Sample records for tausen ice cap

  1. Sensitivity, stability and future evolution of the world's northernmost ice cap, Hans Tausen Iskappe (Greenland)

    NASA Astrophysics Data System (ADS)

    Zekollari, Harry; Huybrechts, Philippe; Noël, Brice; van de Berg, Willem Jan; van den Broeke, Michiel R.

    2017-03-01

    In this study the dynamics and sensitivity of Hans Tausen Iskappe (western Peary Land, Greenland) to climatic forcing is investigated with a coupled ice flow-mass balance model. The surface mass balance (SMB) is calculated from a precipitation field obtained from the Regional Atmospheric Climate Model (RACMO2.3), while runoff is calculated from a positive-degree-day runoff-retention model. For the ice flow a 3-D higher-order thermomechanical model is used, which is run at a 250 m resolution. A higher-order solution is needed to accurately represent the ice flow in the outlet glaciers. Under 1961-1990 climatic conditions a steady-state ice cap is obtained that is overall similar in geometry to the present-day ice cap. Ice thickness, temperature and flow velocity in the interior agree well with observations. For the outlet glaciers a reasonable agreement with temperature and ice thickness measurements can be obtained with an additional heat source related to infiltrating meltwater. The simulations indicate that the SMB-elevation feedback has a major effect on the ice cap response time and stability. This causes the southern part of the ice cap to be extremely sensitive to a change in climatic conditions and leads to thresholds in the ice cap evolution. Under constant 2005-2014 climatic conditions the entire southern part of the ice cap cannot be sustained, and the ice cap loses about 80 % of its present-day volume. The projected loss of surrounding permanent sea ice and resultant precipitation increase may attenuate the future mass loss but will be insufficient to preserve the present-day ice cap for most scenarios. In a warmer and wetter climate the ice margin will retreat, while the interior is projected to thicken, leading to a steeper ice cap, in line with the present-day observed trends. For intermediate- (+4 °C) and high- warming scenarios (+8 °C) the ice cap is projected to disappear around AD 2400 and 2200 respectively, almost independent of the projected

  2. Present-day dynamics and future evolution of the world's northernmost ice cap, Hans Tausen Iskappe (Greenland)

    NASA Astrophysics Data System (ADS)

    Zekollari, Harry; Huybrechts, Philippe; Noël, Brice; van de Berg, Willem Jan; van den Broeke, Michiel R.

    2017-04-01

    In this study the dynamics of Hans Tausen Iskappe (western Peary Land, Greenland) are investigated with a coupled ice flow - mass balance model. Precipitation is obtained from the Regional Climate Model RACMO 2.3 and the surface mass balance is calculated from a Positive Degree-Day runoff/retention model, for which the input parameters are derived from field observations. For the ice flow a 3-D higher-order thermo-mechanical model is used, which is run at a 250 m resolution. Under 1961-1990 climatic conditions a steady state ice cap is obtained that is overall similar in geometry to the present-day ice cap. Ice thickness, temperature and flow velocity in the interior agree well with observations. For the outlet glaciers a reasonable agreement with temperature and ice thickness measurements can only be obtained with an additional heat source related to infiltrating meltwater. The simulations indicate that the SMB-elevation feedback has a major effect on the ice cap response time and stability. This causes the southern part of the ice cap to be extremely sensitive to a change in climatic conditions and leads to thresholds in the ice cap evolution. Under constant 2005-2014 climatic conditions the entire southern part of the ice cap cannot be sustained and the ice cap loses about 80% of its present-day volume. The future projected loss of surrounding permanent sea-ice and corresponding potential sharp precipitation increase may however lead to an attenuation of the retreat and even potential stabilization of the ice cap for a warming of up to 2-3°C. In a warmer and wetter climate the ice margin will retreat while the interior is projected to grow, leading to a steeper ice cap, in line with the present-day observed trends. For intermediate (+4°C) and high warming scenarios (+8°C) the ice cap is projected to disappear respectively around 2400 and 2200 A.D., almost irrespective of the projected precipitation regime and the simulated present-day geometry.

  3. Holocene evolution of Hans Tausen Iskappe (Greenland): merging constraints and models

    NASA Astrophysics Data System (ADS)

    Zekollari, Harry; Lecavalier, Benoit S.; Huybrechts, Philippe

    2017-04-01

    In this study the Holocene evolution of Hans Tausen Iskappe (western Peary Land, Greenland) is investigated. Constraints on the ice cap evolution are combined with climatic records in a numerical ice flow - surface mass balance (SMB) model to better understand the palaeoenvironmental and climatic evolution of this region. Our simulations suggest that after disconnecting from the Greenland Ice Sheet (GrIS) the ice cap had roughly its present-day size and geometry around 8.5-9 ka ago. An ice core drilled to the bed indicates that the southern part of the ice cap subsequently disappeared during the Holocene Thermal Maximum (HTM) and this collapse can be reproduced, but the model suggests that the northern part of the ice cap most likely survived this warmer period. The late Holocene growth of the ice cap to its Little Ice Age (LIA) maximum neoglacial extent can be reproduced from the temperature reconstruction. The simulations suggest that over the last millennia the local precipitation may have been up to 70-80% higher than at present. By coupling the pre-industrial temperature forcing to a post-LIA warming trend, it is concluded that the warming between the end of the LIA and the period 1961-1990 was between 1 and 2°C. In all experiments the ice flow model complexity and horizontal resolution have only a minor effect on the long-term evolution of the ice cap, which is largely driven by SMB changes. On the other hand the glacial isostatic adjustments (GIA) need to be accounted for in a detailed manner, as this has a large impact on the modelled Holocene ice cap evolution.

  4. Polar Ice Caps: a Canary for the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Honsaker, W.; Lowell, T. V.; Sagredo, E.; Kelly, M. A.; Hall, B. L.

    2010-12-01

    Ice caps are glacier masses that are highly sensitive to climate change. Because of their hypsometry they can have a binary state. When relatively slight changes in the equilibrium line altitude (ELA) either intersect or rise above the land the ice can become established or disappear. Thus these upland ice masses have a fast response time. Here we consider a way to extract the ELA signal from independent ice caps adjacent to the Greenland Ice Sheet margin. It may be that these ice caps are sensitive trackers of climate change that also impact the ice sheet margin. One example is the Istorvet Ice Cap located in Liverpool Land, East Greenland (70.881°N, 22.156°W). The ice cap topography and the underlying bedrock surface dips to the north, with peak elevation of the current ice ranging in elevation from 1050 to 745 m.a.s.l. On the eastern side of the ice mass the outlet glaciers extending down to sea level. The western margin has several small lobes in topographic depressions, with the margin reaching down to 300 m.a.s.l. Topographic highs separate the ice cap into at least 5 main catchments, each having a pair of outlet lobes toward either side of the ice cap. Because of the regional bedrock slope each catchment has its own elevation range. Therefore, as the ELA changes it is possible for some catchments of the ice cap to experience positive mass balance while others have a negative balance. Based on weather observations we estimate the present day ELA to be ~1000 m.a.s.l, meaning mass balance is negative for the majority of the ice cap. By tracking glacier presence/absence in these different catchments, we can reconstruct small changes in the ELA. Another example is the High Ice Cap (informal name) in Milne Land (70.903°N, 25.626°W, 1080 m), East Greenland. Here at least 4 unconformities in ice layers found near the southern margin of the ice cap record changing intervals of accumulation and ablation. Therefore, this location may also be sensitive to slight

  5. Paleo ice-cap surfaces and extents

    NASA Astrophysics Data System (ADS)

    Gillespie, A.; Pieri, D.

    2008-12-01

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

  6. Devon island ice cap: core stratigraphy and paleoclimate.

    PubMed

    Koerner, R M

    1977-04-01

    Valuable paleoclimatic information can be gained by studying the distribution of melt layers in deep ice cores. A profile representing the percentage of ice in melt layers in a core drilled from the Devon Island ice cap plotted against both time and depth shows that the ice cap has experienced a period of very warm summers since 1925, following a period of colder summers between about 1600 and 1925. The earlier period was coldest between 1680 and 1730. There is a high correlation between the melt-layer ice percentage and the mass balance of the ice cap. The relation between them suggests that the ice cap mass balance was zero (accumulation equaled ablation) during the colder period but is negative in the present warmer one. There is no firm evidence of a present cooling trend in the summer conditions on the ice cap. A comparison with the melt-layer ice percentage in cores from the other major Canadian Arctic ice caps shows that the variation of summer conditions found for the Devon Island ice cap is representative for all the large ice caps for about 90 percent of the time. There is also a good correlation between melt-layer percentage and summer sea-ice conditions in the archipelago. This suggests that the search for the northwest passage was influenced by changing climate, with the 19th-century peak of the often tragic exploration coinciding with a period of very cold summers.

  7. Little Ice Age Fluctuations of Quelccaya Ice Cap, Peru

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T.

    2009-12-01

    A record of the past extents of Quelccaya Ice Cap (QIC) provides valuable information about tropical climate change from late glacial to recent time. Here, we examine the timing and regional significance of fluctuations of QIC during the Little Ice Age (LIA; ~1300-1850 AD). One prominent set of moraines, known as the Huancane I moraines, is located ~1 km from the present-day western ice cap margin and provides a near-continuous outline of the most recent advance of QIC. This moraine set was radiocarbon dated (~298 ± 134 and 831 ± 87 yr BP) by Mercer and Palacios (1977) and presented as some of the first evidence for cooling in the tropics during the Little Ice Age. Recent field investigations in the QIC region focused on refining the chronology of the Huancane I moraines. In 2008, new stratigraphic sections exposed by local lake-flooding events revealed multiple layers of peat within the Huancane I moraines. In both 2008 and 2009, samples were obtained for 10Be dating of boulders on Huancane I moraines. A combination of radiocarbon and 10Be ages indicate that the Huancane I moraines were deposited by ice cap expansion after ~3800 yr BP and likely by multiple advances at approximately 1000, 600, 400, and 200 yr BP. Radiocarbon and 10Be chronologies of the Huancane I moraines are compared with the Quelccaya ice core records (Thompson et al., 1985; 1986; 2006). Accumulation data from the ice core records are interpreted to indicate a significant wet period at ~1500-1700 AD followed by a significant drought at ~1720-1860 AD. We examine ice marginal fluctuations during these times to determine influence of such events on the ice cap extent.

  8. Holocene history of North Ice Cap, northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Corbett, L. B.; Kelly, M. A.; Osterberg, E. C.; Axford, Y.; Bigl, M.; Roy, E. P.; Thompson, J. T.

    2013-12-01

    Although much research has focused on the past extents of the Greenland Ice Sheet, less is known about the smaller ice caps on Greenland and how they have evolved over time. These small ice caps respond sensitively to summer temperatures and, to a lesser extent, winter precipitation, and provide valuable information about climatic conditions along the Greenland Ice Sheet margins. Here, we investigate the Holocene history of North Ice Cap (76°55'N 68°00'W), located in the Nunatarssuaq region near Thule, northwest Greenland. Our results are based on glacial geomorphic mapping, 10Be dating, and analyses of sediment cores from a glacially fed lake. Fresh, unweathered and unvegetated boulders comprise moraines and drift that mark an extent of North Ice Cap ~25 m outboard of the present ice margin. It is likely that these deposits were formed during late Holocene time and we are currently employing 10Be surface exposure dating to examine this hypothesis. Just outboard of the fresh moraines and drift, boulders and bedrock show significant weathering and are covered with lichen. Based on glacial geomorphic mapping and detailed site investigations, including stone counts, we suggest that the weathered boulders and bedrock were once covered by erosive Greenland Ice Sheet flow from southeast to northwest over the Nunatarssuaq region. Five 10Be ages from the more weathered landscape only 100-200 m outboard of the modern North Ice Cap margin are 52 and 53 ka (bedrock) and 16, 23, and 31 ka (boulders). These ages indicate that recent ice cover has likely been cold-based and non-erosive, failing to remove inherited cosmogenic nuclides from previous periods of exposure, although the youngest boulder may provide a maximum limiting deglaciation age. Sediment cores collected from Delta Sø, a glacially-fed lake ~1.5 km outside of the modern North Ice Cap margin, contain 130 cm of finely laminated sediments overlying coarse sands and glacial till. Radiocarbon ages from just above

  9. The future of the Devon Ice cap: results from climate and ice dynamics modelling

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Rodehacke, Christian; Boberg, Fredrik

    2017-04-01

    The Devon Ice Cap is an example of a relatively well monitored small ice cap in the Canadian Arctic. Close to Greenland, it shows a similar surface mass balance signal to glaciers in western Greenland. Here we use high resolution (5km) simulations from HIRHAM5 to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic ice cap. Observational data from the Devon Ice Cap in Arctic Canada is used to evaluate the surface mass balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon Ice Cap under a warming climate. We find that the Devon Ice Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.

  10. Rapid Collapse of the Vavilov Ice Cap, Russian High Arctic.

    NASA Astrophysics Data System (ADS)

    Willis, M. J.; Zheng, W.; Durkin, W. J., IV; Pritchard, M. E.; Ramage, J. M.; Dowdeswell, J. A.; Benham, T. J.; Glazovsky, A.; Macheret, Y.; Porter, C. C.

    2016-12-01

    Cold based ice caps and glaciers are thought to respond slowly to environmental changes. As sea ice cover evolves in the Arctic, a feedback process alters air-temperatures and precipitation patterns across the region. During the last decades of the 20th century the land-terminating western margin of the Vavilov Ice Cap, on October Revolution Island of the Severnaya Zemlya Archipelago, advanced slowly westwards. The advance was driven by precipitation changes that occurred about half a millennia ago. InSAR shows that in 1996 the margin sustained ice speeds of around 20 m/yr. By 2000 the ice front had moved a short distance into the Kara Sea and had transitioned to a marine-terminating front, although an ice apron around the ice margin indicates the ice there was still frozen to the bed and there is no evidence of calving in satellite imagery. In 2013 ice motions near the terminus had accelerated to around 1 m/day. By late 2015 the main trunk of the newly activated outlet glacier attained speeds of 25 m/day and the inland portion of the ice cap thinned at rates of more than 0.3 m/day. The acceleration of the outlet glacier occurred due to its advance over weak, water-saturated marine sediments that provide little resistance to ice flow, and to the removal of lateral resistive stresses as the glacier advanced out into an open embayment. Longitudinal stretching at the front forces an increase in the surface slope upstream. Rapid rates of motion inland generate frictional melt at the bed, possibly aided by cryohydrological warming. Large areas of the interior of the Vavilov ice cap are now below the equilibrium line and the grounded portion of the ice cap is losing mass at a rate of 4.5 km3 w.e./year. The changes at the Vavilov are likely irrecoverable in a warming climate due to a reduction in the accumulation area of the ice cap. Increased precipitation drove the advance, which accelerated due to the presence of soft sediments. The acceleration lowered the elevation

  11. What Lies Below a Martian Ice Cap

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for larger annotated version

    This image (top) taken by the Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter reveals the layers of ice, sand and dust that make up the north polar ice cap on Mars. It is the most detailed look to date at the insides of this ice cap. The colored map below the radar picture shows the topography of the corresponding Martian terrain (red and white represent higher ground, and green and yellow lower).

    The radar image reveals four never-before-seen thick layers of ice and dust separated by layers of nearly pure ice. According to scientists, these thick ice-free layers represent approximately one-million-year-long cycles of climate change on Mars caused by variations in the planet's tilted axis and its eccentric orbit around the sun. Adding up the entire stack of ice gives an estimated age for the north polar ice cap of about 4 million years a finding that agrees with previous theoretical estimates. The ice cap is about 2 kilometers (1.2 miles) thick.

    The radar picture also shows that the boundary between the ice layers and the surface of Mars underneath is relatively flat (bottom white line on the right). This implies that the surface of Mars is not sagging, or bending, under the weight of the ice cap and this, in turn, suggests that the planet's lithosphere, a combination of the crust and the strong parts of the upper mantle, is thicker than previously thought.

    A thicker lithosphere on Mars means that temperatures increase more gradually with depth toward the interior. Temperatures warm enough for water to be liquid are therefore deeper than previously thought. Likewise, if liquid water does exist in aquifers below the surface of Mars, and if there are any organisms living in that water, they would have to be located deeper in the planet.

    The topography data are from Mars Orbiter Laser Altimeter, which was flown on NASA's Mars Global

  12. Devon Ice cap's future: results from climate and ice dynamics modelling via surface mass balance modelling

    NASA Astrophysics Data System (ADS)

    Rodehacke, C. B.; Mottram, R.; Boberg, F.

    2017-12-01

    The Devon Ice Cap is an example of a relatively well monitored small ice cap in the Canadian Arctic. Close to Greenland, it shows a similar surface mass balance signal to glaciers in western Greenland. Here we various boundary conditions, ranging from ERA-Interim reanalysis data via global climate model high resolution (5km) output from the regional climate model HIRHAM5, to determine the surface mass balance of the Devon ice cap. These SMB estimates are used to drive the PISM glacier model in order to model the present day and future prospects of this small Arctic ice cap. Observational data from the Devon Ice Cap in Arctic Canada is used to evaluate the surface mass balance (SMB) data output from the HIRHAM5 model for simulations forced with the ERA-Interim climate reanalysis data and the historical emissions scenario run by the EC-Earth global climate model. The RCP8.5 scenario simulated by EC-Earth is also downscaled by HIRHAM5 and this output is used to force the PISM model to simulate the likely future evolution of the Devon Ice Cap under a warming climate. We find that the Devon Ice Cap is likely to continue its present day retreat, though in the future increased precipitation partly offsets the enhanced melt rates caused by climate change.

  13. Late-glacial and Holocene history of changes in Quelccaya Ice Cap, Peru

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Lowell, T. V.; Schaefer, J. M.; Finkel, R. C.

    2008-12-01

    Quelccaya Ice Cap in the southeastern Peruvian Andes (~13-14° S latitude) is an icon for climate change. Its rapidly receding outlet, Qori Kalis Glacier, has been monitored since the 1970's. Cores from Quelccaya Ice Cap provide high-resolution information about temperature and precipitation during the past 1,500 years. We extend the understanding of past changes in Quelccaya Ice Cap based on mapping and dating of glacial moraines and associated deposits. Our results include fifty 10Be ages of moraines and bedrock as well as twenty-nine 14C ages of organic material associated with moraines. These results form the basis of a chronology of changes in Quelccaya Ice Cap from ~16,000 yr BP to late Holocene time. Results from 10Be and 14C dating indicate that Quelccaya Ice Cap experienced a significant advance at 12,700-11,400 yr BP. Subsequent to this advance, the ice margin deposited at least three recessional moraine sets. Quelccaya Ice Cap receded to near its present-day margin by ~10,000 yr BP. Neoglacial advances began by ~3,000 yr BP and culminated with a maximum advance during the Little Ice Age. This chronology fits well with prior work which indicates a restricted Quelccaya Ice Cap during middle Holocene time. Moreover, the overlap between moraine and ice core data for the last 1,500 years provides a unique opportunity to assess the influences of temperature and precipitation on past ice cap extents.

  14. Perennial water ice identified in the south polar cap of Mars

    NASA Astrophysics Data System (ADS)

    Bibring, Jean-Pierre; Langevin, Yves; Poulet, François; Gendrin, Aline; Gondet, Brigitte; Berthé, Michel; Soufflot, Alain; Drossart, Pierre; Combes, Michel; Bellucci, Giancarlo; Moroz, Vassili; Mangold, Nicolas; Schmitt, Bernard; OMEGA Team; Erard, S.; Forni, O.; Manaud, N.; Poulleau, G.; Encrenaz, T.; Fouchet, T.; Melchiorri, R.; Altieri, F.; Formisano, V.; Bonello, G.; Fonti, S.; Capaccioni, F.; Cerroni, P.; Coradini, A.; Kottsov, V.; Ignatiev, N.; Titov, D.; Zasova, L.; Pinet, P.; Sotin, C.; Hauber, E.; Hoffman, H.; Jaumann, R.; Keller, U.; Arvidson, R.; Mustard, J.; Duxbury, T.; Forget, F.

    2004-04-01

    The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap.

  15. Holocene Fluctuations of North Ice Cap, a Proxy for Climate Conditions along the Northwestern Margin of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Osterberg, E. C.; Lasher, G. E.; Farnsworth, L. B.; Howley, J. A.; Axford, Y.; Zimmerman, S. R. H.

    2015-12-01

    North Ice Cap (~76.9°N, 68°W, summit elevation 1322 m asl), a small, independent ice cap in northwestern Greenland, is located within ~25 km of the Greenland Ice Sheet margin and Harald Molkte Bræ outlet glacier. We present geochronological, geomorphic and sedimentological data constraining the Holocene extents of North Ice Cap and suggest that its past fluctuations can be used as a proxy for climate conditions along the northwestern margin of the Greenland Ice Sheet. Prior work by Goldthwait (1960) used glacial geomorphology and radiocarbon ages of subfossil plants emerging along shear planes in the ice cap margin to suggest that that North Ice Cap was not present during the early Holocene and nucleated in the middle to late Holocene time, with the onset of colder conditions. Subfossil plants emerging at shear planes in the North Ice Cap margin yield radiocarbon ages of ~4.8-5.9 cal kyr BP (Goldthwait, 1960) and ~AD 1000-1350 (950-600 cal yr BP), indicating times when the ice cap was smaller than at present. In situ subfossil plants exposed by recent ice cap retreat date to ~AD 1500-1840 (450-110 cal yr BP) and indicate small fluctuations of the ice cap margin. 10Be ages of an unweathered, lichen-free drift <100 m from the present North Ice Cap margin range from ~500 to 8000 yrs ago. We suggest that the drift was deposited during the last ~500 yrs and that the older 10Be ages are influenced by 10Be inherited from a prior period of exposure. We also infer ice cap fluctuations using geochemical data from a Holocene-long sediment core from Deltasø, a downstream lake that currently receives meltwater from North Ice Cap. The recent recession of the North Ice Cap margin influenced a catastrophic drainage of a large proglacial lake, Søndre Snesø, that our field team documented in August 2012. To our knowledge, this is the first significant lowering of Søndre Snesø in historical time.

  16. Rapid wastage of the Hazen Plateau ice caps, northeastern Ellesmere Island, Nunavut, Canada

    NASA Astrophysics Data System (ADS)

    Serreze, Mark C.; Raup, Bruce; Braun, Carsten; Hardy, Douglas R.; Bradley, Raymond S.

    2017-01-01

    Two pairs of small stagnant ice bodies on the Hazen Plateau of northeastern Ellesmere Island, the St. Patrick Bay ice caps and the Murray and Simmons ice caps, are rapidly shrinking, and the remnants of the St. Patrick Bay ice caps are likely to disappear entirely within the next 5 years. Vertical aerial photographs of these Little Ice Age relics taken during August of 1959 show that the larger of the St. Patrick Bay ice caps had an area of 7.48 km2 and the smaller one 2.93 km2; the Murray and Simmons ice caps covered 4.37 and 7.45 km2 respectively. Outlines determined from ASTER satellite data for July 2016 show that, compared to 1959, the larger and the smaller of the St. Patrick Bay ice caps had both been reduced to only 5 % of their former area, with the Murray and Simmons ice caps faring better at 39 and 25 %, likely reflecting their higher elevation. Consistent with findings from other glaciological studies in the Queen Elizabeth Islands, ASTER imagery in conjunction with past GPS surveys documents a strikingly rapid wastage of the St. Patrick Bay ice caps over the last 15 years. These two ice caps shrank noticeably even between 2014 and 2015, apparently in direct response to the especially warm summer of 2015 over northeastern Ellesmere Island. The well-documented recession patterns of the Hazen Plateau ice caps over the last 55+ years offer an opportunity to examine the processes of plant recolonization of polar landscapes.

  17. Elevation Changes of Ice Caps in the Canadian Arctic Archipelago

    NASA Technical Reports Server (NTRS)

    Abdalati, W.; Krabill, W.; Frederick, E.; Manizade, S.; Martin, C.; Sonntag, J.; Swift, R.; Thomas, R.; Yungel, J.; Koerner, R.

    2004-01-01

    Precise repeat airborne laser surveys were conducted over the major ice caps in the Canadian Arctic Archipelago in the spring of 1995 and 2000 in order to measure elevation changes in the region. Our measurements reveal thinning at lower elevations (below 1600 m) on most of the ice caps and glaciers, but either very little change or thickening at higher elevations in the ice cap accumulation zones. Recent increases in precipitation in the area can account for the slight thickening where it was observed, but not for the thinning at lower elevations. For the northern ice caps on the Queen Elizabeth Islands, thinning was generally less than 0.5 m/yr , which is consistent with what would be expected from the warm temperature anomalies in the region for the 5-year period between surveys and appears to be a continuation of a trend that began in the mid 1980s. Further south, however, on the Barnes and Penny ice caps on Baffin Island, this thinning was much more pronounced at over 1 m/yr in the lower elevations. Here temperature anomalies were very small, and the thinning at low elevations far exceeds any associated enhanced ablation. The observations on Barnes, and perhaps Penny are consistent with the idea that the observed thinning is part of a much longer term deglaciation, as has been previously suggested for Barnes Ice Cap. Based on the regional relationships between elevation and elevation-change in our data, the 1995-2000 mass balance for the region is estimated to be 25 cu km/yr of ice, which corresponds to a sea level increase of 0.064 mm/ yr . This places it among the more significant sources of eustatic sea level rise, though not as substantial as Greenland ice sheet, Alaskan glaciers, or the Patagonian ice fields.

  18. Surface mass balance of Greenland mountain glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.

    2009-12-01

    Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling melt and accumulation rates on mountain glaciers and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface melting is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. Melt water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.

  19. Field-calibrated model of melt, refreezing, and runoff for polar ice caps: Application to Devon Ice Cap

    NASA Astrophysics Data System (ADS)

    Morris, Richard M.; Mair, Douglas W. F.; Nienow, Peter W.; Bell, Christina; Burgess, David O.; Wright, Andrew P.

    2014-09-01

    Understanding the controls on the amount of surface meltwater that refreezes, rather than becoming runoff, over polar ice masses is necessary for modeling their surface mass balance and ultimately for predicting their future contributions to global sea level change. We present a modified version of a physically based model that includes an energy balance routine and explicit calculation of near-surface meltwater refreezing capacity, to simulate the evolution of near-surface density and temperature profiles across Devon Ice Cap in Arctic Canada. Uniquely, our model is initiated and calibrated using high spatial resolution measurements of snow and firn densities across almost the entire elevation range of the ice cap for the summer of 2004 and subsequently validated with the same type of measurements obtained during the very different meteorological conditions of summer 2006. The model captures the spatial variability across the transect in bulk snowpack properties although it slightly underestimates the flow of meltwater into the firn of previous years. The percentage of meltwater that becomes runoff is similar in both years; however, the spatial pattern of this melt-runoff relationship is different in the 2 years. The model is found to be insensitive to variation in the depth of impermeable layers within the firn but is very sensitive to variation in air temperature, since the refreezing capacity of firn decreases with increasing temperature. We highlight that the sensitivity of the ice cap's surface mass balance to air temperature is itself dependent on air temperature.

  20. Acoustic Monitoring of the Arctic Ice Cap

    NASA Astrophysics Data System (ADS)

    Porter, D. L.; Goemmer, S. A.; Chayes, D. N.

    2012-12-01

    Introduction The monitoring of the Arctic Ice Cap is important economically, tactically, and strategically. In the scenario of ice cap retreat, new paths of commerce open, e.g. waterways from Northern Europe to the Far East. Where ship-going commerce is conducted, the U.S. Navy and U.S. Coast Guard have always stood guard and been prepared to assist from acts of nature and of man. It is imperative that in addition to measuring the ice from satellites, e.g. Icesat, that we have an ability to measure the ice extent, its thickness, and roughness. These parameters play an important part in the modeling of the ice and the processes that control its growth or shrinking and its thickness. The proposed system consists of three subsystems. The first subsystem is an acoustic source, the second is an array of geophones and the third is a system to supply energy and transmit the results back to the analysis laboratory. The subsystems are described below. We conclude with a plan on how to tackle this project and the payoff to the ice cap modeler and hence the users, i.e. commerce and defense. System Two historically tested methods to generate a large amplitude multi-frequency sound source include explosives and air guns. A new method developed and tested by the University of Texas, ARL is a combustive Sound Source [Wilson, et al., 1995]. The combustive sound source is a submerged combustion chamber that is filled with the byproducts of the electrolysis of sea water, i.e. Hydrogen and Oxygen, an explosive mixture which is ignited via a spark. Thus, no additional compressors, gases, or explosives need to be transported to the Arctic to generate an acoustic pulse capable of the sediment and the ice. The second subsystem would be geophones capable of listening in the O(10 Hz) range and transmitting that data back to the laboratory. Thus two single arrays of geophones arranged orthogonal to each other with a range of 1000's of kilometers and a combustive sound source where the two

  1. Form and flow of the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian High Arctic

    NASA Astrophysics Data System (ADS)

    Dowdeswell, J. A.; Bassford, R. P.; Gorman, M. R.; Williams, M.; Glazovsky, A. F.; Macheret, Y. Y.; Shepherd, A. P.; Vasilenko, Y. V.; Savatyuguin, L. M.; Hubberten, H.-W.; Miller, H.

    2002-04-01

    The 5,575-km2 Academy of Sciences Ice Cap is the largest in the Russian Arctic. A 100-MHz airborne radar, digital Landsat imagery, and satellite synthetic aperture radar (SAR) interferometry are used to investigate its form and flow, including the proportion of mass lost through iceberg calving. The ice cap was covered by a 10-km-spaced grid of radar flight paths, and the central portion was covered by a grid at 5-km intervals: a total of 1,657 km of radar data. Digital elevation models (DEMs) of ice surface elevation, ice thickness, and bed elevation data sets were produced (cell size 500 m). The DEMs were used in the selection of a deep ice core drill site. Total ice cap volume is 2,184 km3 (~5.5 mm sea level equivalent). The ice cap has a single dome reaching 749 m. Maximum ice thickness is 819 m. About 200 km, or 42%, of the ice margin is marine. About 50% of the ice cap bed is below sea level. The central divide of the ice cap and several major drainage basins, in the south and east of the ice cap and of up to 975 km2, are delimited from satellite imagery. There is no evidence of past surge activity on the ice cap. SAR interferometric fringes and phase-unwrapped velocities for the whole ice cap indicate slow flow in the interior and much of the margin, punctuated by four fast flowing features with lateral shear zones and maximum velocity of 140 m yr-1. These ice streams extend back into the slower moving ice to within 5-10 km of the ice cap crest. They have lengths of 17-37 km and widths of 4-8 km. Mass flux from these ice streams is ~0.54 km3 yr-1. Tabular icebergs up to ~1.7 km long are produced. Total iceberg flux from the ice cap is ~0.65 km3 yr-1 and probably represents ~40% of the overall mass loss, with the remainder coming from surface melting. Driving stresses are generally lowest (<40 kPa) close to the ice cap divides and in several of the ice streams. Ice stream motion is likely to include a significant basal component and may involve deformable

  2. Interannual observations and quantification of summertime H2O ice deposition on the Martian CO2 ice south polar cap

    USGS Publications Warehouse

    Brown, Adrian J.; Piqueux, Sylvain; Titus, Timothy N.

    2014-01-01

    The spectral signature of water ice was observed on Martian south polar cap in 2004 by the Observatoire pour l'Mineralogie, l'Eau les Glaces et l'Activite (OMEGA) ( Bibring et al., 2004). Three years later, the OMEGA instrument was used to discover water ice deposited during southern summer on the polar cap ( Langevin et al., 2007). However, temporal and spatial variations of these water ice signatures have remained unexplored, and the origins of these water deposits remains an important scientific question. To investigate this question, we have used observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter (MRO) spacecraft of the southern cap during austral summer over four Martian years to search for variations in the amount of water ice. We report below that for each year we have observed the cap, the magnitude of the H2O ice signature on the southern cap has risen steadily throughout summer, particularly on the west end of the cap. The spatial extent of deposition is in disagreement with the current best simulations of deposition of water ice on the south polar cap (Montmessin et al., 2007). This increase in water ice signatures is most likely caused by deposition of atmospheric H2O ice and a set of unusual conditions makes the quantification of this transport flux using CRISM close to ideal. We calculate a ‘minimum apparent‘ amount of deposition corresponding to a thin H2O ice layer of 0.2 mm (with 70% porosity). This amount of H2O ice deposition is 0.6–6% of the total Martian atmospheric water budget. We compare our ‘minimum apparent’ quantification with previous estimates. This deposition process may also have implications for the formation and stability of the southern CO2 ice cap, and therefore play a significant role in the climate budget of modern day Mars.

  3. The Search for Subsurface Ice Caps on Mercury

    NASA Astrophysics Data System (ADS)

    Allen, R. A.; Barlow, N. G.; Vilas, F.

    1996-03-01

    Recent ground-based radar observations of Mercury have detected strong, highly depolarized echoes from the north and south polar regions which have been interpreted as possible polar ice deposits. These radar echoes have been correlated with a number of impact craters. Theoretical studies indicate that such surface ice can be stable within permanently shadowed areas, such as the floors of high latitude impact craters. One proposed hypothesis suggests that stable subsurface ice caps exist at the poles of Mercury, and that several of the impact events that created the high latitude craters exposed this subsurface ice. Thus, our study focused on the possibility of ice caps extending below the mercurian surface, down to some unknown latitude in the polar regions. We used the experiences from Mars, where the depth/diameter ratio (d/D) is smaller for ice rich areas, to investigate whether a comparable latitudinal change in d/D is detectable on Mercury. We found no significant latitudinal differences within the two polar regions of our study or between the north polar and equatorial quadrangles, but craters in the south polar region tend to have slightly lower d/D than those in the north polar region.

  4. Holocene Activity of the Quelccaya Ice Cap: A Working Model

    NASA Astrophysics Data System (ADS)

    Lowell, T. V.; Smith, C. A.; Kelly, M. A.; Stroup, J. S.

    2012-12-01

    The patterns and magnitudes of past climate change in the topics are still under discussion. We contribute here by reporting on patterns of glacier length changes of the largest glacier in the tropics, Quelccaya Ice Cap (~13.9°S, 70.9°W, summit at 5645 m). This ice cap has several local domes that may have different patterns of length changes because of differing elevations of the domes (high to the north, lower to the south). Prior work (Mark et al. 2003, Abbott et al., 2004; Thompson et al., 2005; Buffen, et al., 2009), new radiocarbon ages, and stratigraphic and geomorphic relationships are used to determine the general pattern of length changes for the outlets from this ice cap. We exploit geomorphic relationships and present new radiocarbon ages on interpreted stratigraphic sections to determine the pattern of length changes for this ice cap. Ice retreated during late glacial times (Rodbell and Seltzer, 2000; Kelly et al., in press). By 11,400 yr BP it had reached a position ~1.2 km beyond its present (2000 AD) extent. While length during the early Holocene is problematic, present evidence permits, but does not prove, extents of 0.5 to 1.0 km down-valley from the present margin. Between 6400 and 4400 yr BP the ice cap was smaller than present, but it advanced multiple times during the late Holocene. Lengths of up to 1 km beyond present were achieved at 3400 yr BP and ~500 yr BP. Additionally, the ice advanced to 0.8 km beyond its present margin at 1600 yr BP. Because these glaciers were temperate, we take these lengths to represent primarily changes in temperature. This may suggest that lowering insolation values in the northern hemisphere during the Holocene provide a first order control on tropical temperatures. Alternatively, it may be that major reorganization of the topical circulation belts about 5000 yr BP yields two configurations of the QIC and hence Holocene temperatures - one at the present ice margin and and the second about 1 km beyond the

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  6. The projected demise of Barnes Ice Cap: Evidence of an unusually warm 21st century Arctic

    NASA Astrophysics Data System (ADS)

    Gilbert, A.; Flowers, G. E.; Miller, G. H.; Refsnider, K. A.; Young, N. E.; Radić, V.

    2017-03-01

    As a remnant of the Laurentide Ice Sheet, Barnes Ice Cap owes its existence and present form in part to the climate of the last glacial period. The ice cap has been sustained in the present interglacial climate by its own topography through the mass balance-elevation feedback. A coupled mass balance and ice-flow model, forced by Coupled Model Intercomparison Project Phase 5 climate model output, projects that the current ice cap will likely disappear in the next 300 years. For greenhouse gas Representative Concentration Pathways of +2.6 to +8.5 Wm-2, the projected ice-cap survival times range from 150 to 530 years. Measured concentrations of cosmogenic radionuclides 10Be, 26Al, and 14C at sites exposed near the ice-cap margin suggest the pending disappearance of Barnes Ice Cap is very unusual in the last million years. The data and models together point to an exceptionally warm 21st century Arctic climate.

  7. Retrieving improved multi-temporal CryoSat elevations over ice caps and glaciers - a case study of Barnes ice cap

    NASA Astrophysics Data System (ADS)

    Nilsson, Johan; Burgess, David

    2014-05-01

    The CryoSat mission was launched in 2010 to observe the Earth's cryosphere. In contrast to previous satellite radar altimeters, this mission is expected to monitor the elevation of small ice caps and glaciers, which according to the IPCC will be the largest contributor to 21st century sea level rise. To date the ESA CryoSat SARiN level-2 (L2) elevation product is not yet fully optimized for use over these types of glaciated regions, as its processed with a more universal algorithm. Thus the aim of this study is to demonstrate that with the use of improved processing CryoSat SARiN data can be used for more accurate topography mapping and elevation change detection for ice caps and glaciers. To demonstrate this, elevations and elevation changes over Barnes ice cap, located on Baffin Island in the Canadian Arctic, have been estimated from available data from the years 2010-2013. ESA's CryoSat level-1b (L1b) SARiN baseline "B" data product was used and processed in-house to estimate surface elevations. The resulting product is referred to as DTU-L2. The processing focused on improving the retracker, reducing phase noise and correcting phase ambiguities. The accuracy of the DTU-L2 and the ESA-L2 product was determined by comparing the measured elevations against NASA's IceBridge Airborne Topographic Mapper (ATM) elevations from May 2011. The resulting difference in accuracy was determined by comparing their associated errors. From the multi-temporal measurements spanning the period 2010-2013, elevation changes where estimated and compared to ICESat derived changes from 2003-2009. The result of the study shows good agreement between the NASA measured ATM elevations and the DTU-L2 data. It also shows that the pattern of elevation change is similar to that derived from ICESat data. The accuracy of the DTU-L2 estimated elevations is on average several factors higher compared to the ESA-L2 elevation product. These preliminary results demonstrates that CryoSat elevation data

  8. Martian Polar Caps: Folding, Faulting, Flowing Glaciers of Multiple Interbedded Ices

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.

    2001-12-01

    The Martian south polar cap (permanent CO2 cap and polar layered deposits), exhibit abundant, varied, and widespread deformational phenomena. Folding and boudinage are very common. Strike-slip or normal faults are rarer. Common in the vicinity of major troughs and scarps are signs of convergent flow tectonics manifested as wrinkle-ridge-like surface folds, thrust faults, and viscous forebulges with thin-skinned extensional crevasses and wrinkle-ridge folds. Such flow convergence is predicted by theory. Boudinage and folding at the 300-m wavelength scale, indicating rheologically contrasting materials, is widely exposed at deep levels along erosional scarps. Independent morphologic evidence indicates south polar materials of contrasting volatility. Hence, the south polar cap appears to be a multiphase structure of interbedded ices. The north polar cap locally also exhibits flow indicators, though they are neither as common nor as varied as in the south. The large-scale quasi-spiral structure of the polar caps could be a manifestation of large-scale boudinage. According to this scenario, deep-level boudinage continuously originates under the glacial divide (the polar cap summit). Rod-like boudin structures are oriented transverse to flow and migrate outward with the large-scale flow field. Troughs develop over areas between major boudins. A dynamic competition, and possibly a rough balance, develops between the local flow field in the vicinity of a trough (which tends to close the trough by lateral closure and upwelling flow) and sublimation erosion (which tends to widen and deepen them). Over time, the troughs flow to the margins of the polar cap where they, along with other polar structures, are destroyed by sublimation. Major ice types contributing to rheological and volatility layering may include, in order of highest to lowest mechanical strength, CO2 clathrate hydrate, water ice containing inert/insoluble dust, pure water ice, water ice containing traces of

  9. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap

    USGS Publications Warehouse

    Kieffer, H.H.; Christensen, P.R.; Titus, T.N.

    2006-01-01

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO 2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. ?? 2006 Nature Publishing Group.

  10. Mountain Glaciers and Ice Caps

    USGS Publications Warehouse

    Ananichheva, Maria; Arendt, Anthony; Hagen, Jon-Ove; Hock, Regine; Josberger, Edward G.; Moore, R. Dan; Pfeffer, William Tad; Wolken, Gabriel J.

    2011-01-01

    Projections of future rates of mass loss from mountain glaciers and ice caps in the Arctic focus primarily on projections of changes in the surface mass balance. Current models are not yet capable of making realistic forecasts of changes in losses by calving. Surface mass balance models are forced with downscaled output from climate models driven by forcing scenarios that make assumptions about the future rate of growth of atmospheric greenhouse gas concentrations. Thus, mass loss projections vary considerably, depending on the forcing scenario used and the climate model from which climate projections are derived. A new study in which a surface mass balance model is driven by output from ten general circulation models (GCMs) forced by the IPCC (Intergovernmental Panel on Climate Change) A1B emissions scenario yields estimates of total mass loss of between 51 and 136 mm sea-level equivalent (SLE) (or 13% to 36% of current glacier volume) by 2100. This implies that there will still be substantial glacier mass in the Arctic in 2100 and that Arctic mountain glaciers and ice caps will continue to influence global sea-level change well into the 22nd century.

  11. Textures in south polar ice cap #1

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Textures of the south polar permanent residual ice cap and polar layered terrains. This 30 x 29 km area image (frame 7709) is centered near 87 degrees south, 77 degrees west.

    Figure caption from Science Magazine

  12. Textures in south polar ice cap #2

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Textures of the south polar permanent residual ice cap and polar layered terrains. This 15 x 14 km area image (frame 7306) is centered near 87 degrees south, 341 degrees west.

    Figure caption from Science Magazine

  13. CryoSat swath altimetry to measure ice cap and glacier surface elevation change

    NASA Astrophysics Data System (ADS)

    Tepes, P.; Gourmelen, N.; Escorihuela, M. J.; Wuite, J.; Nagler, T.; Foresta, L.; Brockley, D.; Baker, S.; Roca, M.; Shepherd, A.; Plummer, S.

    2016-12-01

    Satellite altimetry has been used extensively in the past few decades to observe changes affecting large and remote regions covered by land ice such as the Greenland and Antarctic ice sheets. Glaciers and ice caps have been studied less extensively due to limitation of altimetry over complex topography. However their role in current sea-level budgets is significant and is expected to continue over the next century and beyond (Gardner et al., 2011), particularly in the Arctic where mean annual surface temperatures have recently been increasing twice as fast as the global average (Screen and Simmonds, 2010). Radar altimetry is well suited to monitor elevation changes over land ice due to its all-weather year-round capability of observing ice surfaces. Since 2010, the Synthetic Interferometric Radar Altimeter (SIRAL) on board the European Space Agency (ESA) radar altimetry CryoSat (CS) mission has been collecting ice elevation measurements over glaciers and ice caps. Its Synthetic Aperture Radar Interferometric (SARIn) processing feature reduces the size of the footprint along-track and locates the across-track origin of a surface reflector in the presence of a slope. This offers new perspectives for the measurement of regions marked by complex topography. More recently, data from the CS-SARIn mode have been used to infer elevation beyond the point of closest approach (POCA) with a novel approach known as "swath processing" (Hawley et al., 2009; Gray et al., 2013; Christie et al., 2016; Smith et al., 2016). Together with a denser ground track interspacing of the CS mission, the swath processing technique provides unprecedented spatial coverage and resolution for space borne altimetry, enabling the study of key processes that underlie current changes of ice caps and glaciers. In this study, we use CS swath observations to generate maps of ice elevation change for selected ice caps and glaciers. We present a validation exercise and discuss the benefit of swath

  14. Microorganisms on comets, Europa, and the polar ice caps of Mars

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Pikuta, Elena V.

    2004-02-01

    Microbial extremophiles live on Earth wherever there is liquid water and a source of energy. Observations by ground-based observatories, space missions, and satellites have provided strong evidence that water ice exists today on comets, Europa, Callisto, and Ganymede and in the snow, permafrost, glaciers and polar ice caps of Mars. Studies of the cryoconite pools and ice bubble systems of Antarctica suggest that solar heating of dark rocks entrained in ice can cause localized melting of ice providing ideal conditions for the growth of microbial communities with the creation of micro-environments where trapped metabolic gasses produce entrained isolated atmospheres as in the Antarctic ice-bubble systems. It is suggested that these considerations indicate that several groups of microorganisms should be capable of episodic growth within liquid water envelopes surrounding dark rocks in cometary ices and the permafrost and polar caps of Mars. We discuss some of the types of microorganisms we have encountered within the permafrost and snow of Siberia, the cryoconite pools of Alaska, and frozen deep within the Antarctic ice sheet above Lake Vostok.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The Arctic region, and Greenland in particular, is undergoing dramatic change as characterized by atmospheric warming, decreasing sea ice, shifting ocean circulation patterns, and rapid ice sheet mass loss, but longer records are needed to put these changes into context. Ice core records from the Greenland ice sheet have yielded invaluable insight into past climate change both regionally and globally, and provided important constraints on past surface mass balance more directly, but these ice cores are most often from the interior ice sheet accumulation zone, at high altitude and hundreds of kilometers from the coast. Coastal ice caps, situated around the margins of Greenland, have the potential to provide novel high-resolution records of local and regional maritime climate and sea surface conditions, as well as contemporaneous glaciological changes (such as accumulation and surface melt history). But obtaining these records is extremely challenging. Most of these ice caps are unexplored, and thus their thickness, age, stratigraphy, and utility as sites of new and unique paleoclimate records is largely unknown. Access is severely limited due to their high altitude, steep relief, small surface area, and inclement weather. Furthermore, their relatively low elevation and marine moderated climate can contribute to significant surface melting and degradation of the ice stratigraphy. We recently targeted areas near the Disko Bay region of central west Greenland where maritime ice caps are prevalent but unsampled, as potential sites for new multi-decadal to multi-millennial ice core records. In 2014 & 2015 we identified two promising ice caps, one on Disko Island (1250 m. asl) and one on Nuussuaq Peninsula (1980 m. asl) based on airborne and ground-based geophysical observations and physical and glaciochemical stratigraphy from shallow firn cores. In spring 2015 we collected ice cores at both sites using the Badger-Eclipse electromechanical drill, transported by a medley

  16. Rapid onset of Little Ice Age summer cold in the northern North Atlantic derived from precisely dated ice cap records (Invited)

    NASA Astrophysics Data System (ADS)

    Miller, G. H.; Larsen, D.; Geirsdottir, A.; Refsnider, K. A.; Anderson, C.

    2009-12-01

    Precise radiocarbon dates on dead vegetation emerging beneath retreating non-erosive ice caps in NE Arctic Canada define the onset of ice cap growth, and provide a Holocene context for 20th Century warming. Although most plateau ice caps melted during the Medieval Warm Period, a few that are now disappearing remained intact since at least 350 AD. Little Ice Age ice cap inception occurred in two pulses, centered on 1250-1300 AD and around 1450 AD, with ice caps remaining in an expanded state until the warming of the past few decades. Ice cap inception occurred simultaneously (±10 years) over a 200 m elevational range, suggesting an abrupt onset of Little Ice Age cold, rather than a slow cooling over many decades. Similarly, a 3000 year annually resolved lacustrine record of glacier power and a complementary independent proxy for landscape instability in the highlands of central Iceland show an initial jump in both glacier power and landscape instability between 1250 and 1300 AD, with a second step-increase around 1450 AD, and dramatic increases in both proxies around 1800 AD, retracting in the 20th Century. A sub-decadal record of hillslope stability and within-lake primary productivity in sediments from a low-elevation lake in northern Iceland shows parallel changes at similar times. Sea ice proxies and historical records document the first appearance of sea ice around Iceland following Medieval time about 1250 AD. The similarity in the onset and intensification of Little Ice Age cold-weather proxies across a wide region of the northern North Atlantic suggests at least a regional driver of abrupt climate change. The time intervals for which these abrupt changes occur coincide with the three most intense episodes of multiple explosive volcanic eruptions that introduced large volumes of sulfate aerosols into the stratosphere during the past millennium. Although the direct impacts of volcanic aerosols have a duration of only a few years, the memory stored by the

  17. Dual-sensor mapping of mass balance on Russia's northernmost ice caps

    NASA Astrophysics Data System (ADS)

    Nikolskiy, D.; Malinnikov, V.; Sharov, A.; Ukolova, M.

    2012-04-01

    Mass balance of Russia's northernmost ice caps is poorly known and scarcely mapped. Thorough information about glacier fluctuations in the outer periphery of Russian shelf seas is both lacking and highly desired since it may constitute the relevant benchmark for judging and projecting climate change impacts in the entire Arctic. The present study is focussed on geodetic measurements and medium-scale mapping of the mass balance on a dozen insular ice caps, some large and some smaller, homogeneously situated along the Eurasian boundary of Central Arctic Basin. The study region extends for approx. 2.200 km from Victoria and Arthur islands in the west across Rudolph, Eva-Liv, Ushakova, Schmidt and Komsomolets islands in the north to Bennett and Henrietta islands in the east thereby comprising the most distant and least studied ice caps in the Russian Arctic. The situation of insular ice masses close to the edge of summer minimum sea ice proved helpful in analysing spatial asymmetry of glacier accumulation signal. The overall mapping of glacier elevation changes and quantification of mass balance characteristics in the study region was performed by comparing reference elevation models of study glaciers derived from Russian topographic maps 1:200,000 (CI = 20 or 40 m) representing the glacier state as in the 1950s-1960s with modern elevation data obtained from satellite radar interferometry and lidar altimetry. In total, 14 ERS and 4 TanDEM-X high-quality SAR interferograms of 1995/96 and 2011 were acquired, processed in the standard 2-pass DINSAR manner, geocoded, calibrated, mosaicked and interpreted using reference elevation models and co-located ICESat altimetry data of 2003-2010. The DINSAR analysis revealed the existence of fast-flowing outlet glaciers at Arthur, Rudolph, Eva-Liv and Bennett islands. The calculation of separate mass-balance components is complicated in this case because of generally unknown glacier velocities and ice discharge values for the mid-20

  18. Present and Future Surface Mass Budget of Small Arctic Ice Caps in a High Resolution Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Langen, Peter; Koldtoft, Iben; Midefelt, Linnea; Hesselbjerg Christensen, Jens

    2016-04-01

    Globally, small ice caps and glaciers make a substantial contribution to sea level rise; this is also true in the Arctic. Around Greenland small ice caps are surprisingly important to the total mass balance from the island as their marginal coastal position means they receive a large amount of precipitation and also experience high surface melt rates. Since small ice caps and glaciers have had a disproportionate number of long-term monitoring and observational schemes in the Arctic, likely due to their relative accessibility, they can also be a valuable source of data. However, in climate models the surface mass balance contributions are often not distinguished from the main ice sheet and the presence of high relief topography is difficult to capture in coarse resolution climate models. At the same time, the diminutive size of marginal ice masses in comparison to the ice sheet makes modelling their ice dynamics difficult. Using observational data from the Devon Ice Cap in Arctic Canada and the Renland Ice Cap in Eastern Greenland, we assess the success of a very high resolution (~5km) regional climate model, HIRHAM5 in capturing the surface mass balance (SMB) of these small ice caps. The model is forced with ERA-Interim and we compare observed mean SMB and the interannual variability to assess model performance. The steep gradient in topography around Renland is challenging for climate models and additional statistical corrections are required to fit the calculated surface mass balance to the high relief topography. Results from a modelling experiment at Renland Ice Cap shows that this technique produces a better fit between modelled and observed surface topography. We apply this statistical relationship to modelled SMB on the Devon Ice Cap and use the long time series of observations from this glacier to evaluate the model and the smoothed SMB. Measured SMB values from a number of other small ice caps including Mittivakkat and A.P. Olsen ice cap are also compared

  19. Landscape Evolution and the Reincarnation of the Residual CO2 Ice Cap of Mars

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Zuber, M.

    2006-12-01

    Observations of the southern residual CO2 cap of Mars reveal a wide range of landforms including flat-floored quasi-circular pits with steep walls (dubbed Swiss-cheese features). Interannual comparisons show that these depressions are expanding laterally at rates of ~2m/yr to ~4m/yr, prompting suggestions of climate change. The residual CO2 ice cap is up to 10m thick and underlain by an involatile basement, it also contains layers roughly 2m thick representing different accumulation episodes in the recent past. Changes in the appearance of the residual ice between the Mariner 9 and Viking missions indicate that the top-most layer was deposited in that time-frame, soon after the global dust storm of 1971. The spatial density of the Swiss-cheese features, and the rate at which they expand, mean that it is unlikely that any part of the residual ice cap is older than a few centuries. Given this, we may ask: how can there be a residual cap present today for us to observe? To answer this and other questions we have developed a model to examine the evolution of a CO2 ice landscape. This model reproduces the morphologies and expansion rates seen in the actual residual CO2 ice cap. Our model results indicate that the fate of CO2 ice surfaces is controlled by their surface roughness. Surface roughness always increases with time, which results in an unstable situation. When the surface roughness exceeds a critical point small pits can begin to develop. The walls of these pits rapidly steepen and begin retreating which enlarges and deepens the pit. This situation always occurs even if the surface of the CO2 slab has a high enough albedo to have a net mass gain each year. Once these pits begin expanding they quickly erode the entire ice slab. When the underlying non-CO2 material is exposed, it will not frost over again if Mars were to repeat like clockwork every year. We conclude that interannual climatic variability is actually a requirement for the continued existence of a

  20. Correlating Ice Cores from Quelccaya Ice Cap with Chronology from Little Ice Age Glacial Extents

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.

    2010-12-01

    Proxy records indicate Southern Hemisphere climatic changes during the Little Ice Age (LIA; ~1300-1850 AD). In particular, records of change in and around the tropical latitudes require attention because these areas are sensitive to climatic change and record the dynamic interplay between hemispheres (Oerlemans, 2005). Despite this significance, relatively few records exist for the southern tropics. Here we present a reconstruction of glacial fluctuations of Quelccaya Ice Cap (QIC), Peruvian Andes, from pre-LIA up to the present day. In the Qori Kalis valley, extensive sets of moraines exist beginning with the 1963 AD ice margin (Thompson et al., 2006) and getting progressively older down valley. Several of these older moraines can be traced and are continuous with moraines in the Challpa Cocha valley. These moraines have been dated at <1050-1350-AD (Mercer and Palacios, 1977) and interpreted to have been deposited during the Little Ice Age. We present a new suite of surface exposure and radiocarbon dates collected in 2008 and 2009 that constrain the ages of these moraines. Preliminary 10Be ages of boulder surfaces atop the moraines range from ~350-1370 AD. Maximum and minimum-limiting radiocarbon ages bracketing the moraines are ~0-1800 AD. The chronology of past ice cap extents are correlated with ice core records from QIC which show an accumulation increase during ~1500-1700 AD and an accumulation decrease during ~1720-1860 AD (Thompson et al., 1985; 1986; 2006). In addition, other proxy records from Peru and the tropics are correlated with the records at QIC as a means to understand climate conditions during the LIA. This work forms the basis for future modeling of the glacial system during the LIA at QIC and for modeling of past temperature and precipitation regimes at high altitude in the tropics.

  1. South Polar Ice Cap

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-337, 21 April 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the 'swiss cheese' pattern of frozen carbon dioxide on the south polar residual cap. Observation of these materials over two Mars years has revealed that the scarps that bound the mesas and small buttes are retreating-the carbon dioxide ice is subliming away-at a rate of about 3 meters (3 yards) per Mars year in some places. The picture covers an area about 900 m (about 900 yards) wide near 87.1oS, 93.7oW. Sunlight illuminates the scene from the upper left.

  2. Erosion patterns produced by the paleo Haizishan ice cap, SE Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Fu, P.; Stroeven, A. P.; Harbor, J.; Hättestrand, C.; Heyman, J.; Caffee, M. W.

    2017-12-01

    Erosion is a primary driver of landscape evolution, topographic relief production, geochemical cycles, and climate change. Combining in situ 10Be and 26Al exposure age dating, geomorphological mapping, and field investigations, we examine glacial erosion patterns of the almost 4,000 km2 paleo Haizishan ice cap on the southeastern Tibetan Plateau. Our results show that ice caps on the low relief Haizishan Plateau produced a zonal pattern of landscape modification. In locations where apparent exposure ages on bedrock are consistent with the last deglaciation, complete resetting of the cosmogenic exposure age clock indicates glacial erosion of at least a few meters. However, older apparent exposure ages on bedrock in areas known to have been covered by the paleo ice cap during the Last Glacial Maximum indicate inheritance and thus limited glacial erosion. Inferred surface exposure ages from cosmogenic depth profiles through two saprolites vary from resetting and thus saprolite profile truncation to nuclide inheritance indicating limited erosion. Finally, significant nuclide inheritance in river sand samples from basins on the scoured plateau surface also indicate limited glacial erosion during the last glaciation. Hence, for the first time, our study shows clear evidence of preservation under non-erosive ice on the Tibetan Plateau. As patterns of glacial erosion intensity are largely driven by the basal thermal regime, our results confirm earlier inferences from geomorphology for a concentric basal thermal pattern for the paleo Haizishan ice cap during the LGM.

  3. Recent Changes in Arctic Glaciers, Ice Caps, and the Greenland Ice Sheet: Cold Facts About Warm Ice

    NASA Astrophysics Data System (ADS)

    Abdalati, W.

    2005-12-01

    One of the major manifestations of Arctic change can be observed in the state of balance of Arctic glaciers and ice caps and the Greenland ice sheet. These ice masses are estimated to contain nearly 3 million cubic kilometers of ice, which is more than six times greater than all the water stored in the Earth's lakes, rivers, and snow combined and is the equivalent of over 7 meters of sea level. Most of these ice masses have been shrinking in recent in years, but their mass balance is highly variable on a wide range of spatial and temporal scales. On the Greenland ice sheet most of the coastal regions have thinned substantially as melt has increased and some of its outlet glaciers have accelerated. Near the equilibrium line in West Greenland, we have seen evidence of summer acceleration that is linked to surface meltwater production, suggesting a relatively rapid response mechanism of the ice sheet change to a warming climate. At the same time, however, the vast interior regions of the Greenland ice sheet have shown little change or slight growth, as accumulation in these areas may have increased. Throughout much of the rest of the Arctic, many glaciers and ice caps have been shrinking in the past few decades, and in Canada and Alaska, the rate of ice loss seems to have accelerated during the late 1990s. These recent observations offer only a snapshot in time of the long-term behavior, but they are providing crucial information about the current state of ice mass balance and the mechanisms that control it in one of the most climatically sensitive regions on Earth. As we continue to learn more through a combination of remote sensing observations, in situ measurements and improved modeling capabilities, it is important that we coordinate and integrate these approaches effectively in order to predict future changes and their impact on sea level, freshwater discharge, and ocean circulation.

  4. Surface elevation change on ice caps in the Qaanaaq region, northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Saito, Jun; Sugiyama, Shin; Tsutaki, Shun; Sawagaki, Takanobu

    2016-09-01

    A large number of glaciers and ice caps (GICs) are distributed along the Greenland coast, physically separated from the ice sheet. The total area of these GICs accounts for 5% of Greenland's ice cover. Melt water input from the GICs to the ocean substantially contributed to sea-level rise over the last century. Here, we report surface elevation changes of six ice caps near Qaanaaq (77°28‧N, 69°13‧W) in northwestern Greenland based on photogrammetric analysis of stereo pair satellite images. We processed the images with a digital map plotting instrument to generate digital elevation models (DEMs) in 2006 and 2010 with a grid resolution of 500 m. Generated DEMs were compared to measure surface elevation changes between 2006 and 2010. Over the study area of the six ice caps, covering 1215 km2, the mean rate of elevation change was -1.1 ± 0.1 m a-1. This rate is significantly greater than that previously reported for the 2003-2008 period (-0.6 ± 0.1 m a-1) for GICs all of northwestern Greenland. This increased mass loss is consistent with the rise in summer temperatures in this region at a rate of 0.12 °C a-1 for the 1997-2013 period.

  5. Emergent Dead Vegetation and Paired Cosmogenic Isotope Constraints on Ice Cap Activity, Baffin Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Pendleton, S.; Miller, G. H.

    2014-12-01

    Recent summer warming has now raised the equilibrium line above almost all ice caps on Baffin Island, resulting in surface lowering and marginal recession everywhere. As cold-based ice recedes it frequently exposes in situ tundra plants that were living at the time ice expanded across the site. Radiocarbon dates for each plant records when cold summers dropped regional snowline below the site, killing the plants, and snowline remained below the site until the collection date. The kill dates also represent the last time that the climate was warm enough to expose the sampling location. Seventy-six vegetation samples collected in 2013 from the Penny Ice Cap region have been dated, with significant age populations at ~0.5, 1.8, 2.3, and 3.6 ka. The absence of ages around ~1, 2, 3, 4.5, and 5.5 ka suggest periods of either no snowline depression or stability. Sixteen vegetation samples returned ages of >45 ka (2 revisited sites from 2010, 14 new). It is postulated that these radiocarbon dead samples were last exposed during the last interglaciation (~120 ka), the last time climate was as warm as present. In addition to plant collections, bedrock exposures at the ice margins were sampled for 26Al/10Be cosmogenic nuclide dating. Seven samples from and around the Penny Ice cap have returned maximum exposure ages from ~ 0.6-0.9 ma and total histories of ~0.6-1.5 ma. In general, samples from the larger Penny Ice Cap exhibited lower amounts of exposure (~20% of total history) than those samples from smaller, localized ice caps (~55%). Radiocarbon dead sites north of the Penny Ice cap experienced significantly more exposure over their lifetimes than their counterparts east of the Penny Ice cap, suggesting significant differences in local and regional land ice fluctuations over the last 2 million years. Utilizing both the method of in situ moss and 26Al/10Be dating provides new insight into both the recent activity and long-term evolution of ice on Baffin Island. In particular

  6. Improved parameterization of marine ice dynamics and flow instabilities for simulation of the Austfonna ice cap using a large-scale ice sheet model

    NASA Astrophysics Data System (ADS)

    Dunse, T.; Greve, R.; Schuler, T.; Hagen, J. M.; Navarro, F.; Vasilenko, E.; Reijmer, C.

    2009-12-01

    The Austfonna ice cap covers an area of 8120 km2 and is by far the largest glacier on Svalbard. Almost 30% of the entire area is grounded below sea-level, while the figure is as large as 57% for the known surge-type basins in particular. Marine ice dynamics, as well as flow instabilities presumably control flow regime, form and evolution of Austfonna. These issues are our focus in numerical simulations of the ice cap. We employ the thermodynamic, large-scale ice sheet model SICOPOLIS (http://sicopolis.greveweb.net/) which is based on the shallow-ice approximation. We present improved parameterizations of (a) the marine extent and calving and (b) processes that may initiate flow instabilities such as switches from cold to temperate basal conditions, surface steepening and hence, increases in driving stress, enhanced sliding or deformation of unconsolidated marine sediments and diminishing ice thicknesses towards flotation thickness. Space-borne interferometric snapshots of Austfonna revealed a velocity structure of a slow moving polar ice cap (< 10m/a) interrupted by distinct fast flow units with velocities in excess of 100m/a. However, observations of flow variability are scarce. In spring 2008, we established a series of stakes along the centrelines of two fast-flowing units. Repeated DGPS and continuous GPS measurements of the stake positions give insight in the temporal flow variability of these units and provide constrains to the modeled surface velocity field. Austfonna’s thermal structure is described as polythermal. However, direct measurements of the temperature distribution is available only from one single borehole at the summit area. The vertical temperature profile shows that the bulk of the 567m thick ice column is cold, only underlain by a thin temperate basal layer of approximately 20m. To acquire a spatially extended picture of the thermal structure (and bed topography), we used low-frequency (20 MHz) GPR profiling across the ice cap and the

  7. Taxon interactions control the distributions of cryoconite bacteria colonizing a High Arctic ice cap.

    PubMed

    Gokul, Jarishma K; Hodson, Andrew J; Saetnan, Eli R; Irvine-Fynn, Tristram D L; Westall, Philippa J; Detheridge, Andrew P; Takeuchi, Nozomu; Bussell, Jennifer; Mur, Luis A J; Edwards, Arwyn

    2016-08-01

    Microbial colonization of glacial ice surfaces incurs feedbacks which affect the melting rate of the ice surface. Ecosystems formed as microbe-mineral aggregates termed cryoconite locally reduce ice surface albedo and represent foci of biodiversity and biogeochemical cycling. Consequently, greater understanding the ecological processes in the formation of functional cryoconite ecosystems upon glacier surfaces is sought. Here, we present the first bacterial biogeography of an ice cap, evaluating the respective roles of dispersal, environmental and biotic filtration occurring at local scales in the assembly of cryoconite microbiota. 16S rRNA gene amplicon semiconductor sequencing of cryoconite colonizing a Svalbard ice cap coupled with digital elevation modelling of physical parameters reveals the bacterial community is dominated by a ubiquitous core of generalist taxa, with evidence for a moderate pairwise distance-decay relationship. While geographic position and melt season duration are prominent among environmental predictors of community structure, the core population of taxa appears highly influential in structuring the bacterial community. Taxon co-occurrence network analysis reveals a highly modular community structured by positive interactions with bottleneck taxa, predominantly Actinobacteria affiliated to isolates from soil humus. In contrast, the filamentous cyanobacterial taxon (assigned to Leptolyngbya/Phormidesmis pristleyi) which dominates the community and binds together granular cryoconite are poorly connected to other taxa. While our study targeted one ice cap, the prominent role of generalist core taxa with close environmental relatives across the global cryosphere indicate discrete roles for cosmopolitan Actinobacteria and Cyanobacteria as respective keystone taxa and ecosystem engineers of cryoconite ecosystems colonizing ice caps. © 2016 John Wiley & Sons Ltd.

  8. Change in the Extent of Baffin Island's Penny Ice Cap in Response to Regional Warming, 1969 - 2014

    NASA Astrophysics Data System (ADS)

    Cox, M. C.; Cormier, H. M.; Gardner, A. S.

    2014-12-01

    Glaciers are retreating globally in response to warmer atmospheric temperatures, adding large volumes of melt water to the world's oceans. The largest glacierized region and present-day contributor to sea level rise outside of the massive ice sheets is the Canadian Arctic. Recent work has shown that the glaciers of the southern Canadian Arctic (Baffin and Bylot Island) have experienced accelerated rates of ice loss in recent decades, but little is known regarding the spatial and temporal variations in rates of loss. For this study we examine in detail changes in the extent of the Penny Ice Cap (a proxy for ice loss) between 1969 and 2014 to better understand the climatic drivers of the recently observed accelerated rates of ice loss on Baffin Island. To do this, we reconstruct the extent of the ice cap for the year 1969 from historical maps and for the years 1985, 1995, 2010, and 2014 from Landsat 5 TM and Landsat 8 OLI imagery. We use 2009 SPOT HRS imagery and a novel extent comparison algorithm to assess the accuracy of glacier extents derived from Landsat imagery. Regional temperature and precipitation records were used to explain the spatial pattern of change. Due to large variation in elevations, hypsometry was also investigated as a contributor to differences in rates of change across the ice cap. Preliminary results show overall retreat throughout the ice cap but with regional differences in area and length change on either side of the Ice Cap divide.

  9. Seasonal Changes in Mars' North Polar Ice Cap

    NASA Technical Reports Server (NTRS)

    1997-01-01

    These images, which seem to have been taken while NASA's Hubble Space Telescope (HST) was looking directly down on the Martian North Pole, were actually created by assembling mosaics of three sets of images taken by HST in October, 1996 and in January and March, 1997 and projecting them to appear as they would if seen from above the pole. This first mosaic is a view which could not actually be seen in nature because at this season a portion of the pole would have actually been in shadow; the last view, taken near the summer solstice, would correspond to the Midnight Sun on Earth with the pole fully illuminated all day. The resulting polar maps begin at 50 degrees N latitude and are oriented with 0 degrees longitude at the 12 o'clock position. This series of pictures captures the seasonal retreat of Mars' north polar cap.

    October 1996 (early spring in the Northern hemisphere): In this map, assembled from images obtained between Oct. 8 and 15, the cap extends down to 60 degrees N latitude, nearly it's maximum winter extent. (The notches are areas where Hubble data were not available). A thin, comma-shaped cloud of dust can be seen as a salmon-colored crescent at the 7 o'clock position. The cap is actually fairly circular about the geographic pole at this season; the bluish 'knobs' where the cap seems to extend further are actually clouds that occurred near the edges of the three separate sets of images used to make the mosaic.

    January 1997 (mid-spring): Increased warming as spring progresses in the northern hemisphere has sublimated the carbon dioxide ice and frost below 70 degrees north latitude. The faint darker circle inside the cap boundary marks the location of circumpolar sand dunes (see March '97 map); these dark dunes are warmed more by solar heating than are the brighter surroundings, so the surface frost sublimates from the dunes earlier than from the neighboring areas. Particularly evident is the marked hexagonal shape of the polar cap at this season

  10. The little ice age as recorded in the stratigraphy of the tropical quelccaya ice cap.

    PubMed

    Thompson, L G; Mosley-Thompson, E; Dansgaard, W; Grootes, P M

    1986-10-17

    The analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent. Annual variations in visible dust layers, oxygen isotopes, microparticle concentrations, conductivity, and identification of the historical (A.D. 1600) Huaynaputina ash permit accurate dating and time-scale verification. The fact that the Little Ice Age (about A.D. 1500 to 1900) stands out as a significant climatic event in the oxygen isotope and electrical conductivity records confirms the worldwide character of this event.

  11. Cold basal conditions during surges control flow of fringing Arctic ice caps in Greenland

    NASA Astrophysics Data System (ADS)

    Cook, Samuel; Christoffersen, Poul; Todd, Joe; Palmer, Steven

    2017-04-01

    Fringing ice caps separated from larger ice sheets are rarely studied, yet they are an important part of earth's cryosphere, which has become the largest source of global sea-level rise. Understanding marginal ice caps is crucial for being able to predict sea-level change as they are responsible for up to 20% of Greenland's mass loss for 2003-2008. Studies of fringing ice caps can furthermore provide useful insights into processes operating on glaciers that surge. Surging has been the focus of much recent glaciological work, especially with reference to thermal evolution of polythermal glaciers in High Mountain Asia and the High Arctic. This has shown that the classic divide between hydrologically-controlled surges ('hard-bed') in Alaska and thermally-regulated ('soft-bed') surges elsewhere is less stark than previously assumed. Studying marginal ice caps can therefore be valuable in several ways. The largest fringing ice cap in Greenland is Flade Isblink. Previous work has established that this ice cap is showing a range of dynamic behaviour, including subglacial lake drainage and varied patterns of mass-balance change. In particular, a substantial surge, assumed to be caused by a version of the thermally-regulated mechanism, occurred between 1996 and 2000, making the ice cap a useful case study for investigating this process. Here we investigate the surge on Flade Isblink using the open-source, Full-Stokes model Elmer/Ice to invert for basal conditions and englacial temperatures using the adjoint method. We specifically study steady-state conditions representative of the active surge phase in 2000, and the subsequent quiescent phase, using patterns of surface velocity observed in 2000, 2005, 2008 and 2015. Under constant geometry, temperature and geothermal heat, it is shown that surging increases basal freezing rates by over 60% across an area that is twice as large as the area over which the bed freezes in the quiescent phase. The process responsible for this

  12. Variability of Mars' North Polar Water Ice Cap: I. Analysis of Mariner 9 and Viking Orbiter Imaging Data

    USGS Publications Warehouse

    Bass, Deborah S.; Herkenhoff, Kenneth; Paige, David A.

    2000-01-01

    Previous studies interpreted differences in ice coverage between Mariner 9 and Viking Orbiter observations of Mars' north residual polar cap as evidence of interannual variability of ice deposition on the cap. However, these investigators did not consider the possibility that there could be significant changes in the ice coverage within the northern residual cap over the course of the summer season. Our more comprehensive analysis of Mariner 9 and Viking Orbiter imaging data shows that the appearance of the residual cap does not show large-scale variance on an interannual basis. Rather we find evidence that regions that were dark at the beginning of summer look bright by the end of summer and that this seasonal variation of the cap repeats from year to year. Our results suggest that this brightening was due to the deposition of newly formed water ice on the surface. We find that newly formed ice deposits in the summer season have the same red-to-violet band image ratios as permanently bright deposits within the residual cap. We believe the newly formed ice accumulates in a continuous layer. To constrain the minimum amount of deposited ice, we used observed albedo data in conjunction with calculations using Mie theory for single scattering and a delta-Eddington approximation of radiative transfer for multiple scattering. The brightening could have been produced by a minimum of (1) a ~35-μm-thick layer of 50-μm-sized ice particles with 10% dust or (2) a ~14-μm-thick layer of 10-μm-sized ice particles with 50% dust.

  13. Microbial diversity on Icelandic glaciers and ice caps.

    PubMed

    Lutz, Stefanie; Anesio, Alexandre M; Edwards, Arwyn; Benning, Liane G

    2015-01-01

    Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers.

  14. Microbial diversity on Icelandic glaciers and ice caps

    PubMed Central

    Lutz, Stefanie; Anesio, Alexandre M.; Edwards, Arwyn; Benning, Liane G.

    2015-01-01

    Algae are important primary colonizers of snow and glacial ice, but hitherto little is known about their ecology on Iceland's glaciers and ice caps. Due do the close proximity of active volcanoes delivering large amounts of ash and dust, they are special ecosystems. This study provides the first investigation of the presence and diversity of microbial communities on all major Icelandic glaciers and ice caps over a 3 year period. Using high-throughput sequencing of the small subunit ribosomal RNA genes (16S and 18S), we assessed the snow community structure and complemented these analyses with a comprehensive suite of physical-, geo-, and biochemical characterizations of the aqueous and solid components contained in snow and ice samples. Our data reveal that a limited number of snow algal taxa (Chloromonas polyptera, Raphidonema sempervirens and two uncultured Chlamydomonadaceae) support a rich community comprising of other micro-eukaryotes, bacteria and archaea. Proteobacteria and Bacteroidetes were the dominant bacterial phyla. Archaea were also detected in sites where snow algae dominated and they mainly belong to the Nitrososphaerales, which are known as important ammonia oxidizers. Multivariate analyses indicated no relationships between nutrient data and microbial community structure. However, the aqueous geochemical simulations suggest that the microbial communities were not nutrient limited because of the equilibrium of snow with the nutrient-rich and fast dissolving volcanic ash. Increasing algal secondary carotenoid contents in the last stages of the melt seasons have previously been associated with a decrease in surface albedo, which in turn could potentially have an impact on the melt rates of Icelandic glaciers. PMID:25941518

  15. Long-term evolution of a small ice cap in Greenland: a dynamic perspective from numerical flow modelling

    NASA Astrophysics Data System (ADS)

    Vieli, Andreas; Lane, Timothy; Adamson, Kathryn

    2017-04-01

    Small ice caps at the periphery of the Greenland ice sheet are often close to the limit of existence and are therefore expected to respond more sensitively to climate change than the land-margin of the neighboring ice sheet. However, their past evolution and dynamic behavior is poorly understood and their use as climate indicators therefore remains so far limited. We here aim to provide a long-term dynamic reconstruction of Lyngmarksbraeen, a small (32km2) ice cap on Disko Island in West Greenland, with a particular focus on the little ice age (LIA, since 1200AD). We use a 2-dim. time-dependent numerical flow model (SIA) and a PDD-mass balance model in combination with historical observations, geomorphological mapping and exposure dating to simulate its long-term evolution and dynamic behaviour. We specifically focus on retreat since the LIA, which is well constrained by geomorphological evidence and historical maps and length records of several small outlet glaciers and data from local and regional climate stations (Qeqertarssuaq and Ilulisat). We also explore aspects related to flow dynamics and find that the dynamic state of this ice cap is, at any time, far from being balanced and is highly sensitive to the surface elevation mass balance feedback and results in an asynchronous response of the different outlets and hysteresis-type behaviour. The modelling is able to reproduce the observed LIA-extent and the almost continuous retreat over the last hundred years well. It further indicates that the ice cap was already dynamically inert since the 1960s. Today, the ice cap has lost almost its entire accumulation area and even without any further warming in the future, the ice cap is expected to vanish within a couple of decades.

  16. The influence of topographic feedback on a coupled mass balance and ice-flow model for Vestfonna ice-cap, Svalbard

    NASA Astrophysics Data System (ADS)

    Schäfer, Martina; Möller, Marco; Zwinger, Thomas; Moore, John

    2016-04-01

    Using a coupled simulation set-up between a by statistical climate data forced and to ice-cap resolution downscaled mass balance model and an ice-dynamic model, we study coupling effects for the Vestfonna ice cap, Nordaustlandet, Svalbard, by analysing the impacts of different imposed coupling intervals on mass-balance and sea-level rise (SLR) projections. Based on a method to estimate errors introduced by different coupling schemes, we find that neglecting the topographic feedback in the coupling leads to underestimations of 10-20% in SLR projections on century time-scales in our model compared to full coupling (i.e., exchange of properties using smallest occurring time-step). Using the same method it also is shown that parametrising mass-balance adjustment for changes in topography using lapse rates is a - in computational terms - cost-effective reasonably accurate alternative applied to an ice-cap like Vestfonna. We test the forcing imposed by different emission pathways (RCP 2.4, 4.5, 6.0 and 8.5). For most of them, over the time-period explored (2000-2100), fast-flowing outlet glaciers decrease in impacting SLR due to their deceleration and reduced mass flux as they thin and retreat from the coast, hence detaching from the ocean and thereby losing their major mass drainage mechanism, i.e., calving.

  17. A Case for Microorganisms on Comets, Europa and the Polar Ice Caps of Mars

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Pikuta, Elena V.

    2003-01-01

    Microbial extremophiles live on Earth wherever there is liquid water and a source of energy. Observations by ground-based observatories, space missions, and satellites have provided strong evidence that water ice exists today on comets, Europa, Callisto, and Ganymede and in the snow, permafrost, glaciers and polar ice caps of Mars. Studies of the cryoconite pools and ice bubble systems of Antarctica suggest that solar heating of dark rocks entrained in ice can cause localized melting of ice providing ideal conditions for the growth of microbial communities with the creation of micro-environments where trapped metabolic gasses produce entrained isolated atmospheres as in the Antarctic ice-bubble systems. It is suggested that these considerations indicate that several groups of microorganisms should be capable of episodic growth within liquid water envelopes surrounding dark rocks in cometary ices and the permafrost and polar caps of Mars. We discuss some of the types of microorganisms we have encountered within the permafrost and snow of Siberia, the cryoconite pools of Alaska, and frozen deep within the Antarctic ice sheet above Lake Vostok.

  18. Destabilisation of an Arctic ice cap triggered by a hydro-thermodynamic feedback to summer-melt

    NASA Astrophysics Data System (ADS)

    Dunse, T.; Schellenberger, T.; Kääb, A.; Hagen, J. O.; Schuler, T. V.; Reijmer, C. H.

    2014-05-01

    Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the Polar Regions. Here we present continuous GPS measurements and satellite synthetic aperture radar based velocity maps from the Austfonna ice cap, Svalbard, that demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of the ice cap's largest drainage basin, Basin-3. The resulting iceberg discharge of 4.2 ± 1.6 Gt a-1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. After accounting for the terminus advance, the related sea-level rise contribution of 7.2 ± 2.6 Gt a-1 matches the recent annual ice-mass loss from the entire Svalbard archipelago. Our study highlights the importance of dynamic glacier wastage and illuminates mechanisms that may trigger a sustained increase in dynamic glacier wastage or the disintegration of ice-sheets in response to climate warming, which is acknowledged but not quantified in global projections of sea-level rise.

  19. Test results of Thermal Ice Cap prototype and final comments. Final report

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

    Burley, W.

    1982-01-01

    The design and testing of an insulating cover, Ice Cap, for an ice rink are described. The radio-controlled reel system which houses, deploys, and harvests the 17,000 square feet of insulating material is essential to the success of the cover. Photographs showing the use of the system are included. (MHR)

  20. Science goals for a Mars Polar Cap subsurface mission : optical approaches for investiagations of inclusions in ice

    NASA Technical Reports Server (NTRS)

    Mogensen, Claus T.; Carsey, Frank D.; Behar, Alberto; Engelhardt, Hermann; Lane, Arthur L.

    2002-01-01

    The Mars Polar Caps are highly interesting features of Mars and have received much recent attention with new and exciting data on morphology, basal units, and layered outcroppings. We have examined the climatological, glaciological, and geological issues associated with a subsurface exploration of the Mars North Polar Cap and have determined that a finescale optical examination of ice in a borehole, to examine the stratigraphy, geochemistry and geochronology of the ice, is feasible. This information will enable reconstruction of the development of the cap as well as predication of the properties of its ice. We present visible imagery taken of dust inclusions in archived Greenland ice cores as well as in-situ images of accreted lithologic inclusions in West Antarctica, and we argue for use of this kind of data in Mars climate reconstruction as has been successful with Greenland and Antarctic ice core anlaysis.

  1. Science goals for a Mars Polar Cap subsurface mission : optical approaches for investigations of inclusions in ice

    NASA Technical Reports Server (NTRS)

    Carsey, Frank; Mogensen, Claus T.; Behar, Alberto; Engelhardt, Hermann; Lane, Arthur L.

    2002-01-01

    The Mars Polar Caps are highly interesting features of Mars and have received much recent attention with new and exciting data on morphology, basal units, and layered outcroppings. We have examined the climatological, glaciological, and geological issues associated with a subsurface exploration of the Mars North Polar Cap and have determined that a finescale optical examination of ice in a borehole, to examine the stratigraphy, geochemistry and geochronology of the ice, is feasible. This information will enable reconstruction of the development of the cap as well as prediction of the properties of its ice. We present visible imagery taken of dust inclusions in archived Greenland ice cores as well as in-situ images of accreted lithologic inclusions in West Antarctica, and we argue for use of this kind of data in Mars climate reconstruction as has been successful with Greenland and Antarctic ice core analysis. .

  2. Geochronology and paleoclimatic implications of the last deglaciation of the Mauna Kea Ice Cap, Hawaii

    USGS Publications Warehouse

    Anslow, Faron S.; Clark, P.U.; Kurz, M.D.; Hostetler, S.W.

    2010-01-01

    We present new 3He surface exposure ages on moraines and bedrock near the summit of Mauna Kea, Hawaii, which refine the age of the Mauna Kea Ice Cap during the Local Last Glacial Maximum (LLGM) and identify a subsequent fluctuation of the ice margin. The 3He ages, when combined with those reported previously, indicate that the local ice-cap margin began to retreat from its LLGM extent at 20.5??2.5ka, in agreement with the age of deglaciation determined from LLGM moraines elsewhere in the tropics. The ice-cap margin receded to a position at least 3km upslope for ~4.5-5.0kyr before readvancing nearly to its LLGM extent. The timing of this readvance at ~15.4ka corresponds to a large reduction of the Atlantic meridional overturning circulation (AMOC) following Heinrich Event 1. Subsequent ice-margin retreat began at 14.6??1.9ka, corresponding to a rapid resumption of the AMOC and onset of the B??lling warm interval, with the ice cap melting rapidly to complete deglaciation. Additional 3He ages obtained from a flood deposit date the catastrophic outburst of a moraine-dammed lake roughly coeval with the Younger Dryas cold interval, suggesting a more active hydrological cycle on Mauna Kea at this time. A coupled mass balance and ice dynamics model is used to constrain the climate required to generate ice caps of LLGM and readvance sizes. The depression of the LLGM equilibrium line altitude requires atmospheric cooling of 4.5??1??C, whereas the mass balance modeling indicates an accompanying increase in precipitation of as much as three times that of present. We hypothesize (1) that the LLGM temperature depression was associated with global cooling, (2) that the temperature depression that contributed to the readvance occurred in response to an atmospheric teleconnection to the North Atlantic, and (3) that the precipitation enhancement associated with both events occurred in response to a southward shift in the position of the inter-tropical convergence zone (ITCZ). Such a

  3. Crustal movements due to Iceland's shrinking ice caps mimic magma inflow signal at Katla volcano.

    PubMed

    Spaans, Karsten; Hreinsdóttir, Sigrún; Hooper, Andrew; Ófeigsson, Benedikt Gunnar

    2015-05-20

    Many volcanic systems around the world are located beneath, or in close proximity to, ice caps. Mass change of these ice caps causes surface movements, which are typically neglected when interpreting surface deformation measurements around these volcanoes. These movements can however be significant, and may closely resemble movements due to magma accumulation. Here we show such an example, from Katla volcano, Iceland. Horizontal movements observed by GPS on the flank of Katla have led to the inference of significant inflow of magma into a chamber beneath the caldera, starting in 2000, and continuing over several years. We use satellite radar interferometry and GPS data to show that between 2001 and 2010, the horizontal movements seen on the flank can be explained by the response to the long term shrinking of ice caps, and that erratic movements seen at stations within the caldera are also not likely to signify magma inflow. It is important that interpretations of geodetic measurements at volcanoes in glaciated areas consider the effect of ice mass change, and previous studies should be carefully reevaluated.

  4. Diatoms as Proxies for a Fluctuating Ice Cap Margin, Hvitarvatn, Iceland

    NASA Astrophysics Data System (ADS)

    Black, J. L.; Miller, G. H.; Geirsdottir, A.

    2005-12-01

    There are no complete records of terrestrial environmental change for the Holocene (11,000yrs) in Iceland and the status of Icelandic glaciers in the early Holocene remains unclear. It is not even known whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew. Icelandic lakes are particularly well suited to address these uncertainties as: 1) Glacial erosion and soft bedrock result in high lacustrine sedimentation rates, 2) Diagnostic tephras aid the geochronology, 3) Iceland's sensitivity to changes in North Atlantic circulation should produce clear signals in key environmental proxies (diatoms) preserved in lacustrine sequences, and 4) Ice-cap profiles are relatively flat so small changes in the equilibrium line altitude result in large changes in accumulation area. Hence, large changes in ice-sheet margins during the Holocene will impact sedimentation in glacier-dominated lakes and the diatom assemblages at those times. Hvitarvatn is a glacier dominated lake located on the eastern margin of Langjokull Ice Cap in central-western Iceland. The uppermost Hvitarvatn sediments reflect a glacially dominated system with planktonic, silica-demanding diatom taxa that suggest a high dissolved silica and turbid water environment consistent with high fluxes of glacial flour. Below this are Neoglacial sediments deposited when Langjokull was active, but outlet glaciers were not in contact with Hvitarvatn. The diatom assemblage here shows a small increase in abundance, but is still dominated by planktic, silica-demanding taxa. A distinct shift in lake conditions is reflected in the lowermost sediments, composed of predominantly benthic diatoms and deposited in clear water conditions with long growing seasons likely found in an environment with warmer summers than present and with no glacial erosion. Langjokull must have disappeared in the early Holocene for such a diverse, benthic dominated diatom assemblage to flourish.

  5. Modelled non-linear response to climate of Hardangerjøkulen ice cap, southern Norway, since the mid-Holocene

    NASA Astrophysics Data System (ADS)

    Åkesson, Henning; Nisancioglu, Kerim H.; Giesen, Rianne H.; Morlighem, Mathieu

    2016-04-01

    Glacier and ice cap volume changes currently amount to half of the total cryospheric contribution to sea-level rise and are projected to remain substantial throughout the 21st century. To simulate glacier behavior on centennial and longer time scales, models rely on simplified dynamics and tunable parameters for processes not well understood. Model calibration is often done using present-day observations, even though the relationship between parameters and parametrized processes may be altered for significantly different glacier states. In this study, we simulate the Hardangerjøkulen ice cap in southern Norway since the mid-Holocene, through the Little Ice Age (LIA) and into the future. We run an ensemble for both calibration and transient experiments, using a two-dimensional ice flow model with mesh refinement. For the Holocene, we apply a simple mass balance forcing based on climate reconstructions. For the LIA until 1962, we use geomorphological evidence and measured outlet glacier positions to find a mass balance history, while we use direct mass balance measurements from 1963 until today. Given a linear climate forcing, we show that Hardangerøkulen grew from ice-free conditions in the mid-Holocene, to its maximum LIA extent in a highly non-linear fashion. We relate this to local bed topography and demonstrate that volume and area of some but not all outlet glaciers, as well as the entire ice cap, become decoupled for several centuries during our simulation of the late Holocene, before co-varying approaching the LIA. Our model is able to simulate most recorded ice cap and outlet glacier changes from the LIA until today. We show that present-day Hardangerøkulen is highly sensitive to mass balance changes, and estimate that the ice cap will melt completely by the year 2100.

  6. Effects of deliquescent salts in soils of polar Mars on the flow of the Northern Ice Cap

    NASA Astrophysics Data System (ADS)

    Fisher, D. A.; Hecht, M. H.; Kounaves, S.; Catling, D.

    2008-12-01

    The discovery of substantial amounts of magnesium and perchlorate by Phoenix' "Wet Chemistry Lab" (WCL) in the soil of Polar Mars suggests that magnesium perchlorate could be the dominant salt in the polar region's soils. This prospect opens some unexpected doors for moving liquid water around at temperatures as low as -68C. In its fully hydrated form ,this salt water mixture has a high density (~ 1700 kgm /cubic meter) (Besley and Bottomley,1969) and a freezing point of -68C (Pestova et al., 2005).This perchlorate is very deliquescent and gives off heat as it melts ice. About 1.8 gram of ice can be 'melted' by 1 gm of pure magnesium perchlorate . If the reported 1 percent perchlorate is typical of polar soils and if 5 percent of the Northern Permanent Ice Cap is soil then the perchorate , makes up about 0.0005 the of the ice cap. Given the average thickness of the ice cap is about 2000 meters,this suggests there enough perchorate in the ice cap to generate about 2m of salty water at the bed. Because of its density the perclorate salty water would pool over impervious layers and make the bed into a perchorate sludge that could be mobilized and deformed by the overburden of ice. The deformation of mobile beds is a well known phenomenon on some terrestrial glaciers presently and was thought to have played a major role during the Wisconsinan ice age (Fisher et al., 1985) . The perchorate sludge would be deformed and moved outwards possibly resulting its re-introduction to the polar environment. Having a deliquescent salt sludge at the bed whose melting point is -68C would mean that the ice cap could slide on its deformable bed while the ice itself was still very cold and stiff . This possibility has been modeled with a 2D time varying model . Adding the deformable bed material allows ice cap motion even at ice temperatures cold enough to generate and preserve the scarp/trough features. When the perchlorate formation mechanisms and rates are known the ultimate

  7. Extending permanent volcano monitoring networks into Iceland's ice caps

    NASA Astrophysics Data System (ADS)

    Vogfjörd, Kristín S.; Bergsson, Bergur H.; Kjartansson, Vilhjálmur; Jónsson, Thorsteinn; Ófeigsson, Benedikt G.; Roberts, Matthew J.; Jóhannesson, Tómas; Pálsson, Finnur; Magnússon, Eyjólfur; Erlendsson, Pálmi; Ingvarsson, Thorgils; Pálssson, Sighvatur K.

    2015-04-01

    The goals of the FUTUREVOLC project are the establishment of a volcano Supersite in Iceland to enable access to volcanological data from the country's many volcanoes and the development of a multiparametric volcano monitoring and early warning system. However, the location of some of Iceland's most active volcanoes inside the country's largest ice cap, Vatnajökull, makes these goals difficult to achieve as it hinders access and proper monitoring of seismic and deformation signals from the volcanoes. To overcome these obstacles, one of the developments in the project involves experimenting with extending the permanent real-time networks into the ice cap, including installation of stations in the glacier ice. At the onset of the project, only one permanent seismic and GPS site existed within Vatnajökull, on the caldera rim of the Grímsvötn volcano. Two years into the project both seismic and GPS stations have been successfully installed and operated inside the glacier; on rock outcrops as well as on the glacier surface. The specific problems to overcome are (i) harsh weather conditions requiring sturdy and resilient equipment and site installations, (ii) darkness during winter months shutting down power generation for several weeks, (iii) high snow accumulation burying the instruments, solar panels and communication and GPS antennae, and in some locations (iv) extreme icing conditions blocking transmission signals and connection to GPS satellites, as well as excluding the possibility of power generation by wind generators. In 2013, two permanent seismic stations and one GPS station were installed on rock outcrops within the ice cap in locations with 3G connections and powered by solar panels and enough battery storage to sustain operation during the darkest winter months. These sites have successfully operated for over a year with mostly regular maintenance requirements, transmitting data in real-time to IMO for analysis. Preparations for two permanent seismic

  8. Holocene glacier and climate variations in Vestfirðir, Iceland, from the modeling of Drangajökull ice cap

    NASA Astrophysics Data System (ADS)

    Anderson, Leif S.; Flowers, Gwenn E.; Jarosch, Alexander H.; Aðalgeirsdóttir, Guðfinna Th; Geirsdóttir, Áslaug; Miller, Gifford H.; Harning, David J.; Thorsteinsson, Thorsteinn; Magnússon, Eyjólfur; Pálsson, Finnur

    2018-06-01

    Drangajökull is a maritime ice cap located in northwest (Vestfirðir) Iceland. Drangajökull's evolution is therefore closely linked to atmospheric and ocean variability. In order to better constrain the Holocene climate and glacier history of Vestfirðir we model the past evolution of Drangajökull ice cap. Simulations from 10 ka to present are forced by general circulation model output, ice-core-based temperature reconstructions, and sea-surface temperature reconstructions. Based on these 10-thousand year simulations, Drangajökull did not persist through the Holocene. We estimate that air temperatures were 2.5-3.0 °C higher during the Holocene Thermal Maximum than the local 1960-1990 average. Simulations support Drangajökull's late Holocene inception between 2 and 1 ka, though intermittent ice likely occupied cirques as early as 2.6 ka. Drangajökull is primarily a Little Ice Age ice cap: it expanded between 1300 and 1750 CE, with the most rapid growth occurring between 1600 and 1750 CE. The maximum Holocene extent of Drangajökull occurred between 1700 and 1925 CE, despite the lowest late Holocene temperatures, occurring between 1650 and 1720 CE. Between 1700 and 1925 CE temperatures were likely 0.6-0.8 °C lower than the 1950-2015 reference temperature. The modern equilibrium line altitude (ELA) is bracketed by topographic thresholds: a 1 °C temperature increase from the modern ELA would eliminate the ice cap's accumulation area, while a reduction of 0.5 °C would lead to the rapid expansion of the ice cap across Vestfirðir. The proximity of Drangajökull to topographic thresholds may explain its late inception and rapid expansion during the Little Ice Age.

  9. Evaluation of remote-sensing techniques to measure decadal-scale changes of Hofsjokull ice cap, Iceland

    USGS Publications Warehouse

    Hall, D.K.; Williams, R.S.; Barton, J.S.; Sigurdsson, O.; Smith, L.C.; Garvin, J.B.

    2000-01-01

    Dynamic surficial changes and changes in the position of the firn line and the areal extent of Hofsjökull ice cap, Iceland, were studied through analysis of a time series (1973–98) of synthetic-aperture radar (SAR) and Landsat data. A digital elevation model of Hofsjökull, which was constructed using SAR interferometry, was used to plot the SAR backscatter coefficient (σ°) vs elevation and air temperature along transects across the ice cap. Seasonal and daily σ° patterns are caused by freezing or thawing of the ice-cap surface, and abrupt changes in σ° are noted when the air temperature ranges from ∼−5° to 0°C. Late-summer 1997 σ° (SAR) and reflectance (Landsat) boundaries agree and appear to be coincident with the firn line and a SAR σ° boundary that can be seen in the January 1998 SAR image. In January 1994 through 1998, the elevation of this σ° boundary on the ice capwas quite stable, ranging from 1000 to 1300 m, while the equilibrium-line altitude, as measured on the ground, varied considerably. Thus the equilibrium line may be obscured by firn from previous years. Techniques are established to measure long-term changes in the elevation of the firn line and changes in the position of the ice margin.

  10. Glaciers and ice caps outside Greenland

    USGS Publications Warehouse

    Sharp, Marin; Wolken, G.; Burgess, D.; Cogley, J.G.; Copland, L.; Thomson, L.; Arendt, A.; Wouters, B.; Kohler, J.; Andreassen, L.M.; O'Neel, Shad; Pelto, M.

    2015-01-01

    Mountain glaciers and ice caps cover an area of over 400 000 km2 in the Arctic, and are a major influence on global sea level (Gardner et al. 2011, 2013; Jacob et al. 2012). They gain mass by snow accumulation and lose mass by meltwater runoff. Where they terminate in water (ocean or lake), they also lose mass by iceberg calving. The climatic mass balance (Bclim, the difference between annual snow accumulation and annual meltwater runoff) is a widely used index of how glaciers respond to climate variability and change. The total mass balance (ΔM) is defined as the difference between annual snow accumulation and annual mass losses (by iceberg calving plus runoff).

  11. IR spectral properties of dust and ice at the Mars south polar cap

    NASA Astrophysics Data System (ADS)

    Titus, T. N.; Kieffer, H. H.

    2001-11-01

    Removal of atmospheric dust effects is required to derive surface IR spectral emissivity. Commonly, the atmospheric-surface separation is based on radiative transfer (RT) spectral inversion methods using nadir-pointing observations. This methodology depends on a priori knowledge of the spectral shape of each atmospheric aerosol (e.g. dust or water ice) and a large thermal contrast between the surface and atmosphere. RT methods fail over the polar caps due to low thermal contrast between the atmosphere and the surface. We have used multi-angle Emission Phase Function (EPF) observations to estimate the opacity spectrum of dust over the springtime south polar cap and the underlying surface radiance, and thus, the surface emissivity. We include a few EPFs from Hellas Basin as a basis for comparisons between the spectral shape of polar and non-polar dust. Surface spectral emissivities over the seasonal cap are compared to CO2 models. Our results show that the spectral shape of the polar dust opacity is not constant, but is a two-parameter family that can be characterized by the 9 um and 20 um opacities. The 9 um opacity varies from 0.15 to 0.45 and characterizes the overall atmospheric conditions. The 9 um to 20 um opacity ratio varies from 2.0 to 5.1, suggesting changes in dust size distribution over the polar caps. Derived surface temperatures from the EPFs confirm that the slightly elevated temperatures (relative to CO2 frost temperature) observed in ``cryptic'' regions are a surface effect, not atmospheric. Comparison of broad-band reflectivity and surface emissivities to model spectra suggest the bright regions (e.g. perennial cap, Mountains of Mitchell) have higher albedos due to a thin surface layer of fine-grain CO2 (perhaps either frost or fractured ice) with an underlying layer of either coarse grain or slab CO2 ice.

  12. A Chronology of Late-Glacial and Holocene Advances of Quelccaya Ice Cap, Peru, Based on 10Be and Radiocarbon Dating

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Lowell, T. V.; Schaefer, J. M.

    2007-12-01

    The Quelccaya Ice Cap region in the southeastern Peruvian Andes (~13-14°S latitude) is a key location for the development of late-glacial and Holocene terrestrial paleoclimate records in the tropics. We present a chronology of past extents of Quelccaya Ice Cap based on ~thirty internally consistent 10Be dates of boulders on moraines and bedrock as well as twenty radiocarbon dates of organic material associated with moraines. Based on results from both dating methods, we suggest that significant advances of Quelccaya Ice Cap occurred during late-glacial time, at ~12,700-11,400 yr BP, and during Late Holocene time ~400-300 yr BP. Radiocarbon dating of organic material associated with moraines provides maximum and minimum ages for ice advances and recessions, respectively, thus providing an independent check on 10Be dates of boulders on moraines. The opportunity to use both 10Be and radiocarbon dating makes the Quelccaya Ice Cap region a potentially important low-latitude calibration site for production rates of cosmogenic nuclides. Our radiocarbon chronology provides a tighter constraint on maximum ages of late-glacial and Late Holocene ice advances. Upcoming field research will obtain organic material for radiocarbon dating to improve minimum age constrains for late-glacial and Late Holocene ice recessions.

  13. The Effect of CO2 Ice Cap Sublimation on Mars Atmosphere

    NASA Technical Reports Server (NTRS)

    Batterson, Courtney

    2016-01-01

    Sublimation of the polar CO2 ice caps on Mars is an ongoing phenomenon that may be contributing to secular climate change on Mars. The transfer of CO2 between the surface and atmosphere via sublimation and deposition may alter atmospheric mass such that net atmospheric mass is increasing despite seasonal variations in CO2 transfer. My study builds on previous studies by Kahre and Haberle that analyze and compare data from the Phoenix and Viking Landers 1 and 2 to determine whether secular climate change is happening on Mars. In this project, I use two years worth of temperature, pressure, and elevation data from the MSL Curiosity rover to create a program that allows for successful comparison of Curiosity pressure data to Viking Lander pressure data so a conclusion can be drawn regarding whether CO2 ice cap sublimation is causing a net increase in atmospheric mass and is thus contributing to secular climate change on Mars.

  14. Tracking Retreat of the North Seasonal Ice Cap on Mars: Results from the THEMIS Investigation

    NASA Technical Reports Server (NTRS)

    Ivanov, A. B.; Wagstaff, K. L.; Ttus, T. N.

    2005-01-01

    The CO2 ice caps on Mars advance and retreat with the seasons. This phenomenon was first observed by Cassini and then confirmed by numerous ground based observations in 19th and 20th centuries. With the advent of the space age observations of the seasonal ice cap were done by all orbiting spacecraft starting with Mariner 7. Viking Orbiters and more recently the Mars Global Surveyor (particularly Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES) instruments) have accumulated significant data on the retreat of the CO2 seasonal cap. During Mars year 2 of THEMIS operations at Mars, we planned an observational campaign in which the THEMIS instrument (onboard the Mars Odyssey spacecraft) repeatedly observed the north seasonal polar cap from midwinter to late spring. THEMIS allows simultaneous observations in both Thermal IR (12.57 m) and Visible wavelengths (0.65 m). One of the goals for this work is to initiate an interannual program for observations of the seasonal ice caps using the THEMIS instrument. The most efficient way to detect the edge between frost and bare ground is directly onboard of the spacecraft. Prior to onboard software design effort, we have developed two groundbased algorithms for automatically finding the edge of the seasonal polar cap in THEMIS IR data. The first algorithm relies on fully calibrated data and can be used for highly reliable groundbased analyses. The second method was specifically developed for processing raw, uncalibrated data in a highly efficient way. It has the potential to enable automatic, onboard detections of the seasonal cap retreat. We have experimentally confirmed that both methods produce similar results, and we have validated both methods against a model constructed from the MGS TES data from the same season.

  15. Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

    NASA Astrophysics Data System (ADS)

    Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún; van Dam, Tonie; Bordoni, Andrea; Barletta, Valentina; Spada, Giorgio

    2017-06-01

    As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1σ confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements.

  16. Experimental investigation of insolation-driven dust ejection from Mars' CO2 ice caps

    NASA Astrophysics Data System (ADS)

    Kaufmann, E.; Hagermann, A.

    2017-01-01

    Mars' polar caps are - depending on hemisphere and season - partially or totally covered with CO2 ice. Icy surfaces such as the polar caps of Mars behave differently from surfaces covered with rock and soil when they are irradiated by solar light. The latter absorb and reflect incoming solar radiation within a thin layer beneath the surface. In contrast, ices are partially transparent in the visible spectral range and opaque in the infrared. Due to this fact, the solar radiation can penetrate to a certain depth and raise the temperature of the ice or dust below the surface. This may play an important role in the energy balance of icy surfaces in the solar system, as already noted in previous investigations. We investigated the temperature profiles inside CO2 ice samples including a dust layer under Martian conditions. We have been able to trigger dust eruptions, but also demonstrated that these require a very narrow range of temperature and ambient pressure. We discuss possible implications for the understanding of phenomena such as arachneiform patterns or fan shaped deposits as observed in Mars' southern polar region.

  17. High Arctic Holocene temperature record from the Agassiz ice cap and Greenland ice sheet evolution

    PubMed Central

    Lecavalier, Benoit S.; Fisher, David A.; Milne, Glenn A.; Vinther, Bo M.; Tarasov, Lev; Lacelle, Denis; Main, Brittany; Zheng, James; Bourgeois, Jocelyne; Dyke, Arthur S.

    2017-01-01

    We present a revised and extended high Arctic air temperature reconstruction from a single proxy that spans the past ∼12,000 y (up to 2009 CE). Our reconstruction from the Agassiz ice cap (Ellesmere Island, Canada) indicates an earlier and warmer Holocene thermal maximum with early Holocene temperatures that are 4–5 °C warmer compared with a previous reconstruction, and regularly exceed contemporary values for a period of ∼3,000 y. Our results show that air temperatures in this region are now at their warmest in the past 6,800–7,800 y, and that the recent rate of temperature change is unprecedented over the entire Holocene. The warmer early Holocene inferred from the Agassiz ice core leads to an estimated ∼1 km of ice thinning in northwest Greenland during the early Holocene using the Camp Century ice core. Ice modeling results show that this large thinning is consistent with our air temperature reconstruction. The modeling results also demonstrate the broader significance of the enhanced warming, with a retreat of the northern ice margin behind its present position in the mid Holocene and a ∼25% increase in total Greenland ice sheet mass loss (∼1.4 m sea-level equivalent) during the last deglaciation, both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern Greenland. PMID:28512225

  18. Tracking the Martian CO2 Polar Ice Caps in Infrared Images

    NASA Technical Reports Server (NTRS)

    Wagstaff, Kiri L.; Castano, Rebecca; Chien, Steve

    2006-01-01

    Researchers at NASA s Jet Propulsion Laboratory have developed a method for automatically tracking the polar caps on Mars as they advance and recede each year (see figure). The seasonal Mars polar caps are composed mainly of CO2 ice and are therefore cold enough to stand out clearly in infrared data collected by the Thermal Emission Imaging System (THEMIS) onboard the Mars Odyssey spacecraft. The Bimodal Image Temperature (BIT) histogram analysis algorithm analyzes raw, uncalibrated data to identify images that contain both "cold" ("polar cap") and "warm" ("not polar cap") pixels. The algorithm dynamically identifies the temperature that separates these two regions. This flexibility is critical, because in the absence of any calibration, the threshold temperature can vary significantly from image to image. Using the identified threshold, the algorithm classifies each pixel in the image as "polar cap" or "not polar cap," then identifies the image row that contains the spatial transition from "polar cap" to "not polar cap." While this method is useful for analyzing data that has already been returned by THEMIS, it has even more significance with respect to data that has not yet been collected. Instead of seeking the polar cap only in specific, targeted images, the simplicity and efficiency of this method makes it feasible for direct, onboard use. That is, THEMIS could continuously monitor its observations for any detections of the polar-cap edge, producing detections over a wide range of spatial and temporal conditions. This effort can greatly contribute to our understanding of long-term climatic change on Mars.

  19. Mars residual north polar cap - Earth-based spectroscopic confirmation of water ice as a major constituent and evidence for hydrated minerals

    NASA Technical Reports Server (NTRS)

    Clark, R. N.; Mccord, T. B.

    1982-01-01

    A description is presented of new earth-based reflectance spectra of the Martian north residual polar cap. The spectra indicate that the composition is at least mostly water ice plus another component with a 'gray' reflectance. The other minerals in the ice cap appear to be hydrated. The data were obtained with a cooled circular variable filter spectrometer on February 20, 1978, using the 2.2-m telescope on Mauna Kea, Hawaii. It is pointed out that the identification of water ice in the north polar cap alone does not indicate that water makes up all or even most of the bulk of the cap. Kieffer (1970) has shown that a small amount of water will mask the spectral features of CO2.

  20. Calibrating a surface mass-balance model for Austfonna ice cap, Svalbard

    NASA Astrophysics Data System (ADS)

    Schuler, Thomas Vikhamar; Loe, Even; Taurisano, Andrea; Eiken, Trond; Hagen, Jon Ove; Kohler, Jack

    2007-10-01

    Austfonna (8120 km2) is by far the largest ice mass in the Svalbard archipelago. There is considerable uncertainty about its current state of balance and its possible response to climate change. Over the 2004/05 period, we collected continuous meteorological data series from the ice cap, performed mass-balance measurements using a network of stakes distributed across the ice cap and mapped the distribution of snow accumulation using ground-penetrating radar along several profile lines. These data are used to drive and test a model of the surface mass balance. The spatial accumulation pattern was derived from the snow depth profiles using regression techniques, and ablation was calculated using a temperature-index approach. Model parameters were calibrated using the available field data. Parameter calibration was complicated by the fact that different parameter combinations yield equally acceptable matches to the stake data while the resulting calculated net mass balance differs considerably. Testing model results against multiple criteria is an efficient method to cope with non-uniqueness. In doing so, a range of different data and observations was compared to several different aspects of the model results. We find a systematic underestimation of net balance for parameter combinations that predict observed ice ablation, which suggests that refreezing processes play an important role. To represent these effects in the model, a simple PMAX approach was included in its formulation. Used as a diagnostic tool, the model suggests that the surface mass balance for the period 29 April 2004 to 23 April 2005 was negative (-318 mm w.e.).

  1. Mars Secular Obliquity Change Due to Water Ice Caps

    NASA Technical Reports Server (NTRS)

    Rubincam, David P.

    1998-01-01

    Mars may have substantially changed its average axial tilt over geologic time due to the waxing and waning of water ice caps. Depending upon Mars' climate and internal structure, the average obliquity could have increased or decreased through climate friction by tens of degrees. A decrease could account for the apparent youthfulness of the polar layered terrain. Alternatively, Mars' average obliquity may have changed until it became "stuck" at its present value of 24.4 deg.

  2. Holocene fluctuations of Quelccaya Ice Cap, Peru based on lacustrine and surficial geologic archives

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.

    2013-12-01

    Peru's Quelccaya Ice Cap (QIC; 13.9°S, 70.8°W, ~5200-5670 m asl) is an important site for understanding tropical paleoclimate, mainly because of annually layered ice cores that provide an ~1800 year long record of tropical paleoclimatic conditions (e.g., Thompson et al., 2013). Here, we present a detailed record of QIC fluctuations using surficial deposits and lake sediments that extend back to late glacial time. We compare the late Holocene records of QIC 10Be-dated moraines and ice core data with lake sediments from a nearby glacially fed lake to establish the framework we use to interpret a Holocene long sediment record from a glacially fed lake. We also examine sediments from a nearby non-glacial lake to constrain non-glacial clastic input. We collected two ~5 m-long sediment cores, one from Laguna Challpacocha, which is currently fed by QIC meltwater, and one from the Laguna Yanacocha, which has not received QIC meltwater since ~12.3 ka. Changes in magnetic susceptibility, loss on ignition, bulk density and X-ray fluorescence chemistry combined with 14C and 210Pb chronologies provide information about sediment transported to the lakes. Retreat from the late Holocene extent defined by the 10Be-dated moraine record (~0.52 ka) is contemporaneous with a sharp transition from organic to clastic sedimentation in the Challpacocha core at ~ 0.52 ka. This implies that glacially-sourced clastic sedimentation, as tracked by loss on ignition, Ti counts and bulk density, increased during ice cap recession. Based on these same proxy data, we suggest the following Holocene history of QIC: QIC receded from the Challpacocha basin by ~10.6 ka. Increased clastic sedimentation at 8.2 - 4.1, 3.6 - 2.7 ka and from 0.55 ka - present are interpreted as times of ice cap recession. The increased clastic sedimentation at ~8.2 - 4.1 ka is consistent with surficial deposits near the present-day ice margin that indicate that at ~7.0 - 4.6 ka QIC was smaller than at present (Buffen et al

  3. Reconciling different observations of the CO2 ice mass loading of the Martian north polar cap

    USGS Publications Warehouse

    Haberle, R.M.; Mattingly, B.; Titus, T.N.

    2004-01-01

    The GRS measurements of the peak mass loading of the north polar CO2 ice cap on Mars are about 60% lower than those calculated from MGS TES radiation data and those inferred from the MOLA cap thicknesses. However, the GRS data provide the most accurate measurement of the mass loading. We show that the TES and MOLA data can be reconciled with the GRS data if (1) subsurface heat conduction and atmospheric heat transport are included in the TES mass budget calculations, and (2) the density of the polar deposits is ???600 kg m-3. The latter is much less than that expected for slab ice (???1600 kg m-3) and suggests that processes unique to the north polar region are responsible for the low cap density. Copyright 2004 by the American Geophysical Union.

  4. Recent Changes in High-Latitude Glaciers, Ice Caps, and Ice Sheets

    NASA Technical Reports Server (NTRS)

    Abdalati, Waleed

    2006-01-01

    ). While the expansion of the warming oceans is estimated to be about a third of recent sea level rise, (Miller and Douglas 2004) the greatest potential for significantly increasing sea level lies in the Greenland and Antarctic ice sheets. For different reasons, each exhibits characteristics that suggest they are potentially unstable. In Antarctica, large portions of the ice cover rest on a soft bed that lies below sea level, making it vulnerable to runaway retreat. The Greenland ice sheet experiences considerable melt, which has the potential to rapidly accelerate the flow of ice toward the sea. While smaller ice masses, such as the Alaskan Glaciers and the Canadian ice caps, do not have anywhere near the same potential to impact sea level as the vast ice sheets do, many are melting rapidly, posing a significant near-term threat.

  5. Tropical Glaciers in the Common Era: Papua, Indonesia, Quelccaya Ice Cap, Peru and Kilimanjaro, Tanzania

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.

    2011-12-01

    High-resolution ice core stratigraphic records of δ18O (temperature proxy) demonstrate that the current warming at high elevations in mid- to lower latitudes is unprecedented for at least the last two millennia, although at many sites the Early Holocene was much warmer than at present. Here we discuss the interaction of El Niño-Southern Oscillation (ENSO) variability and warming trends as recorded in ice core records from high-altitude tropical glaciers and the implications of the warming trends for the future of these glaciers. ENSO has strong impacts on meteorological phenomena that either directly or indirectly affect most regions on the planet and their populations, particularly throughout the Tropics. Here we examine similarities and differences among ice core records from Papua (Indonesia), Quelccaya Ice Cap (Peru) and Kilimanjaro (Tanzania). Quelccaya, Earth's largest tropical ice cap, has provided continuous, annually-resolved proxy records of climatic and environmental variability preserved in many measurable parameters, especially oxygen and hydrogen isotopic ratios (δ18O, δD) and the net mass balance (accumulation) spanning the last 1800 years. The remarkable similarity between changes in the highland and coastal cultures of Peru and climate variability in the Andes, especially with regard to precipitation, implies a strong connection between prehistoric human activities and climate in this region. The well-documented ice loss on Quelccaya, Kilimanjaro in eastern Africa and the ice fields near Puncak Jaya in Papua, Indonesia presents a possible analog for glacier response in the tropics during the Holocene. The ongoing melting of these ice fields is consistent with model predictions of a vertical amplification of temperature in the Tropics. A sequence of over 50 recently exposed, rooted, soft-bodied plant deposits collected between 2002 and 2011 from the retreating margins of the Quelccaya ice cap provide a longer term perspective for the recent

  6. Rates of Deglaciation during the Last Glaciation and Holocene in the Cordillera Vilcanota-Quelccaya Ice Cap Region, Southeastern Perú

    NASA Astrophysics Data System (ADS)

    Mark, Bryan G.; Seltzer, Geoffrey O.; Rodbell, Donald T.; Goodman, Adam Y.

    2002-05-01

    Moraine chronology is combined with digital topography to model deglacial rates of paleoglacier volumes in both the Huancané Valley on the west side of the Quelccaya Ice Cap and the Upismayo Valley on the northwest side of the Cordillera Vilcanota. The fastest rates of deglaciation (39×10 -5 to 114×10 -5 km 3 yr -1 and 112×10 -5 to 247×10 -5 km 3 yr -1 for each valley, respectively) were calculated for the most recent paleoglaciers, corresponding to the last few centuries. These results are consistent with observations in the Venezuelan Andes showing high rates of deglaciation since the Little Ice Age. These rates also fall within the range of 20th century rates of deglaciation measured on the Quelccaya Ice Cap (29×10 -5 to 220×10 -5 km 3 yr -1, Brecher and Thompson, 1993; Thompson, 2000). These results imply that rates of deglaciation may fluctuate significantly over time and that high rates of deglaciation may not be exclusive to the late 20th century. Equilibrium line altitude (ELA) depressions for the ice volumes of the last glaciation modeled here were computed as 230 m for the Quelccaya Ice Cap and 170 m for the Cordillera Vilcanota. Maximum ELA depressions are lower than previously published: <500 m for the Cordillera Vilcanota and <400 m for the Quelccaya Ice Cap. These lower values could imply a topographic control over paleoglacier extent.

  7. Early 21st-Century Mass loss of the North-Atlantic Glaciers and Ice Caps (Arne Richter Award for Outstanding Young Scientists Lecture)

    NASA Astrophysics Data System (ADS)

    Wouters, Bert; Ligtenberg, Stefan; Moholdt, Geir; Gardner, Alex S.; Noel, Brice; Kuipers Munneke, Peter; van den Broeke, Michiel; Bamber, Jonathan L.

    2016-04-01

    Historically, ice loss from mountain glaciers and ice caps has been one of the largest contributors to sea level rise over the last century. Of particular interest are the glaciers and ice caps in the North-Atlantic region of the Arctic. Despite the cold climate in this area, considerable melting and runoff occurs in summer. A small increase in temperature will have an immediate effect on these processes, so that a large change in the Arctic ice volume can be expected in response to the anticipated climate change in the coming century. Unfortunately, direct observations of glaciers are sparse and are biased toward glaciers systems in accessible, mostly maritime, climate conditions. Remote sensing is therefore essential to monitor the state of the the North-Atlantic glaciers and ice caps. In this presentation, we will discuss the progress that has been made in estimating the ice mass balance of these regions, with a particular focus on measurements made by ESA's Cryosat-2 radar altimeter mission (2010-present). Compared to earlier altimeter mission, Cryosat-2 provides unprecedented coverage of the cryosphere, with a resolution down to 1 km or better and sampling at monthly intervals. Combining the Cryosat-2 measurements with the laser altimetry data from ICESat (2003-2009) gives us a 12 yr time series of glacial mass loss in the North Atlantic. We find excellent agreement between the altimetry measurements and independent observations by the GRACE mission, which directly 'weighs' the ice caps, albeit at a much lower resolution. Mass loss in the region has increased from 120 Gigatonnes per year in 2003-2009 to roughly 140 Gt/yr in 2010-2014, with an important contribution from Greenland's peripheral glaciers and ice caps. Importantly, the mass loss is not stationary, but shows large regional interannual variability, with mass loss shifting between eastern and western regions from year to year. Comparison with regional climate models shows that these shifts can be

  8. Short-term sea ice forecasting: An assessment of ice concentration and ice drift forecasts using the U.S. Navy's Arctic Cap Nowcast/Forecast System

    NASA Astrophysics Data System (ADS)

    Hebert, David A.; Allard, Richard A.; Metzger, E. Joseph; Posey, Pamela G.; Preller, Ruth H.; Wallcraft, Alan J.; Phelps, Michael W.; Smedstad, Ole Martin

    2015-12-01

    In this study the forecast skill of the U.S. Navy operational Arctic sea ice forecast system, the Arctic Cap Nowcast/Forecast System (ACNFS), is presented for the period February 2014 to June 2015. ACNFS is designed to provide short term, 1-7 day forecasts of Arctic sea ice and ocean conditions. Many quantities are forecast by ACNFS; the most commonly used include ice concentration, ice thickness, ice velocity, sea surface temperature, sea surface salinity, and sea surface velocities. Ice concentration forecast skill is compared to a persistent ice state and historical sea ice climatology. Skill scores are focused on areas where ice concentration changes by ±5% or more, and are therefore limited to primarily the marginal ice zone. We demonstrate that ACNFS forecasts are skilful compared to assuming a persistent ice state, especially beyond 24 h. ACNFS is also shown to be particularly skilful compared to a climatologic state for forecasts up to 102 h. Modeled ice drift velocity is compared to observed buoy data from the International Arctic Buoy Programme. A seasonal bias is shown where ACNFS is slower than IABP velocity in the summer months and faster in the winter months. In February 2015, ACNFS began to assimilate a blended ice concentration derived from Advanced Microwave Scanning Radiometer 2 (AMSR2) and the Interactive Multisensor Snow and Ice Mapping System (IMS). Preliminary results show that assimilating AMSR2 blended with IMS improves the short-term forecast skill and ice edge location compared to the independently derived National Ice Center Ice Edge product.

  9. Sea Ice Sensitivities in the 0.72 deg and 0.08 deg Arctic Cap Coupled HYCOM/CICE Models

    DTIC Science & Technology

    2014-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Sea Ice Sensitivities in the 0.72°and 0.08° Arctic Cap...Arctic ice extent, which corresponds to the sea ice that remains during the summer minimum, has decreased over the years 1979–2007 by more than 10% per...Goosse et al. 2009) with the lowest observed sea ice extent in the satellite record (1979-present) occurring in September 2012 (Perovich et al. 2012

  10. Mars Water Ice and Carbon Dioxide Seasonal Polar Caps: GCM Modeling and Comparison with Mars Express Omega Observations

    NASA Technical Reports Server (NTRS)

    Forget, F.; Levrard, B.; Montmessin, F.; Schmitt, B.; Doute, S.; Langevin, Y.; Bibring, J. P.

    2005-01-01

    To better understand the behavior of the Mars CO2 ice seasonal polar caps, and in particular interpret the the Mars Express Omega observations of the recession of the northern seasonal cap, we present some simulations of the Martian Climate/CO2 cycle/ water cycle as modeled by the Laboratoire de Meteorologie Dynamique (LMD) global climate model.

  11. Azimuthal Structure of the Sand Erg that Encircles the North Polar Water-Ice Cap

    NASA Astrophysics Data System (ADS)

    Teodoro, L. A.; Elphic, R. C.; Eke, V. R.; Feldman, W. C.; Maurice, S.; Pathare, A.

    2011-12-01

    The sand erg that completely encircles the perennial water-ice cap that covers the Martian north geographic pole displays considerable azimuthal structure as seen in visible and near-IR images. Much of this structure is associated with the terminations of the many steep troughs that cut spiral the approximately 3 km thick polar ice cap. Other contributions come from the katabatic winds that spill over steep-sided edges of the cap, such as what bounds the largest set of dunes that comprise Olympia Undae. During the spring and summer months when these winds initiate from the higher altitudes that contain sublimating CO2 ice, which is very cold and dry, heat adiabatically when they compress as they lose altitude. These winds should then remove H2O moisture from the uppermost layer of the sand dunes that are directly in their path. Two likely locations where this desiccation may occur preferentially is at the termination of Chasma Boreale and the ice cap at Olympia Undae. We will search for this effect by sharpening the spatial structure of the epithermal neutron counting rates measured at northern high latitudes using the Mars Odyssey Neutron Spectrometer (MONS). The epithermal range of neutron energies is nearly uniquely sensitive to the hydrogen content of surface soils, which should likely be in the form of H2O/OH molecules/radicals. We therefore convert epithermal counting rates in terms of Water-Equivalent-Hydrogen, WEH. However, MONS counting-rate data have a FWHM of ~550 km., which is sufficiently broad to prevent a close association of WEH variability with images of geological features. In this study, we reduce spurious features in the instrument smeared neutron counting rates through deconvolution. We choose the PIXON numerical deconvolution technique for this purpose. This technique uses a statistical approach (Pina 2001, Eke 2001), which is capable of removing spurious features in the data in the presence of noise. We have previously carried out a detailed

  12. Discovery of a hypersaline subglacial lake complex beneath Devon Ice Cap, Canadian Arctic

    PubMed Central

    Blankenship, Donald D.; Schroeder, Dustin M.; Dowdeswell, Julian A.

    2018-01-01

    Subglacial lakes are unique environments that, despite the extreme dark and cold conditions, have been shown to host microbial life. Many subglacial lakes have been discovered beneath the ice sheets of Antarctica and Greenland, but no spatially isolated water body has been documented as hypersaline. We use radio-echo sounding measurements to identify two subglacial lakes situated in bedrock troughs near the ice divide of Devon Ice Cap, Canadian Arctic. Modeled basal ice temperatures in the lake area are no higher than −10.5°C, suggesting that these lakes consist of hypersaline water. This implication of hypersalinity is in agreement with the surrounding geology, which indicates that the subglacial lakes are situated within an evaporite-rich sediment unit containing a bedded salt sequence, which likely act as the solute source for the brine. Our results reveal the first evidence for subglacial lakes in the Canadian Arctic and the first hypersaline subglacial lakes reported to date. We conclude that these previously unknown hypersaline subglacial lakes may represent significant and largely isolated microbial habitats, and are compelling analogs for potential ice-covered brine lakes and lenses on planetary bodies across the solar system. PMID:29651462

  13. A moderate resolution inventory of small glaciers and ice caps surrounding Greenland and the Antarctic peninsula

    NASA Astrophysics Data System (ADS)

    Chen, C.; Box, J. E.; Hock, R. M.; Cogley, J. G.

    2011-12-01

    Current estimates of global Mountain Glacier and Ice Caps (MG&IC) mass changes are subject to large uncertainties due to incomplete inventories and uncertainties in land surface classification. This presentation features mitigative efforts through the creation of a MODIS dependent land ice classification system and its application for glacier inventory. Estimates of total area of mountain glaciers [IPCC, 2007] and ice caps (including those in Greenland and Antarctica) vary 15%, that is, 680 - 785 10e3 sq. km. To date only an estimated 40% of glaciers (by area) is inventoried in the World Glacier Inventory (WGI) and made available through the World Glacier Monitoring System (WGMS) and the National Snow and Ice Data Center [NSIDC, 1999]. Cogley [2009] recently compiled a more complete version of WGI, called WGI-XF, containing records for just over 131,000 glaciers, covering approximately half of the estimated global MG&IC area. The glaciers isolated from the conterminous Antarctic and Greenland ice sheets remain incompletely inventoried in WGI-XF but have been estimated to contribute 35% to the MG&IC sea-level equivalent during 1961-2004 [Hock et al., 2009]. Together with Arctic Canada and Alaska these regions alone make up almost 90% of the area that is missing in the global WGI-XF inventory. Global mass balance projections tend to exclude ice masses in Greenland and Antarctica due to the paucity of data with respect to basic inventory base data such as area, number of glaciers or size distributions. We address the need for an accurate Greenland and Antarctic peninsula land surface classification with a novel glacier surface classification and inventory based on NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data gridded at 250 m pixel resolution. The presentation includes a sensitivity analysis for surface mass balance as it depends on the land surface classification. Works Cited +Cogley, J. G. (2009), A more complete version of the World Glacier

  14. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    7 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.4 m/pixel (5 ft/pixel) view of a typical martian north polar ice cap texture. The surface is pitted and rough at the scale of several meters. The north polar residual cap of Mars consists mainly of water ice, while the south polar residual cap is mostly carbon dioxide. This picture is located near 85.2oN, 283.2oW. The image covers an area approximately 1 km wide by 1.4 km high (0.62 by 0.87 miles). Sunlight illuminates this scene from the lower left.

  15. Polar Cap Formation on Ganymede

    NASA Technical Reports Server (NTRS)

    Pilcher, C. B.; Shaya, E. J.

    1985-01-01

    Since thermal migration is not an effective mechanism for water transport in the polar regions at the Galilean satellites, some other process must be responsible for the formation of Ganymede's polar caps. It is proposed that Ganymede's polar caps are the optical manifestation of a process that began with the distribution of an ice sheet over the surface of Ganymede. The combined processes of impact gardening and thermal migration led, in regions at latitudes less than 40 to 45 deg., to the burial of some fraction of this ice, the migration of some to the polar caps margins, and a depletion of free ice in the optical surface. At higher latitudes, no process was effective in removing ice from the optical surface, so the remanants of the sheet are visible today.

  16. High Artic Glaciers and Ice Caps Ice Mass Change from GRACE, Regional Climate Model Output and Altimetry.

    NASA Astrophysics Data System (ADS)

    Ciraci, E.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.

    2016-12-01

    The Arctic hosts more than the 75% of the ice covered regions outside from Greenland and Antarctica. Available observations show that increased atmospheric temperatures during the last century have contributed to a substantial glaciers retreat in all these regions. We use satellite gravimetry by the NASA's Gravity Recovery and Climate Experiment (GRACE), and apply a least square fit mascon approach to calculate time series of ice mass change for the period 2002-2016. Our estimates show that arctic glaciers have constantly contributed to the sea level rise during the entire observation period with a mass change of -170+/-20 Gt/yr equivalent to the 80% of the total ice mass change from the world Glacier and Ice Caps (GIC) excluding the Ice sheet peripheral GIC, which we calculated to be -215+/-32 GT/yr, with an acceleration of 9+/-4 Gt/yr2. The Canadian Archipelago is the main contributor to the total mass depletion with an ice mass trend of -73+/-9 Gt/yr and a significant acceleration of -7+/-3 Gt/yr2. The increasing mass loss is mainly determined by melting glaciers located in the northern part of the archipelago.In order to investigate the physical processes driving the observed ice mass loss we employ satellite altimetry and surface mass balance (SMB) estimates from Regional climate model outputs available for the same time period covered by the gravimetry data. We use elevation data from the NASA ICESat (2003-2009) and ESA CryoSat-2 (2010-2016) missions to estimate ice elevation changes. We compare GRACE ice mass estimates with time series of surface mass balance from the Regional Climate Model (RACMO-2) and the Modèle Atmosphérique Régional (MAR) and determine the portion of the total mass change explained by the SMB signal. We find that in Iceland and in the and the Canadian Archipelago the SMB signal explains most of the observed mass changes, suggesting that ice discharge may play a secondary role here. In other region, e.g. in Svalbar, the SMB signal

  17. The Navy's First Seasonal Ice Forecasts using the Navy's Arctic Cap Nowcast/Forecast System

    NASA Astrophysics Data System (ADS)

    Preller, Ruth

    2013-04-01

    As conditions in the Arctic continue to change, the Naval Research Laboratory (NRL) has developed an interest in longer-term seasonal ice extent forecasts. The Arctic Cap Nowcast/Forecast System (ACNFS), developed by the Oceanography Division of NRL, was run in forward model mode, without assimilation, to estimate the minimum sea ice extent for September 2012. The model was initialized with varying assimilative ACNFS analysis fields (June 1, July 1, August 1 and September 1, 2012) and run forward for nine simulations using the archived Navy Operational Global Atmospheric Prediction System (NOGAPS) atmospheric forcing fields from 2003-2011. The mean ice extent in September, averaged across all ensemble members was the projected summer ice extent. These results were submitted to the Study of Environmental Arctic Change (SEARCH) Sea Ice Outlook project (http://www.arcus.org/search/seaiceoutlook). The ACNFS is a ~3.5 km coupled ice-ocean model that produces 5 day forecasts of the Arctic sea ice state in all ice covered areas in the northern hemisphere (poleward of 40° N). The ocean component is the HYbrid Coordinate Ocean Model (HYCOM) and is coupled to the Los Alamos National Laboratory Community Ice CodE (CICE) via the Earth System Modeling Framework (ESMF). The ocean and ice models are run in an assimilative cycle with the Navy's Coupled Ocean Data Assimilation (NCODA) system. Currently the ACNFS is being transitioned to operations at the Naval Oceanographic Office.

  18. Peruvian Tropical Glacier May Survive Longer Than Previously Thought: Landsat Image Analysis of Nevado Coropuna Ice Cap, Peru

    NASA Astrophysics Data System (ADS)

    Kochtitzky, W. H.; Edwards, B. R.; Marino, J.; Manrique, N.

    2015-12-01

    Nevado Coropuna is a large volcanic complex in southern Peru (15.56°S, 72.62°N; 6,425 m). The complex is approximately 12 km east-west and 8 km north-south with elevation from ~4,500 m at the base to over 6,000 m at the highest points. This ice cap is the largest hosted by a volcano in the tropics, and one of the ten biggest ice masses in the tropics. Previous workers have predicted that the Coropuna ice cap will completely melt by 2050. We present a new analysis of historic satellite imagery to test this hypothesis. In this study, ice and snow are classified based on unique spectral signatures including spectral band thresholds, Normalized Difference Snow Index, and Band 4/5 ratio. Landsat scenes (L2, 4, 5, 7, and 8) from 1975 to present in addition to one SPOT scene (2013) are used. Previous workers used images from June and July, which are peak snow periods in southern Peru, leading to overestimates of ice area. This study uses November and December images when snow is at an annual minimum. Annual equilibrium line altitudes are calculated for each end of year image (November/December). The glaciers of Nevado Coropuna were found to be shrinking at ~0.5 km2/yr, which is ~1/3 the rate previously published. In this study, SPOT (1.5 m resolution) and Landsat 7 ETM scenes from November 23 and 26, 2013 respectively were used to calibrate the spectral band threshold classification. While this study suggests that the ice cap of Coropuna will persist until 2100 given current rates, water quantity and security remains a concern for Peruvian agriculture. Coropuna is an active volcano, so it poses great risk to surrounding inhabitants from lahars, flooding, and debris avalanches. Our new data suggest that these will continue to be risks late into this century.

  19. Numerical modeling of Drangajökull Ice Cap, NW Iceland

    NASA Astrophysics Data System (ADS)

    Anderson, Leif S.; Jarosch, Alexander H.; Flowers, Gwenn E.; Aðalgeirsdóttir, Guðfinna; Magnússon, Eyjólfur; Pálsson, Finnur; Muñoz-Cobo Belart, Joaquín; Þorsteinsson, Þorsteinn; Jóhannesson, Tómas; Sigurðsson, Oddur; Harning, David; Miller, Gifford H.; Geirsdóttir, Áslaug

    2016-04-01

    Over the past century the Arctic has warmed twice as fast as the global average. This discrepancy is likely due to feedbacks inherent to the Arctic climate system. These Arctic climate feedbacks are currently poorly quantified, but are essential to future climate predictions based on global circulation modeling. Constraining the magnitude and timing of past Arctic climate changes allows us to test climate feedback parameterizations at different times with different boundary conditions. Because Holocene Arctic summer temperature changes have been largest in the North Atlantic (Kaufman et al., 2004) we focus on constraining the paleoclimate of Iceland. Glaciers are highly sensitive to changes in temperature and precipitation amount. This sensitivity allows for the estimation of paleoclimate using glacier models, modern glacier mass balance data, and past glacier extents. We apply our model to the Drangajökull ice cap (~150 sq. km) in NW Iceland. Our numerical model is resolved in two-dimensions, conserves mass, and applies the shallow-ice-approximation. The bed DEM used in the model runs was constructed from radio echo data surveyed in spring 2014. We constrain the modern surface mass balance of Drangajökull using: 1) ablation and accumulation stakes; 2) ice surface digital elevation models (DEMs) from satellite, airborne LiDAR, and aerial photographs; and 3) full-stokes model-derived vertical ice velocities. The modeled vertical ice velocities and ice surface DEMs are combined to estimate past surface mass balance. We constrain Holocene glacier geometries using moraines and trimlines (e.g., Brynjolfsson, etal, 2014), proglacial-lake cores, and radiocarbon-dated dead vegetation emerging from under the modern glacier. We present a sensitivity analysis of the model to changes in parameters and show the effect of step changes of temperature and precipitation on glacier extent. Our results are placed in context with local lacustrine and marine climate proxies as well

  20. Palaeoglaciology of the Alexander Island ice cap, western Antarctic Peninsula, reconstructed from marine geophysical and core data

    NASA Astrophysics Data System (ADS)

    Graham, Alastair G. C.; Smith, James A.

    2012-03-01

    The glacial history of the continental shelf northwest of Alexander Island is not well known, due mainly to a lack of targeted marine data on Antarctica's palaeo-ice sheets in their inter-ice-stream areas. Recently it has been argued that the region was ice-free at the Last Glacial Maximum (LGM) and thus a potential site for glacial refugia. In this paper, multibeam swath bathymetry, sub-bottom profiles and sediment cores are used to map the Alexander Island sector of the Antarctic Peninsula margin, in order to reconstruct the shelf's palaeoglaciology. Sea-floor bedforms provide evidence that an independent ice cap persisted on Alexander Island through the LGM and deglaciation. We show that this ice cap drained via two major, previously-undescribed tidewater outlets (Rothschild and Charcot Glaciers) sourced from an ice dome centred over the west of the island and near-shore areas. The glaciers grounded along deep, fjord-like cross-shelf troughs to within at least ˜10-20 km of the shelf edge, and probably reached the shelf break. Only one small outer-shelf zone appears to have remained free of ice throughout an otherwise extensive LGM. During retreat, grounding-line geomorphology indicates periodic stabilisation of Charcot Glacier on the mid-shelf after 13,500 cal yrs BP, while Rothschild Glacier retreated across its mid-shelf by 14,450 cal yrs BP. The timing of these events is in phase with retreat in nearby Marguerite Trough, and we take this as evidence of a common history and forcing with the Antarctic Peninsula Ice Sheet. The fine details of ice flow documented by our new reconstruction highlight the importance of capturing complex ice flow patterns in models (e.g. in inter-stream areas), for understanding how region-specific parts of Antarctica may change in the future. Moreover, the reconstruction shows that glacial refugia, if present, cannot have been extensive on the Alexander Island shelf at the LGM as indicated by previous biological studies; instead

  1. Ice core records of climate variability on the Third Pole with emphasis on the Guliya ice cap, western Kunlun Mountains

    NASA Astrophysics Data System (ADS)

    Thompson, Lonnie G.; Yao, Tandong; Davis, Mary E.; Mosley-Thompson, Ellen; Wu, Guangjian; Porter, Stacy E.; Xu, Baiqing; Lin, Ping-Nan; Wang, Ninglian; Beaudon, Emilie; Duan, Keqin; Sierra-Hernández, M. Roxana; Kenny, Donald V.

    2018-05-01

    Records of recent climate from ice cores drilled in 2015 on the Guliya ice cap in the western Kunlun Mountains of the Tibetan Plateau, which with the Himalaya comprises the Third Pole (TP), demonstrate that this region has become warmer and moister since at least the middle of the 19th century. Decadal-scale linkages are suggested between ice core temperature and snowfall proxies, North Atlantic oceanic and atmospheric processes, Arctic temperatures, and Indian summer monsoon intensity. Correlations between annual-scale oxygen isotopic ratios (δ18O) and tropical western Pacific and Indian Ocean sea surface temperatures are also demonstrated. Comparisons of climate records during the last millennium from ice cores acquired throughout the TP illustrate centennial-scale differences between monsoon and westerlies dominated regions. Among these records, Guliya shows the highest rate of warming since the end of the Little Ice Age, but δ18O data over the last millennium from TP ice cores support findings that elevation-dependent warming is most pronounced in the Himalaya. This, along with the decreasing precipitation rates in the Himalaya region, is having detrimental effects on the cryosphere. Although satellite monitoring of glaciers on the TP indicates changes in surface area, only a few have been directly monitored for mass balance and ablation from the surface. This type of ground-based study is essential to obtain a better understanding of the rate of ice shrinkage on the TP.

  2. Abnormal Winter Melting of the Arctic Sea Ice Cap Observed by the Spaceborne Passive Microwave Sensors

    NASA Astrophysics Data System (ADS)

    Lee, Seongsuk; Yi, Yu

    2016-12-01

    The spatial size and variation of Arctic sea ice play an important role in Earth’s climate system. These are affected by conditions in the polar atmosphere and Arctic sea temperatures. The Arctic sea ice concentration is calculated from brightness temperature data derived from the Defense Meteorological Satellite program (DMSP) F13 Special Sensor Microwave/Imagers (SSMI) and the DMSP F17 Special Sensor Microwave Imager/Sounder (SSMIS) sensors. Many previous studies point to significant reductions in sea ice and their causes. We investigated the variability of Arctic sea ice using the daily sea ice concentration data from passive microwave observations to identify the sea ice melting regions near the Arctic polar ice cap. We discovered the abnormal melting of the Arctic sea ice near the North Pole during the summer and the winter. This phenomenon is hard to explain only surface air temperature or solar heating as suggested by recent studies. We propose a hypothesis explaining this phenomenon. The heat from the deep sea in Arctic Ocean ridges and/ or the hydrothermal vents might be contributing to the melting of Arctic sea ice. This hypothesis could be verified by the observation of warm water column structure below the melting or thinning arctic sea ice through the project such as Coriolis dataset for reanalysis (CORA).

  3. Is CO2 ice permanent?

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1992-01-01

    Carbon dioxide ice has been inferred to exist at the south pole in summertime, but Earth based measurements in 1969 of water vapor in the Martian atmosphere suggest that all CO2 ice sublined from the southern polar cap and exposed underlying water ice. This implies that the observed summertime CO2 ice is of recent origin. It appears possible to construct an energy balance model that maintains seasonal CO2 ice at the south pole year round and still reasonably simulates the polar cap regression and atmospheric pressure data. This implies that the CO2 ice observed in the summertime south polar cap could be seasonal in origin, and that minor changes in climate could cause CO2 ice to completely vanish, as would appear to have happened in 1969. However, further research remains before it is certain whether the CO2 ice observed in the summertime south polar cap is seasonal or is part of a permanent reservoir.

  4. Mass budget of the glaciers and ice caps of the Queen Elizabeth Islands, Canada, from 1991 to 2015

    NASA Astrophysics Data System (ADS)

    Millan, Romain; Mouginot, Jeremie; Rignot, Eric

    2017-02-01

    Recent studies indicate that the glaciers and ice caps in Queen Elizabeth Islands (QEI), Canada have experienced an increase in ice mass loss during the last two decades, but the contribution of ice dynamics to this loss is not well known. We present a comprehensive mapping of ice velocity using a suite of satellite data from year 1991 to 2015, combined with ice thickness data from NASA Operation IceBridge, to calculate ice discharge. We find that ice discharge increased significantly after 2011 in Prince of Wales Icefield, maintained or decreased in other sectors, whereas glacier surges have little impact on long-term trends in ice discharge. During 1991-2005, the QEI mass loss averaged 6.3 ± 1.1 Gt yr-1, 52% from ice discharge and the rest from surface mass balance (SMB). During 2005-2014, the mass loss from ice discharge averaged 3.5 ± 0.2 Gt yr-1 (10%) versus 29.6 ± 3.0 Gt yr-1 (90%) from SMB. SMB processes therefore dominate the QEI mass balance, with ice dynamics playing a significant role only in a few basins.

  5. The melting sea ice of Arctic polar cap in the summer solstice month and the role of ocean

    NASA Astrophysics Data System (ADS)

    Lee, S.; Yi, Y.

    2014-12-01

    The Arctic sea ice is becoming smaller and thinner than climatological standard normal and more fragmented in the early summer. We investigated the widely changing Arctic sea ice using the daily sea ice concentration data. Sea ice data is generated from brightness temperature data derived from the sensors: Defense Meteorological Satellite Program (DMSP)-F13 Special Sensor Microwave/Imagers (SSM/Is), the DMSP-F17 Special Sensor Microwave Imager/Sounder (SSMIS) and the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) instrument on the NASA Earth Observing System (EOS) Aqua satellite. We tried to figure out appearance of arctic sea ice melting region of polar cap from the data of passive microwave sensors. It is hard to explain polar sea ice melting only by atmosphere effects like surface air temperature or wind. Thus, our hypothesis explaining this phenomenon is that the heat from deep undersea in Arctic Ocean ridges and the hydrothermal vents might be contributing to the melting of Arctic sea ice.

  6. Surface Exposure Dating of the Huancané III Moraines in Peru: A Record of Quelccaya Ice Cap's Maximum Extent during the Last Glacial Period

    NASA Astrophysics Data System (ADS)

    Baranes, H. E.; Kelly, M. A.; Stroup, J. S.; Howley, J. A.; Lowell, T. V.

    2012-12-01

    The climatic conditions that influenced the tropics during the height of the last glacial period are not well defined and controversial. There are disparities in estimates of temperature anomalies (e.g., MARGO, 2009; Rind and Peteet, 1985; CLIMAP, 1976), and critical terrestrial paleotemperature proxy records in tropical regions are poorly dated (e.g., Porter, 2001). Defining these conditions is important for understanding the mechanisms that cause major shifts in climate, as the tropics are a primary driver of atmospheric and oceanic circulation. This study aims to constrain the timing of maximum glacier extents in the Cordillera Oriental in southern Peru during the last glacial period by applying surface exposure (beryllium-10) dating to the Huancané III (Hu-III) moraines. The Hu-III moraines mark the maximum extent of Quelccaya Ice Cap (QIC) (13.93°S, 70.83°W), the largest tropical ice cap, during the last ice age. The eight beryllium-10 ages presented here yield 17,056 ± 520 yrs ago as a minimum age for the onset of recession from the ice cap advance marked by the Hu-III moraines. Comparing this age to other paleoclimate records indicates that the ice cap advance marked by the Hu-III moraines is more likely associated with a North Atlantic climate event known as Heinrich I (H1; 16,800 yrs ago, Bond et al., 1992, 1993) than with global cooling at the Last Glacial Maximum (LGM; ~21,000 yrs ago, Denton and Hughes, 1981). This result suggests that climate processes in the North Atlantic region are linked to climatic conditions in the tropical Andes. A mesoscale climate model and an ice-flow model are currently being developed for QIC. The moraine data presented in this study will be used with these two models to test response of QIC to North Atlantic and global climate events.

  7. Temporal constraints on future accumulation-area loss of a major Arctic ice cap due to climate change (Vestfonna, Svalbard)

    PubMed Central

    Möller, Marco; Schneider, Christoph

    2015-01-01

    Arctic glaciers and ice caps are major contributors to past, present and future sea-level fluctuations. Continued global warming may eventually lead to the equilibrium line altitudes of these ice masses rising above their highest points, triggering unstoppable downwasting. This may feed future sea-level rise considerably. We here present projections for the timing of equilibrium-line loss at the major Arctic ice cap Vestfonna, Svalbard. The projections are based on spatially distributed climatic mass balance modelling driven by the outputs of multiple climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) forced by the Representative Concentration Pathways (RCPs) 2.6, 4.5, 6.0 and 8.5. Results indicate strongly decreasing climatic mass balances over the 21st century for all RCPs considered. Glacier-wide mass-balance rates will drop down to −4 m a−1 w.e. (water equivalent) at a maximum. The date at which the equilibrium line rises above the summit of Vestfonna (630 m above sea level) is calculated to range between 2040 and 2150, depending on scenario. PMID:25628045

  8. Winter mass balance of Drangajökull ice cap (NW Iceland) derived from satellite sub-meter stereo images

    NASA Astrophysics Data System (ADS)

    Belart, Joaquín M. C.; Berthier, Etienne; Magnússon, Eyjólfur; Anderson, Leif S.; Pálsson, Finnur; Thorsteinsson, Thorsteinn; Howat, Ian M.; Aðalgeirsdóttir, Guðfinna; Jóhannesson, Tómas; Jarosch, Alexander H.

    2017-06-01

    Sub-meter resolution, stereoscopic satellite images allow for the generation of accurate and high-resolution digital elevation models (DEMs) over glaciers and ice caps. Here, repeated stereo images of Drangajökull ice cap (NW Iceland) from Pléiades and WorldView2 (WV2) are combined with in situ estimates of snow density and densification of firn and fresh snow to provide the first estimates of the glacier-wide geodetic winter mass balance obtained from satellite imagery. Statistics in snow- and ice-free areas reveal similar vertical relative accuracy (< 0.5 m) with and without ground control points (GCPs), demonstrating the capability for measuring seasonal snow accumulation. The calculated winter (14 October 2014 to 22 May 2015) mass balance of Drangajökull was 3.33 ± 0.23 m w.e. (meter water equivalent), with ∼ 60 % of the accumulation occurring by February, which is in good agreement with nearby ground observations. On average, the repeated DEMs yield 22 % less elevation change than the length of eight winter snow cores due to (1) the time difference between in situ and satellite observations, (2) firn densification and (3) elevation changes due to ice dynamics. The contributions of these three factors were of similar magnitude. This study demonstrates that seasonal geodetic mass balance can, in many areas, be estimated from sub-meter resolution satellite stereo images.

  9. Monitoring and modeling ice-rock avalanches from ice-capped volcanoes: A case study of frequent large avalanches on Iliamna Volcano, Alaska

    USGS Publications Warehouse

    Huggel, C.; Caplan-Auerbach, J.; Waythomas, C.F.; Wessels, R.L.

    2007-01-01

    Iliamna is an andesitic stratovolcano of the Aleutian arc with regular gas and steam emissions and mantled by several large glaciers. Iliamna Volcano exhibits an unusual combination of frequent and large ice-rock avalanches in the order of 1 ?? 106??m3 to 3 ?? 107??m3 with recent return periods of 2-4??years. We have reconstructed an avalanche event record for the past 45??years that indicates Iliamna avalanches occur at higher frequency at a given magnitude than other mass failures in volcanic and alpine environments. Iliamna Volcano is thus an ideal site to study such mass failures and its relation to volcanic activity. In this study, we present different methods that fit into a concept of (1) long-term monitoring, (2) early warning, and (3) event documentation and analysis of ice-rock avalanches on ice-capped active volcanoes. Long-term monitoring methods include seismic signal analysis, and space-and airborne observations. Landsat and ASTER satellite data was used to study the extent of hydrothermally altered rocks and surface thermal anomalies at the summit region of Iliamna. Subpixel heat source calculation for the summit regions where avalanches initiate yielded temperatures of 307 to 613??K assuming heat source areas of 1000 to 25??m2, respectively, indicating strong convective heat flux processes. Such heat flow causes ice melting conditions and is thus likely to reduce the strength at the base of the glacier. We furthermore demonstrate typical seismic records of Iliamna avalanches with rarely observed precursory signals up to two hours prior to failure, and show how such signals could be used for a multi-stage avalanche warning system in the future. For event analysis and documentation, space- and airborne observations and seismic records in combination with SRTM and ASTER derived terrain data allowed us to reconstruct avalanche dynamics and to identify remarkably similar failure and propagation mechanisms of Iliamna avalanches for the past 45??years

  10. Evidence for smaller extents of the northwestern Greenland Ice Sheet and North Ice Cap during the Holocene

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Osterberg, E. C.; Axford, Y.; Bigl, M.; Birkel, S. D.; Corbett, L. B.; Roy, E. P.; Thompson, J. T.; Whitecloud, S.

    2013-12-01

    The Greenland Ice Sheet (GrIS) and local glaciers on Greenland are responding dynamically to warming temperatures with widespread retreat. GRACE satellite data (e.g., Kahn et al., 2010) and the Petermann Glacier calving events document the recent expansion of ice loss into northwestern Greenland. To improve the ability to estimate future ice loss in a warming climate, we are developing records of the response of the northwestern Greenlandic cryosphere to Holocene climatic conditions, with a focus on past warm periods. Our ongoing research includes analyses of glacial geology, sub-fossil vegetation, lake sediment cores, chironomid assemblages and ice cores combined with glaciological modeling. To constrain past ice extents that were as small as, or smaller than, at present, we recovered sub-fossil vegetation exposed at the receding margins of the GrIS and North Ice Cap (NIC) in the Nunatarssuaq region (~76.7°N, 67.4°W) and of the GrIS near Thule (~76.5°N, 68.7°W). We present vegetation types and radiocarbon ages of 30 plant samples collected in August 2012. In the Nunatarssuaq region, five ages of in situ (rooted) vegetation including Polytrichum moss, Saxifraga nathorstii and grasses located <5 m outboard of the GrIS margin are ~120-200 cal yr BP (range of medians of the 2-sigma calibrated age ranges). Nine ages of in situ Polytrichum, Saxifraga oppositafolia and grasses from ~1-5 m inboard of the NIC margin (excavated from beneath ice) range from ~50 to 310 cal yr BP. The growth of these plants occurred when the GrIS and NIC were at least as small as at present and their ages suggest that ice advances occurred in the last 50-120 yrs. In addition to the in situ samples, we collected plants from well-preserved ground material exposed along shear planes in the GrIS margins. In Nunatarssuaq, two Polytrichum mosses rooted in ground material and exposed along a shear plane in the GrIS margin date to 4680 and 4730 cal yr BP. Near Thule, three ages of Salix arctica

  11. Geodetic glacier mass balancing on ice caps - inseparably connected to firn modelling?

    NASA Astrophysics Data System (ADS)

    Saß, Björn L.; Sauter, Tobias; Seehaus, Thorsten; Braun, Matthias H.

    2017-04-01

    Observed melting of glaciers and ice caps in the polar regions contribute to the ongoing global sea level rise (SLR). A rising sea level and its consequences are one of the major challenges for coastal societies in the next decades to centuries. Gaining knowledge about the main drivers of SLR and bringing it together is one recent key-challenge for environmental science. The high arctic Svalbard archipelago faced a strong climatic change in the last decades, associated with a change in the cryosphere. Vestfonna, a major Arctic ice cap in the north east of Svalbard, harbors land and marine terminating glaciers, which expose a variability of behavior. We use high resolution remote sensing data from space-borne radar (TanDEM-X, TerraSAR-X, Sentinel-1a), acquired between 2009 and 2015, to estimate glacier velocity and high accurate surface elevation changes. For DEM registration we use space-borne laser altimetry (ICESat) and an existing in-situ data archive (IPY Kinnvika). In order to separate individual glacier basin changes for a detailed mass balance study and for further SLR contribution estimates, we use glacier outlines from the Global Land Ice Measurements from Space (GLIMS) project. Remaining challenges of space-borne observations are the reduction of measurement uncertainties, in the case of Synthetic Aperture Radar most notably signal penetration into the glacier surface. Furthermore, in order to convert volume to mass change one has to use the density of the changed mass (conversion factor) and one has to account for the mass conservation processes in the firn package (firn compaction). Both, the conversion factor and the firn compaction are not (yet) measurable for extensive ice bodies. They have to be modelled by coupling point measurements and regional gridded climate data. Results indicate a slight interior thickening contrasted with wide spread thinning in the ablation zone of the marine terminating outlets. While one glacier system draining to the

  12. Changes of Arctic Marine Glaciers and Ice Caps from CryoSat Swath Altimetry

    NASA Astrophysics Data System (ADS)

    Tepes, P.; Gourmelen, N.; Weissgerber, F.; Escorihuela, M. J.; Wuite, J.; Nagler, T.; Foresta, L.; Brockley, D.; Baker, S.; Roca, M.; Shepherd, A.; Plummer, S.

    2017-12-01

    Glaciers and ice caps (GICs) are major contributors to the current budget of global mean sea level change. Ice losses from GICs are expected to increase over the next century and beyond (Gardner et al., 2011), particularly in the Arctic where mean annual surface temperatures have recently been increasing twice as fast as the global average (Screen and Simmonds, 2010). Investigating cryospheric changes over GICs from space-based observations has proven to be challenging due in large part to the limited spatial and temporal resolution of present day observation techniques compared to the relatively small size and the steep and complex terrain that often define GICs. As a result, not much is known about modern changes in ice mass in most of these smaller glaciated regions of the Arctic (Moholdt et al., 2012; Carr et al., 2014). Radar altimetry is well suited to monitoring elevation changes over land ice due to its all-weather year-round capability of observing ice surfaces. Since 2010, the Synthetic Interferometric Radar Altimeter (SIRAL) on board the European Space Agency (ESA) radar altimetry CryoSat (CS) mission has been collecting ice elevation measurements over GICs. Data from the CS-SARIn mode have been used to infer high resolution elevation and elevation change rates using "swath processing" (Hawley et al., 2009; Gray et al., 2013; Christie et al., 2016; Foresta et al., 2016; Smith et al., 2016). Together with a denser ground track interspacing of the CS mission, swath processing provides measurements at unprecedented spatial coverage and resolution, enabling the study of key processes that underlie current changes of GICs in the Arctic. In this study, we use CS swath observations to identify patterns of change of marine versus land-terminating glaciers across the Arctic. We generate maps of ice elevation change rates and present estimates of volumetric changes for GICs outside of Greenland. We then compare marine versus land terminating glaciers in terms of

  13. Climate Changes Documented in Ice Core Records from Third Pole Glaciers, with Emphasis on the Guliya Ice Cap in the Western Kunlun Mountains over the Last 100 Years

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Yao, T.; Beaudon, E.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.

    2016-12-01

    The Third Pole (TP) is a rapidly warming region containing 100,000 km2 of ice cover that collectively holds one of Earth's largest stores of freshwater that feeds Asia's largest rivers and helps sustain 1.5 billion people. Information on the accelerating warming in the region, its impact on the glaciers and subsequently on future water resources is urgently needed to guide mitigation and adaptation policies. Ice core histories collected over the last three decades across the TP demonstrate its climatic complexity and diversity. Here we present preliminary results from the flagship project of the Third Pole Environment Program, the 2015 Sino-American cooperative ice core drilling of the Guliya ice cap in the Kunlun Mountains in the western TP near the northern limit of the region influenced by the southwest monsoon. Three ice cores, each 51 meters in length, were recovered from the summit ( 6700 masl) while two deeper cores, one to bedrock ( 310 meters), were recovered from the plateau ( 6200 masl). Across the ice cap the net balance (accumulation) has increased annually by 2.3 cm of water equivalent from 1963-1992 to 1992-2015, and average oxygen isotopic ratios (δ18O) have enriched by 2‰. This contrasts with the recent ablation on the Naimona'nyi glacier located 540 km south of Guliya in the western Himalaya. Borehole temperatures in 2015 on the Guliya plateau have warmed substantially in the upper 30 meters of the ice compared to temperatures in 1992, when the first deep-drilling of the Guliya plateau was conducted. Compared with glaciers in the northern and western TP, the Himalayan ice fields are more sensitive to both fluctuations in the South Asian Monsoon and rising temperatures in the region. We examine the climatic changes of the last century preserved in ice core records from sites throughout the TP and compare them with those reconstructed for earlier warm epochs, such as the Medieval Climate Anomaly ( 950-1250 AD), the early Holocene "Hypsithermal

  14. Sunlight penetration through the Martian polar caps: Effects on the thermal and frost budgets

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1992-01-01

    An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

  15. Sunlight penetration through the Martian polar caps - Effects on the thermal and frost budgets

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard L.

    1992-01-01

    An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer, and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

  16. Differences in Bacterial Diversity and Communities Between Glacial Snow and Glacial Soil on the Chongce Ice Cap, West Kunlun Mountains.

    PubMed

    Yang, Guang Li; Hou, Shu Gui; Le Baoge, Ri; Li, Zhi Guo; Xu, Hao; Liu, Ya Ping; Du, Wen Tao; Liu, Yong Qin

    2016-11-04

    A detailed understanding of microbial ecology in different supraglacial habitats is important due to the unprecedented speed of glacier retreat. Differences in bacterial diversity and community structure between glacial snow and glacial soil on the Chongce Ice Cap were assessed using 454 pyrosequencing. Based on rarefaction curves, Chao1, ACE, and Shannon indices, we found that bacterial diversity in glacial snow was lower than that in glacial soil. Principal coordinate analysis (PCoA) and heatmap analysis indicated that there were major differences in bacterial communities between glacial snow and glacial soil. Most bacteria were different between the two habitats; however, there were some common bacteria shared between glacial snow and glacial soil. Some rare or functional bacterial resources were also present in the Chongce Ice Cap. These findings provide a preliminary understanding of the shifts in bacterial diversity and communities from glacial snow to glacial soil after the melting and inflow of glacial snow into glacial soil.

  17. Mass loss of the Greenland peripheral glaciers and ice caps from satellite altimetry

    NASA Astrophysics Data System (ADS)

    Wouters, Bert; Noël, Brice; Moholdt, Geir; Ligtenberg, Stefan; van den Broeke, Michiel

    2017-04-01

    At its rapidly warming margins, the Greenland Ice Sheet is surrounded by (semi-)detached glaciers and ice caps (GIC). Although they cover only roughly 5% of the total glaciated area in the region, they are estimated to account for 15-20% of the total sea level rise contribution of Greenland. The spatial and temporal evolution of the mass changes of the peripheral GICs, however, remains poorly constrained. In this presentation, we use satellite altimetry from ICESat and Cryosat-2 combined with a high-resolution regional climate model to derive a 14 year time series (2003-2016) of regional elevation and mass changes. The total mass loss has been relatively constant during this period, but regionally, the GICs show marked temporal variations. Whereas thinning was concentrated along the eastern margin during 2003-2009, western GICs became the prime sea level rise contributors in recent years. Mass loss in the northern region has been steadily increasing throughout the record, due to a strong atmospheric warning and a deterioration of the capacity of the firn layer to buffer the resulting melt water.

  18. Using Ice Predictions to Guide Submarines

    DTIC Science & Technology

    2016-01-01

    the Arctic Cap Nowcast/ Forecast System (ACNFS) in September 2013. The ACNFS consists of a coupled ice -ocean model that assimilates available real...of the ice cover. The age of the sea ice serves as an indicator of its physical properties including surface roughness, melt pond coverage, and...the Arctic Cap Nowcast/Forecast System (ACNFS). Ice thickness is in meters for 11 September 2015. Thickness ranges from zero to five meters as shown

  19. Validating Cryosat-2 elevation estimates with airborne laser scanner data for the Greenland ice sheet, Austfonna and Devon ice caps

    NASA Astrophysics Data System (ADS)

    Simonsen, Sebastian B.; Sandberg Sørensen, Louise; Nilsson, Johan; Helm, Veit; Langley, Kirsty A.; Forsberg, Rene; Hvidegaard, Sine M.; Skourup, Henriette

    2015-04-01

    The ESA CryoSat-2 satellite, launched in late 2010, carries a new type of radar altimeter especially designed for monitoring changes of sea and land ice. The radar signal might penetrate into the snow pack and the depth of the radar reflecting surface depends on the ratio between the surface and the volume backscatter, which is a function of several different properties such as snow density, crystal structure and surface roughness. In case of large volume scatter, the radar waveforms become broad and the determination of the range (surface elevation) becomes more difficult. Different algorithms (retrackers) are used for the range determination, and estimated surface penetration is highly dependent on the applied retracker. As part of the ESA-CryoVEx/CryoVal-Land Ice projects, DTU Space has gathered accurate airborne laser scanner elevation measurements. Sites on the Greenland ice sheet, Austfonna and Devon ice caps, has been surveyed repeatedly, aligned with Cryosat-2 ground tracks and surface experiments. Here, we utilize elevation estimates from available Cryosat-2 retrackers (ESA level-2 retracker, DTU retracker, etc.) and validate the elevation measurements against ESA-CryoVEx campaigns. A difference between laser and radar elevations is expected due to radar penetration issues, however an inter-comparison between retrackers will shed light on individual performances and biases. Additionally, the geo-location of the radar return will also be a determining factor for the precision. Ultimately, the use of multiple retrackers can provide information about subsurface conditions and utilize more of the waveform information than presently used in radar altimetry.

  20. Analysis of vanillic acid in polar ice cores as a biomass burning proxy - preliminary results from the Akademii Nauk Ice Cap in Siberia

    NASA Astrophysics Data System (ADS)

    Grieman, M. M.; Jimenez, R.; McConnell, J. R.; Fritzsche, D.; Saltzman, E. S.

    2013-12-01

    Biomass burning influences global climate change and the composition of the atmosphere. The drivers, effects, and climate feedbacks related to fire are poorly understood. Many different proxies have been used to reconstruct past fire frequency from lake sediments and polar ice cores. Reconstruction of historical trends in biomass burning is challenging because of regional variability and the qualitative nature of various proxies. Vanillic acid (4-hydroxy-3-methoxybenzoic acid) is a product of the combustion of conifer lignin that is known to occur in biomass burning aerosols. Biomass burning is likely the only significant source of vanillic acid in polar ice. In this study we describe an analytical method for quantifying vanillic acid in polar ice using HPLC with electrospray ionization and tandem mass spectrometric detection. The method has a detection limit of 100 pM and a precision of × 10% at the 100 pM level for analysis of 100 μl of ice melt water. The method was used to analyze more than 1000 discrete samples from the Akademii Nauk ice cap on Severnaya Zemlya in the high Russia Arctic (79°30'N, 97°45'E) (Fritzsche et al., 2002; Fritzsche et al., 2005; Weiler et al., 2005). The samples range in age over the past 2,000 years. The results show a mean vanillic acid concentration of 440 × 710 pM (1σ), with elevated levels during the periods from 300-600 and 1450-1550 C.E.

  1. South Polar Cap

    NASA Technical Reports Server (NTRS)

    2005-01-01

    8 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows landforms created by sublimation processes on the south polar residual cap of Mars. The bulk of the ice in the south polar residual cap is frozen carbon dioxide.

    Location near: 86.6oS, 342.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  2. MGS TES observations of the water vapor above the seasonal and perennial ice caps during northern spring and summer

    NASA Astrophysics Data System (ADS)

    Pankine, Alexey A.; Tamppari, Leslie K.; Smith, Michael D.

    2010-11-01

    We report on new retrievals of water vapor column abundances from the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data. The new retrievals are from the TES nadir data taken above the 'cold' surface areas in the North polar region ( Tsurf < 220 K, including seasonal frost and permanent ice cap) during spring and summer seasons, where retrievals were not performed initially. Retrievals are possible (with some modifications to the original algorithm) over cold surfaces overlaid by sufficiently warm atmosphere. The retrieved water vapor column abundances are compared to the column abundances observed by other spacecrafts in the Northern polar region during spring and summer and good agreement is found. We detect an annulus of water vapor growing above the edge of the retreating seasonal cap during spring. The formation of the vapor annulus is consistent with the previously proposed mechanism for water cycling in the polar region, according to which vapor released by frost sublimation during spring re-condenses on the retreating seasonal CO 2 cap. The source of the vapor in the vapor annulus, according to this model, is the water frost on the surface of the CO 2 at the retreating edge of the cap and the frost on the ground that is exposed by the retreating cap. Small contribution from regolith sources is possible too, but cannot be quantified based on the TES vapor data alone. Water vapor annulus exhibits interannual variability, which we attribute to variations in the atmospheric temperature. We propose that during spring and summer the water ice sublimation is retarded by high relative humidity of the local atmosphere, and that higher atmospheric temperatures lead to higher vapor column abundances by increasing the water holding capacity of the atmosphere. Since the atmospheric temperatures are strongly influenced by the atmospheric dust content, local dust storms may be controlling the release of vapor into the polar atmosphere. Water vapor

  3. Characterization of Mars' seasonal caps using neutron spectroscopy

    USGS Publications Warehouse

    Prettyman, T.H.; Feldman, W.C.; Titus, T.N.

    2009-01-01

    Mars' seasonal caps are characterized during Mars years 26 and 27 (April 2002 to January 2006) using data acquired by the 2001 Mars Odyssey Neutron Spectrometer. Time-dependent maps of the column abundance of seasonal CO 2 surface ice poleward of 60?? latitude in both hemispheres are determined from spatially deconvolved, epithermal neutron counting data. Sources of systematic error are analyzed, including spatial blurring by the spectrometer's broad footprint and the seasonal variations in the abundance of noncondensable gas at high southern latitudes, which are found to be consistent with results reported by Sprague et al. (2004, 2007). Corrections for spatial blurring are found to be important during the recession, when the column abundance of seasonal CO2 ice has the largest latitude gradient. The measured distribution and inventory of seasonal CO2 ice is compared to simulations by a general circulation model (GCM) calibrated using Viking lander pressure data, cap edge functions determined by thermal emission spectroscopy, and other nuclear spectroscopy data sets. On the basis of the amount of CO2 cycled through the caps during years 26 and 27, the gross polar energy balance has not changed significantly since Viking. The distribution of seasonal CO2 ice is longitudinally asymmetric: in the north, deposition rates of CO2 ice are elevated in Acidalia, which is exposed to katabatic winds from Chasma Borealis; in the south, CO2 deposition is highest near the residual cap. During southern recession, CO 2 ice is present longer than calculated by the GCM, which has implications for the local polar energy balance. Copyright 2009 by the American Geophysical Union.

  4. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps.

    PubMed

    Noël, B; van de Berg, W J; Lhermitte, S; Wouters, B; Machguth, H; Howat, I; Citterio, M; Moholdt, G; Lenaerts, J T M; van den Broeke, M R

    2017-03-31

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36±16 Gt -1 , or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.

  5. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps

    PubMed Central

    Noël, B.; van de Berg, W. J; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.

    2017-01-01

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36±16 Gt−1, or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming. PMID:28361871

  6. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Noël, B.; van de Berg, W. J.; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.

    2017-03-01

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (+/-5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36+/-16 Gt-1, or ~14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.

  7. Ice thickness measurements and volume estimates for glaciers in Norway

    NASA Astrophysics Data System (ADS)

    Andreassen, Liss M.; Huss, Matthias; Melvold, Kjetil; Elvehøy, Hallgeir; Winsvold, Solveig H.

    2014-05-01

    Whereas glacier areas in many mountain regions around the world now are well surveyed using optical satellite sensors and available in digital inventories, measurements of ice thickness are sparse in comparison and a global dataset does not exist. Since the 1980s ice thickness measurements have been carried out by ground penetrating radar on many glaciers in Norway, often as part of contract work for hydropower companies with the aim to calculate hydrological divides of ice caps. Measurements have been conducted on numerous glaciers, covering the largest ice caps as well as a few smaller mountain glaciers. However, so far no ice volume estimate for Norway has been derived from these measurements. Here, we give an overview of ice thickness measurements in Norway, and use a distributed model to interpolate and extrapolate the data to provide an ice volume estimate of all glaciers in Norway. We also compare the results to various volume-area/thickness-scaling approaches using values from the literature as well as scaling constants we obtained from ice thickness measurements in Norway. Glacier outlines from a Landsat-derived inventory from 1999-2006 together with a national digital elevation model were used as input data for the ice volume calculations. The inventory covers all glaciers in mainland Norway and consists of 2534 glaciers (3143 glacier units) covering an area of 2692 km2 ± 81 km2. To calculate the ice thickness distribution of glaciers in Norway we used a distributed model which estimates surface mass balance distribution, calculates the volumetric balance flux and converts it into thickness using the flow law for ice. We calibrated this model with ice thickness data for Norway, mainly by adjusting the mass balance gradient. Model results generally agree well with the measured values, however, larger deviations were found for some glaciers. The total ice volume of Norway was estimated to be 275 km3 ± 30 km3. From the ice thickness data set we selected

  8. Molecular Markers in the Quelccaya Ice Cap, Peru Describe 20th Century Biomass Burning Variability

    NASA Astrophysics Data System (ADS)

    Makou, M. C.; Thompson, L. G.; Eglinton, T. I.; Montluçon, D. B.

    2007-12-01

    Organic geochemical analytical methods were applied to Andean ice core samples, resulting in a multi- molecular biomass burning record spanning 1915 to 2001 AD. The Quelccaya Ice Cap in Peru is situated on the eastern flank of the Andes at 14°S and is well situated to receive aeolian inputs of organic matter derived from Amazonian forest fire events. Compounds of interest, which occur in trace quantities in ice, were recovered by stir bar sorptive extraction and analyzed by gas chromatography/time-of-flight mass spectrometry coupled with thermal desorption. These methods permitted identification and quantitation of numerous biomarkers in sample volumes of as little as 10 ml. At least one wet and dry season sample was analyzed for every year. Observed biomarkers that may be derived from vegetation fires include several polycyclic aromatic hydrocarbons (PAHs), atraric acid, 2-ethylhexyl p-methoxycinnamate, and a range of other aromatic compounds. Abrupt changes in compound abundances were superimposed on decadal variability. Systematic offsets between wet and dry season abundances were not observed, suggesting that the biomass burning signal is not biased by seasonal depositional effects, such as dust delivery. Inputs likely reflect a combination of sources from anthropogenic burning of the Amazon rainforest as well as natural fires related to aridity, and include both high and low elevation vegetation. These compounds and techniques can be applied to older ice in this and other core locations as an independent estimate of aridity.

  9. Ice-atmosphere interactions in the Canadian High Arctic: Implications for the thermo-mechanical evolution of terrestrial ice masses

    NASA Astrophysics Data System (ADS)

    Wohlleben, Trudy M. H.

    Canadian High Arctic terrestrial ice masses and the polar atmosphere evolve codependently, and interactions between the two systems can lead to feedbacks, positive and negative. The two primary positive cryosphere-atmosphere feedbacks are: (1) The snow/ice-albedo feedback (where area changes in snow and/or ice cause changes in surface albedo and surface air temperatures, leading to further area changes in snow/ice); and (2) The elevation - mass balance feedback (where thickness changes in terrestrial ice masses cause changes to atmospheric circulation and precipitation patterns, leading to further ice thickness changes). In this thesis, numerical experiments are performed to: (1) quantify the magnitudes of the two feedbacks for chosen Canadian High Arctic terrestrial ice masses; and (2) to examine the direct and indirect consequences of surface air temperature changes upon englacial temperatures with implications for ice flow, mass flux divergence, and topographic evolution. Model results show that: (a) for John Evans Glacier, Ellesmere Island, the magnitude of the terrestrial snow/ice-albedo feedback can locally exceed that of sea ice on less than decadal timescales, with implications for glacier response times to climate perturbations; (b) although historical air temperature changes might be the direct cause of measured englacial temperature anomalies in various glacier and ice cap accumulation zones, they can also be the indirect cause of their enhanced diffusive loss; (c) while the direct result of past air temperature changes has been to cool the interior of John Evans Glacier, and its bed, the indirect result has been to create and maintain warm (pressure melting point) basal temperatures in the ablation zone; and (d) for Devon Ice Cap, observed mass gains in the northwest sector of the ice cap would be smaller without orographic precipitation and the mass balance---elevation feedback, supporting the hypothesis that this feedback is playing a role in the

  10. An East Siberian ice shelf during the Late Pleistocene glaciations: Numerical reconstructions

    NASA Astrophysics Data System (ADS)

    Colleoni, Florence; Kirchner, Nina; Niessen, Frank; Quiquet, Aurélien; Liakka, Johan

    2016-09-01

    A recent data campaign in the East Siberian Sea has revealed evidence of grounded and floating ice dynamics in regions of up to 1000 m water depth, and which are attributed to glaciations older than the Last Glacial Maximum (21 kyrs BP). The main hypothesis based on this evidence is that a small ice cap developed over Beringia and expanded over the East Siberian continental margin during some of the Late Pleistocene glaciations. Other similar evidence of ice dynamics that have been previously collected on the shallow continental shelves of the Arctic Ocean have been attributed to the penultimate glaciation, i.e. Marine Isotopes Stage 6 (≈140 kyrs BP). We use an ice sheet model, forced by two previously simulated MIS 6 glacial maximum climates, to carry out a series of sensitivity experiments testing the impact of dynamics and mass-balance related parameters on the geometry of the East Siberian ice cap and ice shelf. Results show that the ice cap developing over Beringia connects to the Eurasian ice sheet in all simulations and that its volume ranges between 6 and 14 m SLE, depending on the climate forcing. This ice cap generates an ice shelf of dimensions comparable with or larger than the present-day Ross ice shelf in West Antarctica. Although the ice shelf extent strongly depends on the ice flux through the grounding line, it is particularly sensitive to the choice of the calving and basal melting parameters. Finally, inhibiting a merging of the Beringia ice cap with the Eurasian ice sheet affects the expansion of the ice shelf only in the simulations where the ice cap fluxes are not large enough to compensate for the fluxes coming from the Eurasian ice sheet.

  11. Quantifying the mass loss of peripheral Greenland glaciers and ice caps (1958-2014).

    NASA Astrophysics Data System (ADS)

    Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; van den Broeke, Michiel

    2016-04-01

    Since the 2000s, mass loss from Greenland peripheral glaciers and ice caps (GICs) has accelerated, becoming an important contributor to sea level rise. Under continued warming throughout the 21st century, GICs might yield up to 7.5 to 11 mm sea level rise, with increasing dominance of surface runoff at the expense of ice discharge. However, despite multiple observation campaigns, little remains known about the contribution of GICs to total Greenland mass loss. Furthermore, the relatively coarse resolutions in regional climate models, i.e. 5 km to 20 km, fail to represent the small scale patterns of surface mass balance (SMB) components over these topographically complex regions including also narrow valley glaciers. Here, we present a novel approach to quantify the contribution of GICs to surface melt and runoff, based on an elevation dependent downscaling method. GICs daily SMB components at 1 km resolution are obtained by statistically downscaling the outputs of RACMO2.3 at 11 km resolution to a down-sampled version of the GIMP DEM for the period 1958-2014. This method has recently been successfully validated over the Greenland ice sheet and is now applied to GICs. In this study, we first evaluate the 1 km daily downscaled GICs SMB against a newly available and comprehensive dataset of ablation stake measurements. Then, we investigate present-day trends of meltwater production and SMB for different regions and estimate GICs contribution to total Greenland mass loss. These data are considered valuable for model evaluation and prediction of future sea level rise.

  12. Martian North Polar Water-Ice Clouds During the Viking Era

    NASA Technical Reports Server (NTRS)

    Tamppari, L. K.; Bass, D. S.

    2000-01-01

    The Viking Orbiters determined that the surface of Mars' northern residual cap consists of water ice. Observed atmospheric water vapor abundances in the equatorial regions have been related to seasonal exchange between reservoirs such as the polar caps, the regolith and between different phases in the atmosphere. Kahn modeled the physical characteristics of ice hazes seen in Viking Orbiter imaging limb data, hypothesizing that ice hazes provide a method for scavenging water vapor from the atmosphere and accumulating it into ice particles. Given that Jakosky found that these particles had sizes such that fallout times were of order one Martian sol, these water-ice hazes provided a method for returning more water to the regolith than that provided by adsorption alone. These hazes could also explain the rapid hemispheric decrease in atmospheric water in late northern summer as well as the increase during the following early spring. A similar comparison of water vapor abundance versus polar cap brightness has been done for the north polar region. They have shown that water vapor decreases steadily between L(sub s) = 100-150 deg while polar cap albedo increases during the same time frame. As a result, they suggested that late summer water-ice deposition onto the ice cap may be the cause of the cap brightening. This deposition could be due to adsorption directly onto the cap surface or to snowfall. Thus, an examination of north polar waterice clouds could lend insight into the fate of the water vapor during this time period. Additional information is contained in the original extended abstract.

  13. Basal friction evolution and crevasse distribution during the surge of Basin 3, Austfonna ice-cap - offline coupling between a continuum ice dynamic model and a discrete element model

    NASA Astrophysics Data System (ADS)

    Gong, Yongmei; Zwinger, Thomas; Åström, Jan; Gladstone, Rupert; Schellenberger, Thomas; Altena, Bas; Moore, John

    2017-04-01

    The outlet glacier at Basin 3, Austfonna ice-cap entered its active surge phase in autumn 2012. We assess the evolution of the basal friction during the surge through inverse modelling of basal friction coefficients using recent velocity observation from 2012 to 2014 in a continuum ice dynamic model Elmer/ice. The obtained basal friction coefficient distributions at different time instances are further used as a boundary condition in a discrete element model (HiDEM) that is capable of computing fracturing of ice. The inverted basal friction coefficient evolution shows a gradual 'unplugging' of the stagnant frontal area and northwards and inland expansion of the fast flowing region in the southern basin. The validation between the modeled crevasses distribution and the satellite observation in August 2013 shows a good agreement in shear zones inland and at the frontal area. Crevasse distributions of the summer before and after the glacier reached its maximum velocity in January 2013 (August 2012 and August 2014, respectively) are also evaluated. Previous studies suggest the triggering and development of the surge are linked to surface melt water penetrating through ice to form an efficient basal hydrology system thereby triggering a hydro- thermodynamic feedback. This preliminary offline coupling between a continuum ice dynamic model and a discrete element model will give a hint on future model development of linking supra-glacial to sub-glacial hydrology system.

  14. Lake Sediment Records as an Indicator of Holocene Fluctuations of Quelccaya Ice Cap, Peru and Regional Climate

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Beal, S. A.; Smith, C. A.; Baranes, H. E.

    2012-12-01

    The past fluctuations of Quelccaya Ice Cap, (QIC; 13°S, 70°W, 5200 m asl) located in the southeastern Peruvian Andes, provide a record of tropical climate since the last glacial-interglacial transition. A detailed surficial geomorphic record of past glacial extents developed over the last several decades (e.g. Mercer and Palacios 1977; Buffen et al. 2009; Kelly et al. 2012 accepted) demonstrates that QIC is a dynamic glacial system. These records show that the ice cap was larger than present and retreating by ~11,500 yr BP, and smaller than present between ~7,000 and ~4,600 yr BP. The most recent advance occurred during the late Holocene (Little Ice Age;LIA), dated with 10Be surface exposure ages (510±90 yrs (n = 8)) (Stroup et al. in prep.). This overrode earlier deposits obscuring a complete Holocene record; we aim to address the gaps in glacial chronology using the sedimentary record archived in lakes. We retrieved two sets cores (8 and 5 m-long) from Laguna Challpacocha (13.91°S, 70.86°W, 5040 m asl), a lake that currently receives meltwater from QIC. Four radiocarbon ages from the cores suggest a continuous record dating to at least ~10,500 cal. yr BP. Variations in magnetic susceptibility, percent organic and inorganic carbon, bulk density, grayscale and X-ray fluorescence chemistry indicate changes in the amount of clastic sediment deposition. We interpret clastic sediments to have been deposited from ice cap meltwater, thus indicating more extensive ice. Clastic sediments compose the top of the core from 4 to 30 cm depth, below there is a sharp transition to organic sediments radiocarbon dated to (500±30 and 550±20 cal. yr BP). The radiocarbon ages are similar to the 10Be dated (LIA) glacial position. At least three other clastic units exist in the core; dating to ~2600-4300, ~4800-7300 and older then ~10,500 cal. yr BP based on a linear age model with four radiocarbon dates. We obtained two, ~4 m long, cores from Laguna Yanacocha (13.95°S,70.87

  15. Ice Core Records of Recent Northwest Greenland Climate

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  16. Investigating Mars South Residual CO2 Cap with a Global Climate Model

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.; Dequaire, J.; Hollingsworth, J. L.; Haberle, R. M.

    2016-01-01

    The CO2 cycle is one of the three controlling climate cycles on Mars. One aspect of the CO2 cycle that is not yet fully understood is the existence of a residual CO2 ice cap that is offset from the south pole. Previous investigations suggest that the atmosphere may control the placement of the south residual cap (e.g., Colaprete et al., 2005). These investigations show that topographically forced stationary eddies in the south during southern hemisphere winter produce colder atmospheric temperatures and increased CO2 snowfall over the hemisphere where the residual cap resides. Since precipitated CO2 ice produces higher surface albedos than directly deposited CO2 ice, it is plausible that CO2 snowfall resulting from the zonally asymmetric atmospheric circulation produces surface ice albedos high enough to maintain a residual cap only in one hemisphere. The goal of the current work is to further evaluate Colaprete et al.'s hypothesis by investigating model-predicted seasonally varying snowfall patterns in the southern polar region and the atmospheric circulation components that control them.

  17. Summer South Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    13 April 2004 The martian south polar residual ice cap is composed mainly of frozen carbon dioxide. Each summer, a little bit of this carbon dioxide sublimes away. Pits grow larger, and mesas get smaller, as this process continues from year to year. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of a small portion of the south polar cap as it appeared in mid-summer in January 2004. The dark areas may be places where the frozen carbon dioxide contains impurities, such as dust, or places where sublimation of ice has roughened the surface so that it appears darker because of small shadows cast by irregularities in the roughened surface. The image is located near 86.9oS, 7.6oW. The image covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.

  18. Ice core evidence for extensive melting of the greenland ice sheet in the last interglacial.

    PubMed

    Koerner, R M

    1989-05-26

    Evidence from ice at the bottom of ice cores from the Canadian Arctic Islands and Camp Century and Dye-3 in Greenland suggests that the Greenland ice sheet melted extensively or completely during the last interglacial period more than 100 ka (thousand years ago), in contrast to earlier interpretations. The presence of dirt particles in the basal ice has previously been thought to indicate that the base of the ice sheets had melted and that the evidence for the time of original growth of these ice masses had been destroyed. However, the particles most likely blew onto the ice when the dimensions of the ice caps and ice sheets were much smaller. Ice texture, gas content, and other evidence also suggest that the basal ice at each drill site is superimposed ice, a type of ice typical of the early growth stages of an ice cap or ice sheet. If the present-day ice masses began their growth during the last interglacial, the ice sheet from the earlier (Illinoian) glacial period must have competely or largely melted during the early part of the same interglacial period. If such melting did occur, the 6-meter higher-than-present sea level during the Sangamon cannot be attributed to disintegration of the West Antarctic ice sheet, as has been suggested.

  19. Microbial communities in the subglacial waters of the Vatnajökull ice cap, Iceland

    PubMed Central

    Thór Marteinsson, Viggó; Rúnarsson, Árni; Stefánsson, Andri; Thorsteinsson, Thorsteinn; Jóhannesson, Tómas; Magnússon, Sveinn H; Reynisson, Eyjólfur; Einarsson, Bergur; Wade, Nicole; Morrison, Hilary G; Gaidos, Eric

    2013-01-01

    Subglacial lakes beneath the Vatnajökull ice cap in Iceland host endemic communities of microorganisms adapted to cold, dark and nutrient-poor waters, but the mechanisms by which these microbes disseminate under the ice and colonize these lakes are unknown. We present new data on this subglacial microbiome generated from samples of two subglacial lakes, a subglacial flood and a lake that was formerly subglacial but now partly exposed to the atmosphere. These data include parallel 16S rRNA gene amplicon libraries constructed using novel primers that span the v3–v5 and v4–v6 hypervariable regions. Archaea were not detected in either subglacial lake, and the communities are dominated by only five bacterial taxa. Our paired libraries are highly concordant for the most abundant taxa, but estimates of diversity (abundance-based coverage estimator) in the v4–v6 libraries are 3–8 times higher than in corresponding v3–v5 libraries. The dominant taxa are closely related to cultivated anaerobes and microaerobes, and may occupy unique metabolic niches in a chemoautolithotrophic ecosystem. The populations of the major taxa in the subglacial lakes are indistinguishable (>99% sequence identity), despite separation by 6 km and an ice divide; one taxon is ubiquitous in our Vatnajökull samples. We propose that the glacial bed is connected through an aquifer in the underlying permeable basalt, and these subglacial lakes are colonized from a deeper, subterranean microbiome. PMID:22975882

  20. Ice cap melting and low viscosity crustal root explain narrow geodetic uplift of the Western Alps

    NASA Astrophysics Data System (ADS)

    Chery, Jean; Genti, Manon; Vernant, Philippe

    2016-04-01

    More than 10 years of geodetic measurements demonstrate an uplift rate of 1-3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Three uplift mechanisms have been proposed so far: (1) the isostatic response to denudation. However this process is responsible for only a fraction of the observed uplift and (2) the rebound induced by the Wurmian ice cap melting. This process leads to a broader uplifting region than the one evidenced by geodetic observations. (3) a deep source motion associated with slab motion or some deep isostatic unbalance. Using a numerical model accounting for crustal and mantle rheology of the Alps and its foreland, we model the response to Wurmian ice cap melting. We show that a crustal viscosity contrast between the foreland and the central part of the Alps, the later being weaker with a viscosity of 1021 Pa.s, is needed to produce a narrow uplift. The vertical rates are enhanced if the strong uppermost mantle beneath the Moho is interrupted across the Alps, therefore allowing a weak vertical rheological anomaly thanks to the continuity between the low viscosity parts of the crust and mantle. References: Champagnac, J.-D., F. Schlunegger, K. Norton, F. von Blanckenburg, L. M. Abbühl, and M. Schwab (2009), Erosion-driven uplift of the modern Central Alps, Tectonophysics, 474(1-2), 236-249. Vernant, P., F. Hivert, J. Chéry, P. Steer, R. Cattin, and A. Rigo (2013), Erosion-induced isostatic rebound triggers extension in low convergent mountain ranges, geology, 41(4), 467-470.

  1. Glacial Boundary Features Delineated Using Enhanced-resolution Passive-microwave Data to Determine Melt Season Variation of the Vatnajokull Ice Cap, Iceland

    NASA Astrophysics Data System (ADS)

    Marzillier, D. M.; Ramage, J. M.

    2017-12-01

    Temperate glaciers such as those seen in Iceland experience high annual mass flux, thereby responding to small scale changes in Earth's climate. Decadal changes in the glacial margins of Iceland's ice caps are observable in the Landsat record, however twice daily AMSR-E Calibrated Enhanced-Resolution Passive Microwave Daily EASE-Grid 2.0 Brightness Temperature (CETB) Earth System Data Record (ESDR) allow for observation on a daily temporal scale and a 3.125 km spatial scale, which can in turn be connected to patterns seen over longer periods of time. Passive microwave data allow for careful observation of melt onset and duration in Iceland's glacial regions by recording changes in emissivity of the ice surface, known as brightness temperature (TB), which is sensitive to fluctuations in the liquid water content of snow and ice seen during melting in glaciated regions. Enhanced resolution of this data set allows for a determination of a threshold that defines the melting season. The XPGR snowmelt algorithm originally presented by Abdalati and Steffen (1995) is used as a comparison with the diurnal amplitude variation (DAV) values on Iceland's Vatnajokull ice cap located at 64.4N, -16.8W. Ground-based air temperature data in this region, digital elevation models (DEMs), and river discharge dominated by glacial runoff are used to confirm the glacial response to changes in global climate. Results show that Iceland glaciers have a bimodal distribution of brightness temperature delineating when the snow/ice is melting and refreezing. Ground based temperatures have increased on a decadal trend. Clear glacial boundaries are visible on the passive microwave delineating strong features, and we are working to understand their variability and contribution to glacier evolution. The passive microwave data set allows connections to be made between observations seen on a daily scale and the long term glacier changes observed by the Landsat satellite record that integrates the

  2. Spatial variability in the seasonal south polar CAP of Mars

    NASA Astrophysics Data System (ADS)

    Calvin, Wendy M.; Martin, Terry Z.

    1994-10-01

    The first comprehensive discussion of the south seasonal polar cap spectra obtained by the Mariner 7 infrared spectrometer in the short-wavelength region (2-4 microns) is presented. The infrared spectra is correlated with images acquired by the wide-angle camera. Significant spectral variation is noted in the cap interior and regions of varying water frost abundance, CO2 ice/frost cover, and CO2-ice path length can be distinguished. Many of these spectral variations correlate with heterogeneity noted in the camera images, but certain significant infrared spectral variations are not discernible in the visible. Simple reflectance models are used to classify the observed spectral variations into four regions. Region I is at the cap edge, where there is enhanced absorption beyond 3 microns inferred to be caused by an increased abundance of water frost. The increase in water abundance over that in the interior is on the level of a few parts per thousand or less. Region II is the typical cap interior characterized by spectral features of CO2 ice at grain sizes of several millimeters to centimeters. These spectra also indicate the presence of water frost at the parts per thousand level. A third, unusual region (III), is defined by three spectra in which weak CO2 absorption features are as much as twice as strong as in the average cap spectra and are assumed to be caused by an increased path length in the CO2. Such large paths are inconsistent with the high reflectance in the visible and at 2.2 microns and suggest layered structures or deposition conditions that are not accounted for in current reflectance models. The final region (IV) is an area of thinning frost coverage or transparent ice well in the interior of the seasonal cap. These spectra are a combination of CO2 and ground signatures.

  3. Spatial variability in the seasonal south polar cap of Mars

    NASA Technical Reports Server (NTRS)

    Calvin, Wendy M.; Martin, Terry Z.

    1994-01-01

    The first comprehensive discussion of the south seasonal polar cap spectra obtained by the Mariner 7 infrared spectrometer in the short-wavelength region (2-4 microns) is presented. The infrared spectra is correlated with images acquired by the wide-angle camera. Significant spectral variation is noted in the cap interior and regions of varying water frost abundance, CO2 ice/frost cover, and CO2-ice path length can be distinguished. Many of these spectral variations correlate with heterogeneity noted in the camera images, but certain significant infrared spectral variations are not discernible in the visible. Simple reflectance models are used to classify the observed spectral variations into four regions. Region I is at the cap edge, where there is enhanced absorption beyond 3 microns inferred to be caused by an increased abundance of water frost. The increase in water abundance over that in the interior is on the level of a few parts per thousand or less. Region II is the typical cap interior characterized by spectral features of CO2 ice at grain sizes of several millimeters to centimeters. These spectra also indicate the presence of water frost at the parts per thousand level. A third, unusual region (III), is defined by three spectra in which weak CO2 absorption features are as much as twice as strong as in the average cap spectra and are assumed to be caused by an increased path length in the CO2. Such large paths are inconsistent with the high reflectance in the visible and at 2.2 microns and suggest layered structures or deposition conditions that are not accounted for in current reflectance models. The final region (IV) is an area of thinning frost coverage or transparent ice well in the interior of the seasonal cap. These spectra are a combination of CO2 and ground signatures.

  4. Variability of Seasonal CO2 Ice Caps on Mars for Mars Years 26 through 29

    NASA Astrophysics Data System (ADS)

    Feldman, W. C.; Maurice, S.; Prettyman, T. H.

    2011-12-01

    We have developed an improved thermal, epithermal, and fast neutron counting-rate time series data of the Mars Odyssey Neutron Spectrometer (MONS), optimized to greatly reduce both statistical and systematic uncertainties. This new data set was applied to study temporal and spatial distributions of the growth, decay, and maximum amount of precipitated CO2 ice during Martian years (MY) 26, 27, 28, and 29. For this study, we concentrate on the epithermal counting rate detected using the down-looking prism (P1) of MONS, and a combination of the epithermal and thermal counting rate detected by the forward-looking sensor (P2) of MONS. Although the energy range of neutrons detected by P2 covers both the thermal and epithermal range, it is heavily weighted to the thermal range. We find that the variance of the maximum epithermal counting rate is remarkably small over both north and south seasonal caps, varying by less than 3% over the four-year period. In contrast, although the maximum P2 counting rate over both poles is sensibly the same within error bars (about 2%) during the first three years, it drops by 18% over the north pole and 8% over the south pole during MY 29. The most-likely explanation of this drop is that abundances of the non-condensable gases N2 and Ar, are unusually enhanced during MY 29. Movies were also made of maps of the growth and decay of P2 counting rates summed over the first three years of these data. Careful inspection shows that both the growth and decay in the north were cylindrically symmetric, centered near the geographic north pole. In contrast, both the growth and decay of CO2 buildup in the south were skewed off the geographic pole to the center of the CO2 residual cap, and contained a small, but definitely distinct ring-like annular enhancement centered at a latitude of about 83.5° S spread over a longitude range that extends between about -35° and +35° E. This arc runs parallel to, and overlays, the very steep drop in altitude from

  5. Perchlorate Found by Phoenix Could Provide a Mobile Brine Sludge at the Bed of Mars Northern Ice Cap that Would Allow Flow with Very Low Basal Temperatures: Possible Mechanism for Water Table Re-Charge

    NASA Astrophysics Data System (ADS)

    Fisher, D. A.; Hecht, M.; Kounaves, S.; Catling, D.

    2009-03-01

    The north cap of Mars has basal temperature that precludes the flow of ice. Phoenix discovered polar soils contain perchlorate salts. These salts depress the melting point so it could form a sludge that provides a mobile bed that moves the ice outwards.

  6. Exposure of Water Ice in the Northern Mid-lattitudes of Mars

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.; Kanner, Lisa C.

    2007-01-01

    Water ice is exposed in the martian north polar cap, and is occasionally exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60 deg. We have examined midlatitude areas of the northern plains displaying evidence of residual ice-rich layers, and report possible present-day exposures of ice. These exposures, if confirmed, could constrain the latitudinal and temporal stability of surface ice on Mars.

  7. Evolving Technologies for In-Situ Studies of Mars Ice

    NASA Technical Reports Server (NTRS)

    Carsey, F. D.; Hecht, M. H.

    2003-01-01

    Icy sites on Mars continue to be of high scientific importance. These sites include the polar caps, the southern mid-latitude subsurface permafrost, and the seasonal frost. These sites have interest due to their roles in climate processes, past climates, surface and near-surface water, astrobiology, geomorphology, and other topics. As is the case for many planetary features, remote sensing, while of great value, cannot answer all questions; in-situ examination is essential, and the motivation for in-situ observations generally leads to the subsurface, which, fortunately, is accessible on Mars. It is clear in fact that a Mars polar cap subsurface mission is both scientifically compelling and practical. Recent data from orbiting platforms has provided a remarkable level of information about the Mars ice caps; we know, for example, the size, shape and annual cycle of the cap topography as well as we know that of Earth, and we have more information on stratification that we have of, for example, the ice of East Antarctica. To understand the roles that the Mars polar caps play, it is necessary to gather information on the ice cap surface, strata, composition and bed. In this talk the status of in-situ operations and observations will be summarized, and, since we have conveniently at hand another planet with polar caps, permafrost and ice, the role of testing and validation of experimental procedures on Earth will be addressed.

  8. Inception of the Laurentide Ice Sheet using asynchronous coupling of a regional atmospheric model and an ice model

    NASA Astrophysics Data System (ADS)

    Birch, L.; Cronin, T.; Tziperman, E.

    2017-12-01

    The climate over the past 0.8 million years has been dominated by ice ages. Ice sheets have grown about every 100 kyrs, starting from warm interglacials, until they spanned continents. State-of-the-art global climate models (GCMs) have difficulty simulating glacial inception, or the transition of Earth's climate from an interglacial to a glacial state. It has been suggested that this failure may be related to their poorly resolved local mountain topography, due to their coarse spatial resolution. We examine this idea as well as the possible role of ice flow dynamics missing in GCMs. We investigate the growth of the Laurentide Ice Sheet at 115 kya by focusing on the mountain glaciers of Canada's Baffin Island, where geologic evidence indicates the last inception occurred. We use the Weather Research and Forecasting model (WRF) in a regional, cloud-resolving configuration with resolved mountain terrain to explore how quickly Baffin Island could become glaciated with the favorable yet realizable conditions of 115 kya insolation, cool summers, and wet winters. Using the model-derived mountain glacier mass balance, we force an ice sheet model based on the shallow-ice approximation, capturing the ice flow that may be critical to the spread of ice sheets away from mountain ice caps. The ice sheet model calculates the surface area newly covered by ice and the change in the ice surface elevation, which we then use to run WRF again. Through this type of iterated asynchronous coupling, we investigate how the regional climate responds to both larger areas of ice cover and changes in ice surface elevation. In addition, we use the NOAH-MP Land model to characterize the importance of land processes, like refreezing. We find that initial ice growth on the Penny Ice Cap causes regional cooling that increases the accumulation on the Barnes Ice Cap. We investigate how ice and topography changes on Baffin Island may impact both the regional climate and the large-scale circulation.

  9. Integrated firn elevation change model for glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Saß, Björn; Sauter, Tobias; Braun, Matthias

    2016-04-01

    We present the development of a firn compaction model in order to improve the volume to mass conversion of geodetic glacier mass balance measurements. The model is applied on the Arctic ice cap Vestfonna. Vestfonna is located on the island Nordaustlandet in the north east of Svalbard. Vestfonna covers about 2400 km² and has a dome like shape with well-defined outlet glaciers. Elevation and volume changes measured by e.g. satellite techniques are becoming more and more popular. They are carried out over observation periods of variable length and often covering different meteorological and snow hydrological regimes. The elevation change measurements compose of various components including dynamic adjustments, firn compaction and mass loss by downwasting. Currently, geodetic glacier mass balances are frequently converted from elevation change measurements using a constant conversion factor of 850 kg m-³ or the density of ice (917 kg m-³) for entire glacier basins. However, the natural conditions are rarely that static. Other studies used constant densities for the ablation (900 kg m-³) and accumulation (600 kg m-³) areas, whereby density variations with varying meteorological and climate conditions are not considered. Hence, each approach bears additional uncertainties from the volume to mass conversion that are strongly affected by the type and timing of the repeat measurements. We link and adapt existing models of surface energy balance, accumulation and snow and firn processes in order to improve the volume to mass conversion by considering the firn compaction component. Energy exchange at the surface is computed by a surface energy balance approach and driven by meteorological variables like incoming short-wave radiation, air temperature, relative humidity, air pressure, wind speed, all-phase precipitation, and cloud cover fraction. Snow and firn processes are addressed by a coupled subsurface model, implemented with a non-equidistant layer discretisation. On

  10. A comparison of Holocene fluctuations of the eastern and western margins of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Levy, L.; Kelly, M. A.; Lowell, T. V.; Hall, B. L.; Applegate, P. J.; Howley, J.; Axford, Y.

    2013-12-01

    Determining how the Greenland Ice Sheet (GrIS) responded to past temperature fluctuations is important for assessing its future stability in a changing climate. We present a record of the Holocene extents of the western GrIS margin near Kangerlussuaq (67.0°N, 50.7°W) and compare this with the past fluctuations of Bregne ice cap (71°N, 25.6° W), a small ice cap in the Scoresby Sund region 90 km from the eastern GrIS margin, to examine the mechanisms that influenced past ice margin fluctuations. The past extents of the Bregne ice cap are a proxy for the climatic conditions that influenced the nearby GrIS margin. We used glacial geomorphic mapping, 10Be dating of boulders and bedrock, and sediment cores from proglacial and non-glacial lakes. In western Greenland, 10Be ages on the Keglen moraines, 13 km west of the current GrIS margin and the Ørkendalen moraines, ≤2 km west of the current ice margin date to 7.3 × 0.1 ka (n=6) and 6.8 × 0.3 ka (n=9), respectively. Fresh moraines, ≤50 m from the current ice margin date to AD 1830-1950 and are likely associated with advances during the Little Ice Age (LIA). In some areas, the LIA moraines lie stratigraphically above the Ørkendalen moraines, indicating the GrIS was inboard of the Ørkendalen limit from 6.8 ka to the 20th century. In eastern Greenland, 10Be ages show that Bregne ice cap retreated within its late Holocene limit by 10.7 ka. A lack of clastic sediment in a proglacial lake suggests the ice cap was smaller or completely absent from ~10-2.6 ka. A snowline analysis indicates that temperatures ~0.5°C warmer than present would render the entire ice cap into an ablation zone. Glacial silts in the proglacial lake at ~2.6 and ~1.9 cal kyr BP to present indicate advances of Bregne ice cap. Fresh moraines ≤200 m of Bregne ice cap were deposited ≤2.6 cal kyr BP and mark the largest advance of the Holocene. Both the western GrIS margin and Bregne ice cap were influenced by Northern Hemisphere summer

  11. Atmospheric depositions of natural and anthropogenic trace elements on the Guliya ice cap (northwestern Tibetan Plateau) during the last 340 years

    NASA Astrophysics Data System (ADS)

    Sierra-Hernández, M. Roxana; Gabrielli, Paolo; Beaudon, Emilie; Wegner, Anna; Thompson, Lonnie G.

    2018-03-01

    A continuous record of 29 trace elements (TEs) has been constructed between 1650 and 1991 CE (Common Era) from an ice core retrieved in 1992 from the Guliya ice cap, on the northwestern Tibetan Plateau. Enrichments of Pb, Cd, Zn and Sb were detected during the second half of the 19th century and the first half of the 20th century (∼1850-1950) while enrichments of Sn (1965-1991), Cd and Pb (1975-1991) were detected during the second half of the 20th century. The EFs increased significantly by 20% for Cd and Sb, and by 10% for Pb and Zn during 1850-1950 relative to the pre-1850s. Comparisons of the Guliya TEs data with other ice core-derived and production/consumption data suggest that Northern Hemisphere coal combustion (primarily in Western Europe) is the likely source of Pb, Cd, Zn, and Sb during the 1850-1950 period. Coal combustion in Europe declined as oil replaced coal as the primary energy source. The European shift from coal to oil may have contributed to the observed Sn enrichment in ∼1965 (60% EF increase in 1975-1991), although regional fossil fuel combustion (coal and leaded gasoline) from western China, Central Asia, and South Asia (India, Nepal), as well as Sn mining/smelting in Central Asia, may also be possible sources. The post-1975 Cd and Pb enrichments (40% and 20% EF increase respectively in 1975-1991) may reflect emissions from phosphate fertilizers, fossil fuel combustion, and/or non-ferrous metal production, from western China, Central Asia, and/or South Asia. Leaded gasoline is likely to have also contributed to the post-1975 Pb enrichment observed in this record. The results strongly suggest that the Guliya ice cap has recorded long-distance emissions from coal combustion since the 1850s with more recent contributions from regional agriculture, mining, and/or fossil fuel combustion. This new Guliya ice core record of TEs fills a geographical gap in the reconstruction of the pollution history of this region that extends well beyond modern

  12. Mars polar cap: a habitat for elementary life1

    NASA Astrophysics Data System (ADS)

    Wallis, M. K.; Wickramasinghe, N. C.

    2009-04-01

    Ices in the Martian polar caps are potential habitats for various species of microorganisms. Salts in the ice and biological anti-freeze polymers maintain liquid in cracks in the ices far below 0°C, possibly down to the mean 220-240 K. Sub-surface microbial life is shielded from ultraviolet (UV) radiation, but could potentially be activated on south-facing slopes under the midday, midsummer Sun. Such life would be limited by low levels of vapour, little transport of nutrients, low light levels below a protective dirt-crust, frost accumulation at night and in shadows, and little if any active translocation of organisms. As in the Antarctic and in permafrost, movement to new habitats depends on geo-climatic changes, which for Mars's north polar cap occur on a 50 000 year scale, except for rare meteorite impacts.

  13. The Mars water cycle at other epochs - Recent history of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1993-01-01

    A numerical model is presented of the integrated role of seasonal water cycle on the evolution of polar deposits on Mars over the last 10 million years. From the model, it is concluded that the only major difference between the polar caps which affects their long-term behavior is ultimately the difference in their elevations. Because of that difference, there is a preference for CO2 frost to stay longer on the northern polar cap. The average difference in sublimation at the caps results in a net south-to-north transport of water ice over long time scales. Superimposed on any long-term behavior is a transfer of water ice between the caps on the 10 exp 5 - 10 exp 6 yr time scales. The amount of water exchanged is small compared to the total ice content of the polar deposits.

  14. The Mars water cycle at other epochs - Recent history of the polar caps and layered terrain

    NASA Astrophysics Data System (ADS)

    Jakosky, B. M.; Henderson, B. G.; Mellon, M. T.

    1993-04-01

    A numerical model is presented of the integrated role of seasonal water cycle on the evolution of polar deposits on Mars over the last 10 million years. From the model, it is concluded that the only major difference between the polar caps which affects their long-term behavior is ultimately the difference in their elevations. Because of that difference, there is a preference for CO2 frost to stay longer on the northern polar cap. The average difference in sublimation at the caps results in a net south-to-north transport of water ice over long time scales. Superimposed on any long-term behavior is a transfer of water ice between the caps on the 10 exp 5 - 10 exp 6 yr time scales. The amount of water exchanged is small compared to the total ice content of the polar deposits.

  15. Surface energy balance measurements and modeling on the ice cap of King George Island, West Antarctica

    NASA Astrophysics Data System (ADS)

    Falk, U.; Braun, M.; Sala, H.; Menz, G.

    2012-04-01

    The Antarctic Peninsula is amongst the fastest warming places on Earth and further temperature increase is to be expected. It has undergone rapid environmental changes in the past decades. Exceptional rates of surface air temperature increases (2.5K in 50 years) are concurrent with retreating glacier fronts, an increase in melt areas, surface lowering and rapid retreat, break-up and disintegration of ice shelves. The South Shetland Islands are located on the northern tip of the Peninsula and are especially vulnerable to climate change due to their maritime climate. For King George Island we have compiled a unique data set comprising direct measurements of evaporation and sensible heat flux by eddy covariance on the Warszawa Icefield for the austral summers November 2010 to March 2011 and January to February 2012 in combination with a fully equipped automated weather station measuring long- and short-wave radiation components, profiles of temperature, humidity and wind velocities as well as glacier ice temperatures in profile. The combination with the eddy covariance data allows for analysis of variability and seasonality of surface energy balance components on a glacier for an entire year. Repeat measurements of surface lowering at different locations on King George Island are used for analysis of multi-sensor satellite data to identify melt patterns and bare ice areas during summer. In combination with long-term time series of weather data, these data give indication of the sensitivity of the inland ice cap to the ongoing changes. This research is part of the ESF project IMCOAST funded by BMBF. Field work was carried out at the Dallmann laboratory (Jubany, King George Island) in cooperation of the Instituto Antartico Argentino (Argentina) and the Alfred-Wegener Institute (German).

  16. Volcano-ice interactions on Mars

    NASA Technical Reports Server (NTRS)

    Allen, C. C.

    1979-01-01

    Central volcanic eruptions beneath terrestrial glaciers have built steep-sided, flat-topped mountains composed of pillow lava, glassy tuff, capping flows, and cones of basalt. Subglacial fissure eruptions produced ridges of similar composition. In some places the products from a number of subglacial vents have combined to form widespread deposits. The morphologies of these subglacial volcanoes are distinctive enough to allow their recognition at the resolutions characteristic of Viking orbiter imagery. Analogs to terrestrial subglacial volcanoes have been identified on the northern plains and near the south polar cap of Mars. The polar feature provides probable evidence of volcanic eruptions beneath polar ice. A mixed unit of rock and ice is postulated to have overlain portions of the northern plains, with eruptions into this ground ice having produced mountains and ridges analogous to those in Iceland. Subsequent breakdown of this unit due to ice melting revealed the volcanic features. Estimated heights of these landforms indicate that the ice-rich unit once ranged from approximately 100 to 1200 m thick.

  17. Comparison of Mars Northern Cap Edge Advance and Recession Rates over the Last 6 Mars Years

    NASA Astrophysics Data System (ADS)

    Titus, T. N.; Cushing, G. E.; Langevin, Y.; Brown, A. J.; Themis Science Team; CRISM Science Team

    2011-12-01

    The most observable parameter that describes the Mars polar seasonal caps is their size, which has been measured since the days of Herschel. The advance and retreat of the polar cap from year to year may exhibit many clues to help elucidate little understood physical processes. For example, summertime heat storage in the regolith could delay the onset of seasonal CO2 cap formation. The evolution of the seasonal cap could also be directly affected by the thermal inertia of the near-surface regolith and place constraints on the depth of the ice table. Parameterizations of the seasonal cap edges provide useful constraints on atmospheric GCMs and mesoscale models. Longitudinally resolving the cap edges as they advance and retreat constrains the times when zonal means are appropriate and when longitudinal asymmetries make zonal means invalid. These same kinds of parameterizations can also be used when modeling other data that have low spatial resolutions, such as Gamma Ray Spectrometer (GRS )and Neutron Spectrometer (NS) data. By knowing where the cap edge should be, coarse spatial data can correct for subpixel mixing caused by large point-spread functions including both frosted and frost-free areas. The northern cap exhibits a near symmetric retreat, which has been well characterized at visible wavelengths by both telescopic and spacecraft observations. However, the advance of the cap has not been well characterized until the 21st century. Kieffer and Titus (2001) have used zonal means to observe surface temperature and visible bolometric albedo variations with season using MGS/TES. The TES thermal observations show an almost perfectly symmetrical advance; i.e., condensation at consistent latitude across all longitudes, with the most northern edge of the seasonal cap occurring between longitudes 245°E to 265°E and the most southern edge of the seasonal cap occurring between 280°E and 30°E. The advance of the northern cap typically leads the advance of the edge of

  18. The first complete inventory of the local glaciers and ice caps on Greenland

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Bolch, T.; Mölg, N.; Machguth, H.; Le Bris, R.; Paul, F.

    2012-12-01

    Glacier inventories provide essential baseline information for the determination of water resources, glacier-specific changes in area and volume, climate change impacts as well as past, potential and future contribution of glaciers to sea-level rise. Although Greenland is heavily glacierised and thus highly relevant for all of the above points, a complete inventory of its glaciers was not available so far. Here we present the results and details of a new and complete inventory that has been compiled from more than 70 Landsat scenes (mostly acquired between 1999 and 2002) using semi-automated glacier mapping techniques. A digital elevation model (DEM) was used to derive drainage divides from watershed analysis and topographic attributes for each glacier entity. To serve the needs of different user communities, we assigned to each glacier one of three connectivity levels with the ice sheet (CL0, CL1, CL2; i.e. no, weak, and strong connection) to clearly, but still flexibly, distinguish the local glaciers and ice caps (GIC) from the ice sheet and its outlet glaciers. In total, we mapped ~ 20 300 glaciers larger than 0.05 km2 (of which ~ 900 are marine terminating), covering an area of 130 076 ± 4032 km2, or 89 720 ± 2781 km2 without the CL2 GIC. The latter value is about 50% higher than the mean value of more recent previous estimates. Glaciers smaller than 0.5 km2 contribute only 1.5% to the total area but more than 50% (11 000) to the total number. In contrast, the 25 largest GIC (> 500 km2) contribute 28% to the total area, but only 0.1% to the total number. The mean elevation of the GIC is 1700 m in the eastern sector and around 1000 m otherwise. The median elevation increases with distance from the coast, but has only a weak dependence on mean glacier aspect.

  19. Polar cap formation on Ganymede

    NASA Technical Reports Server (NTRS)

    Shaya, E. J.; Pilcher, C. B.

    1984-01-01

    It is argued that Ganymede's polar caps are the remnants of a more extensive covering of water ice that formed during a period in which the satellite was geologically active. It is inferred that the initial thickness of this covering was a significant fraction of the gardening depth since the covering formed. This suggests an initial thickness of at least a few meters over heavily cratered regions such as the south polar grooved terrain. The absence of similar polar caps on Callisto apparently reflects the absence of comparable geologic activity in the history of this satellite.

  20. Exposed water ice discovered near the south pole of Mars

    USGS Publications Warehouse

    Titus, T.N.; Kieffer, H.H.; Christensen, P.R.

    2003-01-01

    The Mars Odyssey Thermal Emission Imaging System (THEMIS) has discovered water ice exposed near the edge of Mars' southern perennial polar cap. The surface H2O ice was first observed by THEMIS as a region that was cooler than expected for dry soil at that latitude during the summer season. Diurnal and seasonal temperature trends derived from Mars Global Surveyor Thermal Emission Spectrometer observations indicate that there is H2O ice at the surface. Viking observations, and the few other relevant THEMIS observations, indicate that surface H2O ice may be widespread around and under the perennial CO2 cap.

  1. Present-day Exposures of Water Ice in the Northern Mid-latitudes of Mars

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.; Kanner, Lisa C.

    2007-01-01

    Water ice is exposed in the martian north polar cap, but is rarely exposed beyond the cap boundary. Orbital gamma ray spectrometry data strongly imply the presence of water ice within meters of the surface at latitudes north of approximately 60deg. We have examined mid-latitude areas of the northern plains displaying residual ice-rich layers, and report evidence of present-day surface exposures of water ice. These exposures, if confirmed, could con-strain the latitudinal and temporal stability of surface ice on Mars.

  2. Radar Detection of Layering in Ice: Experiments on a Constructed Layered Ice Sheet

    NASA Astrophysics Data System (ADS)

    Carter, L. M.; Koenig, L.; Courville, Z.; Ghent, R. R.; Koutnik, M. R.

    2016-12-01

    The polar caps and glaciers of both Earth and Mars display internal layering that preserves a record of past climate. These layers are apparent both in optical datasets (high resolution images, core samples) and in ground penetrating radar (GPR) data. On Mars, the SHARAD (Shallow Radar) radar on the Mars Reconnaissance Orbiter shows fine layering that changes spatially and with depth across the polar caps. This internal layering has been attributed to changes in fractional dust contamination due to obliquity-induced climate variations, but there are other processes that can lead to internal layers visible in radar data. In particular, terrestrial sounding of ice sheets compared with core samples have revealed that ice density and composition differences account for the majority of the radar reflectors. The large cold rooms and ice laboratory facility at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) provide us a unique opportunity to construct experimental ice sheets in a controlled setting and measure them with radar. In a CRREL laboratory, we constructed a layered ice sheet that is 3-m deep with a various snow and ice layers with known dust concentrations (using JSC Mars-1 basaltic simulant) and density differences. These ice sheets were profiled using a commercial GPR, at frequencies of 200, 400 and 900 MHz, to determine how the radar profile changes due to systematic and known changes in snow and ice layers, including layers with sub-wavelength spacing. We will report results from these experiments and implications for interpreting radar-detected layering in ice on Earth and Mars.

  3. Cosmic Dust in ~50 KG Blocks of Blue Ice from Cap-Prudhomme and Queen Alexandra Range, Antarctica

    NASA Astrophysics Data System (ADS)

    Maurette, M.; Cragin, J.; Taylor, S.

    1992-07-01

    Favorable Antarctic blue ice fields have produced a large number of meteorite finds because of the ice ablation concentration process (Cassidy et al., 1982). Such ice fields should also concentrate cosmic dust grains including both spherules and unmelted micrometeorites. Here we present preliminary results of concentrations of cosmic dust grains in ice from two very different Antarctic blue ice fields. The first sample (~60 kg) was collected in January 1987 from the surface of the blue ice field at Cap-Prudhomme (CP), near the French station of Dumont d'Urville, by a team from the "Laboratoire de Glaciologie du CNRS" (A. Barnola). The second sample (~50 kg), was retrieved from a meteorite stranding surface near the Queen Alexandra range (QUE) by a team (M. Burger, W. Cassidy, and R.Walker) of the ANSMET 1990 field expedition in Antarctica. Both samples were transported frozen to the laboratory where they were subdivided and processed. The CP sample was cut with a stainless steel saw into 4 pieces while the QUE sample, which had the top surface identified, was cut into three equal (~15 cm) horizontal layers to provide constituent variability with depth. All subsequent work on both samples was performed in a class 100 clean room using procedures developed by M. de Angelis and M. Maurette aimed at minimizing the loss of extraterrestrial particles. Pieces of both samples were cleaned by rinsing thoroughly with ultrapure water (Milli-O) and then melted in polyethylene containers in a microwave oven. Aliquots were decanted for chemical analysis and the remaining meltwater was filtered through stainless steel sieves for collection of large (>30 micrometers) particles. Using a 30X binocular microscope particles were hand picked for subsequent SEM/EDX analyses. Our initial objective was to compare the cosmic dust concentration in ice from the two locations. But this comparison was only partial because in the CP-ice, only magnetic spherules of >50 micrometers were studied

  4. The role of water ice clouds in the Martian hydrologic cycle

    NASA Technical Reports Server (NTRS)

    James, Philip B.

    1990-01-01

    A one-dimensional model for the seasonal cycle of water on Mars has been used to investigate the direction of the net annual transport of water on the planet and to study the possible role of water ice clouds, which are included as an independent phase in addition to ground ice and water vapor, in the cycle. The calculated seasonal and spatial patterns of occurrence of water ice clouds are qualitatively similar to the observed polar hoods, suggesting that these polar clouds are, in fact, an important component of water cycle. A residual dry ice in the south acts as a cold trap which, in the absence of sources other than the caps, will ultimately attract the water ice from the north cap; however, in the presence of a source of water in northern midlatitudes during spring, it is possible that the observed distribution of vapor and ice can be in a steady state even if a residual CO2 cap is a permanent feature of the system.

  5. Possible contemporary evaporites formation at the Martian Northern Polar Cap

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Czechowski, Leszek

    Evaporitic minerals are abundant on the surface of Mars (e.g., Wentworth et al. 2005, Velbel 2012, Clark and Van Hart 1981, Wang et al. 2006, Kuzmin et al. 2009), especially within the Circumpolar Dune Field and on the Northern Ice Cap itself (e.g., Langevin et al., 2005, Roach et al. 2007, Horgan et al. 2009, Masse et al. 2010, 2012). Most of their proposed formation mechanisms require significant amounts of liquid water and are thus not possible under current Martian conditions (Arvidson et al. 2006, Andrews-Hanna et al. 2007, Fishbaugh et al. 2007, Szynkiewicz et al. 2010). Some authors have considered the potential role of ice and ice- or snowmelt-related alteration in the weathering of Martian materials (e.g., Catling et al. 2006, Zolotov and Mironenko 2007, Niles and Michalski 2009, Masse et al. 2010). However, none of those studies discussed details of the process leading to the formation of the evaporites or the timing of the processes. The aim of this paper is to model numerically if the current radiant heating is sufficient to melt a thin layer of ice surrounding a single dust grain exposed within the south facing side of the Martian North Polar Cap trench. The results of our initial study suggest that for dust grains with basaltic properties and ice with low values of coefficient of heat conduction, and solar constant = 492 W/m2 liquid water may exist below a dust grain for up to 4 hours a sol. This suggest that contemporary evaporites formation on Martian Polar Cap is possible.

  6. 10Be dating of late-glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap, Peru

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Thompson, L. G.

    2004-12-01

    The surface exposure method, based on the measurement of cosmogenic 10Be produced in quartz, is applied to determine the age of deposition of glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap (about 13° S, 70° W) in southeastern Peru. These data are useful for examining the timing of past glaciation in the tropical Andes and for comparison with chronologies of glaciation at higher latitudes. The preliminary data set consists of more than ten surface exposure ages. Samples used for dating are from the surfaces of boulders on a set of prominent moraines about four kilometers away from the present ice margins. The age of the moraine set was previously bracketed by radiocarbon dating of peat associated with the glacial deposits. Based on radiocarbon ages, these moraines were formed during the late-glacial period, just prior to the last glacial-interglacial transition. The surface exposure dating method enables the direct dating of the moraines. Surface exposure dates are cross-checked with the previously existing radiocarbon dates and provide a means to improve the chronology of past glaciation in the tropical Andes.

  7. Can the Solid State Greenhouse Effect Produce ~100 Year Cycles in the Mars South Polar Residual CO2 Ice Cap?

    NASA Astrophysics Data System (ADS)

    Line, M. R.; Ingersoll, A. P.

    2010-12-01

    Malin et al. (2001) reported that the south perennial cap consists of quasi-circular pits ~8 meters deep, with a flat surface in between. The walls of the pits are retreating at a rate of 1 to 3 meters per year. Byrne and Ingersoll (2003a, 2003b) showed evidence that the floors of the pits are water ice and the upper layer is CO2. This layer will be gone in a few Martian centuries, if the observations are taken at face value. This raises some difficult questions: How likely is it that mankind would be witnessing the final few hundred years of the residual CO2 frost on Mars? Can one imagine extreme weather events that could recharge the residual CO2 frost once it is gone? Both seem unlikely, and we propose a different mechanism. Kieffer et al. (2000) showed that sunlight can penetrate several meters through the seasonal CO2 frost, where it warms the surface below. We have observational evidence that the same is happening in the perennial CO2 frost. Further, we have a model that shows how this "solid-state greenhouse" can lead to cyclic behavior, in which layers of CO2 build up on a water ice substrate, are heated internally by sunlight and lose mass from within. Eventually the layer becomes too weak to support itself, and it collapses to form pits. Then a new CO2 layer accumulates and the process repeats. Our study addresses fundamental questions of long-term stability of the Martian polar caps and how the caps control the atmospheric pressure. Instead of invoking extreme climate events to explain the data, we propose that processes within the frost itself can lead to cyclic growth and collapse of the pits. Our model implies that there is no long-term change in the ~8 meter layer of CO2 and no extreme weather events to make it change.

  8. H2O grain size and the amount of dust in Mars' residual north polar cap

    NASA Technical Reports Server (NTRS)

    Kieffer, Hugh H.

    1990-01-01

    In Mars' north polar cap, the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 microns or more. Ice of this granularity containing 30 percent fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be 'old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain.

  9. H2O grain size and the amount of dust in Mars' residual North polar cap

    USGS Publications Warehouse

    Kieffer, H.H.

    1990-01-01

    In Mars' north polar cap the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 ??m or more. Ice of this granularity containing 30% fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be "old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain. -Author

  10. A GCM Recent History of Northern Martian Polar Layered Deposits: Contribution from Past Equatorial Ice Reservoirs

    NASA Technical Reports Server (NTRS)

    Levrard, B.; Laskar, J.; Montmessin, F.; Forget, F.

    2005-01-01

    Polar layered deposits are exposed in the walls of the troughs cutting the north polar cap of Mars. They consist of alternating ice and dust layers or layers of an ice-dust mixture with varying proportions and are found throughout the cap. Layers thickness ranges from meters to several tens of meters with an approximately 30 meter dominant wavelength. Although their formation processes is not known, they are presumed to reflect changes in ice and dust stability over orbital and axial variations. Intensive 3-D LMD GCM simulations of the martian water cycle have been thus performed to determine the annual rates of exchange of surface ice between the northern cap and tropical areas for a wide range of obliquity and orbital parameters values.These rates have been employed to reconstruct an history of the northern cap and test simple models of dust-ice layers formation over the last 10 Ma orbital variations. We use the 3-D water cycle model simulated by the 3-D LMD GCM with an intermediate grid resolution (7.5 longitude x 5.625 latitude) and 25 vertical levels. The dust opacity is constant and set to 0,15. No exchange of ice with regolith is allowed. The evolution of the northern cap over obliquity and orbital changes (eccentricity, Longitude of perihelion) has been recently described with this model. High summer insolation favors transfer of ice from the northern pole to the Tharsis and Olympus Montes, while at low obliquity, unstable equatorial ice is redeposited in high-latitude and polar areas of both hemisphere. The disappearance of the equatorial ice reservoir leads to a poleward recession of icy high latitude reservoirs, providing an additional source for the cap accumulation during each obliquity or orbital cycle. Furthering the efforts, a quantitative evolution of ice reservoirs is here investigated for various astronomical conditions.

  11. Albedo of Carbon Dioxide Ice in Mars' Residual South Polar Cap

    NASA Astrophysics Data System (ADS)

    James, P. B.; Wolff, M. J.; Bonev, B.

    2015-12-01

    The albedo of surface CO2 deposits in the Residual South Polar Cap (RSPC) of Mars controls their net condensation / sublimation over a martian year and is therefore a crucial parameter in determining RSPC stability. The albedo used in previous analyses is obtained by dividing I/F, determined from radiometrically calibrated imaging data, by the cosine of the incidence angle. Because of atmospheric aerosols, the albedo calculated from I/F above the atmosphere is not the surface albedo that enters into stability considerations. In order to determine the surface albedo, we interpolate optical depths determined from CRISM EPF measurements to provide estimates of the dust and ice opacities over the RSPC (Wolff et al., 2009) and use these to determine the actual surface albedos from MARCI images using the radiative transport program DISORT (Stamnes et al., 1988). Assuming that dust is the only contributor to atmospheric opacity, the retrieved surface albedos for the longer wavelength MARCI filters in MY 28 and 29 are found to be consistent despite very different dust opacities in the two years (James et al., 2014). However, this model fails to reproduce the short wavelength behavior in early summer and suggests either an additional opacity source or modification of the CRISM dust opacity or the dust phase function. The consequences of these changes will be discussed.

  12. Evaluation of glacier mass balance by observing variations in transient snowline positions. [Jostedalsbreen ice cap, Norway

    NASA Technical Reports Server (NTRS)

    Oestrem, G. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The transient snowline on five outlet glaciers from the Jostedalsbreen ice-cap in Southwestern Norway could be determined from ERTS-1 image 1336-10260, when bands MSS 5, 6, and 7 were combined in an additive color viewer. The snowline was situated at a very low altitude at the time of imagery (24 June 1973) indicating that glacier melt was behind normal schedule, a fact that has a hydrologic bearing: one could expect less melt water in the streams. The idea to use ERTS-1 imagery in snowline determinations proved realistic and relatively easy to apply in practice. The method will be useful to estimate the glaciers' mass balance for large areas, provided some ground truth observations are made. Images from the end of the melt season are of course vital in this work.

  13. An examination of Mars' north seasonal polar cap using MGS: Composition and infrared radiation balance

    NASA Astrophysics Data System (ADS)

    Hansen, Gary B.

    2013-08-01

    A detailed analysis of data from one revolution of the Mars Global Surveyor (MGS) is presented. Approximately 80% of this revolution observes the mid-winter northern seasonal polar cap, which covers the surface to <60°N, and which is predominantly within polar night. The surface composition and temperature are determined through analysis of 6-50 μm infrared spectra from the Thermal Emission Spectrometer (TES). The infrared radiative balance, which is the entire heat balance in the polar night except for small subsurface and atmospheric advection terms, is calculated for the surface and atmospheric column. The primary constituent, CO2 ice, also dominates the infrared spectral properties by variations in its grain size and by admixtures of dust and water ice, which cause large variations in the 20-50 μm emissivity. This is modified by incomplete areal coverage, and clouds or hazes. This quantitative analysis reveals CO2 grain radii ranging from ˜100 μm in isolated areas, to 1-5 mm in more widespread regions. The water ice content varies from none to about one part per thousand by mass, with a clear increase towards the periphery of the polar cap. The dust content is typically a few parts per thousand by mass, but is as much as an order of magnitude less abundant in "cold spot" regions, where the low emissivity of pure CO2 ice is revealed. This is the first quantitative analysis of thermal spectra of the seasonal polar cap and the first to estimate water ice content. Our models show that the cold spots represent cleaner, dust-free ice rather than finer grained ice than the background. Our guess is that the dust in cold spots is hidden in the center of the CO2 frost particles rather than not present. The fringes of the cap have more dust and water ice, and become patchy, with warmer water snow filling the gaps on the night side, and warmer bare soil on the day side. A low optical depth (<1 in the visible) water ice atmospheric haze is apparent on the night side

  14. Effects of Atmospheric Dust on Residual South Polar Cap Stability

    NASA Technical Reports Server (NTRS)

    Bonrv, B. P.; Bjorkman, J. E.; Hansen, G. B.; James, P. B.; Wolff, M. J.

    2005-01-01

    The Martian polar caps have been studied from the time of Herschel. Neither polar cap normally disappears in summer. The Residual North Polar Cap (portion that remains through summer) is composed of a mixture of water ice and dust, and its interannual stability is due to its low sublimation rate at the summer temperatures in the North Polar Region. The Residual South Polar Cap (RSPC) is more enigmatic, surviving the relatively hot perihelic summer season despite being composed of much more volatile CO2. It is able to do so because of its unusually high albedo, which is larger than that of other bright regions in the seasonal cap (e.g. Mountains of Mitchel). The proximity of the albedo of the RSPC to the critical albedo for stability raises the question of whether the RSPC exists in every Martian year. The ground based record is somewhat ambivalent. Douglass and Lowell reported that RSPC suddenly vanished at Ls=297deg in 1894 and did not reappear until Ls=0deg [1], and Kuiper reported that it disappeared in 1956 [2]; but both observations were questioned by contemporaries, who tended to attribute them to obscuring dust. Barker [3] reported a large amount of water vapor over the south polar cap in 1969 that could be attributed to exposure of near surface water ice during partial removal of the CO2 in the RSPC in 1969.

  15. Timing of Expansions of the Quelccaya Ice Cap, Peru, and Implications for Cosmogenic Nuclide Production Rate Calibration

    NASA Astrophysics Data System (ADS)

    Lowell, T. V.; Kelly, M. A.; Applegate, P. J.; Smith, C. A.; Phillips, F. M.; Hudson, A. M.

    2010-12-01

    We calibrate the production rate of the cosmogenic nuclide beryllium-10 (10Be) at a low-latitude, high-elevation site, using nuclide concentrations measured in moraine boulders and an independent chronology determined with bracketing radiocarbon dates. The measurement of terrestrial cosmogenic nuclide (TCN) concentrations in earth surface materials has been an important development for understanding a host of earth surface processes. Uncertainty in cosmogenic nuclide production rates has hampered application of this method. Here, we contribute to the estimation of 10Be production rates by reporting both preliminary 10Be concentrations and independent radiocarbon dates from a low latitude, high elevation site. Our study site in the southeastern Peruvian Andes (~13.9°S, 70.9°W, 4850 m asl) is centered on a moraine set, known as the Huancané II moraines, that represents a ~4 km expansion of Quelccaya Ice Cap during late glacial time. At this location, organic material situated both stratigraphically below and above moraines in two adjacent valleys provide material for radiocarbon dating. Based on geomorphic arguments, we correlate results from the two valleys. The timing of ice cap margin advance is bracketed by 13 radiocarbon ages on organic material within the outermost Huancané II moraines that range from 13.6 to 12.5 ka. Two stratigraphic sections upvalley from the moraines yield 6 radiocarbon ages from 11.3 to 12.4 ka, indicating the time of retreat . We computed the probability density function that lies between these two sets of dates, and assign an age of 12.4 ka (+/-???) for the formation of the Huancané II moraines. Calculating beryllium-10 exposure dates from the measured concentrations yield exposure dates that significantly underestimate the independently determined age of the moraine (~8-30%), if existing production rate estimates are used. We suggest that the radiocarbon age for the moraines can be used as a robust independent calibration for 10Be

  16. The hemispherical asymmetry of the residual polar caps on Mars

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1991-01-01

    A model of the polar caps of Mars was created which allows: (1) for light penetration into the cap; (2) ice albedo to vary with age, latitude, hemisphere, dust content, and solar zenith angle; and (3) for diurnal variability. The model includes the radiative effects of clouds and dust, and heat transport as represented by a thermal wind. The model reproduces polar cap regression data very well, including the survival of CO2 frost at the south pole and reproduces the general trend in the Viking Lander pressure data.

  17. Characterizing the Chemical and Physical Signature of the 2015-16 El Niño in the Quelccaya Ice Cap Snow and Ice to Calibrate Past ENSO Reconstructions.

    NASA Astrophysics Data System (ADS)

    Beaudon, E.; Barker, J. D.; Kenny, D. V.; Thompson, L. G.

    2017-12-01

    Pacific Sea Surface Temperature (SST) anomalies have reached +3°C in the Niño 3.4 region in November 2015 making this one of the strongest El Niños in 100 years. This warm phase of the El Niño - Southern Oscillation (ENSO) has pronounced differential impacts across the tropical Pacific as well as in South America. Peru statistically experienced flooding in the northern and central regions and drought conditions in the south on the Altiplano. However, the 2015-16 El Nino event led to drought throughout the Peruvian Andes. El Niño is a warm and dry episode, phase locked with the accumulation season on the Quelccaya Ice Cap (QIC) so that this strong event create conditions favorable for enhanced surface ablation and dry deposition of soluble and insoluble aerosols. Here we present new glaciochemical (major and organic ions, dust, black carbon, oxygen isotopes) results from two consecutive snow and ice sampling campaign on QIC framing the climax of the 2015/2016 El Niño episode in Peru. We allocate the ionic and black carbon sources and describe the biogenic and evaporitic contributions to Quelccaya snow chemistry under El Niño atmospheric conditions. Elution factors and ionic budgets are compared to those of the snow and ice samples collected prior to the El Niño initiation and thereby assess the magnitude of the impact of El Niño-induced post-depositional processes. Our results provide the database needed to verify that: 1) melt and percolation induced by El Niño is identifiable in the prior year's snow layer and thus might be calibrated to the El Niño's strength; and 2) the concentration and co-association of biogenic (e.g., NH4, black carbon) and evaporitic (salts) species is enhanced and detectable deeper in the ice and thereby might serve as a proxy for documenting past El Niño frequency. By capturing the chemical signature of a modern El Niño event occurring in a warming world, these results shed light on past ENSO variability preserved in ice core

  18. Ice crystallization in ultrafine water-salt aerosols: nucleation, ice-solution equilibrium, and internal structure.

    PubMed

    Hudait, Arpa; Molinero, Valeria

    2014-06-04

    Atmospheric aerosols have a strong influence on Earth's climate. Elucidating the physical state and internal structure of atmospheric aqueous aerosols is essential to predict their gas and water uptake, and the locus and rate of atmospherically important heterogeneous reactions. Ultrafine aerosols with sizes between 3 and 15 nm have been detected in large numbers in the troposphere and tropopause. Nanoscopic aerosols arising from bubble bursting of natural and artificial seawater have been identified in laboratory and field experiments. The internal structure and phase state of these aerosols, however, cannot yet be determined in experiments. Here we use molecular simulations to investigate the phase behavior and internal structure of liquid, vitrified, and crystallized water-salt ultrafine aerosols with radii from 2.5 to 9.5 nm and with up to 10% moles of ions. We find that both ice crystallization and vitrification of the nanodroplets lead to demixing of pure water from the solutions. Vitrification of aqueous nanodroplets yields nanodomains of pure low-density amorphous ice in coexistence with vitrified solute rich aqueous glass. The melting temperature of ice in the aerosols decreases monotonically with an increase of solute fraction and decrease of radius. The simulations reveal that nucleation of ice occurs homogeneously at the subsurface of the water-salt nanoparticles. Subsequent ice growth yields phase-segregated, internally mixed, aerosols with two phases in equilibrium: a concentrated water-salt amorphous mixture and a spherical cap-like ice nanophase. The surface of the crystallized aerosols is heterogeneous, with ice and solution exposed to the vapor. Free energy calculations indicate that as the concentration of salt in the particles, the advance of the crystallization, or the size of the particles increase, the stability of the spherical cap structure increases with respect to the alternative structure in which a core of ice is fully surrounded by

  19. Pacing the post-Last Glacial Maximum demise of the Animas Valley glacier and the San Juan Mountain ice cap, Colorado

    NASA Astrophysics Data System (ADS)

    Guido, Zackry S.; Ward, Dylan J.; Anderson, Robert S.

    2007-08-01

    During the Last Glacial Maximum (LGM), a 5000 km2 ice cap covered the San Juan Mountains of southwest Colorado. The largest valley glacier draining this ice cap occupied the Animas Valley and flowed 91 km to the south. To characterize the post-LGM demise of the Animas Valley glacier, we employ cosmogenic 10Be to date the LGM terrace outside the terminal moraines and a suite of seven glacially polished bedrock samples. The 10Be depth profile within the terrace sediments suggests abandonment at 19.4 ± 1.5 ka. As deglaciation began, the ponding of Glacial Lake Durango behind the terminal moraines shut off fluvial sediment supply and caused terrace abandonment. The age of the terrace therefore records the initiation of LGM retreat. Negligible 10Be inheritance in the terrace profile suggests that glacial erosion of the bedrock valley floor from which sediments were derived erased all cosmogenic inventory. Glacial polish exposure ages monotonically decrease up-valley from 17.1 to 12.3 ka, with the single exception of a sample collected from a quartzite rib, yielding an average retreat rate of 15.4 m/yr. This trend and the lack of inherited cosmogenic nuclides in the terrace sediments imply that polish ages accurately record the glacial retreat history. Retreat of the Animas lobe began at a time of regional drying recorded in sediments and shoreline elevations of large lakes. Deglaciation lasted for ˜7.2 k.y., and was complete by 12.3 ± 1.0 ka. The retreat history followed the pattern of increasing insolation and was perhaps fastest during a time of regional drying.

  20. Ice Accretion Formations on a NACA 0012 Swept Wing Tip in Natural Icing Conditions

    NASA Technical Reports Server (NTRS)

    Vargas, Mario; Giriunas, Julius A.; Ratvasky, Thomas P.

    2002-01-01

    An experiment was conducted in the DeHavilland DHC-6 Twin Otter Icing Research Aircraft at NASA Glenn Research Center to study the formation of ice accretions on swept wings in natural icing conditions. The experiment was designed to obtain ice accretion data to help determine if the mechanisms of ice accretion formation observed in the Icing Research Tunnel are present in natural icing conditions. The experiment in the Twin Otter was conducted using a NACA 0012 swept wing tip. The model enabled data acquisition at 0 deg, 15 deg, 25 deg, 30 deg, and 45 deg sweep angles. Casting data, ice shape tracings, and close-up photographic data were obtained. The results showed that the mechanisms of ice accretion formation observed in-flight agree well with the ones observed in the Icing Research Tunnel. Observations on the end cap of the airfoil showed the same strong effect of the local sweep angle on the formation of scallops as observed in the tunnel.

  1. Last Glacial-Interglacial Transition ice dynamics in the Wicklow Mountains, Ireland

    NASA Astrophysics Data System (ADS)

    Knight, Lauren; Boston, Clare; Lovell, Harold; Pepin, Nick

    2017-04-01

    Understanding of the extent and dynamics of former ice masses in the Wicklow Mountains, Ireland, during the Last Glacial-Interglacial Transition (LGIT; 15-10 ka BP) is currently unresolved. Whilst it is acknowledged that the region hosted a local ice cap within the larger British-Irish Ice Sheet at the Last Glacial Maximum (LGM; 27 ka BP), there has been little consideration of ice cap disintegration to a topographically constrained ice mass during the LGIT. This research has produced the first regional glacial geomorphological map, through remote sensing (aerial photograph and digital terrain model interrogation) and field mapping. This has allowed both the style and extent of mountain glaciation and ice recession dynamics during the LGIT to be established. This geomorphological mapping has highlighted that evidence for local glaciation in the Wicklow Mountains is more extensive than previously recognised, and that small icefields and associated outlet valley glaciers existed during the LGIT following disintegration of the Wicklow Ice Cap. A relative chronology based on morphostratigraphic principles is developed, which indicates complex patterns of ice mass oscillation characterised by periods of both sustained retreat and minor readvance. Variations in the pattern of recession across the Wicklow Mountains are evident and appear to be influenced, in part, by topographic controls (e.g. slope, aspect, glacier hypsometry). In summary, this research establishes a relative chronology of glacial events in the region during the LGIT and presents constraints on ice mass extent, dynamics and retreat patterns, offering an insight into small ice mass behaviour in a warming climate.

  2. Palmer Quest: A Feasible Nuclear Fission "Vision Mission" to the Mars Polar Caps

    NASA Technical Reports Server (NTRS)

    Carsey, F. D.; Beegle, L. W.; Nakagawa, R.; Elliott, J. O.; Matthews, J. B.; Coleman, M. L.; Hecht, M. H.; Ivaniov, A. B.; Head, J. W.; Milkovich, S.

    2005-01-01

    We are engaged in a NASA Vision Mission study, called Palmer Quest after the American Antarctic explorer Nathaniel Palmer, to assess the presence of life and evaluate the habitability of the basal domain of the Mars polar caps. We address this goal through four objectives: 1. Determine the presence of amino acids, nutrients, and geochemical heterogeneity in the ice sheet. 2. Quantify and characterize the provenance of the amino acids in Mars ice. 3. Assess the stratification of outcropped units for indications of habitable zones. 4. Determine the accumulation of ice, mineralogic material, and amino acids in Mars ice caps over the present epoch. Because of the defined scientific goal for the vision mission, the Palmer Quest focus is astrobiological; however, the results of the study make us optimistic that aggressive multi-platform in-situ missions that address a wide range of objectives, such as climate change, can be supported by variations of the approach used on this mission. Mission Overview: The Palmer Quest baseline

  3. On the possibility of ice on Greenland during the Eocene-Oligocene transition

    NASA Astrophysics Data System (ADS)

    Langebroek, Petra M.; Nisancioglu, Kerim H.; Lunt, Daniel J.; Kathrine Pedersen, Vivi; Nele Meckler, A.; Gasson, Edward

    2017-04-01

    The Eocene-Oligocene transition ( 34 Ma) is one of the major climate transitions of the Cenozoic era. Atmospheric CO2 decreased from the high levels of the Greenhouse world (>1000 ppm) to values of about 600-700 ppm in the early Oligocene. High latitude temperatures dropped by several degrees, causing a large-scale expansion of the Antarctic ice sheet. Concurrently, in the Northern Hemisphere, the inception of ice caps on Greenland is suggested by indirect evidence from ice-rafted debris and changes in erosional regime. However, ice sheet models have not been able to simulate extensive ice on Greenland under the warm climate of the Eocene-Oligocene transition. We show that elevated bedrock topography is key in solving this inconsistency. During the late Eocene / early Oligocene, East Greenland bedrock elevations were likely higher than today due to tectonic and deep-Earth processes related to the break-up of the North Atlantic and the position of the Icelandic plume. When allowing for higher initial bedrock topography, we do simulate a large ice cap on Greenland under the still relatively warm climate of the early Oligocene. Ice inception takes place at high elevations in the colder regions of North and Northeast Greenland; with the size of the ice cap being strongly dependent on the climate forcing and the bedrock topography applied.

  4. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    USGS Publications Warehouse

    Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-01-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  6. Research Spotlight: No tipping point for Arctic Ocean ice

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2011-03-01

    Declines in the summer sea ice extent have led to concerns within the scientific community that the Arctic Ocean may be nearing a tipping point, beyond which the sea ice cap could not recover. In such a scenario, greenhouse gases in the atmosphere trap outgoing radiation, and as the Sun beats down 24 hours a day during the Arctic summer, temperatures rise and melt what remains of the polar sea ice cap. The Arctic Ocean, now less reflective, would absorb more of the Sun’s warmth, a feedback loop that would keep the ocean ice free. However, new research by Tietsche et al. suggests that even if the Arctic Ocean sees an ice-free summer, it would not lead to catastrophic runaway ice melt. The researchers, using a general circulation model of the global ocean and the atmosphere, found that Arctic sea ice recovers within 2 years of an imposed ice-free summer to the conditions dictated by general climate conditions during that time. Furthermore, they found that this quick recovery occurs whether the ice-free summer is triggered in 2000 or in 2060, when global temperatures are predicted to be 2°C warmer. (Geophysical Research Letters, doi:10.1029/2010GL045698, 2011)

  7. Nature and History of Cenozoic Polar Ice Covers: The Case of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Spielhagen, R.; Thiede, J.

    2009-04-01

    The nature of the modern climate System is characterized by steep temperature gradients between the tropical and polar climatic zones and finds its most spectacular expression in the formation of ice caps in high Northern and Southern latitudes. While polar regions of Planet Earth have been glaciated repeatedly in the long course of their geological history, the Cenozoic transition from a „greenhouse" to an „icehouse" has in fact produced a unique climatic scenario with bipolar glacation, different from all previous glacial events. The Greenland ice sheet is a remainder of the Northern Hemisphere last glacial maximum ice sheets and represents hence a spectacular anomaly. Geological records from Tertiary and Quaternary terrestrial and oceanic sections have documented the presence of ice caps and sea ice covers both on the Southern as well on the Northern hemisphere since Eocene times, aqpprox. 45 Mio. years ago. While this was well known in the case of Antarctica already for some time, previous ideas about the origin of Northern hemisphere glaciation during Pliocene times (approx. 2-3 Mio. years ago) have been superceded by the dramatic findings of coarse, terrigenous ice rafted detritus in Eocene sediments from Lomonosov Ridge (close to the North Pole) apparently slightly older than the oldest Antarctic records of ice rafting.The histories of the onset of Cenozoic glaciation in high Northern and Southern latitudes remain enigmatic and are presently subjects of international geological drilling projects, with prospects to reveal some of their secrets over the coming decades. By virtue of the physical porperties of ice and the processes controlling the dynamics of the turn-over of the ice-sheets only young records of glacial ice caps on Antarctica and on Greemnland have been preserved, on Greenland with ice probably not older than a few hundred thousand years, on Antarctica potentially as old as 1.5-2 Mio. years. Deep-sea cores with their records od ice

  8. 3-D Imaging of Mars’ Polar Ice Caps Using Orbital Radar Data

    PubMed Central

    Foss, Frederick J.; Putzig, Nathaniel E.; Campbell, Bruce A.; Phillips, Roger J.

    2018-01-01

    Since its arrival in early 2006, various instruments aboard NASA’s Mars Reconnaissance Orbiter (MRO) have been collecting a variety of scientific and engineering data from orbit around Mars. Among these is the SHAllow RADar (SHARAD) instrument, supplied by Agenzia Spaziale Italiana (ASI) and designed for subsurface sounding in the 15–25 MHz frequency band. As of this writing, MRO has completed over 46,000 nearly polar orbits of Mars, 30% of which have included active SHARAD data collection. By 2009, a sufficient density of SHARAD coverage had been obtained over the polar regions to support 3-D processing and analysis of the data. Using tools and techniques commonly employed in terrestrial seismic data processing, we have processed subsets of the resulting collection of SHARAD observations covering the north and south polar regions as SHARAD 3-D volumes, imaging the interiors of the north and south polar ice caps known, respectively, as Planum Boreum and Planum Australe. After overcoming a series of challenges revealed during the 3-D processing and analysis, a completed Planum Boreum 3-D volume is currently being used for scientific research. Lessons learned in the northern work fed forward into our 3-D processing and analysis of the Planum Australe 3-D volume, currently under way. We discuss our experiences with these projects and present results and scientific insights stemming from these efforts. PMID:29400351

  9. High LMD GCM Resolution Modeling of the Seasonal Evolution of the Martian Northern Permanent Cap: Comparison with Mars Express OMEGA Observations

    NASA Technical Reports Server (NTRS)

    Levrard, B.; Forget, F.; Montmessin, F.; Schmitt, B.; Doute, S.; Langevin, Y.; Poulet, F.; Bibring, J. P.; Gondet, B.

    2005-01-01

    Analyses of imaging data from Mariner, Viking and MGS have shown that surface properties (albedo, temperature) of the northern cap present significant differences within the summer season and between Mars years. These observations include differential brightening and/or darkening between polar areas from the end of the spring to midsummer. These differences are attributed to changes in grain size or dust content of surface ice. To better understand the summer behavior of the permanent northern polar cap, we perfomed a high resolution modeling (approximately 1 deg x 1 deg.) of northern cap in the Martian Climate/water cycle as simulated by the Laboratoire de Meteorologie Dynamique (LMD) global climate model. We compare the predicted properties of the surface ice (ice thickness, temperature) with the Mars Express Omega summer observations of the northern cap. albedo and thermal inertia svariations model. In particular, albedo variations could be constrained by OMEGA data. Meteorological predictions of the LMD GCM wil be presented at the conference to interpret the unprecedently resolved OMEGA observations. The specific evolution of regions of interest (cap center, Chasma Boreal...) and the possibility of late summer global cap brightening will be discussed.

  10. Initial Insights into the Quaternary Evolution of the Laurentide Ice Sheet on Southeastern Baffin Island

    NASA Astrophysics Data System (ADS)

    Pendleton, S.; Anderson, R. S.; Miller, G. H.; Refsnider, K. A.

    2015-12-01

    Increasing Arctic summer temperatures in recent decades and shrinking cold-based ice caps on Cumberland Peninsula, Baffin Island, are exposing ancient landscapes complete with uneroded bedrock surfaces. Previous work has indicated that these upland surfaces covered with cold-based ice experience negligible erosion compared with the valleys and fjords systems that contain fast-flowing ice. Given the appearance of highly weathered bedrock, it is argued that these landscapes have remained largely unchanged since at least the last interglaciation (~120 ka), and have likely experienced multiple cycles of ice expansion and retraction with little erosion throughout the Quaternary. To explore this hypothesis, we use multiple cosmogenic radionuclides (26Al and 10Be) to investigate and provide insight into longer-term cryosphere activity and landscape evolution. 26Al/10Be in surfaces recently exposed exhibit a wide range of exposure-burial histories. Total exposure-burial times range from ~0.3 - 1.5 My and estimated erosion rates from 0.5 - 6.2 m Ma-1. The upland surfaces of the Penny Ice cap generally experienced higher erosion rates (~0.45 cm ka-1) than those covered by smaller ice caps (~0.2 cm ka-1). The cumulative burial/exposure histories in high, fjord-edge locations indicate that significant erosion north of the Penny Ice Cap ceased between ~600 and 800 ka, suggesting that Laurentide Ice Sheet (LIS) organization and fjord inception was underway by at least this time. Additionally, 26Al/10Be ratios near production values despite high inventories from a coastal summit 50 km east of the Penny Ice Cape suggest that that area has not experienced appreciable burial by ice, suggesting that it was never inundated by the LIS. Moreover, these initial data suggest a variable and dynamic cryosphere in the region and provide insight into how large ice sheets evolved and organized themselves during the Quaternary.

  11. Ice crystals classification using airborne measurements in mixing phase

    NASA Astrophysics Data System (ADS)

    Sorin Vajaiac, Nicolae; Boscornea, Andreea

    2017-04-01

    This paper presents a case study of ice crystals classification from airborne measurements in mixed-phase clouds. Ice crystal shadow is recorded with CIP (Cloud Imaging Probe) component of CAPS (Cloud, Aerosol, and Precipitation Spectrometer) system. The analyzed flight was performed in the south-western part of Romania (between Pietrosani, Ramnicu Valcea, Craiova and Targu Jiu), with a Beechcraft C90 GTX which was specially equipped with a CAPS system. The temperature, during the fly, reached the lowest value at -35 °C. These low temperatures allow the formation of ice crystals and influence their form. For the here presented ice crystals classification a special software, OASIS (Optical Array Shadow Imaging Software), developed by DMT (Droplet Measurement Technologies), was used. The obtained results, as expected are influenced by the atmospheric and microphysical parameters. The particles recorded where classified in four groups: edge, irregular, round and small.

  12. Observations of the north polar water ice annulus on Mars using THEMIS and TES

    USGS Publications Warehouse

    Wagstaff, K.L.; Titus, T.N.; Ivanov, A.B.; Castano, R.; Bandfield, J.L.

    2008-01-01

    The Martian seasonal CO2 ice caps advance and retreat each year. In the spring, as the CO2 cap gradually retreats, it leaves behind an extensive defrosting zone from the solid CO2 cap to the location where all CO2 frost has sublimated. We have been studying this phenomenon in the north polar region using data from the THermal EMission Imaging System (THEMIS), a visible and infra-red (IR) camera on the Mars Odyssey spacecraft, and the Thermal Emission Spectrometer (TES) on Mars Global Surveyor. Recently, we discovered that some THEMIS images of the CO2 defrosting zone contain evidence for a distinct defrosting phenomenon: some areas just south of the CO2 cap edge are too bright in visible wavelengths to be defrosted terrain, but too warm in the IR to be CO2 ice. We hypothesize that we are seeing evidence for a seasonal annulus of water ice (frost) that recedes with the seasonal CO2 cap, as predicted by previous workers. In this paper, we describe our observations with THEMIS and compare them to simultaneous observations by TES and OMEGA. All three instruments find that this phenomenon is distinct from the CO2 cap and most likely composed of water ice. We also find strong evidence that the annulus widens as it recedes. Finally, we show that this annulus can be detected in the raw THEMIS data as it is collected, enabling future long-term onboard monitoring. ?? 2007.

  13. Ice cap melting and low-viscosity crustal root explain the narrow geodetic uplift of the Western Alps

    NASA Astrophysics Data System (ADS)

    Chéry, J.; Genti, M.; Vernant, P.

    2016-04-01

    More than 10 years of geodetic measurements demonstrate an uplift rate of 1-3 mm/yr of the high topography region of the Western Alps. By contrast, no significant horizontal motion has been detected. Two uplift mechanisms have been proposed: (1) the isostatic response to denudation responsible for only a fraction of the observed uplift and (2) the rebound induced by the Wurmian ice cap melting which predicts a broader uplifting region than the one evidenced by geodetic observations. Using a numerical model to fit the geodetic data, we show that a crustal viscosity contrast between the foreland and the central part of the Alps, the latter being weaker with a viscosity of 1021 Pa s, is needed. The vertical rates are enhanced if the strong uppermost mantle beneath the Moho is interrupted across the Alps, therefore allowing a weak vertical rheological anomaly over the entire lithosphere.

  14. The Residual South Polar Cap of Mars: Stable or Transitory?

    NASA Astrophysics Data System (ADS)

    Glenar, David A.; Bonev, B. P.; Hansen, G. B.; James, P. B.; Bjorkman, J. E.

    2006-09-01

    It remains uncertain whether the CO2 residual south polar cap (RSPC) is a permanent feature of the present Mars climate, or whether it occasionally sublimes completely during years marked by dramatic dust storm activity. While there is no firm evidence for complete disappearance of the cap in the past, observations show that the residual cap lost significant CO2 material in the spring / summer season prior to the Mariner 9 encounter. On the other hand, little interannual change has been observed in the RSPC during the MGS mission [1], despite the massive early-spring dust storm which occurred in 2001. We discuss whether a global dust storm beginning near perihelion could enhance the net CO2 sublimation sufficiently to completely remove the RSPC. We utilize a surface-plus-aerosol radiative transfer model under conditions of both modest and heavy atmospheric dust loading. The sublimination behavior depends critically on the extended (visible to thermal IR) albedo spectrum of the polar CO2 ice, which we have strongly constrained [2] from a combination of HST photometric imaging, ground based near-IR imaging spectroscopy and spectroscopic measurements by the Mars Express PFS. The extension of the cap spectrum to thermal IR wavelengths was accomplished by forward modeling using a semi-infinite grid of scattering grains. Results of this analysis depend on the strength of possible feedback mechanisms (increased surface dust content; exposure of water ice) as well as on the possibility of dust confinement by the polar vortex; but the general conclusion is that it would require multiple, intense dust storms in a given year in order to completely remove the CO2 ice veneer layer. This work has been supported by the NASA Planetary Astronomy and Mars Data Analysis Programs. [1] Benson and James, Icarus 174, 513, 2005; [2] Bonev et al., Planet Space Sci. 2006 (accepted).

  15. Snowball Earth: Skating on Thin Ice?

    NASA Astrophysics Data System (ADS)

    Roberson, A. L.; Stout, A. M.; Pollard, D.; Kasting, J. F.

    2011-12-01

    There is evidence of at least two intervals of widespread glaciation during the late Neoproterozoic (600-800 Myr ago), which are commonly referred to as "Snowball Earth" episodes. The global nature of these events is indicated by the fact that glacial deposits are found at low paleolatitudes during this time. Models of a global glacial event have produced a variety of solutions at low latitudes: thick ice, thin ice, slushball, and open ocean . The latter two models are similar, except that the slushball model has its ice-line at higher latitudes. To be viable, a model has to be able to account for the survival of life through the glaciations and also explain the existence of cap carbonates and other glacial debris deposited at low latitudes. The "thick-ice" model is not viable because kilometers of ice prevent the penetration of light necessary for the photosynthetic biota below. The "slushball" model is also not viable as it does not allow the formation of cap carbonates. The "thin-ice" model has been discussed previously and can account for continuation of photosynthetic life and glacial deposits at low paleolatitudes. The recently proposed "open-ocean" or "Jormungand" model also satisfies these requirements. What is it, though, that causes some models to produce thin ice near the equator and others to have open water there? We examine this question using a zonally symmetric energy balance climate model (EBM) with flowing sea glaciers to determine what parameter ranges produce each type of solution.

  16. The Contribution of Water Ice Clouds to the Water Cycle in the North Polar Region of Mars: Preliminary Analysis

    NASA Technical Reports Server (NTRS)

    Bass, D. S.; Tamppari, L. K.

    2000-01-01

    While it has long been known that Mars' north residual polar cap and the Martian regolith are significant sources of atmospheric water vapor, the amount of water vapor observed in the northern spring season by the Viking Mars Atmospheric Water Detector instrument (MAWD) cannot be attributed to cap and regolith sources alone. Kahn suggested that ice hazes may be the mechanism by which additional water is supplied to the Martian atmosphere. Additionally, a significant decrease in atmospheric water vapor was observed in the late northern summer that could not be correlated with the return of the cold seasonal C02 ice. While the detection of water ice clouds on Mars indicate that water exists in Mars' atmosphere in several different phases, the extent to which water ice clouds play a role in moving water through the Martian atmosphere remains uncertain. Work by Bass et. al. suggested that the time dependence of water ice cap seasonal variability and the increase in atmospheric water vapor depended on the polar cap center reaching 200K, the night time saturation temperature. Additionally, they demonstrated that a decrease in atmospheric water vapor may be attributed to deposition of water ice onto the surface of the polar cap; temperatures were still too warm at this time in the summer for the deposition of carbon dioxide. However, whether water ice clouds contribute significantly to this variability is unknown. Additional information is contained in original extended abstract.

  17. Albedo models for the residual south polar cap on Mars: Implications for the stability of the cap under near-perihelion global dust storm conditions

    NASA Astrophysics Data System (ADS)

    Bonev, Boncho P.; Hansen, Gary B.; Glenar, David A.; James, Philip B.; Bjorkman, Jon E.

    2008-02-01

    It is uncertain whether the residual (perennial) south polar cap on Mars is a transitory or a permanent feature in the current Martian climate. While there is no firm evidence for complete disappearance of the cap in the past, clearly observable changes have been documented. Observations suggest that the perennial cap lost more CO 2 material in the spring/summer season prior to the Mariner 9 mission than in those same seasons monitored by Viking and Mars Global Surveyor. In this paper we examine one process that may contribute to these changes - the radiative effects of a planet encircling dust storm that starts during late Martian southern spring on the stability of the perennial south polar cap. To approach this, we model the radiative transfer through a dusty planetary atmosphere bounded by a sublimating CO 2 surface. A critical parameter for this modeling is the surface albedo spectrum from the near-UV to the thermal-IR, which was determined from both space-craft and Earth-based observations covering multiple wavelength regimes. Such a multi-wavelength approach is highly desirable since one spectral band by itself cannot tightly constrain the three-parameter space for polar surface albedo models, namely photon "scattering length" in the CO 2 ice and the amounts of intermixed water and dust. Our results suggest that a planet-encircling dust storm with onset near solstice can affect the perennial cap's stability, leading to advanced sublimation in a "dusty" year. Since the total amount of solid CO 2 removed by a single storm may be less than the total CO 2 thickness, a series of dust storms would be required to remove the entire residual CO 2 ice layer from the south perennial cap.

  18. Atmospheric Depositions of Natural and Anthropogenic Aerosols on the Guliya Ice Cap (Northwestern Tibetan Plateau) during the last 340 years

    NASA Astrophysics Data System (ADS)

    Sierra Hernandez, R.; Gabrielli, P.; Beaudon, E.; Thompson, L. G.; Wegner, A.

    2017-12-01

    Anthropogenic emissions (e.g., greenhouse gases, trace elements (TE) including toxic metals) to the atmosphere have dramatically increased since the Industrial Revolution in the 19th century. High temperature processes such as fossil fuel combustion and pyrometallurgy generate fumes and fine particles (< 0.1µm - 10 µm) containing toxic metals (e.g., Cd, Zn, Pb) that if not captured by emission controls can be transported over long distances by air masses and subsequently deposited far from their emission sources. Atmospheric TE monitoring programs, along with emission inventories, have been conducted in recent decades. However, they lack pre-1900 information which is necessary to contextualize current atmospheric changes. Thus, it is necessary to use natural archives (e.g., ice cores, lake sediments) to reconstruct atmospheric pollution trends. Glaciers and ice sheets preserve atmospheric species that are deposited as snow accumulates over time, creating valuable records of past climatic/environmental conditions. Polar ice cores have been used to obtain TE records. However, only a few non-polar ice core records provide continuous information back to pre-industrial times. Thus, ice core records of TEs from mid- and low-latitudes are needed to assess the spatial and temporal extent and levels of pollution in the environment. Here we present records of 29 TEs spanning the period 1650-1991 CE from the Guliya ice cap in the western Kunlun Mountains, northwest Tibetan Plateau to assess their natural and anthropogenic sources. The Guliya TEs records show two distinct periods with only crustal contributions prior to the 1850s and non-crustal contributions (Pb, Cd, Sb, Zn, Sn) after the 1850s. Enrichments of Pb, Cd, Sb, and Zn in Guliya between 1850 and 1950 can be attributed primarily to coal combustion emissions from western countries (Europe) while regional emissions (fossil fuel combustion, mining/smelting, fertilizers) from Central Asia, and probably from Kashgar in

  19. Self-sustaining Mars colonies utilizing the North Polar Cap and the Martian atmosphere.

    PubMed

    Powell, J; Maise, G; Paniagua, J

    2001-01-01

    A revolutionary new concept for the early establishment of robust, self-sustaining Martian colonies is described. The colonies would be located on the North Polar Cap of Mars and utilize readily available water ice and the CO2 Martian atmosphere as raw materials to produce all of the propellants, fuel, air, water, plastics, food, and other supplies needed by the colony. The colonists would live in thermally insulated large, comfortable habitats under the ice surface, fully shielded from cosmic rays. The habitats and supplies would be produced by a compact, lightweight (~4 metric tons) nuclear powered robotic unit termed ALPH (Atomic Liberation of Propellant and Habitat), which would land 2 years before the colonists arrived. Using a compact, lightweight 5 MW (th) nuclear reactor/steam turbine (1 MW(e)) power source and small process units (e.g., H2O electrolyzer, H2 and O2 liquefiers, methanator, plastic polymerizer, food producer, etc.) ALPH would stockpile many hundreds of tons of supplies in melt cavities under the ice, plus insulated habitats, to be in place and ready for use when the colonists landed. With the stockpiled supplies, the colonists would construct and operate rovers and flyers to explore the surface of Mars. ALPH greatly reduces the amount of Earth supplied material needed and enables large permanent colonies on Mars. It also greatly reduces human and mission risks and vastly increases the capability not only for exploration of the surrounding Martian surface, but also the ice cap itself. The North Polar Cap is at the center of the vast ancient ocean that covered much of the Martian Northern Hemisphere. Small, nuclear heated robotic probes would travel deep (1 km or more) inside the ice cap, collecting data on its internal structure, the composition and properties of the ancient Martian atmosphere, and possible evidence of ancient life forms (microfossils, traces of DNA, etc.) that were deposited either by wind or as remnants of the ancient ocean

  20. Dust-Driven Halos on the Martian South Polar Residual CAP

    NASA Astrophysics Data System (ADS)

    Becerra, P.; Byrne, S.; Brown, A. J.

    2013-12-01

    The CO2 ice South Polar Residual Cap (SPRC) on Mars may be a sensitive indicator of inter-annual planetary climate variability. Imaging by HiRISE [1], and CTX [2] found that many scarps and pits in the 'Swiss cheese terrain' [3] of the SPRC exhibited a bright 'halo' around their edges. These halos appeared during Martian southern summer in Mars Year 28 (MY28, [4]), and have been observed in only one of eight mars years for which observations at high enough resolution exist. We hypothesize that the formation of these features is linked to the late-summer global dust storm of MY28 and report on observations and formation models. We surveyed HiRISE, CTX, and CRISM [5] data to constrain the optical properties and composition of the halos, as well as their time of appearance and location within the SPRC. The halos appeared throughout most of the surface area of the SPRC between Ls 280° and 330° in MY28. The widest portions of the halos occurred adjacent to north-facing walls, and the brightest parts adjacent to sun-facing walls, which points to a connection between insolation and halo appearance. CRISM spectral products rule out the presence of water ice as a factor in the halos' appearance. These data also imply larger CO2 ice grain sizes where the bright halos were seen, which are normally associated with lower, rather than higher, albedos [6]. Thus, we also ruled out CO2 ice grain size differences as the main cause for the halos. The remaining possibility is that the halos appeared due to differences in dust content between the terrain adjacent to the pit walls and the surrounding ice. To investigate this we made a Hapke [7] surface reflectance model in which the CO2 ice grain size, dust volumetric content and dust particle size were free parameters. We used the HiRISE and CRISM bandpass coefficients to simulate HiRISE I/F values and CRISM spectra, and attempted to match the HiRISE RED I/F, HiRISE BG/RED color ratio, and the CRISM 1.43 μm band depths. A self

  1. First continuous flow analysis results from the Greenland ReCAP project

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid

    2016-04-01

    The new Renland ice core was drilled in summer 2015 in Greenland and measured by means of Continuous flow analysis during the last 3 months of 2015. The Renland ice core was obtained as part of the ReCAP project, extending 584.11 meters to the bottom of the Renland ice cap located in east Greenland. The unique position on a mountain saddle above 2000 meters altitude, but close to the coast, ensures that the Renland ice core offers high accumulation, but also reaches far back in time. Preliminary results show that the record holds ice from the past warm interglacial period, the Eemian. The record was analyzed for multiple elements including the forest fire tracers NH4+ and black carbon, insoluble dust particles by means of Abakus laser particle counter and the dust ion Ca2+, sea salt Na and acidity useful for finding volcanic layers to date the core. Further H2O2, and the nutrients Fe and dissolved reactive phosphorus was analyzed as well as the temperature indicator δ18O all by means of continuous flow analysis (CFA). The core was melted at a rate of 3 cm/min providing a temporal resolution for most components determined sufficient to resolve annual layers through the Holocene. The glacial section is strongly thinned, but nonetheless due to the high resolution of the measurements all DO events could be identified. Below the glacial section another ˜20 meters of warm Eemian ice have been analysed. Here we present the first chemistry results as obtained by continuous flow analysis (CFA).

  2. 3D Imaging and Automated Ice Bottom Tracking of Canadian Arctic Archipelago Ice Sounding Data

    NASA Astrophysics Data System (ADS)

    Paden, J. D.; Xu, M.; Sprick, J.; Athinarapu, S.; Crandall, D.; Burgess, D. O.; Sharp, M. J.; Fox, G. C.; Leuschen, C.; Stumpf, T. M.

    2016-12-01

    The basal topography of the Canadian Arctic Archipelago ice caps is unknown for a number of the glaciers which drain the ice caps. The basal topography is needed for calculating present sea level contribution using the surface mass balance and discharge method and to understand future sea level contributions using ice flow model studies. During the NASA Operation IceBridge 2014 arctic campaign, the Multichannel Coherent Radar Depth Sounder (MCoRDS) used a three transmit beam setting (left beam, nadir beam, right beam) to illuminate a wide swath across the ice glacier in a single pass during three flights over the archipelago. In post processing we have used a combination of 3D imaging methods to produce images for each of the three beams which are then merged to produce a single digitally formed wide swath beam. Because of the high volume of data produced by 3D imaging, manual tracking of the ice bottom is impractical on a large scale. To solve this problem, we propose an automated technique for extracting ice bottom surfaces by viewing the task as an inference problem on a probabilistic graphical model. We first estimate layer boundaries to generate a seed surface, and then incorporate additional sources of evidence, such as ice masks, surface digital elevation models, and feedback from human users, to refine the surface in a discrete energy minimization formulation. We investigate the performance of the imaging and tracking algorithms using flight crossovers since crossing lines should produce consistent maps of the terrain beneath the ice surface and compare manually tracked "ground truth" to the automated tracking algorithms. We found the swath width at the nominal flight altitude of 1000 m to be approximately 3 km. Since many of the glaciers in the archipelago are narrower than this, the radar imaging, in these instances, was able to measure the full glacier cavity in a single pass.

  3. North-south geological differences between the residual polar caps on Mars

    USGS Publications Warehouse

    Thomas, P.C.; Malin, M.C.; Edgett, K.S.; Carr, M.H.; Hartmann, W.K.; Ingersoll, A.P.; James, P.B.; Soderblom, L.A.; Veverka, J.; Sullivan, R.

    2000-01-01

    Polar processes can be sensitive indicators of global climate, and the geological features associated with polar ice caps can therefore indicate evolution of climate with time. The polar regions on Mars have distinctive morphologic and climatologic features: thick layered deposits, seasonal CO2 frost caps extending to mid latitudes, and near-polar residual frost deposits that survive the summer. The relationship of the seasonal and residual frost caps to the layered deposits has been poorly constrained, mainly by the limited spatial resolution of the available data. In particular, it has not been known if the residual caps represent simple thin frost cover or substantial geologic features. Here we show that the residual cap on the south pole is a distinct geologic unit with striking collapse and erosional topography; this is very different from the residual cap on the north pole, which grades into the underlying layered materials. These findings indicate that the differences between the caps are substantial (rather than reflecting short-lived differences in frost cover), and so support the idea of long-term asymmetry in the polar climates of Mars.

  4. South polar residual cap of Mars: Features, stratigraphy, and changes

    NASA Astrophysics Data System (ADS)

    Thomas, P. C.; Malin, M. C.; James, P. B.; Cantor, B. A.; Williams, R. M. E.; Gierasch, P.

    2005-04-01

    The south residual polar cap of Mars, rich in CO 2 ice, is compositionally distinct from the north residual cap which is dominantly H 2O ice. The south cap is also morphologically distinct, displaying a bewildering variety of depressions formed in thin layered deposits, which have been observed to change by scarp retreat over an interval of one Mars year (Malin et al., 2001, Science 294, 2146-2148). The climatically sensitive locale of the residual caps suggests that their behavior may help in the interpretation of recent fluctuations or repeatability of the Mars climate. We have used Mars Global Surveyor Mars Orbiter Camera (MOC) images obtained in three southern summers to map the variety of features in the south residual cap and to evaluate changes over two Mars years (Mars y). The images show that there are two distinct layered units which were deposited at different times separated by a period of degradation. The older unit, ˜10 m thick, has layers approximately 2 m thick. The younger unit has variable numbers of layers, each ˜1 m thick. The older unit is eroding by scarp retreat averaging 3.6 m/Mars y, a rate greater than the retreat of 2.2 m/Mars y observed for the younger unit. The rates of scarp retreat and sizes of the different types of depressions indicate that the history of the residual cap has been short periods of deposition interspersed with longer erosional periods. Erosion of the older unit probably occupied ˜100-150 Mars y. One layer may have been deposited after the Mariner 9 observations in 1972. Residual cap layers appear to differ from normal annual winter deposits by having a higher albedo and perhaps by having higher porosities. These properties might be produced by differences in the depositional meteorology that affect the fraction of high porosity snow included in the winter deposition.

  5. Interpreting the Holocene fluctuations of Quelccaya Ice Cap, Peru: using a combination of glacial and non-glacial lake records

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.; Smith, C.; Beal, S. A., Jr.; Tapia, P. M.

    2016-12-01

    The past fluctuations of Quelccaya Ice Cap (QIC) are an indicator of tropical paleoclimate. At QIC, ice core and glacial geological records provide late Holocene climate constraints. However, early and middle Holocene QIC fluctuations are less well-known. To interpret past QIC fluctuations, we present Holocene-long lake sediment records from Challpacocha, a lake fed by QIC meltwater, and Yanacocha, a lake that has not received meltwater during the Holocene. To assess the clastic sediment delivered to Challpacocha by QIC meltwater, we compare visual stratigraphy, X-ray fluorescence chemistry, grainsize, loss on ignition and clastic flux records from both lakes (additional Yanacocha proxies are presented by Axford et al. (this meeting, abstract 157985)). We compare the meltwater derived clastic sediment record from Challpacocha with moraine and stratigraphic records of past ice extents during the late Holocene. This comparison indicates that clastic sediment flux in Challpacocha increased during QIC recession and decreased during QIC advance, or significantly reduced QIC extent. We then use the Challpacocha clastic sediment record to interpret early and middle Holocene QIC fluctuations. Based on the Challpacocha sediment record, combined with prior work, we suggest that from 11 to 6.5 ka QIC was similar to or smaller than its late Holocene extent. From 6.9 to 6.5 ka QIC may have been absent from the landscape. At 3-2.4 and 0.62-0.31 ka QIC experienced the most extensive Holocene fluctuations. We compare the clastic sediment fluxes from Challpacocha and Pacococha (a nearby lake fed by QIC; Rodbell et al., 2008) to infer QIC expansion between 6.5-5 ka. This is supported by 14C ages of in-situ subfossil plants which indicate ice advance at 6.3-4.7 ka (Thompson et al., 2006, 2013; Buffen et al., 2009). Our study highlights the value of using multiple datasets to improve lake sediment record interpretations.

  6. Central Tibetan Plateau atmospheric trace metals contamination: A 500-year record from the Puruogangri ice core.

    PubMed

    Beaudon, Emilie; Gabrielli, Paolo; Sierra-Hernández, M Roxana; Wegner, Anna; Thompson, Lonnie G

    2017-12-01

    A ~500-year section of ice core (1497-1992) from the Puruogangri ice cap has been analyzed at high resolution for 28 trace elements (TEs: Ag, Al, As, Ba, Bi, Cd, Co, Cr, Cs, Cu, Fe, Ga, Li, Mg, Mn, Na, Nb, Ni, Pb, Rb, Sb, Sn, Sr, Ti, Tl, U, V and Zn) to assess different atmospheric contributions to the ice and provide a temporal perspective on the diverse atmospheric influences over the central Tibetan Plateau (TP). At least two volcanic depositions have significantly impacted the central TP over the past 500years, possibly originating from the Billy Mitchell (1580, Papua New Guinea) and the Parker Peak (1641, Philippines) eruptions. A decreasing aeolian dust input to the ice cap allowed the detection of an atmospheric pollution signal. The anthropogenic pollution contribution emerges in the record since the early 1900s (for Sb and Cd) and increases substantially after 1935 (for Ag, Zn, Pb, Cd and Sb). The metallurgy (Zn, Pb and steel smelting) emission products (Cd, Zn, Pb and Ag) from the former Soviet Union and especially from central Asia (e.g., Kyrgyzstan, Kazakhstan) likely enhanced the anthropogenic deposition to the Puruogangri ice cap between 1935 and 1980, suggesting that the westerlies served as a conveyor of atmospheric pollution to central Tibet. The impact of this industrial pollution cumulated with that of the hemispheric coal and gasoline combustion which are respectively traced by Sb and Pb enrichment in the ice. The Chinese steel production accompanying the Great Leap Forward (1958-1961) and the Chinese Cultural Revolution (1966-1976) is proposed as a secondary but proximal source of Pb pollution affecting the ice cap between 1958 and 1976. The most recent decade (1980-1992) of the enrichment time series suggests that Puruogangri ice cap recorded the early Sb, Cd, Zn, Pb and Ag pollution originating from developing countries of South (i.e., India) and East (i.e., China) Asia and transported by the summer monsoonal circulation. Published by

  7. Mars South Polar Cap "Fingerprint" Terrain

    NASA Image and Video Library

    2000-04-24

    This picture is illuminated by sunlight from the upper left. Some portions of the martian south polar residual cap have long, somewhat curved troughs instead of circular pits. These appear to form in a layer of material that may be different than that in which "swiss cheese" circles and pits form, and none of these features has any analog in the north polar cap or elsewhere on Mars. This picture shows the "fingerprint" terrain as a series of long, narrow depressions considered to have formed by collapse and widening by sublimation of ice. Unlike the north polar cap, the south polar region stays cold enough in summer to retain frozen carbon dioxide. Viking Orbiter observations during the late 1970s showed that very little water vapor comes off the south polar cap during summer, indicating that any frozen water that might be there remains solid throughout the year. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was obtained in early southern spring on August 4, 1999. It shows an area 3 x 5 kilometers (1.9 x 3.1 miles) at a resolution of about 7.3 meters (24 ft) per pixel. Located near 86.0°S, 53.9°W. http://photojournal.jpl.nasa.gov/catalog/PIA02373

  8. Detecting Near-Surface Ice Formation Over Time Using the Kennaugh Elements Approach From TerraSAR-X

    NASA Astrophysics Data System (ADS)

    Fernandes, L.

    2016-12-01

    The summer melting has increased substantially at higher elevations on the Canadian Arctic ice caps. The resulting meltwater percolates into the upper layers of snow and firn and then refreeze, building massive ice bodies. It seems likely that these within-firn ice bodies now limit meltwater penetration into the firn and may be creating a feedback whereby the fraction of melt that runs off to the ocean is increasing. Although changes in firn structure as presence of ice layers and ice bodies are well documented over the Devon ice cap, the firm has shown that it exerts a crucial role to predict more accurately the contribution of small ice caps to the sea level rise. However it is still challenging to assess the extent of these features within the shallow subsurface using ice cores and GPR (Ground Penetrating Radar) data collected along a limited number of linear transects. Studying changes in the distribution of ice bodies' formation over time has the potential to provide information about how the growth of ice bodies in the firn is affecting the pattern of water flow in the firn layer. The objective is investigate the potential of Kennaugh Elements (KE) derived from x-band SAR (Synthetic Aperture Radar) for mapping the distribution and growth of large ice bodies within the firn and the evolution of their distribution over time. The evaluation of this method could reveal a new approach suitable for other glacierized regions that would reduce the costs and amount of field work for studying such properties.

  9. Possible recent and ancient glacial ice flow in the south polar region of Mars

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.

    1992-01-01

    Martian polar science began almost as soon as small telescopes were trained on the planet. The seasonal expansion and contraction of the polar caps and their high albedoes led most astronomers to think that water ice is the dominant constituent. In 1911 Lowell perceived a bluish band around the retreating edge of the polar caps, and interpreted it as water from melting polar ice and seasonal snow. An alternative idea in his time was that the polar caps consist of frozen carbonic acid. Lowell rejected the carbonic acid hypothesis on account of his blue band. He also pointed out that carbonic acid would sublimate rather than melt at confining pressures near and below one bar, hence, carbonic acid could not account for the blue band. In comparing Lowell's theories with today's knowledge, it is recognized that (1) sublimation is mainly responsible for the growth and contraction of Mars' polar caps, (2) carbon dioxide is a major component of the southern polar cap, and (3) Lowell's blue band was probably seasonal dust and/or clouds. Geomorphic evidence that glacial ice and glacial melt waters once flowed over broad areas of the southern polar region. Two aspects of the south polar region suggest possible glacial processes during two distinct eras in Mars' history.

  10. Mass Balance Changes and Ice Dynamics of Greenland and Antarctic Ice Sheets from Laser Altimetry

    NASA Astrophysics Data System (ADS)

    Babonis, G. S.; Csatho, B.; Schenk, T.

    2016-06-01

    During the past few decades the Greenland and Antarctic ice sheets have lost ice at accelerating rates, caused by increasing surface temperature. The melting of the two big ice sheets has a big impact on global sea level rise. If the ice sheets would melt down entirely, the sea level would rise more than 60 m. Even a much smaller rise would cause dramatic damage along coastal regions. In this paper we report about a major upgrade of surface elevation changes derived from laser altimetry data, acquired by NASA's Ice, Cloud and land Elevation Satellite mission (ICESat) and airborne laser campaigns, such as Airborne Topographic Mapper (ATM) and Land, Vegetation and Ice Sensor (LVIS). For detecting changes in ice sheet elevations we have developed the Surface Elevation Reconstruction And Change detection (SERAC) method. It computes elevation changes of small surface patches by keeping the surface shape constant and considering the absolute values as surface elevations. We report about important upgrades of earlier results, for example the inclusion of local ice caps and the temporal extension from 1993 to 2014 for the Greenland Ice Sheet and for a comprehensive reconstruction of ice thickness and mass changes for the Antarctic Ice Sheets.

  11. Life in Ice: Implications to Astrobiology

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2009-01-01

    During the 2008 Tawani International Expedition Schirmacher Oasis/Lake Untersee Antarctica Expedition, living and instantly motile bacteria were found in freshly thawed meltwater from ice of the Schirmacher Oasis Lakes, the Anuchin Glacier ice and samples of the that perennial ice sheet above Lake Untersee. This phenomenon of living bacteria encased in ice had previously been observed in the 32,000 year old ice of the Fox Tunnel. The bacteria found in this ice included the strain FTR1T which was isolated and published as valid new species (Carnobacterium pleistocenium) the first validly published living Pleistocene organism still alive today. Living bacteria were also extracted from ancient ice cores from Vostok, Antarctica. The discovery that many strains of bacteria are able to survive and remain alive while frozen in ice sheets for long periods of time may have direct relevance to Astrobiology. The abundance of viable bacteria in the ice sheets of Antarctica suggests that the presence of live bacteria in ice is common, rather than an isolated phenomenon. This paper will discuss the results of recent studies at NSSTC of bacteria cryopreserved in ice. This paper advances the hypothesis that cryopreserved cells, and perhaps even viable bacterial cells, may exist today--frozen in the water-ice of lunar craters, the Polar Caps or craters of Mars; or in the permafrost of Mars; ice and rocks of comets or water bearing asteroids; or in the frozen crusts of the icy moons of Jupiter and Saturn. The existence of bacterial life in ice suggests that it may not be necessary to drill through a thick ice crust to reach liquid water seas deep beneath the icy crusts of Europa, Ganymede and Enceladus. The presence of viable bacteria in the ice of the Earth s Polar Caps suggests that the possibility that cryo-panspermia (i.e., the trans-planetary transfer of microbial life by impact ejection/spallation of bacteria-rich polar ice masses) deserves serious consideration and study as a

  12. Colonization of maritime glacier ice by bdelloid Rotifera.

    PubMed

    Shain, Daniel H; Halldórsdóttir, Katrín; Pálsson, Finnur; Aðalgeirsdóttir, Guðfinna; Gunnarsson, Andri; Jónsson, Þorsteinn; Lang, Shirley A; Pálsson, Hlynur Skagfjörð; Steinþórssson, Sveinbjörn; Arnason, Einar

    2016-05-01

    Very few animal taxa are known to reside permanently in glacier ice/snow. Here we report the widespread colonization of Icelandic glaciers and ice fields by species of bdelloid Rotifera. Specimens were collected within the accumulation zones of Langjökull and Vatnajökull ice caps, among the largest European ice masses. Rotifers reached densities up to ∼100 individuals per liter-equivalent of glacier ice/snow, and were freeze-tolerant. Phylogenetic analyses indicate that glacier rotifers are polyphyletic, with independent ancestries occurring within the Pleistocene. Collectively, these data identify a previously undescribed environmental niche for bdelloid rotifers and suggest their presence in comparable habitats worldwide. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. Pleistocene reduction of polar ice caps: Evidence from Cariaco Basin marine sediments

    USGS Publications Warehouse

    Poore, R.Z.; Dowsett, H.J.

    2001-01-01

    Sea level is projected to rise between 13 and 94 cm over the next 100 yr due to continued climate warming. The sea-level projections assume that polar ice sheets will remain stable or even increase on time scales of centuries, but controversial geologic evidence suggests that current polar ice sheets have been eliminated or greatly reduced during previous Pleistocene interglacials indicating that modern polar ice sheets have become unstable within the natural range of interglacial climates. Sea level may have been more than 20 m higher than today during a presumably very warm interglacial about 400 ka during marine isotope stage 11. Because of the implications for future sea level rise, additional study of the conflicting evidence for warmer conditions and higher sea level during marine isotope stage 11 is needed. Here we present microfossil and isotopic data from marine sediments of the Cariaco Basin supporting the interpretation that global sea level was 10-20 m higher than today during marine isotope stage 11. The increased sea level requires reduction in modern polar ice sheets and is consistent with the interpretation that the West Antarctic ice sheet and the Greenland ice sheet were absent or greatly reduced during marine isotope stage 11. Our results show a warm marine isotope stage 11 interglacial climate with sea level as high as or above modern sea level that lasted for 25 to 30 k.y. Variations in Earth's orbit around the sun (Milankovitch cycles) are considered to be a primary external force driving glacial-interglacial cycles. Current and marine isotope stage 11 Milankovitch forcing are very similar, suggesting that the present interglacial (Holocene) that began ca. 10 ka will continue for another 15 to 20 k.y. Therefore any anthropogenic climate warming will accelerate the natural process toward reduction in polar ice sheets. The potential for increased rates of sea level rise related to polar ice sheet decay should be considered as a potential natural

  14. North-Polar Martian Cap as Habitat for Elementary Life

    NASA Astrophysics Data System (ADS)

    Wallis, M. K.; Wickramasinghe, J. T.; Wickramasinghe, N. C.

    2008-09-01

    North-polar cap over millenia Atmospheric water in Mars tends currently as for the past millenia to distil onto the polar caps and be buried under dust deposits. Diffusive release from ground-ice (and its excavation in meteorite impacts [1]) replenishes atmospheric water, allowing the gradual build up of polar ice-dust deposits. When sunlit, this warmed and sublimating ice-dust mix has interest as a potential habitat for micro-organisms. Modelling shows precipitable vapour at 10-50μm/yr, varying sensitively with small changes in orbitable obliquity around the present 25° [2]. The modelling applies to a globe with regionally uniform albedo, unlike the steep topography and dark layering of the north polar cap whose upper 300m have accumulated over the last 500 kyr [3]. The cliffs and ravines of the north-polar cap are thought to form through south-facing slopes sublimating and gaining a dirt-encrusted surface, while horizontal surfaces brighten through frost deposits. The two-phase surface derives from the dust and frost feedback on surface albedo [4] and the resulting terrain develops over diurnal cycles of frosting and sublimation, and over annual seasonal cycles. The steep south-facing sides of observed ravines when unshadowed would see for a few hours the full intensity of sunlight at near normal incidence, without the atmospheric dimming at similar inclinations on Earth. As exposed ice sublimates at T > 200K (partial pressure exceeds typical martian 0.1 Pa), a crust of dirt develops to maintain quasi-stability. The dirt crust's main function is to buffer the ice against diurnal temperature fluctuations, but it also slows down vapour diffusion - analogous to south polar ice sublimation [5] and the growth of ground-ice [6]. We envisage 1-10 mm/yr as the net sublimation rate, compatible with the 100 kyr life and scales of the north polar ravines. Modelling of icy-dirt crusts in the polar cap Plane-parallel layers have been used to model the changing temperature

  15. A Newly Updated Database of Elevation-changes of the Greenand Ice Sheet to Study Surface Processes and Ice Dynamics

    NASA Astrophysics Data System (ADS)

    Schenk, A. F.; Csatho, B. M.; van den Broeke, M.; Kuipers Munneke, P.

    2015-12-01

    This paper reports about important upgrades of the Greenland Ice Sheet (GrIS) surface elevation and elevation-change database obtained with our Surface Elevation And Change detection (SERAC) software suite. We have developed SERAC to derive information from laser altimetry data, particularly time series of elevation changes and their partitioning into changes caused by ice dynamics. This allows direct investigation of ice dynamic processes that is much needed for improving the predictive power of ice sheet models. SERAC is different from most other change detection methods. It is based on detecting changes of surface patches, about 1 km by 1 km in size, rather than deriving elevation changes from individual laser points. The current database consists of ~100,000 time series with satellite laser altimetry data from ICESat, airborne laser observations obtained by NASA's Airborne Topographic Mapper (ATM) and the Land, Vegetation and Ice Sensor (LVIS). The upgrade is significant, because not only new observations from 2013 and 2014 have been added but also a number of improvements lead to a more comprehensive and consistent record of elevation-changes. First, we used the model that gives in addition to ice sheet also information about ice caps and glaciers (Rastner et al., 2012) for deciding if a laser point is on the ice sheet or ice cap. Then we added small gaps that exist in the ICESat GLA12 data set because the ice sheet mask is not wide enough. The new database is now more complete and will facilitate more accurate comparisons of mass balance studies obtained from the Gravity Recovery and Climate Experiment system (GRACE). For determining the part of a time series caused by ice dynamics we used the new firn compaction model and Surface Mass Balance (SMB) estimates from RACMO2.3. The new database spans the time period from 1993 to 2014. Adding new observations amounts to a spatial densification of the old record and at the same time extends the time domain by two

  16. Boundary Waves on the Ice Surface Created by Currents

    NASA Astrophysics Data System (ADS)

    Naito, K.; Izumi, N.; Yokokawa, M.; Yamada, T.; de Lima, A. C.

    2013-12-01

    The formation of periodic boundary waves, e.g. antidunes and cyclic steps (Parker & Izumi 2000) has been known to be caused by instabilities between flow and bed (e.g. Engelund 1970), and are observed not only on river beds or ocean floors but also on ice surfaces, such as the surface of glaciers and underside of river ice (Carey 1966). In addition, owing to recent advancements of remote sensing technology, it has been found that the surfaces of the polar ice caps on Mars as well as on the Earth have step-like formations (Smith & Holt 2010) which are assumed to be boundary waves, because they are generated perpendicularly to the direction of the currents. These currents acting on the polar ice caps are density airflow, i.e. katabatic wind (Howard et al 2000). The comprehension of the formation process of the Martian polar ice caps may reveal climate changes which have occurred on Mars. Although the formation of boundary waves on river beds or ocean floors has been studied by a number of researchers, there are few works on their formation on ice surfaces. Yokokawa et al (2013) suggested that the temperature distribution of the ambient air, fluid and ice is a factor which determines the direction of migration of boundary waves formed on ice surfaces through their experiments. In this study, we propose a mathematical model in order to describe the formation process of the boundary waves and the direction of their migration. We consider that a liquid is flowing through a flume filled with a flat ice layer on the bottom. The flow is assumed to be turbulent and its temperature is assumed to merge with the ambient temperature at the flow surface and with the melting point of ice at the bottom (ice surface). The ice surface evolution is dependent on the unbalance between the interfacial heat flux of the liquid and ice, and we employ the Reynolds-averaged Navier-Stokes equation, the continuity equation, heat transfer equations for the liquid and ice, and a heat balance

  17. Thermal infrared and visual observations of a water ice lag in the Mars southern summer

    USGS Publications Warehouse

    Titus, T.N.

    2005-01-01

    We present thermal infrared and visual evidence for the existence of water ice lags in the early southern summer. The observed H2O-ice lags lay in and near a chasma and appears to survive between 6-8 sols past the sublimation of the CO2. Possible sources of the H2O that compose the lag are (1) atmospheric H2O that is incorporated into the seasonal cap during condensation, (2) cold trapping of atmospheric water vapor onto the surface of the cap in the spring, or (3) a combination of the 2 processes where water is released from the sublimating cap only to be transported back over the cap edge and cold trapped. We refer to this later process as the "Houben" effect which may enrich the amount of water contained in the seasonal cap at 85??S by as much as a factor of 15. This phenomenon, which has already been identified for the northern retreating cap, may present an important water transport mechanism in the Southern Hemisphere.

  18. Constraints on the Within Season and Between Year Variability of the North Residual Cap from MGS-TES

    NASA Technical Reports Server (NTRS)

    Calvin, W. M.; Titus, T. N.; Mahoney, S. A.

    2003-01-01

    There is a long history of telescopic and spacecraft observations of the polar regions of Mars. The finely laminated ice deposits and surrounding layered terrains are commonly thought to contain a record of past climate conditions and change. Understanding the basic nature of the deposits and their mineral and ice constituents is a continued focus of current and future orbited missions. Unresolved issues in Martian polar science include a) the unusual nature of the CO2 ice deposits ("Swiss Cheese", "slab ice" etc.) b) the relationship of the ice deposits to underlying layered units (which differs from the north to the south), c) understanding the seasonal variations and their connections to the finely laminated units observed in high-resolution images and d) the relationship of dark materials in the wind-swept lanes and reentrant valleys to the surrounding dark dune and surface materials. Our work focuses on understanding these issues in relationship to the north residual ice cap. Recent work using Mars Global Surveyor (MGS) data sets have described evolution of the seasonal CO2 frost deposits. In addition, the north polar residual ice cap exhibits albedo variations between Mars years and within the summer season. The Thermal Emission Spectrometer (TES) data set can augment these observations providing additional constraints such as temperature evolution and spectral properties associated with ice and rocky materials. Exploration of these properties is the subject of our current study.

  19. North Polar Cap Layers and Ledges

    NASA Image and Video Library

    2016-08-24

    At the edge of Mars' permanent North Polar cap, we see an exposure of the internal layers, each with a different mix of water ice, dust and dirt. These layers are believed to correspond to different climate conditions over the past tens of thousands of years. When we zoom in closer, we see that the distinct layers erode differently. Some are stronger and more resistant to erosion, others only weakly cemented. The strong layers form ledges. http://photojournal.jpl.nasa.gov/catalog/PIA21022

  20. Simulating the roles of crevasse routing of surface water and basal friction on the surge evolution of Basin 3, Austfonna ice cap

    NASA Astrophysics Data System (ADS)

    Gong, Yongmei; Zwinger, Thomas; Åström, Jan; Altena, Bas; Schellenberger, Thomas; Gladstone, Rupert; Moore, John C.

    2018-05-01

    The marine-terminating outlet in Basin 3, Austfonna ice cap, has been accelerating since the mid-1990s. Stepwise multi-annual acceleration associated with seasonal summer speed-up events was observed before the outlet entered the basin-wide surge in autumn 2012. We used multiple numerical models to explore hydrologic activation mechanisms for the surge behaviour. A continuum ice dynamic model was used to invert basal friction coefficient distributions using the control method and observed surface velocity data between April 2012 and July 2014. This has provided input to a discrete element model capable of simulating individual crevasses, with the aim of finding locations where meltwater entered the glacier during the summer and reached the bed. The possible flow paths of surface meltwater reaching the glacier bed as well as those of meltwater produced at the bed were calculated according to the gradient of the hydraulic potential. The inverted friction coefficients show the unplugging of the stagnant ice front and expansion of low-friction regions before the surge reached its peak velocity in January 2013. Crevasse distribution reflects the basal friction pattern to a high degree. The meltwater reaches the bed through the crevasses located above the margins of the subglacial valley and the basal melt that is generated mainly by frictional heating flows either to the fast-flowing units or potentially accumulates in an overdeepened region. Based on these results, the mechanisms facilitated by basal meltwater production, crevasse opening and the routing of meltwater to the bed are discussed for the surge in Basin 3.

  1. Variability of the martian seasonal CO2 cap extent over eight Mars Years

    NASA Astrophysics Data System (ADS)

    Piqueux, Sylvain; Kleinböhl, Armin; Hayne, Paul O.; Kass, David M.; Schofield, John T.; McCleese, Daniel J.

    2015-05-01

    We present eight Mars Years of nearly continuous tracking of the CO2 seasonal cap edges from Mars Year (MY) 24 to 31 using Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) and Mars Reconnaissance Orbiter (MRO) Mars Climate Sounder (MCS) thermal infrared data. Spatial and temporal resolutions are 1 pixel per degree and 10°Ls (aerocentric longitude of the Sun). The seasonal caps are defined as the regions where the diurnal radiometric temperature variations at ∼32 μm wavelength do not exceed 5 K. With this definition, terrains with small areal fraction of defrosted regolith able to experience measurable diurnal temperature cycles are not mapped as part of the cap. This technique is adequate to distinguish CO2 from H2O ices, and effective during the polar night or under low illumination conditions. The present analysis answers outstanding questions stemming from fragmented observations at visible wavelengths: (1) the previously sparsely documented growth of the North seasonal caps (160° < Ls < 270°) is shown to be repeatable within 1-2° equivalent latitude, and monotonic over the MY 24-31 time period; high repeatability is observed during the retreat of the caps in non-dusty years (∼1° or less equivalent latitude); (2) the MY 25 storm does not seem to have impacted the growth rate, maximal extents, or recession rate of the North seasonal caps, whereas the MY 28 dust storm clearly sped up the recession of the cap (∼2° smaller on average after the storm, during the recession, compared to other years); (3) during non-dusty years, the growth of the South seasonal cap (350° < Ls < 100°) presents noticeable variability (up to ∼4° equivalent latitude near Ls = 20°) with a maximum extent reached near Ls = 90°; (4) the retreat of the Southern seasonal cap (100° < Ls < 310°) exhibits large inter-annual variability, especially near 190° < Ls < 220°; (5) the recession of the MY 25 South seasonal cap is significantly accelerated during the

  2. Sedimentation Waves on the Martian North Polar Cap: Analogy with Megadunes in Antarctica

    NASA Astrophysics Data System (ADS)

    Herny, C.; Masse, M.; Bourgeois, O.; Carpy, S.; Le Mouelic, S.; Appéré, T.; Smith, I. B.; Spiga, A.; Perret, L.; Rodriguez, S.; Piquet, T.; Gaudin, D.; Le Menn, E.

    2014-12-01

    Complex feedbacks between katabatic winds and the cryosphere may lead to the development of sedimentation waves at the surface of ice sheets. These have been first described and named megadunes in Antarctica. Here we use topographic data, optical images, spectroscopic data and radar soundings, acquired by Mars orbiters, to show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. They have similarities with Antarctic megadunes regarding their surface morphology, texture, grain size, and internal stratigraphic architecture. Based on this analogy, we are currently developing a model of ice/wind interaction at the surface of ice sheets. In Antarctica the accumulation processes on megadunes fields is generally attributed to the wind-blown snow transport while on sedimentation waves of the North Polar Cap of Mars the accumulation seems to be dominated by sublimation/condensation processes at the surface. The model is designed to explore the implication of the water vapor mass transfer and heat transfer on the development of sedimentation waves both on Mars and Earth.

  3. Ice Thickness, Melting Rates and Styles of Activity in Ice-Volcano Interaction

    NASA Astrophysics Data System (ADS)

    Gudmundsson, M. T.

    2005-12-01

    In most cases when eruptions occur within glaciers they lead to rapid ice melting, jokulhlaups and/or lahars. Many parameters influence the style of activity and its impact on the environment. These include ice thickness (size of glacier), bedrock geometry, magma flow rate and magma composition. The eruptions that have been observed can roughly be divided into: (1) eruptions under several hundred meters thick ice on a relatively flat bedrock, (2) eruptions on flat or sloping bed through relatively thin ice, and (3) volcanism where effects are limitied to confinement of lava flows or melting of ice by pyroclastic flows or surges. This last category (ice-contact volcanism) need not cause much ice melting. Many of the deposits formed by Pleistocene volcanism in Iceland, British Columbia and Antarctica belong to the first category. An important difference between this type of activity and submarine activity (where pressure is hydrostatic) is that pressure at vents may in many cases be much lower than glaciostatic due to partial support of ice cover over vents by the surrounding glacier. Reduced pressure favours explosive activity. Thus the effusive/explosive transition may occur several hundred metres underneath the ice surface. Explosive fragmentation of magma leads to much higher rates of heat transfer than does effusive eruption of pillow lavas, and hence much higher melting rates. This effect of reduced pressure at vents will be less pronounced in a large ice sheet than in a smaller glacier or ice cap, since the hydraulic gradient that drives water away from an eruption site will be lower in the large glacier. This may have implications for form and type of eruption deposits and their relationship with ice thickness and glacier size.

  4. Atmospheric precursors of and response to anomalous Arctic sea ice in CMIP5 models

    NASA Astrophysics Data System (ADS)

    Kelleher, Michael; Screen, James

    2018-01-01

    This study examines pre-industrial control simulations from CMIP5 climate models in an effort to better understand the complex relationships between Arctic sea ice and the stratosphere, and between Arctic sea ice and cold winter temperatures over Eurasia. We present normalized regressions of Arctic sea-ice area against several atmospheric variables at extended lead and lag times. Statistically significant regressions are found at leads and lags, suggesting both atmospheric precursors of, and responses to, low sea ice; but generally, the regressions are stronger when the atmosphere leads sea ice, including a weaker polar stratospheric vortex indicated by positive polar cap height anomalies. Significant positive midlatitude eddy heat flux anomalies are also found to precede low sea ice. We argue that low sea ice and raised polar cap height are both a response to this enhanced midlatitude eddy heat flux. The so-called "warm Arctic, cold continents" anomaly pattern is present one to two months before low sea ice, but is absent in the months following low sea ice, suggesting that the Eurasian cooling and low sea ice are driven by similar processes. Lastly, our results suggest a dependence on the geographic region of low sea ice, with low Barents-Kara Sea ice correlated with a weakened polar stratospheric vortex, whilst low Sea of Okhotsk ice is correlated with a strengthened polar vortex. Overall, the results support a notion that the sea ice, polar stratospheric vortex and Eurasian surface temperatures collectively respond to large-scale changes in tropospheric circulation.

  5. Variations in Surface Texture of the North Polar Residual Cap of Mars

    NASA Technical Reports Server (NTRS)

    Milkovich, S. M.; Byrne, S.; Russell, P. S.

    2011-01-01

    The northern polar residual cap (NPRC) of Mars is a water ice deposit with a rough surface made up of pits, knobs, and linear depressions on scales of tens of meters. This roughness manifests as a series of bright mounds and dark hollows in visible images; these bright and dark patches have a characteristic wavelength and orientation. Spectral data indicate that the surface of the NPRC is composed of large-grained (and therefore old) water ice. Due to the presence of this old ice, it is thought that the NPRC is in a current state of net loss of material a result potentially at odds with impact crater statistics, which suggest ongoing deposition over the past 10-20 Kyr.

  6. Sensing the bed-rock movement due to ice unloading from space using InSAR time-series

    NASA Astrophysics Data System (ADS)

    Zhao, W.; Amelung, F.; Dixon, T. H.; Wdowinski, S.

    2014-12-01

    Ice-sheets in the Arctic region are retreating rapidly since late 1990s. Typical ice loss rates are 0.5 - 1 m/yr at the Canadian Arctic Archipelago, ~ 1 m/yr at the Icelandic ice sheets, and several meters per year at the edge of Greenland ice sheet. Such load decreasing causes measurable (several millimeter per year) deformation of the Earth's crust from Synthetic Aperture Radar Interferometry (InSAR). Using small baseline time-series analysis, this signal is retrieved after noises such as orbit error, atmospheric delay and DEM error being removed. We present results from Vatnajokull ice cap, Petermann glacier and Barnes ice cap using ERS, Envisat and TerraSAR-X data. Up to 2 cm/yr relative radar line-of-sight displacement is detected. The pattern of deformation matches the shape of ice sheet very well. The result in Iceland was used to develop a new model for the ice mass balance estimation from 1995 to 2010. Other applications of this kind of technique include validation of ICESat or GRACE based ice sheet model, Earth's rheology (Young's modulus, viscosity and so on). Moreover, we find a narrow (~ 1km) uplift zone close to the periglacial area of Petermann glacier which may due to a special rheology under the ice stream.

  7. Trace Element Determination from the Guliya Ice Core to Characterize Aerosol Deposition over the Western Tibetan Plateau during the Last 500 Years

    NASA Astrophysics Data System (ADS)

    Sierra Hernandez, R.; Gabrielli, P.; Beaudon, E.; Wegner, A.; Thompson, L. G.

    2014-12-01

    The Tibetan Plateau or Third Pole covers over 5 million km2, and has ~46,000 glaciers that collectively contain one of the Earth's largest stores of fresh water. The Guliya ice cap located in the western Kunlun Shan on the Qinghai-Tibetan Plateau, China, is the largest (> 200 km2) ice cap in the subtropical zone. In 1992, a 308.6 m ice core to bedrock was recovered from the Guliya ice cap. The deepest 20 meters yielded the first record extending back through the last glacial cycle found outside of the Polar Regions. Because of its continental location on the northwestern side of the Tibetan Plateau, the atmospheric circulation over the Guliya ice cap is dominated by westerly air flow from the Eurasian region. Therefore the site is expected to be unaffected by the fallout of anthropogenic trace metals originating from the inner Asian continent and rather may serve to characterize trace metal emissions from the western countries. Here we present preliminary results of the determination of 29 trace elements, Rb, Sr, Nb, Mo, Ag, Cd, Sn, Sb, Cs, Ba, Ta, Tl, Pb, Bi, U, Li, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, and As, from Guliya ice core samples spanning the period 1500 - 1992 AD at seasonal (1750-1992 AD) and annual (1500-1750 AD) resolution. This Guliya trace element record will complement the developing records from the Dasuopu glacier, central Himalaya, and from the Puruogangri ice cap in the western Tanggula Shan in central Tibetan Plateau, which in contrast to Guliya are influenced by the monsoon. We investigate the possible sources both natural and anthropogenic of atmospheric trace elements and their fluxes over the Tibetan Plateau during the last 500 years.

  8. CryoScout: A Descent Through the Mars Polar Cap

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Saunders, R. S.

    2003-01-01

    CryoScout was proposed as a subsurface investigation of the stratigraphic climate record embedded in Mars North Polar cap. After landing on a gentle landscape in the midst of the mild summer season, CryoScout was to use the continuous polar sunlight to power the descent of a cryobot, a thermal probe, into the ice at a rate of about 1 m per day. CryoScout would probe deep enough into this time capsule to see the effects of planetary obliquity variations and discrete events such as dust storms or volcanic eruptions. By penetrating tens of meters of ice, the mission would explore at least one of the dominant "MOC layers" observed in exposed layered terrain.

  9. Earth's Climate History from Glaciers and Ice Cores

    NASA Astrophysics Data System (ADS)

    Thompson, Lonnie

    2013-03-01

    Glaciers serve both as recorders and early indicators of climate change. Over the past 35 years our research team has recovered climatic and environmental histories from ice cores drilled in both Polar Regions and from low to mid-latitude, high-elevation ice fields. Those ice core -derived proxy records extending back 25,000 years have made it possible to compare glacial stage conditions in the Tropics with those in the Polar Regions. High-resolution records of δ18O (in part a temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although at many sites the early Holocene was warmer than today. Remarkable similarities between changes in the highland and coastal cultures of Peru and regional climate variability, especially precipitation, imply a strong connection between prehistoric human activities and regional climate. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions today are different from those under which these ice fields originated and have been sustained. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth's climate system is underway. Observations of glacier shrinkage during the 20th and 21st century girdle the globe from the South American Andes, the Himalayas, Kilimanjaro (Tanzania, Africa) and glaciers near Puncak Jaya, Indonesia (New Guinea). The history and fate of these ice caps, told through the adventure, beauty and the scientific evidence from some of world's most remote mountain tops, provide a global perspective for contemporary climate. NSF Paleoclimate Program

  10. High-amplitude, centennial-scale climate oscillations during the last glacial in the western Third Pole as recorded in the Guliya ice cap

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Yao, T.; Mosley-Thompson, E.; Wu, G.; Davis, M. E.; Tian, L.; Lin, P. N.

    2015-12-01

    The Guliya ice cap, located in the Kunlun Mountains in the western Third Pole (TP) region near the northern limit of the southwest monsoon influence, may be the only non-polar ice field that provides detailed histories of climate and environment over the last glacial cycle. A continuous climate record from an ice core drilled in 1992 contains Eemian ice, and basal temperatures measured that year confirmed that the record was not being removed from the bottom. The δ18O record throughout Marine Isotope Stage 2 (MIS2) displays the occurrence of high-amplitude (~20‰) episodes of ~200-year periodicity, and the aerosol records suggest snow cover, regional vegetation and fire frequency that vary in synchrony. These oscillations might reflect the movement of the northernmost penetration of the monsoon precipitation through the Late Glacial Stage, which is restricted by the topographic barrier posed by the Kunlun range, and might also reflect solar-driven nonlinearities in the climate system such as sudden shifts in the jet stream. Recent model simulations suggest that glacial cooling over China was significantly amplified by stationary waves, and the Guliya MIS2 oscillations could reflect cyclical variability in these waves. These results are supported by clumped isotope thermometry of carbonates from the Chinese Loess Plateau, which indicate a 6 to 7oC decrease in Last Glacial Maximum summer temperatures. These studies will lead to a better understanding of the mechanisms driving such high-frequency, high-amplitude oscillations. A review of the 2015 Sino-American cooperative ice core drilling program on Guliya is presented. This program will serve as a flagship for the TP Environment Program, an international, multidisciplinary collaboration among professionals and students in 14 countries designed to investigate environmental changes across the TP. The rapidly warming TP contains ~46,000 glaciers that collectively hold one of Earth's largest stores of fresh water that

  11. The Arctic Gakkel Vents (AGAVE) Expedition: Technology Development and the Search for Deep-Sea Hydrothermal Vent Fields Under the Arctic Ice Cap

    NASA Astrophysics Data System (ADS)

    Reves-Sohn, R. A.; Singh, H.; Humphris, S.; Shank, T.; Jakuba, M.; Kunz, C.; Murphy, C.; Willis, C.

    2007-12-01

    Deep-sea hydrothermal fields on the Gakkel Ridge beneath the Arctic ice cap provide perhaps the best terrestrial analogue for volcanically-hosted chemosynthetic biological communities that may exist beneath the ice-covered ocean of Europa. In both cases the key enabling technologies are robotic (untethered) vehicles that can swim freely under the ice and the supporting hardware and software. The development of robotic technology for deep- sea research beneath ice-covered oceans thus has relevance to both polar oceanography and future astrobiological missions to Europa. These considerations motivated a technology development effort under the auspices of NASA's ASTEP program and NSF's Office of Polar Programs that culminated in the AGAVE expedition aboard the icebreaker Oden from July 1 - August 10, 2007. The scientific objective was to study hydrothermal processes on the Gakkel Ridge, which is a key target for global studies of deep-sea vent fields. We developed two new autonomous underwater vehicles (AUVs) for the project, and deployed them to search for vent fields beneath the ice. We conducted eight AUV missions (four to completion) during the 40-day long expedition, which also included ship-based bathymetric surveys, CTD/rosette water column surveys, and wireline photographic and sampling surveys of remote sections of the Gakkel Ridge. The AUV missions, which lasted 16 hours on average and achieved operational depths of 4200 meters, returned sensor data that showed clear evidence of hydrothermal venting, but for a combination of technical reasons and time constraints, the AUVs did not ultimately return images of deep-sea vent fields. Nevertheless we used our wireline system to obtain images and samples of extensive microbial mats that covered fresh volcanic surfaces on a newly discovered set of volcanoes. The microbes appear to be living in regions where reducing and slightly warm fluids are seeping through cracks in the fresh volcanic terrain. These discoveries

  12. Dust aerosols above the south polar cap of Mars as seen by OMEGA

    NASA Astrophysics Data System (ADS)

    Vincendon, M.; Langevin, Y.; Poulet, F.; Bibring, J.-P.; Gondet, B.; Jouglet, D.; Omega Team

    2008-08-01

    The time evolution of atmospheric dust at high southern latitudes on Mars has been determined using observations of the south seasonal cap acquired in the near infrared (1-2.65 μm) by OMEGA/Mars Express in 2005. Observations at different solar zenith angles and one EPF sequence demonstrate that the reflectance in the 2.64 μm saturated absorption band of the surface CO 2 ice is mainly due to the light scattered by aerosols above most places of the seasonal cap. We have mapped the total optical depth of dust aerosols in the near-IR above the south seasonal cap of Mars from mid-spring to early summer with a time resolution ranging from one day to one week and a spatial resolution of a few kilometers. The optical depth above the south perennial cap is determined on a longer time range covering southern spring and summer. A constant set of optical properties of dust aerosols is consistent with OMEGA observations during the analyzed period. Strong variations of the optical depth are observed over small horizontal and temporal scales, corresponding in part to moving dust clouds. The late summer peak in dust opacity observed by Opportunity in 2005 propagated to the south pole contrarily to that observed in mid spring. This may be linked to evidence for dust scavenging by water ice-rich clouds circulating at high southern latitudes at this season.

  13. Amazonian mid- to high-latitude glaciation on Mars: Supply-limited ice sources, ice accumulation patterns, and concentric crater fill glacial flow and ice sequestration

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.

    2014-02-01

    Concentric crater fill (CCF) occurs in the interior of impact craters in mid- to high latitudes on Mars and is interpreted to have formed by glacial ice flow and debris covering. We use the characteristics and orientation of deposits comprising CCF, the thickness of pedestal deposits in mid- to high-latitude pedestal craters (Pd), the volumes of the current polar caps, and information about regional slopes and ice rheology to address questions about (1) the maximum thickness of regional ice deposits during the Late Amazonian, (2) the likelihood that these deposits flowed regionally, (3) the geological regions and features most likely to induce ice-flow, and (4) the locations and environments in which ice is likely to have been sequestered up to the present. We find that regional ice flow under Late Amazonian climate conditions requires ice thicknesses exceeding many hundreds of meters for slopes typical of the vast majority of the surface of Mars, a thickness for the mid-latitudes that is well in excess of the total volume available from polar ice reservoirs. This indicates that although conditions for mid- to high-latitude glaciation may have persisted for tens to hundreds of millions of years, the process is “supply limited”, with a steady state reached when the polar ice cap water ice supply becomes exhausted. Impact craters are by far the most abundant landform with associated slopes (interior wall and exterior rim) sufficiently high to induce glacial ice flow under Late Amazonian climate conditions, and topographic slope data show that Amazonian impact craters have been clearly modified, undergoing crater interior slope reduction and floor shallowing. We show that these trends are the predictable response of ice deposition and preferential accumulation and retention in mid- to high-latitude crater interiors during episodes of enhanced spin-axis obliquity. We demonstrate that flow from a single episode of an inter-crater terrain layer comparable to Pedestal

  14. Measurements of the north polar cap of Mars and the earth's Northern Hemisphere ice and snow cover

    NASA Technical Reports Server (NTRS)

    Foster, J.; Owe, M.; Capen, C.

    1986-01-01

    The boundaries of the polar caps of Mars have been measured on more than 3000 photographs since 1905 from the plate collection at the Lowell Observatory. For the earth, the polar caps have been accurately mapped only since the mid 1960s when satellites were first available to synoptically view the polar regions. The polar caps of both planets wax and wane in response to changes in the seasons, and interannual differences in polar cap behavior on Mars as well as earth are intimately linked to global energy balance. Data on the year to year variations in the extent of the north polar caps of Mars and earth have been assembled and compared, although only 6 years of concurrent data were available for comparison.

  15. CALICE: Calibrating Plant Biodiversity in Glacier Ice

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  16. Bayesian inference of ice thickness from remote-sensing data

    NASA Astrophysics Data System (ADS)

    Werder, Mauro A.; Huss, Matthias

    2017-04-01

    Knowledge about ice thickness and volume is indispensable for studying ice dynamics, future sea-level rise due to glacier melt or their contribution to regional hydrology. Accurate measurements of glacier thickness require on-site work, usually employing radar techniques. However, these field measurements are time consuming, expensive and sometime downright impossible. Conversely, measurements of the ice surface, namely elevation and flow velocity, are becoming available world-wide through remote sensing. The model of Farinotti et al. (2009) calculates ice thicknesses based on a mass conservation approach paired with shallow ice physics using estimates of the surface mass balance. The presented work applies a Bayesian inference approach to estimate the parameters of a modified version of this forward model by fitting it to both measurements of surface flow speed and of ice thickness. The inverse model outputs ice thickness as well the distribution of the error. We fit the model to ten test glaciers and ice caps and quantify the improvements of thickness estimates through the usage of surface ice flow measurements.

  17. Ice2sea - the future glacial contribution to sea-level rise

    NASA Astrophysics Data System (ADS)

    Vaughan, D. G.; Ice2sea Consortium

    2009-04-01

    The melting of continental ice (glaciers, ice caps and ice sheets) is a substantial source of current sea-level rise, and one that is accelerating more rapidly than was predicted even a few years ago. Indeed, the most recent report from Intergovernmental Panel on Climate Change highlighted that the uncertainty in projections of future sea-level rise is dominated by uncertainty concerning continental ice, and that understanding of the key processes that will lead to loss of continental ice must be improved before reliable projections of sea-level rise can be produced. Such projections are urgently required for effective sea-defence management and coastal adaptation planning. Ice2sea is a consortium of European institutes and international partners seeking European funding to support an integrated scientific programme to improve understanding concerning the future glacial contribution to sea-level rise. This includes improving understanding of the processes that control, past, current and future sea-level rise, and generation of improved estimates of the contribution of glacial components to sea-level rise over the next 200 years. The programme will include targeted studies of key processes in mountain glacier systems and ice caps (e.g. Svalbard), and in ice sheets in both polar regions (Greenland and Antarctica) to improve understanding of how these systems will respond to future climate change. It will include fieldwork and remote sensing studies, and develop a suite of new, cross-validated glacier and ice-sheet model. Ice2sea will deliver these results in forms accessible to scientists, policy-makers and the general public, which will include clear presentations of the sources of uncertainty. Our aim is both, to provide improved projections of the glacial contribution to sea-level rise, and to leave a legacy of improved tools and techniques that will form the basis of ongoing refinements in sea-level projection. Ice2sea will provide exciting opportunities for many

  18. Life in ice: implications to astrobiology

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Pikuta, Elena V.

    2009-08-01

    During previous research expeditions to Siberia, Alaska and Antarctica, it was observed that glaciers and ice wedges contained bacterial cells that became motile as soon as the ice melted. This phenomenon of live bacteria in ice was first documented for microbes in ancient ice cores from Vostok, Antarctica. The first validly published species of Pleistocene bacteria alive on Earth today was Carnobacterium pleistocenium. This extremophile had remained for 32,000 years, encased in ice recently exposed in the Fox Tunnel of Alaska. These frozen bacteria began to swim as soon as the ice was thawed. Dark field microscopy studies revealed that large numbers of bacteria exhibited motility as soon as glacial ice was melted during our recent Expeditions to Alaska and Antarctica led to the conclusion that microbial life in ice was not a rare phenomenon. The ability of bacteria to remain alive while frozen in ice for long periods of time is of great significance to Astrobiology. In this paper, we describe the recent observations and advance the hypothesis that life in ice provides valuable clues to how we can more easily search for evidence of life on the Polar Caps of Mars, comets and other icy bodies of our Solar System. It is suggested that cryopanspermia may have played a far more important role in Origin of Life on Earth and the distribution of Life throughout the Cosmos and than previously thought possible.

  19. An onboard data analysis method to track the seasonal polar caps on Mars

    USGS Publications Warehouse

    Wagstaff, K.L.; Castano, R.; Chien, S.; Ivanov, A.B.; Pounders, E.; Titus, T.N.; ,

    2005-01-01

    The Martian seasonal CO2 ice caps advance and retreat each year. They are currently studied using instruments such as the THermal EMission Imaging System (THEMIS), a visible and infra-red camera on the Mars Odyssey spacecraft [1]. However, each image must be downlinked to Earth prior to analysis. In contrast, we have developed the Bimodal Image Temperature (BIT) histogram analysis method for onboard detection of the cap edge, before transmission. In downlink-limited scenarios when the entire image cannot be transmitted, the location of the cap edge can still be identified and sent to Earth. In this paper, we evaluate our method on uncalibrated THEMIS data and find 1) agreement with manual cap edge identifications to within 28.2 km, and 2) high accuracy even with a smaller analysis window, yielding large reductions in memory requirements. This algorithm is currently being considered as a capability enhancement for the Odyssey second extended mission, beginning in fall 2006.

  20. The seasonal cycle of snow cover, sea ice and surface albedo

    NASA Technical Reports Server (NTRS)

    Robock, A.

    1980-01-01

    The paper examines satellite data used to construct mean snow cover caps for the Northern Hemisphere. The zonally averaged snow cover from these maps is used to calculate the seasonal cycle of zonally averaged surface albedo. The effects of meltwater on the surface, solar zenith angle, and cloudiness are parameterized and included in the calculations of snow and ice albedo. The data allows a calculation of surface albedo for any land or ocean 10 deg latitude band as a function of surface temperature ice and snow cover; the correct determination of the ice boundary is more important than the snow boundary for accurately simulating the ice and snow albedo feedback.

  1. A microphysically-based approach to modeling emissivity and albedo of the martian seasonal caps

    USGS Publications Warehouse

    Eluszkiewicz, J.; Moncet, J.-L.; Titus, T.N.; Hansen, G.B.

    2005-01-01

    A new model of albedo and emissivity of the martian seasonal caps represented as porous CO2 slabs containing spherical voids and dust particles is described. In the model, a radiative transfer model is coupled with a microphysical model in order to link changes in albedo and emissivity to changes in porosity caused by ice metamorphism. The coupled model is capable of reproducing temporal changes in the spectra of the caps taken by the Thermal Emission Spectrometer onboard the Mars Global Surveyor and it can be used as the forward model in the retrievals of the caps' physical properties (porosity, dust abundance, void and dust grain size) from the spectra. Preliminary results from such inversion studies are presented. ?? 2004 Elsevier Inc. All rights reserved.

  2. Central Tibetan Plateau atmospheric trace metals contamination: a 500-year record from the Puruogangri ice core

    NASA Astrophysics Data System (ADS)

    Beaudon, E.; Gabrielli, P.; Sierra Hernandez, R.; Wegner, A.; Thompson, L. G.

    2017-12-01

    Since the 1980s, Asia has experienced enormous industrial development from rapid population growth, industrialization and consequent large-scale environmental changes. The inherent generated atmospheric pollution currently contributes to half of all Earth's anthropogenic trace metals emissions. Asian trace metal aerosols, when deposited on glaciers of the surrounding mountains of the Tibetan Plateau (TP), leave a characteristic chemical fingerprint. Interpreting trace element (TE) records from glaciers implies a thorough comprehension of their provenance and temporal variability. It is then essential to discriminate the TEs' natural background components from their anthropogenic components. Here we present 500-year TE records from the Puruogangri ice core (Tibet, China) that provide a highly resolved account of the impact of past atmospheric influences, environmental processes and human activities on the central TP. A decreasing aeolian dust input to the ice cap allowed the detection of an atmospheric pollution signal. The anthropogenic pollution contribution emerges in the record since the early 1900s and increases substantially after 1935. The metallurgy (Zn, Pb and steel smelting) emission products from the former Soviet Union and especially from central Asia likely enhanced the anthropogenic deposition to the Puruogangri ice cap between 1935 and 1980, suggesting that the westerlies served as a conveyor of atmospheric pollution to central Tibet. The impact of this industrial pollution cumulated with that of the hemispheric coal and gasoline combustion which are respectively traced by Sb and Pb enrichment in the ice. The Chinese steel production accompanying the Great Leap Forward (1958-1961) and the Chinese Cultural Revolution (1966-1976) is proposed as a secondary but proximal source of Pb pollution affecting the ice cap between 1958 and 1976. The most recent decade (1980-1992) of the enrichment time series suggests that Puruogangri ice cap recorded the early

  3. Mars South Polar Cap 'Fingerprint' Terrain

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This picture is illuminated by sunlight from the upper left.

    Some portions of the martian south polar residual cap have long, somewhat curved troughs instead of circular pits. These appear to form in a layer of material that may be different than that in which 'swiss cheese' circles and pits form, and none of these features has any analog in the north polar cap or elsewhere on Mars. This picture shows the 'fingerprint' terrain as a series of long, narrow depressions considered to have formed by collapse and widening by sublimation of ice. Unlike the north polar cap, the south polar region stays cold enough in summer to retain frozen carbon dioxide. Viking Orbiter observations during the late 1970s showed that very little water vapor comes off the south polar cap during summer, indicating that any frozen water that might be there remains solid throughout the year.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was obtained in early southern spring on August 4, 1999. It shows an area 3 x 5 kilometers (1.9 x 3.1 miles) at a resolution of about 7.3 meters (24 ft) per pixel. Located near 86.0oS, 53.9oW.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  4. Evaporites on Ice: Experimental Assessment of Evaporites Formation on Antarctica (and on Martian North Polar Residual Cap)

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Derkowski, Arkadiusz; Skala, Aleksander; Trzcinski, Jerzy

    2016-04-01

    Evaporites are highly water soluble minerals, formed as a result of the evaporation or freezing of bodies of water. They are common weathering minerals found on rocks (including meteorites) on Antarctic ice sheet [1,2,3,4]. The water necessary for the reaction is produced by melting of ice below the dark-colored meteorites which can heat up to a few degrees above 0 °C due to insolation heating during wind-free summer days [5,6]. The Martian North Polar Residual Cap is surrounded by a young [7] dune field that is rich in evaporitic mineral: gypsum [8]. Its existence implies that relatively recently in the Martian history (in late Amazonian, when surface conditions were comparable to the current ones) there was a significant amount of liquid water present on the Mars surface. One of the proposed solutions to this problem is that gypsum is formed by weathering on/in ice [9,10,11,12,13], similarly to the process occurring on the Antarctic ice sheet. Recently, Losiak et al. 2015 showed that that during the warmest days of the Martian summer, solar irradiation may be sufficient to melt pure water ice located below a layer of dark dust particles lying on the steepest sections of the equator-facing slopes of the spiral troughs within Martian NPRC. Under the current irradiation conditions, melting is possible in very restricted areas of the NPRC and it lasts for up to couple of hours, but during the times of high irradiance at the north pole [15] this process could have been much more pronounced. Liquid water can be metastable at the NPRC because the pressure during the summer season is ~760-650 Pa [16] which is above the triple point of water. The rate of free-surface "clean" liquid water evaporation under average Martian conditions determined experimentally by [17] is comparable to the rate of melting determined by [21] (if there is no wind at the surface). In the current study we attempt to determine experimentally how many melting-freezing cycles are required to form

  5. Hyperspectral characterisation of the Martian south polar residual cap using CRISM

    NASA Astrophysics Data System (ADS)

    Campbell, J. D.; Sidiropoulos, P.; Muller, J.-P.

    2017-09-01

    We present our research on hyperspectral characterization of the Martian South Polar Residual Cap (SPRC), with a focus on the detection of organic signatures within the dust content of the ice. The SPRC exhibits unique CO2 ice sublimation features known colloquially as 'Swiss Cheese Terrain' (SCT). These flat floored, circular depressions are highly dynamic, and may expose dust particles previously trapped within the ice in the depression walls and partially on the floors. Here we identify suitable regions for potential dust exposure on the SPRC, and utilise data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA's Mars Reconnaissance Orbiter (MRO) satellite to examine infrared spectra of dark regions to establish their mineral composition, to eliminate the effects of ices on sub-pixel dusty features, and to assess whether ther might be signatures indicative of Polycyclic Aromatic Hydrocarbons (PAHs). Spectral mapping has identified compositional differences between depression rims and the majority of the SPRC and CRISM spectra have been corrected to minimise the influence of CO2 and H2O ice. Whilst no conclusive evidence for PAHs has been found, depression rims are shown to have higher water content than regions of featureless ice, and there are indications of magnesium carbonate within the dark, dusty regions.

  6. Seasonally-Active Water on Mars: Vapour, Ice, Adsorbate, and the Possibility of Liquid

    NASA Astrophysics Data System (ADS)

    Richardson, M. I.

    2002-12-01

    Seasonally-active water can be defined to include any water reservoir that communicates with other reservoirs on time scales of a year or shorter. It is the interaction of these water reservoirs, under the influence of varying solar radiation and in conjunction with surface and atmospheric temperatures, that determines the phase-stability field for water at the surface, and the distribution of water in various forms below, on, and above the surface. The atmosphere is the critical, dynamical link in this cycling system, and also (fortunately) one of the easiest to observe. Viking and Mars Global Surveyor observations paint a strongly asymmetric picture of the global seasonal water cycle, tied proximately to planetary eccentricity, and the existence of residual ice caps of different composition at the two poles. The northern summer experiences the largest water vapour columns, and is associated with sublimation from the northern residual water ice cap. The southern summer residual carbon dioxide ice cap is cold trap for water. Asymmetry in the water cycle is an unsolved problem. Possible solutions may involve the current timing of perihelion (the water cap resides at the pole experiencing the longer but cooler summer), the trapping of water ice in the northern hemisphere by tropical water ice clouds, and the bias in the annual-average, zonal-mean atmospheric circulation resulting from the zonal-mean difference in the elevation of the northern and southern hemispheres. Adsorbed and frozen water have proven harder to constrain. Recent Odyssey Gamma Ray Spectrometer results suggest substantial ground ice in the mid- and high-latitudes, but this water is likely below the seasonal skin depth for two reasons: the GRS results are best fit with such a model, and GCM models of the water cycle produce dramatically unrealistic atmospheric vapour distributions when such a very near surface, GRS-like distribution is initialized - ultimately removing the water to the northern and

  7. Antarctic lakes (above and beneath the ice sheet): Analogues for Mars

    NASA Technical Reports Server (NTRS)

    Rice, J. W., Jr.

    1992-01-01

    The perennial ice covered lakes of the Antarctic are considered to be excellent analogues to lakes that once existed on Mars. Field studies of ice covered lakes, paleolakes, and polar beaches were conducted in the Bunger Hills Oasis, Eastern Antarctica. These studies are extended to the Dry Valleys, Western Antarctica, and the Arctic. Important distinctions were made between ice covered and non-ice covered bodies of water in terms of the geomorphic signatures produced. The most notable landforms produced by ice covered lakes are ice shoved ridges. These features form discrete segmented ramparts of boulders and sediments pushed up along the shores of lakes and/or seas. Sub-ice lakes have been discovered under the Antarctic ice sheet using radio echo sounding. These lakes occur in regions of low surface slope, low surface accumulations, and low ice velocity, and occupy bedrock hollows. The presence of sub-ice lakes below the Martian polar caps is possible. The discovery of the Antarctic sub-ice lakes raises possibilities concerning Martian lakes and exobiology.

  8. Winter ocean-ice interactions under thin sea ice observed by IAOOS platforms during N-ICE2015: Salty surface mixed layer and active basal melt

    NASA Astrophysics Data System (ADS)

    Koenig, Zoé; Provost, Christine; Villacieros-Robineau, Nicolas; Sennéchael, Nathalie; Meyer, Amelie

    2016-10-01

    IAOOS (Ice Atmosphere Arctic Ocean Observing System) platforms, measuring physical parameters at the atmosphere-snow-ice-ocean interface deployed as part of the N-ICE2015 campaign, provide new insights on winter conditions North of Svalbard. The three regions crossed during the drifts, the Nansen Basin, the Sofia Deep, and the Svalbard northern continental slope featured distinct hydrographic properties and ice-ocean exchanges. In the Nansen Basin, the quiescent warm layer was capped by a stepped halocline (60 and 110 m) and a deep thermocline (110 m). Ice was forming and the winter mixed layer salinity was larger by ˜0.1 g/kg than previously observed. Over the Svalbard continental slope, the Atlantic Water (AW) was very shallow (20 m from the surface) and extended offshore from the 500 m isobath by a distance of about 70 km, sank along the slope (40 m from the surface) and probably shed eddies into the Sofia Deep. In the Sofia Deep, relatively warm waters of Atlantic origin extended from 90 m downward. Resulting from different pathways, these waters had a wide range of hydrographic characteristics. Sea-ice melt was widespread over the Svalbard continental slope and ocean-to-ice heat fluxes reached values of 400 W m-2 (mean of ˜150 W m-2 over the continental slope). Sea-ice melt events were associated with near 12 h fluctuations in the mixed-layer temperature and salinity corresponding to the periodicity of tides and near-inertial waves potentially generated by winter storms, large barotropic tides over steep topography, and/or geostrophic adjustments.

  9. TES premapping data: Slab ice and snow flurries in the Martian north polar night

    USGS Publications Warehouse

    Titus, T.N.; Kieffer, H.H.; Mullins, K.F.; Christensen, P.R.

    2001-01-01

    In the 1970s, Mariner and Viking spacecraft observations of the north polar region of Mars revealed polar brightness temperatures that were significantly below the expected kinetic temperatures for CO2 sublimation. For the past few decades, the scientific community has speculated as to the nature of these Martian polar cold spots. Thermal Emission Spectrometer (TES) thermal spectral data have shown these cold spots to result largely from fine-grained, CO2 and have constrained most of these cold spots to the surface (or near-surface). Cold spot formation is strongly dependent on topography, forming preferentially near craters and on polar slopes. TES data, combined with Mars Orbiter Laser Altimeter (MOLA) cloud data, suggest atmospheric condensates form a small fraction of the observed cold spots. TES observations of spectra close to a blackbody indicate that another major component of the polar cap is slab CO2 ice; these spectrally bland regions commonly have a low albedo. The cause is uncertain but may result from most of the light being reflected toward the specular direction, from the slab ice being intrinsically dark, or from it being transparent. Regions of the cap where the difference between the brightness temperatures at 18 ??m (T18) and 25 ??m (T25) is less than 5?? are taken to indicate deposits of slab ice. Slab ice is the dominant component of the polar cap at latitudes outside of the polar night. Copyright 2001 by the American Geophysical Union.

  10. A transient fully coupled climate-ice-sheet simulation of the last glacial inception

    NASA Astrophysics Data System (ADS)

    Lofverstrom, M.; Otto-Bliesner, B. L.; Lipscomb, W. H.; Fyke, J. G.; Marshall, S.; Sacks, B.; Brady, E. C.

    2017-12-01

    The last glacial inception occurred around 115 ka, following a relative minimum in the Northern Hemisphere summer insolation. It is believed that small and spatially separated ice caps initially formed in the high elevation regions of northern Canada, Scandinavia, and along the Siberian Arctic coast. These ice caps subsequently migrated down in the valleys where they coalesced and formed the initial seeds of the large coherent ice masses that covered the northern parts of the North American and Eurasian continents over most of the last glacial cycle. Sea level records show that the initial growth period lasted for about 10 kyrs, and the resulting ice sheets may have lowered the global sea level by as much as 30 to 50 meters. Here we examine the transient climate system evolution over the period between 118 and 110 ka, using the fully coupled Community Earth System Model, version 2 (CESM2). This model features a two-way coupled high-resolution (4x4 km) ice-sheet component (Community Ice Sheet model, version 2; CISM2) that simulates ice sheets as an interactive component of the climate system. We impose a transient forcing protocol where the greenhouse gas concentrations and the orbital parameters follow the nominal year in the simulation; the model topography is also dynamically evolving in order to reflect changes in ice elevation throughout the simulation. The analysis focuses on how the climate system evolves over this time interval, with a special focus on glacial inception in the high-latitude continents. Results will highlight how the evolving ice sheets compare to data and previous model based reconstructions.

  11. Response of faults to climate-driven changes in ice and water volumes on Earth's surface.

    PubMed

    Hampel, Andrea; Hetzel, Ralf; Maniatis, Georgios

    2010-05-28

    Numerical models including one or more faults in a rheologically stratified lithosphere show that climate-induced variations in ice and water volumes on Earth's surface considerably affect the slip evolution of both thrust and normal faults. In general, the slip rate and hence the seismicity of a fault decreases during loading and increases during unloading. Here, we present several case studies to show that a postglacial slip rate increase occurred on faults worldwide in regions where ice caps and lakes decayed at the end of the last glaciation. Of note is that the postglacial amplification of seismicity was not restricted to the areas beneath the large Laurentide and Fennoscandian ice sheets but also occurred in regions affected by smaller ice caps or lakes, e.g. the Basin-and-Range Province. Our results do not only have important consequences for the interpretation of palaeoseismological records from faults in these regions but also for the evaluation of the future seismicity in regions currently affected by deglaciation like Greenland and Antarctica: shrinkage of the modern ice sheets owing to global warming may ultimately lead to an increase in earthquake frequency in these regions.

  12. Glaciers and ice sheets as a biome.

    PubMed

    Anesio, Alexandre M; Laybourn-Parry, Johanna

    2012-04-01

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

  13. The Subsurface Ice Probe (SIPR): A Low-Power Thermal Probe for the Martian Polar Layered Deposits

    NASA Technical Reports Server (NTRS)

    Cardell, G.; Hecht, M. H.; Carsey, F. D.; Engelhardt, H.; Fisher, D.; Terrell, C.; Thompson, J.

    2004-01-01

    The distinctive layering visible in images from Mars Global Surveyor of the Martian polar caps, and particularly in the north polar cap, indicates that the stratigraphy of these polar layered deposits may hold a record of Martian climate history covering millions of years. On Earth, ice sheets are cored to retrieve a pristine record of the physical and chemical properties of the ice at depth, and then studied in exacting detail in the laboratory. On the Martian north polar cap, coring is probably not a practical method for implementation in an autonomous lander. As an alternative, thermal probes that drill by melting into the ice are feasible for autonomous operation, and are capable of reasonable approximations to the scientific investigations performed on terrestrial cores, while removing meltwater to the surface for analysis. The Subsurface Ice Probe (SIPR) is such a probe under development at JPL. To explore the dominant climate cycles, it is postulated that tens of meters of depth should be profiled, as this corresponds to the vertical separation of the major layers visible in the MOC images [1]. Optical and spectroscopic analysis of the layers, presumably demarcated by embedded dust and possibly by changes in the ice properties, would contribute to the construction of a chronology. Meltwater analysis may be used to determine the soluble chemistry of the embedded dust, and to monitor gradients of atmospheric gases, particularly hydrogen and oxygen, and isotopic variations that reflect atmospheric conditions at the time the layer was deposited. Thermal measurements can be used to determine the geothermal gradient and the bulk mechanical properties of the ice.

  14. "Cottage Cheese" Texture on the Martian North Polar Cap in Summer

    NASA Image and Video Library

    2000-04-24

    This image is illuminated by sunlight from the upper left. Martian Dairy Products? If parts of the south polar cap can look like swiss cheese (see "Martian "Swiss Cheese""), then parts of the north polar cap might as well look like some kind of cheese, too. This picture shows a cottage cheese-like texture on the surface of a part of the residual--summertime--north polar cap. The north polar cap surface is mostly covered by pits, cracks, small bumps and knobs. In this image, the cap surface appears bright and the floors of pits look dark. Based upon observations made by the Mariner 9 and Viking orbiters in the 1970s, the north polar residual cap is thought to contain mostly water ice because its summertime temperature is usually near the freezing point of water and water vapor was observed by the Vikings to be coming off the cap during summer. The south residual cap is different--its temperatures in summer remain cold enough to freeze carbon dioxide, and very little to no water vapor has been observed to come off the south cap in summer. The pits that have developed on the north polar cap surface are closely-spaced relative to the very different depressions in the south polar cap. The pits are estimated from the length of shadows cast in them to be less than about 2 meters (5.5 feet) deep. These pits probably develop slowly over thousands of years of successive spring and summer seasons. This picture was taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during northern summer on April 5, 1999. The picture is located near 82.1°N, 329.6°W and covers an area 1.5 km wide by 3 km long (0.9 x 1.8 miles) at a resolution of 3 meters (10 ft) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA02369

  15. Diversity of Holocene life forms in fossil glacier ice

    PubMed Central

    Willerslev, Eske; Hansen, Anders J.; Christensen, Bent; Steffensen, Jørgen Peder; Arctander, Peter

    1999-01-01

    Studies of biotic remains of polar ice caps have been limited to morphological identification of plant pollen and spores. By using sensitive molecular techniques, we now demonstrate a much greater range of detectable organisms; from 2000- and 4000-year-old ice-core samples, we obtained and characterized 120 clones that represent at least 57 distinct taxa and reveal a diversity of fungi, plants, algae, and protists. The organisms derive from distant sources as well as from the local arctic environment. Our results suggest that additional taxa may soon be readily identified, providing a plank for future studies of deep ice cores and yielding valuable information about ancient communities and their change over time. PMID:10393940

  16. Episodic expansion of Drangajökull, Vestfirðir, Iceland, over the last 3 ka culminating in its maximum dimension during the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Harning, David J.; Geirsdóttir, Áslaug; Miller, Gifford H.; Anderson, Leif

    2016-11-01

    Non-linear climate change is often linked to rapid changes in ocean circulation, especially around the North Atlantic. As the Polar Front fluctuated its latitudinal position during the Holocene, Iceland's climate was influenced by both the warm Atlantic currents and cool, sea ice-bearing Arctic currents. Drangajökull is Iceland's fifth largest ice cap. Climate proxies in lake sediment cores, dead vegetation emerging from beneath the ice cap, and moraine segments identified in a new DEM constrain the episodic expansion of the ice cap over the past 3 ka. Collectively, our data show that Drangajökull was advancing at ∼320 BCE, 180 CE, 560 CE, 950 CE and 1400 CE and in a state of recession at ∼450 CE, 1250 CE and after 1850 CE. The Late Holocene maximum extent of Drangajökull occurred during the Little Ice Age (LIA), occupying 262 km2, almost twice its area in 2011 CE and ∼20% larger than recent estimates of its LIA dimensions. Biological proxies from the sediment fill in a high- and low-elevation lake suggest limited vegetation and soil cover at high elevations proximal to the ice cap, whereas thick soil cover persisted until ∼750 CE at lower elevations near the coast. As Drangajökull expanded into the catchment of the high-elevation lake beginning at ∼950 CE, aquatic productivity diminished, following a trend of regional cooling supported by proxy records elsewhere in Iceland. Correlations between episodes of Drangajökull's advance and the documented occurrence of drift ice on the North Icelandic Shelf suggest export and local production of sea ice influenced the evolution of NW Iceland's Late Holocene climate.

  17. The Mars water cycle at other epochs: Recent history of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1992-01-01

    The Martian polar caps and layered terrain presumably evolves by the deposition and removal of small amounts of water and dust each year, the current cap attributes therefore represent the incremental transport during a single year as integrated over long periods of time. The role was studied of condensation and sublimation of water ice in this process by examining the seasonal water cycle during the last 10(exp 7) yr. In the model, axial obliquity, eccentricity, and L sub s of perihelion vary according to dynamical models. At each epoch, the seasonal variations in temperature are calculated at the two poles, keeping track of the seasonal CO2 cap and the summertime sublimation of water vapor into the atmosphere; net exchange of water between the two caps is calculated based on the difference in the summertime sublimation between the two caps (or on the sublimation from one cap if the other is covered with CO2 frost all year). Results from the model can help to explain (1) the apparent inconsistency between the timescales inferred for layer formation and the much older crater retention age of the cap and (2) the difference in sizes of the two residual caps, with the south being smaller than the north.

  18. South Polar Cap Erosion and Aprons

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This scene is illuminated by sunlight from the upper left.

    While Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images have shown that the north and south polar cap surfaces are very different from each other, one thing that the two have in common is that they both seem to have been eroded. Erosion in the north appears mostly to come in the form of pits from which ice probably sublimed to vapor and was transported away from the polar cap by wind. Erosion in the south takes on a wider range of possible processes that include collapse, slumping and mass-movement on slopes, and probably sublimation. Among the landforms created by these process on the south polar cap are the 'aprons' that surround mesas and buttes of remnant layers such as the two almost triangular features in the lower quarter of this image. The upper slopes of the two triangular features show a stair-stepped pattern that suggest these hills are layered.

    This image shows part of the south polar residual cap near 86.9oS, 78.5oW, and covers an area approximately 1.2 by 1.0 kilometers (0.7 x 0.6 miles) in size. The image has a resolution of 2.2 meters per pixel. The picture was taken on September 11, 1999.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  19. Recession of the Northern polar cap from the PFS Mars Express observations

    NASA Astrophysics Data System (ADS)

    Zasova, L. V.; Formisano, V.; Moroz, V. I.; Giuranna, M.; Grassi, D.; Hansen, G.; Ignatiev, N. I.; Maturilli, A.; Pfs Team

    Planetary Fourier Spectrometer (PFS) has two spectral channels, devoted to the thermal and solar reflected spectral range investigations. The first observations by PFS of the Northern hemisphere ,which includes the North pole, occurred at Ls= 342 (northern winter). Surface temperature alone the orbit shows that the CO2 ice polar cap, where the surface temperature is found around 150K and below, is extended down to about 62 N. The spectra at latitudes above 80 N are obtained at polar darkness and at latitudes below 80 at illumination by the low Sun. Retrieved temperature profiles of the atmosphere at darkness show that temperature of the atmosphere is low enough to allow the CO2 condensation up to about 25 km. Between 70 and 80 latitude the upper levels of the atmosphere are heated by the Sun, but condensation of the CO2 may occur in the near surface layer below 5 km. The water ice clouds exist at lower latitudes with maximum opacity at the edge of the polar cap. More detailed investigation of the data obtained in winter as well as of the measurements in the northern spring will be presented.

  20. Cervical Cap

    MedlinePlus

    ... Videos for Educators Search English Español The Cervical Cap KidsHealth / For Teens / The Cervical Cap What's in ... Call the Doctor? Print What Is a Cervical Cap? A cervical cap is a small cup made ...

  1. Ice Mass Changes in the Russian High Arctic from Repeat High Resolution Topography.

    NASA Astrophysics Data System (ADS)

    Willis, Michael; Zheng, Whyjay; Pritchard, Matthew; Melkonian, Andrew; Morin, Paul; Porter, Claire; Howat, Ian; Noh, Myoung-Jong; Jeong, Seongsu

    2016-04-01

    We use a combination of ASTER and cartographically derived Digital Elevation Models (DEMs) supplemented with WorldView DEMs, the ArcticDEM and ICESat lidar returns to produce a time-series of ice changes occurring in the Russian High Arctic between the mid-20th century and the present. Glaciers on the western, Barents Sea coast of Novaya Zemlya are in a state of general retreat and thinning, while those on the eastern, Kara Sea coast are retreating at a slower rate. Franz Josef Land has a complicated pattern of thinning and thickening, although almost all the thinning is associated with rapid outlet glaciers feeding ice shelves. Severnaya Zemlya is also thinning in a complicated manner. A very rapid surging glacier is transferring mass into the ocean from the western periphery of the Vavilov Ice Cap on October Revolution Island, while glaciers feeding the former Matusevich Ice Shelf continue to thin at rates that are faster than those observed during the operational period of ICESat, between 2003 and 2009. Passive microwave studies indicate the total number of melt days is increasing in the Russian Arctic, although much of the melt may refreeze within the firn. It is likely that ice dynamic changes will drive mass loss for the immediate future. The sub-marine basins beneath several of the ice caps in the region suggest the possibility that mass loss rates may accelerate in the future.

  2. Putting Radioactive Wastes on Ice: A Proposal for an International Radionuclide Depository in Antarctica

    ERIC Educational Resources Information Center

    Zeller, E. J.; And Others

    1973-01-01

    Describes need for creating permanent disposal of high-level radioactive wastes accumulating in different countries. Possibilities of establishing facilities for this purpose in Antarctic ice cap are examined. (PS)

  3. Deposition of atmospheric heavy metals to the Greenland ice sheet from the 1783-1784 volcanic eruption of Laki, Iceland

    NASA Astrophysics Data System (ADS)

    Hong, Sungmin; Candelone, Jean-Pierre; Boutron, Claude F.

    1996-11-01

    In order to assess better the influence of major volcanic events on the large scale atmospheric cycles of heavy metals, Greenland ice dated from the time of the fallouts from the great 1783-1784 eruption of Laki volcano in Iceland has been analysed for Pb, Cd, Cu, Zn and sulphate. The concentrations of the four heavy metals investigated are found to be greatly enhanced in the ice layers which correspond to the fallouts from the eruption, confirming that such events do modify the atmospheric cycles of heavy metals. Cumulative fallout of heavy metals to the whole Greenland ice cap from the 1783-1784 Laki eruption ranges from 1 t for Pb and Cd to 40 t for Zn. For Cd, Cu and Zn, it represents a few percent of the cumulative anthropogenic fallout to the ice cap from the Industrial Revolution to the present.

  4. Subglacial carbonate precipitates on central Baffin Island, Arctic Canada may constrain basal conditions for the Foxe sector of the Laurentide Ice Sheet

    NASA Astrophysics Data System (ADS)

    Miller, G. H.; Refsnider, K. A.

    2009-12-01

    Extensive, widespread carbonate deposits on gneissic bedrock have recently been discovered around the Barnes Ice Cap, central Baffin Island. Deposits range from conglomeratic crack-fillings ≤5 cm thick to laminated, striated films plastered on bedrock surfaces, often in the lee of obstacles. A single outcrop of these carbonates was first described by Andrews et al. (1972, Canadian Journal of Earth Sciences, 9, 233-238) and was interpreted as an early Tertiary limestone based on the presence of warm-climate palynomorphs including Liriodendron (tulip tree), Ulmus (elm), and Taxodium (cypress). However, recent fieldwork in the region has demonstrated that these carbonates are far more ubiquitous than previously thought and found on both glacially-polished bedrock surfaces and till boulders that melted out in recent decades from Laurentide ice at the base of the Barnes Ice Cap. In many cases, these carbonates exhibit the characteristic morphologies of subglacial carbonates (flutes, furrows, and striations parallel to the direction of ice flow, columnar spicules, and tufa-dam-like forms). A few deposits include angular sands, gravels, and pebbles. The nearest carbonate bedrock is Paleozoic limestone flooring Foxe Basin 130 km west of the Barnes Ice Cap summit. While subglacial carbonate deposits have been documented adjacent to retreating mountain and outlet glaciers and in areas previously covered by Pleistocene ice sheets, few localities are distant from carbonate bedrock. Thus, the carbon required for carbonate deposition in the Barnes region was either (1) derived from Paleozoic limestone and dissolved in subglacial water that was subject to long-distance transport, or (2) there was sufficient trapped atmospheric CO2 in the ice to yield alkaline basal meltwater which hydrolyzed calcium-bearing silicates in the local bedrock. Given the volume of carbonate deposited at some sites, we find the latter model unlikely. If the former model is applicable, these carbonates

  5. Arctic Sea Ice Decline: Observations, Projections, Mechanisms, and Implications

    NASA Astrophysics Data System (ADS)

    DeWeaver, Eric T.; Bitz, Cecilia M.; Tremblay, L.-Bruno

    This volume addresses the rapid decline of Arctic sea ice, placing recent sea ice decline in the context of past observations, climate model simulations and projections, and simple models of the climate sensitivity of sea ice. Highlights of the work presented here include • An appraisal of the role played by wind forcing in driving the decline; • A reconstruction of Arctic sea ice conditions prior to human observations, based on proxy data from sediments; • A modeling approach for assessing the impact of sea ice decline on polar bears, used as input to the U.S. Fish and Wildlife Service's decision to list the polar bear as a threatened species under the Endangered Species Act; • Contrasting studies on the existence of a "tipping point," beyond which Arctic sea ice decline will become (or has already become) irreversible, including an examination of the role of the small ice cap instability in global warming simulations; • A significant summertime atmospheric response to sea ice reduction in an atmospheric general circulation model, suggesting a positive feedback and the potential for short-term climate prediction. The book will be of interest to researchers attempting to understand the recent behavior of Arctic sea ice, model projections of future sea ice loss, and the consequences of sea ice loss for the natural and human systems of the Arctic.

  6. Environmental Effects on Volcanic Eruptions:From Deep Ocean to Deep Space. Chapter 3. Volcanism and Ice Interactions on Earth and Mars. Chapter 3

    NASA Technical Reports Server (NTRS)

    Chapman, Mary G.; Allen, Carlton C.; Gudmundsson, Magnus T.; Gulick, Virginia C.; Jakobsson, Sveinn P.; Lucchitta, Baerbel K.; Skilling, Ian P.; Waitt, Richard B.

    2000-01-01

    CONCLUSION Volcano/ice interactions produce meltwater. Meltwater can enter the groundwater cycle and under the influence of hydrothermal systems, it can be later discharged to form channels and valleys or cycled upward to melt permafrost. Water or ice-saturated ground can erupt into phreatic craters when covered by lava. Violent mixing of meltwater and volcanic material and rapid release can generate lahars or jokulhlaups, that have the ability to freight coarse material, great distances downslope from the vent. Eruption into meltwater generate unique appearing edifices, that are definitive indicators of volcano/ice interaction. These features are hyaloclastic ridges or mounds and if capped by lava, tuyas. On Earth, volcano/ice interactions are limited to alpine regions and ice-capped polar and temperate regions. On Mars, where precipitation may be an ancient phenomenon, these interactions may be limited to areas of ground ice accumulation or the northern lowlands where water may have ponded fairly late in martian history. The recognition of features caused by volcano/ice interactions could provide strong constraints for the history of volatiles on Mars.

  7. An ice-binding and tandem beta-sandwich domain-containing protein in Shewanella frigidimarina is a potential new type of ice adhesin.

    PubMed

    Vance, Tyler D R; Graham, Laurie A; Davies, Peter L

    2018-04-01

    Out of the dozen different ice-binding protein (IBP) structures known, the DUF3494 domain is the most widespread, having been passed many times between prokaryotic and eukaryotic microorganisms by horizontal gene transfer. This ~25-kDa β-solenoid domain with an adjacent parallel α-helix is most commonly associated with an N-terminal secretory signal peptide. However, examples of the DUF3494 domain preceded by tandem Bacterial Immunoglobulin-like (BIg) domains are sometimes found, though uncharacterized. Here, we present one such protein (SfIBP_1) from the Antarctic bacterium Shewanella frigidimarina. We have confirmed and characterized the ice-binding activity of its ice-binding domain using thermal hysteresis measurements, fluorescent ice plane affinity analysis, and ice recrystallization inhibition assays. X-ray crystallography was used to solve the structure of the SfIBP_1 ice-binding domain, to further characterize its ice-binding surface and unique method of stabilizing or 'capping' the ends of the solenoid structure. The latter is formed from the interaction of two loops mediated by a combination of tandem prolines and electrostatic interactions. Furthermore, given their domain architecture and membrane association, we propose that these BIg-containing DUF3494 IBPs serve as ice-binding adhesion proteins that are capable of adsorbing their host bacterium onto ice. Submitted new structure to the Protein Data Bank (PDB: 6BG8). © 2018 Federation of European Biochemical Societies.

  8. Properties of Filamentary Sublimation Residues from Dispersions of Clay in Ice

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.; Parker, T. J.; Saunders, R. S.; Laue, E. G.; Fanale, F. P.

    1985-01-01

    The properties of sublimate residues are of considerable interest in studies of the thermal modeling of Martian and cometary ice surfaces. The study of the formation of sand grains from this mantle on Martian polar ice is also supported by these experiments. To understand these properties, a series of low temperature vacuum experiments were run during which dirty ices that might be expected to be found in Martian polar caps and in comet nuclei were made and then freeze dried. In addition to using particulate material of appropriate grain size and minerology, particle nucleated ices were simulated by dispersing the particulates in the ice so that they did not contact one another. This noncontact dispersion was the most difficult requirement to achieve but the most rewarding in that it produced a new filamentary sublimate residue that was not a relic of the frozen dispersion. If the siliceous particles are allowed to touch one another in the ice the structure of the contacting particles in the ice will remain as a relic after the ice is sublimed away.

  9. Multi-MICE: Nuclear Powered Mobile Probes to Explore Deep Interiors of the Ice Sheets on Mars and the Jovian Moons

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

    Maise, George; Powell, James; Paniagua, John

    2007-01-30

    The multi-kilometer thick Polar Caps on Mars contain unique and important data about the multi-million year history of its climate, geology, meteorology, volcanology, cosmic ray and solar activity, and meteor impacts. They also may hold evidence of past life on Mars, including microbes, microfossils and biological chemicals. The objective of this paper is to describe a probe that can provide access to the data locked in the Polar Caps. The MICE (Mars Ice Cap Explorer) system would explore the Polar Cap interiors using mobile probes powered by compact, lightweight nuclear reactors. The probes would travel 100's of meters per daymore » along melt channels in the ice sheets created by hot water jets from the 500 kW(th) nuclear reactors, ascending and descending, either vertically or at an angle to the vertical, reaching bedrock at kilometers beneath the surface. The powerful reactor will be necessary to provide sufficient hot water at high velocity to penetrate the extensive horizontal dust/sand layers that separate layers of ice in the Mars Ice Caps. MICE reactors can operate at 500 kW(th) for more than 4 years, and much longer in practice, since power level will be much lower when the probes are investigating locations in detail at low or zero speed. Multiple probes, e.g. six, would be deployed in an interactive network, continuously communicating by RF and acoustic signals with each other and with the surface lander spacecraft. In turn, the lander would continuously communicate in real time, subject to speed of light delays, with scientists on Earth to transmit data and receive instructions for the MICE probes. Samples collected by the probes could be brought to the lander, for return to the Earth at the end of the mission.« less

  10. Brief communication: The global signature of post-1900 land ice wastage on vertical land motion

    NASA Astrophysics Data System (ADS)

    Riva, Riccardo E. M.; Frederikse, Thomas; King, Matt A.; Marzeion, Ben; van den Broeke, Michiel R.

    2017-06-01

    Melting glaciers, ice caps and ice sheets have made an important contribution to sea-level rise through the last century. Self-attraction and loading effects driven by shrinking ice masses cause a spatially varying redistribution of ocean waters that affects reconstructions of past sea level from sparse observations. We model the solid-earth response to ice mass changes and find significant vertical deformation signals over large continental areas. We show how deformation rates have been strongly varying through the last century, which implies that they should be properly modelled before interpreting and extrapolating recent observations of vertical land motion and sea-level change.

  11. Transient bright "halos" on the South Polar Residual Cap of Mars: Implications for mass-balance

    NASA Astrophysics Data System (ADS)

    Becerra, Patricio; Byrne, Shane; Brown, Adrian J.

    2015-05-01

    Spacecraft imaging of Mars' south polar region during mid-southern summer of Mars year 28 (2007) observed bright halo-like features surrounding many of the pits, scarps and slopes of the heavily eroded carbon dioxide ice of the South Polar Residual Cap (SPRC). These features had not been observed before, and have not been observed since. We report on the results of an observational study of these halos, and spectral modeling of the SPRC surface at the time of their appearance. Image analysis was performed using data from MRO's Context Camera (CTX), and High Resolution Imaging Science Experiment (HiRISE), as well as images from Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC). Data from MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) were used for the spectral analysis of the SPRC ice at the time of the halos. These data were compared with a Hapke reflectance model of the surface to constrain their formation mechanism. We find that the unique appearance of the halos is intimately linked to a near-perihelion global dust storm that occurred shortly before they were observed. The combination of vigorous summertime sublimation of carbon dioxide ice from sloped surfaces on the SPRC and simultaneous settling of dust from the global storm, resulted in a sublimation wind that deflected settling dust particles away from the edges of these slopes, keeping these areas relatively free of dust compared to the rest of the cap. The fact that the halos were not exhumed in subsequent years indicates a positive mass-balance for flat portions of the SPRC in those years. A net accumulation mass-balance on flat surfaces of the SPRC is required to preserve the cap, as it is constantly being eroded by the expansion of the pits and scarps that populate its surface.

  12. Land Ice Freshwater Budget of the Arctic and North Atlantic Oceans: 1. Data, Methods, and Results

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Tedstone, A. J.; King, M. D.; Howat, I. M.; Enderlin, E. M.; van den Broeke, M. R.; Noel, B.

    2018-03-01

    The freshwater budget of the Arctic and sub-polar North Atlantic Oceans has been changing due, primarily, to increased river runoff, declining sea ice and enhanced melting of Arctic land ice. Since the mid-1990s this latter component has experienced a pronounced increase. We use a combination of satellite observations of glacier flow speed and regional climate modeling to reconstruct the land ice freshwater flux from the Greenland ice sheet and Arctic glaciers and ice caps for the period 1958-2016. The cumulative freshwater flux anomaly exceeded 6,300 ± 316 km3 by 2016. This is roughly twice the estimate of a previous analysis that did not include glaciers and ice caps outside of Greenland and which extended only to 2010. From 2010 onward, the total freshwater flux is about 1,300 km3/yr, equivalent to 0.04 Sv, which is roughly 40% of the estimated total runoff to the Arctic for the same time period. Not all of this flux will reach areas of deep convection or Arctic and Sub-Arctic seas. We note, however, that the largest freshwater flux anomalies, grouped by ocean basin, are located in Baffin Bay and Davis Strait. The land ice freshwater flux displays a strong seasonal cycle with summer time values typically around five times larger than the annual mean. This will be important for understanding the impact of these fluxes on fjord circulation, stratification, and the biogeochemistry of, and nutrient delivery to, coastal waters.

  13. Pluto: The Ice Plot Thickens

    NASA Image and Video Library

    2015-07-15

    The latest spectra from New Horizons Ralph instrument reveal an abundance of methane ice, but with striking differences from place to place across the frozen surface of Pluto. In the north polar cap, methane ice is diluted in a thick, transparent slab of nitrogen ice resulting in strong absorption of infrared light. In one of the visually dark equatorial patches, the methane ice has shallower infrared absorptions indicative of a very different texture. An Earthly example of different textures of a frozen substance: a fluffy bank of clean snow is bright white, but compacted polar ice looks blue. New Horizons' surface composition team has begun the intricate process of analyzing Ralph data to determine the detailed compositions of the distinct regions on Pluto. This is the first detailed image of Pluto from the Linear Etalon Imaging Spectral Array, part of the Ralph instrument on New Horizons. The observations were made at three wavelengths of infrared light, which are invisible to the human eye. In this picture, blue corresponds to light of wavelengths 1.62 to 1.70 micrometers, a channel covering a medium-strong absorption band of methane ice, green (1.97 to 2.05 micrometers) represents a channel where methane ice does not absorb light, and red (2.30 to 2.33 micrometers) is a channel where the light is very heavily absorbed by methane ice. The two areas outlined on Pluto show where Ralph observations obtained the spectral traces at the right. Note that the methane absorptions (notable dips) in the spectrum from the northern region are much deeper than the dips in the spectrum from the dark patch. The Ralph data were obtained by New Horizons on July 12, 2015. http://photojournal.jpl.nasa.gov/catalog/PIA19712

  14. Arctic Sea Ice Is Losing Its Bulwark Against Warming Summers

    NASA Image and Video Library

    2017-12-08

    Arctic sea ice, the vast sheath of frozen seawater floating on the Arctic Ocean and its neighboring seas, has been hit with a double whammy over the past decades: as its extent shrunk, the oldest and thickest ice has either thinned or melted away, leaving the sea ice cap more vulnerable to the warming ocean and atmosphere. “What we’ve seen over the years is that the older ice is disappearing,” said Walt Meier, a sea ice researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “This older, thicker ice is like the bulwark of sea ice: a warm summer will melt all the young, thin ice away but it can’t completely get rid of the older ice. But this older ice is becoming weaker because there’s less of it and the remaining old ice is more broken up and thinner, so that bulwark is not as good as it used to be.” Read more: go.nasa.gov/2dPJ9zT NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  15. Glaciological reconstruction of Holocene ice margins in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Birkel, S. D.; Osterberg, E. C.; Kelly, M. A.; Axford, Y.

    2014-12-01

    The past few decades of climate warming have brought overall margin retreat to the Greenland Ice Sheet. In order to place recent and projected changes in context, we are undertaking a collaborative field-modeling study that aims to reconstruct the Holocene history of ice-margin fluctuation near Thule (~76.5°N, 68.7°W), and also along the North Ice Cap (NIC) in the Nunatarssuaq region (~76.7°N, 67.4°W). Fieldwork reported by Kelly et al. (2013) reveals that ice in the study areas was less extensive than at present ca. 4700 (GIS) and ca. 880 (NIC) cal. years BP, presumably in response to a warmer climate. We are now exploring Holocene ice-climate coupling using the University of Maine Ice Sheet Model (UMISM). Our approach is to first test what imposed climate anomalies can afford steady state ice margins in accord with field data. A second test encompasses transient simulation of the Holocene, with climate boundary conditions supplied by existing paleo runs of the Community Climate System Model version 4 (CCSM4), and a climate forcing signal derived from Greenland ice cores. In both cases, the full ice sheet is simulated at 10 km resolution with nested domains at 0.5 km for the study areas. UMISM experiments are underway, and results will be reported at the meeting.

  16. The Penetration of Solar Radiation Into Carbon Dioxide Ice

    NASA Astrophysics Data System (ADS)

    Chinnery, H. E.; Hagermann, A.; Kaufmann, E.; Lewis, S. R.

    2018-04-01

    Icy surfaces behave differently to rocky or regolith-covered surfaces in response to irradiation. A key factor is the ability of visible light to penetrate partially into the subsurface. This results in the solid-state greenhouse effect, as ices can be transparent or translucent to visible and shorter wavelengths, while opaque in the infrared. This can lead to significant differences in shallow subsurface temperature profiles when compared to rocky surfaces. Of particular significance for modeling the solid-state greenhouse effect is the e-folding scale, otherwise known as the absorption scale length, or penetration depth, of the ice. While there have been measurements for water ice and snow, pure and with mixtures, to date, there have been no such measurements published for carbon dioxide ice. After an extensive series of measurements we are able to constrain the e-folding scale of CO2 ice for the cumulative wavelength range 300 to 1,100 nm, which is a vital parameter in heat transfer models for the Martian surface, enabling us to better understand surface-atmosphere interactions at Mars' polar caps.

  17. Possible significance of cubic water-ice, H2O-Ic, in the atmospheric water cycle of Mars

    NASA Technical Reports Server (NTRS)

    Gooding, James L.

    1988-01-01

    The possible formation and potential significance of the cubic ice polymorph on Mars is discussed. When water-ice crystallizes on Earth, the ambient conditions of temperature and pressure result in the formation of the hexagonal ice polymorph; however, on Mars, the much lower termperature and pressures may permit the crystallization of the cubic polymorph. Cubic ice has two properties of possible importance on Mars: it is an excellant nucleator of other volatiles (such as CO2), and it undergoes an exothermic transition to hexagonal ice at temperatures above 170 K. These properties may have significant implications for both martian cloud formation and the development of the seasonal polar caps.

  18. Cradle Cap

    MedlinePlus

    Cradle cap Overview Cradle cap causes crusty or oily scaly patches on a baby's scalp. The condition isn't painful or itchy. But it can ... scales that aren't easy to remove. Cradle cap usually clears up on its own in a ...

  19. Reconstructing the last Irish Ice Sheet 2: a geomorphologically-driven model of ice sheet growth, retreat and dynamics

    NASA Astrophysics Data System (ADS)

    Greenwood, Sarah L.; Clark, Chris D.

    2009-12-01

    The ice sheet that once covered Ireland has a long history of investigation. Much prior work focussed on localised evidence-based reconstructions and ice-marginal dynamics and chronologies, with less attention paid to an ice sheet wide view of the first order properties of the ice sheet: centres of mass, ice divide structure, ice flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an ice sheet reconstruction yielding these fundamental ice sheet properties. We present a seven stage model of ice sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of ice from Scotland likely coalesced with local ice caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish Ice Sheet was then established during ice sheet growth, with a branching ice divide structure whose main axis migrated up to 140 km from the west coast towards the east. Ice stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. Ice cover is reconstructed as extending to the continental shelf break. The Irish Ice Sheet became autonomous (i.e. separate from the British Ice Sheet) during deglaciation and fragmented into multiple ice masses, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the ice sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the ice stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid

  20. Interannual and seasonal changes in the south seasonal polar cap of Mars: Observations from MY 28-31 using MARCI

    NASA Astrophysics Data System (ADS)

    Calvin, W. M.; Cantor, B. A.; James, P. B.

    2017-08-01

    The Mars Color Imager (MARCI) camera on the Mars Reconnaissance Orbiter provides daily synoptic coverage that allows monitoring of seasonal cap retreat and interannual changes that occur between Mars Years (MY) and over the southern summer. We present the first analysis of this data for the southern seasonal cap evolution observed in MY 28, 29, 30 and 31 (2/2007 to 07/2013). Observation over multiple Mars years allows us to compare changes between years as well as longer-term evolution of the high albedo deposits at the poles. Seasonal cap retreat is similar in all years and to retreats observed in other years by both optical and thermal instruments. The cryptic terrain has a fairly consistent boundary in each year, but numerous small-scale variations occur in each MY observed. Additionally, numerous small dark deposits are identified outside the classically identified cyptic region, including Inca City and other locations not previously noted. The large water ice outlier is observed to retain seasonal frost the longest (outside the polar dome) and is also highly variable in each MY. The development of the cryptic/anti-cryptic hemispheres is inferred to occur due to albedo variations that develop after dust venting starts and may be caused by recondensation of CO2 ice on the brightest and coldest regions controlled by topographic winds. Ground ice may play a role in which regions develop cryptic terrain, as there is no elevation control on either cryptic terrain or the late season brightest deposits.

  1. The cervical cap.

    PubMed

    1988-10-07

    The US Food and Drug Administration has approved marketing of the Prentif cavity-rim cervical cap. This contraceptive device is being distributed in the US and Canada by Cervical Cap Ltd, Los Gatos, California. The Prentif cap is available in 4 sizes: 22, 25, 28, and 31 mm inside diameter, with a length of 1 1/4-1 1/2 inches. In a multicenter trial involving 522 diaphragm users and 581 cap users followed for 2 years, the cap was 82.6% effective and the diaphragm was 83.3% effective in preventing pregnancy. When pregnancies attributable to user failure were excluded, these rates were increased to 93.6% for the cap and 95.4% for the diaphragm. 4% of cap users compared with only 1.7% of diaphragm users in this study developed abnormal Pap smears after 3 months of use; in addition, a higher proportion of cap users became infected with Gardnerella vaginalis and Monilia. Theoretical hazards include toxic shock syndrome and endometriosis due to backflow of menstrual fluids. Cap users are advised to undergo a Pap test after 3 months of use and discontinue cap use if the results are abnormal. The cap should not be used during menstruation. Although the cap can be left in place for up to 48 hours, its position should be checked before and after each episode of intercourse. The cervical cap requires less spermicide than the diaphragm and is not as messy. In addition, it can be left in the vagina twice as long as the diaphragm, without additional spermicide. Since the cap is smaller than the diaphragm and does not cover the vaginal wall, some women find intercourse more pleasurable with this device.

  2. The Residual Polar Caps of Mars: Geological Differences and Possible Consequences

    NASA Technical Reports Server (NTRS)

    Thomas, P. C.; Sullivan, R.; Ingersoll, A. P.; Murray, B. C.; Danielson, G. E.; Herkenhoff, K. E.; Soderblom, L.; Malin, M. C.; Edgett, K. S.; James, P. B.

    2000-01-01

    The Martian polar regions have been known to have thick layered sequences (presumed to consist of silicates and ice), CO2 seasonal frost, and residual frosts that remain through the summer: H2O in the north, largely CO2 in the south. The relationship of the residual frosts to the underlying layered deposits could not be determined from Viking images. The Mars Orbiter Camera on Mars Global Surveyor has provided a 50-fold increase in resolution that shows more differences between the two poles. The north residual cap surface has rough topography of pits, cracks, and knobs, suggestive of ablational forms. This topography is less than a few meters in height, and grades in to surfaces exposing the layers underneath. In contrast, the south residual cap has distinctive collapse and possibly ablational topography emplaced in four or more layers, each approx. two meters thick. The top surface has polygonal depressions suggestive of thermal contraction cracks. The collapse and erosional forms include circular and cycloidal depressions, long sinuous troughs, and nearly parallel sets of troughs. The distinctive topography occurs throughout the residual cap area, but not outside it. Unconformities exposed in polar layers, or other layered materials, do not approximate the topography seen on the south residual cap. The coincidence of a distinct geologic feature, several layers modified by collapse, ablation, and mass movement with the residual cap indicates a distinct composition and/or climate compared to both the remainder of the south polar layered units and those in the north.

  3. Temperature of nitrogen ice on Pluto and its implications for flux measurements.

    PubMed

    Tryka, K A; Brown, R H; Cruikshank, D P; Owen, T C; Geballe, T R; DeBergh, C

    1994-01-01

    Previous work by K.A. Tryka et al. (Science 261, 751-754, 1993) has shown that the profile of the 2.148-micrometers band of solid nitrogen can be used as a "thermometer" and determined the temperature of nitrogen ice on Triton to be 38(+2)-1 K. Here we reevaluate that data and refine the temperature value to 38 +/- 1 K. Applying the same technique to Pluto we determine that the temperature of the N2 ice on that body is 40 +/- 2 K. Using this result we have created a nonisothermal flux model of the Pluto-Charon system. The model treats Pluto as a body with symmetric N2 polar caps and an equatorial region devoid of N2. Comparison with the infrared and millimeter flux measurements shows that the published fluxes are consistent with models incorporating extensive N2 polar caps (down to +/- 15 degrees or +/- 20 degrees latitude) and an equatorial region with a bolometric albedo < or = 0.2.

  4. Temperature of nitrogen ice on Pluto and its implications for flux measurements

    NASA Technical Reports Server (NTRS)

    Tryka, Kimberly A.; Brown, Robert H.; Chruikshank, Dale P.; Owen, Tobias C.; Geballe, Thomas R.; Debergh, Catherine

    1994-01-01

    Previous work by K. A. Tryka et al. (1993) has shown that the profile of the 2.148-micron band of solid nitrogen can be used as a 'thermometer' and determined the tempertature of nitrogen ice on Triton to be 38(sup +2)(sub -1) K. Here we reevalute that data and refine the temperature value to 38 +/- 1 K. Applying the same technique to Pluto we determine that the temperature of the N2 ice on that body is 40 +/- 2 K. Using this result we have created a nonisothermal flux model of the Pluto-Charon system. The model treats Pluto as a body with symmetric N2 polar caps and an equatorial region devoid of N2. Comparison with the infrared and millimeter flux measurements shows that the published fluxes are consistent with models incorporating extensive N2 polar caps (down to +/- 15 deg ot +/- 20 deg latitude) and an equatorial region with a bolometric albedo less than or equal to 0.2.

  5. A search for polycyclic aromatic hydrocarbons over the Martian South Polar Residual Cap

    NASA Astrophysics Data System (ADS)

    Campbell, J. D.; Sidiropoulos, P.; Muller, J.-P.

    2018-07-01

    We present our research on compositional mapping of the Martian South Polar Residual Cap (SPRC), especially the detection of organic signatures within the dust content of the ice, based on hyperspectral data analysis. The SPRC is the main region of interest for this investigation, because of the unique CO2 ice sublimation features that cover the surface. These flat floored, circular depressions are highly dynamic, and we infer frequently expose dust particles previously trapped within the ice during the wintertime. Here we identify suitable regions for potential dust exposure on the SPRC, and utilise data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA's Mars Reconnaissance Orbiter (MRO) satellite to examine infrared spectra of dark regions assumed to be composed mainly of dust particles to establish their mineral composition, to eliminate the effects of ices on sub-pixel dusty features, and to look for signatures indicative of Polycyclic Aromatic Hydrocarbons (PAHs). Spectral mapping has identified compositional differences between depression rims and the majority of the SPRC and CRISM spectra have been corrected to minimise the influence of CO2 ice. Whilst no conclusive evidence for PAHs has been found within the detectability limits of the CRISM instrument, depression rims are shown to have higher water content than regions of featureless ice, and there are possible indications of magnesium carbonate within the dark, dusty regions.

  6. An observational search for CO2 ice clouds on Mars

    NASA Technical Reports Server (NTRS)

    Bell, James F., III; Calvin, Wendy M.; Pollack, James B.; Crisp, David

    1993-01-01

    CO2 ice clouds were first directly identified on Mars by the Mariner 6 and 7 infrared spectrometer limb scans. These observations provided support for early theoretical modeling efforts of CO2 condensation. Mariner 9 IRIS temperature profiles of north polar hood clouds were interpreted as indicating that these clouds were composed of H2O ice at lower latitudes and CO2 ice at higher latitudes. The role of CO2 condensation on Mars has recently received increased attention because (1) Kasting's model results indicated that CO2 cloud condensation limits the magnitude of the proposed early Mars CO2/H2O greenhouse, and (2) Pollack el al.'s GCM results indicated that the formation of CO2 ice clouds is favorable at all polar latitudes during the fall and winter seasons. These latter authors have shown that CO2 clouds play an important role in the polar energy balance, as the amount of CO2 contained in the polar caps is constrained by a balance between latent heat release, heat advected from lower latitudes, and thermal emission to space. The polar hood clouds reduce the amount of CO2 condensation on the polar caps because they reduce the net emission to space. There have been many extensive laboratory spectroscopic studies of H2O and CO2 ices and frosts. In this study, we use results from these and other sources to search for the occurrence of diagnostic CO2 (and H2O) ice and/or frost absorption features in ground based near-infrared imaging spectroscopic data of Mars. Our primary goals are (1) to try to confirm the previous direct observations of CO2 clouds on Mars; (2) to determine the spatial extent, temporal variability, and composition (H2O/CO2 ratio) of any clouds detected; and (3) through radiative transfer modeling, to try to determine the mean particle size and optical depth of polar hood clouds, thus, assessing their role in the polar heat budget.

  7. Buried CO2 Ice traces in South Polar Layered Deposits of Mars detected by radar sounder

    NASA Astrophysics Data System (ADS)

    Castaldo, L.; Mège, D.; Orosei, R.; Séjourné, A.

    2014-12-01

    SHARAD (SHAllow RADar) is the subsurface sounding radar provided by the Italian Space Agency (ASI) as a facility instrument to NASA's 2005 Mars Reconnaissance Orbiter (MRO). The Reduced Data Record of SHARAD data covering the area of the South Polar Layered Deposits (SPLD), has been used. The elaboration and interpretation of the data, aimed to estimate electromagnetic properties of surface layers, has been performed in terms of permittivity. The theory of electromagnetic scattering from fractal surfaces, and the estimation of geometric parameters from topographic data by Mars Orbiter Laser Altimeter (MOLA) which was one of five instruments on board the Mars Global Surveyor (MGS) spacecraft, has been used. A deep analysis of inversion has been made on all Mars and extended to the South Polar Caps in order to extract the area with a permittivity constant of CO2 ice. Several corrections have been applied to the data, moreover the calibration of the signal requires the determination of a constant that takes into account the power gain due to the radar system and the surface in order to compensate the power losses due to the orbitographic phenomena. The determination of regions with high probability of buried CO2 ice in the first layer of the Martian surface, is obtained extracting the real part of the permittivity constant of the CO2 ice (~2), estimated by other means. The permittivity of CO2ice is extracted from the Global Permittivity Map of Mars using the global standard deviation of itself as following: ɛCO2ice=ɛCO2ice+ Σ (1)where Σ=±std(ɛMapMars)/2Figure 1(a) shows the south polar areas where the values of the permittivity point to the possibility of a CO2 ice layer. Figure 1(b) is the corresponding geologic map. The comparison between the two maps indicates that the area with probable buried CO2 overlaps Hesperian and Amazonian polar units (Hp, Hesperian plains-forming deposits marked by narrow sinuous, anabranching ridges and irregular depressions, and

  8. Arctic spring ozone reduction associated with projected sea ice loss

    NASA Astrophysics Data System (ADS)

    Deser, C.; Sun, L.; Tomas, R. A.; Polvani, L. M.

    2013-12-01

    The impact of Arctic sea ice loss on the stratosphere is investigated using the Whole-Atmosphere Community Climate Model (WACCM), by prescribing the sea ice in the late 20th century and late 21st century, respectively. The localized Sea Surface Temperature (SST) change associated with sea ice melt is also included in the future run. Overall, the model simulates a negative annular-mode response in the winter and spring. In the stratosphere, polar vortex strengthens from February to April, peaking in March. Consistent with it, there is an anomalous cooling in the high-latitude stratosphere, and polar cap ozone reduction is up to 20 DU. Since the difference between these two runs lies only in the sea ice and localized SST in the Arctic, the stratospheric circulation and ozone changes can be attributed to the surface forcing. Eliassen-Palm analysis reveals that the upward propagation of planetary waves is suppressed in the spring as a consequence of sea ice loss. The reduction in propagation causes less wave dissipation and thus less zonal wind deceleration in the extratropical stratosphere.

  9. Surface elevation change over the Patagonia Ice Fields using CryoSat-2 swath altimetry

    NASA Astrophysics Data System (ADS)

    Foresta, Luca; Gourmelen, Noel; José Escorihuela, MarÍa; Garcia Mondejar, Albert; Wuite, Jan; Shepherd, Andrew; Roca, Mònica; Nagler, Thomas; Brockley, David; Baker, Steven; Nienow, Pete

    2017-04-01

    Satellite altimetry has been traditionally used in the past few decades to infer elevation of land ice, quantify changes in ice topography and infer mass balance estimates over large and remote areas such as the Greenland and Antarctic ice sheets. Radar Altimetry (RA) is particularly well suited to this task due to its all-weather year-round capability of observing the ice surface. However, monitoring of ice caps (area < 104 km^2) as well as mountain glaciers has proven more challenging. The large footprint of a conventional radar altimeter and relatively coarse ground track coverage are less suited to monitoring comparatively small regions with complex topography, so that mass balance estimates from RA rely on extrapolation methods to regionalize elevation change. Since 2010, the European Space Agency's CryoSat-2 (CS-2) satellite has collected ice elevation measurements over ice caps with its novel radar altimeter. CS-2 provides higher density of observations w.r.t. previous satellite altimeters, reduces the along-track footprint using Synthetic Aperture Radar (SAR) processing and locates the across-track origin of a surface reflector in the presence of a slope with SAR Interferometry (SARIn). Here, we exploit CS-2 as a swath altimeter [Hawley et al., 2009; Gray et al., 2013; Christie et al., 2016; Ignéczi et al., 2016, Foresta et al., 2016] over the Southern and Northern Patagonian Ice Fields (SPI and NPI, respectively). The SPI and NPI are the two largest ice masses in the southern hemisphere outside of Antarctica and are thinning very rapidly in recent decades [e.g Rignot et al., 2003; Willis et al, 2012]. However, studies of surface, volume and mass change in the literature, covering the entire SPI and NPI, are limited in number due to their remoteness, extremely complex topography and wide range of slopes. In this work, we present rates of surface elevation change for five glaciological years between 2011-2016 using swath-processed CS-2 SARIn heights and

  10. Zonally averaged thermal balance and stability models for nitrogen polar caps on Triton

    NASA Technical Reports Server (NTRS)

    Stansberry, John A.; Lunine, J. I.; Porco, C. C.; Mcewen, A. S.

    1990-01-01

    Voyager four-color imaging data of Triton are analyzed to calculate the bolometric hemispheric albedo as a function of latitude and longitude. Zonal averages of these data have been incorporated into a thermal balance model involving insolation, reradiation, and latent heat of sublimation of N2 ice for the surface. The current average bolometric albedo of Triton's polar caps is 0.8, implying an effective temperature of 34.2 K and a surface pressure of N2 of 1.6 microbar for unit emissivity. This pressure is an order of magnitude lower than the surface pressure of 18 microbar inferred from Voyager data (Broadfoot et al., 1989; Conrath et al., 1989), a discrepancy that can be reconciled if the emissivity of the N2 on Triton's surface is 0.66. The model predicts that Triton's surface north of 15 deg N latitude is experiencing deposition of N2 frosts, as are the bright portions of the south polar cap near the equator. This result explains why the south cap covers nearly the entire southern hemisphere of Triton.

  11. Cradle Cap (For Parents)

    MedlinePlus

    ... Safe Videos for Educators Search English Español Cradle Cap (Infantile Seborrheic Dermatitis) KidsHealth / For Parents / Cradle Cap ( ... many babies develop called cradle cap. About Cradle Cap Cradle cap is the common term for seborrheic ...

  12. Predictions of vertical uplift caused by changing polar ice volumes on a viscoelastic earth

    NASA Technical Reports Server (NTRS)

    Wahr, John; Dazhong, Han; Trupin, Andrew

    1995-01-01

    Measurements of crustal uplift from bedrock around the edges of Antarctica or Greenland could help constrain the mass balance of those ice caps. Present-day changes in ice could cause vertical displacement rates of several mm/yr around Antarctica and up to 10-15 mm/yr around Greenland. Horizontal displacement rates are likely to be about 1/3 the vertical rates. The viscoelastic response of the earth to past changes in ice could cause uplift rates that are several times larger. By measuring both gravity and vertical displacements, it is possible to remove the viscoelastic effects, so that the observations can be used to constrain present-day thickness changes.

  13. Transport of Water Ice to the Martian South Pole 25,000 years ago

    NASA Astrophysics Data System (ADS)

    Montmessin, F.; Haberle, R. M.; Forget, F.

    2004-11-01

    Whereas most of studies on recent climate change address the fate of water with changing obliquities, we would like to show how the precession cycle might affect the stability of the north polar cap on much faster timescales. This study is motivated by the desire to highlight the potential dichotomy, in terms of water stability, between the poles. Not only does this study address perihelion timing, it focuses on the most recent and most significant change of Mars climate. To do so, we use the General Circulation Model (GCM) developed at LMD (Paris/France) to explore the change in water cycle patterns induced by shifting the perihelion date. It is found that, potentially, water ice could have been continuously transferred from north to south pole during episods of "reversed" perihelions. These results have important implications with regards to the recent discovery of thick water ice sheets partially uncovered at the edge of the CO2 residual cap. This work has been funded by the National Research council.

  14. Ir Spectral Mapping of the Martian South Polar Residual CAP Using Crism

    NASA Astrophysics Data System (ADS)

    Campbell, Jacqueline; Sidiropoulos, Panagiotis; Muller, Jan-Peter

    2016-06-01

    Polycyclic aromatic hydrocarbons (PAHs) are considered to be important in theories of abiogenesis (Allamandola, 2011) . There is evidence that PAHs have been detected on two icy Saturnian satellites using the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft (Cruikshank et al., 2007). The hypothesised presence of PAHs in Mars south polar cap has not been systematically examined even though the Mars south polar cap may allow the preservation of organic molecules that are typically destroyed at the Martian surface by UV radiation (Dartnell et al. 2012). This hypothesis is supported by recent analyses of South Polar Residual Cap (SPRC) structural evolution (Thomas et al., 2009) that suggest the possibility that seasonal and long term sublimation may excavate dust particles from within the polar ice. Periodic sublimation is believed to be responsible for the formation of so-called "Swiss Cheese Terrain", a unique surface feature found only in the Martian south polar residual cap consisting of flat floored, circular depressions (Byrne, 2009). We show the first examples of work towards the detection of PAHs in Swiss Cheese Terrain, using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), on board NASA's Mars Reconnaissance Orbiter (MRO). CRISM is designed to search for mineralogical indications of past and present water, thus providing extensive coverage of the south polar cap. In this work, we discuss whether CRISM infrared spectra can be used to detect PAHs in Swiss Cheese Terrain and demonstrate a number of maps showing shifts in spectral profiles over the SPRC.

  15. Long term ice sheet mass change rates and inter-annual variability from GRACE gravimetry.

    NASA Astrophysics Data System (ADS)

    Harig, C.

    2017-12-01

    The GRACE time series of gravimetry now stretches 15 years since its launch in 2002. Here we use Slepian functions to estimate the long term ice mass trends of Greenland, Antarctica, and several glaciated regions. The spatial representation shows multi-year to decadal regional shifts in accelerations, in agreement with increases in radar derived ice velocity. Interannual variations in ice mass are of particular interest since they can directly link changes in ice sheets to the drivers of change in the polar ocean and atmosphere. The spatial information retained in Slepian functions provides a tool to determine how this link varies in different regions within an ice sheet. We present GRACE observations of the 2013-2014 slowdown in mass loss of the Greenland ice sheet, which was concentrated in specific parts of the ice sheet and in certain months of the year. We also discuss estimating the relative importance of climate factors that control ice mass balance, as a function of location of the glacier/ice cap as well as the spatial variation within an ice sheet by comparing gravimetry with observations of surface air temperature, ocean temperature, etc. as well as model data from climate reanalysis products.

  16. Response of ice caves to weather extremes in the southeastern Alps, Europe

    NASA Astrophysics Data System (ADS)

    Colucci, R. R.; Fontana, D.; Forte, E.; Potleca, M.; Guglielmin, M.

    2016-05-01

    High altitude karstic environments often preserve permanent ice deposits within caves, representing the lesser-known portion of the cryosphere. Despite being not so widespread and easily reachable as mountain glaciers and ice caps, ice caves preserve much information about past environmental changes and climatic evolution. We selected 1111 ice caves from the existing cave inventory, predominantly but not exclusively located in the periglacial domain where permafrost is not dominant (i.e., with mean annual air temperature < 3 °C but not in a permafrost environment). The influence of climate and topography on ice cave distribution is also investigated. In order to assess the thickness and the inner structure of the deposits, we selected two exemplary ice caves in the Canin massif (Julian Alps) performing several multifrequency GPR surveys. A strong influence of global and local climate change in the evolution of the ice deposits has been particularly highlighted in the dynamic ice cave type, especially in regard to the role of weather extremes. The natural response of ice caves to a warming climate could lead to a fast reduction of such ice masses. The increased occurrence of weather extremes, especially warmer and more intense precipitation caused by higher mean 0 °C-isotherms, could in fact be crucial in the future mass balance evolution of such permanent ice deposits.

  17. Cosmogenic exposure age constraints on deglaciation and flow behaviour of a marine-based ice stream in western Scotland, 21-16 ka

    NASA Astrophysics Data System (ADS)

    Small, David; Benetti, Sara; Dove, Dayton; Ballantyne, Colin K.; Fabel, Derek; Clark, Chris D.; Gheorghiu, Delia M.; Newall, Jennifer; Xu, Sheng

    2017-07-01

    Understanding how marine-based ice streams operated during episodes of deglaciation requires geochronological data that constrain both timing of deglaciation and changes in their flow behaviour, such as that from unconstrained ice streaming to topographically restricted flow. We present seventeen new 10Be exposure ages from glacial boulders and bedrock at sites in western Scotland within the area drained by the Hebrides Ice Stream, a marine-based ice stream that drained a large proportion of the former British-Irish Ice Sheet. Exposure ages from Tiree constrain deglaciation of a topographic high within the central zone of the ice stream, from which convergent flowsets were produced during ice streaming. These ages thus constrain thinning of the Hebrides Ice Stream, which, on the basis of supporting information, we infer to represent cessation of ice streaming at 20.6 ± 1.2 ka, 3-4 ka earlier than previously inferred. A period of more topographically restricted flow produced flow indicators superimposed on those relating to full ice stream conditions, and exposure ages from up-stream of these constrain deglaciation to 17.5 ± 1.0 ka. Complete deglaciation of the marine sector of the Hebrides Ice Stream occurred by 17-16 ka at which time the ice margin was located near the present coastline. Exposure ages from the southernmost Outer Hebrides (Mingulay and Barra) indicate deglaciation at 18.9 ± 1.0 and 17.1 ± 1.0 ka respectively, demonstrating that an independent ice cap persisted on the southern Outer Hebrides for 3-4 ka after initial ice stream deglaciation. This suggests that deglaciation of the Hebrides Ice Stream was focused along major submarine troughs. Collectively, our data constrain initial deglaciation and changes in flow regime of the Hebrides Ice Stream, final deglaciation of its marine sector, and deglaciation of the southern portion of the independent Outer Hebrides Ice Cap, providing chronological constraints on future numerical reconstructions of

  18. Skin Temperature Processes in the Presence of Sea Ice

    NASA Astrophysics Data System (ADS)

    Brumer, S. E.; Zappa, C. J.; Brown, S.; McGillis, W. R.; Loose, B.

    2013-12-01

    Monitoring the sea-ice margins of polar oceans and understanding the physical processes at play at the ice-ocean-air interface is essential in the perspective of a changing climate in which we face an accelerated decline of ice caps and sea ice. Remote sensing and in particular InfraRed (IR) imaging offer a unique opportunity not only to observe physical processes at sea-ice margins, but also to measure air-sea exchanges near ice. It permits monitoring ice and ocean temperature variability, and can be used for derivation of surface flow field allowing investigating turbulence and shearing at the ice-ocean interface as well as ocean-atmosphere gas transfer. Here we present experiments conducted with the aim of gaining an insight on how the presence of sea ice affects the momentum exchange between the atmosphere and ocean and investigate turbulence production in the interplay of ice-water shear, convection, waves and wind. A set of over 200 high resolution IR imagery records was taken at the US Army Cold Regions Research and Engineering Laboratory (CRREL, Hanover NH) under varying ice coverage, fan and pump settings. In situ instruments provided air and water temperature, salinity, subsurface currents and wave height. Air side profiling provided environmental parameters such as wind speed, humidity and heat fluxes. The study aims to investigate what can be gained from small-scale high-resolution IR imaging of the ice-ocean-air interface; in particular how sea ice modulates local physics and gas transfer. The relationship between water and ice temperatures with current and wind will be addressed looking at the ocean and ice temperature variance. Various skin temperature and gas transfer parameterizations will be evaluated at ice margins under varying environmental conditions. Furthermore the accuracy of various techniques used to determine surface flow will be assessed from which turbulence statistics will be determined. This will give an insight on how ice presence

  19. Thinning of the ice sheet in northwest Greenland over the past forty years.

    PubMed

    Paterson, W S; Reeh, N

    2001-11-01

    Thermal expansion of the oceans, as well as melting of glaciers, ice sheets and ice caps have been the main contributors to global sea level rise over the past century. The greatest uncertainty in predicting future sea level changes lies with our estimates of the mass balance of the ice sheets in Greenland and Antarctica. Satellite measurements have been used to determine changes in these ice sheets on short timescales, demonstrating that surface-elevation changes on timescales of decades or less result mainly from variations in snow accumulation. Here we present direct measurements of the changes in surface elevation between 1954 and 1995 on a traverse across the north Greenland ice sheet. Measurements over a time interval of this length should reflect changes in ice flow-the important quantity for predicting changes in sea level-relatively unperturbed by short-term fluctuations in snow accumulation. We find only small changes in the eastern part of the transect, except for some thickening of the north ice stream. On the west side, however, the thinning rates of the ice sheet are significantly higher and thinning extends to higher elevations than had been anticipated from previous studies.

  20. Glaciers and small ice caps in the macro-scale hydrological cycle - an assessment of present conditions and future changes

    NASA Astrophysics Data System (ADS)

    Lammers, Richard; Hock, Regine; Prusevich, Alexander; Bliss, Andrew; Radic, Valentina; Glidden, Stanley; Grogan, Danielle; Frolking, Steve

    2014-05-01

    Glacier and small ice cap melt water contributions to the global hydrologic cycle are an important component of human water supply and for sea level rise. This melt water is used in many arid and semi-arid parts of the world for direct human consumption as well as indirect consumption by irrigation for crops, serving as frozen reservoirs of water that supplement runoff during warm and dry periods of summer when it is needed the most. Additionally, this melt water reaching the oceans represents a direct input to sea level rise and therefore accurate estimates of this contribution have profound economic and geopolitical implications. It has been demonstrated that, on the scale of glacierized river catchments, land surface hydrological models can successfully simulate glacier contribution to streamflow. However, at global scales, the implementation of glacier melt in hydrological models has been rudimentary or non-existent. In this study, a global glacier mass balance model is coupled with the University of New Hampshire Water Balance/Transport Model (WBM) to assess recent and projected future glacier contributions to the hydrological cycle over the global land surface (excluding the ice sheets of Greenland and Antarctica). For instance, results of WBM simulations indicate that seasonal glacier melt water in many arid climate watersheds comprises 40 % or more of their discharge. Implicitly coupled glacier and WBM models compute monthly glacier mass changes and resulting runoff at the glacier terminus for each individual glacier from the globally complete Randolph Glacier Inventory including over 200 000 glaciers. The time series of glacier runoff is aggregated over each hydrological modeling unit and delivered to the hydrological model for routing downstream and mixing with non-glacial contribution of runoff to each drainage basin outlet. WBM tracks and uses glacial and non-glacial components of the in-stream water for filling reservoirs, transfers of water between

  1. The Unexpected Re-Growth of Ice-Entombed Bryophytes in the Canadian High Arctic

    NASA Astrophysics Data System (ADS)

    La Farge, C.

    2014-12-01

    The rapid retreat of glaciers and ice caps throughout the Canadian Arctic is exposing pristine vegetation preserved beneath cold-based ice. For the past half century this vegetation has been consistently reported as dead. This interpretation has been overturned by the successful re-growth of Little Ice Age (1550-1850 AD) bryophytes emerging from the Teardrop Glacier, Sverdrup Pass, Ellesmere Island (79° N) collected in 2009. Some populations showed regeneration in the field and lab experiments confirmed their capacity to regrow. The species richness of these subglacial populations is exceptional, comprising >62 species that represent 44% of the extant bryophyte flora of Sverdrup Pass. Cold-based glaciers are known to provide critical habitats for a variety of microbiota (i.e., fungi, algae, cyanobacteria, bacteria and viruses) in high latitude ecosystems. The regeneration of Little Ice Age bryophytes fundamentally expands the concept of biological refugia to land plants that was previously restricted to survival above and beyond glacial margins. Given this novel understanding of subglacial ecosystems, fieldwork is now being extended southward to plateau ice caps on Baffin Island, Nunavut, where ice retreat is exposing subglacial populations of greater antiquity (thousands to tens of thousands of radiocarbon years before present). Bryophytes by nature are totipotent (stem cell equivalency) and poikilohydric (desiccation tolerance), which facilitate their unique adaptation to extreme environments. Continuity of the Arctic bryophyte flora extends back through the Holocene to the late Tertiary [Beaufort Fm, 2-5 Ma], when the majority of taxa were the same, based on records spanning the archipelago from Ellesmere to Banks Island. This record contrasts with that of vascular plants, which have had a number of extinctions, necessitating recolonization of arctic populations from outside the region. The biological significance of a stable bryophyte element highlights their

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

    PubMed Central

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

    2002-01-01

    Airborne radar has detected ≈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°C, which is 7°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 km3) and at lower temperatures (−20°C to −35°C) than has heretofore been possible. PMID:12060731

  3. CapZyme-Seq Comprehensively Defines Promoter-Sequence Determinants for RNA 5' Capping with NAD.

    PubMed

    Vvedenskaya, Irina O; Bird, Jeremy G; Zhang, Yuanchao; Zhang, Yu; Jiao, Xinfu; Barvík, Ivan; Krásný, Libor; Kiledjian, Megerditch; Taylor, Deanne M; Ebright, Richard H; Nickels, Bryce E

    2018-05-03

    Nucleoside-containing metabolites such as NAD + can be incorporated as 5' caps on RNA by serving as non-canonical initiating nucleotides (NCINs) for transcription initiation by RNA polymerase (RNAP). Here, we report CapZyme-seq, a high-throughput-sequencing method that employs NCIN-decapping enzymes NudC and Rai1 to detect and quantify NCIN-capped RNA. By combining CapZyme-seq with multiplexed transcriptomics, we determine efficiencies of NAD + capping by Escherichia coli RNAP for ∼16,000 promoter sequences. The results define preferred transcription start site (TSS) positions for NAD + capping and define a consensus promoter sequence for NAD + capping: HRRASWW (TSS underlined). By applying CapZyme-seq to E. coli total cellular RNA, we establish that sequence determinants for NCIN capping in vivo match the NAD + -capping consensus defined in vitro, and we identify and quantify NCIN-capped small RNAs (sRNAs). Our findings define the promoter-sequence determinants for NCIN capping with NAD + and provide a general method for analysis of NCIN capping in vitro and in vivo. Copyright © 2018 Elsevier Inc. All rights reserved.

  4. Weather Features Associated with Aircraft Icing Conditions: A Case Study

    PubMed Central

    Fernández-González, Sergio; Sánchez, José Luis; Gascón, Estíbaliz; López, Laura; García-Ortega, Eduardo; Merino, Andrés

    2014-01-01

    In the context of aviation weather hazards, the study of aircraft icing is very important because of several accidents attributed to it over recent decades. On February 1, 2012, an unusual meteorological situation caused severe icing of a C-212-200, an aircraft used during winter 2011-2012 to study winter cloud systems in the Guadarrama Mountains of the central Iberian Peninsula. Observations in this case were from a MP-3000A microwave radiometric profiler, which acquired atmospheric temperature and humidity profiles continuously every 2.5 minutes. A Cloud Aerosol and Precipitation Spectrometer (CAPS) was also used to study cloud hydrometeors. Finally, ice nuclei concentration was measured in an isothermal cloud chamber, with the goal of calculating concentrations in the study area. Synoptic and mesoscale meteorological conditions were analysed using the Weather Research and Forecasting (WRF) model. It was demonstrated that topography influenced generation of a mesolow and gravity waves on the lee side of the orographic barrier, in the region where the aircraft experienced icing. Other factors such as moisture, wind direction, temperature, atmospheric stability, and wind shear were decisive in the appearance of icing. This study indicates that icing conditions may arise locally, even when the synoptic situation does not indicate any risk. PMID:24701152

  5. Weather features associated with aircraft icing conditions: a case study.

    PubMed

    Fernández-González, Sergio; Sánchez, José Luis; Gascón, Estíbaliz; López, Laura; García-Ortega, Eduardo; Merino, Andrés

    2014-01-01

    In the context of aviation weather hazards, the study of aircraft icing is very important because of several accidents attributed to it over recent decades. On February 1, 2012, an unusual meteorological situation caused severe icing of a C-212-200, an aircraft used during winter 2011-2012 to study winter cloud systems in the Guadarrama Mountains of the central Iberian Peninsula. Observations in this case were from a MP-3000A microwave radiometric profiler, which acquired atmospheric temperature and humidity profiles continuously every 2.5 minutes. A Cloud Aerosol and Precipitation Spectrometer (CAPS) was also used to study cloud hydrometeors. Finally, ice nuclei concentration was measured in an isothermal cloud chamber, with the goal of calculating concentrations in the study area. Synoptic and mesoscale meteorological conditions were analysed using the Weather Research and Forecasting (WRF) model. It was demonstrated that topography influenced generation of a mesolow and gravity waves on the lee side of the orographic barrier, in the region where the aircraft experienced icing. Other factors such as moisture, wind direction, temperature, atmospheric stability, and wind shear were decisive in the appearance of icing. This study indicates that icing conditions may arise locally, even when the synoptic situation does not indicate any risk.

  6. Cradle Cap: Treatment

    MedlinePlus

    Cradle cap Treatment Cradle cap usually doesn't require medical treatment. It clears up on its own within a few months. In the meantime, wash ... tips can help you control and manage cradle cap. Gently rub your baby's scalp with your fingers ...

  7. Effects of exchange bias on magnetotransport in permalloy kagome artificial spin ice

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

    Le, B. L.; Rench, D. W.; Misra, R.

    2015-02-01

    We investigate the magnetotransport properties of connected kagome artificial spin ice networks composed of permalloy nanowires. Our data show clear evidence of magnetic switching among the wires, both in the longitudinal and transverse magnetoresistance. An unusual asymmetry with field sweep direction appears at temperatures below about 20 K that appears to be associated with exchange bias resulting from surface oxidation of permalloy, and which disappears in alumina-capped samples. These results demonstrate that exchange bias is a phenomenon that must be considered in understanding the physics of such artificial spin ice systems, and that opens up new possibilities for their control.

  8. Volatile-rich Crater Interior Deposits in the Polar Regions of Mars: Evidence for Ice Cap Advance and Retreat

    NASA Technical Reports Server (NTRS)

    Russell, Patrick S.; Head, James W.; Hecht, Michael H.

    2003-01-01

    Many craters on Mars are partially filled by distinctive material emplaced by post-impact processes. This crater fill material is an interior mound which is generally separated from the walls of the crater by a trough that may be continuous along the crater circumference (i.e. a ring-shaped trough), or which may only partially contact the crater walls (i.e. a crescent-shaped trough). The fill deposit is frequently offset from the crater center and may be asymmetric in plan view. Populations of such craters include those in the circum-south polar cap region, in Arabia Terra, associated with the Medusae Fossae Formation, and in the northern lowlands proximal to the north polar cap. We focus on those craters in circumpolar regions and assess their relationship to polar cap advance and retreat, especially the possibility that fill material represents remnants of a formerly larger contiguous cap. Volatile-rich deposits have the property of being modifiable by the local stability of the solid volatile, which is governed by local energy balance. Here we test the hypothesis that asymmetries in volatile fill shape, profile, and center-location within a crater result from asymmetries in local energy balance within the crater, due mainly to variation of solar insolation and radiative effects of the crater walls over the crater interior. Model profiles of crater fill are compared with MOLA topographic profiles to assess this hypothesis. If asymmetry in morphology and location of crater fill are consistent with radiative-dominated asymmetries in energy budget within the crater, then 1) the volatile-rich composition of the fill is supported (this process should not be effective at shaping volcanic or sedimentary deposits), and 2) the dominant factor determining the observed shape of volatile-rich crater fill is the local radiative energy budget (and erosive processes such as eolian deflation are secondary or unnecessary). We also use a geographic and energy model approach to

  9. The distribution of Martian ground ice at other epochs

    NASA Technical Reports Server (NTRS)

    Mellon, M. T.; Jakosky, B. M.

    1993-01-01

    The past orbital evolution of Mars is examined in relation to changes in ice stability as well as the condensation, sublimation, and diffusion of atmospheric water in an exchange with the regolith. The Martian obliquity has undergone significant oscillations in its recent past. During periods of high obliquity, the solar energy would have been distributed such that the equatorial and midlatitude regions would have been colder that at present and the polar regions would have been warmer. Warmer polar regions would result in the sublimation of more polar cap water into the atmosphere and thus higher atmospheric water abundances. This combination of effects would have resulted in ground ice being stable globally. During periods of low obliquity the opposite would have occurred. Modeling results of the regolith thermal behavior and the molecular diffusion of water vapor within the regolith and in exchange with the atmosphere have shown significant quantities of ground ice can form at all latitudes within the top 50 cm to 1 m of the regolith during periods of high obliquity. The amount of ice that forms can be as much as the regolith pores can hold. During low obliquity most or all of this ice sublimes and diffuses away. Below this depth a longer-term stability is observed at some latitudes where ice steadily increases in concentration regardless of orbital oscillations that occur.

  10. Evolution of Martian polar landscapes - Interplay of long-term variations in perennial ice cover and dust storm intensity

    NASA Technical Reports Server (NTRS)

    Cutts, J. A.; Blasius, K. R.; Roberts, W. J.

    1979-01-01

    The discovery of a new type of Martian polar terrain, called undulating plain, is reported and the evolution of the plains and other areas of the Martian polar region is discussed in terms of the trapping of dust by the perennial ice cover. High-resolution Viking Orbiter 2 observations of the north polar terrain reveal perennially ice-covered surfaces with low relief, wavelike, regularly spaced, parallel ridges and troughs (undulating plains) occupying areas of the polar terrain previously thought to be flat, and associated with troughs of considerable local relief which exhibit at least partial annual melting. It is proposed that the wavelike topography of the undulating plains originates from long-term periodic variations in cyclical dust precipitation at the margin of a growing or receding perennial polar cap in response to changes in insolation. The troughs are proposed to originate from areas of steep slope in the undulating terrain which have lost their perennial ice cover and have become incapable of trapping dust. The polar landscape thus appears to record the migrations, expansions and contractions of the Martian polar cap.

  11. Basal sublimation and venting of the north seasonal cap of Mars

    NASA Astrophysics Data System (ADS)

    Piqueux, S.; Christensen, P. R.

    2007-12-01

    Spots, fans and dark polygonal patterns form during the spring on the southern seasonal cap of Mars as a consequence of 1) the basal sublimation of the translucent and impermeable slab of carbon dioxide and 2) the venting of the CO2 gas loaded with dust and sand size material scoured from the surface of the polar layered deposits. The dark polygons on the cap have a similar formation process as the spots but the dust and sand erupt from elongated vents rather than point sources. In the summer, spiders and etched polygons remain on the southern polar layered deposits. The spiders are shaped by the scouring action of confined CO2 gas flowing between the cap and the basement and converging toward point sources, whereas the etched polygons result form the forced migration of the CO2 gas over longer distances. Comparable observations during the spring near the north pole on the seasonal cap indicate that similar processes occur in both polar regions and that the venting model developed for the south seasonal cap also operates near the north pole. However, spider and etched polygonal features are extremely uncommon on the north substrate, indicating that the conditions for their formation (e.g. mechanical strength of the slab and the substrate, transparency of the seasonal cap) are not met. The continual erosion and re-sedimentation occurring at the surface of the polar layered deposits by the seasonal degassing is a major geomorphological agent shaping the polar regions. The polar layered deposits have been proposed to contain the stratigraphic record of climatic changes and catastrophic events of very high interest for future missions. Our observations suggest that both polar regions deposits may have been locally disrupted by the seasonal sub-ice gas flow and that the stratigraphic record may have been partially lost. The Phoenix landing site might have been affected in the past and the stratigraphic information associated with the original deposition of the polar

  12. Arctic Sea Ice Sets New Record Winter Low

    NASA Image and Video Library

    2015-03-19

    The sea ice cap of the Arctic appeared to reach its annual maximum winter extent on February 25, according to data from the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder. At 5.61 million square miles (14.54 million square kilometers), this year’s maximum extent was the smallest on the satellite record and also one of the earliest. Credit: NASA Goddard Space Flight Center NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  14. Testing the "Mudball Earth" Hypothesis: Are Neoproterozoic Glacial Deposits Capped with Supraglacial Dust?

    NASA Astrophysics Data System (ADS)

    Goodman, J. C.; Alvim Lage, C.

    2014-12-01

    The Snowball Earth hypothesis has inspired several variants which may help to explain some of the great mysteries of the Neoproterozoic glaciations. One of these, the "Mudball Earth", proposes that as the Earth remained completely frozen for millions of years, a layer of dust accumulated on the ice surface. This dust layer would darken the planet, making it easier for the Earth to escape from the highly stable snowball climate state. This hypothesis is testable: after the ice melted at the end of a glacial era, this dust would sink to the bottom of the ocean, possibly forming a distinct clay, mud, or silt layer on the top of the glacial till deposits: this "clay drape" would then be covered by the cap carbonates that mark a return to warm climate. Sublimation and ice flow during the glacial episode should make this layer thicker at the equator and thinner or absent in the poles. Is this clay layer actually present in the rock record? Is it more prevalent at the paleoequator, as predicted? A clay drape has been noticed anecdotally, but no global survey has been done to date. We conducted a thorough literature review of all sites where Neoproterozoic glacial diamictites have been observed, identifying the type of rock that lies between the diamictite and the postglacial cap carbonate, when present, during both Sturtian and Marinoan glacial periods. Only a few publications identify a distinct clay/silt/mud layer that might represent weathered dust. These sites are not grouped by paleolatitude in any obvious way. With access only to published reports, we cannot determine whether such a layer is absent, went unreported, or was misinterpreted by us. With this work we hope to attract the attention of Neoproterozoic field geologists, inviting them to comment on the presence or absence of strata which could confirm or reject the "Mudball" hypothesis.

  15. Major Holocene block-and-ash fan at the western slope of ice-capped Pico de Orizaba volcano, México: Implications for future hazards

    NASA Astrophysics Data System (ADS)

    Siebe, Claus; Abrams, Michael; Sheridan, Michael F.

    1993-12-01

    A major block-and-ash fan extends more than 14 km westward from the summit of Pico de Orizaba volcano in the eastern part of the Trans-Mexican Volcanic Belt. Radiocarbon dating of charcoal within the fan deposits yielded Holocene ages that range between 4040 ± 80 and 4660 ± 100 y.B.P. Stratigraphical, sedimentological, geochemical, and scanning electron microscope studies indicate that this fan originated within a relatively short time-span by multiple volcanic explosions at the summit crater. This activity produced a series of pyroclastic flows (mainly block-and-ash flows) and lahars which were channelized by a glacial cirque and connecting U-shaped valleys as they descended toward the base of the volcano. A recurrence of a similar eruption today would pose severe hazards to the population of more than 50,000 people, who live in a potentially dangerous zone. A detailed reconstruction of the sequence of events that led to the formation of the block-and-ash fan is presented to help mitigate the risk. Special attention is given to the effects of an ice-cap and the role of pre-existing glacial morphology on the distribution of products from such an eruption.

  16. Differences in community composition of bacteria in four deep ice sheets in western China

    NASA Astrophysics Data System (ADS)

    An, L.; Chen, Y.; Xiang, S.-R.; Shang, T.-C.; Tian, L.-De

    2010-02-01

    Microbial community patterns vary in glaciers world wide, presenting unique responses to global climatic and environmental changes. Four bacterial clone libraries were established by 16S rRNA gene amplification from four ice layers along the 42-m-long ice core MuztB drilled from the Muztag Ata Glacier. A total of 152 bacterial sequences obtained from the ice core MuztB were phylogenetically compared with the 71 previously reported sequences from three ice cores extracted from ice caps Malan, Dunde, and Puruoganri. The six functional clusters Flavisolibacter, Flexibacter (Bacteroidetes), Acinetobacter, Enterobacter (Gammaproteobacteria), Planococcus/Anoxybacillus (Firmicutes), and Propionibacter/Luteococcus (Actinobacteria) frequently occurred along the Muztag Ata Glacier profile. Sequence analysis showed that most of the sequences from the ice core clustered with those from cold environments, and the sequences from the same glacier formed a distinct cluster. Moreover, bacterial communities from the same location or similarly aged ice formed a cluster, and were clearly separate from those from other geographically isolated glaciers. In a summary, the findings provide preliminary evidence of zone distribution of microbial community, support our hypothesis of the spatial and temporal biogeography of microorganisms in glacial ice.

  17. Temperature dependence of the water-ice spectrum between 1 and 4 microns - Application to Europa, Ganymede and Saturn's rings

    NASA Technical Reports Server (NTRS)

    Fink, U.; Larson, H. P.

    1975-01-01

    Reflection spectra of water ice from 1 to 4 microns are presented as a function of temperature. It is found that a feature at 6056 reciprocal cm changes its intensity sufficiently so that it can be used as a spectroscopic measurement of the ice temperature. A temperature calibration curve of this feature down to 55 K is developed and used to determine ice temperatures for the Galilean satellites Europa (95 + or -10 K), Ganymede (103 + or -10 K), and the rings of Saturn (80 + or -5 K). The ice temperatures for the Galilean satellites are lower than their measured brightness temperatures, which can be explained by a higher albedo of the ice-covered regions relative to the rest of the satellite and possibly a concentration of the ice near the polar caps.

  18. Ice dynamics of the Allan Hills meteorite concentration sites revealed by satellite aperture radar interferometry

    NASA Astrophysics Data System (ADS)

    Coren, F.; Delisle, G.; Sterzai, P.

    2003-09-01

    The ice flow conditions of a 100 x 100 km area of Victoria Land, Antarctica were analyzed with the synthetic aperture radar (SAR) technique. The area includes a number of meteorite concentration sites, in particular the Allan Hills ice fields. Regional ice flow velocities around the Mid- western and Near-western ice fields and the Allan Hills main ice field are shown to be 2.5 m yr-1. These sites are located on a horseshoe-shaped area that bounds an area characterized by higher ice flow velocities of up to 5 m yr-1. Meteorite find locations on the Elephant Moraine are located in this "high ice flow" area. The SAR derived digital elevation model (DEM) shows atypical low surface slopes for Antarctic conditions, which are the cause for the slow ice movements. Numerous ice rises in the area are interpreted to cap sub-ice obstacles, which were formed by tectonic processes in the past. The ice rises are considered to represent temporary features, which develop only during warm stages when the regional ice stand is lowered. Ice depressions, which develop in warm stages on the lee side of ice rises, may act as the sites of temporary build-up of meteorite concentrations, which turn inoperative during cold stages when the regional ice level rises and the ice rises disappear. Based on a simplified ice flow model, we argue that the regional ice flow in cold stages is reduced by a factor of at least 3.

  19. The Martian North Polar Cap in Summer - One Year Later

    NASA Technical Reports Server (NTRS)

    2001-01-01

    In the middle of January 2001, Mars Global Surveyor (MGS) completed one Mars year in its 380 km-high (236 mi) mapping orbit. The mapping orbit was originally achieved in late February 1999. In March of that year, MGS conducted a series of operations in preparation for full-up mapping, first calibrating its scientific instruments and then operating in a mode in which the high gain antenna was held fixed against the body of the spacecraft. During this Fixed High Gain Antenna period, 'contingency science' observations were made in case the high gain antenna failed to properly deploy. The wide angle view of the martian north polar cap shown on the left was acquired on March 13, 1999, during early northern summer. The image on the right was acquired almost exactly one Mars year later, on January 26, 2001. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. The north polar cap is roughly 1100 kilometers (680 miles) across. Close inspection will show that there are differences in the frost cover between the two images (for example, in the upper center of each image, and on the left edge center). Although these changes appear small, they are in fact quite large--the change in frost covering is equivalent to the amount of frost that would be evaporated (in the case of areas that are darker) or deposited (in areas where frost is still on the ground) in almost 5 months. What gives rise to such large changes in the heat budget for the polar caps from one year to the next is not known. Changes in the coloration and brightness of the polar cap suggest dust, deposited perhaps by dust storms during critical periods of the year, may play an important role.

  20. Evolution of the early Antarctic ice ages

    NASA Astrophysics Data System (ADS)

    Liebrand, Diederik; de Bakker, Anouk T. M.; Beddow, Helen M.; Wilson, Paul A.; Bohaty, Steven M.; Ruessink, Gerben; Pälike, Heiko; Batenburg, Sietske J.; Hilgen, Frederik J.; Hodell, David A.; Huck, Claire E.; Kroon, Dick; Raffi, Isabella; Saes, Mischa J. M.; van Dijk, Arnold E.; Lourens, Lucas J.

    2017-04-01

    Understanding the stability of the early Antarctic ice cap in the geological past is of societal interest because present-day atmospheric CO2 concentrations have reached values comparable to those estimated for the Oligocene and the Early Miocene epochs. Here we analyze a new high-resolution deep-sea oxygen isotope (δ18O) record from the South Atlantic Ocean spanning an interval between 30.1 My and 17.1 My ago. The record displays major oscillations in deep-sea temperature and Antarctic ice volume in response to the ˜110-ky eccentricity modulation of precession. Conservative minimum ice volume estimates show that waxing and waning of at least ˜85 to 110% of the volume of the present East Antarctic Ice Sheet is required to explain many of the ˜110-ky cycles. Antarctic ice sheets were typically largest during repeated glacial cycles of the mid-Oligocene (˜28.0 My to ˜26.3 My ago) and across the Oligocene-Miocene Transition (˜23.0 My ago). However, the high-amplitude glacial-interglacial cycles of the mid-Oligocene are highly symmetrical, indicating a more direct response to eccentricity modulation of precession than their Early Miocene counterparts, which are distinctly asymmetrical—indicative of prolonged ice buildup and delayed, but rapid, glacial terminations. We hypothesize that the long-term transition to a warmer climate state with sawtooth-shaped glacial cycles in the Early Miocene was brought about by subsidence and glacial erosion in West Antarctica during the Late Oligocene and/or a change in the variability of atmospheric CO2 levels on astronomical time scales that is not yet captured in existing proxy reconstructions.

  1. Evolution of the early Antarctic ice ages

    PubMed Central

    de Bakker, Anouk T. M.; Beddow, Helen M.; Wilson, Paul A.; Bohaty, Steven M.; Pälike, Heiko; Batenburg, Sietske J.; Hilgen, Frederik J.; Hodell, David A.; Huck, Claire E.; Kroon, Dick; Raffi, Isabella; Saes, Mischa J. M.; van Dijk, Arnold E.; Lourens, Lucas J.

    2017-01-01

    Understanding the stability of the early Antarctic ice cap in the geological past is of societal interest because present-day atmospheric CO2 concentrations have reached values comparable to those estimated for the Oligocene and the Early Miocene epochs. Here we analyze a new high-resolution deep-sea oxygen isotope (δ18O) record from the South Atlantic Ocean spanning an interval between 30.1 My and 17.1 My ago. The record displays major oscillations in deep-sea temperature and Antarctic ice volume in response to the ∼110-ky eccentricity modulation of precession. Conservative minimum ice volume estimates show that waxing and waning of at least ∼85 to 110% of the volume of the present East Antarctic Ice Sheet is required to explain many of the ∼110-ky cycles. Antarctic ice sheets were typically largest during repeated glacial cycles of the mid-Oligocene (∼28.0 My to ∼26.3 My ago) and across the Oligocene−Miocene Transition (∼23.0 My ago). However, the high-amplitude glacial−interglacial cycles of the mid-Oligocene are highly symmetrical, indicating a more direct response to eccentricity modulation of precession than their Early Miocene counterparts, which are distinctly asymmetrical—indicative of prolonged ice buildup and delayed, but rapid, glacial terminations. We hypothesize that the long-term transition to a warmer climate state with sawtooth-shaped glacial cycles in the Early Miocene was brought about by subsidence and glacial erosion in West Antarctica during the Late Oligocene and/or a change in the variability of atmospheric CO2 levels on astronomical time scales that is not yet captured in existing proxy reconstructions. PMID:28348211

  2. Seismic Stratigraphic Evidence From SE Ross Sea for Late Oligocene Glaciers and ice Streams Issuing From Marie Byrd Land

    NASA Astrophysics Data System (ADS)

    Sorlien, C. C.; Luyendyk, B. P.; Wilson, D. S.; Decesari, R. C.; Bartek, L. R.; Diebold, J. B.

    2006-12-01

    The extent of the West Antarctic ice sheet during mid-Cenozoic time is controversial and important to climate models. High-resolution multichannel seismic reflection data were acquired using the RVIB Palmer along the edge of the Ross Ice Shelf across the Eastern Basin of Ross Sea, in an area where calving of the ice shelf has exposed seafloor that has not been accessible to marine geophysics in several decades. A sub-basin in the far southeast corner of Ross Sea contains a succession of sediment-filled troughs, each capped by an unconformity. These troughs range between 2 and 20 km across, are 100 to 150 m-deep, with the narrower ones bounded by flat-topped ridges interpreted as moraines. We interpret the troughs interval to slightly predate 25 Ma. Reflections just 100 m below the troughs interval can be directly correlated to near DSDP270 where they underlie strata dated at ~25 Ma. A deeper stack of prograding sequences associated with a flat- topped ridge are interpreted as pre-25 Ma, possibly early Oligocene, deltas formed adjacent to the grounding line of a glacier, and the flat-topped ridge to be a moraine. The shallowest of the stack of unconformities capping the broad troughs can be projected across a basement ridge on trend with Roosevelt Island to a regional angular unconformity ("Red"), present across 70 km to deep sedimentary Eastern Basin. This unconformity represents about 1 km of missing stratigraphic section, is smooth and level, and splits into several major sequence boundaries within deep Eastern Basin. The second shallowest of these boundaries is dated about 14 Ma at DSDP-270. We interpret this unconformity to be cut by regional thick, grounded ice at depths several hundred meters below sea level. Pre-25 Ma strata show evidence of narrow erosional troughs and reflective mounds or ridges on the west flank of the basement ridge, but such features are not present in southern deep Eastern Basin near the ice shelf edge. This is evidence that the

  3. Winter ocean-ice interactions under thin sea ice observed by IAOOS platforms during NICE2015:salty surface mixed layer and active basal melt

    NASA Astrophysics Data System (ADS)

    Provost, C.; Koenig, Z.; Villacieros-Robineau, N.; Sennechael, N.; Meyer, A.; Lellouche, J. M.; Garric, G.

    2016-12-01

    IAOOS platforms, measuring physical parameters at the atmosphere-snow-ice-ocean interface deployed as part of the N-ICE2015 campaign, provide new insights on winter conditions North of Svalbard. The three regions crossed during the drifts, the Nansen Basin, the Sofia Deep and the Svalbard northern continental slope featured distinct hydrographic properties and ice-ocean exchanges. In the Nansen Basin the quiescent warm layer was capped by a stepped halocline (60 and 110 m) and a deep thermocline (110 m). Ice was forming and the winter mixed layer salinity was larger by 0.1 g/kg than previously observed. Over the Svalbard continental slope, the Atlantic Water (AW) was very shallow (20 m from the surface) and extended offshore from the 500 m isobath by a distance of about 70 km, sank along the slope (40 m from the surface) and probably shedded eddies into the Sofia Deep. In the Sofia Deep, relatively warm waters of Atlantic origin extended from 90 m downward. Resulting from different pathways, these waters had a wide range of hydrographic characteristics. Sea-ice melt was widespread over the Svalbard continental slope and ocean-to-ice heat fluxes reached values of 400 Wm-2 (mean of 150 Wm-2 over the continentalslope). Sea-ice melt events were associated with near 12-hour fluctuations in the mixed-layer temperature and salinity corresponding to the periodicity of tides and near-inertial waves potentially generated by winter storms, large barotropic tides over steep topography and/or geostrophic adjustments.

  4. The Ice Cap Zone: A Unique Habitable Zone for Ocean Worlds

    NASA Astrophysics Data System (ADS)

    Ramirez, Ramses M.; Levi, Amit

    2018-03-01

    Traditional definitions of the habitable zone assume that habitable planets contain a carbonate-silicate cycle that regulates CO2 between the atmosphere, surface, and the interior. Such theories have been used to cast doubt on the habitability of ocean worlds. However, Levi et al (2017) have recently proposed a mechanism by which CO2 is mobilized between the atmosphere and the interior of an ocean world. At high enough CO2 pressures, sea ice can become enriched in CO2 clathrates and sink after a threshold density is achieved. The presence of subpolar sea ice is of great importance for habitability in ocean worlds. It may moderate the climate and is fundamental in current theories of life formation in diluted environments. Here, we model the Levi et al. mechanism and use latitudinally-dependent non-grey energy balance and single-column radiative-convective models and find that this mechanism may be sustained on ocean worlds that rotate at least 3 times faster than the Earth. We calculate the circumstellar region in which this cycle may operate for G-M-stars (Teff = 2,600-5,800 K), extending from ˜1.23 - 1.65, 0.69 - 0.873, 0.38-0.528 AU, 0.219-0.308 AU, 0.146-0.206 AU, and 0.0428-0.0617 AU for G2, K3, M0, M3, M5, and M8 stars, respectively. However, unless planets are very young and not tidally-locked, our mechanism would be unlikely to apply to stars cooler than a ˜M3. We predict C/O ratios for our atmospheres (˜0.5) that can be verified by the JWST mission.

  5. The ice cap zone: a unique habitable zone for ocean worlds

    NASA Astrophysics Data System (ADS)

    Ramirez, Ramses M.; Levi, Amit

    2018-07-01

    Traditional definitions of the habitable zone assume that habitable planets contain a carbonate-silicate cycle that regulates CO2 between the atmosphere, surface, and the interior. Such theories have been used to cast doubt on the habitability of ocean worlds. However, Levi et al. have recently proposed a mechanism by which CO2 is mobilized between the atmosphere and the interior of an ocean world. At high enough CO2 pressures, sea ice can become enriched in CO2 clathrates and sink after a threshold density is achieved. The presence of subpolar sea ice is of great importance for habitability in ocean worlds. It may moderate the climate and is fundamental in current theories of life formation in diluted environments. Here, we model the Levi et al. mechanism and use latitudinally dependent non-grey energy balance and single-column radiative-convective climate models and find that this mechanism may be sustained on ocean worlds that rotate at least 3 times faster than the Earth. We calculate the circumstellar region in which this cycle may operate for G-M stars (Teff = 2600-5800 K), extending from ˜1.23-1.65, 0.69-0.954, 0.38-0.528, 0.219-0.308 , 0.146-0.206, and 0.0428-0.0617 au for G2, K2, M0, M3, M5, and M8 stars, respectively. However, unless planets are very young and not tidally locked, our mechanism would be unlikely to apply to stars cooler than a ˜M3. We predict C/O ratios for our atmospheres (˜0.5) that can be verified by the James Webb Space Telescope mission.

  6. A daily, 1 km resolution data set of downscaled Greenland ice sheet surface mass balance (1958-2015)

    NASA Astrophysics Data System (ADS)

    Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; Lhermitte, Stef; Howat, Ian; Fettweis, Xavier; van den Broeke, Michiel R.

    2016-10-01

    This study presents a data set of daily, 1 km resolution Greenland ice sheet (GrIS) surface mass balance (SMB) covering the period 1958-2015. Applying corrections for elevation, bare ice albedo and accumulation bias, the high-resolution product is statistically downscaled from the native daily output of the polar regional climate model RACMO2.3 at 11 km. The data set includes all individual SMB components projected to a down-sampled version of the Greenland Ice Mapping Project (GIMP) digital elevation model and ice mask. The 1 km mask better resolves narrow ablation zones, valley glaciers, fjords and disconnected ice caps. Relative to the 11 km product, the more detailed representation of isolated glaciated areas leads to increased precipitation over the southeastern GrIS. In addition, the downscaled product shows a significant increase in runoff owing to better resolved low-lying marginal glaciated regions. The combined corrections for elevation and bare ice albedo markedly improve model agreement with a newly compiled data set of ablation measurements.

  7. Insight into glacier climate interaction: reconstruction of the mass balance field using ice extent data

    NASA Astrophysics Data System (ADS)

    Visnjevic, Vjeran; Herman, Frédéric; Licul, Aleksandar

    2016-04-01

    With the end of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth's history. We recently developed a model that describes large-scale erosion and its response to climate and dynamical changes with the application to the Alps for the LGM period. Here we will present an inverse approach we have recently developed to infer the LGM mass balance from known ice extent data, focusing on a glacier or ice cap. The ice flow model is developed using the shallow ice approximation and the developed codes are accelerated using GPUs capabilities. The mass balance field is the constrained variable defined by the balance rate β and the equilibrium line altitude (ELA), where c is the cutoff value: b = max(βṡ(S(z) - ELA), c) We show that such a mass balance can be constrained from the observed past ice extent and ice thickness. We are also investigating several different geostatistical methods to constrain spatially variable mass balance, and derive uncertainties on each of the mass balance parameters.

  8. Dione and Rhea seasonal exospheres revealed by Cassini CAPS and INMS

    NASA Astrophysics Data System (ADS)

    Teolis, B. D.; Waite, J. H.

    2016-07-01

    A Dione O2 and CO2 exosphere of similar composition and density to Rhea's is confirmed by Cassini spacecraft Ion Neutral Mass Spectrometer (INMS) flyby data. INMS results from three Dione and two Rhea flybys show exospheric spatial and temporal variability indicative of seasonal exospheres, modulated by winter polar gas adsorption and desorption at the equinoxes. Cassini Plasma Spectrometer (CAPS) pickup ion fluxes also show exospheric structure and evolution at Rhea consistent with INMS, after taking into consideration the anticipated charge exchange, electron impact, and photo-ionization rates. Data-model comparisons show the exospheric evolution to be consistent with polar frost diffusion into the surface regolith, which limits surface exposure and loss of the winter frost cap by sputtering. Implied O2 source rates of ∼45(7) × 1021 s-1 at Dione(Rhea) are ∼50(300) times less than expected from known O2 radiolysis yields from ion-irradiated pure water ice measured in the laboratory, ruling out secondary sputtering as a major exospheric contributor, and implying a nanometer scale surface refractory lag layer consisting of concentrated carbonaceous impurities. We estimate ∼30:1(2:1) relative O2:CO2 source rates at Dione(Rhea), consistent with a stoichiometric bulk composition below the lag layer of 0.01(0.13) C atoms per H2O molecule, deriving from endogenic constituents, implanted micrometeoritic organics, and (in particular at Dione) exogenous H2O delivery by E-ring grains. Impact deposition, gardening and vaporization may thereby control the global O2 source rates by fresh H2O ice exposure to surface radiolysis and trapped oxidant ejection.

  9. Evidence for Possible Exposed Water Ice Deposits in Martian Low Latitude Chasms and Chaos

    NASA Technical Reports Server (NTRS)

    Leovy, C.; Wood, S. E.; Catling, D.; Montgomery, D. R.; Moore, J.; Barnhart, C.; Ginder, E.; Louie, M.

    2004-01-01

    A light-toned interior layer deposit (ILD) on the floor of the deep martian depression Juventae Chasma is found to have a relatively high thermal inertia approx. 500 J m(exp -2) s(exp -1/2) K(exp -1). This could imply rock, but is also similar to the average value of thermal inertia found for north polar layered deposits. Furthermore, ILD-B is found to exhibit a bluff and terrace structure . A terrace structure arises naturally in model simulations of the sublimation of large ice deposits. Such a staircase terrain, of course, is a further characteristic of north polar layered terrain. Morphological similarity, thermal inertia in the range of thermal inertias of the north polar cap layered terrain, and relatively high albedo lead us to propose that the ILD-B may consist of residual water ice partially covered by, and perhaps mixed with, varying amounts of dust or sand. Other ILDs (A-C) are also found in Juventae Chasma. While these ILDs lack the close morphological resemblance to the north polar cap, they share many other common features and appear to be part of the same formation. Similar ILDs are found in chaotic terrain elsewhere in the martian tropics. This leads us to propose that water ice may exist in the martian tropics today and may be implicit in the formation of chaotic terrain.

  10. The antioxidative and hepatoprotective effects comparison of Chinese angelica polysaccharide(CAP)and selenizing CAP (sCAP) in CCl4 induced hepatic injury mice.

    PubMed

    Gao, Zhenzhen; Zhang, Chao; Tian, Weijun; Liu, Kuanhui; Hou, Ranran; Yue, Chanjuan; Wu, Yi; Wang, Deyun; Liu, Jiaguo; Hu, Yuanliang; Yang, Ying

    2017-04-01

    Chinese angelica polysaccharides (CAP) and selenizing CAP (sCAP) were prepared and identified through FTIR and SEM observation. Their antioxidant activities in vitro and hepatoprotective effects in vivo were compared by free radical-scavenging tests or with CCl 4 -induced hepatic injury model mice. The results showed that for DPPH radical, superoxide anion and hydroxyl radical, the scavenging capabilities of sCAP were significantly stronger than those of CAP . In hepatic injury model mice, sCAP could significantly reduce ALT, AST and ALP contents and raised TP content in serum, significantly reduce MDA and ROS contents and raised SOD and T-AOC activities in liver homogenate in comparison with CAP; obviously relieve the pathological changes of liver and significantly inhibit the expressions of p-ERK, p-JNK and p-p38 protein as compared with those in model control group. These results indicate that selenylation modification can enhance the antioxidant and hepatoprotective actions of Chinese angelica polysaccharide. A action mechanism of sCAP is suppressing the protein expression of MAPK signaling pathway. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Infrared Spectra and Thermodynamic Properties of Co2/Methanol Ices

    NASA Astrophysics Data System (ADS)

    Maté, Belén; Gálvez, Óscar; Herrero, Víctor J.; Escribano, Rafael

    2009-01-01

    Ices of mixtures of carbon dioxide and methanol have been studied in a range of temperatures relevant for star-forming regions, comets, polar caps of planets and satellites, and other solar system bodies. We have performed temperature-programmed desorption measurements and recorded IR spectra of various types of samples. The presence of two slightly different structures of CO2 is manifest. A distorted CO2 structure is characterized by bandshifts between 5 cm-1 (ν3) and 10 cm-1 (ν2) with respect to normal CO2. If the samples are heated above 130 K, the distorted CO2 sublimates and only the normal structure remains. The latter can stay trapped until the sublimation of crystalline methanol (150 K). The desorption energy (E d ~ 20 kJ mol-1) of CO2 from methanol ice, and the specific adsorption surface area (6 m2 g-1) of amorphous CH3OH ice, have been determined. CO2 does not penetrate into crystalline ice. Whereas the desorption energy is similar to that of CO2/H2O samples, the specific surface of methanol is much smaller than that of amorphous solid water (ASW). The interaction of CO2 molecules with water and methanol is similar but ices of CH3OH are much less porous than ASW. The inclusion of CO2 into previously formed ices containing these two species would take place preferentially into ASW. However, in processes of simultaneous deposition, methanol ice can admit a larger amount of CO2 than water ice. CO2/CH3OH ices formed by simultaneous deposition admit two orders of magnitude more CO2 than sequentially deposited ices. These findings can have direct relevance to the interpretation of observations from protostellar environments (e.g., RAFGL7009S) and comet nuclei.

  12. Palaeoclimate signal recorded by stable isotopes in cave ice: a modeling approach

    NASA Astrophysics Data System (ADS)

    Perşoiu, A.; Bojar, A.-V.

    2012-04-01

    Ice accumulations in caves preserve a large variety of geochemical information as candidate proxies for both past climate and environmental changes, one of the most significant being the stable isotopic composition of the ice. A series of recent studies have targeted oxygen and hydrogen stable isotopes in cave ice as proxies for past air temperatures, but the results are far from being as straightforward as they are in high latitude and altitude glaciers and ice caps. The main problems emerging from these studies are related to the mechanisms of cave ice formation (i.e., freezing of water) and post-formation processes (melting and refreezing), which both alter the original isotopic signal in water. Different methods have been put forward to solve these issues and a fair understanding of the present-day link between stable isotopes in precipitation and cave ice exists now. However, the main issues still lays unsolved: 1) is it possible to extend this link to older ice and thus reconstruct past changes in air temperature?; 2) to what extent are ice dynamics processes modifying the original climatic signal and 3) what is the best method to be used in extracting a climatic signal from stable isotopes in cave ice? To respond to these questions, we have conducted a modeling experiment, in which a theoretical cave ice stable isotope record was constructed using present-day observations on stable isotope behavior in cave ice and ice dynamics, and different methods (presently used for both polar and cave glaciers), were used to reconstruct the original, known, isotopic values. Our results show that it is possible to remove the effects of ice melting and refreezing on stable isotope composition of cave ice, and thus reconstruct the original isotopic signal, and further the climatic one.

  13. Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

    NASA Astrophysics Data System (ADS)

    Wittmann, Monika; Dorothea Groot Zwaaftink, Christine; Steffensen Schmidt, Louise; Guðmundsson, Sverrir; Pálsson, Finnur; Arnalds, Olafur; Björnsson, Helgi; Thorsteinsson, Throstur; Stohl, Andreas

    2017-03-01

    Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ˜ 1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m-2. At the station located higher on the glacier ( ˜ 1525 m a.s.l.), the model produced nine dust events, with one single event causing ˜ 5 g m-2 of dust deposition and a total deposition of ˜ 10 g m-2 yr-1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of

  14. Ice-Penetrating Robot for Scientific Exploration

    NASA Technical Reports Server (NTRS)

    Zimmerman, Wayne; Carsey, Frank; French, Lloyd

    2007-01-01

    The cryo-hydro integrated robotic penetrator system (CHIRPS) is a partially developed instrumentation system that includes a probe designed to deeply penetrate the European ice sheet in a search for signs of life. The CHIRPS could also be used on Earth for similar exploration of the polar ice caps especially at Lake Vostok in Antarctica. The CHIRPS probe advances downward by a combination of simple melting of ice (typically for upper, non-compacted layers of an ice sheet) or by a combination of melting of ice and pumping of meltwater (typically, for deeper, compacted layers). The heat and electric power for melting, pumping, and operating all of the onboard instrumentation and electronic circuitry are supplied by radioisotope power sources (RPSs) and thermoelectric converters energized by the RPSs. The instrumentation and electronic circuitry includes miniature guidance and control sensors and an advanced autonomous control system that has fault-management capabilities. The CHIRPS probe is about 1 m long and 15 cm in diameter. The RPSs generate a total thermal power of 1.8 kW. Initially, as this power melts the surrounding ice, a meltwater jacket about 1 mm thick forms around the probe. The center of gravity of the probe is well forward (down), so that the probe is vertically stabilized like a pendulum. Heat is circulated to the nose by means of miniature pumps and heat pipes. The probe melts ice to advance in a step-wise manner: Heat is applied to the nose to open up a melt void, then heat is applied to the side to allow the probe to slip down into the melt void. The melt void behind the probe is allowed to re-freeze. Four quadrant heaters on the nose and another four quadrant heaters on the rear (upper) surface of the probe are individually controllable for steering: Turning on two adjacent nose heaters on the nose and two adjacent heaters on the opposite side at the rear causes melt voids to form on opposing sides, such that the probe descends at an angle from

  15. RNA Cap Methyltransferase Activity Assay

    PubMed Central

    Trotman, Jackson B.; Schoenberg, Daniel R.

    2018-01-01

    Methyltransferases that methylate the guanine-N7 position of the mRNA 5′ cap structure are ubiquitous among eukaryotes and commonly encoded by viruses. Here we provide a detailed protocol for the biochemical analysis of RNA cap methyltransferase activity of biological samples. This assay involves incubation of cap-methyltransferase-containing samples with a [32P]G-capped RNA substrate and S-adenosylmethionine (SAM) to produce RNAs with N7-methylated caps. The extent of cap methylation is then determined by P1 nuclease digestion, thin-layer chromatography (TLC), and phosphorimaging. The protocol described here includes additional steps for generating the [32P]G-capped RNA substrate and for preparing nuclear and cytoplasmic extracts from mammalian cells. This assay is also applicable to analyzing the cap methyltransferase activity of other biological samples, including recombinant protein preparations and fractions from analytical separations and immunoprecipitation/pulldown experiments. PMID:29644259

  16. Annually resolved ice core records of tropical climate variability over the past ~1800 years.

    PubMed

    Thompson, L G; Mosley-Thompson, E; Davis, M E; Zagorodnov, V S; Howat, I M; Mikhalenko, V N; Lin, P-N

    2013-05-24

    Ice cores from low latitudes can provide a wealth of unique information about past climate in the tropics, but they are difficult to recover and few exist. Here, we report annually resolved ice core records from the Quelccaya ice cap (5670 meters above sea level) in Peru that extend back ~1800 years and provide a high-resolution record of climate variability there. Oxygen isotopic ratios (δ(18)O) are linked to sea surface temperatures in the tropical eastern Pacific, whereas concentrations of ammonium and nitrate document the dominant role played by the migration of the Intertropical Convergence Zone in the region of the tropical Andes. Quelccaya continues to retreat and thin. Radiocarbon dates on wetland plants exposed along its retreating margins indicate that it has not been smaller for at least six millennia.

  17. Paleoclimatic significance of insoluble microparticle records from Canadian Arctic and Greenland ice cores

    NASA Astrophysics Data System (ADS)

    Zdanowicz, Christian Michel

    1999-10-01

    The past and present variability of climate in the Arctic region is investigated using ice core records of atmospheric dust (microparticles) and volcanic aerosols developed from the Canadian Arctic and Greenland. A high- resolution, 10 4-year long proxy record of atmospheric dust deposition is developed from an ice core (P95) drilled through the Penny Ice Cap, Baffin Island. Snowpit studies indicate that dust deposited on the Penny Ice Cap are representative of background mineral aerosol, and demonstrate that the variability of dust fallout is preserved in the P95 core at multi-annual to longer time scales. The P95 dust record reveals a significant increase in dust deposition on the Penny Ice Cap between ca 7500-5000 yr ago. This increase was driven by early to mid-/late Holocene transformations in the Northern Hemisphere landscape (ice cover retreat, postglacial land emergence) and climate (transition to colder, drier conditions) that led to an expansion of sources and enhanced eolian activity. Comparison between dust records in the P95 and GISP2 (Greenland) ice cores shows an increasing divergence between the two records beginning ca 7500 years ago. The effects of Northern Hemisphere atmospheric circulation and snow cover extent on atmospheric dust deposition in the Arctic are evaluated by comparing the P95 dust record with observational data. Changes in dust deposition are strongly linked to modes of the Northern Hemisphere winter circulation. Most prominently, an inverse relationship between the P95 dust record and the intensity of the winter Siberian High accounts for over 50% of the interannual variance of these two parameters over the period 1899-1995. On inter- to multi- annual time scales, the P95 dust record is significantly anticorrelated with variations in spring, and to a lesser extent fall, snow cover extent in the mid-latitude interior regions of Eurasia and North America. These relationships account for an estimated 10 to 20% of variance in the P95

  18. Black carbon aerosols and the third polar ice cap

    NASA Astrophysics Data System (ADS)

    Menon, S.; Koch, D.; Beig, G.; Sahu, S.; Fasullo, J.; Orlikowski, D.

    2010-05-01

    Recent thinning of glaciers over the Himalayas (sometimes referred to as the third polar region) have raised concern on future water supplies since these glaciers supply water to large river systems that support millions of people inhabiting the surrounding areas. Black carbon (BC) aerosols, released from incomplete combustion, have been increasingly implicated as causing large changes in the hydrology and radiative forcing over Asia and its deposition on snow is thought to increase snow melt. In India BC emissions from biofuel combustion is highly prevalent and compared to other regions, BC aerosol amounts are high. Here, we quantify the impact of BC aerosols on snow cover and precipitation from 1990 to 2010 over the Indian subcontinental region using two different BC emission inventories. New estimates indicate that Indian BC emissions from coal and biofuel are large and transport is expected to expand rapidly in coming years. We show that over the Himalayas, from 1990 to 2000, simulated snow/ice cover decreases by ~0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is ~36%, similar to that simulated for 2000 to 2010. Spatial patterns of modeled changes in snow cover and precipitation are similar to observations (from 1990 to 2000), and are mainly obtained with the newer BC estimates.

  19. Black carbon aerosols and the third polar ice cap

    NASA Astrophysics Data System (ADS)

    Menon, S.; Koch, D.; Beig, G.; Sahu, S.; Fasullo, J.; Orlikowski, D.

    2009-12-01

    Recent thinning of glaciers over the Himalayas (sometimes referred to as the third polar region) have raised concern on future water supplies since these glaciers supply water to large river systems that support millions of people inhabiting the surrounding areas. Black carbon (BC) aerosols, released from incomplete combustion, have been increasingly implicated as causing large changes in the hydrology and radiative forcing over Asia and its deposition on snow is thought to increase snow melt. In India BC from biofuel combustion is highly prevalent and compared to other regions, BC aerosol amounts are high. Here, we quantify the impact of BC aerosols on snow cover and precipitation from 1990 to 2010 over the Indian subcontinental region using two different BC emission inventories. New estimates indicate that Indian BC from coal and biofuel are large and transport is expected to expand rapidly in coming years. We show that over the Himalayas, from 1990 to 2000, simulated snow/ice cover decreases by ~0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is ~30%, similar to that simulated for 2000 to 2010. Spatial patterns of modeled changes in snow cover and precipitation are similar to observations (from 1990 to 2000), and are mainly obtained with the newer BC estimates.

  20. Breaking the Ice: Potential U.S.-Russian Maritime Conflict in the Arctic

    DTIC Science & Technology

    2012-12-01

    meanwhile, has been involved in several altercations involving Russian commercial fishing vessels poaching in the U.S.-claimed waters of the Bering...with an asterisk (*) indicating that this score is higher than it would be if the impact of a particular variable on a country were considered in...political, and military impact of the melting Arctic ice cap, including articles by Arctic experts and scholars, think tank reports, academic theses

  1. Improved regional sea-level estimates from Ice Sheets, Glaciers and land water storage using GRACE time series and other data

    NASA Astrophysics Data System (ADS)

    He, Z.; Velicogna, I.; Hsu, C. W.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.; Fettweis, X.; van den Broeke, M. R.

    2017-12-01

    Changes in ice sheets, glaciers and ice caps (GIC) and land water mass cause regional sea level variations that differ significantly from a uniform re-distribution of mass over the ocean, with a decrease in sea level compared to the global mean sea level contribution (GMSL) near the sources of mass added to the ocean and an increase up to 30% larger than the GMSL in the far field. The corresponding sea level fingerprints (SLF) are difficult to separate from ocean dynamics on short time and spatial scales but as ice melt continues, the SLF signal will become increasingly dominant in the pattern of regional sea level rise. It has been anticipated that it will be another few decades before the land ice SLF could be identified in the pattern of regional sea level rise. Here, we combine 40 years of observations of ice sheet mass balance for Antarctica (1975-present) and Greenland (1978-present), along with surface mass balance reconstructions of glacier and ice caps mass balance (GIC) from 1970s to present to determine the contribution to the SLF from melting land ice (MAR and RACMO). We compare the results with observations from GRACE for the time period 2002 to present for evaluation of our approach. Land hydrology is constrained by GRACE data for the period 2002-present and by the GLDAS-NOAH land hydrology model for the longer time period. Over the long time period, we find that the contribution from land ice dominates. We quantify the contribution to the total SLF from Greenland and Antarctica in various parts of the world over the past 40 years. More important, we compare the cumulative signal from SLF with tide gauge records around the world, corrected for earth dynamics, to determine whether the land ice SLF can be detected in that record. Early results will be reported at the meeting. This work was performed at UC Irvine and at Caltech's Jet Propulsion Laboratory under a contract with NASA's Cryospheric Science Program.

  2. The pharmaceutical vial capping process: Container closure systems, capping equipment, regulatory framework, and seal quality tests.

    PubMed

    Mathaes, Roman; Mahler, Hanns-Christian; Buettiker, Jean-Pierre; Roehl, Holger; Lam, Philippe; Brown, Helen; Luemkemann, Joerg; Adler, Michael; Huwyler, Joerg; Streubel, Alexander; Mohl, Silke

    2016-02-01

    Parenteral drug products are protected by appropriate primary packaging to protect against environmental factors, including potential microbial contamination during shelf life duration. The most commonly used CCS configuration for parenteral drug products is the glass vial, sealed with a rubber stopper and an aluminum crimp cap. In combination with an adequately designed and controlled aseptic fill/finish processes, a well-designed and characterized capping process is indispensable to ensure product quality and integrity and to minimize rejections during the manufacturing process. In this review, the health authority requirements and expectations related to container closure system quality and container closure integrity are summarized. The pharmaceutical vial, the rubber stopper, and the crimp cap are described. Different capping techniques are critically compared: The most common capping equipment with a rotating capping plate produces the lowest amount of particle. The strength and challenges of methods to control the capping process are discussed. The residual seal force method can characterize the capping process independent of the used capping equipment or CCS. We analyze the root causes of several cosmetic defects associated with the vial capping process. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. ENSO variability of Quelccaya Ice Cap δ18O driven by monsoon control of vapor isotope ratios

    NASA Astrophysics Data System (ADS)

    Hurley, J. V.; Vuille, M. F.; Hardy, D. R.

    2016-12-01

    The δ18O from the Quelccaya Ice Cap (QIC), Peru corresponds with and has been used to reconstruct Nino region SSTs but the physical mechanisms that tie ENSO-variable equatorial Pacific SSTs to snow δ18O at 5680 m in the Andes have not been fully described. We use a proxy system forward model to simulate and explore ENSO variable snow δ18O at the QIC, which is observed and accurately simulated with our model to be respectively higher and lower than average during El Nino and La Nina. We then explore the relative roles of ENSO-forcing on components of the forward model: the seasonality of snowfall at the QIC, vapor initial δ18O values, and temperature. The local hydrologic cycle is characterized by earlier onset and reduced duration of peak snowfall during El Nino, and more snow accumulation during La Nina. When we isolate the influence of the local hydrologic cycle in the forward model, El Nino and La Nina snowfall seasonalities yield respectively higher and lower snow δ18O values, compared with the control simulation. The South American summer monsoon (SASM) is characterized by enhanced convection over the Amazon during La Nina and as a consequence, lower vapor δ18O values over the western Amazon Basin. When we isolate the influence of the vapor initial delta-value in the forward model, higher initial delta-values during El Nino yield higher snow δ18O at the QIC. The seasonality of temeratures over the western Amazon Basin and near Quelccaya is amplified during El Nino when there are higher and lower temperatures respectively during austral summer and winter. When we isolate the temperature influence in the forward model, the warmer summer El Nino conditions require a more humid initial vapor and result in lower snow δ18O values. Most (more than two-thirds) of the ENSO variability in QIC δ18O can be accounted for by SASM activity and its influence on the vapor initial delta-value.

  4. The land-ice contribution to 21st-century dynamic sea level rise

    NASA Astrophysics Data System (ADS)

    Howard, T.; Ridley, J.; Pardaens, A. K.; Hurkmans, R. T. W. L.; Payne, A. J.; Giesen, R. H.; Lowe, J. A.; Bamber, J. L.; Edwards, T. L.; Oerlemans, J.

    2014-06-01

    Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere-ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

  5. Genetics Home Reference: cap myopathy

    MedlinePlus

    ... Email Facebook Twitter Home Health Conditions Cap myopathy Cap myopathy Printable PDF Open All Close All Enable Javascript to view the expand/collapse boxes. Description Cap myopathy is a disorder that primarily affects skeletal ...

  6. Reconstruction of past equilibrium line altitude using ice extent data

    NASA Astrophysics Data System (ADS)

    Visnjevic, Vjeran; Herman, Frederic; Podladchikov, Yuri

    2017-04-01

    With the end of the Last Glacial Maximum (LGM), about 20 000 years ago, ended the most recent long-lasting cold phase in Earth's history. This last glacial advance left a strong observable imprint on the landscape, such as abandoned moraines, trimlines and other glacial geomorphic features. These features provide a valuable record of past continental climate. In particular, terminal moraines reflect the extent of glaciers and ice-caps, which itself reflects past temperature and precipitation conditions. Here we present an inverse approach, based on a Tikhonov regularization, we have recently developed to reconstruct the LGM mass balance from observed ice extent data. The ice flow model is developed using the shallow ice approximation and solved explicitly using Graphical Processing Units (GPU). The mass balance field, b, is the constrained variable defined by the ice surface S, balance rate β and the spatially variable equilibrium line altitude field (ELA): b = min (β ṡ(S(x,y)- ELA (x,y)),c). (1) where c is a maximum accumulation rate. We show that such a mass balance, and thus the spatially variable ELA field, can be inferred from the observed past ice extent and ice thickness at high resolution and very efficiently. The GPU implementation allows us solve one 1024x1024 grid points forward model run under 0.5s, which significantly reduces the time needed for our inverse method to converge. We start with synthetic test to demonstrate the method. We then apply the method to LGM ice extents of South Island of New Zealand, the Patagonian Andes, where we can see a clear influence of Westerlies on the ELA, and the European Alps. These examples show that the method is capable of constraining spatial variations in mass balance at the scale of a mountain range, and provide us with information on past continental climate.

  7. Sea ice breakup and marine melt of a retreating tidewater outlet glacier in northeast Greenland (81°N).

    PubMed

    Bendtsen, Jørgen; Mortensen, John; Lennert, Kunuk; K Ehn, Jens; Boone, Wieter; Galindo, Virginie; Hu, Yu-Bin; Dmitrenko, Igor A; Kirillov, Sergei A; Kjeldsen, Kristian K; Kristoffersen, Yngve; G Barber, David; Rysgaard, Søren

    2017-07-10

    Rising temperatures in the Arctic cause accelerated mass loss from the Greenland Ice Sheet and reduced sea ice cover. Tidewater outlet glaciers represent direct connections between glaciers and the ocean where melt rates at the ice-ocean interface are influenced by ocean temperature and circulation. However, few measurements exist near outlet glaciers from the northern coast towards the Arctic Ocean that has remained nearly permanently ice covered. Here we present hydrographic measurements along the terminus of a major retreating tidewater outlet glacier from Flade Isblink Ice Cap. We show that the region is characterized by a relatively large change of the seasonal freshwater content, corresponding to ~2 m of freshwater, and that solar heating during the short open water period results in surface layer temperatures above 1 °C. Observations of temperature and salinity supported that the outlet glacier is a floating ice shelf with near-glacial subsurface temperatures at the freezing point. Melting from the surface layer significantly influenced the ice foot morphology of the glacier terminus. Hence, melting of the tidewater outlet glacier was found to be critically dependent on the retreat of sea ice adjacent to the terminus and the duration of open water.

  8. Remote-Raman and Micro-Raman Studies of Solid CO2, CH4, Gas Hydrates and Ice

    NASA Technical Reports Server (NTRS)

    Sharma, S. K.; Misra, A. K.; Lucey, P. G.; Exarhos, G. J.; Windisch, C. F., Jr.

    2004-01-01

    It is well known that on Mars CO2 is the principal constituent of the thin atmosphere and on a seasonal basis CO2 snow and frost coats the polar caps. Also over 25% of the Martian atmosphere freezes out and sublimes again each year. The Mars Odyssey Emission Imaging system (THEMIS) has discovered water ice exposed near the edge of Mars southern perennials cap. In recent years, it has been suggested that in Martian subsurface CO2 may exist as gas hydrate (8CO2 + 44 H2O) with melting temperature of 10C. Since the crust of Mars has been stable for enough time there is also a possibility that methane formed by magmatic processes and/or as a byproduct of anaerobic deep biosphere activity to have raised toward the planet s surface. This methane would have been captured and stored as methane hydrate, which concentrates methane and water. Determination of abundance and distribution of these ices on the surface and in the near surface are of fundamental importance for understanding Martian atmosphere, and for future exploration of Mars. In this work, we have evaluated feasibility of using remote Raman and micro-Raman spectroscopy as potential nondestructive and non-contact techniques for detecting solid CO2, CH4 gas, and gas hydrates as well as water-ice on planetary surfaces.

  9. The rebirth of the cervical cap.

    PubMed

    Cappiello, J D; Grainger-Harrison, M

    1981-01-01

    In an effort to dispel myths surrounding the cervical cap, the historical and political factors affecting the cap's use in the U.S. are described. Clinical aspects of cap fitting are also included. The cervical cap has found only limited acceptance in the U.S. Skepticisms on the part of physicians may be the result of 2 factors: confusion of the cervical cap with intracervical devices used for artificial insemination and confusion with stem pessaries; and the lack of clinical research and statistical evaluation of efficacy rates. The latter factor prompted Tietze et al. to conduct the only U.S. statistical study of the cap in 1953. Of the 143 women studied, the pregnancy rate was 7.6/100 years of use. Of the 28 unplanned pregnancies, 6 were related to faulty technique or omission of a spermicide and 10 were instances of admittedly irregular use. When these failures are omitted, the theoretical effectiveness rate is about 98%. Some practitioners are concerned about an increased incidence of cervical erosion with cap use. Possibly currently conducted studies will show that cap and spermicide users have a lower incidence of cervical erosion than women using no contraceptive method. Study findings suggest that the cervical cap may afford protection without any spermicidal supplement, but the use of spermicides continues to be recommended to clients. Advantages of the cervical cap include the following: it can be left in place longer than a diaphragm without additional applications of spermicide in the vagina; and the insertion of the cap is unrelated to the time of intercourse. Despite research on toleration of the cap for 3 weeks at a time, it is recommended that the cap be worn for only a few days at a time. At this time there are no manufacturers of cervical caps for contraceptive use in the U.S. The cap is now being imported from England and it costs $6.00. A factor that has made the cap unpopular with many physicians is the lengthy time required for fitting. An

  10. Breaking the Ice Between Reporters and Scientists During IPY

    NASA Astrophysics Data System (ADS)

    Bentley, M.

    2007-12-01

    Communicating scientific information to the general public is a challenge. If the story's not about health advice, a major breakthrough or a natural disaster, scientists may be left wondering how to capture the public's attention and convey the importance of their research. This is a particular challenge in the International Polar Year in which the relevant research has global impacts, but is more nuanced than the headline-grabbing threat of melting ice caps. For example, as ANDRILL punches through ice, it's rock the scientists are after. What can a rock core tell us about how ice comes and goes, and what kind of drill can penetrate 20 million years of strata anyway? In this talk, I will describe how scientists can help communicate to journalists - and thereby the public - the importance of polar research, and give examples of how to help make their work compelling and accessible to those outside of a particular circle of expertise. I will use my experience reporting on science and climate change for the BBC to discuss what frustrations journalists have when talking to scientists and what scientists find difficult in talking to reporters.

  11. High-pressure jet cutters improve capping operations

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

    Abel, L.W.; Campbell, P.J.; Bowden, J.R. Sr.

    1995-05-08

    Advances in abrasive cutting technology have improved the methods for removing damaged equipment and preparing wellheads for capping. This technology, much of which was refined during well control operations in Kuwait in 1991, can improve the safety and efficiency of capping jobs by cutting wellheads or casing quickly and cleanly. The majority of well control jobs involve one of three types of capping operations: capping to a flange, capping by installing a wellhead, or capping to a casing stub. Capping operations are often the first major step in regaining control of the well during blowout intervention. Proper planning of amore » capping operation must take into account the mass flow rate, combustible nature of the flow, well bore geometry, and operations in the post-capping phase of the project. The paper discusses capping vehicles, tree removal, jet cutters, capping to a flange, capping to a stub, swallowing the stub, spin-on technique, capping on fire, stinging, offshore blowouts, firefighting, pollution control, intervention equipment, and rig removal.« less

  12. Capped RNA primer binding to influenza polymerase and implications for the mechanism of cap-binding inhibitors

    PubMed Central

    Pflug, Alexander; Gaudon, Stephanie; Resa-Infante, Patricia; Lethier, Mathilde; Reich, Stefan; Schulze, Wiebke M

    2018-01-01

    Abstract Influenza polymerase uses short capped primers snatched from nascent Pol II transcripts to initiate transcription of viral mRNAs. Here we describe crystal structures of influenza A and B polymerase bound to a capped primer in a configuration consistent with transcription initiation (’priming state’) and show by functional assays that conserved residues from both the PB2 midlink and cap-binding domains are important for positioning the capped RNA. In particular, mutation of PB2 Arg264, which interacts with the triphosphate linkage in the cap, significantly and specifically decreases cap-dependent transcription. We also compare the configuration of the midlink and cap-binding domains in the priming state with their very different relative arrangement (called the ‘apo’ state) in structures where the potent cap-binding inhibitor VX-787, or a close analogue, is bound. In the ‘apo’ state the inhibitor makes additional interactions to the midlink domain that increases its affinity beyond that to the cap-binding domain alone. The comparison suggests that the mechanism of resistance of certain mutations that allow virus to escape from VX-787, notably PB2 N510T, can only be rationalized if VX-787 has a dual mode of action, direct inhibition of capped RNA binding as well as stabilization of the transcriptionally inactive ‘apo’ state. PMID:29202182

  13. Ice Shelf-Ocean Interactions Near Ice Rises and Ice Rumples

    NASA Astrophysics Data System (ADS)

    Lange, M. A.; Rückamp, M.; Kleiner, T.

    2013-12-01

    The stability of ice shelves depends on the existence of embayments and is largely influenced by ice rises and ice rumples, which act as 'pinning-points' for ice shelf movement. Of additional critical importance are interactions between ice shelves and the water masses underlying them in ice shelf cavities, particularly melting and refreezing processes. The present study aims to elucidate the role of ice rises and ice rumples in the context of climate change impacts on Antarctic ice shelves. However, due to their smaller spatial extent, ice rumples react more sensitively to climate change than ice rises. Different forcings are at work and need to be considered separately as well as synergistically. In order to address these issues, we have decided to deal with the following three issues explicitly: oceanographic-, cryospheric and general topics. In so doing, we paid particular attention to possible interrelationships and feedbacks in a coupled ice-shelf-ocean system. With regard to oceanographic issues, we have applied the ocean circulation model ROMBAX to ocean water masses adjacent to and underneath a number of idealized ice shelf configurations: wide and narrow as well as laterally restrained and unrestrained ice shelves. Simulations were performed with and without small ice rises located close to the calving front. For larger configurations, the impact of the ice rises on melt rates at the ice shelf base is negligible, while for smaller configurations net melting rates at the ice-shelf base differ by a factor of up to eight depending on whether ice rises are considered or not. We employed the thermo-coupled ice flow model TIM-FD3 to simulate the effects of several ice rises and one ice rumple on the dynamics of ice shelf flow. We considered the complete un-grounding of the ice shelf in order to investigate the effect of pinning points of different characteristics (interior or near calving front, small and medium sized) on the resulting flow and stress fields

  14. Ground Ice on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Martineau, N.; Pollard, W.

    2003-12-01

    On Mars, just like on Earth, water exists in various phases and participates in a broad range of key processes. Even though present surface conditions on Mars, as defined by climate and atmospheric pressure, prevents the occurrence of liquid water on the surface, there is strong evidence suggesting that water was an important land-forming agent in the past (Carr 1996). This naturally raises the question, "where has the water gone?" Surficial water reservoirs that are directly observable on Mars include seasonal water ice deposits and permanent water ice deposits at the polar caps (Kieffer and Zent 1992, Clifford et al. 2000). Due to the existence of permafrost landform systems, such as polygonal ground, rootless cones, and frost mounts, it also has been speculated that much more water may be preserved as ground ice (Lucchitta 1981, Squyres and Carr 1986, Lanagan et al. 2001). Nevertheless, comparison of the likely patterns of ground ice on Mars with terrestrial equivalents has been limited. Fortunately, NASA's 2001 Odyssey data lends support to this hypothesis by identifying significant shallow ice-rich sediments by means of flux characteristics of neutrons, and gamma radiation, and spatial correlations to regions where it has been predicted that subsurface ice is stable (Bell 2002). The ice contents and stratigraphic distribution of the subsurface sediments on Mars, derived by the Odyssey Science Team, is not unlike the upper layers of terrestrial permafrost. Terrestrial polar environments, in particular the more stable permafrost and ground ice features like ice wedges and massive ground ice, may thus provide valuable clues in the search for water and ice on Mars. Of importance is the fact that these features of the earth's surface do not owe their origin to the seasonal freezing and thawing of the active layer. Under the cold, dry polar climates of the Arctic and Antarctic, periglacial and permafrost landforms have evolved, giving rise to distinctive landscapes

  15. 75 FR 49527 - Caps Visual Communications, LLC; Black Dot Group; Formerly Known as Caps Group Acquisition, LLC...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-13

    ... DEPARTMENT OF LABOR Employment and Training Administration [TA-W-74,195] Caps Visual Communications, LLC; Black Dot Group; Formerly Known as Caps Group Acquisition, LLC Chicago, IL; Amended... of Caps Visual Communications, LLC, Black Dot Group, formerly known as Caps Group Acquisition, LLC...

  16. Equilibrium freezing of leaf water and extracellular ice formation in Afroalpine 'giant rosette' plants.

    PubMed

    Beck, E; Schulze, E D; Senser, M; Scheibe, R

    1984-09-01

    The water potentials of frozen leaves of Afroalpine plants were measured psychrometrically in the field. Comparison of these potentials with the osmotic potentials of an expressed cellular sap and the water potentials of ice indicated almost ideal freezing behaviour and suggested equilibrium freezing. On the basis of the osmotic potentials of expressed cellular sap, the fractions of frozen cellular water which correspond to the measured water potentials of the frozen leaves could be determined (e.g. 74% at -3.0° C). The freezing points of leaves were found to be in the range between 0° C and -0.5° C, rendering evidence for freezing of almost pure water and thus confirming the conclusions drawn from the water-potential measurements. The leaves proved to be frost resistant down to temperatures between -5° C and -15° C, as depending on the species. They tolerated short supercooling periods which were necessary in order to start ice nucleation. Extracellular ice caps and ice crystals in the intercellular space were observed when cross sections of frozen leaves were investigated microscopically at subfreezing temperatures.

  17. Influence of aeolian activities on the distribution of microbial abundance in glacier ice

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Li, X.-K.; Si, J.; Wu, G.-J.; Tian, L.-D.; Xiang, S.-R.

    2014-10-01

    Microorganisms are continuously blown onto the glacier snow, and thus the glacial depth profiles provide excellent archives of microbial communities and climatic and environmental changes. However, it is uncertain about how aeolian processes that cause climatic changes control the distribution of microorganisms in the glacier ice. In the present study, microbial density, stable isotopic ratios, 18O / 16O in the precipitation, and mineral particle concentrations along the glacial depth profiles were collected from ice cores from the Muztag Ata glacier and the Dunde ice cap. The ice core data showed that microbial abundance was often, but not always associated with high concentrations of particles. Results also revealed clear seasonal patterning with high microbial abundance occurring in both the cooling autumn and warming spring-summer seasons. Microbial comparisons among the neighbouring glaciers display a heterogeneous spatial pattern, with the highest microbial cell density in the glaciers lying adjacent to the central Asian deserts and lowest microbial density in the southwestern margin of the Tibetan Plateau. In conclusion, microbial data of the glaciers indicates the aeolian deposits of microorganisms in the glacier ice and that the spatial patterns of microorgansisms are related to differences in sources of microbial flux and intensity of aeolian activities in the current regions. The results strongly support our hypothesis of aeolian activities being the main agents controlling microbial load in the glacier ice.

  18. Geomorphological Evidence for Excess Ice in the Southern Hemisphere of Mars

    NASA Astrophysics Data System (ADS)

    Viola, D.; McEwen, A. S.

    2016-12-01

    Abundant water ice is present in the polar caps and in the subsurface at mid to high latitudes on Mars. Subsurface ice can either be confined to regolith pore spaces (pore-filling) or "excess ice" that exceeds the available pore space. The latitudinal bounds of modern excess ice in the northern hemisphere of Mars have been constrained by observations of recent ice-exposing impacts (Dundas et al., 2014, JGR: Planets): >25 have been found as of July 2016 at latitudes above 38°N. However, new impact craters are less commonly found in the southern hemisphere since impacts into relatively dust-free surfaces are difficult to discover; only 5 ice-exposing impacts have been found, all at >55°S. Therefore, we propose the use of other surface morphological features to define the present mid-latitude excess ice boundary in the southern hemisphere. We primarily focus on "expanded craters" that show evidence for thermokarstic diameter enlargement. These craters likely form when an impact exposes a subsurface excess ice layer that subsequently sublimates, leading to an apparent widening of the crater. It is important to note that expanded craters suggest that ice was present both at the time of impact and today, since the widespread loss of an excess ice layer would lead to the collapse of these features. Expanded craters have been mapped across a broad region of the northern plains, and their distribution is consistent with the latitudinal limits of new ice-exposing craters. We also observe expanded craters in and around Hellas Planitia, and will use images from the Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO) to conduct preliminary mapping of their broader distribution across the southern hemisphere. We will also identify additional features that suggest present or past ice: scallops, polygonal patterned ground, and pedestal craters. This data will be used to infer the latitudinal limit and longitudinal variations of modern excess ice in the southern

  19. Quelccaya Ice Core Evidence of Widespread Atmospheric Pollution from Colonial Metallurgy after the Spanish Conquest of South America (1532 AD)

    NASA Astrophysics Data System (ADS)

    Gabrielli, P.; Uglietti, C.; Cooke, C. A.; Thompson, L. G.

    2014-12-01

    A few ice core records recovered from remote arctic regions suggest a widespread impact of toxic trace elements (Pb, Cu, Sb, As and Bi) to the North Hemisphere atmosphere prior to the onset of the Industrial Revolution (1780s-1830s). In the Southern Hemisphere, evidence for preindustrial trace element emissions are, to date, limited to sediment cores recovered from lakes located within the immediate airshed of major metallurgical centers of South America. Thus it remains unresolved whether they could have had a larger scale impact. Here, we present an annually resolved ice core record of anthropogenic trace element deposition from the remote drilling site of the Quelccaya Ice Cap (Peru) that spans 793-1989 AD. During the pre-Inca period (i.e., prior to ~1450 AD) the deposition of trace elements was dominated by the fallout of aeolian dust from the deglaciated margins of the ice cap and of ash from occasional volcanic eruptions. In contrast, the ice core record indicates a clear anthropogenic signal emerging after the onset of large scale colonial mining and metallurgy (1532-1820 AD), ~300 years prior to the Industrial Revolution during the last part of the Little Ice Age. This shift was coincidental with a major technological transition for silver extraction (1572 AD), from lead-based smelting to mercury amalgamation, that initiated a major increase in ore mining and milling that likely resulted in an increase of metallic dust emissions. While atmospheric trace element deposition resulting from colonial metallurgy was certainly much larger than during the pre-Colonial period, trace element fallout during the Colonial era was still several factors lower than during the 20th century, when the construction of the trans-Andean railway and highways promoted a widespread societal and industrial development of South America.

  20. Placers of cosmic dust in the blue ice lakes of Greenland

    NASA Technical Reports Server (NTRS)

    Maurette, M.; Hammer, C.; Reeh, N.; Brownlee, D. E.; Thomsen, H. H.

    1986-01-01

    A concentration process occurring in the melt zone of the Greenland ice cap has produced the richest known deposit of cosmic dust on the surface of the earth. Extraterrestrial particles collected from this region are well preserved and are collectable in large quantities. The collected particles are generally identical to cosmic spheres found on the ocean floor, but a pure glass type was discovered that has not been seen in deep-sea samples. Iron-rich spheres are conspicuously rare in the collected material.

  1. Surges of outlet glaciers from the Drangajökull ice cap, northwest Iceland

    NASA Astrophysics Data System (ADS)

    Brynjólfsson, Skafti; Schomacker, Anders; Korsgaard, Niels J.; Ingólfsson, Ólafur

    2016-09-01

    Surface elevation and volume changes of the Drangajökull surge-type glaciers, Reykjarfjarðarjökull and Leirufjarðarjökull, were studied by comparing digital elevation models that pre-date and post-date their most recent surges. Annual glacier-frontal measurements were used to estimate average ice velocities during the last surge of the glaciers. The observations show a distinct ice discharge, most of which was from the upper reservoir areas, down to the receiving areas during the surges. The surface draw-down in the reservoir areas was usually 10-30 m during the surges, while the thickening of the receiving areas was significantly more variable, on the order of 10-120 m. Despite a negative geodetic net mass balance derived from the digital elevation models, the reservoir areas have been gaining mass since the surge terminations. This surface thickening along with considerable ablation of the receiving areas will most likely return the glacier surface profiles to the pre-surge stage. Our results indicate that (a) greatest surface thinning in the upper reservoir areas of Drangajökull rather than proximal to the equilibrium line during Vatnajökull surges and (b) development of Drangajökull surges that resembles Svalbard surge-type glaciers rather than Vatnajökull surge-type glaciers. The contrasting surge characteristics could be explained by differences in glacier geometry, topography and substratum of the Drangajökull and Vatnajökull surge-type glaciers.

  2. CLaMS-Ice: Large-scale cirrus cloud simulations in comparison with observations

    NASA Astrophysics Data System (ADS)

    Costa, Anja; Rolf, Christian; Grooß, Jens-Uwe; Spichtinger, Peter; Afchine, Armin; Spelten, Nicole; Dreiling, Volker; Zöger, Martin; Krämer, Martina

    2016-04-01

    Cirrus clouds are an element of uncertainty in the climate system and have received increasing attention since the last IPCC reports. The interactions of different freezing mechanisms, sedimentation rates, updraft velocity fluctuations and other factors that determine the formation and evolution of those clouds is still not fully understood. Thus, a reliable representation of cirrus clouds in models representing real atmospheric conditions is still a challenging task. At last year's EGU, Rolf et al. (2015) introduced the new large-scale microphysical cirrus cloud model CLaMS-Ice: based on trajectories calculated with CLaMS (McKenna et al., 2002 and Konopka et al. 2007), it simulates the development of cirrus clouds relying on the cirrus bulk model by Spichtinger and Gierens (2009). The qualitative agreement between CLaMS-Ice simulations and observations could be demonstrated at that time. Now we present a detailed quantitative comparison between standard ECMWF products, CLaMS-Ice simulations, and in-situ measurements obtained during the ML-Cirrus campaign 2014. We discuss the agreement of the parameters temperature (observational data: BAHAMAS), relative humidity (SHARC), cloud occurrence, cloud particle concentration, ice water content and cloud particle radii (all NIXE-CAPS). Due to the precise trajectories based on ECMWF wind and temperature fields, CLaMS-Ice represents the cirrus cloud vertical and horizontal coverage more accurately than the ECMWF ice water content (IWC) fields. We demonstrate how CLaMS-Ice can be used to evaluate different input settings (e.g. amount of ice nuclei, freezing thresholds, sedimentation settings) that lead to cirrus clouds with the microphysical properties observed during ML-Cirrus (2014).

  3. Troughs on Martian Ice Sheets: Analysis of Their Closure and Mass Balance

    NASA Technical Reports Server (NTRS)

    Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, J.

    2000-01-01

    At the Copenhagen workshop on Martian polar processes, Ralf Greve commented that the flow regime surrounding scarps and troughs of the Martian polar ice sheets cannot be modeled using traditional "plan view" ice-sheet models. Such models are inadequate because they typically use reduced equations that embody certain simplifications applicable only to terrestrial ice sheets where the upper ice sheet surface is smooth. In response to this suggestion, we have constructed a 2-dimensional, time dependent "side view" (two spatial dimensions: one horizontal, one vertical) model of scarp closure that is designed to overcome the difficulties described by Greve. The purpose of the model is to evaluate the scales of stress variation and styles of flow closure so as to estimate errors that may be encountered by "plan view" models. We show that there may be avenues whereby the complications associated with scarp closure can be overcome in "plan view" models through appropriate parameterizations of 3-dimensional effects. Following this, we apply the flow model to simulate the evolution of a typical scarp on the North Polar Cap of Mars. Our simulations investigate: (a) the role of "radiation trapping" (see our companion abstract) in creating and maintaining "spiral-like" scarps on the ice sheet, (b) the consequences of different flowlaws and ice compositions on scarp evolution and, in particular, scarp age, and (c) the role of dust and debris in scarp evolution.

  4. Towards Quantification of Glacier Dynamic Ice Loss through Passive Seismic Monitoring

    NASA Astrophysics Data System (ADS)

    Köhler, A.; Nuth, C.; Weidle, C.; Schweitzer, J.; Kohler, J.; Buscaino, G.

    2015-12-01

    Global glaciers and ice caps loose mass through calving, while existing models are currently not equipped to realistically predict dynamic ice loss. This is mainly because long-term continuous calving records, that would help to better understand fine scale processes and key climatic-dynamic feedbacks between calving, climate, terminus evolution and marine conditions, do not exist. Combined passive seismic/acoustic strategies are the only technique able to capture rapid calving events continuously, independent of daylight or meteorological conditions. We have produced such a continuous calving record for Kronebreen, a tidewater glacier in Svalbard, using data from permanent seismic stations between 2001 and 2014. However, currently no method has been established in cryo-seismology to quantify the calving ice loss directly from seismic data. Independent calibration data is required to derive 1) a realistic estimation of the dynamic ice loss unobserved due to seismic noise and 2) a robust scaling of seismic calving signals to ice volumes. Here, we analyze the seismic calving record at Kronebreen and independent calving data in a first attempt to quantify ice loss directly from seismic records. We make use of a) calving flux data with weekly to monthly resolution obtained from satellite remote sensing and GPS data between 2007 and 2013, and b) direct, visual calving observations in two weeks in 2009 and 2010. Furthermore, the magnitude-scaling property of seismic calving events is analyzed. We derive and discuss an empirical relation between seismic calving events and calving flux which for the first time allows to estimate a time series of calving volumes more than one decade back in time. Improving our model requires to incorporate more precise, high-resolution calibration data. A new field campaign will combine innovative, multi-disciplinary monitoring techniques to measure calving ice volumes and dynamic ice-ocean interactions simultaneously with terrestrial laser

  5. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information: VIS instrument. Latitude 86.5, Longitude 64.5 East (295.5 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation

  6. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information:VIS instrument. Latitude 86.5, longitude 57.4 East (302.6 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is

  7. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information: VIS instrument. Latitude 84.3, Longitude 314.4 East (45.6 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation

  8. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information: VIS instrument. Latitude 84.2, Longitude 57.4 East (302.6 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation

  9. Designing Smart Charter School Caps

    ERIC Educational Resources Information Center

    Dillon, Erin

    2010-01-01

    In 2007, Andrew J. Rotherham proposed a new approach to the contentious issue of charter school caps, the statutory limits on charter school growth in place in several states. Rotherham's proposal, termed "smart charter school caps," called for quality sensitive caps that allow the expansion of high-performing charter schools while also…

  10. Heavy metals in Antarctic ice from Law Dome: Initial results

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

    Hong, S.; Boutron, C.F.; Edwards, R.

    1998-08-01

    Pb, Cd, Cu, and Zn have been measured using ultraclean procedures in eight sections taken from two well-dated ice cores from Law Dome, an independent small size ice cap with high accumulation rate situated in the coastal area of East Antarctica. Seven sections were dated from the 1830s to 1940s and one was dated from three millennia ago. The data show that there are strong seasonal variations in the concentrations of Pb and Cd, with values {approximately} two- to four-fold higher in winter than in spring-summer. Evaluation of the contributions from the different sources suggests that contribution from sea saltmore » spray is relatively important, especially for Cd. Contribution from marine biogenic emissions could also be very significant. The importance of marine contributions is consistent with strong intrusions of marine air masses at this coastal site, especially during wintertime.« less

  11. Water on Mars: Inventory, distribution, and possible sources of polar ice

    NASA Technical Reports Server (NTRS)

    Clifford, S. M.

    1992-01-01

    Theoretical considerations and various lines of morphologic evidence suggest that, in addition to the normal seasonal and climatic exchange of H2O that occurs between the Martian polar caps, atmosphere, and mid to high latitude regolith, large volumes of water have been introduced into the planet's long term hydrologic cycle by the sublimation of equatorial ground ice, impacts, catastrophic flooding, and volcanism. Under the climatic conditions that are thought to have prevailed on Mars throughout the past 3 to 4 b.y., much of this water is expected to have been cold trapped at the poles. The amount of polar ice contributed by each of the planet's potential crustal sources is discussed and estimated. The final analysis suggests that only 5 to 15 pct. of this potential inventory is now in residence at the poles.

  12. 2015 Arctic Sea Ice Maximum Annual Extent Is Lowest On Record

    NASA Image and Video Library

    2015-03-19

    The sea ice cap of the Arctic appeared to reach its annual maximum winter extent on Feb. 25, according to data from the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder. At 5.61 million square miles (14.54 million square kilometers), this year’s maximum extent was the smallest on the satellite record and also one of the earliest. Read more: 1.usa.gov/1Eyvelz Credit: NASA's Goddard Space Flight Center NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  13. 47 CFR 54.507 - Cap.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Universal Service Support for Schools and Libraries § 54.507 Cap. (a) Amount of the annual cap. In funding year 2010 and subsequent funding years, the $2.25 billion funding cap on federal universal service.... For instance, the annual increase in the GDP-CPI from 2008 to 2009 would be used for the 2010 funding...

  14. 47 CFR 54.507 - Cap.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Universal Service Support for Schools and Libraries § 54.507 Cap. (a) Amount of the annual cap. In funding year 2010 and subsequent funding years, the $2.25 billion funding cap on federal universal service.... For instance, the annual increase in the GDP-CPI from 2008 to 2009 would be used for the 2010 funding...

  15. 47 CFR 54.507 - Cap.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Universal Service Support for Schools and Libraries § 54.507 Cap. (a) Amount of the annual cap. In funding year 2010 and subsequent funding years, the $2.25 billion funding cap on federal universal service.... For instance, the annual increase in the GDP-CPI from 2008 to 2009 would be used for the 2010 funding...

  16. 31 CFR 50.15 - Cap disclosure.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 31 Money and Finance: Treasury 1 2010-07-01 2010-07-01 false Cap disclosure. 50.15 Section 50.15... Disclosures as Conditions for Federal Payment § 50.15 Cap disclosure. (a) General. Under section 103(e)(2) of... existence of the $100,000,000,000 cap under section 103(e)(2). The cap disclosure must be made at the time...

  17. CAPS Simulation Environment Development

    NASA Technical Reports Server (NTRS)

    Murphy, Douglas G.; Hoffman, James A.

    2005-01-01

    The final design for an effective Comet/Asteroid Protection System (CAPS) will likely come after a number of competing designs have been simulated and evaluated. Because of the large number of design parameters involved in a system capable of detecting an object, accurately determining its orbit, and diverting the impact threat, a comprehensive simulation environment will be an extremely valuable tool for the CAPS designers. A successful simulation/design tool will aid the user in identifying the critical parameters in the system and eventually allow for automatic optimization of the design once the relationships of the key parameters are understood. A CAPS configuration will consist of space-based detectors whose purpose is to scan the celestial sphere in search of objects likely to make a close approach to Earth and to determine with the greatest possible accuracy the orbits of those objects. Other components of a CAPS configuration may include systems for modifying the orbits of approaching objects, either for the purpose of preventing a collision or for positioning the object into an orbit where it can be studied or used as a mineral resource. The Synergistic Engineering Environment (SEE) is a space-systems design, evaluation, and visualization software tool being leveraged to simulate these aspects of the CAPS study. The long-term goal of the SEE is to provide capabilities to allow the user to build and compare various CAPS designs by running end-to-end simulations that encompass the scanning phase, the orbit determination phase, and the orbit modification phase of a given scenario. Herein, a brief description of the expected simulation phases is provided, the current status and available features of the SEE software system is reported, and examples are shown of how the system is used to build and evaluate a CAPS detection design. Conclusions and the roadmap for future development of the SEE are also presented.

  18. Contrasting sea-ice and open-water boundary layers during melt and freeze-up seasons: Some result from the Arctic Clouds in Summer Experiment.

    NASA Astrophysics Data System (ADS)

    Tjernström, Michael; Sotiropoulou, Georgia; Sedlar, Joseph; Achtert, Peggy; Brooks, Barbara; Brooks, Ian; Persson, Ola; Prytherch, John; Salsbury, Dominic; Shupe, Matthew; Johnston, Paul; Wolfe, Dan

    2016-04-01

    With more open water present in the Arctic summer, an understanding of atmospheric processes over open-water and sea-ice surfaces as summer turns into autumn and ice starts forming becomes increasingly important. The Arctic Clouds in Summer Experiment (ACSE) was conducted in a mix of open water and sea ice in the eastern Arctic along the Siberian shelf during late summer and early autumn 2014, providing detailed observations of the seasonal transition, from melt to freeze. Measurements were taken over both ice-free and ice-covered surfaces, offering an insight to the role of the surface state in shaping the lower troposphere and the boundary-layer conditions as summer turned into autumn. During summer, strong surface inversions persisted over sea ice, while well-mixed boundary layers capped by elevated inversions were frequent over open-water. The former were often associated with advection of warm air from adjacent open-water or land surfaces, whereas the latter were due to a positive buoyancy flux from the warm ocean surface. Fog and stratus clouds often persisted over the ice, whereas low-level liquid-water clouds developed over open water. These differences largely disappeared in autumn, when mixed-phase clouds capped by elevated inversions dominated in both ice-free and ice-covered conditions. Low-level-jets occurred ~20-25% of the time in both seasons. The observations indicate that these jets were typically initiated at air-mass boundaries or along the ice edge in autumn, while in summer they appeared to be inertial oscillations initiated by partial frictional decoupling as warm air was advected in over the sea ice. The start of the autumn season was related to an abrupt change in atmospheric conditions, rather than to the gradual change in solar radiation. The autumn onset appeared as a rapid cooling of the whole atmosphere and the freeze up followed as the warm surface lost heat to the atmosphere. While the surface type had a pronounced impact on boundary

  19. The cervical cap (image)

    MedlinePlus

    The cervical cap is a flexible rubber cup-like device that is filled with spermicide and self-inserted over the cervix ... left in place several hours after intercourse. The cap is a prescribed device fitted by a health ...

  20. A Warmer Atmosphere on Mars near the Noachian-Hesperian Boundary: Evidence from Basal Melting of the South Polar Ice Cap (Dorsa Argentea Formation)

    NASA Astrophysics Data System (ADS)

    Fastook, J. L.; Head, J. W.; Marchant, D. R.; Forget, F.; Madeleine, J.-B.

    2012-05-01

    Eskers in the Dorsa Argentea Formation imply the presence of an ice sheet with a wet bed. With an ice sheet model, we examine a range of geothermal heat fluxes and warmer climates to determine what conditions could produce such an ice sheet.

  1. Ice swimming - 'Ice Mile' and '1 km Ice event'.

    PubMed

    Knechtle, Beat; Rosemann, Thomas; Rüst, Christoph A

    2015-01-01

    Ice swimming for 1 mile and 1 km is a new discipline in open-water swimming since 2009. This study examined female and male performances in swimming 1 mile ('Ice Mile') and 1 km ('1 km Ice event') in water of 5 °C or colder between 2009 and 2015 with the hypothesis that women would be faster than men. Between 2009 and 2015, 113 men and 38 women completed one 'Ice Mile' and 26 men and 13 completed one '1 km Ice event' in water colder than +5 °C following the rules of International Ice Swimming Association (IISA). Differences in performance between women and men were determined. Sex difference (%) was calculated using the equation ([time for women] - [time for men]/[time for men] × 100). For 'Ice Mile', a mixed-effects regression model with interaction analyses was used to investigate the influence of sex and environmental conditions on swimming speed. The association between water temperature and swimming speed was assessed using Pearson correlation analyses. For 'Ice Mile' and '1 km Ice event', the best men were faster than the best women. In 'Ice Mile', calendar year, number of attempts, water temperature and wind chill showed no association with swimming speed for both women and men. For both women and men, water temperature was not correlated to swimming speed in both 'Ice Mile' and '1 km Ice event'. In water colder than 5 °C, men were faster than women in 'Ice Mile' and '1 km Ice event'. Water temperature showed no correlation to swimming speed.

  2. The last forests in Greenland, and the age of the ice sheet

    NASA Astrophysics Data System (ADS)

    Funder, Svend; Schmidt, Astrid M. Z.; Dahl-Jensen, Dorthe; Steffensen, Jørgen Peder; Willerslev, Eske

    2014-05-01

    Recently ancient DNA (aDNA) studies of the basal ice in the Camp Century ice core, northern Greenland, have shown that mixed coniferous-deciduous forest grew here before the area was invaded and permanently covered by the ice sheet. The coring site is situated only 100 km from the present ice margin and more than 500 km from the ice divide, indicating that since this last inception the northern part of the ice sheet never receded more than 100 km from its present margin. Dating of the basal ice and obtaining an age for the forest and for the beginning of the ice sheet's permanency has been attempted by analyzing for optically stimulated luminescence (OSL), meteoric 10Be/36Cl cosmogenic nuclides, 234U/238U recoil. These methods all provide only minimum ages and show that the forest at Cap Century is older than 500 ka. Comparison with other Pleistocene "forest sites" in Greenland - the Kap København Formation in northernmost Greenland, the DYE-3 ice core in the south, the ODP boring 646 south of Greenland, as well as results from basal ice in the GRIP ice core - extends the minimum age to c. 1 ma. The maximum age is provided by the Kap København Formation, which must be older - or contemporaneous. The formation has recently been confirmed to date within the interval 2-2.5 ma, with a preferred age of 2.3-2.4 ma. Surprisingly, application of the molecular clock of insect COI sequences on the Camp Century aDNA now seem to push the minimum age just as far back - to 2.4 ma, suggesting that the timberline boreal forest at Kap København is contemporaneous with the mixed forest at Camp Century, 600 km to the south. From this we conclude that the northern ice sheet dome, which today contains 85% of the total ice sheet volume, has remained within 100 km of its present margin for at least 1 ma, and possibly may go back as far as 2.4 ma. The ice sheet has therefore survived both interglacials and "super interglacials" that were both warmer and longer than the present. This

  3. Ice Bridge Antarctic Sea Ice

    NASA Image and Video Library

    2009-10-21

    Sea ice is seen out the window of NASA's DC-8 research aircraft as it flies 2,000 feet above the Bellingshausen Sea in West Antarctica on Wednesday, Oct., 21, 2009. This was the fourth science flight of NASA’s Operation Ice Bridge airborne Earth science mission to study Antarctic ice sheets, sea ice, and ice shelves. Photo Credit: (NASA/Jane Peterson)

  4. Spatial and temporal patterns of sea ice variations in Vilkitsky strait, Russian High Arctic

    NASA Astrophysics Data System (ADS)

    Ci, T.; Cheng, X.; Hui, F.

    2013-12-01

    The Arctic Ocean has been greatly affected by climate change. Future predications show an even more drastic reduction of the ice cap which will open new areas for the exploration of natural resources and maritime transportation.Shipping through the Arctic Ocean via the Northern Sea Route (NSR) could save about 40% of the sailing distance from Asia (Yokohama) to Europe (Rotterdam) compared to the traditional route via the Suez Canal. Vilkitsky strait is the narrowest and northest portion of the Northern Sea Route with heaviest traffic between the Taimyr Peninsular and the Severnaya Zemlya archipelago. The preliminary results of sea ice variations are presented by using moderate-resolution imaging spectro radiometer(MODIS) data with 250-m resolution in the Vilkitsky strait during 2009-2012. Temporally, the first rupture on sea ice in Vilkitsky strait usually comes up in April and sea ice completely break into pieces in early June. The strait would be ice-free between August and late September. The frequency of ice floes grows while temperature falls down in October. There are always one or two months suitable for transport. Spatially, Sea ice on Laptev sea side breaks earlier than that of Kara sea side while sea ice in central of strait breaks earlier than in shoreside. The phenomena are directly related with the direction of sea wind and ocean current. In summmary, study on Spatial and temporal patterns in this area is significant for the NSR. An additional research issue to be tackled is to seeking the trends of ice-free duration in the context of global warming. Envisat ASAR data will also be used in this study.

  5. Evolution of the Mauthner axon cap.

    PubMed

    Bierman, Hilary S; Zottoli, Steven J; Hale, Melina E

    2009-01-01

    Studies of vertebrate brain evolution have focused primarily on patterns of gene expression or changes in size and organization of major brain regions. The Mauthner cell, an important reticulospinal neuron that functions in the startle response of many species, provides an opportunity for evolutionary comparisons at the cellular level. Despite broad interspecific similarities in Mauthner cell morphology, the motor patterns and startle behaviors it initiates vary markedly. Response diversity has been hypothesized to result, in part, from differences in the structure and function of the Mauthner cell-associated axon cap. We used light microscopy techniques to compare axon cap morphology across a wide range of species, including all four extant basal actinopterygian orders, representatives of a variety of teleost lineages and lungfishes, and we combined our data with published descriptions of axon cap structure. The 'composite' axon cap, observed in teleosts, is an organized conglomeration of glia and fibers of inhibitory and excitatory interneurons. Lungfish, amphibian tadpoles and several basal actinopterygian fishes have 'simple' axon caps that appear to lack glia and include few fibers. Several other basal actinopterygian fishes have 'simple-dense' caps that include greater numbers of fibers than simple caps, but lack the additional elements and organization of composite caps. Phylogenetic mapping shows that through evolution there are discrete transitions in axon cap morphology occurring at the base of gnathostomes, within basal actinopterygians, and at the base of the teleost radiation. Comparing axon cap evolution to the evolution of startle behavior and motor pattern provides insight into the relationship between Mauthner cell-associated structures and their functions in behavior. Copyright 2009 S. Karger AG, Basel.

  6. Thermal drilling in planetary ices: an analytic solution with application to planetary protection problems of radioisotope power sources.

    PubMed

    Lorenz, Ralph D

    2012-08-01

    Thermal drilling has been applied to studies of glaciers on Earth and proposed for study of the martian ice caps and the crust of Europa. Additionally, inadvertent thermal drilling by radioisotope sources released from the breakup of a space vehicle is of astrobiological concern in that this process may form a downward-propagating "warm little pond" that could convey terrestrial biota to a habitable environment. A simple analytic solution to the asymptotic slow-speed case of thermal drilling is noted and used to show that the high thermal conductivity of the low-temperature ice on Europa and Titan makes thermal drilling qualitatively more difficult than at Mars. It is shown that an isolated General Purpose Heat Source (GPHS) "brick" can drill effectively on Earth or Mars, whereas on Titan or Europa with ice at 100 K, the source would stall and become stuck in the ice with a surface temperature of <200 K.

  7. Damages Caps in Medical Malpractice Cases

    PubMed Central

    Nelson, Leonard J; Morrisey, Michael A; Kilgore, Meredith L

    2007-01-01

    This article reviews the empirical literature on the effects of damages caps and concludes that the better-designed studies show that damages caps reduce liability insurance premiums. The effects of damages caps on defensive medicine, physicians’ location decisions, and the cost of health care to consumers are less clear. The only study of whether consumers benefit from lower health insurance premiums as a result of damages caps found no impact. Some state courts have based decisions declaring damages caps legislation unconstitutional on the lack of evidence of their effectiveness, thereby ignoring the findings of conflicting research studies or discounting their relevance. Although courts should be cautious in rejecting empirical evidence that caps are effective, legislators should consider whether they benefit consumers enough to justify limiting tort recoveries for those most seriously injured by malpractice. PMID:17517115

  8. Tip cap for a rotor blade

    NASA Technical Reports Server (NTRS)

    Kofel, W. K.; Tuley, E. N.; Gay, C. H., Jr.; Troeger, R. E.; Sterman, A. P. (Inventor)

    1983-01-01

    A replaceable tip cap for attachment to the end of a rotor blade is described. The tip cap includes a plurality of walls defining a compartment which, if desired, can be divided into a plurality of subcompartments. The tip cap can include inlet and outlet holes in walls thereof to permit fluid communication of a cooling fluid there through. Abrasive material can be attached with the radially outer wall of the tip cap.

  9. Ice Crystal Icing Research at NASA

    NASA Technical Reports Server (NTRS)

    Flegel, Ashlie B.

    2017-01-01

    Ice crystals found at high altitude near convective clouds are known to cause jet engine power-loss events. These events occur due to ice crystals entering a propulsion system's core flowpath and accreting ice resulting in events such as uncommanded loss of thrust (rollback), engine stall, surge, and damage due to ice shedding. As part of a community with a growing need to understand the underlying physics of ice crystal icing, NASA has been performing experimental efforts aimed at providing datasets that can be used to generate models to predict the ice accretion inside current and future engine designs. Fundamental icing physics studies on particle impacts, accretion on a single airfoil, and ice accretions observed during a rollback event inside a full-scale engine in the Propulsion Systems Laboratory are summarized. Low fidelity code development using the results from the engine tests which identify key parameters for ice accretion risk and the development of high fidelity codes are described. These activities have been conducted internal to NASA and through collaboration efforts with industry, academia, and other government agencies. The details of the research activities and progress made to date in addressing ice crystal icing research challenges are discussed.

  10. Ice Crystal Icing Research at NASA

    NASA Technical Reports Server (NTRS)

    Flegel, Ashlie B.

    2017-01-01

    Ice crystals found at high altitude near convective clouds are known to cause jet engine power-loss events. These events occur due to ice crystals entering a propulsion systems core flowpath and accreting ice resulting in events such as uncommanded loss of thrust (rollback), engine stall, surge, and damage due to ice shedding. As part of a community with a growing need to understand the underlying physics of ice crystal icing, NASA has been performing experimental efforts aimed at providing datasets that can be used to generate models to predict the ice accretion inside current and future engine designs. Fundamental icing physics studies on particle impacts, accretion on a single airfoil, and ice accretions observed during a rollback event inside a full-scale engine in the Propulsion Systems Laboratory are summarized. Low fidelity code development using the results from the engine tests which identify key parameters for ice accretion risk and the development of high fidelity codes are described. These activities have been conducted internal to NASA and through collaboration efforts with industry, academia, and other government agencies. The details of the research activities and progress made to date in addressing ice crystal icing research challenges are discussed.

  11. HiRISE observations of gas sublimation-driven activity in Mars' southern polar regions: III. Models of processes involving translucent ice

    USGS Publications Warehouse

    Portyankina, G.; Markiewicz, W.J.; Thomas, N.; Hansen, C.J.; Milazzo, M.

    2010-01-01

    Enigmatic surface features, known as 'spiders', found at high southern martian latitudes, are probably caused by sublimation-driven erosion under the seasonal carbon dioxide ice cap. The Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) has imaged this terrain in unprecedented details throughout southern spring. It has been postulated [Kieffer, H.H., Titus, T.N., Mullins, K.F., Christensen, P.R., 2000. J. Geophys. Res. 105, 9653-9700] that translucent CO2 slab ice traps gas sublimating at the ice surface boundary. Wherever the pressure is released the escaping gas jet entrains loose surface material and carries it to the top of the ice where it is carried downslope and/or downwind and deposited in a fan shape. Here we model two stages of this scenario: first, the cleaning of CO2 slab ice from dust, and then, the breaking of the slab ice plate under the pressure built below it by subliming ice. Our modeling results and analysis of HiRISE images support the gas jet hypothesis and show that outbursts happen very early in spring. ?? 2009 Elsevier Inc. All rights reserved.

  12. Ice sheet margins and ice shelves

    NASA Technical Reports Server (NTRS)

    Thomas, R. H.

    1984-01-01

    The effect of climate warming on the size of ice sheet margins in polar regions is considered. Particular attention is given to the possibility of a rapid response to warming on the order of tens to hundreds of years. It is found that the early response of the polar regions to climate warming would be an increase in the area of summer melt on the ice sheets and ice shelves. For sufficiently large warming (5-10C) the delayed effects would include the breakup of the ice shelves by an increase in ice drainage rates, particularly from the ice sheets. On the basis of published data for periodic changes in the thickness and melting rates of the marine ice sheets and fjord glaciers in Greenland and Antarctica, it is shown that the rate of retreat (or advance) of an ice sheet is primarily determined by: bedrock topography; the basal conditions of the grounded ice sheet; and the ice shelf condition downstream of the grounding line. A program of satellite and ground measurements to monitor the state of ice sheet equilibrium is recommended.

  13. Mining cosmic dust from the blue ice lakes of Greenland

    NASA Technical Reports Server (NTRS)

    Maurette, M.; Brownlee, D. E.; Fehrenback, L.; Hammer, C.; Jehano, C.; Thomsen, H. H.

    1985-01-01

    Extraterrestrial material, most of which invisible settles to Earth's surface as dust particles smaller than a millimeter in size were investigated. Particles of 1/10 millimeter size fall at a rate of one/sq m/yr collection of extraterrestrial dust is important because the recovered cosmic dust particles can provide important information about comets. Comets are the most important source of dust in the solar system and they are probably the major source of extraterrestrial dust that is collectable at the Earth's surface. A new collection site for cosmic dust, in an environment where degradation by weathering is minimal is reported. It is found that the blue ice lakes on the Greenland ice cap provide an ideal location for collection of extraterrestrial dust particles larger than 0.1 mm in size. It is found that the lakes contain large amounts of cosmic dust which is much better preserved than similar particles recovered from the ocean floor.

  14. A comprehensive interpretation of the NEEM basal ice build-up using a multi-parametric approach

    NASA Astrophysics Data System (ADS)

    Goossens, Thomas; Sapart, Célia J.; Dahl-Jensen, Dorthe; Popp, Trevor; El Amri, Saïda; Tison, Jean-Louis

    2016-03-01

    Basal ice is a common expression to describe bottom ice layers of glaciers, ice caps and ice sheets in which the ice is primarily conditioned by processes operating at the bed. It is chemically and/or physically distinct from the ice above and can be characterized by a component of basally derived sediments. The study of basal ice properties provides a rare opportunity to improve our understanding of subglacial environments and processes and to refine ice sheet behaviour modelling. Here, we present and discuss the results of water stable isotopes (δ18O and δD), ice fabrics, debris weight/size distribution and gas content of the basal part of the NEEM (North Greenland Eemian Ice Drilling Project) ice core. Below a depth of 2533.85 m, almost 10 m of basal debris-rich material was retrieved from the borehole, and regular occurrence of frozen sediments with only interstitial ice lenses in the bottom 5 m suggest that the ice-bedrock interface was reached. The sequence is composed of an alternation of three visually contrasting types of ice: clear ice with specks (very small amounts) of particulate inclusions, stratified debris-rich layers and ice containing dispersed debris. The use of water stable isotope signatures (δ18O and δD), together with other parameters, allows discrimination between the different types of ice and to unravel the processes involved in their formation and transformation. The basal debris-rich material presents δ18O values [-39.9 ‰; -34.4 ‰] within the range of the above last 300 m of unaltered meteoric ice [-44.9 ‰; -30.6 ‰] spanning a glacial-interglacial range of values. This rules out the hypothesis of a basal ice layer originating from pre-ice sheet ice overridden by the growing ice sheet, as previously suggested e.g. in the case of GRIP (Greenland Ice Core Project). We show that clear basal ice with specks corresponds to altered meteoric glacial ice where some of the climatic signal could have been preserved. However, the

  15. The polar caps

    NASA Astrophysics Data System (ADS)

    Akasofu, S.-I.

    1985-12-01

    According to the most common definition, the 'polar cap' is the region bounded by the average or statistical auroral oval. Studies of the effects of the interplanetary magnetic field (IMF) on various upper atmospheric phenomena are reviewed. The Antarctic region and the Arctic region represent an area for such investigations. Particular attention is given in this paper to those observations in the highest latitude region which provide some information concerning corresponding changes of the internal structure of the magnetosphere. A definition and working definition of the polar cap are considered along with the IMF and magnetospheric models, the entry of solar energetic electrons, statistical studies regarding the aurora, individual events, polar cap arcs, the cusp aurora, auroral electron precipitation, convection, ionospheric currents and field-aligned currents, the ionosphere, the thermosphere, polar rain, polar wind, and hopping motions of heavy ions.

  16. Stuck fuel rod capping sleeve

    DOEpatents

    Gorscak, Donald A.; Maringo, John J.; Nilsen, Roy J.

    1988-01-01

    A stuck fuel rod capping sleeve to be used during derodding of spent fuel assemblies if a fuel rod becomes stuck in a partially withdrawn position and, thus, has to be severed. The capping sleeve has an inner sleeve made of a lower work hardening highly ductile material (e.g., Inconel 600) and an outer sleeve made of a moderately ductile material (e.g., 304 stainless steel). The inner sleeve may be made of an epoxy filler. The capping sleeve is placed on a fuel rod which is then severed by using a bolt cutter device. Upon cutting, the capping sleeve deforms in such a manner as to prevent the gross release of radioactive fuel material

  17. Assessment of the Relationship between Andean Ice Core Precipitation Indicators and Amazon River Discharge

    NASA Astrophysics Data System (ADS)

    Johnson, N.; Alsdorf, D.; Thompson, L.; Mosley-Thompson, E.; Melack, J.

    2006-12-01

    Prior to the last 100 years, there is a significant lack of hydrologic knowledge for the Amazon Basin. A 100- year record of discharge from the city of Manaus, located at the confluence of the Solimoes and Negro rivers, is the most complete record for the basin. Inundated wetlands play a key role in carbon out-gassing to the atmosphere whereas discharge from the Amazon River contributes about 20% of the total freshwater flux delivered to the world's oceans. As discharge (Q) and inundation are directly related to precipitation, we are developing a method to extend our understanding of Q and inundation into the 19^{th} century. Using proxy data preserved in Andean glaciers and ice caps and recovered from ice cores, annually resolved histories of δ^{18)O and mass accumulation are available. The latter is a proxy for local precipitation amount whereas δ18O is influenced by continental scale processes (i.e., evaporation, convection) as well as by temperature and hence, by varying climate regimes. We have correlated the accumulation and δ18O records from Core 1 drilled on the Quelccaya ice-cap in the southern Andes of Peru with the Manaus discharge data. As ice core annual layers correspond to the thermal year (in Peru, July to June of the following year) and the discharge records are kept daily (January to December), we averaged 365 days of Q data seeking the optimal correlation for each start and end date. The best statistical relationship between δ18O and Q (r = -0.41, p = < 0.001) is attained when Q is averaged from March 16 to March 15 of the following year. We also correlated 23 years of ENSO events, which are linked to both Amazon River discharge and ice core δ18O (r = -0.60, p = < 0.001). These linear relationships are used to create Amazon discharge for the 20^{th} century and to extrapolate Q into the 19^{th} century. Previously developed relationships between Q and mainstem inundated area are then used to estimate inundated area along the main Amazon

  18. Jupiter's and Saturn's ice moons: geophysical aspects and opportunities of geophysical survey of the planetary geoelectrical markers and oreols of the subsurface liquid ocean on the surface ice moons

    NASA Astrophysics Data System (ADS)

    Ozorovich, Yuri; Linkin, Vacheslav; Kosov, Alexandr; Fournier-Sicre, Alain; Klimov, Stanislav; Novikov, Denis; Ivanov, Anton; Skulachev, Dmitriy; Menshenin, Yaroslav

    2016-04-01

    This paper presents a new conceptual and methodological approach for geophysical survey of the planetary geoelectrical markers and oreols of the subsurface liquid ocean on the surface ice moons on the base "conceptual design phase" of the future space missions on the ice moons. At the design stage of such projects is considered the use of various space instruments and tools for the full the complex geophysical studies of the manifestations and planetary processes of the subsurface liquid ocean on the surface ice moons. The existence of various forms of the cryolithozone on terrestrial planets and their moons: advanced Martian permafrost zone in the form of existing of the frozen polar caps, subsurface frozen horizons, geological markers and oreols of the martian ancient (relict) ocean, subsurface oceans of Jupiter's and Saturn's moons-Europe and Enceladus, with the advanced form of permafrost freezes planetary caps, it allows to develop a common methodological basis and operational geophysical instruments (tools) for the future space program and planning space missions on these unique objects of the solar system, specialized for specific scientific problems of planetary missions. Geophysical practices and methodological principles, used in 1985-2015 by aurthors [ 1-5 ], respectively, as an example of the comprehensive geophysical experiment MARSES to study of the Martian permafrost zone and the martian ancient (relict) ocean, creating the preconditions for complex experimental setting and geo-physical monitoring of operational satellites of Jupiter and Saturn- Europe and Enceladus. This range of different planetary (like) planets with its geological history and prehistory of the common planetology formation processes of the planets formation and to define the role of a liquid ocean under the ice as a climate indicator of such planets, which is extremely important for the future construction of the geological and climatic history of the Earth. Main publications: [1

  19. Ice, Ice, Baby!

    NASA Astrophysics Data System (ADS)

    Hamilton, C.

    2008-12-01

    The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an outreach program based on hands-on activities called "Ice, Ice, Baby". These lessons are designed to teach the science principles of displacement, forces of motion, density, and states of matter. These properties are easily taught through the interesting topics of glaciers, icebergs, and sea level rise in K-8 classrooms. The activities are fun, engaging, and simple enough to be used at science fairs and family science nights. Students who have participated in "Ice, Ice, Baby" have successfully taught these to adults and students at informal events. The lessons are based on education standards which are available on our website www.cresis.ku.edu. This presentation will provide information on the activities, survey results from teachers who have used the material, and other suggested material that can be used before and after the activities.

  20. The impact of 21st Century sea ice decline on the hydrological budget of the Arctic

    NASA Astrophysics Data System (ADS)

    Day, J. J.; Bamber, J. L.; Valdes, P. J.; Kohler, J.

    2009-12-01

    The Arctic is a region particularly susceptible to rapid climate change. GCMs suggest a polar amplification of any global warming signal by about 1.5 due, largely, to sea ice feedbacks. The dramatic recent decline in multi-year ice cover lies outside the standard deviation of the ensemble GCM predictions and has lead to the suggestion that the Arctic Ocean could be ice free in summer as soon as ~2014. Sea ice acts as a barrier between cold air and warmer oceans during winter, as well as inhibiting evaporation from the water below during the summer. An ice free Arctic would likely have an altered hydrological cycle with more evaporation from the ocean surface leading to changes in precipitation distribution and amount. For example, changes in sea ice cover are thought to have caused changes in the mass balance of Europe’s largest ice cap, Austfona, Svalbard, by increasing accumulation. Using the U.K. Met Office Regional Climate Model (RCM), HadRM3, the atmospheric effects of the observed and projected reduction in Arctic sea ice are investigated. The RCM is driven by the atmosphere only general circulation model HadAM3. Both models are forced with sea surface temperature and sea ice obtained by extrapolating recent changes into the future using bootstrapping based on the HadISST climatology. Here we use an RCM at 25km resolution over the Arctic which captures well the present-day pattern of precipitation and provides a detailed picture of the projected changes in the behaviour of the oceanic-atmosphere moisture fluxes and how they affect precipitation.

  1. Plankton assembly in an ultra-oligotrophic Antarctic lake over the summer transition from the ice-cover to ice-free period: A size spectra approach

    NASA Astrophysics Data System (ADS)

    Rochera, Carlos; Quesada, Antonio; Toro, Manuel; Rico, Eugenio; Camacho, Antonio

    2017-03-01

    Lakes from the Antarctic maritime region experience climate change as a main stressor capable of modifying their plankton community structure and function, essentially because summer temperatures are commonly over the freezing point and the lake's ice cap thaws. This study was conducted in such seasonally ice-covered lake (Lake Limnopolar, Byers Peninsula, Livingston Is., Antarctica), which exhibits a microbial dominated pelagic food web. An important feature is also the occurrence of benthic mosses (Drepanocladus longifolius) covering the lake bottom. Plankton dynamics were investigated during the ice-thawing transition to the summer maximum. Both bacterioplankton and viral-like particles were higher near the lake's bottom, suggesting a benthic support. When the lake was under dim conditions because of the snow-and-ice cover, autotrophic picoplankters dominated at deep layers. The taxa-specific photopigments indicated dominance of picocyanobacteria among them when the light availability was lower. By contrast, larger and less edible phytoplankton dominated at the onset of the ice melting. The plankton size spectra were fitted to the continuous model of Pareto distribution. Spectra evolved similarly at two sampled depths, in surface and near the bottom, with slopes increasing until mid-January. However, slopes were less steep (i.e., size classes more uniformly distributed) at the bottom, thus denoting a more efficient utilization of resources. These findings suggest that microbial loop pathways in the lake are efficiently channelized during some periods to the metazoan production (mainly the copepod Boeckella poppei). Our results point to that trophic interactions may still occur in these lakes despite environmental harshness. This results of interest in a framework of increasing temperatures that may reduce the climatic restrictions and therefore stimulate biotic interactions.

  2. Thermo-chemical Ice Penetrator for Icy Moons

    NASA Astrophysics Data System (ADS)

    Arenberg, J. W.; Lee, G.; Harpole, G.; Zamel, J.; Sen, B.; Ross, F.; Retherford, K. D.

    2016-12-01

    The ability to place sensors or to take samples below the ice surface enables a wide variety of potential scientific investigations. Penetrating an ice cap can be accomplished via a mechanical drill, laser drill, kinetic impactor, or heated penetrator. This poster reports on the development of technology for the latter most option, namely a self-heated probe driven by an exothermic chemical reaction: a Thermo-chemical ice penetrator (TChIP). Our penetrator design employs a eutectic mix of alkali metals that produce an exothermic reaction upon contact with an icy surface. This reaction increases once the ice starts melting, so no external power is required. This technology is inspired by a classified Cold-War era program developed at Northrop Grumman for the US Navy. Terrestrial demonstration of this technology took place in the Arctic; however, this device cannot be considered high TRL for application at the icy moons of the solar system due to the environmental differences between Earth's Arctic and the icy moons. These differences demand a TChIP design specific to these cold, low mass, airless worlds. It is expected that this model of TChIP performance will be complex, incorporating all of the forces on the penetrator, gravity, the thermo-chemistry at the interface between penetrator and ice, and multi-phase heat and mass transport, and hydrodynamics. Our initial efforts are aimed at the development of a validated set of tools and simulations to predict the performance of the penetrator for both the environment found on these icy moons and for a terrestrial environment. The purpose of the inclusion of the terrestrial environment is to aid in model validation. Once developed and validated, our models will allow us to design penetrators for a specific scientific application on a specific body. This poster discusses the range of scientific investigations that are enabled by TChIP. We also introduce the development plan to advance TChIP to the point where it can be

  3. Curved cap corrugated sheet

    NASA Technical Reports Server (NTRS)

    Davis, R. C.; Bales, T. T.; Royster, D. M.; Jackson, L. R. (Inventor)

    1984-01-01

    The report describes a structure for a strong, lightweight corrugated sheet. The sheet is planar or curved and includes a plurality of corrugation segments, each segment being comprised of a generally U-shaped corrugation with a part-cylindrical crown and cap strip, and straight side walls and with secondary corrugations oriented at right angles to said side walls. The cap strip is bonded to the crown and the longitudinal edge of said cap strip extends beyond edge at the intersection between said crown and said side walls. The high strength relative to weight of the structure makes it desirable for use in aircraft or spacecraft.

  4. Ice stream activity scaled to ice sheet volume during Laurentide Ice Sheet deglaciation.

    PubMed

    Stokes, C R; Margold, M; Clark, C D; Tarasov, L

    2016-02-18

    The contribution of the Greenland and West Antarctic ice sheets to sea level has increased in recent decades, largely owing to the thinning and retreat of outlet glaciers and ice streams. This dynamic loss is a serious concern, with some modelling studies suggesting that the collapse of a major ice sheet could be imminent or potentially underway in West Antarctica, but others predicting a more limited response. A major problem is that observations used to initialize and calibrate models typically span only a few decades, and, at the ice-sheet scale, it is unclear how the entire drainage network of ice streams evolves over longer timescales. This represents one of the largest sources of uncertainty when predicting the contributions of ice sheets to sea-level rise. A key question is whether ice streams might increase and sustain rates of mass loss over centuries or millennia, beyond those expected for a given ocean-climate forcing. Here we reconstruct the activity of 117 ice streams that operated at various times during deglaciation of the Laurentide Ice Sheet (from about 22,000 to 7,000 years ago) and show that as they activated and deactivated in different locations, their overall number decreased, they occupied a progressively smaller percentage of the ice sheet perimeter and their total discharge decreased. The underlying geology and topography clearly influenced ice stream activity, but--at the ice-sheet scale--their drainage network adjusted and was linked to changes in ice sheet volume. It is unclear whether these findings can be directly translated to modern ice sheets. However, contrary to the view that sees ice streams as unstable entities that can accelerate ice-sheet deglaciation, we conclude that ice streams exerted progressively less influence on ice sheet mass balance during the retreat of the Laurentide Ice Sheet.

  5. South Polar Cap, Summer 2000

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This is the south polar cap of Mars as it appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000. In winter and early spring, this entire scene would be covered by frost. In summer, the cap shrinks to its minimum size, as shown here. Even though it is summer, observations made by the Viking orbiters in the 1970s showed that the south polar cap remains cold enough that the polar frost (seen here as white) consists of carbon dioxide. Carbon dioxide freezes at temperatures around -125o C (-193o F). Mid-summer afternoon sunlight illuminates this scene from the upper left from about 11.2o above the horizon. Soon the cap will experience sunsets; by June 2000, this pole will be in autumn, and the area covered by frost will begin to grow. Winter will return to the south polar region in December 2000. The polar cap from left to right is about 420 km (260 mi) across.

  6. The ocean mixed layer under Southern Ocean sea-ice: seasonal cycle and forcing.

    NASA Astrophysics Data System (ADS)

    Violaine, P.; Sallee, J. B.; Schmidtko, S.; Roquet, F.; Charrassin, J. B.

    2016-02-01

    The mixed-layer at the surface of the ocean is the gateway for all exchanges between air and sea. A vast area of the Southern Ocean is however seasonally capped by sea-ice, which alters this gateway and the characteristic the ocean mixed-layer. The interaction between the ocean mixed-layer and sea-ice plays a key role for water-mass formation and circulation, carbon cycle, sea-ice dynamics, and ultimately for the climate as a whole. However, the structure and characteristics of the mixed layer, as well as the processes responsible for its evolution, are poorly understood due to the lack of in-situ observations and measurements. We urgently need to better understand the forcing and the characteristics of the ocean mixed-layer under sea-ice if we are to understand and predict the world's climate. In this study, we combine a range of distinct sources of observation to overcome this lack in our understanding of the Polar Regions. Working on Elephant Seal-derived data as well as ship-based observations and Argo float data, we describe the seasonal cycle of the characteristics and stability of the ocean mixed layer over the entire Southern Ocean (South of 40°S), and specifically under sea-ice. Mixed-layer budgets of heat and freshwater are used to investigate the main forcings of the mixed-layer seasonal cycle. The seasonal variability of sea surface salinity and temperature are primarily driven by surface processes, dominated by sea-ice freshwater flux for the salt budget, and by air-sea flux for the heat budget. Ekman advection, vertical diffusivity and vertical entrainment play only secondary role.Our results suggest that changes in regional sea-ice distribution or sea-ice seasonal cycle duration, as currently observed, would widely affect the buoyancy budget of the underlying mixed-layer, and impacts large-scale water-mass formation and transformation.

  7. The ocean mixed layer under Southern Ocean sea-ice: Seasonal cycle and forcing

    NASA Astrophysics Data System (ADS)

    Pellichero, Violaine; Sallée, Jean-Baptiste; Schmidtko, Sunke; Roquet, Fabien; Charrassin, Jean-Benoît

    2017-02-01

    The oceanic mixed layer is the gateway for the exchanges between the atmosphere and the ocean; in this layer, all hydrographic ocean properties are set for months to millennia. A vast area of the Southern Ocean is seasonally capped by sea-ice, which alters the characteristics of the ocean mixed layer. The interaction between the ocean mixed layer and sea-ice plays a key role for water mass transformation, the carbon cycle, sea-ice dynamics, and ultimately for the climate as a whole. However, the structure and characteristics of the under-ice mixed layer are poorly understood due to the sparseness of in situ observations and measurements. In this study, we combine distinct sources of observations to overcome this lack in our understanding of the polar regions. Working with elephant seal-derived, ship-based, and Argo float observations, we describe the seasonal cycle of the ocean mixed-layer characteristics and stability of the ocean mixed layer over the Southern Ocean and specifically under sea-ice. Mixed-layer heat and freshwater budgets are used to investigate the main forcing mechanisms of the mixed-layer seasonal cycle. The seasonal variability of sea surface salinity and temperature are primarily driven by surface processes, dominated by sea-ice freshwater flux for the salt budget and by air-sea flux for the heat budget. Ekman advection, vertical diffusivity, and vertical entrainment play only secondary roles. Our results suggest that changes in regional sea-ice distribution and annual duration, as currently observed, widely affect the buoyancy budget of the underlying mixed layer, and impact large-scale water mass formation and transformation with far reaching consequences for ocean ventilation.

  8. Life in the Ice

    NASA Technical Reports Server (NTRS)

    Allen, C. C.; Wainwright, N. R.; Grasby, S. E.; Harvey, R. P.

    2003-01-01

    The current Martian surface environment is extremely hostile to any known form of life. The combination of subfreezing temperature, low atmospheric pressure and high ultraviolet flux, combined with desiccated and possibly oxidizing soil, could destroy even the hardiest microorganisms. The Viking biology experiments are generally interpreted to indicate that the surface of Mars is currently devoid of life and organic molecules at the part-per-billion level. Speculation on the possibility of extant or preserved microbial life on Mars thus centers on refuges in some manner protected from the current surface environment, either in space or time. Terrestrial analogs include hydrothermal systems, lakes, caves and subsurface aquifers as well as more clement conditions in the distant past. We are examining the evidence for microbiology in Earth's glaciated polar regions as analogs to the polar caps of Mars. This research concerns the detection of microorganisms or their preserved remains at the surface and within polar glacial ice.

  9. 21 CFR 884.5250 - Cervical cap.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cervical cap. 884.5250 Section 884.5250 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES... cap. (a) Identification. A cervical cap is a flexible cuplike receptacle that fits over the cervix to...

  10. Leveraging Cloud Technology to Provide a Responsive, Reliable and Scalable Backend for the Virtual Ice Sheet Laboratory Using the Ice Sheet System Model and Amazon's Elastic Compute Cloud

    NASA Astrophysics Data System (ADS)

    Perez, G. L.; Larour, E. Y.; Halkides, D. J.; Cheng, D. L. C.

    2015-12-01

    The Virtual Ice Sheet Laboratory(VISL) is a Cryosphere outreach effort byscientists at the Jet Propulsion Laboratory(JPL) in Pasadena, CA, Earth and SpaceResearch(ESR) in Seattle, WA, and the University of California at Irvine (UCI), with the goal of providing interactive lessons for K-12 and college level students,while conforming to STEM guidelines. At the core of VISL is the Ice Sheet System Model(ISSM), an open-source project developed jointlyat JPL and UCI whose main purpose is to model the evolution of the polar ice caps in Greenland and Antarctica. By using ISSM, VISL students have access tostate-of-the-art modeling software that is being used to conduct scientificresearch by users all over the world. However, providing this functionality isby no means simple. The modeling of ice sheets in response to sea and atmospheric temperatures, among many other possible parameters, requiressignificant computational resources. Furthermore, this service needs to beresponsive and capable of handling burst requests produced by classrooms ofstudents. Cloud computing providers represent a burgeoning industry. With majorinvestments by tech giants like Amazon, Google and Microsoft, it has never beeneasier or more affordable to deploy computational elements on-demand. This isexactly what VISL needs and ISSM is capable of. Moreover, this is a promisingalternative to investing in expensive and rapidly devaluing hardware.

  11. CENTRIFUGE END CAP

    DOEpatents

    Beams, J.W.; Snoddy, L.B.

    1960-08-01

    An end cap for ultra-gas centrifuges is designed to impart or remove angular momentum to or from the gas and to bring the entering gas to the temperature of the gas inside the centrifuge. The end cap is provided with slots or fins for adjusting the temperature and the angular momentum of the entering gas to the temperature and momentum of the gas in the centrifuge and is constructed to introduce both the inner and the peripheral stream into the centrifuge.

  12. ROTOR END CAP

    DOEpatents

    Rushing, F.C.

    1959-02-01

    An improved end cap is described for the cylindrical rotor or bowl of a high-speed centrifugal separator adapted to permit free and efficient continuous counter current flow of gas therethrough for isotope separation. The end cap design provides for securely mounting the same to the hollow central shaft and external wall of the centrifuge. Passageways are incorporated and so arranged as to provide for continuous counter current flow of the light and heavy portions of the gas fed to the centrifuge.

  13. Continuous, Pulsed Export of Methane-Supersaturated Meltwaters from the Bed of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Lamarche-Gagnon, G.; Wadham, J.; Beaton, A.; Fietzek, P.; Stanley, K. M.; Tedstone, A.; Sherwood Lollar, B.; Lacrampe Couloume, G.; Telling, J.; Liz, B.; Hawkings, J.; Kohler, T. J.; Zarsky, J. D.; Stibal, M.; Mowlem, M. C.

    2016-12-01

    Both past and present ice sheets have been proposed to cap large quantities of methane (CH4), on orders of magnitude significant enough to impact global greenhouse gas concentrations during periods of rapid ice retreat. However, to date most evidence for sub-ice sheet methane has been indirect, derived from calculations of the methanogenic potential of basal-ice microbial communities and biogeochemical models; field-based empirical measurements are lacking from large ice sheet catchments. Here, we present the first continuous, in situ record of dissolved methane export from a large catchment of the Greenland Ice Sheet (GrIS) in South West Greenland from May-July 2015. Our results indicate that glacial runoff was continuously supersaturated with methane over the observation period (dissolved CH4 concentrations of 30-700 nM), with total methane flux rising as subglacial discharge increased. Periodic subglacial drainage events, characterised by rapid changes (i.e. pulses) in meltwater hydrochemistry, also coincided with a rise in methane concentrations. We argue that these are likely indicative of the flushing of subglacial reservoirs of CH4 beneath the ice sheet. Total methane export was relatively modest when compared to global methane budgets, but too high to be explained by previously determined methanogenic rates from Greenland basal ice. Discrepancies between estimated Greenland methane reserves and observed fluxes stress the need to further investigate GrIS methane fluxes and sources, and suggest a more biogeochemically active subglacial environment than previously considered. Results indicate that future warming, and a coincident increase in ice melt rates, would likely make the GrIS, and by extension the Antarctic Ice Sheet, more significant sources of atmospheric methane, consequently acting as a positive feedback to a warming climate.

  14. High Ice Water Concentrations in the 19 August 2015 Coastal Mesoconvective System

    NASA Technical Reports Server (NTRS)

    Proctor, Fred H.; Harrah, Steven; Switzer, George F.; Strickland, Justin K.; Hunt, Patricia J.

    2017-01-01

    During August 2015, NASA's DC-8 research aircraft was flown into High Ice Water Content (HIWC) events as part of a three-week campaign to collect airborne radar data and to obtain measurements from microphysical probes. Goals for this flight campaign included improved characterization of HIWC events, especially from an airborne radar perspective. This paper focuses on one of the flight days, in which a coastal mesoscale convective system (MCS) was investigated for HIWC conditions. The system appears to have been maintained by bands of convection flowing in from the Gulf of Mexico. These convective bands were capped by a large cloud canopy, which masks the underlying structure if viewed from an infrared sensing satellite. The DC-8 was equipped with an IsoKinetic Probe that measured ice concentrations of up to 2.3 g m(exp -3) within the cloud canopy of this system. Sustained measurements of ice crystals with concentrations exceeding 1 g m(exp -3) were encountered for up to ten minutes of flight time. Airborne Radar reflectivity factors were found to be weak within these regions of high ice water concentrations, suggesting that Radar detection of HIWC would be a challenging endeavor. This case is then investigated using a three-dimensional numerical cloud model. Profiles of ice water concentrations and radar reflectivity factor demonstrate similar magnitudes and scales between the flight measurements and model simulation. Also discussed are recent modifications to the numerical model's ice-microphysics that are based on measurements during the flight campaign. The numerical model and its updated ice-microphysics are further validated with a simulation of a well-known case of a supercell hailstorm measured during the Cooperative Convective Precipitation Experiment. Differences in HIWC between the continental supercell and the coastal MCS are discussed.

  15. The 1994 EUROMET collection of micrometeorites at Cap-Prudhomme, Antarctica

    NASA Astrophysics Data System (ADS)

    Maurette, M.; Immel, G.; Engrand, C.; Kurat, G.; Pillinger, C. T.

    1994-07-01

    Advance funding from IFRTP (Institut Francais pour la Recherche et pour la Technique Polaire) for micrometeorite collection at Cap-Prudhomme has allowed construction of a new micrometeorite 'factory,' conceived to greatly reduce contamination of the ultraclean ice by our activities. The potential problems include fly ash, rust grains, fuel spills 'sticking to the shoes,' and trace elements from the plasticizers used in plastic tubing. In the new factory, intended to produce and then cycle 10-15 tons of melt ice water per day, all parts exposed to water were replaced by either stainless steel or teflon. After examination with a microscope and their transfer into teflon and or glass vials, all samples were frozen the day of their collection. The factory operated from December 15, 1993, through February 6, 1994. Problems included injuries as well as very bad weather conditions, characterized by both the heaviest snow falls observed and unexpected gusts from a blizzard. Also, several new components of the factory did not function properly under the extreme conditions of Antarctica. Our major objective was to obtain the 'cleanest' and 'purest' 25-50 microns micrometeorites ever collected in Antarctica, for comparison with stratospheric Interplanetary Dust Particles (IDPs). We could not fulfill this premise, but we recovered the best 100-400-micron-size fraction of 'giant' micrometeorites ever collected on Earth. Our 26 daily collections are listed,refering to an 'index of quality.' Aliquots of these daily collections will be distributed to major institutions in Austria, England, the U.S.A., and Japan, to be preserved for future generations. The Antarctica ice sheet is truly a gigantic, ultraclean, and inexhaustible micrometeorite collector, but it is very tricky to recover 'ultraclean' micrometeorites from it.

  16. Ice Bridge Antarctic Sea Ice

    NASA Image and Video Library

    2009-10-21

    An iceberg is seen out the window of NASA's DC-8 research aircraft as it flies 2,000 feet above the Amundsen Sea in West Antarctica on Wednesday, Oct., 21, 2009. This was the fourth science flight of NASA’s Operation Ice Bridge airborne Earth science mission to study Antarctic ice sheets, sea ice, and ice shelves. Photo Credit: (NASA/Jane Peterson)

  17. South Polar Residual Cap Geomorphology and Inferred Environmental Changes

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Ingersoll, A.; Pathare, A.

    2003-12-01

    The CO2 southern residual cap (SRC) both controls circulation patterns regionally and buffers the atmospheric pressure globally. In turn this CO2 deposit is affected by changes in environmental conditions wrought by external forces such as dust storm activity. Mars Global Surveyor data of this area have revealed a rich variety of geomorphic features (1) of which there are several distinct classes. These different classes may be end members of the same basic process of insolation driven ablation. We are currently investigating two types of SRC features. Swiss-cheese features (SCF) are depressions characterized by flat floors and steep walls, which retreat 1-3 meters each Martian year (2). In some regions they have a definite symmetry axis along the north-south direction (3). After the seasonal frost disappears the residual ice exposed in the walls has a lower albedo (4). Previously (5) we modeled the evolution and growth of these depressions as a hole in a layer of CO2 ice underlain by water ice, which best explains their morphologic and thermal properties. The observed thickness of the CO2 slab can be as high as 8 meters but in general is much lower. Larger SCF?s commonly possess a raised central island of CO2 surrounded by a moat that penetrates to the underlying water ice (3). The fast rate of wall retreat observed (2) combined with the small sizes of the SCF?s indicate that all SCF?s visible today were created geologically recently. Within a particular region the size distribution is quite narrow (3): no larger (older) or smaller (younger) features were seen indicating that some relatively abrupt change in environmental conditions initiated the growth of this particular population of features. Fingerprint terrain (1) are areas with evenly spaced parallel ridges, which are steeper on one side. These ridges may have small areas of water ice exposed in the intervening troughs. Their wavelength is on the order of 70-90m with the steep edges facing northeast although

  18. Emerging investigator series: a 14-year depositional ice record of perfluoroalkyl substances in the High Arctic.

    PubMed

    MacInnis, John J; French, Katherine; Muir, Derek C G; Spencer, Christine; Criscitiello, Alison; De Silva, Amila O; Young, Cora J

    2017-01-25

    To improve understanding of long-range transport of perfluoroalkyl substances to the High Arctic, samples were collected from a snow pit on the Devon Ice Cap in spring 2008. Snow was analyzed for perfluoroalkyl acids (PFAAs), including perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs), as well as perfluorooctane sulfonamide (FOSA). PFAAs were detected in all samples dated from 1993 to 2007. PFAA fluxes ranged from <1 to hundreds of ng per m 2 per year. Flux ratios of even-odd PFCA homologues were mostly between 0.5 and 2, corresponding to molar ratios expected from atmospheric oxidation of fluorotelomer compounds. Concentrations of perfluorobutanoic acid (PFBA) were much higher than other PFCAs, suggesting PFBA loading on the Devon Ice Cap is influenced by additional sources, such as the oxidation of heat transfer fluids. All PFCA fluxes increased with time, while PFSA fluxes generally decreased with time. No correlations were observed between PFAAs and the marine aerosol tracer, sodium. Perfluoro-4-ethylcyclohexanesulfonate (PFECHS) was detected for the first time in an atmospherically - derived sample, and its presence may be attributed to aircraft hydraulic system leakage. Observations of PFAAs from these samples provide further evidence that atmospheric oxidation of volatile precursors is an important source of PFAAs to the Arctic environment.

  19. Effect of chitosan-carvacrol coating on the quality of Pacific white shrimp during iced storage as affected by caprylic acid.

    PubMed

    Wang, Qianyun; Lei, Jun; Ma, Junjie; Yuan, Gaofeng; Sun, Haiyan

    2018-01-01

    This study aimed to investigate the effect of chitosan-carvacrol coating with or without caprylic acid (CAP) on the quality of Pacific white shrimp (Litopenaeus vannamei) during 10days of iced storage. The result showed that chitosan-carvacrol coating significantly inhibited the increase in total aerobic plate count (TPC), pH and total volatile basic nitrogen content (TVB-N) of shrimp in comparison with the control. Chitosan-carvacrol coating also delayed the melanosis formation and changes of ΔE values, and improved the texture and sensory properties of shrimp. Moreover, incorporation of CAP potentiated the efficacy of chitosan-carvacrol coating in retarding the increase of TPC and TVB-N. Incorporation of CAP into chitosan-carvacrol coating also enabled the texture characteristics of shrimp to be retained greater degrees. These results suggested that chitosan-carvacrol coating may be promising to be used as active packaging for extending the shelf life, and incorporation of CAP may enhance the efficacy of the coating. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Sedimentary record of a fluctuating ice margin from the Pennsylvanian of western Gondwana: Paraná Basin, southern Brazil

    NASA Astrophysics Data System (ADS)

    Vesely, Fernando F.; Trzaskos, Barbara; Kipper, Felipe; Assine, Mario Luis; Souza, Paulo A.

    2015-08-01

    The Paraná Basin is a key locality in the context of the Late Paleozoic Ice Age (LPIA) because of its location east of the Andean proto-margin of Gondwana and west of contiguous interior basins today found in western Africa. In this paper we document the sedimentary record associated with an ice margin that reached the eastern border of the Paraná Basin during the Pennsylvanian, with the aim of interpreting the depositional environments and discussing paleogeographic implications. The examined stratigraphic succession is divided in four stacked facies associations that record an upward transition from subglacial to glaciomarine environments. Deposition took place during deglaciation but was punctuated by minor readvances of the ice margin that deformed the sediment pile. Tillites, well-preserved landforms of subglacial erosion and glaciotectonic deformational structures indicate that the ice flowed to the north and northwest and that the ice margin did not advance far throughout the basin during the glacial maximum. Consequently, time-equivalent glacial deposits that crop out in other localities of eastern Paraná Basin are better explained by assuming multiple smaller ice lobes instead of one single large glacier. These ice lobes flowed from an ice cap covering uplifted lands now located in western Namibia, where glacial deposits are younger and occur confined within paleovalleys cut onto the Precambrian basement. This conclusion corroborates the idea of a topographically-controlled ice-spreading center in southwestern Africa and does not support the view of a large polar ice sheet controlling deposition in the Paraná Basin during the LPIA.

  1. Last Glacial Maximum cirque glaciation in Ireland and implications for reconstructions of the Irish Ice Sheet

    NASA Astrophysics Data System (ADS)

    Barth, Aaron M.; Clark, Peter U.; Clark, Jorie; McCabe, A. Marshall; Caffee, Marc

    2016-06-01

    Reconstructions of the extent and height of the Irish Ice Sheet (IIS) during the Last Glacial Maximum (LGM, ∼19-26 ka) are widely debated, in large part due to limited age constraints on former ice margins and due to uncertainties in the origin of the trimlines. A key area is southwestern Ireland, where various LGM reconstructions range from complete coverage by a contiguous IIS that extends to the continental shelf edge to a separate, more restricted southern-sourced Kerry-Cork Ice Cap (KCIC). We present new 10Be surface exposure ages from two moraines in a cirque basin in the Macgillycuddy's Reeks that provide a unique and unequivocal constraint on ice thickness for this region. Nine 10Be ages from an outer moraine yield a mean age of 24.5 ± 1.4 ka while six ages from an inner moraine yield a mean age of 20.4 ± 1.2 ka. These ages show that the northern flanks of the Macgillycuddy's Reeks were not covered by the IIS or a KCIC since at least 24.5 ± 1.4 ka. If there was more extensive ice coverage over the Macgillycuddy's Reeks during the LGM, it occurred prior to our oldest ages.

  2. 35 GHz Measurements of CO2 Crystals for Simulating Observations of the Martian Polar Caps

    NASA Technical Reports Server (NTRS)

    Foster, J. L.; Chang, A. T. C.; Hall, D. K.; Tait, A. B.; Barton, J. S.

    1998-01-01

    In order to learn more about the Martian polar caps, it is important to compare and contrast the behavior of both frozen H2O and CO2 in different parts of the electromagnetic spectrum. Relatively little attention has been given, thus far, to observing the thermal microwave part of the spectrum. In this experiment, passive microwave radiation emanating from within a 33 cm snowpack was measured with a 35 GHz hand-held radiometer, and in addition to the natural snow measurements, the radiometer was used to measure the microwave emission and scattering from layers of manufactured CO2 (dry ice). A 1 m x 2 m plate of aluminum sheet metal was positioned beneath the natural snow so that microwave emissions from the underlying soil layers would be minimized. Compared to the natural snow crystals, results for the dry ice layers exhibit lower' microwave brightness temperatures for similar thicknesses, regardless of the incidence angle of the radiometer. For example, at 50 degree H (horizontal polarization) and with a covering of 21 cm of snow and 18 cm of dry ice, the brightness temperatures were 150 K and 76 K, respectively. When the snow depth was 33 cm, the brightness temperature was 144 K, and when the total thickness of the dry ice was 27 cm, the brightness temperature was 86 K. The lower brightness temperatures are due to a combination of the lower physical temperature and the larger crystal sizes of the commercial CO2 Crystals compared to the snow crystals. As the crystal size approaches the size of the microwave wavelength, it scatters microwave radiation more effectively, thus lowering the brightness temperature. The dry ice crystals in this experiment were about an order of magnitude larger than the snow crystals and three orders of magnitude larger than the CO2 Crystals produced in the cold stage of a scanning electron microscope. Spreading soil, approximately 2 mm in thickness, on the dry ice appeared to have no effect on the brightness temperatures.

  3. Instability of water-ice interface under turbulent flow

    NASA Astrophysics Data System (ADS)

    Izumi, Norihiro; Naito, Kensuke; Yokokawa, Miwa

    2015-04-01

    It is known that plane water-ice interface becomes unstable to evolve into a train of waves. The underside of ice formed on the water surface of rivers are often observed to be covered with ice ripples. Relatively steep channels which discharge melting water from glaciers are characterized by beds covered with a series of steps. Though the flowing agent inducing instability is not water but gas including water vapor, a similar train of steps have been recently observed on the Polar Ice Caps on Mars (Spiral Troughs). They are expected to be caused by the instability of water-ice interface induced by flowing fluid on ice. There have been some studies on this instability in terms of linear stability analysis. Recently, Caporeale and Ridolfi (2012) have proposed a complete linear stability analysis in the case of laminar flow, and found that plane water-ice interface is unstable in the range of sufficiently large Reynolds numbers, and that the important parameters are the Reynolds number, the slope angle, and the water surface temperature. However, the flow inducing instability on water-ice interface in the field should be in the turbulent regime. Extension of the analysis to the case of fully developed turbulent flow with larger Reynolds numbers is needed. We have performed a linear stability analysis on the instability of water-ice interface under turbulent flow conditions with the use of the Reynolds-averaged Navier-Stokes equations with the mixing length turbulent model, the continuity equation of flow, the diffusion/dispersion equation of heat, and the Stefan equation. In order to reproduce the accurate velocity distribution and the heat transfer in the vicinity of smooth walls with the use of the mixing length model, it is important to take into account of the rapid decrease in the mixing length in the viscous sublayer. We employ the Driest model (1956) to the formulation. In addition, as the thermal boundary condition at the water surface, we describe the

  4. Ice cream structure modification by ice-binding proteins.

    PubMed

    Kaleda, Aleksei; Tsanev, Robert; Klesment, Tiina; Vilu, Raivo; Laos, Katrin

    2018-04-25

    Ice-binding proteins (IBPs), also known as antifreeze proteins, were added to ice cream to investigate their effect on structure and texture. Ice recrystallization inhibition was assessed in the ice cream mixes using a novel accelerated microscope assay and the ice cream microstructure was studied using an ice crystal dispersion method. It was found that adding recombinantly produced fish type III IBPs at a concentration 3 mg·L -1 made ice cream hard and crystalline with improved shape preservation during melting. Ice creams made with IBPs (both from winter rye, and type III IBP) had aggregates of ice crystals that entrapped pockets of the ice cream mixture in a rigid network. Larger individual ice crystals and no entrapment in control ice creams was observed. Based on these results a model of ice crystals aggregates formation in the presence of IBPs was proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Simple energy balance model resolving the seasons and the continents - Application to the astronomical theory of the ice ages

    NASA Technical Reports Server (NTRS)

    North, G. R.; Short, D. A.; Mengel, J. G.

    1983-01-01

    An analysis is undertaken of the properties of a one-level seasonal energy balance climate model having explicit, two-dimensional land-sea geography, where land and sea surfaces are strictly distinguished by the local thermal inertia employed and transport is governed by a smooth, latitude-dependent diffusion mechanism. Solutions of the seasonal cycle for the cases of both ice feedback exclusion and inclusion yield good agreements with real data, using minimal turning of the adjustable parameters. Discontinuous icecap growth is noted for both a solar constant that is lower by a few percent and a change of orbital elements to favor cool Northern Hemisphere summers. This discontinuous sensitivity is discussed in the context of the Milankovitch theory of the ice ages, and the associated branch structure is shown to be analogous to the 'small ice cap' instability of simpler models.

  6. Myofibril growth during cardiac hypertrophy is regulated through dual phosphorylation and acetylation of the actin capping protein CapZ

    PubMed Central

    Lin, Ying-Hsi; Warren, Chad M.; Li, Jieli; McKinsey, Timothy A.; Russell, Brenda

    2016-01-01

    The mechanotransduction signaling pathways initiated in heart muscle by increased mechanical loading are known to lead to long-term transcriptional changes and hypertrophy, but the rapid events for adaptation at the sarcomeric level are not fully understood. The goal of this study was to test the hypothesis that actin filament assembly during cardiomyocyte growth is regulated by post-translational modifications (PTMs) of CapZβ1. In rapidly hypertrophying neonatal rat ventricular myocytes (NRVMs) stimulated by phenylephrine (PE), two-dimensional gel electrophoresis (2DGE) of CapZβ1 revealed a shift toward more negative charge. Consistent with this, mass spectrometry identified CapZβ1 phosphorylation on serine-204 and acetylation on lysine-199, two residues which are near the actin binding surface of CapZβ1. Ectopic expression of dominant negative PKCε (dnPKCε) in NRVMs blunted the PE-induced increase in CapZ dynamics, as evidenced by the kinetic constant (Kfrap) of fluorescence recovery after photobleaching (FRAP), and concomitantly reduced phosphorylation and acetylation of CapZβ1. Furthermore, inhibition of class I histone deacetylases (HDACs) increased lysine-199 acetylation on CapZβ1, which increased Kfrap of CapZ and stimulated actin dynamics. Finally, we show that PE treatment of NRVMs results in decreased binding of HDAC3 to myofibrils, suggesting a signal-dependent mechanism for the regulation of sarcomere-associated CapZβ1 acetylation. Taken together, this dual regulation through phosphorylation and acetylation of CapZβ1 provides a novel model for the regulation of myofibril growth during cardiac hypertrophy. PMID:27185186

  7. Vertical Distribution of Dust and Water Ice Aerosols from CRISM Limb-geometry Observations

    NASA Technical Reports Server (NTRS)

    Smith, Michael Doyle; Wolff, Michael J.; Clancy, Todd; Kleinbohl, Armin; Murchie, Scott L.

    2013-01-01

    [1] Near-infrared spectra taken in a limb-viewing geometry by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the Mars Reconnaissance Orbiter provide a useful tool for probing atmospheric structure. Specifically, the observed radiance as a function of wavelength and height above the limb enables the vertical distribution of both dust and water ice aerosols to be retrieved. More than a dozen sets of CRISM limb observations have been taken so far providing pole-to-pole cross sections, spanning more than a full Martian year. Radiative transfer modeling is used to model the observations taking into account multiple scattering from aerosols and the spherical geometry of the limb observations. Both dust and water ice vertical profiles often show a significant vertical structure for nearly all seasons and latitudes that is not consistent with the well-mixed or Conrath-v assumptions that have often been used in the past for describing aerosol vertical profiles for retrieval and modeling purposes. Significant variations are seen in the retrieved vertical profiles of dust and water ice aerosol as a function of season. Dust typically extends to higher altitudes (approx. 40-50km) during the perihelion season than during the aphelion season (<20km), and the Hellas region consistently shows more dust mixed to higher altitudes than other locations. Detached water ice clouds are common, and water ice aerosols are observed to cap the dust layer in all seasons.

  8. 21 CFR 888.3000 - Bone cap.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Bone cap. 888.3000 Section 888.3000 Food and Drugs... ORTHOPEDIC DEVICES Prosthetic Devices § 888.3000 Bone cap. (a) Identification. A bone cap is a mushroom... polyethylene. It is used to cover the severed end of a long bone, such as the humerus or tibia, to control bone...

  9. 21 CFR 888.3000 - Bone cap.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Bone cap. 888.3000 Section 888.3000 Food and Drugs... ORTHOPEDIC DEVICES Prosthetic Devices § 888.3000 Bone cap. (a) Identification. A bone cap is a mushroom... polyethylene. It is used to cover the severed end of a long bone, such as the humerus or tibia, to control bone...

  10. 21 CFR 888.3000 - Bone cap.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Bone cap. 888.3000 Section 888.3000 Food and Drugs... ORTHOPEDIC DEVICES Prosthetic Devices § 888.3000 Bone cap. (a) Identification. A bone cap is a mushroom... polyethylene. It is used to cover the severed end of a long bone, such as the humerus or tibia, to control bone...

  11. 21 CFR 888.3000 - Bone cap.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Bone cap. 888.3000 Section 888.3000 Food and Drugs... ORTHOPEDIC DEVICES Prosthetic Devices § 888.3000 Bone cap. (a) Identification. A bone cap is a mushroom... polyethylene. It is used to cover the severed end of a long bone, such as the humerus or tibia, to control bone...

  12. 21 CFR 888.3000 - Bone cap.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Bone cap. 888.3000 Section 888.3000 Food and Drugs... ORTHOPEDIC DEVICES Prosthetic Devices § 888.3000 Bone cap. (a) Identification. A bone cap is a mushroom... polyethylene. It is used to cover the severed end of a long bone, such as the humerus or tibia, to control bone...

  13. Experimental provocation of 'ice-cream headache' by ice cubes and ice water.

    PubMed

    Mages, Stephan; Hensel, Ole; Zierz, Antonia Maria; Kraya, Torsten; Zierz, Stephan

    2017-04-01

    Background There are various studies on experimentally provoked 'ice-cream headache' or 'headache attributed to ingestion or inhalation of a cold stimulus' (HICS) using different provocation protocols. The aim of this study was to compare two provocation protocols. Methods Ice cubes pressed to the palate and fast ingestion of ice water were used to provoke HICS and clinical features were compared. Results The ice-water stimulus provoked HICS significantly more often than the ice-cube stimulus (9/77 vs. 39/77). Ice-water-provoked HICS had a significantly shorter latency (median 15 s, range 4-97 s vs. median 68 s, range 27-96 s). There was no difference in pain localisation. Character after ice-cube stimulation was predominantly described as pressing and after ice-water stimulation as stabbing. A second HICS followed in 10/39 (26%) of the headaches provoked by ice water. Lacrimation occurred significantly more often in volunteers with than in those without HICS. Discussion HICS provoked by ice water was more frequent, had a shorter latency, different pain character and higher pain intensity than HICS provoked by ice cubes. The finding of two subsequent HICS attacks in the same volunteers supports the notion that two types of HICS exist. Lacrimation during HICS indicates involvement of the trigeminal-autonomic reflex.

  14. Breakup of Pack Ice, Antarctic Ice Shelf

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Breakup of Pack Ice along the periphery of the Antarctic Ice Shelf (53.5S, 3.0E) produced this mosaic of ice floes off the Antarctic Ice Shelf. Strong offshore winds, probably associated with strong katabatic downdrafts from the interior of the continent, are seen peeling off the edges of the ice shelf into long filamets of sea ice, icebergs, bergy bits and growlers to flow northward into the South Atlantic Ocean. 53.5S, 3.0E

  15. Periodic bedforms generated by sublimation on terrestrial and martian ice sheets under the influence of the turbulent atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Bordiec, Maï; Carpy, Sabrina; Perret, Laurent; Bourgeois, Olivier; Massé, Marion

    2017-04-01

    growth rate, migration direction and velocity of the ripples. The present approach has been first used to model the atmospheric flow developing over wavy terrestrial ice bedforms in the Blue Ice Areas of Antarctica. Both the predicted preferential wavelength and propagation direction of the ice ripple have been found to be in agreement with the observations. The present model has subsequently been applied to the same flow configuration but on Mars. Ice ripples are indeed likely to exist there, given that temperature and pressure conditions in the martian atmosphere favors sublimation/condensation as the dominant mass-transport process. The model has proved able to predict not only the development of ice-ripple on Mars (i.e it showed that some most amplified wavelength also exist under Martian atmospheric conditions) but also both their wavelength and propagation direction. The preferential wavelength of ices-ripples on the Martian polar caps appears to be much larger than on the Earth. Finally, a good match between the most likely ice-ripple wavelength predicted by the model and those deduced from recent available observations of the surface of Martian polar caps is shown.

  16. Effects of rooting and tree growth of selected woodland species on cap integrity in a mineral capped landfill site.

    PubMed

    Hutchings, T R; Moffat, A J; Kemp, R A

    2001-06-01

    The above and below ground growth of three tree species (Alnus glutinosa, Pinus nigra var. maritima and Acer pseudoplatanus) was studied on a containment landfill site at Waterford, Hertfordshire, UK. Tree root architecture was studied using soil inspection pits excavated next to 12 trees of each species and mapped in detail. Tree height was related to soil thickness over the compacted mineral cap. No roots entered the cap where soil thickness was 1.3 m, but a few roots, especially of alder, were observed within it when the soil cover was 1.0 m or less. Micromorphological analysis of undisturbed samples of the mineral cap suggested that roots exploited weaknesses in the cap rather than actively causing penetration into it. Alder roots were more tolerant of anaerobic conditions within the cap than the other species examined. The results confirm that mineral caps should be covered by 1.5 m of soil or soil-forming material if tree establishment is intended over a restored landfill site, unless protected by other parts of a composite capping system.

  17. Ice-shell purification of ice-binding proteins.

    PubMed

    Marshall, Craig J; Basu, Koli; Davies, Peter L

    2016-06-01

    Ice-affinity purification is a simple and efficient method of purifying to homogeneity both natural and recombinant ice-binding proteins. The purification involves the incorporation of ice-binding proteins into slowly-growing ice and the exclusion of other proteins and solutes. In previous approaches, the ice was grown around a hollow brass finger through which coolant was circulated. We describe here an easily-constructed apparatus that employs ice affinity purification that not only shortens the time for purification from 1-2 days to 1-2 h, but also enhances yield and purity. In this apparatus, the surface area for the separation was increased by extracting the ice-binding proteins into an ice-shell formed inside a rotating round-bottom flask partially submerged in a sub-zero bath. In principle, any ice-binding compound can be recovered from liquid solution, and the method is readily scalable. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Quantification of Ice Accretions for Icing Scaling Evaluations

    NASA Technical Reports Server (NTRS)

    Ruff, Gary A.; Anderson, David N.

    2003-01-01

    The comparison of ice accretion characteristics is an integral part of aircraft icing research. It is often necessary to compare an ice accretion obtained from a flight test or numerical simulation to one produced in an icing wind tunnel or for validation of an icing scaling method. Traditionally, this has been accomplished by overlaying two-dimensional tracings of ice accretion shapes. This paper addresses the basic question of how to compare ice accretions using more quantitative methods. For simplicity, geometric characteristics of the ice accretions are used for the comparison. One method evaluated is a direct comparison of the percent differences of the geometric measurements. The second method inputs these measurements into a fuzzy inference system to obtain a single measure of the goodness of the comparison. The procedures are demonstrated by comparing ice shapes obtained in the Icing Research Tunnel at NASA Glenn Research Center during recent icing scaling tests. The results demonstrate that this type of analysis is useful in quantifying the similarity of ice accretion shapes and that the procedures should be further developed by expanding the analysis to additional icing data sets.

  19. Ice Accretions and Icing Effects for Modern Airfoils

    NASA Technical Reports Server (NTRS)

    Addy, Harold E., Jr.

    2000-01-01

    Icing tests were conducted to document ice shapes formed on three different two-dimensional airfoils and to study the effects of the accreted ice on aerodynamic performance. The models tested were representative of airfoil designs in current use for each of the commercial transport, business jet, and general aviation categories of aircraft. The models were subjected to a range of icing conditions in an icing wind tunnel. The conditions were selected primarily from the Federal Aviation Administration's Federal Aviation Regulations 25 Appendix C atmospheric icing conditions. A few large droplet icing conditions were included. To verify the aerodynamic performance measurements, molds were made of selected ice shapes formed in the icing tunnel. Castings of the ice were made from the molds and placed on a model in a dry, low-turbulence wind tunnel where precision aerodynamic performance measurements were made. Documentation of all the ice shapes and the aerodynamic performance measurements made during the icing tunnel tests is included in this report. Results from the dry, low-turbulence wind tunnel tests are also presented.

  20. Sunlight, Sea Ice, and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover

    DTIC Science & Technology

    2013-09-30

    Sea Ice , and the Ice Albedo Feedback in a...COVERED 00-00-2013 to 00-00-2013 4. TITLE AND SUBTITLE Sunlight, Sea Ice , and the Ice Albedo Feedback in a Changing Arctic Sea Ice Cover 5a...during a period when incident solar irradiance is large increasing solar heat input to the ice . Seasonal sea ice typically has a smaller albedo

  1. Modelling West Antarctic ice sheet growth and collapse through the past five million years.

    PubMed

    Pollard, David; DeConto, Robert M

    2009-03-19

    The West Antarctic ice sheet (WAIS), with ice volume equivalent to approximately 5 m of sea level, has long been considered capable of past and future catastrophic collapse. Today, the ice sheet is fringed by vulnerable floating ice shelves that buttress the fast flow of inland ice streams. Grounding lines are several hundred metres below sea level and the bed deepens upstream, raising the prospect of runaway retreat. Projections of future WAIS behaviour have been hampered by limited understanding of past variations and their underlying forcing mechanisms. Its variation since the Last Glacial Maximum is best known, with grounding lines advancing to the continental-shelf edges around approximately 15 kyr ago before retreating to near-modern locations by approximately 3 kyr ago. Prior collapses during the warmth of the early Pliocene epoch and some Pleistocene interglacials have been suggested indirectly from records of sea level and deep-sea-core isotopes, and by the discovery of open-ocean diatoms in subglacial sediments. Until now, however, little direct evidence of such behaviour has been available. Here we use a combined ice sheet/ice shelf model capable of high-resolution nesting with a new treatment of grounding-line dynamics and ice-shelf buttressing to simulate Antarctic ice sheet variations over the past five million years. Modelled WAIS variations range from full glacial extents with grounding lines near the continental shelf break, intermediate states similar to modern, and brief but dramatic retreats, leaving only small, isolated ice caps on West Antarctic islands. Transitions between glacial, intermediate and collapsed states are relatively rapid, taking one to several thousand years. Our simulation is in good agreement with a new sediment record (ANDRILL AND-1B) recovered from the western Ross Sea, indicating a long-term trend from more frequently collapsed to more glaciated states, dominant 40-kyr cyclicity in the Pliocene, and major retreats at

  2. Genetic ablation of root cap cells in Arabidopsis

    NASA Technical Reports Server (NTRS)

    Tsugeki, R.; Fedoroff, N. V.

    1999-01-01

    The root cap is increasingly appreciated as a complex and dynamic plant organ. Root caps sense and transmit environmental signals, synthesize and secrete small molecules and macromolecules, and in some species shed metabolically active cells. However, it is not known whether root caps are essential for normal shoot and root development. We report the identification of a root cap-specific promoter and describe its use to genetically ablate root caps by directing root cap-specific expression of a diphtheria toxin A-chain gene. Transgenic toxin-expressing plants are viable and have normal aerial parts but agravitropic roots, implying loss of root cap function. Several cell layers are missing from the transgenic root caps, and the remaining cells are abnormal. Although the radial organization of the roots is normal in toxin-expressing plants, the root tips have fewer cytoplasmically dense cells than do wild-type root tips, suggesting that root meristematic activity is lower in transgenic than in wild-type plants. The roots of transgenic plants have more lateral roots and these are, in turn, more highly branched than those of wild-type plants. Thus, root cap ablation alters root architecture both by inhibiting root meristematic activity and by stimulating lateral root initiation. These observations imply that the root caps contain essential components of the signaling system that determines root architecture.

  3. Comparisons of Cubed Ice, Crushed Ice, and Wetted Ice on Intramuscular and Surface Temperature Changes

    PubMed Central

    Dykstra, Joseph H; Hill, Holly M; Miller, Michael G; Cheatham, Christopher C; Michael, Timothy J; Baker, Robert J

    2009-01-01

    Context: Many researchers have investigated the effectiveness of different types of cold application, including cold whirlpools, ice packs, and chemical packs. However, few have investigated the effectiveness of different types of ice used in ice packs, even though ice is one of the most common forms of cold application. Objective: To evaluate and compare the cooling effectiveness of ice packs made with cubed, crushed, and wetted ice on intramuscular and skin surface temperatures. Design: Repeated-measures counterbalanced design. Setting: Human performance research laboratory. Patients or Other Participants: Twelve healthy participants (6 men, 6 women) with no history of musculoskeletal disease and no known preexisting inflammatory conditions or recent orthopaedic injuries to the lower extremities. Intervention(s): Ice packs made with cubed, crushed, or wetted ice were applied to a standardized area on the posterior aspect of the right gastrocnemius for 20 minutes. Each participant was given separate ice pack treatments, with at least 4 days between treatment sessions. Main Outcome Measure(s): Cutaneous and intramuscular (2 cm plus one-half skinfold measurement) temperatures of the right gastrocnemius were measured every 30 seconds during a 20-minute baseline period, a 20-minute treatment period, and a 120-minute recovery period. Results: Differences were observed among all treatments. Compared with the crushed-ice treatment, the cubed-ice and wetted-ice treatments produced lower surface and intramuscular temperatures. Wetted ice produced the greatest overall temperature change during treatment and recovery, and crushed ice produced the smallest change. Conclusions: As administered in our protocol, wetted ice was superior to cubed or crushed ice at reducing surface temperatures, whereas both cubed ice and wetted ice were superior to crushed ice at reducing intramuscular temperatures. PMID:19295957

  4. 49 CFR 230.41 - Flexible staybolts with caps.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Flexible staybolts with caps. 230.41 Section 230... Appurtenances Staybolts § 230.41 Flexible staybolts with caps. (a) General. Flexible staybolts with caps shall have their caps removed during every 5th annual inspection for the purpose of inspecting the bolts for...

  5. Residual Cap

    NASA Image and Video Library

    2006-05-10

    This MOC image shows a summertime view of the south polar residual cap of Mars. In this image, mesas composed largely of solid carbon dioxide are separated from one another by irregularly-shaped depressions

  6. JTF CapMed Warrior Transition Division

    DTIC Science & Technology

    2011-01-25

    The Quadruple Aim: Working Together, Achieving Success 2011 Military Health System Conference JTF CapMed Warrior Transition Division 25 January 2011...Colonel Julia Adams 1 Military Health System Conference Joint Task Force National Capital Region Medical (JTF CapMed ) Report Documentation Page Form...DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE JTF CapMed Warrior Transition Division 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  7. Cradle cap

    MedlinePlus

    ... on oily areas such as the scalp. The exact cause of cradle cap is not known. Doctors ... must be authorized in writing by ADAM Health Solutions. About MedlinePlus Site Map FAQs Customer Support Get ...

  8. Inferring Firn Permeability from Pneumatic Testing: A Case Study on the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Sommers, Aleah N.; Rajaram, Harihar; Weber, Eliezer P.; MacFerrin, Michael J.; Colgan, William T.; Stevens, C. Max

    2017-03-01

    and more detailed monitoring, effective permeabilities over a larger scale may be quantified reliably, and multiple measurements during a season and across multiple years could improve understanding of the evolving firn structure and permeability. The technique is also suitable for broad application in Antarctica and other glaciers and ice caps.

  9. Following the south polar cap recession as viewed by OMEGA/MEX using automatic detection of H2O and CO2 ices.

    NASA Astrophysics Data System (ADS)

    Schmidt, F.; Doute, S.; Schmitt, B.

    In order to understand Mars' current climate it is necessary to detect, characterize and monitor CO2 and H2O at the surface (permanent and seasonal icy deposits) and in the atmosphere (vapor and clouds). Here we will focus on the South Seasonal Polar Cap (SSPC) whose recession was previously observed with different techniques : from earth in the visible range with HST [James 1996], or from MGS spacecraft with MOC images [Benson 2005], in the thermal IR range by the TES [Kieffer 2000], in the near infrared by OMEGA/MEX [Langevin submitted]. The time and space evolutions of the SSPC is a major annual climatic signal both at the global and the regional scales. In particular the measurement of the temporal and spatial distributions of CO2 constrains exchange processes between both surface and atmosphere. This exchange may involve preponderant species : H2O, CO2 and dust. In this work we will apply a new detection technique : "wavanglet" in order to follow the recession of the SSPC thanks to OMEGA/MEX observations. This method was especially developed in the goal to classify a huge dataset, such OMEGA ones. We propose to use "wavanglet" as a supervised automatic classification method that identifies spectral features and classifies the image in spectrally homogeneous units. Additionally we will evaluate quantitative detection limits of "wavanglet" based on synthetic dataset simulating OMEGA spectra in typical situation of the SSPC. This detection limit will be discussed in terms of abundance for H2O and CO2 ices in order to improve the interpretation of the classification. Finally we will present the recession of the SSPC using "wavanglet" and we will compare the results with those of earlier investigation. An interpretation of the similarities and disagreements between those maps will be done.

  10. Wave-Ice and Air-Ice-Ocean Interaction During the Chukchi Sea Ice Edge Advance

    DTIC Science & Technology

    2014-09-30

    During cruise CU-B UAF UW Airborne expendable Ice Buoy (AXIB) Ahead, at and inside ice edge Surface meteorology T, SLP ~1 year CU-B UW...Balance (IMB) buoys Inside ice edge w/ >50cm thickness Ice mass balance T in snow-ice-ocean, T, SLP at surface ~1 year WHOI CRREL (SeaState DRI

  11. Strontium Isotopes of Gaskiers Cap Carbonate, Avalon, Newfoundland: Sequential Digestion Aids Interpretation of Petrologic Complexity

    NASA Astrophysics Data System (ADS)

    Tang, T.; Raub, T. D.; Wang, Z.

    2013-12-01

    Harland" of high-Ca, Sr composition; or 4) brine-influenced diagenesis exploiting specific horizons in the cap. As a broader implication, many extant Sr-isotope chemostratigraphies of Marinoan cap carbonate may be inaccurate, and in general, recrystallized impure (and low-Sr) carbonates, and dolomites in particular, are probably best studied with the serial digestion technique. We apply this sequential digestion technique to another Ediacaran cap carbonate with significant siliciclastic content, the anomalous cap limestone synchronous with deglaciation of ~581 Ma Gaskiers ice age in Newfoundland's Avalon zone. Although some textural and compositional differences exist between ~635 Ma Nuccaleena and ~581 Ma Gaskiers cap, the sequential digestion technique again appears to provide clarity by suggesting less-altered and more-altered fractions from various sample levels. We will discuss implications for the nature of Gaskiers glaciation and accompanying environmental oxidation, its global correlations, and the utility of the existing Ediacaran Sr-chemostratigraphic reference curve.

  12. Extensive Ice Fractures in the Beaufort Sea

    NASA Image and Video Library

    2017-12-08

    The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this view of extensive sea-ice fracturing off the northern coast of Alaska. The event began in late-January and spread west toward Banks Island throughout February and March 2013. Visualizations of the Arctic often give the impression that the ice cap is a continuous sheet of stationary, floating ice. In fact, it is a collection of smaller pieces that constantly shift, crack, and grind against one another as they are jostled by winds and ocean currents. Especially during the summer—but even during the height of winter—cracks—or leads—open up between pieces of ice. That was what was happening on the left side of the animation (seen here: bit.ly/10kE7sh) in late January. A high-pressure weather system was parked over the region, producing warmer temperatures and winds that flowed in a southwesterly direction. That fueled the Beaufort Gyre, a wind-driven ocean current that flows clockwise. The gyre was the key force pulling pieces of ice west past Point Barrow, the northern nub of Alaska that protrudes into the Beaufort Sea. “A fracturing event in this area is not unusual because the Beaufort Gyre tends to push ice away from Banks Island and the Canadian Archipelago,” explained Walt Meier of the National Snow & Ice Data Center (NSIDC). “Point Barrow can act like a ‘pin point’ where the ice catches and fractures to the north and east.” In February, however, a series of storms passing over central Alaska exacerbated the fracturing. Strong westerly winds prompted several large pieces of ice to break away in an arc-shaped wave that moved progressively east. By the end of February, large pieces of ice had fractured all the way to the western coast of Banks Island, a distance of about 1,000 kilometers (600 miles). The data used to create the animation came from the longwave infrared (thermal) portion of the electromagnetic spectrum, so the animation illustrates how

  13. Laterally loaded pile cap connections.

    DOT National Transportation Integrated Search

    2010-08-01

    This study investigated the moment capacity and load-displacement response of the pile-to-cap connection details. Lateral load tests were conducted on four pile caps (3 ft H x 3 ft W x 6.5 ft L) with two 40 foot-long steel pipe piles (12.75 inch OD) ...

  14. Fluctuating Arctic Sea ice thickness changes estimated by an in situ learned and empirically forced neural network model

    USGS Publications Warehouse

    Belchansky, G.I.; Douglas, David C.; Platonov, Nikita G.

    2008-01-01

    Sea ice thickness (SIT) is a key parameter of scientific interest because understanding the natural spatiotemporal variability of ice thickness is critical for improving global climate models. In this paper, changes in Arctic SIT during 1982-2003 are examined using a neural network (NN) algorithm trained with in situ submarine ice draft and surface drilling data. For each month of the study period, the NN individually estimated SIT of each ice-covered pixel (25-km resolution) based on seven geophysical parameters (four shortwave and longwave radiative fluxes, surface air temperature, ice drift velocity, and ice divergence/convergence) that were cumulatively summed at each monthly position along the pixel's previous 3-yr drift track (or less if the ice was <3 yr old). Average January SIT increased during 1982-88 in most regions of the Arctic (+7.6 ?? 0.9 cm yr-1), decreased through 1996 Arctic-wide (-6.1 ?? 1.2 cm yr-1), then modestly increased through 2003 mostly in the central Arctic (+2.1 ?? 0.6 cm yr-1). Net ice volume change in the Arctic Ocean from 1982 to 2003 was negligible, indicating that cumulative ice growth had largely replaced the estimated 45 000 km3 of ice lost by cumulative export. Above 65??N, total annual ice volume and interannual volume changes were correlated with the Arctic Oscillation (AO) at decadal and annual time scales, respectively. Late-summer ice thickness and total volume varied proportionally until the mid-1990s, but volume did not increase commensurate with the thickening during 1996-2002. The authors speculate that decoupling of the ice thickness-volume relationship resulted from two opposing mechanisms with different latitudinal expressions: a recent quasi-decadal shift in atmospheric circulation patterns associated with the AO's neutral state facilitated ice thickening at high latitudes while anomalously warm thermal forcing thinned and melted the ice cap at its periphery. ?? 2008 American Meteorological Society.

  15. Pore Water PAH Transport in Amended Sediment Caps

    NASA Astrophysics Data System (ADS)

    Gidley, P. T.; Kwon, S.; Ghosh, U.

    2009-05-01

    Capping is a common remediation strategy for contaminated sediments that creates a physical barrier between contaminated sediments and the water column. Diffusive flux of contaminants through a sediment cap is small. However, under certain hydrodynamic conditions such as groundwater potential and tidal pumping, groundwater advection can accelerate contaminant transport. Hydrophobic organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) could be transported through the cap under advective conditions. To better understand PAH migration under these conditions, physical models of sediment caps were evaluated in the laboratory through direct measurement of pore water using solid phase micro-extraction with gas chromatography and mass spectrometry. Contaminated sediment and capping material was obtained from an existing Superfund site that was capped at Eagle Harbor, Washington. A PAH dissolution model linked to an advection-dispersion equation with retardation using published organic carbon-water partitioning coefficients (Koc) was compared to measured PAHs in the sediment and cap porewater of the physical model.

  16. Ice Front at Venable Ice Shelf

    NASA Image and Video Library

    2013-06-13

    This photo, taken onboard the Chilean Navy P3 aircraft, shows the ice front of Venable Ice Shelf, West Antarctica, in October 2008. It is an example of a small-size ice shelf that is a large melt water producer.

  17. Implications of a reduced Arctic sea ice cover on the large-scale atmospheric energy and moisture budgets

    NASA Astrophysics Data System (ADS)

    Porter, David Felton

    New estimates of the current energy budget of the north polar cap (the region north of 70N) are synthesized by combining data from new atmospheric reanalyses and satellite retrievals. For the period 2000-2005, monthly means from the Clouds and the Earth's Radiant Energy System (CERES) satellite data set are considered to provide the most reliable top-of-atmosphere (TOA) radiation budget. The remaining components of the energy budget, comprising of the energy storage, horizontal convergence of energy, and the net surface flux between the atmospheric and subsurface columns, are compiled using data from the Japanese 25-year Reanalysis Project (JRA) and the NCEP/NCAR Reanalysis (NRA). The annual cycles of energy budget components for the polar cap are fairly consistent between the JRA and NRA, but with some systematic differences. Estimates of the Arctic energy budget from WRF are compared with estimates from reanalyses and satellite observations. Apart from a few systematic shortcomings, WRF sufficiently captures the Arctic energy budget. The major deficiency, with differences from reanalyses and satellite observations as large as 40 W m-2 in summer months, is in the shortwave radiative fluxes at both the surface and top of the atmosphere, due to a specified constant sea ice albedo of 0.8, which is too high during the summer. Finally, the WRF model (version 3.2.0) is used to explore the sensitivity of the large-scale atmospheric circulation to prescribed changes in Arctic sea ice. Observed sea ice fractions and sea surface temperatures (SSTs) from 1996 and 2007, representing years of high and low sea ice extent, respectively, are used as WRF lower boundary conditions. This yields two 15-member ensembles that sample a large range of true climatic variability. Results of the simulations show both local and remote responses to the sea ice reduction. The local response is largest in October and November, dominated by increased turbulent heat fluxes resulting in a

  18. Looking Into and Through the Ross Ice Shelf - ROSETTA-ICE

    NASA Astrophysics Data System (ADS)

    Bell, R. E.

    2015-12-01

    Our current understanding of the structure and stability of the Ross Ice Shelf is based on satellite studies of the ice surface and the 1970's RIGGS program. The study of the flowlines evident in the MODIS imagery combined with surface geophysics has revealed a complex history with ice streams Mercer, Whillans and Kamb changing velocity over the past 1000 years. Here, we present preliminary IcePod and IceBridge radar data acquired in December 2014 and November 2013 across the Ross Ice Shelf that show clearly, for the first time, the structure of the ice shelf and provide insights into ice-ocean interaction. The three major layers of the ice shelf are (1) the continental meteoric ice layer), ice formed on the grounded ice sheet that entered the ice shelf where ice streams and outlet glaciers crossed the grounding line (2) the locally accumulating meteoric ice layer, ice and snow that forms from snowfall on the floating ice shelf and (3) a basal marine ice layer. The locally accumulating meteoric ice layer contains well-defined internal layers that are generally parallel to the ice surface and thickens away from the grounding line and reaches a maximum thickness of 220m along the line crossing Roosevelt Island. The continental meteoric layer is located below a broad irregular internal reflector, and is characterized by irregular internal layers. These internal layers are often folded, likely a result of deformation as the ice flowed across the grounding line. The basal marine ice layer, up to 50m thick, is best resolved in locations where basal crevasses are present, and appears to thicken along the flow at rates of decimeters per year. Each individual flowband of the ice shelf contains layers that are distinct in their structure. For example, the thickness of the locally accumulated layer is a function of both the time since crossing the grounding line and the thickness of the incoming ice. Features in the meteoric ice, such as distinct folds, can be traced between

  19. Effect of capping layer on spin-orbit torques

    NASA Astrophysics Data System (ADS)

    Sun, Chi; Siu, Zhuo Bin; Tan, Seng Ghee; Yang, Hyunsoo; Jalil, Mansoor B. A.

    2018-04-01

    In order to enhance the magnitude of spin-orbit torque (SOT), considerable experimental works have been devoted to studying the thickness dependence of the different layers in multilayers consisting of heavy metal (HM), ferromagnet (FM), and capping layers. Here, we present a theoretical model based on the spin-drift-diffusion formalism to investigate the effect of the capping layer properties such as its thickness on the SOT observed in experiments. It is found that the spin Hall-induced SOT can be significantly enhanced by incorporating a capping layer with an opposite spin Hall angle to that of the HM layer. The spin Hall torque can be maximized by tuning the capping layer thickness. However, in the absence of the spin Hall effect (SHE) in the capping layer, the torque decreases monotonically with the capping layer thickness. Conversely, the spin Hall torque is found to decrease monotonically with the FM layer thickness, irrespective of the presence or absence of the SHE in the capping layer. All these trends are in correspondence with experimental observations. Finally, our model suggests that capping layers with a long spin diffusion length and high resistivity would also enhance the spin Hall torque.

  20. 7 CFR 1714.7 - Interest rate cap.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Interest rate cap. 1714.7 Section 1714.7 Agriculture... PRE-LOAN POLICIES AND PROCEDURES FOR INSURED ELECTRIC LOANS General § 1714.7 Interest rate cap. Except... section, or both the rate disparity test for the interest rate cap and the consumer income test set forth...

  1. Topography of the South Polar Cap and Layered Deposits of Mars: Viking Stereo Grametry at Regional and Local Scales

    NASA Technical Reports Server (NTRS)

    Schenk, P.; Moore, J.; Stoker, C.

    1998-01-01

    Layered deposits and residual polar caps on Mars may record the deposition of ice and sediment modulated by periodic climate change. Topographic information relating to layer thicknesses, erosional processes, and formation of dark spirals within these deposits has been sparce or unreliable until the arrival of MOLA in orbit in September 1997. To assist in evaluating these terrains prior to launch and to assess formation and erosion processes in the polar deposits, we have assembled Viking stereo mosaics of the region and have produced the first reliable DEM models of the south polar deposits using automated stereogrammetry tools. Here we report our preliminary topographic results, pending final image pointing updates. The maximum total thickness of the layered deposits in the south polar region is 2.5 km. The thick layered deposits consist of a series of megaterraces. Each terrace is several tens of kilometers wide and is flat or slopes very gently toward the pole. These terraces step downward from a central plateau near the south pole. Terraces are bounded by relatively steep scarps 100-500 meters high that face toward the equator. These scarps correspond to the pattern of dark spirals observed within the residual cap in southern summer, and are interpreted as ice or frost-free surfaces warmed by solar insolation. Several tongue-shaped troughs, with rounded cirquelike heads, are observed near the margins of the deposit. These troughs are 300-600 meters in deep and may be similar to troughs observed in the northern polar deposit.

  2. Extensive massive basal-ice structures in West Antarctica relate to ice-sheet anisotropy and ice-flow

    NASA Astrophysics Data System (ADS)

    Ross, N.; Bingham, R. G.; Corr, H. F. J.; Siegert, M. J.

    2016-12-01

    Complex structures identified within both the East Antarctic and Greenland ice sheets are thought to be generated by the action of basal water freezing to the ice-sheet base, evolving under ice flow. Here, we use ice-penetrating radar to image an extensive series of similarly complex basal ice facies in West Antarctica, revealing a thick (>500 m) tectonised unit in an area of cold-based and relatively slow-flowing ice. We show that major folding and overturning of the unit perpendicular to ice flow elevates deep, warm ice into the mid ice-sheet column. Fold axes align with present ice flow, and axis amplitudes increase down-ice, suggesting long-term consistency in the direction and convergence of flow. In the absence of basal water, and the draping of the tectonised unit over major subglacial mountain ranges, the formation of the unit must be solely through the deformation of meteoric ice. Internal layer radar reflectivity is consistently greater parallel to flow compared with the perpendicular direction, revealing ice-sheet crystal anisotropy is associated with the folding. By linking layers to the Byrd ice-core site, we show the basal ice dates to at least the last glacial cycle and may be as old as the last interglacial. Deformation of deep-ice in this sector of WAIS, and potentially elsewhere in Antarctica, may be caused by differential shearing at interglacial-glacial boundaries, in a process analogous to that proposed for interior Greenland. The scale and heterogeneity of the englacial structures, and their subsequent impact on ice sheet rheology, means that the nature of ice flow across the bulk of West Antarctica must be far more complex that is currently accounted for by any numerical ice sheet model.

  3. A late Holocene metal record of Andean climate and anthropogenic activity in lake sediments near Quelccaya Ice Cap, Peru

    NASA Astrophysics Data System (ADS)

    Beal, S. A.; Kelly, M. A.; Jackson, B. P.; Stroup, J. S.; Osterberg, E. C.

    2011-12-01

    The tropical hypothesis maintains that major changes in global climate are motivated by phenomena based at tropical latitudes. Evidence for this hypothesis lies in: modern-day observations of El Niño Southern Oscillation (ENSO); East African lake sediment records of Intertropical Convergence Zone (ITCZ) position that precede high-latitude changes; and the potential for ITCZ shifts to cause major CO2 degassing from the Southern Ocean. In order to improve the understanding of these phenomena we present an ~1800 year record of atmospheric metal deposition in a lake sediment core near Quelccaya Ice Cap, Peru (13.9 °S). In June, 2010 we collected a 1.45 meter-long core from Yanacocha - a small, closed-basin tarn that has been isolated from glacial input since ~11,200 BP. The chronology for the core is based on 4 of 6 AMS 14C dates on aquatic macrofossils and one sharp Zr/Ti anomaly at 36 cm, likely derived from the 350 BP eruption of Huaynaputina. We completely digested organic-rich core samples at 1 cm resolution using HNO3, HCl, and HF in a closed-vessel microwave system, and then analyzed the digestates for 67 metals by inductively coupled plasma mass spectrometry. Here we show fluxes of lithogenic metals (Fe, Nb, Ti, and Zr) that reflect changes in wind strength and aridity, fluxes of lithogenic metal isotopes (REEs and Pb) that reflect wind direction, and enrichment factors (EFs) of metals (Ag, As, Cd, Cu, Hg, and Pb) that reflect anthropogenic activity. Five episodic peaks in lithogenic metal fluxes, centered around 1800, 1300, 900, 600, and 100 yrs BP, are thought to result from either drier or windier conditions, potentially caused by a northern ITCZ position or a more persistent El Niño state. The provenance of atmospheric deposition, evidenced by REE ratios (light REEs / heavy REEs), suggest that high lithogenic fluxes are associated with a change in wind direction, possibly caused by a change in the ENSO state, which will be explored with forthcoming Pb

  4. Diagnostic criteria for cryopyrin-associated periodic syndrome (CAPS).

    PubMed

    Kuemmerle-Deschner, Jasmin B; Ozen, Seza; Tyrrell, Pascal N; Kone-Paut, Isabelle; Goldbach-Mansky, Raphaela; Lachmann, Helen; Blank, Norbert; Hoffman, Hal M; Weissbarth-Riedel, Elisabeth; Hugle, Boris; Kallinich, Tilmann; Gattorno, Marco; Gul, Ahmet; Ter Haar, Nienke; Oswald, Marlen; Dedeoglu, Fatma; Cantarini, Luca; Benseler, Susanne M

    2017-06-01

    Cryopyrin-associated periodic syndrome (CAPS) is a rare, heterogeneous disease entity associated with NLRP3 gene mutations and increased interleukin-1 (IL-1) secretion. Early diagnosis and rapid initiation of IL-1 inhibition prevent organ damage. The aim of the study was to develop and validate diagnostic criteria for CAPS. An innovative process was followed including interdisciplinary team building, item generation: review of CAPS registries, systematic literature review, expert surveys, consensus conferences for item refinement, item reduction and weighting using 1000Minds decision software. Resulting CAPS criteria were tested in large cohorts of CAPS cases and controls using correspondence analysis. Diagnostic models were explored using sensitivity analyses. The international team included 16 experts. Systematic literature and registry review identified 33 CAPS-typical items; the consensus conferences reduced these to 14. 1000Minds exercises ranked variables based on importance for the diagnosis. Correspondence analysis determined variables consistently associated with the diagnosis of CAPS using 284 cases and 837 controls. Seven variables were significantly associated with CAPS (p<0.001). The best diagnosis model included: Raised inflammatory markers (C-reactive protein/serum amyloid A) plus ≥two of six CAPS-typical symptoms: urticaria-like rash, cold-triggered episodes, sensorineural hearing loss, musculoskeletal symptoms, chronic aseptic meningitis and skeletal abnormalities. Sensitivity was 81%, specificity 94%. It performed well for all CAPS subtypes and regardless of NLRP3 mutation. The novel approach integrated traditional methods of evidence synthesis with expert consensus, web-based decision tools and innovative statistical methods and may serve as model for other rare diseases. These criteria will enable a rapid diagnosis for children and adults with CAPS. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted

  5. Comparison of ice particle size variations across Ganymede and Callisto

    NASA Astrophysics Data System (ADS)

    Stephan, Katrin; Hoffmann, Harald; Hibbitts, Karl; Wagner, Roland; Jaumann, Ralf

    2016-04-01

    Ratios of band depths of different H2O ice absorptions as measured by the Near Infrared Spectrometer NIMS onboard the Galileo spacecraft [1] have been found to be semi-quantitative indicator of changes in the particle size of ice across the surfaces of the Jovian satellite Ganymede [2]. This method is now applied to Ganymede's neighboring satellite Callisto. On Ganymede, sizes reach from 1 μm near the poles to 1 mm near the equator [2]. Smallest particles occur at latitudes higher than ±30° where the closed magnetic field lines of Ganymede's magnetic field change into open ones and Ganymede's polar caps become apparent. Thus, the formation of these polar caps has often been attributed to brightening effects due to plasma bombardment of the surface [3,4]. Callisto, which does not exhibit an intrinsic magnetic field, however, also shows the same trend as observed on Ganymede with slightly larger particle sizes on Callisto than on Ganymede at low and mid latitude but similar particle sizes in the polar regions. Similar trends in the particle size variations on Callisto and on Ganymede imply that these variations are caused by similar surface processes. Our measurements rather point to a continuous decreasing of ice particle sizes toward the poles on both satellites related to changes of the surface temperatures [5]. Maximum temperatures during the day reach 150 K and 165 K near the equator of Ganymede and Callisto [6, 7], respectively and sublimation of ice particles and crystal growth [8] is expected to be the dominant surface process in these regions. In contrast, polar temperatures do not exceed 80 ± 5 K [5]. Larger particles in the equatorial region of Callisto than on Ganymede could be explained due to the slight higher maximum temperature but also a longer Callistoan day (Callisto: ~ 17 Earth days; Ganymede: ~ 7 Earth days). References: [1] Carlson et al.. (1999) Science 274, 385-388, 1996; [2] Stephan et al., 2009, EPSC, Abstract #EPSC2009-633; [3] Johnson

  6. Ice Roughness in Short Duration SLD Icing Events

    NASA Technical Reports Server (NTRS)

    McClain, Stephen T.; Reed, Dana; Vargas, Mario; Kreeger, Richard E.; Tsao, Jen-Ching

    2014-01-01

    Ice accretion codes depend on models of roughness parameters to account for the enhanced heat transfer during the ice accretion process. While mitigating supercooled large droplet (SLD or Appendix O) icing is a significant concern for manufacturers seeking future vehicle certification due to the pending regulation, historical ice roughness studies have been performed using Appendix C icing clouds which exhibit mean volumetric diameters (MVD) much smaller than SLD clouds. Further, the historical studies of roughness focused on extracting parametric representations of ice roughness using multiple images of roughness elements. In this study, the ice roughness developed on a 21-in. NACA 0012 at 0deg angle of attack exposed to short duration SLD icing events was measured in the Icing Research Tunnel at the NASA Glenn Research Center. The MVD's used in the study ranged from 100 micrometer to 200 micrometers, in a 67 m/s flow, with liquid water contents of either 0.6 gm/cubic meters or 0.75 gm/cubic meters. The ice surfaces were measured using a Romer Absolute Arm laser scanning system. The roughness associated with each surface point cloud was measured using the two-dimensional self-organizing map approach developed by McClain and Kreeger (2013) resulting in statistical descriptions of the ice roughness.

  7. Experimental landfill caps for semi-arid and arid climates.

    PubMed

    Blight, Geoffrey E; Fourie, Andries B

    2005-04-01

    The United States EPA Subtitle D municipal solid waste landfill requirements specify that the permeability of a cap to a landfill be no greater than the permeability of the underliner. In recent years the concept of the evapotranspirative (ET) cap has been developed in which the cap is designed to store all rain infiltration and re-evapotranspire it during dry weather. Concern at the long period required for landfilled municipal solid waste to decompose and stabilize in arid and semi-arid climates has led to an extension of the concept of the ET cap. With the infiltrate-stabilize-evapotranspire (ISE) cap, rain infiltration during wet weather is permitted to enter the underlying waste, thus accelerating the decomposition and stabilization process. Excess infiltration is then removed from both waste and cap by evaporation during dry weather. The paper describes the construction and operation of two sets of experimental ISE caps, one in a winter rainfall semi-arid climate, and the other in a summer rainfall semi-arid climate. Observation of the rainfall, soil evaporation and amount of water stored in the caps has allowed water balances to be constructed for caps of various thicknesses. These observations show that the ISE concept is viable. In the limit, when there is insufficient rainfall to infiltrate the waste, an ISE cap operates as an ET cap.

  8. [Comparison of expression of transforming growth factor-β1 in rat dental pulp during direct pulp capping with 2 capping agents].

    PubMed

    Zhang, Xiao-fang; Yao, Ya-peng; Kang, Hong-ying; Dong, Pei

    2014-04-01

    To examine and compare the expression of transforming growth factor-β1(TGF-β1) in rat dental pulp after direct pulp capping with calcium hydroxide (CH) and mineral trioxide aggregate (MTA). The model of direct dental pulp capping after first molars was established in 28 female Wistar rats with CH and MTA. The rats were sacrificed 1, 3, 5, 7, 14,21 and 28 days after direct pulp capping. TGF-β1 expression in pulp tissues were measured with immunohistochemical staining. The data was analyzed by Dunnett t test and paired t test with SPSS 13.0 software package. The results showed that no TGF-β1 expression was detected in the control group. After direct pulp capping with MTA, TGF-β1 expression gradually increased and reached peak expression on 5 day. TGF-β1 expression gradually decreased afterwards and reached normal on 21 day after direct pulp. TGF-β1 was mainly expressed in neutrophils, odontoblasts cells, vascular endothelial cells and fibroblasts. The expression of TGF-β1 was significantly different between 2 capping agents 1, 3, 5, 7, 14 days after direct pulp capping (P<0.05). The results suggest that TGF-β1 expression increases at first and then decreases after direct pulp capping. The type of capping agents has an impact on the expression of TGF-β1 after direct pulp capping. MTA enhances more TGFβ-1 expression than CH 1, 3, 5, 7 and 14 days after direct pulp capping. Supported by Science and Technology Plan Project of Liaoning Province (2009225001-2).

  9. Time scales of erosion and deposition recorded in the residual south polar cap of Mars

    NASA Astrophysics Data System (ADS)

    Thomas, P. C.; Calvin, W. M.; Gierasch, P.; Haberle, R.; James, P. B.; Sholes, S.

    2013-08-01

    The residual south polar cap (RSPC) of Mars has been subject to competing processes during recent Mars years of high resolution image coverage: continuing erosion of scarps while the maximum extent grows as well as shrinks (Piqueux, S., Christensen, P.R. [2008]. J. Geophys. Res. (Planets) 113, 2006; James, P.B., Thomas, P.C., Malin, M.C. [2010]. Icarus 208, 82-85). Additionally, the cap has a variety of morphologies and erosion (scarp retreat) rates (Thomas, P.C., James, P.B., Calvin, W.M., Haberle, R., Malin, M.C. [2009]. Icarus 203, 352-375). Do these different forms and competing processes indicate an aging and possibly disappearing cap, a growing cap, or a fluctuating cap, and is it possible to infer the timescales of the processes acting on the RSPC? Here we use the latest imaging data from Mars' southern summer in Mars year 30 (Calendar year 2011) to evaluate erosion rates of forms in the RSPC over 6 Mars years, and to map more fully features whose sizes can be used to predict deposit ages. Data through Mars year 30 show that scarp retreat rates in the RSPC have remained approximately the same for at least 6 Mars years and that these rates of erosion also apply approximately over the past 21 Mars years. The thicker units appear to have undergone changes in the locations of new pit formation about 30-50 Mars years ago. The thinner units have some areas that are possibly 80 Mars years old, with some younger materials having accumulated more than a meter in thickness since Mars year 9. Formation of the thicker units probably required over 100 Mars years. The upper surfaces of most areas, especially the thicker units, show little change at the few-cm level over the last 2 Mars years. This observation suggests that current conditions are substantially different from those when the thicker units were deposited. A prime characteristic of the evolution of the RSPC is that some changes are progressive, such as those involving scarp retreat, while others, such as the

  10. Forward Modeling of Oxygen Isotope Variability in Tropical Andean Ice Cores

    NASA Astrophysics Data System (ADS)

    Vuille, M. F.; Hurley, J. V.; Hardy, D. R.

    2016-12-01

    Ice core records from the tropical Andes serve as important archives of past tropical Pacific SST variability and changes in monsoon intensity upstream over the Amazon basin. Yet the interpretation of the oxygen isotopic signal in these ice cores remains controversial. Based on 10 years of continuous on-site glaciologic, meteorologic and isotopic measurements at the summit of the world's largest tropical ice cap, Quelccaya, in southern Peru, we developed a process-based physical forward model (proxy system model), capable of simulating intraseasonal, seasonal and interannual variability in delta-18O as observed in snow pits and short cores. Our results highlight the importance of taking into account post-depositional effects (sublimation and isotopic enrichment) to properly simulate the seasonal cycle. Intraseasonal variability is underestimated in our model unless the effects of cold air incursions, triggering significant monsoonal snowfall and more negative delta-18O values, are included. A number of sensitivity test highlight the influence of changing boundary conditions on the final snow isotopic profile. Such tests also show that our model provides much more realistic data than applying direct model output of precipitation delta-18O from isotope-enabled climate models (SWING ensemble). The forward model was calibrated with and run under present-day conditions, but it can also be driven with past climate forcings to reconstruct paleo-monsoon variability and investigate the influence of changes in radiative forcings (solar, volcanic) on delta-18O variability in Andean snow. The model is transferable and may be used to render a paleoclimatic context at other ice core locations.

  11. Wave-Ice and Air-Ice-Ocean Interaction During the Chukchi Sea Ice Edge Advance

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Wave -Ice and Air-Ice-Ocean Interaction During the...Chukchi Sea in the late summer have potentially changed the impact of fall storms by creating wave fields in the vicinity of the advancing ice edge. A...first) wave -ice interaction field experiment that adequately documents the relationship of a growing pancake ice cover with a time and space varying

  12. Ice Flow in the North East Greenland Ice Stream

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Kwok, Ron; Fahnestock, M.; MacAyeal, Doug

    1999-01-01

    Early observations with ERS-1 SAR image data revealed a large ice stream in North East Greenland (Fahnestock 1993). The ice stream has a number of the characteristics of the more closely studied ice streams in Antarctica, including its large size and gross geometry. The onset of rapid flow close to the ice divide and the evolution of its flow pattern, however, make this ice stream unique. These features can be seen in the balance velocities for the ice stream (Joughin 1997) and its outlets. The ice stream is identifiable for more than 700 km, making it much longer than any other flow feature in Greenland. Our research goals are to gain a greater understanding of the ice flow in the northeast Greenland ice stream and its outlet glaciers in order to assess their impact on the past, present, and future mass balance of the ice sheet. We will accomplish these goals using a combination of remotely sensed data and ice sheet models. We are using satellite radar interferometry data to produce a complete maps of velocity and topography over the entire ice stream. We are in the process of developing methods to use these data in conjunction with existing ice sheet models similar to those that have been used to improve understanding of the mechanics of flow in Antarctic ice streams.

  13. A coupled ice-ocean model of ice breakup and banding in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Smedstad, O. M.; Roed, L. P.

    1985-01-01

    A coupled ice-ocean numerical model for the marginal ice zone is considered. The model consists of a nonlinear sea ice model and a two-layer (reduced gravity) ocean model. The dependence of the upwelling response on wind stress direction is discussed. The results confirm earlier analytical work. It is shown that there exist directions for which there is no upwelling, while other directions give maximum upwelling in terms of the volume of uplifted water. The ice and ocean is coupled directly through the stress at the ice-ocean interface. An interesting consequence of the coupling is found in cases when the ice edge is almost stationary. In these cases the ice tends to break up a few tenths of kilometers inside of the ice edge.

  14. Polar Cap Plasma and Convection

    NASA Technical Reports Server (NTRS)

    Elliott, Heather A.; Craven, Paul D.; Comfort, Richard H.; Chandler, Michael O.; Moore, Thomas E.; Ruohoniemi, J. M.

    1998-01-01

    This presentation will describe the character of the polar cap plasma in 10% AGU Spring 1998 particular the convection velocities at the perigee (about 1.8 Re) and apogee( about 8.9 Re) of Polar in relationship to Interplanetary Magnetic Field (IMF) and solar wind parameters. This plasma is thought to be due to several sources; the polar wind, cleft ion fountain, and auroral outflow. The plasma in the polar cap tends to be mostly field-aligned. At any given point in the polar cap, this plasma could be from a different regions since convection of magnetic field lines can transport this material. it is quite difficult to study such a phenomena with single point measurements. Current knowledge of the polar cap plasma obtained by in situ measurements will be presented along with recent results from the Polar mission. This study also examines the direct electrical coupling between the magnetosphere and ionosphere by comparing convection velocities measured by the Thermal Ion Dynamics Experiment (TIDE) and Magnetic Field Experiment (MFE) instruments in magnetosphere and measurements of the ionosphere by ground-based radars. At times such a comparison is difficult because the Polar satellite at apogee spends a large amount of time in the polar cap which is a region that is not coverage well by the current SuperDam coherent radars. This is impart due to the lack of irregularities that returns the radar signal.

  15. Icing flight research: Aerodynamic effects of ice and ice shape documentation with stereo photography

    NASA Technical Reports Server (NTRS)

    Mikkelsen, K. L.; Mcknight, R. C.; Ranaudo, R. J.; Perkins, P. J., Jr.

    1985-01-01

    Aircraft icing flight research was performed in natural icing conditions. A data base consisting of icing cloud measurements, ice shapes, and aerodynamic measurements is being developed. During research icing encounters the icing cloud was continuously measured. After the encounter, the ice accretion shapes on the wing were documented with a stereo camera system. The increase in wing section drag was measured with a wake survey probe. The overall aircraft performance loss in terms of lift and drag coefficient changes was obtained by steady level speed/power measurements. Selective deicing of the airframe components was performed to determine their contributions to the total drag increase. Engine out capability in terms of power available was analyzed for the iced aircraft. It was shown that the stereo photography system can be used to document ice shapes in flight and that the wake survey probe can measure increases in wing section drag caused by ice. On one flight, the wing section drag coefficient (c sub d) increased approximately 120 percent over the uniced baseline at an aircraft angle of attack of 6 deg. On another flight, the aircraft darg coefficient (c sub d) increased by 75 percent over the uniced baseline at an aircraft lift coefficient (C sub d) of 0.5.

  16. Icing flight research - Aerodynamic effects of ice and ice shape documentation with stereo photography

    NASA Technical Reports Server (NTRS)

    Mikkelsen, K. L.; Mcknight, R. C.; Ranaudo, R. J.; Perkins, P. J., Jr.

    1985-01-01

    Aircraft icing flight research was performed in natural icing conditions. A data base consisting of icing cloud measurements, ice shapes, and aerodynamic measurements is being developed. During research icing encounters the icing cloud was continuously measured. After the encounter, the ice accretion shapes on the wing were documented with a stereo camera system. The increase in wing section drag was measured with a wake survey probe. The overall aircraft performance loss in terms of lift and drag coefficient changes were obtained by steady level speed/power measurements. Selective deicing of the airframe components was performed to determine their contributions to the total drag increase. Engine out capability in terms of power available was analyzed for the iced aircraft. It was shown that the stereo photography system can be used to document ice shapes in flight and that the wake survey probe can measure increases in wing section drag caused by ice. On one flight, the wing section drag coefficient (c sub d) increased approximately 120 percent over the uniced baseline at an aircraft angle of attack of 6 deg. On another flight, the aircraft drag coefficient (c sub d) increased by 75 percent over the uniced baseline at an aircraft lift coefficient (c sub d) of 0.5.

  17. Ice recrystallization inhibition in ice cream as affected by ice structuring proteins from winter wheat grass.

    PubMed

    Regand, A; Goff, H D

    2006-01-01

    Ice recrystallization in quiescently frozen sucrose solutions that contained some of the ingredients commonly found in ice cream and in ice cream manufactured under commercial conditions, with or without ice structuring proteins (ISP) from cold-acclimated winter wheat grass extract (AWWE), was assessed by bright field microscopy. In sucrose solutions, critical differences in moisture content, viscosity, ionic strength, and other properties derived from the presence of other ingredients (skim milk powder, corn syrup solids, locust bean gum) caused a reduction in ice crystal growth. Significant ISP activity in retarding ice crystal growth was observed in all solutions (44% for the most complex mix) containing 0.13% total protein from AWWE. In heat-shocked ice cream, ice recrystallization rates were significantly reduced 40 and 46% with the addition of 0.0025 and 0.0037% total protein from AWWE. The ISP activity in ice cream was not hindered by its inclusion in mix prior to pasteurization. A synergistic effect between ISP and stabilizer was observed, as ISP activity was reduced in the absence of stabilizer in ice cream formulations. A remarkably smoother texture for ice creams containing ISP after heat-shock storage was evident by sensory evaluation. The efficiency of ISP from AWWE in controlling ice crystal growth in ice cream has been demonstrated.

  18. CaP CURE Initiatives and Projects

    PubMed Central

    Soule, Howard R

    2003-01-01

    CaP CURE was founded in 1993 to help find better treatments and a cure for prostate cancer. By reducing the time and complexity required to apply for funding, and by funding many first-time applicants, CaP CURE has attracted a large number of high-level investigators to the field of prostate cancer research. The organization’s Therapy Consortium meets regularly to address major issues that impede progress in clinical development of new treatments for prostate cancer. CaP CURE has also sponsored an initiative to standardize clinical trial design scenarios for the clinical state of rising prostate-specific antigen and intends to present them to the Food and Drug Administration in partnership with the National Dialogue on Cancer. Finally, CaP CURE’s efforts have resulted in a significant increase in federal funding of prostate cancer research programs. PMID:16986049

  19. Atmosphere-Ice-Ocean-Ecosystem Processes in a Thinner Arctic Sea Ice Regime: The Norwegian Young Sea ICE (N-ICE2015) Expedition

    NASA Astrophysics Data System (ADS)

    Granskog, Mats A.; Fer, Ilker; Rinke, Annette; Steen, Harald

    2018-03-01

    Arctic sea ice has been in rapid decline the last decade and the Norwegian young sea ICE (N-ICE2015) expedition sought to investigate key processes in a thin Arctic sea ice regime, with emphasis on atmosphere-snow-ice-ocean dynamics and sea ice associated ecosystem. The main findings from a half-year long campaign are collected into this special section spanning the Journal of Geophysical Research: Atmospheres, Journal of Geophysical Research: Oceans, and Journal of Geophysical Research: Biogeosciences and provide a basis for a better understanding of processes in a thin sea ice regime in the high Arctic. All data from the campaign are made freely available to the research community.

  20. A cyclodextrin-capped histone deacetylase inhibitor.

    PubMed

    Amin, Jahangir; Puglisi, Antonino; Clarke, James; Milton, John; Wang, Minghua; Paranal, Ronald M; Bradner, James E; Spencer, John

    2013-06-01

    We have synthesized a β-cyclodextrin (βCD)-capped histone deacetylase (HDAC) inhibitor 3 containing an alkyl linker and a zinc-binding hydroxamic acid motif. Biological evaluation (HDAC inhibition studies) of 3 enabled us to establish the effect of replacing an aryl cap (in SAHA (vorinostat,)) 1 by a large saccharidic scaffold "cap". HDAC inhibition was observed for 3, to a lesser extent than SAHA, and rationalized by molecular docking into the active site of HDAC8. However, compound 3 displayed no cellular activity. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. The effect of polar caps on obliquity

    NASA Technical Reports Server (NTRS)

    Lindner, B. L.

    1993-01-01

    Rubincam has shown that the Martian obliquity is dependent on the seasonal polar caps. In particular, Rubincam analytically derived this dependence and showed that the change in obliquity is directly proportional to the seasonal polar cap mass. Rubincam concludes that seasonal friction does not appear to have changed Mars' climate significantly. Using a computer model for the evolution of the Martian atmosphere, Haberle et al. have made a convincing case for the possibility of huge polar caps, about 10 times the mass of the current polar caps, that exist for a significant fraction of the planet's history. Since Rubincam showed that the effect of seasonal friction on obliquity is directly proportional to polar cap mass, a scenario with a ten-fold increase in polar cap mass over a significant fraction of the planet's history would result in a secular increase in Mars' obliquity of perhaps 10 degrees. Hence, the Rubincam conclusion of an insignificant contribution to Mars' climate by seasonal friction may be incorrect. Furthermore, if seasonal friction is an important consideration in the obliquity of Mars, this would significantly alter the predictions of past obliquity.

  2. CAP - JET PROPULSION LABORATORY CONTAMINATION ANALYSIS PROGRAM

    NASA Technical Reports Server (NTRS)

    Millard, J. M.

    1994-01-01

    The Jet Propulsion Laboratory Contamination Analysis Program (CAP) is a generalized transient executive analysis computer code which solves realistic mass transport problems in the free molecular flow environment. These transport problems involve mass flux from surface source emission and re-emission, venting, and engine emission. CAP solution capability allows for one-bounce mass reflections if required. CAP was developed to solve thin-film contamination problems in the free molecular flow environment, the intent being to provide a powerful analytic tool for evaluating spacecraft contamination problems. The solution procedure uses an enclosure method based on a lumped-parameter multinodal approach with mass exchange between nodes. Transient solutions are computed by the finite difference Euler method. First-order rate theory is used to represent surface emission and reemission (user care must be taken to insure the problem is appropriate for such behavior), and all surface emission and reflections are assumed diffuse. CAP does not include the effects of post-deposition chemistry or interaction with the ambient atmosphere. CAP reads in a model represented by a multiple-block data stream. CAP allows the user to edit the input data stream and stack sequential editing operations (or cases) in order to make complex changes in behavior (surface temperatures, engine start-up and shut-down, etc.) in a single run if desired. The eight data blocks which make up the input data stream consist of problem control parameters, nodal data (area, temperature, mass, etc.), engine or vent distribution factors (based upon plume definitions), geometric configuration factors (diffuse surface emission), surface capture coefficient tables, source emission rate constant tables, reemission rate constant tables, and partial node to body collapse capability (for deposition rates only). The user must generate this data stream, since neither the problem-specific geometric relationships, the

  3. Rapid Ice Loss at Vatnajokull,Iceland Since Late 1990s Constrained by Synthetic Aperture Radar Interferometry

    NASA Astrophysics Data System (ADS)

    Zhao, W.; Amelung, F.; Dixon, T. H.; Wdowinski, S.

    2012-12-01

    Synthetic aperture radar interferometry time series is applied over Vatnajokull, Iceland by using 15 years ERS data. Ice loss at Vatnajokull accelerates since late 1990s especially after 21th century. Clear uplift signal due to ice mass loss is detected. The rebound signal is generally linear and increases a little bit after 2000. The relative annual velocity (GPS station 7485 as reference) is about 12 mm/yr at the ice cap edge, which matches the previous studies using GPS. The standard deviation compared to 11 GPS stations in this area is about 2 mm/yr. A relative-value modeling method ignoring the effect of viscous flow is chosen assuming elastic half space earth. The final ice loss estimation - 83 cm/yr - matches the climatology model with ground observations. Small Baseline Subsets is applied for time series analysis. Orbit error coupling with long wavelength phase trend due to horizontal plate motion is removed based on a second polynomial model. For simplicity, we do not consider atmospheric delay in this area because of no complex topography and small-scale turbulence is eliminated well after long-term average when calculating the annual mean velocity. Some unwrapping error still exits because of low coherence. Other uncertainties can be the basic assumption of ice loss pattern and spatial variation of the elastic parameters. It is the first time we apply InSAR time series for ice mass balance study and provide detailed error and uncertainty analysis. The successful of this application proves InSAR as an option for mass balance study and it is also important for validation of different ice loss estimation techniques.

  4. GenIce: Hydrogen-Disordered Ice Generator.

    PubMed

    Matsumoto, Masakazu; Yagasaki, Takuma; Tanaka, Hideki

    2018-01-05

    GenIce is an efficient and user-friendly tool to generate hydrogen-disordered ice structures. It makes ice and clathrate hydrate structures in various file formats. More than 100 kinds of structures are preset. Users can install their own crystal structures, guest molecules, and file formats as plugins. The algorithm certifies that the generated structures are completely randomized hydrogen-disordered networks obeying the ice rule with zero net polarization. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

  5. 47 CFR 61.43 - Annual price cap filings required.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Annual price cap filings required. 61.43... (CONTINUED) TARIFFS General Rules for Dominant Carriers § 61.43 Annual price cap filings required. Carriers subject to price cap regulation shall submit annual price cap tariff filings that propose rates for the...

  6. Observed platelet ice distributions in Antarctic sea ice: An index for ocean-ice shelf heat flux

    NASA Astrophysics Data System (ADS)

    Langhorne, P. J.; Hughes, K. G.; Gough, A. J.; Smith, I. J.; Williams, M. J. M.; Robinson, N. J.; Stevens, C. L.; Rack, W.; Price, D.; Leonard, G. H.; Mahoney, A. R.; Haas, C.; Haskell, T. G.

    2015-07-01

    Antarctic sea ice that has been affected by supercooled Ice Shelf Water (ISW) has a unique crystallographic structure and is called platelet ice. In this paper we synthesize platelet ice observations to construct a continent-wide map of the winter presence of ISW at the ocean surface. The observations demonstrate that, in some regions of coastal Antarctica, supercooled ISW drives a negative oceanic heat flux of -30 Wm-2 that persists for several months during winter, significantly affecting sea ice thickness. In other regions, particularly where the thinning of ice shelves is believed to be greatest, platelet ice is not observed. Our new data set includes the longest ice-ocean record for Antarctica, which dates back to 1902 near the McMurdo Ice Shelf. These historical data indicate that, over the past 100 years, any change in the volume of very cold surface outflow from this ice shelf is less than the uncertainties in the measurements.

  7. cap alpha. /sub i/-3 cDNA encodes the. cap alpha. subunit of G/sub k/, the stimulatory G protein of receptor-regulated K/sup +/ channels

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

    Codina, J.; Olate, J.; Abramowitz, J.

    1988-05-15

    cDNA cloning has identified the presence in the human genome of three genes encoding ..cap alpha.. subunits of pertussis toxin substrates, generically called G/sub i/. They are named ..cap alpha../sub i/-1, ..cap alpha../sub i/-2 and ..cap alpha../sub i/-3. However, none of these genes has been functionally identified with any of the ..cap alpha.. subunits of several possible G proteins, including pertussis toxin-sensitive G/sub p/'s, stimulatory to phospholipase C or A/sub 2/, G/sub i/, inhibitory to adenylyl cyclase, or G/sub k/, stimulatory to a type of K/sup +/ channels. The authors now report the nucleotide sequence and the complete predicted aminomore » acid sequence of human liver ..cap alpha../sub i/-3 and the partial amino acid sequence of proteolytic fragments of the ..cap alpha.. subunit of human erythrocyte G/sub k/. The amino acid sequence of the proteolytic fragment is uniquely encoded by the cDNA of ..cap alpha../sub i/-3, thus identifying it as ..cap alpha../sub k/. The probable identity of ..cap alpha../sub i/-1 with ..cap alpha../sub p/ and possible roles for ..cap alpha../sub i/-2, as well as additional roles for ..cap alpha../sub i/-1 and ..cap alpha../sub i/-3 (..cap alpha../sub k/) are discussed.« less

  8. The mass balance of the ice plain of Ice Stream B and Crary Ice Rise

    NASA Technical Reports Server (NTRS)

    Bindschadler, Robert

    1993-01-01

    The region in the mouth of Ice Stream B (the ice plain) and that in the vicinity of Crary Ice Rise are experiencing large and rapid changes. Based on velocity, ice thickness, and accumulation rate data, the patterns of net mass balance in these regions were calculated. Net mass balance, or the rate of ice thickness change, was calculated as the residual of all mass fluxes into and out of subregions (or boxes). Net mass balance provides a measure of the state of health of the ice sheet and clues to the current dynamics.

  9. The origin of 17O-depleted barite in Neoproterozoic cap carbonates in South China: A sedimentological perspective

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Bao, H.; Yuan, X.

    2009-12-01

    deposition of Marinoan cap carbonates. One possibility is that the initially deposited cap carbonate may have been uplifted into a zone influenced by meteoric water due to glacioeustasy and lithospheric rebound as a result of a quick unloading of a massive continental ice cap on the Yangtze Block. Karstic dissolution has also been recognized in cap dolostones in NW Africa and NW Canada. While the voids and cavities in South China may be of a similar karst origin as those in NM Africa, sedimentological evidence, together with multiple sulfur and oxygen isotope data, suggests that the precipitation of the barite in South China may be related to an episode of free Ba2+ supply from deep, anoxic water, in association with a transgression (instead of an sea-level fall) after a karst dissolution. Thus, we suggest that SO42- was present in seawater prior to the beginning of Marinoan meltdown. It was the Ba2+ supply that limited the occurrence of barite to specific stratigraphic horizons in the cap carbonates. If the above inference is true, the 17O-depleted barite has recorded an atmospheric/hydrological condition well after the initial meltdown of the Marinoan "snowball" Earth.

  10. Glacio-isostasy and Glacial Ice Load at Law Dome, Wilkes Land, East Antarctica

    NASA Astrophysics Data System (ADS)

    Goodwin, Ian D.; Zweck, Christopher

    2000-05-01

    The Holocene sea-level high stand or "marine limit" in Wilkes Land, East Antarctica, reached ˜30 m above present sea level at a few dispersed sites. The most detailed marine limit data have been recorded for the Windmill Islands and Budd Coast at the margin of the Law Dome ice cap, a dome of the East Antarctic Ice Sheet (EAIS). Relative sea-level lowering of 30 m and the associated emergence of the Windmill Islands have occurred since 6900 14C (corr.) yr B.P. Numerical modeling of the Earth's rheology is used to determine the glacio-isostatic component of the observed relative sea-level lowering. Glaciological evidence suggests that most of EAIS thickening occurred around its margin, with expansion onto the continental shelf. Consequently, a regional ice history for the last glacial maximum (LGM) was applied in the glacio-isostatic modeling to test whether the observed relative sea-level lowering was primarily produced by regional ice-sheet changes. The results of the modeling indicate that the postglacial (13,000 to 8000 14C yr B.P) removal of an ice load of between 770 and 1000 m from around the margin of the Law Dome and adjacent EAIS have produced the observed relative sea-level lowering. Such an additional ice load would have been associated with a 40- to 65-km expansion of the Law Dome to near the continental shelf break, together with a few hundred meters of ice thickening on the adjoining coastal slope of the EAIS up to 2000 m elevation. Whereas the observed changes in relative sea level are shown to be strongly influenced by regional ice sheet changes, the glacio-isostatic response at the Windmill Islands results from a combination of regional and, to a lesser extent, Antarctic-wide effects. The correspondence between the Holocene relative sea-level lowering interpreted at the margin of the Law Dome and the lowering interpreted along the remainder of the Wilkes Land and Oates Land coasts (105°-160° E) suggests that a similar ice load of up to 1000 m

  11. Operationally Monitoring Sea Ice at the Canadian Ice Service

    NASA Astrophysics Data System (ADS)

    de Abreu, R.; Flett, D.; Carrieres, T.; Falkingham, J.

    2004-05-01

    The Canadian Ice Service (CIS) of the Meteorological Service of Canada promotes safe and efficient maritime operations and protects Canada's environment by providing reliable and timely information about ice and iceberg conditions in Canadian waters. Daily and seasonal charts describing the extent, type and concentration of sea ice and icebergs are provided to support navigation and other activities (e.g. oil and gas) in coastal waters. The CIS relies on a suite of spaceborne visible, infrared and microwave sensors to operationally monitor ice conditions in Canadian coastal and inland waterways. These efforts are complemented by operational sea ice models that are customized and run at the CIS. The archive of these data represent a 35 year archive of ice conditions and have proven to be a valuable dataset for historical sea ice analysis. This presentation will describe the daily integration of remote sensing observations and modelled ice conditions used to produce ice and iceberg products. A review of the decadal evolution of this process will be presented, as well as a glimpse into the future of ice and iceberg monitoring. Examples of the utility of the CIS digital sea ice archive for climate studies will also be presented.

  12. Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.; Cavalieri, Donald J.

    2005-01-01

    Sea ice covers vast areas of the polar oceans, with ice extent in the Northern Hemisphere ranging from approximately 7 x 10(exp 6) sq km in September to approximately 15 x 10(exp 6) sq km in March and ice extent in the Southern Hemisphere ranging from approximately 3 x 10(exp 6) sq km in February to approximately 18 x 10(exp 6) sq km in September. These ice covers have major impacts on the atmosphere, oceans, and ecosystems of the polar regions, and so as changes occur in them there are potential widespread consequences. Satellite data reveal considerable interannual variability in both polar sea ice covers, and many studies suggest possible connections between the ice and various oscillations within the climate system, such as the Arctic Oscillation, North Atlantic Oscillation, and Antarctic Oscillation, or Southern Annular Mode. Nonetheless, statistically significant long-term trends are also apparent, including overall trends of decreased ice coverage in the Arctic and increased ice coverage in the Antarctic from late 1978 through the end of 2003, with the Antarctic ice increases following marked decreases in the Antarctic ice during the 1970s. For a detailed picture of the seasonally varying ice cover at the start of the 21st century, this chapter includes ice concentration maps for each month of 2001 for both the Arctic and the Antarctic, as well as an overview of what the satellite record has revealed about the two polar ice covers from the 1970s through 2003.

  13. Tip cap for a turbine rotor blade

    DOEpatents

    Kimmel, Keith D

    2014-03-25

    A turbine rotor blade with a spar and shell construction, and a tip cap that includes a row of lugs extending from a bottom side that form dovetail grooves that engage with similar shaped lugs and grooves on a tip end of the spar to secure the tip cap to the spar against radial displacement. The lug on the trailing edge end of the tip cap is aligned perpendicular to a chordwise line of the blade in the trailing edge region in order to minimize stress due to the lugs wanting to bend under high centrifugal loads. A two piece tip cap with lugs at different angles will reduce the bending stress even more.

  14. Extensive Ice Fractures in the Beaufort Sea [detail

    NASA Image and Video Library

    2017-12-08

    The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this view of extensive sea-ice fracturing off the northern coast of Alaska. The event began in late-January and spread west toward Banks Island throughout February and March 2013. Visualizations of the Arctic often give the impression that the ice cap is a continuous sheet of stationary, floating ice. In fact, it is a collection of smaller pieces that constantly shift, crack, and grind against one another as they are jostled by winds and ocean currents. Especially during the summer—but even during the height of winter—cracks—or leads—open up between pieces of ice. That was what was happening on the left side of the animation (seen here: bit.ly/10kE7sh) in late January. A high-pressure weather system was parked over the region, producing warmer temperatures and winds that flowed in a southwesterly direction. That fueled the Beaufort Gyre, a wind-driven ocean current that flows clockwise. The gyre was the key force pulling pieces of ice west past Point Barrow, the northern nub of Alaska that protrudes into the Beaufort Sea. “A fracturing event in this area is not unusual because the Beaufort Gyre tends to push ice away from Banks Island and the Canadian Archipelago,” explained Walt Meier of the National Snow & Ice Data Center (NSIDC). “Point Barrow can act like a ‘pin point’ where the ice catches and fractures to the north and east.” In February, however, a series of storms passing over central Alaska exacerbated the fracturing. Strong westerly winds prompted several large pieces of ice to break away in an arc-shaped wave that moved progressively east. By the end of February, large pieces of ice had fractured all the way to the western coast of Banks Island, a distance of about 1,000 kilometers (600 miles). The data used to create the animation came from the longwave infrared (thermal) portion of the electromagnetic spectrum, so the animation illustrates how

  15. Extensive Ice Fractures in the Beaufort Sea [annotated

    NASA Image and Video Library

    2017-12-08

    The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this view of extensive sea-ice fracturing off the northern coast of Alaska. The event began in late-January and spread west toward Banks Island throughout February and March 2013. Visualizations of the Arctic often give the impression that the ice cap is a continuous sheet of stationary, floating ice. In fact, it is a collection of smaller pieces that constantly shift, crack, and grind against one another as they are jostled by winds and ocean currents. Especially during the summer—but even during the height of winter—cracks—or leads—open up between pieces of ice. That was what was happening on the left side of the animation (seen here: bit.ly/10kE7sh) in late January. A high-pressure weather system was parked over the region, producing warmer temperatures and winds that flowed in a southwesterly direction. That fueled the Beaufort Gyre, a wind-driven ocean current that flows clockwise. The gyre was the key force pulling pieces of ice west past Point Barrow, the northern nub of Alaska that protrudes into the Beaufort Sea. “A fracturing event in this area is not unusual because the Beaufort Gyre tends to push ice away from Banks Island and the Canadian Archipelago,” explained Walt Meier of the National Snow & Ice Data Center (NSIDC). “Point Barrow can act like a ‘pin point’ where the ice catches and fractures to the north and east.” In February, however, a series of storms passing over central Alaska exacerbated the fracturing. Strong westerly winds prompted several large pieces of ice to break away in an arc-shaped wave that moved progressively east. By the end of February, large pieces of ice had fractured all the way to the western coast of Banks Island, a distance of about 1,000 kilometers (600 miles). The data used to create the animation came from the longwave infrared (thermal) portion of the electromagnetic spectrum, so the animation illustrates how

  16. Validation and Interpretation of a new sea ice GlobIce dataset using buoys and the CICE sea ice model

    NASA Astrophysics Data System (ADS)

    Flocco, D.; Laxon, S. W.; Feltham, D. L.; Haas, C.

    2012-04-01

    The GlobIce project has provided high resolution sea ice product datasets over the Arctic derived from SAR data in the ESA archive. The products are validated sea ice motion, deformation and fluxes through straits. GlobIce sea ice velocities, deformation data and sea ice concentration have been validated using buoy data provided by the International Arctic Buoy Program (IABP). Over 95% of the GlobIce and buoy data analysed fell within 5 km of each other. The GlobIce Eulerian image pair product showed a high correlation with buoy data. The sea ice concentration product was compared to SSM/I data. An evaluation of the validity of the GlobICE data will be presented in this work. GlobICE sea ice velocity and deformation were compared with runs of the CICE sea ice model: in particular the mass fluxes through the straits were used to investigate the correlation between the winter behaviour of sea ice and the sea ice state in the following summer.

  17. Characterization of Ice Roughness From Simulated Icing Encounters

    NASA Technical Reports Server (NTRS)

    Anderson, David N.; Shin, Jaiwon

    1997-01-01

    Detailed measurements of the size of roughness elements on ice accreted on models in the NASA Lewis Icing Research Tunnel (IRT) were made in a previous study. Only limited data from that study have been published, but included were the roughness element height, diameter and spacing. In the present study, the height and spacing data were found to correlate with the element diameter, and the diameter was found to be a function primarily of the non-dimensional parameters freezing fraction and accumulation parameter. The width of the smooth zone which forms at the leading edge of the model was found to decrease with increasing accumulation parameter. Although preliminary, the success of these correlations suggests that it may be possible to develop simple relationships between ice roughness and icing conditions for use in ice-accretion-prediction codes. These codes now require an ice-roughness estimate to determine convective heat transfer. Studies using a 7.6-cm-diameter cylinder and a 53.3-cm-chord NACA 0012 airfoil were also performed in which a 1/2-min icing spray at an initial set of conditions was followed by a 9-1/2-min spray at a second set of conditions. The resulting ice shape was compared with that from a full 10-min spray at the second set of conditions. The initial ice accumulation appeared to have no effect on the final ice shape. From this result, it would appear the accreting ice is affected very little by the initial roughness or shape features.

  18. Submesoscale sea ice-ocean interactions in marginal ice zones

    NASA Astrophysics Data System (ADS)

    Thompson, A. F.; Manucharyan, G.

    2017-12-01

    Signatures of ocean eddies, fronts and filaments are commonly observed within the marginal ice zones (MIZ) from satellite images of sea ice concentration, in situ observations via ice-tethered profilers or under-ice gliders. Localized and intermittent sea ice heating and advection by ocean eddies are currently not accounted for in climate models and may contribute to their biases and errors in sea ice forecasts. Here, we explore mechanical sea ice interactions with underlying submesoscale ocean turbulence via a suite of numerical simulations. We demonstrate that the release of potential energy stored in meltwater fronts can lead to energetic submesoscale motions along MIZs with sizes O(10 km) and Rossby numbers O(1). In low-wind conditions, cyclonic eddies and filaments efficiently trap the sea ice and advect it over warmer surface ocean waters where it can effectively melt. The horizontal eddy diffusivity of sea ice mass and heat across the MIZ can reach O(200 m2 s-1). Submesoscale ocean variability also induces large vertical velocities (order of 10 m day-1) that can bring relatively warm subsurface waters into the mixed layer. The ocean-sea ice heat fluxes are localized over cyclonic eddies and filaments reaching about 100 W m-2. We speculate that these submesoscale-driven intermittent fluxes of heat and sea ice can potentially contribute to the seasonal evolution of MIZs. With continuing global warming and sea ice thickness reduction in the Arctic Ocean, as well as the large expanse of thin sea ice in the Southern Ocean, submesoscale sea ice-ocean processes are expected to play a significant role in the climate system.

  19. Perturbation and melting of snow and ice by the 13 November 1985 eruption of Nevado del Ruiz, Colombia, and consequent mobilization, flow and deposition of lahars

    USGS Publications Warehouse

    Pierson, T.C.; Janda, R.J.; Thouret, J.-C.; Borrero, C.A.

    1990-01-01

    A complex sequence of pyroclastic flows and surges erupted by Nevado del Ruiz volcano on 13 November 1985 interacted with snow and ice on the summit ice cap to trigger catastrophic lahars (volcanic debris flows), which killed more than 23,000 people living at or beyond the base of the volcano. The rapid transfer of heat from the hot eruptive products to about 10 km2 of the snowpack, combined with seismic shaking, produced large volumes of meltwater that flowed downslope, liquefied some of the new volcanic deposits, and generated avalanches of saturated snow, ice and rock debris within minutes of the 21:08 (local time) eruption. About 2 ?? 107 m3 of water was discharged into the upper reaches of the Molinos, Nereidas, Guali, Azufrado and Lagunillas valleys, where rapid entrainment of valley-fill sediment transformed the dilute flows and avalanches to debris flows. Computed mean velocities of the lahars at peak flow ranged up to 17 m s-1. Flows were rapid in the steep, narrow upper canyons and slowed with distance away from the volcano as flow depth and channel slope diminished. Computed peak discharges ranged up to 48,000 m3 s-1 and were greatest in reaches 10 to 20 km downstream from the summit. A total of about 9 ?? 107 m3 of lahar slurry was transported to depositional areas up to 104 km from the source area. Initial volumes of individual lahars increased up to 4 times with distance away from the summit. The sedimentology and stratigraphy of the lahar deposits provide compelling evidence that: (1) multiple initial meltwater pulses tended to coalesce into single flood waves; (2) lahars remained fully developed debris flows until they reached confluences with major rivers; and (3) debris-flow slurry composition and rheology varied to produce gradationally density-stratified flows. Key lessons and reminders from the 1985 Nevado del Ruiz volcanic eruption are: (1) catastrophic lahars can be generated on ice- and snow-capped volcanoes by relatively small eruptions; (2

  20. Ice Stars

    NASA Image and Video Library

    2017-12-08

    Ice Stars - August 4th, 2002 Description: Like distant galaxies amid clouds of interstellar dust, chunks of sea ice drift through graceful swirls of grease ice in the frigid waters of Foxe Basin near Baffin Island in the Canadian Arctic. Sea ice often begins as grease ice, a soupy slick of tiny ice crystals on the ocean's surface. As the temperature drops, grease ice thickens and coalesces into slabs of more solid ice. Credit: USGS/NASA/Landsat 7 To learn more about the Landsat satellite go to: landsat.gsfc.nasa.gov/ NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook