha Earthquake Have so few Effects on Glacial Lakes?

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Collins, B. D.; Fielding, E. J.; Fujita, K.; Haritashya, U. K.; Hudnut, K. W.; Leonard, G. J.; Shugar, D. H.; Sakai, A.; Jibson, R.

    2015-12-01

    On 25 April 2015, a magnitude 7.8 earthquake struck Nepal. Subsequently many large aftershocks shook the region, including one of magnitude 7.3. Much damage occurred and over 4000 landslides were triggered, but fortunately few earthquake effects on glacier lakes have been identified and no large glacier lake outburst floods (GLOFs) have been clearly attributed to the quakes. Why were the lakes largely unscathed? We will (1) review some cases around the world where earthquakes have apparently triggered responses among glaciers and glacier- or moraine-dammed lakes, and how these responses took place, (2) consider why earthquakes in general might not commonly have such large impacts on glacial lakes as widely expected; (3) show some case examples of glacial moraine-dammed lakes in Nepal and Tibet where few visible effects of the Gorkha earthquake (and aftershocks) were documented; and (4) consider why specifically the Gorkha earthquake (+ aftershocks) caused very few and mild effects. Earthquake shaking and steep slopes result in thousands of landslides when big earthquakes occur in mountains; furthermore, large mass movements into glacial lakes are a known trigger of many GLOFs. Worldwide there is little evidence, contrary to speculation, and now reinforced by the Gorkha quake, that earthquakes—even big ones happening near glacier lakes—are normally a major trigger of GLOFs. There may be several explanations. The Gorkha earthquake might have caused less shaking than its total released energy suggests, thus further sparing the Himalayan lakes from catastrophe. A possible further protective aspect is that glacial lakes mainly occur far up alpine valleys. It is known from other quakes that when there is shallow slip and rugged relief, surface wave modes tend to be absorbed and scattered as these waves propagate across mountain ranges, and body waves are focused into ridges, thus reducing the ground accelerations on valley floors (where lakes occur) and commonly

  16. Index for hazard of Glacier Lake Outburst flood of Lake Merzbacher by satellite-based monitoring of lake area and ice cover

    NASA Astrophysics Data System (ADS)

    Xie, Zunyi; ShangGuan, Donghui; Zhang, Shiqiang; Ding, Yongjian; Liu, Shiyin

    2013-08-01

    Previous studies show that the area of a moraine-dammed lake can provide a good indicator of the significance of its outburst. For a glacier-dammed lake however, because its area and depth fluctuates with the melting of its ice dam, it is difficult to predict the outburst of the glacier-dammed lake by using its area alone.A characteristic of the surface of Lake Merzbacher is a large amount of floating ice therefore, a method is proposed in this article to extract the area of floating ice on the lake and the area of ice free water in the lake by using Environment and Disaster Monitoring Small Satellite images respectively. Furthermore, based on the area of floating ice extracted through the image information of Lake Merzbacher in 2009 and 2010, we determined the relationship between the ice area and the outburst of the lake, then formulated the Index for hazard of Glacier Lake Outburst Flood (IGLOF) of Lake Merzbacher, which cannot only predict the flood outburst, but also determine the specific outburst period after the lake drainage had occurred. This can be shown in a recalculation of the lake drainages in the years 2009 and 2010. Research results indicate that when IGLOF is less than 0.5 and the lake area is larger than 3 km2, the outburst process is in early-warning period and GLOF will occur in the next 5-8 days. Also, the successful outburst prediction of Lake Merzbacher in 2011 showed that the index described in this paper provides a quick methodology for forecasting and warning against Lake Merzbacher outburst floods. However,as our research was based on a short observation period (2009-2011) and also cannot be supplemented by other images, it will still be needed to be checked and validated by continuous observation and improvement in future.

  17. Oxygen-isotope variations in post-glacial Lake Ontario

    NASA Astrophysics Data System (ADS)

    Hladyniuk, Ryan; Longstaffe, Fred J.

    2016-02-01

    The role of glacial meltwater input to the Atlantic Ocean in triggering the Younger Dryas (YD) cooling event has been the subject of controversy in recent literature. Lake Ontario is ideally situated to test for possible meltwater passage from upstream glacial lakes and the Laurentide Ice Sheet (LIS) to the Atlantic Ocean via the lower Great Lakes. Here, we use the oxygen-isotope compositions of ostracode valves and clam shells from three Lake Ontario sediment cores to identify glacial meltwater contributions to ancient Lake Ontario since the retreat of the LIS (∼16,500 cal [13,300 14C] BP). Differences in mineralogy and sediment grain size are also used to identify changes in the hydrologic regime. The average lakewater δ18O of -17.5‰ (determined from ostracode compositions) indicates a significant contribution from glacial meltwater. Upon LIS retreat from the St. Lawrence lowlands, ancient Lake Ontario (glacial Lake Iroquois) lakewater δ18O increased to -12‰ largely because of the loss of low-18O glacial meltwater input. A subsequent decrease in lakewater δ18O (from -12 to -14‰), accompanied by a median sediment grain size increase to 9 μm, indicates that post-glacial Lake Ontario received a final pulse of meltwater (∼13,000-12,500 cal [11,100-10,500 14C] BP) before the onset of hydrologic closure. This meltwater pulse, which is also recorded in a previously reported brief freshening of the neighbouring Champlain Valley (Cronin et al., 2012), may have contributed to a weakening of thermohaline circulation in the Atlantic Ocean. After 12,900 cal [11,020 14C] BP, the meltwater presence in the Ontario basin continued to inhibit entry of Champlain seawater into early Lake Ontario. Opening of the North Bay outlet diverted upper Great Lakes water from the lower Great Lakes causing a period (12,300-8300 cal [10,400-7500 14C] BP) of hydrologic closure in Lake Ontario (Anderson and Lewis, 2012). This change is demarcated by a shift to higher δ18Olakewater

  18. Hydrogeophysical characterisation of ice-marginal moraines, with reference to moraine dam stability, Miage Glacial Lake, Italy

    NASA Astrophysics Data System (ADS)

    Thompson, S. S.; Kulessa, B.

    2010-12-01

    In mountain regions, potentially hazardous glacial lakes are becoming increasingly common as a consequence of climatically driven glacier recession. Lakes can expand rapidly in the space between downwasting or receding glacier fronts and terminal or lateral moraines, and are prone to catastrophic drainage if the moraine dam is breached. Lake drainage can have severe impacts on both fragile mountain ecosystems and local economies. In addition to the moraine-dammed lakes currently in existence, it is likely that many more will form in the coming decades as more glaciers cross the threshold required for rapid lake expansion. A key factor in assessing the stability and future evolution of such systems is a better understanding of the subsurface structure and hydrology of the moraine dams. Here results are presented from electrical geophysical work carried out across the breach moraine complex at the Miage Glacial Lake, Italy. A combination of induced polarisation, normalised induced polarisation and self potentials have been used to characterise the local water table and to identify the subsurface connections between two moraines dammed glacial lakes. The results not only show the depth and distribution of subsurface flow but also the preferential flow pathways, indicating areas of maximum discharge. The results highlight the areas of the moraines where hydrological processes are causing internal degradation and impacting upon the longer term stability of the system. This model therefore, can be employed on much larger systems where the risk of outburst has far greater consequences.

  19. Bathymetry and temperature of some glacial lakes in Wyoming

    PubMed Central

    Leopold, Luna B.

    1980-01-01

    On the west flank of the Wind River Mountains, Wyoming, are several large lakes occupying glacially scoured depressions dammed by terminal moraines. Fremont, Willow, and New Fork Lakes, having maximal depths of 185, 85, and 62 m, respectively, are not only deep, but in 1970-1978 they had no measurable coliform. They have exceptionally low values of total dissolved solids; Fremont Lake has only 12.8 mg/liter, probably the second most dilute large lake in coterminus United States. Summer mixing is restricted to the uppermost 10 m, below which the lakes are essentially isothermal at the maximum density temperature, about 3.9°C. PMID:16592797

  20. Bathymetry and temperature of some glacial lakes in Wyoming.

    PubMed

    Leopold, L B

    1980-04-01

    On the west flank of the Wind River Mountains, Wyoming, are several large lakes occupying glacially scoured depressions dammed by terminal moraines. Fremont, Willow, and New Fork Lakes, having maximal depths of 185, 85, and 62 m, respectively, are not only deep, but in 1970-1978 they had no measurable coliform. They have exceptionally low values of total dissolved solids; Fremont Lake has only 12.8 mg/liter, probably the second most dilute large lake in coterminus United States. Summer mixing is restricted to the uppermost 10 m, below which the lakes are essentially isothermal at the maximum density temperature, about 3.9 degrees C.

  1. Bathymetry and temperature of some glacial lakes in Wyoming.

    PubMed

    Leopold, L B

    1980-04-01

    On the west flank of the Wind River Mountains, Wyoming, are several large lakes occupying glacially scoured depressions dammed by terminal moraines. Fremont, Willow, and New Fork Lakes, having maximal depths of 185, 85, and 62 m, respectively, are not only deep, but in 1970-1978 they had no measurable coliform. They have exceptionally low values of total dissolved solids; Fremont Lake has only 12.8 mg/liter, probably the second most dilute large lake in coterminus United States. Summer mixing is restricted to the uppermost 10 m, below which the lakes are essentially isothermal at the maximum density temperature, about 3.9 degrees C. PMID:16592797

  2. Predicting outflow induced by moraine failure in glacial lakes: the Lake Palcacocha case from an uncertainty perspective

    NASA Astrophysics Data System (ADS)

    Rivas, D. S.; Somos-Valenzuela, M. A.; Hodges, B. R.; McKinney, D. C.

    2015-06-01

    Moraine dam collapse is one of the causes of glacial lake outburst floods. Available models seek to predict both moraine breach formation and lake outflow. The models depend on hydraulic, erosion, and geotechnical parameters that are mostly unknown or uncertain. This paper estimates the outflow hydrograph caused by a potential erosive collapse of the moraine dam of Lake Palcacocha in Peru and quantifies the uncertainty of the results. The overall aim is to provide a simple yet hydraulically robust approach for calculating the expected outflow hydrographs that is useful for risk assessment studies. To estimate the peak outflow and failure time of the hydrograph, we assessed several available empirical equations based on lake and moraine geometries; each equation has defined confidence intervals for peak flow predictions. Complete outflow hydrographs for each peak flow condition were modeled using a hydraulic simulation model calibrated to match the peak flows estimated with the empirical equations. Failure time and peak flow differences between the simulations, and the corresponding empirical equations were used as error parameters. Along with an expected hydrograph, lower and upper bound hydrographs were calculated for Lake Palcacocha, representing the confidence interval of the results. The approach has several advantages: first, it is simple and robust. Second, it evaluates the capability of empirical equations to reproduce the conditions of the lake and moraine dam. Third, this approach accounts for uncertainty in the hydrographs estimations, which makes it appropriate for risk management studies.

  3. Glacial-marine and glacial-lacustrine sedimentation in Sebago Lake, Maine: Locating the marine limit

    SciTech Connect

    Johnston, R.A.; Kelley, J.T. ); Belknap, D. . Dept. of Geological Sciences)

    1993-03-01

    The marine limit in Maine marks a sea-level highstand at approximately 13 ka. It was inferred to cross Sebago Lake near Frye Island by Thompson and Borns (1985) on the Surficial Geological Map of Maine, dividing the lake into a northern glacial-lacustrine basin and a southern glacial-marine basin. This study examined the accuracy of the mapped marine limit in the lake and the nature of glacial-lacustrine and glacial-marine facies in Maine. Recognition of the marine limit is usually based on mapped shorelines, glacial-marine deltas, and contacts with glacial-marine sediments. This study, in Maine's second largest lake, collected 100 kilometers of side-scan sonar images, 100 kilometers of seismic reflection profiles, and one core. Side-scan sonar records show coarse sand and gravel and extensive boulder fields at an inferred grounding-line position near Frye Island, where the marine limit was drawn. ORE Geopulse seismic reflection profiles reveal a basal draping unit similar to glacial-marine units identified offshore. Later channels cut more than 30 m into the basal stratified unit. In addition, till and a possible glacial-tectonic grounding-line feature were identified. Slumps and possible spring disruptions are found in several locations. The top unit is an onlapping ponded Holocene lacustrine unit. Total sediment is much thicker in the southern basin; the northern basin, >97 m deep, north of the marine limit appears to have been occupied by an ice block. Retrieved sediments include 12 meters of rhythmites. Microfossil identifications and dating will resolve the environments and time of deposition in this core.

  4. Coupling glacial lake impact, dam breach, and flood processes: A modeling perspective

    NASA Astrophysics Data System (ADS)

    Worni, Raphael; Huggel, Christian; Clague, John J.; Schaub, Yvonne; Stoffel, Markus

    2014-11-01

    Glacial lake outburst floods (GLOFs) are highly mobile mixtures of water and sediment that occur suddenly and are capable of traveling tens to hundreds of kilometers with peak discharges and volumes several orders of magnitude larger than those of normal floods. They travel along existing river channels, in some instances into populated downstream regions, and thus pose a risk to people and infrastructure. Many recent events involve process chains, such as mass movements impacting glacial lakes and triggering dam breaches with subsequent outburst floods. A concern is that effects of climate change and associated increased instability of high mountain slopes may exacerbate such process chains and associated extreme flows. Modeling tools can be used to assess the hazard of potential future GLOFs, and process modeling can provide insights into complex processes that are difficult to observe in nature. A number of numerical models have been developed and applied to simulate different types of extreme flows, but such modeling faces challenges stemming from a lack of process understanding and difficulties in measuring extreme flows for calibration purposes. Here we review the state of knowledge of key aspects of modeling GLOFs, with a focus on process cascades. Analysis and simulation of the onset, propagation, and potential impact of GLOFs are based on illustrative case studies. Numerical models are presently available for simulating impact waves in lakes, dam failures, and flow propagation but have been used only to a limited extent for integrated simulations of process cascades. We present a spectrum of case studies from Patagonia, the European Alps, central Asia, and the Himalayas in which we simulate single processes and process chains of past and potential future events. We conclude that process understanding and process chain modeling need to be strengthened and that research efforts should focus on a more integrative treatment of processes in numerical models.

  5. Estimation of glacial outburst floods in Himalayan watersheds by means of quantitative modelling

    NASA Astrophysics Data System (ADS)

    Brauner, M.; Agner, P.; Vogl, A.; Leber, D.; Haeusler, H.; Wangda, D.

    2003-04-01

    In the Himalayas intense glacier retreat rates and at quickly developing settlement activity in the downstream valleys, result in dramatically increasing Glacier Lake Outburst risk. As settlement activity concentrates on broad and productive valley areas, being typically 10 to 70 kilometres downstream of the flood source, hazard awareness and preparedness is limited. Therefore application of quantitative assessment methodology is crucial in order to delineate flood prone areas and develop hazard preparedness concepts by means of scenario modelling. For dam breach back-calculation the 1D-simulation tool BREACH is utilised. Generally the initiation by surge waves and the broad sediment size spectrum of tills are difficult to implement. Therefore a tool with long application history has been chosen. The flood propagation is simulated with the 2D-hydraulic simulation model FLO2D which enables water flood and sediment load routing. In three Himalayan watersheds (Pho Chhu valley, Bhutan; Tam Pokhari valley, Nepal) recent Glacier Lake Outbursts (each with more than 20 mill m3 volume) and consecutive floods are simulated and calibrated by means of multi-time morpho-logical information, high water marks, geomorphologic interpretation and eye witness consultation. These calculations show that for these events the dam breach process was slow (within 0.75 to 3 hours), with low flood hydrographs. The flood propagation was governed by a sequence of low-sloping, depositional channel sections, and steep channel section with intense lateral sediment mobilisation and temporary blockage. This resulted in a positive feedback and prolonged the flood. By means of sensitivity analysis the influence of morphological changes during the events and the imporance of the dam breach process to the whole is estimated. It can be shown, that the accuracy of the high water limit is governed by the following processes: sediment mobilisation, breaching process, water volume, morphological changes

  6. An inventory of glacial lakes in the Austrian Alps

    NASA Astrophysics Data System (ADS)

    Buckel, Johannes; Otto, Jan-Christoph; Keuschnig, Markus; Götz, Joachim

    2016-04-01

    The formation of lakes is one of the consequences of glacier retreat due to climate change in mountain areas. Numerous lakes have formed in the past few decades in many mountain regions around the globe. Some of these lakes came into focus due to catastrophic hazard events especially in the Himalayas and the Andes. Glacial lake development and lifetime is controlled by the complex interplay of glacier dynamics, geomorphological process activity and geological boundary conditions. Besides the hazard potential new lakes in formerly glaciated areas will significantly contribute to a new landscape setting and to changing geomorphologic, hydrologic and ecologic conditions at higher alpine altitudes. We present an inventory of high alpine lakes in the Austrian Alps located above an altitude of 1700 m asl. Most of these lakes are assumed to be of glacial origin, but other causes for development, like mass movements are considered as well. The inventory is a central part of the project FUTURELAKES that aims at modelling the potential development of glacial lakes in Austria (we refer to the presentation by Helfricht et al. during the conference for more details on the modelling part). Lake inventory data will serve as one basis for model validation since modelling is performed on different time steps using glacier inventory data. The purpose of the lake inventory is to get new insights into boundary conditions for lake formation and evolution by analysing existing lake settings. Based on these information the project seeks to establish a model of lake sedimentation after glacier retreat in order to assess the potential lifetime of the new lakes in Austria. Lakes with a minimum size of 1000 m² were mapped using multiple aerial imagery sources. The dataset contains information on location, geometry, dam type, and status of sedimentation for each lake. Additionally, various geologic, geomorphic and morphometric parameters describe the lake catchments. Lake data is related to

  7. Identification of Younger Dryas outburst flood path from Lake Agassiz to the Arctic Ocean.

    PubMed

    Murton, Julian B; Bateman, Mark D; Dallimore, Scott R; Teller, James T; Yang, Zhirong

    2010-04-01

    The melting Laurentide Ice Sheet discharged thousands of cubic kilometres of fresh water each year into surrounding oceans, at times suppressing the Atlantic meridional overturning circulation and triggering abrupt climate change. Understanding the physical mechanisms leading to events such as the Younger Dryas cold interval requires identification of the paths and timing of the freshwater discharges. Although Broecker et al. hypothesized in 1989 that an outburst from glacial Lake Agassiz triggered the Younger Dryas, specific evidence has so far proved elusive, leading Broecker to conclude in 2006 that "our inability to identify the path taken by the flood is disconcerting". Here we identify the missing flood path-evident from gravels and a regional erosion surface-running through the Mackenzie River system in the Canadian Arctic Coastal Plain. Our modelling of the isostatically adjusted surface in the upstream Fort McMurray region, and a slight revision of the ice margin at this time, allows Lake Agassiz to spill into the Mackenzie drainage basin. From optically stimulated luminescence dating we have determined the approximate age of this Mackenzie River flood into the Arctic Ocean to be shortly after 13,000 years ago, near the start of the Younger Dryas. We attribute to this flood a boulder terrace near Fort McMurray with calibrated radiocarbon dates of over 11,500 years ago. A large flood into the Arctic Ocean at the start of the Younger Dryas leads us to reject the widespread view that Agassiz overflow at this time was solely eastward into the North Atlantic Ocean.

  8. Hydrology and Glacier-Lake-Outburst Floods (1987-2004) and Water Quality (1998-2003) of the Taku River near Juneau, Alaska

    USGS Publications Warehouse

    Neal, Edward G.

    2007-01-01

    The Taku River Basin originates in British Columbia, Canada, and drains an area of 6,600 square miles at the U.S. Geological Survey's Taku River gaging station. Several mines operated within the basin prior to 1957, and mineral exploration has resumed signaling potential for future mining developments. The U.S. Geological Survey in cooperation with the Douglas Indian Association, Alaska Department of Environmental Conservation, and the U.S. Environmental Protection Agency conducted a water-quality and flood-hydrology study of the Taku River. Water-quality sampling of the Taku River from 1998 through 2003 established a baseline for assessing potential effects of future mining operations on water quality. The annual mean discharge of the Taku River is 13,700 cubic feet per second. The monthly mean discharge ranges from a minimum of 1,940 cubic feet per second in February to a maximum of 34,400 cubic feet per second in June. Nearly 90 percent of the annual discharge is from May through November. The highest spring discharges are sourced primarily from snowmelt and moderate discharges are sustained throughout the summer by glacial meltwaters. An ice cover usually forms over the Taku River in December persisting through the winter into March and occasionally into April. Glacier-lake-outburst floods originating from two glacier-dammed lakes along the margin of the Tulsequah Glacier in British Columbia, Canada, are the source of the greatest peak discharges on the Taku River. The largest flood during the period of record was 128,000 cubic feet per second on June 25, 2004, resulting from an outburst of Lake No Lake. Lake No Lake is the larger of the two lakes. The outburst-flood contribution to peak discharge was 80,000 cubic feet per second. The volume discharged from Lake No Lake is relatively consistent indicating drainage may be triggered when the lake reaches a critical stage. This suggests prediction of the timing of these outburst floods might be possible if lake

  9. Risk estimation for future glacier lake outburst floods based on local land-use changes

    NASA Astrophysics Data System (ADS)

    Nussbaumer, S.; Schaub, Y.; Huggel, C.; Walz, A.

    2014-06-01

    Effects of climate change are particularly strong in high-mountain regions. Most visibly, glaciers are shrinking at a rapid pace, and as a consequence, glacier lakes are forming or growing. At the same time the stability of mountain slopes is reduced by glacier retreat, permafrost thaw and other factors, resulting in an increasing landslide hazard which can potentially impact lakes and therewith trigger far-reaching and devastating outburst floods. To manage risks from existing or future lakes, strategies need to be developed to plan in time for adequate risk reduction measures at a local level. However, methods to assess risks from future lake outbursts are not available and need to be developed to evaluate both future hazard and future damage potential. Here a method is presented to estimate future risks related to glacier lake outbursts for a local site in southern Switzerland (Naters, Valais). To generate two hazard scenarios, glacier shrinkage and lake formation modelling was applied, combined with simple flood modelling and field work. Furthermore, a land-use model was developed to quantify and allocate land-use changes based on local-to-regional storylines and three scenarios of land-use driving forces. Results are conceptualized in a matrix of three land-use and two hazard scenarios for the year 2045, and show the distribution of risk in the community of Naters, including high and very high risk areas. The study underlines the importance of combined risk management strategies focusing on land-use planning, on vulnerability reduction, as well as on structural measures (where necessary) to effectively reduce future risks related to lake outburst floods.

  10. Local land-use change based risk estimation for future glacier lake outburst flood

    NASA Astrophysics Data System (ADS)

    Nussbaumer, S.; Huggel, C.; Schaub, Y.; Walz, A.

    2013-08-01

    Effects of climate change are particularly strong in high-mountain regions. Most visibly, glaciers are shrinking at a rapid pace, and as a consequence, glacier lakes are forming or growing. At the same time the stability of mountain slopes is reduced by glacier retreat, permafrost thaw and other factors, resulting in an increasing risk of landslides which can potentially impact lakes and therewith trigger far reaching and devastating outburst floods. To manage risks from existing or future lakes, strategies need to be developed to plan in time for adequate risk reduction measures at a local level. However, methods to assess risks from future lake outbursts are not available. It is actually a challenge to develop methods to evaluate both, future hazard potential and future damage potential. Here we present an analysis of future risks related to glacier lake outbursts for a local site in southern Switzerland (Naters, Valais). To estimate two hazard scenarios, we used glacier shrinkage and lake formation modelling, simple flood modelling and field work. Further we developed a land-use model to quantify and allocate land-use changes based on local-to-regional storylines and three scenarios of land-use driving forces. Results are conceptualized in a matrix of three land-use and two hazard scenarios for a time period of 2045, and show the distribution of risk in the community of Naters, including high and very high risk areas. The study corroborates the importance of land-use planning to effectively reduce future risks related to lake outburst floods.

  11. Hydrogeologic setting of the Glacial Lake Agassiz Peatlands, northern Minnesota

    USGS Publications Warehouse

    Siegel, Donald I.

    1981-01-01

    Seven test holes drilled in the Glacial Lake Agassiz Peatlands indicate that the thickness of surficial materials along a north-south traverse parallel to Minnesota Highway 72 ranges from 163 feet near Blackduck, Minnesota to 57 feet about 3 miles south of Upper Red Lake. Lenses of sand and gravel occur immediately above bedrock on the Itasca moraine and are interbedded with lake clay and till under the peatlands. Vertical head gradients measured in a piezometer nest near Blackduck on the moraine are downward, indicative of recharge to the regional ground-water-flow system. Vertical head gradients are upward in a piezometer nest on a sand beach ridge in the peatlands 12 miles north of Upper Red Lake. Numerical sectional models indicate that this discharge probably comes from local flow systems recharged from ground-water mounds located under large raised bogs.

  12. Glacier lake outburst floods caused by glacier shrinkage: case study of Ala-Archa valley, Kyrgyz Ala Too, northern Tian Shan, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Petrakov, D.; Erochin, S. A.; Harbor, J.; Ivanov, M.; Rogozhina, I.; Stroeven, A. P.; Usubaliev, R.

    2012-12-01

    Changes in glacier extent and runoff in Central Asia increase socio-economic stress and may result in political conflict between donors of freshwater (Kyrgyzstan, Tajikistan) and recipients of freshwater (Uzbekistan, China). Glaciers in the Pamir and Tian Shan regions have experienced an unprecedented downwasting due to regional climate changes over the past decades. This is because air temperature increases are in some areas accompanied by a decrease in precipitation. Such conditions have already resulted in a reduction of glacier runoff, especially in the northern and western Tian Shan, and an increase of the number and area of glacial lakes in Kyrgyzstan. Even though glacial lakes in the mountains are in general relatively small and located far from densely populated areas, their outbursts often produce destructive debris flows. Such debris flows are especially common in Kyrgyzstan because of its steep river channels and abundance of Holocene and Quaternary glacier deposits that can be remobilized. The glacial lake outburst flood (GLOF) in the Shakhimardan river catchment in 1999, for example, resulted in 100 fatalities in Uzbekistan, and the GLOF from the Zyndan glacial lake led to substantial economic losses in 2009. According to the latest inventory, there are more than 350 glacial lakes in Kyrgyzstan of which about 70 occur in the Kyrgyz Ala Too. The Ala-Archa valley is among the most important glacierized catchments in Kyrgyzstan. Despite the presence of a relatively small glacier-covered area of 36 km2, the Ala-Archa river is of critical importance to the Bishkek area, its agriculture, and its population which currently exceeds one million. GLOFs are therefore a threat to both numerous settlements of touristic value in the Ala-Archa headwaters and to Bishkek. The Teztor lake in the Adygene catchment of the Ala-Archa river system experienced an outburst during 1988 and 2005. On the early morning of July 31, 2012, this lake began draining through a dam

  13. Outburst floods from glacier-dammed lakes: The effect of mode of lake drainage on flood magnitude

    USGS Publications Warehouse

    Walder, J.S.; Costa, J.E.

    1996-01-01

    Published accounts of outburst floods from glacier-dammed lakes show that a significant number of such floods are associated not with drainage through a tunnel incised into the basal ice - the process generally assumed - but rather with ice-marginal drainage, mechanical failure of part of the ice dam, or both. Non-tunnel floods are strongly correlated with formation of an ice dam by a glacier advancing from a tributary drainage into either a main river valley or a pre-existing body of water (lake or fiord). For a given lake volume, non-tunnel floods tend to have significantly higher peak discharges than tunnel-drainage floods. Statistical analysis of data for floods associated with subglacial tunnels yields the following empirical relation between lake volume V and peak discharge script Q signp : script Q signp = 46V0.66 (r2 = 0.70), when script Q signp is expressed in metres per second and V in millions of cubic metres. This updates the so-called Clague-Mathews relation. For non-tunnel floods, the analogous relation is script Q signp = 1100V0.44 (r2 = 0.58). The latter relation is close to one found by Costa (1988) for failure of constructed earthen dams. This closeness is probably not coincidental but rather reflects similarities in modes of dam failure and lake drainage. We develop a simple physical model of the breach-widening process for non-tunnel floods, assuming that (1) the rate of breach widening is controlled by melting of the ice, (2) outflow from the lake is regulated by the hydraulic condition of critical flow where water enters the breach, and (3) the effect of lake temperature may be dealt with as done by Clarke (1982). Calculations based on the model simulate quite well outbursts from Lake George, Alaska. Dimensional analysis leads to two approximations of the form script Q signp ??? Vqf(hi, ??0), where q = 0.5 to 0.6, hi is initial lake depth, ??0 is lake temperature, and the form of f(hi, ??0) depends on the relative importance of viscous

  14. Glacier Dynamics and Outburst Flood Potential from the Imja and Thulagi Glacier-Lake Systems (Nepal)

    NASA Astrophysics Data System (ADS)

    Kargel, Jeffrey; Leonard, Gregory; Regmi, Dhananjay; Haritashya, Umesh; Chand, Mohan; Pradhan, Suresh; Sapkota, Nawaraj; Byers, Alton; Joshi, Sharad; McKinney, Daene; Mool, Pradeep; Somos-Valenzuela, Marcelo; Huggel, Christian

    2015-04-01

    Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e., most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine melt-through or down-cutting mechanisms -- perhaps induced by extreme monsoon precipitation or an earthquake -- could generate outbursts lasting from 10,000-100,000 seconds ("slow GLOFs"), thus limiting peak flows and downstream damage. The potential damage from a slow GLOF from Imja Lake -- even if there is a large total volume -- is lessened by the relatively low peak discharge and because the major villages downstream from Imja Lake are situated just outside of and above a deep, broad outwash and debris-flow channel system. Imja and other glaciers in the area have built a large fan, now deeply trenched, which is able to accommodate the peak discharges of potential slow GLOFs, such that Dingboche and other villages would be spared. However, local geomorphology also bears evidence of "fast GLOFs," such as may be issued by a tsunami, which could be initiated by a large mass movement into Imja Lake and which might override and damage the end moraine in <100 seconds. Dingboche and other villages are vulnerable to

  15. Compounding Hazards Facing Nepalese Villages due to Glacial Lake Thulagi, Extreme Monsoons, and Landslides

    NASA Astrophysics Data System (ADS)

    Leonard, Gregory; Kargel, Jeffrey; Regmi, Dhananjay

    2014-05-01

    Thulagi Tsho is listed by ICIMOD as among the most hazardous glacial lakes in Nepal. The listing is warranted by the physiography and downstream vulnerabilities. Tal Village—along a major trekking route—and a hydroelectric dam and reservoir are notably at risk due to the potential for a glacier lake outburst flood (GLOF), an extreme summer monsoon, extreme spring snowmelt, landslides, and rockfalls. Tal is downstream from Thulagi Lake just a couple meters above river level, and ordinary monsoons already cause an approach toward flood conditions, according to residents. A high flood stage due to an extreme monsoon or unusually rapid springtime melting of a thick winter snowpack could be catastrophic. Two significant mass movements occurred recently in Tal, one having buried some structures in the village in June 2012. In a favorable note, satellite image analysis shows that Thulagi Lake has slowed its elongation in the last couple years. Furthermore, any tsunami or other flood surge would have to traverse and erode a wide end moraine in order to generate a GLOF. On the other hand, remote sensing and field observations show that wasting of Thulagi Glacier has debuttressed the northern lateral moraine, which is slipping toward the growing lake and the thinning/retreating glacier. The landslip itself is not necessarily a bad thing: it is causing a loss of gravitational potential energy of the lateral moraine, and if that process continues gradually, it will result in diminished instability. However, the debuttressing and moraine slip signifies that the moraines are unstable. Will a rapid mass movement dump into the lake? Triggers could include seismicity, extreme rainfall, or a small landslip. The risk of a serious GLOF exceeds that of Imja Lake due to Thulagi Lake's large hydrographic head and the shape of its downstream end, which could funnel and amplify a potential tsunami generated by a large mass movement into the lake. A moraine collapse into the lake would

  16. Insights from analyzing and modelling cascading multi-lake outburst flood events in the Santa Cruz Valley (Cordillera Blanca, Perú)

    NASA Astrophysics Data System (ADS)

    Emmer, Adam; Mergili, Martin; Juřicová, Anna; Cochachin, Alejo; Huggel, Christian

    2016-04-01

    Since the end of Little Ice Age, the Cordillera Blanca of Perú has experienced tens of lake outburst floods (LOFs), resulting in the loss of thousands of lives and significant material damages. Most commonly involving glacial lakes, such events are often directly or indirectly related to glacier retreat. Here we analyze an event on 8th February 2012 involving four lakes and affecting two valleys (Santa Cruz and Artizón) in the northern part of the Cordillera Blanca. Using the combination of field data, satellite images, digital elevation model (DEM) and GIS-based modelling approaches, the main objectives are: (i) to better understand complex multi-lake outburst flood and related foregoing and induced geomorphological processes; and (ii) to evaluate and discuss the suitability, potentials and limitations of the r.avaflow model for modelling such complex process chains. Analyzing field geomorphological evidence and remotely-sensed images, we reconstruct the event as follows: a landslide from the recently deglaciated left lateral moraine of Lake Artizón Alto (4 639 m a.s.l.), characterized by steep slopes and a height of more than 200 m produced a displacement wave which overtopped the bedrock dam of the lake. The resulting flood wave breached the dam of the downstream moraine-/landslide-dammed Lake Artizón Bajo (4 477 m a.s.l.), decreasing the lake level by 10 m and releasing 3 x 105 m3 of water. Significant amounts of material were eroded from the steeper parts of the Artizón Valley (mean slope >15°) and deposited further downstream in the flatter part of the Santa Cruz Valley (mean slope <2°; confluence of the two valleys at 3 985 m a.s.l.). The flood affected two debris cone-dammed lakes (Jatuncocha and Ichiccocha) in the Santa Cruz Valley. Some minor damages to the dam of Lake Jatuncocha were documented. Geomprohological evidence of the event was observed more than 20 km downstream from Lake Artizón Alto. The described multi-LOF event was employed as a

  17. Isotopically-depleted late Pleistocene groundwater in Columbia River Basalt aquifers: Evidence for recharge of glacial Lake Missoula floodwaters?

    NASA Astrophysics Data System (ADS)

    Brown, Kyle B.; McIntosh, Jennifer C.; Baker, Victor R.; Gosch, Damian

    2010-11-01

    Late Pleistocene outburst flooding of ice-dammed glacial Lake Missoula, and possible discharge from the Cordilleran Ice Sheet (CIS), catastrophically altered the northwestern United States landscape, yet little is known about potential infiltration of flood waters into the subsurface. This study provides compelling evidence for the presence of late Pleistocene CIS-related recharge waters in the Columbia River Basalt Aquifers (CRBAs) in central Washington. CRBA groundwaters with corrected 14C ages from 15.7 and 33.3 k yrs BP (during periods of flood events) have anomalously low δ18O values (-18.9 to -17.6‰), compared to late Pleistocene soil waters (-16.1 to -13.4‰) and modern precipitation in the region (average -15.9‰), consistent with CIS-related meltwater recharge. These results have implications for our understanding of megaflood phenomena on earth and Mars.

  18. Turbidite megabeds in an Oceanic Rift Valley recording jokulhlaups of late Pleistocene glacial lakes of the western United States

    USGS Publications Warehouse

    Zuffa, G.G.; Normark, W.R.; Serra, F.; Brunner, C.A.

    2000-01-01

    Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) 14C dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS 14C ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one ~60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jokulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River.

  19. Recent drainage events of glacial Lake Cachet 2, Patagonia

    NASA Astrophysics Data System (ADS)

    Casassa, G.; Wendt, J.; Wendt, A.; Escobar, F.; Lopez, P.; Carrasco, J.; Rivera, A.; Leidich, J.

    2009-04-01

    Lake Cachet 2 (47°12' S, 73°15' W, 422 m a.s.l.) is a proglacial lake of 4 km2 located on the eastern margin of the Northern Patagonia Icefield (3,953 km2, Rivera et al., 2007), which is dammed on its southern margin by Colonia Glacier. Until April 2008 there was no historical evidence of catastrophic flooding of this lake. In 2008 three sudden drainage events occurred at Lake Cachet 2 (April 6-7; October 7-8 and 21-22 December). During each event the flood wave traveled down Colonia River to the confluence with Baker River, then affected Baker River to a distance of up to 25 km upstream from the confluence and downstream all the way to its mouth on the Pacific Ocean fjords at Caleta Tortel (100 km to the southwest), transporting abundant sediments. In April the runoff of Baker River close to the confluence with Colonia River increased from a base level of 1,200 m3/s on April 7 to a peak runoff of 3,570 m3/s within a period of less than 48 hours, resulting in a river level increase of 4.5 m and an associated water temperature drop from 8°C to 4°C. In October the base level was 573 m3/s, with a peak runoff of 3,007 m3/s, a river level increase of 4.7 m and a water temperature drop from 7.3°C to 4.8°C, while in December the corresponding values were 1,145 m3/s, 3,052 m3/s, 11°C and 8°C. The flood affected roads, bridges, farms and cattle, fortunately not resulting in any human damage. Similar floods had been reported on Colonia River several decades ago, the last having occurred in the 1970s, all of which originated at that time at glacial Lake Arco, located south of Colonia Glacier. Airborne and ground explorations carried out after each event in 2008 confirmed that the floods originated at Lake Cachet 2, draining under Colonia Glacier for a distance of 8 km and emerging at the front of the glacier. As a result parts of the glacier front collapsed after each event, where large ice fractures could be observed. During the October event a complete drainage of

  20. Contrasted evolution of glacial lakes along the Hindu Kush Himalaya mountain range between 1990 and 2009

    NASA Astrophysics Data System (ADS)

    Gardelle, Julie; Arnaud, Yves; Berthier, Etienne

    2011-01-01

    In this study, we present a first regional assessment of glacial lake distribution and evolution in the Hindu Kush Himalaya (HKH). Seven sites have been selected between Bhutan and Afghanistan, to capture the climatic variability along the 2000-km long mountain range. For each site, glacial lakes have been mapped with LANDSAT satellite imagery acquired in 1990, 2000 and 2009, using an automatic classification. In the East (India, Nepal and Bhutan), glacial lakes are bigger and more numerous than in the West (Pakistan, Afghanistan), and have grown continuously between 1990 and 2009 by 20% to 65%. On the other hand, during the same period, the glacial lake coverage has shrunk in the Hindu Kush (-50%) and the Karakorum (-30%). This east/west pattern of lake changes seems in agreement with sparse glaciological measurements that suggest less (or even no) ice loss in the western part of the HKH.

  1. Glacial lakes amplify glacier recession in the central Himalaya

    NASA Astrophysics Data System (ADS)

    King, Owen; Quincey, Duncan; Carrivick, Jonathan; Rowan, Ann

    2016-04-01

    The high altitude and high latitude regions of the world are amongst those which react most intensely to climatic change. Across the Himalaya glacier mass balance is predominantly negative. The spatial and temporal complexity associated with this ice loss across different glacier clusters is poorly documented however, and our understanding of the processes driving change is limited. Here, we look at the spatial variability of glacier hypsometry and glacial mass loss from three catchments in the central Himalaya; the Dudh Koshi basin, Tama Koshi basin and an adjoining section of the Tibetan Plateau. ASTER and SETSM digital elevation models (2014/15), corrected for elevation dependant biases, co-registration errors and along or cross track tilts, are differenced from Shuttle Radar Topographic Mission (SRTM) data (2000) to yield surface lowering estimates. Landsat data and a hypsometric index (HI), a classification scheme used to group glaciers of similar hypsometry, are used to examine the distribution of glacier area with altitude in each catchment. Surface lowering rates of >3 m/yr can be detected on some glaciers, generally around the clean-ice/debris-cover boundary, where dark but thin surface deposits are likely to enhance ablation. More generally, surface lowering rates of around 1 m/yr are more pervasive, except around the terminus areas of most glaciers, emphasising the influence of a thick debris cover on ice melt. Surface lowering is only concentrated at glacier termini where glacial lakes have developed, where surface lowering rates are commonly greater than 2.5 m/yr. The three catchments show contrasting hypsometric distributions, which is likely to impact their future response to climatic changes. Glaciers of the Dudh Koshi basin store large volumes of ice at low elevation (HI > 1.5) in long, debris covered tongues, although their altitudinal range is greatest given the height of mountain peaks in the catchment. In contrast, glaciers of the Tama Koshi

  2. Influence of glacial meltwater on equilibrium process of two Tibetan lakes indicated by δ18O

    NASA Astrophysics Data System (ADS)

    Gao, J.

    2009-12-01

    δ18O measurements based on systematic sampling and isotopic model have been adopted to study the affects of glacial meltwater in two lake basins (Lakes Yamdrok-tso and Puma Yum-tso) at two different elevations on the southern Tibetan Plateau. Temporally, δ18O values in precipitation and lake water display a seasonal fluctuation in both lakes. Spatially, δ18O values in the two lake basins increase by 10‰ from the termini of glaciers to the lake shores, by about 1‰ from the lakeshores to the lake center, by 0.4‰ from the water surface to depth in these lakes. The obvious annual δ18O variations indicate that lake water mixes sufficient in a short time. Model results show that glacial meltwater is an important factor on lake water equilibrium process. Equilibrium δ18O values decrease 0.8‰ for Yamdrok-tso Lake and 0.6‰ for Puma Yum-tso Lake when contributions of glacial meltwater to these lakes shrink by 60%. δ18O increases rapidly during the initial stages and then it takes a long time to approach the equilibrium value. The modeled results also show that the surface lake water temperature has only a little impact on this process.

  3. Holocene and Late Glacial varved sediments from Czechowskie Lake (Poland)

    NASA Astrophysics Data System (ADS)

    Ott, Florian; Brauer, Achim; Słowiński, Michał; Dulski, Peter; Plessen, Birgit; Blaszkiewicz, Miroslaw

    2013-04-01

    Annual laminated (varved) sediment records are essential for detailed paleoclimate and environmental reconstructions as they function as a natural memory beyond instrumental datasets. In order to determine Holocene inter-annual and decadal-scale variability we investigated varved Lake Czechowskie (53°52' N/ 18°14' E, 108 m asl.), northern Poland. During two coring campaigns in 2009 and 2012 we recovered several long and short cores with the longest core reaching 14.5 m. Based on correlation with a biostratigraphically and tephrochronologically dated neighboring paleolake sediment record (Trzechowskie mire) the record extends back in to the Late Glacial. Lake Czechowskie is well suited for climate reconstruction as varves are almost entirely well (88 %) or poorly (5%) preserved. Only 7 % of the sediment profile are non-varved. Detailed investigations have been carried out for the last 2000 years of the sediment profile applying micro-facies analyses combined with X-ray fluorescence element scanning (µ-XRF) at 200 µm resolution and carbon and nitrogen analyses (TOC, TC, TN) at five-varveresolution. The chronology has been established by a multiple dating approach with 137Cs (for the last ca. 50 years), AMS 14C on plant macro remains (back to 2800 cal BP) and varve counting. Varve formation and preservation ceases at the beginning of the 20th century whereas the younger sediments are again faintly varved. Micro-facies analyses reveal that the sediment consists of biogenic calcite varves with intercalated diatom rich layers. Three distinct 100 to 200 years long periods of up to threefold thicker varves (approx. 1.4 to 5.0 mm/year) are predominantly caused by an increase in the diatom sub-layers and indicate distinct short-term climatic and environmental fluctuations. Possible reasons for these changes that occurred abruptly with only few years are either changes in lake water circulation or in nutrient supply to the lake. This study is a contribution to the Virtual

  4. Glacial geology, glacial recession, proglacial lakes, and postglacial environments, Fishers Island, New York

    SciTech Connect

    Sirkin, L. ); Funk, R.E. . Anthropological Survey)

    1993-03-01

    The Fishers Island Moraine, a complex of three parallel ice margin depositional trends, forms the west-central segment of a major recessional moraine of the Connecticut-Rhode Island Lobe of the late Wisconsinan glacier. As such, the moraine links the Orient Point Moraine of eastern Long Island and the Charlestown Moraine of western Rhode Island and marks a prominent recessional ice margin. The moraine is correlative with the Roanoke Point Moraine of the Connecticut Lobe of northeastern Long Island. Pollen stratigraphy of >13,180 ka bog sediments begins early in the spruce (A) pollen zone with evidence of a cold, late-glacial climate. The pine (B) pollen zone, beginning prior to 11,145 ka, and the oak (C) pollen zone, dating from about 9,000 ka with hickory and hemlock subzones, are well represented. However, after about 2,000 ka, the stratigraphic record in the bog sections is missing in most cases due to peat harvesting. Pollen spectra from several archeological sites fall within the late oak pollen zone, well within the land clearing interval with evidence of hardwood forests and locally holly and cedar. Evidence of cultigens in the pollen record is sparse. Marine deposits over fresh water bog and proglacial lake sediments show that some coastal bogs were drowned by sea level rise.

  5. A subtropical fate awaited freshwater discharged from glacial Lake Agassiz

    DOE PAGES

    Condron, Alan; Winsor, Peter

    2011-02-10

    The 8.2 kyr event is the largest abrupt climatic change recorded in the last 10,000 years, and is widely hypothesized to have been triggered by the release of thousands of kilometers cubed of freshwater into the North Atlantic Ocean. Using a high-resolution (1/6°) global, ocean-ice circulation model we present an alternative view that freshwater discharged from glacial Lake Agassiz would have remained on the continental shelf as a narrow, buoyant, coastal current, and would have been transported south into the subtropical North Atlantic. The pathway we describe is in contrast to the conceptual idea that freshwater from this lake outburstmore » spread over most of the sub-polar North Atlantic, and covered the deep, open-ocean, convection regions. This coastally confined freshwater pathway is consistent with the present-day routing of freshwater from Hudson Bay, as well as paleoceanographic evidence of this event. In this study, using a coarse-resolution (2.6°) version of the same model, we demonstrate that the previously reported spreading of freshwater across the sub-polar North Atlantic results from the inability of numerical models of this resolution to accurately resolve narrow coastal flows, producing instead a diffuse circulation that advects freshwater away from the boundaries. To understand the climatic impact of freshwater released in the past or future (e.g. Greenland and Antarctica), the ocean needs to be modeled at a resolution sufficient to resolve the dynamics of narrow, coastal buoyant flows.« less

  6. New insights on the late-stage history of glacial Lake Ojibway: implications for meltwater discharges of the last deglaciation

    NASA Astrophysics Data System (ADS)

    Roy, Martin; Veillette, Jean J.; Godbout, Pierre-Marc

    2016-04-01

    The decay of the Laurentide ice sheet is believed to be responsible for abrupt climate variations during the last deglaciation and early Holocene, notably through massive discharges of meltwater that had accumulated in large ice-dammed lakes such as Lake Agassiz and Lake Ojibway. Indeed, high-resolution North Atlantic marine records indicate that the ocean's circulation was affected by several outbursts of meltwater during the late deglacial interval. Yet, field evidence and geological data supporting multi-step drawdowns of Lake Agassiz-Ojibway are relatively limited, underlying important uncertainties in the late-stage history of these glacial lakes. Furthermore, physical evidence for the drainage of glacial lakes remains relatively rare in depositional records, giving rise to much debate on the location of outlets and discharge pathways, as well as on the climate impact of the attendant meltwater forcing. Recent investigations of geomorphological and sedimentary records in northern Ontario and Quebec (Canada) have revealed new insights on the late-stage evolution of Lake Ojibway. The number of Ojibway lake phases have so far remained poorly documented mainly because of the dominance of fine-grained glaciolacustrine sediments in the lake basin that prevented the formation of extensive sandy/bouldery strandlines. We thus developed an alternative approach based on the study of a complex sequence of relict terraces carved in the Ojibway clay plain. The elevation measurement of 154 raised wave-cut scarps provided evidence for four distinct shorelines, three of which projecting well below the main outlet that controlled the elevation of the lake during the deglaciation. The elevation, uplift gradients, and areal extent of these shorelines indicate that these low-elevation lake levels formed during the late stages of the deglaciation, following abrupt drawdowns of the lake's surface. Insights on the origin of these late-stage phases are provided from sediment sequences

  7. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean

    PubMed Central

    Glasser, Neil F.; Jansson, Krister N.; Duller, Geoffrey A. T.; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-01-01

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface “hosing” to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate. PMID:26869235

  8. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean.

    PubMed

    Glasser, Neil F; Jansson, Krister N; Duller, Geoffrey A T; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-01-01

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface "hosing" to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate. PMID:26869235

  9. Glacial lake drainage in Patagonia (13-8 kyr) and response of the adjacent Pacific Ocean.

    PubMed

    Glasser, Neil F; Jansson, Krister N; Duller, Geoffrey A T; Singarayer, Joy; Holloway, Max; Harrison, Stephan

    2016-02-12

    Large freshwater lakes formed in North America and Europe during deglaciation following the Last Glacial Maximum. Rapid drainage of these lakes into the Oceans resulted in abrupt perturbations in climate, including the Younger Dryas and 8.2 kyr cooling events. In the mid-latitudes of the Southern Hemisphere major glacial lakes also formed and drained during deglaciation but little is known about the magnitude, organization and timing of these drainage events and their effect on regional climate. We use 16 new single-grain optically stimulated luminescence (OSL) dates to define three stages of rapid glacial lake drainage in the Lago General Carrera/Lago Buenos Aires and Lago Cohrane/Pueyrredón basins of Patagonia and provide the first assessment of the effects of lake drainage on the Pacific Ocean. Lake drainage occurred between 13 and 8 kyr ago and was initially gradual eastward into the Atlantic, then subsequently reorganized westward into the Pacific as new drainage routes opened up during Patagonian Ice Sheet deglaciation. Coupled ocean-atmosphere model experiments using HadCM3 with an imposed freshwater surface "hosing" to simulate glacial lake drainage suggest that a negative salinity anomaly was advected south around Cape Horn, resulting in brief but significant impacts on coastal ocean vertical mixing and regional climate.

  10. Glacial landforms of the southern Ungava Bay region (Canada): implications for the late-glacial dynamics and the damming of glacial Lake Naskaupi

    NASA Astrophysics Data System (ADS)

    Dube-Loubert, Hugo; Roy, Martin

    2014-05-01

    The Laurentide ice sheet played an important role in the late Pleistocene climate, notably through discharges of icebergs and meltwater. In this context, the Ungava Bay region in northern Quebec-Labrador appears particularly important, especially during the last deglaciation when the retreating ice margin dammed major river valleys, creating large proglacial lakes (e.g., McLean, aux Feuilles). The history of these lakes is closely related to the temporal evolution of the Labrador-Quebec ice dome. There are, however, large uncertainties regarding the position of its ice divide system through time, thereby limiting our understanding of the history of these glacial lakes. Here we focus on glacial and deglacial landforms present in the George River valley, south of Ungava Bay, in order to bring additional constraints on the late-glacial ice dynamics of this region, which also comprised glacial Lake Naskaupi. This work is based on surficial mapping using aerial photos and satellite imagery, combined with extensive fieldwork and sediment sampling. Our investigation showed significant differences in the distribution of glacial landforms across the region. The area east of the George River is characterized by well-developed Naskaupi shorelines while the elevated terrains show a succession of geomorphological features indicative of cold-based ice or ice with low basal velocities. In the easternmost part of this sector, ice flow directional data indicate that the ice was flowing towards ENE, against the regional slope. Eskers show paleocurrent directions indicating a general ice retreat from east to west. In the western part of this sector, near the George River valley, eskers are absent and the region is covered by felsenmeer and ground moraine that likely reflect the presence of a residual ice mass that was no longer dynamic. The presence of a stagnant ice represents the best mechanism to explain the formation of glacial lakes in the George River valley and its main

  11. Role of the Lakes in Groundwater Recharge and Discharge in the Young Glacial Area, Northern Poland.

    PubMed

    Jaworska-Szulc, Beata

    2016-07-01

    The aim of this research was to delineate characteristic hydrogeological lake types in the Young Glacial Area (YGA). The YGA is in the central and east part of the Kashubian Lake District (KLD) in Northern Poland, an area covered by deposits of Quaternary glaciation. All the bigger lakes were investigated in the area of about 1500 km(2) (39 lakes). The role of lakes in groundwater recharge and discharge was determined from total dissolved solids (TDS) in lake waters and also from groundwater flow simulation. The general trend was that gaining lakes, as determined by flow modeling, had higher values of TDS than losing lakes. In addition to typical gaining lakes (with TDS > 250 mg/l), there were losing lakes perched on glacial till deposits with very low TDS (<100 mg/l). Two groups of losing lakes were delineated: ones with very low TDS and another group with slightly higher TDS (due to local contact with groundwater). Flow-through lakes with TDS of 170-200 mg/l were also delineated.

  12. Role of the Lakes in Groundwater Recharge and Discharge in the Young Glacial Area, Northern Poland.

    PubMed

    Jaworska-Szulc, Beata

    2016-07-01

    The aim of this research was to delineate characteristic hydrogeological lake types in the Young Glacial Area (YGA). The YGA is in the central and east part of the Kashubian Lake District (KLD) in Northern Poland, an area covered by deposits of Quaternary glaciation. All the bigger lakes were investigated in the area of about 1500 km(2) (39 lakes). The role of lakes in groundwater recharge and discharge was determined from total dissolved solids (TDS) in lake waters and also from groundwater flow simulation. The general trend was that gaining lakes, as determined by flow modeling, had higher values of TDS than losing lakes. In addition to typical gaining lakes (with TDS > 250 mg/l), there were losing lakes perched on glacial till deposits with very low TDS (<100 mg/l). Two groups of losing lakes were delineated: ones with very low TDS and another group with slightly higher TDS (due to local contact with groundwater). Flow-through lakes with TDS of 170-200 mg/l were also delineated. PMID:26619113

  13. Recognition of Drainage Tunnels during Glacier Lake Outburst Events from Terrestrial Image Sequences

    NASA Astrophysics Data System (ADS)

    Schwalbe, E.; Koschitzki, R.; Maas, H.-G.

    2016-06-01

    In recent years, many glaciers all over the world have been distinctly retreating and thinning. One of the consequences of this is the increase of so called glacier lake outburst flood events (GLOFs). The mechanisms ruling such GLOF events are still not yet fully understood by glaciologists. Thus, there is a demand for data and measurements that can help to understand and model the phenomena. Thereby, a main issue is to obtain information about the location and formation of subglacial channels through which some lakes, dammed by a glacier, start to drain. The paper will show how photogrammetric image sequence analysis can be used to collect such data. For the purpose of detecting a subglacial tunnel, a camera has been installed in a pilot study to observe the area of the Colonia Glacier (Northern Patagonian Ice Field) where it dams the Lake Cachet II. To verify the hypothesis, that the course of the subglacial tunnel is indicated by irregular surface motion patterns during its collapse, the camera acquired image sequences of the glacier surface during several GLOF events. Applying tracking techniques to these image sequences, surface feature motion trajectories could be obtained for a dense raster of glacier points. Since only a single camera has been used for image sequence acquisition, depth information is required to scale the trajectories. Thus, for scaling and georeferencing of the measurements a GPS-supported photogrammetric network has been measured. The obtained motion fields of the Colonia Glacier deliver information about the glacier's behaviour before during and after a GLOF event. If the daily vertical glacier motion of the glacier is integrated over a period of several days and projected into a satellite image, the location and shape of the drainage channel underneath the glacier becomes visible. The high temporal resolution of the motion fields may also allows for an analysis of the tunnels dynamic in comparison to the changing water level of the lake.

  14. Photogrammetric recognition of subglacial drainage channels during glacier lake outburst events

    NASA Astrophysics Data System (ADS)

    Schwalbe, Ellen; Koschitzki, Robert

    2016-04-01

    In recent years, many glaciers all over the world have been distinctly retreating and thinning. One of the consequences of this is the increase of so called glacier lake outburst flood events (GLOFs): Lakes that have been dammed by a glacier spontaneously start to drain through a subglacial channel underneath the glacier due to their outweighing hydrostatic pressure. In a short period of time, the lake water drains under the glacier and causes floods in downstream valleys. In many cases the latter become hazardous for people and their property. Due to glacier movement, the tunnel will soon collapse, and the glacier lake refills, thus starting a new GLOF cycle. The mechanisms ruling GLOF events are yet still not fully understood by glaciologists. Thus, there is a demand for data and measurement values that can help to understand and model the phenomena. In view of the above, we will show how photogrammetric image sequence analysis can be used to collect data which allows for drawing conclusions about the location and development of a subglacial channel. The work is a follow-up on earlier work on a photogrammetric GLOF early warning system (Mulsow et. al., 2013). For the purpose of detecting the subglacial tunnel, a camera has been installed in a pilot study to observe the area of the Colonia glacier (Northern Patagonian ice field) where it dams the lake Lago Cachet II. To verify the hypothesis, that the course of the subglacial tunnel is indicated by irregular surface motion patterns during its collapse, the camera acquired image sequences of the glacier surface during several GLOF events. Applying LSM-based tracking techniques to these image sequences, surface feature motion trajectories could be obtained for a dense raster of glacier points. Since only a single camera has been used for image sequence acquisition, depth information is required to scale the trajectories. Thus, for scaling and georeferencing of the measurements a GPS-supported photogrammetric network

  15. Chronology and stratigraphy for the MIS 2 damming of glacial Lake Wisconsin, USA

    NASA Astrophysics Data System (ADS)

    Carson, E. C.; Attig, J. W.; Rawling, J. E., III

    2015-12-01

    Glacial Lake Wisconsin formed during the Marine Isotope Stage (MIS) 2 glaciation when the Green Bay Lobe (GBL) of the Laurentide Ice Sheet dammed the Wisconsin River at the Baraboo Hills in south-central Wisconsin. Despite nearly a century of research, the precise chronology for the Green Bay Lobe's advance to and retreat from its maximum position, and the resulting damming and subsequent drainage of glacial Lake Wisconsin, remains unsettled (e.g., Colgan, 1992; Attig et al., 2011; Ullman et al., 2014). Age estimates from core collected in ice-proximal lacustrine sediment beyond the glacial margin provide chronologic constraint for ice margin fluctuations that controlled glacial Lake Wisconsin's formation and drainage. Additional cores collected in glacial sediment at and behind the MIS 2 ice margin provide stratigraphic evidence for the dynamics of the GBL during the end of advance to, and the start of retreat from, the MIS 2 maximum. The combined data from these cores suggest that glacial Lake Wisconsin may have filled only once to its highest stage during the MIS 2 maximum, after ice blocked both the east end of the Baraboo Hills and the south end of the Devils Lake gorge. When the ice reached its maximum position and blocked the north end of the gorge, Devils Lake was isolated from glacial Lake Wisconsin and rose to a higher level. Radiocarbon and OSL ages from the Devils Lake gorge indicate that the GBL advanced to the MIS 2 maximum position by 24.6 ka, and remained at or near that location through 19.2 ± 3.2 ka. Radiocarbon ages from lacustrine sediment in a sub-basin of glacial Lake Wisconsin indicate that ice continued to block the Wisconsin River between 21.6 ka and 17.4 ka. The stratigraphy evident in cores at the Devils Lake gorge and south of the Baraboo Hills indicates that ice thinned and advanced immediately prior to retreat, likely in response to reduced basal shear stress as the bed of the glacier thawed.

  16. Abrupt climate-triggered lake ecosystem changes recorded in late glacial lake sediments in northern Poland

    NASA Astrophysics Data System (ADS)

    Slowinski, M. M.; Zawiska, I.; Ott, F.; Noryskiewicz, A. M.; Apolinarska, K.; Lutynska, M.; Michczynska, D. J.; Brauer, A.; Wulf, S.; Skubala, P.; Blaszkiewicz, M.

    2013-12-01

    The aim of this study was to better understand how local lake ecosystems responded to abrupt climate changes through applying multi-proxy sediment analyses. Therefore, we carried out a detailed and high-resolution case study on the late glacial sediment from the Trzechowskie palaeolake located in the eastern part of the Pomeranian Lakeland, northern Poland. We reconstructed climate induced environmental changes in the paleolake and its catchment using biotic proxies (macrofossils, pollen, cladocera, diatoms, oribatidae mite) and classical geochemical proxies (δ18O, δ13C, loss-on-ignition, CaCO3 content) in combination with high-resolution μ-XRF element core scanning. The core chronology has been established by means of biostratigraphy, AMS 14C-dating on plant macro remains, varve counting in laminated intervals and tephrochronology. The latter was possible by the discovery of the late Allerød Laacher See Tephra for the first time at such eastern location. Biogenic accumulation in the lake started rather late during the lateglacial interstadial at 13903×170 cal yrs BP. The rapid and pronounced cooling at the beginning of the Younger Dryas had a major impact on the lake and its catchment as clearly reflected by both, biotic and geochemical proxies. The depositional environment of the lake abruptly changed from a varved to massive gytjia. The pronounced warming at the demise of Younger Dryas cooling is well-reflected in all environmental indicators but with conspicuous leads and lags reflecting complex responses of lake ecosystems to climate warming. The research was supported by the National Science Centre Poland - NN306085037. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association.

  17. Late Pleistocene outburst flooding from pluvial Lake Alvord into the Owyhee River, Oregon

    USGS Publications Warehouse

    Carter, D.T.; Ely, L.L.; O'Connor, J. E.; Fenton, C.R.

    2006-01-01

    At least one large, late Pleistocene flood traveled into the Owyhee River as a result of a rise and subsequent outburst from pluvial Lake Alvord in southeastern Oregon. Lake Alvord breached Big Sand Gap in its eastern rim after reaching an elevation of 1292 m, releasing 11.3 km3 of water into the adjacent Coyote Basin as it eroded the Big Sand Gap outlet channel to an elevation of about 1280 m. The outflow filled and then spilled out of Coyote Basin through two outlets at 1278 m and into Crooked Creek drainage, ultimately flowing into the Owyhee and Snake Rivers. Along Crooked Creek, the resulting flood eroded canyons, stripped bedrock surfaces, and deposited numerous boulder bars containing imbricated clasts up to 4.1 m in diameter, some of which are located over 30 m above the present-day channel. Critical depth calculations at Big Sand Gap show that maximum outflow from a 1292- to 1280-m drop in Lake Alvord was ??? 10,000 m3 s- 1. Flooding became confined to a single channel approximately 40 km downstream of Big Sand Gap, where step-backwater calculations show that a much larger peak discharge of 40,000 m3 s- 1 is required to match the highest geologic evidence of the flood in this channel. This inconsistency can be explained by (1) a single 10,000 m3 s- 1 flood that caused at least 13 m of vertical incision in the channel (hence enlarging the channel cross-section); (2) multiple floods of 10,000 m3 s- 1 or less, each producing some incision of the channel; or (3) an earlier flood of 40,000 m3 s- 1 creating the highest flood deposits and crossed drainage divides observed along Crooked Creek drainage, followed by a later 10,000 m3 s- 1 flood associated with the most recent shorelines in Alvord and Coyote Basins. Well-developed shorelines of Lake Alvord at 1280 m and in Coyote Basin at 1278 m suggest that after the initial flood, postflood overflow persisted for an extended period, connecting Alvord and Coyote Basins with the Owyhee River of the Columbia River

  18. Late Pleistocene outburst flooding from pluvial Lake Alvord into the Owyhee River, Oregon

    NASA Astrophysics Data System (ADS)

    Carter, Deron T.; Ely, Lisa L.; O'Connor, Jim E.; Fenton, Cassandra R.

    2006-05-01

    At least one large, late Pleistocene flood traveled into the Owyhee River as a result of a rise and subsequent outburst from pluvial Lake Alvord in southeastern Oregon. Lake Alvord breached Big Sand Gap in its eastern rim after reaching an elevation of 1292 m, releasing 11.3 km 3 of water into the adjacent Coyote Basin as it eroded the Big Sand Gap outlet channel to an elevation of about 1280 m. The outflow filled and then spilled out of Coyote Basin through two outlets at 1278 m and into Crooked Creek drainage, ultimately flowing into the Owyhee and Snake Rivers. Along Crooked Creek, the resulting flood eroded canyons, stripped bedrock surfaces, and deposited numerous boulder bars containing imbricated clasts up to 4.1 m in diameter, some of which are located over 30 m above the present-day channel. Critical depth calculations at Big Sand Gap show that maximum outflow from a 1292- to 1280-m drop in Lake Alvord was ˜ 10,000 m 3 s - 1 . Flooding became confined to a single channel approximately 40 km downstream of Big Sand Gap, where step-backwater calculations show that a much larger peak discharge of 40,000 m 3 s - 1 is required to match the highest geologic evidence of the flood in this channel. This inconsistency can be explained by (1) a single 10,000 m 3 s - 1 flood that caused at least 13 m of vertical incision in the channel (hence enlarging the channel cross-section); (2) multiple floods of 10,000 m 3 s - 1 or less, each producing some incision of the channel; or (3) an earlier flood of 40,000 m 3 s - 1 creating the highest flood deposits and crossed drainage divides observed along Crooked Creek drainage, followed by a later 10,000 m 3 s - 1 flood associated with the most recent shorelines in Alvord and Coyote Basins. Well-developed shorelines of Lake Alvord at 1280 m and in Coyote Basin at 1278 m suggest that after the initial flood, postflood overflow persisted for an extended period, connecting Alvord and Coyote Basins with the Owyhee River of the

  19. Glacial Lake Musselshell: Late Wisconsin slackwater on the Laurentide ice margin in central Montana, USA

    USGS Publications Warehouse

    Davis, N.K.; Locke, W. W.; Pierce, K.L.; Finkel, R.C.

    2006-01-01

    Cosmogenic surface exposure ages of glacial boulders deposited in ice-marginal Lake Musselshell suggest that the lake existed between 20 and 11.5 ka during the Late Wisconsin glacial stage (MIS 2), rather than during the Late Illinoian stage (MIS 6) as traditionally thought. The altitude of the highest ice-rafted boulders and the lowest passes on the modern divide indicate that glacial lake water in the Musselshell River basin reached at least 920-930 m above sea level and generally remained below 940 m. Exposures of rhythmically bedded silt and fine sand indicate that Lake Musselshell is best described as a slackwater system, in which the ice-dammed Missouri and Musselshell Rivers rose and fell progressively throughout the existence of the lake rather than establishing a lake surface with a stable elevation. The absence of varves, deltas and shorelines also implies an unstable lake. The changing volume of the lake implies that the Laurentide ice sheet was not stable at its southernmost position in central Montana. A continuous sequence of alternating slackwater lake sediment and lacustrine sheetflood deposits indicates that at least three advances of the Laurentide ice sheet occurred in central Montana between 20 and 11.5 ka. Between each advance, it appears that Lake Musselshell drained to the north and formed two outlet channels that are now occupied by extremely underfit streams. A third outlet formed when the water in Lake Musselshell fully breached the Larb Hills, resulting in the final drainage of the lake. The channel through the Larb Hills is now occupied by the Missouri River, implying that the present Missouri River channel east of the Musselshell River confluence was not created until the Late Wisconsin, possibly as late as 11.5 ka. ?? 2005 Elsevier B.V. All rights reserved.

  20. Fieldtrip stop #2-6 Twin Lakes glacial geology and mining history

    USGS Publications Warehouse

    Ruleman, C.A.; Shorba, R.R.; Edited by Simmons, Beth

    2013-01-01

    The area of Twin Lakes has been of interest to geologists going back to the days of the Hayden Survey (1874) and continues to be studied for its spectacular glacial geology. Twin Lakes (2747 m; 9015 ft) was settled in 1879 (Scott, 2003) as the Leadville silver rush began, when prospectors found the first traces and outcrops of the Gordon, Tiger, Little Joe, and other rich lodes west of Twin Lakes. Between 1860 and 1950, the Twin Lakes area produced at least 2.5 million dollars in placer gold, much of which was produced when the official U.S. Government price of gold was $20.67 per troy once.

  1. Impact on the Columbia River of an outburst of Spirit Lake

    USGS Publications Warehouse

    Sikonia, W.G.

    1985-01-01

    A one-dimensional sediment-transport computer model was used to study the effects of an outburst of Spirit Lake on the Columbia River. According to the model, flood sediment discharge to the Columbia from the Cowlitz would form a blockage to a height of 44 feet above the current streambed of the Columbia River, corresponding to a new streambed elevation of -3 feet, that would impound the waters of the Columbia River. For an average flow of 233,000 cubic feet in that river, water surface elevations would continue to increase for 16 days after the blockage had been formed. The river elevation at the Trojan nuclear power plant, 5 miles upstream of the Cowlitz River, would rise to 32 feet, compared to a critical elevation of 45 feet, above which the plant would be flooded. For comparison, the Columbia River at average flow without the blockage has an elevation at this location of 6 feet. Correspondingly high water surface elevations would occur along the river to Bonneville Dam , with that at Portland, Oregon, for example, rising also to 32 feet, compared to 10 feet without the blockage. (USGS)

  2. 20th-century glacial-marine sedimentation in Vitus Lake, Bering Glacier, Alaska, U.S.A.

    USGS Publications Warehouse

    Molnia, B.F.; Post, A.; Carlson, P.R.

    1996-01-01

    Vitus Lake, the ice-marginal basin at the southeastern edge of Bering Glacier, Alaska, U.S.A., is a site of modern, rapid, glacial-marine sedimentation. Rather than being a fresh-water lake, Vitus Lake is a tidally influenced, marine to brackish embayment connected to the Pacific Ocean by an inlet, the Seal River. Vitus Lake consists of five deep bedrock basins, separated by interbasinal highs. Glacial erosion has cut these basins as much as 250 m below sea level. High-resolution seismic reflection surveys conducted in 1991 and 1993 of four of Vitus Lake's basins reveal a complex, variable three-component acoustic stratigraphy. Although not fully sampled, the stratigraphy is inferred to be primarily glacial-marine units of (1) basal contorted and deformed glacial-marine and glacial sediments deposited by basal ice-contact processes and submarine mass-wasting; (2) acoustically well-stratified glacial-marine sediment, which unconformably overlies the basal unit and which grades upward into (3) acoustically transparent or nearly transparent glacial-marine sediment. Maximum thicknesses of conformable glacial-marine sediment exceed 100 m. All of the acoustically transparent and stratified deposits in Vitus Lake are modern in age, having accumulated between 1967 and 1993. The basins where these three-part sequences of "present-day" glacial-marine sediment are accumulating are themselves cut into older sequences of stratified glacial and glacial-marine deposits. These older units outcrop on the islands in Vitus Lake. In 1967, as the result of a major surge, glacier ice completely filled all five basins. Subsequent terminus retreat, which continued through August 1993, exposed these basins, providing new locations for glacial-marine sediment accumulation. A correlation of sediment thicknesses measured from seismic profiles at specific locations within the basins, with the year that each location became ice-free, shows that the sediment accumulation at some locations

  3. Gorkha earthquake-induced landslides and dammed lakes: Evolution and outburst modeling

    NASA Astrophysics Data System (ADS)

    Shugar, D. H.; Immerzeel, W.; Wanders, N.; Kargel, J. S.; Leonard, G. J.; Haritashya, U. K.; Collins, B. D.

    2015-12-01

    On 25 April 2015, the Gorkha Earthquake (Mw 7.8) struck Nepal, generating thousands of landslides in Nepal, Tibet (China), and India. While the majority of these hazards were triggered co-seismically, many are considered secondary effects occurring during the weeks following the main shock, based on high-resolution WorldView satellite imagery. Here we report on a series of shallow, post-seismic landslides into the upper Marsyangdi River in the Annapurna region of the central Nepal Himalayas. These landslides constricted and blocked the river, causing impoundments that presented acute flood risks to communities downstream. On April 27, two days following the main shock, ~4.7 x 104 m3 of water was impounded behind a series of small constrictions. By May 28, the total volume of impounded water had increased to ~6.4 x 105 m3. The downstream flood risk was especially significant in the event of a domino-like cascade of dam breaches. We examine the timing, distribution and evolution of the landslide-dammed lakes and quantify the risk of inundation-scenarios to downstream communities with a hydrological model. The model uses a fully kinematic wave simulation at a 30 m-spatial and 2 sec-temporal resolution to resolve the height, timing and volume of a possible outburst flood wave. Our modeling shows that a rapid dam burst involving only the lowest, largest lake would increase water levels at the nearest village of Lower Pisang ~2 km downstream by >7m in a matter of minutes. Approximately 70 km downstream, the flood wave would be mostly attenuated, raising water levels only tens of centimeters. Fortunately, at the time of writing, no flood had occurred.

  4. Linking glacial deposits and lake sediments for paleoclimate studies in the Northern Romanian Carpathians

    NASA Astrophysics Data System (ADS)

    Zamosteanu, Andrei; Mindrescu, Marcel; Anselmetti, Flavio; Akçar, Naki; Lowick, Sally E.; Vogel, Hendrik

    2015-04-01

    Timing and extent of glaciations in the Carpathian mountains are still controversely discussed, mostly due to the lack of well dated geomorphological and geochronological studies. We present the preliminary results of geomorphological and sedimentological analyses of glacial and lacustrine deposits in Bistricioara Valley located in the Rodna Mountains (Northern Romanian Carpathians). Most of the glacial deposits in the Romanian Carpathians, such as moraines, typically occur above 1600 m a.s.l. marking the maximum lowering of past glaciations. Most of the glacial lakes occur between 1800 and 2000 m a.s.l. Field surveys included mapping of moraines and erratic boulders using detailed topographical maps and aerial photos. A Digital Elevation Model (DEM) was derived using GIS (ArcMap 10.1) from 1:25000 topographic maps, which was further completed by field survey data. The resulting geomorphological map shows a series of moraines, which indicate the occurrence of several glacial phases in the study area. Sediment samples were collected from a peat bog (1630 m a.s.l.) dammed by a large lateral moraine within Bistricioara Mare, one of the largest glacial cirques in the Romanian Carpathians. A Russian corer was used to extract the sediment profile from the peat bog (approx. 5 m long sediment core). A X-ray computed tomography (CT) system was employed for the study of sedimentary and deformation structures and X-ray fluorescence spectroscopy (XRF) for multi-element analysis at high resolution. Glacial deposits from the lateral moraine in front of the peat bog were also sampled, as well as from the frontal moraines, upstream and downstream of the peat bog. This set of samples from multiple archives allows to link and merge the chronologies and the paleoenvironmental records of glacial deposits and lake sediments. Moreover, we employed cosmogenic nuclide dating for the reconstruction of glacial stages and their paleoclimatic implications during deglaciation in this area of

  5. Pattern of shoreline spawning by sockeye salmon in a glacially turbid lake: evidence for subpopulation differentiation

    USGS Publications Warehouse

    Burger, C.V.; Finn, J.E.; Holland-Bartels, L.

    1995-01-01

    Alaskan sockeye salmon typically spawn in lake tributaries during summer (early run) and along clear-water lake shorelines and outlet rivers during fall (late run). Production at the glacially turbid Tustumena Lake and its outlet, the Kasilof River (south-central Alaska), was thought to be limited to a single run of sockeye salmon that spawned in the lake's clear-water tributaries. However, up to 40% of the returning sockeye salmon enumerated by sonar as they entered the lake could not be accounted for during lake tributary surveys, which suggested either substantial counting errors or that a large number of fish spawned in the lake itself. Lake shoreline spawning had not been documented in a glacially turbid system. We determined the distribution and pattern of sockeye salmon spawning in the Tustumena Lake system from 1989 to 1991 based on fish collected and radiotagged in the Kasilof River. Spawning areas and time were determined for 324 of 413 sockeye salmon tracked upstream into the lake after release. Of these, 224 fish spawned in tributaries by mid-August and 100 spawned along shoreline areas of the lake during late August. In an additional effort, a distinct late run was discovered that spawned in the Kasilof River at the end of September. Between tributary and shoreline spawners, run and spawning time distributions were significantly different. The number of shoreline spawners was relatively stable and independent of annual escapement levels during the study, which suggests that the shoreline spawning component is distinct and not surplus production from an undifferentiated run. Since Tustumena Lake has been fully deglaciated for only about 2,000 years and is still significantly influenced by glacier meltwater, this diversification of spawning populations is probably a relatively recent and ongoing event.

  6. Influence of glacial meltwater and humidity on evaporation of two Tibetan lakes indicated by delta 18O

    NASA Astrophysics Data System (ADS)

    Gao, J.

    2009-04-01

    delta 18O and model results are adopted to study the affects of glacial meltwater and relative humidity in two lake basins (Lakes Yamdrok-tso and Puma Yum-tso) at two different elevations on the southern Tibetan Plateau. Temporally, the lake water delta 18O of Yamdrok-tso Lake displays a seasonal fluctuation, whereas the lake water delta 18O is stable in Puma Yum-tso Lake in whole year. Spatially, the delta 18O value in Yamdrok-tso Lake is 2‰ higher than that in Puma Yum-tso Lake. delta 18O values in the two lake basins increase by 10‰ from the termini of glaciers to the lake shores, by about 1‰ from the lakeshores to the lake center, by 0.4‰ from the water surface to depth in these lakes. The largest difference, from the terminus of the Qiangyong Glacier to the depth of 35 m, is 14.1‰ and demonstrates the importance of glacial meltwater. Evaporation alters the changes of delta 18O in the two lake basins. Model results show that relative humidity is a major controlling factor of evaporation. delta 18O values of both Yamdrok-tso and Puma Yum-tso Lakes are at their steady condition, but Puma Yum-tso Lake has taken a longer time to approach the current condition, which might be attributed to higher humidity and more glacial meltwater at the lake.

  7. Deeply Frozen Lakes in a Terrestrial Peri-Glacial Environment

    NASA Astrophysics Data System (ADS)

    Doran, P. T.; Fritsen, C. H.

    1998-01-01

    Some of the largest lakes in the McMurdo Dry Valleys, Antarctica, have largely been ignored during past limnological studies because they were thought to be frozen solid. However, recent investigations have revealed the presence of saline water bodies beneath up to 19 m of permanent ice in two of these so-called "ice block" lakes (Lake Vida and Lake House). Lakes throughout the dry valleys that have been studied in detail more typically have ice covers ranging between 3 and 5 m. The existence of saline lakes with extremely thick ice covers is atypical, even among lakes in this region, which are themselves unique aquatic systems. These "deeply ice-covered" lakes are aquatic systems on the edge of cold-termination, and they warrant study as analogs of lakes purported to have existed on the surface of Mars in the past. Several lakes in the McMurdo Dry Valleys were presumed in the past to be frozen solid based largely on attempts at drilling the lake ice covers. Lake Vida has been the most intriguing because it is one of the two largest (in terms of surface area) lakes in the dry valleys, and yet it apparently contained no year-round liquid water at depth. Recently a ground-penetrating radar (GPR) survey was carried out on Lake Vida and another purported ice block lake, Lake House. In a large central portion of Lake Vida, the survey showed attenuation of the radar signal at approximately 19 m, suggesting saline water at this depth. Because GPR radar signals are absorbed by saline water, the depth of the water body (i.e., distance from the ice bottom to sediments) could not be determined. In Lake House, a similar water body was inferred at about 12 m depth. Ice Coring and Physical Properties: Ice cores (to 14 and 15.8 in depth) extracted in 1996 from Lake Vida contained ice bubbles with unique morphologies that were atypical when compared to other vapor inclusions in 3-5 in ice covers. Most of the vapor inclusions at depths greater than about 6 m contained hoar frost

  8. Contrasted evolution of glacial lakes along the Hindu-Kush Himalaya mountain range between 1990 and 2009

    NASA Astrophysics Data System (ADS)

    Gardelle, J.; Yves, A.; Berthier, E.

    2011-12-01

    In this study, we present the first assessment of glacial lake distribution and evolution in the Hindu Kush Himalaya (HKH). Seven sites have been selected between Bhutan and Afghanistan, to capture the climatic variability along the 2000-km long mountain range. For each site, glacial lakes have been mapped with LANDSAT satellite imagery acquired in 1990, 2000 and 2009, using an automatic classification. In the East (India, Nepal and Bhutan) glacial lakes are bigger and more numerous than in the West (Pakistan, Afghanistan), and have grown continuously between 1990 and 2009 by 20% to 65%. Conversely, during the same period, the glacial lake coverage has shrunk in the Hindu Kush (-50%) and the Karakorum (-30%). This east/west pattern of lake changes seems in agreement with sparse glaciological measurements that suggest less (or even no) ice loss in the western part of the HKH.

  9. Heat transport in the Red Lake Bog, Glacial Lake Agassiz Peatlands

    USGS Publications Warehouse

    McKenzie, J.M.; Siegel, D.I.; Rosenberry, D.O.; Glaser, P.H.; Voss, C.I.

    2007-01-01

    We report the results of an investigation on the processes controlling heat transport in peat under a large bog in the Glacial Lake Agassiz Peatlands. For 2 years, starting in July 1998, we recorded temperature at 12 depth intervals from 0 to 400 cm within a vertical peat profile at the crest of the bog at sub-daily intervals. We also recorded air temperature 1 m above the peat surface. We calculate a peat thermal conductivity of 0.5 W m-1 ??C-1 and model vertical heat transport through the peat using the SUTRA model. The model was calibrated to the first year of data, and then evaluated against the second year of collected heat data. The model results suggest that advective pore-water flow is not necessary to transport heat within the peat profile and most of the heat is transferred by thermal conduction alone in these waterlogged soils. In the spring season, a zero-curtain effect controls the transport of heat through shallow depths of the peat. Changes in local climate and the resulting changes in thermal transport still may cause non-linear feedbacks in methane emissions related to the generation of methane deeper within the peat profile as regional temperatures increase. Copyright ?? 2006 John Wiley & Sons, Ltd.

  10. Predicting outflow induced by moraine failure in glacial lakes: the Lake Palcacocha case from an uncertainty perspective

    NASA Astrophysics Data System (ADS)

    Rivas, D. S.; Somos-Valenzuela, M. A.; McKinney, D. C.; Hodges, B. R.

    2014-09-01

    Moraine dam collapse is one of the causes of Glacier Lake Outburst Floods. Available models seek to predict both moraine breach formation and lake outflow. The models depend on hydraulic, erosion, and geotechnical parameters that are mostly unknown or uncertain. This paper estimates the outflow hydrograph caused by a potential collapse of the moraine dam of Lake Palcacocha in Peru and quantifies the uncertainty of the results. The overall aim is to provide a simple and robust method of calculation of the expected outflow hydrographs that is useful for risk assessment studies. To estimate the peak outflow and failure time of the hydrograph, we assessed several available empirical equations based on lake and moraine geometries; each equation has defined confidence intervals for peak flow predictions. Complete outflow hydrographs for each peak flow condition were modeled using a~hydraulic simulation model calibrated to meet the peak flows estimated with the empirical equations. Failure time and peak flow differences between the simulations and the corresponding empirical equations were used as error parameters. Along with an expected hydrograph, lower and upper bound hydrographs were calculated for Lake Palcacocha, representing the confidence interval of the results. The method has several advantages: first, it is simple and robust. Second, it evaluates the capability of empirical equations to reproduce the conditions of the lake and moraine dam. Third, this method accounts for uncertainty in the hydrographs estimations, which makes it appropriate for risk management studies.

  11. Influence of glacial meltwater on water balance processes of two Tibetan lakes indicated by δ18O

    NASA Astrophysics Data System (ADS)

    Gao, J.; Itpcas

    2011-12-01

    δ18O measurements based on systematic sampling and isotopic modeling have been adopted to study the affects of glacial meltwater in two lake basins (Lakes Yamdrok-tso and Puma Yum-tso) at two different elevations on the southern Tibetan Plateau. Temporally, δ18O values in precipitation and lake water display a seasonal fluctuation in both lakes. Spatially, δ18O values in the two lake basins increase by 10% from the termini of glaciers to the lake shores, by about 1% from the lakeshores to the lake center, by 0.4% from the water surface to depth in these lakes. The obvious annual δ18O variations indicate that lake water mixes sufficiently in a short time. Model results show that glacial meltwater is an important factor on lake water balance process. Equilibrium δ18O values decrease 0.8% for Yamdrok-tso Lake and 0.6% for Puma Yum-tso Lake when contributions of glacial meltwater to these lakes shrink by 60%. δ18O ratios increase rapidly during the initial stages and take a relatively longer time to approach the equilibrium value. The modeled results also show that the surface lake water temperature has a minimal impact on this process.
    Dr. Jing Gao

  12. Glacial lake deltas in New England record continuous, not delayed, postglacial rebound

    NASA Astrophysics Data System (ADS)

    Hooke, Roger LeBaron; Ridge, John Charles

    2016-05-01

    Deltas formed in Lake Hitchcock, a glacial lake that developed in the Connecticut River Valley, New England, between ˜18.3 and 12.5 ka. The heights of topset/foreset contacts of these deltas presently increase northward, linearly, at rate of ˜0.9 m/km. Others have interpreted this as indicating that isostatic rebound did not begin until after the lake drained, several kiloyears after glacial retreat began. However, (non-elastic) adjustment of Earth's lithosphere to changing loads is known to occur on time scales of years. Late-glacial shoreline features elsewhere in New England also increase in elevation with distance from the LGM margin at ˜0.9 m/km, suggesting that this is a result of fundamental properties of the crust and mantle, and independent of the history of glacier retreat. On the basis of a numerical model of flexure of the lithosphere beneath a circular load, we suggest that deflection of the lithosphere is remarkably linear in a zone 50-200 km wide between the retreating ice margin and a forebulge, and that initial rebound of this zone is spatially quite uniform for some kiloyears before differential rebound starts. Thus, lake shorelines, formed over a period of some centuries during deglaciation would, today, rise linearly northward.

  13. Glacial lake deltas in New England record continuous, not delayed, postglacial rebound

    NASA Astrophysics Data System (ADS)

    Hooke, Roger LeBaron; Ridge, John Charles

    2016-05-01

    Deltas formed in Lake Hitchcock, a glacial lake that developed in the Connecticut River Valley, New England, between ∼18.3 and 12.5 ka. The heights of topset/foreset contacts of these deltas presently increase northward, linearly, at rate of ∼0.9 m/km. Others have interpreted this as indicating that isostatic rebound did not begin until after the lake drained, several kiloyears after glacial retreat began. However, (non-elastic) adjustment of Earth's lithosphere to changing loads is known to occur on time scales of years. Late-glacial shoreline features elsewhere in New England also increase in elevation with distance from the LGM margin at ∼0.9 m/km, suggesting that this is a result of fundamental properties of the crust and mantle, and independent of the history of glacier retreat. On the basis of a numerical model of flexure of the lithosphere beneath a circular load, we suggest that deflection of the lithosphere is remarkably linear in a zone 50-200 km wide between the retreating ice margin and a forebulge, and that initial rebound of this zone is spatially quite uniform for some kiloyears before differential rebound starts. Thus, lake shorelines, formed over a period of some centuries during deglaciation would, today, rise linearly northward.

  14. Rapid geomorphic change caused by glacial outburst floods and debris flows along Tahoma Creek, Mount Rainier, Washington, USA

    USGS Publications Warehouse

    Walder, J.S.; Driedger, C.L.

    1994-01-01

    As part of a hazards-assessment study, we examined the nature and rate of geomorphic change caused by outburst floods and debris flows along Tahoma Creek, Mount Rainier, since 1967. Archival aerial photographs of the area proved to be a rich source of qualitative geomorphic information. On the basis of limited direct evidence and considerations of stream hydrology, we conclude that nearly all of these debris flows began as outburst floods from South Tahoma Glacier. The water floods transformed to debris flows by incorporating large masses of sediment in a 2-km-long channel reach where the stream has incised proglacial sediments and debris-rich, stagnant glacier ice. Comparison of topographic maps for 1970 and 1991 shows that the average sediment flux out of the incised reach has been about 2 to 4 ?? 105 m3 a-1, corresponding to an average denudation rate in the upper part of the Tahoma Creek drainage basin of about 20 to 40 mm a-1, a value exceeded only rarely in basins affected by debris flows. Little of this sediment has yet passed out of the Tahoma Creek basin. -from Authors

  15. 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

  16. The glacial/deglacial history of sedimentation in Bear Lake, Utah and Idaho

    USGS Publications Warehouse

    Rosenbaum, J.G.; Heil, C.W.

    2009-01-01

    Bear Lake, in northeastern Utah and southern Idaho, lies in a large valley formed by an active half-graben. Bear River, the largest river in the Great Basin, enters Bear Lake Valley ???15 km north of the lake. Two 4-m-long cores provide a lake sediment record extending back ???26 cal k.y. The penetrated section can be divided into a lower unit composed of quartz-rich clastic sediments and an upper unit composed largely of endogenic carbonate. Data from modern fluvial sediments provide the basis for interpreting changes in provenance of detrital material in the lake cores. Sediments from small streams draining elevated topography on the east and west sides of the lake are characterized by abundant dolomite, high magnetic susceptibility (MS) related to eolian magnetite, and low values of hard isothermal remanent magnetization (HIRM, indicative of hematite content). In contrast, sediments from the headwaters of the Bear River in the Uinta Mountains lack carbonate and have high HIRM and low MS. Sediments from lower reaches of the Bear River contain calcite but little dolomite and have low values of MS and HIRM. These contrasts in catchment properties allow interpretation of the following sequence from variations in properties of the lake sediment: (1) ca. 26 cal ka-onset of glaciation; (2) ca. 26-20 cal ka-quasicyclical, millennial-scale variations in the concentrations of hematite-rich glacial fl our derived from the Uinta Mountains, and dolomite- and magnetite-rich material derived from the local Bear Lake catchment (reflecting variations in glacial extent); (3) ca. 20-19 cal ka-maximum content of glacial fl our; (4) ca. 19-17 cal ka-constant content of Bear River sediment but declining content of glacial fl our from the Uinta Mountains; (5) ca. 17-15.5 cal ka-decline in Bear River sediment and increase in content of sediment from the local catchment; and (6) ca. 15.5-14.5 cal ka-increase in content of endogenic calcite at the expense of detrital material. The onset

  17. High resolution paleoenvironment reconstruction for Lake Khanka since the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Liu, Yanguang; Chen, Jiaojie; Ge, Shulan; Li, Chaoxin

    2014-05-01

    A novel sedimentary sequence is presented based on sediment core in the Khanka Lake (XKH1, collected form the small Khanka Lake) by using of paleomagnetic stratigraphy, grain size and organic geochemical data. The sedimentary history of XKH1 is distinctly retrieved to 24 ka BP by comparing with the geomagnetic inclination lows recorded in XKH1 and Lake Biwa. Multi-proxies paleoenvironmental reconstruction for Lake Khanka since the last glacial maximum (LGM) by grain size, total organic carbon (TOC), magnetic susceptibility (MS), and color reflectance. During 24 and 19.5 ka BP, Lake Khanka experienced low lake level and cooling-wet climate approved by the decreasing mean grain size, high sediment brightness and MS values, and low TOC value. The relatively high sand fraction and slightly variation also indicate a low lake condition between 19.5 and 15 ka BP. High TOC content and marked variation in others proxies represent a peat swamp deposition environment during 19 and 16 ka BP, which may associated with lower precipitation and probably modulated by the restrained Asian summer monsoon. From 16 to 15 ka BP, the lake condition change to cold-dry and the sediment has lower content of TOC and coarser grain size. During the deglaciation, together with global temperature rising, the effective precipitation increase around Lake Khanka, result in rising of lake level. The fluctuating characteristics of the environment sensitive grain content are corresponding well to the Oldest Dryas/Bolling-Allerod/Younger Dryas periods. Since 10.6 ka BP, the lake level slightly declining under warm climate because a successive sand bar developed between the small Khanka Lake and the main water area.

  18. Early and late Holocene glacial fluctuations and tephrostratigraphy, Cabin Lake, Alaska

    USGS Publications Warehouse

    Zander, Paul D.; Kaufman, Darrell S.; Kuehn, Stephen C.; Wallace, Kristi L.; Anderson, R. Scott

    2013-01-01

    Marked changes in sediment types deposited in Cabin Lake, near Cordova, Alaska, represent environmental shifts during the early and late Holocene, including fluctuations in the terminal position of Sheridan Glacier. Cabin Lake is situated to receive meltwater during periods when the outwash plain of the advancing Sheridan Glacier had aggraded. A brief early Holocene advance from 11.2 to 11.0 cal ka is represented by glacial rock flour near the base of the sediment core. Non-glacial lake conditions were restored for about 1000 years before the water level in Cabin Lake lowered and the core site became a fen. The fen indicates drier-than-present conditions leading up to the Holocene thermal maximum. An unconformity spanning 5400 years during the mid-Holocene is overlain by peat until 1110 CE when meltwater from Sheridan Glacier returned to the basin. Three intervals of an advanced Sheridan Glacier are recorded in the Cabin Lake sediments during the late Holocene: 1110–1180, 1260–1540 and 1610–1780 CE. The sedimentary sequence also contains the first five reported tephra deposits from the Copper River delta region, and their geochemical signatures suggest that the sources are the Cook Inlet volcanoes Redoubt, Augustine and Crater Peak, and possibly Mt Churchill in the Wrangell Volcanic field.

  19. Dating the Little Ice Age Advance of Jakobshavn Isbrae, Greenland, Using Pro-glacial Lake Sediments.

    NASA Astrophysics Data System (ADS)

    Stewart, H. A.; Briner, J. P.; Csatho, B. M.

    2009-05-01

    The Greenland Ice Sheet's (GIS) largest and fastest outlet glacier, Jakobshavn Isbrae, is one of the most significant contributors to GIS mass loss, draining an estimated 6.5% of the GIS area (Rignot and Kanagaratnam, 2006). Jakobshavn Isbrae has retreated significantly since the Little Ice Age (LIA, ca. 1250- 1900; Csatho et al., 2008), and continues to exhibit rapid changes in velocity and ice calving front position (Joughin et al., 2004). However, it is unknown for how long Jakobshavn Isbrae was at or near its extensive LIA position because there is a lack of chronological control on the LIA advance phase. We collected sediment cores from lakes just beyond the LIA margin to constrain the time when the advancing glacier's silt-laden meltwater entered the lake basins. Sediment cores from South Oval and Ice Boom lakes (informal names), which no longer receive glacial meltwater from Jakobshavn Isbrae because it has retreated out of their catchments, contain gyttja/glacial-silt/gyttja sequences that represent their non-glacial/pro-glacial/non-glacial histories. One additional site, ice-dammed Lake Morten (informal name), completely drained sometime between 1985 and 2001 AD. Outcrops of laminated sediments in the lake basin overly an intact tundra landscape. Four AMS radiocarbon dates from macrofossils immediately below the LIA sediments from the three lake basins reveal that Jakobshavn Isbrae reached its LIA maximum extent between 530±10 and 370±60 cal yr BP (1400-1640 AD). Furthermore, the continuous nature of the LIA-sediment units in all sites indicates that Jakobshavn Isbrae remained at or near its LIA maximum position between 1400-1640 AD and into the 20th century. Finally, pre-LIA organic-rich sediments at all sites continue uninterrupted down to basal sediments deposited during regional deglaciation in the Early Holocene. AMS radiocarbon ages on macrofossils from basal sediments at all sites range from 7220±40 to 8130±60 cal yr BP. We therefore interpret

  20. Early Holocene dune activity linked with final destruction of Glacial Lake Minong, eastern Upper Michigan, USA

    NASA Astrophysics Data System (ADS)

    Loope, Henry M.; Loope, Walter L.; Goble, Ronald J.; Fisher, Timothy G.; Jol, Harry M.; Seong, J. C.

    2010-07-01

    The early Holocene final drainage of glacial Lake Minong is documented by 21 OSL ages on quartz sand from parabolic dunes and littoral terraces and one radiocarbon age from a lake sediment core adjacent to mapped paleoshorelines in interior eastern Upper Michigan. We employ a simple model wherein lake-level decline exposes unvegetated littoral sediment to deflation, resulting in dune building. Dunes formed subsequent to lake-level decline prior to stabilization by vegetation and provide minimum ages for lake-level decline. Optical ages range from 10.3 to 7.7 ka; 15 ages on dunes adjacent to the lowest Lake Minong shoreline suggest final water-level decline ˜ 9.1 ka. The clustering of optical ages from vertically separated dunes on both sides of the Nadoway-Gros Cap Barrier around 8.8 ka and a basal radiocarbon date behind the barrier (8120 ± 40 14C yr BP [9.1 cal ka BP]) support the hypothesis that the barrier was breached and the final lake-level drop to the Houghton Low occurred coincident with (1) high meltwater flux into the Superior basin and (2) an abrupt, negative shift in oxygen isotope values in Lake Huron.

  1. Glacial-interglacial variations of microbial communities in permafrost and lake deposits in the Siberian Arctic

    NASA Astrophysics Data System (ADS)

    Mangelsdorf, Kai; Bischoff, Juliane; Gattinger, Andreas; Wagner, Dirk

    2013-04-01

    The Artic regions are expected to be very sensitive to the currently observed climate change. When permafrost is thawing, the stored carbon becomes available again for microbial degradation, forming a potential source for the generation of carbon dioxide and methane with their positive feedback effect on the climate warming. For the prediction of future climate evolution it is, therefore, important to improve our knowledge about the microbial-driven greenhouse gas dynamics in the Siberian Arctic and their response to glacial-interglacial changes in the past. Sample material was drilled on Kurungnahk Island (Russian-German LENA expedition) located in the southern part of the Lena delta and in lake El'gygytgyn (ICDP-project) in the eastern part of Siberia. The Kurungnahk samples comprise Late Pleistocene to Holocene deposits, whereas the lake El'gygytgyn samples cover Middle to Late Pleistocene sediments. Samples were investigated applying a combined biogeochemical and microbiological approach. The methane profile of the Kurungnahk core reveals highest methane contents in the warm and wet Holocene and Late Pleistocene (LP) deposits and correlates largly to the organic carbon (TOC) contents. Archaeol concentrations, being a biomarker for past methanogenic archaea, are also high during the warm and wet Holocene and LP intervals and low during the cold and dry LP periods. This indicates that part of the methane might be produced and trapped in the past. However, biomarkers for living microorganisms (bacteria and archaea) and microbial activity measurements of methanogens point, especially, for the Holocene to a viable archaeal community, indicating a possible in-situ methane production. Furthermore, warm/wet-cold/dry climate cycles are recorded in the archaeal diversity as revealed by genetic fingerprint analysis. Although the overlying lake water buffers the temperature effect on the lake sediments, which never became permafrost, the bacterial and archaeal biomarker

  2. Glacier Melting Increases the Solute Concentrations of Himalayan Glacial Lakes.

    PubMed

    Salerno, Franco; Rogora, Michela; Balestrini, Raffaella; Lami, Andrea; Tartari, Gabriele A; Thakuri, Sudeep; Godone, Danilo; Freppaz, Michele; Tartari, Gianni

    2016-09-01

    Over the past two decades, we observed a substantial rise in ionic content that was mainly determined by the sulfate concentration at 20 remote high elevation lakes located in central southern Himalaya. At LCN9, which was monitored on an annual basis for the last 20 years, the sulfate concentrations increased over 4-fold. Among the main causes, we exclude a change in the composition of wet atmospheric deposition, as well as a possible influence of decrease in seasonal snow cover duration, which could have exposed larger basin surfaces to alteration processes. Glacier retreat likely was the main factor responsible for the observed increase of sulfate concentrations. We attribute this chemical changes mainly to the sulfide oxidation processes that occur in subglacial environments. Moreover, we observe that the weakened monsoon of the past two decades has only partially contributed to the lakes enrichment through runoff waters that are more concentrated in solutes or lowering the water table, resulting in more rock exposed to air and enhanced mineral oxidation. PMID:27466701

  3. Detection of Supra-Glacial Lakes on the Greenland Ice Sheet Using MODIS Images

    NASA Astrophysics Data System (ADS)

    Verin, Gauthier; Picard, Ghislain; Libois, Quentin; Gillet-Chaulet, Fabien; Roux, Antoine

    2015-04-01

    During melt season, supra-glacial lakes form on the margins of the Greenland ice sheet. Because of their size exceeding several kilometers, and their concentration, they affect surface albedo leading to an amplification of the regional melt. Furthermore, they foster hydro-fracturing that propagate liquid water to the bedrock and therefore enhance the basal lubrication which may affect the ice motion. It is known that Greenland ice sheet has strongly responded to recent global warming. As air temperature increases, melt duration and melt intensity increase and surface melt area extends further inland. These recent changes may play an important role in the mass balance of the Greenland ice sheet. In this context, it is essential to better monitor and understand supra-glacial spatio-temporal dynamics in order to better assess future sea level rise. In this study MODIS (Moderate Resolution Imaging Spectroradiometer) images have been used to detect supra-glacial lakes. The observation site is located on the West margin of the ice sheet, between 65°N and 70°N where the concentration of lake is maximum. The detection is performed by a fully automatic algorithm using images processing techniques introduced by Liang et al. (2012) which can be summarized in three steps: the selection of usable MODIS images, mainly we exclude images with too many clouds. The detection of lake and the automatic correction of false detections. This algorithm is capable to tag each individual lake allowing a survey of all lake geometrical properties over the entire melt season. We observed a large population of supra-glacial lakes over 14 melt seasons, from 2000 to 2013 on an extended area of 70.000 km2. In average, lakes are observed from June 9 ± 8.7 days to September 13 ± 13.9 days, and reach a maximum total area of 699 km2 ± 146 km2. As the melt season progresses, lakes form higher in altitude up to 1800 m above sea level. Results show a very strong inter-annual variability in term of

  4. Early Pleistocene Glacial Lake Lesley, West Branch Susquehanna River valley, central Pennsylvania

    NASA Astrophysics Data System (ADS)

    Ramage, Joan M.; Gardner, Thomas W.; Sasowsky, Ira D.

    1998-02-01

    Laurentide glaciers extended into north central Pennsylvania repeatedly during at least the last 2 million years. Early Pleistocene glaciation extended farther south into central Pennsylvania than any subsequent glaciation, reaching the West Branch Susquehanna River (WBSR) valley. Early Pleistocene ice dammed the northeast-flowing West Branch Susquehanna River at Williamsport, forming Glacial Lake Lesley, a 100-km-long proglacial lake. In this paper, we present compelling evidence for the lake and its age. Maximum lake volume (˜ 100 km 3) was controlled by the elevation of the lowest drainage divide, ˜ 340 m above sea level at Dix, Pennsylvania. Stratified deposits at McElhattan and Linden are used to reconstruct depositional environments in Glacial Lake Lesley. A sedimentary section 40 m thick at McElhattan fines upward from crossbedded sand to fine, wavy to horizontally laminated clay, consistent with lake deepening and increasing distance from the sediment source with time. At Linden, isolated cobbles, interpreted as dropstones, locally deform glacio-lacustrine sediment. We use paleomagnetism as an age correlation tool in the WBSR valley to correlate contemporaneous glaciofluvial and proglacial lacustrine sediments. Reversed remanent polarity in finely-laminated lacustrine clay and silt at McElhattan ( I = 20.4°, D = 146.7°, α95 = 17.7°) and in interbedded silt and sand at Linden ( I = 55.3°, D = 175.2°, α95 = 74.6°) probably corresponds to the latter part of the Matuyama Reversed Polarity Chron, indicating an age between ˜ 770 and ˜ 970 ka. At McElhattan, a diamicton deformed the finely laminated silt and clay by loading and partial fluidization during or soon after lake drainage. As a result, the deformed clay at McElhattan lacks discrete bedding and records a different characteristic remanent magnetism from underlying, undeformed beds. This difference indicates that the characteristic remanent magnetism is detrital. An electrical resistivity

  5. Glacial erosion of bedrock and preliminary Quaternary stratigraphy in the western Lake Erie coastal region

    SciTech Connect

    Shideler, G.I. ); Stone, B.D. )

    1994-04-01

    An analysis of 120 km of high-resolution seismic reflection profiles and onshore well records in the southwestern Lake Erie coastal zone shows a highly dissected bedrock surface. Regional subsurface data confirm extensive glacial modification of the preglacial landscape and the differential erosion of bedrock units. Areas of deep glacial scour coincide with shale and dolostone subcrop belts, in which bedrock strike direction was subparallel to glacial flow directions during early and late phases of glaciation. Locally, deep scouring also occurred over zones of fractured bedrock. In southeastern Michigan, large bedrock valleys, widened and deepened by glacial erosion, are preserved on the north side of the area of the Erie ice lobe. To the south in areas of axial flow of the Erie lobe and southerly ice flow during glacial maxima, traces of preglacial valleys have been more severely modified by glacial erosion in diverging directions. Striations in the region record three such diverging ice-flow directions of the last ice sheet. In one quarry, the position and cross-cutting erosional relationships of the three striation sets indicate their relative ages, from oldest to youngest: SSW, SW, and W. The SSW-trending set is overlain by a compact, loamy till containing abundant Canadian-shield crystalline gravel clasts. The till and the striations record the initial Late Wisconsinan ice advance into the region. The younger striation sets are overlain by the clayey, shale-rich till of the Erie lobe. Onshore, glaciolacustrine massive silty clay overlies the clayey till and fills broad troughs between areas of till at the surface. Offshore, seismic profiles reveal stratification in the clay, which is overlain by late Holocene mud. A nearby test hole through the beach west of Turtle Creek suggests a valley-fill sequence consisting of Late Wisconsinan till overlain by 5 m of organic mud deposited during the late Holocene transgression of Late Erie.

  6. A chronology for glacial Lake Agassiz shorelines along Upham's namesake transect

    NASA Astrophysics Data System (ADS)

    Lepper, Kenneth; Buell, Alex W.; Fisher, Timothy G.; Lowell, Thomas V.

    2013-07-01

    Four traditionally recognized strandline complexes in the southern basin of glacial Lake Agassiz are the Herman, Norcross, Tintah and Campbell, whose names correspond to towns in west-central Minnesota that lie on a linear transect defined by the Great Northern railroad grade; the active corridor for commerce at the time when Warren Upham was mapping and naming the shorelines of Lake Agassiz (ca.1880-1895). Because shorelines represent static water planes, their extension around the lake margin establishes time-synchronous lake levels. Transitions between shoreline positions represent significant water-level fluctuations. However, geologic ages have never been obtained from sites near the namesake towns in the vicinity of the southern outlet. Here we report the first geologic ages for Lake Agassiz shorelines obtained at field sites along the namesake transect, and evaluate the emerging chronology in light of other paleoclimate records. Our current work from 11 sampling sites has yielded 16 independent ages. These results combined with a growing OSL age data set for Lake Agassiz's southern basin provide robust age constraints for the Herman, Norcross and Campbell strandlines with averages and standard deviations of 14.1 ± 0.3 ka, 13.6 ± 0.2 ka, and 10.5 ± 0.3 ka, respectively.

  7. Influence of glacial landform hydrology on phosphorus budgets of shallow lakes on the Boreal Plain, Canada

    NASA Astrophysics Data System (ADS)

    Plach, Janina M.; Ferone, Jenny-Marie; Gibbons, Zabrina; Smerdon, Brian D.; Mertens, Alexander; Mendoza, Carl A.; Petrone, Richard M.; Devito, Kevin J.

    2016-04-01

    A comparative study of three shallow lake catchments in contrasting glacial landscapes (coarse-textured outwash, fine-textured-till hummocky moraines and glacio-lacustrine clay-till plains) demonstrated a distinct landform control on the proportion and type of surface and groundwater sources influencing total phosphorus ([P]) and total dissolved phosphorus ([DP]) concentrations, and P budgets of lakes on the Boreal Plain of the Western Boreal Forest, Alberta, Canada. Lakes located on fine-textured landforms had high [P] and [DP] (median 148 and 148 μg L-1 glacio-lacustrine plains; 99 and 63 μg L-1 moraine, respectively) linked to shallow groundwater loadings from near-surface peat with high [P] from adjacent wetlands. In contrast, the lowest lake [P] and [DP] (median 50 and 11 μg L-1, respectively) occurred on the coarse-textured landform, reflecting greater inputs of deep mineral-groundwater with low [P] from quartz-rich substrates. Annual lake P budgets reflected lake connectivity to the surrounding landform and relative contributions of P by surface versus groundwater. They also reflected distinct scales of groundwater (larger-scale versus short, shallow-flow paths) with differing [P] between landform types and occurrence of internal biogeochemical P cycling within landforms. A regional lake survey reflected trends from the catchment-scale, linking landform type to potential P sources as well as topographic position to potential trophic status across the Boreal Plain. Together, the results provide a conceptual framework for the scale of interactions between lakes and surrounding source waters influencing P loadings in differing hydrogeological landscapes, important to management strategies and predicting impacts of land-use disturbances on productivity of Boreal Plain lakes.

  8. Late Glacial and Holocene sedimentary evolution of Czechowskie Lake (Eastern Pomerania, North Central Poland)

    NASA Astrophysics Data System (ADS)

    Kordowski, Jarosław; Błaszkiewicz, Mirosław; Kramkowski, Mateusz; Noryśkiewicz, Agnieszka M.; Słowiński, Michał; Tyszkowski, Sebastian; Brauer, Achim; Ott, Florian

    2015-04-01

    transient increase of organic sedimentation. Increased deposition of colluvial deposits took place in Late Glacial and again about 200 years ago due to transient deforestation of the lake vicinity. Acknowledgements: This study is a contribution to the Virtual Institute of Integrated Climate and Landscape Evolution (ICLEA) of the Helmholtz Association.

  9. Basal ice flow regime influenced by glacial lake formation in Rhonegletscher, Switzerland

    NASA Astrophysics Data System (ADS)

    Nishimura, D.; Tsutaki, S.; Sugiyama, S.

    2010-12-01

    After the retreat of glacier terminus over a bedrock bump, a glacial lake has formed in front of Rhonegletscher, Switzerland. It is suspected that ice flow regime is now significantly influenced by the lake water. To investigate the impact of lake formation on glacier dynamics, we carried out surface and borehole observations in the terminus region of Rhonegletscher. In 2008 and 2009 summer seasons, we drilled more than 20 boreholes to measure borehole deformation by repeated inclinometry. Ice surface speed was measured by surveying stakes installed nearby the boreholes. We used a borehole televiewer to measure basal sliding speed by tracking stones and markers at the bottom of the boreholes. We also measured basal sediment layer thickness by hammering a penetrometer at the bottom of the boreholes. Our measurements showed clear decrease in the ice deformation rate near the lake (Fig. 1). Ice deformation accounted for 60-80% in the upper part of our study site (e.g. boreholes 1 and 5), whereas it is less than 10% near the lake (e.g. boreholes 7, 10 and 11). This result suggests that the basal ice flow near the lake is enhanced by the lake water. According to the basal sliding speed measurement in borehole 2, sliding accounted for less than 10% of basal flow speed from 2 to 31 August 2009. Deformation of a subglacial sediment layer is thus important in this region. The penetrometer measurement confirmed that the study site is underlain by a subglacial sediment layer whose thickness was in a range of 0-70 m. Fig.1 Terminus of Rhonegletscher and proglacial lakes indicated by the shaded areas. The columns show ice surface and deformation speeds measured at each borehole site from 9 July to 5 September in 2009. Ice deformation speed was negligibly small at boreholes 7, 10, and 11. Surface contour spacing is 20 m.

  10. Asynchronous ice lobe retreat and glacial Lake Bascom: Deglaciation of the Hoosic and Vermont valleys, southwestern Vermont

    SciTech Connect

    Small, E.; Desimone, D. . Dept. of Geology)

    1993-03-01

    Deglaciation of the Hoosic River drainage basin in southwestern Vermont was more complex than previously described. Detailed surficial mapping, stratigraphic relationships, and terrace levels/delta elevations reveal new details in the chronology of glacial Lake Bascom: (1) a pre-Wisconsinan proglacial lake was present in a similar position to Lake Bascom as ice advanced: (2) the northern margin of 275m (900 ft) glacial Lake Bascom extended 10 km up the Vermont Valley; (3) the 215m (705 ft) Bascom level was stable and long lived; (4) intermediate water planes existed between 215m and 190m (625 ft) levels; and (5) a separate ice tongue existed in Shaftsbury Hollow damming a small glacial lake, here named glacial Lake Emmons. This information is used to correlate ice margins to different lake levels. Distance of ice margin retreat during a lake level can be measured. Lake levels are then used as control points on a Lake Bascom relative time line to compare rate of retreat of different ice tongues. Correlation of ice margins to Bascom levels indicates ice retreat was asynchronous between nearby tongues in southwestern Vermont. The Vermont Valley ice tongue retreated between two and four times faster than the Hoosic Valley tongue during the Bascom 275m level. Rate of retreat of the Vermont Valley tongue slowed to one-half of the Hoosic tongue during the 215m--190m lake levels. Factors responsible for varying rates of retreat are subglacial bedrock gradient, proximity to the Hudson-Champlain lobe, and the presence of absence of a calving margins. Asynchronous retreat produced splayed ice margins in southwestern Vermont. Findings from this study do not support the model of parallel, synchronous retreat proposed by many workers for this region.

  11. Glacier dynamics and lake development on South Georgia during the late-glacial and early Holocene.

    NASA Astrophysics Data System (ADS)

    Rosqvist, Gunhild; Davies, Sarah; Leng, Melanie

    2014-05-01

    Geochemical records from lakes on South Georgia provide data on glacier variation and lake development since 18.6 ka. Glaciers retreated and lakes had developed already by 18.6 ka BP. The retreat was probably a response to the increased insolation combined with sea-ice decline that also have been suggested to be the key factors responsible for the pre-18 ka BP warming registered on the Antarctic peninsula. South Georgia glaciers responded earlier compared to glaciers located in southernmost South America and in the New Zealand Alps. The lake records show a terrestrial response to the Antarctic Cold Reversal (ACR) confirming, together with marine evidence, the extent to which an Antarctic climate pattern is registered in the Southern Ocean at this time. The timing of glacier retreat after 12 ka BP on South Georgia coincides with major glacier recession in Southern South America and New Zealand. Our data indicate that the glaciers on South Georgia kept a relatively advanced position until ca 8 ka BP after which they retreated rapidly to above 200 m a sl. The South Georiga lake records reveal a terrestrial response, but of opposite sign, to changes in the North Atlantic during the late glacial indicating that a link exist between terrestrial sub-Antarctic and the Northern Hemisphere during deglaciation.

  12. New exposure ages for the Last Glacial Cycle in the Sanabria Lake region (northwestern Spain)

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rodríguez, Laura; Jiménez-Sánchez, Montserrat; Domínguez-Cuesta, María Jose; Rinterknecht, Vincent; Pallàs, Raimon; Braucher, Régis; Bourlès, Didier; Valero-Garcés, Blas

    2013-04-01

    The Sanabria Lake region is located in the Trevinca Massif, a mid-latitude mountain area up to 2128 m asl in the northwest corner of the Iberian Peninsula (42oN 6oW). An ice cap glaciation took place during the Last Glacial Cycle in this massif, with an equilibrium line altitude of 1687 m for the Tera glacial outlet at its local maximum (Cowton et al., 2009). A well preserved glacial sequence occurs on an area of 45 km2 around the present Sanabria Lake (1000 m asl) and is composed by lateral and end moraines in close relationship with glaciolacustrine deposits. This sequence shows the ice snout oscillations of the former Tera glacier during the Last Glacial Cycle and offers a good opportunity to compare radiocarbon and OSL- based chronological models with new cosmogenic isotope dates. The new dataset of 10Be exposure ages presented here for the Sanabria Lake moraines is based on measurements conducted on 23 boulders and is compared with previous radiocarbon and OSL data conducted on ice related deposits (Pérez-Alberti et al., 2011; Rodríguez-Rodríguez et al., 2011). Our results are coherent with the available deglaciation radiocarbon chronology, and support a last deglaciation origin for the whole set of end moraines that are downstream the Sanabria Lake (19.2 - 15.7 10Be ka). Discrepancies between results of the different dating methods concern the timing of the local glacial maximum, with the cosmogenic exposure method always yielding the youngest minimum ages. As proposed to explain similar observations made elsewhere (Palacios et al., 2012), reconciling the ages from different dating methods would imply the occurrence of two glacial advances close enough in extent to generate an overlapping polygenic moraine. Cowton, T., Hughes, P.D., Gibbard, P.L., 2009. Palaeoglaciation of Parque Natural Lago de Sanabria, northwest Spain. Geomorphology 108, 282-291. Rodríguez-Rodríguez, L., Jiménez-Sánchez, M., Domínguez-Cuesta, M.J., Rico, M.T., Valero-Garcés, B

  13. Two episodes of meltwater influx from glacial Lake Agassiz into the Lake Michigan basin and their climatic contrasts

    USGS Publications Warehouse

    Colman, Steven M.; Keigwin, L.D.; Forester, R.M.

    1994-01-01

    Two episodes of meltwater influx from glacial Lake Agassiz are recorded as prominent sedimentologic, isotopic, magnetic, and faunal signatures in southern Lake Michigan profundal sediments. As a tributary to the main path of eastward Lake Agassiz flow, southern Lake Michigan recorded only the largest, catastrophic discharges. The distinctive Wilmette Bed, a massive gray mud that interrrupts laminated red glaciolacustrine clays, marks the first episode, which occurred near the beginning of the Younger Dryas cooling events. The associated discharge may have played a role in the inception or severity of the Younger Dryas event. An oxygen isotope excursion in biogenic carbonate and changes in ostracode assemblages mark the second episode, which appears to have had at least two pulses, dated by accelerator mass spectrometer 14C ages on biogenic carbonate at about 8.9 and 8.6 ka. The second episode occurred during the early Holocene peak in global meltwater discharge and apparently had little widespread climatic or oceanographic effect. The contrast between the effects associated with these two episodes of meltwater discharge emphasizes the complexity of the ice sheet-ocean-climate system. -Authors

  14. Reconstructing the lake-level history of former glacial lakes through the study of relict wave-cut terraces: the case of Lake Ojibway (eastern Canada)

    NASA Astrophysics Data System (ADS)

    Roy, Martin; Veillette, Jean; Daubois, Virginie

    2014-05-01

    The reconstruction of the history of former glacial lakes is commonly based on the study of strandlines that generally consist of boulder ridges, sandy beaches and other near-shore deposits. This approach, however, is limited in some regions where the surficial geology consists of thick accumulation of fine-grained glaciolacustrine sediments that mask most deglacial landforms. This situation is particularly relevant to the study of Lake Ojibway, a large proglacial lake that developed in northern Ontario and Quebec following the retreat of the southern Laurentide ice sheet margin during the last deglaciation. The history of Ojibway lake levels remains poorly known, mainly due to the fact that this lake occupied a deep and featureless basin that favored the sedimentation of thick sequences of rhythmites and prevented the formation of well-developed strandlines. Nonetheless, detailed mapping revealed a complex sequence of discontinuous small-scale cliffs that are scattered over the flat-lying Ojibway clay plain. These terrace-like features range in size from 4 to 7 m in height and can be followed for 10 to 100's of meters. These small-scale geomorphic features are interpreted to represent raised shorelines that were cut into glaciolacustrine sediments by lakeshore erosional processes (i.e., wave action). These so-called wave-cut scarps (WCS) occur at elevations ranging from 3 to 30 m above the present level of Lake Abitibi (267 m), one of the lowest landmarks in the area. Here we evaluate the feasibility of using this type of relict shorelines to constrain the evolution of Ojibway lake levels. For this purpose, a series of WCS were measured along four transects of about 40 km in length in the Lake Abitibi region. The absolute elevation of 154 WCS was determined with a Digital Video Plotter software package using 1:15K air-photos, coupled with precise measurements of control points, which were measured with a high-precision Global Navigation Satellite System tied up to

  15. Impacts of post-glacial lake drainage events and revised chronology of the Champlain Sea episode 13-9 ka

    USGS Publications Warehouse

    Cronin, T. M.; Manley, P.L.; Brachfeld, S.; Manley, T.O.; Willard, D.A.; Guilbault, J.-P.; Rayburn, J.A.; Thunell, R.; Berke, M.

    2008-01-01

    Lithologic, CHIRP (Compressed High Intensity Radar Pulse) sonar, paleomagnetic, stable isotopic and micropaleontological analyses of sediment cores from Lake Champlain (New York, Vermont) were used to determine the age of the post-glacial Champlain Sea marine episode, the timing of salinity changes and their relationship to freshwater discharge from mid-continent glacial lakes. Calibrated radiocarbon ages on plant material provide an improved post-glacial chronology overcoming problems from shell ages caused by carbon reservoir effects up to 1500 yr. The final drainage of glacial Lake Vermont and the inception of marine conditions occurred ∼ 13.1–12.8 ka (kiloannum, calendar years) and a sharp decrease in Champlain Sea salinity from ∼ 25 to 7–8 psu (practical salinity units) occurred approximately 11.4–11.2 ka. Reduced salinity was most likely caused by rapid freshwater inflow eastward from glacial Lake Algonquin into the Champlain Basin. The timing of inferred freshwater event coincides with the widespread climatic cooling called the Preboreal Oscillation.

  16. Lake sediment record of neo-glacial advances in the southwestern Cordillera Raura, Peruvian Andes

    NASA Astrophysics Data System (ADS)

    Stansell, N. D.; Abbott, M. B.

    2006-12-01

    Radiocarbon dated lake sediments are used to identify the timing of middle and late Holocene glacial advances in the southwestern Cordillera Raura of central Peru. Elemental iron, titanium and calcium data, obtained using scanning X-Ray Fluorescence (XRF), record relative changes in the rate of deposition of titanium/iron-rich versus calcium-rich sediments. Magnetic susceptibility, coulometry and digital color analyses of high- resolution core-scan images complement the XRF data. Combined, the data indicate that glacial advances in the watershed took place from 3320 to 2490 cal. yr BP, 2400 to 2190 cal. yr BP, 1780 to 1385 cal. yr BP and 790 to 270 cal. yr BP. Independent ice core data and lake level records suggest that the advances from 3320 to 2490 and from 2400 to 2190 cal. yr BP took place during colder and drier periods. The advance from 1780 to 1385 cal. yr BP was initially during a cold and drier period from 1780 to 1615 cal. yr BP, followed by a warmer and wetter period from 1615 to 1385 cal. yr BP. Likewise, the advance from 790 to 270 cal. yr BP initially took place during a cold and drier period followed by a cold and wetter period from 620 to 270 cal. yr BP.

  17. Last glacial maximum and Holocene lake levels of Owens Lake, eastern California, USA

    USGS Publications Warehouse

    Bacon, S.N.; Burke, R.M.; Pezzopane, S.K.; Jayko, A.S.

    2006-01-01

    Stratigraphic investigations of fluvio-deltaic and lacustrine sediments exposed in stream cuts, quarry walls, and deep trenches east of the Sierra Nevada in Owens Valley near Lone Pine, California have enabled the reconstruction of pluvial Owens Lake level oscillations. Age control for these sediments is from 22 radiocarbon (14C) dates and the identification and stratigraphic correlation of a tephra, which when plotted as a function of age versus altitude, define numerous oscillations in the level of pluvial Owens Lake during the latest Pleistocene and early Holocene. We have constructed a lake-level altitude curve for the time interval ???27,000 cal yr BP to present that is based on the integration of this new stratigraphic analysis with published surface stratigraphic data and subsurface core data. Pluvial Owens Lake regressed from its latest Pleistocene highstands from ???27,000 to ???15,300 cal yr BP, as recorded by ???15 m of down cutting of the sill from the altitudes of ???1160 to 1145 m. By ???11,600 cal yr BP, the lake had dropped ???45 m from the 1145 m sill. This lowstand was followed by an early Holocene transgression that attained a highstand near 1135 m before dropping to 1120 m at 7860-7650 cal yr BP that had not been recognized in earlier studies. The lake then lowered another ???30 m to shallow and near desiccation levels between ???6850 and 4300 cal yr BP. Fluvial cut-and-fill relations north of Lone Pine and well-preserved shoreline features at ???1108 m indicate a minor lake-level rise after 4300 cal yr BP, followed by alkaline and shallow conditions during the latest Holocene. The new latest Quaternary lake-level record of pluvial Owens Lake offers insight to the hydrologic balance along the east side of the southern Sierra Nevada and will assist regional paleoclimatic models for the western Basin and Range. ?? 2005 Elsevier Ltd. All rights reserved.

  18. Deglaciation of the James Bay Lowlands and Northern Abitibi: Insights on Late-Glacial Ice Readvances and Drainage of Glacial Lake Ojibway

    NASA Astrophysics Data System (ADS)

    Roy, M.; Veillette, J. J.; Dell'Oste, F.

    2008-12-01

    Deglaciation in the James Bay region was marked by the scission of the Laurentide ice sheet margin into the Hudson dome to the west and the New-Quebec dome to the east, which subsequently retreated northward, in contact with the waters of glacial Lake Ojibway. Previous work based on air photo-interpretation and field observations indicate that ice retreat in the region was highly dynamic, with the occurrence of at least three ice readvances into the basin of Lake Objiway prior to the final deglaciation, and the incursion of the post- glacial Tyrrell Sea at ~8 ka (Hardy, 1976). Our investigations of stratigraphic sections exposed along the Harricana, Nottaway, Broadback, and Rupert rivers in the lowlands of Quebec indicate that only part of these events are preserved in these sedimentary sequences. The base of the late-glacial sequence generally consists of a carbonate-bearing clayey readvance till that lies on older tills of the last glacial cycle, or truncate Lake Ojibway glaciolacustrine sediments. None of the sections showed more than one till of the three (Cochrane I, Rupert, Cochrane II) readvances documented in the region. Nonetheless, an extensive Ojibway sequence located just south from the lowlands shows three intervals with significant increases in detrital carbonate and coarsening of the varve sequence that can be linked with these late-glacial surges. In the lowlands, the readvance till is commonly capped by a thick sequence of Ojibway varves. The contact between the glaciolacustrine sediments and the overlying Tyrrell Sea marine deposits is marked by a ~50 cm-thick horizon composed at the bottom of thinly laminated reddish and grey silt beds containing abundant rounded clay balls, overlain by coarser silts and fine sands with disseminated clasts. This horizon is here interpreted to reflect the abrupt drainage of Lake Ojibway. Recent radiocarbon dating of mollusks and foraminifers from the uppermost part of this horizon yielded ages of ~7.7 ka and ~8

  19. Ice-walled-lake plains: Implications for the origin of hummocky glacial topography in middle North America

    USGS Publications Warehouse

    Clayton, L.; Attig, J.W.; Ham, N.R.; Johnson, M.D.; Jennings, C.E.; Syverson, K.M.

    2008-01-01

    Ice-walled-lake plains are prominent in many areas of hummocky-till topography left behind as the Laurentide Ice Sheet melted from middle North America. The formation of the hummocky-till topography has been explained by: (1) erosion by subglacial floods; (2) squeezing of subglacial till up into holes in stagnant glacial ice; or (3) slumping of supraglacial till. The geomorphology and stratigraphy of ice-walled-lake plains provide evidence that neither the lake plains nor the adjacent hummocks are of subglacial origin. These flat lake plains, up to a few kilometers in diameter, are perched as much as a few tens of meters above surrounding depressions. They typically are underlain by laminated, fine-grained suspended-load lake sediment. Many ice-walled-lake plains are surrounded by a low rim ridge of coarser-grained shore sediment or by a steeper rim ridge of debris that slumped off the surrounding ice slopes. The ice-walled lakes persisted for hundreds to thousands of years following glacial stagnation. Shells of aquatic molluscs from several deposits of ice-walled-lake sediment in south-central North Dakota have been dated from about 13 500 to 10 500??B.P. (calibrated radiocarbon ages), indicating a climate only slightly cooler than present. This is confirmed by recent palaeoecological studies in nearby non-glacial sites. To survive so long, the stagnant glacial ice had to be well-insulated by a thick cover of supraglacial sediment, and the associated till hummocks must be composed primarily of collapsed supraglacial till. ?? 2007 Elsevier B.V. All rights reserved.

  20. Fingerprinting of glacial silt in lake sediments yields continuous records of alpine glaciation (35–15 ka), western USA

    USGS Publications Warehouse

    Rosenbaum, Joseph G.; Reynolds, Richard L.; Colman, Steven M.

    2012-01-01

    Fingerprinting glacial silt in last glacial-age sediments from Upper Klamath Lake (UKL) and Bear Lake (BL) provides continuous radiocarbon-dated records of glaciation for the southeastern Cascade Range and northwestern Uinta Mountains, respectively. Comparing of these records to cosmogenic exposure ages from moraines suggests that variations in glacial flour largely reflect glacial extent. The two areas are at similar latitudes and yield similar records of glacial growth and recession, even though UKL lies less than 200 km from the ocean and BL is in the continental interior. As sea level began to fall prior to the global Last Glacial Maximum (LGM), existing glaciers in the UKL area expanded. Near the beginning of the global LGM (26.5 ka), the BL record indicates onset of glaciation and UKL-area glaciers underwent further expansion. Both records indicate that local glaciers reached their maximum extents near the end of the global LGM, remained near their maxima for ~1000 yr, and underwent two stages of retreat separated by a short period of expansion.

  1. New Geomorphic map of SW Fraser Lowland, NW Washington, Shows Multiple Post-LGM Moraines, Fossil Shorelines, Outburst Flood and Glacial Outwash Features

    NASA Astrophysics Data System (ADS)

    Easterbrook, D. J.; Kovanen, D. J.; Haugerud, R. A.

    2008-12-01

    We have interpreted a ~1 pulse/m2 lidar survey (acquired in 2006 in leaf-on conditions under contract to the USGS) to construct a geomorphic map of western Whatcom County. The new lidar data reveal the existence of previously unrecognized landforms. Within this landscape, we see these features that reflect a rich post-LGM history: Glacial: Ice contact deposits interpreted as moraines reveal at least 8 successive moraines associated with the late Pleistocene Fraser Glaciation. At least two of the moraine crests were formed during ice re- advance; others may mark stillstands during ice retreat. All are older than about 10,250 14C yrs BP, based on basal peat from a kettle in outwash associated with the youngest moraine. Marine: Extensive and successive fossil shorelines, wave-cut notches, wave-washed surfaces, down- slope truncation of gullies, and deltas along the fringe of uplands surrounding the SW Fraser Lowland document former relative sea level and probable glacioisostatic tilting. The highest shorelines are at nearly 150 m above sea level. Some shorelines are cut into moraines, while others are truncated by them. Uplifted back-beach surfaces of likely mid-Holocene age at Birch Bay and Neptune Beach (elevations ~1 m and ~3 m higher than modern back-beach surfaces) suggest Holocene uplift. Glaciofluvial: Large, stepped, sediment wave bed-forms, with wavelengths of 430 to 850 m and heights from 1 to 3.5 m, record deposition associated with high discharge and rapid water release. Sub-parallel, narrow scour troughs are up to 4 km in length and 8 m in depth. These high energy geomorphic features record at least three large discharge events. Their apparent associations with former ice margins indicate that they are the result of outburst floods. Multiple outwash surfaces in the lowland are also related to former ice margins. Fluvial: At present the Nooksack River flows west from the town of Everson and reaches Bellingham Bay just south of Ferndale. Relatively low

  2. The role of geophysical modeling of glacio-isostasy in paleohydrological reconstructions of the glacial Great Lakes

    SciTech Connect

    Clark, J.A.; Ehlers, T.A. )

    1992-01-01

    The volume and chronology of late-glacial and postglacial lakes of the Great Lakes region were controlled by the elevation of their outlets which moved vertically relative to the geoid because of glacial isostasy. The shorelines of these lakes and their drainages are now tilted and deformed so that correlation of these discontinuous features usually requires an estimate of the amount of vertical movement throughout the region. The authors approach is to use a computer model of a spherical viscoelastic and self-gravitating earth to simulate earth deformation as the Laurentide ice sheet advanced into its glacial maximum and subsequently retreated. Because neither the earth's viscosity structure nor the ice sheet thickness are well known, they have used a range of likely ice/earth models each resulting in predicted shoreline deformation that can be compared directly to observations. Results indicate that many of the shorelines as well as present rates of tilt determined from lake-level gauges can be understood through the modeling. The chronology of the various lakes is also explained through predictions of the time-dependent changes in the elevation of the various outlets relative to each other. In contrast to common interpretations none of their results indicate that the southern part of the Great Lakes region is now or ever has been geodynamically stable''.

  3. Late glacial and Holocene sedimentary environments of Quesnel Lake, British Columbia

    NASA Astrophysics Data System (ADS)

    Gilbert, Robert; Desloges, Joseph R.

    2012-12-01

    At 512 m Quesnel Lake is the third deepest in North America and at 100 km long its drainage basin spans from the arid interior plateau to the high mountains of the eastern Cordillera where small glaciers are a significant source of sediment. In most of the lake sediment is 0 to 40 m thick, reaching a maximum of just over 100 m thick near the junction of the three arms. Cores from three locations in the lake provide evidence that the entire Holocene record is contained in the upper 4 to 6 m of the sedimentary record where rates of accumulation have been constant or have decreased slowly. The highest rates (0.35 to 0.72 mm/a) occur near points of inflow, while the lowest rate (0.22 mm/a) occurs in a sheltered environment with limited inflow, and significant hypolimnic circulation which may flush water and suspended sediment from the water column. Late Pleistocene sediment beneath has a similar acoustic signature to the cored Holocene record above, suggesting that the sedimentary processes governing its deposition were not greatly different than in the present lake but that extensive glacial and paraglacial sources contributed to a significantly higher rate of accumulation. Mazama ash analyzed from two locations near points of inflow has an age of 7576 ± 60 cal. BP according to our chronology. Vivianite, which is uncommon in lakes of the Cordillera, occurs in the middle of the cores mainly associated with macroscopic wood fragments and indicates reducing conditions within the sediment.

  4. Northern hemisphere climate control on the environmental dynamics in the glacial Black Sea "Lake"

    NASA Astrophysics Data System (ADS)

    Wegwerth, Antje; Kaiser, Jérôme; Dellwig, Olaf; Shumilovskikh, Lyudmila S.; Nowaczyk, Norbert R.; Arz, Helge W.

    2016-03-01

    The Marine Isotope Stage (MIS) 3 stands out due to its abrupt changes from cold and dry stadials to warm and humid interstadials, the so-called Dansgaard-Oeschger cycles that also affected temperature and rainfall in the Black Sea region. This study is based on a gravity core from the southeastern (SE) Black Sea that covers the last glacial lake stage from 64 to 20 ka BP. By using the composition of major and trace elements in the sediments, terrestrial plant-derived n-alkane flux, and Sr/Ca from benthic ostracods, we reconstruct the variability of riverine and aeolian input, salinity, and productivity in the SE Black Sea region in response to the Northern Hemisphere climate oscillations. During colder and drier stadials, the aeolian input increased relative to the riverine discharge, potentially due to southward shifted and/or stronger westerly winds and due to changes in the vegetation cover. An evaporation exceeding freshwater supply by rainfall and rivers possibly caused higher salinity and a lower lake level. The environmental status during MIS 4 and 2 is very much comparable with the stadial conditions during MIS 3. During warmer and more humid interstadials, lower salinity and presumably positive lake level changes most likely resulted from increased precipitation and river discharge. This likely increased primary productivity through an augmented nutrient supply. Lowest average salinities are suggested for the middle part of MIS 3 in response to enhanced meltwater from the disintegrating Fennoscandian Ice Sheet and/or by generally more humid conditions.

  5. A Late Glacial to Holocene record of environmental change from Lake Dojran (Macedonia, Greece)

    NASA Astrophysics Data System (ADS)

    Francke, A.; Wagner, B.; Leng, M. J.; Rethemeyer, J.

    2013-02-01

    A Late Glacial to Holocene sediment sequence (Co1260, 717 cm) from Lake Dojran, located at the boarder of the F.Y.R. of Macedonia and Greece, has been investigated to provide information on climate variability in the Balkan region. A robust age-model was established from 13 radiocarbon ages, and indicates that the base of the sequence was deposited at ca. 12 500 cal yr BP, when the lake-level was low. Variations in sedimentological (H2O, TOC, CaCO3, TS, TOC/TN, TOC/TS, grain-size, XRF, δ18Ocarb, δ13Ccarb, δ13Corg) data were linked to hydro-acoustic data and indicate that warmer and more humid climate conditions characterised the remaining period of the Younger Dryas until the beginning of the Holocene. The Holocene exhibits significant environmental variations, including the 8.2 and 4.2 ka cooling events, the Medieval Warm Period and the Little Ice Age. Human induced erosion processes in the catchment of Lake Dojran intensified after 2800 cal yr BP.

  6. Effects of seismic surge waves and implications for moraine-dammed lake outburst

    NASA Astrophysics Data System (ADS)

    Du, Cui; Yao, Lingkan; Huang, Yidan; Yan, Jiahong; Shakya, Subhashsagar

    2016-09-01

    Moraine dams usually collapse due to overtopping by the surge wave in the dammed lake, and the surge wave is most likely caused by an earthquake. The seismic water wave (SWW) is a major factor causing the dam to break in the earthquake zone. This paper focused on the SWW by model experiments with a shaking water tank under conditions of various water depths, seismic waves, and peak ground accelerations. Two empirical equations were obtained for estimating maximal wave height for the low and high frequency, respectively. Finally, we present the application of the empirical equations on Midui Glacier Lake in Tibet plateau.

  7. Impact of nanoparticles and colloids on glacial meltwater: A comparative study of rare earth elements in glacial meltwater rivers and terminal lakes in Iceland and New Zealand

    NASA Astrophysics Data System (ADS)

    Tepe, Nathalie; Bau, Michael

    2014-05-01

    Global warming accelerates the retreat of glaciers in both polar and temperate climatic regions and enhances the input of glacial meltwater and its load of particulates, colloids and nanoparticles into the ocean. In addition to the worldwide trend imposed by global warming, enhanced glacial melting in Iceland is occasionally caused by high geothermal heat flux and/or sub-glacial eruptions related to volcanic activity. This might even cause catastrophic melting events. We here report results of geochemical studies of meltwater rivers from southern Iceland sampled between 2010 and 2013 and of glacial terminal lakes and one meltwater river from the Southern Alps in New Zealand's South Island from 2013. In addition to the dissolved concentrations of Rare Earths and Yttrium (REY) in 200 nm-filtered waters, we also studied the respective filter residues (particles >200 nm). The REY are highly particle-reactive and show low solubilties, and therefore only a small fraction of the total REY concentration determined in 200 nm-filtered freshwaters is truly dissolved, whereas the majority is associated with colloids and nanoparticles. Nevertheless, in 200 nm-filtered water samples the REY are often below the lower limit of quantification even by sensitive analytical techniques such as ICPMS. The chemical composition of glacial meltwater rivers in Iceland is affected by volcanic eruptions due to the input of (colloid- and nano-) particles from volcanic ashes, whereas the chemical composition of glacial terminal lakes and meltwater rivers in New Zealand is affected by particles derived by erosion of rocks in the respective catchment. In marked contrast to Iceland, single events do play a minor role in New Zealand. In Iceland, all studied meltwater rivers display the same shale-normalized REY patterns with pronounced depletion of light and heavy REY relative to the middle REY (LaSN/GdSN: 0.41-0.45; GdSN/YbSN: 1.70-2.44). They show positive Eu anomalies, but no La, Ce or Y

  8. The 24 July 2008 outburst flood at the western Zyndan glacier lake and recent regional changes in glacier lakes of the Teskey Ala-Too range, Tien Shan, Kyrgyzstan

    NASA Astrophysics Data System (ADS)

    Narama, C.; Duishonakunov, M.; Kääb, A.; Daiyrov, M.; Abdrakhmatov, K.

    2010-04-01

    On 24 July 2008, a glacier lake outburst flood (GLOF) occurred at the western (w-) Zyndan glacier lake in the Tong District of Ysyk-Köl Oblast, Kyrgyzstan. The flood killed three people and numerous livestock, destroyed infrastructure, and devastated potato and barley crops as well as pastures. Tuurasuu village and a downstream reservoir on the Zyndan river escaped heavy damage because the main flood was diverted toward the Tong river. RTK-GPS and satellite data (Landsat 7 ETM+, ALOS/PRISM, and ALOS/AVNIR-2) reveal that the flood reduced the lake area from 0.0422 km2 to 0.0083 km2, discharging 437 000 m3 of water. This glacier lake was not present in a Landsat 7 ETM+ image taken on 26 April 2008. It formed rapidly over just two and half months from early May to the late July, when large amounts of snow and glacier melt water became trapped in a basin in the glacier terminus area, blocked by temporary closure of the drainage channel through the terminal moraine that included much dead-ice. In the same mountain region, most other glacier-lake expansions were not particularly large during the period from 1999-2008. Although events like the w-Zyndan glacier lake outburst occur infrequently in the high Central Asian mountains, such fast developing, short-lived lakes are particularly dangerous and not easy to monitor using satellite data. Appropriate measures to protect against such lake outburst hazards in this region include educating residents on glacier hazards and monitoring techniques, providing frequently updated maps of glacier lakes, and planning and monitoring land-use, including house locations.

  9. A new varved late Glacial and Holocene sediment record from Lake Jelonek (North Poland) - preliminary results

    NASA Astrophysics Data System (ADS)

    Kramkowski, Mateusz; Filbrandt-Czaja, Anna; Ott, Florian; Słowiński, Michał; Tjallingii, Rik; Błaszkiewicz, Mirosław; Brauer, Achim

    2015-04-01

    Anually laminated (varved) lake deposits are suitable natural archives for reconstructing past climatic and environmental changes at seasonal resolution. A major advantage of such records is that varve counting allows constructing robust and independent chronologies, a key challenge for paleoclimate research. Recently, a new annually laminated sediment record has been obtained from Lake Jelonek, located in the eastern part of the Pomeranian Lakeland in northern Poland (Tuchola Pinewoods). The lake is surrounded by forest and covers an area of 19,9 ha and has a maximum depth of 13,8 m. Three overlapping series of 14,3 m - long sediment records have been cored with an UWITEC 90 mm diameter piston corer from the deepest part of the lake. A continuous master composite profile has been established comprising the entire postglacial lacustrine sediment infill. Preliminary analyses including micro-facies analyses on thin sections from selected intervals as well as X-ray fluorescence element scanning (µ-XRF) reveal that the sediments are to a large part annually laminated. Here we present detailed varve models for different sediment intervals and discuss high-resolution geochemical variation in the entire sediment record. A preliminary age model based on radiocarbon dating and major biostratigraphical boundaries based on pollen data will be presented as well. These data will form the fundament for the planned multi-proxy study for detailed reconstructions of climatic and environmental variability during the late glacial and Holocene in the southern Baltic. This study is a contribution to the Virtual Institute ICLEA (Integrated Climate and Landscape Evolution Analysis) funded by the Helmholtz Association and National Science Centre Poland NCN 2011/01/B/ST10/07367.

  10. A scuba diving direct sediment sampling methodology on benthic transects in glacial lakes: procedure description, safety measures, and tests results.

    PubMed

    Pardo, Alfonso

    2014-11-01

    This work presents an in situ sediment sampling method on benthic transects, specifically intended for scientific scuba diver teams. It was originally designed and developed to sample benthic surface and subsurface sediments and subaqueous soils in glacial lakes up to a maximum depth of 25 m. Tests were conducted on the Sabocos and Baños tarns (i.e., cirque glacial lakes) in the Spanish Pyrenees. Two 100 m transects, ranging from 24.5 to 0 m of depth in Sabocos and 14 m to 0 m deep in Baños, were conducted. In each test, 10 sediment samples of 1 kg each were successfully collected and transported to the surface. This sampling method proved operative even in low visibility conditions (<2 m). Additional ice diving sampling tests were conducted in Sabocos and Truchas tarns. This sampling methodology can be easily adapted to accomplish underwater sampling campaigns in nonglacial lakes and other continental water or marine environments.

  11. Age and extent of a giant glacial-dammed lake at Yarlung Tsangpo gorge in the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Liu, Weiming; Lai, Zhongping; Hu, Kaiheng; Ge, Yonggang; Cui, Peng; Zhang, Xiaogang; Liu, Feng

    2015-10-01

    Many glacier dams on major rivers at the southeastern edge of the Tibetan Plateau had been previously determined through remote sensing and glacier terminal position calculation. It was hypothesized that such damming substantially impeded river incision into the plateau interior. Investigation on the large glacial-dammed lake at the entrance of Tsangpo gorge is critical for understanding this hypothesis. So far, the issues, such as age, lake surface elevation, and stages of this dammed lake, are still in debate. Our field survey of lacustrine deposits and loess distribution along the middle Yarlung Tsangpo River and its tributary, Nyang River, suggested that the lake surface elevation was at about 3180 m asl. The 23 quartz optically stimulated luminescence (OSL) and 4 organic AMS 14C ages all fall into the Last Glacial period (~ 41-13 ka). The OSL and 14C ages are in general agreement with each other where applicable. There might be only one long damming event because the ages of lacustrine deposits from 2970 to 3100 m asl are similar, and every lacustrine section is sustained for a long time. The estimated lake surface area was 1089 km2, and the volume was ~ 170 km3, which differ from previous estimations which suggested two-stage (about early Holocene and 1.5 ka) lakes, and the largest lake surface elevation reached 3500 m.

  12. Glacially conditioned specific stream powers in low-relief river catchments of the southern Laurentian Great Lakes

    NASA Astrophysics Data System (ADS)

    Phillips, R. T. J.; Desloges, J. R.

    2014-02-01

    Fluvial systems of the southern Laurentian Great Lakes region are carved into a complex glacial landscape shaped by continental ice and meltwater of the late Pleistocene. These glacially conditioned river catchments are typically small with drainage areas < 104 km2. A 10-m digital elevation model (DEM) is used to map the spatial distribution of stream gradient for 22 major river catchments of peninsular southern Ontario, which drain to base levels in the lower Great Lakes (Huron, St. Clair, Erie, and Ontario). Raw data from the DEM show stream gradients that exhibit multiscale variance from real and from artifact sources. Based on a vertical slice and multiple-pass moving-window averaging approach, slope data are generalised to the river reach scale (1-2 km) as a representative spatial scale for fluvial processes operating over Holocene timescales. Models of specific stream power are then compared with glacial landform and surface geology mapping. Inherited glacial signatures in river slope appear as deviations in a stream length-gradient index (SL/K index), where river reaches are frequently oversteepened or understeepened. Based on a slope-area analysis, and complementary to theories of channel pattern discrimination, constant stream power curves (with power-law exponent of - 0.4) provide a first-order approach to stratify river reaches in terms of glacial conditioning and expected planform morphologies. However, multiple-channel planform types are rare and localised in southern Ontario, indicating that oversteepened reaches with high stream powers may often be moderated by (1) sediment calibre, with cobble-beds from inherited glacial sediments; and/or (2) relative bank strength, with limited channel widening particularly in gravel and sand-bed channels. Further discrimination of glacially conditioned fluvial process domains will ultimately require consideration of alluvial floodplain characteristics in addition to general observations of river morphology and

  13. Last glacial megafaunal death assemblage and early human occupation at Lake Menindee, southeastern Australia

    NASA Astrophysics Data System (ADS)

    Cupper, Matthew L.; Duncan, Jacqui

    2006-09-01

    The Tedford subfossil locality at Lake Menindee preserves a diverse assemblage of marsupials, monotremes and placental rodents. Of the 38 mammal taxa recorded at the site, almost a third are of extinct megafauna. Some of the bones are articulated or semi-articulated and include almost complete skeletons, indicating that aeolian sediments rapidly buried the animals following death. New optical ages show the site dates to the early part of the last glacial (55,700 ± 1300 yr weighted mean age). This is close to the 51,200-39,800 yr Australia-wide extinction age for megafauna suggested by Roberts et al. [2001, Science 292:1888-1892], but like all previous researchers, we cannot conclusively determine whether humans were implicated in the deaths of the animals. Although an intrusive hearth at the site dating to 45,100 ± 1400 yr ago is the oldest evidence of human occupation of the Darling River, no artifacts were identified in situ within the sub-fossil-bearing unit. Non-anthropogenic causes, such as natural senescence or ecosystem stress due to climatic aridity, probably explain the mortality of the faunal assemblage at Lake Menindee.

  14. Experimental modelling of outburst flood - bed interactions

    NASA Astrophysics Data System (ADS)

    Carrivick, J. L.; Xie, Z.; Sleigh, A.; Hubbard, M.

    2009-04-01

    Outburst floods are a sudden release and advancing wave of water and sediment, with a peak discharge that is often several orders of magnitude greater than perennial flows. Common outburst floods from natural sources include those from glacial and moraine-impounded lakes, freshwater dyke and levee bursts, volcanic debris dams, landslides, avalanches, coastal bay-bars, and those from tree or vegetation dams. Outburst flood hazards are regularly incorporated into risk assessments for urban, coastal and mountainous areas, for example. Outburst flood hazards are primarily due to direct impacts, caused by a frontal surge wave, from debris within a flow body, and from the mass and consistency of the flows. A number of secondary impacts also pose hazards, including widespread deposition of sediment and blocked tributary streams. It is rapid landscape change, which is achieved the mobilization and redistribution of sediment that causes one of the greatest hazards due to outburst floods. The aim of this project is therefore to parameterise hydrodynamic - sedimentary interactions in experimental outburst floods. Specifically, this project applies laboratory flume modelling, which offers a hitherto untapped opportunity for examining complex interactions between water and sediment within outburst floods. The experimental set-up is of a tradition lock-gate design with a straight 4 m long tank. Hydraulics are scaled at 1:20 froude scale and the following controls on frontal wave flow-bed interactions and hence on rapid landscape change are being investigated: 1. Pre-existing mobile sediment effects, fixed bed roughness effects, sediment concentration effects, mobile bed effects. An emphasis is being maintained on examining the downstream temporal and spatial change in physical character of the water / sediment frontal wave. Facilities are state-of-the-art with a fully-automated laser bed-profiler to measure bed elevation after a run, Seatek arrays to measure transient flow

  15. Tropically mediated global responses to cataclysmic flooding in the eastern North Pacific by Glacial Lake Missoula (and variations in response based on initial onset)

    NASA Astrophysics Data System (ADS)

    Gambs, M. F.; Thompson, L.; Hautala, S. L.; Bitz, C. M.

    2012-12-01

    The Missoula Floods (18.6 to 14.5 ka) were a series of jökulhlaups (freshwater glacial-outburst floods) from proglacial Lake Missoula, during the Last Glacial Maximum (LGM). These episodic floods carved the Quaternary landscape of Eastern Washington and northern Oregon, flowing rapidly into the Pacific Ocean via the Columbia River. This study investigates the short-term global ocean and climate response to the freshwater discharge from the Missoula Floods into the eastern North Pacific Ocean. We simulate the floods by adding freshwater north of 42°N and east of 140°W, from the surface, tapering to 920 m and restarting a run of the Community Climate System Model, version 3 (CCSM3) configured for Last Glacial Maximum conditions. The method is similar to that used in freshwater hosing experiments in the North Atlantic. Fourteen runs were completed, seven initialize during El Niño conditions, and seven during La Niña conditions as defined by the Niño 3.4 index (5°S to 5°N and 170°W to 120°W). Ensemble means are made and compared against control ensembles without the freshwater input. We find a global response within one year of freshwater input, with warming to the west of the hosing region and cooling to the south. The response is larger for La Niña conditions, with warming in the tropical Pacific of more than 0.5°C and an even larger warming throughout Antarctica with warming of more than 1.5°C, in the first year following freshening. The Southern Ocean also warms, particularly in the Atlantic sector. During El Niño conditions, Greenland warms by more than 1°C and there is warming confined to the Pacific Sector over Greenland and the Southern Ocean. The changes in surface temperatures are accompanied by changes in sea-ice extent in both hemispheres. Changes in the Tropical Pacific are initiated by sea surface temperature gradients associated with the freshwater input that then modify the winds in the subtropics.

  16. Patterns and Potential Drivers of a Seasonal Glacial Sediment Plume derived from Landsat CDR Data, Lake Clark, Alaska

    NASA Astrophysics Data System (ADS)

    Baughman, C. A.; Jones, B. M.; Bartz, K. K.; Young, D. B.; Zimmerman, C. E.

    2015-12-01

    Lake Clark is large freshwater lake in Southcentral Alaska. Central to Lake Clark National Park and Preserve, Lake Clark is an important nursery lake for sockeye salmon (Oncorhynchus nerka) in the headwaters of Bristol Bay, Alaska, the most productive wild salmon fishery in the world. Lake Clark water clarity is seasonally influenced by a dynamic glacier fed sediment plume. We reconstructed lake-wide water clarity for Lake Clark using the Landsat TM and ETM+ Climate Data Record archive. Our study period consisted of May - October for 1985-2015. We found 151 (98 partial- and 53 whole-lake) Landsat scenes that captured the lake and/or sediment plume. Water clarity fluctuated on an annual basis with specific conditions common to certain months. Plume development and peak turbidity dates could be estimated for a number of years and mid-season gyres appear to represent wind-induced mixing of lake water. Our results showed short term (sub-decadal) trends in water clarity but little to no long term trend between 1991 and 2014. We did, however, detect interannual variation that exhibited a non-significant (r2 = 0.20) but positive correlation (r = 0.20) with regional mean summer air temperature and found the month of May exhibited a significant positive trend (r2 = 0.68, p-value = 0.02) in turbidity between 2000 and 2014. These results are important because reductions in water clarity within Alaska lake systems as a result of increased glacial runoff have been shown to reduce salmon production via reduced abundance of preferred prey items of juvenile salmon, such as zooplankton and macroinvertebrates.

  17. Glacial megasequences as a basis for ground-water sensitivity mapping at the head of Lake Michigan

    SciTech Connect

    Bleuer, N.K.; Woodfield, M.C. )

    1994-04-01

    The Valparaiso and Calumet megasequences mapped at the head of Lake Michigan in northwestern Indiana are large-scale, three-dimensional, glacial-lacustrine, and lacustrine packages successively inset into basins left by the collapse of earlier ice masses. These map units are the basis for assessing groundwater sensitivity in Porter County, an area representative of the rural to heavily industrialized southern Lake Michigan rim. Facies within these megasequences record repeated southward and upward progression of more ice-proximal facies, representative of repeated southward and upward progression of more ice-proximal facies, representative of repeated ice advance out of the basin. The Valparaiso megasequence is a single lake-bottom to subaerial head-of-fan progression. The inset Calumet megasequence (Lake Border/Wheeler sequences; Lake Michigan sequence) is a multiple lake, subaqueous fan, to push-moraine progression followed by further inset of multiple lake bottom, delta, and beach progressions related to early phases of Lake Michigan. The variability within the megasequences make traditional surficial mapping or DRASTIC''-style ground-water sensitivity analysis difficult to justify. Instead, the nature of variability itself is of absolute importance. For this reason, an extensively illustrated atlas serves as a map explanation, type'' gamma-ray-log profiles illustrate variation in vertical sequence, and cross sections illustrate variation in overall geometry. Accompanying discussions outline elements of ground-water sensitivity related to various between and within-sequence geometries.

  18. Stable isotope evidence for glacial lake drainage through the St. Lawrence Estuary, eastern Canada, ~13.1-12.9 ka

    USGS Publications Warehouse

    Cronin, T. M.; Rayburn, J.A.; Guilbault, J.-P.; Thunell, R.; Franzi, D.A.

    2012-01-01

    Postglacial varved and rhythmically-laminated clays deposited during the transition from glacial Lake Vermont (LV) to the Champlain Sea (CS) record hydrological changes in the Champlain-St. Lawrence Valley (CSLV) at the onset of the Younger Dryas ∼13.1–12.9 ka linked to glacial lake drainage events. Oxygen isotope (δ18O) records of three species of benthic foraminifera (Cassidulina reniforme, Haynesina orbiculare, Islandiella helenae) from six sediment cores and the freshwater ostracode Candona from one core were studied. Results show six large isotope excursions (∼0.5 to >2‰) in C. reniforme δ18O values, five excursions in H. orbiculare (<0.5 to ∼1.8‰), and five smaller changes in I. helenae (<0.5‰). δ18O values in Candona show a 1.5–2‰ increase in the same interval. These isotopic excursions in co-occurring marine and freshwater species in varve-like sediments indicate complex hydrological changes in the earliest Champlain Sea, including brief (sub-annual) periods of complete freshening. One hypothesis to explain these results is that multiple abrupt freshwater influx events caused surface-to-bottom freshening of the Champlain Sea over days to weeks. The most likely source of freshwater would have been drainage of the Morehead Phase of glacial Lake Agassiz, perhaps in a series of floods, ultimately draining out the St. Lawrence Estuary.

  19. Evidence of multiple late-Wisconsin floods from glacial Lake Missoula in Badger Coulee, Washington

    NASA Astrophysics Data System (ADS)

    Bunker, Russell C.

    1982-07-01

    Catastrophic floods from glacial Lake Missoula entered the Pasco Basin in south-central Washington and backflooded its marginal valleys. Badger Coulee, one such valley, contains beds of fine-grained slackwater sediment deposited by these floods. The slackwater sediment contains two ash layers of the Mount St. Helens set S tephra, about 13,000 yr old. The ash was deposited on a ground surface developed atop slackwater sediment deposited during preash flooding. Evidence of the former ground surface includes the reworked ash, inferred trace fossils, stream and debris-flow deposits, slopewash and/or eolian sediment, and colluvium at the ash horizon. These features and the ash were buried by slackwater sediment deposited during postash flooding. Nonflood, subaerial deposits are not present atop other beds. Instead, beds commonly are reversely graded across "contacts," suggesting that multiple beds were continuously deposited. The exposed beds thus record at least two late-Wisconsin floods, one preash, the other postash. The pre- and postash floods may be correlative with earlier-reported floods thought to have occurred 17,500-14,000 and 14,000-13,000 yr B.P., respectively.

  20. Understanding past climatic and hydrological variability in the Mediterranean from Lake Prespa sediment isotope and geochemical record over the Last Glacial cycle

    NASA Astrophysics Data System (ADS)

    Leng, Melanie J.; Wagner, Bernd; Boehm, Anne; Panagiotopoulos, Konstantinos; Vane, Christopher H.; Snelling, Andrea; Haidon, Cheryl; Woodley, Ewan; Vogel, Hendrik; Zanchetta, Gianni; Baneschi, Ilaria

    2013-04-01

    Here we present stable isotope and geochemical data from Lake Prespa (Macedonia/Albania border) over the Last Glacial cycle (Marine Isotope Stages 5-1) and discuss past lake hydrology and climate (TIC, oxygen and carbon isotopes), as well as responses to climate of terrestrial and aquatic vegetation (TOC, Rock Eval pyrolysis, carbon isotopes, pollen). The Lake Prespa sediments broadly fall into 5 zones based on their sedimentology, geochemistry, palynology and the existing chronology. The Glacial sediments suggest low supply of carbon to the lake, but high summer productivity; intermittent siderite layers suggest that although the lake was likely to have mixed regularly leading to enhanced oxidation of organic matter, there must have been within sediment reducing conditions and methanogenesis. MIS 5 and 1 sediments suggest much more productivity, higher rates of organic material preservation possibly due to more limited mixing with longer periods of oxygen-depleted bottom waters. We also calculated lakewater δ18O from siderite (authigenic/Glacial) and calcite (endogenic/Holocene) and show much lower lakewater δ18O values in the Glacial when compared to the Holocene, suggesting the lake was less evaporative in the Glacial, probably as a consequence of cooler summers and longer winter ice cover. In the Holocene the oxygen isotope data suggests general humidity, with just 2 marked arid phases, features observed in other Eastern and Central Mediterranean lakes.

  1. Deep lakes in the Polar Urals - unique archives for reconstructing the Quaternary climate and glacial history in the Russian Arctic

    NASA Astrophysics Data System (ADS)

    Svendsen, J.; Gyllencreutz, R.; Henriksen, M.; Lohne, O. S.; Mangerud, J.; Nazarov, D.

    2009-12-01

    A lake coring campaign in the Polar Urals is carried out within the framework of the Norwegian-Russian IPY-project “The Ice Age Development and Human Settlement in Northern Eurasia” (ICEHUS). The overall aim of the project is to improve the description and understanding of the Late Quaternary environmental and climate changes in the Russian Arctic and how these changes may have affected the early human occupation. In order to obtain a continuous record of climate variability back in time seismic records and sediment cores have been collected from selected mountain lakes. The summer of 2009 we cored two lakes situated near the water shed in the interior northernmost Urals. Seismic profiles show that both these glacially eroded basins contain thick sequences of Quaternary sediments. The thickest strata were found in Bolshoye Shuchye, the largest and deepest lake in the Ural Mountains. This lake is 13 km long and 140 m deep and contains more than 130 m of acoustically laminated sediments. These strata probably accumulated over a rather long time span, possibly covering several interglacial-glacial cycles. Up to 24 m long cores were obtained from the lake floors. We anticipate that they will provide unique high resolution records of the climate and glacial history during the last Ice Age. The seismic records and the sediment cores will form a well-founded basis for assessing the potential and possibilities to core also the deeper strata that could not be reached with the applied coring equipment. In view of the obtained results from the investigated basins, as well as other geological and geochronological data from the surrounding areas, we find it highly unlikely that any glaciers extended into these lakes during the Last Glacial Maximum (LGM), supporting our current hypothesis that the local glaciers in the Polar Urals remained small during the LGM. Our observations indicate that the mountain valleys have been essentially ice free since Marine Isotope Stage 4, at

  2. Glacial to Holocene climate changes in the SE Pacific. The Raraku Lake sedimentary record (Easter Island, 27°S)

    NASA Astrophysics Data System (ADS)

    Sáez, Alberto; Valero-Garcés, Blas L.; Giralt, Santiago; Moreno, Ana; Bao, Roberto; Pueyo, Juan J.; Hernández, Armand; Casas, David

    2009-12-01

    Easter Island (SE Pacific, 27°S) provides a unique opportunity to reconstruct past climate changes in the South Pacific region based on terrestrial archives. Although the general climate evolution of the south Pacific since the Last Glacial Maximum (LGM) is coherent with terrestrial records in southern South America and Polynesia, the details of the dynamics of the shifting Westerlies, the South Pacific Convergence Zone and the South Pacific Anticyclone during the glacial-interglacial transition and the Holocene, and the large scale controls on precipitation in tropical and extratropical regions remain elusive. Here we present a high-resolution reconstruction of lake dynamics, watershed processes and paleohydrology for the last 34 000 cal yrs BP based on a sedimentological and geochemical multiproxy study of 8 cores from the Raraku Lake sediments constrained by 22 AMS radiocarbon dates. This multicore strategy has reconstructed the sedimentary architecture of the lake infilling and provided a stratigraphic framework to integrate and correlate previous core and vegetation studies conducted in the lake. High lake levels and clastic input dominated sedimentation in Raraku Lake between 34 and 28 cal kyr BP. Sedimentological and geochemical evidences support previously reported pollen data showing a relatively open forest and a cold and relatively humid climate during the Glacial period. Between 28 and 17.3 cal kyr BP, including the LGM period, colder conditions contributed to a reduction of the tree coverage in the island. The coherent climate patterns in subtropical and mid latitudes of Chile and Eastern Island for the LGM (more humid conditions) suggest stronger influence of the Antarctic circumpolar current and an enhancement of the Westerlies. The end of Glacial Period occurred at 17.3 cal kyr BP and was characterized by a sharp decrease in lake level conducive to the development of major flood events and erosion of littoral sediments. Deglaciation (Termination

  3. Historical telecommunication in the Hindukush-Karakoram-Himalayas: An ancient early warning system for glacier lake outbursts

    NASA Astrophysics Data System (ADS)

    Iturrizaga, Lasafam

    2016-04-01

    Mountain societies are in a crucial transition phase in terms of the management of natural hazards. Advances in geographic technologies, such as a variety of remote-sensing tools and mobile communication systems, have drastically changed the way of early warning methods in difficult accessible high mountain environments compared to those of ancient times. In order to implement new natural hazard policies, it is essential to unravel the traditional ways of disaster management which is presented here by a case study from the Hindukush-Karakoram-Himalayas. In the rugged relief of the Himalaya Region, the exchange of information was a labor-intensive and time-consuming task for remote high mountain villages before the infrastructural development and the introduction of modern communication systems. Therefore, early warning of natural hazards with long run-out distances seems to have been rather impossible. However, in the present study a historical optical long-distance and fast operating communication system over horizontal distances of several hundred kilometers was discovered during field investigations in the Hindukush-Karakoram and the transmission paths reconstructed in the following years. The so called Puberanch-system relied on a chain of fire signals as used by ancient societies in other mountain and coastal environments in the world. It was originally in use for the alert against war attacks from hostile neighboring communities. Later on, it served as an early warning system for glacier lake outbursts, which have been in the end of the 19th century and beginning of the 20th century one of the most devastating natural hazards in the region. Remarkable is the fact that fire posts were located in extremely harsh environments at altitudes above 4000 m requiring a highly sophisticated supply system of fire wood and food. Interviews with local inhabitants, the evaluation of historical travel records and international newspapers proved, that the system has been

  4. Paleomonsoonal Precipitation and Hydroclimate Variability from Glacial to Interglacial Climates in the Southwest: The Stoneman Lake, Arizona Record

    NASA Astrophysics Data System (ADS)

    Garcia, D.; Fawcett, P. J.; Anderson, R. S.; Sharp, Z. D.

    2015-12-01

    Oxygen isotope values from diatom silica have been used to determine past hydrological conditions in a variety of settings including differentiating summer monsoonal paleoprecipitation from winter frontal paleoprecipitation in the American southwest. Lacustrine cores from the Valles Caldera, New Mexico, show a distinct change in silica oxygen isotope values from glacial to interglacial as a switch from a purely winter frontal precipitation during the glacial to a mix of winter frontal and summer monsoonal precipitation during the interglacial. A relatively large (ca. 20‰) and rapid increase in δ18O following the glacial termination implies an abrupt onset of the North American monsoon. We plan to elaborate on this research to see if this is true elsewhere in the southwest. Two lacustrine sediment cores (70 m deep and 30 m deep respectively) were recovered from Stoneman Lake, northern Arizona in October of 2014. With these cores we plan to determine regional hydroclimate variability between the Pleistocene-Holocene glacial transition ca. 14 ka. Oxygen isotope analysis from diatom silica will allow us to determine past sources of precipitation to the basin (Gulf of Mexico vs North Pacific), and paleoprecipitation variability. In conjunction with other proxies, we can determine if the onset of paleomonsoonal precipitation in central Arizona occurs immediately after the glacial termination as in NM, or if there is some component of monsoonal precipitation during the late glacial period. Diatom sampling was performed at approximately every 50 cm. To purify the diatoms, the samples are chemically and physically separated. The step wise fluorination and laser ablation technique are then applied to remove water & hydroxyl groups and to extract O2 & SiF4 respectively.If results from the Stoneman Lake core are similar to that of the Valles Caldera core, we should expect to see a nearly 20‰ increase in δ18Olake water. This would suggest a: 1) collapse of the summer

  5. Orbital- versus glacial-mode forcing of tropical African climate: Results of scientific drilling in Lake Malawi, East Africa

    NASA Astrophysics Data System (ADS)

    Scholz, C. A.; Cohen, A. S.; Johnson, T. C.; King, J. W.; Brown, E. T.; Lyons, R. P.; Stone, J. R.; Beuning, K. R.

    2007-12-01

    Lake Malawi extends from 9-14 degrees S within the East African Rift Valley, and at 700 m deep, contains more than 20 percent of the surface water on the African continent. In 2005 the Lake Malawi Scientific Drilling Project drilled 7 holes at two sites in the lake, recovering a continuous sediment record that samples much of the Quaternary. Detailed studies completed to date on sediments deposited during the past 145 ka indicate periods of severe aridity at precessional frequency between 135 and 75 ka, when the lake's water volume was periodically reduced by at least 95 percent. These dramatic drops in lake level (more than 550 m), signifying markedly arid conditions in the catchment, are documented in sediment lithology (decreased organic carbon content and increased authigenic carbonate content during severe lowstands), aquatic microfossils (appearance of a littoral ostracode fauna, and saline/alkaline lake diatom flora during extreme low lake stages), as well as in dramatic reductions in catchment pollen production. These intervals of pronounced tropical African aridity in the early late-Pleistocene were much more severe than the Last Glacial Maximum, and are consistent with sediment records from Lakes Tanganyika (East Africa) and Bosumtwi (West Africa). In all three lakes a major rise in water levels and a shift to more humid conditions is observed after ~70 ka. The transition to wetter, more stable conditions coincides with the relaxation of orbital eccentricity and a reduction in the amplitude of precession. The observed climate mode switch to decreased environmental variability is consistent with terrestrial and marine records from in and around tropical Africa, but these new drill cores provide evidence for dramatically drier conditions prior to 70 ka that have not as yet been detected in marine sediment records. Such climate change may have stimulated the expansion and migrations of early modern human populations.

  6. A scuba diving direct sediment sampling methodology on benthic transects in glacial lakes: procedure description, safety measures, and tests results.

    PubMed

    Pardo, Alfonso

    2014-11-01

    This work presents an in situ sediment sampling method on benthic transects, specifically intended for scientific scuba diver teams. It was originally designed and developed to sample benthic surface and subsurface sediments and subaqueous soils in glacial lakes up to a maximum depth of 25 m. Tests were conducted on the Sabocos and Baños tarns (i.e., cirque glacial lakes) in the Spanish Pyrenees. Two 100 m transects, ranging from 24.5 to 0 m of depth in Sabocos and 14 m to 0 m deep in Baños, were conducted. In each test, 10 sediment samples of 1 kg each were successfully collected and transported to the surface. This sampling method proved operative even in low visibility conditions (<2 m). Additional ice diving sampling tests were conducted in Sabocos and Truchas tarns. This sampling methodology can be easily adapted to accomplish underwater sampling campaigns in nonglacial lakes and other continental water or marine environments. PMID:24943883

  7. Hubbard Glacier, Alaska: growing and advancing in spite of global climate change and the 1986 and 2002 Russell Lake outburst floods

    USGS Publications Warehouse

    Trabant, Dennis C.; March, Rod S.; Thomas, Donald S.

    2003-01-01

    Hubbard Glacier, the largest calving glacier on the North American Continent (25 percent larger than Rhode Island), advanced across the entrance to 35-mile-long Russell Fiord during June 2002, temporarily turning it into a lake. Hubbard Glacier has been advancing for more than 100 years and has twice closed the entrance to Russell Fiord during the last 16 years by squeezing and pushing submarine glacial sediments across the mouth of the fiord. Water flowing into the cutoff fiord from mountain streams and glacier melt causes the level of Russell Lake to rise. However, both the 1986 and 2002 dams failed before the lake altitude rose enough for water to spill over a low pass at the far end of the fiord and enter the Situk River drainage, a world-class sport and commercial fishery near Yakutat, Alaska.

  8. Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Barbante, C.; Gabrielli, P.; Turetta, C.; Planchon, F.; Boutron, C.; Petit, J. R.; Bulat, S.; Hong, S.; Cozzi, G.; Cescon, P.

    2009-12-01

    We report the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g-1 for Ce and 0.0035- 0.24 pg g-1 for Lu in glacier ice, and between <0.1-24 pg g-1 for Ce and <0.0004-0.02 pg g-1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC1;characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC1 formation. Interestingly, if the LREE enrichment found in AC1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

  9. Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica

    NASA Astrophysics Data System (ADS)

    Gabrielli, Paolo; Planchon, Frederic; Barbante, Carlo; Boutron, Claude F.; Petit, Jean Robert; Bulat, Sergey; Hong, Sungmin; Cozzi, Giulio; Cescon, Paolo

    2009-10-01

    This paper reports the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g -1 for Ce and 0.0035-0.24 pg g -1 for Lu in glacier ice, and between <0.1-24 pg g -1 for Ce and <0.0004-0.02 pg g -1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC 1; characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC 2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC 1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC 1 formation. Interestingly, if the LREE enrichment found in AC 1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

  10. Using discontinuous wave-cut terraces to reconstruct the history of former glacial lake levels: the example of Lake Ojibway in NW Quebec (Canada)

    NASA Astrophysics Data System (ADS)

    Daubois, V.; Roy, M.; Veillette, J. J.

    2012-12-01

    The decay of the southern Laurentide ice sheet maring during the last deglaciation led to the development of Lake Agassiz and Lake Ojibway that covered large areas in the western prairies and in NE Ontario-NW Quebec, respectively. The history of glacial lakes is commonly based on the study of strandlines that generally consist of sandy beaches (and near-shore facies) or boulder ridges. However, the use of this approach is limited in the main Ojibway basin where the surficial geology consists predominantly of thick accumulation of fine-grained glaciolacustrine deposits that mask most deglacial landforms and the underlying bedrock. Nonetheless, earlier mapping programs in this flat-lying clay plain revealed a complex sequence of discontinuous small-scale cliffs that are made of Ojibway rhythmites. These terrace-like features range in size from 4 to 7 m in height and can generally be followed for 10 to 100's of meters, and sometimes for several kms. These small-scale features are interpreted to represent raised shorelines that were cut into glaciolacustrine sediments by lakeshore erosional processes (i.e., wave action). These so-called wave-cut benches (WCBs) occur at elevations ranging mostly from 3 to 30 m above the present level of Lake Abitibi (267 m), one of the lowest landmarks in the area. Here we evaluate the feasibility of using this type of shorelines to constrain the evolution of Ojibway lake levels in NW Quebec. For this purpose, a series of wave-cut terraces (WCBs) were measured along two north-south transects of about 40 km in length in the Lake Abitibi region. The absolute elevation of more than 70 WCBs was determined with a Digital Video Plotter software package using 1:15K air-photos, coupled with precise measurements (x,y,z coordinates) of control points, which were measured with a high-precision Global Navigation Satellite System tied up to known geodesic survey markers. Preliminary results suggest that Lake Ojibway experienced at least three

  11. Glacial areas, lake areas, and snow lines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    NASA Astrophysics Data System (ADS)

    Hanshaw, M. N.; Bookhagen, B.

    2014-03-01

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 158 multi-spectral satellite images spanning almost 4 decades, from 1975 to 2012, to obtain glacial- and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. Additionally, we have estimated the snow-line altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota (1988 glacial area: 361 km2) have been declining at a rate of 3.99 ± 1.15 km2 yr-1 (22 year average, 1988-2010, with 95% confidence interval (CI), n = 8 images). Since 1980, the Quelccaya Ice Cap (1980 glacial area: 63.1 km2) has been declining at a rate of 0.57 ± 0.10 km2 yr-1 (30 year average, 1980-2010, with 95% CI, n = 14). Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2010) as compared to the preceding decade (1988-1999) with an average increase from 37.5 to 42.3 × 10-3 km2 yr-1 km-2 (13%). Third, glaciers with lower median elevations are declining at higher rates than those with higher median elevations. Specifically, glaciers with median elevations around 5200 m a.s.l. are retreating to higher elevations at a rate of ~1 m yr-1 faster than glaciers with median elevations around 5400 m a.s.l. Fourth, as glacial regions have decreased, 77% of lakes connected to glacial watersheds have either remained stable or shown a roughly synchronous increase in lake area, while 42% of lakes not connected to glacial

  12. Tracking Holocene glacial and high-altitude alpine environments fluctuations from minerogenic and organic markers in proglacial lake sediments (Lake Blanc Huez, Western French Alps)

    NASA Astrophysics Data System (ADS)

    Simonneau, Anaëlle; Chapron, Emmanuel; Garçon, Marion; Winiarski, Thierry; Graz, Yann; Chauvel, Catherine; Debret, Maxime; Motelica-Heino, Mickaël; Desmet, Marc; Di Giovanni, Christian

    2014-04-01

    Holocene palaeoenvironmental evolution and glacial fluctuations at high-altitude in the western French Alps are reconstructed based on a multiproxy approach within Lake Blanc Huez (2550 m a.s.l.) drainage basin. The combination of seismic profiling (3.5 kHz), piston coring and radiocarbon dating in proglacial lacustrine sediments together with a detailed organic analysis of autochthonous and allochthonous supply allows documenting the evolution of glacier activity during the Holocene. Over the last 9700 years, the Holocene lake record has a bimodal pattern whose transition is progressive and occurring between 5400 and 4700 cal BP. During the Early Holocene, the organic lacustrine facies reflects reduced glacial activity in the catchment. This major glacial retreat seems to result from solar forcing and high summer insolation. After 5400 cal BP, lacustrine sedimentation is marked by the gradual increase both of minerogenic supply and soil erosion, suggesting a progressive transition to wetter climatic conditions. This climate change is synchronous both from the gradual decrease of summer insolation and the gradual reorganization of oceanic and atmospheric circulations, characterizing the beginning of the Neoglacial period. Both colder temperature and humid climate induced significant glacier advance, since 4700 cal BP. Over this global trend, three periods are particularly associated with higher runoff processes and higher soil erosion interpreted as wetter time intervals resulting from enhanced northern Westerlies regimes across the North Atlantic and Western Europe. They are dated from 8700 to 7000, 4700 to 2500 and 1200 to 200 cal BP. These wetter phases drastically contrast with periods of reduced glacial activities dated from the Early Bronze Age (ca 3870-3770 cal BP), the Iron Age (ca 2220-2150 cal BP), the Roman period (ca AD115-330) and the Medieval Warm Period (ca AD760-1160). In addition, these dryer periods are associated with mining activities at high-altitude.

  13. Buried bedrock topography, evidence of overdeepening of Winimusset Brook bedrock valley, and reinterpretation of the extent of glacial Lake Winimusset, Ware quadrangle, Massachusetts

    USGS Publications Warehouse

    Lapham, W.W.; Maevsky, A.

    1991-01-01

    Results from 15 test borings and 8 seismic-refraction surveys in the northeastern quarter of the Ware quadrangle, Massachusetts, provide information on the buried-bedrock topography, evidence of overdeepening of Winimusset Brook valley, information on the thickness and lithology of lacustrine deposits in glacial Lake Winimusset, and indicate a need for reinterpretation of the areal extent of the lake. Glacial Lake Winimusset, which occupied this bedrock valley during the last stages of deglaciation, was more extensive and accumulated thicker lacustrine deposits than previously postulated. Lacustrine silt and clay deposited in this lake are as much as 100 feet thick. The lake extended at least 1 mile north of the Town of Wheelwright. -from Authors

  14. Climatic Oscillations 10,000-155,000 yr B.P. at Owens Lake, California Reflected in Glacial Rock Flour Abundance and Lake Salinity in Core OL-92

    USGS Publications Warehouse

    Bischoff, J.L.; Menking, K.M.; Fitts, J.P.; Fitzpatrick, J.A.

    1997-01-01

    Chemical analyses of the acid-soluble and clay-size fractions of sediment samples (1500-yr resolution) reveal oscillations of lake salinity and of glacial advances in core OL-92 back to 155,000 yr B.P. Relatively saline conditions are indicated by the abundance of carbonate and smectite (both pedogenic and authigenic), reflected by Ca, Sr, and Mg in the acid-soluble suite, and by Cs2O, excess MgO, and LOI (loss on ignition) in the clay-size fraction. Rock flour produced during glacial advances is represented by the abundance of detrital plagioclase and biotite in the clay-size fraction, the ratio of which remains essentially constant over the entire time span. These phases are quantitatively represented by Na2O, TiO2, Ba, and Mn in the clay fraction. The rock-flour record indicates two major ice-advances during the penultimate glacial cycle corresponding to marine isotope stage (MIS) 6, no major advances during the last interglaciation (entire MIS 5), and three major advances during the last glacial cycle (MIS 2, 3, and 4). The ages of the latter three correspond rather well to 36Cl dates reported for Sierra Nevada moraines. The onset of the last interglaciation is shown by abrupt increases in authigenic CaCO3 and an abrupt decrease in rock flour, at about 118,000 yr B.P. according to our time scale. In contrast, the boundary appears to be gradual in the ??18O record in which the change from light to heavy values begins at about 140,000 yrs B.P. The exact position of the termination, therefore, may be proxy-dependent. Conditions of high carbonate and low rock flour prevailed during the entire period from 118,000 yr B.P. until the glacial advance at 53,000 yr B.P. signaled the end of this long interglaciation. ?? 1997 University of Washington.

  15. Glacier and glacial lake changes and their relationship in the context of climate change, Central Tibetan Plateau 1972-2010

    NASA Astrophysics Data System (ADS)

    Wang, Xu; Siegert, Florian; Zhou, Ai-guo; Franke, Jonas

    2013-12-01

    The alpine ecosystem of the Western Nyainqentanglha region, located in the Central Tibetan Plateau, has experienced a lot of changes in the context of climatic change. The long data record of remote sensing data allowed us to evaluate spatio-temporal change in this remote area. The ecosystem changes of the Western Nyainqentanglha region were detected by using Landast MSS/TM/ETM +, Hexagon KH-9, Glas/ICESat, SRTM3 DEM remote sensing data and GIS techniques. The area of glacier lakes was delineated by visual interpretation, while for the inland lake by image classification. The change of glacier thickness was obtained by Glas/ICESat data of 2004 and 2008. Results show high variation in extent of glaciers and lakes with increased temperature and precipitation in the past 40 years. These variations include glacial retreat, increased water level of inland lakes and increased number of glacier lakes to higher altitudes. Glaciers lost 22% of its coverage from 1977 to 2010, and the annual shrinkage rate accelerated in the last decade compared with the previous time period of 1977-2001. In average, the thickness of the monitored glaciers reduced by 4.48 m from 2004 to 2008 with an annual rate of 1.12 m. From 1972 to 2009, the number of new formed glacier lakes increased by 150 and the area of glacier lakes increased by 173% (4.53 km2). At the same time, the surface area of the largest salt lake in Tibet expanded by 4.13% (80.18 km2). These variations appear to be associated with an increase in mean annual temperature of 0.05 °C per year, and an increase in annual precipitation of 1.83 mm per year in the last four decades. By analyzing the relationship between the decreased glacier area and the increased number and extent of lakes in the vertical zones over the past 40 years, there is a high correlation of 0.81. These results indicate that the climate change has great impacts on glaciers and glacier lakes on the central Tibetan Plateau. Further detailed investigations are

  16. Glacial areas, lake areas, and snowlines from 1975 to 2012: status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    NASA Astrophysics Data System (ADS)

    Hanshaw, M. N.; Bookhagen, B.

    2013-02-01

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975-2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 ± 1.70 km2 yr-1 (22-yr average, 1988-2010, with 95% confidence interval). The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 ± 0.18 km2 yr-1 since 1980 (31-yr average, 1980-2011, also with 95% confidence interval); Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2011) as compared to the preceding decade (1990-2000); Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61% of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84% of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 yr provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further studies

  17. Glacial areas, lakes areas, and snowlines from 1975-2012: Status of the Cordillera Vilcanota, including the Quelccaya Ice Cap, northern central Andes, Peru

    NASA Astrophysics Data System (ADS)

    Hanshaw, Maiana Natania

    Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 144 multi-spectral satellite images spanning almost four decades, from 1975-2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. In a second step, we have estimated the snowline altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: First, since 1988 glacial areas throughout the Cordillera Vilcanota have been declining at a rate of 5.46 +/- 1.70 km2/yr (22-year average, 1988-2010, with 95 % confidence interval). The Quelccaya Ica Cap, specifically, has been declining at a rate of 0.67 +/- 0.18 km2/yr since 1980 (31-year average, 1980-2011, also with 95 % confidence interval); Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000-2011) as compared to the preceding decade (1990-2000); Third, the snowline of the Quelccaya Ice Cap is retreating to higher elevations as glacial areas decrease, by a total of almost 300 m between its lowest recorded elevation in 1989 and its highest in 1998; and fourth, as glacial regions have decreased, 61 % of lakes connected to glacial watersheds have shown a roughly synchronous increase in lake area, while 84 % of lakes not connected to glacial watersheds have remained stable or have declined in area. Our new and detailed data on glacial and lake areas over 37 years provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further

  18. Late Glacial-Holocene Pollen-Based Vegetation History from Pass Lake, Prince of Wales Island, Southeastern Alaska

    USGS Publications Warehouse

    Ager, Thomas A.; Rosenbaum, Joseph G.

    2009-01-01

    A radiocarbon-dated history of vegetation development since late Wisconsin deglaciation has been reconstructed from pollen evidence preserved in a sediment core from Pass Lake on Prince of Wales Island, southeastern Alaska. The shallow lake is in the south-central part of the island and occupies a low pass that was filled by glacial ice of local origin during the late Wisconsin glaciation. The oldest pollen assemblages indicate that pine woodland (Pinus contorta) had developed in the area by ~13,715 cal yr B.P. An abrupt decline in the pine population, coinciding with expansion of alder (Alnus) and ferns (mostly Polypodiaceae) began ~12,875 yr B.P., and may have been a response to colder, drier climates during the Younger Dryas climatic interval. Mountain hemlock (Tsuga mertensiana) began to colonize central Prince of Wales Island by ~11,920 yr B.P. and was soon followed by Sitka spruce (Picea sitchensis). Pollen of western hemlock (Tsuga heterophylla) began to appear in Pass Lake sediments soon after 11,200 yr B.P. The abundance of western hemlock pollen in the Pass Lake core during most of the Holocene appears to be the result of wind transport from trees growing at lower altitudes on the island. The late Holocene pollen record from Pass Lake is incomplete because of one or more unconformities, but the available record suggests that a vegetation change occurred during the late Holocene. Increases in pollen percentages of pine, cedar (probably yellow cedar, Chamaecyparis nootkatensis), and heaths (Ericales) suggest an expansion of muskeg vegetation occurred in the area during the late Holocene. This vegetation change may be related to the onset of cooler, wetter climates that began as early as ~3,774 yr B.P. in the region. This vegetation history provides the first radiocarbon-dated Late Glacial-Holocene terrestrial paleoecological framework for Prince of Wales Island. An analysis of magnetic properties of core sediments from Pass Lake suggests that unconformities

  19. Mechanism of instantaneous coal outbursts

    SciTech Connect

    Guan, P.; Wang, H.Y.; Zhang, Y.X.

    2009-10-15

    Thousands of mine workers die every year from mining accidents, and instantaneous coal outbursts in underground coal mines are one of the major killers. Various models for these outbursts have been proposed, but the precise mechanism is still unknown. We hypothesize that the mechanism of coal outbursts is similar to magma fragmentation during explosive volcanic eruptions; i.e., it is caused by high gas pressure inside coal but low ambient pressure on it, breaking coal into pieces and releasing the high-pressure gas in a shock wave. Hence, coal outbursts may be regarded as another type of gas-driven eruption, in addition to explosive volcanic, lake, and possible ocean eruptions. We verify the hypothesis by experiments using a shock-tube apparatus. Knowing the mechanism of coal outbursts is the first step in developing prediction and mitigation measures. The new concept of gas-driven solid eruption is also important to a better understanding of salt-gas outbursts, rock-gas outbursts, and mud volcano eruptions.

  20. Glacial-interglacial continental temperature variability in the Beringian Arctic: the MBT/CBT record of Lake El'gygytgyn

    NASA Astrophysics Data System (ADS)

    Castaneda, I. S.; Finkelstein, D. B.; Phu, V.; Brigham-Grette, J.; Wilkie, K. M.; D'anjou, R. M.; Wei, J. H.; Urann, B. M.

    2012-12-01

    In 2009, deep drilling at El'gygytgyn Crater Lake (Far East Russian Arctic) recovered sediments covering the past 3.6 Ma. These sediments provide the first terrestrial Arctic paleoclimate record spanning the Pliocene-Pleistocene from the largest and oldest unglaciated Arctic lake basin. Lake El'gygytgyn sediments thus offer a unique opportunity to examine high-latitude climate variability beyond the 100 Ka interval captured by Greenland ice core records. In this study we utilize an organic geochemical paleothermometer, the MBT/CBT Index based on branched glycerol dialkyl glycerol tetraethers (GDGTs; Weijers et al., 2007), to examine continental temperature variability during several key time intervals of interest. In particular, we focus on Marine Isotope Stages (MIS) 1-6, MIS 9-11, MIS 31 and during the earliest formation of lacustrine sediments in the impact basin in the middle Pliocene. Previous work on Lake El'gygytgyn sediments has identified MIS 11c and MIS 31 as "super" interglacials, which were characterized by significantly warmer temperatures than at present largely based on pollen spectra and modern analog analysis (Melles et al., 2012). Our results show that relative changes in MBT/CBT-derived temperatures display similar overall patterns of glacial-interglacial climate variability noted in temperature reconstructions from Lake El'gygytgyn (Melles et al., 2012) as well as Greenland ice core records, North Atlantic sea surface temperature records (e.g. Lawrence et al., 2010), and the global benthic δ18O stack (Lisiecki and Raymo, 2005). We demonstrate that MBT/CBT is a sensitive proxy for recording temperature variability at Lake El'gygytgyn. Interestingly, while pronounced warming is noted during interglacials, a number of abrupt and short-lived temperature reversals are also observed within these intervals, such as during MIS 5a and MIS 5e. Overall, we find that MBT/CBT temperatures closely track changes in local summer insolation at 67°N, in

  1. Cold active hydrolytic enzymes production by psychrotrophic Bacilli isolated from three sub-glacial lakes of NW Indian Himalayas.

    PubMed

    Yadav, Ajar Nath; Sachan, Shashwati Ghosh; Verma, Priyanka; Kaushik, Rajeev; Saxena, Anil Kumar

    2016-03-01

    The diversity of culturable, cold-active enzymes producing Bacilli was investigated from three sub-glacial lakes of north western Indian Himalayas. Amplified ribosomal DNA restriction analysis (ARDRA) using three restriction enzymes Alu I, Msp I, and Hae III led to the clustering of 136 Bacilli into 26, 23, and 22 clusters at 75% similarity index from Chandratal Lake, Dashair Lake, and Pangong Lake, respectively. Phylogenetic analysis based on 16S rRNA gene sequencing led to the identification of 35 Bacilli that could be grouped in seven families viz.: Bacillaceae (48%), Staphylococcaceae (14%), Bacillales incertae sedis (13%), Planococcaceae (12%), Paenibacillaceae (9%), Sporolactobacillaceae (3%), and Carnobacteriaceae (1%), which included twelve different genera Bacillus, Desemzia, Exiguobacterium, Jeotgalicoccus, Lysinibacillus, Paenibacillus, Planococcus, Pontibacillus, Sinobaca, Sporosarcina, Staphylococcus, and Virgibacillus. Based on their optimal temperature for growth, 35 Bacilli were grouped as psychrophilic (11 strains), psychrotrophic (17 strains), or psychrotolerant (7 strains), respectively. The representative isolates from each cluster were screened for cold-active enzyme activities. Amylase, β-glucosidase, pectinase, and protease activities at 4 °C were detected in more than 80% of the strains while approximately 40, 31, 23, 14, 11, and 9% of strains possessed cellulase, xylanase, β-galactosidase, laccase, chitinase, and lipase activity, respectively. Among 35 Bacilli, Bacillus amyloliquefaciens, Bacillus marisflavi, Exiguobacterium indicum, Paenibacillus terrae, Pontibacillus sp., Sporosarcina globispora, and Sporosarcina psychrophila were efficient producers of different cold-active enzymes. These cold-adapted Bacilli could play an important role in industrial and agricultural processes. PMID:26933936

  2. Late-stage phases of glacial Lake Ojibway in the central Abitibi region, eastern Canada

    NASA Astrophysics Data System (ADS)

    Roy, Martin; Veillette, Jean J.; Daubois, Virginie; Ménard, Maxime

    2015-11-01

    The decay of the Laurentide ice sheet southern margin during the last deglaciation led to the development of Lake Ojibway that covered large expanses of northeastern Ontario and northwestern Quebec. The history of Ojibway lake phases is poorly detailed mainly because of the physical configuration of the lake basin and the dominance of fine-grained glaciolacustrine sediments that prevent the formation of well-developed and extensive sandy strandlines. Here we use a complex sequence of relict terraces carved in glaciolacustrine rhythmites to document the evolution of Lake Ojibway in northwestern Quebec. Specifically, lake levels were constrained by measuring the elevation of 154 raised wave-cut scarps present in the eastern Lake Abitibi region. Results provide evidence for four distinct shorelines with elevations of 299, 289, 282, and 272 m (± 1 m) at the latitude of La Sarre. The highest lake level documented appears to be linked to one of the two known (Kinojévis) phases of Lake Ojibway, while the three other lake levels project well below the main outlet system that controlled the elevation of the lake during the deglaciation. The elevation, uplift gradients, and areal extent of these lower shorelines suggest that the two intermediate lake levels likely formed during late stages of the deglaciation, following abrupt drawdowns of the lake's surface. The fourth and lowest shoreline is associated with a postglacial lake that developed after the complete withdrawal of Ojibway water from the region. These low-elevation shorelines bring new evidence for significant changes in the areal extent and depth of Lake Ojibway near the end of the deglaciation. Although the origin of these late-stage phases remains unspecified, the associated drawdowns likely implied routing events into newly deglaciated regions and/or (subglacial) meltwater discharges into the North Atlantic.

  3. Beryllium isotopes as tracers of Lake Lisan (last Glacial Dead Sea) hydrology and the Laschamp geomagnetic excursion

    NASA Astrophysics Data System (ADS)

    Belmaker, Reuven; Stein, Mordechai; Beer, Jürg; Christl, Marcus; Fink, David; Lazar, Boaz

    2014-08-01

    The content of the cosmogenic isotope 10Be (t1/2=1.39 Ma) in lacustrine sediments that deposit in lakes with a large watershed is susceptible to both climate and cosmogenic production rate variations. In order to distinguish between these two controls, we measured 10Be and major elements in several sections of the annually laminated sediments of the Lake Lisan (the last Glacial precursor of the Dead Sea) that are composed of detrital sediments and primary (evaporitic) aragonites. The sections were selected to represent regional hydrology and climate as reflected by different lake configurations (level rise, drop and high-stands) and rapid change in the 10Be production rate during the Laschamp geomagnetic excursion. Since the short-lived cosmogenic “sister” of 10Be, 7Be (t1/2=53.3 d) has virtually no recycled component, the recycled 10Be in Lake Lisan detrital sediments was evaluated by measuring 7Be in their modern equivalents: modern flood suspended matter, dust and mud cracks. Our results demonstrate that although the recycled 10Be component is significant, secular variations in the 10Be concentration in Lake Lisan sediments correlate with hydrological variations and geomagnetic excursions. During periods of moderate variations in 10Be production rate, the 10Be concentration in the Lisan detrital sediments positively correlates with lake level, Al + Fe content and the (Al + Fe)/(Ca + Mg) ratio. These correlations suggest that the 10Be is adsorbed on the fine silicate component (probably clays) of the detrital laminae. The fine silicates together with carbonates were transported to Dead Sea drainage basin mainly as airborne dust that after a short residence time was washed into Lake Lisan as flood suspended matter. We suggest that preferential dissolution of carbonates in the flood suspended matter concentrated the residual fine component leading to the positive correlation between 10Be and the (Al + Fe)/(Ca + Mg) ratio. During periods of increased water

  4. Preliminary Vertical Slip Rate for the West Tahoe Fault from six new Cosmogenic 10Be Exposure Ages of Late Pleistocene Glacial Moraines at Cascade Lake, Lake Tahoe, California

    NASA Astrophysics Data System (ADS)

    Pierce, I. K. D.; Wesnousky, S. G.; Kent, G. M.; Owen, L. A.

    2015-12-01

    The West Tahoe Fault is the primary range bounding fault of the Sierra Nevada at the latitude of Lake Tahoe. It is a N-NW striking, east dipping normal fault that has a pronounced onshore quaternary scarp extending from highway 50 southwest of Meyers, CA to Emerald Bay. At Cascade Lake, the fault cuts and progressively offsets late Pleistocene right lateral moraines. The fault vertically offsets the previously mapped Tahoe moraine ~83 m and the Tioga moraine ~23 m, measured from lidar data. Seventeen samples were collected for 10Be cosmogenic age analysis from boulders on both the hanging and footwalls of the fault along the crests of these moraines.We report here the initial analysis of 6 of these boulders and currently await processing of the remainder. The 10Be exposure ages of 3 boulders each on the younger Tioga and older Tahoe moraines range from 12.7 +/- 1.6 to 20.7 +/- 3.3 ka and 13.3 +/- 2.1 to 72.5 +/- 8.8 ka, respectively. Using the oldest ages as minima, these preliminary results suggest that the slip rate has averaged ~1 mm/yr since the penultimate glaciation, in accord with estimates of previous workers, and place additional bounds on the age of glaciation in the Lake Tahoe basin. The Last Glacial Maxima and penultimate glaciation near Lake Tahoe thus appear to coincide with the Tioga and Tahoe II glaciations of the Eastern Sierra.

  5. Late Glacial and Holocene environmental history of Wielkopolska region (western Poland) recorded in sediments of Strzeszyńskie Lake and Kierskie Lake

    NASA Astrophysics Data System (ADS)

    Pleskot, Krzysztof; Szczuciński, Witold; Tjallingii, Rik; Makohonienko, Mirosław; Nowaczyk, Norbert; Brauer, Achim

    2016-04-01

    The growing amount of publications concerning reconstructions of Late Glacial and Holocene environment based on analysis of lake sediments gives us robust insight into general patterns of that record. However, it is still challenging to decipher processes and events that occurred on local scale, as they record may be strongly affected by the type, catchment, size and depth of a lake. Therefore in the present study we focus on application of sedimentological and geochemical methods in order to reveal environmental history from two neighbouring lakes located within city of Poznań, Wielkopolska (western Poland). The lake sediments analysis cover Late Glacial and Holocene in case of smaller Strzeszyńskie Lake (SL) and the last 8 ka in deeper Kierskie Lake (KL). The study is based on two 8.5 (SL) and 14 (KL) m long sediment cores, which were described and analyzed in thin sections and on smear slides. The relative chemical composition variations within the cores were measured using an X-ray fluorescence (XRF). Moreover, the cores were measured for magnetic susceptibility and sampled for pollen analysis. The chronology has been established by a AMS 14C dating of bulk samples of lake sediments. To assess the reservoir effect, selected samples were analyzed for soluble and residual carbon fractions. Our results suggest the onset of authigenic sedimentation in SL in Allerød. The sediments from this period are characterized by high organic matter and low carbonate content. This trend changed into opposite at the beginning of the Younger Dryas, while at its termination sediments again became more organic. The transition to Holocene is marked by spread of Betula forest, gradual increase in magnetic susceptibility and Ca content together with decreasing organic matter and clastic input. During Preboreal and Boreal period the relatively stable conditions was noted. Then, ca. 8.5 ka BP, sharp decrease in magnetic susceptibility occurred coincided with deciduous forest

  6. Endogenic carbonate sedimentation in Bear Lake, Utah and Idaho, over the last two glacial-interglacial cycles

    USGS Publications Warehouse

    Dean, W.E.

    2009-01-01

    that is at least 50 yr old, and probably older. Apparently, the microbialite mound also stopped forming aragonite cement sometime after Bear River diversion. Because of reworking of old aragonite, the bulk mineralogy of carbonate in bottom sediments has not changed very much since the diversion. However, the diversion is marked by very distinct changes in the chemical and isotopic composition of the bulk carbonate. After the last glacial interval (LGI), a large amount of endogenic carbonate began to precipitate in Bear Lake when the Pacific moisture that filled the large pluvial lakes of the Great Basin during the LGI diminished, and Bear River apparently abandoned Bear Lake. At first, the carbonate that formed was low-Mg calcite, but ???11,000 years ago, salinity and Mg2+:Ca2+ thresholds must have been crossed because the amount of aragonite gradually increased. Aragonite is the dominant carbonate mineral that has accumulated in the lake for the past 7000 years, with the addition of high-Mg calcite after the diversion of Bear River into the lake at the beginning of the twentieth century. Copyright ?? 2009 The Geological Society of America.

  7. Hydrogeology of glacial-terrain lakes, with management and planning applications

    USGS Publications Warehouse

    Born, S.M.; Smith, S.A.; Stephenson, D.A.

    1979-01-01

    The subject of the relationship between groundwater and lakes is characterized by sparse information and, in general, has received limited attention by hydrologists. Nevertheless, the hydrogeologic regime of lakes must be adequately assessed in order to intelligently manage lakes and their related shorelands. This paper is a compilation of hydrogeologic data for numerous lakes in North America and presents a preliminary classification framework for lakes based on hydrogeologic considerations. The classification leads to systematic categorization of lake types for planning and management purposes. The main hydrogeologic factors for assessing lake environments are: (1) regime dominance, the relative magnitude of groundwater in the total water budget of a lake; (2) system efficiency, a description of the rate aspects of surface and groundwater movement through a lake system; and (3) position within a groundwater flow system. We indicate the significance and difficulty of measuring these descriptive characteristics and provide examples of each category. Additionally, a variety of lake-related activities that illustrate the value of hydrogeologic information for planning and management purposes are presented. ?? 1979.

  8. Seasonal Daphnia biomass in winterkill and nonwinterkill glacial lakes of South Dakota

    USGS Publications Warehouse

    Isermann, D.A.; Chipps, S.R.; Brown, M.L.

    2004-01-01

    We compared the seasonal biomass (??g dry weight/L) and body size of Daphnia pulex populations between South Dakota lakes that experienced nearly complete winterkill (n = 2) and those that did not experience fish winterkill the previous winter (n = 2). In spring (March-May), D. pulex biomass was substantially lower in winterkill lakes (0.4-1.9 ??g/L) than in nonwinterkill lakes (13.8-129.4 ??g/L). In summer months (June-July), D. pulex biomass increased in all lakes but was generally higher in winterkill lakes (332.1-469. 3 ??g/L) than in nonwinterkill lakes (88.6-204.2 ??g/L). By September, D. pulex biomass was substantially higher in winterkill lakes (243.8 ??g/L) than in nonwinterkill lakes (1.0 ??g/L). The mean size of D. pulex increased significantly from March to August in winterkill lakes but not in nonwinterkill lakes. The seasonal differences in D. pulex biomass and size may have been related to size-selective predation by planktivorous fishes because the ratio of spine length to body length in D. pulex was significantly lower in winterkill lakes (mean, 0.34) than in nonwinterkill lakes (mean, 0.43). Moreover, seasonal patterns in chlorophyll-a biomass were inversely related to D. pulex biomass. The production and subsequent hatching of resting eggs may be important for recolonization of Daphnia populations after severe winter conditions. The survival and growth of zooplanktivorous fish that are stocked to repopulate winterkill lakes may be increased by delaying stocking until Daphnia populations recover from severe winterkill.

  9. Impacts of climate and humans on the vegetation in NW Turkey: palynological insights from Lake Iznik since the Last Glacial

    NASA Astrophysics Data System (ADS)

    Miebach, A.; Niestrath, P.; Roeser, P.; Litt, T.

    2015-11-01

    The Marmara region in northwestern Turkey provides a unique opportunity for studying the vegetation history in response to climate changes and anthropogenic impacts because of its location between different climate and vegetation zones and its long settlement history. Geochemical and mineralogical investigations of the largest lake in the region, Lake Iznik, already registered climate related changes of the lake level and the lake mixing. However, a palynological investigation encompassing the Late Pleistocene to Middle Holocene was still missing. Here, we present the first pollen record of the last ca. 31 ka cal BP (calibrated kilo years before 1950) inferred from Lake Iznik sediments as an independent proxy for paleoecological reconstructions. Our study reveals that the vegetation in the Iznik area changed generally between steppe during glacial/stadial conditions, forest-steppe during interstadial conditions, and oak dominated mesic forest during interglacial conditions. Moreover, a pronounced succession of pioneer trees, cold temperate, warm temperate, and Mediterranean trees appeared since the Lateglacial. Rapid climate changes, which are reflected by vegetation changes, can be correlated with Dansgaard-Oeschger (DO) events such as DO-4, DO-3, and DO-1, the Younger Dryas, and probably also the 8.2 event. Since the mid-Holocene, the vegetation was influenced by anthropogenic activities. During early settlement phases, the distinction between climate-induced and human-induced changes of the vegetation is challenging. Still, evidence for human activities consolidates since the Early Bronze Age (ca. 4.8 ka cal BP): cultivated trees, crops, and secondary human indicator taxa appeared, and forests got cleared. Subsequent fluctuations between extensive agricultural use and regeneration of the natural vegetation become apparent.

  10. Impacts of climate and humans on the vegetation in northwestern Turkey: palynological insights from Lake Iznik since the Last Glacial

    NASA Astrophysics Data System (ADS)

    Miebach, Andrea; Niestrath, Phoebe; Roeser, Patricia; Litt, Thomas

    2016-03-01

    The Marmara region in northwestern Turkey provides a unique opportunity for studying the vegetation history in response to climate changes and anthropogenic impacts because of its location between different climate and vegetation zones and its long settlement history. Geochemical and mineralogical investigations of the largest lake in the region, Lake Iznik, already registered climate-related changes of the lake level and the lake mixing. However, a palynological investigation encompassing the Late Pleistocene to Middle Holocene was still missing. Here, we present the first pollen record of the last ca. 31 ka cal BP (calibrated kilo years before 1950) inferred from Lake Iznik sediments as an independent proxy for paleoecological reconstructions. Our study reveals that the vegetation in the Iznik area changed generally between (a) steppe during glacials and stadials indicating dry and cold climatic conditions, (b) forest-steppe during interstadials indicating milder and moister climatic conditions, and (c) oak-dominated mesic forest during interglacials indicating warm and moist climatic conditions. Moreover, a pronounced succession of pioneer trees, cold temperate, warm temperate, and Mediterranean trees appeared since the Lateglacial. Rapid climate changes, which are reflected by vegetation changes, can be correlated with Dansgaard-Oeschger (DO) events such as DO-4, DO-3, and DO-1, the Younger Dryas, and probably also the 8.2 event. Since the mid-Holocene, the vegetation was influenced by anthropogenic activities. During early settlement phases, the distinction between climate-induced and human-induced changes of the vegetation is challenging. Still, evidence for human activities consolidates since the Early Bronze Age (ca. 4.8 ka cal BP): cultivated trees, crops, and secondary human indicator taxa appeared, and forests were cleared. Subsequent fluctuations between extensive agricultural uses and regenerations of the natural vegetation become apparent.

  11. Late-Glacial to early Holocene basin development of annually laminated Lake Tiefer See

    NASA Astrophysics Data System (ADS)

    Theuerkauf, Martin; Lorenz, Sebastian; Schult, Manuela; Lampe, Reinhard; Dräger, Nadine; Wulf, Sabine; Brauer, Achim

    2014-05-01

    Lake Tiefer See (N 53.59°, E 12.53°) is one of the rare lakes with a long sequence of annually laminated Holocene sediments in northern Central Europe. The lake is thus of great potential for past climate, vegetation and human land use studies. It furthermore provides a valuable link between laminated lakes in more oceanic climates of the Eifel region and NW Germany and laminated lakes in the more continental climate of Poland. The sediments of Lake Tiefer See are not uniform but show repeated changes in varve composition and include several non-varved sequences. Interpreting these changes requires a sound understanding of the deposition processes in the lake and the development of the lake basin itself. While modern sediment deposition is studied in an extensive monitoring program, we explore lake basin development using numerous cores from the lake margins down to the bottom of the lake. The lake is exceptionally deep (62 m) with steep slopes and may thus be susceptible to sediment re-deposition and focusing. Most marginal cores, which reach down to 10 m water depth, show a prominent basal peat layer. This peat layer indicates that basin development started by paludification of an originally flat surface following dead-ice melting. However, even in neighboring cores the timing of the onset of peat formation appears to differ substantially. While in some cores, the prominent Laacher See Tephra (12.880 cal. BP) is found at the bottom of the peat layer, it is found well above the peat basis in other cores. Dead-ice melting may thus initially have produced a pattern of shallow depressions with ongoing peat formation within a still terrestrial surface. The formation of the deep lake is than indicated by an abrupt shift to calcareous gyttjas, which show an initially increased silicate content. The lake obviously only developed long after first peat deposition, possibly in the early Holocene. Further dates to verify this hypothesis are expected. In several marginal

  12. Ecosystem responses during Late Glacial period recorded in the sediments of Lake Łukie (East Poland)

    NASA Astrophysics Data System (ADS)

    Zawiska, Izabela; Słowiński, Michał; Correa-Metrio, Alex; Obremska, Milena; Luoto, Tomi; Nevalainen, Liisa; Woszczyk, Michał; Milecka, Krystyna

    2014-05-01

    The main objectives of this study was to reconstruct climate impact on the functioning of Lake Łukie and its catchment (Łęczna Włodawa Lake District, East European Plain) during Late Glacial period. In order to reconstruct climatic fluctuations and corresponding ecosystem responses, we analysed lake sediments for pollen, subfossil Cladocera, plant macrofossils and chemical composition of the sediment. Of these, plant macrofossils and Cladocera were used to infer minimum and mean July temperatures and ordination analysis was used to examine biotic community shifts. Multiproxy analyses of late-glacial sediments of Lake Łukie clearly show that the main driver of aquatic and terrestrial ecosystems as well as geomorphological processes in the catchment was climate variation. The history of the lake initiated during the Older Dryas. In that period, Łęczna Włodawa Lake District was covered by open habitats dominated by grasses (Poaceae), humid sites were occupied by tundra plant communities with less clubmoss (Selaginella selaginoides), dry sites by dominated by steppe-like vegetation with light-demanding species such as Helianthemum, Artemisia, Chenopodiaceae, and juniper bushes (Juniperus). Cold climate limited the growth and development of organisms in the lake, Cladocera community species composition was poor, with only few species present there all the time. During this time period, permafrost was still present in the ground limiting infiltration of rainwater and causing high erosion in the catchment area. Surface runoff is confirmed by the presence of sclerotia of Cenococcum geophilum and high terrigenous silica content. The warming of the early Allerød caused a remarkable change in the natural environment of this area. This is in accordance with the temperature rise reconstructed with the use of plant macrofossils though the Cladocera reconstruction did not recorded the rise than. This temperature increase resulted in turnover of vegetation in the

  13. Active Neotectonic Structures in Glacial and Postglacial Sediment in Lake Timiskaming, Timiskaming Graben, Ontario/Quebec Canada

    NASA Astrophysics Data System (ADS)

    Doughty, M.; Eyles, N.; Eyles, C.

    2009-05-01

    The Timiskaming Graben (TG) is a northwest-trending arm of the Ottawa-Bonnechere Graben and the St. Lawrence Rift System (SLRS) in eastern Canada. Together they form a 600 km long failed rift in the Canadian Shield, extending southward along the border of Ontario and Quebec to the St.Lawrence River Valley onto the Hudson Valley and Lake Champlain in the USA. The Timiskaming Graben preserves faulted outliers of Early Paleozoic limestones and has been reactivated several time during the Phanerozoic most recently during the breakup of Pangea. The 110 kilometre-long, ~100 m deep Lake Timiskaming fills the inner part of the Timiskaming Graben along the border of Ontario and Quebec. It is the postglacial successor to glacial Lake Barlow ponded against the northward-retreating Laurentide Ice Sheet some 9,000 years BP. The sedimentary record of Lake Timiskaming was established by collecting more than 1000 line kilometres of high-resolution 'chirp' seismic profiles, side scan and multibeam survey data between 2003 and 2007. These show that bathymetric relief is the product of ongoing tectonic subsidence where lateglacial Barlow glaciolacustrine and postglacial sediments are extensively deformed by closely-spaced horst and grabens. The greatest subsidence has occurred within a narrow (< 3 km) and deep (up to 209 m) central graben basin. We are able to infer the presence of hitherto unrecognized bounding and relay faults within the graben, and a 20 km long 8 m high fault scarp and sand blows produced by large postglacial earthquakes. The region is one of the most seismically active areas in eastern North America (Western Quebec Seismic Zone) with frequent moderate to large magnitude (> M5) intracratonic earthquakes. Structural activity is ongoing along the Timiskaming Graben and its lateglacial and postglacial sediment record provides the clearest evidence to date of modern intracratonic faulting anywhere in eastern North America.

  14. Numerical simulation of ground-water flow through glacial deposits and crystalline bedrock in the Mirror Lake area, Grafton County, New Hampshire

    SciTech Connect

    Tiedeman, C.R.; Goode, D.J.; Hsieh, P.A.

    1997-12-31

    This report documents the development of a computer model to simulate steady-state (long-term average) flow of ground water in the vicinity of Mirror Lake, which lies at the eastern end of the Hubbard Brook valley in central New Hampshire. The 10-km{sup 2} study area includes Mirror Lake, the three streams that flow into Mirror Lake, Leeman`s Brook, Paradise Brook, and parts of Hubbard Brook and the Pemigewasset River. The topography of the area is characterized by steep hillsides and relatively flat valleys. Major hydrogeologic units include glacial deposits, composed of till containing pockets of sand and gravel, and fractured crystal-line bedrock, composed of schist intruded by granite, pegmatite, and lamprophyre. Ground water occurs in both the glacial deposits and bedrock. Precipitation and snowmelt infiltrate to the water table on the hillsides, flow downslope through the saturated glacial deposits and fractured bedrock, and discharge to streams and to Mirror Lake. The model domain includes the glacial deposits, the uppermost 150 m of bedrock, Mirror Lake, the layer of organic sediments on the lake bottom, and streams and rivers within the study area. A streamflow routing package was included in the model to simulate baseflow in streams and interaction between streams and ground water. Recharge from precipitation is assumed to be areally uniform, and riparian evapotranspiration along stream banks is assumed negligible. The spatial distribution of hydraulic conductivity is represented by dividing the model domain into several zones, each having uniform hydraulic properties. Local variations in recharge and hydraulic conductivities are ignored; therefore, the simulation results characterize the general ground-water system, not local details of groundwater movement. 47 refs., 25 figs., 10 tabs.

  15. A ~13,000 year history of glacial variability in the tropical Andes recorded in lake sediments from the Peruvian Andes

    NASA Astrophysics Data System (ADS)

    Stansell, N. D.; Rodbell, D. T.; Mark, B. G.; Sedlak, C. M.

    2012-04-01

    Pro-glacial lake sediments from Peru contain continuous records of climatic variability spanning the Holocene. Here we present results from multiple alpine lake basins along an east-west transect through the Peruvian Andes that contain high-resolution records of clastic sediment variability for the last ~13,000 years. Radiocarbon-dated sediment cores were measured by scanning X-ray Fluorescence, and for magnetic susceptibility, carbon content, biogenic silica and calcium carbonate concentrations. Samples of bedrock and sediments from glacial moraines in the watersheds were analyzed using ICP-MS in order to fingerprint and trace the source of glacial sediments deposited in the lakes. Preliminary results indicate that glaciers retreated after after ~13,000 cal yr BP and remained less extensive during the remaining late Glacial Stage and early Holocene. Gradually increasing clastic sediments through most of the remaining Holocene indicate that glaciers became progressively larger, or more erosive, during the last ~10,000 years. This overall Holocene trend of increasing glacier extent was interrupted by a pronounced decrease in clastic sediments from ~2500 to 550 cal yr BP, and glaciers then advanced again during the Little Ice Age (~550 to 70 cal yr BP). Periods of ice advance in the Peruvian Andes generally correspond to times of increased moisture-balance and lower temperatures that are recorded in other regional, terrestrial proxy records.

  16. Late-Glacial to Holocene Hydroclimatic Change in the Mojave Desert: Silver Lake, CA

    NASA Astrophysics Data System (ADS)

    Kirby, M. E.; Knell, E. J.; Anderson, W. T., Jr.; Lachniet, M. S.; Eeg, H.; Lucero, R.; Murrieta, R.; Arevalo, A.; Silveira, E.; Hiner, C.; Palermo, J. A.

    2014-12-01

    Silver Lake is the modern terminal playa of the Mojave River. As a result, it is well located to record both influences from the winter precipitation dominated San Bernardino Mountains - the source of the Mojave River - as well as the late-summer to early-fall North American monsoon. Here, we present various physical and geochemical data from a new 8.2 m sediment core taken from Silver Lake, CA that spans modern through 14.8 kcal yrs BP. Age control is based on six bulk organic C radiocarbon dates processed with Bacon v2.2 to generate an age model. Texturally, the core varies between a silty clay and a silty sand, often with abrupt sedimentological transitions. Our working hypothesis states that high percent clay values indicate persistent standing water wherein the deposition, accumulation, and preservation of fine grain sediment exceeds some undefined thickness that inhibits deflation during succeeding desiccation events or ephemeral lake environments. Based on this clay - lake status hypothesis, the sediment core is divided into five lake status intervals. Clay values are highest between 14.4 - 13.5 kcal yrs BP, coeval to Lake Mojave II. Clay values decrease abruptly at 13.5 kcal yrs BP (encapsulating the Younger Dryas) indicating a return to an ephemeral lake. At 11.3 kcal yrs BP, clay values rise abruptly indicating a return to a perennial lake; this early Holocene pluvial ended abruptly at 7.8 kcal yrs BP. From 7.8 - 4.2 kcal yrs BP, clay is low, but variable and mudcracks are common. At 4.2 kcal yrs BP, clay values increase but only moderately indicating a return to more frequent sustained perennial lakes. The early Holocene pluvial is likely a result of higher summer insolation, which generated a more intense and spatially expansive North American monsoon. Coupled with lower winter insolation and thus more winter storms across the region, Silver Lake flourished. A comparison to stable carbon isotope data from Leviathan Cave (NV), support our interpretation

  17. Recent increases in the large glacial-relict calanoid Limnocalanus macrurus in Lake Michigan

    USGS Publications Warehouse

    Barbiero, R.P.; Bunnell, D.B.; Rockwell, D.C.; Tuchman, M.L.

    2009-01-01

    Since 2004, population density of the large hypolimnetic calanoid Limnocalanus macrurus Sars. has increased dramatically in Lake Michigan. The average summer biomass of this species between 2004 and 2006 was roughly three times that of the period 1984–2003, and at levels unprecedented in our 22-year dataset, making L. macrurus the dominant zooplankter in the lake in terms of biomass. These increases have been accentuated by coincident population declines of the main daphnid, Daphnia mendotae, in the lake with the result that in 2006, L. macrurus accounted for 75% and 50% of the large (> 0.9 mm) crustacean biomass in the northern and southern basins of Lake Michigan, respectively. The increases in L. macrurus populations have closely coincided with equally dramatic increases in summer water clarity. Recent extinction coefficients are among the lowest recorded for the lake, and deepening light penetration has permitted increases in the size of the deep chlorophyll layer. In addition, planktivorous fish populations have declined coincidently with the increases in L. macrurus. It seems likely that an increase in sub-epilimnetic production has resulted in increased food resources for the deep-living L. macrurus, while low planktivore abundances have reduced predation loss, permitting L. macrurus to respond to these increases in sub-epilimnetic production.

  18. Quantifying Groundwater Nutrient Discharge to a Large Glacial Lake using a Watershed Loading Model

    NASA Astrophysics Data System (ADS)

    Schilling, K. E.

    2015-12-01

    Groundwater discharge to a lake is an important, if often neglected, component to water and nutrient budgets. Point measurements of groundwater discharge into a lake are prone to error, so in this study of 15.57 km2 West Lake Okoboji, Iowa, a watershed-based groundwater loading model was developed. Located in northwest Iowa, West Lake Okoboji is considered one of Iowa's premier tourist destinations but is threatened by eutrophication. A network of 21 observation wells was installed in the watershed to evaluate groundwater recharge and quality under representative land cover types in a range of landscape positions. Our objective was to develop typical groundwater responses from various land cover-landscape associations for scaling up to unmonitored areas in the watershed. Results indicated substantial variation in groundwater recharge and quality in the 3847 ha watershed. Recharge was similar among land covers under vegetation but was much lower under urban pavement. Nitrate-nitrogen concentrations were highest under cropped fields and lowest under perennial grassland and golf courses, whereas dissolved phosphorus was highest under residential and urban areas, including an engineered bioswale. A groundwater load allocation model indicated 91% of the nitrate load was from cropped areas and 7% from residential areas. In contrast, P loads were more equally divided among cropped fields (43%), perennial grass (36%) and residential (19%) areas. Based on the mass of nitrate and P in the lake, groundwater accounts for 71% and 18% of the nutrient inputs, respectively.

  19. The glacial sedimentology and geomorphological evolution of an outwash head/moraine-dammed lake, South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Evans, David J. A.; Rother, Henrik; Hyatt, Olivia M.; Shulmeister, James

    2013-02-01

    Extensive exposures through the glacial landforms around southern Lake Pukaki, New Zealand, comprise seven lithofacies (LFs 1-7). LFs 1-3 are grouped together as LFA 1 (Pukaki Member) and record pulsed subaqueous grounding line fan progradation, cohesionless debris flows, underflow activity and rhythmite deposition by suspension settling, iceberg rafting of dropstones, and pulsed traction current activity. Localized disturbance of these deposits by glacitectonic deformation and multi-generational hydrofracture fills records minor readvances by the glacier snout and the emplacement of a glacitectonite (LF 4) derived from cannibalization of glacilacustrine sediments. LFs 4-6 are grouped together as LFA 2 (Twizel Member) and record direct glacigenic deposition of glacitectonite (LF 4), subglacial traction till (LF 5) and supraglacially dumped boulder rubble (LF 6). Stratigraphic relationships between LFA 1 with LFA 2 record the oscillatory behaviour of the former Tasman Glacier snout when it formed a calving margin in a proglacial and locally supraglacial lake dammed by a glacitectonically disturbed outwash head and lateral moraine ridges. This is entirely consistent with the landform-sediment record of its coeval terrestrial margins, where flutings and push moraines are diagnostic of active temperate glacier recession from a glacially overridden outwash head, the latter being recorded by the vertically stacked sub-horizontally bedded and coarse-grained gravels of LF 7 (Waitaki Member). Previous proposals that late Pleistocene lake damming was initiated by an ice-cored moraine arc appear unfounded, because the glacilacustrine deposits only lie above the altitude of the outwash head/lateral moraine arc in locations where they have been glacitectonically compressed. Alternatively, it is proposed that the overdeepened subglacial topography was produced by the construction of an outwash head, leading to a glacilacustrine sediment sink which operates at times when the

  20. A high resolution Late Glacial to Holocene record of climatic and environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

    NASA Astrophysics Data System (ADS)

    Lacey, Jack; Francke, Alexander; Leng, Melanie; Vane, Chris; Wagner, Bernd

    2015-04-01

    Lake Ohrid (Macedonia/Albania) is one of the world's oldest lakes and is renowned for its high degree of biological diversity. It is the target site for the ICDP SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) project, an international research initiative to study the links between geology, environment and the evolution of endemic taxa. In 2011 a 10-meter core was recovered from the western shore of Lake Ohrid adjacent to the Lini Peninsula. Here we present high-resolution stable isotope and geochemical data from this core through the Late Glacial to Holocene to reconstruct past climate and hydrology (TIC, δ18Ocalcite, δ13Ccalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock-Eval pyrolysis). The data identify 3 main zones: (1) the Late Glacial-Holocene transition represented by low TIC, TOC and higher isotope values, (2) the early to mid-Holocene characterised by higher TOC, TOC/N and lower δ18Ocalcite, and (3) the late Holocene which shows a marked decrease in TIC and TOC. In general there is an overall trend of increasing δ18Ocalcite from 9 ka to present, suggesting progressive aridification through the Holocene, which is consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the SCOPSCO project cores recovered in spring-summer 2013 dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history.

  1. A high-resolution Late Glacial to Holocene record of environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

    NASA Astrophysics Data System (ADS)

    Lacey, Jack H.; Francke, Alexander; Leng, Melanie J.; Vane, Christopher H.; Wagner, Bernd

    2015-09-01

    Lake Ohrid (Macedonia/Albania) is the oldest extant lake in Europe and exhibits an outstanding degree of endemic biodiversity. Here, we provide new high-resolution stable isotope and geochemical data from a 10 m core (Co1262) through the Late Glacial to Holocene and discuss past climate and lake hydrology (TIC, δ13Ccalcite, δ18Ocalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock Eval pyrolysis). The data identifies 3 main zones: (1) the Late Glacial-Holocene transition represented by low TIC and TOC contents, (2) the early to mid-Holocene characterised by high TOC and increasing TOC/N and (3) the Late Holocene-Present which shows a marked decrease in TIC and TOC. In general, an overall trend of increasing δ18Ocalcite from 9 ka to present suggests progressive aridification through the Holocene, consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of past Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the International Continental scientific Drilling Program Scientific Collaboration On Past Speciation Conditions in Lake Ohrid project cores recovered in spring-summer 2013, potentially dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history.

  2. Late-glacial and Holocene record of vegetation and climate from Cynthia Bay, Lake St Clair, Tasmania

    NASA Astrophysics Data System (ADS)

    Hopf, F. V. L.; Colhoun, E. A.; Barton, C. E.

    2000-10-01

    A Late-glacial-Holocene pollen record was obtained from a 3.96 m sediment core taken from Lake St Clair, central Tasmania. Modern vegetation and pollen analyses formed the basis for interpretation of the vegetation and climate history. Following deglaciation and before ca. 18450 yr BP Podocarpus lawrencei coniferous heath and Astelia-Plantago wet alpine herbfield became established at Lake St Clair. A distinct Poaceae-Plantago peak occurs between 18450 and 11210 yr BP and a mean annual temperature depression from ca. 6.2°C to 3°C below present is inferred for this period. The marked reduction in Podocarpus and strong increase of Poaceae suggests reduced precipitation levels during the period of widespread deglaciation (ca. 18.5-11 kyr BP). The local Late Pleistocene-Holocene non-forest to forest biostratigraphical boundary is dated at 11.2 kyr BP. It is characterised by expansion of the subalpine taxa Athrotaxis/Diselma with Nothofagus gunnii, and by the establishment of Nothofagus cunninghamii with Eucalyptus spp. A Phyllocladus bulge prior to the expansion of Nothofagus cunninghamii, reported at other Tasmanian sites, is not present at Lake St Clair. Nothofagus cunninghamii cool temperate rainforest peaked at 7800 yr BP, probably under wetter climatic conditions than present. The maximum development of rainforest in the early-middle Holocene may indicate that the temperature was slightly warmer than present, but the evidence is not definitive. The expansion of Eucalyptus spp. and Poaceae after 6000 yr BP may be partly a disclimax effect as a result of Aboriginal burning, but appears also to reflect reduced precipitation. The changes in vegetation and inferred climate can be explained by major changes in synoptic patterns of southern Australia and the adjacent southwest Pacific.

  3. Quantitative Temperature Reconstructions from Holocene and Late Glacial Lake Sediments in the Tropical Andes using Chironomidae (non-biting midges)

    NASA Astrophysics Data System (ADS)

    Matthews-Bird, F.; Gosling, W. D.; Brooks, S. J.; Montoya, E.; Coe, A. L.

    2014-12-01

    Chironomidae (non-biting midges) is a family of two-winged aquatic insects of the order Diptera. They are globally distributed and one of the most diverse families within aquatic ecosystems. The insects are stenotopic, and the rapid turnover of species and their ability to colonise quickly favourable habitats means chironomids are extremely sensitive to environmental change, notably temperature. Through the development of quantitative temperature inference models chironomids have become important palaeoecological tools. Proxies capable of generating independent estimates of past climate are crucial to disentangling climate signals and ecosystem response in the palaeoecological record. This project has developed the first modern environmental calibration data set in order to use chironomids from the Tropical Andes as quantitative climate proxies. Using surface sediments from c. 60 lakes from Bolivia, Peru and Ecuador we have developed an inference model capable of reconstructing temperatures, with a prediction error of 1-2°C, from fossil assemblages. Here we present the first Lateglacial and Holocene chironomid-inferred temperature reconstructions from two sites in the tropical Andes. The first record, from a high elevation (4153 m asl) lake in the Bolivian Andes, shows persistently cool temperatures for the past 15 kyr, punctuated by warm episodes in the early Holocene (9-10 kyr BP). The chironomid-inferred Holocene temperature trends from a lake sediment record on the eastern Andean flank of Ecuador (1248 m asl) spanning the last 5 millennia are synchronous with temperature changes in the NGRIP ice core record. The temperature estimates suggest along the eastern flank of the Andes, at lower latitudes (~1°S), climate closely resemble the well-established fluctuations of the Northern Hemisphere for this time period. Late-glacial climate fluctuations across South America are still disputed with some palaeoecological records suggesting evidence for Younger Dryas

  4. Climatic oscillations in central Italy during the Last Glacial-Holocene transition: the record from Lake Accesa

    NASA Astrophysics Data System (ADS)

    Magny, Michel; de Beaulieu, Jacques-Louis; Drescher-Schneider, Ruth; Vannière, Boris; Walter-Simonnet, Anne-Véronique; Millet, Laurent; Bossuet, Gilles; Peyron, Odile

    2006-05-01

    This paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake-level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial-early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north-central Italy). On the basis of an age-depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas-Bølling warming event was dated to ca. 14 560 cal. yr BP and the Younger Dryas event to ca. 12 700-11 650 cal. yr BP. Four sub-millennial scale cooling phases were recognised from pollen data at ca. 14 300-14 200, 13 900-13 700, 13 400-13 100 and 11 350-11 150 cal.yrBP. The last three may be Mediterranean equivalents to the Older Dryas (GI-1d), Intra-Allerød (GI-1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice-core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra-Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake-level record shows that the sub-millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2ka cold reversal. Copyright

  5. Assessing the variability of glacier lake bathymetries and potential peak discharge based on large-scale measurements in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Cochachin, Alejo; Huggel, Christian; Salazar, Cesar; Haeberli, Wilfried; Frey, Holger

    2015-04-01

    Over timescales of hundreds to thousands of years ice masses in mountains produced erosion in bedrock and subglacial sediment, including the formation of overdeepenings and large moraine dams that now serve as basins for glacial lakes. Satellite based studies found a total of 8355 glacial lakes in Peru, whereof 830 lakes were observed in the Cordillera Blanca. Some of them have caused major disasters due to glacial lake outburst floods in the past decades. On the other hand, in view of shrinking glaciers, changing water resources, and formation of new lakes, glacial lakes could have a function as water reservoirs in the future. Here we present unprecedented bathymetric studies of 124 glacial lakes in the Cordillera Blanca, Huallanca, Huayhuash and Raura in the regions of Ancash, Huanuco and Lima. Measurements were carried out using a boat equipped with GPS, a total station and an echo sounder to measure the depth of the lakes. Autocad Civil 3D Land and ArcGIS were used to process the data and generate digital topographies of the lake bathymetries, and analyze parameters such as lake area, length and width, and depth and volume. Based on that, we calculated empirical equations for mean depth as related to (1) area, (2) maximum length, and (3) maximum width. We then applied these three equations to all 830 glacial lakes of the Cordillera Blanca to estimate their volumes. Eventually we used three relations from the literature to assess the peak discharge of potential lake outburst floods, based on lake volumes, resulting in 3 x 3 peak discharge estimates. In terms of lake topography and geomorphology results indicate that the maximum depth is located in the center part for bedrock lakes, and in the back part for lakes in moraine material. Best correlations are found for mean depth and maximum width, however, all three empirical relations show a large spread, reflecting the wide range of natural lake bathymetries. Volumes of the 124 lakes with bathymetries amount to 0

  6. Response of Terrestrial Vegetation to Variations in Temperature and Aridity Since the Last Glacial Maximum in Lake Chalco, Mexico

    NASA Astrophysics Data System (ADS)

    Werne, J. P.; Rubesch, M.; Brown, E. T.; Ortega, B.; Caballero, M.; Lozano-Garcia, S.

    2011-12-01

    The water balance of the Southwestern United States and most of Mexico is dependent on regional climate systems, including the Mexican (or North American) Monsoon. The Mexican Monsoon leads to significant summer rainfall across a broad swath of the continent, which constitutes the major source of annual precipitation over much of this region. The position of the ITCZ and the strength of the accompanying monsoon are affected by variability in insolation. Stronger northern hemisphere summer insolation shifts the ITCZ northward, bringing about a more intense monsoon. Here we discuss a new geochemical climate record from Lake Chalco, Mexico, which couples inorganic (X-ray fluorescence) and organic (biomarkers and stable isotopes) geochemical proxies to reconstruct temperature and aridity over the past 45,000 years, as well as the response of terrestrial vegetation to such climate changes. The Basin of Mexico is a high altitude closed lacustrine basin (20°N, 99°W; 2240 m.a.s.l.) in the Trans Mexican Volcanic Belt. The plain of Lake Chalco, located near Mexico City in the southern sub-basin, has an area of 120 km2 and a catchment of 1100 km2. Though the present-day lake has been reduced to a small marsh due to historic diversion of its waters, over longer timescales the lake has been a sensitive recorder of hydroclimatic variations. Low Ca concentrations indicate more arid periods during the late glacial (34 - 15 kybp) compared to the last interstadial or early Holocene. This observation is supported by the ratio of terrestrial to aquatic lipid biomarkers (long vs. short chain n-alkanes), which indicate greater relative inputs of aquatic biomarkers during wetter periods. The changes in aridity as shown in these geochemical proxies are compared with temperature as reflected in glycerol dialkyl glycerol tetraether (GDGT) based paleotemperature proxies to assess the extent to which insolation may have driven aridity variations, and with terrestrial and aquatic biomarker

  7. Response of Terrestrial Vegetation to Variations in Temperature and Aridity Since the Last Glacial Maximum in Lake Chalco, Mexico

    NASA Astrophysics Data System (ADS)

    Werne, J. P.; Halbur, J.; Rubesch, M.; Brown, E. T.; Ortega, B.; Caballero, M.; Correa-Metrio, A.; Lozano, S.

    2013-05-01

    The water balance of the Southwestern United States and most of Mexico is dependent on regional climate systems, including the Mexican (or North American) Monsoon. The Mexican Monsoon leads to significant summer rainfall across a broad swath of the continent, which constitutes the major source of annual precipitation over much of this region. The position of the ITCZ and the strength of the accompanying monsoon are affected by variability in insolation. Stronger northern hemisphere summer insolation shifts the ITCZ northward, bringing about a more intense monsoon. Here we discuss a new geochemical climate record from Lake Chalco, Mexico, which couples inorganic (X-ray fluorescence) and organic (biomarkers and stable isotopes) geochemical proxies to reconstruct temperature and aridity over the past 45,000 years, as well as the response of terrestrial vegetation to such climate changes. The Basin of Mexico is a high altitude closed lacustrine basin (20°N, 99°W; 2240 m.a.s.l.) in the Trans Mexican Volcanic Belt. The plain of Lake Chalco, located near Mexico City in the southern sub-basin, has an area of 120 km2 and a catchment of 1100 km2. Though the present-day lake has been reduced to a small marsh due to historic diversion of its waters, over longer timescales the lake has been a sensitive recorder of hydroclimatic variations. Low Ca concentrations indicate more arid periods during the late glacial (34 - 15 kybp) compared to the last interstadial or early Holocene. This observation is supported by the ratio of terrestrial to aquatic lipid biomarkers (long vs. short chain n-alkanes), which indicate greater relative inputs of aquatic biomarkers during wetter periods. The changes in aridity as shown in these geochemical proxies are compared with temperature as reflected in glycerol dialkyl glycerol tetraether (GDGT) based paleotemperature proxies to assess the extent to which insolation may have driven aridity variations, and with terrestrial and aquatic biomarker

  8. Climate-induced variations in lake levels: A mechanism for short-term sea level change during non-glacial times

    SciTech Connect

    Jacobs, D. ); Sahagian, D. . Dept of Geological Sciences)

    1992-01-01

    Variations in insolation due to periodic orbital parameters can cause climatic changes and associated variations in the intensity of monsoonal circulation. This can lead to significant variations in the levels of internally draining lakes on timescales of 10,000 to 100,000 years in regions affected by the monsoon (20,000 years for orbital precession). These variations may be responsible for small scale (few meters) eustatic sea level changes in an ice-free Earth, and may contribute to sea level changes in the presence of ice as well. The authors have estimated the volume of empty present lake basins in the regions of Asia and North Africa influenced by the monsoon. The surface water volume alone of these basins is equivalent to a two meter difference in sea level, but is considerably augmented by groundwater associated with an increase in lake level. The lake variation mechanism for sea level change has its basis in the Quaternary record of climate change and associated explanatory models. However, the argument also applies to earlier, non-glacial periods of geologic time. Clear evidence for the presence of ice in the Triassic is lacking. However, there is evidence for short-term periodic fluctuations of lake levels as well as sea level during that time. These sea level changes, as well as those in the Devonian, Jurassic, and Cretaceous, may be driven by periodic fluctuation in lacustrine and groundwater storage resulting from orbitally forced changes in monsoon intensity, even in the absence of significant glacial ice.

  9. Effects of glacial meltwater inflows and moat freezing on mixing in an ice-covered antarctic lake as interpreted from stable isotope and tritium distributions

    USGS Publications Warehouse

    Miller, L.G.; Aiken, G.R.

    1996-01-01

    Perennially ice-covered lakes in the McMurdo Dry Valleys have risen several meters over the past two decades due to climatic warming and increased glacial meltwater inflow. To elucidate the hydrologic responses to changing climate and the effects on lake mixing processes we measured the stable isotope (??18O and ??D) and tritium concentrations of water and ice samples collected in the Lake Fryxell watershed from 1987 through 1990. Stable isotope enrichment resulted from evaporation in stream and moat samples and from sublimation in surface lake-ice samples. Tritium enrichment resulted from exchange with the postnuclear atmosphere in stream and moat samples. Rapid injection of tritiated water into the upper water column of the make and incorporation of this water into the ice cover resulted in uniformly elevated tritium contents (> 3.0 TU) in these reservoirs. Tritium was also present in deep water, suggesting that a component of bottom water was recently at the surface. During summer, melted lake ice and stream water forms the moat. Water excluded from ice formation during fall moat freezing (enriched in solutes and tritium, and depleted in 18O and 2H relative to water below 15-m depth) may sink as density currents to the bottom of the lake. Seasonal lake circulation, in response to climate-driven surface inflow, is therefore responsible for the distribution of both water isotopes and dissolved solutes in Lake Fryxell.

  10. Proglacial lakes: character, behaviour and geological importance

    NASA Astrophysics Data System (ADS)

    Carrivick, Jonathan L.; Tweed, Fiona S.

    2013-10-01

    Proglacial lakes are ubiquitous within the Quaternary record and can provide exceptional breadth and depth of palaeoenvironmental information. Present deglaciation is increasing the number and size of proglacial lakes around the world. This study provides a synthesis of knowledge on proglacial lake character and behaviour and critically evaluates the importance of proglacial lakes from a geological perspective. We show how ‘ice-marginal' or ‘ice-contact' lakes and other distal proglacial lakes can be distinguished from each other by geomorphological, sedimentological, chemical and biological characteristics. The key controls on proglacial lake geomorphology and sedimentology are outlined and discussed. Proglacial lakes can exacerbate mountain glacier and ice sheet margin ablation via mechanical and thermal stresses, but very large lakes can moderate summer air temperatures and relatively retard summer ice ablation. Proglacial lakes interrupt meltwater flux and are very efficient sediment traps. Hydrological routing and consequent geomorphological activity can be radically modified by sudden drainage of proglacial lakes and resultant glacial lake outburst floods; exceptionally large proglacial lake drainages affected global ocean circulation and global climate during the Quaternary. Overall, analyses of proglacial lakes can provide a valuable insight into (i) patterns, character and behaviour of mountain glaciers, ice sheets and glaciations, and (ii) the impacts of past, present and future deglaciation.

  11. Sediment analysis to support the recent glacial origin of DDT pollution in Lake Iseo (Northern Italy).

    PubMed

    Bettinetti, Roberta; Galassi, Silvana; Guilizzoni, Piero; Quadroni, Silvia

    2011-09-01

    In the present study, a depth-related distribution of Persistent Organic Pollutants (POPs) in sediments of Lake Iseo, one of the major southern Alpine Italian lakes, is reported in order to further test the hypothesis of melting Alpine glaciers as a secondary source of contamination. In a previous paper, a "glacier contamination hypothesis" was suggested to explain the unexpected contamination of the biota of Lake Iseo, mainly fed by the Alpine melting ice. The sediment core analyses covered around the last 50 years. The organic matter profile evaluated as a Loss-On-Ignition percentage indicated transition of the basin from an oligotrophic to a mesotrophic status at around the early 1970s, but there was no evidence of the shift to eutrophy in the 1980s. Among DDTs, pp'DDE was the predominant metabolite, accounting on average for 79.4% of the total DDT concentrations and ranging from 6.4 to 447.5 ng g(-1)d.w. PCBs ranged from 5.0 to 163.7 ng g(-1)d.w. The maximum PCB concentrations were found in sediment layers corresponding to the 1970s when the highest production and use of these compounds occurred in Italy. In contrast, concentrations of DDTs showed a sharp increase from the early 1990s, long after their agricultural use was banned in Italy. This delayed pollution provides support for the hypothesis that the recent retreat of glaciers represents a secondary pollution source for old pesticides that were stored in the ice at the time of their use in agriculture.

  12. Progressive incision of the Channeled Scablands by outburst floods

    NASA Astrophysics Data System (ADS)

    Larsen, Isaac J.; Lamb, Michael P.

    2016-10-01

    The surfaces of Earth and Mars contain large bedrock canyons that were carved by catastrophic outburst floods. Reconstructing the magnitude of these canyon-forming floods is essential for understanding the ways in which floods modify planetary surfaces, the hydrology of early Mars and abrupt changes in climate. Flood discharges are often estimated by assuming that the floods filled the canyons to their brims with water; however, an alternative hypothesis is that canyon morphology adjusts during incision such that bed shear stresses exceed the threshold for erosion by a small amount. Here we show that accounting for erosion thresholds during canyon incision results in near-constant discharges that are five- to ten-fold smaller than full-to-the-brim estimates for Moses Coulee, a canyon in the Channeled Scablands, which was carved during the Pleistocene by the catastrophic Missoula floods in eastern Washington, USA. The predicted discharges are consistent with flow-depth indicators from gravel bars within the canyon. In contrast, under the assumption that floods filled canyons to their brims, a large and monotonic increase in flood discharge is predicted as the canyon was progressively incised, which is at odds with the discharges expected for floods originating from glacial lake outbursts. These findings suggest that flood-carved landscapes in fractured rock might evolve to a threshold state for bedrock erosion, thus implying much lower flood discharges than previously thought.

  13. Past seismic activity in Eastern Anatolia recorded over several glacial/interglacial cycles in the sediments of Lake Van

    NASA Astrophysics Data System (ADS)

    Stockhecke, M.; Anselmetti, F.; Sturm, M.

    2012-12-01

    Lake sediments document besides paleoenvironmental and paleoclimate conditions also paleoseismic activity through various forms of deformation structures. These are especially visible in finely-laminated sediments. Being situated in a tectonically active region, the partly annually-laminated sedimentary sequence of the terminal Lake Van, recovered in 2010 under the context of the ICDP Paleovan project, shows dozens of earthquake-triggered microdeformations that document past seismic events of the last half a million years. Lithological and multiproxy analysis revealed that the Lake Van's depositional conditions varied in correspondence to Milankovitch and sub-Milankovitch cycles. Glacial/stadial and interglacial/interstadial conditions were recorded continuously over the last half a million years excluding two discontinuities, which indicate major hydrological and geomorphological changes in Lake Van's early history. Two sites were drilled 10 km apart: A primary drill site, situated on a ridge, covers the entire lake history since its initial transgression in the middle Pleistocene; A secondary drill site, located in a more shallow northern basin, covers the past 90'000 years. Multiple coring at both drill sites allows to establish two almost complete 220 m and 145 m long composite sections, respectively. Observing deformation structures in multiple parallel cores at each site is used as a criteria to distinguish 'true' paleoseismic deformation structures from potential drilling artifacts. Deformation structures consist of i) silt-filled vertical fractures, ii) microfaults with displacements at cm-scale, iii) microfolds, iv) liquefaction structures (mushroom, pseudonodules), iv) disturbed varve laminations and v) mixed layers. While the ridge site records the paleoseismic events as microdeformations, the northern basinal site rather records seismic events through the deposition of seismo-turbidites. In some cases, individual earthquake events can even be identified

  14. Constraints on Lake Agassiz discharge through the late-glacial Champlain Sea (St. Lawrence Lowlands, Canada) using salinity proxies and an estuarine circulation model

    USGS Publications Warehouse

    Katz, B.; Najjar, R.G.; Cronin, T.; Rayburn, J.; Mann, M.E.

    2011-01-01

    During the last deglaciation, abrupt freshwater discharge events from proglacial lakes in North America, such as glacial Lake Agassiz, are believed to have drained into the North Atlantic Ocean, causing large shifts in climate by weakening the formation of North Atlantic Deep Water and decreasing ocean heat transport to high northern latitudes. These discharges were caused by changes in lake drainage outlets, but the duration, magnitude and routing of discharge events, factors which govern the climatic response to freshwater forcing, are poorly known. Abrupt discharges, called floods, are typically assumed to last months to a year, whereas more gradual discharges, called routing events, occur over centuries. Here we use estuarine modeling to evaluate freshwater discharge from Lake Agassiz and other North American proglacial lakes into the North Atlantic Ocean through the St. Lawrence estuary around 11.5 ka BP, the onset of the Preboreal oscillation (PBO). Faunal and isotopic proxy data from the Champlain Sea, a semi-isolated, marine-brackish water body that occupied the St. Lawrence and Champlain Valleys from 13 to 9 ka, indicate salinity fell about 7-8 (range of 4-11) around 11.5 ka. Model results suggest that minimum (1600 km3) and maximum (9500 km3) estimates of plausible flood volumes determined from Lake Agassiz paleoshorelines would produce the proxy-reconstructed salinity decrease if the floods lasted <1 day to 5 months and 1 month to 2 years, respectively. In addition, Champlain Sea salinity responds very quickly to the initiation (within days) and cessation (within weeks) of flooding events. These results support the hypothesis that a glacial lake flood, rather than a sustained routing event, discharged through the St. Lawrence Estuary during the PBO. ?? 2011 Elsevier Ltd.

  15. Hydroclimatic Changes in Coastal Southern California at the Last Glacial Termination (~33 to 10 Ka): Pollen and Macrofossil Evidence from Lake Elsinore

    NASA Astrophysics Data System (ADS)

    Heusser, L. E.; Kirby, M. E.; Feakins, S. J.; Peteet, D. M.; Wu, M.; Pavia, F. J.

    2013-12-01

    High-resolution (1 cm ≈ 14 yrs) pollen analyses from a well-dated sediment core from Lake Elsinore record changes in coastal southern California upland and lowland vegetation at the end of the last glacial (~33 to 10 ka). Montane (>2200m) conifer forests expanded to lower elevations in the full glacial, with peak abundances at ~33ka near the beginning of the first wetland episode when aquatic macrofossils such as Potomogeton and Zannichellia seeds were present. In the Holocene, conifers were replaced by mid-elevation (1400-2100 m) oak woodlands and chaparral. Early Holocene abundance of algae and microcharcoal, absence of macrosfossils, and high total carbonate imply warmer epilimnion, eutrophication, and lower precipitation. Three general climate modes are reconstructed from the Lake Elsinore pollen data based on modern California pollen/vegetation/ hydroclimate relationships. First, beginning ~33ka, the record is characterized by a 10 kyr-long interval of high frequency changes in precipitation during which two expanded wetland episodes bracket repeated expansions of saline/alkaline vegetation. Second, low-amplitude variations in effective moisture characterize the last Glacial Maximum (23 to 15 kyrs). Third, rapid, abrupt high-amplitude changes in water availability occur during the Bølling, Allerod and Younger Dryas chronozones. Patterns of hydroclimatic change inferred from the pollen data are consistent with hydrologic variability reconstructed from lithologic and biochemical analyses of coeval samples from the Lake Elsinore core. The timing and character of the response of coastal southern California ecosystems at the termination of the last glacial is correlative with northeast Pacific Ocean climate events and with general patterns of global climate change.

  16. Luminescence chronology of non-glacial sediments in Changeable Lake, Russian High Arctic, and implications for limited Eurasian ice-sheet extent during the LGM

    NASA Astrophysics Data System (ADS)

    Berger, Glenn W.; Melles, Martin; Banerjee, Debabrata; Murray, Andrew S.; Raab, Alexandra

    2004-07-01

    A 10.5 m core from Changeable Lake in the Severnaya Zemlya Archipelago just north of the Taymyr Peninsula intersects ca. 30 cm of diamicton at its base, interpreted as a basal till. Because the upper 10.13 m of this core consists of non-glacial sediments, a maximum numeric age for these non-glacial sediments would provide a clear lower limit to the timing of the last glaciation in the area of Changeable Lake. Radiocarbon (14C) dating of several materials from this core yielded widely scattered results. Consequently we applied photonic dating to sediments above the diamicton. The experimental single-aliquot-regenerative (SAR) dose fine-grain method was applied to two samples, using the double SAR approach. With one exception, these fine-grain SAR results and the results of application of the SAR method to sand-sized quartz grains from two samples, at ca. 9.95 m and ca. 10.05 m depth, are discrepant with age estimates from the multi-aliquot infrared-photon-stimulated luminescence (IR-PSL) method applied to fine grains. Multi-aliquot IR-PSL dating of 10 samples produces ages increasing monotonically from ca. 4 ka at 2 m to 53 +/- 4 ka at 9.97 m. These self-consistent multi-aliquot IR-PSL ages, along with limiting 14C ages of >47 ka at ca. 10 m, provide direct evidence that glacial ice did not advance over this lake basin during the Last Glacial Maximum, and thus delimit the northeastern margin of the Barents-Kara Sea ice-sheet to somewhere west of this archipelago. The last regional glaciation probably occurred during marine isotope stage (MIS) 4 or earlier. Copyright

  17. Bottom-current and wind-pattern changes as indicated by Late Glacial and Holocene sediments from western Lake Geneva (Switzerland)

    USGS Publications Warehouse

    Girardclos, S.; Baster, I.; Wildi, W.; Pugin, A.; Rachoud-Schneider, A. -M.

    2003-01-01

    The Late-Glacial and Holocene sedimentary history of the Hauts-Monts area (western Lake Geneva, Switzerland) is reconstructed combining high resolution seismic stratigraphy and well-dated sedimentary cores. Six reflections and seismic units are defined and represented by individual isopach maps, which are further combined to obtain a three-dimensional age-depth model. Slumps, blank areas and various geometries are identified using these seismic data. The sediment depositional areas have substantially changed throughout the lake during the end of the Late-Glacial and the Holocene. These changes are interpreted as the result of variations in the intensity of deep lake currents and the frequency of strong winds determining the distribution of sediment input from the Versoix River and from reworking of previously deposited sediments within the lacustrine basin. The identified changes in sediment distribution allowed us to reconstruct the lake's deep-current history and the evolution of dominant strong wind regimes from the Preboreal to present times.

  18. Postglacial development of the eastern Gulf of Finland: from Pleistocene glacial lake basins to Holocene lagoon systems

    NASA Astrophysics Data System (ADS)

    Ryabchuk, Daria; Sergeev, Alexander; Kotilainen, Aarno; Hyttinen, Outi; Grigoriev, Andrey; Gerasimov, Dmitry; Anisimov, Mikhail; Gusentsova, Tatiana; Zhamoida, Vladimir; Amantov, Aleksey; Budanov, Leonid

    2016-04-01

    Despite significant amount of data, there are still lots of debatable questions and unsolved problems concerning postglacial geological history of the Eastern Gulf of Finland, the Baltic Sea. Among these problems are: 1) locations of the end moraine and glacio-fluvial deposits; 2) time and genesis of the large accretion forms (spits, bars, dunes); 3) basinwide correlations of trangression/regression culminations with the other parts of the Baltic Sea basin; 4) study of salinity, timing, frequency and intensity of Holocene saline water inflows and their links of sedimentation processes associated with climate change. Aiming to receive new data about regional postglacial development, the GIS analyses of bottom relief and available geological and geophysical data was undertaken, the maps of preQuaternary relief, moraine and Late Pleistocene surfaces, glacial moraine and Holocene sediments thicknesses were compiled. High-resolution sediment proxy study of several cores, taken from eastern Gulf of Finland bottom, allows to study grain-size distribution and geochemical features of glacial lake and Holocene sediments, to reveal sedimentation rates and paleoenvironment features of postglacial basins. Interdisciplinary geoarcheological approaches offer new opportunities for studying the region's geological history and paleogeography. Based on proxy marine geological and coastal geoarcheological studies (e.g. off-shore acoustic survey, side-scan profiling and sediment sampling, on-shore ground-penetrating radar (GPR SIR 2000), leveling, drilling, grain-size analyses and radiocarbon dating and archeological research) detailed paleogeographical reconstruction for three micro-regions - Sestroretsky and Lahta Lowlands, Narva-Luga Klint Bay and Southern Ladoga - were compiled. As a result, new high resolution models of Holocene geological development of the Eastern Gulf of Finland were received. Model calibration and verification used results from proxy geoarcheological research

  19. Map of Western Copper River Basin, Alaska, Showing Lake Sediments and Shorelines, Glacial Moraines, and Location of Stratigraphic Sections and Radiocarbon-Dated Samples

    USGS Publications Warehouse

    Williams, John R.; Galloway, John P.

    1986-01-01

    The purpose of this report is to make available basic data on radiocarbon dating of 61 organic samples from 40 locations in the western Copper River Basin and adjacent uplands and in the uppermost Matanuska River Valley. The former distribution of late Quaternary glacial lakes and of glaciers as mapped from field work and photo interpretation is provided as background for interpretation of the radiocarbon dates and are the basic data needed for construction of the late Quaternary chronology. The glacial boundaries, formed and expressed by moraines, ice-contact margins, marginal channels, deltas, and other features, are obscured by a drape of glaciolacustrine deposits in a series of glacial lakes. The highest lake, represented by bottom sediments as high as 914 m to 975 m above sea level, extends from Fog Lakes lowland on Susitna River upstream into the northwestern part of the Copper River Basin (the part now draining to Susitna River) where it apparently was held in by an ice border. It was apparently dammed by ice from the Mt. McKinley area, by Talkeetna G1acier, and may have had a temporary drainage threshold at the headwaters of Chunilna Creek. No shorelines have been noted within the map area, although Nichols and Yehle (1961) reported shorelines within the 914-975 m range in the Denali area to the north of that mapped. Recent work by geologic consultants for the Susitna Hydroelectric Project has confirmed the early inferences (Karlstrom, 1964) about the existence of a lake in the Susitna canyon, based originally on drilling by the Bureau of Reclamation about 35 years ago. According to dating of deposits at Tyone Bluff (map locations 0, P), Thorson and others (1981) concluded that a late Wisconsin advance of the glaciers between 11,535 and 21,730 years ago was followed by a brief interval of lacustrine sedimentation, and was preceded by a long period of lake deposition broken by a lowering of the lake between 32,000 and about 25,000 years ago. An alternate

  20. Discovery of relict subglacial lakes and their geometry and mechanism of drainage.

    PubMed

    Livingstone, Stephen J; Utting, Daniel J; Ruffell, Alastair; Clark, Chris D; Pawley, Steven; Atkinson, Nigel; Fowler, Andrew C

    2016-06-13

    Recent proxy measurements reveal that subglacial lakes beneath modern ice sheets periodically store and release large volumes of water, providing an important but poorly understood influence on contemporary ice dynamics and mass balance. This is because direct observations of how lake drainage initiates and proceeds are lacking. Here we present physical evidence of the mechanism and geometry of lake drainage from the discovery of relict subglacial lakes formed during the last glaciation in Canada. These palaeo-subglacial lakes comprised shallow (<10 m) lenses of water perched behind ridges orientated transverse to ice flow. We show that lakes periodically drained through channels incised into bed substrate (canals). Canals sometimes trend into eskers that represent the depositional imprint of the last high-magnitude lake outburst. The subglacial lakes and channels are preserved on top of glacial lineations, indicating long-term re-organization of the subglacial drainage system and coupling to ice flow.

  1. Discovery of relict subglacial lakes and their geometry and mechanism of drainage

    PubMed Central

    Livingstone, Stephen J.; Utting, Daniel J.; Ruffell, Alastair; Clark, Chris D.; Pawley, Steven; Atkinson, Nigel; Fowler, Andrew C.

    2016-01-01

    Recent proxy measurements reveal that subglacial lakes beneath modern ice sheets periodically store and release large volumes of water, providing an important but poorly understood influence on contemporary ice dynamics and mass balance. This is because direct observations of how lake drainage initiates and proceeds are lacking. Here we present physical evidence of the mechanism and geometry of lake drainage from the discovery of relict subglacial lakes formed during the last glaciation in Canada. These palaeo-subglacial lakes comprised shallow (<10 m) lenses of water perched behind ridges orientated transverse to ice flow. We show that lakes periodically drained through channels incised into bed substrate (canals). Canals sometimes trend into eskers that represent the depositional imprint of the last high-magnitude lake outburst. The subglacial lakes and channels are preserved on top of glacial lineations, indicating long-term re-organization of the subglacial drainage system and coupling to ice flow. PMID:27292049

  2. Discovery of relict subglacial lakes and their geometry and mechanism of drainage.

    PubMed

    Livingstone, Stephen J; Utting, Daniel J; Ruffell, Alastair; Clark, Chris D; Pawley, Steven; Atkinson, Nigel; Fowler, Andrew C

    2016-01-01

    Recent proxy measurements reveal that subglacial lakes beneath modern ice sheets periodically store and release large volumes of water, providing an important but poorly understood influence on contemporary ice dynamics and mass balance. This is because direct observations of how lake drainage initiates and proceeds are lacking. Here we present physical evidence of the mechanism and geometry of lake drainage from the discovery of relict subglacial lakes formed during the last glaciation in Canada. These palaeo-subglacial lakes comprised shallow (<10 m) lenses of water perched behind ridges orientated transverse to ice flow. We show that lakes periodically drained through channels incised into bed substrate (canals). Canals sometimes trend into eskers that represent the depositional imprint of the last high-magnitude lake outburst. The subglacial lakes and channels are preserved on top of glacial lineations, indicating long-term re-organization of the subglacial drainage system and coupling to ice flow. PMID:27292049

  3. Using a Hydrodynamic Lake Model to Predict the Impact of Avalanche Events at Lake Palcacocha, Peru

    NASA Astrophysics Data System (ADS)

    Chisolm, R. E.; Somos-Valenzuela, M. A.; McKinney, D. C.; Hodges, B. R.

    2013-12-01

    Accelerated retreat of Andean glaciers in recent decades due to a warming climate has caused the emergence and growth of glacial lakes. As these lakes continue to grow, they pose an increasing risk of glacial lake outburst floods (GLOFs). GLOFs can be triggered by moraine failures or by avalanches, rockslides, or ice calving into glacial lakes. Many of the processes influencing GLOF risk are still poorly understood. For many decades Lake Palcacocha in the Cordillera Blanca, Peru has posed a threat to citizens living in the watershed below, including the city of Huaraz which was devastated by a GLOF in 1941. A safety system for Lake Palcacocha was put in place in the 1970's to control the lake level with a tunnel and reinforced dyke, but the lake has since grown to the point where the lake is once again dangerous. Overhanging ice from the Palcaraju glacier and a relatively low freeboard level make the lake vulnerable to avalanches and landslides. A siphon system has been put in place to lower the lake below the level of the tunnel, but this system is temporary and the potential reduction in the water level is limited. Lake Palcacocha is used as a case study to investigate the impact of an avalanche event on the lake dynamics and the ensuing flood hydrograph. Empirical equations are used to determine the initial wave characteristics of an impulse wave created by three different avalanche scenarios that represent small, medium and large events. The characteristics of the initial impulse wave are used as inputs to a three-dimensional hydrodynamic model to predict the wave propagation across the lake and the moraine overtopping volume. The results from this model will be used as inputs to a downstream GLOF model to predict the impact from an outburst flood event. Additionally several scenarios are considered to evaluate the downstream impact from avalanche events with a reduction in the lake level. Use of a robust three-dimensional hydrodynamic lake model enables more

  4. Biological nitrate utilization in south Siberian lakes (Baikal and Hovsgol) during the Last Glacial period: the influence of climate change on primary productivity

    NASA Astrophysics Data System (ADS)

    Nara, Fumiko Watanabe; Watanabe, Takahiro; Kakegawa, Takeshi; Minoura, Koji; Imai, Akio; Fagel, Nathalie; Horiuchi, Kazuho; Nakamura, Toshio; Kawai, Takayoshi

    2014-04-01

    Stable nitrogen isotope ratios (δ15N) in sediment cores recovered from two Siberian lakes (Baikal and Hovsgol) are determined in order to evaluate the biologically mediated nitrogen cycle from the Last Glacial period to the postglacial period. The ranges of δ15N values from the two lakes are similar, varying from +2.8‰ to +6.7‰. The high values of δ15N (around +6‰) during the Last Glacial Maximum (LGM, 26.5-19 cal ka BP) indicate that a larger fraction of the available nitrate in both lakes was utilised by phytoplankton. A cool and dry climate during the LGM may have limited the input of terrestrial nitrate, resulting in the use of a large fraction of the nitrate, and low productivity, in both lakes. The use of a smaller fraction of the nitrate by phytoplankton in both lakes after the LGM (19-12 cal ka BP) is reflected in the lower δ15N values (down to +3.0‰). The increase in summer insolation after the LGM caused increased vertical mixing of the lake water column, which transported nitrate upwards from the deeper waters and into the photic zone. The reduced rate of nitrogen consumption after the LGM indicates that nitrate was more readily available to phytoplankton at this time and did not limit their activities. This change suggests that other factors limited phytoplankton activity during this period. At the climatic transition between Oxygen Isotope Stages 2 and 1 (around 11.5 cal ka BP), the rapid increase in δ15N (from +3.0‰ to +6.0‰) reflected a rapid increase in nitrate utilization. At this transition, increases in precipitation and lake levels, which were associated with the increased intensity of the East Asian Monsoon, may have brought a large influx of nutrients required by the phytoplankton into the lakes from the watershed. This hydrological change led to increased phytoplankton activity in both lakes, resulting in increased nitrate consumption. The δ15N data obtained here from the sediments of lakes Baikal and Hovsgol suggest that

  5. Supraglacial lakes on Himalayan debris-covered glacier (Invited)

    NASA Astrophysics Data System (ADS)

    Sakai, A.; Fujita, K.

    2013-12-01

    currents driven by winds at the lake surface with a positive feedback process. The risk of GLOFs (glacial lake outburst flood) are analysed for Himalayan glacial lakes. We proposed an objective index for GLOF probability, based on depression angle from the lakeshore, which allows the lakes to be assessed using remotely sensed digital elevation models (DEMs). The index was verified by pre-GLOF topography derived by spy satellite imageries. We screened 2800 Himalayan glacial lakes and identified 49 lakes with potential flood volumes over 10 million m3.

  6. Late-glacial to Early Holocene lake basin and river valley formation within Pomeranian moraine belt near Dobbertin (Mecklenburg-Vorpommern, NE Germany)

    NASA Astrophysics Data System (ADS)

    Zawiska, Izabela; Lorenz, Sebastian; Börner, Andreas; Niessner, Dominique; Słowiński, Michał; Theuerkauf, Martin; Pieper, Hagen; Lampe, Reinhard

    2014-05-01

    In central Mecklenburg-Vorpommern vast areas between the terminal moraine belts of the Frankfurt (W1F) and Pomeranian Phase (W2) were covered by glaciolacustrine basins which were embedded in the outwash plains. With deglaciation of the Pomeranian Phase around 17-18 ka BP the basins north to the villages Dobbertin and Dobbin were part of a glaciofluvial river system in combination with ice-dammed lake basins. During the late-glacial after ~14 ka cal BP the melting of buried dead ice reshaped the lake basin morphology by new depressions, in- and outlets. We study late-glacial basin and landscape development using cores collected along a pipeline trench crossing the Dobbin-Dobbertin basin. Core analysis includes sedimentological (carbon content, grainsize distribution) and palaeoecological (pollen, plant macrofossils, Cladocera) proxies. Radiocarbon dates indicate that peat formation started soon after the start of the Weichselian late-glacial. High resolution analysis of a basal peat layer indicates that initial organic and lacustrine sedimentation started in shallow ponding mires, evolving from buried dead ice sinks in the glaciofluvial sequence, in which telmatic plants (Carex aquatilis, Schoenoplectus lacustris) dominated. Chydorus sphaericus, the only cladocera species recorded, is ubiquitous and can survive in almost all reservoir types in very harsh conditions. Findings of Characeae than point at the formation of shallow lakes. The expansion of rich fen communities, including Scorpidium scorpoides, and a decline in Cladocera diversity show that these lakes soon again terrestrialised with peat formation. The appearance of Alona costata points at a lowering of pH values in that process. A tree trunk of birch (14.2 ka cal. BP) shows that first trees established during this first telmatic period. At this position in the basin, the basal peat layer is covered by minerogenic sediments, which points at a period of higher water levels and fluvial dynamics, possibly

  7. Numerical simulation of ground-water flow through glacial deposits and crystalline bedrock in the Mirror Lake area, Grafton County, New Hampshire

    USGS Publications Warehouse

    Tiedeman, Claire R.; Goode, Daniel J.; Hsieh, P.A.

    1997-01-01

    This report documents the development of a computer model to simulate steady-state (long-term average) flow of ground water in the vicinity of Mirror Lake, which lies at the eastern end of the Hubbard Brook valley in central New Hampshire. The 10-km2 study area includes Mirror Lake, the three streams that flow into Mirror Lake, Leeman's Brook, Paradise Brook, and parts of Hubbard Brook and the Pemigewasset River. The topography of the area is characterized by steep hillsides and relatively flat valleys. Major hydrogeologic units include glacial deposits, composed of till containing pockets of sand and gravel, and fractured crystalline bedrock, composed of schist intruded by granite, pegmatite, and lamprophyre. Ground water occurs in both the glacial deposits and bedrock. Precipitation and snowmelt infiltrate to the water table on the hillsides, flow downslope through the saturated glacial deposits and fractured bedrock, and discharge to streams and to Mirror Lake. The model domain includes the glacial deposits, the uppermost 150m of bedrock, Mirror Lake, the layer of organic sediments on the lake bottom, and streams and rivers within the study area. A streamflow routing package was included in the model to simulate baseflow in streams and interaction between streams and ground water. Recharge from precipitation is assumed to be areally uniform, and riparian evapotranspiration along stream banks is assumed negligible. The spatial distribution of hydraulic conductivity is represented by dividing the model domain into several zones, each having uniform hydraulic properties. Local variations in recharge and hydraulic conductivities are ignored; therefore, the simulation results characterize the general ground-water system, not local details of ground-water movement. The model was calibrated using a nonlinear regression method to match hydraulic heads measured in piezometers and wells, and baseflow in three inlet streams to Mirror Lake. Model calibration indicates that

  8. A Reassessment of U-Th and 14C Ages for Late-Glacial High-Frequency Hydrological Events at Searles Lake, California

    USGS Publications Warehouse

    Lin, J.C.; Broecker, W.S.; Hemming, S.R.; Hajdas, I.; Anderson, Robert F.; Smith, G.I.; Kelley, M.; Bonani, G.

    1998-01-01

    U-Th isochron ages of tufas formed on shorelines suggest that the last pluvial event in Lake Lahontan and Searles Lake was synchronous at about 16,500 cal yr B.P. (equivalent to a radiocarbon age of between 14,000 and 13,500 yr B.P.), whereas the timing of this pluvial event determined by radiocarbon dating is on the order of 1000 yr younger. The timing of seven distinct periods of near desiccation in Searles Lake during late-glacial time has been reinvestigated for U-Th age determination by mass spectrometry. U-Th dating of evaporite layers in the interbedded mud and salt unit called the Lower Salt in Searles Lake was hampered by the uncertainty in assessing the initial 230Th/232Th of the samples. The resulting ages, corrected by a conservative range of initial 230Th/ 232Th ratios, suggest close correlation of the abrupt changes recorded in Greenland ice cores (Dansgaard-Oeschger events) and wet-dry conditions in Searles Lake between 35,000 and 24,000 Cal yr B.P. ?? 1998 University of Washington.

  9. Characteristics of the water and dissolved matter circulation in the young-glacial catchment of the Czechowskie lake (Tuchola Pinewood Forest, Poland)

    NASA Astrophysics Data System (ADS)

    Brykala, Dariusz; Gierszewski, Piotr; Kaszubski, Michal

    2014-05-01

    The studies on the conditions of the water and dissolved matter circulation in the young-glacial catchment of the Czechowskie lake (Tuchola Pinewood Forest) have been conducted since 2012. They are implemented on the basis of an organised network monitoring surface water and groundwater. An important aim of the study is to assess the impact of both modern and fossil lakes on the regime of the outflow and the transformation of the water chemical properties. A high stability of the first groundwater table was recorded. During the study period the range of the groundwater level ranged from 0.17 to 0.92 m. In comparison with the small fluctuations in the groundwater level within the sandy outwash areas, a relatively high instability was shown by the shallow waters of the lake terraces. The measurements of the discharge showed that its average value at the outflow from the Czechowskie lake is 30 dm3s-1. It almost equals the total amount of water flowing into the lake through watercourses. The average specific runoff from the basin of the Czechowskie lake was 3 dm3s-1km-2. The total water mineralisation expressed as the sum of the ions is in the range from 70 to 750 mg dm-3. Both surface water, i.e. the water in streams and lakes, and underground water from different depths represent the bicarbonate-calcium-sulphate type characteristic of the young- glacial environment. The results of hydrochemical mapping and the analysis of the ionic composition of the water showed large spatial variability of the physico-chemical properties of the tested waters and, at the same time, high stability of their ionic composition. At the present stage of the research it is possible to identify the water enrichment zones in salts, which are basins of paleolakes filled with the organic-carbonate sediment, and the zones of salt precipitation within the contemporary lakes. The situation described above creates a specific, cascade model of the transformation of chemical properties of water

  10. Climatic and morphological controls on post-glacial lake and river valley evolution in the Weichselian belt - an example from the Wda valley, Northern Poland

    NASA Astrophysics Data System (ADS)

    Kramkowski, M. A.; Błaszkiewicz, M.; Piotrowski, J. A.; Brauer, A.; Gierszewski, P.; Kordowski, J.; Lamparski, P.; Lorenz, S.; Noryśkiewicz, A. M.; Ott, F.; Slowinski, M. M.; Tyszkowski, S.

    2014-12-01

    The River Wda valley is a classical example of a polygenetic valley, consisting of former lake basins joined by erosive gap sections. In its middle section, which was the subject of our research, a fragment of an abandoned Lateglacial river valley is preserved, which is unique for the Weichselian moraine belt in the Central European Lowlands. The analysis of the relationship between the lacustrine and fluvial sediments and landforms enabled the authors to report many evolutionary connections between the initial period of the river system formation and the emergence of lakes during the Weichselian Lateglacial. The surface drainage essentially determined the progress of melting of dead ice blocks buried in the glacial depressions, which finally led to lake formation there. Most of the lake basins in the study area were formed during the Bølling-Allerød period. However, one section of the subglacial channel was not exposed to the thermokarst conditions and was therefore preserved with dead ice blocks throughout the entire Lateglacial. The dead ice decay at the beginning of the Holocene, as well as the emergence of another lake, created a lower base level of erosion in the close vicinity of the abandoned valley and induced a change of the river's course. Both fluvial and lacustrine deposits and landforms distributed in the central section of the River Wda valley indicate two processes, which proceeded simultaneously: (1) emergence of fluvially joined lake basins within a glacial channel, (2) degradation of the river bed in the gap sections interfering between the lakes. The processes described for the central section of the River Wda channel indicate a very dynamic river valley development during the Weichselian Lateglacial and the early Holocene. The valley formation was tightly interwoven with the morphogenesis of the primary basins within the valley, mainly with the melting of the buried blocks of dead ice and the development of lakes. This study is a contribution

  11. Reflection of global late glacial and Holocene paleoclimate oscillations in the palynological record from bottom sediments of Tavatui Lake (Middle Urals)

    NASA Astrophysics Data System (ADS)

    Maslennikova, A. V.; Udachin, V. N.; Anfilogov, V. N.; Deryagin, V. V.

    2016-06-01

    The palynological analysis of the reliably dated core section of bottom sediments from Tavatui Lake revealed consistency between the chronology and succession of Late Pleistocene and Early Pliocene events (GI-a/b, CS-1, GH-11.2) in the Middle Urals and the North Atlantic region. It is established that the Holocene thermal maximum (5.3-8.0 cal. ka ago) in the Middle Urals was characterized by high temperatures and humidity. The initial stage of the Subboreal cooling was reffered to the interval of 4.5-5.3 cal. ka ago. The data obtained provided grounds for the conclusion that the palynological record in the Tavatui Lake section reflects in detail global and regional climate oscillations, which allows it to be used as a Holocene and late glacial reference section, as well as for predicting the behavior of the natural system of the Middle Urals in response to future climate change.

  12. Paired proglacial lake sediment and cosmogenic ages reveal the timing of Late Glacial and Holocene glacier fluctuations in the Huaguruncho Massif of Peru

    NASA Astrophysics Data System (ADS)

    Stansell, Nathan; Rodbell, Donald; Licciardi, Joseph; Schweinsberg, Avriel; Huss, Elizabeth; Finkel, Robert; Zimmerman, Susan

    2015-04-01

    The pairing of cosmogenic ages on moraine boulders and radiocarbon-dated lake sediments provides a powerful tool for reconstructing past climates based on former ice positions. Surface exposure ages (10Be) and clastic sediment records from a proglacial lake at Nevado Huaguruncho, Peru, document the waxing and waning of tropical alpine glaciers in the Eastern Cordillera during the last ca. 15 ka. Moraine ages indicate that glaciers were advanced at ca. 14.1 ± 0.4 ka, a pattern that is consistent with cooling associated with the Antarctic Cold Reversal. Yanacocha is located immediately upvalley from this 14.1 ka moraine, and lake sediments and cosmogenic ages also suggest that glaciers advanced just prior to, or at the start of, the Younger Dryas from 13.1 to 12.5 ka. Lake sediments and cosmogenic ages then indicate that glaciers retreated after ca. 12.5 ka, and again advanced during the early Holocene between ca. 12 and 9 ka. Short-lived increases in clastic lake sediment values suggest that ice margins advanced briefly at times through the middle Holocene from ca. 8 to 4 ka, and the lack of moraine boulders dating to this interval suggest that glaciers were less extensive than during the late Holocene. Lake sediments suggest that glaciers experienced a relatively limited advance at the start of the late Holocene from ca. 4 to 2 ka, followed by retreat until the start of the Medieval Climate Anomaly at ca. 1.1 ka. Clastic sediment values in the lake sediments then suggest that ice began advancing during the MCA, and the most pronounced Holocene advance at Huaguruncho occurred during the Little Ice Age (ca. 0.4 to 0.2 ka) under colder and wetter conditions. The pattern of glacier variability in Huaguruncho during the Late Glacial and Holocene provides further evidence that tropical Atlantic Ocean conditions drove much of the observed temperature and precipitation changes along the Eastern Cordillera.

  13. Integrating physical and chemical characteristics of lakes into the glacially influenced landscape of the Northern Cascade Mountains, Washington State, USA

    USGS Publications Warehouse

    Larson, Gary L.; Lomnicky, G.A.; Liss, W.J.; Deimling, E.

    1999-01-01

    A basic knowledge of the physical and chemical characteristics of lakes is needed by management to make informed decisions to protect water resources. In this study we investigated some of the physical and chemical characteristics of 58 lakes in alpine, subalpine, and forest vegetation zones in a natural area (North Cascades National Park Service Complex) between 1989 and 1993. The objectives of the study were to: (1) document the time of ice-out relative to lake elevation; (2) determine how a sharp climate gradient west and east of the hydrologic divide affected the time of ice-out for subalpine lakes; and (3) assess how lake water quality was associated with lake elevation, lake depth, and basin geology. As expected, lake ice-out times occurred earlier with decreasing elevation. East-slope subalpine lakes iced-out earlier than did west-slope subalpine lakes because the east slope of the study area was drier and warmer than the west slope. On average, the lakes were relatively cold, neutral in pH, and low in dissolved substances and concentrations of nitrogen and phosphorus. Although some shallow lakes (depth ,10 m) exhibited the highest alkalinities, conductivities, and concentrations of phosphorus and nitrogen, most shallow lakes exhibited low values for these variables that were comparable to values observed in deep lakes. Geology did not play a major role in segregating the lakes based on water quality. Overall, lake temperature, pH, alkalinity, conductivity, and concentrations of total phosphorus and total Kjeldahl N increased with decreasing elevation. These changes in water quality with decreasing elevation in this temperate mountainous region corresponded with warmer air temperatures and increased vegetation biomass, soil depth and maturity, and dissolved substances and nutrients.

  14. Estimating the volume of supra-glacial melt lakes across Greenland: A study of uncertainties derived from multi-platform water-reflectance models

    NASA Astrophysics Data System (ADS)

    Cordero-Llana, L.; Selmes, N.; Murray, T.; Scharrer, K.; Booth, A. D.

    2012-12-01

    Large volumes of water are necessary to propagate cracks to the glacial bed via hydrofractures. Hydrological models have shown that lakes above a critical volume can supply the necessary water for this process, so the ability to measure water depth in lakes remotely is important to study these processes. Previously, water depth has been derived from the optical properties of water using data from high resolution optical satellite images, as such ASTER, (Advanced Spaceborne Thermal Emission and Reflection Radiometer), IKONOS and LANDSAT. These studies used water-reflectance models based on the Bouguer-Lambert-Beer law and lack any estimation of model uncertainties. We propose an optimized model based on Sneed and Hamilton's (2007) approach to estimate water depths in supraglacial lakes and undertake a robust analysis of the errors for the first time. We used atmospherically-corrected data from ASTER and MODIS data as an input to the water-reflectance model. Three physical parameters are needed: namely bed albedo, water attenuation coefficient and reflectance of optically-deep water. These parameters were derived for each wavelength using standard calibrations. As a reference dataset, we obtained lake geometries using ICESat measurements over empty lakes. Differences between modeled and reference depths are used in a minimization model to obtain parameters for the water-reflectance model, yielding optimized lake depth estimates. Our key contribution is the development of a Monte Carlo simulation to run the water-reflectance model, which allows us to quantify the uncertainties in water depth and hence water volume. This robust statistical analysis provides better understanding of the sensitivity of the water-reflectance model to the choice of input parameters, which should contribute to the understanding of the influence of surface-derived melt-water on ice sheet dynamics. Sneed, W.A. and Hamilton, G.S., 2007: Evolution of melt pond volume on the surface of the

  15. Metabolic and molecular characterization of bacterial community associated to Patagonian Chilean oligotrophic-lakes of quaternary glacial origin.

    PubMed

    Leon, Carla; Campos, Víctor; Urrutia, Roberto; Mondaca, María-Angélica

    2012-04-01

    The Patagonian Lakes have particular environmental conditions with or without intermittent disturbances. The study of the microorganisms present in aquatic ecosystems has increased notably because they can be used as micro-scale bioindicators of, among others, anthropogenic pollution and climatic change. The aim of the work was to compare the composition of the bacterial communities associated with sediments of three Patagonian Lakes with different geomorphologic patterns and disturbances. The lake sediments were characterized by molecular techniques, physiology profiles and physico-chemical analyses. The metabolic and physiological profiles of the microbial community demonstrated that non-impacted Tranquilo Lake is statistically different to impacted Bertrand and Plomo Lakes. Similar results were detected by DGGE profiles. FISH results demonstrated that betaproteobacteria showed the highest count in the Tranquilo Lake while gammaproteobacteria showed the highest counts in the Bertrand and Plomo Lakes, indicating that their sediments are highly dystrophic. The results demonstrate differences in the metabolic activity and structural and functional composition of bacterial communities of the studied lakes, which have different geomorphological patterns due to disturbances such as volcanic activity and the climatic change.

  16. A fan dam for Tulare Lake, California, and implications for the Wisconsin glacial history of the Sierra Nevada.

    USGS Publications Warehouse

    Atwater, B.F.

    1986-01-01

    Four stratigraphically consistent 14C dates on peat and wood give an age of 26 000 yr BP for the start of Tulare Lake's late Wisconsin transgression. An earlier enlargement of Tulare Lake probably resulted from a fan dam produced by the penultimate major (Tahoe) glaciation of the Sierra Nevada. Average sedimentation rates inferred from depths to a 600 000-yr-old clay and from radiocarbon dates indicate that this earlier lake originated no later than 100 000 yr BP. The Tahoe glaciation therefore is probably pre- Wisconsin. -from Authors

  17. Lake sediment multi-taxon DNA from North Greenland records early post-glacial appearance of vascular plants and accurately tracks environmental changes

    NASA Astrophysics Data System (ADS)

    Epp, L. S.; Gussarova, G.; Boessenkool, S.; Olsen, J.; Haile, J.; Schrøder-Nielsen, A.; Ludikova, A.; Hassel, K.; Stenøien, H. K.; Funder, S.; Willerslev, E.; Kjær, K.; Brochmann, C.

    2015-06-01

    High Arctic environments are particularly sensitive to climate changes, but retrieval of paleoecological data is challenging due to low productivity and biomass. At the same time, Arctic soils and sediments have proven exceptional for long-term DNA preservation due to their constantly low temperatures. Lake sediments contain DNA paleorecords of the surrounding ecosystems and can be used to retrieve a variety of organismal groups from a single sample. In this study, we analyzed vascular plant, bryophyte, algal (in particular diatom) and copepod DNA retrieved from a sediment core spanning the Holocene, taken from Bliss Lake on the northernmost coast of Greenland. A previous multi-proxy study including microscopic diatom analyses showed that this lake experienced changes between marine and lacustrine conditions. We inferred the same environmental changes from algal DNA preserved in the sediment core. Our DNA record was stratigraphically coherent, with no indication of leaching between layers, and our cross-taxon comparisons were in accordance with previously inferred local ecosystem changes. Authentic ancient plant DNA was retrieved from nearly all layers, both from the marine and the limnic phases, and distinct temporal changes in plant presence were recovered. The plant DNA was mostly in agreement with expected vegetation history, but very early occurrences of vascular plants, including the woody Empetrum nigrum, document terrestrial vegetation very shortly after glacial retreat. Our study shows that multi-taxon metabarcoding of sedimentary ancient DNA from lake cores is a valuable tool both for terrestrial and aquatic paleoecology, even in low-productivity ecosystems such as the High Arctic.

  18. Paleogeography and paleoenvironments of southwestern Baffin Island (Nunavut, Canada): post-glacial isostatic uplift and isolation of Nettilling Lake from marine influence

    NASA Astrophysics Data System (ADS)

    Narancic, Biljana; Pienitz, Reinhard; Francus, Pierre; Rolland, Nicolas; Wagner, Anne-Marie

    2013-04-01

    radiometric dating of the isolation contacts helps refine regional glacio-isostatic rebound and the duration and extent of the postglacial Tyrrell Sea marine phase. Post-glacial marine regression and the associated changes in paleosalinity are also reflected in the sediment core sedimentology and geochemistry analysed using a Multi Sensor Core Logger and a microfluorescence scanner. Jacobs J. D., Headley A. N., Maus L. A., Mode W. N. et Simms E. L., 1997. Climate and vegetation of the interior lowlands of southern Baffin Island : long-term stability at the low artic limit. Arctic 50 (2) : 167-177. Oliver D. R., 1964. A limnological investigation of a large Arctic lake, Nettilling lake, Baffin island. Papers University of Calgary 17 : 69-83. Pienitz R., Douglas M. S. V. et Smol P. J., 2004 Paleolimnological research in polar regions : An introduction. In : Pienitz R., Douglas M. S. V., Smol P. J. (Eds) Long- term environmental change in Arctic and Antarctic lakes. Springer, Dordrecht, 562 p.

  19. Lacustrine sediments in Lake Ohau, central South Island, New Zealand - An archive of erosion, earthquakes and paleoclimate since the Late Glacial

    NASA Astrophysics Data System (ADS)

    Upton, P.; Vandergoes, M. J.; Howarth, J.; Levy, R. H.; Mackenzie Basin Lakes Project members

    2011-12-01

    Located east of the main divide in the central Southern Alps, the Mackenzie Lakes, Ohau, Pukaki and Tekapo, occupy fault controlled glacial valleys and contain a high resolution sedimentary record of the last ~16 ka. Recorded in these sediments are climatic events, earthquakes along the Alpine Fault to the northwest, the landscape response following Alpine Fault earthquakes and land use changes. It is possible that earthquakes on smaller, more proximal faults such as the Ostler Fault and the Irishman Creek Fault are also preserved in one or more of the lakes. We focus this study on Lake Ohau, the smallest and shallowest of the three lakes. A 5 m core collected from the distal end of Lake Ohau at a depth of 60 m comprises finely laminated, light and dark sediment couplets. Preliminary estimates of sedimentation rate = c. 5 mm/yr suggest that the core contains a record of approximately the last 1000 years. We use HydroTrend, a climate-driven hydrological model, coupled to Sedflux, a basin filling stratigraphic model, to simulate sediment deposition within the lake basin. A high resolution simulation, run at daily timesteps over the last 60 years and constrained by measured climate parameters, is compared to the top 30cm of the core which has been dated to this time interval. Our results show that the laminations within the core represent large storm events rather than an annual layering. Much of the catchment of Lake Ohau is located within 30-50 km of the Alpine Fault, within the region expected to experience shaking strong enough to generate significant landsliding (≥MM8 shaking intensity) and thus create a wealth of sediment available to be transported through the sedimentary system. Following an earthquake, the next major rain event will transport the first pulse of that sediment into Lake Ohau. Comparison with recognised earthquake signals in offshore cores suggest that this pulse is likely to form a coarser grainsize layer (Gomez et al., 2007). Subsequent

  20. An In-Situ Deep-UV Optical Probe for Examining Biochemical Presence in Deep Glaciers and Sub-Glacial Lakes

    NASA Astrophysics Data System (ADS)

    Lane, A. L.; Behar, A.; Bhartia, R.; Conrad, P. G.; Hug, W. F.

    2007-12-01

    The quest to study and understand extremophiles has led to many quite different research paths in the past 30 years. One of the more difficult directions has been the study of biochemical material in deep glacial ice and in subglacial lakes. Lake Vostok in Eastern Antarctica has been perhaps the most discussed subglacial lake because of its large size (~14,000 sq km), deep location under >3700 m of overlying ice, and thick sediment bed (~200m). Once the physical conditions of the Lake were assessed, questions immediately arose about the potential existence of biological material - either extinct or possibly extant under conditions of extremely limited energy and nutrients [1-2]. To investigate the biology of Vostok, via in-situ methods, is a major issue that awaits proven techniques that will not contaminate the Lake beyond what may have occurred to date. Lake Ellsworth, in West Antarctica, also discovered by ice penetrating radar, is of significantly smaller size, but is also >3500 m below the overlying ice. It represents a wonderful opportunity to design, engineer and build in-situ delivery systems that consider bio-cleanliness approaches to enable examination of its water, sediment bed and the "roof" area accretion ice for biochemicals [3]. Our laboratory has been developing deep UV fluorescence and UV Raman instrumentation to locate and classify organic material at a variety of extremophile locations. The confluence of the measurement techniques and the engineering for high external pressure instrument shells has enabled us to design and begin prototype fabrication of a biochemical sensing probe that can be inserted into a hot-water drilled ice borehole, functioning as a local area mapper in water environments as deep as 6000 m. Real-time command and control is conducted from a surface science station. We have been using the deep Vostok ice cores at the U.S. National Ice Core Lab to validate our science and data analysis approaches with an "inverted" system

  1. Hydrologic hazards along Squaw Creek from a hypothetical failure of the glacial moraine impounding Carver Lake near Sisters, Oregon

    USGS Publications Warehouse

    Laenen, Antonius; Scott, K.M.; Costa, J.E.; Orzol, L.L.

    1987-01-01

    A hydrologic hazard exists that could create a large-magnitude, but short-duration, flood in the Squaw Creek drainage and inundate areas in and around the community of Sisters, Oregon. There is a 1 to 5% probability that Carver Lake, located at elevation 7,800 ft above sea level on the east slope of South Sister mountain, Oregon, could catastrophically empty. At the U.S. Geological Survey gage (14075000) on Squaw Creek between Carver Lake and Sisters, the magnitude of the breakout flood would be 10 times that of a 1% probability meteorological flood. In Sisters, the magnitude of the breakout flood would be about five times that of a 1% probability meteorological flood. Several conditions at Carver Lake indicate the potential hazard: (1) The lake is very deep for its size; the lake contains 740 acre-ft of water and is more than 100 ft deep; (2) There is a probability that a large magnitude avalanche and consequent overtopping of the lake could occur. There are steep slopes of unstable volcanic rock and an extensively cravassed glacier located above the lake; (3) The moraine dam confining the lake is steep-faced, rendering the dam unstable, and unvegetated making it highly erodible; (4) Large amounts of readily erodible material available for transport would increase the magnitude of a large flood and keep the flood from attenuating in the steep reaches of the Squaw Creek channel; (5) and, Geologically, there is a greater than normal possibility for the area to become seismically active. Earthquakes could cause rock and ice to fall into the lake. A one-dimensional unsteady-state streamflow model was used to route a hypothetical flood down the Squaw Creek drainage. This scenario creates a starting hydrograph with a peak of 180,000 cu ft/sec. The ensuing hypothetical flood would incorporate readily erodible debris and sediments in the steep canyons, increasing the total volume of the flood by a factor of two. As the peak emerges from the steeper slopes into a more

  2. Temperature profile for glacial ice at the South Pole: implications for life in a nearby subglacial lake.

    PubMed

    Price, P Buford; Nagornov, Oleg V; Bay, Ryan; Chirkin, Dmitry; He, Yudong; Miocinovic, Predrag; Richards, Austin; Woschnagg, Kurt; Koci, Bruce; Zagorodnov, Victor

    2002-06-11

    Airborne radar has detected approximately 100 lakes under the Antarctic ice cap, the largest of which is Lake Vostok. International planning is underway to search in Lake Vostok for microbial life that may have evolved in isolation from surface life for millions of years. It is thought, however, that the lakes may be hydraulically interconnected. If so, unsterile drilling would contaminate not just one but many of them. Here we report measurements of temperature vs. depth down to 2,345 m in ice at the South Pole, within 10 km from a subglacial lake seen by airborne radar profiling. We infer a temperature at the 2,810-m deep base of the South Pole ice and at the lake of -9 degrees C, which is 7 degrees C below the pressure-induced melting temperature of freshwater ice. To produce the strong radar signal, the frozen lake must consist of a mix of sediment and ice in a flat bed, formed before permanent Antarctic glaciation. It may, like Siberian and Antarctic permafrost, be rich in microbial life. Because of its hydraulic isolation, proximity to South Pole Station infrastructure, and analog to a Martian polar cap, it is an ideal place to test a sterile drill before risking contamination of Lake Vostok. From the semiempirical expression for strain rate vs. shear stress, we estimate shear vs. depth and show that the IceCube neutrino observatory will be able to map the three-dimensional ice-flow field within a larger volume (0.5 km(3)) and at lower temperatures (-20 degrees C to -35 degrees C) than has heretofore been possible. PMID:12060731

  3. Digital models of a glacial outwash aquifer in the Pearl-Sallie Lakes area, west-central Minnesota

    USGS Publications Warehouse

    Larson, S.P.; McBride, Mark S.; Wolf, R.J.

    1975-01-01

    -p^e need for study of lake-ground-water interchange has been accentuated by eutrophication of lakes in the Pearl-Sallie Lakes area of west-central Minnesota. The local ground-water flow system is dominated by an outwash aquifer that is sandwiched between two till layers in the western part of the area and exposed at the land surface in the eastern part. Ground water discharges from the aquifer into lakes in the outwash area but is recharged from lakes in the till-covered area. Irregular aquifer geometry resulted in a complex ground-water flow system. Simulation of the system by areal and vertical-section models showed that the lakes significantly control groundwater flow near their boundaries. Inadequate field data and complex geology caused difficulty in obtaining solutions with the vertical-section model. The models may be used to guide collection and interpretation of field data, and quantification of the ground-water flow system. With modification, they could be used to predict aquifer response to transient stresses. They also could be incorporated into more complex models to determine the movement of solutes in the ground-water system.

  4. Assessing downstream flood impacts due to a potential GLOF from Imja Lake in Nepal

    NASA Astrophysics Data System (ADS)

    Somos-Valenzuela, M. A.; McKinney, D. C.; Byers, A. C.; Rounce, D. R.; Portocarrero, C.; Lamsal, D.

    2014-11-01

    Glacial-dominated areas pose unique challenges to downstream communities in adapting to recent and continuing global climate change, including increased threats of glacial lake outburst floods (GLOFs) that can increase risk due to flooding of downstream communities and cause substantial impacts on regional social, environmental and economic systems. The Imja glacial lake in Nepal, with potential to generate a GLOF, was studied using a two-dimensional debris flow inundation model in order to evaluate the effectiveness of proposed measures to reduce possible flooding impacts to downstream communities by lowering the lake level. The results indicate that only minor flood impact reduction is achieved in the downstream community of Dingboche with modest (~3 m) lake lowering. Lowering the lake by 10 m shows a significant reduction in inundated area. However, lowering the lake by 20 m almost eliminates all flood impact at Dingboche. Further downstream at Phakding, the impact of the GLOF is significant and similar reductions in inundation are likely as a result of lake lowering.

  5. Potential effects of climate change on inland glacial lakes and implications for lake-dependent biota in Wisconsin: final report April 2013

    USGS Publications Warehouse

    Meyer, Michael W.; Walker, John F.; Kenow, Kevin P.; Rasmussen, Paul W.; Garrison, Paul J.; Hanson, Paul C.; Hunt, Randall J.

    2013-01-01

    F statewide, and an increase in precipitation of 1”–2”. However, summer precipitation in the northern part of the state is expected to be less and winter precipitation will be greater. By the end of the 21st century, the magnitude of changes in temperature and precipitation are expected to intensify. Such climatic changes have altered, and would further alter hydrological, chemical, and physical properties of inland lakes. Lake-dependent wildlife sensitive to changes in water quality, are particularly susceptible to lake quality-associated habitat changes and are likely to suffer restrictions to current breeding distributions under some climate change scenarios. We have selected the common loon (Gavia immer) to serve as a sentinel lake-dependent piscivorous species to be used in the development of a template for linking primary lake-dependent biota endpoints (e.g., decline in productivity and/or breeding range contraction) to important lake quality indicators. In the current project, we evaluate how changes in freshwater habitat quality (specifically lake clarity) may impact common loon lake occupancy in Wisconsin under detailed climate-change scenarios. In addition, we employ simple land-use/land cover and habitat scenarios to illustrate the potential interaction of climate and land-use/land cover effects. The methods employed here provide a template for studies where integration of physical and biotic models is used to project future conditions under various climate and land use change scenarios. Findings presented here project the future conditions of lakes and loons within an important watershed in northern Wisconsin – of importance to water resource managers and state citizens alike.

  6. Atmospheric production signal in 10Be from varved sediments of Lake Meerfelder Maar during the late glacial-early Holocene transition

    NASA Astrophysics Data System (ADS)

    Czymzik, Markus; Adolphi, Florian; Muscheler, Raimund; Brauer, Achim; Mekhaldi, Florian; Martin-Puertas, Celia; Tjallingii, Rik; Aldahan, Ala; Possnert, Göran

    2016-04-01

    Beryllium 10 concentrations (10Becon) were measured at 20-year resolution in annually laminated (varved) sediments of Lake Meerfelder Maar (western Germany) covering the late glacial-early Holocene transition 11310-13130 varve years before present. Comparing the 10Becon record to environmental proxy records from the same archive indicates that varying sediment accumulation and composition only slightly modify trends, but do not substantially influence multi-decadal to centennial 10Becon excursions. Corrected for potential environmental biases using multiple-regression analysis, the resulting 10Beatmosphere time-series likely represents an alternative mid-latitude 10Be production record, exhibiting broad similarities but also some differences to radionuclide records as 14C in tree rings and 10Be in polar ice cores. The preservation of the globally common atmospheric production signal in 10Be from varved lake sediments indicates the, to date, largely unexplored potential of these archives for the synchronization to other radionuclide records around the globe, complementing existing solar activity reconstructions and Sun-climate studies.

  7. Waterborne and on-land electrical surveys to suggest the geological evolution of a glacial lake in NW Italy

    NASA Astrophysics Data System (ADS)

    Colombero, Chiara; Comina, Cesare; Gianotti, Franco; Sambuelli, Luigi

    2014-06-01

    Geophysical surveys on and around the Candia Lake, located NE of Turin (NW Italy), in the internal depression of the Ivrea Morainic Amphitheater (IMA) right frontal sector, are reported in this paper. The surveys were intended to obtain a geophysical characterization of the lakebed, to investigate the interconnection paths between surface water and groundwater and to be used as a first general survey for suggesting the geological processes which lead to the actual morphology. An extensive waterborne continuous vertical electrical sounding (CVES) survey consisting of 15 profiles, with a total length of about 19 km of acquisition, was carried out on the lake surface. The processing of the acquired profiles with a laterally constrained inversion (LCI) approach lead to the reconstruction of the lakebed sediment distribution, down to 10 m depth. Self potential (SP) data recorded on the lake surface have also been analyzed. Moreover, to verify the areal distribution of the deposits, three electrical resistivity tomographies (ERTs) were carried out on land near the northern and southern shores of the lake. The combination of the geophysical survey results with hydrogeological information and geological observations and interpretations allowed the characterization of the submerged deposits, the probable identification of the main areas of groundwater recharge and the preliminary reconstruction of the lake genesis.

  8. Evidence for insolation and Pacific forcing of late glacial through Holocene climate in the Central Mojave Desert (Silver Lake, CA)

    NASA Astrophysics Data System (ADS)

    Kirby, Matthew E.; Knell, Edward J.; Anderson, William T.; Lachniet, Matthew S.; Palermo, Jennifer; Eeg, Holly; Lucero, Ricardo; Murrieta, Rosa; Arevalo, Andrea; Silveira, Emily; Hiner, Christine A.

    2015-09-01

    Silver Lake is the modern terminal playa of the Mojave River in southern California (USA). As a result, it is well located to record both influences from the winter precipitation dominated San Bernardino Mountains - the source of the Mojave River - and from the late summer to early fall North American monsoon at Silver Lake. Here, we present various physical, chemical and biological data from a new radiocarbon-dated, 8.2 m sediment core taken from Silver Lake that spans modern through 14.8 cal ka BP. Texturally, the core varies between sandy clay, clayey sand, and sand-silt-clay, often with abrupt sedimentological transitions. These grain-size changes are used to divide the core into six lake status intervals over the past 14.8 cal ka BP. Notable intervals include a dry Younger Dryas chronozone, a wet early Holocene terminating 7.8 - 7.4 cal ka BP, a distinct mid-Holocene arid interval, and a late Holocene return to ephemeral lake conditions. A comparison to potential climatic forcings implicates a combination of changing summer - winter insolation and tropical and N Pacific sea-surface temperature dynamics as the primary drivers of Holocene climate in the central Mojave Desert.

  9. Mendenhall Glacier (Juneau, Alaska) icequake seismicity and its relationship to the 2012 outburst flood and other environmental forcing

    NASA Astrophysics Data System (ADS)

    Morgan, P. M.; Walter, J. I.; Peng, Z.; Amundson, J. M.; Meng, X.

    2013-12-01

    Glacial outburst floods occur when ice-dammed lakes or other reservoirs on the glacier release large volumes of water usually due to the failure of an ice dam. In 2011 and 2012 these types of floods have occurred at Mendenhall Glacier in Southeast Alaska, 15 km northwest of Juneau. The floods emanated from a lake within a remnant branch of Mendenhall Glacier, called Suicide Basin, and rapidly changed the levels of Mendenhall Lake. Homes on the shore of Mendenhall Lake were threatened by rapidly rising lake levels during such floods. We analyze data from a set of 4 short and broadband period seismometers placed in ice-boreholes in an array on Mendenhall Glacier for a period of 4 months in 2012. We also examine the outburst flood that occurred between July 4th and 8th 2012. We first manually pick icequakes as high-frequency bursts recorded by at least two stations. Next, we use a matched-filter technique to help complete the icequake record by detecting missed events with similar waveforms to those hand-picked events. While high-frequency noise was present during the flooding, the impulsive icequake activity did not appear to be modulated significantly during periods of flooding, suggesting that the flooding does not significantly deform the overlying ice. Impulsive icequake activity appears to show strongly diurnal periodicity, indicating that the icequakes were mainly caused by expansion/contraction of ice during daytime. We also analyze the activity in concert with GPS velocity and meteorological data from the area. By analyzing the temporal and spatial patterns of the events we hope to reveal more about the fundamental processes occurring beneath Mendenhall Glacier.

  10. Three-Dimensional Simulation of Avalanche-Generated Impulse Waves and Evaluation of Lake-Lowering Scenarios at Lake Palcacocha, Peru

    NASA Astrophysics Data System (ADS)

    Chisolm, R. E.; McKinney, D. C.

    2014-12-01

    Accelerated retreat of Andean glaciers in recent decades due to a warming climate has caused the emergence and growth of glacial lakes. As these lakes continue to grow, they pose an increasing risk of glacial lake outburst floods (GLOFs). GLOFs can be triggered by moraine failures or by avalanches, rockslides, or ice calving into glacial lakes. For many decades Lake Palcacocha in the Cordillera Blanca, Peru has threatened citizens living in the city of Huaraz which was devastated by a GLOF in 1941. A safety system for Lake Palcacocha was put in place in the 1970's to control the lake level, but the lake has since grown to the point where it is once again dangerous. Overhanging ice from the glaciers above and a relatively low freeboard make the lake vulnerable to avalanches and landslides. Lake Palcacocha is used as a case study to investigate the impact of an avalanche event on the lake dynamics. Three-dimensional lake modeling in the context of glacial hazards is not common, but 3D simulations can enhance our understanding of avalanche-generated impulse waves and their downstream impacts. In this work, a 3D hydrodynamic model is used to simulate the generation of an impulse wave from an avalanche falling into the lake, wave propagation, and overtopping of the terminal moraine. These results are used as inputs to a downstream model to predict the impact from a GLOF. As lowering the level of the lake is the most likely mitigation alternative, several scenarios are considered to evaluate the impact from avalanche events with a reduction in the lake level. The results of this work can be used to evaluate the effectiveness of the current lake management system and potential lake-lowering alternatives. Use of a robust 3D lake model enables more accurate predictions of peak flows during GLOF events and the time scales of these events so that mitigation strategies can be developed that reduce the risk to communities living downstream of hazardous lakes.

  11. History of late glacial runoff from the southern Laurentide ice sheet in Indiana

    SciTech Connect

    Fraser, G.S. ); Fleming, A.H. )

    1992-01-01

    The history of late glacial runoff from the southern Laurentide ice sheet in Indiana is one of long periods of normal'' meltwater flow punctuated by extreme flows. Meltwater flow down the Wabash began about 26 ka when ice of the Lake Michigan lobe entered the headwaters of its northern and western tributaries. This flow was augmented by meltwater from the Huron-Erie lobe which entered the basin about 24 ka, and there ensued a period when normal meltwater flow and outwash sedimentation prevailed through successive advances from these two sources. This ended about 17 ka ( ) when two extreme flow events occurred. The first involved a subglacial breakout of stored water in a stagnating sheet of Erie-Huron lobe ice and the second occurred when a proglacial lake stored behind a Huron-Erie Lobe recessional moraine in northeastern Indiana drained catastrophically into the Wabash. A second period of normal flow and sedimentation followed as successive episodes of advance and active backwasting of Huron-Erie lobe ice left a series of recessional moraines in northeastern Indiana. Lake Maumee (of ancestral Lake Erie) formed behind the last of these, and the final extreme flow down the Wabash occurred about 14 ka ( ) when this moraine was breached. During the final stages of glaciation in Indiana, very large volumes of meltwater were supplied to the Illinois river system through the Kankakee sluiceway by both the Lake Michigan lobe and the Saginaw lobe. For the most part, these were not extreme flows, but catastrophic subglacial outburst(s) of water from the Lake Michigan lobe did occur about 13 ka ( ) along the Valparaiso Moraine. Most of this meltwater was directed down the Kankakee sluiceway and into the Illinois River, but some may have flowed around the east end of the iroquois Moraine and into the Wabash River.

  12. Semi-automted analysis of high-resolution aerial images to quantify docks in Upper Midwest glacial lakes

    USGS Publications Warehouse

    Beck, Marcus W.; Vondracek, Bruce C.; Hatch, Lorin K.; Vinje, Jason

    2013-01-01

    Lake resources can be negatively affected by environmental stressors originating from multiple sources and different spatial scales. Shoreline development, in particular, can negatively affect lake resources through decline in habitat quality, physical disturbance, and impacts on fisheries. The development of remote sensing techniques that efficiently characterize shoreline development in a regional context could greatly improve management approaches for protecting and restoring lake resources. The goal of this study was to develop an approach using high-resolution aerial photographs to quantify and assess docks as indicators of shoreline development. First, we describe a dock analysis workflow that can be used to quantify the spatial extent of docks using aerial images. Our approach incorporates pixel-based classifiers with object-based techniques to effectively analyze high-resolution digital imagery. Second, we apply the analysis workflow to quantify docks for 4261 lakes managed by the Minnesota Department of Natural Resources. Overall accuracy of the analysis results was 98.4% (87.7% based on ) after manual post-processing. The analysis workflow was also 74% more efficient than the time required for manual digitization of docks. These analyses have immediate relevance for resource planning in Minnesota, whereas the dock analysis workflow could be used to quantify shoreline development in other regions with comparable imagery. These data can also be used to better understand the effects of shoreline development on aquatic resources and to evaluate the effects of shoreline development relative to other stressors.

  13. Spatiotemporal patterns of high-mountain lakes and related hazards in western Austria

    NASA Astrophysics Data System (ADS)

    Emmer, Adam; Merkl, Sarah; Mergili, Martin

    2015-10-01

    Climate-induced environmental changes are triggering the dynamic evolution of high-mountain lakes worldwide, a phenomenon that has to be monitored in terms of lake outburst hazards. We analyzed the spatial distribution and recent temporal development of high-mountain lakes in a study area of 6139 km2, covering the central European Alps over most of the province of Tyrol and part of the province of Salzburg in western Austria. We identified 1024 natural lakes. While eight lakes are ice-dammed, one-third of all lakes are located in the immediate vicinity of recent glacier tongues, half of them impounded by moraines, half by bedrock. Two-thirds of all lakes are apparently related to LIA or earlier glaciations. One landslide-dammed lake was identified in the study area. The evolution of nine selected (pro)glacial lakes was analyzed in detail, using multitemporal remotely sensed images and field reconnaissance. Considerable glacier retreat led to significant lake growth at four localities, two lakes experienced stagnant or slightly negative areal trends, one lake experienced a more significant negative areal trend, and two lakes drained completely during the investigation period. We further (i) analyzed the susceptibility of selected lakes to glacial lake outburst floods (GLOFs), using two different methods; (ii) identified potential triggers and mechanisms of GLOFs; (iii) calculated possible flood magnitudes for predefined flood scenarios for a subset of the lakes; and (iv) delineated potentially impacted areas. We distinguished three phases of development of bedrock-dammed lakes: (a) a proglacial, (b) a glacier-detached, and (c) a nonglacial phase. The dynamics - and also the susceptibility of a lake to GLOFs - decrease substantially from (a) to (c). Lakes in the stages (a) and (b) are less prominent in our study area, compared to other glacierized high-mountain regions, leading us to the conclusion that (i) the current threat to the population by GLOFs is lower but

  14. Climate and human impacts on the vegetation in NW Turkey: palynological insights from Lake Iznik since the Last Glacial

    NASA Astrophysics Data System (ADS)

    Miebach, Andrea; Niestrath, Phoebe; Roeser, Patricia A.; Litt, Thomas

    2015-04-01

    The reconstruction of the climate and vegetation history of the Marmara region in northwestern Turkey is of particular interest because of its long occupation history and its location between different climate and vegetation zones. Geochemical and mineralogical investigations of the largest lake in the region, Lake Iznik, already registered climate related changes of the lake level and the lake mixing during the last 31 ka cal BP (Roeser 2014). However, a palynological investigation, encompassing the Late Pleistocene to Middle Holocene, was still missing. Here, we present the first pollen record of the last 31 ka cal BP from Lake Iznik sediments as an independent proxy for paleoecological reconstructions. Lake Iznik is situated east of the Marmara Sea. Its catchment area is located in a climatic transition zone between the Mediterranean and Pontic climate zones. Today, the region is highly influenced by (sub-) Euxinian temperate deciduous and mixed forests dominated by deciduous oak and beech. Coastal areas of the southeastern Marmara Sea and the Aegean Sea are dominated by (sub-) Mediterranean woods and shrubs with sclerophyllous and evergreen elements (Zohary 1973). The pollen record of Lake Iznik reflects typical Eastern Mediterranean vegetation pattern and northern hemispheric climate changes. In contrast to the recent vegetation, a steppe vegetation dominated during the Late Pleistocene. In response to Dansgaard-Oeschger events, the vegetation changed rapidly into a steppe-forest. A remarkable expansion of deciduous oak forest, indicating warmer temperatures, is registered since the Bölling-Alleröd. A short period of dryer and/or cooler climate, corresponding to the Younger Dryas, is marked by an increase of steppe components and by a decrease of several trees. Deciduous oaks predominated the vegetation since the Early Holocene. They were successively accompanied by cold temperate, warm temperate, and Mediterranean trees. In addition to the climate impact

  15. Post-glacial inflation-deflation cycles, tilting, and faulting in the Yellowstone Caldera based on Yellowstone Lake shorelines

    USGS Publications Warehouse

    Pierce, Kenneth L.; Cannon, Kenneth P.; Meyer, Grant A.; Trebesch, Matthew J.; Watts, Raymond D.

    2002-01-01

    The Yellowstone caldera, like many other later Quaternary calderas of the world, exhibits dramatic unrest. Between 1923 and 1985, the center of the Yellowstone caldera rose nearly one meter along an axis between its two resurgent domes (Pelton and Smith, 1979, Dzurisin and Yamashita, 1987). From 1985 until 1995-6, it subsided at about two cm/yr (Dzurisin and others, 1990). More recent radar interferometry studies show renewed inflation of the northeastern resurgent dome between 1995 and 1996; this inflation migrated to the southwestern resurgent dome from 1996 to 1997 (Wicks and others, 1998). We extend this record back in time using dated geomorphic evidence of postglacial Yellowstone Lake shorelines around the northern shore, and Yellowstone River levels in the outlet area. We date these shorelines using carbon isotopic and archeological methods. Following Meyer and Locke (1986) and Locke and Meyer (1994), we identify the modern shoreline as S1 (1.9 ? 0.3 m above the lake gage datum), map paleoshoreline terraces S2 to S6, and infer that the prominent shorelines were cut during intracaldera uplift episodes that produced rising water levels. Doming along the caldera axis reduces the gradient of the Yellowstone River from Le Hardys Rapids to the Yellowstone Lake outlet and ultimately causes an increase in lake level. The 1923-1985 doming is part of a longer uplift episode that has reduced the Yellowstone River gradient to a ?pool? with a drop of only 0.25 m over most of this 5 km reach. We also present new evidence that doming has caused submergence of some Holocene lake and river levels. Shoreline S5 is about 14 m above datum and estimated to be ~12.6 ka, because it post-dates a large hydrothermal explosion deposit from the Mary Bay area (MB-II) that occurred ~13 ka. S4 formed about 8 m above datum ~10.7 ka as dated by archeology and 14C, and was accompanied by offset on the Fishing Bridge fault. About 9.7 ka, the Yellowstone River eroded the ?S-meander?, followed

  16. The Last Glacial Maximum at 44°S documented by a 10Be moraine chronology at Lake Ohau, Southern Alps of New Zealand

    NASA Astrophysics Data System (ADS)

    Putnam, Aaron E.; Schaefer, Joerg M.; Denton, George H.; Barrell, David J. A.; Birkel, Sean D.; Andersen, Bjørn G.; Kaplan, Michael R.; Finkel, Robert C.; Schwartz, Roseanne; Doughty, Alice M.

    2013-02-01

    Determining whether glaciers registered the classic Last Glacial Maximum (LGM; ˜26,500-˜19,000 yrs ago) coevally between the hemispheres can help to discriminate among hypothesized drivers of ice-age climate. Here, we present a record of glacier behavior from the Southern Alps of New Zealand during the 'local LGM' (LLGM). We used 10Be surface-exposure dating methods and detailed glacial geomorphologic mapping to produce a robust chronology of well-preserved terminal moraines deposited during the LLGM near Lake Ohau on central South Island. We then used a glaciological model to estimate a LLGM glacier snowline and atmospheric temperature from the Ohau glacier record. Seventy-three 10Be surface-exposure ages place culminations of terminal moraine construction, and hence completions of glacier advances to positions outboard of present-day Lake Ohau, at 138,600 ± 10,600 yrs, 32,520 ± 970 yrs ago, 27,400 ± 1300 yrs ago, 22,510 ± 660 yrs ago, and 18,220 ± 500 yrs ago. Recessional moraines document glacier recession into the Lake Ohau trough by 17,690 ± 350 yrs ago. Exposure of an ice-molded bedrock bench located inboard of the innermost LLGM moraines by 17,380 ± 510 yrs ago indicates that the ice tongue had receded about 40% of its overall length by that time. Comparing our chronology with distances of retreat suggests that the Ohau glacier terminus receded at a mean net rate of about 77 m yr-1 and its surface lowered by 200 m between 17,690 and 17,380 yrs ago. A long-term continuation of ice retreat in the Ohau glacier catchment is implied by moraine records at the head of Irishman Stream valley, a tributary of the Ohau glacier valley. The Irishman Stream cirque glacier advanced to produce a set of Lateglacial moraines at 13,000 ± 500 yrs ago, implying that the cirque glacier was less extensive prior to that advance. We employed a glaciological model, fit to these mapped and dated LLGM moraines, to derive snowline elevations and temperature parameters from the

  17. Lake Clark fault, assessment of tectonic activity based on reconnaissance mapping of glacial deposits, northwestern Cook Inlet Alaska

    NASA Astrophysics Data System (ADS)

    Reger, R. D.; Koehler, R. D.

    2009-12-01

    The Lake Clark fault extends ~247 km from the vicinity of Lake Clark in the Alaska-Aleutian Range batholith northeastward to the Castle Mountain fault along the northern margin of Cook Inlet. Documented Tertiary deformation along the fault includes dextral offsets (5-26 km) and north-side-up reverse displacements (500-1,000 m). The fault is along strike with the Holocene-active Castle Mountain fault and adjacent to the active northern Cook Inlet fold belt. As part of the STATEMAP program, the State of Alaska has begun a 2-year geologic mapping project in the vicinity of the Lake Clark fault, including assessment of Quaternary fault activity and its role in accommodating deformation in the Aleutian forearc. Here we present preliminary Quaternary mapping and tectonic geomorphic observations aimed at assessing the fault activity. Between the Beluga and Chakachatna rivers, large lateral moraines of the late Wisconsinan Naptowne glaciation cross the fault and are not displaced. In the vicinity of Lone Ridge, the fault is expressed as a ~25-m southeast-facing scarp in bedrock associated with springs and vertically offset Stage 4 or 6 moraines. In the Chuitna River drainage basin beyond the Naptowne ice limit, the fault extends across a fairly flat plateau with drumlins and ice-stagnation deposits related to Stage 4 or 6 glaciation. There the fault is expressed by subtle vegetation and tonal lineaments on air photos; however, scarps and lateral offsets were not observed. Stream profiles perpendicular to the fault along the Chuitna River and Chuitna Creek have convex profiles that could be related to tectonic folding. Our observations indicate that this part of the Lake Clark fault may be Quaternary active, but has been relatively quiescent in the late Pleistocene. Thus, blind thrust faults associated with the northern Cook Inlet fold belt may accommodate the majority of the tectonic deformation in this part of the Aleutian forearc. This information is applicable to

  18. Modelling the influence of Lake Agassiz on Glacial Isostatic Adjustment and deglaciation of the Laurentide ice sheet

    NASA Astrophysics Data System (ADS)

    Berends, Tijn; van de Wal, Roderik; de Boer, Bas; Bradley, Sarah

    2016-04-01

    ANICE is a 3-D ice-sheet-shelf model, which simulates ice dynamics on the continental scale. It uses a combination of the SIA and SSA approximations and here it is forced with benthic δ18O records using an inverse routine. It is coupled to SELEN, a model, which solves the gravitationally self-consistent sea-level equation and the solid earth deformation of a spherically symmetrical rotating Maxwell visco-elastic earth, accounting for all major GIA effects. The coupled ANICE-SELEN model thus captures ice-sea-level feedbacks and can be used to accurately simulate variations in local relative sea-level over geological time scales. In this study it is used to investigate the mass loss of the Laurentide ice-sheet during the last deglaciation, accounting in particular for the presence of the proglacial Lake Agassiz by way of its GIA effects and its effect on the ice sheet itself. We show that the mass of the water can have a significant effect on local relative sea-level through the same mechanisms as the ice-sheet - by perturbing the geoid and by deforming the solid earth. In addition we show that calving of the ice-shelf onto the lake could have had a strong influence on the behaviour of the deglaciation. In particular, when allowing lake calving, the ice-sheet retreats rapidly over the deepening bed of Hudson Bay during the deglaciation, resulting in a narrow ice dam over Hudson Strait. This dam collapses around 8.2 Kyr causing a global sea level rise of approximately 1 meter - an observation that agrees well with field data (for example, LaJeunesse and St. Onge, 2008). Without lake calving the model predicts a drainage towards the Arctic ocean in the North.

  19. Morphological determinants of the course of laminated sedimentation in the basin of Lake Czechowskie (northern Poland) in the Late Glacial and Holocene

    NASA Astrophysics Data System (ADS)

    Kramkowski, Mateusz; Kordowski, Jarosław; Tyszkowski, Sebastian; Błaszkiewicz, Mirosław

    2014-05-01

    The analyses of the annually laminated lacustrine sediments are particularly important in the studies of global climate change. They provide information about the ecosystem response to environmental and climate changes. The condition for the laminated sedimentation with the annual resolution is the calm sedimentation environment where there is no mixing and thus there are anaerobic conditions in the benthic zone. Water mixing occurs mainly as a result of weather factors such as wind and temperature. Below a certain depth water does not undergo mixing evoked by waves and also has a constant temperature which causes its stagnation. In shallower areas such conditions are favoured by the morphology of the lake basin and the long presence of ice cover (bradymictic). The combination of these environmental features predispose to the deposition of laminated sediments. Lake Czechowskie is situated in a deep kettle-hole type basin in the marginal zone of the maximum range of the Pomeranian Phase of the last Weichselian ice sheet. Taking into account the thickness of the lacustrine sediments, the maximum depth of the basin exceeds 70 m. Detailed surveying as well as geological drilling using the GIS techniques made it possible to reconstruct the morphology of the basin of Lake Czechowskie and its adjacent areas back to the state from before the biogenic sedimentation started in Allerød. The analysis of the morphology of the lake basin becomes the basis for modelling the sedimentation conditions considering, inter alia, the wind direction and velocity, fluctuations in water levels and the degree of filling the basin with the deposits in different periods of the Late Glacial and Holocene. It allows specifying the variability and sedimentation rate within the basin. The analysis shows the spatial variation of erosion and accumulation zones, and enables to determine the zones of quiet sedimentation revealing places particularly predisposed to accumulate annually laminated

  20. Complex patterns of glacier advances during the late glacial in the Chagan Uzun Valley, Russian Altai

    NASA Astrophysics Data System (ADS)

    Gribenski, Natacha; Jansson, Krister N.; Lukas, Sven; Stroeven, Arjen P.; Harbor, Jonathan M.; Blomdin, Robin; Ivanov, Mikhail N.; Heyman, Jakob; Petrakov, Dmitry A.; Rudoy, Alexei; Clifton, Tom; Lifton, Nathaniel A.; Caffee, Marc W.

    2016-10-01

    The Southern part of the Russian Altai Mountains is recognized for its evidence of catastrophic glacial lake outbursts. However, little is known about the late Pleistocene paleoglacial history, despite the interest in such reconstructions for constraining paleoclimate. In this study, we present a detailed paleoglaciological reconstruction of the Chagan Uzun Valley, in the Russian Altai Mountains, combining for the first time detailed geomorphological mapping, sedimentological logging, and in situ cosmogenic 10Be and 26Al surface exposure dating of glacially-transported boulders. The Chagan Uzun Valley exhibits the most impressive glacial landforms of this sector of the Altai, with extensive lobate moraine belts deposited in the intramontane Chuja Basin, reflecting a series of pronounced former glacial advances. Observations of "hillside-scale" folding and extensive faulting of pre-existing soft sediments within the outer moraine belts, together with the geomorphology, strongly indicate that these moraine belts were formed during surge-like events. Identification of surge-related features is essential for paleoclimate inference because these features correspond to a glacier system that is not in equilibrium with the contemporary climate, but instead largely influenced by various internal and external factors. Therefore, no strict relationship can be established between climatic variables and the pronounced distal glacial extent observed in the Chagan Uzun Valley/Chuja basin. In contrast, the inner (up-valley) glacial landforms of the Chagan Uzun valley were likely deposited during retreat of temperate valley glaciers, close to equilibrium with climate, and so most probably triggered by a general warming. Cosmogenic ages associated with the outermost, innermost, and intermediate moraines all indicate deposition times clustered around 19 ka. However, the actual deposition time of the outermost moraine may slightly predate the 10Be ages due to shielding caused by

  1. Unusual configuration of the Devonian-Pleistocene unconformity in the Susquehanna Valley, Oneonta, New York: Evidence for a subglacial meltwater inlet to glacial Lake Otego

    SciTech Connect

    Kucewicz, J. Jr.; Ebert, J.; Rasquin, C.; Sherman, R.; Nethaway, R.; Gardner, J.; Milunich, K.; Weber, J.; Wohlford, T.; Franz, J.; Brillon, S. . Dept. of Earth Sciences)

    1993-03-01

    A recently drilled test well and nearby abandoned bore hole have revealed anomalously shallow bedrock in a portion of the Susquehanna Valley near Oneonta, New York. Gravimetric and seismic refraction studies were conducted in the area to better delineate the Devonian--Pleistocene unconformity. On the northern flank of the valley, geophysical surveys indicate the presence of a shallowly buried bedrock shelf that is rimmed by a bedrock ridge. South of the ridge, bedrock drops abruptly beneath the thickening valley fill. This configuration contradicts predictions based upon projection of the valley walls to a classic U shape. These unusual features coincide with an extremely narrow portion of the valley, a recessional moraine and other stagnant ice features. The bedrock shelf may represent the initial glaciated valley floor. Incision of the valley floor below this surface can be attributed to scour by subglacial meltwaters at a nick point. As such, the narrow, deepest part of the bedrock valley may represent a subglacial inlet to glacial Lake Otego.

  2. Orbital forcing of glacial/interglacial variations in chemical weathering within the White Nile basin: stable-isotope and biomarker evidence from Lakes Victoria and Edward

    NASA Astrophysics Data System (ADS)

    Cockerton, Helen E.; Alayne Street-Perrott, F.; Barker, Philip A.; Leng, Melanie J.; Sloane, Hilary J.; Horstwood, Matthew S. A.; Snelling, Andrea

    2014-05-01

    The continental Si cycle on Quaternary time scales has been largely neglected. Emphasis has been placed on long-term geochemical processes of silicate-rock weathering and the resulting drawdown of atmospheric CO2, rather than on shorter-term biogenic processes occurring along the land-ocean continuum. Si-accumulating plants (notably tropical rainforest hardwoods, savanna and wetland grasses, and Papyrus) and aquatic organisms (such as diatoms and sponges in lakes, rivers and swamps) have the potential to take up, store and recycle significant amounts of Si, thereby modifying the riverine flux of Si to the oceans, the productivity of siliceous marine organisms and the rate of atmospheric CO2 drawdown on an orbital time scale. The main aim of this study was to investigate spatial and temporal patterns of Si cycling along the Nile system during the last 20ka BP. Utilising sediment cores from Lakes Victoria and Edward, coupled measurements of stable Si and O isotopes on cleaned diatom separates were employed to reconstruct millennial-scale variations in biotic Si cycling and palaeohydrology, respectively. Abundance ratios of lipid biomarkers (n-alkanes) were used to track major changes in terrestrial and aquatic ecosystems. The results have been interpreted in the light of multi-isotope analyses (2H,18O,30Si) of modern water samples collected along the courses of the modern White and Blue Niles during both wet- and dry-season conditions. During drier intervals (the Last Glacial Maximum and the late Holocene: high 18Odiatom), Si cycling was greatly reduced. Diminished vegetation cover, reduced biotic rock weathering, a declining soil stock of amorphous silica (ASi) and decreased runoff resulted in reduced dissolved silica (DSi) supply to the lakes in relation to aquatic demand (high 30Sidiatom). In contrast, enhanced monsoon rainfall (low 18Odiatom) during the early to mid-Holocene promoted a substantial increase in terrestrial biomass within the White Nile headwaters

  3. Controlling factors on a paleo-lake oxygen isotope record (Yammoûneh, Lebanon) since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Develle, Anne-Lise; Herreros, Julien; Vidal, Laurence; Sursock, Alexandre; Gasse, Françoise

    2010-04-01

    Late Quaternary paleoclimatic changes in the Levant are difficult to extract from carbonate oxygen isotope records partly because the factors controlling the terrestrial δ 18O signals are not fully understood in this region characterized by sharp climatic gradients. Here, we address this purpose by presenting the first 14C-dated isotope record from the northern Levant. The record is based on oxygen isotopes from ostracod shells from lacustrine-palustrine deposits accumulated in a small karstic, hydrologically open basin (Yammoûneh), located on the eastern flank of Mount Lebanon. We have first constructed a composite isotopic record obtained from three different ostracod taxa. This yields an oxygen isotope record of ostracods (δ ost) related to the most widespread species ( Ilyocypris inermis), and converted to δ 18O values coeval with calcite precipitated in equilibrium (δ C) with the lake water (δ L). As with other records from the Mediterranean region, the Yammoûneh profile shows maximum and minimum δ C values during the LGM and the early Holocene, respectively, and a slight late Holocene increase. In order to discuss the potential causes of the observed δ 18O values fluctuations (e.g., changes in the isotopic composition of the moisture source, temperature, precipitation minus evaporation (P-E) balance, or atmospheric circulation), we tentatively reconstruct the lake water isotope composition by correcting the δ C values for lake water temperature using regional paleotemperature estimates. Inferred δ L values were then corrected for the isotopic composition of the Eastern Mediterranean sea surface water (the moisture source) derived from planktonic foraminifera δ 18O values corrected for alkenone-based sea surface temperature. Our study suggests that Holocene δ L fluctuations are primarily linked to changes in the sea surface water composition (source effect) amplified by enhanced inland rainfall during the early Holocene. During the LGM, low δ L

  4. Glacial history and runoff components of the Tlikakila River Basin, Lake Clark National Park and Preserve, Alaska

    USGS Publications Warehouse

    Brabets, Timothy P.; March, Rod S.; Trabant, Dennis C.

    2004-01-01

    The Tlikakila River is located in Lake Clark National Park and Preserve and drains an area of 1,610 square kilometers (622 square miles). Runoff from the Tlikakila River Basin accounts for about one half of the total inflow to Lake Clark. Glaciers occupy about one third of the basin and affect the runoff characteristics of the Tlikakila River. As part of a cooperative study with the National Park Service, glacier changes and runoff characteristics in the Tlikakila River Basin were studied in water years 2001 and 2002. Based on analyses of remote sensing data and on airborne laser profiling, most glaciers in the Tlikakila River Basin have retreated and thinned from 1957 to the present. Volume loss from 1957-2001 from the Tanaina Glacier, the largest glacier in the Tlikakila River Basin, was estimated to be 6.1 x 109 cubic meters or 1.4 x 108 cubic meters per year. For the 2001 water year, mass balance measurements made on the three largest glaciers in the Tlikakila River BasinTanaina, Glacier Fork, and North Forkall indicate a negative mass balance. Runoff measured near the mouth of the Tlikakila River for water year 2001 was 1.70 meters. Of this total, 0.18 meters (11 percent) was from glacier ice melt, 1.27 meters (75 percent) was from snowmelt, 0.24 meters (14 percent) was from rainfall runoff, and 0.01 meters (1 percent) was from ground water. Although ground water is a small component of runoff, it provides a critical source of warm water for fish survival in the lower reaches of the Tlikakila River.

  5. Arctic Temperature and Moisture Variability Associated with the Pliocene M2 Glacial Event from Lake El'gygytgyn, NE Russia

    NASA Astrophysics Data System (ADS)

    Salacup, J. M.; Castañeda, I. S.; Brigham-Grette, J.

    2014-12-01

    The early Late Pliocene (3.6-3.0 Ma) is the last time atmospheric CO2 concentrations equaled today's values (~400 ppm). Despite this, and the warmer than modern climate it fostered, this period experienced an intense global glaciation during marine isotope stage (MIS) M2 (~3.3 Ma). Constraints imposed by the estimated sea level drop associated with this event suggest ice growth was not isolated to Antarctica, as had previously been the case, but that ice grew in high northern latitudes as well. M2 is unique during the Pliocene and is likely the first attempt of Northern Hemisphere ice sheets to grow into those experienced during Pleistocene ice ages. However, the effects of MIS M2, and any attendant Northern Hemisphere ice sheets, on Arctic terrestrial temperature and hydrology are not well understood. Here we present and compare results from the biomarker-based MBT/CBT paleotemperature proxy with δDleaf wax results, sensitive to both temperature hydrology, from Lake El'gygytgyn (NE Russia) in an attempt to isolate and characterize variability in both air temperature and moisture source/availability. We compare our results with more coarsely resolved preexisting pollen-based temperature and moisture reconstructions. Our temperature reconstruction is, as far as we know, the highest resolution terrestrial record of this dramatic global cooling event. It implies a ~6°C cooling circa 3.29 Ma was accomplished in two steps before a rebound of ~7°C into the start of the mid-Pliocene Warm Period. Removal of the temperature effect from M2 δDleaf wax profiles using our MBT/CBT results provide insight into changes in local hydrology during this event that are compared with pollen-based estimates of minimum, maximum, and mean annual precipitation in order to discuss changes in amount and seasonality of moisture delivery to Lake El'gygytgyn (NE Russia) during the expansion of Northern Hemisphere ice sheets.

  6. Eastern Mediterranean hydroclimate over the late glacial and Holocene, reconstructed from the sediments of Nar lake, central Turkey, using stable isotopes and carbonate mineralogy

    NASA Astrophysics Data System (ADS)

    Dean, Jonathan R.; Jones, Matthew D.; Leng, Melanie J.; Noble, Stephen R.; Metcalfe, Sarah E.; Sloane, Hilary J.; Sahy, Diana; Eastwood, Warren J.; Roberts, C. Neil

    2015-09-01

    There is a lack of high-resolution records of hydroclimate variability in the Eastern Mediterranean from the late glacial and early Holocene. More knowledge of the speed of climate shifts and the degree to which they were synchronous with changes in the North Atlantic or elsewhere is required to understand better the controls on Eastern Mediterranean climate. Using endogenic carbonate from a sediment sequence from Nar Gölü, a maar lake in central Turkey, dated by varve counting and uranium-thorium methods, we present high-resolution (˜25 years) oxygen (δ18O) and carbon isotope records, supported by carbonate mineralogy data, spanning the late glacial and Holocene. δ18Ocarbonate at Nar Gölü has been shown previously to be a strong proxy for regional water balance. After a dry period (i.e. evaporation far exceeding precipitation) in the Younger Dryas, the data show a transition into the relatively wetter early Holocene. In the early Holocene there are two drier periods that appear to peak at ˜9.3 ka and ˜8.2 ka, coincident with cooling 'events' seen in North Atlantic records. After this, and as seen in other records from the Eastern Mediterranean, there is a millennial-scale drying trend through the Mid Holocene Transition. The relatively dry late Holocene is punctuated by centennial-scale drought intervals, at the times of 4.2 ka 'event' and Late Bronze Age societal 'collapse'. Overall, we show that central Turkey is drier when the North Atlantic is cooler, throughout this record and at multiple timescales, thought to be due to a weakening of the westerly storm track resulting from reduced cyclogenesis in the North Atlantic. However, some features, such as the Mid Holocene Transition and the fact the early Holocene dry episodes at Nar Gölü are of a longer duration than the more discrete 'events' seen in North Atlantic records, imply there are additional controls on Eastern Mediterranean hydroclimate.

  7. Changes in Precipitation Sources over Glacial/Interglacial MIS 11 and 12 Examined by Δ17O of SiO2 Obtained from Diatoms along the Valles Caldera Lake Core, NM

    NASA Astrophysics Data System (ADS)

    Gibbons, J.; Sharp, Z. D.; Fawcett, P. J.

    2015-12-01

    Quantitative estimates of the isotopic composition of paleo-lake water have been made using 18O/16O (ẟ18O) in diatom silica (Dodd and Sharp, GCA, 2010). Post-mortem diatom silica equilibrates with ambient lake water within six months, chronicling the bulk oxygen isotope composition of the lake and resulting in silica that is near the quartz-water fractionation line (Dodd et al, GGG, 2012). The δ18O values of lacustrine diatoms from the Valles Caldera, NM, vary by ~25‰ between glacial and interglacial periods and suggest a collapse of the summer monsoon that currently provides 50% of the modern precipitation in NM. Triple oxygen isotope measurements of diatom silica may serve as a proxy for the isotopic composition of the lake water and as an estimate of paleo-humidity over the precipitation source. The deuterium excess parameter (d= ẟD - 8 ẟ18O) has been used along ice cores as a source relative humidity index, but is difficult to make in lake sediments. Instead, high precision 17O-excess (∆17O) measurements (=ẟ17O - 0.528 ẟ18O) may provide paleo-humidity information. Landais et al. (GRL, 2008) found a ∆17O difference of 0.02‰ in the Vostok ice core between glacial and interglacial times, interpreted as a function of changing relative humidity of the precipitation source. A 0.03‰ change was observed in glacial (∆17O=-0.22‰) and interglacial (∆17O=-0.19‰) diatom silica along the Valles Caldera lake core. Further information regarding the δ18O value of meteoric water can be calculated from paired δ18O-δ17O measurements. The combined δ18O-δ17O values of interglacial diatoms suggest a δ18Ometeoric water value of -9‰. Modern δ18O value of monsoonal precipitation in NM is ~-10‰. The δ18O of glacial diatoms suggest a δ18Ometeoric water = -20‰. Modern δ18O value of winter precipitation in NM is ~-20‰. These results suggest that the seasonality of precipitation in New Mexico can be inferred based on changes in the relative

  8. Spatial distribution and temporal development of high-mountain lakes in western Austria

    NASA Astrophysics Data System (ADS)

    Merkl, Sarah; Emmer, Adam; Mergili, Martin

    2015-04-01

    Glacierized high-mountain environments are characterized by active morphodynamics, favouring the rapid appearance and disappearance of lakes. On the one hand, such lakes indicate high-mountain environmental changes such as the retreat of glaciers. On the other hand, they are sometimes susceptible to sudden drainage, leading to glacial lake outburst floods (GLOFs) putting the downstream population at risk. Whilst high-mountain lakes have been intensively studied in the Himalayas, the Pamir, the Andes or the Western Alps, this is not the case for the Eastern Alps. A particular research gap, which is attacked with the present work, concerns the western part of Austria. We consider a study area of approx. 6,140 km², covering the central Alps over most of the province of Tyrol and part of the province of Salzburg. All lakes ≥250 m² located higher than 2000 m asl are mapped from high-resolution Google Earth imagery and orthophotos. The lakes are organized into seven classes: (i) ice-dammed; near-glacial (ii) moraine-dammed and (iii) bedrock-dammed; (iv) moraine-dammed and (v) bedrock-dammed distant to the recent glaciers; (vi) landslide-dammed; (vii) anthropogenic. The temporal development of selected lakes is investigated in detail, using aerial photographs dating back to the 1950s. 1045 lakes are identified in the study area. Only eight lakes are ice-dammed (i). One third of all lakes is located in the immediate vicinity of recent glacier tongues, half of them impounded by moraine (ii), half of them by bedrock (iii). Two thirds of all lakes are impounded by features (either moraines or bedrock) shaped by LIA or Pleistocenic glaciers at some distance to the present glacier tongues (iv and v). Only one landslide-dammed lake (vi) is identified in the study area, whilst 21 lakes are of anthropogenic origin (vii). 72% of all lakes are found at 2250-2750 m asl whilst less than 2% are found above 3000 m asl. The ratio of rock-dammed lakes increases with increasing

  9. Post-glacial Evolution and Human Alteration of Two Contrasting Riverine Landscapes

    NASA Astrophysics Data System (ADS)

    Beechie, T. J.; Pess, G. R.; Imaki, H.

    2011-12-01

    Historical reconstructions of pre-settlement landscapes and geomorphic processes in two Pacific Northwest USA river basins highlight long-term processes that constrain the potential of the modern-day riverscape, as well as an understanding of how land uses have altered today's habitats for Pacific salmon. Following retreat of the continental ice sheet (~14,000 ybp), the Skagit River incised several hundred meters into valley-filling glacial sediments, creating a series of terraces bounding a wide floodplain with a rich diversity of salmon habitats. By contrast, much of the Columbia River basin was not glaciated, and glacial outburst floods from Lake Missoula scoured the Columbia plateau and left deep silt deposits in several tributary basins, creating wide floodplains and groundwater-fed salmon habitats. These glacial histories constrain riverine habitat potential and genetic diversity of salmon in both basins, and also predispose each landscape to specific patterns of resource use. Since the mid-1800s, diking and ditching of floodplain and delta streams of the Skagit basin has obliterated more than 50% of salmon rearing habitat, but the arid Columbia basin has been most altered by construction of 18 large dams that produce hydropower and irrigate more than 2700 km2 of former sagebrush steppe. We illustrate how intensive river management in both basins has shifted the riverscape away from diverse habitats maintained by natural disturbance regimes to simplified habitats and dampened disturbance regimes.

  10. Microbial Community Structure and Activity Linked to Contrasting Biogeochemical Gradients in Bog and Fen Environments of the Glacial Lake Agassiz Peatland

    PubMed Central

    Lin, X.; Green, S.; Tfaily, M. M.; Prakash, O.; Konstantinidis, K. T.; Corbett, J. E.; Chanton, J. P.; Cooper, W. T.

    2012-01-01

    The abundances, compositions, and activities of microbial communities were investigated at bog and fen sites in the Glacial Lake Agassiz Peatland of northwestern Minnesota. These sites contrast in the reactivity of dissolved organic matter (DOM) and the presence or absence of groundwater inputs. Microbial community composition was characterized using pyrosequencing and clone library construction of phylogenetic marker genes. Microbial distribution patterns were linked to pH, concentrations of dissolved organic carbon and nitrogen, C/N ratios, optical properties of DOM, and activities of laccase and peroxidase enzymes. Both bacterial and archaeal richness and rRNA gene abundance were >2 times higher on average in the fen than in the bog, in agreement with a higher pH, labile DOM content, and enhanced enzyme activities in the fen. Fungi were equivalent to an average of 1.4% of total prokaryotes in gene abundance assayed by quantitative PCR. Results revealed statistically distinct spatial patterns between bacterial and fungal communities. Fungal distribution did not covary with pH and DOM optical properties and was vertically stratified, with a prevalence of Ascomycota and Basidiomycota near the surface and much higher representation of Zygomycota in the subsurface. In contrast, bacterial community composition largely varied between environments, with the bog dominated by Acidobacteria (61% of total sequences), while the Firmicutes (52%) dominated in the fen. Acetoclastic Methanosarcinales showed a much higher relative abundance in the bog, in contrast to the dominance of diverse hydrogenotrophic methanogens in the fen. This is the first quantitative and compositional analysis of three microbial domains in peatlands and demonstrates that the microbial abundance, diversity, and activity parallel with the pronounced differences in environmental variables between bog and fen sites. PMID:22843538

  11. Formation of mega-scale glacial lineations on the Dubawnt Lake Ice Stream bed: 1. size, shape and spacing from a large remote sensing dataset

    NASA Astrophysics Data System (ADS)

    Stokes, C. R.; Spagnolo, M.; Clark, C. D.; Ó Cofaigh, C.; Lian, O. B.; Dunstone, R. B.

    2013-10-01

    Mega-scale glacial lineations (MSGLs) are the largest flow parallel bedforms produced by ice sheets and are formed beneath rapidly-flowing ice streams. Knowledge of their characteristics and genesis is likely to result in an improved understanding of the rate at which ice and sediment are discharged by ice sheets, but there is little consensus as to how they are formed and there are few quantitative datasets of their characteristics with which to formulate or test hypotheses. This paper presents the results of a remote sensing survey of ˜46,000 bedforms on the Dubawnt Lake palaeo-ice stream bed, focussing on a central transect of 17,038 that includes highly elongate bedforms previously described as MSGLs. Within this transect, lineations exceed 10 km in length (max. >20 km) and 23% have elongation ratios >10:1 (max. 149:1). Highly elongate features are interspersed with much shorter drumlin-like features, but longer bedforms are typically narrower, suggesting that their length develops more quickly than, or at the expense of, their width. Bedforms are broadly symmetrical in plan-form and have a preferred lateral spacing of 50-250 m, which implies a regular, rather than random, pattern of corrugations. Comparison with drumlins reveals that the more attenuated MSGLs simply extend the 'tail' of the distribution of data, rather than plotting as a separate population. Taken together, this supports the idea of a subglacial bedform continuum primarily controlled by ice velocity, but existing hypotheses of MSGL formation are either not supported, or are insufficiently developed to explain our observations. Rather, we conclude that, under conditions of rapid ice flow, MSGLs attain their great length relatively quickly (decades) through a probable combination of subglacial deformation, which attenuates ridges, and erosional processes that removes material from between them.

  12. Time-series analysis for the episodic production and transport of methane from the Glacial Lake Agassiz peatlands, northern Minnesota. Final report

    SciTech Connect

    Siegel, D.I.

    1998-01-01

    The large peat basins of North America are an important reservoir in the global carbon cycle and a significant source of atmospheric methane. The authors investigated carbon cycling in the Glacial Lake Agassiz peatlands (GLAP) of Minnesota. Initially in 1990, they identified a dramatic change in the concentration of methane in the pore-waters of the raised bogs in the GLAP during an extreme drought. This methane dissipated when the drought broke in 1991 and the occurrence of deep methane is related to changes in the direction of groundwater flow in the peat column. The production of methane and its diffusive loss to the atmosphere was modeled and was about 10 times less than that measured directly in chambers at the land surface. It is clear from the reversals in hydraulic heat, changes in pore-water chemical composition over time, and paleostratigraphic markers, that regional ground water flow systems that are controlled by climate change are unexpectedly a major control over methanogenesis and carbon cycling in GLAP. Seismic profiles made showed that buried bedrock ridges particularly deflect regional groundwater flow upwards towards the land surface and towards raised bog landforms. In addition, high-resolution GPS measurements from data stations funded by this DOE project have shown this year that the peakland land surface elevation changes daily on a scale of cms, and seasonally on a scale of 10s of cm. This most recent observation is exciting because it may reflect episodic degassing of free phase methane from the peat column to the atmosphere, a source for methane previously unaccounted for by methane researchers.

  13. Development and characteristics of alpine lakes in the upper catchment of the Amu Darya river, Central Asia

    NASA Astrophysics Data System (ADS)

    Müller, J. P.; Mergili, M.; Schneider, J. F.

    2012-04-01

    The Amu Darya is one of the most important rivers in the lowlands of Central Asia, ensuring the supply of irrigation water for agriculture in that arid region. Control of the water flow due to hydropower generation in Tajikistan (Norak Dam, planned Rogun Dam) is a highly political issue. The sources of the Amu Darya are located in the glacierized high-mountain areas of Tajikistan, Kyrgyzstan and Afghanistan (Pamir, Alai and Hindukush mountains). These environments are highly dynamic systems particularly sensitive to climate fluctuations and changes. During the previous decades, numerous lakes have developed or enlarged in the forefields of the retreating glaciers. Other lakes in the area are embedded in older glacial landscapes or retained by rocky swells, block or debris dams. The latter two types of dams are usually formed by landslides or moraines, Usoi Dam impounding lake Sarez is the highest landslide dam in the world and goes back to an earthquake in 1911. Whilst the safety situation of Lake Sarez is still discussed controversially, a number of glacial lakes poses a threat to the mountain communities downstream. At least two significant glacial lake outburst floods (GLOFs) were recorded in the study are in the last ten years, one of which caused major destruction. Besides the hazards, lakes may also offer a potential for hydropower generation. Furthermore, they mirror the dynamics of the high-mountain environment and therefore indicate fluctuations and changes. Consequently, up-to date information on the lakes present in the watershed is required. A comprehensive multi-temporal lake inventory for the upper catchment of the Amu Darya river was prepared and analyzed, based on remotely sensed data. ASTER and Landsat scenes were used as well as Corona images from the late 1960s. The satellite information was complemented by helicopter surveys and in-detail field investigations of selected lakes in 2003, 2009 and 2011. Lake type, size, drainage and development

  14. Infrared outburst in Arp 299

    NASA Astrophysics Data System (ADS)

    Mattila, Seppo; Meikle, Peter; Kotak, Rubina; Perez-Torres, Miguel; Romero-Canizales, Cristina; Alberdi, Antxon

    2011-05-01

    Arp 299 is one of the nearest examples of a luminous infrared galaxy. We discovered a strong outburst in Arp 299 which is apparent at infrared (IR) wavelengths but not in the optical indicating emission from warm dust and a high extinction. This source could originate from an IR 'dust echo' resulting either from a highly obscured outburst in an active galactic nucleus or an energetic supernova. To continue our study of the origin of this outburst we propose short IRAC observations.

  15. Late Glacial to Holocene environments in the present-day coldest region of the Northern Hemisphere inferred from a pollen record of Lake Billyakh, Verkhoyansk Mts, NE Siberia

    NASA Astrophysics Data System (ADS)

    Müller, S.; Tarasov, P. E.; Andreev, A. A.; Diekmann, B.

    2009-03-01

    In this study, a radiocarbon-dated pollen record from Lake Billyakh (65°17' N, 126°47' E; 340 m a.s.l.) in the Verkhoyansk Mountains was used to reconstruct vegetation and climate change since about 15 kyr BP. The pollen record and pollen-based biome reconstruction suggest that open cool steppe (STEP) and grass and sedge tundra (TUND) communities with Poaceae, Cyperaceae, Artemisia, Chenopodiaceae, Caryophyllaceae and Selaginella rupestris dominated the area from 15 to 13.5 kyr BP. On the other hand, the constant presence of Larix pollen in quantities comparable to today's values points to the constant presence of boreal deciduous conifer (CLDE) trees in the regional vegetation during the Late Glacial. A major spread of shrub tundra communities, including birch (Betula sect. Nanae), alder (Duschekia fruticosa) and willow (Salix) species, is dated to 13.5-12.7 kyr BP, indicating a noticeable increase in precipitation toward the end of the Last Glaciation, particularly during the Bølling-Allerød Interstadial. Between 12.7 and 11.4 kyr BP pollen percentages of herbaceous taxa rapidly increased, whereas shrub taxa percentages decreased, suggesting strengthening of the steppe communities associated with the relatively cold and dry Younger Dryas Stadial. However, the pollen data in hand indicate that Younger Dryas climate was less severe than the climate during the earlier interval from 15 to 13.5 kyr BP. The onset of the Holocene is marked in the pollen record by the highest values of shrub and lowest values of herbaceous taxa, suggesting a return of warmer and wetter conditions after 11.4 kyr BP. Percentages of tree taxa increase gradually and reach maximum values after 7 kyr BP, reflecting the spread of boreal cold deciduous and taiga forests in the region. An interval between 7 and 2 kyr BP is noticeable for the highest percentages of Scots pine (Pinus subgen. Diploxylon), spruce (Picea) and fir (Abies) pollen, indicating mid-Holocene spread of boreal forest

  16. Climate history of the Southern Hemisphere Westerlies belt during the last glacial-interglacial transition revealed from lake water oxygen isotope reconstruction of Laguna Potrok Aike (52° S, Argentina)

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Lücke, A.; Wissel, H.; Mayr, C.; Enters, D.; Kim, K. Ja; Ohlendorf, C.; Schäbitz, F.; Zolitschka, B.

    2014-12-01

    The Southern Hemisphere Westerlies (SHW) play a crucial role in large-scale ocean circulation and global carbon cycling. Accordingly, the reconstruction of how the latitudinal position and intensity of the SHW belt changed during the last glacial termination is essential for understanding global climatic fluctuations. The southernmost part of the South American continent is the only continental mass intersecting a large part of the SHW belt. However, due to the scarcity of suitable palaeoclimate archives continuous proxy records back to the last glacial are rare in southern Patagonia. Here, we show an oxygen isotope record from cellulose and purified bulk organic matter of submerged aquatic moss shoots from Laguna Potrok Aike (52° S, 70° W), a deep maar lake located in semi-arid, extra-Andean Patagonia, covering the last glacial-interglacial transition (26 000 to 8500 cal BP). Based on the highly significant correlation between oxygen isotope values of modern aquatic mosses and their host waters and abundant well-preserved moss remains in the sediment record a high-resolution reconstruction of the lake water oxygen isotope (δ18Olw-corr) composition is presented. The reconstructed δ18Olw-corr values for the last glacial are ca. 3‰ lower than modern values, which can best be explained by generally cooler air temperatures and changes in the moisture source area, together with the occurrence of permafrost leading to a prolonged lake water residence time. Thus, the overall glacial δ18Olw-corr level until 21 000 cal BP is consistent with a scenario of weakened or absent SHW at 52° S compared to the present. During the last deglaciation, reconstructed δ18Olw-corr values reveal a significant two-step rise describing the detailed response of the lake's hydrological balance to this fundamental climatic shift. Rapid warming is seen as the cause of the first rise of ca. 2&permil, in δ18Olw-corr during the first two millennia of deglaciation (17 600 to 15 600 cal BP

  17. Orbital forcing of glacial/interglacial variations in chemical weathering and silicon cycling within the upper White Nile basin, East Africa: Stable-isotope and biomarker evidence from Lakes Victoria and Edward

    NASA Astrophysics Data System (ADS)

    Cockerton, Helen E.; Street-Perrott, F. Alayne; Barker, Philip A.; Leng, Melanie J.; Sloane, Hilary J.; Ficken, Katherine J.

    2015-12-01

    On Quaternary time scales, the global biogeochemical cycle of silicon is interlocked with the carbon cycle through biotic enhancement of silicate weathering and uptake of dissolved silica by vascular plants and aquatic microalgae (notably diatoms, for which Si is an essential nutrient). Large tropical river systems dominate the export of Si from the continents to the oceans. Here, we investigate variations in Si cycling in the upper White Nile basin over the last 15 ka, using sediment cores from Lakes Victoria and Edward. Coupled measurements of stable O and Si isotopes on diatom separates were used to reconstruct past changes in lake hydrology and Si cycling, while the abundances of lipid biomarkers characteristic of terrestrial/emergent higher plants, submerged/floating aquatic macrophytes and freshwater algae document past ecosystem changes. During the late-glacial to mid-Holocene, 15-5.5 ka BP, orbital forcing greatly enhanced monsoon rainfall, forest cover and chemical weathering. Riverine inputs of dissolved silica from the lake catchments exceeded aquatic demand and may also have had lower Si-isotope values. Since 5.5 ka BP, increasingly dry climates and more open vegetation, reinforced by the spread of agricultural cropland over the last 3-4 ka, have reduced dissolved silica inputs into the lakes. Centennial-to millennial-scale dry episodes are also evident in the isotopic records and merit further investigation.

  18. Outbursts in Symbiotic Binaries

    NASA Technical Reports Server (NTRS)

    Sonneborn, George (Technical Monitor); Kenyon, Scott J.

    2004-01-01

    Two models have been proposed for the outbursts of symbiotic stars. In the thermonuclear model, outbursts begin when the hydrogen burning shell of a hot white dwarf reaches a critical mass. After a rapid increase in the luminosity and effective temperature, the white dwarf evolves at constant luminosity to lower effective temperatures, remains at optical maximum for several years, and then returns to quiescence along a white dwarf cooling curve. In disk instability models, the brightness rises when the accretion rate from the disk onto the central white dwarf abruptly increases by factors of 5-20. After a few month to several year period at maximum, both the luminosity and the effective temperature of the disk decline as the system returns to quiescence. If most symbiotic stars undergo thermonuclear eruptions, then symbiotics are probably poor candidates for type I supernovae. However, they can then provide approx. 10% of the material which stars recycle back into the interstellar medium. If disk instabilities are the dominant eruption mechanism, symbiotics are promising type Ia candidates but recycle less material into the interstellar medium.

  19. Lake

    ERIC Educational Resources Information Center

    Wien, Carol Anne

    2008-01-01

    The lake is blue black and deep. It is a glaciated finger lake, clawed out of rock when ice retracted across Nova Scotia in a northerly direction during the last ice age. The lake is narrow, a little over a mile long, and deep, 90 to 190 feet in places according to local lore, off the charts in others. The author loves to swim there, with a sense…

  20. ACCRETION OUTBURSTS IN CIRCUMPLANETARY DISKS

    SciTech Connect

    Lubow, S. H.; Martin, R. G.

    2012-04-20

    We describe a model for the long-term evolution of a circumplanetary disk that is fed mass from a circumstellar disk and contains regions of low turbulence (dead zones). We show that such disks can be subject to accretion-driven outbursts, analogous to outbursts previously modeled in the context of circumstellar disks to explain FU Ori phenomena. Circumplanetary disks around a proto-Jupiter can undergo outbursts for infall accretion rates onto the disks in the range M-dot{sub infall} approx. 10{sup -9} to 10{sup -7} M{sub Sun} yr{sup -1}, typical of accretion rates in the T Tauri phase. During outbursts, the accretion rate and disk luminosity increases by several orders of magnitude. Most of the planet mass growth during planetary gas accretion may occur via disk outbursts involving gas that is considerably hotter than predicted by steady state models. For low infall accretion rates M-dot{sub infall} {approx}< 10{sup -10} M{sub sun} yr{sup -1} that occur in late stages of disk accretion, disk outbursts are unlikely to occur, even if dead zones are present. Such conditions are favorable for the formation of icy satellites.

  1. Glacial hazards: communicating the science and managing the risk

    NASA Astrophysics Data System (ADS)

    Reynolds, J. M.

    2009-04-01

    The recession of glaciers worldwide has received huge media coverage over the last few years in association with the issue of climate change. Young people at schools and colleges are increasingly aware of the environmental pressures due to ‘global warming'. Yet simultaneously, there appears to be an increasing move away from studying science both at pre-university and undergraduate levels. One of the oft cited reasons is that students cannot see the application of the subjects being taught them. Glacial hazards are one of the most obvious adverse effects of climate change, with many, often poor, communities in remote mountain areas being the most affected by frequently devastating Glacial Lake Outburst Floods (GLOFs). When students are exposed to examples of these hazards and the science behind them, many become enthused by the subject and want to study it further. There has been a huge increase in the number of students selecting projects on glacial hazards as well as a large increase in the number of institutions offering to teach modules on this subject. In an effort to provide a basic visualisation, Peter Kennett has taken the principle of GLOFs and developed a cheap but highly visual demonstration of the potentially devastating effect of melting ice within a moraine leading to subsidence and subsequent dam failure. This is available on www.earthlearningidea.com as ‘Dam burst danger - modelling the collapse of a natural dam in the mountains - and the disaster that might follow'. Furthermore, the methods by which glacial hazards are assessed provide excellent applications of geophysics, geology, geography (physical and Human), engineering, mathematics, and glaciology. By exploring the potential vulnerability of communities downstream, the applications can be extended to include sociology, economics, geopolitics and even psychology. Glacial hazards have been the subject of presentations to the Earth Science Teachers Association (ESTA) in the UK to demonstrate

  2. Late Pleistocene ice margin fluctuations in the Nahanni National Park-UNESCO World Heritage Site and their impact on glacial lake formation and architecture of drainage systems across the Yukon-NWT continental divide

    NASA Astrophysics Data System (ADS)

    Duk-Rodkin, A.; Barendregt, R. W.

    2009-12-01

    In the late Pleistocene the southern Mackenzie region was glaciated by ice masses from a Cordilleran and continental source (Laurentide). Stratigraphic and geomorphologic evidence indicate that the two glaciers occupied this region at different times during the Late Pleistocene. The continental ice sheet advanced over the foothills and up major valleys reaching its maximum extent, ca. 30 ka. B. P. This took place when Cordilleran glaciers were in their initial stages of development. The Laurentide Ice Sheet blocked the drainage of the South Nahanni River near Virginia Falls, forming a glacial lake which inundated an area of approximately 900 km2 at its maximum stand, and had an outlet to the southwest, across the continental divide into the Yukon Territory and eventually into the Pacific Ocean. Lacustrine sediments at various sites reach thicknesses ranging from 110 to 120 metres, at an elevation of around 700 m. Cordilleran glaciers advanced eastward and approximately 5000 years later blocked this southwestward drainage, rerouting it to the east and north along the Mackenzie Mountain front. The drainage was confined between the mountains and continental ice margin where it incised major canyons into the limestone bedrock, and produced a spectacular karst landscape, which today forms part of the Nahanni National Park. During the retreat of the Laurentide and advance of Cordilleran glaciers, glacial Lake Nahanni cut an outlet to the east at First Canyon. This outlet drained into a continuous northbound network of marginal meltwater channels joining the north-flowing drainage that eventually reached the Arctic Ocean, and during further retreat of the ice sheet established the Mackenzie River in its modern location. The presence of Laurentide ice in this region is evidenced by large granite boulders carried from the Canadian Shield. Erratics are found up to 100 km west of the mountain front. Neotectonic activity in the area is interpreted from exposures such as those

  3. Energy source for comet outbursts

    NASA Technical Reports Server (NTRS)

    Patashnick, H.; Schuerman, D. W.; Rupprecht, G.

    1974-01-01

    Development of a mechanism explaining the internal source of energy of comet outbursts. A mechanism is proposed which automatically provides a source of particulate matter which creates a huge surface area which contains a substantial percentage of amorphous ice, so that the phase transition of the amorphous ice to a cubic structure provides a release of energy which may be responsible for the outbursts observed in many comets. In addition, the volume into which the transition can propagate is estimated for a spherical comet with a radius of 5 km.

  4. Late glacial aridity in southern Rocky Mountains

    SciTech Connect

    Davis, O.K.; Pitblado, B.L.

    1995-09-01

    While the slopes of the present-day Colorado Rocky Mountains are characterized by large stands of subalpine and montane conifers, the Rockies of the late glacial looked dramatically different. Specifically, pollen records suggest that during the late glacial, Artemisia and Gramineae predominated throughout the mountains of Colorado. At some point between 11,000 and 10,000 B.P., however, both Artemisia and grasses underwent a dramatic decline, which can be identified in virtually every pollen diagram produced for Colorado mountain sites, including Como Lake (Sangre de Cristo Mountains), Copley Lake and Splains; Gulch (near Crested Butte), Molas Lake (San Juan Mountains), and Redrock Lake (Boulder County). Moreover, the same pattern seems to hold for pollen spectra derived for areas adjacent to Colorado, including at sites in the Chuska Mountains of New Mexico and in eastern Wyoming. The implications of this consistent finding are compelling. The closest modem analogues to the Artemisia- and Gramineae-dominated late-glacial Colorado Rockies are found in the relatively arid northern Great Basin, which suggests that annual precipitation was much lower in the late-glacial southern Rocky Mountains than it was throughout the Holocene.

  5. Mars Express MARSIS Radar: A Prediction of the Effect of Overlying Ice on Detecting Polar Basal Lakes and Inter-Glacial Aquifers

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Plaut, J. J.; Gurnett, D. A.; Picardi, G.

    2004-01-01

    The penetration of the MARSIS radar signal into the polar ice mass is modeled to determine the capability of the instrument to locate sub-glacial aquifers. As a ground penetrating radar, the orbiting MARSIS transmits a signal greater than 1 W between 1-5 MHz. In this work we will investigate the effect of ice conductive losses on the radar-detection of subsurface aquifers. Based on wave propagation analysis, it is found that for a bulk ice conductivity below 10-5 S/m, conductive losses in the medium are not significant. However, if the bulk ice conductivity is relatively large (greater than 10-5 S/m), the reflected signal from any deep aquifer will be absorbed as it propagates in the lossy ice medium limiting the probing depth.

  6. Late-glacial and Holocene Vegetation and Climate Variability, Including Major Droughts, in the Sky Lakes Region of Southeastern New York State

    NASA Technical Reports Server (NTRS)

    Menking, Kirsten M.; Peteet, Dorothy M.; Anderson, Roger Y.

    2012-01-01

    Sediment cores from Lakes Minnewaska and Mohonk in the Shawangunk Mountains of southeastern New York were analyzed for pollen, plantmacrofossils, macroscopic charcoal, organic carbon content, carbon isotopic composition, carbon/nitrogen ratio, and lithologic changes to determine the vegetation and landscape history of the greater Catskill Mountain region since deglaciation. Pollen stratigraphy generally matches the New England pollen zones identified by Deevey (1939) and Davis (1969), with boreal genera (Picea, Abies) present during the late Pleistocene yielding to a mixed Pinus, Quercus and Tsuga forest in the early Holocene. Lake Minnewaska sediments record the Younger Dryas and possibly the 8.2 cal kyr BP climatic events in pollen and sediment chemistry along with an 1400 cal yr interval of wet conditions (increasing Tsuga and declining Quercus) centered about 6400 cal yr BP. BothMinnewaska andMohonk reveal a protracted drought interval in themiddle Holocene, 5700-4100 cal yr BP, during which Pinus rigida colonized the watershed, lake levels fell, and frequent fires led to enhanced hillslope erosion. Together, the records show at least three wet-dry cycles throughout the Holocene and both similarities and differences to climate records in New England and central New York. Drought intervals raise concerns for water resources in the New York City metropolitan area and may reflect a combination of enhanced La Niña, negative phase NAO, and positive phase PNA climatic patterns and/or northward shifts of storm tracks.

  7. Luminescence Chronology for the Formation of Glacial Lake Calgary, Southern Alberta, Canada: Age Constraints for the Initiation of the Late Pleistocene Retreat of the Laurentide Ice Sheet from its Western Margin

    NASA Astrophysics Data System (ADS)

    Munyikwa, K.; Rittenour, T. M.

    2014-12-01

    Glacial Lake Calgary in southern Alberta, Canada, was a Late Pleistocene proglacial lake that formed along the southwest margin of the Laurentide Ice Sheet (LIS), dammed by the retreating ice sheet margin. Attempts to constrain the age of the lake using radiocarbon methods have been hampered by the lack of datable organic material. In an effort to apply an alternative chronometer, this study uses two optically stimulated luminescence (OSL) dating approaches to date fine grained sand and silt that were deposited in the lake during its existence. OSL dating determines the depositional ages of sediments by measuring the energy from ionizing radiation that is stored in mineral grains such as quartz and feldspar. Dividing the stored energy, also referred to as the paleodose, by the rate at which the dose accumulated, allows an age to be ascertained. In one method applied in this study, the paleodose stored in the feldspar component of the sediment is determined using normalized infrared stimulated luminescence signals acquired using a portable OSL reader. In the second method, blue optically stimulated luminescence signals obtained from quartz separates from the sediment by employing a regular OSL reader and standard protocols are used to determine the paleodose. After correcting the feldspar data for anomalous fading, the age results from the two dating approaches are compared. The ages signify a time period by which the LIS had retreated from the study area and, hence, serve as constraints for the initiation of the retreat of the ice sheet from its western limit. Advantages and limitations of the dating methods are briefly discussed. Constraining the chronology of the retreat of the LIS from western Canada allows for a better understanding of the driving forces behind ice sheet retreat. Secondly, assigning a temporal scale to the postglacial evolution of the environment of the region permits a better insight into the dynamics of the physical and biological

  8. Obsidian hydration dates glacial loading?

    PubMed

    Friedman, I; Pierce, K L; Obradovich, J D; Long, W D

    1973-05-18

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming. The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow. PMID:17806883

  9. Obsidian hydration dates glacial loading?

    PubMed

    Friedman, I; Pierce, K L; Obradovich, J D; Long, W D

    1973-05-18

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming. The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  10. Obsidian hydration dates glacial loading?

    USGS Publications Warehouse

    Friedman, I.; Pierce, K.L.; Obradovich, J.D.; Long, W.D.

    1973-01-01

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming . The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  11. Airborne LiDAR analysis and geochronology of faulted glacial moraines in the Tahoe-Sierra frontal fault zone reveal substantial seismic hazards in the Lake Tahoe region, California-Nevada USA

    USGS Publications Warehouse

    Howle, James F.; Bawden, Gerald W.; Schweickert, Richard A.; Finkel, Robert C.; Hunter, Lewis E.; Rose, Ronn S.; von Twistern, Brent

    2012-01-01

    We integrated high-resolution bare-earth airborne light detection and ranging (LiDAR) imagery with field observations and modern geochronology to characterize the Tahoe-Sierra frontal fault zone, which forms the neotectonic boundary between the Sierra Nevada and the Basin and Range Province west of Lake Tahoe. The LiDAR imagery clearly delineates active normal faults that have displaced late Pleistocene glacial moraines and Holocene alluvium along 30 km of linear, right-stepping range front of the Tahoe-Sierra frontal fault zone. Herein, we illustrate and describe the tectonic geomorphology of faulted lateral moraines. We have developed new, three-dimensional modeling techniques that utilize the high-resolution LiDAR data to determine tectonic displacements of moraine crests and alluvium. The statistically robust displacement models combined with new ages of the displaced Tioga (20.8 ± 1.4 ka) and Tahoe (69.2 ± 4.8 ka; 73.2 ± 8.7 ka) moraines are used to estimate the minimum vertical separation rate at 17 sites along the Tahoe-Sierra frontal fault zone. Near the northern end of the study area, the minimum vertical separation rate is 1.5 ± 0.4 mm/yr, which represents a two- to threefold increase in estimates of seismic moment for the Lake Tahoe basin. From this study, we conclude that potential earthquake moment magnitudes (Mw) range from 6.3 ± 0.25 to 6.9 ± 0.25. A close spatial association of landslides and active faults suggests that landslides have been seismically triggered. Our study underscores that the Tahoe-Sierra frontal fault zone poses substantial seismic and landslide hazards.

  12. Lake trout in northern Lake Huron spawn on submerged drumlins

    USGS Publications Warehouse

    Riley, Stephen C.; Binder, Thomas; Wattrus, Nigel J.; Faust, Matthew D.; Janssen, John; Menzies, John; Marsden, J. Ellen; Ebener, Mark P.; Bronte, Charles R.; He, Ji X.; Tucker, Taaja R.; Hansen, Michael J.; Thompson, Henry T.; Muir, Andrew M.; Krueger, Charles C.

    2014-01-01

    Recent observations of spawning lake trout Salvelinus namaycush near Drummond Island in northern Lake Huron indicate that lake trout use drumlins, landforms created in subglacial environments by the action of ice sheets, as a primary spawning habitat. From these observations, we generated a hypothesis that may in part explain locations chosen by lake trout for spawning. Most salmonines spawn in streams where they rely on streamflows to sort and clean sediments to create good spawning habitat. Flows sufficient to sort larger sediment sizes are generally lacking in lakes, but some glacial bedforms contain large pockets of sorted sediments that can provide the interstitial spaces necessary for lake trout egg incubation, particularly if these bedforms are situated such that lake currents can penetrate these sediments. We hypothesize that sediment inclusions from glacial scavenging and sediment sorting that occurred during the creation of bedforms such as drumlins, end moraines, and eskers create suitable conditions for lake trout egg incubation, particularly where these bedforms interact with lake currents to remove fine sediments. Further, these bedforms may provide high-quality lake trout spawning habitat at many locations in the Great Lakes and may be especially important along the southern edge of the range of the species. A better understanding of the role of glacially-derived bedforms in the creation of lake trout spawning habitat may help develop powerful predictors of lake trout spawning locations, provide insight into the evolution of unique spawning behaviors by lake trout, and aid in lake trout restoration in the Great Lakes.

  13. The paleoclimatology of Lake Baikal: A diatom synthesis and prospectus

    NASA Astrophysics Data System (ADS)

    Mackay, Anson W.

    2007-06-01

    region. Links to changes in North Atlantic ocean thermohaline circulation via teleconnections are also evident in the nature of the abrupt ecological changes in the lake throughout the last 60 ka, linked to ice-rafting into the North Atlantic, otherwise known as Heinrich events. New robust radiocarbon chronologies for sediments deposited during the late glacial and Holocene in Lake Baikal allow detailed, multi-decadal records to be constructed for the last 14,000 years. Cooling events associated with millennial-scale cycles are also apparent in the Lake Baikal record, and both the diatom record and oxygen isotope record of the diatom silica highlight that biological responses to these abrupt events are almost simultaneous. Comparisons made between Lake Baikal records with others worldwide highlights that many of the Holocene cooling events are associated with melt-water outburst from the Laurentide ice sheet, and changes in solar insolation. During the last 1000 years, snow cover on Lake Baikal has been inferred from past diatom assemblages, and is closely linked to weakening of the North Atlantic Oscillation, allowing increasing intensity of the Siberian High to develop and during the 17th and 18th centuries. In the last 150 years, diatom species have been shown to be sensitive indicators of recent warming. However, impacts from future global warming will be complex, and are likely to impact not only on the balance between endemic and cosmopolitan diatoms throughout the lake, but on the balance between siliceous and non-siliceous algae, and sources of primary productivity.

  14. A GCM comparison of Plio-Pleistocene interglacial-glacial periods in relation to Lake El'gygytgyn, NE Arctic Russia

    NASA Astrophysics Data System (ADS)

    Coletti, A. J.; DeConto, R. M.; Brigham-Grette, J.; Melles, M.

    2014-08-01

    Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stage (MIS) 1 (9 ka), 5e (127 ka), 11c (409 ka), and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the Mean Temperature of the Warmest Month (MTWM) indicate conditions 2.1, 0.5 and 3.1 °C warmer than today during MIS 5e, 11c, and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer orbital forcing, the extraordinary warmth of MIS 11c relative to the other interglacials in the proxy records remain difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice, and circum-Arctic land ice feedbacks on the climate of the Beringian interior. Simulations accounting for climate-vegetation-land surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on Northeast Asian temperature during the warmth of stage 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic ocean has some effect on Beringian climate, suggesting intrahemispheric coupling seen in comparisons between Lake El'gygytgyn and Antarctic sediment records might be related to linkages between Antarctic ice volume and ocean circulation. The exceptional warmth of MIS 11c remains enigmatic however, relative to the modest orbital and greenhouse gas forcing during that interglacial. Large Northern Hemisphere ice sheets during Plio-Pleistocene glaciation causes a substantial decrease in Mean Temperature of the Coldest Month (MTCM) and

  15. The pre-outburst flare of the A 0535+26 August/September 2005 outburst

    NASA Astrophysics Data System (ADS)

    Caballero, I.; Santangelo, A.; Kretschmar, P.; Staubert, R.; Postnov, K.; Klochkov, D.; Camero-Arranz, A.; Finger, M. H.; Kreykenbohm, I.; Pottschmidt, K.; Rothschild, R. E.; Suchy, S.; Wilms, J.; Wilson, C. A.

    2008-03-01

    Aims:We study the spectral and temporal behavior of the High Mass X-ray Binary A 0535+26 during a “pre-outburst flare” which took place 5 d before the peak of a normal (type I) outburst in August/September 2005. We compare the studied behavior with that observed during the outburst. Methods: We analyse RXTEobservations that monitored A 0535+26 during the outburst. We complete spectral and timing analyses of the data. We study the evolution of the pulse period, present energy-dependent pulse profiles both at the initial pre-outburst flare and close to outburst maximum, and measure how the cyclotron resonance-scattering feature (hereafter CRSF) evolves. Results: We present three main results: a constant period P = 103.3960(5) sis measured until periastron passage, followed by a spin-up with a decreasing period derivative of dot{P} = (-1.69 ±0.04) ×10-8 ss-1 at MJD 53 618, and P remains constant again at the end of the main outburst. The spin-up provides evidence for the existence of an accretion disk during the normal outburst. We measure a CRSF energy of Ecyc 50 keV during the pre-outburst flare, and Ecyc 46 keVduring the main outburst. The pulse shape, which varies significantly during both pre-outburst flare and main outburst, evolves strongly with photon energy.

  16. Measuring Cooling Curves Following Magnetar Outbursts

    NASA Astrophysics Data System (ADS)

    Kaspi, Victoria

    2012-09-01

    Magnetars have been observed to increase their flux output by several orders of magnitude in outbursts. Following outbursts they cool on timescales of months to years. We propose to observe two magnetars, Swift J1822.3-1606 and 1E 1547.0-5408, using Chandra as they approach their quiescent state following their recent outbursts in 2011 and 2009, respectively. We will apply a newly developed crustal cooling model to these cooling curves to constrain the properties of the magnetars, such as the crust thickness and heat capacity, and of their outbursts, such as the location of energy deposition.

  17. Processing, Analysis, and General Evaluation of Well-Driller Logs for Estimating Hydrogeologic Parameters of the Glacial Sediments in a Ground-Water Flow Model of the Lake Michigan Basin

    USGS Publications Warehouse

    Arihood, Leslie D.

    2009-01-01

    In 2005, the U.S. Geological Survey began a pilot study for the National Assessment of Water Availability and Use Program to assess the availability of water and water use in the Great Lakes Basin. Part of the study involves constructing a ground-water flow model for the Lake Michigan part of the Basin. Most ground-water flow occurs in the glacial sediments above the bedrock formations; therefore, adequate representation by the model of the horizontal and vertical hydraulic conductivity of the glacial sediments is important to the accuracy of model simulations. This work processed and analyzed well records to provide the hydrogeologic parameters of horizontal and vertical hydraulic conductivity and ground-water levels for the model layers used to simulated ground-water flow in the glacial sediments. The methods used to convert (1) lithology descriptions into assumed values of horizontal and vertical hydraulic conductivity for entire model layers, (2) aquifer-test data into point values of horizontal hydraulic conductivity, and (3) static water levels into water-level calibration data are presented. A large data set of about 458,000 well driller well logs for monitoring, observation, and water wells was available from three statewide electronic data bases to characterize hydrogeologic parameters. More than 1.8 million records of lithology from the well logs were used to create a lithologic-based representation of horizontal and vertical hydraulic conductivity of the glacial sediments. Specific-capacity data from about 292,000 well logs were converted into horizontal hydraulic conductivity values to determine specific values of horizontal hydraulic conductivity and its aerial variation. About 396,000 well logs contained data on ground-water levels that were assembled into a water-level calibration data set. A lithology-based distribution of hydraulic conductivity was created by use of a computer program to convert well-log lithology descriptions into aquifer or

  18. Recurring middle Pleistocene outburst floods in east-central Alaska

    USGS Publications Warehouse

    Froese, D.G.; Smith, D.G.; Westgate, J.A.; Ager, T.A.; Preece, S.J.; Sandhu, A.; Enkin, R.J.; Weber, F.

    2003-01-01

    Recurring glacial outburst floods from the Yukon-Tanana Upland are inferred from sediments exposed along the Yukon River near the mouth of Charley River in east-central Alaska. Deposits range from imbricate gravel and granules indicating flow locally extending up the Yukon valley, to more distal sediments consisting of at least 10 couplets of planar sands, granules, and climbing ripples with up-valley paleocurrent indicators overlain by massive silt. An interglacial organic silt, occurring within the sequence, indicates at least two flood events are associated with an earlier glaciation, and at least three flood events are associated with a later glaciation which postdates the organic silt. A minimum age for the floods is provided by a glass fission track age of 560,000 ?? 80,000 yr on the GI tephra, which occurs 8 m above the flood beds. A maximum age of 780,000 yr for the floods is based on normal magnetic polarity of the sediments. These age constraints allow us to correlate the flood events to the early-middle Pleistocene. And further, the outburst floods indicate extensive glaciation of the Yukon-Tanana Upland during the early-middle Pleistocene, likely representing the most extensive Pleistocene glaciation of the area. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

  19. Monsoonal Variations of Supraglacial Lakes, Langtang Khola, Nepal

    NASA Astrophysics Data System (ADS)

    Miles, E. S.; Willis, I. C.; Arnold, N. S.; Pellicciotti, F.

    2013-12-01

    As Himalayan debris-covered glaciers retreat and thin in response to climate warming, their long, low-gradient tongues and undulating surfaces tend to form supraglacial lakes. The conceptual response of debris-covered valley glaciers progresses from thinning and stagnation to the development of supraglacial ponds, which eventually may coalesce into very large lakes bounded by terminal moraines. Large terminal lakes are a topic of frequent study due to the public safety hazard of glacier lake outburst floods (GLOFs). However, smaller, transient ponds that form on the glacier's surface may play an important role in determining annual mass balance. Development of surpaglacial ponds may be controlled by the magnitudes of surface undulations, meltwater inputs, and the glacier's general surface gradient. These lakes are not necessarily permanent: they enlarge by enhanced ice-cliff ablation, they are advected and deformed by glacial strain, they may disappear due to englacial drainage or prolonged evaporation, and they may not recur in the same locations each year due to changes in surface topography and hydrologic routing. The prevalence and character of such lakes varies greatly throughout the year. In the cold, dry winter (October-March), the debris surface is largely snow-covered and supraglacial lakes are frozen. During the arid premonsoon (April-May), lakes thaw and the debris surface is dry and free of snow. The debris surface becomes nearly-saturated by monsoonal rains (June-September) leading to surface runoff and widespread lake-filling. During this dynamic monsoon period, ponded water substantially alters the glacier's specific energy balance by increasing the effective thermal conductivity between atmosphere and ice, acting as a heat reservoir, and reducing albedo. Additionally, supraglacial ponds often enhance ablation processes in proximal areas by initiating lake-marginal calving and exposing debris-free ice cliffs. Through these processes supraglacial

  20. CNO nucleosynthesis and the nova outburst

    NASA Technical Reports Server (NTRS)

    Starrfield, S.; Truran, J.; Sparks, W.

    1977-01-01

    Predictions for CNO nucleosynthesis by the classical nova outburst are presented. Properties of the nova phenomenon pertinent to the production of CNO isotopes are discussed, the effect of beta(+) unstable nuclei on outburst evolution is examined, and the need for enhanced CNO nuclei in the envelope is described. Possible mechanisms for producing such enhancement are considered, and recent observations of enhanced CNO nuclei in nova ejecta are reviewed. Results of model evolutionary calculations are outlined which show that a thermonuclear runaway in the hydrogen envelope of a carbon-oxygen white dwarf can reproduce the gross features of the classical nova outburst, that the behavior of the outburst depends at least on the hydrogen-envelope mass and the degree of CNO enhancement, and that all degrees of isotopic enhancement result in an outburst that may be compared with observed events. Two enhancement mechanisms are identified, both of which involve mixing in the envelope.

  1. Eclipse Mapping Experiments in Dwarf Novae Outbursts

    NASA Astrophysics Data System (ADS)

    Borges, B. W.; Baptista, R.

    2006-06-01

    In this work, we report the eclipse mapping analysis of CCD photometric data of two short period dwarf novae - V4140 Sgr (Borges & Baptista 2005) and HT Cas (Borges, Baptista & Catalán, in preparation) - during observed outburst events. The analysis of the observations of V4140 Sgr, done between 1991 and 2001, reveals that the object was in the decline from an outburst in 1992 and again in outburst in 2001. A distance of d = 170+/-30 pc is obtained from a method similar to that used to constrain the distance to open clusters. From this distance, disc radial brightness temperature distributions are determined, and the disc temperatures remain below the critical effective temperature T_{crit} at all disc radii during the outburst. The distributions in quiescence and in outburst are significantly different from those of other dwarf novae of similar orbital period. These results cannot be explained within the framework of the disc instability model and the small amplitude outbursts of V4140 Sgr can be due bursts of enhanced mass transfer rate from the secondary star. Our HT Cas data consist of V and R CCD photometric observations done in 2005 November with the 0.95-m James Gregory Telescope (JGT) and cover a outburst cycle. We used the entropy associated to the eclipse maps to obtain the semi-opening disc angle α evolution throught the outburst. The obtained angles are systematically lower than those obtained by Ioannou et al. (1999) and we can conclude that the outburst radial profiles must be flatter than the the T ∝ r^{-3/4} law of steady state dics, against the expectations of the disc instability model. Our intensity radial distributions presents the same ``outside-in'' outburst behavior as obtained by the referred author.

  2. Sources of glacial moisture in Mesoamerica

    USGS Publications Warehouse

    Bradbury, J.P.

    1997-01-01

    Paleoclimatic records from Mesoamerica document the interplay between Atlantic and Pacific sources of precipitation during the last glacial stage and Holocene. Today, and throughout much of the Holocene, the entire region receives its principal moisture in the summer from an interaction of easterly trade winds with the equatorial calms. Glacial records from sites east of 95?? W in Guatemala, Florida, northern Venezuela and Colombia record dry conditions before 12 ka, however. West of 95?? W, glacial conditions were moister than in the Holocene. For example, pollen and diatom data show that Lake Pa??tzcuaro in the central Mexican highlands was cool, deep and fresh during this time and fossil pinyon needles in packrat middens in Chihuahua, Sonora, Arizona, and Texas indicate cooler glacial climates with increased winter precipitation. Cold Gulf of Mexico sea-surface temperatures and reduced strength of the equatorial calms can explain arid full and late glacial environments east of 95?? W whereas an intensified pattern of winter, westerly air flow dominated hydrologic balances as far south as 20?? N. Overall cooler temperatures may have increased effective moisture levels during dry summer months in both areas. ?? 1997 INQUA/ Elsevier Science Ltd.

  3. Late Glacial to Holocene environments in the present-day coldest region of the Northern Hemisphere inferred from a pollen record of Lake Billyakh, Verkhoyansk Mts, NE Siberia

    NASA Astrophysics Data System (ADS)

    Müller, S.; Tarasov, P. E.; Andreev, A. A.; Diekmann, B.

    2008-11-01

    In this study a radiocarbon-dated pollen record from Lake Billyakh (65°17'N, 126°47'E; 340 m a.s.l.) in the Verkhoyansk Mountains was used to reconstruct vegetation and climate change since about 15 kyr BP (1 kyr=1000 cal. yr). The pollen record and pollen-based biome reconstruction suggest that open cool steppe and grass and sedge tundra communities with Poaceae, Cyperaceae, Artemisia, Chenopodiaceae, Caryophyllaceae and Selaginella rupestris dominated the area from 15 to 13.5 kyr BP. On the other hand, the constant presence of Larix pollen in quantities comparable to today's values points to the constant presence of boreal deciduous conifer trees in the regional vegetation during the last glaciation. A major spread of shrub tundra communities, including birch (Betula sect. Nanae), alder (Duschekia fruticosa) and willow (Salix) species, is dated to 13.5 12.7 kyr BP, indicating a noticeable increase in precipitation toward the end of the last glaciation, particularly during the Allerød Interstadial. Between 12.7 and 11.4 kyr BP pollen percentages of herbaceous taxa rapidly increased, whereas shrub taxa percentages decreased, suggesting strengthening of the steppe communities associated with the relatively cold and dry Younger Dryas Stadial. However, the pollen data in hand indicate that Younger Dryas climate was less severe than the climate during the earlier interval from 15 to 13.5 kyr BP. The onset of the Holocene is marked in the pollen record by the highest values of shrub and lowest values of herbaceous taxa, suggesting a return of warmer and wetter conditions after 11.4 kyr BP. Percentages of tree taxa increase gradually and reach maximum values after 7 kyr BP, reflecting the spread of boreal cold deciduous and taiga forests in the region. An interval between 7 and 2 kyr BP is noticeable for the highest percentages of Scots pine (Pinus subgen. Diploxylon), spruce (Picea) and fir (Abies) pollen, indicating mid-Holocene spread of boreal forest communities

  4. Late-glacial and postglacial history of the hill'', Norwich University campus, Northfield, Vermont

    SciTech Connect

    Larsen, F.D. . Dept. of Geology)

    1993-03-01

    The central part of the Norwich University campus at Northfield is built on a kame about 60 ft high on the side of the Dog River valley. Significant excavations made between 1979 and 1991 in the flank of the hill provide details about its glacial origin. Collapsed ice-contact lake deposits on the northwestern flank of the kame are overlain by undisturbed lake sediments formed by turbidity currents that moved southward in glacial Lake Roxbury. Lake Roxbury formed when the retreating ice margin blocked the north-draining Dog River valley and caused melt water to drain south over a 1,010-foot threshold at Roxbury. The lowest deposits exposed on the southeast flank of the kame are highly deformed and include a chaotic slide breccia overlain by progressively less deformed lake-bottom sediments. Northward retreat of the ice margin permitted Lake Roxbury to drop 80 ft to the level of glacial Lake Winooski, which still left 80 ft of lake water over the top of the hill''. Following the lowering of Lake Winooski, stream terraces were cut on the west flank of the hill''. The terraces are underlain by imbricated pebble gravel deposited by the north-flowing Dog River that probably was graded to a lower glacial lake in the Winooski River valley to the north. Downcutting by the Dog River and subsequent lateral migration of its meanders produced the topography the authors see today. The late-glacial and postglacial history can be summarized as follows: (1) deposition of lake sediments in contact with buried ice, (2) collapse and continued deposition of lake sediments during melting of buried ice, (3) deposition of undeformed lake sediments, (4) drainage of glacial lakes, and (5) development of stream terraces and the modern flood plain.

  5. Quaternary glacial and post-glacial depositional history associated with the Green Bay lobe, east-central Wisconsin

    SciTech Connect

    Thieme, L.D.; Smith, G.L. . Dept. of Geology)

    1993-03-01

    Multiple layers of peat and wood fragments indicate that Quaternary glaciation of the east-central region of Wisconsin was punctuated by at least two interglacial periods. Till, outwash, and glaciolacustrine deposits suggest that deposition took place in alternating glacial and non-glacial environments due to oscillations in the position of the Green Bay Lobe terminus. The data for this study consists of 36 auger borings, 70 geologic logs and 100 well-construction reports from water wells. Nine vibracores were taken at the northern margin of Lake Winnebago in order to document in detail the post-glacial history of Glacial Lake Oshkosh/Lake Winnebago. Local bedrock consists of limestones and dolomites of the Middle Ordovician Sinnipee Group. Bedrock elevations range from 211--237 m; bedding dips regionally to the southeast at 1--2 degrees. Bedrock is overlain by a 3--13 m-thick layer of alternating red clay and gray silty-clay (basal Kewaunee Formation ) perhaps deposited in a proglacial lake. These sediments are overlain by apeat/wood layer indicating marsh deposition. This peat/wood layer is overlain by more proglacial lake sediment, 3--10 m of gray brown clay to silty-clay. A second peat/wood layer overlies the gray/brown sediment and may correlate with the Two Creeks buried forest bed. The uppermost unit consists of 2--3 m red silty-clay till (Middle Inlet Member of the Kewaunee Formation). Along the northern margin of present-day Lake Winnebago, red silty-clay is overlain by silty-sand deposited by Glacial Lake Oshkosh. Future work includes obtaining radiocarbon dates from buried peat/wood layers to verify these tentative correlations between east-central Wisconsin and the Lake Michigan Basin.

  6. The reproducible radio outbursts of SS Cygni

    NASA Astrophysics Data System (ADS)

    Russell, T. D.; Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; O'Brien, T. J.; Page, K. L.; Templeton, M. R.; Körding, E. G.; Knigge, C.; Rupen, M. P.; Fender, R. P.; Heinz, S.; Maitra, D.; Markoff, S.; Migliari, S.; Remillard, R. A.; Russell, D. M.; Sarazin, C. L.; Waagen, E. O.

    2016-08-01

    We present the results of our intensive radio observing campaign of the dwarf nova SS Cyg during its 2010 April outburst. We argue that the observed radio emission was produced by synchrotron emission from a transient radio jet. Comparing the radio light curves from previous and subsequent outbursts of this system (including high-resolution observations from outbursts in 2011 and 2012) shows that the typical long and short outbursts of this system exhibit reproducible radio outbursts that do not vary significantly between outbursts, which is consistent with the similarity of the observed optical, ultraviolet and X-ray light curves. Contemporaneous optical and X-ray observations show that the radio emission appears to have been triggered at the same time as the initial X-ray flare, which occurs as disc material first reaches the boundary layer. This raises the possibility that the boundary region may be involved in jet production in accreting white dwarf systems. Our high spatial resolution monitoring shows that the compact jet remained active throughout the outburst with no radio quenching.

  7. Are Comet Outbursts the Result of Avalanches?

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan; Melosh, H. Jay

    2016-10-01

    Recently, Rosetta became the first spacecraft to make high-resolution observations of a comet outburst (a rapid, ephemeral increase in dust production) emerging from the surface of a comet nucleus. These outbursts occurred near perihelion, lasted only a few minutes, and produced a highly collimated outburst plume without any corresponding increase in H2O or CO2 gas production (See abstract by Rinaldi et al.). These observations cannot be explained by proposed driving outburst mechanisms (such as crystallization of amorphous ice, cryovolcanic gas exsolution, or explosive outgasing of subsurface chambers), all of which are driven by gas, and would therefore lead to an increase in the gas production.We propose instead that the observed outbursts on Comet 67P/Churyumov-Gerasimenko (hereafter 67P) are the result of cometary avalanches. The surface of 67P contains many cliffs and scarps, with dusty surface layers blanketing the shallower slopes above and below these steep surfaces. The Rosetta spacecraft returned clear evidence of mass wasting, which form icy talus fields that are the source of much of 67P's cometary activity. Additionally, Rosetta observed morphological changes over time in the shallower, dusty surface layers above these steep slopes, which suggest that avalanches periodically release dusty materials onto these active talus fields.Here we present the results of a numerical simulation of dusty material avalanching into an active area (active talus field). These simulations show that such avalanches will generate a transient, highly collimated outburst plume that closely matches the observed morphology of the outbursts emanating from the surface of 67P. This mechanism predicts that cometary outbursting should not be directly associated with any increase in gas production, consistent with observations. Additionally, we show that regions of the nucleus that have sourced outburst plumes contain steep surfaces (above the angle of repose), which is required

  8. Protoplanetary Formation and the FU Orionis Outburst

    NASA Technical Reports Server (NTRS)

    Bodenheimer, P. H.

    1996-01-01

    The following three publications which reference the above grant from the NASA Origins of Solar Systems program are attached and form the final technical report for this project. The research involved comparisons of the spectral energy distributions of FU Orionis objects with theoretical models and associated studies of the structure of the outbursting accretion disks, as well as related studies on the effects of magnetic fields in disks, which will lead in the future to models of FU Orionis outbursts which include the effects of magnetic fields. The project was renewed under a new grant NAGW-4456, entitled 'Effects of FU Orionis Outbursts on Protoplanetary Disks'. Work now being prepared for publication deals more specifically with the issue of the effects of the outbursts on protoplanetary formation. Models of the spectral energy distribution of FU Orionis stars. A simple model of a buoyant magnetic dynamo in accretion disks and a numerical study of magnetic buoyancy in an accretion disk have been submitted.

  9. Dwarf Nova Outbursts with Magnetorotational Turbulence

    NASA Astrophysics Data System (ADS)

    Coleman, M. S. B.; Kotko, I.; Blaes, O.; Lasota, J.-P.; Hirose, S.

    2016-08-01

    The phenomenological Disc Instability Model has been successful in reproducing the observed light curves of dwarf nova outbursts by invoking an enhanced Shakura-Sunyaev α parameter ˜0.1 - 0.2 in outburst compared to a low value ˜0.01 in quiescence. Recent thermodynamically consistent simulations of magnetorotational (MRI) turbulence with appropriate opacities and equation of state for dwarf nova accretion discs have found that thermal convection enhances α in discs in outburst, but only near the hydrogen ionization transition. At higher temperatures, convection no longer exists and α returns to the low value comparable to that in quiescence. In order to check whether this enhancement near the hydrogen ionization transition is sufficient to reproduce observed light curves, we incorporate this MRI-based variation in α into the Disc Instability Model, as well as simulation-based models of turbulent dissipation and convective transport. These MRI-based models can successfully reproduce observed outburst and quiescence durations, as well as outburst amplitudes, albeit with different parameters from the standard Disc Instability Models. The MRI-based model lightcurves exhibit reflares in the decay from outburst, which are not generally observed in dwarf novae. However, we highlight the problematic aspects of the quiescence physics in the Disc Instability Model and MRI simulations that are responsible for this behavior.

  10. Dwarf nova outbursts with magnetorotational turbulence

    NASA Astrophysics Data System (ADS)

    Coleman, M. S. B.; Kotko, I.; Blaes, O.; Lasota, J.-P.; Hirose, S.

    2016-11-01

    The phenomenological disc instability model has been successful in reproducing the observed light curves of dwarf nova outbursts by invoking an enhanced Shakura-Sunyaev α parameter ˜0.1-0.2 in outburst compared to a low value ˜0.01 in quiescence. Recent thermodynamically consistent simulations of magnetorotational instability (MRI) turbulence with appropriate opacities and equation of state for dwarf nova accretion discs have found that thermal convection enhances α in discs in outburst, but only near the hydrogen ionization transition. At higher temperatures, convection no longer exists and α returns to the low value comparable to that in quiescence. In order to check whether this enhancement near the hydrogen ionization transition is sufficient to reproduce observed light curves, we incorporate this MRI-based variation in α into the disc instability model, as well as simulation-based models of turbulent dissipation and convective transport. These MRI-based models can successfully reproduce observed outburst and quiescence durations, as well as outburst amplitudes, albeit with different parameters from the standard disc instability models. The MRI-based model light curves exhibit reflares in the decay from outburst, which are not generally observed in dwarf novae. However, we highlight the problematic aspects of the quiescence physics in the disc instability model and MRI simulations that are responsible for this behaviour.

  11. The Be X-ray Binary Outburst Zoo II

    NASA Astrophysics Data System (ADS)

    Kuehnel, M.; Kretschmar, P.; Nespoli, E.; Okazaki, A. T.; Schoenherr, G.; Wilson-Hodge, C. A.; Falkner, S.; Brand, T.; Anders, F.; Schwarm, F.-W.; Kreykenbohm, I.; Mueller, S.; Pottschmidt, K.; Fuerst, F.; Grinberg, V.; Wilms, J.

    2015-03-01

    We have continued our recently started systematic study of Be X-ray binary (BeXRB) outbursts. Specifically, we are developing a catalogue of outbursts including their basic properties based on nearly all available X-ray all-sky-monitors. These properties are derived by fitting asymmetric Gaussians to the outburst lightcurves. This model describes most of the outbursts covered by our preliminary catalogue well; only 13% of all datasets show more complex outburst shapes. Analyzing the basic properties, we reveal a strong correlation between the outburst length and the reached peak flux. As an example, we discuss possible models describing the observed correlation in EXO 2030+375.

  12. Inflow, outflow, and water levels in Lake Michigan during the last part of the Wisconsin glaciation

    SciTech Connect

    Clayton, L.; Attig, J.W. ); Mickelson, D.M. . Dept. of Geology and Geophysics)

    1992-01-01

    Between about 14,000 and 10,000 B.P., water flowed to and from Lake Michigan through several channels connected with adjacent glacial lakes and the Mississippi basin. Inflow and outflow depend on lake-level fluctuations, but no known lake-level chronology for the Lake Michigan basin explains all the supposed facts. Several kinds of information can be use to construct such a chronology: elevations of beaches, elevations and locations of outlets, ice-margin positions, till stratigraphy, and glacial history relative to outlets and lake-sediment distribution. If the crustal rebound predicted by J.A. Clark (bracketed by glacial Lake Wisconsin and Door Peninsula water planes) is used as the basis for a lake-level chronology, lake elevations would have been much higher than previously recognized, beaches previously thought to be late glacial must be middle Holocene, and the predicted sequence of spillways from glacial Lake Oshkosh, in the Green Bay basin, to Lake Michigan seems incompatible with the till stratigraphy of the region. On the other hand, a hinge line model such as proposed by J.W. Goldthwait allows far less rebound than is required by their knowledge of present-day rebound and by the rebound interpreted from shore features of glacial Lake Wisconsin. Therefore major flaws exist in their understanding of the glacial chronology and stratigraphy, of the glacial lake deposits, or of the crustal rebound; the reconstructed of inflow and outflow will remain uncertain until these conflicts are resolved.

  13. Glacial integrative modelling.

    PubMed

    Ganopolski, Andrey

    2003-09-15

    Understanding the mechanisms of past climate changes requires modelling of the complex interaction between all major components of the Earth system: atmosphere, ocean, cryosphere, lithosphere and biosphere. This paper reviews attempts at such an integrative approach to modelling climate changes during the glacial age. In particular, the roles of different factors in shaping glacial climate are compared based on the results of simulations with an Earth-system model of intermediate complexity, CLIMBER-2. It is shown that ice sheets, changes in atmospheric compositions, vegetation cover, and reorganization of the ocean thermohaline circulation play important roles in glacial climate changes. Another example of this approach is the modelling of two major types of abrupt glacial climate changes: Dansgaard-Oeschger and Heinrich events. Our results corroborate some of the early proposed mechanisms, which relate abrupt climate changes to the internal instability of the ocean thermohaline circulation and ice sheets. At the same time, it is shown that realistic representation of the temporal evolution of the palaeoclimatic background is crucial to simulate observed features of the glacial abrupt climate changes.

  14. Glacial integrative modelling.

    PubMed

    Ganopolski, Andrey

    2003-09-15

    Understanding the mechanisms of past climate changes requires modelling of the complex interaction between all major components of the Earth system: atmosphere, ocean, cryosphere, lithosphere and biosphere. This paper reviews attempts at such an integrative approach to modelling climate changes during the glacial age. In particular, the roles of different factors in shaping glacial climate are compared based on the results of simulations with an Earth-system model of intermediate complexity, CLIMBER-2. It is shown that ice sheets, changes in atmospheric compositions, vegetation cover, and reorganization of the ocean thermohaline circulation play important roles in glacial climate changes. Another example of this approach is the modelling of two major types of abrupt glacial climate changes: Dansgaard-Oeschger and Heinrich events. Our results corroborate some of the early proposed mechanisms, which relate abrupt climate changes to the internal instability of the ocean thermohaline circulation and ice sheets. At the same time, it is shown that realistic representation of the temporal evolution of the palaeoclimatic background is crucial to simulate observed features of the glacial abrupt climate changes. PMID:14558899

  15. Glacier changes since Local Last Glacial Maximum in the South-West slope of Nevado Hualcán, Cordillera Blanca, Peru, deduced from moraine mapping and GIS-based analysis

    NASA Astrophysics Data System (ADS)

    Giráldez, Claudia; Palacios, David; Haeberli, Wilfried; Úbeda, Jose; Schauwecker, Simone; Torres, Judith

    2014-05-01

    Anticipating and assessing hazards and risks associated with the shrinking of surface and subsurface ice in cold mountain chains is facilitated by empirical-quantitative data on present and past rates of change, as well as by a general understanding of related landforms and landscape evolution through time. Rock/ice avalanches and devastating outburst floods from glacial lakes indeed constitute a major cause of severe damage in populated mountain areas such as the Cordillera Blanca whose combination of tectonic, topographic and glaciological characteristics make it a threatened region. This study focuses on the Río Chucchún catchment above the city of Carhuaz, which was recently affected by a flood/debris flow from a rock/ice avalanche impacting a recently grown lake (Laguna 513). Traces left by past glaciations strongly affect the current geomorphodinamic behaviour of the catchment. For instance, a prominent sediment-filled glacial overdeepening behind Younger Dryas (YD) moraines (Pampa de Shonquil) with its retention function strongly influenced the chain of processes initiated by the outburst of Laguna 513. The aim of this study is to reconstruct earlier glacial phases in the SW slope of Nevado Hualcán (Río Chucchún catchment), in order to compile quantitative information on surface areas and Equilibrium Line Altitudes (ELAs). To do so, glacier stages were assigned to five different glacial phases, through photointerpretation and moraine cartography: 2003; 1962; Hualcán-I-LIA (15th to 18th centuries); Hualcán-II-YD (~12,5 ka BP); and Hualcán-III-LLGM (~34 to 21 ka BP). Glacial stages Hualcán-I-LIA, Hualcán-II-YD and Hualcán-III-LLGM present relative dating based on previous studies from different authors in the Peruvian Andes. Once glaciers were delimited, their surface areas and Equilibrium Line Altitudes (ELAs) were calculated. For ELA estimation three different methods were used: the mid-range elevation, the Accumulation Area Ratio (AAR), and the

  16. Extensive glaciation in Transbaikalia, Siberia, at the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Margold, Martin; Jansen, John D.; Gurinov, Artem L.; Codilean, Alexandru T.; Fink, David; Preusser, Frank; Reznichenko, Natalya V.; Mifsud, Charles

    2016-01-01

    Successively smaller glacial extents have been proposed for continental Eurasia during the stadials of the last glacial period leading up to the Last Glacial Maximum (LGM). At the same time the large mountainous region east of Lake Baikal, Transbaikalia, has remained unexplored in terms of glacial chronology despite clear geomorphological evidence of substantial past glaciations. We have applied cosmogenic 10Be exposure dating and optically stimulated luminescence to establish the first quantitative glacial chronology for this region. Based on eighteen exposure ages from five moraine complexes, we propose that large mountain ice fields existed in the Kodar and Udokan mountains during Oxygen Isotope Stage 2, commensurate with the global LGM. These ice fields fed valley glaciers (>100 km in length) reaching down to the Chara Depression between the Kodar and Udokan mountains and to the valley of the Vitim River northwest of the Kodar Mountains. Two of the investigated moraines date to the Late Glacial, but indications of incomplete exposure among some of the sampled boulders obscure the specific details of the post-LGM glacial history. In addition to the LGM ice fields in the highest mountains of Transbaikalia, we report geomorphological evidence of a much more extensive, ice-cap type glaciation at a time that is yet to be firmly resolved.

  17. Nucleosynthesis and the nova outburst

    NASA Technical Reports Server (NTRS)

    Starrfield, S.; Truran, J.W.; Wiescher, M.; Sparks, W.M.

    1995-01-01

    A nova outburst is the consequence of the accretion of hydrogen rich material onto a white dwarf and it can be considered as the largest hydrogen bomb in the Universe. The fuel is supplied by a secondary star in a close binary system while the strong degeneracy of the massive white dwarf acts to contain the gas during the early stages of the explosion. The containment allows the temperature in the nuclear burning region to exceed 10(sup 8)K under all circumstances. As a result a major fraction of CNO nuclei in the envelope are transformed into (beta)(sup +)-unstable nuclei. We discuss the effects of these nuclei on the evolution. Recent observational studies have shown that there are two compositional classes of novae; one which occurs on carbon-oxygen white dwarfs, and a second class that occurs on oxygen-neon-magnesium white dwarfs. In this review we will concentrate on the latter explosions since they produce the most interesting nucleosynthesis. We report both on the results of new observational determinations of nova abundances and, in addition, new hydrodynamic calculations that examine the consequences of the accretion process on 1.0M(sub (circle dot)), 1.25M(sub (circle dot)), and 1.35M(sub (circle dot)) white dwarfs. Our results show that novae can produce (sup 22)Na, (sup 26)Al, and other intermediate mass nuclei in interesting amounts. We will present the results of new calculations, done with updated nuclear reaction rates and opacities, which exhibit quantitative differences with respect to published work.

  18. Nucleosynthesis and the nova outburst

    SciTech Connect

    Starrfield, S.; Truran, J.W.; Wiescher, M.; Sparks, W.M.

    1995-12-31

    A nova outburst is the consequence of the accretion of hydrogen rich material onto a white dwarf and it can be considered as the largest hydrogen bomb in the Universe. The fuel is supplied by a secondary star in a close binary system while the strong degeneracy of the massive white dwarf acts to contain the gas during the early stages of the explosion. The containment allows the temperature in the nuclear burning region to exceed 10{sup 8}K under all circumstances. As a result a major fraction of CNO nuclei in the envelope are transformed into {beta}{sup +}-unstable nuclei. We discuss the effects of these nuclei on the evolution. Recent observational studies have shown that there are two compositional classes of novae; one which occurs on carbon-oxygen white dwarfs, and a second class that occurs on oxygen-neon-magnesium white dwarfs. In this review we will concentrate on the latter explosions since they produce the most interesting nucleosynthesis. We report both on the results of new observational determinations of nova abundances and, in addition, new hydrodynamic calculations that examine the consequences of the accretion process on 1.0M{sub {circle_dot}}, 1.25M{sub {circle_dot}}, and 1.35M{sub {circle_dot}} white dwarfs. Our results show that novae can produce {sup 22}Na, {sup 26}Al, and other intermediate mass nuclei in interesting amounts. We will present the results of new calculations, done with updated nuclear reaction rates and opacities, which exhibit quantitative differences with respect to published work.

  19. Glacial Geology of Wisconsin.

    ERIC Educational Resources Information Center

    Madison Public Schools, WI.

    This publication is a teacher's resource and guidebook for the presentation of the three filmstrips in the "Glacial Geology of Wisconsin" series. The first filmstrip is subtitled, "Evidence of the Glaciers," the second "How the Glaciers Reshaped the Landscape," and the third "Fossils of the Ice Age." Included are a list of objectives, an outline…

  20. Review of the classical nova outburst

    SciTech Connect

    Starrfield, S.; Sparks, W.M.

    1986-06-01

    Observational studies have not only identified a new class of novae but theoretical simulations of this class have been found to be in excellent agreement with the observations. This new class consists of outbursts occurring on ONeMg white dwarfs in close binar systems in contrast to the other outbursts which are occurring on CO white dwarfs. We also review the effects of the ..beta../sup +/-unstable nuclei and show how their presence has a major effect on the evolution. 77 refs.

  1. A Failed outburst of H1743-322

    NASA Astrophysics Data System (ADS)

    Capitanio, F.; Belloni, T.; Del Santo, M.; Ubertini, P.

    2010-07-01

    H1743-322 is a bright BHC observed by HEAO-1 in 1977. The source underwent again in outburst in 2003 after about 25 years. After the 2003 outburst (the brightest one) the source exhibited other 5 outbursts. We report a brief summary of the results found during a campaign of X-ray observations performed with RXTE during the two 2008 outbursts. In particular the October 2008 outburst showed a singular behaviour that has been rarely observed in transient X-ray binaries.

  2. Lakes-paleolakes cascade system and its role in shaping the runoff and chemical properties of water in the young-glacial catchment - example from the Tuchola Pinewood Forest (Northern Poland)

    NASA Astrophysics Data System (ADS)

    Gierszewski, Piotr; Brykała, Dariusz; Kaszubski, Michał; Plessen, Birgit

    2016-04-01

    The impact of paleolake basins, filled up with organic mineral deposits, in the transformation of the chemical properties of the outflow is generally ignored. Defining their role and importance in the water and matter cycles is one of the objectives of the hydrological and hydrochemical monitoring, which has been run in the catchment of Lake Czechowskie since mid-2012. The axis of the Lake Czechowskie catchment is a hydrographical system made of river and lake sections. Lake sections are not only present-day lakes (Głęboczek and Czechowskie), but also basins of the lakes functioned in the past, which are now biogenic plains. Lake sections of the system are connected by short valley sections, mostly of a gap character. The size and variability of surface water runoff from the basin is mainly affected by groundwater and the size of evaporation. Stable groundwater table provides stability of the river discharge, even during the periods of significant precipitation deficit. Groundwater fluctuation ranges registered during the period from May 2012 to September 2015 were between 0.17 and 1.25 m. The smallest were in the deepest piezometers located in watershed areas, and the largest in the shallow groundwater of lake terraces. The small dynamics of the groundwater states is reflected by slight fluctuations of water levels in Lake Czechowskie, which in the analyzed period amounted 0.40 cm. The surface of paleolake Trzechowskie, cut by a system of drainage ditches, is the area where an essential part of the surface runoff from the monitored catchment is formed. Large water resources in this part of the catchment are evidenced by the specific runoff value, which amounts to 25 dm3s‑1km2. It is much larger than the whole basin specific runoff which reaches 11 dm3s‑1km2. The measurements showed that the average surface runoff from Lake Czechowskie in the analyzed period was 0,065 m3s‑1 and was similar to the size of the water influx via watercourses supplying the lake

  3. Lakes-paleolakes cascade system and its role in shaping the runoff and chemical properties of water in the young-glacial catchment - example from the Tuchola Pinewood Forest (Northern Poland)

    NASA Astrophysics Data System (ADS)

    Gierszewski, Piotr; Brykała, Dariusz; Kaszubski, Michał; Plessen, Birgit

    2016-04-01

    The impact of paleolake basins, filled up with organic mineral deposits, in the transformation of the chemical properties of the outflow is generally ignored. Defining their role and importance in the water and matter cycles is one of the objectives of the hydrological and hydrochemical monitoring, which has been run in the catchment of Lake Czechowskie since mid-2012. The axis of the Lake Czechowskie catchment is a hydrographical system made of river and lake sections. Lake sections are not only present-day lakes (Głęboczek and Czechowskie), but also basins of the lakes functioned in the past, which are now biogenic plains. Lake sections of the system are connected by short valley sections, mostly of a gap character. The size and variability of surface water runoff from the basin is mainly affected by groundwater and the size of evaporation. Stable groundwater table provides stability of the river discharge, even during the periods of significant precipitation deficit. Groundwater fluctuation ranges registered during the period from May 2012 to September 2015 were between 0.17 and 1.25 m. The smallest were in the deepest piezometers located in watershed areas, and the largest in the shallow groundwater of lake terraces. The small dynamics of the groundwater states is reflected by slight fluctuations of water levels in Lake Czechowskie, which in the analyzed period amounted 0.40 cm. The surface of paleolake Trzechowskie, cut by a system of drainage ditches, is the area where an essential part of the surface runoff from the monitored catchment is formed. Large water resources in this part of the catchment are evidenced by the specific runoff value, which amounts to 25 dm3s-1km2. It is much larger than the whole basin specific runoff which reaches 11 dm3s-1km2. The measurements showed that the average surface runoff from Lake Czechowskie in the analyzed period was 0,065 m3s-1 and was similar to the size of the water influx via watercourses supplying the lake. On

  4. Outbursts in ultracompact X-ray binaries

    NASA Astrophysics Data System (ADS)

    Hameury, J.-M.; Lasota, J.-P.

    2016-10-01

    Context. Very faint X-ray binaries appear to be transient in many cases with peak luminosities much fainter than that of usual soft X-ray transients, but their nature still remains elusive. Aims: We investigate the possibility that this transient behaviour is due to the same thermal/viscous instability which is responsible for outbursts of bright soft X-ray transients, occurring in ultracompact binaries for adequately low mass-transfer rates. More generally, we investigate the observational consequences of this instability when it occurs in ultracompact binaries. Methods: We use our code for modelling the thermal-viscous instability of the accretion disc, assumed here to be hydrogen poor. We also take into account the effects of disc X-ray irradiation, and consider the impact of the mass-transfer rate on the outburst brightness. Results: We find that one can reproduce the observed properties of both the very faint and the brighter short transients (peak luminosity, duration, recurrence times), provided that the viscosity parameter in quiescence is slightly smaller (typically a factor of between two and four) than in bright soft X-ray transients and normal dwarf nova outbursts, the viscosity in outburst being unchanged. This possibly reflects the impact of chemical composition on non-ideal magnetohydrodynamic effects affecting magnetically driven turbulence in poorly ionized discs.

  5. Numerical modelling of the classical nova outburst

    SciTech Connect

    Kutter, G.S.; Sparks, W.M.

    1987-01-01

    We describe a mechanism that promises to explain how nova outbursts take place on white dwarf of 1 Msub solar or less and for accretion rates of 4 x 10/sup -10/ Msub solar yr/sup -1/ or greater. 7 refs.

  6. Negative consequences of glacial turbidity for the survival of freshwater planktonic heterotrophic flagellates.

    PubMed

    Sommaruga, Ruben; Kandolf, Georg

    2014-02-17

    Heterotrophic (phagotrophic) flagellates are key components of planktonic food webs in freshwater and marine ecosystems because they are the main consumers of bacteria. Although they are ubiquitous in aquatic ecosystems, they were numerically undetectable in turbid glacier-fed lakes. Here we show that glacial particles had negative effects on the survival and growth of heterotrophic flagellates. The effect of glacial particles was concentration-dependent and was caused by their interference with bacterial uptake rather than by physical damage. These results are the first to reveal why establishment of heterotrophic flagellates populations is hindered in very turbid glacial lakes. Because glaciers are vanishing around the world, recently formed turbid meltwater lakes represent an excellent opportunity to understand the environmental conditions that probably shaped the establishment of lake communities at the end of the last glaciation.

  7. Glacial atmospheric phosphorus deposition

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid; Dallmayr, Remi; Gabrieli, Jacopo; Goto-Azuma, Kumiko; Hirabayashi, Motohiro; Svensson, Anders; Vallelonga, Paul

    2016-04-01

    Phosphorus in the atmosphere is poorly studied and thus not much is known about atmospheric phosphorus and phosphate transport and deposition changes over time, though it is well known that phosphorus can be a source of long-range nutrient transport, e.g. Saharan dust transported to the tropical forests of Brazil. In glacial times it has been speculated that transport of phosphorus from exposed shelves would increase the ocean productivity by wash out. However whether the exposed shelf would also increase the atmospheric load to more remote places has not been investigated. Polar ice cores offer a unique opportunity to study the atmospheric transport of aerosols on various timescales, from glacial-interglacial periods to recent anthropogenic influences. We have for the first time determined the atmospheric transport of phosphorus to the Arctic by means of ice core analysis. Both total and dissolved reactive phosphorus were measured to investigate current and past atmospheric transport of phosphorus to the Arctic. Results show that glacial cold stadials had increased atmospheric total phosphorus mass loads of 70 times higher than in the past century, while DRP was only increased by a factor of 14. In the recent period we find evidence of a phosphorus increase over the past 50 yrs in ice cores close to human occupation likely correlated to forest fires. References: Kjær, Helle Astrid, et al. "Continuous flow analysis method for determination of dissolved reactive phosphorus in ice cores." Environmental science & technology 47.21 (2013): 12325-12332. Kjær, Helle Astrid, et al. "Greenland ice cores constrain glacial atmospheric fluxes of phosphorus." Journal of Geophysical Research: Atmospheres120.20 (2015).

  8. Glacial curvilineations: gradual or catastrophic origin?

    NASA Astrophysics Data System (ADS)

    Clark, Chris; Livingstone, Stephen

    2016-04-01

    Glacial curvilineations (GCLs) are enigmatic landforms that have recently been discovered in Poland (Lesemann et al., 2010, 2014). They comprise parallel sets of sinuous ridges separated by troughs that are found in tunnel valleys and replicate the morphology and pattern of the valley sides. The sedimentology for some has been reported to indicate that the sediment composition relates to a pre-GCL phase. So far just one theory for their formation exists - erosion by longitudinal-vortices within high-energy subglacial meltwater flows (Lesemann et al., 2010). Here, we provide an alternative hypothesis for their formation developed from observations of GCLs found along the southern sector of the Laurentide Ice Sheet. In all cases GCLs were found associated with tunnel valley widenings or hollows and occur as distinct parallel sets that mimic each other in terms of nicks and cusps. Using analogies from tree-rings and coral growth we take such mimicry as indicating either incremental growth or development from a template over time. Although without a strong physical explanation we find it much less likely that a series of parallel water channels would maintain such strong mimicry. We instead suggest that subglacial thawing of frozen ground in association with discrete water bodies (tunnel valleys or subglacial lakes) resulted in retrogressive bank failure, possibly along a glide plane provided by a frozen surface. References: Lesemann, J.-E., Piotrowski, J. a, Wysota, W., 2010. "Glacial curvilineations": New glacial landforms produced by longitudinal vortices in subglacial meltwater flows. Geomorphology 120, 153-161. Lesemann, J.-E., Piotrowski, J. a, Wysota, W., 2014. Genesis of the "glacial curvilineation" landscape by meltwater processes under the former Scandinavian Ice Sheet, Poland. Sediment. Geol. 312, 1-18.

  9. EDITORIAL: Cryospheric ecosystems: a synthesis of snowpack and glacial research

    NASA Astrophysics Data System (ADS)

    Hodson, Andy; Brock, Ben; Pearce, David; Laybourn-Parry, Johanna; Tranter, Martyn

    2015-11-01

    The fourteen letters that contributed to this focus issue on cryospheric ecosytems provide an excellent basis for considering the state of the science following a marked increase in research attention since the new millennium. Research letters from the focus issue provide significant insights into the biogeochemical and biological processes associated with snow, glacier ice and glacial sediments. This has been achieved via a significant, empirical effort that has given particular emphasis to glacier surface habitats. However, far less is known about aerobiology, glacial snow covers, supraglacial lakes and sub-ice sedimentary habitats, whose access for sampling and in-situ monitoring remains a great challenge to scientists. Furthermore, the use of models to explore key fluxes, processes and impacts of a changing glacial cryosphere are conspicuous by their absence. As a result, a range of process investigations and modelling studies are required to address the increasing urgency and uncertainty that is associated with understanding the response of cryospheric ecosystems to global change.

  10. Giant glacial cirques of non-mountainous terrains

    NASA Astrophysics Data System (ADS)

    Amantov, A.; Amantova, M.

    2012-04-01

    Cirques are usually considered as specific landforms of hill and mountain terrains produced by alpine glaciers, and/or slope failures (landslides). However, glacial cirques seem to be present also in non-mountainous terrains that underwent extensive Pleistocene ice-sheet glaciations and strong glacial and fluvio-glacial erosion. The largest form in the Baltic region is Severoladozhsky (North Lake Ladoga) cirque, probably the world's largest representative, with the length and width close to 100 km. Another example is the deepest Landsort basin of the Baltic Sea. In those cases Meso-Neoproterozoic sediments were subject to selected erosion, with evident overdeepening of the bedrock surface in comparison with surrounding crystalline frame. The bowl headwall shape of the cirque-like landforms was determined by the outline of the margin of exhumed basin. The origin of the major basins of margins of the Baltic and Canadian shields are similar. However, direct analogues of giant cirques are not well developed in this part of North America due to geological deviations and dominant directions of ice movement. Comparable landforms (like the South Chippewa basin of the Lake Michigan) are therefore less mature. We define glacial cirque as an amphitheatre-shape depression with comparable values of length and width, steep headwall with adjacent side slopes and gentle lip with commonly increased glacial accumulation. They are usually located within an ice stream that created typical relief profile with normal horseshoe overdeepening, and in areas predefined by geological and geomorphological peculiarities. This definition likely fits both classic mountain cirques, and giant ones created in favorable conditions in domains that underwent extensive glaciations and relevant selective glacial erosion. Length/width ratio typical for giant cirques group is close to 1:1, being comparable with classical alpine ones. Major differences (like length/height ratio of other order and possible

  11. Is rate of glacial retreat accelerated in Indian Himalaya? (Invited)

    NASA Astrophysics Data System (ADS)

    Kulkarni, A. V.

    2013-12-01

    The Himalaya has one of the largest concentration of glaciers and rivers like Indus, Ganga and Bramhputra originate from this region. The snow and glacier melt is an important source of water for these rivers. However, this source of water may get affected in the near future due to changes in the cryosphere. Therefore, retreat of Himalayan glaciers are discussed extensively in scientific and public forums in India. Conventionally health of glaciers is assessed using changes in glacial length, as it is widely measured. However changes in glacial length and loss in areal extent near terminus needs to be interpreted carefully, as these changes can be influenced by numerous terrain and climatically sensitive parameters. The terrain parameters which can influence glacial retreat are slope, area altitude distribution, debris cover and orientation. In addition, climatically sensitive parameters like mass balance, glacial lakes and black carbon can also influence glacier retreat. These multiple influences can produce a complex pattern of glacial retreat. In this paper long-term glacier retreat in three river basins in the Indian Himalaya as Tista, Baspa and Parbati will be discussed. These basins are located in different climatically sensitive regions and each basin has unique dominant process of mass wasting. In addition to terrain parameters, influence of process like formation and expansion of moraine dammed lakes in Tista basin, deposition of black carbon on accumulation area in Baspa basin and debris cover in Parbati basin will also be discussed. This will provide understanding on varying influence of different mass wasting processes on glacial retreat during last five decades in the Indian Himalaya.

  12. Seismic reflection study of recessional moraines beneath Lake Superior and their relationship to regional deglaciation

    USGS Publications Warehouse

    Landmesser, C.W.; Johnson, T.C.; Wold, R.J.

    1982-01-01

    Approximately 8000 km of continuous seismic reflection profiles throughout Lake Superior were examined for evidence of recessional moraines and other ice-margin deposits associated with the retreat of late Wisconsin ice. These features are correlated with the record of glacial-lake evolution in western Lake Superior. An offlapping sequence of glacial and glacial-lacustrine dediments overlying bedrock is recognized in west-central Lake Superior that is progressively younger to the northeast. The sequence underlies more recent glaical-lacustrine and postglacial sediments. Four facies are recognized on the basis of geomorphologic and acoustic properties and are interpreted to represent a southwest-to-northeast assemblage of: proglacial stratified drift (facies A), drift in major end moraines (facies B), till deposited as glacial retreat resumed, or possibly late-stage ablation till (facies C), and basal till (facies D). The prominent moraines of facies B are unusually thick and are believed to mark the ice-margin shorelines of successive major proglacial lakes that formerly occupied parts of western Lake Superior. The moraines are tentatively correlated with Glacial Lake Duluth (unit 1), Glacial Lake Washburn (unit 2), and Glacial Lake Beaver Bay (unit 3), the most prominent of lakes drained via the progressively lower outlets via the Moose Lake/ Brule-St. Croix Rivers, the Huron Mountains, and the Au Train-Whitefish regions, respectively. ?? 1982.

  13. Origin of the 2006 Orionid Outburst

    NASA Astrophysics Data System (ADS)

    Sato, Mikiya; Watanabe, Jun-Ichi

    2007-08-01

    The Orionid outburst observed in 2006 resulted in strong activity, continuing for about four days. We have found that this activity was caused by the dust trails formed by meteoroids ejected from 1P/Halley in -1265, -1197, and -910. These meteoroids had six times the Jovian orbital period, and their orbit was able to intersect the Earth's orbit at the present day because of this mean motion resonance with Jupiter.

  14. Comet outbursts and the meteor showers

    NASA Astrophysics Data System (ADS)

    Guliyev, A. S.; Kokhirova, G. I.; Poladova, U. D.

    2014-07-01

    The features of 116 comets that have shown an outbursts in their brightness, are considered in the paper. The hypothesis on that the outburst in activity of comets are caused by their passing through meteoroid streams is studied. For this purpose the orbital elements of such comets relative to the planes of motion of 68 meteor showers from Cook's catalogue are analyzed. It was found that four of the nearest and distant nodes of comet orbits relative to the planes of motion of nine meteor showers exceeds the average statistical background with confidence probability from 0.90 to 0.95, and more than 0.95, respectively. The October Draconids, Aurigids, kappa-Serpentids, delta-Draconids, sigma-Hydrids}, Coma Berenicids, Leonids, Leo Minorids, and Perseids showers are the most effective. The results of calculation show that often, the comets outbursts may be caused by collisions of comets with meteoroids under the passing through the meteoroid streams that are producing listed meteor showers as well as solar activity.

  15. VARIABLE ACCRETION OUTBURSTS IN PROTOSTELLAR EVOLUTION

    SciTech Connect

    Bae, Jaehan; Hartmann, Lee; Zhu, Zhaohuan; Gammie, Charles E-mail: lhartm@umich.edu E-mail: gammie@illinois.edu

    2013-02-20

    We extend the one-dimensional, two-zone models of long-term protostellar disk evolution with infall of Zhu et al. to consider the potential effects of a finite viscosity in regions where the ionization is too low for the magnetorotational instability (MRI) to operate (the {sup d}ead zone{sup )}. We find that the presence of a small but finite dead zone viscosity, as suggested by simulations of stratified disks with MRI-active outer layers, can trigger inside-out bursts of accretion, starting at or near the inner edge of the disk, instead of the previously found outside-in bursts with zero dead zone viscosity, which originate at a few AU in radius. These inside-out bursts of accretion bear a qualitative resemblance to the outburst behavior of one FU Ori object, V1515 Cyg, in contrast to the outside-in burst models, which more closely resemble the accretion events in FU Ori and V1057 Cyg. Our results suggest that the type and frequency of outbursts are potentially a probe of transport efficiency in the dead zone. Simulations must treat the inner disk regions, R {approx}< 0.5 AU, to show the detailed time evolution of accretion outbursts in general and to observe the inside-out bursts in particular.

  16. Outbursts in Two New Cool Pulsating DA White Dwarfs

    NASA Astrophysics Data System (ADS)

    Bell, Keaton J.; Hermes, J. J.; Montgomery, M. H.; Gentile Fusillo, N. P.; Raddi, R.; Gänsicke, B. T.; Winget, D. E.; Dennihy, E.; Gianninas, A.; Tremblay, P.-E.; Chote, P.; Winget, K. I.

    2016-10-01

    The unprecedented extent of coverage provided by Kepler observations recently revealed outbursts in two hydrogen-atmosphere pulsating white dwarfs (DAVs) that cause hours-long increases in the overall mean flux of up to 14%. We have identified two new outbursting pulsating white dwarfs in K2, bringing the total number of known outbursting white dwarfs to four. EPIC 211629697, with {T}{eff} = 10,780 ± 140 K and {log} g = 7.94 ± 0.08, shows outbursts recurring on average every 5.0 days, increasing the overall flux by up to 15%. EPIC 229227292, with {T}{eff} = 11,190 ± 170 K and {log} g = 8.02 ± 0.05, has outbursts that recur roughly every 2.4 days with amplitudes up to 9%. We establish that only the coolest pulsating white dwarfs within a small temperature range near the cool, red edge of the DAV instability strip exhibit these outbursts.

  17. Last Glacial vegetation and climate change in the southern Levant

    NASA Astrophysics Data System (ADS)

    Miebach, Andrea; Chen, Chunzhu; Litt, Thomas

    2015-04-01

    Reconstructing past climatic and environmental conditions is a key task for understanding the history of modern mankind. The interaction between environmental change and migration processes of the modern Homo sapiens from its source area in Africa into Europe is still poorly understood. The principal corridor of the first human dispersal into Europe and also later migration dynamics crossed the Middle East. Therefore, the southern Levant is a key area to investigate the paleoenvironment during times of human migration. In this sense, the Last Glacial (MIS 4-2) is particularly interesting to investigate for two reasons. Firstly, secondary expansions of the modern Homo sapiens are expected to occur during this period. Secondly, there are ongoing discussions on the environmental conditions causing the prominent lake level high stand of Lake Lisan, the precursor of the Dead Sea. This high stand even culminated in the merging of Lake Lisan and Lake Kinneret (Sea of Galilee). To provide an independent proxy for paleoenvironmental reconstructions in the southern Levant during the Last Glacial, we investigated pollen assemblages of the Dead Sea/Lake Lisan and Lake Kinneret. Located at the Dead Sea Transform, the freshwater Lake Kinneret is nowadays connected via the Jordan with the hypersaline Dead Sea, which occupies Earth's lowest elevation on land. The southern Levant is a transition area of three different vegetation types. Therefore, also small changes in the climate conditions effect the vegetation and can be registered in the pollen assemblage. In contrast to the Holocene, our preliminary results suggest another vegetation pattern during the Last Glacial. The vegetation belt of the fragile Mediterranean biome did no longer exist in the vicinity of Lake Kinneret. Moreover, the vegetation was rather similar in the whole study area. A steppe vegetation with dwarf shrubs, herbs, and grasses predominated. Thermophilous elements like oaks occurred in limited amounts. The

  18. Geomorphic change caused by outburst floods and debris flows at Mount Rainier, Washington, with emphasis on Tahoma Creek valley

    USGS Publications Warehouse

    Walder, J.S.; Driedger, C.L.

    1994-01-01

    Debris flows have caused rapid geomorphic change in several glacierized drainages on Mount Rainier, Washington. Nearly all of these flows began as glacial outburst floods, then transformed to debris flows by incorporating large masses of sediment in channel reaches where streams have incised proglacial sediments and stagnant glacier ice. This stagnant ice is a relic of advanced glacier positions achieved during the mid-nineteenth century Little Ice Age maximum and the readvance of the 1960's and 1970's. Debris flows have been especially important agents of geomorphic change along Tahoma Creek, which drains South Tahoma Glacier. Debris flows in Tahoma Creek valley have transported downstream about 107 m3 Of sediment since 1967, causing substantial aggradation and damage to roads and facilities in Mount Rainier National Park. The average denudation rate in the upper part of the Tahoma Creek drainage basin in the same period has been extraordinarily high: more than 20 millimeters per year, a value exceeded only rarely in basins affected by debris flows. However, little or none of this sediment has yet passed out of the Tahoma Creek drainage basin. Outburst floods from South Tahoma Glacier form by release of subglacially stored water. The volume of stored water discharged during a typical outburst flood would form a layer several tens of millimeters thick over the bed of the entire glacier, though it is more likely that large linked cavities account for most of the storage. Statistical analysis shows that outburst floods usually occur during periods of atypically hot or rainy weather in summer or early autumn, and that the probability of an outburst increases with temperature (a proxy measure of ablation rate) or rainfall rate. On the basis of these results, we suggest that outburst floods are triggered when rapid input of water to the glacier bed causes transient increase in water pressure, thereby destabilizing the linked-cavity system. The probabilistic nature of

  19. Outburst-related period changes of recurrent nova CI aquilae

    SciTech Connect

    Wilson, R. E.; Honeycutt, R. K. E-mail: rewilson@ufl.edu

    2014-11-01

    Pre-outburst and post-outburst light curves and post-outburst eclipse timings are analyzed to measure any period (P) change related to nova CI Aql's outburst of early 2000 and a mean post-outburst dP/dt, which then lead to estimates of the accreting component's rate of mass (M) change and its overall outburst-related change of mass over roughly a decade of observations. We apply a recently developed procedure for unified analysis of three timing-related data types (light curves, radial velocities, and eclipse timings), although with only light curves and timings in this case. Fits to the data are reasonably good without need for a disk in the light-curve model, although the disk certainly exists and has an important role in our post-outburst mass flow computations. Initial experiments showed that, although there seems to be an accretion hot spot, it has essentially no effect on derived outburst-related ΔP or on post-outburst dP/dt. Use of atomic time (HJED) in place of HJD also has essentially nil effect on ΔP and dP/dt. We find ΔP consistently negative in various types of solutions, although at best only marginally significant statistically in any one experiment. Pre-outburst HJD {sub 0} and P results are given, as are post-outburst HJD {sub 0}, P, and dP/dt, with light curves and eclipse times as joint input, and also with only eclipse time input. Post-outburst dP/dt is negative at about 2.4σ. Explicit formulae for mass transfer rates and epoch-to-epoch mass change are developed and applied. A known offset in the magnitude zero point for 1991-1994 is corrected.

  20. Geomorphic Expression of Abrupt Climate Change in Southwestern North America at the Glacial Termination

    NASA Astrophysics Data System (ADS)

    Anderson, Roger Y.; Allen, Bruce D.; Menking, Kirsten M.

    2002-05-01

    Eolian and subaqueous landforms composed of gypsum sand provide geomorphic evidence for a wet episode at the termination of glacial climate in southwestern North America. Drying of pluvial Lake Estancia, central New Mexico, occurred after ca. 12,000 14C yr B.P. Thereafter, eolian landforms on the old lake floor, constructed of gypsum sand, were overridden by rising lake water, modified by subaqueous processes, and organized into beach ridges along the lake's eastern shore. Preservation of preexisting eolian landforms in the shallow lake suggests abupt changes in lake level and climate. Available radiocarbon ages suggest that the final highstand recorded by beach ridges may have developed during the Younger Dryas (YD) stade. The beach ridges provide information about lake surface area, which was 45% of the lake area reached during the maximum highstands of the late Pleistocene. A similar proportional response has been reported for YD climate changes outside the North Atlantic region.

  1. Big lake records preserved in a little lake's sediment: An example from Silver Lake, Michigan, USA

    USGS Publications Warehouse

    Fisher, T.G.; Loope, W.L.; Pierce, W.; Jol, H.M.

    2007-01-01

    We reconstruct postglacial lake-level history within the Lake Michigan basin using soil stratigraphy, ground-penetrating radar (GPR), sedimentology and 14C data from the Silver Lake basin, which lies adjacent to Lake Michigan. Stratigraphy in nine vibracores recovered from the floor of Silver Lake appears to reflect fluctuation of water levels in the Lake Michigan basin. Aeolian activity within the study area from 3,000 years (cal yr. B.P.) to the present was inferred from analysis of buried soils, an aerial photograph sequence, and GPR. Sediments in and around Silver Lake appear to contain a paleoenvironmental record that spans the entire post-glacial history of the Lake Michigan basin. We suggest that (1) a pre-Nipissing rather than a Nipissing barrier separated Silver Lake basin from the Lake Michigan basin, (2) that the Nipissing transgression elevated the water table in the Silver Lake basin about 6,500 cal yr. B.P., resulting in reestablishment of a lake within the basin, and (3) that recent dune migration into Silver Lake is associated with levels of Lake Michigan.

  2. AG Pegasi - now a classical symbiotic star in outburst?

    NASA Astrophysics Data System (ADS)

    Tomov, T. V.; Stoyanov, K. A.; Zamanov, R. K.

    2016-11-01

    Optical spectroscopy study of the recent AG Pegasi (AG Peg) outburst observed during the second half of 2015 is presented. Considerable variations of the intensity and the shape of the spectral features as well as the changes of the hot component parameters, caused by the outburst, are discussed and certain similarities between the outburst of AG Peg and the outburst of a classical symbiotic stars are shown. It seems that after the end of the symbiotic nova phase, AG Peg became a member of the classical symbiotic stars group.

  3. AG Pegasi - now a classical symbiotic star in outburst?

    NASA Astrophysics Data System (ADS)

    Tomov, T. V.; Stoyanov, K. A.; Zamanov, R. K.

    2016-08-01

    Optical spectroscopy study of the recent AG Peg outburst observed during the second half of 2015 is presented. Considerable variations of the intensity and the shape of the spectral features as well as the changes of the hot component parameters, caused by the outburst, are discussed and certain similarities between the outburst of AG Peg and the outburst of a classical symbiotic stars are shown. It seems that after the end of the symbiotic nova phase, AG Peg became a member of the classical symbiotic stars group.

  4. The influence of glacial meltwater on alpine aquatic ecosystems: a review.

    PubMed

    Slemmons, Krista E H; Saros, Jasmine E; Simon, Kevin

    2013-10-01

    The recent and rapid recession of alpine glaciers over the last 150 years has major implications for associated aquatic communities. Glacial meltwater shapes many of the physical features of high altitude lakes and streams, producing turbid environments with distinctive hydrology patterns relative to nival systems. Over the past decade, numerous studies have investigated the chemical and biological effects of glacial meltwater on freshwater ecosystems. Here, we review these studies across both lake and stream ecosystems. Focusing on alpine regions mainly in the Northern Hemisphere, we present examples of how glacial meltwater can affect habitat by altering physical and chemical features of aquatic ecosystems, and review the subsequent effects on the biological structure and function of lakes and streams. Collectively or separately, these factors can drive the overall distribution, diversity and behavior of primary producers, triggering cascading effects throughout the food web. We conclude by proposing areas for future research, particularly in regions where glaciers are soon projected to disappear. PMID:24056713

  5. The influence of glacial meltwater on alpine aquatic ecosystems: a review.

    PubMed

    Slemmons, Krista E H; Saros, Jasmine E; Simon, Kevin

    2013-10-01

    The recent and rapid recession of alpine glaciers over the last 150 years has major implications for associated aquatic communities. Glacial meltwater shapes many of the physical features of high altitude lakes and streams, producing turbid environments with distinctive hydrology patterns relative to nival systems. Over the past decade, numerous studies have investigated the chemical and biological effects of glacial meltwater on freshwater ecosystems. Here, we review these studies across both lake and stream ecosystems. Focusing on alpine regions mainly in the Northern Hemisphere, we present examples of how glacial meltwater can affect habitat by altering physical and chemical features of aquatic ecosystems, and review the subsequent effects on the biological structure and function of lakes and streams. Collectively or separately, these factors can drive the overall distribution, diversity and behavior of primary producers, triggering cascading effects throughout the food web. We conclude by proposing areas for future research, particularly in regions where glaciers are soon projected to disappear.

  6. A long pollen record from lowland Amazonia: Forest and cooling in glacial times

    SciTech Connect

    Colinvaux, P.A.; Moreno, J.E.; Bush, M.B.

    1996-10-04

    A continuous pollen history of more than 40,000 years was obtained from a lake in the lowland Amazon rain forest. Pollen spectra demonstrate that tropical rain forest occupied the region continuously and that savannas or grasslands were not present during the last glacial maximum. The data suggest that the western Amazon forest was not fragmented into refugia in glacial times and that the lowlands were not a source of dust. Glacial age forests were comparable to modern forests but also included species now restricted to higher evaluations by temperature, suggesting a cooling of the order of 5{degrees} to 6{degrees}C. 23 refs., 22 tabs.

  7. Symbiotic variable V4018 Sgr in outburst

    NASA Astrophysics Data System (ADS)

    Elizabeth O. Waagen

    2012-09-01

    The symbiotic variable V4018 Sgr is undergoing an outburst, according to observations reported to the AAVSO and confirmed by spectroscopy by Ulisse Munari et al. Prompted by an observation and comment from John Bortle (Stormville, NY) (16 June 2012, visual magnitude 12.2) about a possible outburst, Steven O'Connor (St. George's, Bermuda) obtained an observation (10 August 2012, 11.44V) that confirmed V4018 Sgr was bright. His subsequent BVRI observations in September and visual observations by Bortle and Andrew Pearce (Nedlands, Western Australia) show the system brightening and at V magnitude 11.07 as of 2012 Sep. 17.091 UT. Ulisse Munari (INAF Astr. Obs. Padua, Italy) and colleagues Paolo Valisa and Sergio Dallaporta (ANS Collaboration), after being informed by the AAVSO of the bright state of V4018 Sgr, carried out spectroscopy. Munari writes: "A low resolution, absolutely fluxed 4000-8650 Ang spectrum of V4018 Sgr was obtained on Sept 13.90 UT with the 0.6m telescope ! of the Schiaparelli Observatory in Varese (Italy). It shows the spectrum of the M giant overwhelmed by a blue continuum up to 6000 Ang, and all high ionization emission lines typical of quiescence are gone, leaving only hydrogen Balmer and weak HeI lines in emission. The spectrum looks like a template one for a symbiotic star in outburst. CCD photometry was obtained on Sept 13.79 UT and provides V=11.027 ± 0.002, B-V=+0.621 ± 0.003. The B-V color is appreciably bluer and the V magnitude much brighter than typical in quiescence (on average V=13.3, B-V=+1.09; Henden and Munari 2008, Baltic Astronomy 17, 293), and support the idea V4018 Sgr is undergoing an outburst." According to Munari, the last bright outburst of V4018 Sgr was underway in June 1990. Observations in the AAVSO International Database from Albert Jones (Nelson, New Zealand) beginning in May 1992 show the variable at visual magnitude 11.0, with fluctuations between 10.5 and 11.9 through October 1995. Numerous ! other observers

  8. MCNeil's Nebula in Orion: The Outburst History

    NASA Astrophysics Data System (ADS)

    Briceño, C.; Vivas, A. K.; Hernández, J.; Calvet, N.; Hartmann, L.; Megeath, T.; Berlind, P.; Calkins, M.; Hoyer, S.

    2004-05-01

    We present a sequence of I-band images obtained at the Venezuela 1 m Schmidt telescope during the outburst of the nebula recently discovered by J. W. McNeil in the Orion L1630 molecular cloud. We derive photometry spanning the preoutburst state and the brightening itself, which is a unique record including 14 epochs and spanning a timescale of ~5 years. We constrain the beginning of the outburst at some time between 2003 October 28 and November 15. The light curve of the object at the vertex of the nebula, the likely exciting source of the outburst, reveals that it has brightened ~5 mag in about 4 months. The timescale for the nebula to develop is consistent with the light-travel time, indicating that we are observing light from the central source scattered by the ambient cloud into the line of sight. We also show recent FLWO optical spectroscopy of the exciting source and of the nearby HH 22. The spectrum of the source is highly reddened; in contrast, the spectrum of HH 22 shows a shock spectrum superposed on a continuum, most likely the result of reflected light from the exciting source reaching the HH object through a much less reddened path. The blue portion of this spectrum is consistent with an early B spectral type, similar to the early outburst spectrum of the FU Orionis variable star V1057 Cygni; we estimate a luminosity of L~219 Lsolar. The eruptive behavior of McNeil's Nebula, its spectroscopic characteristics and luminosity, suggest that we may be witnessing an FU Ori event on its way to maximum. By further monitoring this object, we will be able decide whether or not it qualifies as a member of this rare class of objects. Based on observations obtained at the Llano del Hato National Astronomical Observatory of Venezuela, operated by CIDA for the Ministerio de Ciencia y Tecnología, and at the Fred Lawrence Whipple Observatory (FLWO) of the Smithsonian Institution.

  9. Swift observations of the 2015 outburst of AG Peg - from slow nova to classical symbiotic outburst

    NASA Astrophysics Data System (ADS)

    Ramsay, Gavin; Sokoloski, J. L.; Luna, G. J. M.; Nuñez, N. E.

    2016-10-01

    Symbiotic stars often contain white dwarfs with quasi-steady shell burning on their surfaces. However, in most symbiotics, the origin of this burning is unclear. In symbiotic slow novae, however, it is linked to a past thermonuclear runaway. In 2015 June, the symbiotic slow nova AG Peg was seen in only its second optical outburst since 1850. This recent outburst was of much shorter duration and lower amplitude than the earlier eruption, and it contained multiple peaks - like outbursts in classical symbiotic stars such as Z And. We report Swift X-ray and UV observations of AG Peg made between 2015 June and 2016 January. The X-ray flux was markedly variable on a time-scale of days, particularly during four days near optical maximum, when the X-rays became bright and soft. This strong X-ray variability continued for another month, after which the X-rays hardened as the optical flux declined. The UV flux was high throughout the outburst, consistent with quasi-steady shell burning on the white dwarf. Given that accretion discs around white dwarfs with shell burning do not generally produce detectable X-rays (due to Compton-cooling of the boundary layer), the X-rays probably originated via shocks in the ejecta. As the X-ray photoelectric absorption did not vary significantly, the X-ray variability may directly link to the properties of the shocked material. AG Peg's transition from a slow symbiotic nova (which drove the 1850 outburst) to a classical symbiotic star suggests that shell burning in at least some symbiotic stars is residual burning from prior novae.

  10. The experience of aggressive outbursts in intermittent explosive disorder

    PubMed Central

    Kulper, Daniel A.; Kleiman, Evan M.; McCloskey, Michael S.; Berman, Mitchell E.; Coccaro, Emil F.

    2014-01-01

    Conceptualizations of Intermittent Explosive Disorder (IED) have suffered from a scarcity of research investigating the subjective experience and phenomenology of the aggressive outbursts among those with IED relative to those who partake in more normative forms of aggression. Furthermore, though some studies have shown that individuals with IED are more impaired and have a poorer quality of life, few studies looked at negative outcomes specific to an individual with IED’s aggressive behavior. The purpose of this study was to examine the subjective experience and social, occupational, and legal consequences of aggressive outbursts in IED. We assessed individuals with IED (n = 410), psychiatric controls (n = 133), and healthy controls (n = 154) in the experiential correlates present before, during, and after an aggressive outburst as well as the consequences of aggressive outbursts. Results indicated that before and during aggressive outbursts, individuals with IED experienced more intense anger, physiological reactivity, and feelings of dyscontrol as well as more remorse after an aggressive outburst. Furthermore, individuals with IED report more negative consequences of their aggressive outbursts. These results provide an account of how the subjective experience and consequences of aggressive outbursts in IED differ from those with more normative forms of aggression. PMID:25541537

  11. The prototype symbiotic star AX Per is in outburst

    NASA Astrophysics Data System (ADS)

    Munari, U.; Dallaporta, S.; Righetti, G. L.; Castellani, F.; Cherini, G.

    2014-08-01

    The prototype symbiotic star AX Per is in outburst. This is the third such event in the current series of outbursts, the previous two peaking at V=10.41 on 2009 May 26 and at V=10.03 on 2012 Aug 28, according to ANS Collaboration intensive monitoring.

  12. The 1987 outburst of the BL Lacertid AO 0235 + 164

    NASA Astrophysics Data System (ADS)

    Webb, J. R.; Smith, A. G.

    1989-08-01

    The violently variable BL Lacertid AO 0235 + 164 displayed a 3.24 magnitude outburst in early 1987. This outburst was observed intensively from Rosemary Hill Observatory in three colors. Long term monitoring observations made at Rosemary Hill are examined in an effort to find any recurring timescales associated with this outburst and previous large amplitude outbursts. The energetics of the 1987 outburst are analyzed in terms of the Shields and Wheeler model of a magnetized accretion disk. The timescales identified in the power spectrum (2.8 and 1.6 yr) are input into the model as the storage timescales. Since the emitted energy calculated from the optical burst cannot be stored in a magnetized disk at an allowable radius, it is concluded that either the storage timescales are longer than those identified in the power spectrum, or relativistic beaming effects must be considered, with a Doppler factor of 1.3 to 1.6.

  13. Geology of the Ohio portion of Lake Erie

    SciTech Connect

    Fuller, J.A. ); Oldale, R.N. ); Circe, R. )

    1994-04-01

    Seismic-reflection records from the Ohio portion of Lake Erie were interpreted to map the acoustic boundaries inferred to represent the contacts between the postglacial lacustrine deposits and the glacial deposits, and between the glacial deposits and the bedrock. All interpretations were checked against available ground trust data (cores, borings, jetted holes). Generally, in the nearshore the postglacial and glacial deposits pinch out against a rising bedrock surface. Offshore of most of the major rivers there is an indication of down-cutting of the glacial deposits and/or the bedrock. The shale bedrock in the eastern part of the lake has a relatively smooth surface. On the other hand, the carbonate bedrock shows local relief up to 20 m. From the shore, the bedrock surface and overlying sediments dip independently toward the centers of the western and central basins, except where bedrock is at or near the lake floor. In these areas, the bedrock surface controls the distribution of the overlying glacial and postglacial deposits. The glacial deposit has, in places, internal reflectors which may represent multiple tills. These internal reflectors are most common in the central basin. Also, there is evidence that the late Wisconsinan Lake Border Moraine crosses the lake near Cleveland. The last glacier left the Lake Erie basin about 12,600 years ago causing a low stand of the lake. The postglacial deposits began to accumulate during this low and are thickest in the central part of the basins where there has been continuous lacustrine deposition since deglaciation.

  14. Morpho-Sedimentary Impacts By The Late-Pleistocene - Holocene Jökulhlaups In The Þjórsá-Tungnaá Fluvio-Glacial System

    NASA Astrophysics Data System (ADS)

    Schneider, Jean Luc; van Vliet-Lanoe, Brigitte; Naaim, Mohamed; Salles, Tristan; Bjornsson, Helgi; Palsson, Finnur

    2013-04-01

    In Iceland, jökulhlaups correspond to glacial outburst floods that are generally related to sublagial volcanic and hydrothermal activities. They affect the main fluvial outwash plains around the ice caps. They result of the sudden outflow of a large volume of melt water with variable sediment charges drained from a (sub)glacial or an ice-dammed marginal lake that feeds short (hours to days) cataclysmic floods with peak discharges (103 to 107 m3.s-1), up to 10-100 times the magnitude of classical hydrometeorological fluvial floods. Despite their short duration, and because of large peak discharges, they have important erosive and sediment transport capacities. Consequently, repeated events have a strong morpho-sedimentary impact on the inundated areas. The connected watersheds of the Þjórsá and Tungnaá rivers (200 km long; ˜5000 km2, South Island), west of Vatnajökull, correspond to the largest periglacial fluvial system in Iceland. It has drained numerous jökulhlaup floods during the Late Pleistocene deglaciation and the Holocene during periods of increase of the volcanic activity and heat flow. Jökulhlaups were emitted from at least two outlets along the western edge of Vatnajökull that fed the Kaldakvísl and Tungnaá rivers. The subglacial depressions (calderas) of the Bárðarbunga-Hamarinn volcanic system are favorable to the storage of large volumes of water that can feed major jökulhlaups. The Þjórsá-Tungnaá jökulhlaup system can be subdivided into three parts: (1) the source located at the outlets of the subglacial hydraulic network, (2) a proximal transit zone along which erosional processes are dominant (erosively incised rocky substratum - scablands, abraded scoria cones, scour structures, residual buttes of the sedimentary cover) with minor lateral slackwater deposits, flood overflow ponded lakes, and hydraulic dunes along constrictions of the fluvial network, and (3) a distal depositional zone that corresponds to the coastal sandur, the

  15. Common plankton of Twin Lakes, Colorado

    SciTech Connect

    Lieberman, D.M.

    1983-02-01

    A series of studies is being performed to evaluate the effects of the Mt. Elbert Pumped-Storage Powerplant on the ecology of Twin Lakes. Twin Lakes are a pair of connected dimictic lakes, formed as the result of glacial action on alluvial deposits. This report presents a taxonomic species study of the common plankton collected since 1974 from Twin Lakes. A total of 11 zooplankters and 14 phytoplankters were identified from the limnetic zone of Twin Lakes and the associated Mt. Elbert Forebay. The four divisions of zooplankton included four species of Rotifera (rotifer), three species of Copepoda (copepod), three species of Cladocera (cladoceran), and one species of Mysidacea (opossum shrimp).

  16. Kennebunk glacial advance: A reappraisal

    NASA Astrophysics Data System (ADS)

    Smith, Geoffrey W.

    1981-06-01

    Evidence for the Kennebunk glacial advance (readvance) in southwestern Maine is discussed in light of recent geologic mapping. Orientations of glacially produced lineations record the response of ice to major topographic controls and do not indicate glacial readvance. Minor end moraines and large stratified end moraines associated with deformed marine sediments of the Presumpscot Formation occur throughout the southwestern coastal zone. These features outline the general pattern of ice retreat from this part of the coastal zone and suggest that withdrawal of the last ice from southwestern Maine occurred with minor stillstands and local frontal fluctuations but without significant readvance. The Kennebunk glacial advance (readvance) appears to have been one of many local fluctuations of the ice front during general recession, occurring at about 13,200 yr B.P.

  17. The last glacial maximum

    USGS Publications Warehouse

    Clark, P.U.; Dyke, A.S.; Shakun, J.D.; Carlson, A.E.; Clark, J.; Wohlfarth, B.; Mitrovica, J.X.; Hostetler, S.W.; McCabe, A.M.

    2009-01-01

    We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ???14.5 ka.

  18. The Last Glacial Maximum.

    PubMed

    Clark, Peter U; Dyke, Arthur S; Shakun, Jeremy D; Carlson, Anders E; Clark, Jorie; Wohlfarth, Barbara; Mitrovica, Jerry X; Hostetler, Steven W; McCabe, A Marshall

    2009-08-01

    We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level approximately 14.5 ka.

  19. Subglacial Antarctic Lake Environment Research in the IPY

    NASA Astrophysics Data System (ADS)

    Kennicutt, M. C.; Priscu, J. C.

    2006-12-01

    Subglacial environments are continental-scale phenomena that occur under thick ice sheets. These environments differ in geologic setting, age, evolutionary history, and limnological conditions and may be connected by sub-ice hydrologic systems. Evidence suggests that subglacial lakes are linked to the onset of ice streams influencing the dynamics of overlying ice sheets. Outbursts of fresh water from subglacial environments have been invoked as an agent of landscape change in the past and there is speculation that subglacial freshwater discharges have influenced past climate. Subglacial environments rest at the intersection of continental ice sheets and the underlying lithosphere. The distribution of subglacial lakes is determined by the availability of water and basins for it to collect in. The distribution of water in subglacial environments is related to surface temperature, accumulation rates, ice thickness, ice velocities, and geothermal flux. The interconnectedness of these environments exerts a fundamental influence on subglacial physical, chemical, and ecological environments; the degree of isolation; and the evolution of life. Subglacial hydrology at a continental-scale must be mapped and modeled to evaluate past drainage events, map subglacial water, and quantify subglacial discharges. The geologic records of past hydrologic events will be reveal the impact of hydrological events on sediment distribution and landscape evolution. Subglacial environments are "natural" earth-bound macrocosms. In some instances these environments trace their origins to more than 35 million years before present when Antarctica became encased in ice. As opposed to other habitats on Earth, where solar energy is a primary influence, processes in subglacial environments are mediated by the flow of the overlying ice a glacial boundary condition and the flux of heat and possibly fluids from the underlying basin a tectonic control. Recent findings suggest that a third control on

  20. Statistical analysis of properties of dwarf novae outbursts

    NASA Astrophysics Data System (ADS)

    Otulakowska-Hypka, Magdalena; Olech, Arkadiusz; Patterson, Joseph

    2016-08-01

    We present a statistical study of all measurable photometric features of a large sample of dwarf novae during their outbursts and superoutbursts. We used all accessible photometric data for all our objects to make the study as complete and up to date as possible. Our aim was to check correlations between these photometric features in order to constrain theoretical models which try to explain the nature of dwarf novae outbursts. We managed to confirm a few of the known correlations, that is the Stolz and Schoembs relation, the Bailey relation for long outbursts above the period gap, the relations between the cycle and supercycle lengths, amplitudes of normal and superoutbursts, amplitude and duration of superoutbursts, outburst duration and orbital period, outburst duration and mass ratio for short and normal outbursts, as well as the relation between the rise and decline rates of superoutbursts. However, we question the existence of the Kukarkin-Parenago relation but we found an analogous relation for superoutbursts. We also failed to find one presumed relation between outburst duration and mass ratio for superoutbursts. This study should help to direct theoretical work dedicated to dwarf novae.

  1. Prevalence and clinical correlates of explosive outbursts in Tourette syndrome.

    PubMed

    Chen, Kevin; Budman, Cathy L; Diego Herrera, Luis; Witkin, Joanna E; Weiss, Nicholas T; Lowe, Thomas L; Freimer, Nelson B; Reus, Victor I; Mathews, Carol A

    2013-02-28

    The aim of this study was to examine the prevalence and clinical correlates of explosive outbursts in two large samples of individuals with Tourette syndrome (TS), including one collected primarily from non-clinical sources. Participants included 218 TS-affected individuals who were part of a genetic study (N=104 from Costa Rica (CR) and N=114 from the US). The relationships between explosive outbursts and comorbid attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), tic severity, and prenatal and perinatal complications were examined using regression analyses. Twenty percent of participants had explosive outbursts, with no significant differences in prevalence between the CR (non-clinical) and the US (primarily clinical) samples. In the overall sample, ADHD, greater tic severity, and lower age of tic onset were strongly associated with explosive outbursts. ADHD, prenatal exposure to tobacco, and male gender were significantly associated with explosive outbursts in the US sample. Lower age of onset and greater severity of tics were significantly associated with explosive outbursts in the CR sample. This study confirms previous studies that suggest that clinically significant explosive outbursts are common in TS and associated with ADHD and tic severity. An additional potential risk factor, prenatal exposure to tobacco, was also identified.

  2. YOUNG AGN OUTBURST RUNNING OVER OLDER X-RAY CAVITIES

    SciTech Connect

    Bogdán, Ákos; Van Weeren, Reinout J.; Kraft, Ralph P.; Forman, William R.; Randall, Scott; Jones, Christine; Giacintucci, Simona; Churazov, Eugene; O'Dea, Christopher P.; Baum, Stefi A.; Noell-Storr, Jacob

    2014-02-20

    Although the energetic feedback from active galactic nuclei (AGNs) is believed to have a profound effect on the evolution of galaxies and clusters of galaxies, details of AGN heating remain elusive. Here, we study NGC 193—a nearby lenticular galaxy—based on X-ray (Chandra) and radio (Very Large Array and Giant Meter-wave Radio Telescope) observations. These data reveal the complex AGN outburst history of the galaxy: we detect a pair of inner X-ray cavities, an outer X-ray cavity, a shock front, and radio lobes extending beyond the inner cavities. We suggest that the inner cavities were produced ∼78 Myr ago by a weaker AGN outburst, while the outer cavity, the radio lobes, and the shock front are due to a younger (13-26 Myr) and 4-8 times more powerful outburst. Combining this with the observed morphology of NGC 193, we conclude that NGC 193 likely represents the first example of a second, more powerful, AGN outburst overrunning an older, weaker outburst. These results help us to understand how the outburst energy is dissipated uniformly in the core of galaxies, and therefore may play a crucial role in resolving how AGN outbursts suppress the formation of large cooling flows at cluster centers.

  3. Young AGN Outburst Running over Older X-Ray Cavities

    NASA Astrophysics Data System (ADS)

    Bogdan, Akos; van Weeren, Reinout Johannes; Kraft, Ralph; Forman, William; Scott, Randall; Giacintucci, Simona; Churazov, Eugene; O'Dea, Christopher; Baum, Stefi; Noell-Storr, Jacob; Jones, Christine

    2015-08-01

    Although the energetic feedback from active galactic nuclei (AGNs) is believed to have a profound effect on the evolution of galaxies and clusters of galaxies, details of AGN heating remain elusive. Here, we study NGC 193 -- a nearby lenticular galaxy in a group -- based on X-ray and radio observations. These data reveal the complex AGN outburst history of the galaxy: we detect a pair of inner X-ray cavities, an outer X-ray cavity, a shock front, and radio lobes extending beyond the inner cavities. We suggest that the inner cavities were produced about 78 Myr ago by a weaker AGN outburst, while the outer cavity, the radio lobes, and the shock front are due to a younger (13-26 Myr) and 4-8 times more powerful outburst. Combining this with the observed morphology of NGC 193, we conclude that NGC 193 likely represents the first example of a second, more powerful, AGN outburst overrunning an older, weaker outburst. These results help us to understand how the outburst energy is dissipated uniformly in the core of galaxies, and therefore may play a crucial role in resolving how AGN outbursts suppress the formation of large cooling flows at cluster centers.

  4. GIANT OUTBURSTS IN Be/X-RAY BINARIES

    SciTech Connect

    Martin, Rebecca G.; Nixon, Chris; Armitage, Philip J.; Lubow, Stephen H.; Price, Daniel J.

    2014-08-01

    Be/X-ray binary systems exhibit both periodic (Type I) X-ray outbursts and giant (Type II) outbursts, whose origins have remained elusive. We suggest that Type II X-ray outbursts occur when a highly misaligned decretion disk around the Be star becomes eccentric, allowing the compact object companion to capture a large amount of material at periastron. Using three-dimensional smoothed particle hydrodynamics simulations, we model the long-term evolution of a representative Be/X-ray binary system. We find that periodic (Type I) X-ray outbursts occur when the neutron star is close to periastron for all disk inclinations. Type II outbursts occur for large misalignment angles and are associated with eccentricity growth which occurs on a timescale of about 10 orbital periods. Mass capture from the eccentric decretion disk results in an accretion disk around the neutron star whose estimated viscous time is long enough to explain the extended duration of Type II outbursts. Previous studies suggested that the outbursts are caused by a warped disk but our results suggest that this is not sufficient; the disk must be both highly misaligned and eccentric to initiate a Type II accretion event.

  5. V1331 Cyg- An outburst of results

    NASA Astrophysics Data System (ADS)

    Choudhary, Arpita; Stecklum, Bringfried; Stapelfeldt, Karl

    2013-07-01

    FU Orionis objects are a class of young stars with large brightness outbursts in the optical. The outbursts lead to strong increase in luminosity due to enhanced accretion and dust removal by the accompanying wind. All FUors have large infrared excess emission from circumstellar dust, and some drive bipolar jets and outflows. V1331 Cyg is a pre-outburst FUor candidate: At distance of ~ 550 pc, at the border of the dark cloud LDN 981. It is associated with an arc-like reflection nebula. It has two nested rings of 9000 and 3300 AU radii respectively, encircled by an expanding CO ring. The HST-WFPC2 imaging was done in 2000 and 2009. The first epoch images were obtained for F606W and F814W filters. The second epoch observations were deeper with one more filter, F450W introduced. Wind-driven expansion has an imprint on the colour profile of the ring, the study of which will be the next step to do. There is a missing ring section to the NW not due to extinction by the dark cloud but represent a shadow, originating close to the star. Our PSF -subtracted planetary camera frames disclosed a knot at ~0.4" from the star in the same direction. Also our analysis of archival Subaru coronagraphic H-band imaging reveals scattered light associated with this feature which was not seen before. Both findings suggest increased height of the matter at distances of ~300 AU which casts the shadow. This might be related to planet formation in the circumstellar disk. The scattering knot is associated with two spiral arms which stretch further out. The UKIDSS JHK images show faint reddened stars in the gap, confirming the presence of dense matter from probably both the protostellar environment and the molecular cloud. Herschel and SCUBA data confirm that V1331 Cyg is the most luminous object in the surroundings, ONLY possible young stellar candidate responsible for the outflow. Narrow-band imaging in the Hα and [SII] line revealed a bipolar outflow, presumed to have a substantial

  6. Lake and bog development at Glimmerglass lake in the Sylvania Wilderness Area, Michigan

    SciTech Connect

    Brugam, R.B.; Owen, B.; McKeever, K.

    1995-06-01

    We used pollen and diatom analysis to reconstruct post-glacial development of Glimmerglass Lake and its adjacent Sphagnum peatland using transacts of cores. Glimmerglass lake has existed since late-glacial times with little or no change in water levels. In contrast the peatland began growing as a floating mat in a pond that was separated from the main lake by a spit of land. Over time, the floating mat became grounded in the pond but continued growing to cover an adjacent low area that had never been underwater. The peatland continues to grow even though it is approximately 2 m above the level of the adjacent lake. It seems that the peat has slowed drainage into the lake and allowed the peatland to grow above the level of the lake. It is unclear whether climatic change or hydrology controls the rate of accumulation of the peat.

  7. Outburst activity of the symbiiotic binary AG Dra

    NASA Astrophysics Data System (ADS)

    Gális, R.; Hric, L.; Leedjärv, L.; Merc, J.

    2016-03-01

    The outburst activity of the symbiotic system AG Dra has been studied using extensive spectroscopic observational material. High luminosity and temperature of the hot component of AG Dra indicate that quasi-steady thermonuclear shell burning takes place on the surface of the white dwarf. The major (cool) outbursts at the beginning of active phases might occur due to enhanced thermonuclear burning triggered by disk instability. Smaller scale hot outbursts might be explained by the accretion disc instability model like in dwarf novae. We discovered significant similarities in photometric and spectroscopic behaviour of AG Dra and prototypical symbiotic star Z And.

  8. EUVE photometry of SS Cygni: Dwarf nova outbursts and oscillations

    SciTech Connect

    Mauche, C.W.

    1995-05-15

    The authors present EUVE Deep Survey photometry and AAVSO optical measurements of the 1993 August and 1994 June/July outbursts of the dwarf nova SS Cygni. The EUV and optical light curves are used to illustrate the different response of the accretion disk to outbursts which begin at the inner edge and propagate outward, and those which begin at the outer edge and propagate inward. Furthermore, the authors describe the properties of the quasi-coherent 7--9 s sinusoidal oscillations in the EUV flux detected during the rise and plateau stages of these outbursts.

  9. Glacial and Quaternary geology of the northern Yellowstone area, Montana and Wyoming

    USGS Publications Warehouse

    Pierce, Kenneth L.; Licciardi, Joseph M.; Krause, Teresa R.; Whitlock, Cathy

    2014-01-01

    This field guide focuses on the glacial geology and paleoecology beginning in the Paradise Valley and progressing southward into northern Yellowstone National Park. During the last (Pinedale) glaciation, the northern Yellowstone outlet glacier flowed out of Yellowstone Park and down the Yellowstone River Valley into the Paradise Valley. The field trip will traverse the following Pinedale glacial sequence: (1) deposition of the Eightmile terminal moraines and outwash 16.5 ± 1.4 10Be ka in the Paradise Valley; (2) glacial recession of ~8 km and deposition of the Chico moraines and outwash 16.1 ± 1.7 10Be ka; (3) glacial recession of 45 km to near the northern Yellowstone boundary and moraine deposition during the Deckard Flats readjustment 14.2 ± 1.2 10Be ka; and (4) glacial recession of ~37 km and deposition of the Junction Butte moraines 15.2 ± 1.3 10Be ka (this age is a little too old based on the stratigraphic sequence). Yellowstone's northern range of sagebrush-grasslands and bison, elk, wolf, and bear inhabitants is founded on glacial moraines, sub-glacial till, and outwash deposited during the last glaciation. Floods released from glacially dammed lakes and a landslide-dammed lake punctuate this record. The glacial geologic reconstruction was evaluated by calculation of basal shear stress, and yielded the following values for flow pattern in plan view: strongly converging—1.21 ± 0.12 bars (n = 15); nearly uniform—1.04 ± 0.16 bars (n = 11); and strongly diverging—0.84 ± 0.14 bars (n = 16). Reconstructed mass balance yielded accumulation and ablation each of ~3 km3/yr, with glacial movement near the equilibrium line altitude dominated by basal sliding. Pollen and charcoal records from three lakes in northern Yellowstone provide information on the postglacial vegetation and fire history. Following glacial retreat, sparsely vegetated landscapes were colonized first by spruce parkland and then by closed subalpine forests. Regional fire activity

  10. A POWERFUL AGN OUTBURST IN RBS 797

    SciTech Connect

    Cavagnolo, K. W.; McNamara, B. R.; Wise, M. W.; Nulsen, P. E. J.; Gitti, M.; Brueggen, M.; Rafferty, D. A.

    2011-05-10

    Utilizing {approx}50 ks of Chandra X-Ray Observatory imaging, we present an analysis of the intracluster medium (ICM) and cavity system in the galaxy cluster RBS 797. In addition to the two previously known cavities in the cluster core, the new and deeper X-ray image has revealed additional structure associated with the active galactic nucleus (AGN). The surface brightness decrements of the two cavities are unusually large and are consistent with elongated cavities lying close to our line of sight. We estimate a total AGN outburst energy and mean jet power of {approx}(3-6) x 10{sup 60} erg and {approx}(3-6) x 10{sup 45} erg s{sup -1}, respectively, depending on the assumed geometrical configuration of the cavities. Thus, RBS 797 is apparently among the most powerful AGN outbursts known in a cluster. The average mass accretion rate needed to power the AGN by accretion alone is {approx}1 M{sub sun} yr{sup -1}. We show that accretion of cold gas onto the AGN at this level is plausible, but that Bondi accretion of the hot atmosphere is probably not. The brightest cluster galaxy (BCG) harbors an unresolved, non-thermal nuclear X-ray source with a bolometric luminosity of {approx}2 x 10{sup 44} erg s{sup -1}. The nuclear emission is probably associated with a rapidly accreting, radiatively inefficient accretion flow. We present tentative evidence that star formation in the BCG is being triggered by the radio jets and suggest that the cavities may be driving weak shocks (M {approx} 1.5) into the ICM, similar to the process in the galaxy cluster MS 0735.6+7421.

  11. The 2010 outburst and pre-outburst optical spectrum of the recurrent nova U Scorpii

    NASA Astrophysics Data System (ADS)

    Anupama, G. C.; Kamath, U. S.; Ramaprakash, A. N.; Kantharia, N. G.; Hegde, M.; Mohan, V.; Kulkarni, M.; Bode, M. F.; Eyres, S. P. S.; Evans, A.; O'Brien, T. J.

    2013-11-01

    Aims: We study the evolution of the recurrent nova U Scorpii during its outburst in 2010. Methods: Optical spectroscopic observations of the nova were obtained during 0.83-162.5 days after outburst maximum. Optical linear polarisation observations were made before the onset of the super soft X-ray source (SSS) phase and during the SSS phase. Radio continuum observations were made in the 1280 MHz band during the early decline phase, and in the 610 MHz band at the onset and end of the SSS phase. We also present optical spectra obtained in the pre-outburst quiescence phase. Results: The overall spectral evolution during the 2010 outburst is similar to the previous outbursts. However, the dense temporal coverage, especially during the early phases, reveals several short term variations not reported previously. The early phase emission line widths indicate extremely high velocities for the nova ejecta, ~10 000 km s-1. The line profiles are broad, boxy and structured. Narrow P-Cygni absorptions, at ~500 km s-1 are seen associated with the He I lines, and also the Ca II, N I and hydrogen lines (at wavelengths >8000 Å) in the spectrum of day 6.83, obtained immediately after an optical flare. This absorption component could be arising in the plasma emitting the Nitrogen lines seen in X-rays, that probably lies outside the binary orbit. Rapid variations are detected in the strength of the 4660 Å N III feature, which shows a significant increase in the line strength on days 8.83 and 13.82, at orbital phases of 0.75 and 0.25, respectively. Instrinsic polarisation is detected just before the onset, and during the SSS phase, with pv ~ 1.4% during the SSS phase. The flux variations of the N III feature and the intrinsic polarisation are most likely associated with the reforming accretion disc/stream. We estimate the mass of the ejected (hydrogen) shell to be ~4.6 × 10-6 M⊙, for a spherical shell geometry. The non-detection of U Sco in the 1280 MHz and 610 MHz radio bands is

  12. Fluctuations of the Última Esperanza ice lobe (52°S), Chilean Patagonia, during the last glacial maximum and termination 1

    NASA Astrophysics Data System (ADS)

    Sagredo, E. A.; Moreno, P. I.; Villa-Martínez, R.; Kaplan, M. R.; Kubik, P. W.; Stern, C. R.

    2011-01-01

    We present a new record from the Última Esperanza region (51°25'-52°25'S), southwestern Patagonia, to unravel the timing and structure of glacial fluctuations during the Last Glacial Termination (T1). This sector of southern South America represents the only windward-facing continental landmass in the Southern Hemisphere that intersects the core of the Southern Westerly Wind belt. Geomorphic, stratigraphic and geochronological evidence indicate the following stages during and since the Last Glacial Maximum (LGM): (i) deposition of prominent moraine complexes during at least two advances dated between ~ 39 and > 17.5 ka; (ii) development of an ice-dammed proglacial lake (glacial lake Puerto Consuelo) accompanying ice recession; (iii) active deposition of moraine complexes at intermediate positions followed by recession at ≥ 15.2 ka; (iv) lake level drop and subsequent stabilization between 15.2-12.8 ka; (v) a glacial readvance in glacial lake Puerto Consuelo between 14.8-12.8 ka; (vi) ice recession, stabilization, and lake level lowering between 12.8-10.3 ka; and (vii) glacial withdrawal and disappearance of glacial lake Puerto Consuelo prior to 10.3 ka. By comparing our results with the chronologies from neighboring regions we explore whether there was a consistent temporal/geographic pattern of glacial fluctuations during the LGM and T1, and examine their implications at regional, hemispheric, and global scales. The correspondence of these variations with key paleoclimate events recorded in the Southern and the Northern Hemispheres suggest a common forcing that, most likely, propagated through the atmosphere. Regional heterogeneities at millennial timescales probably reflect the influence of processes related to deep ocean circulation, and changes in the position/intensity of the Antarctic Polar Front and Southern Westerly Winds.

  13. Spawning distribution of sockeye salmon in a glacially influenced watershed: The importance of glacial habitats

    USGS Publications Warehouse

    Young, D.B.; Woody, C.A.

    2007-01-01

    The spawning distribution of sockeye salmon Oncorhynchus nerka was compared between clear and glacially turbid habitats in Lake Clark, Alaska, with the use of radiotelemetry. Tracking of 241 adult sockeye salmon to 27 spawning locations revealed both essential habitats and the relationship between spawn timing and seasonal turbidity cycles. Sixty-six percent of radio-tagged sockeye salmon spawned in turbid waters (???5 nephelometric turbidity units) where visual observation was difficult. Spawning in turbid habitats coincided with seasonal temperature declines and associated declines in turbidity and suspended sediment concentration. Because spawn timing is heritable and influenced by temperature, the observed behavior suggests an adaptive response to glacier-fed habitats, as it would reduce embryonic exposure to the adverse effects of fine sediments. ?? Copyright by the American Fisheries Society 2007.

  14. The September 1996 outbursts of Comet Hale-Bopp

    NASA Astrophysics Data System (ADS)

    Larson, S. M.; Samarasinha, N.; Tao, J.; Hergenrother, C.

    2000-10-01

    Digitally enhanced pre-perihelion groundbased images of Comet Hale-Bopp taken in September 1996 show intersting morphology resulting from at least two outbursts. During that apparition, the coma was dominated by radial ``porcupine" morphology. However, a 2 magnitude outburst starting on 1996 September 9.5 UT (Tao et al., 2000, Plan. Sp. Sci. 48, 153-161) resulted in two expanding dust shells with apparent expansion speeds of 112 and 225 m/s and an arc in the NW quadrant. This morphology is very similar to that seen in post-perihelion NICMOS images of a similar outburst on 1997 August 27 (see Campins et al., DPS 2000 abstract). Similar, but less pronounced outburst activity can be seen later in the month and include evidence for ejection of discrete fragments. We explore the possible mechanisms for the observed morphology. This work is supported in part by the NASA Planetary Atmospheres Program.

  15. Prominent outburst of the blazar CTA 102 in 2012

    NASA Astrophysics Data System (ADS)

    Larionov, V. M.; Blinov, D. A.; Jorstad, S. G.; Marscher, A. P.; Villata, M.; Raiteri, C. M.; Agudo, I.; Smith, P. S.; Morozova, D. A.; Troitsky, I. S.; Clemens, D. P.

    2013-12-01

    After a few years of quiescence, the blazar CTA 102 underwent a large outburst in the fall of 2012. The flare has been tracked from γ-rays to near-infrared, including Fermi and Swift data as well as polarimetric data from several observatories. An intensive GASP-WEBT collaboration campaign in optical and NIR bands, with the addition of previously unpublished archival data, allows comparison of this outburst with the previous activity period of this blazar in the early 2000s. We find remarkable similarity between the optical and γ-ray behavior of CTA 102 during the outburst, without any time lag between the two light curves, indicating co-spatiality of the optical and γ-ray emission regions. A strong harder-when-brighter spectral dependence is seen both in γ-rays and optical. The polarimetric behavior of CTA 102 during the outburst conforms with a shock-in-jet interpretation.

  16. Precession of parent bodies from historical meteor outbursts

    NASA Astrophysics Data System (ADS)

    Ahn, S.-H.

    2015-01-01

    We collect records of meteor outbursts from world-wide historical archives, and analyzed them to see which meteor outbursts have existed during the last two millennia. We calculate the dates of occurrence within the sidereal year for each record, and find four prominent major meteor streams having existed continuously. The prominent and continuous meteor streams are the Lyrids, the Perseids, the Leonids, and the eta- Aquariids/Orionids pair. We also check the regression of nodal points of these streams, and find that both the Leonids and the eta-Aquariids/Orionids pair have relatively large precession rates, while the other streams have small rates. We discuss that the near-type outbursts have occurred more frequently than the far-type outbursts.

  17. New Outburst of Centaur Comet (60558) 174P/Echeclus

    NASA Astrophysics Data System (ADS)

    Choi, Young-Jun; Ishiguro, Masateru; Moon, Hong-Kyu

    2015-03-01

    We report observations of new outburst of Centaur (60558) 174P/Echeclus, using Suprime-Cam of Subaru tele-scope. The outburst was detected by Jager on May 30, 2011 (Jaeger et al., 2011). We made several follow-up observations for this outburst with 1m telescope at Mt. Lemon Optical Astronomy Observatory located in US and 60cm telescope at Sobaeksan Optical Astronomy Observatory in Korea. The very first presence of coma around (60558) 2000 EC98 has been detected by Choi and Weissman (2006) on 2005 December 30.50 UT with the Palomar 5m telescope. Soon after, the object was given the periodic comet designa-tion 174P/Echeclus. We will present the characterstics and discuss the reason of this recursive outburst.

  18. Physical Mechanism of Comet (and Asteroid) Outbursts: The Movie

    NASA Astrophysics Data System (ADS)

    Hartmann, W. K.

    2015-07-01

    A film made during impact experiments at NASA Ames illustrates a mechanism in which regolith can become gas charged and then erupt to create outbursts as observed on comets (and "asteroids" such as 2060 Chiron).

  19. The Holocene Paleolimnology of Lake Superior

    NASA Astrophysics Data System (ADS)

    Hyodo, A.; Longstaffe, F. J.

    2010-12-01

    This study describes contributions of glacial meltwater to Lake Superior over the last 11,000 cal BP. Rhythmites (interpreted as varves), lithological and mineralogical variations, and radiocarbon dating were used to establish chronostratigraphic correlation among four sediment cores from Lake Superior (Duluth, Caribou and Ile Parisienne basins, Thunder Bay Trough). Glacial sediments were deposited between 10,850 and 8,800 cal BP. The oxygen-isotope compositions of ostracodes record the presence of glacial meltwater in ancient Lake Superior as the Laurentide Ice Sheet waxed and waned. Glacial meltwater was increasingly dominant between ~10,850 and ~9,250 cal BP, particularly as thick varves formed in northern portions of the Lake Superior Basin (10,400-10,200, 9,900 and 9,300-9,200 cal BP). Glacial meltwater supply was reduced in the Thunder Bay Trough between 9,250 and 8,950 cal BP, but returned from 8,950 to 8,800 cal BP. Glacial meltwater flow from the Lake Superior Basin probably bypassed the Huron Basin several times during this period. Final termination of glacial meltwater supply occurred at 8,800 cal BP - coincident with cessation of varve formation and inception of ancient Lakes Agassiz-Ojibway and Houghton. Primary productivity was very low and algal growth occurred under conditions of extreme nitrogen deficiency - as determined using TOC, TN and C/N ratios - until glacial meltwater supply to the Basin was ended. The postglacial sediments are non-calcareous. The diatom silica proxy record shows that oxygen-isotope compositions of water rapidly increased after glacial meltwater termination, reaching -10 per mil during the Holocene Thermal Maximum. The oxygen-isotope compositions of water decreased at 3,000 cal BP in response to the Holocene Neoglacial Interval before gradually rising to Lake Superior’s modern value of -8.7 per mil. Aquatic primary productivity, inferred using TOC, TN, and the carbon- and nitrogen isotope compositions, has increased

  20. Glacial marine sedimentation: Paleoclimatic significance

    SciTech Connect

    Anderson, J.B.; Ashley, G.M.

    1991-01-01

    This publication resulted from a symposium held during the 1988 Annual Meeting of the Geological Society of America. Many, but not all, contributors to the symposium have papers in this volume. This Special Paper consists of 14 chapters and a Subject/Geographic index. Each chapter has is own list of references. The papers cover a wide range of modem climate/ ocean environments, including papers on glacial marine sediments from Antarctica, the fiords of Alaska, and sediments from the Canadian High Arctic. In addition, three papers discuss [open quote]old[close quotes] glacial marine records (i.e., pre-Tertiary), and one paper discusses the Yakataga Formation of the Gulf of Alaska which is a Miocene-to-late-Pleistocene sequence. The last chapter in the book includes a survey and summary of the evidence for the paleoclimatic significance of glacial marine sediments by the two editors, John Anderson and Gail Ashley. It is worth noting that Anderson and Domack state in the Foreword that there is a considerable variation in terminology; hence they employ a series of definitions which they urge the other authors to employ. They define and explain what they mean by [open quotes]polar ice cap,[close quotes] [open quote]polar tundra (subpolar),[close quotes] and [open quotes]temperate oceanic and boreal[close quotes] in terms of the dominant glacial and glacial marine processes. Although one might quarrel with the terminology, the broad differences between these three glaciological regimes are indeed fundamental and need to be sought in the geological record. The flavor of the volume can be judged by some of the chapter titles. Contributions on Antarctica include a paper by Anderson and other entitled [open quote]Sedimentary facies associated with Antarctica's floating ice masses[close quotes] and a companion paper by Anderson and Domack which deals with the extremely complex glacial marine facies (13 facies are delimited) in McMurdo Sound, Antarctica.

  1. Outburst of the recurrent nova V745 Sco

    NASA Astrophysics Data System (ADS)

    Waagen, Elizabeth O.

    2014-02-01

    The outburst of the recurrent nova V745 Sco (Nova Sco 1937) by Rod Stubbings (Tetoora Road, VIC, Australia) at visual magnitude 9.0 on 2014 February 6.694 UT is reported. This recurrent nova is fading quickly. Follow-up observations of all types (visual, CCD, DSLR) are strongly encouraged, as is spectroscopy; fast time-series of this nova may be useful to detect possible flaring activity as was observed during the outburst of U Scorpii in 2010. Coincident time-series by multiple observers would be most useful for such a study, with a V-filter being preferred. Observations reported to the AAVSO International Database show V745 Sco at visual mag. 10.2 on 2014 Feb. 07.85833 UT (A. Pearce, Nedlands, W. Australia). Finder charts with sequence may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp). Observations should be submitted to the AAVSO International Database. Previous outbursts occurred in 1937 and 1989. The 1937 outburst was detected in 1958 (in decline at magnitude 11.0 on 1937 May 11.1 UT; outburst had occurred within the previous 19 days) by Lukas Plaut on plates taken by Hendrik van Gent at the Leiden Observatory; the object was announced as Nova Sco 1937 and later assigned the GCVS name V745 Sco. The 1989 outburst was detected on 1989 August 1.55 UT by Mati Morel (MMAT, Thornton, NSW, Australia) at visual magnitude 10.4 and in decline. Dr. Bradley Schaefer (Louisiana State University) reports (2010ApJS..187..275S) in his comprehensive analysis of the 10 known galactic recurrent novae (including V745 Sco) that the median interval between recurrent novae outbursts is 24 years. The interval since the 1989 outburst of V745 Sco is 24.10 years. See the Alert Notice for additional visual and multicolor photometry and for more details.

  2. Optical and EUV light curves of dwarf nova outbursts

    SciTech Connect

    Mauche, C W; Mattei, J A; Bateson, F M

    2000-11-15

    We combine AAVSO and VSS/RASNZ optical and Extreme Ultraviolet Explorer EUV light curves of dwarf novae in outburst to place constraints on the nature of dwarf nova outbursts. From the observed optical-EUV time delays of {approx} 0.75-1.5 days, we show that the propagation velocity of the dwarf nova instability heating wave is {approx} 3 km s{sup -1}.

  3. Sub-glacial volcanic eruptions

    USGS Publications Warehouse

    White, Donald Edward

    1956-01-01

    The literature on sub-glacial volcanic eruptions and the related flood phenomena has been reviewed as a minor part of the larger problem of convective and conductive heat transfer from intrusive magma. (See Lovering, 1955, for a review of the extensive literature on this subject.) This summary of data on sub-glacial eruptions is part of a program that the U.S. Geological Survey is conducting in connection with its Investigations of Geologic Processes project on behalf of the Division of Research, U.S. Atomic Energy Commission.

  4. The latest LGM culmination of the Garda Glacier (Italian Alps) and the onset of glacial termination. Age of glacial collapse and vegetation chronosequence

    NASA Astrophysics Data System (ADS)

    Ravazzi, Cesare; Pini, Roberta; Badino, Federica; De Amicis, Mattia; Londeix, Laurent; Reimer, Paula J.

    2014-12-01

    In the deglacial sequence of the largest end moraine system of the Italian Alps, we focused on the latest culmination of the Last Glacial Maximum, before a sudden downwasting of the piedmontane lobe occupying the modern lake basin. We obtained a robust chronology for this culmination and for the subsequent deglacial history by cross-radiocarbon dating of a proximal fluvioglacial plain and of a deglacial continuous lake sedimentation. We used reworked dinocysts to locate sources of glacial abrasion and to mark the input of glacial meltwater until depletion. The palynological record from postglacial lake sediments provided the first vegetation chronosequence directly reacting to the early Lateglacial withdrawal so far documented in the Alps. Glacier collapse occurred soon after 17.46 ± 0.2 ka cal BP, which is, the Manerba advance culmination. Basin deglaciation of several overdeepened foreland piedmont lakes on southern and northern sides of the Alps appears to be synchronous at millennial scale and near-synchronous with large-scale glacial retreat at global scale. The pioneering succession shows a first afforestation step at a median modeled age of 64 years after deglaciation, while rapid tree growth lagged 7 centuries. Between 16.4 ± 0.16 and 15.5 ± 0.16 ka cal BP, a regressive phase interrupted forest growth marking a Lateglacial phase of continental-dry climate predating GI-1. This event, spanning the most advanced phases of North-Atlantic H1, is consistently radiocarbon-framed at three deglacial lake records so far investigated on the Italian side of the Alps. Relationships with the Gschnitz stadial from the Alpine record of Lateglacial advances are discussed.

  5. Outbursts In Symbiotic Binaries (FUSE 2000)

    NASA Technical Reports Server (NTRS)

    Kenyon, Scott J.; Sonneborn, George (Technical Monitor)

    2002-01-01

    During the past year, we made good progress on analysis of FUSE observations of the symbiotic binary Z And. For background, Z And is a binary system composed of a red giant and a hot component of unknown status. The orbital period is roughly 750 days. The hot component undergoes large-scale eruptions every 10-20 yr. An outburst began several years ago, triggering this FUSE opportunity. First, we obtained an excellent set of ground-based optical data in support, of the FUSE observations. We used FAST, a high throughput low resolution spectrograph on the 1.5-m telescope at Mt. Hopkins, Arizona. A 300 g/ mm grating blazed at 4750 A, a 3 in. slit, and a thinned Loral 512 x 2688 CCD gave us spectra covering 3800-7500 A at a resolution of 6 A. The wavelength solution for each spectrum has a probable error of +/- 0.5 A or better. Most of the resulting spectra have moderate signal-to-noise, S/.N approx. greater than 30 per pixel. The time coverage for these spectra is excellent. Typically, we acquired spectra every 1-2 nights during dark runs at Mt. Hopkins. These data cover most of the rise and all of the decline of the recent outburst. The spectra show a wealth of emission lines, including H I, He I, He II, [Fe V11], and the Raman scattering bands at 6830 A and 7088 A. The Raman bands and other high ionization features vary considerably throughout the outburst. These features will enable us to correlate variations in the FUSE spectra with variations in the optical spectra. Second, we began an analysis of FUSE spectra of Z And. We have carefully examined the spectra, identifying real features and defects. We have identified and measured fluxes for all strong emission lines, including the O VI doublet at 1032 A and 1038 A. These and several other strong emission lines display pronounced P Cygni absorption components indicative of outgrowing gas. We will attempt to correlate these velocities with similar profiles observed on optical spectra. The line velocities - together

  6. Late Wisconsinan glacial, lacustrine and marine stratigraphy in the Champlain Valley, New York and Vermont

    SciTech Connect

    Franzi, D.A. . Center for Earth and Environmental Science); Hunt, A.S. . Dept. of Geology)

    1993-03-01

    The stratigraphy of late-glacial, and postglacial deposits and landforms in the Champlain Lowland is interpreted from high-resolution (3.5 khz transducer) acoustical profiling and piston core analysis of sediments beneath Lake Champlain in conjunction with detailed morphologic sequence mapping of surficial deposits. The sediments of Lake Champlain have been grouped by acoustic, lithologic, and biostratigraphic criteria into three stratigraphic units that were deposited successively into Lake Vermont, the Champlain Sea, and Lake Champlain. The maximum thickness of unconsolidated sediment is known to exceed 200 meters locally. Biostratigraphic subdivision of these units using pollen, diatoms, ostracodes, and foraminifera provides further definition of late-glacial and postglacial events in the region and indicates that transitional environments occurred as conditions changed from proglacial lake to marine estuary to freshwater lake. The stratigraphy of surficial deposits records proglacial lake sequences in the Champlain Valley and its tributaries. Interbasinal correlation of the tributary proglacial lake sequences and reconstructed ice marginal positions, is consistent with a model of generally synchronous, northward recession controlled primarily by backwasting of active continental ice lobes. Minor asynchroneity of retreat rates may be attributed to local differences in subglacial topography and changes in proglacial lake level, both of which may affect calving rates. Northward ice recession of the Champlain Lobe allowed successive inundation of tributary valleys by Lake Vermont. Elevations of deltaic sandplains reveal at least three distinct lake levels in the northwestern Champlain Valley. The highest level corresponds to the Coveville Stage while the lower two represent levels of the Fort Ann Stage.

  7. History of late glacial flow through the middle Mississippi and Illinois Valleys

    SciTech Connect

    Hajic, E.R. ) Bettis, E.A. III )

    1992-01-01

    Nearly the entire late glacial is represented by the sedimentologic, stratigraphic and geomorphic record. Sources and types of discharge and sediment varied considerably in response to style and timing of retreat and readvance of glacial lobes; drainage diversions; magnitude and timing of glacial lake discharges; and non-meltwater inputs. Sedimentology of backflood, slackwater, and tributary and main stem fluvial sediments associated with late Wisconsinan terraces, preserved in Mississippi tributary valley mouths, suggests that from before 16,000 until about 13,300 B.P., when the valleys were undergoing net aggradation during ice retreat, floods were of relatively small to moderate magnitude. Catastrophic flooding out of moraine--dammed lakes occurred down the Illinois Valley between about 16,000 and 15,500 B.P., and down the Mississippi Valley out of Lake Wisconsin around 15,000 B.P. Large-scale, but not necessarily catastrophic, paleochannels in the Illinois Valley were active at least intermittently between 15,500 and about 9,800 B.P. After about 12,200 B.P., the character of Mississippi River discharge changed greatly. Between 12,200 and about 9,500 B.P., multiple relatively large magnitude floods, some catastrophic, from Lake Agassiz, Des Moines lobe englacial or subglacial lakes, and other glacial lakes, passed through the valley causing downcutting, terrace formation, and locally extensive valley widening and left remnants of large-scale paleochannels and streamlined bars. Either catastrophic floods did not pass through the Illinois Valley after 13,300 B.P. or they were sharply attenuated by the time they reached the lower valley; the reverse sloping clayey surface of the Savanna Terrace and associated lacustrine deposits in the lower Illinois Valley show no depositional or erosional evidence suggestive of modification by catastrophic flooding.

  8. Why study lakes? An overview of USGS lake studies in Wisconsin

    USGS Publications Warehouse

    Garn, Herbert S.; Elder, J.F.; Robertson, D.M.

    2003-01-01

    Wisconsin’s 15,000 lakes are prominent features in its landscape and an important public resource. In the northern part of the State, the recent glaciation (ending about 10,000 years ago) created one of the densest clusters of lakes found anywhere in the world, containing lakes that occupy depressions in the glacial moraines and outwash deposits (fig. 1). This Northern Lakes and Forests Ecoregion contains more than 80 percent of the State’s lakes (Wisconsin Department of Natural Resources, 2001). South of this ecoregion, there are fewer lakes, but they still are common. Usually situated in agricultural or urban land- scapes, lakes in southern Wisconsin generally have higher levels of nutrients and alkalinity, and higher biological productivity than their northern counterparts. For most lakes in Wisconsin, phosphorus is the nutrient that limits algal growth (Lillie and Mason, 1983).

  9. Draconid 2011 outburst observations from Slovenia

    NASA Astrophysics Data System (ADS)

    Kac, Javor

    2015-06-01

    The 2011 Draconid outburst results are presented based on visual, video and photographic observations. A population index of r = 2.6 ± 0.1 and a maximum zenithal hourly rate of 460 ± 60 on 2011 October 8 at 20h11m UT are obtained from the visual observations. Twelve double-station Draconids form an average geocentric radiant at α = 262°4 ± 0°8, δ = +55°4 ± 0°4, with a velocity v_∞ = 22.4 ± 0.4 km/s. Single-station video observations indicate a radiant at α = 261°4 ± 1°4, δ = +55°8 ± 1°4, and a velocity of v_∞ = 20.6 ± 0.5 km/s. A flux profile is presented based on 358 video Draconids, and a maximum flux of 87 Draconids per 1000 km^{2} per hour is found on 2011 October 8 at 20h15m UT.

  10. Persistent Energetic Ion Outbursts from the Sun

    NASA Astrophysics Data System (ADS)

    Bucik, R.; Innes, D.; Mason, G. M.

    2014-12-01

    Following the greatest elongation in 2011, STEREO-A and -B, along with the near-Earth Solar Dynamics Observatory, have provided for the first time a view of the full solar surface. This allows continual tracking of solar active regions for their entire lifetime. With the advantage of a wide angular separation between the two STEREOs and the near-Earth Advanced Composition Explorer, we present the first report of multiple 3He-rich solar energetic particle (SEP) outbursts occurring in single active regions for relatively long time periods, lasting at least a quarter of a solar rotation. We identified several long-lasting 3He- or Fe-rich SEP sources with particle emissions successively observed at least on two of STEREO-B, ACE and STEREO-A spacecraft. Previous single spacecraft observations showed such energetic ion bursts over a limited time interval (about one day) presumably due to the loss of magnetic connection to the flare sites. These new observations reveal that the physical processes responsible for particle acceleration and escape from the Sun appear to be more continuous than previously thought. We discuss conditions in the solar sources which could lead to the reappearance of 3He-rich SEPs by comparing with the cases showing no such feature.

  11. Multiband Microvariability of BL Lac During Outburst

    NASA Astrophysics Data System (ADS)

    Clements, S. D.; Carini, M. T.; Noble, J. C.

    1998-01-01

    The blazar BL Lac recently underwent a major outburst. A search for microvariability was made with the 0.76 m telescope at the University of Florida's Rosemary Hill Observatory. Nearly 300 CCD observations in V and R were made over ten nights in July. During that time, BL Lac varied by more than 1.5 magnitudes and exhibited substantial microvariability. In fact, it exhibited microvariability each of the eight nights multiple exposures were made, being most active when brightest on July 29. On this night, four mini-flares were seen within 7 hours. During one of these flares, BL Lac brightened by more than 0.5 magnitude in less than 2.5 hours. The variations in V and R were simultaneous within the limits of the observations. However, the V and R magnitudes did not always change at the same rate. On July 3, BL Lac brightened in R faster than in V. Then on July 4, it dimmed in V faster than in R. Yet over the ten nights observed, BL Lac became bluer as it brightened. Another interesting difference between the V and R data was seen on July 4 when a mini-flare was seen in V but not in R. Clearly, while the V and R variations are highly correlated, there are compelling differences. Here we present these observations and discuss them in relation to models intended to explain microvariability. The authors gratefully acknowledge the support of NASA grant NCC5-228.

  12. High-resolution mapping of glacial landforms in the North Alpine Foreland, Austria

    NASA Astrophysics Data System (ADS)

    Salcher, Bernhard C.; Hinsch, Ralph; Wagreich, Michael

    2010-10-01

    In this study results from traditional field mapping were merged with precise elevation information from airborne LiDAR (Light detection and ranging) surveys. Morphological and sedimentological data provide new results from the Austrian (eastern) part of the Salzach piedmont glacier during times of and shortly after the Last Glacial Maximum (LGM). The variations in meltwater discharge had a major impact on the development of glacial landforms. In areas with high meltwater supply erosional or debris reworking processes play a major role, represented by drainage channels, drumlins and kettled, low relief hummocky moraine with low slope angles. Low discharge areas are associated with distinct depositional forms such as high relief end moraines (up to 30 m) and hummocky moraine (averaging 20 m) with high slope angles. Isolated conical kames may reach heights up to 45 m. Fluvial activity is supposed to rise towards the end of the glacial cycle causing high melting rates and comprehensive debris reworking. The formation of terminal lakes and associated widespread, inorganic lake clays are the last deposits within the study area before the Salzach Glacier completely receded to its main valley. The survey of glacial landforms through the combination of field mapping and high-resolution DEM derived from airborne LiDAR missions gives precise information on transport and deposition during the last glacial cycle of the eastern Salzach Glacier piedmont lobe.

  13. The geomorphic and sedimentary record of past subglacial water outbursts, Sabrina Coast, East Antarctica

    NASA Astrophysics Data System (ADS)

    Fernandez-Vasquez, R. A.; Domack, E. W.; Lavoie, C.; Gulick, S. P. S.; Saustrup, S., Sr.; Frederick, B.; Leventer, A.; Shevenell, A.; Blankenship, D. D.

    2014-12-01

    The drainage basin of Totten Glacier (TG) comprises nearly one-eighth of the East Antarctic Ice Sheet and contains an estimated ice volume equivalent to 6.9 m of eustatic sea level rise, a value greater than the entire West Antarctic Ice Sheet. Adjacent, and partially covering the area presently corresponding to TG drainage basin, is the Aurora Subglacial Basin, a deep trough that reaches more than 1 km below sea level where geophysical data suggest the existence of numerous subglacial water bodies. Such water bodies maintain zero basal shear stress relatively to the overlying ice. It is theorized that subglacial outburst would decrease the shear stress at the bottom of marine ice sheets near the margin, inducing ice acceleration, thinning and ultimately contributing to the collapse of the ice sheet. In this contribution we present part of the preliminary results of the first geological and geophysical marine survey (NBP1402) to the inner continental shelf off the Sabrina Coast in the Totten Glacier/Moscow University Ice Shelf area, East Antarctica. We describe a set of subglacial features that we interpret as representing the sedimentary and geomorphic record of past subglacial water outbursts. These features, which we refer as "feather moraines", were imaged by high-resolution multichannel seismic (MCS) and CHIRP data to consist of a stack of subglacial sediments separated by erosional unconformities, and were shown in the swath bathymetry to consist of feather-like areas exhibiting cross and cut relationships between different sets, with distinct step-wise borders on the downstream side. They are superimposed on megascale glacial lineations (MSGL) and are elongated in generally the same direction as the MSGLs. The upstream side of the feather moraines coincides with the initiation of the MSGL and an area of drumlins near the limit of the glacial sediments and the outcropping of bedrock. A network of channels carved in bedrock just south of the feather moraines

  14. Outburst of a Black Hole X-ray Binary V4641 Sgr in 2004 July

    NASA Astrophysics Data System (ADS)

    Uemura, M.; Mennickent, R.; Stubbings, R.; Bolt, G.; Monard, B.; Cook, L. M.; Williams, P.; Ishioka, R.; Imada, A.; Kato, T.; Nogami, D.; Starkey, D.; Maehara, H.; Nakajima, K.; Meszaros, Sz.; Szekely, P.; Kiss, L. L.; Lindstrom, C.; Griffin, J.

    2005-05-01

    We report an outburst of a black hole X-ray binary, V4641 Sgr in 2004 July. We succeeded in performing time-series photometry during the outburst, which showed repetitive short flares having a timescale of 10 min. Even after the outburst, it remained active for 17 d, as observed after an outburst in 2002. In conjunction with a low X-ray flux, we suggest that the 2004 outburst has the same nature as those in 2002 and 2003, though the total released energy during the outburst seems to be less in 2004.

  15. Clinical Features of Young Children Referred for Impairing Temper Outbursts

    PubMed Central

    Klein, Rachel G.; Angelosante, Aleta; Bar-Haim, Yair; Leibenluft, Ellen; Hulvershorn, Leslie; Dixon, Erica; Dodds, Alice; Spindel, Carrie

    2013-01-01

    Abstract Objective In light of the current controversy about whether severe temper outbursts are diagnostic of mania in young children, we conducted a study to characterize such children, focusing on mania and other mood disorders, emotion regulation, and parental psychiatric history. Methods Study participants included 51 5–9-year-old children with frequent, impairing outbursts (probands) and 24 non-referred controls without outbursts. Parents completed a lifetime clinical interview about their child, and rated their child's current mood and behavior. Teachers completed a behavior rating scale. To assess emotion regulation, children were administered the Balloons Game, which assesses emotion expressivity in response to frustration, under demands of high and low regulation. Parental lifetime diagnoses were ascertained in blind clinical interviews. Results No child had bipolar disorder, bipolar disorder not otherwise specified (NOS), or major depression (MDD). The most prevalent disorder was oppositional defiant disorder (88.2%), followed by attention-deficit/hyperactivity disorder (74.5%), anxiety disorders (49.0%), and non-MDD depressive disorders (33.3%). Eleven probands (21.6%) met criteria for severe mood dysregulation. During the Balloons Game, when there were no demands for self-regulation, children with severe outbursts showed reduced positive expressivity, and also showed significant deficits in controlling negative facial expressions when asked to do so. Anxiety disorders were the only diagnoses significantly elevated in probands' mothers. Conclusions Overall, young children with severe temper outbursts do not present with bipolar disorder. Rather, disruptive behavior disorders with anxiety and depressive mood are common. In children with severe outbursts, deficits in regulating emotional facial expressions may reflect deficits controlling negative affect. This work represents a first step towards elucidating mechanisms underlying severe outbursts in

  16. Chronology of the last glacial maximum in the upper Bear River Basin, Utah

    USGS Publications Warehouse

    Laabs, B.J.C.; Munroe, J.S.; Rosenbaum, J.G.; Refsnider, K.A.; Mickelson, D.M.; Singer, B.S.; Caffee, M.W.

    2007-01-01

    The h