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Sample records for active ice margin

  1. Analysis of methanogenic and methanotrophic activity at the western margin of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Broemsen, E. L.; Webster, K. D.; Dieser, M.; Pratt, L. M.; Christner, B. C.

    2012-12-01

    Anoxic conditions in environments beneath the world's glaciers and ice sheets provide plausible habitats supporting the microbial production of methane. Recent reports of potential methane sources beneath the Greenland Ice Sheet (GrIS) suggest in situ production by an active community of methanogens. Beneath the GrIS, microbially derived methane can be dissolved in subglacial water, and during periods of melting, can exchange with the atmosphere at sites of subglacial discharge. Transfer of methane from subglacial fluids to the atmosphere could be a significant climate factor, but few data are available to make such assessments. The specific aim of this study was to characterize the composition and activity of methanogens and methanotrophs present in samples of subglacial outflow at the ice sheet margin near Kangerlussuaq, Greenland. Subglaical water was collected twice-weekly over a nine week period (mid July to mid September of 2012) and the dissolved methane concentration in the samples was determined via gas chromatography. Extracted RNA and DNA from the subglacial water was analyzed by analysis of 16s rRNA and rRNA genes present in the subglacial assemblages. From the molecular results we infer the presence of active methanogens related to the order Methanosarcinales. Further, locally elevated concentrations of atmospheric methane as high as 1.92 ± 0.03 ppmv, were detected in the ice tunnel of the subglacial outflow using open-path laser spectrometry. From these data we estimate rates of methane release at the ice sheet margin during the summer melt months at this geographical location. The results provide a context for addressing the impact that deglaciation will have on the release of greenhouse gases from ice sheets on a warming Earth.

  2. Sea ice structure and biological activity in the Antarctic marginal ice zone

    NASA Astrophysics Data System (ADS)

    Clarke, D. B.; Ackley, S. F.

    1984-03-01

    Ice cores obtained during October-November 1981 from Weddell Sea pack ice were analyzed for physical, chemical, and biological parameters. Frazil ice, which is associated with dynamic, turbulent conditions in the water column, predominated (70%). Both floe thickness and salinity indicate ice which is less than 1 year old. Chemical analyses, particularly with regard to the nutrients, revealed a complex picture. Phosphate values are scattered relative to the dilution curve. Nitrate and silicate values are lower than expected from simple scaling with salinity and suggest diatom growth within the ice. Nitrite values are higher in the ice than in adjacent waters. Frazil ice formation which probably concentrates algal cells from the water column into ice floes results in higher initial chlorophyll a concentrations in the ice than in adjacent waters. This mechanical concentration is further enhanced by subsequent reproduction within the ice. Ice core chlorophyll ranged from 0.09 to 3.8 mg/m3, comparable to values previously reported for this area but significantly lower than values for Antarctic coastal fast ice. The dominance of frazil ice in the Weddell is one of the major differences between this area and others. Consequently, we believe that ice structural conditions significantly influence the biological communities in the ice.

  3. Ice marginal dynamics during surge activity, Kuannersuit Glacier, Disko Island, West Greenland

    NASA Astrophysics Data System (ADS)

    Roberts, David H.; Yde, Jacob C.; Knudsen, N. Tvis; Long, Antony J.; Lloyd, Jerry M.

    2009-02-01

    The Kuannersuit Glacier surged 11 km between 1995 and 1998. The surge resulted in the formation of an ice cored thrust moraine complex constructed by subglacial and proglacial glaciotectonic processes. Four main thrust zones are evident in the glacier snout area with phases of compressional folding and thrusting followed by hydrofracture in response to the build-up of compressional stresses and the aquicludal nature of submarginal permafrost and naled. Various types of stratified debris-rich ice facies occur within the marginal zone: The first (Facies I) comprises laterally continuous strata of ice with sorted sediment accumulations, and is reworked and thrust naled ice. The second is laterally discontinuous stratified debris-rich ice with distinct tectonic structures, and is derived through subglacial extensional deformation and localised regelation (Facies II), whilst the third type is characterised by reworked and brecciated ice associated with the reworking and entrainment of meteoric ice (Facies III). Hydrofracture dykes and sills (Facies IV) cross-cut the marginal ice cored thrust moraines, with their sub-vertically frozen internal contact boundaries and sedimentary structures, suggesting supercooling operated as high-pressure evacuation of water occurred during thrusting, but this is not related to the formation of basal stratified debris-rich ice. Linear distributions of sorted fines transverse to ice flow, and small stratified sediment ridges that vertically cross-cut the ice surface up-ice of the thrust zone relate to sediment migration along crevasse traces and fluvial infilling of crevasses. From a palaeoglaciological viewpoint, marginal glacier tectonics, ice sediment content and sediment delivery mechanisms combine to control the development of this polythermal surge valley landsystem. The bulldozing of proglacial sediments and the folding and thrusting of naled leads to the initial development of the outer zone of the moraine complex. This becomes

  4. A Signal of Ice Loading in Late Pleistocene Activity of the Sudetic Marginal Fault (Central Europe)

    NASA Astrophysics Data System (ADS)

    Hartvich, F.; Stepancikova, P.; Rockwell, T. K.; Nývlt, D.; Stemberk, J.; Rood, D. H.; Hók, J.; Ortuňo, M.; Myers, M.; Luttrell, K. M.; Wechsler, N.

    2014-12-01

    We combine paleoseismic trench and cosmogenic dating results to study the late Pleistocene-Holocene history of morphologically pronounced NW-SE trending Sudetic Marginal Fault (SMF) situated at the northeastern limit of the Bohemian Massif in central Europe. Eighteen trenches were excavated at the Bila Voda site to study 3D distribution of a beheaded alluvial fan on the NE block of the fault and to find the offset "feeder channel" that sourced the deposits. We interpret a small drainage of about 40-60 m to the SE of the fan apex as the feeder channel. A 2.5 m depth profile was collected for cosmogenic exposure dating from a well-preserved part of the fan. Using a simple model that accounts for pre-depositional exposure (inheritance) and assuming no surface erosion, 10Be concentrations are well-fit with an apparent exposure age of ~12 ka. However, this is a minimum limiting age if the surface was eroded by gelifluction in the late Pleistocene. Assuming a ~25 ka OSL age for the base of the fan apex it gives a left-lateral slip rate of ~2 mm/yr. As the Holocene deposits do not show significant displacement, most of the recorded slip took place during Late Pleistocene with corresponding slip rate of 2.8 to 3.5 mm/yr. Bila Voda site lies ~150 km south from the Late Pleistocene Weichselian maximum (~20 ka) ice-sheet front. Thus, we hypothesize that the slip rate acceleration was due to ice-loading and subsequent unloading during deglaciation. To test this, we calculated the stress induced in the lithosphere from ablation of the Weichselian ice sheet modeled as a flexing elastic plate. Preliminary modeling results indicate that complete deglaciation alters the stress field such that it would inhibit left lateral failure on the SMF, consistent with observations suggesting no slip occurred during the Holocene. Although the SMF is ~150 km from the Weichselian ice sheet front, it is well within the flexural rebound area of the ice sheet, causing normal stress on the SMF to

  5. Different bulk and active bacterial communities in cryoconite from the margin and interior of the Greenland ice sheet.

    PubMed

    Stibal, Marek; Schostag, Morten; Cameron, Karen A; Hansen, Lars H; Chandler, David M; Wadham, Jemma L; Jacobsen, Carsten S

    2015-04-01

    Biological processes in the supraglacial ecosystem, including cryoconite, contribute to nutrient cycling within the cryosphere and may affect surface melting, yet little is known of the diversity of the active microbes in these environments. We examined the bacterial abundance and community composition of cryoconite over a melt season at two contrasting sites at the margin and in the interior of the Greenland ice sheet, using sequence analysis and quantitative polymerase chain reaction of coextracted 16S rDNA and rRNA. Significant differences were found between bulk (rDNA) and potentially active (rRNA) communities, and between communities sampled from the two sites. Higher concentrations of rRNA than rDNA were detected at the interior site, whereas at the margin several orders of magnitude less rRNA was found compared with rDNA, which may be explained by a lower proportion of active bacteria at the margin site. The rRNA communities at both sites were dominated by a few taxa of Cyanobacteria and Alpha- and/or Betaproteobacteria. The bulk alpha diversity was higher in the margin site community, suggesting that local sources may be contributing towards the gene pool in addition to long distance transport.

  6. Ocean-ice interaction in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Peng, Chich Y.

    1994-01-01

    Ocean ice interaction processes in the Marginal Ice Zone (MIZ) by wind, waves, and mesoscale features, such as upwelling and eddies, are studied using ERS-1 Synthetic Aperture Radar (SAR) images and ocean ice interaction model. A sequence of SAR images of the Chukchi Sea MIZ with three days interval are studied for ice edge advance/retreat. Simultaneous current measurements from the northeast Chukchi Sea as well as the Barrow wind record are used to interpret the MIZ dynamics.

  7. Cenozoic ice volume and margin erosion

    SciTech Connect

    Miller, K.C.; Fairbanks, R.G.; Mountain, G.S.

    1985-01-01

    Cenozoic benthic foraminiferal oxygen isotopic data indicates that the world was glaciated in the early Oligocene, middle Oligocene, latest Oligocene, and middle Miocene to Recent, but are insufficient to resolve if the world was ice free at other times. The authors relate Oligocene and younger intervals of ice growth to continental margin erosional events. Relationships between eustasy and continental margin sedimentation are controversial. Coastal onlap is indirectly linked with rising sea level, occurring either when subsidence exceeds the rate of sea level fall or during sea-level rise. Although chronostratigraphic breaks are often local in origin, inter-regional unconformities result from eustatic lowerings. Strong evidence for eustatic lowerings is provided by the incision of canyons on margins. Chronostratigraphic breaks and canyons have noted on the US and Irish margins near the lower/upper Oligocene and middle/upper Miocene boundaries. These periods of margin erosion are temporally linked with oxygen isotopic evidence for ice growth, with erosion correlating with the greatest rate of ice growth. If the Eocene was ice free, there may have been mechanistic differences between Eocene erosion and Oligocene to Recent glacio-eustatic erosion. The authors present seismic stratigraphic evidence from the New Jersey margin that indicates contrasting styles of margin erosion between the Lower Tertiary and Upper Tertiary.

  8. Norwegian remote sensing experiment in a marginal ice zone

    USGS Publications Warehouse

    Farrelly, B.; Johannessen, J.A.; Svendsen, E.; Kloster, K.; Horjen, I.; Matzler, C.; Crawford, J.; Harrington, R.; Jones, L.; Swift, C.; Delnore, V.E.; Cavalieri, D.; Gloersen, P.; Hsiao, S.V.; Shemdin, O.H.; Thompson, T.W.; Ramseier, R.O.; Johannessen, O.M.; Campbell, W.J.

    1983-01-01

    The Norwegian Remote Sensing Experiment in the marginal ice zone north of Svalbard took place in fall 1979. Coordinated passive and active microwave measurements were obtained from shipborne, airborne, and satellite instruments together with in situ observations. The obtained spectra of emissivity (frequency range, 5 to 100 gigahertz) should improve identification of ice types and estimates of ice concentration. Mesoscale features along the ice edge were revealed by a 1.215-gigahertz synthetic aperture radar. Ice edge location by the Nimbus 7 scanning multichannel microwave radiometer was shown to be accurate to within 10 kilometers.

  9. Energy transport in the marginal ice zone

    NASA Astrophysics Data System (ADS)

    Dixon, Tony W.; Squire, Vernon A.

    2001-09-01

    A novel approach to modeling ocean wave scattering in the marginal ice zone that uses the coherent potential approximation to compute the energy transport velocity is reported. The necessary theory is developed by considering sea ice floes to be thin elastic beams governed by the Euler-Bernoulli equation, with the open water surrounding each floe subject to the same equation with its material coefficients set to be very small quantities. This mathematical stratagem facilitates the solution of the problem and yields interesting results about the speed at which wave energy propagates through a marginal ice zone, the dispersion relation for a random mixture of ice floes and water, and the mean free path or attenuation coefficient. Results from the model are compared with data reported by Wadhams et al. [1988].

  10. Subglacial hydrology and ice stream margin locations

    NASA Astrophysics Data System (ADS)

    Perol, Thibaut; Rice, James R.; Platt, John D.; Suckale, Jenny

    2015-07-01

    Fast-flowing ice streams in West Antarctica are separated from the nearly stagnant ice in the adjacent ridge by zones of highly localized deformation known as shear margins. It is presently uncertain what mechanisms control the location of shear margins and possibly allow them to migrate. In this paper we show how subglacial hydrological processes can select the shear margin location, leading to a smooth transition from a slipping to a locked bed at the base of an ice stream. Our study uses a two-dimensional thermomechanical model in a cross section perpendicular to the direction of flow. We confirm that the intense straining at the shear margins can generate large temperate regions within the deforming ice. Assuming that the melt generated in the temperate ice collects in a drainage channel at the base of the margin, we show that a channel locally decreases the pore pressure in the subglacial till. Therefore, the basal shear strength just outside the channel, assuming a Coulomb-plastic rheology, can be substantially higher than that inferred under the majority of the stream. Results show that the additional basal resistance produced by the channel lowers the stress concentrated on the locked portion of the bed. Matching the model to surface velocity data, we find that shear margins are stable when the slipping-to-locked bed transition occurs less than 500 m away from a channel operating at an effective pressure of 200 kPa and for a hydraulic transmissivity equivalent to a basal water film of order 0.2 mm thickness.

  11. Microwave and physical properties of sea ice in the winter marginal ice zone

    NASA Technical Reports Server (NTRS)

    Tucker, W. B., III; Perovich, D. K.; Gow, A. J.; Grenfell, T. C.; Onstott, R. G.

    1991-01-01

    Surface-based active and passive microwave measurements were made in conjunction with ice property measurements for several distinct ice types in the Fram Strait during March and April 1987. Synthesis aperture radar imagery downlinked from an aircraft was used to select study sites. The surface-based radar scattering cross section and emissivity spectra generally support previously inferred qualitative relationships between ice types, exhibiting expected separation between young, first-year and multiyear ice. Gradient ratios, calculated for both active and passive data, appear to allow clear separation of ice types when used jointly. Surface flooding of multiyear floes, resulting from excessive loading and perhaps wave action, causes both active and passive signatures to resemble those of first-year ice. This effect could possibly cause estimates of ice type percentages in the marginal ice zone to be in error when derived from aircraft- or satellite-born sensors.

  12. Modeling Wave-Ice Interactions in the Marginal Ice Zone

    NASA Astrophysics Data System (ADS)

    Orzech, Mark; Shi, Fengyan; Bateman, Sam; Veeramony, Jay; Calantoni, Joe

    2015-04-01

    The small-scale (O(m)) interactions between waves and ice floes in the marginal ice zone (MIZ) are investigated with a coupled model system. Waves are simulated with the non-hydrostatic finite-volume model NHWAVE (Ma et al., 2012) and ice floes are represented as bonded collections of smaller particles with the discrete element system LIGGGHTS (Kloss et al., 2012). The physics of fluid and ice are recreated as authentically as possible, to allow the coupled system to supplement and/or substitute for more costly and demanding field experiments. The presentation will first describe the development and validation of the coupled system, then discuss the results of a series of virtual experiments in which ice floe and wave characteristics are varied to examine their effects on energy dissipation, MIZ floe size distribution, and ice pack retreat rates. Although Wadhams et al. (1986) suggest that only a small portion (roughly 10%) of wave energy entering the MIZ is reflected, dissipation mechanisms for the remaining energy have yet to be delineated or measured. The virtual experiments are designed to focus on specific properties and processes - such as floe size and shape, collision and fracturing events, and variations in wave climate - and measure their relative roles the transfer of energy and momentum from waves to ice. Questions to be examined include: How is energy dissipated by ice floe collisions, fracturing, and drag, and how significant is the wave attenuation associated with each process? Do specific wave/floe length scale ratios cause greater wave attenuation? How does ice material strength affect the rate of wave energy loss? The coupled system will ultimately be used to test and improve upon wave-ice parameterizations for large-scale climate models. References: >Kloss, C., C. Goniva, A. Hager, S. Amberger, and S. Pirker (2012). Models, algorithms and validation for opensource DEM and CFD-DEM. Progress in Computational Fluid Dynamics 12(2/3), 140-152. >Ma, G

  13. Mapping and Assessing Variability in the Antarctic Marginal Ice Zone, the Pack Ice and Coastal Polynyas

    NASA Astrophysics Data System (ADS)

    Stroeve, Julienne; Jenouvrier, Stephanie

    2016-04-01

    Sea ice variability within the marginal ice zone (MIZ) and polynyas plays an important role for phytoplankton productivity and krill abundance. Therefore mapping their spatial extent, seasonal and interannual variability is essential for understanding how current and future changes in these biological active regions may impact the Antarctic marine ecosystem. Knowledge of the distribution of different ice types to the total Antarctic sea ice cover may also help to shed light on the factors contributing towards recent expansion of the Antarctic ice cover in some regions and contraction in others. The long-term passive microwave satellite data record provides the longest and most consistent data record for assessing different ice types. However, estimates of the amount of MIZ, consolidated pack ice and polynyas depends strongly on what sea ice algorithm is used. This study uses two popular passive microwave sea ice algorithms, the NASA Team and Bootstrap to evaluate the distribution and variability in the MIZ, the consolidated pack ice and coastal polynyas. Results reveal the NASA Team algorithm has on average twice the MIZ and half the consolidated pack ice area as the Bootstrap algorithm. Polynya area is also larger in the NASA Team algorithm, and the timing of maximum polynya area may differ by as much as 5 months between algorithms. These differences lead to different relationships between sea ice characteristics and biological processes, as illustrated here with the breeding success of an Antarctic seabird.

  14. The role of the margins in ice stream dynamics

    NASA Technical Reports Server (NTRS)

    Echelmeyer, Keith; Harrison, William

    1993-01-01

    At first glance, it would appear that the bed of the active ice stream plays a much more important role in the overall force balance than do the margins, especially because the ratio of the half-width to depth for a typical ice stream is large (15:1 to 50:1). On the other hand, recent observations indicate that at least part of the ice stream is underlain by a layer of very weak till (shear strength about 2 kPa), and this weak basal layer would then imply that some or all of the resistive drag is transferred to the margins. In order to address this question, a detailed velocity profile near Upstream B Camp, which extends from the center of the ice stream, across the chaotic shear margin, and onto the Unicorn, which is part of the slow-moving ice sheet was measured. Comparison of this observed velocity profile with finite-element models of flow shows several interesting features. First, the shear stress at the margin is on the order of 130 kPa, while the mean value along the bed is about 15 kPa. Integration of these stresses along the boundaries indicates that the margins provide 40 to 50 percent, and the bed, 60 to 40 percent of the total resistive drag needed to balance the gravitational driving stress in this region. (The range of values represents calculations for different values of surface slope.) Second, the mean basal stress predicted by the models shows that the entire bed cannot be blanketed by the weak till observed beneath upstream B - instead there must be a distribution of weak till and 'sticky spots' (e.g., 85 percent till and 15 percent sticky spots of resistive stress equal to 100 kPa). If more of the bed were composed of weak till, then the modeled velocity would not match that observed. Third, the ice must exhibit an increasing enhancement factor as the margins are approached (E equals 10 in the chaotic zone), in keeping with laboratory measurements on ice under prolonged shear strain. Also, there is either a narrow zone of somewhat stiffer ice (E

  15. Microwave properties of sea ice in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Onstott, R. G.; Larson, R. W.

    1986-01-01

    Active microwave properties of summer sea ice were measured. Backscatter data were acquired at frequencies from 1 to 17 GHz, at angles from 0 to 70 deg from vertical, and with like and cross antenna polarizations. Results show that melt-water, snow thickness, snowpack morphology, snow surface roughness, ice surface roughness, and deformation characteristics are the fundamental scene parameters which govern the summer sea ice backscatter response. A thick, wet snow cover dominates the backscatter response and masks any ice sheet features below. However, snow and melt-water are not distributed uniformly and the stage of melt may also be quite variable. These nonuniformities related to ice type are not necessarily well understood and produce unique microwave signature characteristics.

  16. Waves and mesoscale features in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Peng, Chih Y.

    1993-01-01

    Ocean-ice interaction processes in the Marginal Ice Zone (MIZ) by waves and mesoscale features, such as upwelling and eddies, are studied using ERS-1 Synthetic Aperture Radar (SAR) imagery and wave-ice interaction models. Satellite observations of mesoscale features can play a crucial role in ocean-ice interaction study.

  17. 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.

  18. Remote sensing of the Fram Strait marginal ice zone

    USGS Publications Warehouse

    Shuchman, R.A.; Burns, B.A.; Johannessen, O.M.; Josberger, E.G.; Campbell, W.J.; Manley, T.O.; Lannelongue, N.

    1987-01-01

    Sequential remote sensing images of the Fram Strait marginal ice zone played a key role in elucidating the complex interactions of the atmosphere, ocean, and sea ice. Analysis of a subset of these images covering a 1-week period provided quantitative data on the mesoscale ice morphology, including ice edge positions, ice concentrations, floe size distribution, and ice kinematics. The analysis showed that, under light to moderate wind conditions, the morphology of the marginal ice zone reflects the underlying ocean circulation. High-resolution radar observations showed the location and size of ocean eddies near the ice edge. Ice kinematics from sequential radar images revealed an ocean eddy beneath the interior pack ice that was verified by in situ oceanographic measurements.

  19. The disappearance of a "classical" ice marginal position in NE-Germany: the Frankfurt phase puzzle

    NASA Astrophysics Data System (ADS)

    Böse, Margot; Lüthgens, Christopher; Nitzsche, Carolin; Hardt, Jacob

    2016-04-01

    The Frankfurt phase of the Weichselian glaciation is a classical ice marginal position in the North European plain according to all geological and geomorphological maps since the end of the 19th century. Its detection is based on the connection of prominent, but rather isolated landscape features to a supposed ice margin. As in NE-Germany no till layer is connected to the proposed ice marginal position, it is usually considered to represent an active ice margin which formed during a stability phase of the downwasting from the maximum Weichselian ice extent, the Brandenburg phase, which is located about 60 km further south. This is in contrast to the supposed equivalent of the Frankfurt ice marginal position in Poland, the Poznan phase, which is documented by a more prominent landform record and an associated till. New investigations and a reinterpretation of the topography, a reevaluation of sediments in sand pits, as well as geochronological data of glaciofluvial sediments give new insights into the glacial processes as well as in the timing. The landscape was widely formed by glaciofluvial processes forming a complex pattern of intercalated outwash sediments of the advancing, as well as of the downwasting glacier of the Brandenburg phase. A detailed study of the topography by LIDAR data gives evidence of a successive ice retreat pattern south of the so called Frankfurt ice marginal area, documented in the form of a differentiated pattern of glaciofluvial sediments and till on top. An outwash plain, the Müncheberger Sandur, on which several eskers have been mapped, was classically interpreted as a proglacial feature of the Frankfurt ice marginal position. Nevertheless, a series of OSL-ages shows Weichselian ages which are not in accordance with the supposed timing as an outwash plain related to the Frankfurt ice marginal position. The ages, as well as sedimentological evidence suggest that the sandy glaciofluvial sediments belong to the proglacial sediment cycle

  20. Changes in ice-margin processes and sediment routing during ice-sheet advance across a marginal moraine

    USGS Publications Warehouse

    Knight, P.G.; Jennings, C.E.; Waller, R.I.; Robinson, Z.P.

    2007-01-01

    Advance of part of the margin of the Greenland ice sheet across a proglacial moraine ridge between 1968 and 2002 caused progressive changes in moraine morphology, basal ice formation, debris release, ice-marginal sediment storage, and sediment transfer to the distal proglacial zone. When the ice margin is behind the moraine, most of the sediment released from the glacier is stored close to the ice margin. As the margin advances across the moraine the potential for ice-proximal sediment storage decreases and distal sediment flux is augmented by reactivation of moraine sediment. For six stages of advance associated with distinctive glacial and sedimentary processes we describe the ice margin, the debris-rich basal ice, debris release from the glacier, sediment routing into the proglacial zone, and geomorphic processes on the moraine. The overtopping of a moraine ridge is a significant glaciological, geomorphological and sedimentological threshold in glacier advance, likely to cause a distinctive pulse in distal sediment accumulation rates that should be taken into account when glacial sediments are interpreted to reconstruct glacier fluctuations. ?? 2007 Swedish Society for Anthropology and Geography.

  1. Heat Flow and the Pleistocene Ice Margin

    NASA Astrophysics Data System (ADS)

    Klenner, R.; Gosnold, W.

    2012-04-01

    Several observations lead us to suggest that the geothermal gradient measurements near the Pleistocene ice margin require re-analysis to account for the effects of micro-climates at the drill holes, including modification of the temperature gradients by recent climate change and by post-glacial warming. Post-glacial climatic changes affect temperature gradients in the upper two kilometers of the crust and this has not been consistently accounted for in previously published heat flow values. Human and natural drivers affecting our climate lead us to suggest that the geothermal gradients in shallow boreholes have been significantly underestimated of present day heat flow. In most cases, heat flow increases with depth in northern hemisphere periglacial regions in Eurasia and North America. This includes temperature gradients increasing with depth in thick clastic rocks in the Williston Basin where compaction causes an increase in thermal conductivity. Using a pollen analyses in upland lakes in southern Manitoba indicate that MJJA surface temperatures are 13 ° C higher than they were 12,500 ka. Conductive heat flow models using the pollen temperature history as a forcing signal for surface temperature produce temperature vs. depth profiles with increasing gradients that are similar to profiles observed in the Williston Basin. Other observational evidence includes heat flow calculated from radioactivity in Minnesota is systematically higher than borehole measurements. This evidence leads us to believe the temperature has increased 15° C since the last glaciation and temperature gradients are underestimated by 25-40%. This study proposes corrections for post-glacial warming using conductive heat flow models based on 15 degrees of warming and for recent warming.

  2. 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.

  3. Wave effects on ocean-ice interaction in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Hakkinen, Sirpa; Peng, Chih Y.

    1993-01-01

    The effects of wave train on ice-ocean interaction in the marginal ice zone are studied through numerical modeling. A coupled two-dimensional ice-ocean model has been developed to include wave effects and wind stress for the predictions of ice edge dynamics. The sea ice model is coupled to the reduced-gravity ocean model through interfacial stresses. The main dynamic balance in the ice momentum is between water-ice stress, wind stress, and wave radiation stresses. By considering the exchange of momentum between waves and ice pack through radiation stress for decaying waves, a parametric study of the effects of wave stress and wind stress on ice edge dynamics has been performed. The numerical results show significant effects from wave action. The ice edge is sharper, and ice edge meanders form in the marginal ice zone owing to forcing by wave action and refraction of swell system after a couple of days. Upwelling at the ice edge and eddy formation can be enhanced by the nonlinear effects of wave action; wave action sharpens the ice edge and can produce ice meandering, which enhances local Ekman pumping and pycnocline anomalies. The resulting ice concentration, pycnocline changes, and flow velocity field are shown to be consistent with previous observations.

  4. Seismic exploration noise reduction in the Marginal Ice Zone.

    PubMed

    Tollefsen, Dag; Sagen, Hanne

    2014-07-01

    A sonobuoy field was deployed in the Marginal Ice Zone of the Fram Strait in June 2011 to study the spatial variability of ambient noise. High noise levels observed at 10-200 Hz are attributed to distant (1400 km range) seismic exploration. The noise levels decreased with range into the ice cover; the reduction is fitted by a spreading loss model with a frequency-dependent attenuation factor less than for under-ice interior Arctic propagation. Numerical modeling predicts transmission loss of the same order as the observed noise level reduction and indicates a significant loss contribution from under-ice interaction. PMID:24993237

  5. Marginal Ice Zone Processes Observed from Unmanned Aerial Systems

    NASA Astrophysics Data System (ADS)

    Zappa, C. J.

    2015-12-01

    Recent years have seen extreme changes in the Arctic. Marginal ice zones (MIZ), or areas where the "ice-albedo feedback" driven by solar warming is highest and ice melt is extensive, may provide insights into the extent of these changes. Furthermore, MIZ play a central role in setting the air-sea CO2 balance making them a critical component of the global carbon cycle. Incomplete understanding of how the sea-ice modulates gas fluxes renders it difficult to estimate the carbon budget in MIZ. Here, we investigate the turbulent mechanisms driving mixing and gas exchange in leads, polynyas and in the presence of ice floes using both field and laboratory measurements. Measurements from unmanned aerial systems (UAS) in the marginal ice zone were made during 2 experiments: 1) North of Oliktok Point AK in the Beaufort Sea were made during the Marginal Ice Zone Ocean and Ice Observations and Processes EXperiment (MIZOPEX) in July-August 2013 and 2) Fram Strait and Greenland Sea northwest of Ny-Ålesund, Svalbard, Norway during the Air-Sea-Ice Physics and Biogeochemistry Experiment (ASIPBEX) April - May 2015. We developed a number of new payloads that include: i) hyperspectral imaging spectrometers to measure VNIR (400-1000 nm) and NIR (900-1700 nm) spectral radiance; ii) net longwave and net shortwave radiation for ice-ocean albedo studies; iii) air-sea-ice turbulent fluxes as well as wave height, ice freeboard, and surface roughness with a LIDAR; and iv) drone-deployed micro-drifters (DDµD) deployed from the UAS that telemeter temperature, pressure, and RH as it descends through the atmosphere and temperature and salinity of the upper meter of the ocean once it lands on the ocean's surface. Visible and IR imagery of melting ice floes clearly defines the scale of the ice floes. The IR imagery show distinct cooling of the skin sea surface temperature (SST) as well as an intricate circulation and mixing pattern that depends on the surface current, wind speed, and near

  6. A coupled ice-ocean model of upwelling in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Roed, L. P.; Obrien, J. J.

    1983-01-01

    A dynamical coupled ice-ocean numerical model for the marginal ice zone (MIZ) is suggested and used to study upwelling dynamics in the MIZ. The nonlinear sea ice model has a variable ice concentration and includes internal ice stress. The model is forced by stresses on the air/ocean and air/ice surfaces. The main coupling between the ice and the ocean is in the form of an interfacial stress on the ice/ocean interface. The ocean model is a linear reduced gravity model. The wind stress exerted by the atmosphere on the ocean is proportional to the fraction of open water, while the interfacial stress ice/ocean is proportional to the concentration of ice. A new mechanism for ice edge upwelling is suggested based on a geostrophic equilibrium solution for the sea ice medium. The upwelling reported in previous models invoking a stationary ice cover is shown to be replaced by a weak downwelling due to the ice motion. Most of the upwelling dynamics can be understood by analysis of the divergence of the across ice edge upper ocean transport. On the basis of numerical model, an analytical model is suggested that reproduces most of the upwelling dynamics of the more complex numerical model.

  7. Sea ice melting in the marginal ice zone.

    USGS Publications Warehouse

    Josberger, E.G.

    1983-01-01

    The heat and salt flux boundary conditions together with the freezing curve relationship are a necessary component of any ice- sea water thermodynamic model. A neutral two-layer oceanic planetary boundary layer model that incorporates these boundary conditions is used. The results are discussed. -from Author

  8. Modelling the Laurentide Ice Sheet using improved ice margin chronologies and glacio-isostatic observations

    NASA Astrophysics Data System (ADS)

    Gowan, Evan; Tregoning, Paul; Purcell, Anthony; Lambeck, Kurt

    2013-04-01

    Creating models of the Laurentide ice sheet is challenging, due to the deficiency of chronological constraints and the uneven spatial resolution of data to determine the evolution of the glacio-isostatic response after deglaciation. Previous models relied on uncalibrated radiocarbon constrained margins that proved to have deficiencies in recent studies. Additionally, many recent Laurentide ice sheet models have been developed by incorporating climatic parameters that are poorly resolved for the late glacial period. We present a new ice sheet model by an iterative process of changing basal shear stress values and ice sheet margin location. A particular focus of this study is to determine the thickness and extent of the western Laurentide ice sheet, where there were few well dated observations of glacio-isostatic motion until recently. The volume of an ice sheet during long periods depends mostly on basal shear stress and margin position, which are the main parameters that we vary to fit our model to glacio-isostatic observations. We build our ice model using the assumption of perfectly plastic, steady-state conditions, with variable basal shear stress. Basal shear stress values depend on the surficial geology underlying the ice, and are at a minimum in offshore regions that have soft, deformable sediments, and at a maximum in areas with exposed crystalline bedrock. This approach may not capture dynamic and short lived features of the ice sheet, such as ice streams and stagnant ice, but gives an approximation of average conditions to produce ice volumes that fit geophysical observations. We adjust the margin location when the shear stress conditions alone cannot account for the observed glacio-isostatic response. The constraints on the response include relative sea level benchmarks, sea level highstand positions and proglacial lakes. We repeat the analysis using different rheological profiles to determine the dependence the Earth model has on the estimation of ice

  9. Discharge of debris from ice at the margin of the Greenland ice sheet

    USGS Publications Warehouse

    Knight, P.G.; Waller, R.I.; Patterson, C.J.; Jones, A.P.; Robinson, Z.P.

    2002-01-01

    Sediment production at a terrestrial section of the ice-sheet margin in West Greenland is dominated by debris released through the basal ice layer. The debris flux through the basal ice at the margin is estimated to be 12-45 m3 m-1 a-1. This is three orders of magnitude higher than that previously reported for East Antarctica, an order of magnitude higher than sites reported from in Norway, Iceland and Switzerland, but an order of magnitude lower than values previously reported from tidewater glaciers in Alaska and other high-rate environments such as surging glaciers. At our site, only negligible amounts of debris are released through englacial, supraglacial or subglacial sediment transfer. Glacio-fluvial sediment production is highly localized, and long sections of the ice-sheet margin receive no sediment from glaciofluvial sources. These findings differ from those of studies at more temperate glacial settings where glaciofluvial routes are dominant and basal ice contributes only a minor percentage of the debris released at the margin. These data on debris flux through the terrestrial margin of an outlet glacier contribute to our limited knowledge of debris production from the Greenland ice sheet.

  10. Color of Greenland: Tracing the Dark Ice Exposed at the Ice Sheet Margin

    NASA Astrophysics Data System (ADS)

    Starke, S. E.; Bell, R. E.; Tinto, K. J.; Das, I.; Winckler, G.

    2014-12-01

    The color and albedo of the surface of a large ice sheet is critical to its response to a changing climate. Decreasing the ice surface albedo enhances surface melt and has been suggested as a mechanism to trigger rapid collapse. Each summer, dark bands of ice 20-40 km wide are exposed along the margin of the Greenland ice sheet. These dark bands are clearly visible in satellite imagery and best developed along the west coast. We use airborne radar data in both northeast and western Greenland to demonstrate that the dark bands are the result of outcropping stratigraphy. Where these dark bands are exposed at the ice surface correlate with locations where the well defined stratigraphy imaged with airborne radar is truncated at the surface. Surface work in the northeast by Boogild and coworkers (2010) has constrained the age of the three major intervals of exposed strata. Pink or brown Pleistocene ice lies closest to the ice margin, and is overlain by white pre-Boreal ice. The impurity-rich dark strata, are dated as early Holocene. The dark strata are likely a result of either periods of elevated dust during the Holocene or excess melt during the Holocene Climatic Optimum. We use satellite data to map the extent of the exposed dark ice in Greenland using imagery from Landsat 8, Landsat 7, ASTER VNIR, EO1 Ali, and Quickbird with spatial resolutions ranging from 0.65m to 30m. Image acquisition focused on the months of July and August when the stratigraphy is best exposed. Little dark ice is presently exposed in the southeastern margin of the Greenland ice sheet as this region experiences higher surface accumulation. By examining satellite images from multiple years we have identified areas where the patterns of the dark ice are changing. Both movement of the strata towards the margin due to ice flow and inland retreat due to increased erosion are documented. An outstanding question is what will be color of the strata exposed as the bare ice region expands in Greenland

  11. Sensitivity studies with a coupled ice-ocean model of the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Roed, L. P.

    1983-01-01

    An analytical coupled ice-ocean model is considered which is forced by a specified wind stress acting on the open ocean as well as the ice. The analysis supports the conjecture that the upwelling dynamics at ice edges can be understood by means of a simple analytical model. In similarity with coastal problems it is shown that the ice edge upwelling is determined by the net mass flux at the boundaries of the considered region. The model is used to study the sensitivity of the upwelling dynamics in the marginal ice zone to variation in the controlling parameters. These parameters consist of combinations of the drag coefficients used in the parameterization of the stresses on the three interfaces atmosphere-ice, atmosphere-ocean, and ice-ocean. The response is shown to be sensitive to variations in these parameters in that one set of parameters may give upwelling while a slightly different set of parameters may give downwelling.

  12. Using ISSM to Simulate the LIA to Present Ice Margin Change at Upernavik Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Haubner, K.; Larour, E. Y.; Box, J.; Schlegel, N.; Larsen, S. H.; Kjeldsen, K. K.; Kjaer, K. H.

    2015-12-01

    The possibility for rapid melting of the Greenland ice sheet ranks among the most serious societal climate threats. This project puts the rate of contemporary climate change-driven Greenland ice mass change in a temporal context, by simulating the Greenland ice sheet margin throughout the Holocene and comparing the results with past ice margin positions (e.g. Andresen et al., 2014; Bjørk et al., 2012) and records of glacier activity based on fjord sediment strata (Andresen et al. 2012). Here we show first steps to achieve this goal and model the evolution of the Upernavik Isstrøm, a set of marine-terminating glaciers in Northwest Greenland, during the 20thcentury, using the Ice Sheet System Model (ISSM) (Larour et. al 2012). The simulation runs from 1900, shortly after the Little Ice Age (LIA), to year 2013, initialized using trimline data marking the former extent of the ice sheet and forced by a surface mass balance reconstruction after Box (2013). We address uncertainties in ice front positions and thickness by comparing our simulation output with present ice margin positions in the area. Finally, we investigate the possibility of simulating historic changes at ice sheet margins with this finite element ice sheet model. Andresen, C. S., Kjeldsen, K. K., Harden, B., Nørgaard-Pedersen, N. and Kjær, K. H. 2014. Outlet glacier dynamics and bathymetry at Upernavik Isstrøm and Upernavik Isfjord, North-West Greenland. GEUS Bulletin 31 Andresen, C. S., Straneo, F., Ribergaard, M. H., Bjørk, A. A., Andersen, T.J., Kuijpers, A., Nørgaard-Pedersen, N., Kjær, K. H., Schjøth, F., Weckström, K. and Ahlstrøm, A. P. 2012: Rapid response of Helheim Glacier in Greenland to climate variability over the past century. Nature Geoscience 5 Bjørk, A. A., Kjær, K. H., Korsgaard, N. J., Khan, A., S., Kjeldsen, K. K., Andresen, C. S., Box, J. E., Larsen, N. K. and Funder, S. 2012. Historical aerial photographs uncover eighty years of ice-climate interaction in southeast

  13. Melt ponds and marginal ice zone from new algorithm of sea ice concentration retrieval

    NASA Astrophysics Data System (ADS)

    Repina, Irina; Tikhonov, Vasiliy; Komarova, Nataliia; Raev, Mikhail; Sharkov, Evgeniy

    2016-04-01

    Studies of spatial and temporal properties of sea ice distribution in polar regions help to monitor global environmental changes and reveal their natural and anthropogenic factors, as well as make forecasts of weather, marine transportation and fishing conditions, assess perspectives of mineral mining on the continental shelf, etc. Contact methods of observation are often insufficient to meet the goals, very complicated technically and organizationally and not always safe for people involved. Remote sensing techniques are believed to be the best alternative. Its include monitoring of polar regions by means of passive microwave sensing with the aim to determine spatial distribution, types, thickness and snow cover of ice. However, the algorithms employed today to retrieve sea ice characteristics from passive microwave sensing data for different reasons give significant errors, especially in summer period and also near ice edges and in cases of open ice. A new algorithm of sea ice concentration retrieval in polar regions from satellite microwave radiometry data is discussed. Beside estimating sea ice concentration, the algorithm makes it possible to indicate ice areas with melting snow and melt ponds. Melt ponds are an important element of the Arctic climate system. Covering up to 50% of the surface of drifting ice in summer, they are characterized by low albedo values and absorb several times more incident shortwave radiation than the rest of the snow and ice cover. The change of melt ponds area in summer period 1987-2015 is investigated. The marginal ice zone (MIZ) is defined as the area where open ocean processes, including specifically ocean waves, alter significantly the dynamical properties of the sea ice cover. Ocean wave fields comprise short waves generated locally and swell propagating from the large ocean basins. Depending on factors like wind direction and ocean currents, it may consist of anything from isolated, small and large ice floes drifting over a

  14. Variability in the Antarctic Marginal Ice Zone and Pack Ice in Observations and NCAR CESM

    NASA Astrophysics Data System (ADS)

    Stroeve, J. C.; Campbell, G. G.; Holland, M. M.; Landrum, L.

    2015-12-01

    Sea ice around Antarctica reached another record high extent in September 2014, recording a maximum extent of more than 20 million km2 for the first time since the modern satellite data record began in October 1978. This follows previous record maxima in 2012 and 2013, resulting in an overall increase in Antarctic September sea ice extent of 1.3% per decade since 1979. Several explanations have been put forward to explain the increasing trends, such as anomalous short-term wind patterns that both grow and spread out the ice, and freshening of the surface ocean layer from increased melting of floating ice from the continent. These positive trends in Antarctic sea ice are at odds with climate model forecasts that suggest the sea ice should be declining in response to increasing greenhouse gases and stratospheric ozone depletion. While the reasons for the increases in total extent remain poorly understood, it is likely that these changes are not just impacting the total ice extent, but also the distribution of pack ice, the marginal ice zone (MIZ) and polynyas, with important ramifications for phytoplankton productivity that in turn impact zooplankton, fish, sea birds and marine mammals. This study evaluates changes in the distribution of the pack ice, polynyas and the marginal ice zone around Antarctica from two sea ice algorithms, the NASA Team and the Bootstrap. These results are further compared with climate model simulations from the CESM large ensemble output. Seasonal analysis of the different ice types using NASA Team and Bootstrap shows that during ice advance, the ice advances as pack ice, with a seasonal peak in September (broader peak for Bootstrap), and as the pack ice begins to retreat, it first converts to a wide area of MIZ, that reaches its peak around November (NASA Team) or December (Bootstrap). CESM also shows a similar seasonal cycle, with a peak in the pack ice in August, and a December/January peak in the MIZ. Seasonal variability and trends are

  15. Coupled ice-ocean dynamics in the marginal ice zones Upwelling/downwelling and eddy generation

    NASA Technical Reports Server (NTRS)

    Hakkinen, S.

    1986-01-01

    This study is aimed at modeling mesoscale processes such as upwelling/downwelling and ice edge eddies in the marginal ice zones. A two-dimensional coupled ice-ocean model is used for the study. The ice model is coupled to the reduced gravity ocean model through interfacial stresses. The parameters of the ocean model were chosen so that the dynamics would be nonlinear. The model was tested by studying the dynamics of upwelling. Wings parallel to the ice edge with the ice on the right produce upwelling because the air-ice momentum flux is much greater than air-ocean momentum flux; thus the Ekman transport is greater than the ice than in the open water. The stability of the upwelling and downwelling jets is discussed. The downwelling jet is found to be far more unstable than the upwelling jet because the upwelling jet is stabilized by the divergence. The constant wind field exerted on a varying ice cover will generate vorticity leading to enhanced upwelling/downwelling regions, i.e., wind-forced vortices. Steepening and strengthening of vortices are provided by the nonlinear terms. When forcing is time-varying, the advection terms will also redistribute the vorticity. The wind reversals will separate the vortices from the ice edge, so that the upwelling enhancements are pushed to the open ocean and the downwelling enhancements are pushed underneath the ice.

  16. Stressing, Hydraulic and Locking Processes at Ice Stream Margins

    NASA Astrophysics Data System (ADS)

    Perol, T.; Platt, J. D.; Rice, J. R.; Suckale, J.

    2012-12-01

    Ice streams are concentrated zones of fast flowing ice lying between ridges of almost stationary ice. Due to their high speeds they make a large contribution to the total mass flux out of the ice sheet, yet their mechanics is still poorly understood. The bed beneath the stream is thought to be temperate and deforming, providing limited resistance to shearing through a yield stress. Beneath the bordering ridges the bed is undeforming, and thus said to be locked. The transition from a deforming to locked bed at the ice stream margin leads to a large shear stress on the locked portion of the bed. Previous models that analyzed deformation and temperature fields at ice stream margins have either enforced zero slip beneath the ridge [Jacobson and Raymond 1998], or assumed a sharply varying yield stress profile that naturally locks the margin [Schoof 2004]. Here we model the transition from a slipping to locked bed as an anti-plane crack problem, with the transition line being the crack tip, to determine under what conditions the margin will lock. The shear strain rate at such a sharp margin is singular, and a balance between gravity and bed resistance sets the intensity of shearing, for negligible axial force gradients. However, if the margin is somehow blunted then the maximum stress will be bounded. Since the margins are thought to be zones of intense water generation [Jacobson and Raymond 1998;Schoof 2004] we analyze the effect a drainage R-channel there [Perol and Rice, subm. 2012] could have on the stress field. If the slipping to locked transition occurs across a semi-circular channel then we can solve for the shear stress applied to the locked portion of the bed assuming a Newtonian rheology and a yield stress on the deforming portion of the bed. In the neighborhood of a R-channel the pore pressures are expected to be lower, leading to high effective stresses and a large yield stress. We compare our shear stress predictions with a hydrologic model for the yield

  17. Investigation of the iced flowfield characteristics related to the stall margin instrumentation used in icing conditions

    NASA Astrophysics Data System (ADS)

    Pederson, Erik Thomas

    The purpose of this dissertation is to investigate the relationship between the flowfield surrounding an iced airfoil and the stall margin instrumentation developed for use in icing conditions. The stall margin system indicates to the pilot the change in available lift due to ice accretions on the leading edge of an airfoil. This system displays the change in the form of a normalized lift coefficient. Four pressure ports are chosen to specifically maintain a constant calibration curve, for pressure versus normalized lift coefficient, regardless of ice shape. This allows these pressures to be used to determine the change in maximum lift coefficient. The instrumentation currently maintains an accuracy of +/-10%. There was a need to investigate the relationship between the flowfield and the port locations, and the airfoil shape and the port locations. This allowed further understanding of the placement of these ports. Through this investigation, better port locations have been determined and the accuracy and usefulness of the instrumentation has been increased. This investigation was conducted using wind tunnel testing techniques. A 2-D NACA 23012 pressure model and a 2-D NACA 23012 force model were constructed and tested to determine initial port locations for the stall margin instrumentation. Simulated ice shapes were produced using the LEWICE software from NASA Glenn. The flowfield around the airfoil was mapped using smoke wire flow visualization and hotwire anemometry. A single wire system was used to determine a 2-D profile of the turbulence intensity levels surrounding the ice covered wing. The movement of the separation region behind the ice shape, with change in angle of attack, was also investigated. The relationship between this movement and the port locations was documented and its significance determined. Through these observations, better port locations for the stall margin instrumentation were determined thus allowing accuracy of the instrumentation to

  18. Evaluating ice sheet model spinup procedures using chronological data constraining ice margin positions over time on Greenland

    NASA Astrophysics Data System (ADS)

    Applegate, P. J.; Kirchner, N.; Levy, L.; Kelly, M. A.; Lowell, T. V.; Greve, R.

    2011-12-01

    We compare a recently-published ice sheet model run to field data constraining ice margin positions over time on Greenland, to assess presently-accepted model spinup procedures. Computer models describing ice flow and mass balance are important tools for learning about the future behavior of ice sheets in a warming world. Because ice softness is temperature-sensitive and the thermal field within the ice sheet is mostly unknown, ice sheet models must be "spun up" using paleoclimate data before future changes can be estimated. The models produce ice margin positions over time during the spinup, allowing comparison with field data such as cosmogenic exposure dates and radiocarbon dating of organic matter. If the agreement between modeled and reconstructed ice margin positions is good, we can have increased confidence in the models' ability to forecast future changes. For the present study, we use a model setup from Greve et al. (2011; Annals of Glaciology 52, 23-30; sicopolis.greveweb.net), and a preliminary collection of chronological data. We aggregate the chronological data to the model grid, then plot the data and modeled ice margin positions as time-distance diagrams along west-east transects. Our results have implications for the use of the Summit ice cores to predict mass balance around the margins of the ice sheet and future projections of sea level rise using ice sheet models.

  19. Ocean-ice interaction in the marginal ice zone using synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Peng, Chich Y.; Weingartner, Thomas J.

    1994-01-01

    Ocean-ice interaction processes in the marginal ice zone (MIZ) by wind, waves, and mesoscale features, such as up/downwelling and eddies are studied using Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) images and an ocean-ice interaction model. A sequence of seven SAR images of the MIZ in the Chukchi Sea with 3 or 6 days interval are investigated for ice edge advance/retreat. Simultaneous current measurements from the northeast Chukchi Sea, as well as the Barrow wind record, are used to interpret the MIZ dynamics. SAR spectra of waves in ice and ocean waves in the Bering and Chukchi Sea are compared for the study of wave propagation and dominant SAR imaging mechanism. By using the SAR-observed ice edge configuration and wind and wave field in the Chukchi Sea as inputs, a numerical simulation has been performed with the ocean-ice interaction model. After 3 days of wind and wave forcing the resulting ice edge configuration, eddy formation, and flow velocity field are shown to be consistent with SAR observations.

  20. Mapping and assessing variability in the Antarctic marginal ice zone, pack ice and coastal polynyas in two sea ice algorithms with implications on breeding success of snow petrels

    NASA Astrophysics Data System (ADS)

    Stroeve, Julienne C.; Jenouvrier, Stephanie; Campbell, G. Garrett; Barbraud, Christophe; Delord, Karine

    2016-08-01

    Sea ice variability within the marginal ice zone (MIZ) and polynyas plays an important role for phytoplankton productivity and krill abundance. Therefore, mapping their spatial extent as well as seasonal and interannual variability is essential for understanding how current and future changes in these biologically active regions may impact the Antarctic marine ecosystem. Knowledge of the distribution of MIZ, consolidated pack ice and coastal polynyas in the total Antarctic sea ice cover may also help to shed light on the factors contributing towards recent expansion of the Antarctic ice cover in some regions and contraction in others. The long-term passive microwave satellite data record provides the longest and most consistent record for assessing the proportion of the sea ice cover that is covered by each of these ice categories. However, estimates of the amount of MIZ, consolidated pack ice and polynyas depend strongly on which sea ice algorithm is used. This study uses two popular passive microwave sea ice algorithms, the NASA Team and Bootstrap, and applies the same thresholds to the sea ice concentrations to evaluate the distribution and variability in the MIZ, the consolidated pack ice and coastal polynyas. Results reveal that the seasonal cycle in the MIZ and pack ice is generally similar between both algorithms, yet the NASA Team algorithm has on average twice the MIZ and half the consolidated pack ice area as the Bootstrap algorithm. Trends also differ, with the Bootstrap algorithm suggesting statistically significant trends towards increased pack ice area and no statistically significant trends in the MIZ. The NASA Team algorithm on the other hand indicates statistically significant positive trends in the MIZ during spring. Potential coastal polynya area and amount of broken ice within the consolidated ice pack are also larger in the NASA Team algorithm. The timing of maximum polynya area may differ by as much as 5 months between algorithms. These

  1. Deglaciation-induced uplift along the Greenland ice margin observed with InSAR

    NASA Astrophysics Data System (ADS)

    Lu, Q.; Amelug, F.

    2015-12-01

    The Greenland ice sheet is rapidly shrinking with the fastest retreat and thinning occurring at the ice sheet margin and near the outlet glaciers. The changes of the ice mass cause an elastic response of the bedrock. Ice mass loss during the summer months is associated with uplift, whereas ice mass increase during the winter months is associated with subsidence. The German TerraSAR-X satellite has systematically observed selected sites along the Greenland ice sheet margin since summer 2012. Here we present ground deformation observations obtained using an InSAR time-series approach based on small baseline interferograms. The deformation data reveal the seasonal variations and net uplift. Relative variations in the seasonal amplitude for different sites along the ice sheet margin points to spatial variations in ice loss. The combination of ground deformation observations and independent observations of ice volume changes from airborne and spaceborne altimeters places constraints on the firn density of the lost ice volume.

  2. Formation processes of floe size distribution in the marginal ice zone (Invited)

    NASA Astrophysics Data System (ADS)

    Toyota, T.; Kohout, A.; Fraser, A.

    2013-12-01

    Since the marginal ice zone (MIZ) is the outer sea ice zone, its behavior is key to the understanding of the variability of sea ice extent associated with climate change. Especially for the melting processes in MIZ, where relatively small ice floes are dominant, floe size distribution (FSD) is an important parameter because smaller ice floes are subject to stronger lateral melting due to their larger cumulative perimeters. As the MIZ is characterized by vigorous interaction between sea ice and waves, breakup of sea ice due to flexural forcing and collisions is considered to play an essential role in the determination of FSD there. However, the available data have been very limited so far. Analysis of the observations of ice floes with a heli-borne video camera, focusing on the floe size ranging from 2 m to 100 m, in the Sea of Okhotsk, the Weddell Sea and off East Antarctica, revealed that while FSD is basically scale-invariant, a regime shift occurs at a size of about a few tens of meters, irrespective of the study region. It was also shown 1) that the floe size at which regime shift occurs slightly increases from 20 to 40 m with ice thickness, consistent with the theory of the flexural failure of sea ice; and 2) that to explain the scale invariance in FSD for smaller floes, a fragility of sea ice which is relevant to the strength of sea ice relative to waves can be a useful physical parameter to be correlated with the fractal dimension. Thus these results confirm the importance of wave-ice interaction to the formation of FSD. Based on this, a possible mechanism of the melting process was hypothesized that in the melting season sea ice extent retreats keeping the FSD relative to the ice edge nearly constant. As a next step and to confirm and further investigate this result, we planned to conduct the concurrent measurements of FSD, wave activities, and ice thickness off East Antarctica during the Sea Ice Physics and Ecosystem Experiment 2 (SIPEX2) in September to

  3. Various remote sensing approaches to understanding roughness in the marginal ice zone

    NASA Astrophysics Data System (ADS)

    Gupta, Mukesh

    Multi-platform based measurement approaches to understanding complex marginal ice zone (MIZ) are suggested in this paper. Physical roughness measurements using ship- and helicopter-based laser systems combined with ship-based active microwave backscattering (C-band polarimetric coherences) and dual-polarized passive microwave emission (polarization ratio, PR and spectral gradient ratios, GR at 37 and 89 GHz) are presented to study diverse sea ice types found in the MIZ. Autocorrelation functions are investigated for different sea ice roughness types. Small-scale roughness classes were discriminated using data from a ship-based laser profiler. The polarimetric coherence parameter ρHHVH , is not found to exhibit any observable sensitivity to the surface roughness for all incidence angles. Rubble-ridges, pancake ice, snow-covered frost flowers, and dense frost flowers exhibit separable signatures using GR-H and GR-V at >70° incidence angles. This paper diagnosed changes in sea ice roughness on a spatial scale of ∼0.1-4000 m and on a temporal scale of ∼1-240 days (ice freeze-up to summer melt). The coupling of MIZ wave roughness and aerodynamic roughness in conjunction with microwave emission and backscattering are future avenues of research. Additionally, the integration of various datasets into thermodynamic evolution model of sea ice will open pathways to successful development of inversion models of MIZ behavior.

  4. MIZEX East 1987: Winter Marginal Ice Zone Program in the Fram Strait and Greenland Sea

    NASA Astrophysics Data System (ADS)

    MIZEX'87 Group

    The overall objective o f MIZEX is to gain a better understanding of the mesoscale physical and biological processes by which atmosphere, ice, and ocean interact in the marginal ice zones (MIZ) that are found at the boundaries between ice-covered and open oceans. Improved modeling and better prediction of ice-edge position, ice concentration, and ice type in these regions would be a major step toward expanding human activities, for example, seaborne commerce, fishing, oil exploration and production, and naval operations. In addition, when more accurate parameterizations of mesoscale physical processes are available for inclusion in large-scale models, the result will be a major improvement in hemispherical climatological studies.Winter MIZEX '87 was conducted during March and April 1987 in the Fram Strait and Greenland Sea (see cover) and extended along the MIZ from about 75°N-79°N and 5°W-5°E. The experiment included an intensive 2-day investigation of the Barents Sea MIZ carried out between the southern tip of Svalbard and Bear Island. Two Norwegian ships, R/V Håakon Mosby and the ice-strengthened R/V Polar Circle, and the R/V Valdivia of the Federal Republic of Germany participated in the experiment. Flight operations were carried out by two Canadian aircraft equipped with Synthetic Aperature Radar (SAR), a U.S. plane equipped with passive microwave sensors, a Norwegian P3 aircraft, and a helicopter based on the Polar Circle.

  5. Constraining the margins of Neoproterozoic ice masses: depositional signature, palaeoflow and glaciodynamics

    NASA Astrophysics Data System (ADS)

    Busfield, Marie; Le Heron, Daniel

    2016-04-01

    The scale and distribution of Neoproterozoic ice masses remains poorly understood. The classic Snowball Earth hypothesis argues for globally extensive ice sheets, separated by small ocean refugia, yet the positions of palaeo-ice sheet margins and the extent of these open water regions are unknown. Abundant evidence worldwide for multiple cycles of ice advance and recession is suggestive of much more dynamic mass balance changes than previously predicted. Sedimentological analysis enables an understanding of the changing ice margin position to be gained through time, in some cases allowing it to be mapped. Where the maximum extent of ice advance varies within a given study area, predictions can also be made on the morphology of the ice margin, and the underlying controls on this morphology e.g. basin configuration. This can be illustrated using examples from the Neoproterozoic Kingston Peak Formation in the Death Valley region of western USA. Throughout the Sperry Wash, northern Kingston Range and southern Kingston Range study sites the successions show evidence of multiple cycles of ice advance and retreat, but the extent of maximum ice advance is extremely variable, reaching ice-contact conditions at Sperry Wash but only ice-proximal settings in the most distal southern Kingston Range. The overall advance is also much more pronounced at Sperry Wash, from ice-distal to ice-contact settings, as compared to ice-distal to ice-proximal settings in the southern Kingston Range. Therefore, the position of the ice margin can be located at the Sperry Wash study site, where the more pronounced progradation is used to argue for topographically constrained ice, feeding the unconstrained shelf through the northern into the southern Kingston Range. This raises the question as to whether Neoproterozoic ice masses could be defined as topographically constrained ice caps, or larger ice sheets feeding topographically constrained outlet glaciers.

  6. Ocean - ice sheet interaction along the NW European margin during the last glacial phases

    NASA Astrophysics Data System (ADS)

    Becker, L. W. M.; Sejrup, H. P.; Haflidason, H.; Hjelstuen, B. O. B.

    2015-12-01

    The NW European continental margin was repeatedly covered by shelf edge glaciations during the last glacial cycles. Here, we present a compilation of new and previously published data from a SW to NE transect of 8 sediment cores raised along the upper continental slope. This study aims to investigate the interaction between sea surface conditions and the variability seen in the British Irish Ice Sheet (BIIS) and the Fennoscandian Ice Sheet (FIS) during the last 13-40 ka BP. Ice Rafted Debris (IRD) counts, IRD flux data, grain size data, the content of the polar planktonic foraminifera Neogloboquadrina pachyderma (sin) and ∂18O measurements were compiled and combined with new Bayesian age models. From 40-24.5 ka BP the build up and consecutive confluence of the BIIS and the FIS are reflected in sediment composition and flux data. Pulses of large quantities of fine material to the southern part of the transect suggest riverine BIIS related influx. The sediment composition in cores close to the Norwegian channel indicates that the Norwegian Channel Ice Stream (NCIS) was only active between 24.5-18.5 ka BP during the last glacial stage. The planktonic foraminifera data during this period strongly suggests a dependence of NCIS extent variability and pulses in warm Atlantic water entering the Nordic Seas. In the northernmost cores rapidly deposited, laminated sediments and ∂18O spikes in planktonic foraminifera dated to 18.5 ka BP were interpreted as meltwater plume deposits. This may reflect NCIS retreat allowing BIIS and FIS to unzip and route ice dammed lake- and meltwater to the margin. In conclusion, the investigation suggests a close co-variation in extent of marine based parts of the BIIS, the FIS and ocean circulation while demonstrating the strong influence of the local glacial history on standard open marine proxies. This suggests that tuning chronologies of single marine records to ice cores in some regions might be more challenging than previously

  7. 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.

  8. Pleistocene marine ice sheets and ice shelves at the East Siberian continental margin

    NASA Astrophysics Data System (ADS)

    Niessen, Frank; Kuk Hong, Jong; Hegewald, Anne; Matthiessen, Jens; Stein, Rüdiger; Kim, Sookwan; Jensen, Laura; Jokat, Wilfried; Nam, Seung Il

    2014-05-01

    RV "Polarstern" cruise ARK-XIII/3 (2008) and RV "Araon" cruise ARA03B (2012) investigated an area in the Arctic Ocean located between the Chukchi Borderland and the East Siberian Sea (between 165°W and 170°E). Based on swath bathymetry, sediment echosounding, seismic profiling and sediment coring we present evidence that the western Arctic Ocean had a glaciated continental margin during several glacial periods of the Pleistocene (Niessen et al. 2013). At the southern end of the Mendeleev Ridge and on the Chukchi and East Siberian continental slopes ice sheets and ice shelves grounded in up to 1200 m present water depth. We found mega-scale glacial lineations (MSGL) associated with deposition of glaciogenic wedges and debris-flow deposits indicative of sub-glacial erosion and deposition close to the former grounding lines. Glacially lineated areas are associated with large-scale erosion, capped with diamicton and draped by, in places, several metres of pelagic sediments. On the Arlis Plateau, a detailed bathymetric map exhibits several generations of MSGL, which we interpret as relicts of different Pleistocene glaciations. Traces of former grounding line positions suggest that an ice shelf of approximately 900 m in thickness has spread across the Southern Mendeleev Ridge in a north-easterly direction. According to our results, ice sheets of more than one km in thickness continued onto, and likely centered over, the East Siberian Shelf. A preliminary age model suggests that the youngest and shallowest grounding event of an ice sheet should be within Marine Isotope Stage (MIS) 3 and clearly predates the Last Glacial Maximum. The oldest and deepest event predates MIS 6. The youngest grounding event on the Arlis Plateau is tentatively dated to have occurred during MIS 4. These results have important implication for the former distribution of thick ice masses in the Arctic Ocean during the Pleistocene. They are relevant for albedo, ocean-atmosphere heat exchange

  9. Ice Nucleation Activity in Lichens

    PubMed Central

    Kieft, Thomas L.

    1988-01-01

    A newly discovered form of biological ice nucleus associated with lichens is described. Ice nucleation spectra of a variety of lichens from the southwestern United States were measured by the drop-freezing method. Several epilithic lichen samples of the genera Rhizoplaca, Xanthoparmelia, and Xanthoria had nuclei active at temperatures as warm as −2.3°C and had densities of 2.3 × 106 to more than 1 × 108 nuclei g−1 at −5°C (2 to 4 orders of magnitude higher than any plants infected with ice nucleation-active bacteria). Most lichens tested had nucleation activity above −8°C. Lichen substrates (rocks, plants, and soil) showed negligible activity above −8°C. Ice nucleation-active bacteria were not isolated from the lichens, and activity was not destroyed by heat (70°C) or sonication, indicating that lichen-associated ice nuclei are nonbacterial in origin and differ chemically from previously described biological ice nuclei. An axenic culture of the lichen fungus Rhizoplaca chrysoleuca showed detectable ice nucleation activity at −1.9°C and an ice nucleation density of 4.5 × 106 nuclei g−1 at −5°C. It is hypothesized that these lichens, which are both frost tolerant and dependent on atmospheric moisture, derive benefit in the form of increased moisture deposition as a result of ice nucleation. PMID:16347678

  10. Ice nucleation activity in lichens.

    PubMed

    Kieft, T L

    1988-07-01

    A newly discovered form of biological ice nucleus associated with lichens is described. Ice nucleation spectra of a variety of lichens from the southwestern United States were measured by the drop-freezing method. Several epilithic lichen samples of the genera Rhizoplaca, Xanthoparmelia, and Xanthoria had nuclei active at temperatures as warm as -2.3 degrees C and had densities of 2.3 x 10 to more than 1 x 10 nuclei g at -5 degrees C (2 to 4 orders of magnitude higher than any plants infected with ice nucleation-active bacteria). Most lichens tested had nucleation activity above -8 degrees C. Lichen substrates (rocks, plants, and soil) showed negligible activity above -8 degrees C. Ice nucleation-active bacteria were not isolated from the lichens, and activity was not destroyed by heat (70 degrees C) or sonication, indicating that lichen-associated ice nuclei are nonbacterial in origin and differ chemically from previously described biological ice nuclei. An axenic culture of the lichen fungus Rhizoplaca chrysoleuca showed detectable ice nucleation activity at -1.9 degrees C and an ice nucleation density of 4.5 x 10 nuclei g at -5 degrees C. It is hypothesized that these lichens, which are both frost tolerant and dependent on atmospheric moisture, derive benefit in the form of increased moisture deposition as a result of ice nucleation.

  11. Glacitectonic deformation around the retreating margin of the last Irish ice sheet

    NASA Astrophysics Data System (ADS)

    Knight, J.

    2008-12-01

    Evidence for ice-marginal glacitectonic shunting and deformation of bedrock slabs is described from three sites around the west coast of Ireland. These sites (Brandon Bay, County Kerry; Pigeon Point, County Mayo; Inishcrone, County Sligo) are all locations where the late Devensian ice margin retreated on land and was confined to within limestone bedrock embayments. At these sites, flat-lying bedrock slabs (< 8 m long) have been dissociated from rockhead and moved seaward (in the direction of ice flow) by glacitectonic shunting. At all of the sites, bedrock slabs have been variously stacked, rotated, deformed into open folds, and brecciated. Separating the bedrock slabs is either a thin layer (< 20 cm) of brecciated and mylonitised cemented bedrock that shows internal folding; or a thicker (< 50 cm) normally-graded diamicton with a fine matrix. Together, the presence of these features suggests oscillation of a polythermal and clean basal ice margin that was strongly associated with basal freeze-on and the presence of proglacial permafrost. Subglacial sediment-laden meltwater was focused from behind the ice margin and through permafrost taliks. It is suggested that hydrofracturing under high hydraulic pressure, and through a frozen-bed ice margin, forced sediment injection into bedrock fractures and bedding planes and away from the ice margin, and that bedrock slabs were moved in part by hydraulic lift as well as thrust-style ice-marginal tectonics. The presence of a mosaic of warm and frozen ice-bed patches, in combination with strong geologic control and meltwater generation from behind the ice margin, can help explain formation of these unusual bedrock slab features.

  12. Proglacial deltaic landforms and stratigraphic architecture as a proxy for reconstructing past ice-sheet margin positions

    NASA Astrophysics Data System (ADS)

    Dietrich, Pierre; Ghienne, Jean-François; Normandeau, Alexandre; Lajeunesse, Patrick

    2016-04-01

    Deltaic landforms and related stratigraphic architectures are frequently used as proxy for reconstruction of past continental or marine environmental evolutions. Indeed, in addition to autocyclic processes, emplacement of deltaic systems is primarily controlled by changes in sediment supply and relative sea-level (RSL). In our study, we investigated several proglacial deltaic complexes emplaced since the last deglaciation over more than 700 km along the St. Lawrence North Shore (Québec, Canada). Their geomorphic and stratigraphic records allowed us to infer the retreat pattern of the Laurentide Ice Sheet fronts. Field investigation of representative deltaic complexes revealed an archetypal morphostratigraphic evolution forced by the retreat of the ice margin in a context of falling RSL (glacio-isostatic rebound). The base of the stratigraphic successions consists of outwash fan deposits emplaced in the early deglaciation when ice margin stillstanded immediately beyond the depositional area. The middle part of the succession consists of proglacial delta deposits corresponding to the retreat of the ice margin in the hinterland. At that time, glaciogenic supplies allowed an active progradation preventing fluvial entrenchment in spite of the forced regressive context. The upper part of the succession consists of staged shoreline deposits reworking the rim of the proglacial deltas. These deposits mark the retreat of the ice margin from the drainage basin and the subsequent drop in glaciogenics. Important fluvial entrenchment occurred in the same time, though rates of RSL fall were reduced. We generalize this stratigraphic framework by using solely the landforms (from DEM, aerial photographs or satellite images) tied to deltaic complex developments along the St. Lawrence North Shore. This approach permits an integrated study at the scale of the whole basin even where no field data is available. Recognizing the three steps evidenced from the stratigraphic record ads

  13. A coupled dynamic-thermodynamic model of an ice-ocean system in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Hakkinen, Sirpa

    1987-01-01

    Thermodynamics are incorporated into a coupled ice-ocean model in order to investigate wind-driven ice-ocean processes in the marginal zone. Upswelling at the ice edge which is generated by the difference in the ice-air and air-water surface stresses is found to give rise to a strong entrainment by drawing the pycnocline closer to the surface. Entrainment is shown to be negligible outside the areas affected by the ice edge upswelling. If cooling at the top is included in the model, the heat and salt exchanges are further enhanced in the upswelling areas. It is noted that new ice formation occurs in the region not affected by ice edge upswelling, and it is suggested that the high-salinity mixed layer regions (with a scale of a few Rossby radii of deformation) will overturn due to cooling, possibly contributing to the formation of deep water.

  14. Local effects of ice floes and leads on skin sea surface temperature, mixing and gas transfer in the marginal ice zone

    NASA Astrophysics Data System (ADS)

    Zappa, Christopher; Brumer, Sophia; Brown, Scott; LeBel, Deborah; McGillis, Wade; Schlosser, Peter; Loose, Brice

    2014-05-01

    Recent years have seen extreme changes in the Arctic. Marginal ice zones (MIZ), or areas where the "ice-albedo feedback" driven by solar warming is highest and ice melt is extensive, may provide insights into the extent of these changes. Furthermore, MIZ play a central role in setting the air-sea CO2 balance making them a critical component of the global carbon cycle. Incomplete understanding of how the sea-ice modulates gas fluxes renders it difficult to estimate the carbon budget in MIZ. Here, we investigate the turbulent mechanisms driving gas exchange in leads, polynyas and in the presence of ice floes using both field and laboratory measurements. Here, we present measurements of visible and IR imagery of melting ice floes in the marginal ice zone north of Oliktok Point AK in the Beaufort Sea made during the Marginal Ice Zone Ocean and Ice Observations and Processes EXperiment (MIZOPEX) in July-August 2013. The visible and IR imagery were taken from the unmanned airborne vehicle (UAV) ScanEagle. The visible imagery clearly defines the scale of the ice floes. The IR imagery show distinct cooling of the skin sea surface temperature (SST) as well as an intricate circulation and mixing pattern that depends on the surface current, wind speed, and near-surface vertical temperature/salinity structure. Individual ice floes develop turbulent wakes as they drift and cause transient mixing of an influx of colder surface (fresh) melt water. We capture a melting and mixing event that explains the changing pattern observed in skin SST and is substantiated using laboratory experiments. The Gas Transfer through Polar Sea Ice experiment was performed at the US Army Cold Regions Research and Engineering Laboratory (Hanover, NH) under varying ice coverage, winds speed, fetch and currents. Supporting measurements were made of air and water temperature, humidity, salinity and wave height. Air-side profiling provided momentum, heat, and CO2 fluxes. Transfer velocities are also

  15. Holocene ice marginal fluctuations of the Qassimiut lobe in South Greenland

    PubMed Central

    Larsen, Nicolaj K.; Find, Jesper; Kristensen, Anders; Bjørk, Anders A.; Kjeldsen, Kristian K.; Odgaard, Bent V.; Olsen, Jesper; Kjær, Kurt H.

    2016-01-01

    Knowledge about the Holocene evolution of the Greenland ice sheet (GrIS) is important to put the recent observations of ice loss into a longer-term perspective. In this study, we use six new threshold lake records supplemented with two existing lake records to reconstruct the Holocene ice marginal fluctuations of the Qassimiut lobe (QL) – one of the most dynamic parts of the GrIS in South Greenland. Times when the ice margin was close to present extent are characterized by clastic input from the glacier meltwater, whereas periods when the ice margin was behind its present day extent comprise organic-rich sediments. We find that the overall pattern suggests that the central part of the ice lobe in low-lying areas experienced the most prolonged ice retreat from ~9–0.4 cal. ka BP, whereas the more distal parts of the ice lobe at higher elevation re-advanced and remained close to the present extent during the Neoglacial between ~4.4 and 1.8 cal. ka BP. These results demonstrate that the QL was primarily driven by Holocene climate changes, but also emphasises the role of local topography on the ice marginal fluctuations. PMID:26940998

  16. Dynamic Inland Propagation of Thinning Due to Ice Loss at the Margins of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Wang, Wei Li; Li, Jun J.; Zwally, H. Jay

    2012-01-01

    Mass-balance analysis of the Greenland ice sheet based on surface elevation changes observed by the European Remote-sensing Satellite (ERS) (1992-2002) and Ice, Cloud and land Elevation Satellite (ICESat) (2003-07) indicates that the strongly increased mass loss at lower elevations (<2000 m) of the ice sheet, as observed during 2003-07, appears to induce interior ice thinning at higher elevations. In this paper, we perform a perturbation experiment with a three-dimensional anisotropic ice-flow model (AIF model) to investigate this upstream propagation. Observed thinning rates in the regions below 2000m elevation are used as perturbation inputs. The model runs with perturbation for 10 years show that the extensive mass loss at the ice-sheet margins does in fact cause interior thinning on short timescales (i.e. decadal). The modeled pattern of thinning over the ice sheet agrees with the observations, which implies that the strong mass loss since the early 2000s at low elevations has had a dynamic impact on the entire ice sheet. The modeling results also suggest that even if the large mass loss at the margins stopped, the interior ice sheet would continue thinning for 300 years and would take thousands of years for full dynamic recovery.

  17. Dynamics of coupled ice-ocean system in the marginal ice zone: Study of the mesoscale processes and of constitutive equations for sea ice

    NASA Technical Reports Server (NTRS)

    Hakkinen, S.

    1984-01-01

    This study is aimed at the modelling of mesoscale processed such as up/downwelling and ice edge eddies in the marginal ice zones. A 2-dimensional coupled ice-ocean model is used for the study. The ice model is coupled to the reduced gravity ocean model (f-plane) through interfacial stresses. The constitutive equations of the sea ice are formulated on the basis of the Reiner-Rivlin theory. The internal ice stresses are important only at high ice concentrations (90-100%), otherwise the ice motion is essentially free drift, where the air-ice stress is balanced by the ice-water stress. The model was tested by studying the upwelling dynamics. Winds parallel to the ice edge with the ice on the right produce upwilling because the air-ice momentum flux is much greater that air-ocean momentum flux, and thus the Ekman transport is bigger under the ice than in the open water. The upwelling simulation was extended to include temporally varying forcing, which was chosen to vary sinusoidally with a 4 day period. This forcing resembles successive cyclone passings. In the model with a thin oceanic upper layer, ice bands were formed.

  18. Extensive dynamic thinning on the margins of the Greenland and Antarctic ice sheets.

    PubMed

    Pritchard, Hamish D; Arthern, Robert J; Vaughan, David G; Edwards, Laura A

    2009-10-15

    Many glaciers along the margins of the Greenland and Antarctic ice sheets are accelerating and, for this reason, contribute increasingly to global sea-level rise. Globally, ice losses contribute approximately 1.8 mm yr(-1) (ref. 8), but this could increase if the retreat of ice shelves and tidewater glaciers further enhances the loss of grounded ice or initiates the large-scale collapse of vulnerable parts of the ice sheets. Ice loss as a result of accelerated flow, known as dynamic thinning, is so poorly understood that its potential contribution to sea level over the twenty-first century remains unpredictable. Thinning on the ice-sheet scale has been monitored by using repeat satellite altimetry observations to track small changes in surface elevation, but previous sensors could not resolve most fast-flowing coastal glaciers. Here we report the use of high-resolution ICESat (Ice, Cloud and land Elevation Satellite) laser altimetry to map change along the entire grounded margins of the Greenland and Antarctic ice sheets. To isolate the dynamic signal, we compare rates of elevation change from both fast-flowing and slow-flowing ice with those expected from surface mass-balance fluctuations. We find that dynamic thinning of glaciers now reaches all latitudes in Greenland, has intensified on key Antarctic grounding lines, has endured for decades after ice-shelf collapse, penetrates far into the interior of each ice sheet and is spreading as ice shelves thin by ocean-driven melt. In Greenland, glaciers flowing faster than 100 m yr(-1) thinned at an average rate of 0.84 m yr(-1), and in the Amundsen Sea embayment of Antarctica, thinning exceeded 9.0 m yr(-1) for some glaciers. Our results show that the most profound changes in the ice sheets currently result from glacier dynamics at ocean margins.

  19. Subglacial hydrology as a control on ice stream shear margin locations

    NASA Astrophysics Data System (ADS)

    Perol, Thibaut; Rice, James R.; Platt, John D.; Suckale, Jenny

    2015-11-01

    Ice streams are fast-flowing bands of ice separated from the nearly stagnant ice in the adjacent ridge by zones of highly localized deformation known as shear margins. However, it is presently unclear what mechanisms can control the location of shear margins. Within the shear margin, the transition from a slipping bed beneath the ice stream to a locked bed beneath the ridge concentrates stresses. We show that subglacial hydrology can select the shear margin location by strengthening the till within the margin. Our study uses a two-dimensional thermo-mechanical model in a cross-section perpendicular to the direction of flow. We show that the intense straining at the shear margins can generate large temperate regions within the deforming ice. Assuming that the melt generated in the temperate ice collects in a drainage channel at the base, we show that the channel locally decreases the pore pressure in the till. For a Coulomb-plastic rheology, this depressed pore pressure leads to a basal strength substantially higher than that inferred under the majority of the stream. Our results show that the additional basal resistance produced by the channel can reduce the stresses concentrated on the locked bed. Matching the model to surface velocity data at Whillans ice stream margin, we show that a stable shear margin occurs when the slipping-to-locked bed transition is less than 500 m away from a channel operating at an effective pressure of 200 kPa if the basal hydraulic transmissivity is equivalent to that of a water-film 0.2 mm thick.

  20. An assessment of the rapid evolution of ice-marginal and proglacial systems due to ongoing climate change.

    NASA Astrophysics Data System (ADS)

    Carrivick, Jonathan

    2015-04-01

    Ice-marginal and proglacial systems are rapidly evolving due to ongoing climate change, which is primarily manifest in deglaciation and thawing permafrost. Evolution of ice-marginal and proglacial systems can be recognised specifically in geomorphological and hydrological processes, landforms and sediments. These changes will have important and immediate consequences for landscape stability and for water and sediment fluxes, and hence for biogeochemical cycles, ecology and human activity. This presentation will discuss three hot topics; (i) the general response of alpine catchments to deglaciation and permafrost thawing, (ii) the impact of proglacial lakes on ice margins and on proglacial systems, (iii) the role of sudden onset glacier floods, or 'jökulhlaups', in ice-marginal and proglacial systems. In all three topics an emphasis will be made on the state of conceptual knowledge, outstanding requirement for quantitative measurement and analysis, and opportunities offered by emerging technology. The presentation will finish with a look forwards to suggest ways of integrating ideas and approaches, resources and methods across research disciplines.

  1. 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

  2. Lateral shear-moraines and lateral marginal-moraines of palaeo-ice streams

    NASA Astrophysics Data System (ADS)

    Batchelor, C. L.; Dowdeswell, J. A.

    2016-11-01

    An understanding of the nature of sedimentation at ice-stream lateral margins is important in reconstructing the dynamics of former ice sheets and modelling the mechanisms by which sediment is transported beneath contemporary ice streams. Theories of the formation of ice-stream lateral moraines (ISLMs) have hitherto been based on a relatively limited number of terrestrial and marine examples. Here, an inventory of ISLMs is compiled from available studies, together with independent analysis of seismic-reflection and bathymetric datasets. The locations and dimensions of 70 ISLMs, alongside a synthesis of their key architectural and geomorphic characteristics, are presented. Two different types of ISLMs are identified. Type 1 ISLMs are up to 3.5 km wide and 60 m thick. They maintain a constant width, thickness and cross-sectional shape along their length. Type 1 ISLMs are interpreted and referred to as ice-stream lateral shear-moraines that form subglacially in the shear zone between ice streams and slower-flowing regions of an ice sheet. In contrast, Type 2 ISLMs are up to 50 km wide and 300 m thick. They are only identified close to the shelf break in the marine environment. Type 2 ISLMs exhibit an increase in width and thickness along their length and their distal slopes become steeper in a seaward direction. They contain internal dipping reflections that indicate sediment progradation away from the former ice stream. Type 2 ISLMs are interpreted and referred to as ice-stream lateral marginal-moraines that were formed at the lateral boundary between ice streams and seafloor terrain that was free of grounded ice. We suggest that, using bathymetric images and acoustic profiles, it is possible to differentiate between ice-stream lateral shear-moraines and lateral marginal-moraines in the geological record. This distinction is important for understanding the mechanisms of sediment transfer beneath ice streams and for making inferences about the conditions that existed

  3. Expanded Late Wisconsinan ice cap and ice sheet margins in the western Queen Elizabeth Islands, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Nixon, F. Chantel; England, John H.

    2014-05-01

    Recent mapping of surficial geology and geomorphology in the western Canadian High Arctic (Melville and Eglinton islands), together with new radiocarbon dates acquired from ice-contact raised marine sediments, document expanded late Wisconsinan ice limits for the northwest Laurentide Ice Sheet and the western Innuitian Ice Sheet. An extension of the northwestern margin of the Laurentide Ice Sheet onto Eglinton Island is proposed based on evidence from till containing erratics derived from the Canadian Shield and a pattern of meltwater channels indicating ice retreat offshore into M'Clure Strait. Expansion of the western Melville Island Ice Cap (part of the western, lowland sector of the Innuitian Ice Sheet) to its offshore late Wisconsinan limit was facilitated by coalescence with the Laurentide Ice Sheet, whose buttressing allowed thickening to occur. Estimates of ice extent and thickness (>500 m) of the western Melville Island Ice Cap are in agreement with high marine limits (≤70 m asl). Lateral and proglacial meltwater channels, moraines and glaciomarine, glaciolacustrine and glaciofluvial deposits indicate radial retreat of the western Melville Island Ice Cap onto central highlands after ˜13.0 cal ka BP. Older marine limit shorelines on southern Eglinton Island (˜13.6 cal ka BP) are broadly synchronous with the early and rapid deglaciation of other areas formerly glaciated by the northwestern Laurentide Ice Sheet to the southeast and southwest (˜14.2-13.6 cal ka BP). The collapse of the northwest Laurentide Ice Sheet in M'Clure Strait beginning at ˜14.2 cal ka BP, in addition to prior inferred thinning, opens the possibility that it made a significant contribution to meltwater pulse 1A.

  4. Local response of a glacier to annual filling and drainage of an ice-marginal lake

    USGS Publications Warehouse

    Walder, J.S.; Trabant, D.C.; Cunico, M.; Fountain, A.G.; Anderson, S.P.; Anderson, R. Scott; Malm, A.

    2006-01-01

    Ice-marginal Hidden Creek Lake, Alaska, USA, outbursts annually over the course of 2-3 days. As the lake fills, survey targets on the surface of the 'ice dam' (the glacier adjacent to the lake) move obliquely to the ice margin and rise substantially. As the lake drains, ice motion speeds up, becomes nearly perpendicular to the face of the ice dam, and the ice surface drops. Vertical movement of the ice dam probably reflects growth and decay of a wedge of water beneath the ice dam, in line with established ideas about jo??kulhlaup mechanics. However, the distribution of vertical ice movement, with a narrow (50-100 m wide) zone where the uplift rate decreases by 90%, cannot be explained by invoking flexure of the ice dam in a fashion analogous to tidal flexure of a floating glacier tongue or ice shelf. Rather, the zone of large uplift-rate gradient is a fault zone: ice-dam deformation is dominated by movement along high-angle faults that cut the ice dam through its entire thickness, with the sense of fault slip reversing as the lake drains. Survey targets spanning the zone of steep uplift gradient move relative to one another in a nearly reversible fashion as the lake fills and drains. The horizontal strain rate also undergoes a reversal across this zone, being compressional as the lake fills, but extensional as the lake drains. Frictional resistance to fault-block motion probably accounts for the fact that lake level falls measurably before the onset of accelerated horizontal motion and vertical downdrop. As the overall fault pattern is the same from year to year, even though ice is lost by calving, the faults must be regularly regenerated, probably by linkage of surface and bottom crevasses as ice is advected toward the lake basin.

  5. Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet

    PubMed Central

    Dieser, Markus; Broemsen, Erik L J E; Cameron, Karen A; King, Gary M; Achberger, Amanda; Choquette, Kyla; Hagedorn, Birgit; Sletten, Ron; Junge, Karen; Christner, Brent C

    2014-01-01

    Microbial processes that mineralize organic carbon and enhance solute production at the bed of polar ice sheets could be of a magnitude sufficient to affect global elemental cycles. To investigate the biogeochemistry of a polar subglacial microbial ecosystem, we analyzed water discharged during the summer of 2012 and 2013 from Russell Glacier, a land-terminating outlet glacier at the western margin of the Greenland Ice Sheet. The molecular data implied that the most abundant and active component of the subglacial microbial community at these marginal locations were bacteria within the order Methylococcales (59–100% of reverse transcribed (RT)-rRNA sequences). mRNA transcripts of the particulate methane monooxygenase (pmoA) from these taxa were also detected, confirming that methanotrophic bacteria were functional members of this subglacial ecosystem. Dissolved methane ranged between 2.7 and 83 μM in the subglacial waters analyzed, and the concentration was inversely correlated with dissolved oxygen while positively correlated with electrical conductivity. Subglacial microbial methane production was supported by δ13C-CH4 values between −64‰ and −62‰ together with the recovery of RT-rRNA sequences that classified within the Methanosarcinales and Methanomicrobiales. Under aerobic conditions, >98% of the methane in the subglacial water was consumed over ∼30 days incubation at ∼4 °C and rates of methane oxidation were estimated at 0.32 μM per day. Our results support the occurrence of active methane cycling beneath this region of the Greenland Ice Sheet, where microbial communities poised in oxygenated subglacial drainage channels could serve as significant methane sinks. PMID:24739624

  6. Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet.

    PubMed

    Dieser, Markus; Broemsen, Erik L J E; Cameron, Karen A; King, Gary M; Achberger, Amanda; Choquette, Kyla; Hagedorn, Birgit; Sletten, Ron; Junge, Karen; Christner, Brent C

    2014-11-01

    Microbial processes that mineralize organic carbon and enhance solute production at the bed of polar ice sheets could be of a magnitude sufficient to affect global elemental cycles. To investigate the biogeochemistry of a polar subglacial microbial ecosystem, we analyzed water discharged during the summer of 2012 and 2013 from Russell Glacier, a land-terminating outlet glacier at the western margin of the Greenland Ice Sheet. The molecular data implied that the most abundant and active component of the subglacial microbial community at these marginal locations were bacteria within the order Methylococcales (59-100% of reverse transcribed (RT)-rRNA sequences). mRNA transcripts of the particulate methane monooxygenase (pmoA) from these taxa were also detected, confirming that methanotrophic bacteria were functional members of this subglacial ecosystem. Dissolved methane ranged between 2.7 and 83 μM in the subglacial waters analyzed, and the concentration was inversely correlated with dissolved oxygen while positively correlated with electrical conductivity. Subglacial microbial methane production was supported by δ(13)C-CH4 values between -64‰ and -62‰ together with the recovery of RT-rRNA sequences that classified within the Methanosarcinales and Methanomicrobiales. Under aerobic conditions, >98% of the methane in the subglacial water was consumed over ∼30 days incubation at ∼4 °C and rates of methane oxidation were estimated at 0.32 μM per day. Our results support the occurrence of active methane cycling beneath this region of the Greenland Ice Sheet, where microbial communities poised in oxygenated subglacial drainage channels could serve as significant methane sinks.

  7. Local Effects of Ice Floes on Skin Sea Surface Temperature in the Marginal Ice Zone from UAVs

    NASA Astrophysics Data System (ADS)

    Zappa, C. J.; Brown, S.; Emery, W. J.; Adler, J.; Wick, G. A.; Steele, M.; Palo, S. E.; Walker, G.; Maslanik, J. A.

    2013-12-01

    Recent years have seen extreme changes in the Arctic. Particularly striking are changes within the Pacific sector of the Arctic Ocean, and especially in the seas north of the Alaskan coast. These areas have experienced record warming, reduced sea ice extent, and loss of ice in areas that had been ice-covered throughout human memory. Even the oldest and thickest ice types have failed to survive through the summer melt period in areas such as the Beaufort Sea and Canada Basin, and fundamental changes in ocean conditions such as earlier phytoplankton blooms may be underway. Marginal ice zones (MIZ), or areas where the "ice-albedo feedback" driven by solar warming is highest and ice melt is extensive, may provide insights into the extent of these changes. Airborne remote sensing, in particular InfraRed (IR), offers a unique opportunity to observe physical processes at sea-ice margins. It permits monitoring the ice extent and coverage, as well as the ice and ocean temperature variability. It can also be used for derivation of surface flow field allowing investigation of turbulence and mixing at the ice-ocean interface. Here, we present measurements of visible and IR imagery of melting ice floes in the marginal ice zone north of Oliktok Point AK in the Beaufort Sea made during the Marginal Ice Zone Ocean and Ice Observations and Processes EXperiment (MIZOPEX) in July-August 2013. The visible and IR imagery were taken from the unmanned airborne vehicle (UAV) ScanEagle. The visible imagery clearly defines the scale of the ice floes. The IR imagery show distinct cooling of the skin sea surface temperature (SST) as well as a intricate circulation and mixing pattern that depends on the surface current, wind speed, and near-surface vertical temperature/salinity structure. Individual ice floes develop turbulent wakes as they drift and cause transient mixing of an influx of colder surface (fresh) melt water. The upstream side of the ice floe shows the coldest skin SST, and

  8. Subglacial hydrology as a control on ice stream shear margin locations

    NASA Astrophysics Data System (ADS)

    Perol, T.; Rice, J. R.; Platt, J. D.; Suckale, J.

    2015-12-01

    Ice streams are fast-flowing bands of ice separated from the nearly stagnant ice in the adjacent ridge by zones of highly localized deformation known as shear margins. However, it is presently unclear what mechanisms can control the location of shear margins, and possibly allow them to migrate. Within the shear margin, the transition from a freely slipping bed beneath the ice stream to a locked bed beneath the ridge concentrates stresses on the locked bed. We show that subglacial hydrological processes can select the shear margin location by strengthening the subglacial till within the margin, reducing the stress concentration associated with the transition from a slipping to a locked bed. Our study uses a two-dimensional thermo-mechanical model in a cross-section perpendicular to the direction of flow. We show that the intense straining at the shear margins can generate large temperate regions within the deforming ice. Assuming that the melt generated in the temperate ice collects in a drainage channel at the base of the margin, we show that the channel locally decreases the pore pressure in the subglacial till. For a Coulomb-plastic rheology, this depressed pore pressure leads to a basal shear strength substantially higher than that inferred under the majority of the stream. Our results show that the additional basal resistance produced by the channel can offset the large stresses concentrated on the locked bed, allowing the drainage channel to select the margin location. Matching the model to surface velocity data near Dragon Margin within Whillans ice stream B2, we show that a stable shear margin occurs when the slipping-to-locked bed transition is less than 500 m away from a channel operating at an effective pressure of 200 kPa if the basal hydraulic transmissivity is equivalent to that of a water-film ~0.2 mm thick. Extending these results we explore how the shear margin location varies with the effective pressure of the channel and hydraulic properties of

  9. Retreat of northern margins of George VI and Wilkins Ice Shelves, Antarctic Peninsula

    USGS Publications Warehouse

    Lucchitta, B.K.; Rosanova, C.E.

    1998-01-01

    The George VI and Wilkins Ice Shelves are considered at risk of disintegration due to a regional atmospheric warming trend on the Antarctic Peninsula. Retreat of the northern margin of the George VI Ice Shelf has been observed previously, but the Wilkins Ice Shelf was thought to be stable. We investigated the positions of the northern fronts of these shelves from the literature and looked for changes on 1974 Landsat and 1992 and 1995 European remote-sensing satellite (ERS) synthetic aperture radar images. Our investigation shows that the northern George VI Ice Shelf lost a total of 906 km2 between 1974 and 1992, and an additional 87 km2 by 1995. The northern margin of the Wilkins Ice Shelf lost 796 km2 between 1990 and 1992, and another 564 km2 between 1992 and 1995. Armadas of tabular icebergs were visible in front of this shelf in the ERS images. These two ice shelves mark the southernmost documented conspicuous retreat of ice-shelf margins.

  10. Subglacial source of meltwater discharge in an emerging ice-marginal channel, Bering Glacier, Alaska

    SciTech Connect

    Priscott, G.; Fleisher, P.J. . Dept. of Earth Sciences)

    1993-03-01

    The retreating eastern margin of Bering Piedmont Glacier terminates in two ice-contact lakes separated by an island that has been uncovered in the last decade. A semi-continuous aerial photo record (1978--1991) and field observations (1992) confirms a newly-developed ice-marginal channel linking these two lakes that is fed by a persistent subglacial conduit system. This investigation documents channel characteristic, discharge, turbidity, water temperature and the location of the present ice margin. Bathymetry along the channel reveals a highly irregular profile consisting of low-gradient reaches 3--5 m deep interrupted by shallow sills (< 1 m) of grounded, subaqueous ice and a 40 m basin among ice islands. Channel dimensions measured in 5 cross section reveal abrupt, small-scale changes typical of sub-bottom ice. Discharge varies from 72.24 cms near a node of upwelling to 40.38 cms 2 km down stream, then back up to 42.25 cms within 0.4 km, where the channel enters a lake. Turbidity values between 1.67 g/l and 4.20 g/l, of 10 water samples vary irregularly along the channel and with depth at-a-station. Early July water temperatures from 7 widely-spaced locations indicate the thermocline occurs at depths from 1 to 3 m and separates surface water at +1.1 C from supercooled water at [minus]1.0 C. Clusters of in situ platy frazil ice crystals several centimeters in diameter were observed on floating ice in the area of upwelling supercooled water. The presence of upwelling, highly-turbid, supercooled water indicates that the primary meltwater source is a subglacial conduit network at the ice margin, from which flow separates and discharges through a leaky channel into both lakes.

  11. Geomicrobiology of Meltwater From the Western Margin of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Hagedorn, B.; Dieser, M.; Choquette, K.; Cameron, K. A.; Sletten, R. S.; Liu, L.; Junge, K.; Christner, B. C.

    2014-12-01

    Subglacial environments are cold, dark, and possess a range of redox conditions. These environments are gaining attention in global biogeochemical cycles as to their role in releasing bioavailable micronutrients such as Fe and the production of greenhouse gases. However, there is uncertainty about how the microbial communities interact with lithology and mediate geochemical reactions under glacial conditions. We examined the microbial communities and their influence on elemental cycling in two glacial environments along the western Greenland Ice Sheet margin: Thule in the north (76ºN, 68ºW) and Kangerlussuaq in the south (67ºN, 51ºW). The north is dominated by supraglacial melting with considerable contribution from the periglacial environment; the south has a well-developed subglacial drainage system. The lithology is sedimentary rocks in the north and crystalline rocks in the south and this difference was reflected in the geochemistry of the drainages. Runoff in the north was oxygen saturated throughout the season. A change from Na and Cl dominance in spring to Ca and SO4 and overall increase in solute concentration marked a stronger contribution from active layer thawing. In the south, waters were undersaturated in oxygen at times, presumably due to biological and chemical sinks of subglacial origin. The meltwater here was dominated by HCO3, SO4 and Ca. In subglacial outflows Fe (oxyhydr)oxide concentrations increased with decreasing oxygen concentration suggesting their formation under oxygen limiting conditions. The high abundance of sulfate implies oxidation of iron sulfides which is consistent with inverse modeling of subglacial weathering processes under anoxic conditions. Meltwater in both locations transported reactive particulate iron which in the north consisted mainly of Fe oxides while Fe(oxyhydr)oxides dominated in the south. DNA and RNA signatures indicate microbial phylotypes that are active in iron reduction, sulfidic mineral weathering

  12. Upper Ocean Evolution Across the Beaufort Sea Marginal Ice Zone from Autonomous Gliders

    NASA Astrophysics Data System (ADS)

    Lee, Craig; Rainville, Luc; Perry, Mary Jane

    2016-04-01

    The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g., the relatively warm Pacific Summer (PSW) and Atlantic (AW) waters), and elevated surface wave energy that acts to deform and fracture sea ice. Spatial and temporal variability in ice properties and open water fraction impact these processes. To investigate how upper ocean structure varies with changing ice cover, and how the balance of processes shift as a function of ice fraction and distance from open water, four long-endurance autonomous Seagliders occupied sections that extended from open water, through the marginal ice zone, deep into the pack during summer 2014 in the Beaufort Sea. Sections reveal strong fronts where cold, ice-covered waters meet waters that have been exposed to solar warming, and O(10 km) scale eddies near the ice edge. In the pack, Pacific Summer Water and a deep chlorophyll maximum form distinct layers at roughly 60 m and 80 m, respectively, which become increasingly diffuse as they progress through the MIZ and into open water. The isopynal layer between 1023 and 1024 kgm‑3, just above the PSW, consistently thickens near the ice edge, likely due to mixing or energetic vertical exchange associated with strong lateral gradients in this region. This presentation will discuss the upper ocean variability, its relationship to sea ice extent, and evolution over the summer to the start of freeze up.

  13. Surface ice motion deviating toward the margins during speed-up events at Gornergletscher, Switzerland

    NASA Astrophysics Data System (ADS)

    Sugiyama, S.; Bauder, A.; Riesen, P.; Funk, M.

    2010-09-01

    High frequency ice flow measurements during speed-up events in Gornergletscher, Switzerland, revealed intriguing ice motion which has never been reported in detail before. During the summer 2005, more than a 100% flow speed increase was observed three times at four GPS stations installed across Gornergletscher. The speed-ups were accompanied by a decimeter scale surface uplift. Two of the events were triggered by intensive surface melt and rainfall, while the third one was due to the outburst of Gornersee, a glacier-dammed lake located 2 km upglacier. An interesting observation was ice motion deviating toward the side margins during the events. As the glacier accelerated, a transverse (cross glacier) velocity component was generated, turning the flow direction away from the central flow line toward the margins. When the glacier decelerated, the transverse velocity component reversed so that the ice flowed back to the azimuth of the initial flow direction. In the most significant case, the trajectory of the survey stake deviated from the original track by 0.2 m in the transverse direction. We hypothesize that the observed lateral ice motion was caused by locally elevated subglacial water pressure. When the ice sole decoupled from the bed at a part of the glacier, a point source of vertical displacement was transmitted to the surface through viscous ice. This caused the transverse as well as vertical surface motion, as observed in ground motion during magma intrusion. The hypothesis was tested with a two-dimensional ice flow model applied to the transverse glacier cross section. The model confirmed that the surface ice would move toward the margins as observed in Gornergletscher, if subglacial water pressure exceeded the ice overburden pressure over a limited part of the bed.

  14. Model of the western Laurentide Ice Sheet from glacio-isostatic adjustment analysis and revised margin locations

    NASA Astrophysics Data System (ADS)

    Gowan, E. J.; Tregoning, P.; Purcell, A.

    2013-12-01

    Uncertainties in ice sheet extent and thickness during the retreat of the western Laurentide Ice Sheet from the last glacial maximum affect estimates of its contribution to global climate and sea level change during the late Pleistocene and early Holocene. These difficulties arise due to a lack of chronological constraints on the timing of margin retreat in many areas and a lack of observations of the glacio-isostatic deformation due the ice sheet. We present a model of the western Laurentide ice sheet in North America based on new ice margin reconstructions and well dated glacial lake strandlines. The model of the Laurentide ice sheet is constructed based on the assumption of perfectly plastic, steady state conditions with temporally variable basal shear stress and margin location. Initial models of basal shear stress were based on modern surficial geology and geography, and adjusted in an iterative process to reflect the volume of ice needed to fit observations of earth deformation caused by the ice sheet. The ice margins were developed by determining the minimum timing of retreat and using that as a constraint on the absolute maximum possible ice margin location. By using the ice margin as the starting point of modelling, assumptions on the location of ice domes and saddles were avoided. Initial results of the modelling indicate that ice thickness remained below 1500 m throughout the Western Canadian Sedimentary Basin region at the last glacial maximum as a result of low basal shear stress. Modelled flow direction matches geomorphic ice flow indicators lending confidence to the glaciological model. Ice sheet margin retreat was limited until after 15,000 cal yr BP. The most significant ice volume losses happened after retreat from southern Alberta and after retreat began on the Canadian Shield.

  15. Ice nucleation activity of polysaccharides

    NASA Astrophysics Data System (ADS)

    Bichler, Magdalena; Felgitsch, Laura; Haeusler, Thomas; Seidl-Seiboth, Verena; Grothe, Hinrich

    2015-04-01

    Heterogeneous ice nucleation is an important process in the atmosphere. It shows direct impact on our climate by triggering ice cloud formation and therefore it has much influence on the radiation balance of our planet (Lohmann et al. 2002; Mishchenko et al. 1996). The process itself is not completely understood so far and many questions remain open. Different substances have been found to exhibit ice nucleation activity (INA). Due to their vast differences in chemistry and morphology it is difficult to predict what substance will make good ice nuclei and which will not. Hence simple model substances must be found and be tested regarding INA. Our work aims at gaining to a deeper understanding of heterogeneous ice nucleation. We intend to find some reference standards with defined chemistry, which may explain the mechanisms of heterogeneous ice nucleation. A particular focus lies on biological carbohydrates in regards to their INA. Biological carbohydrates are widely distributed in all kingdoms of life. Mostly they are specific for certain organisms and have well defined purposes, e.g. structural polysaccharides like chitin (in fungi and insects) and pectin (in plants), which has also water-binding properties. Since they are widely distributed throughout our biosphere and mostly safe to use for nutrition purposes, they are well studied and easily accessible, rendering them ideal candidates as proxies. In our experiments we examined various carbohydrates, like the already mentioned chitin and pectin, as well as their chemical modifications. Lohmann U.; A Glaciation Indirect Aerosol Effect Caused by Soot Aerosols; J. Geoph. Res.; Vol. 24 No.4; pp 11-1 - 11-4; 2002 Mishchenko M.I., Rossow W.B., Macke A., Lacis A. A.; Sensitivity of Cirrus Cloud Albedo, Bidirectional Reflectance and Optical Thickness Retrieval Accuracy to Ice Particle Shape, J. Geoph. Res.; Vol. 101, No D12; pp. 16,973 - 16,985; 1996

  16. Flow variability and ongoing margin shifts on Bindschadler and MacAyeal Ice Streams, West Antarctica

    NASA Astrophysics Data System (ADS)

    Hulbe, C. L.; Scambos, T. A.; Klinger, M.; Fahnestock, M. A.

    2016-02-01

    Ice streams on the Ross Sea side of the West Antarctic Ice Sheet are known to experience flow variability on hourly, annual, and multicentury time scales. We report here on observations of flow variability at the decade scale on the Bindschadler and MacAyeal Ice Streams (BIS and MacIS). Our analysis makes use of archived ice velocity data and new mappings from composited Landsat 7 and Landsat 8 imagery that together span the interval from 1985 to 2014. Both ice streams speedup and slowdown in a range of about ±5 m a-2 over our various comparison intervals. The rates of change are variable in both time and space, and there is no evidence of external forcing at work across the two streams. Widespread changes are most likely linked to instability in the subglacial till and/or subglacial water flow. Sticky spots near the confluence of the two ice streams are loci for speed changes. These relatively young and slow-flowing features appear to be forcing shifts in margin position near the outlets of both streams. The margin jumps reduce the effective outlet widths of the streams by 20% and 30% on BIS and MacIS, respectively. Those magnitudes are similar to the outlet narrowing experienced by Kamb Ice Stream prior to its stagnation.

  17. Drumlin evolution and ice sheet oscillations along the NE Atlantic margin, Donegal Bay, western Ireland

    NASA Astrophysics Data System (ADS)

    Knight, Jasper; McCabe, A. Marshall

    1997-07-01

    Satellite imagery of Donegal Bay, northwestern Ireland, reveals two streamlined subglacial bedform sets produced during the late Devensian glaciation (ca. 22,000-15,000 yrs B.P.). The first bedform set trends northeast-southwest and records fast ice flow from inland ice domes onto the eastern Atlantic continental shelf. The second bedform set, trending east-west, crosscuts and partially reorientates the first. Morphological and sedimentary evidence show that the second set corresponds to the last phase of fast ice flow (drumlinization) in northwestern Ireland. Morphological characteristics of the Donegal Bay drumlin field, and sedimentary characteristics of the Mullinasole drumlin, Donegal Bay, support a two-stage interpretation of drumlin evolution. These are the following. (1) Deposition of glaciomarine mud and diamict facies at a tidewater glacier margin. Stratified diamicts record debris flow events and sediment reworking. This facies sequence is erosionally truncated. (2) Deposition of subglacial diamict and sand facies recording ice readvance and drumlinization. Drumlinization (sediment streamlining) reflects ice mass-balance destabilization, episodic: fast ice flow and ice-marginal oscillation, and may be correlated with millennial-time scale climate changes in the circum-North Atlantic.

  18. Autonomous Investigations of Marginal Ice Zone Processes- Changing Feedbacks and Observational Challenges

    NASA Astrophysics Data System (ADS)

    Lee, Craig; Doble, Martin; Maslowski, Wieslaw; Stanton, Tim; Timmermans, Mary-Louise; Thomson, Jim; Wilkinson, Jeremy

    2015-04-01

    The observed reduction of Arctic summertime sea ice extent and expansion of the marginal ice zone (MIZ) have profound impacts on the balance of processes controlling sea ice evolution, including the introduction of several positive feedback mechanisms that may act to accelerate melting. Examples of such feedbacks include increased upper ocean warming though absorption of solar radiation, elevated internal wave energy and mixing that may entrain heat stored in subsurface watermasses (e.g. the relatively warm Pacific Summer (PSW) and Atlantic (AW) waters) and elevated surface wave energy that acts to deform and fracture sea ice, all of which grow in importance with increasing open water extent. Investigations of MIZ dynamics must resolve the short spatial and temporal scales associated with the processes that govern the exchange of momentum, heat and freshwater near the atmosphere-ice-ocean interface while also achieving the spatial scope and temporal persistence required to characterize how the balance of processes shifts as a function of evolving open water fraction and open water fetch to the south. The recent Office of Naval Research (ONR) Marginal Ice Zone program employed an integrated system of autonomous platforms to provide high-resolution measurements that extend from open water, through the MIZ and deep into ice-covered regions while providing persistence to quantify evolution over an entire summertime melt season. This presentation will provide an overview of the strategy developed by the ONR MIZ team and present early results from the 2014 field program.

  19. Upper Ocean Temperature, Salinity, and Turbulence Across the Marginal Ice Zone from Autonomous Seaglider Surveys

    NASA Astrophysics Data System (ADS)

    Rainville, L.; Lee, C.

    2014-12-01

    We present initial results from several autonomous Seaglider deployments during summer 2014 in the ice-free region, under ice, and in the marginal ice zone (MIZ) of the Beaufort Sea. Measuring temperature and salinity of the upper ocean on scales of 2-3 km, these surveys resolve the short temporal and spatial scales associated with key upper ocean processes in the MIZ.Gliders also carry temperature and shear microstructure sensors, providing direct direct estimates of turbulent dissipation rates at the base of the surface mixed layer and in the halocline. The objective of this work to understand the balance and interplay of processes that supply freshwater and heat to the ice ocean boundary layer and their variations as a function of ice cover.

  20. A high detail benchmark dataset of mid-1980's ice margin positions for all Greenland ice masses

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Ahlstrom, A. P.

    2012-12-01

    because the splitting of ice masses essentially independent but in topological contact with the ice sheet includes a degree of subjectivity. However, terminus positions and individual ice masses can easily be compared between the two datasets. A third dataset, the GIMP 15 m ice cover grid based on 1999-2001 panchromatic Landsat 7 scenes (Howat & Negrete, in prep.) has recently become available. It offers a level of detail closer to the PROMICE map, and we discuss several cases of marked frontal changes, particularly at marine terminating glaciers, and detection of glacier surge events. The mid-1980's PROMICE glacier outlines provide a regionally-synchronous benchmark of ice margin positions from before the widespread availability of high resolution satellite imagery, and with a higher detail than the products currently being released based on pre-SLC failure Landsat 7.

  1. Air-sea exchange of carbon dioxide in the Southern Ocean and Antarctic marginal ice zone

    NASA Astrophysics Data System (ADS)

    Butterworth, Brian J.; Miller, Scott D.

    2016-07-01

    Direct carbon dioxide flux measurements using eddy covariance from an icebreaker in the high-latitude Southern Ocean and Antarctic marginal ice zone are reported. Fluxes were combined with the measured water-air carbon dioxide partial pressure difference (ΔpCO2) to compute the air-sea gas transfer velocity (k, normalized to Schmidt number 660). The open water data showed a quadratic relationship between k (cm h-1) and the neutral 10 m wind speed (U10n, m s-1), kopen = 0.245 U10n2 + 1.3, in close agreement with decades old tracer-based results and much lower than cubic relationships inferred from previous open ocean eddy covariance studies. In the marginal ice zone, the effective gas transfer velocity decreased in proportion to sea ice cover, in contrast with predictions of enhanced gas exchange in the presence of sea ice. The combined open water and marginal ice zone results affect the calculated magnitude and spatial distribution of Southern Ocean carbon flux.

  2. Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Hopkins, Thomas L.; Torres, Joseph J.

    1989-04-01

    The structure of the food web in the vicinity of a marginal ice zone was investigated in the western Weddell Sea during austral autumn 1986. The diets of 40 species of zooplankton and micronekton occurring in the epipelagic zone were examined and compared using non-hierarchical clustering procedures. Over half the species were in three clusters of predominantly small-particle (phytoplankton; protozoans) grazers. These included biomass dominants Calanoides acutus, Calanus propinquus, Metridia gerlachei and Salpa thompsoni. Six clusters contained omnivores that had diets consisting of small particles as well as a substantial fraction of metazoan food. Among these was Euphausia superba. Seven groups were carnivorous, including species of copepods (1), chaetognaths (3), and fishes (5). Copepods were the most frequent food of carnivores; however krill also were important in the diets of three fish species. Among small-particle grazers, phytoplankton occurred more frequently in guts of individuals from open water; carnivory was more in evidence in samples collected under the pack ice. Regional comparisons of material taken on this and several previous cruises indicate that, in most of the dominant species, diets remain relatively consistent with respect to major food categories. Seasonal impact on feeding dynamics appears to be great: the guts of grazing species were generally much more full (visual evidence) during summer bloom conditions than during the autumn. The following trophic sequence is suggested for grazing zooplankton species in ice-covered regions of the Antarctic: (1) Active small-particle grazing during the summer bloom period; (2) reduced ingestion rates in autumn as primary production declines and the system becomes more oligotrophic, with some species augmenting grazing with carnivory; (3) descent of zooplankton biomass species into the mesopelagic zone in late autumn-early winter with feeding largely terminated. The sequence applies to the dominant

  3. Ice Sheet History from Antarctic Continental Margin Sediments: The ANTOSTRAT Approach

    USGS Publications Warehouse

    Barker, P.F.; Barrett, P.J.; Camerlenghi, A.; Cooper, A. K.; Davey, F.J.; Domack, E.W.; Escutia, C.; Kristoffersen, Y.; O'Brien, P.E.

    1998-01-01

    The Antarctic Ice Sheet is today an important part of the global climate engine, and probably has been so for most of its long existence. However, the details of its history are poorly known, despite the measurement and use, over two decades, of low-latitude proxies of ice sheet volume. An additional way of determining ice sheet history is now available, based on understanding terrigenous sediment transport and deposition under a glacial regime. It requires direct sampling of the prograded wedge of glacial sediments deposited at the Antarctic continental margin (and of derived sediments on the continental rise) at a small number of key sites, and combines the resulting data using numerical models of ice sheet development. The new phase of sampling is embodied mainly in a suite of proposals to the Ocean Drilling Program, generated by separate regional proponent groups co-ordinated through ANTOSTRAT (the Antarctic Offshore Acoustic Stratigraphy initiative). The first set of margin sites has now been drilled as ODP Leg 178 to the Antarctic Peninsula margin, and a first, short season of inshore drilling at Cape Roberts, Ross Sea, has been completed. Leg 178 and Cape Roberts drilling results are described briefly here, together with an outline of key elements of the overall strategy for determining glacial history, and of the potential contributions of drilling other Antarctic margins investigated by ANTOSTRAT. ODP Leg 178 also recovered continuous ultra-high-resolution Holocene biogenic sections at two sites within a protected, glacially-overdeepened basin (Palmer Deep) on the inner continental shelf of the Antarctic Peninsula. These and similar sites from around the Antarctic margin are a valuable resource when linked with ice cores and equivalent sections at lower latitude sites for studies of decadal and millenial-scale climate variation.

  4. Fluctuations of the Greenland Ice Sheet since the last ice age: comparisons of the response of marine and land-terminating ice margins to Holocene climate changes

    NASA Astrophysics Data System (ADS)

    Levy, Laura; Larsen, Nicolaj; Kelly, Meredith; Kjær, Kurt; Bjørk, Anders; Kjeldsen, Kristian; Funder, Svend; Applegate, Patrick; Howley, Jennifer; Virginia, Ross

    2016-04-01

    Fluctuations of the margins of the Greenland Ice Sheet (GrIS) in response to Holocene climate change may be used as a proxy for how they may respond to future climate change. Here, we present records of Holocene fluctuations of the margins of the GrIS in southeastern and southwestern Greenland based on geomorphic mapping and 10Be dating of boulders on moraines and boulders on bedrock. We show that in southeastern Greenland the marine-terminating outlet glaciers retreated from the outer coast between 10.4 and 9.4 ka and responded rapidly to early Holocene warming, retreating up-fjord at a rate of ~70-100 m yr-1. These rates are comparable, or higher than, modern retreat rates of 30-100 m yr-1. In contrast, the terrestrial margin of the GrIS in the Kangerlussuaq region of southwestern Greenland retreated only ~25 m yr-1 throughout the early and middle Holocene. These data indicate that forcings such as warm ocean waters, fjord geometry, fjord bathymetry and ice dynamics are potential mechanisms that caused differences in retreat rates between marine and terrestrial-terminating margins of the ice sheet. Additionally, they show that the margins of the GrIS responded sensitively to Holocene climate change.

  5. Ice stream activity scaled to ice sheet volume during Laurentide Ice Sheet deglaciation

    NASA Astrophysics Data System (ADS)

    Stokes, C. R.; Margold, M.; Clark, C. D.; Tarasov, L.

    2016-02-01

    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.

  6. 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. PMID:26887494

  7. Wave observation in the marginal ice zone with the TerraSAR-X satellite

    NASA Astrophysics Data System (ADS)

    Gebhardt, Claus; Bidlot, Jean-Raymond; Gemmrich, Johannes; Lehner, Susanne; Pleskachevsky, Andrey; Rosenthal, Wolfgang

    2016-07-01

    This article investigates the penetration of ocean waves into the marginal ice zone (MIZ), observed by satellite, and likewise provides a basis for the future cross-validation of respective models. To this end, synthetic aperture radar images from the TerraSAR-X satellite (TS-X) and numerical simulations of the European Centre for Medium-Range Weather Forecasts (ECMWF) are used. The focus is an event of swell waves, developed during a storm passage in the Atlantic, penetrating deeply into the MIZ off the coast of Eastern Greenland in February 2013. The TS-X scene which is the basis for this investigation extends from the ice-free open ocean to solid ice. The variation of the peak wavelength is analysed and potential sources of variability are discussed. We find an increase in wavelength which is consistent with the spatial dispersion of deep water waves, even within the ice-covered region.

  8. Airborne remote sensing of ocean wave directional wavenumber spectra in the marginal ice zone

    NASA Astrophysics Data System (ADS)

    Sutherland, Peter; Gascard, Jean-Claude

    2016-05-01

    Interactions between surface waves and sea ice are thought to be an important, but poorly understood, physical process in the atmosphere-ice-ocean system. In this work, airborne scanning lidar was used to observe ocean waves propagating into the marginal ice zone (MIZ). These represent the first direct spatial measurements of the surface wavefield in the polar MIZ. Data were compared against two attenuation models, one based on viscous dissipation and one based on scattering. Both models were capable of reproducing the measured wave energy. The observed wavenumber dependence of attenuation was found to be consistent with viscous processes, while the spectral spreading of higher wavenumbers suggested a scattering mechanism. Both models reproduced a change in peak direction due to preferential directional filtering. Floe sizes were recorded using colocated visible imagery, and their distribution was found to be consistent with ice breakup by the wavefield.

  9. Hydrogen ICE Vehicle Testing Activities

    SciTech Connect

    J. Francfort; D. Karner

    2006-04-01

    The Advanced Vehicle Testing Activity teamed with Electric Transportation Applications and Arizona Public Service to develop and monitor the operations of the APS Alternative Fuel (Hydrogen) Pilot Plant. The Pilot Plant provides 100% hydrogen, and hydrogen and compressed natural gas (H/CNG)-blended fuels for the evaluation of hydrogen and H/CNG internal combustion engine (ICE) vehicles in controlled and fleet testing environments. Since June 2002, twenty hydrogen and H/CNG vehicles have accumulated 300,000 test miles and 5,700 fueling events. The AVTA is part of the Department of Energy’s FreedomCAR and Vehicle Technologies Program. These testing activities are managed by the Idaho National Laboratory. This paper discusses the Pilot Plant design and monitoring, and hydrogen ICE vehicle testing methods and results.

  10. The Floe Size Distribution in the Marginal Ice Zone of the Beaufort and Chukchi Seas

    NASA Astrophysics Data System (ADS)

    Schweiger, A. J. B.; Stern, H. L., III; Stark, M.; Zhang, J.; Steele, M.; Hwang, P. B.

    2014-12-01

    Several key processes in the Marginal Ice Zone (MIZ) of the Arctic Ocean are related to the size of the ice floes, whose diameters range from meters to tens of kilometers. The floe size distribution (FSD) influences the mechanical properties of the ice cover, air-sea momentum and heat transfer, lateral melting, and light penetration. However, no existing sea-ice/ocean models currently simulate the FSD in the MIZ. Model development depends on observations of the FSD for parameterization, calibration, and validation. To support the development and implementation of the FSD in the Marginal Ice Zone Modeling and Assimilation System (MIZMAS), we have analyzed the FSD in the Beaufort and Chukchi seas using multiple sources of satellite imagery: NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites (250 m pixel size), the USGS Landsat 8 satellite (80 m pixel size), the Canadian Space Agency's synthetic aperture radar (SAR) on RADARSAT (50 meter pixel size), and declassified National Technical Means imagery from the Global Fiducials Library (GFL) of the USGS (1 m pixel size). The procedure for identifying ice floes in the imagery begins with manually delineating cloud-free regions (if necessary). A threshold is then chosen to separate ice from water. Morphological operations and other semi-automated techniques are used to identify individual floes, whose properties are then easily calculated. We use the mean caliper diameter as the measure of floe size. The FSD is adequately described by a power-law in which the exponent characterizes the relative number of large and small floes. Changes in the exponent over time and space reflect changes in physical processes in the MIZ, such as sea-ice deformation, fracturing, and melting. We report results of FSD analysis for the spring and summer of 2013 and 2014, and show how the FSD will be incorporated into the MIZMAS model.

  11. High-resolution mapping of ice-marginal landforms in the Barnim region, northeast Germany

    NASA Astrophysics Data System (ADS)

    Hardt, Jacob; Hebenstreit, Robert; Lüthgens, Christopher; Böse, Margot

    2015-12-01

    Despite more than a 100-year-long research history, timing and position of the last glacial ice margins in the northeast German lowland are still up for debate. The Barnim region, a till plain in the northeast German young morainic landscape, is traversed by the contradictorily discussed Frankfurt ice marginal position. It is located in a key position to reassess the current state of research with help of a geographic information system (GIS) and field methods. A qualitative geomorphological analysis of a high resolution LiDAR digital elevation model (DEM) in the Barnim area uncovers a variety of landforms that were previously not described. The most prominent discovery is a set of about 10 lobe-shaped ridges in the middle Barnim area. Fieldwork and geophysical measurements were carried out to investigate the structure of the ridges. The ridges are 1000-1500 m in length and their widths vary from 10 to 15 km. They are raised some 6-10 m from their surroundings. The Frankfurt ice marginal position can only partially be traced in the DEM. Sedimentological and geophysical investigations indicate that the ridges are composed of glacial till that was deposited on glaciofluvial sediments. Their formation most probably took place during the ice retreat of the Brandenburg phase (W1B) and hence represents the W1F phase in the region.

  12. Bimodal pattern of seismicity detected at the ocean margin of an Antarctic ice shelf

    NASA Astrophysics Data System (ADS)

    Lombardi, Denis; Benoit, Lionel; Camelbeeck, Thierry; Martin, Olivier; Meynard, Christophe; Thom, Christian

    2016-08-01

    In Antarctica, locally grounded ice, such as ice rises bordering floating ice shelves, plays a major role in the ice mass balance as it stabilizes the ice sheet flow from the hinterland. When in direct contact with the ocean, the ice rise buttressing effect may be altered in response of changing ocean forcing. To investigate this vulnerable zone, four sites near the boundary of an ice shelf with an ice rise promontory in Dronning Maud Land, East-Antarctica were monitored for a month in early 2014 with new instruments that include both seismic and GPS sensors. Our study indicated that this transition zone experiences periodic seismic activity resulting from surface crevassing during oceanic tide-induced flexure of the ice shelf. The most significant finding is the observation of apparent fortnightly tide-modulated low-frequency, long-duration seismic events at the seaward front of the ice rise promontory. A basal origin of these events is postulated with the ocean water surge at each new spring tide triggering basal crevassing or basal slip on a local bedrock asperity. Detection and monitoring of such seismicity may help identifying ice rise zones vulnerable to intensified ocean forcing.

  13. Bimodal pattern of seismicity detected at the ocean margin of an Antarctic ice shelf

    NASA Astrophysics Data System (ADS)

    Lombardi, Denis; Benoit, Lionel; Camelbeeck, Thierry; Martin, Olivier; Meynard, Christophe; Thom, Christian

    2016-06-01

    In Antarctica, locally grounded ice, such as ice rises bordering floating ice shelves, plays a major role in the ice mass-balance as it stabilizes the ice sheet flow from the hinterland. When in direct contact with the ocean, the ice rise buttressing effect may be altered in response of changing ocean forcing. To investigate this vulnerable zone, four sites near the boundary of an ice shelf with an ice rise promontory in Dronning Maud Land, East-Antarctica were monitored for a month in early 2014 with new instruments that include both seismic and GPS sensors. Our study indicated that this transition zone experiences periodic seismic activity resulting from surface crevassing during oceanic tide-induced flexure of the ice shelf. The most significant finding is the observation of apparent fortnightly tide-modulated low frequency, long duration seismic events at the seaward front of the ice rise promontory. A basal origin of these events is postulated with the ocean water surge at each new spring tide triggering basal crevassing or basal slip on a local bedrock asperity. Detection and monitoring of such seismicity may help identifying ice rise zones vulnerable to intensified ocean forcing.

  14. The Importance of Basal Topography for Greenland Ice Sheet Margin Hydrology

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Smith, L. C.; Pitcher, L. H.; Chu, V. W.

    2012-12-01

    Nearly half of the Greenland ice sheet's total mass loss is controlled by surface mass balance, primarily driven by meltwater runoff exiting at its margin via supra-, en-, and sub-glacial drainage networks into fjords and pro-glacial lakes and rivers. Despite the importance of meltwater runoff, Greenland's hydrologic drainage patterns are not well understood. This is partly due to a scarcity of ice sheet meltwater runoff observations and detailed information about supra- and sub-glacial topography, which are responsible for dictating runoff flow patterns. However, such data are available locally in southwest Greenland for the Akuliarusiarsuup Kuua (AK) River watershed. In this study, NASA IceBridge supra-glacial (Airborne Topographic Mapper (ATM)) and sub-glacial (Multichannel Coherent Radar Depth Sounder (MCoRDS)) topography and in situ hydrologic data from 2009-2012 are used to study three nested riverine systems within the AK River watershed ranging from 8 to 101 km2. Examination of relationships between drainage patterns modeled from topographic data and actual ice sheet runoff losses provide insight into drainage basin delineation accuracy, scale-dependency, and surface and sub-glacial topography controls on ice sheet margin hydrology. Finally, an assessment is made to determine the importance of incorporating basal topography within meltwater runoff models versus surface topography alone.

  15. Response of salt structures to ice-sheet loading: implications for ice-marginal and subglacial processes

    NASA Astrophysics Data System (ADS)

    Lang, Jörg; Hampel, Andrea; Brandes, Christian; Winsemann, Jutta

    2014-10-01

    During the past decades the effect of glacioisostatic adjustment has received much attention. However, the response of salt structures to ice-sheet loading and unloading is poorly understood. Our study aims to test conceptual models of the interaction between ice-sheet loading and salt structures by finite-element modelling. The results are discussed with regard to their implications for ice-marginal and subglacial processes. Our models consist of 2D plane-strain cross-sections, which represent simplified geological cross-sections from the Central European Basin System. The model layers represent (i) sedimentary rocks of elastoplastic rheology, (ii) a viscoelastic diapir and layer of salt and (iii) an elastoplastic basement. On top of the model, a temporarily variable pressure simulates the advance and retreat of an ice sheet. The durations of the individual loading phases were defined to resemble the durations of the Pleistocene ice advances in northern central Europe. The geometry and rheology of the model layers and the magnitude, spatial distribution and timing of ice-sheet loading were systematically varied to detect the controlling factors. All simulations indicate that salt structures respond to ice-sheet loading. An ice advance towards the diapir causes salt flow from the source layer below the ice sheet towards the diapir, resulting in an uplift of up to +4 m. The diapir continues to rise as long as the load is applied to the source layer but not to the crest of the diapir. When the diapir is transgressed by the ice sheet the diapir is pushed down (up to -36 m) as long as load is applied to the crest of the diapir. During and after ice unloading large parts of the displacement are compensated by a reversal of the salt flow. Plastic deformation of the overburden is restricted to the area immediately above the salt diapir. The displacements after unloading range between -3.1 and +2.7 m. Larger displacements are observed in models with deep-rooted diapirs

  16. Pleistocene ice streaming and marine-margin breakup revealed by multibeam bathymetry data: The Minch, NW Scotland

    NASA Astrophysics Data System (ADS)

    Bradwell, Tom; Stoker, Martyn

    2013-04-01

    Extensive dynamically driven breakup and rapid ice loss is currently ongoing at tidewater margins of the Greenland and Antarctica Ice Sheets, yet few good analogues from the palaeo-record exist. Using ca. 55,000 km2 of echosounder bathymetry data from the continental shelf around NW Scotland we have mapped submarine glacial landforms relating to an ice sheet that covered much of the continental shelf during the Late Pleistocene and had extensive tidewater margins. Focusing on new multibeam bathymetry from the inner part of the shelf (The Minch), we present seabed geomorphological evidence showing breakup of a large marine portion of a palaeo-ice stream within the British-Irish Ice Sheet. Clearly defined, well preserved glacial lineations, elongate bedforms and seabed drumlins indicate former fast flow of a grounded palaeo-ice stream in a northerly direction in The Minch. In addition, the absence of moraines and grounding-line features deposited during ice sheet retreat and the abundance of large overprinted iceberg scours collectively indicate rapid marine-margin breakup by flotation and thinning. We suggest that this marine-margin breakup event was probably driven by unstable ice sheet retreat into shoreward deepening water and was inextricably linked with the abrupt demise of The Minch palaeo-ice stream. Importantly, this new evidence indicates that potentially large areas of the ice sheet margin were floating at times during British-Irish Ice Sheet retreat on the continental shelf. Ongoing work is seeking to date the timing of ice sheet breakup and ice stream demise in northern Scotland.

  17. Arctic cyclogenesis at the marginal ice zone: A contributory mechanism for the temperature amplification ?

    NASA Astrophysics Data System (ADS)

    Inoue, J.; Hori, M. E.

    2011-12-01

    Rapid sea-ice retreat over the Arctic Ocean has a leading role in Arctic amplification. The sea-ice extent ramatically recovers during every freezing season, so despite the recent summer sea-ice retreat, there must be extraordinary heat exchange between the lower atmosphere and upper ocean. However, the underlying mechanisms for this remain uncertain. Here we show that autumn frontal cyclogenesis is a crucial event in the Arctic air-sea coupled system. Our shipboard Doppler radar and intensive radiosonde observations at the marginal ice zone detected an explosive frontal cyclogenesis, with coupling between upper and lower tropospheric vortices. The thermal contrast between ocean and ice surfaces is likely favorable to cyclogenesis with an identical life-cycle to that at mid-latitudes. This suggests a northward shift of meridional heat transport. The 1.5 K temperature decrease in the upper ocean after the cold front has passed reveals that a large amount of heat is transported into the atmosphere. This is an invaluable example of the fact that sea ice retreat contributes to polar amplification of surface air temperature increase.

  18. Arctic cyclogenesis at the marginal ice zone: A contributory mechanism for the temperature amplification?

    NASA Astrophysics Data System (ADS)

    Inoue, Jun; Hori, Masatake E.

    2011-06-01

    Rapid sea-ice retreat over the Arctic Ocean has a leading role in Arctic amplification. The sea-ice extent dramatically recovers during every freezing season, so despite the recent summer sea-ice retreat, there must be extraordinary heat exchange between the lower atmosphere and upper ocean. However, the underlying mechanisms for this remain uncertain. Here we show that autumn frontal cyclogenesis is a crucial event in the Arctic air-sea coupled system. Our shipboard Doppler radar and intensive radiosonde observations at the marginal ice zone detected an explosive frontal cyclogenesis, with coupling between upper and lower tropospheric vortices. The thermal contrast between ocean and ice surfaces is likely favorable to cyclogenesis with an identical life-cycle to that at mid-latitudes. This suggests a northward shift of meridional heat transport. The 1.5 K temperature decrease in the upper ocean after the cold front has passed reveals that a large amount of heat is transported into the atmosphere. This is an invaluable example of the fact that sea ice retreat contributes to polar amplification of surface air temperature increase.

  19. Is Frost Cracking By Segregation Ice Growth One of the Mechanisms That Erode Bedrock River Margins?

    NASA Astrophysics Data System (ADS)

    Alden, L. L.; Sklar, L. S.

    2014-12-01

    Rivers cut vertically and laterally into bedrock. However, control on the width of bedrock rivers is an unsolved problem. In alpine settings, frost cracking is one of the mechanisms that break down bedrock. Segregation ice drives growth of ice lenses within rock masses. When the temperature of the rock is within the "frost cracking window" of -3 to -8 °C, ice lenses can attract liquid water. Expanding ice lenses can exert sufficient pressure to fracture the rock. We hypothesize that alpine rivers may promote segregation ice growth at the river margin by supplying water, but also may inhibit frost cracking by supplying heat. We find support for this hypothesis in data collected along the Tuolumne and Mokelumne rivers in the Sierra Nevada, California. A 1D heat flow model predicts that frost cracking should occur above 2325 masl in this area. To test for a river effect, we measured fracture density along the Tuolumne River at ~2600 masl, finding that density at the river margin is significantly greater than on adjacent hillslopes in the Cathedral Peak granodiorite. We then deployed data loggers on the Mokelumne River (at 2486 masl) over the winter of 2013/2014 to record water, surface and subsurface rock temperatures at varying depths and distances from the river. Temperatures within the frost cracking window were only recorded at a distance of ~5 m from the river, suggesting an insulating effect from the river and snow cover. Rock temperatures 1 m deep equilibrated at ~ 2 °C, significantly colder than predicted by the 1D model. Ongoing work includes terrestrial LIDAR scans to detect erosion of the river bank at the Mokelumne site, and development of a 2D heat flow model to predict subsurface rock temperatures for varying surface boundary conditions and channel morphology. We expect that further analysis will reveal systematic relationships between the surface boundary conditions and rock temperature at depth, enabling predictive modeling of frost cracking

  20. Decadal changes in carbon fluxes at the East Siberian continental margin: interactions of ice cover, ocean productivity, particle sedimentation and benthic life

    NASA Astrophysics Data System (ADS)

    Boetius, A.; Bienhold, C.; Felden, J.; Fernandez Mendez, M.; Gusky, M.; Rossel, P. E.; Vedenin, A.; Wenzhoefer, F.

    2015-12-01

    The observed and predicted Climate-Carbon-Cryosphere interactions in the Arctic Ocean are likely to alter productivity and carbon fluxes of the Siberian continental margin and adjacent basins. Here, we compare field observations and samples obtained in the nineties, and recently in 2012 during the sea ice minimum, to assess decadal changes in the productivity, export and recycling of organic matter at the outer East Siberian margin. In the 90s, the Laptev Sea margin was still largely ice-covered throughout the year, and the samples and measurements obtained represent an ecological baseline against which current and future ecosystem shifts can be assessed. The POLARSTERN expedition IceArc (ARK-XXVII/3) returned in September 2012 to resample the same transects between 60 and 3400 m water depth as well as stations in the adjacent deep basins. Our results suggest that environmental changes in the past two decades, foremost sea ice thinning and retreat, have led to a substantial increase in phytodetritus sedimentation to the seafloor, especially at the lower margin and adjacent basins. This is reflected in increased benthic microbial activities, leading to higher carbon remineralization rates, especially deeper than 3000 m. Besides a relative increase in typical particle degrading bacterial types in surface sediments, bacterial community composition showed little variation between the two years, suggesting that local microbial communities can cope with changing food input. First assessments of faunal abundances suggest an increase in polychaetes,holothurians and bivalves at depth, which fits the prediction of higher productivity and particle deposition rates upon sea ice retreat. The presentation also discusses the controversial issue whether there is evidence for an Arctic-wide increase in carbon flux, or whether we are looking at a spatial shift of the productive marginal ice zone as the main factor to enhance carbon flux to the deep Siberian margin.

  1. Late glacial and Holocene history of the Greenland Ice Sheet margin, Nunatarssuaq, Northwestern Greenland

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    Defining the late glacial and Holocene fluctuations of the Greenland Ice Sheet (GrIS) margin, particularly during periods that were as warm or warmer than present, provides a longer-term perspective on present ice margin fluctuations and informs how the GrIS may respond to future climate conditions. We focus on mapping and dating past GrIS extents in the Nunatarssuaq region of northwestern Greenland. During the summer of 2014, we conducted geomorphic mapping and collected rock samples for 10Be surface exposure dating as well as subfossil plant samples for 14C dating. We also obtained sediment cores from an ice-proximal lake. Preliminary 10Be ages of boulders deposited during deglaciation of the GrIS subsequent to the Last Glacial Maximum range from ~30-15 ka. The apparently older ages of some samples indicate the presence of 10Be inherited from prior periods of exposure. These ages suggest deglaciation occurred by ~15 ka however further data are needed to test this hypothesis. Subfossil plants exposed at the GrIS margin on shear planes date to ~ 4.6-4.8 cal. ka BP and indicate less extensive ice during middle Holocene time. Additional radiocarbon ages from in situ subfossil plants on a nunatak date to ~3.1 cal. ka BP. Geomorphic mapping of glacial landforms near Nordsø, a large proglacial lake, including grounding lines, moraines, paleo-shorelines, and deltas, indicate the existence of a higher lake level that resulted from a more extensive GrIS margin likely during Holocene time. A fresh drift limit, characterized by unweathered, lichen-free clasts approximately 30-50 m distal to the modern GrIS margin, is estimated to be late Holocene in age. 10Be dating of samples from these geomorphic features is in progress. Radiocarbon ages of subfossil plants exposed by recent retreat of the GrIS margin suggest that the GrIS was at or behind its present location at AD ~1650-1800 and ~1816-1889. Results thus far indicate that the GrIS margin in northwestern Greenland

  2. Cenozoic ice sheet history from East Antarctic Wilkes Land continental margin sediments

    USGS Publications Warehouse

    Escutia, C.; De Santis, L.; Donda, F.; Dunbar, R.B.; Cooper, A. K.; Brancolini, Giuliano; Eittreim, S.L.

    2005-01-01

    The long-term history of glaciation along the East Antarctic Wilkes Land margin, from the time of the first arrival of the ice sheet to the margin, through the significant periods of Cenozoic climate change is inferred using an integrated geophysical and geological approach. We postulate that the first arrival of the ice sheet to the Wilkes Land margin resulted in the development of a large unconformity (WL-U3) between 33.42 and 30 Ma during the early Oligocene cooling climate trend. Above WL-U3, substantial margin progradation takes place with early glacial strata (e.g., outwash deposits) deposited as low-angle prograding foresets by temperate glaciers. The change in geometry of the prograding wedge across unconformity WL-U8 is interpreted to represent the transition, at the end of the middle Miocene "climatic optimum" (14-10 Ma), from a subpolar regime with dynamic ice sheets (i.e., ice sheets come and go) to a regime with persistent but oscillatory ice sheets. The steep foresets above WL-U8 likely consist of ice proximal sediments (i.e., water-lain till and debris flows) deposited when grounded ice-sheets extended into the shelf. On the continental rise, shelf progradation above WL-U3 results in an up-section increase in the energy of the depositional environment (i.e., seismic facies indicative of more proximal turbidite and of bottom contour current deposition from the deposition of the lower WL-S5 sequence to WL-S7). Maximum rates of sediment delivery to the rise occur during the development of sequences WL-S6 and WL-S7, which we infer to be of middle Miocene age. During deposition of the two uppermost sequences, WL-S8 and WL-S9, there is a marked decrease in the sediment supply to the lower continental rise and a shift in the depocenters to more proximal areas of the margin. We believe WL-S8 records sedimentation during the final transition from a dynamic to a persistent but oscillatory ice sheet in this margin (14-10 Ma). Sequence WL-S9 forms under a polar

  3. Meso- and submesoscale structures in marginal ice zone in Arctic ocean using Sentinel-1 data

    NASA Astrophysics Data System (ADS)

    Tarasenko, Anastasiia

    2016-07-01

    A marginal sea ice zone is a region where ocean currents interact with the sea ice. Recently freezed small sea ice particles (frazil) can be used as a passive tracer for the ocean surface dynamics studies. Sentinel-1 SAR images with a high spatial resolution (40 or 25 m) permit to exploit this approach of "frazil as surface current's passive tracer". A preliminary research on meso- and submesoscale structures in marginal sea ice zone was carried out using Sentinel-1 SAR data. A new dataset of mesoscale structures was created for Eastern Greenland, Barents and Kara seas for 2014-2015. The raw data was processed with SNAP (Sentinel application Platform designed by ESA). A classical method of maximum cross-correlation was tested together with a method developed based on (Kudriavtsev et al, 2014) for eddy-like structures detection. References: Kudryavtsev, Vladimir, I. Kozlov, Bertrand Chapron, and J. A. Johannessen. "Quad-polarization SAR features of ocean currents." Journal of Geophysical Research: Oceans 119, no. 9 (2014): 6046-6065.

  4. Short-term sea ice forecasts with the RASM-ESRL coupled model: A testbed for improving simulations of ocean-ice-atmosphere interactions in the marginal ice zone

    NASA Astrophysics Data System (ADS)

    Solomon, A.; Cox, C. J.; Hughes, M.; Intrieri, J. M.; Persson, O. P. G.

    2015-12-01

    The dramatic decrease of Arctic sea-ice has led to a new Arctic sea-ice paradigm and to increased commercial activity in the Arctic Ocean. NOAA's mission to provide accurate and timely sea-ice forecasts, as explicitly outlined in the National Ocean Policy and the U.S. National Strategy for the Arctic Region, needs significant improvement across a range of time scales to improve safety for human activity. Unfortunately, the sea-ice evolution in the new Arctic involves the interaction of numerous physical processes in the atmosphere, ice, and ocean, some of which are not yet understood. These include atmospheric forcing of sea-ice movement through stress and stress deformation; atmospheric forcing of sea-ice melt and formation through energy fluxes; and ocean forcing of the atmosphere through new regions of seasonal heat release. Many of these interactions involve emerging complex processes that first need to be understood and then incorporated into forecast models in order to realize the goal of useful sea-ice forecasting. The underlying hypothesis for this study is that errors in simulations of "fast" atmospheric processes significantly impact the forecast of seasonal sea-ice retreat in summer and its advance in autumn in the marginal ice zone (MIZ). We therefore focus on short-term (0-20 day) ice-floe movement, the freeze-up and melt-back processes in the MIZ, and the role of storms in modulating stress and heat fluxes. This study uses a coupled ocean-atmosphere-seaice forecast model as a testbed to investigate; whether ocean-sea ice-atmosphere coupling improves forecasts on subseasonal time scales, where systematic biases develop due to inadequate parameterizations (focusing on mixed-phase clouds and surface fluxes), how increased atmospheric resolution of synoptic features improves the forecasts, and how initialization of sea ice area and thickness and snow depth impacts the skill of the forecasts. Simulations are validated with measurements at pan-Arctic land

  5. Satellite and aircraft passive microwave observations during the Marginal Ice Zone Experiment in 1984

    NASA Astrophysics Data System (ADS)

    Gloersen, Per; Campbell, William J.

    1988-06-01

    During the Marginal Ice Zone Experiment in the Fram Strait in June-July 1984, a number of aircraft with microwave sensors and the scanning multichannel microwave radiometer (SMMR) on board the Nimbus 7 satellite were used to acquire large-scale and mesoscale ice-ocean observations in conjunction with local surface measurements made by experimenters based on helicopter-equipped ice-strengthened vessels. An analysis of the data acquired during six flights of one such aircraft, the NASA CV-990 airborne laboratory, is discussed in this paper. Included in the instrument complement of the CV-990 were two passive microwave imagers operating at wavelengths of 0.33 and 1.55 cm and the airborne multichannel microwave radiometer (AMMR) operating at wavelengths of 0.81, 1.4, and 1.7 cm for both horizontal and vertical polarizations. Total and multiyear sea ice concentrations calculated from the AMMR data were found to agree with similar calculations using SMMR data. This is the first check of the performance of the SMMR Team ice algorithm for near-melting point conditions. The temperature dependence of the multiyear sea ice concentration determination near the melting point was found to be the same for both airborne and spacecraft instrument data and to be correlated with presence or absence of clouds. Finally, it was found that a spectral gradient ratio using the data from both the 0.33- and 1.55-cm radiometers provides more reliable distinctions between low total ice concentrations and open water storm effects near the ice edge than does either singly.

  6. The Late Devensian (<22,000 BP) Irish Sea Basin: The sedimentary record of a collapsed ice sheet margin

    NASA Astrophysics Data System (ADS)

    Eyles, Nicholas; Marshall McCabe, A.

    The Late Devensian (<20 ka BP) glacial geology of the Irish Sea Basin (4000 km 2) is an event stratigraphy recording the entry of marine waters into a glacio-isostatically-depressed basin, and the rapid retreat of the Irish Sea Glacier as a tidewater ice margin. Marine limits occur up to 140 m O.D. Across much of the central basin, the ice margin was uncoupled from its bed exposing a subglacially-scoured topography to glaciomarine processes. The Irish Sea Glacier was a major drainage conduit of the last British Ice Sheet; calving of the marine ice margin resulted in fast flow (surging) of ice streams recorded by drumlin fields around the northern basin margin and tunnel valleys. Rapid evacuation of the basin may have stranded large areas of dead ice in peripheral zones (e.g. Cheshire/Shropshire Lowlands) and initiated the collapse of the ice sheet. Thick wedges of ice-contact glaciomarine sediments were deposited during ice retreat as morainal bank complexes by successive tidewater ice margins stabilized at pinning points around the Irish Sea coast. Where morainal banks occur on the seaward side of drumlin swarms there is a clear sequential relationship between rapid ice loss from calving ice margins, the development of fast flowing ice streams, drumlinization and the pumping of subglacial sediment to tidewater. Raised delta complexes are locally associated with marine limits along the high relief coastal margins of Wales, east central Ireland, and the Lake District. Associated valley infill complexes record downslope resedimentation of heterogenous sediments into the marine environment during ice retreat. Co-eval offshore deposits are represented by well-stratified glaciomarine complexes that infill a subglacially-scoured topography that shows networks of tunnel valleys. Glaciomarine mud drapes occur well to the south of the maximum limit of grounded ice in the basin (e.g. North Devon, Scilly Islands, Southern Ireland). The age of these distal sediments

  7. Identification of paleo Arctic winter sea ice limits and the marginal ice zone: Optimised biomarker-based reconstructions of late Quaternary Arctic sea ice

    NASA Astrophysics Data System (ADS)

    Belt, Simon T.; Cabedo-Sanz, Patricia; Smik, Lukas; Navarro-Rodriguez, Alba; Berben, Sarah M. P.; Knies, Jochen; Husum, Katrine

    2015-12-01

    Analysis of >100 surface sediments from across the Barents Sea has shown that the relative abundances of the mono-unsaturated sea ice diatom-derived biomarker IP25 and a tri-unsaturated highly branched isoprenoid (HBI) lipid (HBI III) are characteristic of the overlying surface oceanographic conditions, most notably, the location of the seasonal sea ice edge. Thus, while IP25 is generally limited to locations experiencing seasonal sea ice, with higher abundances found for locations with longer periods of ice cover, HBI III is found in sediments from all sampling locations, but is significantly enhanced in sediments within the vicinity of the retreating sea ice edge or marginal ice zone (MIZ). The response of HBI III to this well-defined sea ice scenario also appears to be more selective than that of the more generic phytoplankton biomarker, brassicasterol. The potential for the combined analysis of IP25 and HBI III to provide more detailed assessments of past sea ice conditions than IP25 alone has been investigated by quantifying both biomarkers in three marine downcore records from locations with contrasting modern sea ice settings. For sediment cores from the western Barents Sea (intermittent seasonal sea ice) and the northern Norwegian Sea (ice-free), high IP25 and low HBI III during the Younger Dryas (ca. 12.9-11.9 cal. kyr BP) is consistent with extensive sea cover, with relatively short periods of ice-free conditions resulting from late summer retreat. Towards the end of the YD (ca. 11.9-11.5 cal. kyr BP), a general amelioration of conditions resulted in a near winter maximum ice edge scenario for both locations, although this was somewhat variable, and the eventual transition to predominantly ice-free conditions was later for the western Barents Sea site (ca. 9.9 cal. kyr BP) compared to NW Norway (ca. 11.5 cal. kyr BP). For both locations, coeval elevated HBI III (but absent IP25) potentially provides further evidence for increased Atlantic Water inflow

  8. Got Ice? Teaching Ice-Skating as a Lifelong Activity

    ERIC Educational Resources Information Center

    Tarkinton, Brenda C.; Karp, Grace Goc

    2010-01-01

    With today's focus on the importance of lifelong physical activity, educators are increasingly offering a variety of such activities in their classes, as well as in before- and after-school programs. This article describes the benefits of offering ice skating as a challenging and rewarding lifetime activity, either before or after school or in…

  9. Transverse, supraglacially derived crevasse infillings in a Pleistocene ice-sheet margin zone (eastern Poland): Genesis and sedimentary record

    NASA Astrophysics Data System (ADS)

    Godlewska, Anna; Terpiłowski, Sławomir

    2012-08-01

    The so-called 'crevasse infillings' in the marginal zone of the Saalian ice sheet in eastern Poland are atypical relief forms for lowlands glaciated in the Pleistocene. They are located on a high of the Cretaceous/Palaeogene substratum and form isolated ridges arranged in trains parallel to the former ice-sheet margin, i.e., transverse to the movement of the ice sheet. The sedimentary succession of the crevasse infillings consists mainly of undeformed glaciodeltaic deposits. We propose a model of the crevasse infilling development in three phases against the background of ice mass dynamics: 1) ice-sheet advance over a high of the substratum — compressive ice flow that bumped against the high's slope and enrichment of the ice with debris; 2) an overriding of the substratum high by ice masses — a tensional ice-flow regime resulted in significant crevassing; and 3) ice mass stagnation — low energy, supraglacial deltaic sedimentation in isolated ponds between disintegrated ice blocks under frozen bed conditions. Considering this genesis, we suggest classifying these forms as kames instead of crevasse infillings.

  10. A 35.000-year long record of major ice-marginal fluctuations in SE Greenland

    NASA Astrophysics Data System (ADS)

    Larsen, Nicolaj; Jacobsen, Karina; Kjær, Kurt; Olsen, Jesper; Odgaard, Bent; Bjørk, Anders

    2013-04-01

    In 2011 cores from the Torqulertivit Imiat (TI) threshold lake in SE Greenland were retrieved to constrain the Holocene glaciation history of the Greenland ice sheet. The cores were analysed using XRF core scanning, magnetic susceptibility, loess-on-ignition, and grain-size analysis. A total of 20 terrestrial macrofossils and bulk sediment samples were used to date the 3.5 m long main core from the central part of the lake. The age-depth model of the main core show increasing age with depth down to 35 cal. ka BP except two outliers in the upper part of the core. The results suggest that the bulk ages in the lower part of the core are reliable although comparison between bulk and terrestrial macrofossil from the same interval show an age difference between 500-1.000 years. Our preliminary interpretation of the TI record suggests that the Greenland ice sheet advanced to the LGM position on the shelf from c. 26-20 cal. ka BP where there is a hiatus in the TI record. At c. 20 cal. ka BP the sedimentation resumed in TI and it continued up to c. 10.7 cal. ka BP suggesting that the ice margin had retreated behind the present coastline. Then follows a hiatus at c. 10.7 cal. ka BP suggesting that the ice made a readvance and covered the coastal areas including TI, after which the sedimentation continued up to the present. The final Early Holocene deglaciation of TI corresponds to independent cosmogenic exposure ages from the same locality showing deglaciation between c. 11-10 ka (Roberts et al., 2008). During the Holocene Thermal Maximum (HTM) the ice margin retreated behind its present position and out of the catchment of TI and here it remained until the Neoglacial where it returned to its present position. The new results demonstrate that lake records may survive a full glaciation like the LGM and may reveal important information about the longterm glacial history of the Greenland ice sheet. Roberts, D.H., Long, A.J., Schnabel, C., Freeman, S., Simpson, M.J.R., 2008. The

  11. Subsea ice-bearing permafrost on the U.S. Beaufort Margin: 2. Borehole constraints

    USGS Publications Warehouse

    Ruppel, Carolyn; Herman, Bruce M.; Brothers, Laura L.; Hart, Patrick E.

    2016-01-01

    Borehole logging data from legacy wells directly constrain the contemporary distribution of subsea permafrost in the sedimentary section at discrete locations on the U.S. Beaufort Margin and complement recent regional analyses of exploration seismic data to delineate the permafrost's offshore extent. Most usable borehole data were acquired on a ∼500 km stretch of the margin and within 30 km of the contemporary coastline from north of Lake Teshekpuk to nearly the U.S.-Canada border. Relying primarily on deep resistivity logs that should be largely unaffected by drilling fluids and hole conditions, the analysis reveals the persistence of several hundred vertical meters of ice-bonded permafrost in nearshore wells near Prudhoe Bay and Foggy Island Bay, with less permafrost detected to the east and west. Permafrost is inferred beneath many barrier islands and in some nearshore and lagoonal (back-barrier) wells. The analysis of borehole logs confirms the offshore pattern of ice-bearing subsea permafrost distribution determined based on regional seismic analyses and reveals that ice content generally diminishes with distance from the coastline. Lacking better well distribution, it is not possible to determine the absolute seaward extent of ice-bearing permafrost, nor the distribution of permafrost beneath the present-day continental shelf at the end of the Pleistocene. However, the recovery of gas hydrate from an outer shelf well (Belcher) and previous delineation of a log signature possibly indicating gas hydrate in an inner shelf well (Hammerhead 2) imply that permafrost may once have extended across much of the shelf offshore Camden Bay.

  12. Beaufort-Chukchi Seas summer and fall ice margin data from Seasat - Conditions with similarities to the Labrador Sea

    NASA Technical Reports Server (NTRS)

    Carsey, Frank D.; Pihos, Greg

    1989-01-01

    The margin of the sea-ice pack of the Beaufort and Chukchi Seas is examined using the microwave data from Seasat taken during the summer to early fall, July 4 through October 8, 1978, and the observations are compared to the analogous observations taken in LIMEX'87. The sensors used are synthetic-aperture radar (SAR), the Seasat-A scatterometer system, and the Scanning Multichannel Microwave Radiometer. The examination indicates that the ice edge in summer and early fall is compact; that is, in most cases the pack undergoes an abrupt change in ice concentration from zero over open water to a substantial value (over 70 percent) in the marginal ice zone. This change takes place over the space of a few kilometers. Adjacent to the edge there is a zone of intermediate ice concentration 50-100-km wide. In late summer there is a band of ice at the edge which is largely featureless in the 25-m resolution of the Seasat SAR and is taken to be ice cakes with diameters less than 100 m. Eddylike structures seem to be present in the margin on scales from 5-200 km; bands and tadpole streamers are also observable. All three instruments locate the ice edge with varying degrees of precision.

  13. 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.

  14. On the drivers of phytoplankton blooms in the Antarctic marginal ice zone: A modeling approach

    NASA Astrophysics Data System (ADS)

    Taylor, Marc H.; Losch, Martin; Bracher, Astrid

    2013-01-01

    Abstract The pelagic province of the Southern Ocean generally has low levels of primary production attributable to a short growing season in the higher latitudes, a deep mixed layer, and iron limitation. Exceptions include phytoplankton blooms in the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone (MIZ) during spring and summer sea-<span class="hlt">ice</span> retreat. The prevailing hypothesis as to the drivers of the blooms is that sea-<span class="hlt">ice</span> retreat increases the vertical stability of the water column through the production of melt water and provides shelter from wind mixing in areas of partial sea-<span class="hlt">ice</span> coverage. These conditions are favorable to phytoplankton growth by allowing them to maintain their position in the upper reaches of the water column. This work investigates the drivers of MIZ blooms using a biochemically coupled global circulation model. Results support the hypothesis in that physical conditions related to a shallow, vertically stable water column (e.g., mixed layer depth and available light) were the most significant predictors of bloom dynamics, while nutrient limitation was of lesser importance. We estimate that MIZ blooms account for 15% of yearly net primary production in the Southern Ocean and that the earlier phases of the MIZ bloom, occurring under partial <span class="hlt">ice</span> coverage and invisible to remote sensing, account for about two thirds of this production. MIZ blooms were not found to enhance depth-integrated net primary production when compared to similar ecological provinces outside of the MIZ, although the elevated phytoplankton concentrations in surface waters are hypothesized to provide important feeding habitats for grazing organisms such as krill.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70030660','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70030660"><span id="translatedtitle">Glacial Lake Musselshell: Late Wisconsin slackwater on the Laurentide <span class="hlt">ice</span> <span class="hlt">margin</span> in central Montana, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Davis, N.K.; Locke, W. W.; Pierce, K.L.; Finkel, R.C.</p> <p>2006-01-01</p> <p>Cosmogenic surface exposure ages of glacial boulders deposited in <span class="hlt">ice-marginal</span> Lake Musselshell suggest that the lake existed between 20 and 11.5 ka during the Late Wisconsin glacial stage (MIS 2), rather than during the Late Illinoian stage (MIS 6) as traditionally thought. The altitude of the highest <span class="hlt">ice</span>-rafted boulders and the lowest passes on the modern divide indicate that glacial lake water in the Musselshell River basin reached at least 920-930 m above sea level and generally remained below 940 m. Exposures of rhythmically bedded silt and fine sand indicate that Lake Musselshell is best described as a slackwater system, in which the <span class="hlt">ice</span>-dammed Missouri and Musselshell Rivers rose and fell progressively throughout the existence of the lake rather than establishing a lake surface with a stable elevation. The absence of varves, deltas and shorelines also implies an unstable lake. The changing volume of the lake implies that the Laurentide <span class="hlt">ice</span> sheet was not stable at its southernmost position in central Montana. A continuous sequence of alternating slackwater lake sediment and lacustrine sheetflood deposits indicates that at least three advances of the Laurentide <span class="hlt">ice</span> sheet occurred in central Montana between 20 and 11.5 ka. Between each advance, it appears that Lake Musselshell drained to the north and formed two outlet channels that are now occupied by extremely underfit streams. A third outlet formed when the water in Lake Musselshell fully breached the Larb Hills, resulting in the final drainage of the lake. The channel through the Larb Hills is now occupied by the Missouri River, implying that the present Missouri River channel east of the Musselshell River confluence was not created until the Late Wisconsin, possibly as late as 11.5 ka. ?? 2005 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2013-03-13/pdf/2013-05791.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2013-03-13/pdf/2013-05791.pdf"><span id="translatedtitle">78 FR 15876 - <span class="hlt">Activation</span> of <span class="hlt">Ice</span> Protection</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a></p> <p></p> <p>2013-03-13</p> <p>... final rule published on August 22, 2011 (76 FR 52241). In that rule, the FAA amended its regulations to... Protection,'' (76 FR 52241). In that final rule the FAA added operating rules for flight in <span class="hlt">icing</span> conditions... Federal Aviation Administration 14 CFR Part 121 RIN 2120-AJ43 <span class="hlt">Activation</span> of <span class="hlt">Ice</span> Protection AGENCY:...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4438723','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4438723"><span id="translatedtitle">Shallow methylmercury production in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone of the central Arctic Ocean</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Heimbürger, Lars-Eric; Sonke, Jeroen E.; Cossa, Daniel; Point, David; Lagane, Christelle; Laffont, Laure; Galfond, Benjamin T.; Nicolaus, Marcel; Rabe, Benjamin; van der Loeff, Michiel Rutgers</p> <p>2015-01-01</p> <p>Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79°N). Here we present the first central Arctic Ocean (79–90°N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone (81–85°N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150–200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea <span class="hlt">ice</span>, extension of the seasonal sea <span class="hlt">ice</span> zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production. PMID:25993348</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...510318H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...510318H"><span id="translatedtitle">Shallow methylmercury production in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone of the central Arctic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heimbürger, Lars-Eric; Sonke, Jeroen E.; Cossa, Daniel; Point, David; Lagane, Christelle; Laffont, Laure; Galfond, Benjamin T.; Nicolaus, Marcel; Rabe, Benjamin; van der Loeff, Michiel Rutgers</p> <p>2015-05-01</p> <p>Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79°N). Here we present the first central Arctic Ocean (79-90°N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone (81-85°N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150-200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea <span class="hlt">ice</span>, extension of the seasonal sea <span class="hlt">ice</span> zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25993348','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25993348"><span id="translatedtitle">Shallow methylmercury production in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone of the central Arctic Ocean.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Heimbürger, Lars-Eric; Sonke, Jeroen E; Cossa, Daniel; Point, David; Lagane, Christelle; Laffont, Laure; Galfond, Benjamin T; Nicolaus, Marcel; Rabe, Benjamin; van der Loeff, Michiel Rutgers</p> <p>2015-05-20</p> <p>Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79 °N). Here we present the first central Arctic Ocean (79-90 °N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone (81-85 °N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150-200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea <span class="hlt">ice</span>, extension of the seasonal sea <span class="hlt">ice</span> zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16958762','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16958762"><span id="translatedtitle"><span class="hlt">Ice-active</span> characteristics of soil bacteria selected by <span class="hlt">ice</span>-affinity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wilson, Sandra L; Kelley, Deborah L; Walker, Virginia K</p> <p>2006-10-01</p> <p>As an initial screen for microorganisms that produce <span class="hlt">ice-active</span> macromolecules, <span class="hlt">ice</span>-affinity was used to select microorganisms from soil consortia originating from three temperate regions. Once selected and subsequently purified to single colonies, these microbes were putatively identified by 16S ribosomal RNA sequencing and assayed for various <span class="hlt">ice-active</span> properties. <span class="hlt">Ice</span>-affinity selection appeared to select for bacteria with <span class="hlt">ice</span>-associating <span class="hlt">activities</span>: inhibition of <span class="hlt">ice</span> recrystallization; <span class="hlt">ice</span> nucleation; <span class="hlt">ice</span> shaping. Although none of these <span class="hlt">activities</span> were observed in Paenibacillus amyloliticus C8, others such as Chryseobacterium sp. GL8, demonstrated both <span class="hlt">ice</span> recrystallization inhibition and <span class="hlt">ice</span>-shaping <span class="hlt">activities</span>. Pseudomonas borealis DL7 was classified as a type I <span class="hlt">ice</span> nucleator, Flavobacterium sp. GL7, was identified as a type III <span class="hlt">ice</span> nucleator and Acinetobacter radioresistens DL5 demonstrated <span class="hlt">ice</span> recrystallization inhibition. In all, 19 different culturable bacteria were selected from the thousands of microbes in late-summer collected soil samples. Many of the selected microbes have been previously reported in glacial <span class="hlt">ice</span> cores or polar sea <span class="hlt">ice</span>, and of five isolates that were further characterized, four showed <span class="hlt">ice</span>-associating <span class="hlt">activities</span>. These results indicate the significant potential of <span class="hlt">ice</span>-affinity selection even with temperate climate soils, suggesting that sampling in more extreme and remote areas is not required for the isolation of <span class="hlt">ice-active</span> bacteria. PMID:16958762</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DSRII.131...28T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DSRII.131...28T"><span id="translatedtitle">Formation processes of sea <span class="hlt">ice</span> floe size distribution in the interior pack and its relationship to the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone off East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Toyota, Takenobu; Kohout, Alison; Fraser, Alexander D.</p> <p>2016-09-01</p> <p>To understand the behavior of the Seasonal <span class="hlt">Ice</span> Zone (SIZ), which is composed of sea-<span class="hlt">ice</span> floes of various sizes, knowledge of the floe size distribution (FSD) is important. In particular, FSD in the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone (MIZ), controlled by wave-<span class="hlt">ice</span> interaction, plays an important role in determining the retreating rates of sea-<span class="hlt">ice</span> extent on a global scale because the cumulative perimeter of floes enhances melting. To improve the understanding of wave-<span class="hlt">ice</span> interaction and subsequent effects on FSD in the MIZ, FSD measurements were conducted off East Antarctica during the second Sea <span class="hlt">Ice</span> Physics and Ecosystems eXperiment (SIPEX-2) in late winter 2012. Since logistical reasons limited helicopter operations to two interior <span class="hlt">ice</span> regions, FSD in the interior <span class="hlt">ice</span> region was determined using a combination of heli-photos and MODIS satellite visible images. The possible effect of wave-<span class="hlt">ice</span> interaction in the MIZ was examined by comparison with past results obtained in the same MIZ, with our analysis showing: (1) FSD in the interior <span class="hlt">ice</span> region is basically scale invariant for both small- (<100 m) and large- (>1 km) scale regimes; (2) although fractal dimensions are quite different between these two regimes, they are both rather close to that in the MIZ; and (3) for floes <100 m in diameter, a regime shift which appeared at 20-40 m in the MIZ is absent. These results indicate that one role of wave-<span class="hlt">ice</span> interaction is to modulate the FSD that already exists in the interior <span class="hlt">ice</span> region, rather than directly determine it. The possibilities of floe-floe collisions and storm-induced lead formation are considered as possible formation processes of FSD in the interior pack.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5432642','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5432642"><span id="translatedtitle">Recent changes at the northwest <span class="hlt">margin</span> of the Barnes <span class="hlt">Ice</span> Cap, Baffin Island, N. W. T. , Canada</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jacobs, J.D. ); Heron, R. ); Luther, J.E. )</p> <p>1993-11-01</p> <p>A climate change monitoring site has been established at the northwest <span class="hlt">margin</span> of the Barnes <span class="hlt">Ice</span> Cap, in the vicinity of the Lewis Glacier. Three years of climatic data (1989 to 1992) and field observations, supplemented by satellite imagery, provide the basis for updating previous studies of local change at the <span class="hlt">ice</span> cap <span class="hlt">margin</span>, including climatology and substrate colonization by lichens. Climatic data from the <span class="hlt">ice</span> cap summit permit extrapolation of seasonal temperatures from the <span class="hlt">ice</span> <span class="hlt">marginal</span> station as a basis for equilibrium line altitude estimates. Results are discussed against the background of studies from the 1960s. Retreat of the Lewis Glacier continues at about 25 m yr[sup [minus]1], whereas other areas of the northwest <span class="hlt">margin</span> are retreating by 10 to 30 m yr[sup [minus]1]. Lower regional summer temperatures over the past three decades have not significantly slowed the recession that has been underway in this sector of the <span class="hlt">ice</span> cap for the past three centuries. 41 refs., 7 figs., 2 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002SedG..149..111D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002SedG..149..111D"><span id="translatedtitle">Sedimentology of a glaciofluvial landsystem, Lough Ree area, Central Ireland: implications for <span class="hlt">ice</span> <span class="hlt">margin</span> characteristics during Devensian deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delaney, Catherine</p> <p>2002-05-01</p> <p>Eskers in a glaciofluvial landsystem in the Lough Ree area, Central Ireland, exhibit two orientations. The most southerly esker in the area, the Athlone Esker, forms part of a dendritic esker system with paleocurrent directions indicating eastward drainage, while the Rooskagh Esker and associated eskers and kames immediately to the north were formed during southward drainage. Sediments indicate that sharp-crested, steep-sided sections of both ridges were formed within subglacial tunnels, while fan-shaped and flat-topped areas were formed as subaqueous outwash fans and deltas in standing water immediately in front of an <span class="hlt">ice-margin</span>. The deposition of <span class="hlt">ice-marginal</span> deposits indicating southward paleoflows against the side of the eastward flowing Athlone Esker indicates a 90° shift in the direction of <span class="hlt">ice</span> surface slope, and a similar shift in the likely orientation of the <span class="hlt">ice</span> <span class="hlt">margin</span>. The absence of any evidence of intermediate <span class="hlt">ice</span>- or water-flow directions indicates that the shift reflects a recession of <span class="hlt">ice</span>, followed by a readvance from the north.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C23B0624M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C23B0624M"><span id="translatedtitle">Crevasse Detection and Avoidance for Safe Traversing on the Dynamic and Annually Changing <span class="hlt">Margin</span> of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mercer, J. L.; Lever, J. H.; Newman, S. D.; Deeb, E. J.; Tracy, B.; Weale, J. C.; Delaney, A. J.; Davies, R.; Emery, K. S.</p> <p>2010-12-01</p> <p>The Greenland Inland Traverse (GrIT) is an ~740 mile overland resupply effort to transport fuel and cargo from a deep-water port (Thule) to inland research stations (NEEM and Summit). The current route starts at the <span class="hlt">margin</span> of the Greenland <span class="hlt">Ice</span> Sheet where the original Thule Take-Off (Camp TUTO) served as a staging area for the traverse to Camp Century during the 1960’s. Crew safety is of utmost importance, and while a short and efficient route is desirable, this area has historically been known to be crevassed and the first ~70 miles have proven to be increasingly dynamic since GrIT’s initial route assessment in 2007. Through a combination of high-resolution satellite imagery analysis, ground penetrating radar (GPR) analysis, route planning and guidance, precise vehicle maneuvering, and mountaineering safety measures, the GrIT’s Strategic Crevasse Avoidance Team (SCAT) has successfully navigated around and documented newly formed crevasses each operational season. Here, we present our methodology for successful navigation, and show the imagery analysis and field assessment by which we’ve discovered increasing numbers and sizes of crevasses and crevasse fields in the <span class="hlt">ice</span> <span class="hlt">margin</span>. Half-meter resolution WorldView 1 satellite imagery is taken each August/September to expose crevasses after summer melting has occurred and bridges are sagging or have failed. While it is not possible to determine crevasse widths or bridge depths with this imagery, it does allow identification of most crevasse locations, their lengths and overall crevasse-field size. This provides a roadmap for SCAT to navigate in-and-around crevasse fields. Field measurements show crevasses ranging in size from several centimeters to large chasms tens of meters across. Bridge depths measured in March 2010 ranged from 1.5 meters up to 9 meters. While the data confirm this area is dynamic and rapidly changing, it is difficult to determine whether increased glacial speeds (i.e. surge), a degree of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC31A1163Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC31A1163Z"><span id="translatedtitle">Changes in Arctic Sea <span class="hlt">Ice</span> Floe Size Distribution in the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone in a Thickness and Floe Size Distribution Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, J.; Stern, H. L., III; Hwang, P. B.; Schweiger, A. J. B.; Stark, M.; Steele, M.</p> <p>2015-12-01</p> <p>To better describe the state of sea <span class="hlt">ice</span> in the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone (MIZ) with floes of varying thicknesses and sizes, both an <span class="hlt">ice</span> thickness distribution (ITD) and a floe size distribution (FSD) are needed. We have developed a FSD theory [Zhang et al., 2015] that is coupled to the ITD theory of Thorndike et al. [1975] in order to explicitly simulate the evolution of FSD and ITD jointly. The FSD theory includes a FSD function and a FSD conservation equation in parallel with the ITD equation. The FSD equation takes into account changes in FSD due to <span class="hlt">ice</span> advection, thermodynamic growth, and lateral melting. It also includes changes in FSD because of mechanical redistribution of floe size due to <span class="hlt">ice</span> opening, ridging and, particularly, <span class="hlt">ice</span> fragmentation induced by stochastic ocean surface waves. The floe size redistribution due to <span class="hlt">ice</span> fragmentation is based on the assumption that wave-induced breakup is a random process such that when an <span class="hlt">ice</span> floe is broken, floes of any smaller sizes have an equal opportunity to form, without being either favored or excluded. It is also based on the assumption that floes of larger sizes are easier to break because they are subject to larger flexure-induced stresses and strains than smaller floes that are easier to ride with waves with little bending; larger floes also have higher areal coverages and therefore higher probabilities to break. These assumptions with corresponding formulations ensure that the simulated FSD follows a power law as observed by satellites and airborne surveys. The FSD theory has been tested in the Pan-arctic <span class="hlt">Ice</span>/Ocean Modeling and Assimilation System (PIOMAS). The existing PIOMAS has 12 categories each for <span class="hlt">ice</span> thickness, <span class="hlt">ice</span> enthalpy, and snow depth. With the implementation of the FSD theory, PIOMAS is able to represent 12 categories of floe sizes ranging from 0.1 m to ~3000 m. It is found that the simulated 12-category FSD agrees reasonably well with FSD derived from SAR and MODIS images. In this study, we will</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.1763V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.1763V"><span id="translatedtitle">The Little <span class="hlt">Ice</span> Age and Solar <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Velasco Herrera, Victor Manuel; Leal Silva, C. M. Carmen; Velasco Herrera, Graciela</p> <p></p> <p>We analyze the <span class="hlt">ice</span> winter severity index on the Baltic region since 1501-1995. We found that the variability of this index is modulated among other factors by the secular solar <span class="hlt">activity</span>. The little <span class="hlt">ice</span> ages that have appeared in the North Hemisphere occurred during periods of low solar <span class="hlt">activity</span>. Seemingly our star is experiencing a new quiet stage compared with Maunder or Dalton minimum, this is important because it is estimated that even small changes in weather can represent a great impact in <span class="hlt">ice</span> index. These results are relevant since <span class="hlt">ice</span> is a very important element in the climate system of the Baltic region and it can affect directly or indirectly many of the oceanographic, climatic, eco-logical, economical and cultural patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C51B0690L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C51B0690L"><span id="translatedtitle">New constraints on the deglaciation chronology of the southeastern <span class="hlt">margin</span> of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levy, L.; Larsen, N. K.; Kjaer, K. H.; Bjork, A. A.; Kjeldsen, K. K.; Funder, S.; Kelly, M. A.; Howley, J. A.; Zimmerman, S. R. H.</p> <p>2015-12-01</p> <p>The Greenland <span class="hlt">Ice</span> Sheet (GrIS) is responding rapidly to climate change. Marine terminating outlet glaciers that drain the GrIS have responded especially sensitively to present-day climate change by accelerating, thinning and retreating. In southeastern Greenland several outlet glaciers are undergoing rapid changes in mass balance and <span class="hlt">ice</span> dynamics. To improve our understanding of the future, long-term response of these marine-terminating outlet glaciers to climate change, we focus on the response of three outlet glaciers to climate change since the Last Glacial Maximum. The timing and rates of late-glacial and early Holocene deglaciation of the southeastern sector of the GrIS are relatively unconstrained due to the inaccessibility of the region. Using a helicopter and a sailboat, we collected samples for 10Be surface exposure dating from three fjords in southeastern Greenland: Skjoldungen (63.4N), Uvtorsiutit (62.7N), and Lindenow (60.6N). These fjords drain marine terminating glaciers of the GrIS. Here we present 18 new 10Be ages from ~50 km long transects along these fjords that mark the timing of deglaciation from the outer coast inland to the present-day GrIS <span class="hlt">margin</span>. Together with previously constrained deglaciation chronologies from Bernstorffs, Sermilik, and Kangerdlussuaq fjords in southeastern Greenland, these new chronologies offer insight into the late-glacial and early Holocene dynamics of the southeastern GrIS outlet glaciers. We compare the timing and rate of deglaciation in southeastern Greenland to climate records from the region to examine the mechanisms that drove deglaciation during late-glacial and early Holocene time. These new 10Be ages provide a longer-term perspective of marine terminating outlet glacier fluctuations in southeastern Greenland and can be used to model the <span class="hlt">ice</span> sheet's response to late-glacial and early Holocene climate changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1560F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1560F"><span id="translatedtitle">Molecular <span class="hlt">Ice</span> Nucleation <span class="hlt">Activity</span> of Birch Pollen</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Felgitsch, Laura; Bichler, Magdalena; Häusler, Thomas; Weiss, Victor U.; Marchetti-Deschmann, Martina; Allmaier, Günter; Grothe, Hinrich</p> <p>2015-04-01</p> <p>Heterogeneous <span class="hlt">ice</span> nucleation plays a major part in ecosystem and climate. Due to the triggering of <span class="hlt">ice</span> cloud formation it influences the radiation balance of the earth, but also on the ground it can be found to be important in many processes of nature. So far the process of heterogeneous <span class="hlt">ice</span> nucleation is not fully understood and many questions remain to be answered. Biological <span class="hlt">ice</span> nucleation is hereby from great interest, because it shows the highest freezing temperatures. Several bacteria and fungi act as <span class="hlt">ice</span> nuclei. A famous example is Pseudomonas syringae, a bacterium in commercial use (Snomax®), which increases the freezing from homogeneous freezing temperatures of approx. -40° C (for small volumes as in cloud droplets) to temperatures up to -2° C. In 2001 it was found that birch pollen can trigger <span class="hlt">ice</span> nucleation (Diehl et al. 2001; Diehl et al. 2002). For a long time it was believed that this is due to macroscopic features of the pollen surface. Recent findings of Bernhard Pummer (2012) show a different picture. The <span class="hlt">ice</span> nuclei are not attached on the pollen surface directly, but on surface material which can be easily washed off. This shows that not only the surface morphology, but also specific molecules or molecular structures are responsible for the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of birch pollen. With various analytic methods we work on elucidating the structure of these molecules as well as the mechanism with which they trigger <span class="hlt">ice</span> nucleation. To solve this we use various instrumental analytic techniques like Nuclear Magnetic Resonance spectroscopy (NMR), Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS), and Gas-phase Electrophoretic Mobility Molecular Analysis (GEMMA). Also standard techniques like various chromatographic separation techniques and solvent extraction are in use. We state here that this feature might be due to the aggregation of small molecules, with agglomerates showing a specific surface structure. Our results</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6852396','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6852396"><span id="translatedtitle">Seismic stratigraphy of the Antarctic Peninsula pacific <span class="hlt">margin</span>: A record of Pliocene-Pleistocene <span class="hlt">ice</span> volume and paleoclimate</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Larter, R.D.; Barker, P.F. )</p> <p>1989-08-01</p> <p>Multichannel seismic profiles across the Pacific <span class="hlt">margin</span> of the Antarctic Peninsula show a series of oblique progradational sequences. These sequences exhibit a variety of unusual characteristics that suggest they were produced by the action of <span class="hlt">ice</span> sheets grounded out to the shelf edge at times of glacial maximum. Reflection events from deeper stratigraphic levels, followed down the continental slope and onto the rise, overlie ocean crust of known age, showing that at least eight such glacial sequences have been deposited within the past 6 m.y. Similar groundings have probably occurred on most Antarctic <span class="hlt">margins</span>, but the depositional record is particularly well preserved at this <span class="hlt">margin</span> because of Pliocene-Pleistocene thermal subsidence. Neogene global sea-level fluctuations have been attributed to changes in volume of continental <span class="hlt">ice</span> sheets. The depositional sequences on the Pacific <span class="hlt">margin</span> of the Antarctic Peninsula are thought to record West Antarctic <span class="hlt">ice</span>-sheet fluctuations directly. Further investigation of these sequences would assess the relation between fluctuations in <span class="hlt">ice</span> volume and the low-latitude record of global sea-level change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070016601&hterms=Ecological+zones&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3D%2528Ecological%2Bzones%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070016601&hterms=Ecological+zones&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3D%2528Ecological%2Bzones%2529"><span id="translatedtitle">Variations in the Sea <span class="hlt">Ice</span> Edge and the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone on Different Spatial Scales as Observed from Different Satellite Sensor</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Markus, Thorsten; Henrichs, John</p> <p>2006-01-01</p> <p>The <span class="hlt">Marginal</span> sea <span class="hlt">Ice</span> Zone (MIZ) and the sea <span class="hlt">ice</span> edge are the most dynamic areas of the sea <span class="hlt">ice</span> cover. Knowledge of the sea <span class="hlt">ice</span> edge location is vital for routing shipping in the polar regions. The <span class="hlt">ice</span> edge is the location of recurrent plankton blooms, and is the habitat for a number of animals, including several which are under severe ecological threat. Polar lows are known to preferentially form along the sea <span class="hlt">ice</span> edge because of induced atmospheric baroclinicity, and the <span class="hlt">ice</span> edge is also the location of both vertical and horizontal ocean currents driven by thermal and salinity gradients. Finally, sea <span class="hlt">ice</span> is both a driver and indicator of climate change and monitoring the position of the <span class="hlt">ice</span> edge accurately over long time periods enables assessment of the impact of global and regional warming near the poles. Several sensors are currently in orbit that can monitor the sea <span class="hlt">ice</span> edge. These sensors, though, have different spatial resolutions, different limitations, and different repeat frequencies. Satellite passive microwave sensors can monitor the <span class="hlt">ice</span> edge on a daily or even twice-daily basis, albeit with low spatial resolution - 25 km for the Special Sensor Microwave Imager (SSM/I) or 12.5 km for the Advanced Microwave Scanning Radiometer (AMSR-E). Although special methods exist that allow the detection of the sea <span class="hlt">ice</span> edge at a quarter of that nominal resolution (PSSM). Visible and infrared data from the Advanced Very High Resolution Radiometer (AVHRR) and from the Moderate Resolution Imaging Spectroradiometer (MODIS) provide daily coverage at 1 km and 250 m, respectively, but the surface observations me limited to cloud-free periods. The Landsat 7 Enhanced Thematic Mapper (ETM+) has a resolution of 15 to 30 m but is limited to cloud-free periods as well, and does not provide daily coverage. Imagery from Synthetic Aperture Radar (SAR) instruments has resolutions of tens of meters to 100 m, and can be used to distinguish open water and sea <span class="hlt">ice</span> on the basis of surface</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900047002&hterms=Discrimination&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DDiscrimination','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900047002&hterms=Discrimination&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DDiscrimination"><span id="translatedtitle">Airborne discrimination between <span class="hlt">ice</span> and water - Application to the laser measurement of chlorophyll-in-water in a <span class="hlt">marginal</span> <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoge, Frank E.; Wright, C. Wayne; Swift, Robert N.; Yungel, James K.</p> <p>1989-01-01</p> <p>The concurrent <span class="hlt">active</span>-passive measurement capabilities of the NASA Airborne Oceanographic Lidar have been used to (1) discriminate between <span class="hlt">ice</span> and water in a large <span class="hlt">ice</span> field within the Greenland Sea and (2) achieve the detection and measurement of chlorophyll-in-water by laser-induced and water-Raman-normalized pigment fluorescence. Passive upwelled radiances from sea <span class="hlt">ice</span> are significantly stronger than those from the neighboring water, even when the optical receiver field-of-view is only partially filled with <span class="hlt">ice</span>. Thus, weaker passive upwelled radiances, together with concurrently acquired laser-induced spectra, can rather confidently be assigned to the intervening water column. The laser-induced spectrum can then be processed using previously established methods to measure the chlorophyll-in-water concentration. Significant phytoplankton patchiness and elevated chlorophyll concentrations were found within the waters of the melting <span class="hlt">ice</span> compared to <span class="hlt">ice</span>-free regions just outside the <span class="hlt">ice</span> field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C11A0335P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C11A0335P"><span id="translatedtitle">Distribution of Phytoplankton and Particulate Organic Carbon in the Beaufort Sea during the 2014 <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone Experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perry, M. J.; Lee, C.; Yang, E. J.; Cetinic, I.; Kang, S. H.</p> <p>2014-12-01</p> <p>Spatial and temporal distributions of phytoplankton and particulate organic carbon in the newly emerging <span class="hlt">marginal</span> <span class="hlt">ice</span> zone in the Beaufort Sea are assessed from autonomous Seaglider surveys in summer 2014 as part of the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone (MIZ) Experiment, an international project sponsored by ONR. In late July 2014 four Seagliders were deployed in the Beaufort Sea to follow the retreat of the MIZ. Sampling in open water, through the MIZ and under the <span class="hlt">ice</span> is expected through mid-September, with gliders navigating under <span class="hlt">ice</span> from moored acoustic sound sources embedded in the MIZ autonomous observing array. The sensor suite carried by Seagliders include temperature, temperature microstructure, salinity, oxygen, chlorophyll fluorescence, optical backscatter, and multi-spectral downwelling irradiance. A rigorous sensor inter-calibration program with simultaneous ship CTD and glider profiles is an essential component of glider deployment and recovery protocol, as well as during opportunistic glider encounters with the IBRV Araon during August. Ship-based water sampling will allow construction of regional libraries of optical proxies for chlorophyll, pigment spectral absorption coefficient, and particulate organic carbon. Since irradiance under the <span class="hlt">ice</span> is dependent on <span class="hlt">ice</span> thickness and presence of melt ponds and leads, phytoplankton distribution is expected to vary spatially. Both the vertical and horizontal distributions of pigment spectral absorption coefficients are expected to play a role in the feedback between phytoplankton and <span class="hlt">ice</span> melt. Glider data will allow us to apply a light and chlorophyll primary productivity model to estimate and compare phytoplankton productivity under various <span class="hlt">ice</span>-cover and <span class="hlt">ice</span>-free conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23625082','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23625082"><span id="translatedtitle">The <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of extremophilic algae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kviderova, Jana; Hajek, Josef; Worland, Roger M</p> <p>2013-01-01</p> <p>Differences in the level of cold acclimation and cryoprotection estimated as <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> in snow algae (Chlamydomonas cf. nivalis and Chloromonas nivalis), lichen symbiotic algae (Trebouxia asymmetrica, Trebouxia erici and Trebouxia glomerata), and a mesophilic strain (Chlamydomonas reinhardti) were evaluated. <span class="hlt">Ice</span> nucleation <span class="hlt">activity</span> was measured using the freezing droplet method. Measurements were performed using suspensions of cells of A750 (absorbance at 750 nm) ~ 1, 0.1, 0.01 and 0.001 dilutions for each strain. The algae had lower <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>, with the exception of Chloromonas nivalis contaminated by bacteria. The supercooling points of the snow algae were higher than those of lichen photobionts. The supercooling points of both, mesophilic and snow Chlamydomonas strains were similar. The lower freezing temperatures of the lichen algae may reflect either the more extreme and more variable environmental conditions of the original localities or the different cellular structure of the strains examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.H23E1429C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.H23E1429C"><span id="translatedtitle">Continuous monitoring of deep groundwater at the <span class="hlt">ice</span> <span class="hlt">margin</span>, Kangerlussuaq, West Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Claesson Liljedahl, L.; Lehtinen, A. M.; Ruskeeniemi, T.; Engström, J.; Hansson, K.; Sundberg, J.; Henkemans, E.; Frape, S.; Johansson, S.; Acuna, J.</p> <p>2012-12-01</p> <p>The deep geologic repository (DGR) concept for the long-term management of used nuclear fuel involves the containment and isolation of used nuclear fuel at depths of approximately 500-1000 m below ground surface within a suitable geological formation for hundreds of thousands of years. A key objective of the used fuel DGR research programs of the Swedish, Finnish and Canadian nuclear waste management organizations (SKB, POSIVA and NWMO, respectively) is to further understanding of geosphere stability and long-term evolution. Future glaciation represents an intense external perturbation of a DGR situated in northern latitudes. To advance the understanding of processes associated with glaciation and their impact on the long-term performance of a DGR, the Greenland Analogue Project (GAP) was initiated by SKB, POSIVA and NWMO. The GAP was initiated in 2008 as a four-year field and modelling study utilizing the Greenland <span class="hlt">ice</span> sheet and sub-surface conditions in West Greenland as an analogue for the conditions expected to prevail in Fennoscandia and Canada during future glacial cycles. One of the main aims of the GAP is to improve the understanding of how groundwater flow and water chemistry is influenced by an existing <span class="hlt">ice</span> sheet and continuous permafrost. One way to study this is by monitoring deep drillholes. A 645 m deep drillhole (DH-GAP04) was drilled and instrumented in July 2011 at the <span class="hlt">ice</span>-sheet <span class="hlt">margin</span> in Kangerlussuaq, West Greenland to investigate the hydrogeochemical and hydrogeological conditions of a subglacial environment. Of particular interest is the recharge of glacial meltwater, and understanding to what depth it intrudes into the bedrock and whether it affects the chemistry and physico-chemical properties of the deep groundwater. DH-GAP04 is instrumented with a two-packer multi-sensor system, installed at a depth of 560 m, dividing the hole into three sections. The upper section extends from the base of permafrost (about 350 m) down to the upper packer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028746','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028746"><span id="translatedtitle">Hydrography and circulation of <span class="hlt">ice-marginal</span> lakes at Bering Glacier, Alaska, U.S.A.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Josberger, E.G.; Shuchman, R.A.; Meadows, G.A.; Savage, S.; Payne, J.</p> <p>2006-01-01</p> <p>An extensive suite of physical oceanographic, remotely sensed, and water quality measurements, collected from 2001 through 2004 in two <span class="hlt">ice-marginal</span> lakes at Bering Glacier, Alaska-Berg Lake and Vitus Lake-show that each has a unique circulation controlled by their specific physical forcing within the glacial system. Conductivity profiles from Berg Lake, perched 135 m a.s.l., show no salt in the lake, but the temperature profiles indicate an apparently unstable situation, the 4??C density maximum is located at 10 m depth, not at the bottom of the lake (90 m depth). Subglacial discharge from the Steller Glacier into the bottom of the lake must inject a suspended sediment load sufficient to <span class="hlt">marginally</span> stabilize the water column throughout the lake. In Vitus Lake, terminus positions derived from satellite imagery show that the glacier terminus rapidly retreated from 1995 to the present resulting in a substantial expansion of the volume of Vitus Lake. Conductivity and temperature profiles from the tidally influenced Vitus Lake show a complex four-layer system with diluted (???50%) seawater in the bottom of the lake. This lake has a complex vertical structure that is the result of convection generated by <span class="hlt">ice</span> melting in salt water, stratification within the lake, and freshwater entering the lake from beneath the glacier and surface runoff. Four consecutive years, from 2001 to 2004, of these observations in Vitus Lake show little change in the deep temperature and salinity conditions, indicating limited deep water renewal. The combination of the lake level measurements with discharge measurements, through a tidal cycle, by an acoustic Doppler Current Profiler (ADCP) deployed in the Seal River, which drains the entire Bering system, showed a strong tidal influence but no seawater entry into Vitus Lake. The ADCP measurements combined with lake level measurements established a relationship between lake level and discharge, which when integrated over a tidal cycle, gives a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006HyPr...20.1909H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006HyPr...20.1909H"><span id="translatedtitle">Pixel-scale evaluation of SSM/I sea-<span class="hlt">ice</span> algorithms in the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone during early fall freeze-up</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hwang, Byong Jun; Barber, David G.</p> <p>2006-06-01</p> <p>Observed reduction in recent sea <span class="hlt">ice</span> areal extent and thickness has focused attention on the fact that the Arctic marine system appears to be responding to global-scale climate variability and change. Passive microwave remote-sensing data are the primary source underpinning these reports, yet problems remain in geophysical inversion of information on <span class="hlt">ice</span> type and concentration. Uncertainty in sea-<span class="hlt">ice</span> concentration (SIC) retrievals is highest in the summer and fall, when water occurs in liquid phase within the snow-sea-<span class="hlt">ice</span> system. Of particular scientific interest is the timing and rate of new <span class="hlt">ice</span> formation due to the control that this form of sea <span class="hlt">ice</span> has on mass, energy and gas fluxes across the ocean-sea-<span class="hlt">ice</span>-atmosphere interface. In this paper we examine the critical fall freeze-up period using in situ data from a ship-based and aerial survey programme known as the Canadian Arctic Shelf Exchange study combined with microwave and optical Earth observations data.Results show that: (1) the overall physical conditions observed from aerial survey photography were well matched with coincident moderate-resolution imaging spectroradiometer data and Radarsat ScanSAR imagery; (2) the shortwave albedo was linearly related to old <span class="hlt">ice</span> concentration derived from survey photography; (3) the three SSM/I SIC algorithms (NASA Team (NT), NASA Team 2 (NT2), and Bootstrap (BT)) showed considerable discrepancies in pixel-scale comparison with the Radarsat ScanSAR SICs well calibrated by the aerial survey data. The major causes of the discrepancies are attributed to (1) the inherent inability to detect the new thin <span class="hlt">ice</span> in the NT and BT algorithms, (2) mismatches of the thin-<span class="hlt">ice</span> tie point of the NT2 algorithm, and (3) sub-pixel ambiguity between the thin <span class="hlt">ice</span> and the mixture of open water and sea <span class="hlt">ice</span>. These results suggest the need for finer resolution of passive microwave sensors, such as AMSR-E, to improve the precision of the SSM/I SIC algorithms in the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone during early</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22113659','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22113659"><span id="translatedtitle">Determination of the Nonlethal <span class="hlt">Margin</span> Inside the Visible '<span class="hlt">Ice</span>-Ball' During Percutaneous Cryoablation of Renal Tissue</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Georgiades, Christos; Rodriguez, Ronald; Azene, Ezana Weiss, Clifford; Chaux, Alcides Gonzalez-Roibon, Nilda Netto, George</p> <p>2013-06-15</p> <p>Objective. The study was designed to determine the distance between the visible '<span class="hlt">ice</span>-ball' and the lethal temperature isotherm for normal renal tissue during cryoablation. Methods. The Animal Care Committee approved the study. Nine adult swine were used: three to determine the optimum tissue stain and six to test the hypotheses. They were anesthetized and the left renal artery was catheterized under fluoroscopy. Under MR guidance, the kidney was ablated and (at end of a complete ablation) the nonfrozen renal tissue (surrounding the '<span class="hlt">ice</span>-ball') was stained via renal artery catheter. Kidneys were explanted and sent for slide preparation and examination. From each slide, we measured the maximum, minimum, and an in-between distance from the stained to the lethal tissue boundaries (<span class="hlt">margin</span>). We examined each slide for evidence of 'heat pump' effect. Results. A total of 126 measurements of the <span class="hlt">margin</span> (visible '<span class="hlt">ice</span>-ball'-lethal <span class="hlt">margin</span>) were made. These measurements were obtained from 29 slides prepared from the 6 test animals. Mean width was 0.75 {+-} 0.44 mm (maximum 1.15 {+-} 0.51 mm). It was found to increase adjacent to large blood vessels. No 'heat pump' effect was noted within the lethal zone. Data are limited to normal swine renal tissue. Conclusions. Considering the effects of the 'heat pump' phenomenon for normal renal tissue, the <span class="hlt">margin</span> was measured to be 1.15 {+-} 0.51 mm. To approximate the efficacy of the 'gold standard' (partial nephrectomy, {approx}98 %), a minimum <span class="hlt">margin</span> of 3 mm is recommended (3 Multiplication-Sign SD). Given these assumptions and extrapolating for renal cancer, which reportedly is more cryoresistant with a lethal temperature of -40 Degree-Sign C, the recommended <span class="hlt">margin</span> is 6 mm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015GeoRL..42.1863C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015GeoRL..42.1863C&link_type=ABSTRACT"><span id="translatedtitle">In situ measurements of an energetic wave event in the Arctic <span class="hlt">marginal</span> <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Collins, Clarence O.; Rogers, W. Erick; Marchenko, Aleksey; Babanin, Alexander V.</p> <p>2015-03-01</p> <p>R/V Lance serendipitously encountered an energetic wave event around 77°N, 26°E on 2 May 2010. Onboard GPS records, interpreted as the surface wave signal, show the largest waves recorded in the Arctic region with <span class="hlt">ice</span> cover. Comparing the measurements with a spectral wave model indicated three phases of interaction: (1) wave blocking by <span class="hlt">ice</span>, (2) strong attenuation of wave energy and fracturing of <span class="hlt">ice</span> by wave forcing, and (3) uninhibited propagation of the peak waves and an extension of allowed waves to higher frequencies (above the peak). Wave properties during fracturing of <span class="hlt">ice</span> cover indicated increased groupiness. Wave-<span class="hlt">ice</span> interaction presented binary behavior: there was zero transmission in unbroken <span class="hlt">ice</span> and total transmission in fractured <span class="hlt">ice</span>. The fractured <span class="hlt">ice</span> front traveled at some fraction of the wave group speed. Findings do not motivate new dissipation schemes for wave models, though they do indicate the need for two-way, wave-<span class="hlt">ice</span> coupling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP21A1311F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP21A1311F"><span id="translatedtitle">Extensive mapping of <span class="hlt">ice</span> <span class="hlt">marginal</span> landforms in northern Russia (25°E - 112°E); new precise constraints on <span class="hlt">ice</span> sheet limits of the Eurasian <span class="hlt">ice</span> sheets in Russia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fredin, O.; Rubensdotter, L.; van Welden, A.; Larsen, E.; Lyså, A.; Jensen, M.</p> <p>2009-12-01</p> <p><span class="hlt">Ice</span> sheet extent for the last glaciation(s) are well established in most previously glaciated areas, most notably in North America and Europe. However, in Russia, which have hosted major sectors of the Scandinavian-, Barents sea-, and Kara sea <span class="hlt">ice</span> sheets, knowledge of exact <span class="hlt">ice</span> <span class="hlt">marginal</span> positions is sporadic. Most evidence of <span class="hlt">ice</span> sheet extent so far, have been from drift distribution, and only limited attempts have been made to use remote sensing data to precisely locate <span class="hlt">ice</span> <span class="hlt">marginal</span> zones. This is probably because of difficulties in using optical remote sensing data (typically Landsat ETM+ and ASTER) in low relief, densely forested areas (Taiga), and sheer scale of the mapped areas. Furthermore, no reliable elevation model has existed north of 60°N, aiding interpretation of optical remote sensing data. We have used recently digitized Russian topographic maps (scale 1:100,000) and the new ASTER GDEM 15 m resolution elevation model to map <span class="hlt">ice</span> <span class="hlt">marginal</span> moraines in Russia (25°E - 112°E), thereby covering most formerly glaciated areas in Russia. The majority of the mapping was made using shaded relief maps. Critical interpretation was made using the ASTER GDEM elevation model combined with multispectral Landsat ETM+ data to construct a synthetic stereo-model, which was analyzed in 3D using ERDAS Stereo Analyst® software. Several operators have worked independently to insure unbiased interpretation of the landforms. So far we have mapped about 2.1E6 km2. Many of the mapped moraines are distinct at the mapping scale, with a typical relief of 20 - 120 m, and a cross-sectional width of 500 - 1500 m. Moreover, several moraines are hundreds kilometers long! Many mapped <span class="hlt">ice</span> <span class="hlt">marginal</span> moraines exhibit a very lobate morphology, reflecting low gradient <span class="hlt">ice</span> lobes extending into the low relief river valleys. We infer very low basal shear stresses in the valleys, indicating glacier flow on soft sediments and possible flotation of <span class="hlt">ice</span> tongues on <span class="hlt">ice</span> dammed lakes. There are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS11B1649M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS11B1649M"><span id="translatedtitle">Evolution of a Directional Wave Spectrum in a 3D <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone with Random Floe Size Distribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montiel, F.; Squire, V. A.</p> <p>2013-12-01</p> <p>A new ocean wave/sea-<span class="hlt">ice</span> interaction model is proposed that simulates how a directional wave spectrum evolves as it travels through a realistic <span class="hlt">marginal</span> <span class="hlt">ice</span> zone (MIZ), where wave/<span class="hlt">ice</span> dynamics are entirely governed by coherent conservative wave scattering effects. Field experiments conducted by Wadhams et al. (1986) in the Greenland Sea generated important data on wave attenuation in the MIZ and, particularly, on whether the wave spectrum spreads directionally or collimates with distance from the <span class="hlt">ice</span> edge. The data suggest that angular isotropy, arising from multiple scattering by <span class="hlt">ice</span> floes, occurs close to the edge and thenceforth dominates wave propagation throughout the MIZ. Although several attempts have been made to replicate this finding theoretically, including by the use of numerical models, none have confronted this problem in a 3D MIZ with fully randomised floe distribution properties. We construct such a model by subdividing the discontinuous <span class="hlt">ice</span> cover into adjacent infinite slabs of finite width parallel to the <span class="hlt">ice</span> edge. Each slab contains an arbitrary (but finite) number of circular <span class="hlt">ice</span> floes with randomly distributed properties. <span class="hlt">Ice</span> floes are modeled as thin elastic plates with uniform thickness and finite draught. We consider a directional wave spectrum with harmonic time dependence incident on the MIZ from the open ocean, defined as a continuous superposition of plane waves traveling at different angles. The scattering problem within each slab is then solved using Graf's interaction theory for an arbitrary incident directional plane wave spectrum. Using an appropriate integral representation of the Hankel function of the first kind (see Cincotti et al., 1993), we map the outgoing circular wave field from each floe on the slab boundaries into a directional spectrum of plane waves, which characterizes the slab reflected and transmitted fields. Discretizing the angular spectrum, we can obtain a scattering matrix for each slab. Standard recursive</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.5202G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.5202G"><span id="translatedtitle">The <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of biological aerosols</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grothe, H.; Pummer, B.; Bauer, H.; Bernardi, J.</p> <p>2012-04-01</p> <p>Primary Biological Aerosol Particles (PBAPs), including bacteria, spores and pollen may be important for several atmospheric processes. Particularly, the <span class="hlt">ice</span> nucleation caused by PBAPs is a topic of growing interest, since their impact on <span class="hlt">ice</span> cloud formation and thus on radiative forcing, an important parameter in global climate is not yet fully understood. In laboratory model studies we investigated the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of selected PBAPs. We studied the immersion mode freezing using water-oil emulsion, which we observed by optical microscopy. We particularly focused on pollen. We show that pollen of different species strongly differ in their <span class="hlt">ice</span> nucleation behavior. The average freezing temperatures in laboratory experiments range from 240 K to 255 K. As the most efficient nuclei (silver birch, Scots pine and common juniper pollen) have a distribution area up to the Northern timberline, their <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> might be a cryoprotective mechanism. For comparison the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of Snomax, fungal spores, and mushrooms will be discussed as well. In the past, pollen have been rejected as important atmospheric IN, as they are not as abundant in the atmosphere as bacteria or mineral dust and are too heavy to reach higher altitudes. However, in our experiments (Pummer et al. 2011) it turned out that water, which had been in contact with pollen and then been separated from the bodies, nucleates as good as the pollen grains themselves. So the <span class="hlt">ice</span> nuclei have to be easily-suspendable macromolecules (100-300 kDa) located on the pollen. Once extracted, they can be distributed further through the atmosphere than the heavy pollen grains and so augment the impact of pollen on <span class="hlt">ice</span> cloud formation even in the upper troposphere. It is widely known, that material from the pollen, like allergens and sugars, can indeed leave the pollen body and be distributed independently. The most probable mechanism is the pollen grain bursting by rain, which releases</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70014093','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70014093"><span id="translatedtitle">Glaciotectonic origin of the Massachusetts coastal end moraines and a fluctuating late Wisconsinan <span class="hlt">ice</span> <span class="hlt">margin</span>.</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Oldale, R.N.; O'Hara, C. J.</p> <p>1984-01-01</p> <p>Late Wisconsinan end moraines on Cape Cod and islands south and west of Cape Cod are believed to be glaciotectonic features formed by advancing <span class="hlt">ice</span> fronts. Evidence for major <span class="hlt">ice</span> readvances during general recession includes the moraines themselves, till atop stratified drift, and the numerous basal tills that are inferred to exist beneath Cape Cod Bay. The Thompson Glacier end moraine in the Canadian Arctic Archipelago is considered to be a modern example of how late Wisconsinan end moraines on Cape Cod and the islands were formed. It is overriding its outwash plain, displacing outwash deposits forward and upward beyond the <span class="hlt">ice</span> front. New sheets are added to the base of the moraine as the <span class="hlt">ice</span> overrides it. Retreat of the <span class="hlt">ice</span> from Cape Cod and the islands may have been similar to the retreat of the Lake Michigan lobe, deposits of which contain evidence of at least 12 moraine-building episodes caused by readvancing <span class="hlt">ice</span>.-from Authors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGD....1212611F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGD....1212611F"><span id="translatedtitle">Influence of timing of sea <span class="hlt">ice</span> retreat on phytoplankton size during <span class="hlt">marginal</span> <span class="hlt">ice</span> zone bloom period in the Chukchi and Bering shelves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujiwara, A.; Hirawake, T.; Suzuki, K.; Eisner, L.; Imai, I.; Nishino, S.; Kikuchi, T.; Saitoh, S. I.</p> <p>2015-08-01</p> <p>Timing of sea <span class="hlt">ice</span> retreat (TSR) as well as cell size of primary producers (i.e., phytoplankton) plays crucial roles in seasonally <span class="hlt">ice</span>-covered marine ecosystem. Thus, it is important to monitor the temporal and spatial distribution of phytoplankton community size structure. Prior to this study, an ocean color algorithm has been developed to derive phytoplankton size index FL, which is defined as the ratio of chlorophyll a derived from the cells larger than 5 μm to the total chl a using satellite remote sensing for the Chukchi and Bering shelves. Using this method, we analyzed pixel-by-pixel relationships between FL during <span class="hlt">marginal</span> <span class="hlt">ice</span> zone (MIZ) bloom period and TSR over a period of 1998-2013. The influence of TSR on sea surface temperature (SST) and changes in ocean heat content (ΔOHC) during the MIZ bloom period were also investigated. A significant negative relationship between FL and TSR was widely found in the shelf region during MIZ bloom season. On the other hand, we found a significant positive (negative) relationship between SST (ΔOHC) and TSR. That is, earlier sea-<span class="hlt">ice</span> retreat was associated with a dominance of larger phytoplankton during a colder and weakly stratified MIZ bloom season, suggesting that duration of nitrate supply, which is important for large-sized phytoplankton growth in this region (i.e., diatoms), can change according to TSR. In addition, under-<span class="hlt">ice</span> phytoplankton blooms are likely to occur in years with late <span class="hlt">ice</span> retreat, because sufficient light for phytoplankton growth can pass through the <span class="hlt">ice</span> and penetrate into the water columns due to an increase in solar radiation toward the summer solstice. Moreover, we found not only the length of <span class="hlt">ice</span>-free season but also annual median of FL positively correlated with annual net primary production (APP). Thus, both phytoplankton community composition and growing season are important for APP in the study area. Our findings showed quantitative relationship between the inter-annual variability of FL</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016BGeo...13..115F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016BGeo...13..115F"><span id="translatedtitle">Influence of timing of sea <span class="hlt">ice</span> retreat on phytoplankton size during <span class="hlt">marginal</span> <span class="hlt">ice</span> zone bloom period on the Chukchi and Bering shelves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujiwara, A.; Hirawake, T.; Suzuki, K.; Eisner, L.; Imai, I.; Nishino, S.; Kikuchi, T.; Saitoh, S.-I.</p> <p>2016-01-01</p> <p>The size structure and biomass of a phytoplankton community during the spring bloom period can affect the energy use of higher-trophic-level organisms through the predator-prey body size relationships. The timing of the sea <span class="hlt">ice</span> retreat (TSR) also plays a crucial role in the seasonally <span class="hlt">ice</span>-covered marine ecosystem, because it is tightly coupled with the timing of the spring bloom. Thus, it is important to monitor the temporal and spatial distributions of a phytoplankton community size structure. Prior to this study, an ocean colour algorithm was developed to derive phytoplankton size index FL, which is defined as the ratio of chlorophyll <Ei>a</Emphasis> (chl <Emphasis Type="Italic">a) derived from cells larger than 5 µm to the total chl a, using satellite remote sensing for the Chukchi and Bering shelves. Using this method, we analysed the pixel-by-pixel relationships between F<Subscript>L</Subscript> during the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone (MIZ) bloom period and TSR over the period of 1998-2013. The influences of the TSR on the sea surface temperature (SST) and changes in ocean heat content (ΔOHC) during the MIZ bloom period were also investigated. A significant negative relationship between FL and the TSR was widely found in the shelf region during the MIZ bloom season. However, we found a significant positive (negative) relationship between the SST (ΔOHC) and TSR. Specifically, an earlier sea <span class="hlt">ice</span> retreat was associated with the dominance of larger phytoplankton during a colder and weakly stratified MIZ bloom season, suggesting that the duration of the nitrate supply, which is important for the growth of large-sized phytoplankton in this region (i.e. diatoms), can change according to the TSR. In addition, under-<span class="hlt">ice</span> phytoplankton blooms are likely to occur in years with late <span class="hlt">ice</span> retreat, because sufficient light for phytoplankton growth can pass through the <span class="hlt">ice</span> and penetrate into the water columns as a result of an increase in solar radiation toward the summer solstice</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70018390','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70018390"><span id="translatedtitle"><span class="hlt">Active</span> volcanism beneath the West Antarctic <span class="hlt">ice</span> sheet and implications for <span class="hlt">ice</span>-sheet stability</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Blankenship, D.D.; Bell, R.E.; Hodge, S.M.; Brozena, J.M.; Behrendt, John C.; Finn, C.A.</p> <p>1993-01-01</p> <p>IT is widely understood that the collapse of the West Antarctic <span class="hlt">ice</span> sheet (WAIS) would cause a global sea level rise of 6 m, yet there continues to be considerable debate about the detailed response of this <span class="hlt">ice</span> sheet to climate change1-3. Because its bed is grounded well below sea level, the stability of the WAIS may depend on geologically controlled conditions at the base which are independent of climate. In particular, heat supplied to the base of the <span class="hlt">ice</span> sheet could increase basal melting and thereby trigger <span class="hlt">ice</span> streaming, by providing the water for a lubricating basal layer of till on which <span class="hlt">ice</span> streams are thought to slide4,5. <span class="hlt">Ice</span> streams act to protect the reservoir of slowly moving inland <span class="hlt">ice</span> from exposure to oceanic degradation, thus enhancing <span class="hlt">ice</span>-sheet stability. Here we present aerogeophysical evidence for <span class="hlt">active</span> volcanism and associated elevated heat flow beneath the WAIS near the critical region where <span class="hlt">ice</span> streaming begins. If this heat flow is indeed controlling <span class="hlt">ice</span>-stream formation, then penetration of ocean waters inland of the thin hot crust of the <span class="hlt">active</span> portion of the West Antarctic rift system could lead to the disappearance of <span class="hlt">ice</span> streams, and possibly trigger a collapse of the inland <span class="hlt">ice</span> reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008epsc.conf..156K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008epsc.conf..156K"><span id="translatedtitle">Pedestal Craters in Utopia Planitia and Malea Planum: Evidence for a Past <span class="hlt">Ice</span>-Rich Substrate from <span class="hlt">Marginal</span> Sublimation Pits.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kadish, S. J.; Head, J. W.; Barlow, N. G.; Marchant, D. R.</p> <p>2008-09-01</p> <p>Introduction: Pedestal craters (Pd) are a subclass of impact craters unique to Mars [1] characterized by a crater perched near the center of a pedestal (mesa or plateau) that is surrounded by a quasi-circular, outward-facing scarp. The <span class="hlt">marginal</span> scarp is usually several crater diameters from the crater rim (Figs. 2,4,5), and tens to over 100 meters above the surrounding plains (Fig. 2). Pd have been interpreted to form by armoring of the proximal substrate during the impact event. Hypotheses for the armoring mechanism include an ejecta covering [e.g., 3], increased ejecta mobilization caused by volatile substrates [4], distal glassy/melt-rich veneers [5], and/or an atmospheric blast/thermal effect [6]. Subsequently, a <span class="hlt">marginal</span> scarp forms by preferential erosion of the substrate surrounding the armored region, most commonly thought to involve eolian removal of fine-grained, non-armored material [e.g., 3]. An understanding of the distribution of Pd, which form predominantly poleward of ~40°N and S latitude [7-9] (Fig. 1), and the role of redistribution of <span class="hlt">ice</span> and dust during periods of climate change [e.g., 10-11], suggests that the substrate might have been volatile-rich [8-9, 12-14]. As such, some researchers [e.g., 8-9] have proposed a model for Pd formation that involves impact during periods of higher obliquity, when mid- to high-latitude substrates were characterized by thick deposits of snow and <span class="hlt">ice</span> [e.g., 15]. Subsequent sublimation of the volatile units, except below the armored regions, yielded the perched Pd. Thus, this model predicts that thick deposits of snow/<span class="hlt">ice</span> should underlie Pd. This is in contrast to the eolian model [3], which calls primarily for deflation of sand and dust. Here, we show the results of our study [8,16] that has documented and characterized 2461 Pd on Mars equatorward of ~65° N and S latitude (Fig. 1) in order to test these hypotheses for the origin of pedestal craters. In particular, we report on the detection of 50 Pd in Utopia</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.2146B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.2146B"><span id="translatedtitle">Post-glacial coast development and human settling of the North European <span class="hlt">Ice</span> <span class="hlt">Marginal</span> Landscape (IML)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bregman, I. Kant Baltic Federal State University, Kaliningrad, Russia, E. P. H.; Netherlands, Utrecht University, the; Druzhinina, I. Kant Baltic Federal State University, Kaliningrad, Russia, O. A.</p> <p>2012-04-01</p> <p>In North Europe, in the <span class="hlt">Ice</span> <span class="hlt">Marginal</span> Landscapes (IML) from the Netherlands to Estonia, human settling is in the Late-Pleistocene - Holocene strongly influenced by post-glacial relative coast development(MESO, 2010; SINCOS, 2002-2009; Machu, 2006-2009, IGCP project 346, CoPaF, 2009-2012) and glacio-isostasy. Geological processes like updoming and tectonic block displacements not only influenced sedimentation of river systems in delta's (e.g. Cohen, 2003), but influenced coastal development and human settling too in the North Sea area (e.g. Peeters, 2009; Hijma e.a., 2011) the Wadden areas (e.g. de Langen, 2011) and lagoons (e.g. Druzhinina, 2010). An overview of shoreline development at the distal side of the Late Glacial forbulge related to glaciological and geophysical processes however does not exist and coastal development models are also not correlated with human settling. Our project( 2012 - 2018) has the aim to describe the influence of shifting coast on the way of settling and living of ancient man in the IML. The main questions to be answered are as follow: (i) Is coast development influenced by glaciations a result of interaction between endo- and exogenic (glaciological-, geological-, and geophysical) forces in general and at the local scale of morphological elements? (ii) Did ancient man adept to changes in natural circumstances and what did that mean for his social behavior and economy? (iii) Were forms of human society and economy in the IML primarily dependent on the natural environment with regard to geophysical and geological differences and related to post-glacial response of the earth crust? Detailed integrated studying of "key-areas", with attention to deep geology, will allow to get new insight of the impact of post-glacial shoreline changes and history of man on the coast in the IML with focus on his past (history of relations) and future (impact of climate change. The project is an international project, with participation of institutes all</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JGR...10511889O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JGR...10511889O"><span id="translatedtitle">Dynamics and energetics of the cloudy boundary layer in simulations of off-<span class="hlt">ice</span> flow in the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olsson, Peter Q.; Harrington, Jerry Y.</p> <p>2000-05-01</p> <p>The case under consideration occurred on March 4, 1993, and was observed as part of the Radiation and Eddy Flux Experiment (REFLEX II) 1993 observational campaign northwest of Spitsbergen. The off-<span class="hlt">ice</span> flow on this day brought very cold surface air temperatures (-35°C) over a relatively warm ocean surface. The resultant latent and sensible surface heat fluxes produced intense convection and a thermal internal boundary layer (TIBL) which deepened with distance from the <span class="hlt">ice</span> edge. Two-dimensional cloud-resolving model (CRM) simulations were performed to determine the impact of various cloud parameterizations on the structure and evolution of the TIBL. The model was able to reproduce the observed thermal structure of the boundary layer to within the acknowledged limitations of the CRM approach. Sensitivity studies of cloud type showed that inclusion of mixed-phase microphysics had a large impact of BL depth and structure. Radiative heating of the cloud near cloud base and cooling near cloud top along with latent heat release were found to be significant sources of turbulence kinetic energy even in the present case where very strong surface heat fluxes occur. <span class="hlt">Ice</span>-phase precipitation processes rapidly depleted the BL of condensate, weakening the radiative thermal forcing. A further consequence of condensate depletion in the mixed-phase cloud was a less humid boundary layer that was able to maintain a larger surface latent heat flux and continuously extract heat through condensation and deposition. Not surprisingly, the presence of clouds had a profound impact on the radiative budget at the surface, with the cloudy BL reducing surface radiative losses more that 60% over clear-sky values. Inclusion of the <span class="hlt">ice</span> phase significantly affected the radiative budget as compared to purely liquid clouds, illustrating the importance of <span class="hlt">ice</span>-phase-radiative couplings for accurate simulations of arctic clouds and boundary layer dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....5684L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....5684L"><span id="translatedtitle">Sedimentation processes on the Mid Norwegian <span class="hlt">margin</span> during the last 40ka: impact of <span class="hlt">ice</span> sheet fluctuations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lekens, W. A. H.; Sejrup, H. P.; Haflidason, H.</p> <p>2003-04-01</p> <p>The Mid-Norwegian <span class="hlt">margin</span> is characterized by large-scale geological processes during the Late Quaternary, such as glacigenic debris flows, turbidites, huge translational slides, contourites and large-scale hemipelagic deposits. By using high resolution cores and seismic data these processes are further characterized and both their timing and interrelation are presented for the last 40ka. It has been found that the deposition of glacigenic debris flows is associated with advances of the Norwegian Channel <span class="hlt">Ice</span> Stream (NCIS). These events are followed by large scale meltwater plume deposition, which was later partly redeposited downslope in the Storegga slide. The influence of meltwater on the oxygen isotope records is widely shown within the region and large plumite deposits have been recognized from X-ray and high resolution seismic profiles. It has been suggested that northward currents shaped the sediment plume along the Mid Norwegian <span class="hlt">margin</span>. The sedimentation rates and bulk accumulation rates show the variability of deposition and input to the <span class="hlt">margin</span> and are mainly governed by the changes in deglaciation rate of the Fennoscandian <span class="hlt">ice</span> sheet and the regional weathering rate on the surrounding mainland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008epsc.conf..156K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008epsc.conf..156K&link_type=ABSTRACT"><span id="translatedtitle">Pedestal Craters in Utopia Planitia and Malea Planum: Evidence for a Past <span class="hlt">Ice</span>-Rich Substrate from <span class="hlt">Marginal</span> Sublimation Pits.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kadish, S. J.; Head, J. W.; Barlow, N. G.; Marchant, D. R.</p> <p>2008-09-01</p> <p>Introduction: Pedestal craters (Pd) are a subclass of impact craters unique to Mars [1] characterized by a crater perched near the center of a pedestal (mesa or plateau) that is surrounded by a quasi-circular, outward-facing scarp. The <span class="hlt">marginal</span> scarp is usually several crater diameters from the crater rim (Figs. 2,4,5), and tens to over 100 meters above the surrounding plains (Fig. 2). Pd have been interpreted to form by armoring of the proximal substrate during the impact event. Hypotheses for the armoring mechanism include an ejecta covering [e.g., 3], increased ejecta mobilization caused by volatile substrates [4], distal glassy/melt-rich veneers [5], and/or an atmospheric blast/thermal effect [6]. Subsequently, a <span class="hlt">marginal</span> scarp forms by preferential erosion of the substrate surrounding the armored region, most commonly thought to involve eolian removal of fine-grained, non-armored material [e.g., 3]. An understanding of the distribution of Pd, which form predominantly poleward of ~40°N and S latitude [7-9] (Fig. 1), and the role of redistribution of <span class="hlt">ice</span> and dust during periods of climate change [e.g., 10-11], suggests that the substrate might have been volatile-rich [8-9, 12-14]. As such, some researchers [e.g., 8-9] have proposed a model for Pd formation that involves impact during periods of higher obliquity, when mid- to high-latitude substrates were characterized by thick deposits of snow and <span class="hlt">ice</span> [e.g., 15]. Subsequent sublimation of the volatile units, except below the armored regions, yielded the perched Pd. Thus, this model predicts that thick deposits of snow/<span class="hlt">ice</span> should underlie Pd. This is in contrast to the eolian model [3], which calls primarily for deflation of sand and dust. Here, we show the results of our study [8,16] that has documented and characterized 2461 Pd on Mars equatorward of ~65° N and S latitude (Fig. 1) in order to test these hypotheses for the origin of pedestal craters. In particular, we report on the detection of 50 Pd in Utopia</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRII..55.2330T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRII..55.2330T"><span id="translatedtitle">Pelagic and sympagic contribution of organic matter to zooplankton and vertical export in the Barents Sea <span class="hlt">marginal</span> <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tamelander, Tobias; Reigstad, Marit; Hop, Haakon; Carroll, Michael L.; Wassmann, Paul</p> <p>2008-10-01</p> <p> exported from the euphotic zone was derived from pelagic primary production, but at 3 of 11 stations within the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone (MIZ), the <span class="hlt">ice</span> algal signal dominated the isotope composition of sinking material. The δ 13C of settling organic matter was positively related to the vertical flux of particulate organic carbon, with maximum values around -21‰ during the peak bloom phase. Sedimentation of isotopically light copepod faecal pellets (mean δ 13C -25.4‰) was reflected in a depletion of 13C in the sinking material. The results illustrate tight pelagic-benthic coupling in the Barents Sea MIZ through vertical export of fresh phytodetritus during phytoplankton blooms and episodic export of <span class="hlt">ice</span> algae.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1715613W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1715613W"><span id="translatedtitle">The impacts of intense moisture transport on the deep and <span class="hlt">marginal</span> sea-<span class="hlt">ice</span> zones of the Arctic during winter</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Woods, Cian; Caballero, Rodrigo</p> <p>2015-04-01</p> <p> warming at the surface. There are an average of 14 such events that enter the polar cap each winter, driving about 50% of the seasonal variation in surface temperature over the deep Arctic. We show that, over the last 30 years, the <span class="hlt">marginal</span> <span class="hlt">ice</span>-zones in the Barents, Labrador and Chukchi Seas have experienced roughly a doubling in the frequency of these intense moisture intrusion events during winter. Interestingly, these are the regions that have experienced the most rapid wintertime <span class="hlt">ice</span> loss in the Arctic, raising the question: to what extent has the recent Arctic warming been driven by local vs. interannual/remote processes?</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012QSRv...52....1L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012QSRv...52....1L"><span id="translatedtitle">Age of the Ørkendalen moraines, Kangerlussuaq, Greenland: constraints on the extent of the southwestern <span class="hlt">margin</span> of the Greenland <span class="hlt">Ice</span> Sheet during the Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levy, Laura B.; Kelly, Meredith A.; Howley, Jennifer A.; Virginia, Ross A.</p> <p>2012-10-01</p> <p>Although Greenland <span class="hlt">ice</span> core records register relatively stable Holocene climate conditions, the lower elevation <span class="hlt">margins</span> of the Greenland <span class="hlt">Ice</span> Sheet (GrIS) experienced significant Holocene fluctuations. These fluctuations include <span class="hlt">ice</span> sheet recession during the Holocene Thermal Maximum (9-5 ka) and advance during the Little <span class="hlt">Ice</span> Age (LIA; ˜A.D. 1350-1880). Determining the extent and timing of these fluctuations is important for understanding the response of the GrIS to interglacial climate conditions both warmer and colder than at present and for developing accurate <span class="hlt">ice</span> sheet models. Sets of moraines marking past extents of the southwestern GrIS <span class="hlt">margin</span> occur in the Kangerlussuaq region. We focus on the Ørkendalen moraines, a prominent moraine set located within 2 km of the modern <span class="hlt">ice</span> <span class="hlt">margin</span> and just outboard of the LIA moraines. We present the first 10Be ages of the Ørkendalen moraines indicating they were deposited at 6.8 ± 0.3 ka. The geomorphic relationship between the Ørkendalen and LIA moraines indicates that the <span class="hlt">ice</span> sheet <span class="hlt">margin</span> was inboard of its Ørkendalen extent between ˜6.8 ka and the culmination of the LIA. The age of the Ørkendalen moraines provides an important constraint on the extent of the southwestern GrIS during the middle Holocene.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860023453','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860023453"><span id="translatedtitle"><span class="hlt">Ice</span> nucleus <span class="hlt">activity</span> measurements of solid rocket motor exhaust particles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Keller, V. W. (Compiler)</p> <p>1986-01-01</p> <p>The <span class="hlt">ice</span> Nucleus <span class="hlt">activity</span> of exhaust particles generated from combustion of Space Shuttle propellant in small rocket motors has been measured. The <span class="hlt">activity</span> at -20 C was substantially lower than that of aerosols generated by unpressurized combustion of propellant samples in previous studies. The <span class="hlt">activity</span> decays rapidly with time and is decreased further in the presence of moist air. These tests corroborate the low effectivity <span class="hlt">ice</span> nucleus measurement results obtained in the exhaust ground cloud of the Space Shuttle. Such low <span class="hlt">ice</span> nucleus <span class="hlt">activity</span> implies that Space Shuttle induced inadvertent weather modification via an <span class="hlt">ice</span> phase process is extremely unlikely.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP42B..04N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP42B..04N"><span id="translatedtitle">Marine <span class="hlt">ice</span> sheets of Pleistocene age on the East Siberian Continental <span class="hlt">Margin</span> (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niessen, F.; Hong, J.; Hegewald, A.; Matthiessen, J. J.; Stein, R. H.; Kim, H.; Kim, S.; Jensen, L.; Jokat, W.; Nam, S.; Kang, S.</p> <p>2013-12-01</p> <p>Based on swath bathymetry, sediment echosounding, seismic profiling and sediment coring we present results of the RV "Polarstern' cruise ARK-XIII/3 (2008) and RV "Araon" cruise ARA03B (2012), which investigated an area between the Chukchi Borderland and the East Siberian Sea between 165°W and 170°E. At the southern end of the Mendeleev Ridge, close to the Chukchi and East Siberian shelves, evidence is found for the existence of Pleistocene <span class="hlt">ice</span> sheets/<span class="hlt">ice</span> shelves, which have grounded several times in up to 1200 m present water depth. We found mega-scale glacial lineations associated with deposition of glaciogenic wedges and debris-flow deposits indicative of sub-glacial erosion and deposition close to the former grounding lines. Glacially lineated areas are associated with large-scale erosion, accentuated by a conspicuous truncation of pre-glacial strata typically capped with mostly thin layers of diamicton draped by pelagic sediments. Our tentative age model suggests that the youngest and shallowest grounding event of an <span class="hlt">ice</span> sheet should be within Marine Isotope Stage (MIS) 3. The oldest and deepest event predates MIS 6. According to our results, <span class="hlt">ice</span> sheets of more than one km in thickness continued onto, and likely centered over, the East Siberian Shelf. They were possibly linked to previously suggested <span class="hlt">ice</span> sheets on the Chukchi Borderland and the New Siberian Islands. We propose that the <span class="hlt">ice</span> sheets extended northward as thick <span class="hlt">ice</span> shelves, which grounded on the Mendeleev Ridge to an area up to 78°N within MIS 5 and/or earlier. These results have important implication for the former distribution of thick <span class="hlt">ice</span> masses in the Arctic Ocean during the Pleistocene. They are relevant for global sea-level variations, albedo, ocean-atmosphere heat exchange, freshwater export from the Arctic Ocean at glacial terminations and the formation of submarine permafrost. The existence of km-thick Pleistocene <span class="hlt">ice</span> sheets in the western Arctic Ocean during glacial times predating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JGR....96.6829M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JGR....96.6829M"><span id="translatedtitle">Unlocking the <span class="hlt">Ice</span> House: Oligocene-Miocene oxygen isotopes, eustasy, and <span class="hlt">margin</span> erosion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miller, Kenneth G.; Wright, James D.; Fairbanks, Richard G.</p> <p>1991-04-01</p> <p>Oxygen isotope records and glaciomarine sediments indicate at least an intermittent presence of large continental <span class="hlt">ice</span> sheets on Antarctica since the earliest Oligocene (circa 35 Ma). The growth and decay of <span class="hlt">ice</span> sheets during the Oligocene to modern "<span class="hlt">ice</span> house world" caused glacioeustatic sea level changes. The early Eocene was an <span class="hlt">ice</span>-free "greenhouse world," but it is not clear if <span class="hlt">ice</span> sheets existed during the middle to late Eocene "doubt house world." Benthic foraminiferal δ18O records place limits on the history of glaciation, suggesting the presence of <span class="hlt">ice</span> sheets at least intermittently since the earliest Oligocene. The best indicator of <span class="hlt">ice</span> growth is a coeval increase in global benthic and western equatorial planktonic δ18O records. Although planktonic isotope records from the western equatorial regions are limited, subtropical planktonic foraminifera may also record such <span class="hlt">ice</span> volume changes. It is difficult to apply these established principles to the Cenozoic δ18O record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events. We improved Oligocene to Miocene correlations of δ18O records and erected eight oxygen isotope zones (Oi1-Oi2, Mi1-Mi6). Benthic foraminiferal δ18O increases which are associated with the bases of Zones Oil (circa 35.8 Ma), Oi2 (circa 32.5 Ma), and Mil (circa 23.5 Ma) can be linked with δ18O increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near Antarctica. Our new correlations of middle Miocene benthic and western equatorial planktonic δ18O records show remarkable agreement in timing and amplitude. We interpret benthic-planktonic covariance to reflect substantial <span class="hlt">ice</span> volume increases near the bases of Zones Mi2 (circa 16.1 Ma), Mi3 (circa 13.6 Ma), and possibly Mi5 (circa 11.3 Ma). Possible glacioeustatic lowerings are associated with the δ18O increases which culminated with the bases of Zone Mi4 (circa 12.6 Ma) and Mi6 (circa 9</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090030611','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090030611"><span id="translatedtitle"><span class="hlt">Icing</span> Branch Current Research <span class="hlt">Activities</span> in <span class="hlt">Icing</span> Physics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vargas, Mario</p> <p>2009-01-01</p> <p>Current development: A grid block transformation scheme which allows the input of grids in arbitrary reference frames, the use of mirror planes, and grids with relative velocities has been developed. A simple <span class="hlt">ice</span> crystal and sand particle bouncing scheme has been included. Added an SLD splashing model based on that developed by William Wright for the LEWICE 3.2.2 software. A new area based collection efficiency algorithm will be incorporated which calculates trajectories from inflow block boundaries to outflow block boundaries. This method will be used for calculating and passing collection efficiency data between blade rows for turbo-machinery calculations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16346333','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16346333"><span id="translatedtitle">Toxicity of smoke to epiphytic <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zagory, D; Lindow, S E; Parmeter, J R</p> <p>1983-07-01</p> <p>Wheat straw smoke aerosols and liquid smoke condensates reduced significantly both the viability and the <span class="hlt">ice</span>-nucleating <span class="hlt">activity</span> of Pseudomonas syringae pv. syringae and Erwinia herbicola in vitro and on leaf surfaces in vivo. Highly significant reductions in numbers of bacterial <span class="hlt">ice</span> nuclei on the surface of both corn and almond were observed after exposure to smoke aerosols. At -5 degrees C, frost injury to corn seedlings colonized by <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria was reduced after exposure to smoke aerosols. Effects on -9 degrees C <span class="hlt">ice</span> nuclei, although significant, were less than on <span class="hlt">ice</span> nuclei <span class="hlt">active</span> at -5 degrees C. These results suggest that smoke from wildfires or smudge pots may reduce plant frost susceptibility and sources of <span class="hlt">ice</span> nuclei important in other natural processes under some conditions. PMID:16346333</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS51C1006B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS51C1006B"><span id="translatedtitle">Advection of Sea-<span class="hlt">Ice</span> Meltwater and Halocline Water Along the Siberian Continental <span class="hlt">Margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bauch, D.; Torres-Valdes, S.; Polyakov, I.; Chernyavskaya, E.; Novikhin, A.; Dmitrenko, I.; McKay, J. L.; Mix, A. C.</p> <p>2014-12-01</p> <p>Our study is based on hydrochemical and stable oxygen isotope data at the Laptev Sea continental slope from summers 2005-2009 and reveals a general pattern in water mass distribution and potential shelf-basin exchange. Despite considerable inter-annual variations, a frontal system can be inferred between shelf, continental slope and central Eurasian Basin waters in the upper 100 m of the water column along the continental slope. Net sea-<span class="hlt">ice</span> melt is consistently found at the continental slope. However, the sea-<span class="hlt">ice</span> meltwater signal is independent from the local retreat of the sea-<span class="hlt">ice</span> edge and appears to be advected from upwind locations. In addition to the along-slope frontal system at the continental shelf break, a strong gradient is identified on the Laptev Sea shelf at ~122-126°E with an eastward increase of riverine and sea-<span class="hlt">ice</span> related brine water contents. These waters cross the shelf break at ~140°E and feed the Low Salinity Halocline Water (LSHW, salinity S<33) in the upper 50 m of the water column. High silicate concentrations in Laptev Sea bottom waters may lead to speculation about a link to the local silicate maximum found within the salinity range of ~33 to 34.5, typical for the Lower Halocline Water (LHW) at the continental slope. However brine signatures and nutrient ratios from the central Laptev Sea differ from those observed at the continental slope. Similar to the advection of the sea-<span class="hlt">ice</span> melt signal along the Laptev Sea continental slope the nutrient signal at 50-70 m water depth within the LHW might also be fed by advection parallel to the slope. Thus, our analyses suggest that advective processes from upstream locations play a significant role in the meltwater distribution and halocline formation in the northern Laptev Sea. Inter-annual variations within the properties of LHW are further investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP14B..08A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP14B..08A"><span id="translatedtitle">Insect-Based Holocene (and Last Interglacial?) Paleothermometry from the E and NW Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">Margins</span>: A Fly's-Eye View of Warmth on Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Axford, Y.; Bigl, M.; Carrio, C.; Corbett, L. B.; Francis, D. R.; Hall, B. L.; Kelly, M. A.; Levy, L.; Lowell, T. V.; Osterberg, E. C.; Richter, N.; Roy, E.; Schellinger, G. C.</p> <p>2011-12-01</p> <p>Here we present new paleotemperature reconstructions based upon insect (Chironomidae) assemblages and other proxies from lake sediment cores recovered in east Greenland at ~71° N near Scoresby Sund and in northwest Greenland at ~77° N near Thule/Qaanaaq. In east Greenland, Last Chance Lake (informal name) is a small, non-glacial lake situated ~90 km east of the Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">margin</span>. The lake preserves a sedimentary record of the entire Holocene (Levy et al. 2013). Chironomids from Last Chance Lake record cold summer temperatures (and establishment of a cold-climate fauna including abundant Oliveridia and Pseudodiamesa) during the late Holocene, preceded by summer temperatures estimated to have been 3 to 6°C warmer during the first half of the Holocene (when summer insolation forcing was greater than today). In northwest Greenland, Delta Sø and Wax Lips Lake (informal name) both preserve Holocene sediments. Here we discuss the late Holocene chironomid record from Delta Sø, whereas from Wax Lips Lake (a small, non-glacial lake situated ~2 km west of the <span class="hlt">ice</span> sheet <span class="hlt">margin</span>) we present a longer sedimentary and biostratigraphic record. The deeper portions of cores from Wax Lips Lake yield pre-Holocene and nonfinite radiocarbon ages, suggesting that this lake preserves sediments predating the Last Glacial Maximum. Abundant chironomids in the pre-glacial sediments appear to record interglacial conditions, and we infer that these sediments may date to the Last Interglacial (Eemian). The preservation of in situ Last Interglacial lacustrine sediments so close to the modern <span class="hlt">ice</span> sheet <span class="hlt">margin</span> suggests a minimally erosive glacierization style throughout the last glacial period, like that inferred for other Arctic locales such as on Baffin Island (Briner et al. 2007), ~750 km southwest of our study site. Our study sites are situated nearby key <span class="hlt">ice</span> core sites (including NEEM, Camp Century, Agassiz and Renland) and very close to the <span class="hlt">ice</span> sheet <span class="hlt">margin</span>. These chironomid</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPP14B..08A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPP14B..08A"><span id="translatedtitle">Insect-Based Holocene (and Last Interglacial?) Paleothermometry from the E and NW Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">Margins</span>: A Fly's-Eye View of Warmth on Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Axford, Y.; Bigl, M.; Carrio, C.; Corbett, L. B.; Francis, D. R.; Hall, B. L.; Kelly, M. A.; Levy, L.; Lowell, T. V.; Osterberg, E. C.; Richter, N.; Roy, E.; Schellinger, G. C.</p> <p>2013-12-01</p> <p>Here we present new paleotemperature reconstructions based upon insect (Chironomidae) assemblages and other proxies from lake sediment cores recovered in east Greenland at ~71° N near Scoresby Sund and in northwest Greenland at ~77° N near Thule/Qaanaaq. In east Greenland, Last Chance Lake (informal name) is a small, non-glacial lake situated ~90 km east of the Greenland <span class="hlt">Ice</span> Sheet <span class="hlt">margin</span>. The lake preserves a sedimentary record of the entire Holocene (Levy et al. 2013). Chironomids from Last Chance Lake record cold summer temperatures (and establishment of a cold-climate fauna including abundant Oliveridia and Pseudodiamesa) during the late Holocene, preceded by summer temperatures estimated to have been 3 to 6°C warmer during the first half of the Holocene (when summer insolation forcing was greater than today). In northwest Greenland, Delta Sø and Wax Lips Lake (informal name) both preserve Holocene sediments. Here we discuss the late Holocene chironomid record from Delta Sø, whereas from Wax Lips Lake (a small, non-glacial lake situated ~2 km west of the <span class="hlt">ice</span> sheet <span class="hlt">margin</span>) we present a longer sedimentary and biostratigraphic record. The deeper portions of cores from Wax Lips Lake yield pre-Holocene and nonfinite radiocarbon ages, suggesting that this lake preserves sediments predating the Last Glacial Maximum. Abundant chironomids in the pre-glacial sediments appear to record interglacial conditions, and we infer that these sediments may date to the Last Interglacial (Eemian). The preservation of in situ Last Interglacial lacustrine sediments so close to the modern <span class="hlt">ice</span> sheet <span class="hlt">margin</span> suggests a minimally erosive glacierization style throughout the last glacial period, like that inferred for other Arctic locales such as on Baffin Island (Briner et al. 2007), ~750 km southwest of our study site. Our study sites are situated nearby key <span class="hlt">ice</span> core sites (including NEEM, Camp Century, Agassiz and Renland) and very close to the <span class="hlt">ice</span> sheet <span class="hlt">margin</span>. These chironomid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRII..55..365W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRII..55..365W"><span id="translatedtitle">Summertime mixed layer development in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone off the Mawson coast, East Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, G. D.; Nicol, S.; Raymond, B.; Meiners, K.</p> <p>2008-02-01</p> <p>Two small-scale Antarctic marine ecosystem surveys were conducted offshore from the Mawson coast (61-66∘E), in the austral summers of January 2001 and 2003. Striking differences were observed in the state of the marine ecosystem between the surveys; in particular krill abundance and penguin breeding success were significantly lower in 2003. In this paper we examine the variability in the physical oceanography between the two surveys, and identify the development of the summer mixed layer (SML) as the key physical process influencing the differences in ecological conditions. The mixed layer in 2003 was warmer, fresher and reduced in both dissolved oxygen content and fluorescence relative to 2001. In 2001 the mean mixed-layer depth was 68.5±12.4m. In 2003, the mean mixed-layer depth was 33.8±11.2m, and increased through the remaining 14 days of the survey. The SML in 2003 was underdeveloped by over a month relative to the 2001 hydrography and we relate this to the seasonal variability in the pattern and timing of sea-<span class="hlt">ice</span> melt. AVHRR satellite images show a region of fast <span class="hlt">ice</span> against the Mawson coast that had greater spatial and temporal extent in 2003. We conclude that delayed mixed layer development due to persistent sea <span class="hlt">ice</span> is likely to have a negative impact on the marine ecosystem of the Antarctic shelf. This may have important implications for predicting the impact of future variability in the sea-<span class="hlt">ice</span> growth/melt transition due to climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5446900','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5446900"><span id="translatedtitle">Unlocking the <span class="hlt">ice</span> house: Oligocene-Miocene oxygen isotopes, eustasy, and <span class="hlt">margin</span> erosion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Miller, K.G. Columbia Univ., Palisades, NY ); Wright, J.D.; Fairbanks, R.G. )</p> <p>1991-04-10</p> <p>Benthic foraminiferal {delta}{sup 18}O records place limits on the history of glaciation, suggesting the presence of <span class="hlt">ice</span> sheets at least intermittently since the earliest Oligocene. The best indicator of <span class="hlt">ice</span> growth is a coeval increase in global benthic and western equatorial planktonic {delta}{sup 18}O records. Although planktonic isotope records from the western equatorial regions are limited, subtropical planktonic foraminifera may also record such <span class="hlt">ice</span> volume changes. It is difficult to apply these established principles to the Cenozoic {delta}{sup 18}O record because of the lack of adequate data and problems in stratigraphic correlations that obscure isotope events. The authors improved Oligocene to Miocene correlations of {delta}{sup 18}O records and erected eight oxygen isotope zones (Oi1-Oi2, Mi1-Mi6). Benthic foraminiferal {delta}{sup 18}O increases which can be linked with {delta}{sup 18}O increases in subtropical planktonic foraminifera and with intervals of glacial sedimentation on or near Antarctica. These new correlations of middle Miocene benthic and western equatorial planktonic {delta}{sup 18}O records show remarkable agreement in timing and amplitude. They interpret benthic-planktonic covariance to reflect substantial <span class="hlt">ice</span> volume increases near the bases of Zones Mi2 (circa 16.1 Ma), Mi3 (circa 13.6 Ma), and possibly Mi5 (circa 11.3 Ma). Possible glacioeustatic lowerings are associated with the {delta}{sup 18}O increases which culminated with the bases of Zone Mi4 (circa 12.6 Ma) and Mi6 (circa 9.6 Ma), although low-latitude planktonic {delta}{sup 18}O records are required to test this. These inferred glacioeustatic lowerings can be linked to seismic and rock disconformities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9486D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9486D"><span id="translatedtitle">Surface exposure dating of glacial lake shorelines: implications for constraining <span class="hlt">ice</span> <span class="hlt">margin</span> positions and meltwater outbursts during the last deglaciation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dube-Loubert, Hugo; Roy, Martin; Schaefer, Joerg</p> <p>2016-04-01</p> <p>The Laurentide <span class="hlt">ice</span> sheet (LIS) played an important role in the climate variability of the last deglaciation, notably through large discharges of meltwater to the North Atlantic that disturbed the ocean's circulation and heat transport. Deglaciation of the northeastern sector of the LIS was complex and included the development of large <span class="hlt">ice</span>-dammed lakes that were confined within the main river valleys draining northward into Ungava Bay. The history of these lakes is closely related to the temporal evolution of the Labrador <span class="hlt">ice</span> dome, but large uncertainties regarding the position and dynamic of the <span class="hlt">ice</span> <span class="hlt">margin</span> through time currently limit our understanding of these glacial lakes. In the Ungava lowlands, glacial lake Naskaupi invaded the George River valley, leaving a series of well-developed shorelines and deltas. These spectacular raised shorelines are 10 to 20 meters wide and can be followed for several kilometers. Our field investigations and remote sensing analysis indicate that Lake Naskaupi experienced a complex history, as shown by the succession of shorelines that likely reflect the opening of new topographic outlets during <span class="hlt">ice</span> retreat. Constraining the timing of the different phases of the lake and its drainage has traditionally been challenging, as organic material suitable for radiocarbon dating is scarce or lacking. Recent progress in Surface Exposure Dating (SED) by cosmogenic nuclides now inspires novel approaches to glacial and deglacial geomorphology. Here we apply 10Be SED to boulders that form part of these shorelines and mark the main (high-level) stage of Lake Naskaupi. We sampled 4-6 multi-meter size boulders at 4 different sites. Preliminary results show high internal consistency and, indicate that the main lake phase developed very late in the regional deglaciation, which extends from about 8500 to 6800 cal. yr BP (Dyke and Prest, 1987). We also present SED results from boulders deposited by a substantial outburst flood presumably associated with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70029682','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70029682"><span id="translatedtitle">Glacially-influenced late Pleistocene stratigraphy of a passive <span class="hlt">margin</span>: New Jersey's Record of the North American <span class="hlt">ice</span> sheet</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Carey, J.S.; Sheridan, R.E.; Ashley, G.M.; Uptegrove, J.</p> <p>2005-01-01</p> <p>Glacial isostasy and the sediment supply changes associated with the waxing and waning of <span class="hlt">ice</span> sheets have dramatic effects on the stratigraphy of adjacent continental shelves. In ancient stratigraphic records, the glacial influences on such deposits could be difficult to recognize because of the removal of coeval terrestrial glacial deposits by erosion. This study illustrates the effects of the Laurentide <span class="hlt">Ice</span> Sheet on a basin near its maximum limit, the New Jersey continental shelf. Analysis of 1600 km of Geopulse???, Uniboom???, Minisparker??? and airgun profiles reveals four depositional sequences that have a maximum thickness of ???75 m near the shelf edge. Sequences I and IV correspond to the major glacial-interglacial sea level changes at Marine Isotope Chron (MIC) 6/5e and 2/1, whereas sequences II and III reflect smaller-scale sea-level fluctuations during chrons 4/3c and 3b/3a, respectively. Sequences I and IV are characterized by relatively thick low stand to early transgressive deposits near the shelf edge formed during times of increased sediment supply, but are thin and discontinuous across much of the shelf. Reflection horizons in these units deepen northward in the northern half of the study area due to collapse of a peripheral bulge that formed at the <span class="hlt">margin</span> of the Laurentide <span class="hlt">Ice</span> Sheet. The Hudson River moved from a more southerly drainage pattern to the modern Hudson Shelf Valley position, possibly under the influence of the advancing peripheral bulge. Sequences II and III are largely preserved within a broad mid-shelf swale likely created by the migration of an ancestral Hudson River, and their thickness implies much higher sedimentation rates during chrons 4 and 3 than seen today. If the terrestrial glacial record was eroded, the increased rates of sedimentation during the Pleistocene, dominance of sediments derived from northern New England, and northward tilting of strata could be interpreted as a result of uplift of a northern source area. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.8833C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EGUGA..17.8833C&link_type=ABSTRACT"><span id="translatedtitle">Sea <span class="hlt">ice</span> trends and cyclone <span class="hlt">activity</span> in the Southern Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coggins, Jack; McDonald, Adrian; Rack, Wolfgang; Dale, Ethan</p> <p>2015-04-01</p> <p>Significant trends in the extent of Southern Hemisphere sea <span class="hlt">ice</span> have been noted over the course of the satellite record, with highly variable trends between different seasons and regions. In this presentation, we describe efforts to assess the impact of cyclones on these trends. Employing a maximum cross-correlation method, we derive Southern Ocean <span class="hlt">ice</span>-motion vectors from daily gridded SSMI 85.5 GHz brightness temperatures. We then derive a sea <span class="hlt">ice</span> budget from the NASA-Team 25 km square daily sea <span class="hlt">ice</span> concentrations. The budget quantifies the total daily change in sea <span class="hlt">ice</span> area, and includes terms representing the effects of <span class="hlt">ice</span> advection and divergence. A residual term represents the processes of rafting, ridging, freezing and thawing. We employ a cyclone tracking algorithm developed at the University of Canterbury to determine the timing, location, size and strength of Southern Hemisphere cyclones from mean sea-level pressure fields of the ERA-Interim reanalysis. We then form composites of the of sea <span class="hlt">ice</span> budget below the location of cyclones. Unsurprisingly, we find that clockwise atmospheric flow around Southern Hemisphere cyclones exerts a strong influence on the movement of sea <span class="hlt">ice</span>, an effect which is visible in the advection and divergence terms. Further, we assess the climatological importance of cyclones by comparing seasons of sea <span class="hlt">ice</span> advance for periods with varying numbers of cyclones. This analysis is performed independently for each sea <span class="hlt">ice</span> concentration pixel, thus affording us insight into the geographical importance of storm systems. We find that Southern Hemisphere sea <span class="hlt">ice</span> extent is highly sensitive to the presence of cyclones in the periphery of the pack in the advance season. Notably, the sensitivity is particularly high in the northern Ross Sea, an area with a marked positive trend in sea <span class="hlt">ice</span> extent. We discuss whether trends in cyclone <span class="hlt">activity</span> in the Southern Ocean may have contributed to sea <span class="hlt">ice</span> extent trends in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP24A..04D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP24A..04D"><span id="translatedtitle">Pre-glacial, Early Glacial, and <span class="hlt">Ice</span> Sheet Stratigraphy Cored During NBP1402, Sabrina Coast, East Antarctic <span class="hlt">Margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Domack, E. W.; Gulick, S. P. S.; Fernandez-Vasquez, R. A.; Frederick, B.; Lavoie, C.; Leventer, A.; Shevenell, A.; Saustrup, S., Sr.; Bohaty, S. M.; Sangiorgi, F.</p> <p>2014-12-01</p> <p>Western Wilkes Land provides an unusual setting with regard to passive <span class="hlt">margin</span> subsidence and exposure of Cenozoic sedimentary units across the continental shelf, due to the unique rift to drift history off of the Australian-Antarctic Discordance and subsequent deep glacial erosion of the evolved continental shelf. The first factor has provided extensive accommodation space for the preservation of stratigraphic sequences that in turn represent critical periods in the climate evolution of Antarctica. Glacial erosion has then provided access to this stratigraphy that is usually inaccessible to all but deep drilling programs. Such stratigraphies are well exposed to within cm of the seafloor off the Sabrina Coast. Cruise NBP1402 investigated this region via a combination of multi-channel seismic imaging and innovative, strategic coring. The geophysical data imaged the geologic evolution of the <span class="hlt">margin</span>, which exhibits a continuum from non-glacial, partly glaciated, to fully glaciated depo- and erosional systems. Based on the seismic stratigraphy, we collected dredges and one barrel Jumbo Piston Cores (JPCs) across areas of outcropping strata imaged seismically, a unique strategy that allowed us to identify and sample specific reflectors. The stratigraphically deepest coring targeted sections for which the seismic character suggested a pre-glacial context, with non-glaciated continental <span class="hlt">margin</span> sequences including deltas. Coring recovered dark organic rich siltstones and sandy mudstones, and a large concretion whose center contained a cm-sized plant fossil. In addition, the sediments contain a fossil snail. These fossils provide a glimpse into the pre-glacial terrestrial environment in Antarctica. Overlying this section, coring recovered similar dark siltstones with a 20 cm thick horizon with abundant large angular clasts of variable lithology, interpreted to be <span class="hlt">ice</span>-rafted debris and indicative of early glacial <span class="hlt">ice</span> in Antarctica. Finally, JPCs targeting a younger part of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=fishery&pg=3&id=EJ960318','ERIC'); return false;" href="http://eric.ed.gov/?q=fishery&pg=3&id=EJ960318"><span id="translatedtitle">Investigating Continental <span class="hlt">Margins</span>: An <span class="hlt">Activity</span> to Help Students Better Understand the Continental <span class="hlt">Margins</span> of North America</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Poli, Maria-Serena; Capodivacca, Marco</p> <p>2011-01-01</p> <p>Continental <span class="hlt">margins</span> are an important part of the ocean floor. They separate the land above sea level from the deep ocean basins below and occupy about 11% of Earth's surface. They are also economically important, as they harbor both mineral resources and some of the most valuable fisheries in the world. In this article students investigate North…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27167635','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27167635"><span id="translatedtitle">Timescales of methane seepage on the Norwegian <span class="hlt">margin</span> following collapse of the Scandinavian <span class="hlt">Ice</span> Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Crémière, Antoine; Lepland, Aivo; Chand, Shyam; Sahy, Diana; Condon, Daniel J; Noble, Stephen R; Martma, Tõnu; Thorsnes, Terje; Sauer, Simone; Brunstad, Harald</p> <p>2016-01-01</p> <p>Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean-atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220-400 m, in the southwest Barents and Norwegian seas where grounded <span class="hlt">ice</span> sheets led to thickening of the gas hydrate stability zone during the last glaciation. The onset of methane release was coincident with deglaciation-induced pressure release and thinning of the hydrate stability zone. Methane efflux continued for 7-10 kyr, tracking hydrate stability changes controlled by relative sea-level rise, bottom water warming and fluid pathway evolution in response to changing stress fields. The protracted nature of seafloor methane emissions probably attenuated the impact of hydrate dissociation on the climate system. PMID:27167635</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27167635','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27167635"><span id="translatedtitle">Timescales of methane seepage on the Norwegian <span class="hlt">margin</span> following collapse of the Scandinavian <span class="hlt">Ice</span> Sheet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Crémière, Antoine; Lepland, Aivo; Chand, Shyam; Sahy, Diana; Condon, Daniel J; Noble, Stephen R; Martma, Tõnu; Thorsnes, Terje; Sauer, Simone; Brunstad, Harald</p> <p>2016-05-11</p> <p>Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean-atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220-400 m, in the southwest Barents and Norwegian seas where grounded <span class="hlt">ice</span> sheets led to thickening of the gas hydrate stability zone during the last glaciation. The onset of methane release was coincident with deglaciation-induced pressure release and thinning of the hydrate stability zone. Methane efflux continued for 7-10 kyr, tracking hydrate stability changes controlled by relative sea-level rise, bottom water warming and fluid pathway evolution in response to changing stress fields. The protracted nature of seafloor methane emissions probably attenuated the impact of hydrate dissociation on the climate system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4865861','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4865861"><span id="translatedtitle">Timescales of methane seepage on the Norwegian <span class="hlt">margin</span> following collapse of the Scandinavian <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Crémière, Antoine; Lepland, Aivo; Chand, Shyam; Sahy, Diana; Condon, Daniel J.; Noble, Stephen R.; Martma, Tõnu; Thorsnes, Terje; Sauer, Simone; Brunstad, Harald</p> <p>2016-01-01</p> <p>Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean–atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220–400 m, in the southwest Barents and Norwegian seas where grounded <span class="hlt">ice</span> sheets led to thickening of the gas hydrate stability zone during the last glaciation. The onset of methane release was coincident with deglaciation-induced pressure release and thinning of the hydrate stability zone. Methane efflux continued for 7–10 kyr, tracking hydrate stability changes controlled by relative sea-level rise, bottom water warming and fluid pathway evolution in response to changing stress fields. The protracted nature of seafloor methane emissions probably attenuated the impact of hydrate dissociation on the climate system. PMID:27167635</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000091536','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000091536"><span id="translatedtitle">Outlet Glacier and <span class="hlt">Margin</span> Elevation Changes: Near - Coastal Thinning of The Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abdalati, W.; Krabill, W.; Frederick, E.; Manizade, S.; Martin, C.; Sonntag, J.; Swift, R.; Thomas, R.; Wright, W.; Yungel, J.; Busalacchi, Antonio (Technical Monitor)</p> <p>2000-01-01</p> <p>Repeat surveys by aircraft laser altimeter in 1993/4 and 1998/9 reveal significant thinning along 70% of the coastal parts of the Greenland <span class="hlt">ice</span> sheet at elevations below about 2000 m. Thinning rates of more than 1 m/yr are common along many outlet glaciers, at all latitudes and, in some cases, at elevations up to 1500 m. Warmer summers along parts of the coast may have caused a few tens of cm/yr additional melting, but most of the observed thinning probably results from increased glacier velocities and associated creep rates. Three glaciers in the northeast all show patterns of thickness change indicative of surging behavior, and one has been independently documented as a surging glacier. There are a few areas of significant thickening (over 1 m/yr), and these are probably related to higher than normal accumulation rates during the observation period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...711509C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...711509C"><span id="translatedtitle">Timescales of methane seepage on the Norwegian <span class="hlt">margin</span> following collapse of the Scandinavian <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crémière, Antoine; Lepland, Aivo; Chand, Shyam; Sahy, Diana; Condon, Daniel J.; Noble, Stephen R.; Martma, Tõnu; Thorsnes, Terje; Sauer, Simone; Brunstad, Harald</p> <p>2016-05-01</p> <p>Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean-atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220-400 m, in the southwest Barents and Norwegian seas where grounded <span class="hlt">ice</span> sheets led to thickening of the gas hydrate stability zone during the last glaciation. The onset of methane release was coincident with deglaciation-induced pressure release and thinning of the hydrate stability zone. Methane efflux continued for 7-10 kyr, tracking hydrate stability changes controlled by relative sea-level rise, bottom water warming and fluid pathway evolution in response to changing stress fields. The protracted nature of seafloor methane emissions probably attenuated the impact of hydrate dissociation on the climate system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNS21A1915R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNS21A1915R"><span id="translatedtitle">Flow Dynamics and Stability of the NE Greenland <span class="hlt">Ice</span> Stream from <span class="hlt">Active</span> Seismics and Radar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riverman, K. L.; Alley, R. B.; Anandakrishnan, S.; Christianson, K. A.; Peters, L. E.; Muto, A.</p> <p>2015-12-01</p> <p>We find that dilatant till facilitates rapid <span class="hlt">ice</span> flow in central Greenland, and regions of dryer till limit the expansion of <span class="hlt">ice</span> flow. The Northeast Greenland <span class="hlt">Ice</span> Stream (NEGIS) is the largest <span class="hlt">ice</span> stream in Greenland, draining 8.4% of the <span class="hlt">ice</span> sheet's area. Fast <span class="hlt">ice</span> flow initiates near the <span class="hlt">ice</span> sheet summit in a region of high geothermal heat flow and extends some 700km downstream to three outlet glaciers along the NE Coast. The flow pattern and stability mechanism of this <span class="hlt">ice</span> stream are unique to others in Greenland and Antarctica, and merit further study to ascertain the sensitivity of this <span class="hlt">ice</span> stream to future climate change. In this study, we present the results of the first-ever ground-based geophysical survey of the initiation zone of NEGIS. Based on radar and preliminary seismic data, Christianson et al. (2014, EPSL) propose a flow mechanism for the <span class="hlt">ice</span> stream based on topographically driven hydropotential lows which generate 'sticky' regions of the bed under the <span class="hlt">ice</span> stream <span class="hlt">margins</span>. We further test this hypothesis using a 40km reflection seismic survey across both <span class="hlt">ice</span> stream <span class="hlt">margins</span>. We find that regions of 'sticky' bed as observed by the radar survey are coincident with regions of the bed with seismic returns indicating drier subglacial sediments. These findings are further supported by five amplitude-verses-offset seismic surveys indicating dilatant till within the <span class="hlt">ice</span> stream and consolidated sediments within its <span class="hlt">margins</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5717873','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5717873"><span id="translatedtitle">Transition from a passive continental <span class="hlt">margin</span> to an <span class="hlt">active</span> <span class="hlt">margin</span> documented by time-facies profiles and geohistory diagrams</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kenter, J.A.M.; Reymer, J.J.G.; van der Straaten, H.C.</p> <p>1988-08-01</p> <p>The Upper Cretaceous to Neogene sediments in the northern part of the external zone of the Betic Cordilleras (southeast Spain) reflect the evolution of a passive continental <span class="hlt">margin</span> into an <span class="hlt">active</span> <span class="hlt">margin</span>. Time-facies profiles and geohistory diagrams were constructed to identify and date tectonic events and sea level changes in the sedimentary record. During Late Cretaceous to middle Eocene time, parallel-trending shallow marine facies belts at the edge of a slowly subsiding basin evidence a passive continental <span class="hlt">margin</span> setting. The period from middle Eocene to early Miocene is rather poorly documented. After initial shallowing the whole area emerged and continental conditions prevailed from the late Eocene to early Miocene. The subareal exposure may have been caused by the compound effect of the worldwide Oligocene sea level drop and overall tectonic uplift. Miocene sediments reflect the compressional tectonic regime of an <span class="hlt">active</span> <span class="hlt">margin</span>. The parallel facies belts were disrupted and the area was segmented into several tectonic blocks, each displaying an individual sedimentary record due to differential vertical movement. During middle to late Miocene time a major compressional phase generated northeast-trending folds and <span class="hlt">activated</span> strike-slip and thrust faults. This tectonic phase led to a highly differentiated topography, resulting in the development of local depocenters - each with a unique tectonic and depositional record.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7150N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7150N"><span id="translatedtitle">Vertical distribution of tropospheric BrO in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone of the Northern Weddell Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nasse, Jan-Marcus; Zielcke, Johannes; Lampel, Johannes; Buxmann, Joelle; Frieß, Udo; Platt, Ulrich</p> <p>2015-04-01</p> <p>The free radical bromine monoxide (BrO) strongly influences the chemistry of the troposphere in Polar regions. During springtime with the return of sunlight after Polar night BrO is released in an autocatalytic reaction mechanism from saline surfaces (bromine explosion). Then BrO affects the oxidative properties of the lower atmosphere and can induce complete depletion of ozone within a matter of days or even hours. In addition, elemental mercury can be oxidized by BrO which makes this toxic compound soluble leading to a deposition into the biosphere. Despite numerous observations of elevated BrO levels in the Polar troposphere, bromine radical sources, as well as the details of the mechanisms leading to bromine explosions and the interactions between atmospheric dynamics and chemistry are not yet completely understood. To improve the understanding of these processes, an accurate determination of the spatio-temporal distribution of BrO is crucial. Here we present measurements of BrO performed during two cruises of the German research <span class="hlt">ice</span> breaker Polarstern in the <span class="hlt">marginal</span> sea <span class="hlt">ice</span> zone of the Antarctic Weddell Sea between June and October 2013 when four major periods with elevated BrO concentrations and simultaneous ozone depletion occurred. The events were observed by (1) a ship-based Multi AXis Differential Absorption Spectroscopy (MAX-DOAS) instrument on Polarstern and (2) a compact MAX-DOAS instrument operated on a helicopter. Several flights were performed in the boundary layer as well as in the free troposphere up to altitudes of 2300 m on days with elevated BrO levels. Vertical profiles of aerosol extinction and BrO concentrations were retrieved for both instruments using our HEIPRO (HEIdelberg Profile) retrieval algorithm based on optimal estimation. Elevated BrO levels in the time series from ship-borne measurements show a strong correlation to southerly wind directions indicating transport from sea <span class="hlt">ice</span> areas. Maximum retrieved BrO mixing ratios at ground</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811030K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1811030K&link_type=ABSTRACT"><span id="translatedtitle">The moisture updrafts on the cold pool captured by the continuously radiosonde observation passing through the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone in Laptev Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Komatsu, Kensuke; Tachibana, Yoshihiro; Alexeev, Vladimir</p> <p>2016-04-01</p> <p>In summer 2013, we conducted 6 hourly radiosonde observation between off-<span class="hlt">ice</span> and on-<span class="hlt">ice</span> by Russian icebreaker "Akademik Fedorov" passing through the <span class="hlt">marginal</span> <span class="hlt">ice</span>-zone in Laptev Sea during NABOS project (Nansen and Amundsen Basins Obsevational System). During observation period, the warmer and humid air mass was advected by southeasterly wind from Siberia to Laptev sea because the low-pressure system was passing The temperature profiles bellow 600 m was maintaining the cold pool associated with a sea <span class="hlt">ice</span> and the inversion layer formed above it. The humidity profiles were, however, not trapped until the height of inversion layer, they reached at higher levels (< 5000 m). These observational evidences implied that the humid air from Siberia was lifted on the cold pool maintained by sea <span class="hlt">ice</span> and this process could transport the moisture to upper level in the arctic region. To verify these processes and examine the impact of the existence of sea <span class="hlt">ice</span>, we conducted the numerical experiment by WRF. Three boundary conditions were adopted to simulation; present sea <span class="hlt">ice</span>, removed all sea <span class="hlt">ice</span>, and increased sea <span class="hlt">ice</span> area. As primary results, the trajectories of air parcel from Siberia was rising to upper level with released the latent heat due to the condensation of humid air. The case of present sea <span class="hlt">ice</span> transported much moisture vertically in the arctic region than other two cases. More detail results will be reported on the day. The process of the vertical moisture lifting due to the cold pool could contribute to the heat transport from the mid-latitude surface to the upper level in the arctic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20160006706&hterms=energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Denergy','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20160006706&hterms=energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Denergy"><span id="translatedtitle">Thermodynamic Derivation of the <span class="hlt">Activation</span> Energy for <span class="hlt">Ice</span> Nucleation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barahona, D.</p> <p>2015-01-01</p> <p>Cirrus clouds play a key role in the radiative and hydrological balance of the upper troposphere. Their correct representation in atmospheric models requires an understanding of the microscopic processes leading to <span class="hlt">ice</span> nucleation. A key parameter in the theoretical description of <span class="hlt">ice</span> nucleation is the <span class="hlt">activation</span> energy, which controls the flux of water molecules from the bulk of the liquid to the solid during the early stages of <span class="hlt">ice</span> formation. In most studies it is estimated by direct association with the bulk properties of water, typically viscosity and self-diffusivity. As the environment in the <span class="hlt">ice</span>-liquid interface may differ from that of the bulk, this approach may introduce bias in calculated nucleation rates. In this work a theoretical model is proposed to describe the transfer of water molecules across the <span class="hlt">ice</span>-liquid interface. Within this framework the <span class="hlt">activation</span> energy naturally emerges from the combination of the energy required to break hydrogen bonds in the liquid, i.e., the bulk diffusion process, and the work dissipated from the molecular rearrangement of water molecules within the <span class="hlt">ice</span>-liquid interface. The new expression is introduced into a generalized form of classical nucleation theory. Even though no nucleation rate measurements are used to fit any of the parameters of the theory the predicted nucleation rate is in good agreement with experimental results, even at temperature as low as 190 K, where it tends to be underestimated by most models. It is shown that the <span class="hlt">activation</span> energy has a strong dependency on temperature and a weak dependency on water <span class="hlt">activity</span>. Such dependencies are masked by thermodynamic effects at temperatures typical of homogeneous freezing of cloud droplets; however, they may affect the formation of <span class="hlt">ice</span> in haze aerosol particles. The new model provides an independent estimation of the <span class="hlt">activation</span> energy and the homogeneous <span class="hlt">ice</span> nucleation rate, and it may help to improve the interpretation of experimental results and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACP....1513819B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACP....1513819B"><span id="translatedtitle">Thermodynamic derivation of the <span class="hlt">activation</span> energy for <span class="hlt">ice</span> nucleation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barahona, D.</p> <p>2015-12-01</p> <p>Cirrus clouds play a key role in the radiative and hydrological balance of the upper troposphere. Their correct representation in atmospheric models requires an understanding of the microscopic processes leading to <span class="hlt">ice</span> nucleation. A key parameter in the theoretical description of <span class="hlt">ice</span> nucleation is the <span class="hlt">activation</span> energy, which controls the flux of water molecules from the bulk of the liquid to the solid during the early stages of <span class="hlt">ice</span> formation. In most studies it is estimated by direct association with the bulk properties of water, typically viscosity and self-diffusivity. As the environment in the <span class="hlt">ice</span>-liquid interface may differ from that of the bulk, this approach may introduce bias in calculated nucleation rates. In this work a theoretical model is proposed to describe the transfer of water molecules across the <span class="hlt">ice</span>-liquid interface. Within this framework the <span class="hlt">activation</span> energy naturally emerges from the combination of the energy required to break hydrogen bonds in the liquid, i.e., the bulk diffusion process, and the work dissipated from the molecular rearrangement of water molecules within the <span class="hlt">ice</span>-liquid interface. The new expression is introduced into a generalized form of classical nucleation theory. Even though no nucleation rate measurements are used to fit any of the parameters of the theory the predicted nucleation rate is in good agreement with experimental results, even at temperature as low as 190 K, where it tends to be underestimated by most models. It is shown that the <span class="hlt">activation</span> energy has a strong dependency on temperature and a weak dependency on water <span class="hlt">activity</span>. Such dependencies are masked by thermodynamic effects at temperatures typical of homogeneous freezing of cloud droplets; however, they may affect the formation of <span class="hlt">ice</span> in haze aerosol particles. The new model provides an independent estimation of the <span class="hlt">activation</span> energy and the homogeneous <span class="hlt">ice</span> nucleation rate, and it may help to improve the interpretation of experimental results and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C33C0530P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C33C0530P"><span id="translatedtitle">Ground penetrating radar survey of the <span class="hlt">ice</span>-filled <span class="hlt">active</span> crater of Mount Baker, Washington</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, M.; Clark, D. H.; Caplan-Auerbach, J.</p> <p>2010-12-01</p> <p>Sherman Crater, the center of volcanic <span class="hlt">activity</span> at Mount Baker, in northwest Washington, provides an excellent site to study glacier dynamics in an <span class="hlt">active</span> crater because of its history of sudden, significant increases in geothermal <span class="hlt">activity</span>, its confined geometry, the potential hazards it poses to downstream reservoirs, and the paucity of recent research related to these hazards. We present results from a ground penetrating radar (GPR) survey of the crater conducted in the summers of 2009 and 2010, including characterization of the subglacial crater morphology, estimates for the crater glacier’s volume, maximum depth, annual mass balance and surface velocity and for the crater’s geothermal flux density. We used a GSSI SIR-3000 GPR system and a low frequency (80 MHz) antenna in common-offset (reflection) collection mode to image subglacial conditions along several west-east and south-north transects within the crater. We processed the GPR data with GSSI’s RADAN 6.0 and paired the surface elevations of each transect to the <span class="hlt">ice</span>-surface topography using GPS locations and spot altimeter readings. GPR profiles reveal several sets of distinct basal and englacial reflectors. Along west-east (longitudinal) transects, the crater’s bedrock topography largely follows the glacier’s surface (high to the west, descending to the east), but the <span class="hlt">ice</span> thins dramatically along the <span class="hlt">margin</span> nearest the crater rim’s eastern breach. The prominent basal reflectors in the GPR transects are consistent with an <span class="hlt">ice</span>/hydrothermally altered rock interface, but short more well-defined segments suggest the presence of bedrock (towards the center of the crater) and water (near the eastern breach) at the base of the <span class="hlt">ice</span>. GPR data combined with surface <span class="hlt">ice</span> melting measurements yield a first-order estimate for the area-averaged accumulation rate of 4.8 +/- 0.1 m yr-1 and ablation rate of 2.4 +/- 0.3 m yr-1 water equivalent from surface melting. The resulting calculated geothermal flux for</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990SPIE.1302..225T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990SPIE.1302..225T"><span id="translatedtitle">Helicopter- and ship-based measurements of mesoscale ocean color and thermal features in the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanis, Fred J.; Manley, Thomas O.; Mitchell, Brian G.</p> <p>1990-09-01</p> <p>Eddies along the Polar Front/<span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone (MIZ) in Fram Strait are thought to make important contributions to nutrient flux and stimulation of primary productivity. During the Coordinated Eastern Arctic Regional Experiment (CEAREX) helicopter-based measurements of upwelling radiance were made in four visible spectral bands and in the thermal IR across mesoscale features associated with the MIZ. These structures were mapped by flying a grid pattern over the ocean surface to define eddy boundaries. Subsequently, the area was also sampled vertically with CTD and spectral radiometer profilers. Data obtained from a single structure were integrated to construct a three dimensional picture of physical and optical properties. Volume modeling of temperature, salinity, and density fields obtained from CTD survey define the subsurface eddy structure and are in good agreement with infrared derived characteristics. Maximum temperature in the core was found to be four degrees higher than the surrounding water. Volume modeling further indicates that a subsurface layer of Arctic Intermediate Water is intrinsically associated with the surface expression of the eddy. The ratio of upwelling radiances, L(44l)/L(565), was found to be correlated to surface chlorophyll, particulate absorption coefficient, and in water determinations of L using the optical profiling system. The remote sensing reflectance ratio along with the IR sea surface temperature were found to be useful to detect the surface expression of the eddy and to indicate near surface biological and physical processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DSRII..55.2266D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DSRII..55.2266D"><span id="translatedtitle">Trophic interactions of macro-zooplankton (krill and amphipods) in the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone of the Barents Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dalpadado, Padmini; Yamaguchi, Atsushi; Ellertsen, Bjørnar; Johannessen, Signe</p> <p>2008-10-01</p> <p>The diets of krill and amphipods were examined using light microscopy on field-collected specimens from 2004 to 2005 from the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone of the northwestern Barents Sea, north and east of Spitsbergen. Stomach content analyses indicate dominant krill species to have a filter-feeding mode, whereas amphipods seem to be mainly raptorial feeders. The dominant krill, Thysanoessa inermis, is primarily regarded as an herbivore feeding mostly on diatoms. Alternatively, Thysanoessa longicaudata fed occasionally on calanoid copepods in addition to being a suspension feeder on phytoplankton. The largest of the krill species, Meganyctiphanes norvegica, showed a mixed diet with regular feeding on calanoid copepods and phytoplankton. The degree of carnivory varied between stations and was determined by examining the size and shape of the mandible of copepods. M. norvegica, with a total length of between 26 and 41 mm, had up to two copepods in their stomachs, with a mandible width of the copepods varying from 32 to 154 μm, corresponding, respectively, to a computed prosome length of 0.3 and 2.6 mm. Themisto libellula fed primarily on C3 and C4 copepodite stages of Calanus glacialis and Calanus hyperboreus, and up to three copepods were found in the stomach contents of T. libellula. Themisto abyssorum fed on herbivorous and omnivorous prey such as copepods and appendicularians. The presence of Metridia spp. and appendicularians, e.g., Oikopleura vanhoeffeni in the diet of T. abyssorum may indicate feeding in the deeper layers (>200 m).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7161495','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7161495"><span id="translatedtitle">Multi-year elevation changes near the west <span class="hlt">margin</span> of the Greenland <span class="hlt">ice</span> sheet from satellite radar altimetry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lingle, C.S.; Brenner, A.C.; Zwally, H.J.; DiMarzio, J.P.</p> <p>1992-03-01</p> <p>Mean changes in the surface elevation near the west <span class="hlt">margin</span> of the Greenland <span class="hlt">ice</span> sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean surface. Seasonal mean changes in the surface height are recognizable during the Geosat ERM. The multi-year measurements indicate the surface was lower by 0.4 +/- 0.4 m on average in late summer 1987 than in late summer 1978. The surface was lower by 0.2 +/- 0.5 m on average in late summer 1988 than in late summer 1978. As a control case, the computations are also carried out using altimetry referenced to orbits not adjusted into a common ocean surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970003047','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970003047"><span id="translatedtitle">Multi-Year Elevation Changes Near the West <span class="hlt">Margin</span> of the Greenland <span class="hlt">Ice</span> Sheet from Satellite Radar Altimetry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lingle, Craig S.; Brenner, Anita C.; Zwally, H. Jay; DiMarzio, John P.</p> <p>1991-01-01</p> <p>Mean changes in the surface elevation near the west <span class="hlt">margin</span> of the Greenland <span class="hlt">ice</span> sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean surface. Seasonal mean changes in the surface height are recognizable during the Geosat ERM. The multi-year measurements indicate the surface was lower by 0.4 +/- 0.4 m on average in late summer 1987 than in late summer 1978. The surface was lower by 0.2 +/- 0.5 m on average in late summer 1988 than in late summer 1978. As a control case, the computations art also carried out using altimetry referenced to orbits not adjusted into a common ocean surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP13A2061W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP13A2061W"><span id="translatedtitle">The deglacial retreat of the Laurentide <span class="hlt">Ice</span> Sheet's southern <span class="hlt">margin</span>: Meltwater provenance insights from the Gulf of Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williams, C.; Brown, E. A.; Hastings, D. W.; Lowell, T. V.; Shiller, A. M.; Shevenell, A.; Flower, B. P.</p> <p>2012-12-01</p> <p>Northern Gulf of Mexico (GOM) sediments document abrupt millennial-scale variability that may be linked to Laurentide <span class="hlt">Ice</span> Sheet (LIS) melting and significant changes in Atlantic Meridional Overturning Circulation (AMOC) during the last deglaciation and Holocene (24-7 ka). To investigate the deglacial response of the southern <span class="hlt">margin</span> of the LIS, the impact of meltwater on the GOM, and the influence of GOM meltwater events on the AMOC, we undertook a multi-proxy (foraminiferal δ18O, Mg/Ca, and Ba/Ca) geochemical study of a high-resolution (45 cm/kyr) sedimentary sequence from core MD02-2550, recovered from Orca Basin (2248 m water depth) in the GOM. Paired G. ruber (white and pink, separately) δ18O and Mg/Ca analyses allow us to use Mg/Ca paleothermometry to remove the temperature component of the δ18O signal, leaving behind a record of seawater δ18O (δ18Osw). After correcting the δ18Osw record for global <span class="hlt">ice</span> volume, the resulting GOM δ18Oivc-sw record is primarily influenced by LIS meltwater. To assess how meltwater pulses influenced GOM salinity during deglaciation, we paired our δ18Oivc-sw record with a foraminiferal Ba/Ca record that reflects river discharge-induced salinity changes. Mississippi River Ba concentrations are elevated relative to GOM seawater (400 vs. 85 nM) and modern seawater Ba/Ca (Ba/Casw) exhibits a linear relationship with salinity (>20 psu). Because foraminiferal Ba/Ca exhibits a predictable relationship to Ba/Casw, it may be used to calculate changes in salinity arising from deglacial variations in Mississippi River discharge. A complicating factor for Ba/Ca-based salinity interpretations is that Ba concentrations vary spatially throughout the Mississippi River watershed. For example, modern Missouri and Upper Mississippi River Ba concentrations (633 and 436 nM, respectively) are higher than that of the Ohio River (253 nM). Thus, GOM Ba/Ca variability could reflect changes in total Mississippi River input and/or shifts in the dominant</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACP....13.5751H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACP....13.5751H"><span id="translatedtitle">Immersion freezing of <span class="hlt">ice</span> nucleation <span class="hlt">active</span> protein complexes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartmann, S.; Augustin, S.; Clauss, T.; Wex, H.; Šantl-Temkiv, T.; Voigtländer, J.; Niedermeier, D.; Stratmann, F.</p> <p>2013-06-01</p> <p>Utilising the Leipzig Aerosol Cloud Interaction Simulator (LACIS), the immersion freezing behaviour of droplet ensembles containing monodisperse particles, generated from a Snomax™ solution/suspension, was investigated. Thereto <span class="hlt">ice</span> fractions were measured in the temperature range between -5 °C to -38 °C. Snomax™ is an industrial product applied for artificial snow production and contains Pseudomonas syringae} bacteria which have long been used as model organism for atmospheric relevant <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA) bacteria. The <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of such bacteria is controlled by INA protein complexes in their outer membrane. In our experiments, <span class="hlt">ice</span> fractions increased steeply in the temperature range from about -6 °C to about -10 °C and then levelled off at <span class="hlt">ice</span> fractions smaller than one. The plateau implies that not all examined droplets contained an INA protein complex. Assuming the INA protein complexes to be Poisson distributed over the investigated droplet populations, we developed the CHESS model (stoCHastic modEl of similar and poiSSon distributed <span class="hlt">ice</span> nuclei) which allows for the calculation of <span class="hlt">ice</span> fractions as function of temperature and time for a given nucleation rate. Matching calculated and measured <span class="hlt">ice</span> fractions, we determined and parameterised the nucleation rate of INA protein complexes exhibiting class III <span class="hlt">ice</span> nucleation behaviour. Utilising the CHESS model, together with the determined nucleation rate, we compared predictions from the model to experimental data from the literature and found good agreement. We found that (a) the heterogeneous <span class="hlt">ice</span> nucleation rate expression quantifying the <span class="hlt">ice</span> nucleation behaviour of the INA protein complex is capable of describing the <span class="hlt">ice</span> nucleation behaviour observed in various experiments for both, Snomax™ and P. syringae bacteria, (b) the <span class="hlt">ice</span> nucleation rate, and its temperature dependence, seem to be very similar regardless of whether the INA protein complexes inducing <span class="hlt">ice</span> nucleation are attached</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1816263P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1816263P"><span id="translatedtitle">Soot Aerosol Particles as Cloud Condensation Nuclei: from <span class="hlt">Ice</span> Nucleation <span class="hlt">Activity</span> to <span class="hlt">Ice</span> Crystal Morphology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pirim, Claire; Ikhenazene, Raouf; Ortega, Isamel Kenneth; Carpentier, Yvain; Focsa, Cristian; Chazallon, Bertrand; Ouf, François-Xavier</p> <p>2016-04-01</p> <p>Emissions of solid-state particles (soot) from engine exhausts due to incomplete fuel combustion is considered to influence <span class="hlt">ice</span> and liquid water cloud droplet <span class="hlt">activation</span> [1]. The <span class="hlt">activity</span> of these aerosols would originate from their ability to be important centers of <span class="hlt">ice</span>-particle nucleation, as they would promote <span class="hlt">ice</span> formation above water homogeneous freezing point. Soot particles are reported to be generally worse <span class="hlt">ice</span> nuclei than mineral dust because they <span class="hlt">activate</span> nucleation at higher <span class="hlt">ice</span>-supersaturations for deposition nucleation and at lower temperatures for immersion freezing than ratios usually expected for homogeneous nucleation [2]. In fact, there are still numerous opened questions as to whether and how soot's physico-chemical properties (structure, morphology and chemical composition) can influence their nucleation ability. Therefore, systematic investigations of soot aerosol nucleation <span class="hlt">activity</span> via one specific nucleation mode, here deposition nucleation, combined with thorough structural and compositional analyzes are needed in order to establish any association between the particles' <span class="hlt">activity</span> and their physico-chemical properties. In addition, since the morphology of the <span class="hlt">ice</span> crystals can influence their radiative properties [3], we investigated their morphology as they grow over both soot and pristine substrates at different temperatures and humidity ratios. In the present work, Combustion Aerosol STandart soot samples were produced from propane using various experimental conditions. Their nucleation <span class="hlt">activity</span> was studied in deposition mode (from water vapor), and monitored using a temperature-controlled reactor in which the sample's relative humidity is precisely measured with a cryo-hygrometer. Formation of water/<span class="hlt">ice</span> onto the particles is followed both optically and spectroscopically, using a microscope coupled to a Raman spectrometer. Vibrational signatures of hydroxyls (O-H) emerge when the particle becomes hydrated and are used to characterize <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25584435','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25584435"><span id="translatedtitle">Identification of <span class="hlt">ice</span> nucleation <span class="hlt">active</span> sites on feldspar dust particles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zolles, Tobias; Burkart, Julia; Häusler, Thomas; Pummer, Bernhard; Hitzenberger, Regina; Grothe, Hinrich</p> <p>2015-03-19</p> <p>Mineral dusts originating from Earth's crust are known to be important atmospheric <span class="hlt">ice</span> nuclei. In agreement with earlier studies, feldspar was found as the most <span class="hlt">active</span> of the tested natural mineral dusts. Here we investigated in closer detail the reasons for its <span class="hlt">activity</span> and the difference in the <span class="hlt">activity</span> of the different feldspars. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. K-feldspar showed by far the highest <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. Finally, we give a potential explanation of this effect, finding alkali-metal ions having different hydration shells and thus an influence on the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of feldspar surfaces. PMID:25584435</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4368087','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4368087"><span id="translatedtitle">Identification of <span class="hlt">Ice</span> Nucleation <span class="hlt">Active</span> Sites on Feldspar Dust Particles</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2015-01-01</p> <p>Mineral dusts originating from Earth’s crust are known to be important atmospheric <span class="hlt">ice</span> nuclei. In agreement with earlier studies, feldspar was found as the most <span class="hlt">active</span> of the tested natural mineral dusts. Here we investigated in closer detail the reasons for its <span class="hlt">activity</span> and the difference in the <span class="hlt">activity</span> of the different feldspars. Conclusions are drawn from scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, and oil-immersion freezing experiments. K-feldspar showed by far the highest <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. Finally, we give a potential explanation of this effect, finding alkali-metal ions having different hydration shells and thus an influence on the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of feldspar surfaces. PMID:25584435</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22164468','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22164468"><span id="translatedtitle">[The economic <span class="hlt">margins</span> of <span class="hlt">activities</span> of a bovine practitioner on dairy farms].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>van Genugten, A J M; van Haaften, J A; Hogeveen, H</p> <p>2011-11-01</p> <p>Because of lower <span class="hlt">margins</span> and market liberalisation veterinarians and farmers are increasingly negotiating rates. Therefore, the <span class="hlt">margins</span> of veterinarians are under pressure. In addition, the sales if drugs, performance of operations or giving of advice are more and more separated. These developments give veterinarians uncertainty about the profitability of their <span class="hlt">activities</span> for dairy farmers. Not much is known about <span class="hlt">margins</span> on veterinary <span class="hlt">activities</span> on dairy farms. Moreover, it is interesting to see how much <span class="hlt">margins</span> of the bovine practitioner differ between veterinary practises and dairy farms. In this study, invoices for bovine <span class="hlt">activities</span> of 14 veterinary practises were combined with milk production registration data of the dairy farms of these practices. This way, the gross <span class="hlt">margin</span> per bovine practitioner could be studied for the different veterinary practise. Moreover the relation between gross <span class="hlt">margin</span> and specification of the veterinary practise could be studied. Finally, the gross <span class="hlt">margin</span> per dairy farm and the factors that influenced this gross <span class="hlt">margin</span> were studied. The most important result was the observation that the gross <span class="hlt">margin</span> per bovine practitioner was dependent on the number of dairy farms per practitioner, the <span class="hlt">margin</span> on drugs and the region of the veterinary practise. The size of the veterinary practise, the share of the dairy farming within the practise and the source of the gross <span class="hlt">margin</span> (drugs, time or operations) did not influence the gross <span class="hlt">margin</span>. Variables that explained the gross <span class="hlt">margin</span> per dairy farm were, amongst others, the number of dairy cows, the milk production level of the farms and participation in PIR-DAP (a system to support the veterinarians herd health and management program). There is no relation of gross <span class="hlt">margin</span> per dairy farm and the veterinary practise or region. PMID:22164468</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998DSRI...45.1357C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998DSRI...45.1357C"><span id="translatedtitle">Changes in lipid composition of copepods and Euphausia superba associated with diet and environmental conditions in the <span class="hlt">marginal</span> <span class="hlt">ice</span> zone, Bellingshausen Sea, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cripps, G. C.; Hill, H. J.</p> <p>1998-08-01</p> <p>The effect of varying diet and environmental conditions at the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone (MIZ) on the fatty acid and hydrocarbon compositions of five species of copepod and krill, Euphausia superba, was investigated. Zooplankton at the MIZ experienced a range of conditions, from a low algal biomass (mainly flagellates) under pack-<span class="hlt">ice</span> to a spring bloom dominated by diatoms in the open ocean. Principal Component Analysis classified the copepods into three dietary regimes: (i) omnivores or general algal feeders under the pack <span class="hlt">ice</span>, (ii) dinoflagellate feeders, and (iii) diatom feeders in the open ocean. This classification was supported by the distribution of the diatom marker n-heneicosahexaene ( n-C 21:6) and a general indicator of herbivory, the isoprenoid pristane. The fatty acid and hydrocarbon composition reflected dietary preferences and availability as the season progressed. Of the copepods under the pack-<span class="hlt">ice</span>, Oithona spp. was omnivorous whereas Calanus propinquus was feeding preferentially on flagellates. Metridia gerlachei fed on flagellates in all conditions, but also included diatoms in its diet during the bloom. Calanoides acutus and Rhincalanus gigas, which passed the winter in diapause, were feeding almost exclusively on diatoms in the open ocean. Euphausia superba, which were also mainly diatom feeders in the open ocean, were feeding on the sea-<span class="hlt">ice</span> algae (diatoms) and suspended material from the water column (dinoflagellates) under the pack-<span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C43C0565R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C43C0565R"><span id="translatedtitle">Deglaciation of the Western <span class="hlt">Margin</span> of the Barents Sea <span class="hlt">Ice</span> Sheet - a Swath Bathymetric and Sub-Bottom Seismic Study from Eglacom Nice-Streams Data in the Kveithola Trough</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rebesco, M.; Liu, Y.; Camerlenghi, A.; Winsborrow, M. C.; Laberg, J.; Caburlotto, A.; Diviacco, P.; Accettella, D.; Sauli, C.; Wardell, N.</p> <p>2010-12-01</p> <p>IPY <span class="hlt">Activity</span> N. 367 focusing on Neogene <span class="hlt">ice</span> streams and sedimentary processes on high- latitude continental <span class="hlt">margins</span> (NICE-STREAMS) resulted in two coordinated cruises on the adjacent Storfjorden and Kveithola trough-mouth fans in the NW Barents Sea: SVAIS Cruise of BIO Hespérides, summer 2007, and EGLACOM Cruise of Cruise R/V OGS-Explora, summer 2008. The objectives were to acquire a high-resolution set of bathymetric, seismic and sediment core data in order to decipher the Neogene architectural development of the glacially-dominated NW Barents Sea continental <span class="hlt">margin</span> in response to natural climate change. The paleo-<span class="hlt">ice</span> streams drained <span class="hlt">ice</span> from southern Spitsbergen, Spitsbergen Bank, and Bear Island. The short distance from the <span class="hlt">ice</span> source to the calving front produced a short residence time of <span class="hlt">ice</span>, and therefore a rapid response to climatic changes. We describe here the EGLACOM data collected within the Kveithola Trough, an E-W trending glacial trough in the NW Barents Sea, NW of the Bear Island. Swath bathymetry shows that the seafloor is characterised by E-W trending mega-scale glacial lineations (MSGL) that record a fast flowing <span class="hlt">ice</span> stream draining the Svalbard/Barents Sea <span class="hlt">Ice</span> Sheet (SBIS) during the Last Glacial Maximum (LGM). MSGL are overprinted by transverse sediment ridges about 15 km apart which give rise to a staircase axial profile of the trough. Such transverse ridges are interpreted as grounding-zone wedges (GZW) formed by deposition of unconsolidated, saturated subglacial till during episodic <span class="hlt">ice</span> stream retreat. Sub-bottom (CHIRP) and multi-channel reflection seismic data show that present-day morphology is largely inherited from the palaeo-seafloor topography at the time of deposition of the transverse ridges, overlain by a draping glaciomarine unit up to over 15 m thick. Our data allow the reconstruction of depositional processes that accompanied the deglaciation of the Spitsbergen Bank area. The sedimentary drape deposited on top of the GZWs which</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QSRv..146..300W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QSRv..146..300W"><span id="translatedtitle">Sedimentary and structural evolution of a Pleistocene small-scale push moraine in eastern Poland: New insight into paleoenvironmental conditions at the <span class="hlt">margin</span> of an advancing <span class="hlt">ice</span> lobe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Włodarski, Wojciech; Godlewska, Anna</p> <p>2016-08-01</p> <p>Recent studies of push moraines have focused on the interplay between the dynamics of <span class="hlt">ice</span> <span class="hlt">margins</span> and the environmental variables of the foreland into which they advance. These studies showed that the spatial distribution, geometry and style of the glaciotectonic deformation of push moraines are controlled by <span class="hlt">ice</span>-induced stresses, the strain rate, the rheology of the deposits and hydraulic conductivity. In this work, we provide new insight into this interplay at a small spatio-temporal scale, specifically, the ancient glacial system of the Liwiec <span class="hlt">ice</span> lobe within the younger Saalian <span class="hlt">ice</span> sheet in eastern Poland. The paleoenvironmental variables that are analysed here refer to the dynamics of the hydrological processes that affected the patterns and sediment deposition rate on the terminoglacial fan and the resulting mechanical stratigraphy and hydraulic conductivity of the foreland. We document the progradational sequence of the fan deposits that developed as a result of the <span class="hlt">ice</span> lobe thickening and the steepening of its stationary front. The sedimentary features of the fan, the lithology of its basement and the hydraulic conductivity of the foreland strongly influenced the geometry and kinematics of fold growth during the advance of the <span class="hlt">ice</span> lobe. The predominance of flexural slip and the development of fractures, including fold-accommodation faults, were interpreted to be an effect of buckle folding due to horizontal shortening induced by <span class="hlt">ice</span> advance. The partial overriding of the push moraine by the <span class="hlt">ice</span> lobe and, thus, the submarginal conditions for deformation were inferred from the significant hinge migration and internal deformation of the strata under undrained conditions in one of the folds. The synfolding deposition pattern of the fan growth strata allowed us to suggest that the push moraine was probably formed by a sustained advance rather than surge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000101018&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Continental%2BDrift%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000101018&hterms=Continental+Drift&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Continental%2BDrift%2529"><span id="translatedtitle"><span class="hlt">Active</span> Microwave Remote Sensing Observations of Weddell Sea <span class="hlt">Ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Drinkwater, Mark R.</p> <p>1997-01-01</p> <p>Since July 1991, the European Space Agency's ERS-1 and ERS-2 satellites have acquired radar data of the Weddell Sea, Antarctica. The <span class="hlt">Active</span> Microwave Instrument on board ERS has two modes; SAR and Scatterometer. Two receiving stations enable direct downlink and recording of high bit-rate, high resolution SAR image data of this region. When not in an imaging mode, when direct SAR downlink is not possible, or when a receiving station is inoperable, the latter mode allows normalized radar cross-section data to be acquired. These low bit-rate ERS scatterometer data are tape recorded, downlinked and processed off-line. Recent advances in image generation from Scatterometer backscatter measurements enable complementary medium-scale resolution images to be made during periods when SAR images cannot be acquired. Together, these combined C-band microwave image data have for the first time enabled uninterrupted night and day coverage of the Weddell Sea region at both high (25 m) and medium-scale (-20 km) resolutions. C-band ERS-1 radar data are analyzed in conjunction with field data from two simultaneous field experiments in 1992. Satellite radar signature data are compared with shipborne radar data to extract a regional and seasonal signature database for recognition of <span class="hlt">ice</span> types in the images. Performance of automated sea-<span class="hlt">ice</span> tracking algorithms is tested on Antarctic data to evaluate their success. Examples demonstrate that both winter and summer <span class="hlt">ice</span> can be effectively tracked. The kinematics of the main <span class="hlt">ice</span> zones within the Weddell Sea are illustrated, together with the complementary time-dependencies in their radar signatures. Time-series of satellite images are used to illustrate the development of the Weddell Sea <span class="hlt">ice</span> cover from its austral summer minimum (February) to its winter maximum (September). The combination of time-dependent microwave signatures and <span class="hlt">ice</span> dynamics tracking enable various drift regimes to be defined which relate closely to the circulation of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21898102','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21898102"><span id="translatedtitle">Environmental controls on microbial abundance and <span class="hlt">activity</span> on the greenland <span class="hlt">ice</span> sheet: a multivariate analysis approach.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stibal, Marek; Telling, Jon; Cook, Joe; Mak, Ka Man; Hodson, Andy; Anesio, Alexandre M</p> <p>2012-01-01</p> <p>Microbes in supraglacial ecosystems have been proposed to be significant contributors to regional and possibly global carbon cycling, and quantifying the biogeochemical cycling of carbon in glacial ecosystems is of great significance for global carbon flow estimations. Here we present data on microbial abundance and productivity, collected along a transect across the ablation zone of the Greenland <span class="hlt">ice</span> sheet (GrIS) in summer 2010. We analyse the relationships between the physical, chemical and biological variables using multivariate statistical analysis. Concentrations of debris-bound nutrients increased with distance from the <span class="hlt">ice</span> sheet <span class="hlt">margin</span>, as did both cell numbers and <span class="hlt">activity</span> rates before reaching a peak (photosynthesis) or a plateau (respiration, abundance) between 10 and 20 km from the <span class="hlt">margin</span>. The results of productivity measurements suggest an overall net autotrophy on the GrIS and support the proposed role of <span class="hlt">ice</span> sheet ecosystems in carbon cycling as regional sinks of CO(2) and places of production of organic matter that can be a potential source of nutrients for downstream ecosystems. Principal component analysis based on chemical and biological data revealed three clusters of sites, corresponding to three 'glacier ecological zones', confirmed by a redundancy analysis (RDA) using physical data as predictors. RDA using data from the largest 'bare <span class="hlt">ice</span> zone' showed that glacier surface slope, a proxy for melt water flow, accounted for most of the variation in the data. Variation in the chemical data was fully explainable by the determined physical variables. Abundance of phototrophic microbes and their proportion in the community were identified as significant controls of the carbon cycling-related microbial processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813422S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813422S"><span id="translatedtitle"><span class="hlt">Ice</span> Nucleation <span class="hlt">Activity</span> of Various Agricultural Soil Dust Aerosol Particles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schiebel, Thea; Höhler, Kristina; Funk, Roger; Hill, Thomas C. J.; Levin, Ezra J. T.; Nadolny, Jens; Steinke, Isabelle; Suski, Kaitlyn J.; Ullrich, Romy; Wagner, Robert; Weber, Ines; DeMott, Paul J.; Möhler, Ottmar</p> <p>2016-04-01</p> <p>Recent investigations at the cloud simulation chamber AIDA (Aerosol Interactions and Dynamics in the Atmosphere) suggest that agricultural soil dust has an <span class="hlt">ice</span> nucleation ability that is enhanced up to a factor of 10 compared to desert dust, especially at temperatures above -26 °C (Steinke et al., in preparation for submission). This enhancement might be caused by the contribution of very <span class="hlt">ice-active</span> biological particles. In addition, soil dust aerosol particles often contain a considerably higher amount of organic matter compared to desert dust particles. To test agricultural soil dust as a source of <span class="hlt">ice</span> nucleating particles, especially for <span class="hlt">ice</span> formation in warm clouds, we conducted a series of laboratory measurements with different soil dust samples to extend the existing AIDA dataset. The AIDA has a volume of 84 m3 and operates under atmospherically relevant conditions over wide ranges of temperature, pressure and humidity. By controlled adiabatic expansions, the ascent of an air parcel in the troposphere can be simulated. As a supplement to the AIDA facility, we use the INKA (<span class="hlt">Ice</span> Nucleation Instrument of the KArlsruhe Institute of Technology) continuous flow diffusion chamber based on the design by Rogers (1988) to expose the sampled aerosol particles to a continuously increasing saturation ratio by keeping the aerosol temperature constant. For our experiments, soil dust was dry dispersed into the AIDA vessel. First, fast saturation ratio scans at different temperatures were performed with INKA, sampling soil dust aerosol particles directly from the AIDA vessel. Then, we conducted the AIDA expansion experiment starting at a preset temperature. The combination of these two different methods provides a robust data set on the temperature-dependent <span class="hlt">ice</span> <span class="hlt">activity</span> of various agriculture soil dust aerosol particles with a special focus on relatively high temperatures. In addition, to extend the data set, we investigated the role of biological and organic matter in more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19790037323&hterms=ice+nucleation+active&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dice%2Bnucleation%2Bactive','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19790037323&hterms=ice+nucleation+active&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dice%2Bnucleation%2Bactive"><span id="translatedtitle">Rocket effluent - Its <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> and related properties</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parungo, F. P.; Allee, P. A.</p> <p>1978-01-01</p> <p>To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager I and II launches. The aerosol's morphology, concentration and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. <span class="hlt">Ice</span> nucleus concentration was measured with a subfreezing thermal diffusion chamber. The particles' physical and chemical properties were related to their <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce <span class="hlt">active</span> <span class="hlt">ice</span> nuclei. Their consequences for potential inadvertant weather modification demand additional study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790001950','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790001950"><span id="translatedtitle">Rocket effluent: Its <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> and related properties</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Parungo, F. P.; Allee, P. A.</p> <p>1978-01-01</p> <p>To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. <span class="hlt">Ice</span> nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce <span class="hlt">active</span> <span class="hlt">ice</span> nuclei and modify local weather in suitable meteorological conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B31C0568W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B31C0568W"><span id="translatedtitle">The effect of warm summer 2012 on seasonal and annual methane dynamics in adjacent small lakes on the <span class="hlt">ice</span>-free <span class="hlt">margin</span> of Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>White, J. R.; Cadieux, S. B.; Pratt, L. M.</p> <p>2015-12-01</p> <p>In thermally stratified lakes, the greatest annual CH4 emissions typically occur during thermal overturn events. In July of 2012, Greenland experienced significant warming that resulted in substantial melting of the Greenland <span class="hlt">Ice</span> Sheet and enhanced runoff events. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating on lake thermal structure and CH4 dynamics and compare these observations with those from the following year when temperatures were within normal conditions. In this study, we present CH4 concentrations within the water column of 5 adjacent small lakes on the <span class="hlt">ice</span>-free <span class="hlt">margin</span> of Southwest Greenland under open-water and <span class="hlt">ice</span>-covered conditions from 2012-2014. Enhanced warming of the epilimnion in 2012 lead to strong thermal stability and the development of an anoxic hypolimnia in each of the lakes. As a result, mean dissolved CH4 concentrations were significantly (p < 0.0001) greater under open water conditions in 2012 than in 2013. In all of the lakes, mean CH4 concentrations under <span class="hlt">ice</span>-covered conditions were significantly (p < 0.0001) greater than under open-water conditions, suggesting spring overturn may be the period with the largest annual CH4 flux to the atmosphere. As the climate continues to warm, greater heat income and warming of lake surface waters will lead to increased thermal stratification and hypolimnetic anoxia, which will result in increased water column inventories of CH4. Additionally, continual warming will result in shorter <span class="hlt">ice</span> cover durations, which may reduce the winter inventory of CH4 and lead to a decrease in total CH4 flux during <span class="hlt">ice</span>-melt. Taken together, these results indicate that in Arctic lakes, a shortening of winter <span class="hlt">ice</span> cover and increased thermal stratification during open-water conditions will lead to increased CH4 production, higher water column CH4 inventories and greater CH4 emissions at fall overturn.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ACPD...1221321H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ACPD...1221321H&link_type=ABSTRACT"><span id="translatedtitle">Immersion freezing of <span class="hlt">ice</span> nucleating <span class="hlt">active</span> protein complexes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hartmann, S.; Augustin, S.; Clauss, T.; Voigtländer, J.; Niedermeier, D.; Wex, H.; Stratmann, F.</p> <p>2012-08-01</p> <p>Biological particles, e.g. bacteria and their <span class="hlt">Ice</span> Nucleating <span class="hlt">Active</span> (INA) protein complexes, might play an important role for the <span class="hlt">ice</span> formation in atmospheric mixed-phase clouds. Therefore, the immersion freezing behavior of INA protein complexes generated from a SnomaxTM solution/suspension was investigated as function of temperature in a range of -5 °C to -38 °C at the Leipzig Aerosol Cloud Interaction Simulator (LACIS). The immersion freezing of droplets containing small numbers of INA protein complexes occurs in a temperature range of -7 °C and -10 °C. The experiments performed in the lower temperature range, where all droplets freeze which contain at least one INA protein complex, are used to determine the average number of INA protein complexes present, assuming that the INA protein complexes are Poisson distributed over the droplet ensemble. Knowing the average number of INA protein complexes, the heterogeneous <span class="hlt">ice</span> nucleation rate and rate coefficient of a single INA protein complex is determined by using the newly-developed CHESS model (stoCHastic model of idEntical poiSSon distributed <span class="hlt">ice</span> nuclei). Therefore, we assume the <span class="hlt">ice</span> nucleation process to be of stochastic nature, and a parameterization of the INA protein complex's nucleation rate. Analyzing the results of immersion freezing experiments from literature (SnomaxTM and Pseudomonas syringae bacteria), to results gained in this study, demonstrates that first, a similar temperature dependence of the heterogeneous <span class="hlt">ice</span> nucleation rate for a single INA protein complex was found in all experiments, second, the shift of the <span class="hlt">ice</span> fraction curves to higher temperatures can be explained consistently by a higher average number of INA protein complexes being present in the droplet ensemble, and finally the heterogeneous <span class="hlt">ice</span> nucleation rate of one single INA protein complex might be also applicable for intact Pseudomonas syringae bacteria cells. The results obtained in this study allow a new perspective on the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JGR....9522229N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JGR....9522229N"><span id="translatedtitle">Physical and biological oceanographic interaction in the spring bloom at the Bering Sea <span class="hlt">marginal</span> <span class="hlt">ice</span> edge zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niebauer, H. J.; Alexander, Vera; Henrichs, Susan</p> <p>1990-12-01</p> <p>At the edge of the melting sea <span class="hlt">ice</span> pack in the Bering Sea in spring, physical, biological, and chemical oceanographic processes combine to generate a short-lived, intense phytoplankton bloom that is associated with the retreating <span class="hlt">ice</span> edge. The bloom begins a week or so before the first of May triggered by insolation and by the low-salinity meltwater stratification in the presence of high nitrate concentrations (˜ > 25 μM). Meltwater (salinity) stratification delineates <span class="hlt">ice</span> edge blooms from open water blooms where temperature gradients generate the stratification. Five cross-<span class="hlt">ice</span> sections of temperature, salinity, σt, chlorophyll, and nitrate are presented as a time series from April 27 to May 5 illustrating the bloom. Evidence of two separate but concurrent blooms in the <span class="hlt">ice</span> edge zone are presented. In addition, meteorological and oceanographic conditions were observed that should have been conducive to <span class="hlt">ice</span> edge up welling. While significant <span class="hlt">ice</span> and water movement occurred, upwelling was not observed. Finally, the Bering Sea <span class="hlt">ice</span> edge spring bloom is compared with other <span class="hlt">ice</span> edge systems in both hemispheres, showing that initial Bering Sea nitrate concentrations are among the highest observed but quickly become limiting owing to the rapid build up of phytoplankton populations. This primary production is not coupled to the pelagic Zooplankton because Zooplankton are largely absent on account of the cold temperatures. Observed maximum chlorophyll concentrations in the bloom are several times greater than those observed in other systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACP....13.4223M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACP....13.4223M"><span id="translatedtitle">Urediospores of rust fungi are <span class="hlt">ice</span> nucleation <span class="hlt">active</span> at > -10 °C and harbor <span class="hlt">ice</span> nucleation <span class="hlt">active</span> bacteria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, C. E.; Sands, D. C.; Glaux, C.; Samsatly, J.; Asaad, S.; Moukahel, A. R.; Gonçalves, F. L. T.; Bigg, E. K.</p> <p>2013-04-01</p> <p>Various features of the biology of the rust fungi and of the epidemiology of the plant diseases they cause illustrate the important role of rainfall in their life history. Based on this insight we have characterized the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> (INA) of the aerially disseminated spores (urediospores) of this group of fungi. Urediospores of this obligate plant parasite were collected from natural infections of 7 species of weeds in France, from coffee in Brazil and from field and greenhouse-grown wheat in France, the USA, Turkey and Syria. Immersion freezing was used to determine freezing onset temperatures and the abundance of <span class="hlt">ice</span> nuclei in suspensions of washed spores. Microbiological analyses of spores from France, the USA and Brazil, and subsequent tests of the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of the bacteria associated with spores were deployed to quantify the contribution of bacteria to the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of the spores. All samples of spores were <span class="hlt">ice</span> nucleation <span class="hlt">active</span>, having freezing onset temperatures as high as -4 °C. Spores in most of the samples carried cells of <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> strains of the bacterium Pseudomonas syringae (at rates of less than 1 bacterial cell per 100 urediospores), but bacterial INA accounted for only a small fraction of the INA observed in spore suspensions. Changes in the INA of spore suspensions after treatment with lysozyme suggest that the INA of urediospores involves a polysaccharide. Based on data from the literature, we have estimated the concentrations of urediospores in air at cloud height and in rainfall. These quantities are very similar to those reported for other biological <span class="hlt">ice</span> nucleators in these same substrates. However, at cloud level convective <span class="hlt">activity</span> leads to widely varying concentrations of particles of surface origin, so that mean concentrations can underestimate their possible effects on clouds. We propose that spatial and temporal concentrations of biological <span class="hlt">ice</span> nucleators <span class="hlt">active</span> at temperatures > -10 </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000ARep...44..825K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000ARep...44..825K"><span id="translatedtitle">The Nitrate Content of Greenland <span class="hlt">Ice</span> and Solar <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kocharov, G. E.; Kudryavtsev, I. V.; Ogurtsov, M. G.; Sonninen, E.; Jungner, H.</p> <p>2000-12-01</p> <p>Past solar <span class="hlt">activity</span> is studied based on analysis of data on the nitrate content of Greenland <span class="hlt">ice</span> in the period from 1576 1991. Hundred-year (over the entire period) and quasi-five-year (in the middle of the 18th century) variations in the nitrate content are detected. These reflect the secular solar-<span class="hlt">activity</span> cycle and cyclicity in the flare <span class="hlt">activity</span> of the Sun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.P11D..03P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.P11D..03P"><span id="translatedtitle">Refractory Organic Compounds in Enceladus' <span class="hlt">Ice</span> Grains and Hydrothermal <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Postberg, F.; Khawaja, N.; Hsu, H. W.; Sekine, Y.; Shibuya, T.</p> <p>2015-12-01</p> <p>Cassini's Cosmic Dust Analyzer (CDA) generates time-of-flight mass spectra of individual grains impinging on the instruments target-plate. Following the analysis of salt rich <span class="hlt">ice</span> grains emitted by Enceladus that indicated a salt-water ocean in contact with the moon's rocky core [1,2] a recent CDA analysis of nano-phase silica particles pointed at hydrothermal <span class="hlt">activity</span> at the moon's rock/water interface [3]. The results imply temperatures above 80 - 90°C and alkaline pH values around 10 reminiscent of alkaline hydrothermal vents on Earth like the Lost City Hydrothermal Field. In this context the compositional analysis of organic components in CDA mass spectra of the ejected <span class="hlt">ice</span> grains is of particular relevance. A multitude of volatile organic species has already been identified in the gas component of the plume [4]. As expected, we find more complex organic molecules in <span class="hlt">ice</span> grains than in the gas indicating aromatic species, amines, and carbonyl group species. The composition of organic-bearing <span class="hlt">ice</span> grains displays a great diversity indicating a variety of different organic species in varying concentrations. Recent spatially resolved CDA in situ measurements inside Enceladus' plume indicate that these organic compounds are especially frequent in 'young' <span class="hlt">ice</span> grains that have just been ejected by high velocity jets. We investigate the implications of our findings with respect to <span class="hlt">ice</span> grain formation at the water surface and inside the icy vents. We constrain the generation of organic compounds at the rock/water interface in the light of hydrothermal <span class="hlt">activity</span> and the potential for the formation of life precursor molecules in Enceladus' ocean. Ref:[1] Postberg et al., Nature 459, 1098-1101 (2009). [2] Postberg et al., Nature 474, 620-622 (2011). [3]. Hsu, Postberg, Sekine et al., Nature, 519, 207-210 (2015). [4] Waite et al., Nature 460, 487-490 (2009).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C11A0355C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C11A0355C"><span id="translatedtitle">Measurement and parameterization of wave attenuation and scattering in the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone using Sentinel-1 SAR data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Collard, F.; Ardhuin, F.; Guitton, G.; Dumont, D.; Nicot, P.; Accenti, M.; Girard-Ardhuin, F.</p> <p>2014-12-01</p> <p>Sentinel-1A launched by the European Space Agency in April 2014 will complete its full calibration and validation phase including Level2 products early in 2015 but image quality is already good enought for scientific exploitation of observed wave modulations. The larger frequency bandwidth and new acquisition modes are providing a much improved capability for imaging ocean waves in the open water and in the <span class="hlt">ice</span> compared to Envisat. Here we estimate wave spectra in the Arctic assuming a spatially uniform modulation transfer function where the backscatter over <span class="hlt">ice</span> is homogeneous, matching the wave heights in open ocean and <span class="hlt">ice</span> at the <span class="hlt">ice</span> edge. These wave properties are used to estimate attenuation scales for wavelength longer than twice the radar image resolution. These estimated attenuations are compared to model results based on WAVEWATCH III, where attenuation and scattering uses a combination of friction below the <span class="hlt">ice</span> and scattering adapted from Dumont et al. (2011) and Williams et al. (2013).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMED41A0832J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMED41A0832J"><span id="translatedtitle">Comparison of submarine gully morphologies in passive and <span class="hlt">active</span> <span class="hlt">margin</span> settings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackson, C.; Shumaker, L.; Johnstone, S.; Graham, S. A.</p> <p>2015-12-01</p> <p>Passive and <span class="hlt">active</span> tectonic <span class="hlt">margins</span> have inherently different hypsometry, due to local patterns of deformation and subsequent impacts on the style of sedimentation. One way we can analyze and compare the two settings is through observation of submarine gullies, which are small channel features that form along the continental slope as it descends to the ocean floor. By documenting the geometries of gullies that have formed on passive <span class="hlt">margins</span> and gullies that have formed on <span class="hlt">active</span> <span class="hlt">margins</span>, we attempt to distinguish differences in gully morphologies in these two settings. We manually mapped over 600 gullies and interfluves from shaded relief and contour maps generated from bathymetric data across the globe, including the coast of California, the Beaufort Sea, and the Black Sea. We extrapolated and plotted elevation profiles of the gullies along their downslope distance, and compared a range of gully properties, such as length, spacing, and slope, to look at the correlations among those elements of gullies and their tectonic setting. We find that gullies forming on <span class="hlt">active</span> <span class="hlt">margins</span> show the greatest variability in their slopes, exhibiting both the steepest and the shallowest slopes of the dataset. The slopes of the passive <span class="hlt">margin</span> gullies fall within the range of the <span class="hlt">active</span> <span class="hlt">margin</span> gully slopes, but interestingly, we note patterns in the ranges of gully steepness at different localities. These results differ from our our anticipation that <span class="hlt">active</span> <span class="hlt">margin</span> gullies are steeper than passive <span class="hlt">margin</span> gullies, but suggest that gullies in all settings display a variety of morphologies. Additional mapping of <span class="hlt">active</span> <span class="hlt">margin</span> gullies will better determine if there are morphological differences between the two settings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ACP....1210667A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ACP....1210667A"><span id="translatedtitle">Effects of atmospheric conditions on <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of Pseudomonas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Attard, E.; Yang, H.; Delort, A.-M.; Amato, P.; Pöschl, U.; Glaux, C.; Koop, T.; Morris, C. E.</p> <p>2012-11-01</p> <p>Although <span class="hlt">ice</span> nuclei from bacterial origin are known to be efficient at the highest temperatures known for <span class="hlt">ice</span> catalysts, quantitative data are still needed to assess their role in cloud processes. Here we studied the effects of three typical cloud conditions (i) acidic pH (ii) NO2 and O3 exposure and (iii) UV-A exposure on the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> (INA) of four Pseudomonas strains. Three of the Pseudomonas syringae strains were isolated from cloud water and the phyllosphere and Pseudomonas fluorescens strain CGina-01 was isolated from Antarctic glacier <span class="hlt">ice</span> melt. Among the three conditions tested, acidic pH caused the most significant effects on INA likely due to denaturation of the <span class="hlt">ice</span> nucleation protein complex. Exposure to NO2 and O3 gases had no significant or only weak effects on the INA of two P. syringae strains whereas the INA of P. fluorescens CGina-01 was significantly affected. The INA of the third P. syringae strain showed variable responses to NO2 and O3 exposure. These differences in the INA of different Pseudomonas suggest that the response to atmospheric conditions could be strain-specific. After UV-A exposure, a substantial loss of viability of all four strains was observed whereas their INA decreased only slightly. This corroborates the notion that under certain conditions dead bacterial cells can maintain their INA. Overall, the negative effects of the three environmental factors on INA were more significant at the warmer temperatures. Our results suggest that in clouds where temperatures are near 0 °C, the importance of bacterial <span class="hlt">ice</span> nucleation in precipitation processes could be reduced by some environmental factors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ACPD...12.9491A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ACPD...12.9491A"><span id="translatedtitle">Effects of atmospheric conditions on <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of Pseudomonas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Attard, E.; Yang, H.; Delort, A.-M.; Amato, P.; Pöschl, U.; Glaux, C.; Koop, T.; Morris, C. E.</p> <p>2012-04-01</p> <p>Although <span class="hlt">ice</span> nuclei from bacterial origin are known to be efficient at the highest temperatures known for <span class="hlt">ice</span> catalysts, quantitative data are still needed to assess their role in cloud processes. Here we studied the effects of three typical cloud conditions (i) acidic pH (ii) NO2 and O3 exposure and (iii) UV-A exposure on the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> (INA) of four Pseudomonas strains. Three of the Pseudomonas syringae strains were isolated from cloud water and the phyllosphere and Pseudomonas fluorescens strain CGina-01 was isolated from Antarctic glacier <span class="hlt">ice</span> melt. Among the three conditions tested, acidic pH caused the most significant effects on INA likely due to denaturation of the <span class="hlt">ice</span> nucleation protein complex. Exposure to NO2 and O3 gases had no significant or only weak effects on the INA of two P. syringae strains whereas the INA of P. fluorescens CGina-01 was significantly affected. The INA of the third P. syringae strain showed variable responses to NO2 and O3 exposure. These differences in the INA of different Pseudomonas suggest that the response to atmospheric conditions could be strain-specific. After UV-A exposure, a substantial loss of viability of all four strains was observed whereas their INA decreased only slightly. This corroborates the notion that under certain conditions dead bacterial cells can maintain their INA. Overall, the negative effects of the three environmental factors on INA were more significant at the warmer temperatures. Our results suggest that in clouds where temperatures are near 0 °C, the importance of bacterial <span class="hlt">ice</span> nucleation in precipitation processes could be reduced by some environmental factors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009AGUFM.C23A0490D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009AGUFM.C23A0490D&link_type=ABSTRACT"><span id="translatedtitle">Late Pleistocene <span class="hlt">ice</span> <span class="hlt">margin</span> fluctuations in the Nahanni National Park-UNESCO World Heritage Site and their impact on glacial lake formation and architecture of drainage systems across the Yukon-NWT continental divide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duk-Rodkin, A.; Barendregt, R. W.</p> <p>2009-12-01</p> <p>In the late Pleistocene the southern Mackenzie region was glaciated by <span class="hlt">ice</span> masses from a Cordilleran and continental source (Laurentide). Stratigraphic and geomorphologic evidence indicate that the two glaciers occupied this region at different times during the Late Pleistocene. The continental <span class="hlt">ice</span> sheet advanced over the foothills and up major valleys reaching its maximum extent, ca. 30 ka. B. P. This took place when Cordilleran glaciers were in their initial stages of development. The Laurentide <span class="hlt">Ice</span> Sheet blocked the drainage of the South Nahanni River near Virginia Falls, forming a glacial lake which inundated an area of approximately 900 km2 at its maximum stand, and had an outlet to the southwest, across the continental divide into the Yukon Territory and eventually into the Pacific Ocean. Lacustrine sediments at various sites reach thicknesses ranging from 110 to 120 metres, at an elevation of around 700 m. Cordilleran glaciers advanced eastward and approximately 5000 years later blocked this southwestward drainage, rerouting it to the east and north along the Mackenzie Mountain front. The drainage was confined between the mountains and continental <span class="hlt">ice</span> <span class="hlt">margin</span> where it incised major canyons into the limestone bedrock, and produced a spectacular karst landscape, which today forms part of the Nahanni National Park. During the retreat of the Laurentide and advance of Cordilleran glaciers, glacial Lake Nahanni cut an outlet to the east at First Canyon. This outlet drained into a continuous northbound network of <span class="hlt">marginal</span> meltwater channels joining the north-flowing drainage that eventually reached the Arctic Ocean, and during further retreat of the <span class="hlt">ice</span> sheet established the Mackenzie River in its modern location. The presence of Laurentide <span class="hlt">ice</span> in this region is evidenced by large granite boulders carried from the Canadian Shield. Erratics are found up to 100 km west of the mountain front. Neotectonic <span class="hlt">activity</span> in the area is interpreted from exposures such as those</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70027352','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70027352"><span id="translatedtitle">Fault-dominated deformation in an <span class="hlt">ice</span> dam during annual filling and drainage of a <span class="hlt">marginal</span> lake</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Walder, J.S.; Trabant, D.C.; Cunico, M.; Anderson, S.P.; Anderson, R. Scott; Fountain, A.G.; Malm, A.</p> <p>2005-01-01</p> <p><span class="hlt">Ice</span>-dammed Hidden Creek Lake, Alaska, USA, outbursts annually in about 2-3 days. As the lake fills, a wedge of water penetrates beneath the glacier, and the surface of this '<span class="hlt">ice</span> dam' rises; the surface then falls as the lake drains. Detailed optical surveying of the glacier near the lake allows characterization of <span class="hlt">ice</span>-dam deformation. Surface uplift rate is close to the rate of lake-level rise within about 400 m of the lake, then decreases by 90% over about 100 m. Such a steep gradient in uplift rate cannot be explained in terms of <span class="hlt">ice</span>-dam flexure. Moreover, survey targets spanning the zone of steep uplift gradient move relative to one another in a nearly reversible fashion as the lake fills and drains. Evidently, the zone of steep uplift gradient is a fault zone, with the faults penetrating the entire thickness of the <span class="hlt">ice</span> dam. Fault motion is in a reverse sense as the lake fills, but in a normal sense as the lake drains. As the overall fault pattern is the same from year to year, even though <span class="hlt">ice</span> is lost by calving, the faults must be regularly regenerated, probably by linkage of surface and bottom crevasses as <span class="hlt">ice</span> is advected toward the lake basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014BGD....1112697F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014BGD....1112697F"><span id="translatedtitle"><span class="hlt">Ice</span> Nucleation <span class="hlt">Activity</span> in the Widespread Soil Fungus Mortierella alpina</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fröhlich-Nowoisky, J.; Hill, T. C. J.; Pummer, B. G.; Franc, G. D.; Pöschl, U.</p> <p>2014-08-01</p> <p>Biological residues in soil dust are a potentially strong source of atmospheric <span class="hlt">ice</span> nuclei (IN). So far, however, the abundance, diversity, sources, seasonality, and role of biological - in particular, fungal - IN in soil dust have not been characterized. By analysis of the culturable fungi in topsoils, from a range of different land use and ecosystem types in south-east Wyoming, we found <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA) fungi to be both widespread and abundant, particularly in soils with recent inputs of decomposable organic matter. Across all investigated soils, 8% of fungal isolates were INA. All INA isolates initiated freezing at -5 to -6 °C, and belonged to a single zygomycotic species, Mortierella alpina (Mortierellales, Mortierellomycotina). By contrast, the handful of fungal species so far reported as INA all belong within the Ascomycota or Basidiomycota phyla. M. alpina is known to be saprobic, widespread in soil and present in air and rain. Sequencing of the ITS region and the gene for γ-linolenic-elongase revealed four distinct clades, affiliated to different soil types. The IN produced by M. alpina seem to be proteinaceous, <300 kDa in size, and can be easily washed off the mycelium. <span class="hlt">Ice</span> nucleating fungal mycelium will ramify topsoils and probably also release cell-free IN into it. If these IN survive decomposition or are adsorbed onto mineral surfaces, their contribution might accumulate over time, perhaps to be transported with soil dust and influencing its <span class="hlt">ice</span> nucleating properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SedG..332....1V&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SedG..332....1V&link_type=ABSTRACT"><span id="translatedtitle">Geochemical discrimination of siliciclastic sediments from <span class="hlt">active</span> and passive <span class="hlt">margin</span> settings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Verma, Surendra P.; Armstrong-Altrin, John S.</p> <p>2016-03-01</p> <p>Discrimination of <span class="hlt">active</span> and passive <span class="hlt">margins</span> is important from both academic and economic aspects. This can only be successfully achieved, however, if there are major compositional differences among sediments derived from different continental <span class="hlt">margins</span>. A worldwide database of <span class="hlt">active</span> and passive <span class="hlt">margin</span> settings was established from published major and trace element geochemical data of Neogene to Quaternary siliciclastic sediments. These data were used to evaluate the performance of existing discrimination diagrams, which were shown to work unsatisfactorily with success values of mostly between 0% and 30%. Because these diagrams were not based on a statistically coherent methodology, we proposed two new discriminant functions from linear discriminant analysis of multinormally distributed isometric log-transformed ratios of major and combined major and trace elements. These new diagrams showed very high percent success values of about 87%-97% and 84%-86% for the <span class="hlt">active</span> and passive <span class="hlt">margins</span>, respectively, for the original database. Excellent performance of the multidimensional diagrams and related discriminant functions was confirmed from 11 test studies involving Quaternary to Holocene siliciclastic sediments from known tectonic <span class="hlt">margins</span>. The expected result of an <span class="hlt">active</span> or passive <span class="hlt">margin</span> was obtained, with most samples plotting correctly in the respective field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4681458','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4681458"><span id="translatedtitle">Abbot <span class="hlt">Ice</span> Shelf, structure of the Amundsen Sea continental <span class="hlt">margin</span> and the southern boundary of the Bellingshausen Plate seaward of West Antarctica</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cochran, James R; Tinto, Kirsty J; Bell, Robin E</p> <p>2015-01-01</p> <p>Inversion of NASA Operation <span class="hlt">Ice</span>Bridge airborne gravity over the Abbot <span class="hlt">Ice</span> Shelf in West Antarctica for subice bathymetry defines an extensional terrain made up of east-west trending rift basins formed during the early stages of Antarctica/Zealandia rifting. Extension is minor, as rifting jumped north of Thurston Island early in the rifting process. The Amundsen Sea Embayment continental shelf west of the rifted terrain is underlain by a deeper, more extensive sedimentary basin also formed during rifting between Antarctica and Zealandia. A well-defined boundary zone separates the mildly extended Abbot extensional terrain from the deeper Amundsen Embayment shelf basin. The shelf basin has an extension factor, β, of 1.5–1.7 with 80–100 km of extension occurring across an area now 250 km wide. Following this extension, rifting centered north of the present shelf edge and proceeded to continental rupture. Since then, the Amundsen Embayment continental shelf appears to have been tectonically quiescent and shaped by subsidence, sedimentation, and the advance and retreat of the West Antarctic <span class="hlt">Ice</span> Sheet. The Bellingshausen Plate was located seaward of the Amundsen Sea <span class="hlt">margin</span> prior to incorporation into the Antarctic Plate at about 62 Ma. During the latter part of its independent existence, Bellingshausen plate motion had a clockwise rotational component relative to Antarctica producing convergence across the north-south trending Bellingshausen Gravity Anomaly structure at 94°W and compressive deformation on the continental slope between 94°W and 102°W. Farther west, the relative motion was extensional along an east-west trending zone occupied by the Marie Byrd Seamounts. Key Points: Abbot <span class="hlt">Ice</span> Shelf is underlain by E-W rift basins created at ∼90 Ma Amundsen shelf shaped by subsidence, sedimentation, and passage of the <span class="hlt">ice</span> sheet Bellingshausen plate boundary is located near the base of continental slope and rise PMID:26709352</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.T51F2977Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.T51F2977Z"><span id="translatedtitle">Initiation of Extension in South China Continental <span class="hlt">Margin</span> during the <span class="hlt">Active</span>-Passive <span class="hlt">Margin</span> Transition: Thermochronological and Kinematic Constraints</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zuo, X.; Chan, L. S.</p> <p>2015-12-01</p> <p>The South China continental <span class="hlt">margin</span> is characterized by a widespread magmatic belt, prominent NE-striking faults and numerous rifted basins filled by Cretaceous-Eocene sediments. The geology denotes a transition from <span class="hlt">active</span> to passive <span class="hlt">margin</span>, which led to rapid modifications of crustal stress configuration and reactivation of older faults in this area. Our zircon fission-track data in this region show two episodes of exhumation: The first episode, occurring during 170-120Ma, affected local parts of the Nanling Range. The second episode, a more regional exhumation event, occurred during 115-70Ma, including the Yunkai Terrane and the Nanling Range. Numerical geodynamic modeling was conducted to simulate the subduction between the paleo-Pacific plate and the South China Block. The modeling results could explain the fact that exhumation of the granite-dominant Nanling Range occurred earlier than that of the gneiss-dominant Yunkai Terrane. In addition to the difference in rock types, the heat from Jurassic-Early Cretaceous magmatism in Nanling may have softened the upper crust, causing the area to exhume more readily than Yunkai. Numerical modeling results also indicate that (1) high lithospheric geothermal gradient, high slab dip angle and low convergence velocity favor the reversal of crustal stress state from compression to extension in the upper continental plate; (2) late Mesozoic magmatism in South China was probably caused by a slab roll-back; and (3) crustal extension could have occurred prior to the cessation of plate subduction. The inversion of stress regime in the continental crust from compression to crustal extension imply that the Late Cretaceous-early Paleogene red-bed basins in South China could have formed during the late stage of the subduction, accounting for the occurrence of volcanic events in some sedimentary basins. We propose that the rifting started as early as Late Cretaceous, probably before the cessation of subduction process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20100028441&hterms=Ice+Age&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Ice%2BAge%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20100028441&hterms=Ice+Age&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2528Ice%2BAge%2529"><span id="translatedtitle">One-Hundred-km-Scale Basins on Enceladus: Evidence for an <span class="hlt">Active</span> <span class="hlt">Ice</span> Shell</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schenk, Paul M.; McKinnon, William B.</p> <p>2009-01-01</p> <p>Stereo-derived topographic mapping of 50% of Enceladus reveals at least 6 large-scale, ovoid depressions (basins) 90-175 km across and 800-to-1500 m deep and uncorrelated with geologic boundaries. Their shape and scale are inconsistent with impact, geoid deflection, or with dynamically supported topography. Isostatic thinning of Enceladus <span class="hlt">ice</span> shell associated with upwellings (and tidally-driven <span class="hlt">ice</span> melting) can plausibly account for the basins. Thinning implies upwarping of the base of the shell of 10-20 km beneath the depressions, depending on total shell thickness; loss of near-surface porosity due to enhanced heat flow may also contribute to basin lows. Alternatively, the basins may overly cold, inactive, and hence denser <span class="hlt">ice</span>, but thermal isostasy alone requires thermal expansion more consistent with clathrate hydrate than water <span class="hlt">ice</span>. In contrast to the basins, the south polar depression (SPD) is larger (350 wide) and shallower (0.4-to-0.8 km deep) and correlates with the area of tectonic deformation and <span class="hlt">active</span> resurfacing. The SPD also differs in that the floor is relatively flat (i.e., conforms roughly to the global triaxial shape, or geoid) with broad, gently sloping flanks. The relative flatness across the SPD suggests that it is in or near isostatic equilibrium, and underlain by denser material, supporting the polar sea hypothesis of Collins and Goodman. Near flatness is also predicted by a crustal spreading origin for the "tiger stripes (McKinnon and Barr 2007, Barr 2008); the extraordinary, high CIRS heat flows imply half-spreading rates in excess of 10 cm/yr, a very young surface age (250,000 yr), and a rather thin lithosphere (hence modest thermal topography). Topographic rises in places along the outer <span class="hlt">margin</span> of the SPD correlate with parallel ridges and deformation along the edge of the resurfaced terrain, consistent with a compressional, imbricate thrust origin for these ridges, driven by the spreading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMEP11A..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMEP11A..03R"><span id="translatedtitle">Sediment movement and dispersal patterns on the Grand Banks continental shelf and slope were tied to the dynamics of the Laurentide <span class="hlt">ice</span>-sheet <span class="hlt">margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rashid, H.; MacKillop, K.; Piper, D.; Vermooten, M.; Higgins, J.; Marche, B.; Langer, K.; Brockway, B.; Spicer, H. E.; Webb, M. D.; Fournier, E.</p> <p>2015-12-01</p> <p>The expansion and contraction of the late Pleistocene Laurentide <span class="hlt">ice</span>-sheet (LIS) was the crucial determining factor for the geomorphic features and shelf and slope sediment mobility on the eastern Canadian continental <span class="hlt">margin</span>, with abundant mass-transport deposits (MTDs) seaward of <span class="hlt">ice</span> <span class="hlt">margins</span> on the upper slope. Here, we report for the first time sediment failure and mass-transport deposits from the central Grand Banks slope in the Salar and Carson petroleum basins. High-resolution seismic profiles and multibeam bathymetry show numerous sediment failure scarps in 500-1600 m water depth. There is no evidence for an <span class="hlt">ice</span> <span class="hlt">margin</span> on the upper slope younger than MIS 6. Centimeter-scale X-ray fluorescence analysis (XRF), grain size, and oxygen isotope data from piston cores constrain sediment processes over the past 46 ka. Geotechnical measurements including Atterberg limit tests, vane shear measurements and triaxial and multi-stage isotropic consolidation tests allowed us to assess the instability on the continental <span class="hlt">margin</span>. Cores with continuous undisturbed stratigraphy in contourite silty muds show normal downcore increase in bulk density and undrained peak shear strength. Heinrich (H) layers are identifiable by a marked increase in the bulk density, high Ca (ppm), increase in iceberg-rafted debris and lighter δ18O in the polar planktonic foram Neogloboquadrina pachyderma (sinistral): with a few C-14 dates they provide a robust chronology. There is no evidence for significant supply of sediment from the Grand Banks at the last-glacial maximum. Mass-transport deposits (MTD) are marked by variability in the bulk density, undrained shear strength and little variation in bulk density or Ca (ppm) values. The MTD are older than 46 ka on the central Grand Banks slope, whereas younger MTDs are present in southern Flemish Pass. Factor of safety calculations suggest the slope is statically stable up to gradients of 10°, but more intervals of silty mud may fail during earthquake</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007DSRI...54..109H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007DSRI...54..109H"><span id="translatedtitle">Spatial and temporal variations in deep-sea meiofauna assemblages in the <span class="hlt">Marginal</span> <span class="hlt">Ice</span> Zone of the Arctic Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoste, Eveline; Vanhove, Sandra; Schewe, Ingo; Soltwedel, Thomas; Vanreusel, Ann</p> <p>2007-01-01</p> <p>In order to understand the response of the deep-sea meiobenthos to a highly varying, <span class="hlt">ice</span>-edge-related input of phytodetritus, we investigated the abundance and composition of the meiobenthos at the arctic long-term deep-sea station HAUSGARTEN (79°N, 4°E) along a bathymetric transect (1200-5500 m water depth) over 5 consecutive years (from 2000 to 2004) in relation to changes in environmental conditions. Results showed high sediment-bound pigment concentrations (chlorophyll a and degradation products) ranging from 4.5 to 41.6 μg/cm 3, and coinciding high meiobenthic densities ranging from 149±3 to 3409±525 ind/10 cm 2. Nematodes dominated the metazoan meiofaunal communities at every depth and time (85-99% of total meiofauna abundance), followed by harpacticoid copepods (0-4.6% of total meiofauna abundance). The expected pattern of gradually decreasing meiobenthic densities with increasing water depth was not confirmed. Instead, the bathymetric transect could be subdivided into a shallow area with equally high nematode and copepod densities from 1000 to 2000 m water depth (means: 2259±157 Nematoda/10 cm 2, and 50±4 Copepoda/10 cm 2), and a deeper area from 3000 to 5500 m water depth with similar low nematode and copepod densities (means: 595±52 Nematoda/10 cm 2, and 11±2 Copepoda/10 cm 2). Depth-related investigations on the meiobenthos at the HAUSGARTEN site showed a significant correlation between meiobenthos densities, microbial exo-enzymatic <span class="hlt">activity</span> (esterase turnover) and phytodetrital food availability (chlorophyll a and phaeophytines). In time-series investigations, our data showed inter-annual variations in meiofauna abundance. However, no consistent relationship between nematode and copepod densities, and measures for organic matter input were found.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990PalOc...5..921A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990PalOc...5..921A"><span id="translatedtitle">Cryosphere/ocean interactions at the <span class="hlt">margin</span> of the Laurentide <span class="hlt">Ice</span> Sheet during the Younger Dryas Chron: SE Baffin Shelf, northwest Territories</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andrews, J. T.; Evans, L. W.; Williams, K. M.; Briggs, W. M.; Jull, A. J. T.; Erlenkeuser, H.; Hardy, I.</p> <p>1990-12-01</p> <p>Cores HU82-034-057 and HU84-035-008, Resolution Basin, SE Baffin Shelf, contain 200 and 450 cm, respectively, of sediment that spans the Younger Dryas chron. In both cores the interval is bracketed by 14C dates on foraminifera or molluscs. These sites were close to the <span class="hlt">margin</span> of the late Wisconsin (Foxe) <span class="hlt">ice</span> sheet as it flowed toward the Labrador Sea. Prior to 11 ka, both cores record moderate to high accumulations of foraminifera, relatively high del 18O values in planktonic foraminifera, and low values of detrital carbonate. The diatom and percent opal records imply occasional seasonally open water conditions. During part of the Younger Dryas chron both the diatom and opal analyses imply a shutoff of biogenic silica production, suggesting surface water conditions affected by increased sea <span class="hlt">ice</span> and/or reduced nutrients. In addition, the Younger Dryas interval is marked by an increase in coarse sand and detrital carbonate, a decrease in total organic carbon and foraminifera, and high rates of sediment accumulation. The inferred environment during the Younger Dryas is <span class="hlt">ice</span>-proximal. In HU82-034-057, the foraminifera and other data suggest a change in conditions during the middle part of the Younger Dryas chron.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A11B0015D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A11B0015D"><span id="translatedtitle">Biological <span class="hlt">Ice</span> Nucleation <span class="hlt">Activity</span> in Cloud Water (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delort, A.</p> <p>2013-12-01</p> <p><span class="hlt">Ice</span> nucleation <span class="hlt">active</span> (INA) biological particles, in particular microorganisms, were studied in cloud water. Twelve cloud samples were collected over a period of 16 months from the puy de Dôme summit (1465 m, France) using sterile cloud droplet impactors. The samples were characterized through biological (cultures, cell counts) and physico-chemical measurements (pH, ion concentrations, carbon content...), and biological <span class="hlt">ice</span> nuclei were investigated by droplet-freezing assays from -3°C to -13°C. The concentration of total INA particles within this temperature range typically varied from ~1 to ~100 per mL of cloud water; the concentrations of biological IN were several orders of magnitude higher than the values previously reported for precipitations. At -12°C, at least 76% of the IN were biological in origin, i.e. they were inactivated by heating at 95°C, and at temperatures above -8°C only biological material could induce <span class="hlt">ice</span>. By culture, 44 Pseudomonas-like strains of bacteria were isolated from cloud water samples; 16% of them were found INA at the temperature of -8°C and they were identified as Pseudomonas syringae, Xanthomonas sp. and Pseudoxanthomonas sp.. Two strains induced freezing at as warm as -2°C, positioning them among the most <span class="hlt">active</span> <span class="hlt">ice</span> nucleators described so far. We estimated that, in average, 0.18% and more than 1%.of the bacterial cells present in clouds (~104 mL-1) are INA at the temperatures of -8°C and -12°C, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=creep&pg=3&id=ED559864','ERIC'); return false;" href="http://eric.ed.gov/?q=creep&pg=3&id=ED559864"><span id="translatedtitle">No <span class="hlt">Margin</span>, No Mission: Entrepreneurial <span class="hlt">Activities</span> at Three Benedictine Institutions</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gozum, Allan Dural</p> <p>2013-01-01</p> <p>This research adds to the body of scholarly work by addressing the study's primary research question: "What are the different organizational arrangements that enable entrepreneurial <span class="hlt">activities</span> to thrive at Catholic Benedictine colleges and universities where teaching is the primary mission?" The research examined: (1) what these…</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25309807','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25309807"><span id="translatedtitle">Batch Mode <span class="hlt">Active</span> Sampling based on <span class="hlt">Marginal</span> Probability Distribution Matching.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chattopadhyay, Rita; Wang, Zheng; Fan, Wei; Davidson, Ian; Panchanathan, Sethuraman; Ye, Jieping</p> <p>2012-01-01</p> <p><span class="hlt">Active</span> Learning is a machine learning and data mining technique that selects the most informative samples for labeling and uses them as training data; it is especially useful when there are large amount of unlabeled data and labeling them is expensive. Recently, batch-mode <span class="hlt">active</span> learning, where a set of samples are selected concurrently for labeling, based on their collective merit, has attracted a lot of attention. The objective of batch-mode <span class="hlt">active</span> learning is to select a set of informative samples so that a classifier learned on these samples has good generalization performance on the unlabeled data. Most of the existing batch-mode <span class="hlt">active</span> learning methodologies try to achieve this by selecting samples based on varied criteria. In this paper we propose a novel criterion which achieves good generalization performance of a classifier by specifically selecting a set of query samples that minimizes the difference in distribution between the labeled and the unlabeled data, after annotation. We explicitly measure this difference based on all candidate subsets of the unlabeled data and select the best subset. The proposed objective is an NP-hard integer programming optimization problem. We provide two optimization techniques to solve this problem. In the first one, the problem is transformed into a convex quadratic programming problem and in the second method the problem is transformed into a linear programming problem. Our empirical studies using publicly available UCI datasets and a biomedical image dataset demonstrate the effectiveness of the proposed approach in comparison with the state-of-the-art batch-mode <span class="hlt">active</span> learning methods. We also present two extensions of the proposed approach, which incorporate uncertainty of the predicted labels of the unlabeled data and transfer learning in the proposed formulation. Our empirical studies on UCI datasets show that incorporation of uncertainty information improves performance at later iterations while our studies on 20</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFMGC13A1045G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFMGC13A1045G&link_type=ABSTRACT"><span id="translatedtitle">A high altitude paleoclimate record from an <span class="hlt">ice</span> core retrieved at the northern <span class="hlt">margin</span> of the Mediterranean basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gabrielli, P.; Barbante, C.; Carturan, L.; Davis, M. E.; Dalla Fontana, G.; Dreossi, G.; Dinale, R.; Draga, G.; Gabrieli, J.; Kehrwald, N. M.; Mair, V.; Mikhalenko, V.; Oeggl, K.; Schotterer, U.; Seppi, R.; Spolaor, A.; Stenni, B.; Thompson, L. G.; Tonidandel, D.</p> <p>2013-12-01</p> <p>Atmospheric temperatures in the Alps are increasing at twice the global rate and this change may be amplified at the highest elevations. There is a scarcity of paleo-climate information from high altitudes to place this current rapid climate change in a paleo-perspective. The 'Ortles Project' is an international scientific effort gathering institutes from six nations with the primary goal of obtaining a high altitude paleo-climate record in the Mediterranean area. In 2011 four <span class="hlt">ice</span> cores were extracted from Alto dell'Ortles (3859 m, South Tyrol, Italy) the highest glacier in the eastern Alps. This site is located ~30 km away from where the famous ~5.2 kyr old Tyrolean <span class="hlt">Ice</span> Man was discovered emerging from an ablating <span class="hlt">ice</span> field (Hauslabjoch, 3210 m) in 1991. The good state of conservation of this mummy suggested that the current warming trend is unprecedented in South Tyrol during the late Holocene and that unique prehistoric <span class="hlt">ice</span> was still present in this region. During the <span class="hlt">ice</span> core drilling operations we found that the glacier Alto dell'Ortles shows a very unusual thermic behavior as it is transitioning from a cold to a temperate state. In fact, below a 30 meter thick temperate firn portion, we observed cold <span class="hlt">ice</span> layers sitting on a frozen bedrock (-2.8 C). These represent remnants of the colder climate before ~1980 AD, when an instrumental record indicates a ~2 C lower temperature in this area during the period 1864-1980 AD. By analyzing one of the Ortles cores for stable isotopes, dust and major ions, we found an annually preserved climatic signal embedded in the deep cold <span class="hlt">ice</span> of this glacier. Alto dell'Ortles is therefore the first low-accumulation (850 mm w.e. per year) alpine drilling site where both winter and summer layers can be identified. Preliminary annual layer counting and two absolute time markers suggest that the time period covered by the Ortles <span class="hlt">ice</span> cores spans from several centuries to a few millennia. In particular, a Larix (larch) leaf discovered at</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11400053','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11400053"><span id="translatedtitle">Sensitivity of partially purified <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of Fusarium acuminatum SRSF 616.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Humphreys, T L; Castrillo, L A; Lee, M R</p> <p>2001-05-01</p> <p>Factors that affect bacterial <span class="hlt">ice</span> nucleation, including growth medium, growth phase, nutrient deprivation, and cold-temperature exposure, were investigated in the <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA) fungus Fusarium acuminatum SRSF 616. <span class="hlt">Ice</span> nucleation <span class="hlt">activity</span> remained relatively constant throughout the growth cycle, and the cell-free culture supernatant consistently displayed higher <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> than the hyphal pellet. Although nutrient starvation and low-temperature exposure enhance bacterial <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>, reducing the concentration of C, N, or P in synthetischer nährstoffarmer broth (SNB) did not increase fungal <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>, nor did exposure to 4 degrees C or 15 degrees C. From the SNB supernatant, selected INA chromatography fractions were obtained that demonstrated increased sensitivity to proteinase K and heat compared with culture supernatant. We propose that partial purification of the fungal <span class="hlt">ice</span> nuclei resulted in removal of low-molecular-weight stabilizing factors. PMID:11400053</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ACPD...1226143M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ACPD...1226143M"><span id="translatedtitle">Urediospores of Puccinia spp. and other rusts are warm-temperature <span class="hlt">ice</span> nucleators and harbor <span class="hlt">ice</span> nucleation <span class="hlt">active</span> bacteria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morris, C. E.; Sands, D. C.; Glaux, C.; Samsatly, J.; Asaad, S.; Moukahel, A. R.; Gonçalves, F. L. T.; Bigg, E. K.</p> <p>2012-10-01</p> <p>In light of various features of the biology of the rust fungi and of the epidemiology of the plant diseases they cause that illustrate the important role of rainfall in their life history, we have characterized the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> (INA) of the aerially disseminated spores (urediospores) of this group of fungi. Urediospores of this obligate plant parasite were collected from natural infections from 7 species of weeds in France, from coffee in Brazil and from field and greenhouse-grown wheat in France, the USA, Turkey and Syria. Immersion freezing was used to determine freezing onset temperatures and the abundance of <span class="hlt">ice</span> nuclei in suspensions of washed spores. Microbiological analyses of spores and subsequent tests of the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of the bacteria associated with spores were deployed to quantify the contribution of bacteria to the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of the spores. All samples of spores were <span class="hlt">ice</span> nucleation <span class="hlt">active</span> having freezing onset temperatures as warm as -4 °C. Spores in most of the samples carried cells of <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> strains of the bacterium Pseudomonas syringae (at rates of less than 1 bacterial cell per 100 urediospores), but bacterial INA accounted for only a small fraction of the INA observed in spore suspensions. Changes in the INA of spore suspensions after treatment with lysozyme suggest that the INA of urediospores involves a polysaccharide. Based on data from the literature, we have estimated the concentrations of urediospores in air at cloud height and in rainfall. These quantities are very similar to those reported for other biological <span class="hlt">ice</span> nucleators in these same substrates. We suggest that air sampling techniques have ignored the spatial and temporal variability of atmospheric concentrations that occur under conditions propitious for precipitation that could increase their local abundance intermittently. Nevertheless, we propose that the relative low abundance of warm-temperature biological <span class="hlt">ice</span> nucleators in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9976F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9976F"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation <span class="hlt">activity</span> in the widespread soil fungus Mortierella alpina</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fröhlich-Nowoisky, Janine; Hill, Thomas C. J.; Pummer, Bernhard G.; Yordanova, Petya; Franc, Gary D.; Pöschl, Ulrich</p> <p>2015-04-01</p> <p>Biological residues in soil dust are a potentially strong source of atmospheric <span class="hlt">ice</span> nucleators (IN). However, the sources and characteristics of biological - in particular, fungal - IN in soil dust have not been characterized. By analysis of the culturable fungi in topsoils, from a range of different land use and ecosystem types in south-east Wyoming, we found <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA, i.e., inducing <span class="hlt">ice</span> formation in the probed range of temperature and concentration) fungi to be both widespread and abundant, particularly in soils with recent inputs of decomposable organic matter. For example, in harvested and ploughed sugar beet and potato fields, and in the organic horizon beneath Lodgepole pine forest, their relative abundances and concentrations among the cultivable fungi were 25% (8 x 103 CFU g-1), 17% (4.8 x 103 CFU g-1) and 17% (4 x 103 CFU g-1), respectively. Across all investigated soils, 8% (2.9 x 103 CFU g-1) of fungal isolates were INA. All INA isolates initiated freezing at -5° C to -6° C and all belonged to a single zygomycotic species, Mortierella alpina (Mortierellales, Mortierellomycotina). By contrast, the handful of fungal species so far reported as INA all belong within the Ascomycota or Basidiomycota phyla. Mortierella alpina is known to be saprobic (utilizing non-living organic matter), widespread in soil and present in air and rain. Sequencing of the ITS region and the gene for γ-linolenic elongase revealed four distinct clades, affiliated to different soil types. The IN produced by M. alpina seem to be extracellular proteins of 100-300 kDa in size which are not anchored in the fungal cell wall. <span class="hlt">Ice</span> nucleating fungal mycelium will ramify topsoils and probably also release cell-free IN into it. If these IN survive decomposition or are adsorbed onto mineral surfaces, these small cell-free IN might contribute to the as yet uncharacterized pool of atmospheric IN released by soils as dusts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810765K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810765K"><span id="translatedtitle">Evidence for the Late Cenozoic Antarctic <span class="hlt">Ice</span> Sheet evolution and bottom current dynamics in the central-western Ross Sea outer <span class="hlt">margin</span>, Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Sookwan; De Santis, Laura; Kuk Hong, Jong; Cottlerle, Diego; Petronio, Lorenzo; Colizza, Ester; Bergamasco, Andrea; Kim, Young-Gyun; Kang, Seung-Goo; Kim, Hyoungjun; Kim, Suhwan; Wardell, Nigel; Geletti, Riccardo; McKay, Robert; Jin, Young Keun; Kang, Sung-Ho</p> <p>2016-04-01</p> <p>Sedimentary records in polar continental <span class="hlt">margins</span> provide clues for understanding paleo-depositional environments, related to <span class="hlt">ice</span> sheet evolution and bottom-water current dynamics, during times of past climate and global sea level changes. Previous seismostratigraphic studies of the Ross Sea embayment, Antarctica, illustrated its general stratigraphic framework and the distribution of glacial sedimentary features over the continental shelf, since the onset of Antarctic <span class="hlt">ice</span>-sheets at the Eocene-Oligocene boundary (~34.0 Ma). In contrast, there are a fewer studies for the outer continental <span class="hlt">margin</span>, where continuous sedimentary deposits generally preserve the record of past climate cycles with minimum hiatus, comparing to the inner- and mid-continental shelf, where grounding <span class="hlt">ice</span> streams eroded most of the sediments. Here we present a seismostratigraphic analysis of 2-D multichannel seismic reflection profiles, from the Central Basin located in the central-western Ross Sea outer <span class="hlt">margin</span>. A glacial prograding wedge developed at the mouth of the Joides Basin since early-middle Miocene times (RSU4: ~14.0 Ma). And the Central Basin was filled with stacked debris-flow deposits and turbidites. The sediment depocenter shifted from the Central Basin toward the slope in the Pliocene (after RSU2: ~3.3 Ma). Pliocene foreset beds are steep and pinch out at the base of the continental slope. Bottom current controlled sediment drifts well developed since the middle Miocene, along the western slope of the central Basin and on the basement highs These areas are far from the mouth of the Joides trough, where most of the glacial sediment is deposited, and they are also more elevated than the basinal areas, where gravity flow maximum thickness accumulated. Along the western slope of the central Basin and over the basement highs, the signature in the sediments of the action of bottom current reworking and shaping the sea floor can be then clearly recognized. We present the sediment drifts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22406212','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22406212"><span id="translatedtitle">Freezing <span class="hlt">activities</span> of flavonoids in solutions containing different <span class="hlt">ice</span> nucleators.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kuwabara, Chikako; Wang, Donghui; Kasuga, Jun; Fukushi, Yukiharu; Arakawa, Keita; Koyama, Toshie; Inada, Takaaki; Fujikawa, Seizo</p> <p>2012-06-01</p> <p>In this study, we examined the effects on freezing of 26 kinds of flavonoid compounds, which were randomly selected as compounds with structures similar to those of flavonoid compounds existing in deep supercooling xylem parenchyma cells (XPCs) in trees, in solutions containing different kinds of <span class="hlt">ice</span> nucleators, including the <span class="hlt">ice</span> nucleation bacterium (INB) Erwinia ananas, INB Xanthomonas campestris, silver iodide, phloroglucinol and unidentified airborne impurities in buffered Milli-Q water (BMQW). Cumulative freezing spectra were obtained in each solution by cooling 2 μL droplets at 0.2 °C/min by a droplet freezing assay. Freezing temperature of 50% droplets (FT(50)) was obtained from each spectra in a separate analysis with more than 20 droplets and mean FT(50) were obtained from more than five separate analyses using more than 100 droplets in total in each flavonoid. Supercooling-promoting <span class="hlt">activities</span> (SCA) or <span class="hlt">ice</span> nucleation-enhancing <span class="hlt">activities</span> (INA) of these flavonoids were determined by the difference in FT(50) between control solutions without flavonoids and experimental solutions with flavonoids. In mean values, most of the compounds examined exhibited SCA in solutions containing the INB E. ananas, INB X. campestris, silver iodide, and phloroglucinol although the magnitudes of their <span class="hlt">activities</span> were different depending on the <span class="hlt">ice</span> nucleator. In solutions containing the INB E. ananas, 10 compounds exhibited SCAs with significant differences (p<0.05) in the range of 1.4-4.2 °C. In solutions containing silver iodide, 23 compounds exhibited SCAs with significant differences in the range of 2.0-7.1 °C. In solutions containing phloroglucinol, six compounds exhibited SCAs with significant differences in the range of 2.4-3.5 °C. In solutions containing the INB X. campestris, only three compounds exhibited SCAs with significant differences in the range of 0.9-2.3 °C. In solutions containing unidentified airborne impurities (BMQW alone), on the other hand, many</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22406212','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22406212"><span id="translatedtitle">Freezing <span class="hlt">activities</span> of flavonoids in solutions containing different <span class="hlt">ice</span> nucleators.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kuwabara, Chikako; Wang, Donghui; Kasuga, Jun; Fukushi, Yukiharu; Arakawa, Keita; Koyama, Toshie; Inada, Takaaki; Fujikawa, Seizo</p> <p>2012-06-01</p> <p>In this study, we examined the effects on freezing of 26 kinds of flavonoid compounds, which were randomly selected as compounds with structures similar to those of flavonoid compounds existing in deep supercooling xylem parenchyma cells (XPCs) in trees, in solutions containing different kinds of <span class="hlt">ice</span> nucleators, including the <span class="hlt">ice</span> nucleation bacterium (INB) Erwinia ananas, INB Xanthomonas campestris, silver iodide, phloroglucinol and unidentified airborne impurities in buffered Milli-Q water (BMQW). Cumulative freezing spectra were obtained in each solution by cooling 2 μL droplets at 0.2 °C/min by a droplet freezing assay. Freezing temperature of 50% droplets (FT(50)) was obtained from each spectra in a separate analysis with more than 20 droplets and mean FT(50) were obtained from more than five separate analyses using more than 100 droplets in total in each flavonoid. Supercooling-promoting <span class="hlt">activities</span> (SCA) or <span class="hlt">ice</span> nucleation-enhancing <span class="hlt">activities</span> (INA) of these flavonoids were determined by the difference in FT(50) between control solutions without flavonoids and experimental solutions with flavonoids. In mean values, most of the compounds examined exhibited SCA in solutions containing the INB E. ananas, INB X. campestris, silver iodide, and phloroglucinol although the magnitudes of their <span class="hlt">activities</span> were different depending on the <span class="hlt">ice</span> nucleator. In solutions containing the INB E. ananas, 10 compounds exhibited SCAs with significant differences (p<0.05) in the range of 1.4-4.2 °C. In solutions containing silver iodide, 23 compounds exhibited SCAs with significant differences in the range of 2.0-7.1 °C. In solutions containing phloroglucinol, six compounds exhibited SCAs with significant differences in the range of 2.4-3.5 °C. In solutions containing the INB X. campestris, only three compounds exhibited SCAs with significant differences in the range of 0.9-2.3 °C. In solutions containing unidentified airborne impurities (BMQW alone), on the other hand, many</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AtmEn..70..392J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AtmEn..70..392J"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation <span class="hlt">activity</span> of bacteria isolated from cloud water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Joly, Muriel; Attard, Eléonore; Sancelme, Martine; Deguillaume, Laurent; Guilbaud, Caroline; Morris, Cindy E.; Amato, Pierre; Delort, Anne-Marie</p> <p>2013-05-01</p> <p>Some Gamma-Proteobacteria can catalyze <span class="hlt">ice</span> formation thereby potentially contributing to the induction of precipitation in supercooled clouds and subsequently to bacterial deposition. Forty-four bacterial strains from cloud water were screened for their capacity to induce freezing. Seven strains (16%) were <span class="hlt">active</span> at -8 °C or warmer and were identified as Pseudomonas syringae, Xanthomonas spp. and Pseudoxanthomonas sp. Phylogenetic analysis revealed that the P. syringae strains in clouds at the Puy de Dôme belonged to clades that are among the most infrequently detected in the environment, while widespread clades were absent suggesting some extent of selection or unusual biogeography of the bacteria at the sampling site. Three strains induced freezing at -3 °C while the others nucleated <span class="hlt">ice</span> at -4 °C to -6 °C. The freezing profiles revealed that the peaks of <span class="hlt">activity</span> were centered around -3.5 °C, -5 °C and/or -8.5 °C depending on the strain. The frequency of <span class="hlt">ice</span>-nuclei (IN) per cell at -6 °C was generally below 0.5% and reached up to 4.2% in one strain. We estimated that clouds influenced by vegetated areas would carry between less than 1 and ˜500 bacterial IN mL-1 of water <span class="hlt">active</span> between -3 °C and -10 °C depending on the season. These data will contribute to modeling the impact of bacterial IN on precipitation at regional scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24106783','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24106783"><span id="translatedtitle">Improving <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of zein film through layer-by-layer deposition of extracellular <span class="hlt">ice</span> nucleators.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shi, Ke; Yu, Hailong; Lee, Tung-Ching; Huang, Qingrong</p> <p>2013-11-13</p> <p>Zein protein has been of scientific interest in the development of biodegradable functional food packaging. This study aimed at developing a novel zein-based biopolymer film with <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> through layer-by-layer deposition of biogenic <span class="hlt">ice</span> nucleators, that is, extracellular <span class="hlt">ice</span> nucleators (ECINs) isolated from Erwinia herbicola , onto zein film surface. The adsorption behaviors and mechanisms were investigated using quartz crystal microbalance with dissipation monitoring (QCM-D). On unmodified zein surface, the highest ECINs adsorption occurred at pH 5.0; on UV/ozone treated zein surface followed by deposition of poly(diallyldimethylammonium chloride) (PDADMAC) layer, the optimum condition for ECINs adsorption occurred at pH 7.0 and I 0.05 M, where the amount of ECINs adsorbed was also higher than that on unmodified zein surface. QCM-D analyses further revealed a two-step adsorption process on unmodified zein surfaces, compared to a one-step adsorption process on PDADMAC-modified zein surface. Also, significantly, in order to quantify the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of ECINs-coated zein films, an empirical method was developed to correlate the number of <span class="hlt">ice</span> nucleators with the <span class="hlt">ice</span> nucleation temperature measured by differential scanning calorimetry. Calculated using this empirical method, the highest <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of ECINs on ECINs-modified zein film reached 64.1 units/mm(2), which was able to elevate the <span class="hlt">ice</span> nucleation temperature of distilled water from -15.5 °C to -7.3 °C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27227961','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27227961"><span id="translatedtitle"><span class="hlt">Ice-Active</span> Substances from the Infective Juveniles of the Freeze Tolerant Entomopathogenic Nematode, Steinernema feltiae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ali, Farman; Wharton, David A</p> <p>2016-01-01</p> <p>Steinernema feltiae is a moderately freezing tolerant nematode, that can withstand intracellular <span class="hlt">ice</span> formation. We investigated recrystallization inhibition, thermal hysteresis and <span class="hlt">ice</span> nucleation <span class="hlt">activities</span> in the infective juveniles of S. feltiae. Both the splat cooling assay and optical recrystallometry indicate the presence of <span class="hlt">ice</span> <span class="hlt">active</span> substances that inhibit recrystallization in the nematode extract. The substance is relatively heat stable and largely retains the recrystallization inhibition <span class="hlt">activity</span> after heating. No thermal hysteresis <span class="hlt">activity</span> was detected but the extract had a typical hexagonal crystal shape when grown from a single seed crystal and weak <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. An <span class="hlt">ice</span> <span class="hlt">active</span> substance is present in a low concentration, which may be involved in the freezing survival of this species by inhibiting <span class="hlt">ice</span> recrystallization. PMID:27227961</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882034','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4882034"><span id="translatedtitle"><span class="hlt">Ice-Active</span> Substances from the Infective Juveniles of the Freeze Tolerant Entomopathogenic Nematode, Steinernema feltiae</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ali, Farman; Wharton, David A.</p> <p>2016-01-01</p> <p>Steinernema feltiae is a moderately freezing tolerant nematode, that can withstand intracellular <span class="hlt">ice</span> formation. We investigated recrystallization inhibition, thermal hysteresis and <span class="hlt">ice</span> nucleation <span class="hlt">activities</span> in the infective juveniles of S. feltiae. Both the splat cooling assay and optical recrystallometry indicate the presence of <span class="hlt">ice</span> <span class="hlt">active</span> substances that inhibit recrystallization in the nematode extract. The substance is relatively heat stable and largely retains the recrystallization inhibition <span class="hlt">activity</span> after heating. No thermal hysteresis <span class="hlt">activity</span> was detected but the extract had a typical hexagonal crystal shape when grown from a single seed crystal and weak <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. An <span class="hlt">ice</span> <span class="hlt">active</span> substance is present in a low concentration, which may be involved in the freezing survival of this species by inhibiting <span class="hlt">ice</span> recrystallization. PMID:27227961</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C23B0610L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C23B0610L"><span id="translatedtitle">Late glacial and Early Holocene climatic conditions along the <span class="hlt">margin</span> of the Greenland <span class="hlt">Ice</span> Sheet, registered by glacial extents in Milne Land, east Greenland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Levy, L.; Kelly, M. A.; Lowell, T. V.</p> <p>2010-12-01</p> <p> to 10,410 yr, indicating that glacial advances occurred during the late Younger Dryas and early Holocene time. The ELA depression of 3-4°C associated with these advances indicates strong seasonality during this time period. These new ages do not show an influence of 10Be inherited from prior periods of exposure, an issue that has hindered applications of 10Be dating in the region in the past. Thus, these ages demonstrate clear evidence for advances of late glacial and early Holocene cooling that must have also influenced the <span class="hlt">margin</span> of the Greenland <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS23E..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS23E..04C"><span id="translatedtitle">Tracking small mountainous river derived terrestrial organic carbon across the <span class="hlt">active</span> <span class="hlt">margin</span> marine environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Childress, L. B.; Blair, N. E.; Orpin, A. R.</p> <p>2015-12-01</p> <p><span class="hlt">Active</span> <span class="hlt">margins</span> are particularly efficient in the burial of organic carbon due to the close proximity of highland sources to marine sediment sinks and high sediment transport rates. Compared with passive <span class="hlt">margins</span>, <span class="hlt">active</span> <span class="hlt">margins</span> are dominated by small mountainous river systems, and play a unique role in marine and global carbon cycles. Small mountainous rivers drain only approximately 20% of land, but deliver approximately 40% of the fluvial sediment to the global ocean. Unlike large passive <span class="hlt">margin</span> systems where riverine organic carbon is efficiently incinerated on continental shelves, small mountainous river dominated systems are highly effective in the burial and preservation of organic carbon due to the rapid and episodic delivery of organic carbon sourced from vegetation, soil, and rock. To investigate the erosion, transport, and burial of organic carbon in <span class="hlt">active</span> <span class="hlt">margin</span> small mountainous river systems we use the Waipaoa River, New Zealand. The Waipaoa River, and adjacent marine depositional environment, is a system of interest due to a large sediment yield (6800 tons km-2 yr-1) and extensive characterization. Previous studies have considered the biogeochemistry of the watershed and tracked the transport of terrestrially derived sediment and organics to the continental shelf and slope by biogeochemical proxies including stable carbon isotopes, lignin phenols, n-alkanes, and n-fatty acids. In this work we expand the spatial extent of investigation to include deep sea sediments of the Hikurangi Trough. Located in approximately 3000 m water depth 120 km from the mouth of the Waipaoa River, the Hikurangi Trough is the southern extension of the Tonga-Kermadec-Hikurangi subduction system. Piston core sediments collected by the National Institute of Water and Atmospheric Research (NIWA, NZ) in the Hikurangi Trough indicate the presence of terrestrially derived material (lignin phenols), and suggest a continuum of deposition, resuspension, and transport across the <span class="hlt">margin</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6391J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6391J"><span id="translatedtitle">Cenozoic uplift on the West Greenland <span class="hlt">margin</span>: <span class="hlt">active</span> sedimentary basins in quiet Archean terranes.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jess, Scott; Stephenson, Randell; Brown, Roderick</p> <p>2016-04-01</p> <p>The North Atlantic is believed by some authors to have experienced tectonically induced uplift within the Cenozoic. Examination of evidence, onshore and offshore, has been interpreted to imply the presence of kilometre scale uplift across the <span class="hlt">margins</span> of the Barents Sea, North Sea, Baffin Bay and Greenland Sea. Development of topography on the West Greenland <span class="hlt">margin</span> (Baffin Bay), in particular, has been subject to much discussion and dispute. A series of low temperature thermochronological (AFT and AHe) studies onshore and interpretation of seismic architecture offshore have suggested uplift of the entire <span class="hlt">margin</span> totalling ~3km. However, challenges to this work and recent analysis on the opposing <span class="hlt">margin</span> (Baffin Island) have raised questions about the validity of this interpretation. The present work reviews and remodels the thermochronological data from onshore West Greenland with the aim of re-evaluating our understanding of the <span class="hlt">margin</span>'s history. New concepts within the discipline, such as effect of radiation damage on Helium diffusivity, contemporary modelling approaches and denudational mapping are all utilised to investigate alternative interpretations to this <span class="hlt">margins</span> complex post rift evolution. In contrast to earlier studies our new approach indicates slow protracted cooling across much of the region; however, reworked sedimentary samples taken from the Cretaceous Nuussuaq Basin display periods of rapid reheating and cooling. These new models suggest the Nuussuaq Basin experienced a tectonically <span class="hlt">active</span> Cenozoic, while the surrounding Archean basement remained quiet. Faults located within the basin appear to have been reactivated during the Palaeocene and Eocene, a period of well-documented inversion events throughout the North Atlantic, and may have resulted in subaerial kilometre scale uplift. This interpretation of the <span class="hlt">margin</span>'s evolution has wider implications for the treatment of low temperature thermochronological data and the geological history of the North</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930022706&hterms=evidence+climate+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Devidence%2Bclimate%2Bchange','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930022706&hterms=evidence+climate+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Devidence%2Bclimate%2Bchange"><span id="translatedtitle">Aerogeophysical evidence for <span class="hlt">active</span> volcanism beneath the West Antarctic <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blankenship, Donald D.; Bell, Robin E.; Hodge, Steven M.; Brozena, John M.; Behrendt, John C.</p> <p>1993-01-01</p> <p>Although it is widely understood that the collapse of the West Antarctic <span class="hlt">Ice</span> Sheet (WAIS) would cause a global sea-level rise of 6 m, there continues to be considerable debate about the response of this <span class="hlt">ice</span> sheet to climate change. The stability of the WAIS, which is characterized by a bed grounded well below sea level, may depend on geologically controlled conditions at the base, which are independent of climate. <span class="hlt">Ice</span> streams moving up to 750 m/yr disperse material from the interior through to the oceans. As these <span class="hlt">ice</span> streams tend to buffer the reservoir of slow-moving inland <span class="hlt">ice</span> from exposure to oceanic degradation, understanding the <span class="hlt">ice</span>-streaming process is important for evaluating WAIS stability. There is strong evidence that <span class="hlt">ice</span> streams slide on a lubricating layer of water-saturated till. Development of this basal layer requires both water and easily eroded sediments. <span class="hlt">Active</span> lithospheric extension may elevate regional heat flux, increase basal melting, and trigger <span class="hlt">ice</span> streaming. If a geologically defined boundary with a sharp contrast in geothermal flux exists beneath the WAIS, <span class="hlt">ice</span> streams may only be capable of operating as a buffer over a restricted region. Should ocean waters penetrate beyond this boundary, the <span class="hlt">ice</span>-stream buffer would disappear, possibly triggering a collapse of the inland <span class="hlt">ice</span> reservoir. Aerogeophysical evidence for <span class="hlt">active</span> volcanism and elevated heat flux beneath the WAIS near the critical region where <span class="hlt">ice</span> streaming begins is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9801D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9801D"><span id="translatedtitle">Model estimating the effect of <span class="hlt">marginal</span> <span class="hlt">ice</span> zone processes on the phytoplankton primary production and air-sea flux of CO2 in the Barents Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dvornikov, Anton; Sein, Dmitry; Ryabchenko, Vladimir; Gorchakov, Victor; Martjyanov, Stanislav</p> <p>2016-04-01</p> <p>This study is aimed to assess the impact of sea <span class="hlt">ice</span> on the primary production of phytoplankton (PPP) and air-sea CO2 flux in the Barents Sea. To get the estimations, we apply a three-dimensional eco-hydrodynamic model based on the Princeton Ocean Model which includes: 1) a module of sea <span class="hlt">ice</span> with 7 categories, and 2) the 11-component module of marine pelagic ecosystem developed in the St. Petersburg Branch, Institute of Oceanology. The model is driven by atmospheric forcing, prescribed from the reanalysis NCEP / NCAR, and conditions on the open sea boundary, prescribed from the regional model of the atmosphere-ocean-sea <span class="hlt">ice</span>-ocean biogeochemistry, developed at Max Planck Institute for Meteorology, Hamburg. Comparison of the model results for the period 1998-2007 with satellite data showed that the model reproduces the main features of the evolution of the sea surface temperature, seasonal changes in the <span class="hlt">ice</span> extent, surface chlorophyll "a" concentration and PPP in the Barents Sea. Model estimates of the annual PPP for whole sea, APPmod, appeared in 1.5-2.3 times more than similar estimates, APPdata, from satellite data. The main reasons for this discrepancy are: 1) APPdata refers to the open water, while APPmod, to the whole sea area (under the pack <span class="hlt">ice</span> and <span class="hlt">marginal</span> <span class="hlt">ice</span> zone (MIZ) was produced 16 - 38% of PPP); and 2) values of APPdata are underestimated because of the subsurface chlorophyll maximum. During the period 1998-2007, the modelled maximal (in the seasonal cycle) sea <span class="hlt">ice</span> area has decreased by 15%. This reduction was accompanied by an increase in annual PPP of the sea at 54 and 63%, based, respectively, on satellite data and the model for the open water. According to model calculations for the whole sea area, the increase is only 19%. Using a simple 7-component model of oceanic carbon cycle incorporated into the above hydrodynamic model, the CO2 exchange between the atmosphere and sea has been estimated in different conditions. In the absence of biological</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4639768','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4639768"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation <span class="hlt">active</span> particles are efficiently removed by precipitating clouds</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stopelli, Emiliano; Conen, Franz; Morris, Cindy E.; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine</p> <p>2015-01-01</p> <p><span class="hlt">Ice</span> nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of <span class="hlt">ice</span> nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ18O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs <span class="hlt">active</span> at temperatures ≥ −10 °C (INPs−10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs <span class="hlt">active</span> at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space. PMID:26553559</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26553559','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26553559"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation <span class="hlt">active</span> particles are efficiently removed by precipitating clouds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stopelli, Emiliano; Conen, Franz; Morris, Cindy E; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine</p> <p>2015-01-01</p> <p><span class="hlt">Ice</span> nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of <span class="hlt">ice</span> nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ(18)O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs <span class="hlt">active</span> at temperatures ≥ -10 °C (INPs-10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs <span class="hlt">active</span> at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatSR...516433S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatSR...516433S"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation <span class="hlt">active</span> particles are efficiently removed by precipitating clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stopelli, Emiliano; Conen, Franz; Morris, Cindy E.; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine</p> <p>2015-11-01</p> <p><span class="hlt">Ice</span> nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of <span class="hlt">ice</span> nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ18O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs <span class="hlt">active</span> at temperatures ≥ -10 °C (INPs-10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs <span class="hlt">active</span> at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26553559','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26553559"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation <span class="hlt">active</span> particles are efficiently removed by precipitating clouds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stopelli, Emiliano; Conen, Franz; Morris, Cindy E; Herrmann, Erik; Bukowiecki, Nicolas; Alewell, Christine</p> <p>2015-01-01</p> <p><span class="hlt">Ice</span> nucleation in cold clouds is a decisive step in the formation of rain and snow. Observations and modelling suggest that variations in the concentrations of <span class="hlt">ice</span> nucleating particles (INPs) affect timing, location and amount of precipitation. A quantitative description of the abundance and variability of INPs is crucial to assess and predict their influence on precipitation. Here we used the hydrological indicator δ(18)O to derive the fraction of water vapour lost from precipitating clouds and correlated it with the abundance of INPs in freshly fallen snow. Results show that the number of INPs <span class="hlt">active</span> at temperatures ≥ -10 °C (INPs-10) halves for every 10% of vapour lost through precipitation. Particles of similar size (>0.5 μm) halve in number for only every 20% of vapour lost, suggesting effective microphysical processing of INPs during precipitation. We show that INPs <span class="hlt">active</span> at moderate supercooling are rapidly depleted by precipitating clouds, limiting their impact on subsequent rainfall development in time and space. PMID:26553559</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GGG....16.1421C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GGG....16.1421C"><span id="translatedtitle">Abbot <span class="hlt">Ice</span> Shelf, structure of the Amundsen Sea continental <span class="hlt">margin</span> and the southern boundary of the Bellingshausen Plate seaward of West Antarctica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cochran, James R.; Tinto, Kirsty J.; Bell, Robin E.</p> <p>2015-05-01</p> <p>Inversion of NASA Operation <span class="hlt">Ice</span>Bridge airborne gravity over the Abbot <span class="hlt">Ice</span> Shelf in West Antarctica for subice bathymetry defines an extensional terrain made up of east-west trending rift basins formed during the early stages of Antarctica/Zealandia rifting. Extension is minor, as rifting jumped north of Thurston Island early in the rifting process. The Amundsen Sea Embayment continental shelf west of the rifted terrain is underlain by a deeper, more extensive sedimentary basin also formed during rifting between Antarctica and Zealandia. A well-defined boundary zone separates the mildly extended Abbot extensional terrain from the deeper Amundsen Embayment shelf basin. The shelf basin has an extension factor, β, of 1.5-1.7 with 80-100 km of extension occurring across an area now 250 km wide. Following this extension, rifting centered north of the present shelf edge and proceeded to continental rupture. Since then, the Amundsen Embayment continental shelf appears to have been tectonically quiescent and shaped by subsidence, sedimentation, and the advance and retreat of the West Antarctic <span class="hlt">Ice</span> Sheet. The Bellingshausen Plate was located seaward of the Amundsen Sea <span class="hlt">margin</span> prior to incorporation into the Antarctic Plate at about 62 Ma. During the latter part of its independent existence, Bellingshausen plate motion had a clockwise rotational component relative to Antarctica producing convergence across the north-south trending Bellingshausen Gravity Anomaly structure at 94°W and compressive deformation on the continental slope between 94°W and 102°W. Farther west, the relative motion was extensional along an east-west trending zone occupied by the Marie Byrd Seamounts. The copyright line for this article was changed on 5 JUN 2015 after original online publication.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18666500','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18666500"><span id="translatedtitle">Transdental photo-<span class="hlt">activation</span> technique: hardness and <span class="hlt">marginal</span> adaptation of composite restorations using different light sources.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alves, Eliane Bemerguy; Alonso, Roberta Caroline Bruschi; Correr, Gisele Maria; Correr, Américo Bortolazzo; de Moraes, Rafael Ratto; Sinhoreti, Mário Alexandre Coelho; Correr-Sobrinho, Lourenço</p> <p>2008-01-01</p> <p>This study investigated the influence of different light sources associated with a transdental photoactivation technique on the <span class="hlt">marginal</span> adaptation and hardness of composite restorations. Cavities (3 mm wide x 3 mm long x 1.5 mm in deep) were prepared on flattened bovine dentin and filled with Z250 composite (3M ESPE). Nine groups (n=10) were defined according to the curing technique (direct; transdental--photo-<span class="hlt">activation</span> through 1 mm of enamel and 2 mm of dentin; mixed--transdental + direct) and light source (QTH XL2500, 3M ESPE; PAC Apollo 95E, DMD; LED Ultrablue Is, DMC) combination. <span class="hlt">Marginal</span> adaptation was evaluated using a dye staining method, and the percentage of stained <span class="hlt">margins</span> was recorded. Knoop Hardness readings were made across the transversal section of the fillings. Data were submitted to two-way ANOVA and Tukey's test (p< or =0.05). For <span class="hlt">margin</span> analysis, although none of the curing conditions provided perfect adaptation, the mixed technique showed lower gap formation. No significant differences were detected between the transdental and other techniques, and no significant differences were detected among the light sources. For hardness, the direct technique showed slightly greater hardness than the mixed technique. Also, the mixed technique yielded greater hardness than the transdental technique. Among the light sources, the LED showed greater hardness than the PAC; whereas, no significant differences between the QTH and other sources were detected. The mixed technique might improve the <span class="hlt">marginal</span> adaptation of restorations, while not being detrimental to composite hardness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GML....36...81C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GML....36...81C"><span id="translatedtitle">Glaciomarine sedimentation and bottom current <span class="hlt">activity</span> on the north-western and northern continental <span class="hlt">margins</span> of Svalbard during the late Quaternary</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chauhan, Teena; Noormets, Riko; Rasmussen, Tine L.</p> <p>2016-04-01</p> <p>Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea <span class="hlt">Ice</span> Sheet (SBIS) on the depositional environment along the northern Svalbard <span class="hlt">margins</span> are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO3) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current <span class="hlt">activity</span> and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2-1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea <span class="hlt">ice</span> or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard <span class="hlt">margin</span> attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard <span class="hlt">margin</span> suggests that the oceanographic conditions and <span class="hlt">ice</span> sheet processes have exerted first-order control on sediment properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1613705S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1613705S"><span id="translatedtitle">Varying depositional environments across the Oligocene-Miocene boundary and their relevance for East Antarctic <span class="hlt">ice</span> sheet history: IODP Site U1356, Wilkes Land <span class="hlt">margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salabarnada, Ariadna; Escutia, Carlota; Nelson, Hans; Damuth, John E.; Brinkhuis, Henk</p> <p>2014-05-01</p> <p>IODP Expedition 318 drilled seven sites in two transects across the Wilkes Land (WL) <span class="hlt">margin</span> of Antarctica. The objective was to obtain a long-term record of the Cenozoic Antarctic glaciation in response to climatic changes, including major transitions. Our work focuses on the study of nearly 300 meters of Oligocene-early Miocene sediments from Site 1356 (cores 42R to 72R) located on a channel levee in the lower continental rise. Shipboard core descriptions reported these sediments to consist of strongly bioturbated claystone and calcareous claystone with Zoophycos or Nereites ichnofacies. Subordinate lithofacies include: 1) laminated silty claystones, 2) convoluted claystones, sandstones and conglomerates; 3) mudstones and sandstones, with a few dispersed to common clasts; and 4) graded or cross-laminated siltstones and sandstones. Based on our study of facies associations in the cores, we differentiate 3 major sedimentary phases, representing important changes in the depositional environments off the WL <span class="hlt">margin</span>. During the early-late Oligocene, sediments record deposition in a deep-water setting, with bottom currents reworking hemipelagic sediments. Late Oligocene sedimentary processes are dominated by successive fine- to coarse-grained debris-flow mass transport deposits. In the early Miocene, turbidites and hemipelagic sedimentation, characteristic of levee deposition, dominate. With this interpretation of sedimentary environments, plus the correlation between Site U1356 and seismic reflection profiles at the site and vicinity, we can begin to link the relation between along-slope and down-slope processes to the evolution of the East Antarctic <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pet.hw.ac.uk/icgh7/programme.html','USGSPUBS'); return false;" href="http://www.pet.hw.ac.uk/icgh7/programme.html"><span id="translatedtitle">Evidence and biogeochemical implications for glacially-derived sediments in an <span class="hlt">active</span> <span class="hlt">margin</span> cold seep</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pohlman, John W.; Riedel, Michael; Novosel, Ivana; Bauer, James E.; Canuel, Elizabeth A.; Paull, Charles K.; Coffin, Richard B.; Grabowski, Kenneth S.; Knies, David L.; Hyndman, Roy D.; Spence, George D.</p> <p>2011-01-01</p> <p>Delineating sediment organic matter origins and sediment accumulation rates at gas hydratebearing and hydrocarbon seeps is complicated by the microbial transfer of 13C-depleted and 14Cdepleted methane carbon into sedimentary pools. Sediment 13C and 14C measurements from four cores recovered at Bullseye vent on the northern Cascadia <span class="hlt">margin</span> are used to identify methane carbon assimilation into different carbon pools. While the total organic carbon (TOC) is mostly unaltered and primarily terrigenous in origin, planktonic foraminifera and the bulk carbonate display evidence of methane overprinting. Mass balance models are applied to determine the extent to which methane overprinting increased the radiocarbon ages of the biogenic foraminifera. The corrected and calibrated foraminifera ages between sediment depths of 70 and 573 cm are from 14.9 to 15.9 ka BP, which coincides with the retreat of the late Quaternary Cordilleran <span class="hlt">Ice</span> Sheet from Vancouver Island. Uniform TOC _13C values of -24.5 ± 0.5‰ from the upper 8 meters of sediment at Bullseye vent suggest all cored material is Pleistocene-derived glacimarine material deposited as the <span class="hlt">ice</span> edge retreated landward. Bullseye vent is located within an uplifted sediment block isolated from turbidite deposition and has been a site of non-deposition since the <span class="hlt">ice</span> sheet retreated from the shelf. Biogeochemical implications of seep sediments being dominated by aged, organic-poor (<0.4 wt% TOC) material are that methane is the primary energy source, and microbes directly and indirectly associated with the anaerobic oxidation of methane (AOM) will dominate the seep microbial community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.B54B..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.B54B..06M"><span id="translatedtitle">Microbial <span class="hlt">activity</span> in debris-rich basal <span class="hlt">ice</span>; adaption to sub-zero, saline conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montross, S. N.; Skidmore, M. L.; Christner, B. C.; Griggs, R.; Tison, J.; Sowers, T. A.</p> <p>2011-12-01</p> <p>Polycrystalline <span class="hlt">ice</span> in glaciers and <span class="hlt">ice</span> sheets has a high preservation potential for biological material and chemical compounds that can be used to document the presence of <span class="hlt">active</span> microbial metabolism at sub-zero temperatures. The concentration and isotopic composition of gases, in conjunction with other aqueous chemical species in debris-rich basal glacier <span class="hlt">ice</span> from Taylor Glacier, Antarctica were used as direct evidence that cells entrained in the <span class="hlt">ice</span> remain metabolically <span class="hlt">active</span> at temperatures as low as -17°C, likely in thin films of liquid water along <span class="hlt">ice</span> crystal and mineral grain boundaries. δ18O2 and δ13CO2 values measured in the <span class="hlt">ice</span> are consistent with the hypothesis that abrupt changes measured in O2 and CO2 concentrations between debris-rich and debris-poor <span class="hlt">ice</span> are due to in situ microbial mineralization of organic carbon. Low temperature culture-based experiments conducted using organisms isolated from the <span class="hlt">ice</span> indicate the ability to respire organic carbon to CO2 under oxic conditions and under anoxic conditions couple carbon mineralization to dissimilatory iron reduction using Fe3+ as an electron acceptor. Microorganisms that are <span class="hlt">active</span> in the debris-rich basal <span class="hlt">ice</span> layers in terrestrial polar <span class="hlt">ice</span> masses need to be adapted to surviving subzero temperatures and saline conditions on extended timescales. Thus these terrestrial glacial systems and the isotopic and geochemical biomarkers therein provide good analogues for guiding exploration and analysis of debris-rich <span class="hlt">ices</span> in extraterrestrial settings, for example, on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1818434P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1818434P"><span id="translatedtitle">A new model for the development of the <span class="hlt">active</span> Afar volcanic <span class="hlt">margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pik, Raphaël; Stab, Martin; Bellahsen, Nicolas; Leroy, Sylvie</p> <p>2016-04-01</p> <p>Volcanic passive <span class="hlt">margins</span>, that represent more than the three quarters of continental <span class="hlt">margins</span> worldwide, are privileged witnesses of the lithospheric extension processes thatform new oceanic basins. They are characterized by voluminous amounts of underplated, intruded and extruded magmas, under the form of massive lavas prisms (seaward-dipping reflectors, or SDR) during the course of thinning and stretching of the lithosphere, that eventually form the ocean-continent transition. The origin and mechanisms of formation of these objects are still largely debated today. We have focussed our attention in the last few years on the Afar volcanic province which represents an <span class="hlt">active</span> analogue of such volcanic <span class="hlt">margins</span>. We explored the structural and temporal relationships that exist between the development of the major thinning and stretching structures and the magmatic production in Central Afar. Conjugate precise fieldwork analysis along with lavas geochronology allowed us to revisit the timing and style of the rift formation, since the early syn-rift period of time in the W-Afar <span class="hlt">marginal</span> area to present days. Extension is primarily accommodated over a wide area at the surface since the very initial periods of extension (~ 25 Ma) following the emplacement of Oligocene CFBs. We propose in our reconstruction of central Afar <span class="hlt">margin</span> history that extension has been associated with important volumes of underplated mafic material that compensate crustal thinning. This has been facilitated by major crustal-scale detachments that help localize the thinning and underplating at depth. In line with this 'magmatic wide-rift' mode of extension, we demonstrate that episodic extension steps alternate with more protracted magmatic phases. The production of syn-rift massive flood basalts (~ 4 Ma) occurs after early thinning of both the crust and the lithosphere, which suggests that SDR formation, is controlled by previous tectonic event. We determined how the melting regime evolved in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5282N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5282N"><span id="translatedtitle">Can we define an asymptotic value for the <span class="hlt">ice</span> <span class="hlt">active</span> surface site density for heterogeneous <span class="hlt">ice</span> nucleation?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niedermeier, Dennis; Augustin-Bauditz, Stefanie; Hartmann, Susan; Wex, Heike; Ignatius, Karoliina; Stratmann, Frank</p> <p>2015-04-01</p> <p>The formation of <span class="hlt">ice</span> in atmospheric clouds has a substantial influence on the radiative properties of clouds as well as on the formation of precipitation. Therefore much effort has been made to understand and quantify the major <span class="hlt">ice</span> formation processes in clouds. Immersion freezing has been suggested to be a dominant primary <span class="hlt">ice</span> formation process in low and mid-level clouds (mixed-phase cloud conditions). It also has been shown that mineral dust particles are the most abundant <span class="hlt">ice</span> nucleating particles in the atmosphere and thus may play an important role for atmospheric <span class="hlt">ice</span> nucleation (Murray et al., 2012). Additionally, biological particles like bacteria and pollen are suggested to be potentially involved in atmospheric <span class="hlt">ice</span> formation, at least on a regional scale (Murray et al., 2012). In recent studies for biological particles (SNOMAX and birch pollen), it has been demonstrated that freezing is induced by <span class="hlt">ice</span> nucleating macromolecules and that an asymptotic value for the mass density of these <span class="hlt">ice</span> nucleating macromolecules can be determined (Hartmann et al., 2013; Augustin et al., 2013, Wex et al., 2014). The question arises whether such an asymptotic value can also be determined for the <span class="hlt">ice</span> <span class="hlt">active</span> surface site density ns, a parameter which is commonly used to describe the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of e.g., mineral dust. Such an asymptotic value for ns could be an important input parameter for atmospheric modeling applications. In the presented study, we therefore investigated the immersion freezing behavior of droplets containing size-segregated, monodisperse feldspar particles utilizing the Leipzig Aerosol Cloud Interaction Simulator (LACIS). For all particle sizes considered in the experiments, we observed a leveling off of the frozen droplet fraction reaching a plateau within the heterogeneous freezing temperature regime (T > -38°C) which was proportional to the particle surface area. Based on these findings, we could determine an asymptotic value for the <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23197526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23197526"><span id="translatedtitle"><span class="hlt">Ice</span>-sheet response to oceanic forcing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Joughin, Ian; Alley, Richard B; Holland, David M</p> <p>2012-11-30</p> <p>The <span class="hlt">ice</span> sheets of Greenland and Antarctica are losing <span class="hlt">ice</span> at accelerating rates, much of which is a response to oceanic forcing, especially of the floating <span class="hlt">ice</span> shelves. Recent observations establish a clear correspondence between the increased delivery of oceanic heat to the <span class="hlt">ice</span>-sheet <span class="hlt">margin</span> and increased <span class="hlt">ice</span> loss. In Antarctica, most of these processes are reasonably well understood but have not been rigorously quantified. In Greenland, an understanding of the processes by which warmer ocean temperatures drive the observed retreat remains elusive. Experiments designed to identify the relevant processes are confounded by the logistical difficulties of instrumenting <span class="hlt">ice</span>-choked fjords with <span class="hlt">actively</span> calving glaciers. For both <span class="hlt">ice</span> sheets, multiple challenges remain before the fully coupled <span class="hlt">ice</span>-ocean-atmosphere models needed for rigorous sea-level projection are available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22472363','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22472363"><span id="translatedtitle">Neutrinos in <span class="hlt">Ice</span>Cube from <span class="hlt">active</span> galactic nuclei</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kalashev, O.; Semikoz, D.; Tkachev, I.</p> <p>2015-03-15</p> <p>Recently, the <span class="hlt">Ice</span>Cube collaboration reported first evidence for the astrophysical neutrinos. Observation corresponds to the total astrophysical neutrino flux of the order of 3 × 10{sup −8} GeV cm{sup −2} s{sup −1} sr{sup −1} in a PeV energy range [1]. <span class="hlt">Active</span> galactic nuclei (AGN) are natural candidate sources for such neutrinos. To model the neutrino creation in AGNs, we study photopion production processes on the radiation field of the Shakura-Sunyaev accretion discs in the black hole vicinity. We show that this model can explain the detected neutrino flux and at the same time avoids the existing constraints from the gamma-ray and cosmic-ray observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011TRACE..11..101A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011TRACE..11..101A"><span id="translatedtitle">Application of <span class="hlt">Ice</span> Nucleation - <span class="hlt">Active</span> Bacteria to Food</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arai, Soichi; Watanabe, Michiko</p> <p></p> <p><span class="hlt">Ice</span> nucleation-<span class="hlt">active</span> bacteria act as nuclei and are able to freeze water without supercooling to a great degree. They are known as a major cause of the frost damage to crops. We have been trying with success to positively apply these bacteria to freeze texturing of food materials, freeze concentration of fresh liquid foods, formation of new physical properties of foods by freezing, and so forth. The most useful species for these applications is Xanthomonas campestris which has recently been designated as a food additive by the Japan Ministry of Health and Welfare and produced on an industrial scale. This paper reviews these topics, with some practical examples quoted primarily from our studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026696','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026696"><span id="translatedtitle">Glacier <span class="hlt">ice</span> mass fluctuations and fault instability in tectonically <span class="hlt">active</span> Southern Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Sauber, J.M.; Molnia, B.F.</p> <p>2004-01-01</p> <p> change during the 1899-1979 time period to calculate the change in the fault stability <span class="hlt">margin</span> (FSM) prior to the 1979 St. Elias earthquake. Our results suggest that a cumulative decrease in the fault stability <span class="hlt">margin</span> at seismogenic depths, due to <span class="hlt">ice</span> wastage over 80 years, was large, up to ???2 MPa. <span class="hlt">Ice</span> wastage would promote thrust faulting in events such as the 1979 earthquake and subsequent aftershocks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27348980','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27348980"><span id="translatedtitle">Microbial Contamination of <span class="hlt">Ice</span> Machines Is Mediated by <span class="hlt">Activated</span> Charcoal Filtration Systems in a City Hospital.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yorioka, Katsuhiro; Oie, Shigeharu; Hayashi, Koji; Kimoto, Hiroo; Furukawa, Hiroyuki</p> <p>2016-06-01</p> <p>Although microbial contamination of <span class="hlt">ice</span> machines has been reported, no previous study has addressed microbial contamination of <span class="hlt">ice</span> produced by machines equipped with <span class="hlt">activated</span> charcoal (AC) filters in hospitals. The aim of this study was to provide clinical data for evaluating AC filters to prevent microbial contamination of <span class="hlt">ice</span>. We compared microbial contamination in <span class="hlt">ice</span> samples produced by machines with (n = 20) and without an AC filter (n = 40) in Shunan City Shinnanyo Municipal Hospital. All samples from the <span class="hlt">ice</span> machine equipped with an AC filter contained 10-116 CFUs/g of glucose nonfermenting gram-negative bacteria such as Pseudomonas aeruginosa and Chryseobacterium meningosepticum. No microorganisms were detected in samples from <span class="hlt">ice</span> machines without AC filters. After the AC filter was removed from the <span class="hlt">ice</span> machine that tested positive for Gram-negative bacteria, the <span class="hlt">ice</span> was resampled (n = 20). Analysis found no contaminants. <span class="hlt">Ice</span> machines equipped with AC filters pose a serious risk factor for <span class="hlt">ice</span> contamination. New filter-use guidelines and regulations on bacterial detection limits to prevent contamination of <span class="hlt">ice</span> in healthcare facilities are necessary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27348980','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27348980"><span id="translatedtitle">Microbial Contamination of <span class="hlt">Ice</span> Machines Is Mediated by <span class="hlt">Activated</span> Charcoal Filtration Systems in a City Hospital.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yorioka, Katsuhiro; Oie, Shigeharu; Hayashi, Koji; Kimoto, Hiroo; Furukawa, Hiroyuki</p> <p>2016-06-01</p> <p>Although microbial contamination of <span class="hlt">ice</span> machines has been reported, no previous study has addressed microbial contamination of <span class="hlt">ice</span> produced by machines equipped with <span class="hlt">activated</span> charcoal (AC) filters in hospitals. The aim of this study was to provide clinical data for evaluating AC filters to prevent microbial contamination of <span class="hlt">ice</span>. We compared microbial contamination in <span class="hlt">ice</span> samples produced by machines with (n = 20) and without an AC filter (n = 40) in Shunan City Shinnanyo Municipal Hospital. All samples from the <span class="hlt">ice</span> machine equipped with an AC filter contained 10-116 CFUs/g of glucose nonfermenting gram-negative bacteria such as Pseudomonas aeruginosa and Chryseobacterium meningosepticum. No microorganisms were detected in samples from <span class="hlt">ice</span> machines without AC filters. After the AC filter was removed from the <span class="hlt">ice</span> machine that tested positive for Gram-negative bacteria, the <span class="hlt">ice</span> was resampled (n = 20). Analysis found no contaminants. <span class="hlt">Ice</span> machines equipped with AC filters pose a serious risk factor for <span class="hlt">ice</span> contamination. New filter-use guidelines and regulations on bacterial detection limits to prevent contamination of <span class="hlt">ice</span> in healthcare facilities are necessary. PMID:27348980</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70012725','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70012725"><span id="translatedtitle">Comparison of marine gas hydrates in sediments of an <span class="hlt">active</span> and passive continental <span class="hlt">margin</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kvenvolden, K.A.</p> <p>1985-01-01</p> <p>Two sites of the Deep Sea Drilling Project in contrasting geologic settings provide a basis for comparison of the geochemical conditions associated with marine gas hydrates in continental <span class="hlt">margin</span> sediments. Site 533 is located at 3191 m water depth on a spit-like extension of the continental rise on a passive <span class="hlt">margin</span> in the Atlantic Ocean. Site 568, at 2031 m water depth, is in upper slope sediment of an <span class="hlt">active</span> accretionary <span class="hlt">margin</span> in the Pacific Ocean. Both sites are characterized by high rates of sedimentation, and the organic carbon contents of these sediments generally exceed 0.5%. Anomalous seismic reflections that transgress sedimentary structures and parallel the seafloor, suggested the presence of gas hydrates at both sites, and, during coring, small samples of gas hydrate were recovered at subbottom depths of 238m (Site 533) and 404 m (Site 568). The principal gaseous components of the gas hydrates wer methane, ethane, and CO2. Residual methane in sediments at both sites usually exceeded 10 mll-1 of wet sediment. Carbon isotopic compositions of methane, CO2, and ??CO2 followed parallel trends with depth, suggesting that methane formed mainly as a result of biological reduction of oxidized carbon. Salinity of pore waters decreased with depth, a likely result of gas hydrate formation. These geochemical characteristics define some of the conditions associated with the occurrence of gas hydrates formed by in situ processes in continental <span class="hlt">margin</span> sediments. ?? 1984.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4096504','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4096504"><span id="translatedtitle">Chinese Wild-Growing Vitis amurensis <span class="hlt">ICE</span>1 and <span class="hlt">ICE</span>2 Encode MYC-Type bHLH Transcription <span class="hlt">Activators</span> that Regulate Cold Tolerance in Arabidopsis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xu, Weirong; Jiao, Yuntong; Li, Ruimin; Zhang, Ningbo; Xiao, Dongming; Ding, Xiaoling; Wang, Zhenping</p> <p>2014-01-01</p> <p>Winter hardiness is an important trait for grapevine breeders and producers, so identification of the regulatory mechanisms involved in cold acclimation is of great potential value. The work presented here involves the identification of two grapevine <span class="hlt">ICE</span> gene homologs, Va<span class="hlt">ICE</span>1 and Va<span class="hlt">ICE</span>2, from an extremely cold-tolerant accession of Chinese wild-growing Vitis amurnensis, which are phylogenetically related to other plant <span class="hlt">ICE</span>1 genes. These two structurally different <span class="hlt">ICE</span> proteins contain previously reported <span class="hlt">ICE</span>-specific amino acid motifs, the bHLH-ZIP domain and the S-rich motif. Expression analysis revealed that Va<span class="hlt">ICE</span>1 is constitutively expressed but affected by cold stress, unlike Va<span class="hlt">ICE</span>2 that shows not such changed expression as a consequence of cold treatment. Both genes serve as transcription factors, potentiating the transactivation <span class="hlt">activities</span> in yeasts and the corresponding proteins localized to the nucleus following transient expression in onion epidermal cells. Overexpression of either Va<span class="hlt">ICE</span>1 or Va<span class="hlt">ICE</span>2 in Arabidopsis increase freezing tolerance in nonacclimated plants. Moreover, we show that they result in multiple biochemical changes that were associated with cold acclimation: Va<span class="hlt">ICE</span>1/2-overexpressing plants had evaluated levels of proline, reduced contents of malondialdehyde (MDA) and decreased levels of electrolyte leakage. The expression of downstream cold responsive genes of CBF1, COR15A, and COR47 were significantly induced in Arabidopsis transgenically overexpressing Va<span class="hlt">ICE</span>1 or Va<span class="hlt">ICE</span>2 upon cold stress. Va<span class="hlt">ICE</span>2, but not Va<span class="hlt">ICE</span>1 overexpression induced KIN1 expression under cold-acclimation conditions. Our results suggest that Va<span class="hlt">ICE</span>1 and Va<span class="hlt">ICE</span>2 act as key regulators at an early step in the transcriptional cascade controlling freezing tolerance, and modulate the expression levels of various low-temperature associated genes involved in the C-repeat binding factor (CBF) pathway. PMID:25019620</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22519974','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22519974"><span id="translatedtitle">Life at the wedge: the <span class="hlt">activity</span> and diversity of arctic <span class="hlt">ice</span> wedge microbial communities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wilhelm, Roland C; Radtke, Kristin J; Mykytczuk, Nadia C S; Greer, Charles W; Whyte, Lyle G</p> <p>2012-04-01</p> <p>The discovery of polygonal terrain on Mars underlain by <span class="hlt">ice</span> heightens interest in the possibility that this water-bearing habitat may be, or may have been, a suitable habitat for extant life. The possibility is supported by the recurring detection of terrestrial microorganisms in subsurface <span class="hlt">ice</span> environments, such as <span class="hlt">ice</span> wedges found beneath tundra polygon features. A characterization of the microbial community of <span class="hlt">ice</span> wedges from the high Arctic was performed to determine whether this <span class="hlt">ice</span> environment can sustain <span class="hlt">actively</span> respiring microorganisms and to assess the ecology of this extreme niche. We found that <span class="hlt">ice</span> wedge samples contained a relatively abundant number of culturable cells compared to other <span class="hlt">ice</span> habitats (∼10(5) CFU·mL(-1)). Respiration assays in which radio-labeled acetate and in situ measurement of CO(2) flux were used suggested low levels of microbial <span class="hlt">activity</span>, though more sensitive techniques are required to confirm these findings. Based on 16S rRNA gene pyrosequencing, bacterial and archaeal <span class="hlt">ice</span> wedge communities appeared to reflect surrounding soil communities. Two Pseudomonas sp. were the most abundant taxa in the <span class="hlt">ice</span> wedge bacterial library (∼50%), while taxa related to ammonia-oxidizing Thaumarchaeota occupied 90% of the archaeal library. The tolerance of a variety of isolates to salinity and temperature revealed characteristics of a psychrotolerant, halotolerant community. Our findings support the hypothesis that <span class="hlt">ice</span> wedges are capable of sustaining a diverse, plausibly <span class="hlt">active</span> microbial community. As such, <span class="hlt">ice</span> wedges, compared to other forms of less habitable ground <span class="hlt">ice</span>, could serve as a reservoir for life on permanently cold, water-scarce, <span class="hlt">ice</span>-rich extraterrestrial bodies and are therefore of interest to astrobiologists and ecologists alike. .</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22519974','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22519974"><span id="translatedtitle">Life at the wedge: the <span class="hlt">activity</span> and diversity of arctic <span class="hlt">ice</span> wedge microbial communities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wilhelm, Roland C; Radtke, Kristin J; Mykytczuk, Nadia C S; Greer, Charles W; Whyte, Lyle G</p> <p>2012-04-01</p> <p>The discovery of polygonal terrain on Mars underlain by <span class="hlt">ice</span> heightens interest in the possibility that this water-bearing habitat may be, or may have been, a suitable habitat for extant life. The possibility is supported by the recurring detection of terrestrial microorganisms in subsurface <span class="hlt">ice</span> environments, such as <span class="hlt">ice</span> wedges found beneath tundra polygon features. A characterization of the microbial community of <span class="hlt">ice</span> wedges from the high Arctic was performed to determine whether this <span class="hlt">ice</span> environment can sustain <span class="hlt">actively</span> respiring microorganisms and to assess the ecology of this extreme niche. We found that <span class="hlt">ice</span> wedge samples contained a relatively abundant number of culturable cells compared to other <span class="hlt">ice</span> habitats (∼10(5) CFU·mL(-1)). Respiration assays in which radio-labeled acetate and in situ measurement of CO(2) flux were used suggested low levels of microbial <span class="hlt">activity</span>, though more sensitive techniques are required to confirm these findings. Based on 16S rRNA gene pyrosequencing, bacterial and archaeal <span class="hlt">ice</span> wedge communities appeared to reflect surrounding soil communities. Two Pseudomonas sp. were the most abundant taxa in the <span class="hlt">ice</span> wedge bacterial library (∼50%), while taxa related to ammonia-oxidizing Thaumarchaeota occupied 90% of the archaeal library. The tolerance of a variety of isolates to salinity and temperature revealed characteristics of a psychrotolerant, halotolerant community. Our findings support the hypothesis that <span class="hlt">ice</span> wedges are capable of sustaining a diverse, plausibly <span class="hlt">active</span> microbial community. As such, <span class="hlt">ice</span> wedges, compared to other forms of less habitable ground <span class="hlt">ice</span>, could serve as a reservoir for life on permanently cold, water-scarce, <span class="hlt">ice</span>-rich extraterrestrial bodies and are therefore of interest to astrobiologists and ecologists alike. . PMID:22519974</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....16.2025W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....16.2025W"><span id="translatedtitle">Pre-<span class="hlt">activation</span> of <span class="hlt">ice</span>-nucleating particles by the pore condensation and freezing mechanism</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wagner, Robert; Kiselev, Alexei; Möhler, Ottmar; Saathoff, Harald; Steinke, Isabelle</p> <p>2016-02-01</p> <p>In spite of the resurgence in <span class="hlt">ice</span> nucleation research a comparatively small number of studies deal with the phenomenon of pre-<span class="hlt">activation</span> in heterogeneous <span class="hlt">ice</span> nucleation. Fifty years ago, it was shown that various mineral dust and volcanic ash particles can be pre-<span class="hlt">activated</span> to become nuclei for <span class="hlt">ice</span> crystal formation even at temperatures as high as 270-271 K. Pre-<span class="hlt">activation</span> was achieved under <span class="hlt">ice</span>-subsaturated conditions without any preceding macroscopic <span class="hlt">ice</span> growth by just temporarily cooling the particles to temperatures below 228 K. A two-step mechanism involving capillary condensation of supercooled water and subsequent homogeneous freezing was proposed to account for the particles' enhanced <span class="hlt">ice</span> nucleation ability at high temperatures. This work reinvestigates the efficiency of the proposed pre-<span class="hlt">activation</span> mechanism in temperature-cycling experiments performed in a large cloud chamber with suspended particles. We find the efficiency to be highest for the clay mineral illite as well as for highly porous materials like zeolite and diatomaceous earth, whereas most aerosols generated from desert dust surface samples did not reveal a measurable pre-<span class="hlt">activation</span> ability. The pre-<span class="hlt">activation</span> efficiency is linked to particle pores in a certain size range. As estimated by model calculations, only pores with diameters between about 5 and 8 nm contribute to pre-<span class="hlt">activation</span> under <span class="hlt">ice</span>-subsaturated conditions. This range is set by a combination of requirements from the negative Kelvin effect for condensation and a critical size of <span class="hlt">ice</span> embryos for <span class="hlt">ice</span> nucleation and melting. In contrast to the early study, pre-<span class="hlt">activation</span> is only observed for temperatures below 260 K. Above that threshold, the particles' improved <span class="hlt">ice</span> nucleation ability disappears due to the melting of <span class="hlt">ice</span> in the pores.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1710208L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1710208L"><span id="translatedtitle">Identification and quantification of <span class="hlt">ice</span> nucleation <span class="hlt">active</span> microorganisms by digital droplet PCR (ddPCR)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Linden, Martin; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine</p> <p>2015-04-01</p> <p>Several bioaerosol types, including bacteria, fungi, pollen and lichen, have been identified as sources of biological <span class="hlt">ice</span> nucleators (IN) which induce <span class="hlt">ice</span> formation already at temperatures as high as -10 °C or above. Accordingly, they potentially contribute widely to environmental <span class="hlt">ice</span> nucleation in the atmosphere and are of great interest in the study of natural heterogenous <span class="hlt">ice</span> nucleation processes. <span class="hlt">Ice</span> nucleation <span class="hlt">active</span> microorganisms have been found and studied among bacteria (Proteobacteria) and fungi (phyla Basidiomycota and Ascomycota). The mechanisms enabling the microorganisms to <span class="hlt">ice</span> nucleation are subject to ongoing research. While it has been demonstrated that whole cells can act as <span class="hlt">ice</span> nucleators in the case of bacteria due to the presence of specific membrane proteins, cell-free <span class="hlt">ice</span> nucleation <span class="hlt">active</span> particles seem to be responsible for this phenomenon in fungi and lichen. The identification and quantification of these <span class="hlt">ice</span> nucleation <span class="hlt">active</span> microorganisms and their IN in atmospheric samples is crucial to understand their contribution to the pool of atmospheric IN. This is not a trivial task since the respective microorganisms are often prevalent in lowest concentrations and a variety of states, be it viable cells, spores or cell debris from dead cells. Molecular biology provides tools to identify and quantify <span class="hlt">ice</span> nucleation <span class="hlt">active</span> microorganisms independent of their state by detecting genetic markers specific for the organism of interest. Those methods are not without their drawbacks in terms of sample material concentration required or reliable standardization. Digital Droplet Polymerase Chain Reaction (ddPCR) was chosen for our demands as a more elegant, quick and specific method in the investigation of <span class="hlt">ice</span> nucleation <span class="hlt">active</span> microorganisms in atmospheric samples. The advantages of ddPCR lie in the simultaneous detection and quantification of genetic markers and their original copy numbers in a sample. This is facilitated by the fractionation of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJEaS.105.2013O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJEaS.105.2013O"><span id="translatedtitle">Carbonate sedimentation in an extensional <span class="hlt">active</span> <span class="hlt">margin</span>: Cretaceous history of the Haymana region, Pontides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okay, Aral I.; Altiner, Demir</p> <p>2016-10-01</p> <p>The Haymana region in Central Anatolia is located in the southern part of the Pontides close to the İzmir-Ankara suture. During the Cretaceous, the region formed part of the south-facing <span class="hlt">active</span> <span class="hlt">margin</span> of the Eurasia. The area preserves a nearly complete record of the Cretaceous system. Shallow marine carbonates of earliest Cretaceous age are overlain by a 700-m-thick Cretaceous sequence, dominated by deep marine limestones. Three unconformity-bounded pelagic carbonate sequences of Berriasian, Albian-Cenomanian and Turonian-Santonian ages are recognized: Each depositional sequence is preceded by a period of tilting and submarine erosion during the Berriasian, early Albian and late Cenomanian, which corresponds to phases of local extension in the <span class="hlt">active</span> continental <span class="hlt">margin</span>. Carbonate breccias mark the base of the sequences and each carbonate sequence steps down on older units. The deep marine carbonate deposition ended in the late Santonian followed by tilting, erosion and folding during the Campanian. Deposition of thick siliciclastic turbidites started in the late Campanian and continued into the Tertiary. Unlike most forearc basins, the Haymana region was a site of deep marine carbonate deposition until the Campanian. This was because the Pontide arc was extensional and the volcanic detritus was trapped in the intra-arc basins and did not reach the forearc or the trench. The extensional nature of the arc is also shown by the opening of the Black Sea as a backarc basin in the Turonian-Santonian. The carbonate sedimentation in an <span class="hlt">active</span> <span class="hlt">margin</span> is characterized by synsedimentary vertical displacements, which results in submarine erosion, carbonate breccias and in the lateral discontinuity of the sequences, and differs from blanket like carbonate deposition in the passive <span class="hlt">margins</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJEaS.tmp...23O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJEaS.tmp...23O"><span id="translatedtitle">Carbonate sedimentation in an extensional <span class="hlt">active</span> <span class="hlt">margin</span>: Cretaceous history of the Haymana region, Pontides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okay, Aral I.; Altiner, Demir</p> <p>2016-03-01</p> <p>The Haymana region in Central Anatolia is located in the southern part of the Pontides close to the İzmir-Ankara suture. During the Cretaceous, the region formed part of the south-facing <span class="hlt">active</span> <span class="hlt">margin</span> of the Eurasia. The area preserves a nearly complete record of the Cretaceous system. Shallow marine carbonates of earliest Cretaceous age are overlain by a 700-m-thick Cretaceous sequence, dominated by deep marine limestones. Three unconformity-bounded pelagic carbonate sequences of Berriasian, Albian-Cenomanian and Turonian-Santonian ages are recognized: Each depositional sequence is preceded by a period of tilting and submarine erosion during the Berriasian, early Albian and late Cenomanian, which corresponds to phases of local extension in the <span class="hlt">active</span> continental <span class="hlt">margin</span>. Carbonate breccias mark the base of the sequences and each carbonate sequence steps down on older units. The deep marine carbonate deposition ended in the late Santonian followed by tilting, erosion and folding during the Campanian. Deposition of thick siliciclastic turbidites started in the late Campanian and continued into the Tertiary. Unlike most forearc basins, the Haymana region was a site of deep marine carbonate deposition until the Campanian. This was because the Pontide arc was extensional and the volcanic detritus was trapped in the intra-arc basins and did not reach the forearc or the trench. The extensional nature of the arc is also shown by the opening of the Black Sea as a backarc basin in the Turonian-Santonian. The carbonate sedimentation in an <span class="hlt">active</span> <span class="hlt">margin</span> is characterized by synsedimentary vertical displacements, which results in submarine erosion, carbonate breccias and in the lateral discontinuity of the sequences, and differs from blanket like carbonate deposition in the passive <span class="hlt">margins</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20919453','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20919453"><span id="translatedtitle"><span class="hlt">Ice-active</span> proteins from New Zealand snow tussocks, Chionochloa macra AND C. rigida.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wharton, D A; Selvanesan, L; Marshall, C J</p> <p>2010-01-01</p> <p>The <span class="hlt">ice</span> <span class="hlt">active</span> protein profile of New Zealand snow tussocks Chionochloa macra and C. rigida consisted of <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> but no antifreeze or recrystallization inhibition <span class="hlt">activity</span>. The <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> was similar in the two species, despite them being collected at different altitudes and at different times. The <span class="hlt">activity</span> is intrinsic to the plant and is associated with the surface of the leaves. Snow tussocks collect water from fog. Nucleation sites on the surface of their leaves may aid the efficiency of this process. PMID:20919453</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5685A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5685A"><span id="translatedtitle">Extensive <span class="hlt">ice</span> stream <span class="hlt">activity</span> on the North-East Greenland Continental Shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arndt, Jan Erik; Jokat, Wilfried; Dorschel, Boris</p> <p>2015-04-01</p> <p>Even though approximately 20% of the modern day Greenland <span class="hlt">ice</span> sheet is drained via the North-East Greenland Continental Shelf (NEGCS), its submarine geomorphology is only poorly resolved. Acting as the main export region for Arctic sea-<span class="hlt">ice</span> transported southward by the cold East Greenland Current, the NEGCS shows year-round harsh <span class="hlt">ice</span> conditions that limit the accessibility for research vessels to conduct swath bathymetric surveys. While studies based on radiocarbon dating were arguing if the <span class="hlt">ice</span> sheet reached on the shelf during full-glacial periods, two studies using high-resolution swath bathymetric data from single cruise tracks showed submarine glacial seafloor features, including mega-scale glacial lineations and retreat moraines that gave direct marine evidence of past <span class="hlt">ice</span> stream <span class="hlt">activity</span> at least to the middle shelf in Westwind Trough. We have newly processed swath bathymetry and sub-bottom profiler data of 18 cruises of RV Polarstern from 1985 until 2014. This data was investigated for submarine glacial seafloor features to better constrain the past <span class="hlt">ice</span> sheet configuration, including its maximum extent and retreat history. Amongst others, we have now first marine evidence for <span class="hlt">ice</span> stream <span class="hlt">activity</span> in Norske Trough and in general a more intense <span class="hlt">ice</span> streaming <span class="hlt">activity</span> on the shelf. In addition, our data indicates that possibly a small separate <span class="hlt">ice</span> sheet was present offshore the modern day Greenland coast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4407212','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4407212"><span id="translatedtitle">Evidence of <span class="hlt">Active</span> Methanogen Communities in Shallow Sediments of the Sonora <span class="hlt">Margin</span> Cold Seeps</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>L'Haridon, Stéphane; Godfroy, Anne; Roussel, Erwan G.; Cragg, Barry A.; Parkes, R. John; Toffin, Laurent</p> <p>2015-01-01</p> <p>In the Sonora <span class="hlt">Margin</span> cold seep ecosystems (Gulf of California), sediments underlying microbial mats harbor high biogenic methane concentrations, fueling various microbial communities, such as abundant lineages of anaerobic methanotrophs (ANME). However, the biodiversity, distribution, and metabolism of the microorganisms producing this methane remain poorly understood. In this study, measurements of methanogenesis using radiolabeled dimethylamine, bicarbonate, and acetate showed that biogenic methane production in these sediments was mainly dominated by methylotrophic methanogenesis, while the proportion of autotrophic methanogenesis increased with depth. Congruently, methane production and methanogenic Archaea were detected in culture enrichments amended with trimethylamine and bicarbonate. Analyses of denaturing gradient gel electrophoresis (DGGE) fingerprinting and reverse-transcribed PCR-amplified 16S rRNA sequences retrieved from these enrichments revealed the presence of <span class="hlt">active</span> methylotrophic Methanococcoides burtonii relatives and several new autotrophic Methanogenium lineages, confirming the cooccurrence of Methanosarcinales and Methanomicrobiales methanogens with abundant ANME populations in the sediments of the Sonora <span class="hlt">Margin</span> cold seeps. PMID:25769831</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70178178','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70178178"><span id="translatedtitle">Subsea <span class="hlt">ice</span>-bearing permafrost on the U.S. Beaufort <span class="hlt">Margin</span>: 1. Minimum seaward extent defined from multichannel seismic reflection data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brothers, Laura; Herman, Bruce M.; Hart, Patrick E.; Ruppel, Carolyn</p> <p>2016-01-01</p> <p>Subsea <span class="hlt">ice</span>-bearing permafrost (IBPF) and associated gas hydrate in the Arctic have been subject to a warming climate and saline intrusion since the last transgression at the end of the Pleistocene. The consequent degradation of IBPF is potentially associated with significant degassing of dissociating gas hydrate deposits. Previous studies interpreted the distribution of subsea permafrost on the U.S. Beaufort continental shelf based on geographically sparse data sets and modeling of expected thermal history. The most cited work projects subsea permafrost to the shelf edge (∼100 m isobath). This study uses a compilation of stacking velocity analyses from ∼100,000 line-km of industry-collected multichannel seismic reflection data acquired over 57,000 km2 of the U.S. Beaufort shelf to delineate continuous subsea IBPF. Gridded average velocities of the uppermost 750 ms two-way travel time range from 1475 to 3110 m s−1. The monotonic, cross-shore pattern in velocity distribution suggests that the seaward extent of continuous IBPF is within 37 km of the modern shoreline at water depths < 25 m. These interpretations corroborate recent Beaufort seismic refraction studies and provide the best, <span class="hlt">margin</span>-scale evidence that continuous subsea IBPF does not currently extend to the northern limits of the continental shelf.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C13B0616B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C13B0616B"><span id="translatedtitle">Virus <span class="hlt">activity</span> on the surface of glaciers and <span class="hlt">ice</span> sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bellas, C. M.; Anesio, A. M.; Telling, J.; Stibal, M.; Barker, G.; Tranter, M.; Yallop, M.; Cook, J.</p> <p>2012-12-01</p> <p>Viruses are found wherever there is life. They are major components of aquatic ecosystems and through interactions with their hosts they significantly alter global biogeochemical cycles and drive evolutionary processes. Here we focus on the interactions between bacteriophages and their hosts inhabiting the microbially dominated supraglacial ecosystems known as cryoconite holes. The diversity of phages present in the sediments of cryoconites was examined for the first time by using a molecular based approach to target the T4-type bacteriophage. Through phylogenetic analysis it was determined that the phage community was diverse, consisting of strains that grouped with those from other global habitats and those that formed several completely new T4-type phage clusters. The <span class="hlt">activity</span> of the viral community present on glaciers from Svalbard and the Greenland <span class="hlt">Ice</span> Sheet was also addressed through a series of incubation experiments. Here new virus production was found to be capable of turning over the viral population approximately twice a day, a rate comparable to marine and freshwater sediments around the globe. This large scale viral production was found to be theoretically capable of accounting for all heterotrophic bacterial mortality in cryoconite holes. The mode of infection that viruses employ in cryoconite holes was also addressed to show that a variety of viral life strategies are likely responsible for the continued dominance of viruses in these unique habitats. The implications of viral <span class="hlt">activity</span> are discussed in terms of carbon cycling in supraglacial ecosystems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/7765721','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/7765721"><span id="translatedtitle">Enhancing effect of 4-hydroxy-3-nitrophenylacetic acid on transcription of the <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> gene of Xanthomonas campestris.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Watanabe, M; Watanabe, J; Michigami, Y</p> <p>1994-12-01</p> <p>Cultivation of an <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> strain of Xanthomonas campestris in the presence (1 ppm) of 4-hydroxy-3-nitrophenylacetic acid resulted in enhancement of its <span class="hlt">ice</span>-nucleation <span class="hlt">activity</span>. Both the <span class="hlt">ice-nucleation-active</span> protein, InaX, and its mRNA were effectively expressed in the bacterial cells cultured in the presence of this compound. This indicates that this compound stimulated the biosynthesis of the <span class="hlt">ice-nucleation-active</span> protein. PMID:7765721</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20977900','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20977900"><span id="translatedtitle"><span class="hlt">Ice</span> restructuring inhibition <span class="hlt">activities</span> in antifreeze proteins with distinct differences in thermal hysteresis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yu, Sally O; Brown, Alan; Middleton, Adam J; Tomczak, Melanie M; Walker, Virginia K; Davies, Peter L</p> <p>2010-12-01</p> <p>Antifreeze proteins (AFPs) share two related properties: the ability to depress the freezing temperature below the melting point of <span class="hlt">ice</span> (thermal hysteresis; TH); and the ability to inhibit the restructuring of <span class="hlt">ice</span> into larger crystals. Since the 'hyperactive' AFPs, which have been more recently discovered, show an order of magnitude more TH than previously characterized AFPs, we have now determined their <span class="hlt">activities</span> in <span class="hlt">ice</span> restructuring inhibition (IrI) assays. IrI <span class="hlt">activities</span> of three TH-hyperactive AFPs and three less TH-<span class="hlt">active</span> AFPs varied over an 8-fold range. There was no obvious correlation between high TH <span class="hlt">activity</span> and high IrI <span class="hlt">activity</span>. However, the use of mutant AFPs demonstrated that severe disruption of <span class="hlt">ice</span>-binding residues diminished both TH and IrI similarly, revealing that that the same <span class="hlt">ice</span>-binding residues are crucial for both <span class="hlt">activities</span>. In addition, bicarbonate ions, which are known to enhance the TH <span class="hlt">activity</span> of AFPs, also enhanced their IrI <span class="hlt">activity</span>. We suggest that these seemingly contradictory observations can be partially explained by differences in the coverage of <span class="hlt">ice</span> by TH-hyperactive and non-hyperactive AFPs, and by differences in the stability of AFP-bound <span class="hlt">ice</span> under supercooled and recrystallization conditions. PMID:20977900</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..MARH25003B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..MARH25003B"><span id="translatedtitle">Why are hyperactive <span class="hlt">ice</span>-binding-proteins so <span class="hlt">active</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braslavsky, Ido; Celik, Yeliz; Pertaya, Natalya; Eun Choi, Young; Bar, Maya; Davies, Peter L.</p> <p>2008-03-01</p> <p><span class="hlt">Ice</span> binding proteins (IBPs), also called `antifreeze proteins' or `<span class="hlt">ice</span> structuring proteins', are a class of proteins that protect organisms from freezing injury. These proteins have many applications in medicine and agriculture, and as a platform for future biotechnology applications. One of the interesting questions in this field focuses on the hyperactivity of some IBPs. <span class="hlt">Ice</span> binding proteins can be classified in two groups: moderate ones that can depress the freezing point up to ˜1.0 ^oC and hyperactive ones that can depress the freezing point several-fold further even at lower concentrations. It has been suggested that the hyperactivity of IBPs stem from the fact that they block growth out of specific <span class="hlt">ice</span> surfaces, more specifically the basal planes of <span class="hlt">ice</span>. Here we show experimental results based on fluorescence microscopy, highlighting the differences between moderate IBPs and hyperactive IBPs. These include direct evidence for basal plane affinity of hyperactive IBPs, the effects of IBPs on growth-melt behavior of <span class="hlt">ice</span> and the dynamics of their interaction with <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Geomo.258...40E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Geomo.258...40E"><span id="translatedtitle">Crevasse-squeeze ridge corridors: Diagnostic features of late-stage palaeo-<span class="hlt">ice</span> stream <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evans, David J. A.; Storrar, Robert D.; Rea, Brice R.</p> <p>2016-04-01</p> <p>A 200-km-long and 10-km-wide linear assemblage of till-filled geometrical ridges on the bed of the Maskwa palaeo-<span class="hlt">ice</span> stream of the late Wisconsinan southwest Laurentide <span class="hlt">Ice</span> Sheet are interpreted as crevasse-squeeze ridges (CSR) developed during internal flow unit reorganization, immediately prior to <span class="hlt">ice</span> stream shutdown. Ridge orientations are predominantly orientated WNW-ESE, with a subordinate WSW-ENE alignment, both indicative of <span class="hlt">ice</span> fracture development transverse to former <span class="hlt">ice</span> stream flow, as indicated by NNE-SSW aligned MSGL. Subglacial till injection into basal and/or full depth, mode I and II crevasses occurred at the approximate centreline of the <span class="hlt">ice</span> stream, in response to extension and fracturing. Landform preservation indicates that this took place during the final stages of <span class="hlt">ice</span> streaming, immediately prior to <span class="hlt">ice</span> stream shutdown. This linear zone of <span class="hlt">ice</span> fracturing therefore likely represents the narrowing of the fast-flowing trunk, similar to the plug flow identified in some surging valley glaciers. Lateral drag between the final <span class="hlt">active</span> flow unit and the slower moving <span class="hlt">ice</span> on either side is likely recorded by the up-<span class="hlt">ice</span> bending of the CSR limbs. The resulting CSR corridor, here related to an individual <span class="hlt">ice</span> stream flow unit, constitutes a previously unreported style of crevasse infilling and contrasts with two existing CSR patterns: (1) wide arcuate zones of CSRs related to widespread fracturing within glacier surge lobes; and (2) narrow concentric arcs of CSRs and recessional push moraines related to submarginal till deformation at <span class="hlt">active</span> temperate glacier lobes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18363389','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18363389"><span id="translatedtitle">Heterogeneous <span class="hlt">ice</span> nucleation in aqueous solutions: the role of water <span class="hlt">activity</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zobrist, B; Marcolli, C; Peter, T; Koop, T</p> <p>2008-05-01</p> <p>Heterogeneous <span class="hlt">ice</span> nucleation experiments have been performed with four different <span class="hlt">ice</span> nuclei (IN), namely nonadecanol, silica, silver iodide and Arizona test dust. All IN are either immersed in the droplets or located at the droplets surface. The IN were exposed to various aqueous solutions, which consist of (NH4)2SO4, H2SO4, MgCl2, NaCl, LiCl, Ca(NO3)2, K2CO3, CH3COONa, ethylene glycol, glycerol, malonic acid, PEG300 or a NaCl/malonic acid mixture. Freezing was studied using a differential scanning calorimeter and a cold finger cell. The results show that the heterogeneous <span class="hlt">ice</span> freezing temperatures decrease with increasing solute concentration; however, the magnitude of this effect is solute dependent. In contrast, when the results are analyzed in terms of the solution water <span class="hlt">activity</span> a very consistent behavior emerges: heterogeneous <span class="hlt">ice</span> nucleation temperatures for all four IN converge each onto a single line, irrespective of the nature of the solute. We find that a constant offset with respect to the <span class="hlt">ice</span> melting point curve, Deltaaw,het, can describe the observed freezing temperatures for each IN. Such a behavior is well-known for homogeneous <span class="hlt">ice</span> nucleation from supercooled liquid droplets and has led to the development of water-<span class="hlt">activity</span>-based <span class="hlt">ice</span> nucleation theory. The large variety of investigated solutes together with different general types of <span class="hlt">ice</span> nuclei studied (monolayers, ionic crystals, covalently bound network-forming compounds, and a mixture of chemically different crystallites) underlines the general applicability of water-<span class="hlt">activity</span>-based <span class="hlt">ice</span> nucleation theory also for heterogeneous <span class="hlt">ice</span> nucleation in the immersion mode. Finally, the <span class="hlt">ice</span> nucleation efficiencies of the various IN, as well as the atmospheric implication of the developed parametrization are discussed. PMID:18363389</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25086201','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25086201"><span id="translatedtitle">Anti-<span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of polyphenol compounds against silver iodide.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koyama, Toshie; Inada, Takaaki; Kuwabara, Chikako; Arakawa, Keita; Fujikawa, Seizo</p> <p>2014-10-01</p> <p>Freeze-avoiding organisms survive sub-zero temperatures without freezing in several ways, such as removal of <span class="hlt">ice</span> nucleating agents (INAs), production of polyols, and dehydration. Another way is production of anti-<span class="hlt">ice</span> nucleating agents (anti-INAs), such as has been reported for several antifreeze proteins (AFPs) and polyphenols, that inhibit <span class="hlt">ice</span> nucleation by inactivating INAs. In this study, the anti-<span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of five polyphenol compounds, including flavonoid and tannin compounds of both biological and synthetic origin, against silver iodide (AgI) was examined by measuring the <span class="hlt">ice</span> nucleation temperature in emulsified polyphenol solutions containing AgI particles. The emulsified solutions eliminated the influence of contamination by unidentified INAs, thus enabling examination of the anti-<span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of the polyphenols against AgI alone. Results showed that all five polyphenol compounds used here have anti-<span class="hlt">ice</span> nucleating <span class="hlt">activities</span> that are unique compared with other known anti-INAs, such as fish AFPs (type I and III) and synthetic polymers (poly(vinyl alcohol), poly(vinylpyrrolidone) and poly(ethylene glycol)). All five polyphenols completely inactivated the <span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of AgI even at relatively low temperatures, and the first <span class="hlt">ice</span> nucleation event was observed at temperatures between -14.1 and -19.4°C, compared with between -8.6 and -11.8°C for the fish AFPs and three synthetic polymers. These anti-<span class="hlt">ice</span> nucleating <span class="hlt">activities</span> of the polyphenols at such low temperatures are promising properties for practical applications where freezing should be prevented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25086201','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25086201"><span id="translatedtitle">Anti-<span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of polyphenol compounds against silver iodide.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koyama, Toshie; Inada, Takaaki; Kuwabara, Chikako; Arakawa, Keita; Fujikawa, Seizo</p> <p>2014-10-01</p> <p>Freeze-avoiding organisms survive sub-zero temperatures without freezing in several ways, such as removal of <span class="hlt">ice</span> nucleating agents (INAs), production of polyols, and dehydration. Another way is production of anti-<span class="hlt">ice</span> nucleating agents (anti-INAs), such as has been reported for several antifreeze proteins (AFPs) and polyphenols, that inhibit <span class="hlt">ice</span> nucleation by inactivating INAs. In this study, the anti-<span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of five polyphenol compounds, including flavonoid and tannin compounds of both biological and synthetic origin, against silver iodide (AgI) was examined by measuring the <span class="hlt">ice</span> nucleation temperature in emulsified polyphenol solutions containing AgI particles. The emulsified solutions eliminated the influence of contamination by unidentified INAs, thus enabling examination of the anti-<span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of the polyphenols against AgI alone. Results showed that all five polyphenol compounds used here have anti-<span class="hlt">ice</span> nucleating <span class="hlt">activities</span> that are unique compared with other known anti-INAs, such as fish AFPs (type I and III) and synthetic polymers (poly(vinyl alcohol), poly(vinylpyrrolidone) and poly(ethylene glycol)). All five polyphenols completely inactivated the <span class="hlt">ice</span> nucleating <span class="hlt">activity</span> of AgI even at relatively low temperatures, and the first <span class="hlt">ice</span> nucleation event was observed at temperatures between -14.1 and -19.4°C, compared with between -8.6 and -11.8°C for the fish AFPs and three synthetic polymers. These anti-<span class="hlt">ice</span> nucleating <span class="hlt">activities</span> of the polyphenols at such low temperatures are promising properties for practical applications where freezing should be prevented. PMID:25086201</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27192099','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27192099"><span id="translatedtitle">Passive Anti-<span class="hlt">Icing</span> and <span class="hlt">Active</span> Deicing Films.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Tuo; Zheng, Yonghao; Raji, Abdul-Rahman O; Li, Yilun; Sikkema, William K A; Tour, James M</p> <p>2016-06-01</p> <p>Anti-<span class="hlt">icing</span> and deicing are the two major pathways for suppressing adhesion of <span class="hlt">ice</span> on surfaces, yet materials with dual capabilities are rare. In this work, we have designed a perfluorododecylated graphene nanoribbon (FDO-GNR) film that takes advantage of both the low polarizability of perfluorinated carbons and the intrinsic conductive nature of graphene nanoribbons. The FDO-GNR films are superhydrophobic with a sheet resistance below 8 kΩ·sq(-1) and then exhibit an anti-<span class="hlt">icing</span> property that prevents freezing of incoming <span class="hlt">ice</span>-cold water down to -14 °C. After that point, voltage can be applied to the films to resistively heat and deice the surface. Further a lubricating liquid can be employed to create a slippery surface to improve the film's deicing performance. The FDO-GNR films can be easily switched between the superhydrophobic anti-<span class="hlt">icing</span> mode and the slippery deicing mode by applying the lubricant. A spray-coating method makes it suitable for large-scale applications. The anti-<span class="hlt">icing</span> and deicing properties render the FDO-GNR films with promise for use in extreme environments. PMID:27192099</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3897189','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3897189"><span id="translatedtitle">Motor-driven <span class="hlt">marginal</span> band coiling promotes cell shape change during platelet <span class="hlt">activation</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Diagouraga, Boubou; Grichine, Alexei; Fertin, Arnold; Wang, Jin; Khochbin, Saadi</p> <p>2014-01-01</p> <p>Platelets float in the blood as discoid particles. Their shape is maintained by microtubules organized in a ring structure, the so-called <span class="hlt">marginal</span> band (MB), in the periphery of resting platelets. Platelets are <span class="hlt">activated</span> after vessel injury and undergo a major shape change known as disc to sphere transition. It has been suggested that actomyosin tension induces the contraction of the MB to a smaller ring. In this paper, we show that antagonistic microtubule motors keep the MB in its resting state. During platelet <span class="hlt">activation</span>, dynein slides microtubules apart, leading to MB extension rather than contraction. The MB then starts to coil, thereby inducing the spherical shape of <span class="hlt">activating</span> platelets. Newly polymerizing microtubules within the coiled MB will then take a new path to form the smaller microtubule ring, in concerted action with actomyosin tension. These results present a new view of the platelet <span class="hlt">activation</span> mechanism and reveal principal mechanistic features underlying cellular shape changes. PMID:24421335</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.6775H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.6775H"><span id="translatedtitle">Recent tectonic <span class="hlt">activity</span> on Pluto driven by phase changes in the <span class="hlt">ice</span> shell</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hammond, Noah P.; Barr, Amy C.; Parmentier, Edgar M.</p> <p>2016-07-01</p> <p>The New Horizons spacecraft has found evidence for geologic <span class="hlt">activity</span> on the surface of Pluto, including extensional tectonic deformation of its water <span class="hlt">ice</span> bedrock see Moore et al. (2016). One mechanism that could drive extensional tectonic <span class="hlt">activity</span> is global surface expansion due to the partial freezing of an ocean. We use updated physical properties for Pluto and simulate its thermal evolution to understand the survival of a possible subsurface ocean. For thermal conductivities of rock less than 3 W m-1 K-1, an ocean forms and at least partially freezes, leading to recent extensional stresses in the <span class="hlt">ice</span> shell. In scenarios where the ocean freezes and the <span class="hlt">ice</span> shell is thicker than 260 km, <span class="hlt">ice</span> II forms and causes global volume contraction. Since there is no evidence for recent compressional tectonic features, we argue that <span class="hlt">ice</span> II has not formed and that Pluto's ocean has likely survived to present day.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16664039','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16664039"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation temperature of individual leaves in relation to population sizes of <span class="hlt">ice</span> nucleation <span class="hlt">active</span> bacteria and frost injury.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hirano, S S; Baker, L S; Upper, C D</p> <p>1985-02-01</p> <p><span class="hlt">Ice</span> nucleation temperatures of individual leaves were determined by a tube nucleation test. With this assay, a direct quantitative relationship was obtained between the temperatures at which <span class="hlt">ice</span> nucleation occurred on individual oat (Avena sativa L.) leaves and the population sizes of <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA) bacteria present on those leaves. In the absence of INA bacteria, nucleation of supercooled growth-chamber grown oat leaves did not occur until temperatures were below approximately -5 degrees C. Both nucleation temperature and population size of INA bacteria were determined on the same individual, field-grown oat leaves. Leaves with higher <span class="hlt">ice</span> nucleation temperatures harbored larger populations of INA bacteria than did leaves with lower nucleation temperatures. Log(10) mean populations of INA bacteria per leaf were 5.14 and 3.51 for leaves with nucleation temperatures of -2.5 degrees C and -3.0 degrees C, respectively. Nucleation frequencies (the ratio of <span class="hlt">ice</span> nuclei to viable cells) of INA bacteria on leaves were lognormally distributed. Strains from two very different collections of Pseudomonas syringae and one of Erwinia herbicola were cultured on nutrient glycerol agar and tested for nucleation frequency at -5 degrees C. Nucleation frequencies of these bacterial strains were also lognormally distributed within each of the three sets. The tube nucleation test was used to determine the frequency with which individual leaves in an oat canopy harbored large populations of INA bacteria throughout the growing season. This test also predicted relative frost hazard to tomato (Lycopersicon esculentum Mill) plants. PMID:16664039</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1064500','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1064500"><span id="translatedtitle"><span class="hlt">Ice</span> Nucleation Temperature of Individual Leaves in Relation to Population Sizes of <span class="hlt">Ice</span> Nucleation <span class="hlt">Active</span> Bacteria and Frost Injury</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hirano, Susan S.; Baker, L. Stuart; Upper, Christen D.</p> <p>1985-01-01</p> <p><span class="hlt">Ice</span> nucleation temperatures of individual leaves were determined by a tube nucleation test. With this assay, a direct quantitative relationship was obtained between the temperatures at which <span class="hlt">ice</span> nucleation occurred on individual oat (Avena sativa L.) leaves and the population sizes of <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA) bacteria present on those leaves. In the absence of INA bacteria, nucleation of supercooled growth-chamber grown oat leaves did not occur until temperatures were below approximately −5°C. Both nucleation temperature and population size of INA bacteria were determined on the same individual, field-grown oat leaves. Leaves with higher <span class="hlt">ice</span> nucleation temperatures harbored larger populations of INA bacteria than did leaves with lower nucleation temperatures. Log10 mean populations of INA bacteria per leaf were 5.14 and 3.51 for leaves with nucleation temperatures of −2.5°C and −3.0°C, respectively. Nucleation frequencies (the ratio of <span class="hlt">ice</span> nuclei to viable cells) of INA bacteria on leaves were lognormally distributed. Strains from two very different collections of Pseudomonas syringae and one of Erwinia herbicola were cultured on nutrient glycerol agar and tested for nucleation frequency at −5°C. Nucleation frequencies of these bacterial strains were also lognormally distributed within each of the three sets. The tube nucleation test was used to determine the frequency with which individual leaves in an oat canopy harbored large populations of INA bacteria throughout the growing season. This test also predicted relative frost hazard to tomato (Lycopersicon esculentum Mill) plants. PMID:16664039</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A11B0031H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A11B0031H"><span id="translatedtitle">Direct Quantification of <span class="hlt">Ice</span> Nucleation <span class="hlt">Active</span> Bacteria in Aerosols and Precipitation: Their Potential Contribution as <span class="hlt">Ice</span> Nuclei</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hill, T. C.; DeMott, P. J.; Garcia, E.; Moffett, B. F.; Prenni, A. J.; Kreidenweis, S. M.; Franc, G. D.</p> <p>2013-12-01</p> <p><span class="hlt">Ice</span> nucleation <span class="hlt">active</span> (INA) bacteria are a potentially prodigious source of highly <span class="hlt">active</span> (≥-12°C) atmospheric <span class="hlt">ice</span> nuclei, especially from agricultural land. However, we know little about the conditions that promote their release (eg, daily or seasonal cycles, precipitation, harvesting or post-harvest decay of litter) or their typical contribution to the pool of boundary layer <span class="hlt">ice</span> nucleating particles (INP). To initiate these investigations we developed a quantitative Polymerase Chain Reaction (qPCR) test of the ina gene, the gene that codes for the <span class="hlt">ice</span> nucleating protein, to directly count INA bacteria in environmental samples. The qPCR test amplifies most forms of the gene and is highly sensitive, able to detect perhaps a single gene copy (ie, a single bacterium) in DNA extracted from precipitation. Direct measurement of the INA bacteria is essential because environmental populations will be a mixture of living, viable-but-not culturable, moribund and dead cells, all of which may retain <span class="hlt">ice</span> nucleating proteins. Using the qPCR test on leaf washings of plants from three farms in Wyoming, Colorado and Nebraska we found INA bacteria to be abundant on crops, especially on cereals. Mid-summer populations on wheat and barley were ~108/g fresh weigh of foliage. Broadleaf crops, such as corn, alfalfa, sugar beet and potato supported 105-107/g. Unexpectedly, however, in the absence of a significant physical disturbance, such as harvesting, we were unable to detect the ina gene in aerosols sampled above the crops. Likewise, in fresh snow samples taken over two winters, ina genes from a range of INA bacteria were detected in about half the samples but at abundances that equated to INA bacterial numbers that accounted for only a minor proportion of INP <span class="hlt">active</span> at -10°C. By contrast, in a hail sample from a summer thunderstorm we found 0.3 INA bacteria per INP at -10°C and ~0.5 per hail stone. Although the role of the INA bacteria as warm-temperature INP in these samples</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850003124','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850003124"><span id="translatedtitle"><span class="hlt">Active</span> microwave measurements of sea <span class="hlt">ice</span> under fall conditions: The RADARSAT/FIREX fall experiment. [in the Canadian Arctic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Onstott, R. G.; Kim, Y. S.; Moore, R. K.</p> <p>1984-01-01</p> <p>A series of measurements of the <span class="hlt">active</span> microwave properties of sea <span class="hlt">ice</span> under fall growing conditions was conducted. <span class="hlt">Ice</span> in the inland waters of Mould Bay, Crozier Channel, and intrepid inlet and <span class="hlt">ice</span> in the Arctic Ocean near Hardinge Bay was investigated. <span class="hlt">Active</span> microwave data were acquired using a helicopter borne scatterometer. Results show that multiyear <span class="hlt">ice</span> frozen in grey or first year <span class="hlt">ice</span> is easily detected under cold fall conditions. Multiyear <span class="hlt">ice</span> returns were dynamic due to response to two of its scene constituents. Floe boundaries between thick and thin <span class="hlt">ice</span> are well defined. Multiyear pressure ridge returns are similar in level to background <span class="hlt">ice</span> returns. Backscatter from homogeneous first year <span class="hlt">ice</span> is seen to be primarily due to surface scattering. Operation at 9.6 GHz is more sensitive to the detailed changes in scene roughness, while operation at 5.6 GHz seems to track roughness changes less ably.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.2699S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.2699S"><span id="translatedtitle">Protection of drinking water reservoirs in buried glacial valleys in the <span class="hlt">ice-marginal</span> landscape for securing future demand in the European perspective (ENCORE-Project).</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smit, F. W. H.; Bregman, E. P. H.</p> <p>2012-04-01</p> <p>Quaternary glaciations have left a significant sedimentological fingerprint in the subsurface of north Europe, in the form of buried glacial valleys. These structures are important drinking water reservoirs for millions of people in the <span class="hlt">ice-marginal</span> landscape, but are increasingly threatened by anthropogenic pollution (nitrate, sulphate and organic pollutants) and geogenic pollution (salinization). That is one of the conclusion of a recent overview study in the IML of northern Europe from the North Sea to the southern Baltic area. Adequate policy making is yet not possible for several reasons: - Large amounts of data are needed to get a good grip on the lateral continuity of the complex infill. - The BurVal Working Group (2006) has shown that a combination of high resolution seismic survey, together with transient electromagnetic (TEM) surveys can provide realistic data for 3D hydrogeological models. However, these data have not yet been retrieved on a European scale. - Available borehole data can only be used as control points in 3D hydrological models, since the infill of buried glacial valleys is often lateral too complex to make sound interpolations possible. Pollution in buried glacial valleys crosses national borders in northern Europe and therefore national geological surveys have to cooperate in a newly formed European project on protection of these structures. The ENCORE - project (Environmental Conference of the European Regions) has shown in the past that it can facilitate fruitful European cooperation, which is urgently needed due to the costs of gathering data and due to knowledge gaps between different countries. By working together in a European context, these problems can be reduced so that better policy making is possible in order to secure our future drinking water availability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70032866','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70032866"><span id="translatedtitle">Sediment geochemical records of productivity and oxygen depletion along the <span class="hlt">margin</span> of western North America during the past 60,000 years: teleconnections with Greenland <span class="hlt">Ice</span> and the Cariaco Basin</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dean, W.E.</p> <p>2007-01-01</p> <p>Many sediment records from the <span class="hlt">margins</span> of the Californias (Alta and Baja) collected in water depths between 60 and 1200 m contain anoxic intervals (laminated sediments) that can be correlated with interstadial intervals as defined by the oxygen-isotope composition of Greenland <span class="hlt">ice</span> (Dansgaard-Oeschger, D-O, cycles). These intervals include all or parts of Oxygen Isotope Stage 3 (OIS3; 60-24 cal ka), the Bo??lling/Allero??d warm interval (B/A; 15-13 cal ka), and the Holocene. This study uses organic carbon (Corg) and trace-element proxies for anoxia and productivity, namely elevated concentrations and accumulation rates of molybdenum and cadmium, in these laminated sediments to suggest that productivity may be more important than ventilation in producing changes in bottom-water oxygen (BWO) conditions on open, highly productive continental <span class="hlt">margins</span>. The main conclusion from these proxies is that during the last glacial interval (LGI; 24-15 cal ka) and the Younger Dryas cold interval (YD; 13-11.6 cal ka) productivity was lower and BWO levels were higher than during OIS3, the B/A, and the Holocene on all <span class="hlt">margins</span> of the Californias. The Corg and trace-element profiles in the LGI-B/A-Holocene transition in the Cariaco Basin on the <span class="hlt">margin</span> of northern Venezuela are remarkably similar to those in the transition on the northern California <span class="hlt">margin</span>. Correlation between D-O cycles in Greenland <span class="hlt">ice</span> with gray-scale measurements in varved sediments in the Cariaco Basin also is well established. Synchronous climate-driven changes as recorded in the sediments on the <span class="hlt">margins</span> of the Californias, sediments from the Cariaco Basin, and in the GISP-2 Greenland <span class="hlt">ice</span> core support the hypothesis that changes in atmospheric dynamics played a major role in abrupt climate change during the last 60 ka. Millennial-scale cycles in productivity and oxygen depletion on the <span class="hlt">margins</span> of the Californias demonstrate that the California Current System was poised at a threshold whereby perturbations of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18835384','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18835384"><span id="translatedtitle">Characterization of a family of <span class="hlt">ice-active</span> proteins from the Ryegrass, Lolium perenne.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kumble, Krishnanand D; Demmer, Jerome; Fish, Steven; Hall, Claire; Corrales, Sofia; DeAth, Angela; Elton, Clare; Prestidge, Ross; Luxmanan, Selvanesan; Marshall, Craig J; Wharton, David A</p> <p>2008-12-01</p> <p>Five genes coding for <span class="hlt">ice-active</span> proteins were identified from an expressed sequence tag database of Lolium perenne cDNA libraries. Each of the five genes were characterized by the presence of an N-terminal signal peptide, a region enriched in hydrophilic amino acids and a leucine-rich region in four of the five genes that is homologous with the receptor domain of receptor-like protein kinases of plants. The C-terminal region of all five genes contains sequence homologous with Lolium and Triticum <span class="hlt">ice-active</span> proteins. Of the four <span class="hlt">ice-active</span> proteins (IAP1, IAP2, IAP3 and IAP5) cloned, three could be expressed in Escherichia coli and recovered in a functional form in order to study their <span class="hlt">ice</span> <span class="hlt">activity</span>. All three <span class="hlt">ice-active</span> proteins had recrystallization inhibition <span class="hlt">activity</span> but showed no detectable antifreeze or <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> at the concentration tested. IAP2 and IAP5 formed distinct hexagonal-shaped crystals in the nanolitre osmometer as compared to the weakly hexagonal crystals produced by IAP3. PMID:18835384</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS23B2015W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS23B2015W"><span id="translatedtitle">Evaluating <span class="hlt">Active</span> Methane Hydrate Dissociation Along the Washington <span class="hlt">Margin</span> in Response to Bottom Water Warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Whorley, T. L.; Solomon, E. A.; Torres, M. E.; Johnson, H. P.; Berg, R. D.; Philip, B. T.</p> <p>2015-12-01</p> <p>Water column temperature data acquired on the upper continental slope (UCS) of the Washington (WA) section of the Cascadia <span class="hlt">margin</span> shows gradual warming of bottom water at the upper limit of the methane hydrate stability zone (MHSZ) over the last 4 decades. Thermal models based on these records predict downslope retreat of the MHSZ by ~1-2 km (~40 m in depth), potentially destabilizing methane hydrate and releasing CH4into the sediment and water column. To test for contemporaneous methane hydrate dissociation along the UCS of the WA <span class="hlt">margin</span>, we conducted a comprehensive geophysical and geochemical survey of <span class="hlt">active</span> seep sites at the upper limit of the MHSZ from 48° to 46°N on the R/V Thompson in October 2014. We identified 9 <span class="hlt">active</span> seep sites within this corridor and imaged 22 bubble plumes that commonly rise to ~300 m water depth with some reaching to near the sea surface. Some seep sites appear to be controlled by local <span class="hlt">margin</span> structure, mainly extensional faults and ridges. We collected 22 gravity cores and 20 CTD/hydrocasts from the 9 seeps and processed ~350 sediment samples for pore water chemistry. Hydrocarbons heavier than CH4were not detected in bottom water samples, suggesting any gas hydrate present is Structure I. Preliminary pore water data show decreasing salinity downcore at each site with measured values as low as 10 psu and the sulfate-methane transition zone occurs between 50-80 cm below the sea floor. Pore water solute, noble gas, and isotope ratio data indicate freshening from at least one site is not the result of hydrate dissociation, but rather is due to clay dehydration at depths where temperatures exceed 60°C. Very few of the sites show pore water profiles that are in steady state, suggesting a dynamic biogeochemical system at the UCS along the entire WA <span class="hlt">margin</span>. Further analyses and modeling are underway to constrain the nature and timing of these transient profiles and whether they are the result of recent methane hydrate dissociation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.T43B4717N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.T43B4717N"><span id="translatedtitle">Seismo-turbidite Sedimentology: Implications for <span class="hlt">Active</span> Tectonic <span class="hlt">Margin</span> Stratigraphy and Sediment Facies Patterns</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nelson, C. H.; Goldfinger, C.; Gutierrez Pastor, J.; Polonia, A.; Van Daele, M. E.</p> <p>2014-12-01</p> <p>Earthquakes generate mass transport deposits (MTDs); megaturbidites (MTD overlain by coeval turbidite); multi-pulsed, stacked, and mud homogenite seismo-turbidites; tsunamites; and seiche deposits. The strongest (Mw 9) earthquake shaking signatures appear to create multi-pulsed individual turbidites, where the number and character of multiple coarse-grained pulses for correlative turbidites generally remain constant both upstream and downstream in different channel systems. Multiple turbidite pulses, that correlate with multiple ruptures shown in seismograms of historic earthquakes (e.g. Chile 1960, Sumatra 2004 and Japan 2011), support this hypothesis. The weaker (Mw = or < 8) (e.g. northern California San Andreas) earthquakes generate dominantly upstream simple fining-up (uni-pulsed) turbidites in single tributary canyons and channels; however, downstream stacked turbidites result from synchronously triggered multiple turbidity currents that deposit in channels below confluences of the tributaries. Proven tsunamites, which result from tsunami waves sweeping onshore and shallow water debris into deeper water, are a fine-grained turbidite cap over other seismo-turbidites. In contrast, MTDs and seismo-turbidites result from slope failures. Multiple great earthquakes cause seismic strengthening of slope sediment, which results in minor MTDs in basin floor turbidite system deposits (e.g. maximum run-out distances of MTDs across basin floors along <span class="hlt">active</span> <span class="hlt">margins</span> are up to an order of magnitude less than on passive <span class="hlt">margins</span>). In contrast, the MTDs and turbidites are equally intermixed in turbidite systems of passive <span class="hlt">margins</span> (e.g. Gulf of Mexico). In confined basin settings, earthquake triggering results in a common facies pattern of coeval megaturbidites in proximal settings, thick stacked turbidites downstream, and ponded muddy homogenite turbidites in basin or sub-basin centers, sometimes with a cap of seiche deposits showing bi-directional flow patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25193694','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25193694"><span id="translatedtitle">Perturbation of bacterial <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> by a grass antifreeze protein.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tomalty, Heather E; Walker, Virginia K</p> <p>2014-09-26</p> <p>Certain plant-associating bacteria produce <span class="hlt">ice</span> nucleation proteins (INPs) which allow the crystallization of water at high subzero temperatures. Many of these microbes are considered plant pathogens since the formed <span class="hlt">ice</span> can damage tissues, allowing access to nutrients. Intriguingly, certain plants that host these bacteria synthesize antifreeze proteins (AFPs). Once freezing has occurred, plant AFPs likely function to inhibit the growth of large damaging <span class="hlt">ice</span> crystals. However, we postulated that such AFPs might also serve as defensive mechanisms against bacterial-mediated <span class="hlt">ice</span> nucleation. Recombinant AFP derived from the perennial ryegrass Lolium perenne (LpAFP) was combined with INP preparations originating from the grass epiphyte, Pseudomonas syringae. The presence of INPs had no effect on AFP <span class="hlt">activity</span>, including thermal hysteresis and <span class="hlt">ice</span> recrystallization inhibition. Strikingly, the <span class="hlt">ice</span> nucleation point of the INP was depressed up to 1.9°C in the presence of LpAFP, but a recombinant fish AFP did not lower the INP-imposed freezing point. Assays with mutant LpAFPs and the visualization of bacterially-displayed fluorescent plant AFP suggest that INP and LpAFP can interact. Thus, we postulate that in addition to controlling <span class="hlt">ice</span> growth, plant AFPs may also function as a defensive strategy against the damaging effects of <span class="hlt">ice</span>-nucleating bacteria.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25193694','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25193694"><span id="translatedtitle">Perturbation of bacterial <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> by a grass antifreeze protein.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tomalty, Heather E; Walker, Virginia K</p> <p>2014-09-26</p> <p>Certain plant-associating bacteria produce <span class="hlt">ice</span> nucleation proteins (INPs) which allow the crystallization of water at high subzero temperatures. Many of these microbes are considered plant pathogens since the formed <span class="hlt">ice</span> can damage tissues, allowing access to nutrients. Intriguingly, certain plants that host these bacteria synthesize antifreeze proteins (AFPs). Once freezing has occurred, plant AFPs likely function to inhibit the growth of large damaging <span class="hlt">ice</span> crystals. However, we postulated that such AFPs might also serve as defensive mechanisms against bacterial-mediated <span class="hlt">ice</span> nucleation. Recombinant AFP derived from the perennial ryegrass Lolium perenne (LpAFP) was combined with INP preparations originating from the grass epiphyte, Pseudomonas syringae. The presence of INPs had no effect on AFP <span class="hlt">activity</span>, including thermal hysteresis and <span class="hlt">ice</span> recrystallization inhibition. Strikingly, the <span class="hlt">ice</span> nucleation point of the INP was depressed up to 1.9°C in the presence of LpAFP, but a recombinant fish AFP did not lower the INP-imposed freezing point. Assays with mutant LpAFPs and the visualization of bacterially-displayed fluorescent plant AFP suggest that INP and LpAFP can interact. Thus, we postulate that in addition to controlling <span class="hlt">ice</span> growth, plant AFPs may also function as a defensive strategy against the damaging effects of <span class="hlt">ice</span>-nucleating bacteria. PMID:25193694</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18944584','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18944584"><span id="translatedtitle">Role of <span class="hlt">ice</span> nucleation and antifreeze <span class="hlt">activities</span> in pathogenesis and growth of snow molds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Snider, C S; Hsiang, T; Zhao, G; Griffith, M</p> <p>2000-04-01</p> <p>ABSTRACT We examined the ability of snow molds to grow at temperatures from -5 to 30 degrees C and to influence the growth of <span class="hlt">ice</span> through assays for <span class="hlt">ice</span> nucleation and antifreeze <span class="hlt">activities</span>. Isolates of Coprinus psychromorbidus (low temperature basidiomycete variant), Microdochium nivale, Typhula phacorrhiza, T. ishikariensis, T. incarnata, and T. canadensis all grew at -5 degrees C, whereas Sclerotinia borealis and S. homoeocarpa did not grow at temperatures below 4 degrees C. The highest threshold <span class="hlt">ice</span> nucleation temperature was -7 degrees C. Because snow molds are most damaging to their hosts at temperatures above this, our results imply that the pathogenesis of these fungi is not dependent on <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> to cause freeze-wounding of host plants. All snow molds that grew at subzero temperatures also exhibited antifreeze <span class="hlt">activity</span> in the growth medium and in the soluble and insoluble hyphal fractions, with the exception of M. nivale and one isolate of T. canadensis. The lack of high <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> combined with the presence of antifreeze <span class="hlt">activity</span> in all fungal fractions indicates that snow molds can moderate their environment to inhibit or modify intra- and extracellular <span class="hlt">ice</span> formation, which helps explain their ability to grow at subzero temperatures under snow cover.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7069830','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7069830"><span id="translatedtitle">Crustal recycling at <span class="hlt">active</span> convergent <span class="hlt">margins</span> and growth of the continents</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Morris, J. . Dept. of Earth and Planetary Sciences Carnegie Institution of Washington, DC ); Zheng, S.H. . Dept. of Geological Sciences)</p> <p>1993-03-01</p> <p>Subduction of continental materials at <span class="hlt">active</span> convergent <span class="hlt">margins</span> provides an opportunity to evaluate mechanisms and magnitude of subduction-driven crustal recycling and its potential role in continental growth. Continental materials, in the form of detrital sediments and elements adsorbed out of seawater onto settling sediment particles, are continuously supplied to subduction trenches. The sediments may be accreted and re-attached to the continental crust through collisional processes subducted to depth and subsequently involved in arc magma generation (magmatic recycling) or subducted past the arc into the deep mantle. Cosmogenic 10Be, which is strongly adsorbed onto settling sediment particles, may be used to investigate all aspects of sediment recycling. Because of its atmospheric source and short half-life, the high 10Be concentrations observed in many volcanic arc magmas require that the uppermost part of the sediment column be subducted to depth and some part of it returned to the surface in arc magmas within the measurable 10Be lifetime, effectively a few million years. In the Aleutians, Middle America and Marianas, 10Be is present only in the upper 12m, 100m and 25m, respectively of the subducting oceanic sediment column. Using von Huene and Scholl's 1991 estimate of oceanic sediment supply to trenches, the authors evidence for sediment bypassing of accretionary <span class="hlt">margins</span>, and the limited recycling of most major elements in arc volcanism, estimates of sediment subduction are nearly equal to those required in a steady-state, recycling model for growth of the continents through time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646349','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4646349"><span id="translatedtitle">Latent <span class="hlt">Ice</span> Recrystallization Inhibition <span class="hlt">Activity</span> in Nonantifreeze Proteins: Ca2+-<span class="hlt">Activated</span> Plant Lectins and Cation-<span class="hlt">Activated</span> Antimicrobial Peptides</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2015-01-01</p> <p>Organisms living in polar regions have evolved a series of antifreeze (glyco) proteins (AFGPs) to enable them to survive by modulating the structure of <span class="hlt">ice</span>. These proteins have huge potential for use in cellular cryopreservation, <span class="hlt">ice</span>-resistant surfaces, frozen food, and cryosurgery, but they are limited by their relatively low availability and questions regarding their mode of action. This has triggered the search for biomimetic materials capable of reproducing this function. The identification of new structures and sequences capable of inhibiting <span class="hlt">ice</span> growth is crucial to aid our understanding of these proteins. Here, we show that plant c-type lectins, which have similar biological function to human c-type lectins (glycan recognition) but no sequence homology to AFPs, display calcium-dependent <span class="hlt">ice</span> recrystallization inhibition (IRI) <span class="hlt">activity</span>. This IRI <span class="hlt">activity</span> can be switched on/off by changing the Ca2+ concentration. To show that more (nonantifreeze) proteins may exist with the potential to display IRI, a second motif was considered, amphipathicity. All known AFPs have defined hydrophobic/hydrophilic domains, rationalizing this choice. The cheap, and widely used, antimicrobial Nisin was found to have cation-dependent IRI <span class="hlt">activity</span>, controlled by either acid or addition of histidine-binding ions such as zinc or nickel, which promote its amphipathic structure. These results demonstrate a new approach in the identification of antifreeze protein mimetic macromolecules and may help in the development of synthetic mimics of AFPs. PMID:26407233</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26407233','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26407233"><span id="translatedtitle">Latent <span class="hlt">Ice</span> Recrystallization Inhibition <span class="hlt">Activity</span> in Nonantifreeze Proteins: Ca2+-<span class="hlt">Activated</span> Plant Lectins and Cation-<span class="hlt">Activated</span> Antimicrobial Peptides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mitchell, Daniel E; Gibson, Matthew I</p> <p>2015-10-12</p> <p>Organisms living in polar regions have evolved a series of antifreeze (glyco) proteins (AFGPs) to enable them to survive by modulating the structure of <span class="hlt">ice</span>. These proteins have huge potential for use in cellular cryopreservation, <span class="hlt">ice</span>-resistant surfaces, frozen food, and cryosurgery, but they are limited by their relatively low availability and questions regarding their mode of action. This has triggered the search for biomimetic materials capable of reproducing this function. The identification of new structures and sequences capable of inhibiting <span class="hlt">ice</span> growth is crucial to aid our understanding of these proteins. Here, we show that plant c-type lectins, which have similar biological function to human c-type lectins (glycan recognition) but no sequence homology to AFPs, display calcium-dependent <span class="hlt">ice</span> recrystallization inhibition (IRI) <span class="hlt">activity</span>. This IRI <span class="hlt">activity</span> can be switched on/off by changing the Ca2+ concentration. To show that more (nonantifreeze) proteins may exist with the potential to display IRI, a second motif was considered, amphipathicity. All known AFPs have defined hydrophobic/hydrophilic domains, rationalizing this choice. The cheap, and widely used, antimicrobial Nisin was found to have cation-dependent IRI <span class="hlt">activity</span>, controlled by either acid or addition of histidine-binding ions such as zinc or nickel, which promote its amphipathic structure. These results demonstrate a new approach in the identification of antifreeze protein mimetic macromolecules and may help in the development of synthetic mimics of AFPs. PMID:26407233</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26407233','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26407233"><span id="translatedtitle">Latent <span class="hlt">Ice</span> Recrystallization Inhibition <span class="hlt">Activity</span> in Nonantifreeze Proteins: Ca2+-<span class="hlt">Activated</span> Plant Lectins and Cation-<span class="hlt">Activated</span> Antimicrobial Peptides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mitchell, Daniel E; Gibson, Matthew I</p> <p>2015-10-12</p> <p>Organisms living in polar regions have evolved a series of antifreeze (glyco) proteins (AFGPs) to enable them to survive by modulating the structure of <span class="hlt">ice</span>. These proteins have huge potential for use in cellular cryopreservation, <span class="hlt">ice</span>-resistant surfaces, frozen food, and cryosurgery, but they are limited by their relatively low availability and questions regarding their mode of action. This has triggered the search for biomimetic materials capable of reproducing this function. The identification of new structures and sequences capable of inhibiting <span class="hlt">ice</span> growth is crucial to aid our understanding of these proteins. Here, we show that plant c-type lectins, which have similar biological function to human c-type lectins (glycan recognition) but no sequence homology to AFPs, display calcium-dependent <span class="hlt">ice</span> recrystallization inhibition (IRI) <span class="hlt">activity</span>. This IRI <span class="hlt">activity</span> can be switched on/off by changing the Ca2+ concentration. To show that more (nonantifreeze) proteins may exist with the potential to display IRI, a second motif was considered, amphipathicity. All known AFPs have defined hydrophobic/hydrophilic domains, rationalizing this choice. The cheap, and widely used, antimicrobial Nisin was found to have cation-dependent IRI <span class="hlt">activity</span>, controlled by either acid or addition of histidine-binding ions such as zinc or nickel, which promote its amphipathic structure. These results demonstrate a new approach in the identification of antifreeze protein mimetic macromolecules and may help in the development of synthetic mimics of AFPs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19801462','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19801462"><span id="translatedtitle">Low salinity and high-level UV-B radiation reduce single-cell <span class="hlt">activity</span> in antarctic sea <span class="hlt">ice</span> bacteria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martin, Andrew; Hall, Julie; Ryan, Ken</p> <p>2009-12-01</p> <p>Experiments simulating the sea <span class="hlt">ice</span> cycle were conducted by exposing microbes from Antarctic fast <span class="hlt">ice</span> to saline and irradiance regimens associated with the freeze-thaw process. In contrast to hypersaline conditions (<span class="hlt">ice</span> formation), the simulated release of bacteria into hyposaline seawater combined with rapid exposure to increased UV-B radiation significantly reduced metabolic <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25510620','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25510620"><span id="translatedtitle">New explanations for old observations: <span class="hlt">marginal</span> band coiling during platelet <span class="hlt">activation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sadoul, K</p> <p>2015-03-01</p> <p>Blood platelets are tiny cell fragments derived from megakaryocytes. Their primary function is to control blood vessel integrity and ensure hemostasis if a vessel wall is damaged. Circulating quiescent platelets have a flat, discoid shape maintained by a circumferential microtubule bundle, called the <span class="hlt">marginal</span> band (MB). In the case of injury platelets are <span class="hlt">activated</span> and rapidly adopt a spherical shape due to microtubule motor-induced elongation and subsequent coiling of the MB. Platelet <span class="hlt">activation</span> and shape change can be transient or become irreversible. This depends on the strength of the <span class="hlt">activation</span> stimulus, which is translated into a cytoskeletal crosstalk between microtubules, their motors and the actomyosin cortex, ensuring stimulus-response coupling. Following microtubule motor-driven disc-to-sphere transition, a strong stimulus will lead to compression of the sphere through actomyosin cortex contraction. This will concentrate the granules in the center of the platelet and accelerate their exocytosis. Once granules are released, platelets have crossed the point of no return to irreversible <span class="hlt">activation</span>. This review summarizes the current knowledge of the molecular mechanism leading to platelet shape change, with a special emphasis on microtubules, and refers to previously published observations, which have been essential for generating an integrated view of cytoskeletal rearrangements during platelet <span class="hlt">activation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/7743815','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/7743815"><span id="translatedtitle">Differential effects of growth temperature on <span class="hlt">ice</span> nuclei <span class="hlt">active</span> at different temperatures that are produced by cells of Pseudomonas syringae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gurian-Sherman, D; Lindow, S E</p> <p>1995-04-01</p> <p>The temperature at which <span class="hlt">ice</span>-nucleating bacteria are grown causes differences of 100- to 10,000-fold in the fraction of cells that nucleate <span class="hlt">ice</span> at a given temperature (<span class="hlt">ice</span> nucleation frequency). <span class="hlt">Ice</span> nucleation frequencies of cells of Pseudomonas syringae grown at temperatures that ranged from 9 to 33 degrees C were examined in order to more accurately characterize physiological effects on <span class="hlt">ice</span> nuclei <span class="hlt">active</span> at temperatures of from about -2 to -10 degrees C, the temperature range for this phenotype. Large differences in <span class="hlt">ice</span> nucleation frequency occurred at all but the lowest assay temperatures in cells of P. syringae grown in the temperature range of 15 to 33 degrees C. These differences in <span class="hlt">ice</span> nucleation frequency may be attributed, at least in part, to post-translational factors. Because other studies have indicated that <span class="hlt">ice</span> nuclei <span class="hlt">active</span> at the lowest assay temperatures may reflect the amount of <span class="hlt">ice</span> nucleation protein produced, while higher nucleation temperatures reflect aggregates of this <span class="hlt">ice</span> nucleation protein, data was normalized to the frequency of <span class="hlt">ice</span> nuclei <span class="hlt">active</span> at the lowest <span class="hlt">ice</span> nucleation temperatures (which also correspond to the most abundant nuclei). This was done in order to develop a baseline of comparison for cells grown at different temperatures that more clearly shows possible post-translational effects such as aggregation of the nucleation protein. After this normalization was performed, and in contrast to the results noted above, the number of <span class="hlt">ice</span> nuclei in cells grown at 9, 15, and 20 degrees C that were <span class="hlt">active</span> at different assay temperatures was very similar. Differences in <span class="hlt">ice</span> nucleation frequency that occurred over all assay temperatures in cells grown between 9 and 20 degrees C may be attributed to differences in the total number of nuclei present in the population of cells. The large effects of growth temperature on nucleation frequency have important implications for estimating numbers of <span class="hlt">ice</span> nucleating bacteria in environmental samples</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.6434E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.6434E"><span id="translatedtitle"><span class="hlt">Active</span> deformation of the Congo intracratonic basin and its eastern <span class="hlt">margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Everaerts, Michel; Delvaux, Damien; Beoka, Ateba</p> <p>2015-04-01</p> <p>The Congo basin, one of the largest intracontinental sedimentary basin in the world, developed in Central Africa since the early Neoproterozoic during successive tectonically controlled stages. It formed over an heterogeneous basement as highlighted by aeromagnetic data, composed of Archean cores welded by Proterozoic mobile belts. It contains an average of 4 km and locally up to 8 km of Neoproterozoic to Mesozoic sediments. Since late Mesozoic (Cenomanian), it was submitted to intraplate stresses due to the action of ridge-push forces related to the spreading of the South Atlantic. As a result, most part of the basin entered in an erosional stage while only a small part is still accumulating sediments. <span class="hlt">Active</span> deformation of this vast region (5°N-11°S and 12-27°E) is indicated by a certain level of seismic <span class="hlt">activity</span>, with about 270 earthquakes instrumentally recorded with magnitudes ranging from 2.2 to 5.5 inside the basin and up to up to 6.3 along its NW (Gabon) and NW (Katanga) <span class="hlt">margins</span>. The dozen available focal mechanisms indicate that the basin is under ENE-WSW horizontal compression, under a compressional regime in its center and strike-slip regime along its northern and western <span class="hlt">margins</span>. Low-angle slickensided fault planes are observed in the Samba cored well, constraining the onset of the recent compressional setting in the late Albian, at a time when South America was already separated from Africa and the South Atlantic Ridge was already functioning. Although subtle, recent tectonic deformations (faulting and buckling undulations) can also be inferred from the reflection seismic profiles and the topography and river network. The overall neotectonic picture is inferred as reflecting the development of compressional tectonic instabilities in the basin fill and its <span class="hlt">margins</span> under the action of intraplate stress field and the control of the basement heterogeneity. This is a contribution to preparation of the Seismotectonic Map of Africa by the working group of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A31E3067W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A31E3067W"><span id="translatedtitle">Enhanced High-Temperature <span class="hlt">Ice</span> Nucleation Ability of Crystallized Aerosol Particles after Pre-<span class="hlt">Activation</span> at Low Temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wagner, R.; Moehler, O.; Saathoff, H.; Schnaiter, M.</p> <p>2014-12-01</p> <p>The term pre-<span class="hlt">activation</span> in heterogeneous <span class="hlt">ice</span> nucleation describes the observation that the <span class="hlt">ice</span> nucleation ability of solid <span class="hlt">ice</span> nuclei may improve after they have already been involved in <span class="hlt">ice</span> crystal formation or have been exposed to a temperature lower than 235 K. This can be explained by the retention of small <span class="hlt">ice</span> embryos in cavities or crevices at the particle surface or by the capillary condensation and freezing of supercooled water, respectively. In recent cloud chamber experiments with crystallized aqueous ammonium sulfate, oxalic acid, and succinic acid solution droplets, we have unraveled a further pre-<span class="hlt">activation</span> mechanism under <span class="hlt">ice</span> subsaturated conditions which does not require the preceding growth of <span class="hlt">ice</span> on the seed aerosol particles (Wagner, R. et al., J. Geophys. Res. Atmos., 119, doi: 10.1002/2014JD021741). First cloud expansion experiments were performed at a high temperature (267 - 244 K) where the crystallized particles did not promote any heterogeneous <span class="hlt">ice</span> nucleation. <span class="hlt">Ice</span> nucleation at this temperature, however, could be triggered by temporarily cooling the crystallized particles to a lower temperature. This is because upon crystallization, residuals of the aqueous solution are trapped within the crystals. These captured liquids can freeze when cooled below their respective homogeneous or heterogeneous freezing temperature, leading to the formation of <span class="hlt">ice</span> pockets in the crystalline particles. When warmed again to the higher temperature, <span class="hlt">ice</span> formation by the pre-<span class="hlt">activated</span> particles occurred via depositional and deliquescence-induced <span class="hlt">ice</span> growth, with <span class="hlt">ice</span> <span class="hlt">active</span> fractions ranging from 1 to 4% and 4 to 20%, respectively. Pre-<span class="hlt">activation</span> disappeared above the eutectic temperature, which for the organic acids are close to the melting point of <span class="hlt">ice</span>. This mechanism could therefore contribute to the very small fraction of atmospheric aerosol particles that are still <span class="hlt">ice</span> <span class="hlt">active</span> well above 263 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24044688','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24044688"><span id="translatedtitle">Anthropogenic <span class="hlt">activities</span> have contributed moderately to increased inputs of organic materials in <span class="hlt">marginal</span> seas off China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Liang-Ying; Wei, Gao-Ling; Wang, Ji-Zhong; Guan, Yu-Feng; Wong, Charles S; Wu, Feng-Chang; Zeng, Eddy Y</p> <p>2013-10-15</p> <p>Sediment has been recognized as a gigantic sink of organic materials and therefore can record temporal input trends. To examine the impact of anthropogenic <span class="hlt">activities</span> on the <span class="hlt">marginal</span> seas off China, sediment cores were collected from the Yellow Sea, the inner shelf of the East China Sea (ECS), and the South China Sea (SCS) to investigate the sources and spatial and temporal variations of organic materials, i.e., total organic carbon (TOC) and aliphatic hydrocarbons. The concentration ranges of TOC were 0.5-1.29, 0.63-0.83, and 0.33-0.85%, while those of Σn-C14-35 (sum of n-alkanes with carbon numbers of 14-35) were 0.08-1.5, 0.13-1.97, and 0.35-0.96 μg/g dry weight in sediment cores from the Yellow Sea, ECS inner shelf, and the SCS, respectively. Terrestrial higher plants were an important source of aliphatic hydrocarbons in marine sediments off China. The spatial distribution of Σn-C14-35 concentrations and source diagnostic ratios suggested a greater load of terrestrial organic materials in the Yellow Sea than in the ECS and SCS. Temporally, TOC and Σn-C14-35 concentrations increased with time and peaked at either the surface or immediate subsurface layers. This increase was probably reflective of elevated inputs of organic materials to <span class="hlt">marginal</span> seas off China in recent years, and attributed partly to the impacts of intensified anthropogenic <span class="hlt">activities</span> in mainland China. Source diagnostics also suggested that aliphatic hydrocarbons were mainly derived from biogenic sources, with a minority in surface sediment layers from petroleum sources, consistent with the above-mentioned postulation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6046B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6046B"><span id="translatedtitle">Shelfal sediment transport by undercurrents forces turbidity current <span class="hlt">activity</span> during high sea level, Chile continental <span class="hlt">margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bernhardt, Anne; Hebbeln, Dierk; Regenberg, Marcus; Lückge, Andreas; Strecker, Manfred. R.</p> <p>2016-04-01</p> <p>Understanding the links between terrigenous sediment supply and marine transport and depositional processes along tectonically <span class="hlt">active</span> <span class="hlt">margins</span> is essential to decipher turbidite successions as potential archives of climatic and seismic forcings and to comprehend timing and quantity of marine clastic deposition. Sequence stratigraphic models predict coarse-grained terrigenous sediment delivery to deep-marine sites mainly during sea-level fall and lowstand. Marine clastic deposition during periods of transgression and highstand has been attributed to the continued geomorphic connectivity between terrestrial sediment sources and marine sinks (e.g., rivers connected to submarine canyons) often facilitated by narrow shelves, high sediment supply causing delta migration to the shelf edge, and/or abrupt increases in sediment supply due to climatic variability or catastrophic events. To decipher the controls on Holocene highstand turbidite deposition, we analyzed twelve sediment cores of spatially disparate, coeval Holocene turbidite systems along the Chile <span class="hlt">margin</span> (29-40°S) with changing climatic and geomorphic characteristics but uniform changes of sea level. Intraslope basins in north-central Chile (29-33°S) offshore a narrow to absent shelf record a shut-off of turbidite <span class="hlt">activity</span> during the Holocene. In contrast, core sites in south-central Chile (36-40°S) offshore a wide continental shelf have repeatedly experienced turbidite deposition during sea-level highstand conditions, even though most of the depocenters are not connected via canyons to sediment sources. The interplay of stable high sediment supply related to strong onshore precipitation in combination with a wide shelf, over which undercurrents move sediment towards the shelf edge, appears to control Holocene turbidite sedimentation and sediment export to the deep sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3920166','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3920166"><span id="translatedtitle">In-<span class="hlt">ice</span> evolution of RNA polymerase ribozyme <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Attwater, James; Wochner, Aniela; Holliger, Philipp</p> <p>2014-01-01</p> <p>Mechanisms of molecular self-replication have the potential to shed light upon the origins of life. In particular, self-replication through RNA-catalysed templated RNA synthesis is thought to have supported a primordial ‘RNA World’. However, existing polymerase ribozymes lack the capacity to synthesise RNAs approaching their own size. Here we report the in vitro evolution of such catalysts directly in the RNA-stabilising medium of water-<span class="hlt">ice</span>, which yielded RNA polymerase ribozymes specifically adapted to sub-zero temperatures and able to synthesise RNA in <span class="hlt">ices</span> at temperatures as low as −19°C. Combination of cold-adaptive mutations with a previously described 5′ extension operating at ambient temperatures enabled the design of a first polymerase ribozyme capable of catalysing the accurate synthesis of an RNA sequence longer than itself (adding up to 206 nucleotides), an important stepping stone towards RNA self-replication. PMID:24256864</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NatCh...5.1011A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NatCh...5.1011A"><span id="translatedtitle">In-<span class="hlt">ice</span> evolution of RNA polymerase ribozyme <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Attwater, James; Wochner, Aniela; Holliger, Philipp</p> <p>2013-12-01</p> <p>Mechanisms of molecular self-replication have the potential to shed light on the origins of life. In particular, self-replication through RNA-catalysed templated RNA synthesis is thought to have supported a primordial ‘RNA world’. However, existing polymerase ribozymes lack the capacity to synthesize RNAs approaching their own size. Here, we report the in vitro evolution of such catalysts directly in the RNA-stabilizing medium of water <span class="hlt">ice</span>, which yielded RNA polymerase ribozymes specifically adapted to sub-zero temperatures and able to synthesize RNA in <span class="hlt">ices</span> at temperatures as low as -19 °C. The combination of cold-adaptive mutations with a previously described 5‧ extension operating at ambient temperatures enabled the design of a first polymerase ribozyme capable of catalysing the accurate synthesis of an RNA sequence longer than itself (adding up to 206 nucleotides), an important stepping stone towards RNA self-replication.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24256864','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24256864"><span id="translatedtitle">In-<span class="hlt">ice</span> evolution of RNA polymerase ribozyme <span class="hlt">activity</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Attwater, James; Wochner, Aniela; Holliger, Philipp</p> <p>2013-12-01</p> <p>Mechanisms of molecular self-replication have the potential to shed light on the origins of life. In particular, self-replication through RNA-catalysed templated RNA synthesis is thought to have supported a primordial 'RNA world'. However, existing polymerase ribozymes lack the capacity to synthesize RNAs approaching their own size. Here, we report the in vitro evolution of such catalysts directly in the RNA-stabilizing medium of water <span class="hlt">ice</span>, which yielded RNA polymerase ribozymes specifically adapted to sub-zero temperatures and able to synthesize RNA in <span class="hlt">ices</span> at temperatures as low as -19 °C. The combination of cold-adaptive mutations with a previously described 5' extension operating at ambient temperatures enabled the design of a first polymerase ribozyme capable of catalysing the accurate synthesis of an RNA sequence longer than itself (adding up to 206 nucleotides), an important stepping stone towards RNA self-replication. PMID:24256864</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930003898','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930003898"><span id="translatedtitle">Application of theoretical models to <span class="hlt">active</span> and passive remote sensing of saline <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Han, H. C.; Kong, Jin AU; Shin, Robert T.; Nghiem, Son V.; Kwok, R.</p> <p>1992-01-01</p> <p>The random medium model is used to interpret the polarimetric <span class="hlt">active</span> and passive measurements of saline <span class="hlt">ice</span>. The <span class="hlt">ice</span> layer is described as a host <span class="hlt">ice</span> medium embedded with randomly distributed inhomogeneities, and the underlying sea water is considered as a homogeneous half-space. The scatterers in the <span class="hlt">ice</span> layer are modeled with an ellipsoidal correlation function. The orientation of the scatterers is vertically aligned and azimuthally random. The strong permittivity fluctuation theory is employed to calculate the effective permittivity and the distorted Born approximation is used to obtain the polarimetric scattering coefficients. We also calculate the thermal emissions based on the reciprocity and energy conservation principles. The effects of the random roughness at the air-<span class="hlt">ice</span>, and <span class="hlt">ice</span>-water interfaces are accounted for by adding the surface scattering to the volume scattering return incoherently. The above theoretical model, which has been successfully applied to analyze the radar backscatter data of the first-year sea <span class="hlt">ice</span> near Point Barrow, AK, is used to interpret the measurements performed in the CRRELEX program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1215646','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1215646"><span id="translatedtitle">Seismicity on the western Greenland <span class="hlt">Ice</span> Sheet: Surface fracture in the vicinity of <span class="hlt">active</span> moulins</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Carmichael, Joshua D.; Joughin, Ian; Behn, Mark D.; Das, Sarah; King, Matt A.; Stevens, Laura; Lizarralde, Dan</p> <p>2015-06-25</p> <p>We analyzed geophone and GPS measurements collected within the ablation zone of the western Greenland <span class="hlt">Ice</span> Sheet during a ~35 day period of the 2011 melt season to study changes in <span class="hlt">ice</span> deformation before, during, and after a supraglacial lake drainage event. During rapid lake drainage, <span class="hlt">ice</span> flow speeds increased to ~400% of winter values, and icequake <span class="hlt">activity</span> peaked. At times >7 days after drainage, this seismicity developed variability over both diurnal and longer periods (~10 days), while coincident <span class="hlt">ice</span> speeds fell to ~150% of winter values and showed nightly peaks in spatial variability. Approximately 95% of all detected seismicity in the lake basin and its immediate vicinity was triggered by fracture propagation within near-surface <span class="hlt">ice</span> (<330 m deep) that generated Rayleigh waves. Icequakes occurring before and during drainage frequently were collocated with the down flow (west) end of the primary hydrofracture through which the lake drained but shifted farther west and outside the lake basin after the drainage. We interpret these results to reveal vertical hydrofracture opening and local uplift during the drainage, followed by enhanced seismicity and <span class="hlt">ice</span> flow on the downstream side of the lake basin. This region collocates with interferometric synthetic aperture radar-measured speedup in previous years and could reflect the migration path of the meltwater supplied to the bed by the lake. The diurnal seismic signal can be associated with nightly reductions in surface melt input that increase effective basal pressure and traction, thereby promoting elevated strain in the surficial <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930063900&hterms=saline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsaline','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930063900&hterms=saline&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsaline"><span id="translatedtitle">Application of theoretical models to <span class="hlt">active</span> and passive remote sensing of saline <span class="hlt">ice</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Han, H. C.; Kong, J. A.; Shin, R. T.; Nghiem, S. V.; Kwok, R.</p> <p>1992-01-01</p> <p>The random medium model is used to interpret the polarimetric <span class="hlt">active</span> and passive measurements of saline <span class="hlt">ice</span>. The <span class="hlt">ice</span> layer is described as a host <span class="hlt">ice</span> medium embedded with randomly distributed inhomogeneities, and the underlying sea water is considered as a homogeneous half-space. The scatterers in the <span class="hlt">ice</span> layer are modeled with an ellipsoidal correlation function. The orientation of the scatterers is vertically aligned and azimuthally random. The strong permittivity fluctuation theory is used to calculate the effective permittivity and the distorted Born approximation is used to obtain the polarimetric scattering coefficients. Thermal emissions based on the reciprocity and energy conservation principles are calculated. The effects of the random roughness at the air-<span class="hlt">ice</span>, and <span class="hlt">ice</span>-water interfaces are explained by adding the surface scattering to the volume scattering return incoherently. The theoretical model, which has been successfully applied to analyze the radar backscatter data of first-year sea <span class="hlt">ice</span>, is used to interpret the measurements performed in the Cold Regions Research and Engineering Laboratory's CRRELEX program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18028424','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18028424"><span id="translatedtitle">Effect of annealing time of an <span class="hlt">ice</span> crystal on the <span class="hlt">activity</span> of type III antifreeze protein.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Takamichi, Manabu; Nishimiya, Yoshiyuki; Miura, Ai; Tsuda, Sakae</p> <p>2007-12-01</p> <p>Antifreeze proteins (AFPs) possess a unique ability to bind to a seed <span class="hlt">ice</span> crystal to inhibit its growth. The strength of this binding has been evaluated by thermal hysteresis (TH). In this study, we examined the dependence of TH on experimental parameters, including cooling rate, annealing time, annealing temperature and the size of the seed <span class="hlt">ice</span> crystal for an isoform of type III AFP from notched-fin eelpout (nfeAFP8). TH of nfeAFP8 dramatically decreased when using a fast cooling rate (0.20 degrees C x min(-1)). It also decreased with increasing seed crystal size under a slow cooling rate (0.01 degrees C x min(-1)), but such dependence was not detected under the fast cooling rate. TH was enhanced 1.4- and 2.5-fold when <span class="hlt">ice</span> crystals were annealed for 3 h at 0.05 and 0.25 degrees C below T(m), respectively. After annealing for 2 h at 0.25 degrees C below T(m), TH <span class="hlt">activity</span> showed marked dependence on the size of <span class="hlt">ice</span> crystals. These results suggest that annealing of an <span class="hlt">ice</span> crystal for 2-3 h significantly increased the TH value of type III AFP. Based on a proposed adsorption-inhibition model, we assume that type III AFP undergoes additional <span class="hlt">ice</span> binding to the convex <span class="hlt">ice</span> front over a 2-3 h time scale, which results in the TH dependence on the annealing time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013BGeo...10.8083P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013BGeo...10.8083P"><span id="translatedtitle">Spores of many common airborne fungi reveal no <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> in oil immersion freezing experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pummer, B. G.; Atanasova, L.; Bauer, H.; Bernardi, J.; Druzhinina, I. S.; Fröhlich-Nowoisky, J.; Grothe, H.</p> <p>2013-12-01</p> <p>Fungal spores are ubiquitous biological aerosols, which are considered to act as <span class="hlt">ice</span> nuclei. In this study the <span class="hlt">ice</span> nucleation (IN) <span class="hlt">activity</span> of spores harvested from 29 fungal strains belonging to 21 different species was tested in the immersion freezing mode by microscopic observation of water-in-oil emulsions. Spores of 8 of these strains were also investigated in a microdroplet freezing array instrument. The focus was laid on species of economical, ecological or sanitary significance. Besides common molds (Ascomycota), some representatives of the widespread group of mushrooms (Basidiomycota) were also investigated. Fusarium avenaceum was the only sample showing IN <span class="hlt">activity</span> at relatively high temperatures (about 264 K), while the other investigated fungal spores showed no freezing above 248 K. Many of the samples indeed froze at homogeneous <span class="hlt">ice</span> nucleation temperatures (about 237 K). In combination with other studies, this suggests that only a limited number of species may act as atmospheric <span class="hlt">ice</span> nuclei. This would be analogous to what is already known for the bacterial <span class="hlt">ice</span> nuclei. Apart from that, we selected a set of fungal strains from different sites and exposed them to occasional freezing stress during their cultivation. This was in order to test if the exposure to a cold environment encourages the expression of <span class="hlt">ice</span> nuclei during growth as a way of adaptation. Although the total protein expression was altered by this treatment, it had no significant impact on the IN <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C21A0615A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C21A0615A"><span id="translatedtitle">Observational data from the Programme for Monitoring of the Greenland <span class="hlt">Ice</span> Sheet (PROMICE)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andersen, S. B.; Ahlstrom, A. P.; Andersen, M. L.; Box, J. E.; Citterio, M.; Fausto, R. S.; van As, D.; Forsberg, R.; Skourup, H.; Sandberg, L.; Kristensen, S. S.; Petersen, D.</p> <p>2013-12-01</p> <p>Climate change in the Arctic has resulted in accelerated mass loss from the Greenland <span class="hlt">Ice</span> Sheet. The shortage of observations on the Greenland <span class="hlt">ice</span> sheet infers large uncertainties in estimates of the <span class="hlt">ice</span> mass loss and in predicting the contribution to sea level rise. For this reason the Programme for Monitoring of the Greenland <span class="hlt">Ice</span> Sheet (PROMICE) was established in 2007. The aim of the programme is to quantify the mass loss of the Greenland <span class="hlt">ice</span> sheet and track changes in the extent of the glaciers, <span class="hlt">ice</span> caps and <span class="hlt">ice</span> sheet <span class="hlt">margin</span>. Within PROMICE data sets from several <span class="hlt">activities</span> are collected. These include: A network of currently 19 automatic weather stations on the <span class="hlt">margin</span> of the Greenland <span class="hlt">ice</span> sheet measuring <span class="hlt">ice</span> ablation and snow fall as well as meteorological parameters. Airborne surveys, yielding surface elevation and <span class="hlt">ice</span> depth along the entire <span class="hlt">margin</span> of the Greenland <span class="hlt">ice</span> sheet. Mapping of all Greenland <span class="hlt">ice</span> masses, based on the highest detail aero-photogrammetric maps produced from mid-80's aerial photographs. Real-time data from the PROMICE automatic weather station network is shown in at the PROMICE web site www.promice.org and the data is freely available for download. Data from the airborne surveys and mapping <span class="hlt">activities</span> will also become freely available. Data from PROMICE also contribute to the website www.polarportal.org which is a new Danish web site for providing updated information on the arctic cryosphere to the public.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015QSRv..120...71B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015QSRv..120...71B&link_type=ABSTRACT"><span id="translatedtitle">Turbidite paleoseismology along the <span class="hlt">active</span> continental <span class="hlt">margin</span> of Chile - Feasible or not?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bernhardt, Anne; Melnick, Daniel; Hebbeln, Dierk; Lückge, Andreas; Strecker, Manfred R.</p> <p>2015-07-01</p> <p>Much progress has been made in estimating recurrence intervals of great and giant subduction earthquakes using terrestrial, lacustrine, and marine paleoseismic archives. Recent detailed records suggest these earthquakes may have variable recurrence periods and magnitudes forming supercycles. Understanding seismic supercycles requires long paleoseismic archives that record timing and magnitude of such events. Turbidite paleoseismic archives may potentially extend past earthquake records to the Pleistocene and can thus complement commonly shorter-term terrestrial archives. However, in order to unambiguously establish recurring seismicity as a trigger mechanism for turbidity currents, synchronous deposition of turbidites in widely spaced, isolated depocenters has to be ascertained. Furthermore, characteristics that predispose a seismically <span class="hlt">active</span> continental <span class="hlt">margin</span> to turbidite paleoseismology and the correct sample site selection have to be taken into account. Here we analyze 8 marine sediment cores along 950 km of the Chile <span class="hlt">margin</span> to test for the feasibility of compiling detailed and continuous paleoseismic records based on turbidites. Our results suggest that the deposition of areally widespread, synchronous turbidites triggered by seismicity is largely controlled by sediment supply and, hence, the climatic and geomorphic conditions of the adjacent subaerial setting. The feasibility of compiling a turbidite paleoseismic record depends on the delicate balance between sufficient sediment supply providing material to fail frequently during seismic shaking and sufficiently low sedimentation rates to allow for coeval accumulation of planktonic foraminifera for high-resolution radiocarbon dating. We conclude that offshore northern central Chile (29-32.5°S) Holocene turbidite paleoseismology is not feasible, because sediment supply from the semi-arid mainland is low and almost no Holocene turbidity-current deposits are found in the cores. In contrast, in the humid region</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMDI31A2162Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMDI31A2162Z"><span id="translatedtitle">Three-Dimensional Numerical Modeling of Crustal Growth at <span class="hlt">Active</span> Continental <span class="hlt">Margins</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, G.; Gerya, T.; Tackley, P. J.</p> <p>2011-12-01</p> <p><span class="hlt">Active</span> <span class="hlt">margins</span> are important sites of new continental crust formation by magmatic processes related to the subduction of oceanic plates. We investigate these phenomena using a three-dimensional coupled petrological-geochemical-thermomechanical numerical model, which combines a finite-difference flow solver with a non-diffusive marker-in-cell technique for advection (I3ELVIS code, Gerya and Yuen, PEPI,2007). The model includes mantle flow associated with the subducting plate, water release from the slab, fluid propagation that triggers partial melting at the slab surface, melt extraction and the resulting volcanic crustal growth at the surface. The model also accounts for variations in physical properties (mainly density and viscosity) of both fluids and rocks as a function of local conditions in temperature, pressure, deformation, nature of the rocks, and chemical exchanges. Our results show different patterns of crustal growth and surface topography, which are comparable to nature, during subduction at <span class="hlt">active</span> continental <span class="hlt">margins</span>. Often, two trench-parallel lines of magmatic <span class="hlt">activity</span>, which reflect two maxima of melt production atop the slab, are formed on the surface. The melt extraction rate controls the patterns of new crust at different ages. Moving free water reflects the path of fluids, and the velocity of free water shows the trend of two parallel lines of magmatic <span class="hlt">activity</span>. The formation of new crust in particular time intervals is distributed in finger-like shapes, corresponding to finger-like and ridge-like cold plumes developed atop the subducting slabs (Zhu et al., G-cubed,2009; PEPI,2011). Most of the new crust is basaltic, formed from peridotitic mantle. Granitic crust extracted from melted sediment and upper crust forms in a line closer to the trench, and its distribution reflects the finger-like cold plumes. Dacitic crust extracted from the melted lower crust forms in a line farther away from the trench, and its distribution is anticorrelated with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009GeoRL..3616202S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009GeoRL..3616202S"><span id="translatedtitle">One-hundred-km-scale basins on Enceladus: Evidence for an <span class="hlt">active</span> <span class="hlt">ice</span> shell</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schenk, Paul M.; McKinnon, William B.</p> <p>2009-08-01</p> <p>Stereo-derived topographic mapping of ˜50% of Enceladus reveals at least 6 large-scale, ovoid depressions (basins) 90-175 km across and 800-to-1500 m deep and uncorrelated with geologic boundaries. In contrast, the south polar depression is larger and apparently shallower and correlates with <span class="hlt">active</span> resurfacing. The shape and scale of the basins is inconsistent with impact, geoid surface deflections, or with dynamically supported topography. Isostatic thinning of Enceladus' <span class="hlt">ice</span> shell associated with upwellings (and tidally-driven <span class="hlt">ice</span> melting) can plausibly account for these basins. Thinning implies upwarping of the base of the shell of ˜10-20 km beneath the depressions, depending on total shell thickness; loss of near-surface porosity due to enhanced heat flow may also contribute to basin lows. Alternatively, the basins may overly cold, inactive, and hence denser <span class="hlt">ice</span>, but thermal isostasy alone requires thermal expansion more consistent with clathrate hydrate than water <span class="hlt">ice</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.C33B0723K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.C33B0723K"><span id="translatedtitle">Basal conditions and <span class="hlt">ice</span> dynamics inferred from radar-derived internal stratigraphy of the Northeast Greenland <span class="hlt">Ice</span> Stream</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keisling, B. A.; Christianson, K. A.; Alley, R. B.; Peters, L. E.; Christian, J. E.; Anandakrishnan, S.; Riverman, K. L.; Muto, A.; Jacobel, R. W.</p> <p>2013-12-01</p> <p>We present radio-echo sounding (RES), global positioning system (GPS) and <span class="hlt">active</span> source seismic data from the central portion of the Northeast Greenland <span class="hlt">Ice</span> Stream ~150 km downstream from the onset of streaming flow, which likely initiates due to locally high geothermal flux (~1 W/m2) near the <span class="hlt">ice</span> sheet summit. Our geophysical data show that <span class="hlt">ice</span> stream extent is limited via a feedback between basal hydrology and <span class="hlt">ice</span> sheet surface elevation change. <span class="hlt">Active</span>-source seismic data reveal water-saturated till beneath the central trunk of streaming flow. Subglacial till becomes increasingly dewatered and consolidated toward the shear <span class="hlt">margins</span>. We hypothesize that <span class="hlt">ice</span> accelerates and thins as it flows into NEGIS, producing <span class="hlt">marginal</span> troughs in surface topography. These troughs create steep gradients in the subglacial hydropotential that generate parallel slippery and sticky bands beneath the <span class="hlt">margins</span>, which limit <span class="hlt">ice</span> entrainment across the <span class="hlt">margin</span> and thus restrict further widening. Complex steady-state folds in radar reflectors within the shear <span class="hlt">margins</span> form due to the combined influence of geothermal flux, varying basal shear stress, flow convergence, and bands of variable basal friction. Our strain rate and flux analysis of radar internal layers indicates no major changes in flow dynamics during the past ~10,000 years. However, strain rate modeling suggests that steady-state basal shear heating produces plentiful meltwater beneath the central trunk of streaming flow in addition to that supplied by geothermal flux. This meltwater supports the basal lubrication necessary to maintain streaming flow and may allow remobilization of dewatered <span class="hlt">marginal</span> till. While the main trunk of streaming flow is remarkably stable, complex processes occurring within the shear <span class="hlt">margins</span> merit closer scrutiny. The feedback between surface elevation change and basal water routing could mobilize currently unconsolidated sediments in the <span class="hlt">margins</span> and result in shifts in <span class="hlt">ice</span> dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.C11A0471H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.C11A0471H"><span id="translatedtitle">Evaluating Subglacial Bedform Internal Composition as a Control on Elongation - a Case Study From the Southern <span class="hlt">Margin</span> of the Laurentide <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hess, D. P.; Briner, J.; Menzies, J.</p> <p>2008-12-01</p> <p>Paleo-<span class="hlt">ice</span> streams played a crucial role in the behavior and stability of the Laurentide <span class="hlt">Ice</span> Sheet (LIS). Several studies have identified the signature of fast-moving <span class="hlt">ice</span> on the landscape once occupied by the LIS. A growing body of literature supports the use of subglacial bedform elongation (length/width) as a relative measure of paleo-<span class="hlt">ice</span> flow velocity. Internal sediment rheology has been proposed as a control on elongation in addition to the velocity of overriding <span class="hlt">ice</span>. To test this hypothesis we investigate the internal properties of drumlins and megaflutes in the New York Drumlin Field that display extreme differences in elongation. Exposures created by wave action along the southern shore of Lake Ontario provide access to the internal structure of several drumlins. In addition, roadcuts and quarrying expose drumlins and megaflutes within the interior of the field. Several bedforms are dominated by matrix-supported diamicton with occasional macroscale sand stringers and intraclasts. In contrast, others display sections of massive, well-sorted sand. One exposure (Parmalee) presents a complex stratigraphy with sharp contacts between units of significantly different rheology. Upon comparison, little spatial correlation is found between observed internal composition and bedform elongation. This finding further supports the use of bedform elongation as a proxy measure of <span class="hlt">ice</span> velocity thereby providing confidence in <span class="hlt">ice</span> sheet reconstructions based upon geomorphologic evidence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A11Q..02M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A11Q..02M"><span id="translatedtitle">The Fifth International <span class="hlt">Ice</span> Nucleation Workshop <span class="hlt">Activities</span> FIN-1 and FIN-2: Overview and Selected Results</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moehler, O.; Cziczo, D. J.; DeMott, P. J.; Hiranuma, N.; Petters, M. D.</p> <p>2015-12-01</p> <p>The role of aerosol particles for <span class="hlt">ice</span> formation in clouds is one of the largest uncertainties in understanding the Earth's weather and climate systems, which is related to the poor knowledge of <span class="hlt">ice</span> nucleation microphysics or of the nature and atmospheric abundance of <span class="hlt">ice</span> nucleating particles (INPs). During the recent years, new mobile instruments were developed for measuring the concentration, size and chemical composition of INPs, which were tested during the three-part Fifth International <span class="hlt">Ice</span> Nucleation (FIN) workshop. The FIN <span class="hlt">activities</span> addressed not only instrument issues, but also important science topics like the nature of atmospheric INP and cloud <span class="hlt">ice</span> residuals, the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of relevant atmospheric aerosols, or the parameterization of <span class="hlt">ice</span> formation in atmospheric weather and climate models. The first <span class="hlt">activity</span> FIN-1 was conducted during November 2014 at the AIDA cloud chamber. It involved co-locating nine single particle mass spectrometers to evaluate how well they resolve the INP and <span class="hlt">ice</span> residual composition and how spectra from different instruments compare for relevant atmospheric aerosols. We conducted about 90 experiments with mineral, carbonaceous and biological aerosol types, some also coated with organic and inorganic compounds. The second <span class="hlt">activity</span> FIN-2 was conducted during March 2015 at the AIDA facility. A total of nine mobile INP instruments directly sampled from the AIDA aerosol chambers. Wet suspension and filter samples were also taken for offline INP processing. A refereed blind intercomparison was conducted during two days of the FIN-2 <span class="hlt">activity</span>. The third <span class="hlt">activity</span> FIN-3 will take place at the Desert Research Institute's Storm Peak Laboratory (SPL) in order to test the instruments' performance in the field. This contribution will introduce the FIN <span class="hlt">activities</span>, summarize first results from the formal part of FIN-2, and discuss selected results, mainly from FIN-1 for the effect of coating on the <span class="hlt">ice</span> nucleation (IN) by mineral</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008BGeo....5.1425M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008BGeo....5.1425M"><span id="translatedtitle">Heterogeneous <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of bacteria: new laboratory experiments at simulated cloud conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Möhler, O.; Georgakopoulos, D. G.; Morris, C. E.; Benz, S.; Ebert, V.; Hunsmann, S.; Saathoff, H.; Schnaiter, M.; Wagner, R.</p> <p>2008-10-01</p> <p>The <span class="hlt">ice</span> nucleation <span class="hlt">activities</span> of five different Pseudomonas syringae, Pseudomonas viridiflava and Erwinia herbicola bacterial species and of Snomax™ were investigated in the temperature range between -5 and -15°C. Water suspensions of these bacteria were directly sprayed into the cloud chamber of the AIDA facility of Forschungszentrum Karlsruhe at a temperature of -5.7°C. At this temperature, about 1% of the Snomax™ cells induced immersion freezing of the spray droplets before the droplets evaporated in the cloud chamber. The living cells didn't induce any detectable immersion freezing in the spray droplets at -5.7°C. After evaporation of the spray droplets the bacterial cells remained as aerosol particles in the cloud chamber and were exposed to typical cloud formation conditions in experiments with expansion cooling to about -11°C. During these experiments, the bacterial cells first acted as cloud condensation nuclei to form cloud droplets. Then, only a minor fraction of the cells acted as heterogeneous <span class="hlt">ice</span> nuclei either in the condensation or the immersion mode. The results indicate that the bacteria investigated in the present study are mainly <span class="hlt">ice</span> <span class="hlt">active</span> in the temperature range between -7 and -11°C with an <span class="hlt">ice</span> nucleation (IN) <span class="hlt">active</span> fraction of the order of 10-4. In agreement to previous literature results, the <span class="hlt">ice</span> nucleation efficiency of Snomax™ cells was much larger with an IN <span class="hlt">active</span> fraction of 0.2 at temperatures around -8°C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A13B0319S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A13B0319S"><span id="translatedtitle">Highly <span class="hlt">Active</span> <span class="hlt">Ice</span> Nuclei from Tree Leaf Litters Retain <span class="hlt">Activity</span> for Decades</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schnell, R. C.; Hill, T. C. J.</p> <p>2015-12-01</p> <p>Biogenic <span class="hlt">ice</span> nuclei (IN) studied since the 1960s were first observed in tree leaf litters, in a few bacteria species and later in fungi and lichens. Recently, viable IN bacteria in precipitation have been used as a metric of their possible role in precipitation formation. Although bacterial IN <span class="hlt">activity</span> is deactivated by a variety of common environmental stresses, we present data showing that IN found in a potpourri of decayed plant leaves, bacteria, molds and fungi etc. in plant litters are exceptionally stable and <span class="hlt">active</span> over decades while in storage. As such, their atmospheric IN potential is worthy of further study due to their environmental persistence. In August 1970 litter collected in a grove of deciduous trees near Red Deer, AB, Canada was tested for IN (drop freezing technique). The sample initiated <span class="hlt">ice</span> at -4C with 109 IN per gram of litter <span class="hlt">active</span> at -10C. A few kilograms were stored in a plastic bag and tested every few years for IN content; the IN <span class="hlt">activity</span> remained essentially unchanged over 40 years. In 2011, litter collected in the same grove had the same IN <span class="hlt">activity</span> as the sample tested over the intervening 40 years. Boiling a gram sample of this litter in 100 grams of water deactivated 99 % of the IN <span class="hlt">activity</span> down to -13C. None of 88 different bacteria cultures several of which appeared to Pseudomonads (common IN producing bacteria) from the fresh litter produced any <span class="hlt">active</span> IN. A sample of the litter was placed on the top of a 15 cm column of laboratory grade kaolin and water dripped onto the litter. Ten days later the water reached the bottom of the column. The kaolin was dried and tested for IN. The prior essentially IN free kaolin now exhibited IN <span class="hlt">activity</span> at -4C with 105 IN <span class="hlt">active</span> at -10C. The litter exposed kaolin retained the IN <span class="hlt">activity</span> for 25 years. Baking the kaolin removed the <span class="hlt">active</span> IN. This suggests that IN <span class="hlt">activity</span> attributed to kaolin particles sometimes seen at the nucleus of snow crystals could be of biological origin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......400S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......400S"><span id="translatedtitle">Direct Optical <span class="hlt">Ice</span> Sensing and Closed-Loop Controller Design for <span class="hlt">Active</span> De-<span class="hlt">icing</span> of Wind Turbines Using Distributed Heating</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shajiee, Shervin</p> <p></p> <p><span class="hlt">Ice</span> accumulation on wind turbines operating in cold regions reduces power generation by degrading aerodynamic efficiency and causes mass imbalance and fatigue loads on the blades. Due to blade rotation and variation of the pitch angle, different locations on the blade experience large variations of Reynolds number, Nusselt number, heat loss, and non-uniform <span class="hlt">ice</span> distribution. Hence, applying different amounts of heat flux in different blade locations can provide more effective de-<span class="hlt">icing</span> for the same total power consumption. This large variation of required heat flux motivates using distributed resistive heating, with the capability of locally adjusting thermal power as a function of location on the blade. The main contributions of this research are developing the experimental feasibility of direct <span class="hlt">ice</span> sensing using an optical sensing technique as well as development of a computational framework for implementation of closed-loop localized <span class="hlt">active</span> de-<span class="hlt">icing</span> using distributed sensing. A script-base module was developed in a commercial finite-element software (ANSYS) which provides the capability of (i) Closed-loop de-<span class="hlt">icing</span> simulations for a distributed network of sensors and actuators, (ii) investigating different closed-loop thermal control schemes and their de-<span class="hlt">icing</span> efficiency (iii) optimizing thermal actuation for a distributed resistive heating, and (iv) analyzing different faulty scenarios for sensors and thermal actuators under known faults in the network. Different surrogate models were used to enhance the computational efficiency of this approach. The results showed that optimal value of control parameters in a distributed network of heaters depends on convective heat transfer characteristics, layout of heaters and type of closed-loop controller scheme used for thermal actuation. Furthermore, It was shown that closed-loop control provides much faster de-<span class="hlt">icing</span> than the open-loop constant heat flux thermal actuation. It was observed both experimentally and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C31B0280A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C31B0280A"><span id="translatedtitle">Observations from the Programme for Monitoring of the Greenland <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andersen, S. B.; Ahlstrom, A. P.; Andersen, M. L.; Box, J. E.; Citterio, M.; Colgan, W. T.; Fausto, R. S.; van As, D.; Forsberg, R.; Skourup, H.; Sandberg Sørensen, L.; Kristensen, S. S.; Dall, J.; Kusk, A.; Petersen, D.</p> <p>2014-12-01</p> <p>The Programme for Monitoring of the Greenland <span class="hlt">Ice</span> Sheet (PROMICE) is as an on-going effort initiated in 2007 to monitor changes in the mass budget of the Greenland <span class="hlt">Ice</span> Sheet. The aim of the programme is to quantify the mass loss of the Greenland <span class="hlt">ice</span> sheet and track changes in the extent of the glaciers, <span class="hlt">ice</span> caps and <span class="hlt">ice</span> sheet <span class="hlt">margin</span>. Specifically, PROMICE aims to estimate the mass loss derived from three fundamentally different sources: Surface melt water runoff from the <span class="hlt">ice</span> sheet <span class="hlt">margin</span> Iceberg production Mass loss of individual glaciers and <span class="hlt">ice</span> caps surrounding the <span class="hlt">ice</span> sheet The first is observed by a network of automatic weather stations (AWS) on the <span class="hlt">ice</span> sheet <span class="hlt">margin</span> measuring <span class="hlt">ice</span> ablation as well as meteorological parameters. The second is determined by establishing a so-called 'flux gate' along the entire <span class="hlt">ice</span> sheet <span class="hlt">margin</span> and keeping track of the <span class="hlt">ice</span> passing through this gate. The flux gate is obtained from airborne surveys of <span class="hlt">ice</span> sheet surface elevation and thickness. The volume of the <span class="hlt">ice</span> passing through the gate is derived from maps of the surface velocity of the <span class="hlt">ice</span> sheet, produced from satellite radar. The third is investigated through regular mapping of area and elevation of the approximately 20.000 individual glaciers and <span class="hlt">ice</span> caps in Greenland. Mapping is carried out using recent satellite imagery as well as aerial ortho-photos. Within PROMICE data sets from these <span class="hlt">activities</span> are collected. They include observations from the network of currently about 20 AWS on the <span class="hlt">margin</span> of the Greenland <span class="hlt">ice</span> sheet. Airborne surveys, yielding surface elevation and <span class="hlt">ice</span> depth along the entire <span class="hlt">margin</span> of the Greenland <span class="hlt">ice</span> sheet carried out in 2007 and 2011. A map of all Greenland <span class="hlt">ice</span> masses, based on the highest detail aero-photogrammetric maps produced from mid-80's aerial photographs. Real-time data from the PROMICE AWS network is shown at the web site www.promice.org and the data is freely available for download. Data from the airborne surveys and mapping <span class="hlt">activities</span> are</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008BGD.....5.1445M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008BGD.....5.1445M"><span id="translatedtitle">Heterogeneous <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of bacteria: new laboratory experiments at simulated cloud conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Möhler, O.; Georgakopoulos, D. G.; Morris, C. E.; Benz, S.; Ebert, V.; Hunsmann, S.; Saathoff, H.; Schnaiter, M.; Wagner, R.</p> <p>2008-04-01</p> <p>The <span class="hlt">ice</span> nucleation <span class="hlt">activities</span> of five different Pseudomonas syringae, Pseudomonas viridiflava and Erwinia herbicola bacterial species and of SnomaxTM were investigated in the temperature range between -5 and -15°C. Water suspensions of these bacteria were directly spray into the cloud chamber of the AIDA facility of Forschungszentrum Karlsruhe at a temperature of -5.7°. At this temperature, about 1% of the SnomaxTM cells induced freezing of the spray droplets before they evaporated in the cloud chamber. The other suspensions of living cells didn't induce any measurable <span class="hlt">ice</span> concentration during spray formation at -5.7°. The remaining aerosol was exposed to typical cloud <span class="hlt">activation</span> conditions in subsequent experiments with expansion cooling to about -11°C. During these experiments, the bacterial cells first acted as cloud condensation nuclei to form cloud droplets and then eventually acted as <span class="hlt">ice</span> nuclei to freeze the droplets. The results indicate that the bacteria investigated in the present study are mainly <span class="hlt">ice</span> <span class="hlt">active</span> in the temperature range between -7 and -11°C with an INA fraction of the order of 10-4. The <span class="hlt">ice</span> nucleation efficiency of SnomaxTM cells was much larger with an INA fraction of 0.2 at temperatures around -8°C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20040364','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20040364"><span id="translatedtitle">Analysis of supercooling-facilitating (anti-<span class="hlt">ice</span> nucleation) <span class="hlt">activity</span> of flavonol glycosides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kasuga, Jun; Fukushi, Yukiharu; Kuwabara, Chikako; Wang, Donghui; Nishioka, Atsushi; Fujikawa, Emiko; Arakawa, Keita; Fujikawa, Seizo</p> <p>2010-04-01</p> <p>Deep supercooling xylem parenchyma cells (XPCs) of katsura tree (Cercidiphyllum japonicum) contain four kinds of flavonol glycosides with high supercooling-facilitating (anti-<span class="hlt">ice</span> nucleation) <span class="hlt">activities</span>. These flavonol glycosides have very similar structures, but their supercooling-facilitating <span class="hlt">activities</span> are very different. In this study, we analyzed the supercooling-facilitating <span class="hlt">activities</span> of 12 kinds of flavonol glycosides in order to determine the chemical structures that might affect supercooling-facilitating <span class="hlt">activity</span>. All of the flavonol glycosides tested showed supercooling-facilitating <span class="hlt">activity</span>, although the magnitudes of <span class="hlt">activity</span> differed among the compounds. It was clear that the combination of the position of attachment of the glycosyl moiety, the kind of attached glycosyl moiety and the structure of aglycone determined the magnitude of anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. However, there is still some ambiguity preventing the exact identification of features that affect the magnitude of supercooling-facilitating <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16662901','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16662901"><span id="translatedtitle">Frost injury and heterogeneous <span class="hlt">ice</span> nucleation in leaves of tuber-bearing solanum species : <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of external source of nucleants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rajashekar, C B; Li, P H; Carter, J V</p> <p>1983-04-01</p> <p>The heterogeneous <span class="hlt">ice</span> nucleation characteristics and frost injury in supercooled leaves upon <span class="hlt">ice</span> formation were studied in nonhardened and cold-hardened species and crosses of tuber-bearing Solanum. The <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of the leaves was low at temperatures just below 0 degrees C and further decreased as a result of cold acclimation. In the absence of supercooling, the nonhardened and cold-hardened leaves tolerated extracellular freezing between -3.5 degrees and -8.5 degrees C. However, if <span class="hlt">ice</span> initiation in the supercooled leaves occurred at any temperature below -2.6 degrees C, the leaves were lethally injured.To prevent supercooling in these leaves, various nucleants were tested for their <span class="hlt">ice</span> nucleating ability. One% aqueous suspensions of fluorophlogopite and acetoacetanilide were found to be effective in <span class="hlt">ice</span> nucleation of the Solanum leaves above -1 degrees C. They had threshold temperatures of -0.7 degrees and -0.8 degrees C, respectively, for freezing in distilled H(2)O. Although freezing could be initiated in the Solanum leaves above -1 degrees C with both the nucleants, 1% aqueous fluorophlogopite suspension showed overall higher <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> than acetoacetanilide and was nontoxic to the leaves. The cold-hardened leaves survived between -2.5 degrees and -6.5 degrees using 1% aqueous fluorophlogopite suspension as a nucleant. The killing temperatures in the cold-hardened leaves were similar to those determined using <span class="hlt">ice</span> as a nucleant. However, in the nonhardened leaves, use of fluorophlogopite as a nucleant resulted in lethal injury at higher temperatures than those estimated using <span class="hlt">ice</span> as a nucleant. PMID:16662901</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.7621M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18.7621M&link_type=ABSTRACT"><span id="translatedtitle">Research Station "<span class="hlt">Ice</span> Base "Cape Baranov"- overview of <span class="hlt">activities</span> in 2013 - 2015 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Makshtas, Alexander; Sokolov, Vladimir; Bogorodskii, Peter; Kustov, Vasily; Movchan, Vadim; Laurila, Tuomas; Asmi, Eija; Popovicheva, Olga; Eleftheriadis, Kostas</p> <p>2016-04-01</p> <p>Research Station "<span class="hlt">Ice</span> base "Cape Baranov" of Arctic and Antarctic Research Institute (AARI) had been opened in the fall 2013 on the Bolshevik Island, Archipelago Severnaya Zemlia. Now it is going as the integrated observatory, conducting comprehensive studies in practically all areas of Earth Sciences: from free atmosphere to sea <span class="hlt">ice</span> and sea water structure in the Shokalsky Strait, from glaciers to permafrost, from paleogeography to ornithology. Overview of <span class="hlt">activities</span> together with some preliminary results of field works at the station performing in 2014 - 2015 years by international multidisciplinary team in frame of free atmosphere, atmospheric surface layer, greenhouse gases and aerosol studies is presented together with model estimations of <span class="hlt">active</span> soil layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=182997','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=182997"><span id="translatedtitle">Topical Application of <span class="hlt">Ice-Nucleating-Active</span> Bacteria Decreases Insect Cold Tolerance †</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Strong-Gunderson, Janet M.; Lee, Richard E.; Lee, Marcia R.</p> <p>1992-01-01</p> <p>The majority of overwintering insects avoid lethal freezing by lowering the temperature at which <span class="hlt">ice</span> spontaneously nucleates within their body fluids. We examined the effect of <span class="hlt">ice-nucleating-active</span> bacteria on the cold-hardiness of the lady beetle, Hippodamia convergens, a freeze-intolerant species that overwinters by supercooling to ca. −16°C. Topical application of the <span class="hlt">ice-nucleating-active</span> bacteria Pseudomonas syringae increased the supercooling point to temperatures as high as −3°C. This decrease in cold tolerance was maintained for at least 3 days after treatment. Various treatment doses (108, 106, and 104 bacteria per ml) and modes of action (bacterial ingestion and topical application) were also compared. At the highest concentration of topically applied P. syringae, 50% of the beetles froze between −2 and −4°C. After topical application at the lowest concentration, 50% of the individuals froze by −11°C. In contrast, beetles fed bacteria at this concentration did not begin to freeze until −10°C, and 50% were frozen only at temperatures of −13°C or less. In addition to reducing the supercooling capacity in H. convergens, <span class="hlt">ice-nucleating-active</span> bacteria also significantly reduced the cold-hardiness of four additional insects. These data demonstrate that <span class="hlt">ice-nucleating-active</span> bacteria can be used to elevate the supercooling point and thereby decrease insect cold tolerance. The results of this study support the proposition that <span class="hlt">ice-nucleating-active</span> bacteria may be used as a biological insecticide for the control of insect pests during the winter. Images PMID:16348764</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813839S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813839S"><span id="translatedtitle">Mass transport deposits as witness of Holocene seismic <span class="hlt">activity</span> on the Ligurian <span class="hlt">margin</span>, Western Mediterranean (ASTARTE project)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Samalens, Kevin; Cattaneo, Antonio; Migeon, Sébastien</p> <p>2016-04-01</p> <p>The Ligurian <span class="hlt">Margin</span> (Western Mediterranean) is at the transition between the Southern Alpes and the Liguro-Provençal <span class="hlt">margin</span> and it is one of the most seismic areas of France. Several historic earthquakes have been indexed; the strongest, on February 23rd, 1887, occurred offshore Menton and Imperia and also caused a tsunami wave. Its equivalent magnitude has been estimated between 6 and 6.5. In addition, a moderate recurrent seismicity shakes the <span class="hlt">margin</span>. The aim of this study is to understand the link between seismic <span class="hlt">activity</span> and slope destabilization, and to identify the sedimentary deposits resulting from mass transport or turbidity currents. During Malisar (Geoazur laboratory), Prisme 2 and Prisme 3 (Ifremer) cruises, bathymetry, seafloor imagery (SAR), geophysics data (CHIRP SYSIF and high resolution seismics), and sediment cores have been acquired on the continental slope, focussing on canyons and submarine landslides, and in the basin. These data record numerous mass transport deposits (slump, debrites) in the different physiographic areas of the <span class="hlt">margin</span>. To search for evidences of past Ligurian <span class="hlt">margin</span> seismicity during the Holocene, we focused on the northeast part of the <span class="hlt">margin</span>, the Finale area. We identified and sampled acoustically transparent Mass Transport Deposits up to 20-m thick in the bottom of three coaleshing canyons: Noli, Pora and Centa canyons from W to E in the area offshore Finale Ligure. We also recovered an MTD in the collecting deeper canyon system. MTDs in cores appear as sediment with different degrees of deformation (tilted blocks, slump, debrites) and are topped by hemipelagites. The radiocarbon age of the top of MTDs can be considered synchronous and centered around 4900 yr BP. Mass wasting occurring over more than 50 km of the Ligurian <span class="hlt">margin</span> could indicate that an earthquake stroke the Finale area sector at that time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/5875434','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/5875434"><span id="translatedtitle"><span class="hlt">Active</span> processes on a mixed clastic carbonate Brazilian shelf <span class="hlt">margin</span>: Importance for hydrocarbon exploration in turbidites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cainelli, C. )</p> <p>1991-03-01</p> <p>The search for subtle hydrocarbon accumulations in turbidite systems requires additional approaches for more successful exploration, particularly when direct recognition on seismic lines is difficult. This includes the determination and understanding of processes controlling sand distribution on the shelf and the mapping of sand pathways from the shelf to the slop/basin that can guide efforts to look for more favorable sites for turbidite sandstone deposition. The approach can be exemplified in the Sergipe-Alagoas basin, on the Brazillian Atlantic passive <span class="hlt">margin</span>. The section analyzed is the Piacabucu Formation, a thick seaward prograding wedge composed of coastal sandstones and shelf edge carbonates on a narrow shelf and slope-basin shales with turbidite lenses. Waves and currents control the redistribution of sediments transported to the shelf by rivers. More wave energy is expended in ten hours in the San Francisco delta than in an entire year in the Mississippi delta. Such environment precludes deposition of mud on the shelf, but it stimulates the development of shelf edge carbonates. Rimed carbonates along the shelf break serve as a barrier for downslope movements of coarse-grained sediment, where turbidites are oil targets. The search for gaps in the carbonate barrier which can tap the behind-barrier sands is critical for sand-rich turbidite development. It is believed that canyons create these gaps and act as <span class="hlt">active</span> turbidity current routes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1813675Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..1813675Y&link_type=ABSTRACT"><span id="translatedtitle">Characterization of the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of an airborne Penicillium species</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yordanova, Petya; Hill, Thomas C. J.; Pummer, Bernhard G.; Franc, Gary D.; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine</p> <p>2016-04-01</p> <p>Microorganisms are ubiquitous both on and above the Earth. Several bacterial and fungal spe-cies are the focus of atmospheric studies due to their ability to trigger <span class="hlt">ice</span> formation at high subzero temperatures. Thus, they have potential to modify cloud albedo, lifetime and precipita-tion, and ultimately the hydrological cycle. Several fungal strains have already been identified as possessing <span class="hlt">ice</span> nucleation (IN) <span class="hlt">activity</span>, and recent studies have shown that IN <span class="hlt">active</span> fungi are present in the cultivable community of air and soil samples [1, 2]. However, the abundance, diversity, and sources of fungal <span class="hlt">ice</span> nuclei in the atmosphere are still poorly characterized. In this study, fungal colonies obtained from air samples were screened for IN <span class="hlt">activity</span> in the droplet-freezing assay described in Fröhlich-Nowoisky et al., 2015 [2]. Out of 128 tested iso-lates, two were found to catalyze <span class="hlt">ice</span> formation at temperatures up to -4°C. By DNA analysis, both isolates were classified as Penicillium spp. The freezing <span class="hlt">activity</span> of both was further char-acterized after different filtration, heat, and enzymatic treatments in the temperature range from ‑4°C to ‑15°C. Preliminary results show that a proteinaceous compound is responsible for the IN <span class="hlt">activity</span>. Furthermore, ongoing experiments indicate that the <span class="hlt">activity</span> is associated only with the hyphae. [1] Huffman, et al. (2013): Atmos. Chem. Phys., 13, 6151-6164. [2] Fröhlich-Nowoisky et al. (2015): Biogeosciences, 12: 1057-1071.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1813675Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1813675Y"><span id="translatedtitle">Characterization of the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of an airborne Penicillium species</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yordanova, Petya; Hill, Thomas C. J.; Pummer, Bernhard G.; Franc, Gary D.; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine</p> <p>2016-04-01</p> <p>Microorganisms are ubiquitous both on and above the Earth. Several bacterial and fungal spe-cies are the focus of atmospheric studies due to their ability to trigger <span class="hlt">ice</span> formation at high subzero temperatures. Thus, they have potential to modify cloud albedo, lifetime and precipita-tion, and ultimately the hydrological cycle. Several fungal strains have already been identified as possessing <span class="hlt">ice</span> nucleation (IN) <span class="hlt">activity</span>, and recent studies have shown that IN <span class="hlt">active</span> fungi are present in the cultivable community of air and soil samples [1, 2]. However, the abundance, diversity, and sources of fungal <span class="hlt">ice</span> nuclei in the atmosphere are still poorly characterized. In this study, fungal colonies obtained from air samples were screened for IN <span class="hlt">activity</span> in the droplet-freezing assay described in Fröhlich-Nowoisky et al., 2015 [2]. Out of 128 tested iso-lates, two were found to catalyze <span class="hlt">ice</span> formation at temperatures up to -4°C. By DNA analysis, both isolates were classified as Penicillium spp. The freezing <span class="hlt">activity</span> of both was further char-acterized after different filtration, heat, and enzymatic treatments in the temperature range from -4°C to -15°C. Preliminary results show that a proteinaceous compound is responsible for the IN <span class="hlt">activity</span>. Furthermore, ongoing experiments indicate that the <span class="hlt">activity</span> is associated only with the hyphae. [1] Huffman, et al. (2013): Atmos. Chem. Phys., 13, 6151-6164. [2] Fröhlich-Nowoisky et al. (2015): Biogeosciences, 12: 1057-1071.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.5036N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.5036N"><span id="translatedtitle">Can we define an asymptotic value for the <span class="hlt">ice</span> <span class="hlt">active</span> surface site density for heterogeneous <span class="hlt">ice</span> nucleation?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Niedermeier, Dennis; Augustin-Bauditz, Stefanie; Hartmann, Susan; Wex, Heike; Ignatius, Karoliina; Stratmann, Frank</p> <p>2015-05-01</p> <p>The immersion freezing behavior of droplets containing size-segregated, monodisperse feldspar particles was investigated. For all particle sizes investigated, a leveling off of the frozen droplet fraction was observed reaching a plateau within the heterogeneous freezing temperature regime (T >- 38°C). The frozen fraction in the plateau region was proportional to the particle surface area. Based on these findings, an asymptotic value for <span class="hlt">ice</span> <span class="hlt">active</span> surface site density ns, which we named ns⋆, could be determined for the investigated feldspar sample. The comparison of these results with those of other studies not only elucidates the general feasibility of determining such an asymptotic value but also shows that the value of ns⋆ strongly depends on the method of the particle surface area determination. However, such an asymptotic value might be an important input parameter for atmospheric modeling applications. At least it shows that care should be taken when ns is extrapolated to lower or higher temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10949298','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10949298"><span id="translatedtitle">Water <span class="hlt">activity</span> as the determinant for homogeneous <span class="hlt">ice</span> nucleation in aqueous solutions</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koop; Luo; Tsias; Peter</p> <p>2000-08-10</p> <p>The unique properties of water in the supercooled (metastable) state are not fully understood. In particular, the effects of solutes and mechanical pressure on the kinetics of the liquid-to-solid phase transition of supercooled water and aqueous solutions to <span class="hlt">ice</span> have remained unresolved. Here we show from experimental data that the homogeneous nucleation of <span class="hlt">ice</span> from supercooled aqueous solutions is independent of the nature of the solute, but depends only on the water <span class="hlt">activity</span> of the solution--that is, the ratio between the water vapour pressures of the solution and of pure water under the same conditions. In addition, we show that the presence of solutes and the application of pressure have a very similar effect on <span class="hlt">ice</span> nucleation. We present a thermodynamic theory for homogeneous <span class="hlt">ice</span> nucleation, which expresses the nucleation rate coefficient as a function of water <span class="hlt">activity</span> and pressure. Recent observations from clouds containing <span class="hlt">ice</span> are in good agreement with our theory and our results should help to overcome one of the main weaknesses of numerical models of the atmosphere, the formulation of cloud processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A13B0312B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A13B0312B"><span id="translatedtitle">Insights Into the Effects of Internal Variability, External Variability, and <span class="hlt">Active</span> Sites on Heterogeneous <span class="hlt">Ice</span> Nucleation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beydoun, H.; Sullivan, R. C.; Polen, M.</p> <p>2015-12-01</p> <p>Heterogeneous <span class="hlt">ice</span> nucleation (HIN) remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating HIN processes with relevant atmospheric conditions have largely contributed to the absence of a consistent and comprehensive parameterization. Here we formulate a new <span class="hlt">ice</span> <span class="hlt">active</span> surface site-based stochastic model of HIN with the unique feature of invoking a continuum assumption on the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> (contact angle) of an aerosol particle's surface. The result is a particle specific property g that defines a distribution of local surface <span class="hlt">ice</span> nucleation rates. Upon integration this yields a full freezing probability function for an <span class="hlt">ice</span> nucleating particle. Current cold plate droplet freezing measurements provide a great resource for studying the freezing ability of many atmospheric aerosol systems. A method based on statistical significance and critical area analysis is presented that can resolve the two-dimensional nature of the <span class="hlt">ice</span> nucleation ability of aerosol particles: variability in <span class="hlt">active</span> sites and freezing rates along an individual particle's surface, as well as variability between two particles of the same type in an aerosol population. When applied to published experimental data, the method demonstrates its ability to comprehensively interpret droplet freezing spectra of variable particle mass and surface area concentrations. By fitting the high concentration freezing curves to a statistically significant <span class="hlt">active</span> site density function, the lower concentration freezing curves are successfully fitted via a process of random sampling from the statistically significant distribution. Using the new scheme, comprehensive parameterizations that can track the frozen fraction of cloud droplets in larger atmospheric models are derived.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/7781327','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/7781327"><span id="translatedtitle">Membrane fluidity as a factor in production and stability of bacterial <span class="hlt">ice</span> nuclei <span class="hlt">active</span> at high subfreezing temperatures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lindow, S E</p> <p>1995-06-01</p> <p>Detailed measurements were made of the rate of appearance of bacterial <span class="hlt">ice</span> nuclei upon cooling of suspensions of Pseudomonas syringae cells and the disappearance of <span class="hlt">ice</span> nuclei upon warming of the cells before assay for <span class="hlt">ice</span> nucleation <span class="hlt">activity</span>. While no substantial change in numbers of <span class="hlt">ice</span> nuclei <span class="hlt">active</span> at either -5 or at -9 degrees C was observed in cells that were grown at temperatures lower than 24 degrees C and cooled to 21 degrees C before assay, large increases in -5 but not -9 degrees C <span class="hlt">ice</span> nuclei were observed in cells grown at temperatures greater than 24 degrees C. <span class="hlt">Ice</span> nucleation <span class="hlt">activity</span> of cells subjected to a decrease in temperature before assay increased immediately upon temperature shift, but 8 to 12 min was required before maximum rates of increase in numbers of <span class="hlt">ice</span> nuclei were observed. The rate of appearance of <span class="hlt">ice</span> nuclei in cell suspensions incubated at relatively cold temperatures prior to assay was substantially less than those incubated at temperatures approaching 24 degrees C. Cells rapidly lost <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> when warmed to above 27 degrees C before assay; the rate of loss of <span class="hlt">ice</span> nuclei in cells grown at a given temperature increased rapidly as the temperature to which they were warmed before assay increased. <span class="hlt">Ice</span> nuclei disappeared most rapidly when cells grown at low temperatures were warmed before assay, suggesting that <span class="hlt">ice</span> nucleus stability was lower in highly fluid membranes. The logarithm of the half-life of <span class="hlt">ice</span> nuclei in cells was directly related to the concentration of the membrane fluidizing agent, 2-phenethyl alcohol, in which they were suspended. PMID:7781327</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/876351','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/876351"><span id="translatedtitle">Three-dimensional representations of salt-dome <span class="hlt">margins</span> at four <span class="hlt">active</span> strategic petroleum reserve sites.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rautman, Christopher Arthur; Stein, Joshua S.</p> <p>2003-01-01</p> <p>Existing paper-based site characterization models of salt domes at the four <span class="hlt">active</span> U.S. Strategic Petroleum Reserve sites have been converted to digital format and visualized using modern computer software. The four sites are the Bayou Choctaw dome in Iberville Parish, Louisiana; the Big Hill dome in Jefferson County, Texas; the Bryan Mound dome in Brazoria County, Texas; and the West Hackberry dome in Cameron Parish, Louisiana. A new modeling algorithm has been developed to overcome limitations of many standard geological modeling software packages in order to deal with structurally overhanging salt <span class="hlt">margins</span> that are typical of many salt domes. This algorithm, and the implementing computer program, make use of the existing interpretive modeling conducted manually using professional geological judgement and presented in two dimensions in the original site characterization reports as structure contour maps on the top of salt. The algorithm makes use of concepts of finite-element meshes of general engineering usage. Although the specific implementation of the algorithm described in this report and the resulting output files are tailored to the modeling and visualization software used to construct the figures contained herein, the algorithm itself is generic and other implementations and output formats are possible. The graphical visualizations of the salt domes at the four Strategic Petroleum Reserve sites are believed to be major improvements over the previously available two-dimensional representations of the domes via conventional geologic drawings (cross sections and contour maps). Additionally, the numerical mesh files produced by this modeling <span class="hlt">activity</span> are available for import into and display by other software routines. The mesh data are not explicitly tabulated in this report; however an electronic version in simple ASCII format is included on a PC-based compact disk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70017052','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70017052"><span id="translatedtitle">Dissolution of bedded rock salt: A seismic profile across the <span class="hlt">active</span> eastern <span class="hlt">margin</span> of the Hutchinson Salt Member, central Kansas</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Anderson, N.L.; Hopkins, J.; Martinez, A.; Knapp, R.W.; Macfarlane, P.A.; Watney, W.L.; Black, R.</p> <p>1994-01-01</p> <p>Since late Tertiary, bedded rock salt of the Permian Hutchinson Salt Member has been dissolved more-or-less continuously along its <span class="hlt">active</span> eastern <span class="hlt">margin</span> in central Kansas as a result of sustained contact with unconfined, undersaturated groundwater. The associated westward migration of the eastern <span class="hlt">margin</span> has resulted in surface subsidence and the contemporaneous sedimentation of predominantly valley-filling Quarternary alluvium. In places, these alluvium deposits extend more than 25 km to the east of the present-day edge of the main body of contiguous rock salt. The <span class="hlt">margin</span> could have receded this distance during the past several million years. From an environmental perspective, the continued leaching of the Hutchinson Salt is a major concern. This predominantly natural dissolution occurs in a broad zone across the central part of the State and adversely affects groundwater and surface-water quality as nonpoint source pollution. Significant surface subsidence occurs as well. Most of these subsidence features have formed gradually; others developed in a more catastrophic manner. The latter in particular pose real threats to roadways, railways, and buried oil and gas pipelines. In an effort to further clarify the process of natural salt dissolution in central Kansas and with the long-term goal of mitigating the adverse environmental affects of such leaching, the Kansas Geological Survey acquired a 4-km seismic profile across the eastern <span class="hlt">margin</span> of the Hutchinson Salt in the Punkin Center area of central Kansas. The interpretation of these seismic data (and supporting surficial and borehole geologic control) is consistent with several hypotheses regarding the process and mechanisms of dissolution. More specifically these data support the theses that: 1. (1) Dissolution along the <span class="hlt">active</span> eastern <span class="hlt">margin</span> of the Hutchinson Salt Member was initiated during late Tertiary. Leaching has resulted in the steady westward migration of the eastern <span class="hlt">margin</span>, surface subsidence, and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994CG.....20..889A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994CG.....20..889A"><span id="translatedtitle">Dissolution of bedded rock salt: A seismic profile across the <span class="hlt">active</span> eastern <span class="hlt">margin</span> of the Hutchinson Salt Member, central Kansas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, Neil L.; Hopkins, John; Martinez, Alex; Knapp, Ralph W.; Macfarlane, P. Allan; Watney, W. Lynn; Black, Ross</p> <p>1994-06-01</p> <p>Since late Tertiary, bedded rock salt of the Permian Hutchinson Salt Member has been dissolved more-or-less continuously along its <span class="hlt">active</span> eastern <span class="hlt">margin</span> in central Kansas as a result of sustained contact with unconfined, undersaturated groundwater. The associated westward migration of the eastern <span class="hlt">margin</span> has resulted in surface subsidence and the contemporaneous sedimentation of predominantly valley-filling Quarternary alluvium. In places, these alluvium deposits extend more than 25 km to the east of the present-day edge of the main body of contiguous rock salt. The <span class="hlt">margin</span> could have receded this distance during the past several million years. From an environmental perspective, the continued leaching of the Hutchinson Salt is a major concern. This predominantly natural dissolution occurs in a broad zone across the central part of the State and adversely affects groundwater and surface-water quality as nonpoint source pollution. Significant surface subsidence occurs as well. Most of these subsidence features have formed gradually; others developed in a more catastrophic manner. The latter in particular pose real threats to roadways, railways, and buried oil and gas pipelines. In an effort to further clarify the process of natural salt dissolution in central Kansas and with the long-term goal of mitigating the adverse environmental affects of such leaching, the Kansas Geological Survey acquired a 4-km seismic profile across the eastern <span class="hlt">margin</span> of the Hutchinson Salt in the Punkin Center area of central Kansas. The interpretation of these seismic data (and supporting surficial and borehole geologic control) is consistent with several hypotheses regarding the process and mechanisms of dissolution. More specifically these data support the theses that: (1) Dissolution along the <span class="hlt">active</span> eastern <span class="hlt">margin</span> of the Hutchinson Salt Member was initiated during late Tertiary. Leaching has resulted in the steady westward migration of the eastern <span class="hlt">margin</span>, surface subsidence, and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1215646-seismicity-western-greenland-ice-sheet-surface-fracture-vicinity-active-moulins','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1215646-seismicity-western-greenland-ice-sheet-surface-fracture-vicinity-active-moulins"><span id="translatedtitle">Seismicity on the western Greenland <span class="hlt">Ice</span> Sheet: Surface fracture in the vicinity of <span class="hlt">active</span> moulins</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Carmichael, Joshua D.; Joughin, Ian; Behn, Mark D.; Das, Sarah; King, Matt A.; Stevens, Laura; Lizarralde, Dan</p> <p>2015-06-25</p> <p>We analyzed geophone and GPS measurements collected within the ablation zone of the western Greenland <span class="hlt">Ice</span> Sheet during a ~35 day period of the 2011 melt season to study changes in <span class="hlt">ice</span> deformation before, during, and after a supraglacial lake drainage event. During rapid lake drainage, <span class="hlt">ice</span> flow speeds increased to ~400% of winter values, and icequake <span class="hlt">activity</span> peaked. At times >7 days after drainage, this seismicity developed variability over both diurnal and longer periods (~10 days), while coincident <span class="hlt">ice</span> speeds fell to ~150% of winter values and showed nightly peaks in spatial variability. Approximately 95% of all detected seismicitymore » in the lake basin and its immediate vicinity was triggered by fracture propagation within near-surface <span class="hlt">ice</span> (<330 m deep) that generated Rayleigh waves. Icequakes occurring before and during drainage frequently were collocated with the down flow (west) end of the primary hydrofracture through which the lake drained but shifted farther west and outside the lake basin after the drainage. We interpret these results to reveal vertical hydrofracture opening and local uplift during the drainage, followed by enhanced seismicity and <span class="hlt">ice</span> flow on the downstream side of the lake basin. This region collocates with interferometric synthetic aperture radar-measured speedup in previous years and could reflect the migration path of the meltwater supplied to the bed by the lake. The diurnal seismic signal can be associated with nightly reductions in surface melt input that increase effective basal pressure and traction, thereby promoting elevated strain in the surficial <span class="hlt">ice</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP51D1161M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP51D1161M"><span id="translatedtitle">Luminescence Chronology for the Formation of Glacial Lake Calgary, Southern Alberta, Canada: Age Constraints for the Initiation of the Late Pleistocene Retreat of the Laurentide <span class="hlt">Ice</span> Sheet from its Western <span class="hlt">Margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Munyikwa, K.; Rittenour, T. M.</p> <p>2014-12-01</p> <p>Glacial Lake Calgary in southern Alberta, Canada, was a Late Pleistocene proglacial lake that formed along the southwest <span class="hlt">margin</span> of the Laurentide <span class="hlt">Ice</span> Sheet (LIS), dammed by the retreating <span class="hlt">ice</span> sheet <span class="hlt">margin</span>. Attempts to constrain the age of the lake using radiocarbon methods have been hampered by the lack of datable organic material. In an effort to apply an alternative chronometer, this study uses two optically stimulated luminescence (OSL) dating approaches to date fine grained sand and silt that were deposited in the lake during its existence. OSL dating determines the depositional ages of sediments by measuring the energy from ionizing radiation that is stored in mineral grains such as quartz and feldspar. Dividing the stored energy, also referred to as the paleodose, by the rate at which the dose accumulated, allows an age to be ascertained. In one method applied in this study, the paleodose stored in the feldspar component of the sediment is determined using normalized infrared stimulated luminescence signals acquired using a portable OSL reader. In the second method, blue optically stimulated luminescence signals obtained from quartz separates from the sediment by employing a regular OSL reader and standard protocols are used to determine the paleodose. After correcting the feldspar data for anomalous fading, the age results from the two dating approaches are compared. The ages signify a time period by which the LIS had retreated from the study area and, hence, serve as constraints for the initiation of the retreat of the <span class="hlt">ice</span> sheet from its western limit. Advantages and limitations of the dating methods are briefly discussed. Constraining the chronology of the retreat of the LIS from western Canada allows for a better understanding of the driving forces behind <span class="hlt">ice</span> sheet retreat. Secondly, assigning a temporal scale to the postglacial evolution of the environment of the region permits a better insight into the dynamics of the physical and biological</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70026440','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70026440"><span id="translatedtitle">Evidence for stagnation of the Harvard sublobe (Lake Michigan lobe) in Northeastern Illinois, U.S.A., from 24 000 to 17 600 BP and subsequent tundra-like <span class="hlt">ice-marginal</span> paleoenvironments from 17 600 to 15 700 BP</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Curry, B. Brandon; Yansa, C.H.</p> <p>2004-01-01</p> <p>Glacial deposits of the last glaciation associated with the Harvard sublobe (Lake Michigan lobe) in northeastern Illinois, U.S.A., occur between sediment with dateable organics. The lower organics include fragments of Picea sp. as young as 24 000 ?? 270 BP. The supraglacial organics occur sparsely in laminated silt and fine sand in landforms that are positioned relatively high on the landscape, such as deposits from <span class="hlt">ice</span>-walled lakes. These terrestrial organics yield ages that are 2500 to 1300 14C years older than organics at the base of sediment successions in nearby kettle basins. Basal 14C ages from four upland sites range from 17 610 ?? 270 to 16 120 ?? 80 BP. Our revised time-distance diagram of the Harvard sublobe now reflects a period of stagnation from 24 000 to about 17 600 BP. The supraglacial lacustrine silt yielded plant macrofossil assemblages of primarily tundra plants, including Salix herbacea and Dryas integrifolia. These plants likely grew in supraglacial and <span class="hlt">ice-marginal</span> environments. The ostracode fauna include Cytherissa lacustris and Limnocythere friabilis. Geomorphic relations and ostracode ecology indicate that more than 17 m of <span class="hlt">ice</span> buttressed some of the supraglacial lakes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013018','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013018"><span id="translatedtitle">Analysis of the Effect of Water <span class="hlt">Activity</span> on <span class="hlt">Ice</span> Formation Using a New Theory of Nucleation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barahona, Donifan</p> <p>2013-01-01</p> <p>In this work a new theory of nucleation is developed and used to investigate the effect of water <span class="hlt">activity</span> on the formation of <span class="hlt">ice</span> within super-cooled droplets. The new theory is based on a novel concept where the interface is assumed to be made of liquid molecules trapped by the solid matrix. Using this concept new expressions are developed for the critical <span class="hlt">ice</span> germ size and the nucleation work, with explicit dependencies on temperature and water <span class="hlt">activity</span>. However unlike previous approaches, the new theory does not depend on the interfacial tension between liquid and <span class="hlt">ice</span>. Comparison against experimental results shows that the new theory is able to reproduce the observed effect of water <span class="hlt">activity</span> on nucleation rate and freezing temperature. It allows for the first time a theoretical derivation of the constant shift in water <span class="hlt">activity</span> between melting and nucleation. The new theory offers a consistent thermodynamic view of <span class="hlt">ice</span> nucleation, simple enough to be applied in atmospheric models of cloud formation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013086','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013086"><span id="translatedtitle">PeV Neutrinos Observed by <span class="hlt">Ice</span>Cube from Cores of <span class="hlt">Active</span> Galactic Nuclei</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stecker, Floyd W.</p> <p>2013-01-01</p> <p>I show that the high energy neutrino flux predicted to arise from <span class="hlt">active</span> galactic nuclei cores can explain the PeV neutrinos detected by <span class="hlt">Ice</span>Cube without conflicting with the constraints from the observed extragalactic cosmic-ray and gamma-ray backgrounds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.671..218A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.671..218A"><span id="translatedtitle">Pre-collisional accretionary growth of the southern Laurasian <span class="hlt">active</span> <span class="hlt">margin</span>, Central Pontides, Turkey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aygül, Mesut; Okay, Aral I.; Oberhänsli, Roland; Sudo, Masafumi</p> <p>2016-03-01</p> <p>Cretaceous subduction-accretionary complexes crop out over wide areas in the central part of the Pontides, northern Turkey. To the north, the wedge consists of a low-grade metaflysch sequence with blocks of marble, Na-amphibole-bearing metabasite (PT = 7-12 kbar; 400 ± 70 °C) and serpentinite. 40Ar/39Ar phengite ages from the phyllites of the metaflysch are ca. 100 Ma. The metaflysch sequence is underlain by oceanic crust-derived HP/LT metabasites and micaschists along a major detachment fault. The metabasites are epidote-blueschists consisting of glaucophane, epidote, titanite, and phengite locally with garnet. Fresh lawsonite-blueschists are exposed as blocks along the detachment fault. Peak metamorphic conditions of a garnet-blueschist are constrained to 17 ± 1 kbar and 500 ± 40 °C and of a lawsonite-blueschist to 14 ± 2 kbar and 370-440 °C. 40Ar/39Ar phengite dating on the micaschists constrains the HP/LT metamorphism as 101-92 Ma, younging southward. Middle Jurassic (ca. 160 Ma) accretionary complexes consisting of blueschist to lower greenschist facies metabasites, marble and volcanogenic metasediment intercalations are exposed at the southern part of the Cretaceous wedge. In the studied area, the North Anatolian Fault forms the contact between Cretaceous and Middle Jurassic HP/LT metamorphic rocks. Wide distribution of Cretaceous subduction-accretionary complexes implies accretionary tectonic continental growth along the Laurasian <span class="hlt">active</span> <span class="hlt">margin</span>. High amount of clastic sediment flux into the trench has a major effect on enlarging the wedge during the Albian. Tectonic thickening of the oceanic HP/LT metamorphic sequence, however, was possibly achieved by propagation of the décollement along the retreating slab which can create the space necessary for progressive deep level basal underplating and extension of the wedge for subsequent syn-subduction exhumation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.T13B0503M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.T13B0503M"><span id="translatedtitle"><span class="hlt">Active</span> Tectonics along the Carboneras Fault (SE Iberian <span class="hlt">Margin</span>): Onshore-Offshore Paleoseismological Approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moreno, X.; Masana, E.; Gràcia, E.; Pallàs, R.; Santanach, P.; Dañobeitia, J. J.; Party, I.</p> <p>2006-12-01</p> <p>The southern <span class="hlt">margin</span> of the Iberian Peninsula hosts the convergent boundary between the European and African Plates. At the eastern Betic Cordillera, the Neogene and Quaternary shortening has mainly been absorbed by left-lateral strike-slip faults, which in the Iberian Peninsula is represented by the Eastern Betics Shear Zone (EBSZ). One of the longest structures in the EBSZ is the Carboneras Fault, with almost 50 km onshore and more than 100 km offshore. The low record seismicity along its trace, suggest either non seismic behaviour or long recurrence intervals (104 years). The aim of this work is an integrated onshore-offshore neotectonic and paleoseismological study of the Carboneras Fault Zone to characterize its seismic potential. The onshore study was made through regional geological and geomorphological analysis, geophysical prospecting, microtopography, trenching, and dating (14 C, U/Th, TL). Onshore macro and microstructures as beheaded and offset alluvial fans and S-C microstructures in the fault zone reveals a Quaternary left-lateral strike-slip motion combined with a vertical component along the fault. Trenching reveals this fault is seismogenic, with at least four late Quaternary events. The oldest occurred between 54.9 and 32.2 ka BP, the second one between 40.9 and 27.1 ka BP, and the two most recent events occurred between 30.8 and 0.875 ka BP. The thickness of the colluvial wedges suggest a Mw=7 for the first and Mw=6.6 for the second event. The mean recurrence rate is 14 ka, and the minimum elapsed time is 875 years. The offshore portion, studied by high-resolution marine geophysical methods, shows very similar strike-slip structures. The marine paleoseismic data will be integrated with the onland results in order to accurately determine the recent <span class="hlt">activity</span> and seismic parameters of the entire Carboneras Fault.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMPP43B0672L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMPP43B0672L"><span id="translatedtitle">Phosphate oxygen isotope ratio proxy for specific microbial <span class="hlt">activity</span> in marine sediments (Peru <span class="hlt">Margin</span>)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Y.; Blake, R. E.</p> <p>2005-12-01</p> <p>Oxygen (O) isotope ratios of biogenic apatites have been widely used as paleotemperature and environmental geochemical proxies. With improved knowledge of the phosphate O isotope effects of different P cycling pathways, the δ18O value of inorganic phosphate (δ18OP) has been proposed as a useful proxy and tracer of biological reactions and P cycling in natural environments[1,2,3,4]. Being the only way of removing P from oceanic water, sedimentary P burial is one of the most important processes during biogeochemical cycling of P. The high concentrations of organic matter and pronounced microbial <span class="hlt">activity</span> at ODP Site 1230 along the Peru <span class="hlt">Margin</span> result in unusually high interstitial water phosphate concentrations, which provides a unique opportunity to use δ18OP to investigate inorganic phosphate (Pi) regeneration and P cycling pathways in marine sediments. The isotopic measurements of both dissolved inorganic phosphate (DIP) and bulk sediment Pi show that DIP δ18OP values are affected by three different processes, which are all induced by specific microbial <span class="hlt">activities</span> present in the sediments. In sediments at ~ 65 to 120 mbsf, porewater DIP is derived from dissolved organophosphorus compounds (DOP) through enzymatic degradation pathways, evidenced by both DIP δ18OP values and interstitial water chemistry. Measured porewater DIP δ18OP values also suggest that 4 to 8% of interstitial water DIP reflects regeneration of Pi from Porg by microbially-synthesized enzymes. Throughout the sediment column and especially at ~ 120 to 150 mbsf, DIP is released from the sediments by microbially-induced reductive dissolution of Fe-oxides, which contributes to the overall high DIP concentrations at Site 1230. The third and dominant process controlling measured DIP δ18OP values is microbial turnover of regenerated Pi. The presence of high microbial <span class="hlt">activities</span> in organic-rich Site 1230 sediments promotes the remobilization of P and affects marine P cycling by potentially enhancing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Tectp.591..175K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Tectp.591..175K"><span id="translatedtitle">3D crustal-scale heat-flow regimes at a developing <span class="hlt">active</span> <span class="hlt">margin</span> (Taranaki Basin, New Zealand)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kroeger, K. F.; Funnell, R. H.; Nicol, A.; Fohrmann, M.; Bland, K. J.; King, P. R.</p> <p>2013-04-01</p> <p>The Taranaki Basin in the west of New Zealand's North Island has evolved from a rifted Mesozoic Gondwana <span class="hlt">margin</span> to a basin straddling the Neogene convergent Australian-Pacific plate <span class="hlt">margin</span>. However, given its proximity to the modern subduction front, Taranaki Basin is surprisingly cold when compared to other convergent <span class="hlt">margins</span>. To investigate the effects of <span class="hlt">active</span> <span class="hlt">margin</span> evolution on the thermal regime of the Taranaki Basin we developed a 3D crustal-scale forward model using the petroleum industry-standard basin-modelling software Petromod™. The crustal structure inherited from Mesozoic Gondwana <span class="hlt">margin</span> breakup and processes related to modern Hikurangi convergent <span class="hlt">margin</span> initiation are identified to be the main controls on the thermal regime of the Taranaki Basin. Present-day surface heat flow across Taranaki on average is 59 mW/m2, but varies by as much as 30 mW/m2 due to the difference in crustal heat generation between mafic and felsic basement terranes alone. In addition, changes in mantle heat advection, tectonic subsidence, crustal thickening and basin inversion, together with related sedimentary processes result in variability of up to 10 mW/m2. Modelling suggests that increased heating of the upper crust due to additional mantle heat advection following the onset of subduction is an ongoing process and heating has only recently begun to reach the surface, explaining the relatively low surface heat flow. We propose that the depth of the subducted slab and related mantle convection processes control the thermal and structural regimes in the Taranaki Basin. The thermal effects of the subduction initiation process are modified and overprinted by the thickness, structure and composition of the lithosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009EGUGA..11.4947Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009EGUGA..11.4947Z&link_type=ABSTRACT"><span id="translatedtitle">Hygroscopic growth and <span class="hlt">activation</span> of uncoated and coated soot particles and their relation to <span class="hlt">ice</span> nucleation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ziese, M.; Henning, S.; Mildenberger, K.; Stratmann, F.; Möhler, O.; Benz, S.; Buchholz, A.; Mentel, Th.; Aida/Lacis-Mobile-Team</p> <p>2009-04-01</p> <p>Measurements of the hygroscopic growth (HTDMA, LACIS-mobile), <span class="hlt">activation</span> behavior (DMT-CCNC) - scope of this paper - and <span class="hlt">ice</span> nucleation (AIDA chamber) were performed to estimate the cloud-forming potential of pure and coated soot particles. Globally, soot particles contribute up to 2.5 % to the atmospheric aerosol. In the framework of the investigations described here, soot particles were generated either applying a graphite-spark-generator (GFG1000) or a flame-soot-generator (Mini-CAST). With respect to the hygroscopic growth and <span class="hlt">activation</span> behavior, the influences of the carrier-gas (GFG-soot), the OC-content (CAST-soot) and of different coating materials were investigated. Differences in the hygroscopic growth and <span class="hlt">activation</span> behavior of GFG generated soot particles were found for the two carrier-gases considered. If nitrogen was used, neither hygroscopic growth nor <span class="hlt">activation</span> were observed. In contrast, when argon was used, particles featured a slight hygroscopic growth and were easier to <span class="hlt">activate</span>. Hygroscopic growth increases with decreasing OC-content of the CAST-soot, up to growth factor 1.04 at 98.4 % relative humidity. Lower OC-contents also result in the particles being <span class="hlt">activated</span> more easily. Coating with sulfuric acid enhances the hygroscopic growth and <span class="hlt">activation</span> behavior of CAST-soot for different OC-contents. If the soot (GFG & CAST) was coated with dicarboxylic acids (oxalic and succinic acid), no enhancement of hygroscopic growth and <span class="hlt">activation</span> was observed. This is most likely due to evaporation of the coating material. In comparison to the hygroscopic growth and <span class="hlt">activation</span> behavior, the same trends were observed in the <span class="hlt">ice</span>-nucleation behavior. That is, the more <span class="hlt">active</span> a particle is as cloud condensation nuclei, the better it functions as <span class="hlt">ice</span> nuclei. GFG-soot with argon as carrier-gas acts as a better <span class="hlt">ice</span> nuclei than GFG-soot with nitrogen. For the CAST-soot the <span class="hlt">ice</span>-nucleation <span class="hlt">activity</span> decreases with increasing OC-content. Coating with sulfuric acid</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.C51A0484G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.C51A0484G"><span id="translatedtitle">Identifying the Influence of Variable <span class="hlt">Ice</span> Types on Passive and <span class="hlt">Active</span> Microwave Measurements for the Purpose of SWE Retrieval</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gunn, G. E.; Duguay, C. R.; Derksen, C.</p> <p>2010-12-01</p> <p>Dual polarized airborne passive microwave (PM) brightness temperatures (Tbs) at 6.9, 19 and 37 GHz H/V and satellite X-band (9.65 GHz VV/VH) <span class="hlt">active</span> microwave backscatter measurements were combined with coincident in-situ measurements of snow and <span class="hlt">ice</span> characteristics to determine the potential of unique emission/interaction caused by variable <span class="hlt">ice</span> properties. Algorithms designed to estimate snow water equivalent (SWE) using the common brightness temperature difference approach (37GHz - 19 GHz) continually underestimate in-situ levels when applied to pure-<span class="hlt">ice</span> pixels in the Canadian subarctic. <span class="hlt">Ice</span> thickness measurements were positively correlated with 19 GHz vertically polarised (V pol) passive microwave emissions (R= 0.67), and negatively with 19 GHz horizontally polarised (H pol) emissions (R = -0.79), indicating that surface conditions at the <span class="hlt">ice</span>/snow interface affect the emissivity at H pol. This study examines the effect of <span class="hlt">ice</span> types on coincident passive and <span class="hlt">active</span> microwave measurements for free-floating <span class="hlt">ice</span> in two lakes (Sitidgi, Husky Lakes). <span class="hlt">Ice</span> types are delineated using the SAR segmentation program MAGIC (MAp Guided <span class="hlt">Ice</span> Classification) that has previously been used to characterize sea <span class="hlt">ice</span> types. Based on output <span class="hlt">ice</span> types produced by MAGIC, the relationship between <span class="hlt">active</span> and passive microwave measurements is examined. Output <span class="hlt">ice</span> classes corresponded well to those measured at coincident in-situ sampling sites. Emissions at 19 GHz H and cross-polarised X-band backscatter (9.65 GHz) increase coincident to <span class="hlt">ice</span> types that exhibit more scattering potential. Clear <span class="hlt">ice</span> exhibits the lowest return, followed by a transition zone between clear <span class="hlt">ice</span> and grey <span class="hlt">ice</span>. Grey <span class="hlt">ice</span> exhibits higher returns as a result of the inclusion of spherical air bubbles, followed by rafted <span class="hlt">ice</span>, which exhibits an excess of scattering potential. Concurrently, transects of dual polarized 6.9 and 19 GHz PM Tbs exhibited a positive relationship with cross-polarized <span class="hlt">active</span> microwave backscatter (VH</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.4210M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.4210M"><span id="translatedtitle">Topography, river network and recent fault <span class="hlt">activity</span> at the <span class="hlt">margins</span> of the Central Main Ethiopian Rift (East Africa)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Molin, Paola; Corti, Giacomo; Sembroni, Andrea</p> <p>2016-04-01</p> <p>Along its length, the Main Ethiopian Rift (MER) in East Africa records a transition from early fault-dominated morphology in the South to axial magma assisted-rifting typical of continental break-up in the North. It is one of the few locations on Earth offering a complete picture of the evolution of continental rifting and thus provides a unique opportunity to directly analyze how the drainage network reorganize under extensional tectonic forcing. In this paper we present a new analysis of the river network and relative landforms - complemented with a summary of recent geological data - at both rift <span class="hlt">margins</span> of the Central MER, a key sector of the rift capturing the phase of drainage reorganization between incipient and mature rifting. This analysis shows that hydrography is strongly influenced by recent tectonics. Rectangular drainage patterns, windgaps, and lacustrine/swampy areas formed by structural dams document that the rivers are in continuous competition with fault <span class="hlt">activity</span>. The irregular longitudinal profiles (with knickpoints/knickzones in correspondence with faults) also suggest that rivers are in a transient state of disequilibrium related to recent tectonic <span class="hlt">activity</span> at rift <span class="hlt">margins</span>, in agreement with previous geological and seismological data. A more regional analysis extended to the adjoining Northern and Southern MER indicates that rifting evolves from initial stages characterized by <span class="hlt">margins</span> poorly incised by rivers with gentle channel gradients (except in correspondence with faults), to mature phases in which rift <span class="hlt">margins</span> are highly incised by a well organized fluvial network composed by concave and steep rivers. Our regional analysis also indicates a stronger and/or more recent tectonic <span class="hlt">activity</span> at the rift <span class="hlt">margins</span> proceeding to the south, in line with previous models of rift development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Tectp.664...67M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Tectp.664...67M"><span id="translatedtitle">Topography, river network and recent fault <span class="hlt">activity</span> at the <span class="hlt">margins</span> of the Central Main Ethiopian Rift (East Africa)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Molin, Paola; Corti, Giacomo</p> <p>2015-11-01</p> <p>Along its length, the Main Ethiopian Rift (MER) in East Africa records a transition from early fault-dominated morphology in the South to axial magma assisted-rifting typical of continental break-up in the North. It is one of the few locations on Earth offering a complete picture of the evolution of continental rifting and thus provides a unique opportunity to directly analyze how the drainage network reorganizes under extensional tectonic forcing. In this paper we present a new analysis of the river network and relative landforms-complemented with a summary of recent geological data-at both rift <span class="hlt">margins</span> of the Central MER, a key sector of the rift capturing the phase of drainage reorganization between incipient and mature rifting. This analysis shows that hydrography is strongly influenced by recent tectonics. Rectangular drainage patterns, windgaps, and lacustrine/swampy areas formed by structural dams document that the rivers are in continuous competition with fault <span class="hlt">activity</span>. The irregular longitudinal profiles (with knickpoints/knickzones in correspondence with faults) also suggest that rivers are in a transient state of disequilibrium related to recent tectonic <span class="hlt">activity</span> at rift <span class="hlt">margins</span>, in agreement with previous geological and seismological data. A more regional analysis extended to the adjoining Northern and Southern MER indicates that rifting evolves from initial stages characterized by <span class="hlt">margins</span> poorly incised by rivers with gentle channel gradients (except in correspondence with faults), to mature phases in which rift <span class="hlt">margins</span> are highly incised by a well organized fluvial network composed by concave and steep rivers. Our regional analysis also indicates a stronger and/or more recent tectonic <span class="hlt">activity</span> at the rift <span class="hlt">margins</span> proceeding to the south, in line with previous models of rift development.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=201718','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=201718"><span id="translatedtitle">Bacterial Standing Stock, <span class="hlt">Activity</span>, and Carbon Production during Formation and Growth of Sea <span class="hlt">Ice</span> in the Weddell Sea, Antarctica †</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Grossmann, Sönnke; Dieckmann, Gerhard S.</p> <p>1994-01-01</p> <p>Bacterial response to formation and growth of sea <span class="hlt">ice</span> was investigated during autumn in the northeastern Weddell Sea. Changes in standing stock, <span class="hlt">activity</span>, and carbon production of bacteria were determined in successive stages of <span class="hlt">ice</span> development. During initial <span class="hlt">ice</span> formation, concentrations of bacterial cells, in the order of 1 × 108 to 3 × 108 liter-1, were not enhanced within the <span class="hlt">ice</span> matrix. This suggests that physical enrichment of bacteria by <span class="hlt">ice</span> crystals is not effective. Due to low concentrations of phytoplankton in the water column during freezing, incorporation of bacteria into newly formed <span class="hlt">ice</span> via attachment to algal cells or aggregates was not recorded in this study. As soon as the <span class="hlt">ice</span> had formed, the general metabolic <span class="hlt">activity</span> of bacterial populations was strongly suppressed. Furthermore, the ratio of [3H]leucine incorporation into proteins to [3H]thymidine incorporation into DNA changed during <span class="hlt">ice</span> growth. In thick pack <span class="hlt">ice</span>, bacterial <span class="hlt">activity</span> recovered and growth rates up to 0.6 day-1 indicated <span class="hlt">actively</span> dividing populations. However, biomass-specific utilization of organic compounds remained lower than in open water. Bacterial concentrations of up to 2.8 × 109 cells liter-1 along with considerably enlarged cell volumes accumulated within thick pack <span class="hlt">ice</span>, suggesting reduced mortality rates of bacteria within the small brine pores. In the course of <span class="hlt">ice</span> development, bacterial carbon production increased from about 0.01 to 0.4 μg of C liter-1 h-1. In thick <span class="hlt">ice</span>, bacterial secondary production exceeded primary production of microalgae. PMID:16349347</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C21B0570B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C21B0570B"><span id="translatedtitle">Dynamic crevasses on the northwest <span class="hlt">margin</span> of the Greenland <span class="hlt">Ice</span> Sheet: observations of rapid change and relationships to geophysical and climatological trends</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burzynski, A. M.; Mercer, J. L.; Deeb, E. J.; Newman, S. D.; Lever, J. H.; Delaney, A. J.; Davies, R.; Dossin, G.</p> <p>2012-12-01</p> <p>The Greenland Inland Traverse (GrIT) annually transports fuel and cargo approximately 740 miles over the <span class="hlt">ice</span> sheet from Thule, a deep-water port on the northwest coast, to resupply inland research stations (NEEM and Summit). The first ~70 miles of the GrIT route are heavily crevassed. These hazardous features are dynamic and must be assessed each year to select a safely navigable traverse route. Since GrIT's initial route assessment in 2007 we have observed increasing sizes and numbers of crevasses/crevasse fields using satellite imagery analysis, field-based ground penetrating radar (GPR) acquisition/analysis, helicopter reconnaissance, and in-situ measurements. The cause of this observed rapid change is yet to be determined. For example, increased crevassing may be attributed to increased flow rates of outlet glaciers, climatological trends, presence of subsurface liquid water, isostatic rebound, or by seismic events. Here we present relationships between observed changes in crevassing along the GrIT route and trends in remotely sensed data, including <span class="hlt">ice</span> velocity, elevation, and meteorology. Understanding the behavior and timing of past <span class="hlt">ice</span> dynamics in this region will enable us to better predict future changes, facilitating safe and efficient GrIT route selection and science support. Results of tracking annual crevasses and spatially analyzing available ancillary datasets may yield a better understanding of regional <span class="hlt">ice</span> dynamics in the determination of mass balance trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSM.A31A..03K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSM.A31A..03K"><span id="translatedtitle">Conversion of Atmospheric Aerosol by Bacteria and Their Influence on <span class="hlt">Ice</span>-Nucleation <span class="hlt">Activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kos, G.; Shawi, M.; Ariya, P. A.</p> <p>2004-05-01</p> <p>The presence of microorganisms such as bacteria and fungi in the boundary layer of the atmosphere has been established for some time. These species can also convert organic aerosol species (e.g. dicarboxylic acids), a transformation that was so far assumed to occur only via physico-chemical pathways. As a result, the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of certain aerosol species can be altered by biochemical transformations including metabolite production and bacterial growth and these new species as well as the microorganisms themselves can act as <span class="hlt">ice</span> nuclei. In this study we have used dicarboxylic acids (DCA) as model nutrients, which are commonly observed in the aerosol population of the boundary layer. Pseudomonas syringae and Erwinia herbicolae are two types of bacteria that have been found to possess <span class="hlt">ice</span> nucleation ability, caused by lipoglycoprotein, which consists of a sequence of amino acids that favor the formation of <span class="hlt">ice</span>. The main objective was to look into the conversion of DCA by bacterial species, their <span class="hlt">ice</span> nucleating ability and the identification of metabolites from bacterial <span class="hlt">activity</span>. Furthermore, the influence of different parameters on the <span class="hlt">ice</span> nucleation of bacteria was investigated. A Freezing Nuclei apparatus was used in order to assess the freezing temperature of a population of small drops to study both homogenous and heterogeneous nucleation of different concentrations of malonic acid containing bacterial species. An acid concentration in the lower Fg/l-range was chosen, matching earlier observations in an urban environment. Other varied parameters include the pH and bacterial membrane shearing. All labware was sterilized prior to use and airtight containers minimized external contamination. Malonic acid concentration was determined by gas chromatography with mass spectrometric detection (GC-MS) after esterification with a mixture of borontrifluoride and 1-propanol, modified from Kawamura, 1991. Malonic acid and its metabolites were identified by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS12A..05L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS12A..05L"><span id="translatedtitle">Violent Gas Venting on the Heng-Chun Mud Volcano, South China Sea <span class="hlt">Active</span> Continental <span class="hlt">Margin</span> offshore SW Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, S.; Cheng, W. Y.; Tseng, Y. T.; Chen, N. C.; Hsieh, I. C.; Yang, T. F.</p> <p>2014-12-01</p> <p>Accumulation of methane as gas hydrate under the sea floor has been considered a major trap for both thermal and biogenic gas in marine environment. Aided by rapid AOM process near the sea floor, fraction of methane escaping the sea floor has been considered at minuscule. However, most studies focused mainly on deepwater gas hydrate systems where gas hydrate remain relatively stable. We have studied methane seeps on the <span class="hlt">active</span> <span class="hlt">margin</span> offshore Taiwan, where rapid tectonic <span class="hlt">activities</span> occur. Our intention is to evaluate the scale and condition of gas seeps in the tectonic <span class="hlt">active</span> region. Towcam, coring, heat probe, chirp, multibeam bathymetric mapping and echo sounding were conducted at the study areas. Our results showed that gas is violently venting at the <span class="hlt">active</span> <span class="hlt">margin</span>, not only through sediments, but also through overlying sea water, directly into the atmosphere. Similar ventings, but, not in this scale, have also been identified previously in the nearby region. High concentrations of methane as well as traces of propane were found in sediments and in waters with flares. In conjunction, abundant chemosynthetic community, life mussel, clams, tube worms, bacterial mats together with high concentrations of dissolve sulfide, large authigenic carbonate buildups were also found. Our results indicate that methane could be another major green house gas in the shallow water <span class="hlt">active</span> <span class="hlt">margin</span> region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17774792','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17774792"><span id="translatedtitle">Stress fields of the overriding plate at convergent <span class="hlt">margins</span> and beneath <span class="hlt">active</span> volcanic arcs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Apperson, K D</p> <p>1991-11-01</p> <p>Tectonic stress fields in the overriding plate at convergent plate <span class="hlt">margins</span> are complex and vary on local to regional scales. Volcanic arcs are a common element of overriding plates. Stress fields in the volcanic arc region are related to deformation generated by subduction and to magma generation and ascent processes. Analysis of moment tensors of shallow and intermediate depth earthquakes in volcanic arcs indicates that the seismic strain field in the arc region of many convergent <span class="hlt">margins</span> is subhorizontal extension oriented nearly perpendicular to the arc. A process capable of generating such a globally consistent strain field is induced asthenospheric corner flow below the arc region. PMID:17774792</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4577968','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4577968"><span id="translatedtitle">Probing the Biomimetic <span class="hlt">Ice</span> Nucleation Inhibition <span class="hlt">Activity</span> of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2015-01-01</p> <p>Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) <span class="hlt">ice</span> formation. These processes are typically controlled by <span class="hlt">ice</span> nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit <span class="hlt">ice</span> growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its <span class="hlt">ice</span> nucleation inhibition (INI) <span class="hlt">activity</span>, in contrast to its established <span class="hlt">ice</span> growth inhibitory properties and compared to other synthetic polymers. It is shown that <span class="hlt">ice</span> nucleation inhibition <span class="hlt">activity</span> of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL–1. Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible <span class="hlt">activity</span>, highlighting the unique <span class="hlt">ice</span>/water interacting properties of PVA. These findings both aid our understanding of <span class="hlt">ice</span> nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control <span class="hlt">ice</span> formation/growth processes PMID:26258729</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26258729','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26258729"><span id="translatedtitle">Probing the Biomimetic <span class="hlt">Ice</span> Nucleation Inhibition <span class="hlt">Activity</span> of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Congdon, Thomas; Dean, Bethany T; Kasperczak-Wright, James; Biggs, Caroline I; Notman, Rebecca; Gibson, Matthew I</p> <p>2015-09-14</p> <p>Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) <span class="hlt">ice</span> formation. These processes are typically controlled by <span class="hlt">ice</span> nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit <span class="hlt">ice</span> growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its <span class="hlt">ice</span> nucleation inhibition (INI) <span class="hlt">activity</span>, in contrast to its established <span class="hlt">ice</span> growth inhibitory properties and compared to other synthetic polymers. It is shown that <span class="hlt">ice</span> nucleation inhibition <span class="hlt">activity</span> of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL(-1). Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible <span class="hlt">activity</span>, highlighting the unique <span class="hlt">ice</span>/water interacting properties of PVA. These findings both aid our understanding of <span class="hlt">ice</span> nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control <span class="hlt">ice</span> formation/growth processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26258729','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26258729"><span id="translatedtitle">Probing the Biomimetic <span class="hlt">Ice</span> Nucleation Inhibition <span class="hlt">Activity</span> of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Congdon, Thomas; Dean, Bethany T; Kasperczak-Wright, James; Biggs, Caroline I; Notman, Rebecca; Gibson, Matthew I</p> <p>2015-09-14</p> <p>Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) <span class="hlt">ice</span> formation. These processes are typically controlled by <span class="hlt">ice</span> nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit <span class="hlt">ice</span> growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its <span class="hlt">ice</span> nucleation inhibition (INI) <span class="hlt">activity</span>, in contrast to its established <span class="hlt">ice</span> growth inhibitory properties and compared to other synthetic polymers. It is shown that <span class="hlt">ice</span> nucleation inhibition <span class="hlt">activity</span> of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL(-1). Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible <span class="hlt">activity</span>, highlighting the unique <span class="hlt">ice</span>/water interacting properties of PVA. These findings both aid our understanding of <span class="hlt">ice</span> nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control <span class="hlt">ice</span> formation/growth processes. PMID:26258729</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3753075','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3753075"><span id="translatedtitle">Provider’s Perspectives on the Impact of Immigration and Customs Enforcement (<span class="hlt">ICE</span>) <span class="hlt">Activity</span> on Immigrant Health</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hacker, Karen; Chu, Jocelyn; Arsenault, Lisa; Marlin, Robert P.</p> <p>2013-01-01</p> <p>Introduction Increasing Immigration and Customs Enforcement (<span class="hlt">ICE</span>) <span class="hlt">activities</span> such as raids, detention and deportation may be affecting the health and well-being of immigrants. This study sought to understand the impact of <span class="hlt">ICE</span> <span class="hlt">activities</span> on immigrant health from the perspective of health care providers. Methods An online survey of primary care and emergency medicine providers was conducted to determine whether <span class="hlt">ICE</span> <span class="hlt">activity</span> was negatively affecting immigrant patients. Results Of 327 providers surveyed, 163 responded (50%) and 156 (48%) met criteria for inclusion. Seventy-five (48%) of them observed negative effects of <span class="hlt">ICE</span> enforcement on the health or health access of immigrant patients. Forty-three providers gave examples of the impact on emotional health, ability to comply with health care recommendations and access. Conclusions Health care providers are witnessing the negative effects of <span class="hlt">ICE</span> <span class="hlt">activities</span> on their immigrant patients’ psychological and physical health. This should be considered an important determinant of immigrant health. PMID:22643614</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7742G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7742G"><span id="translatedtitle">Sedimentology of seismo-turbidites off the Cascadia and northern California <span class="hlt">active</span> tectonic continental <span class="hlt">margins</span>, Pacific Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gutierrez Pastor, Julia; Nelson, Hans; Goldfinger, Chris; Escutia, Carlota</p> <p>2013-04-01</p> <p>Holocene turbidites from turbidite channel systems along the <span class="hlt">active</span> tectonic continental <span class="hlt">margins</span> of the Cascadia subduction zone (offshore Vancouver Island to Mendocino Triple Junction) and the northern San Andreas Transform Fault (the Triple Junction to San Francisco Bay), have been analyzed for sedimentologic features related to their seismic origin. Centimeter thick silt/sand beds (turbidite base) capped by mud layers (turbidite tail) and interbedded with hemipelagic silty clay intervals with high biogenic content have been characterized by visual core descriptions, grain-size analysis, X-ray radiographs and physical properties. Along the northern California <span class="hlt">margin</span> in upstream single tributary canyons and channels, most turbidites are uni-pulsed (classic fining up) whereas downstream below multiple tributary canyon and channel confluences, most deposits are stacked turbidites. Because each set of stacked turbidites has no hemipelagic sediment between each turbidite unit and each unit has a distinct mineralogy from a different tributary canyon, we interpret that a stacked turbidite is deposited by several coeval turbidity currents fed by multiple tributary canyons and channels with synchronous triggering from a single San Andreas Fault earthquake. The Cascadia <span class="hlt">margin</span> is characterized by individual multi-pulsed turbidites that contain multiple coarse-grained sub-units without hemipelagic sediment between pulses. Because the number and character of multiple coarse-grained pulses for each correlative multi-pulsed turbidite is almost always constant both upstream and downstream in different channel systems for 600 km along the <span class="hlt">margin</span>,we interpret that the earthquake shaking or aftershock signature is usually preserved, for the much stronger Cascadia (≥9 Mw) compared to weaker California (≥8Mw) earthquakes, which result in upstream uni-pulsed turbidites and downstream stacked turbidites. Consequently, both the strongest (≥9 Mw) great earthquakes and downstream</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMPP21C1453S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMPP21C1453S"><span id="translatedtitle">Identification and Dating of a key Late Pleistocene Stratigraphic Unit in the St. Lawrence Estuary and Gulf (Eastern Canada): Implications for the 400-m Thick Quaternary Sequence at the Former <span class="hlt">Margin</span> of the Laurentide <span class="hlt">Ice</span> Sheet</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>St-Onge, G.; Lajeunesse, P.; Duchesne, M.; Gagné, H.</p> <p>2008-12-01</p> <p>A recently acquired 8-m long sediment core along with high-resolution seismic-reflection and sub-bottom profiler sections allowed the identification, characterization and dating of a widespread seismic unit extending from the head of the Laurentian Channel (Lower St. Lawrence Estuary) to Honguedo Strait (Gulf of St. Lawrence), Eastern Canada. This seismic unit (termed unit 2) is characterized by a series of parallel high- amplitude reflections with thicknesses ranging from 68 m near the head of the Laurentian Channel to <5 m in Honguedo Strait. This seismic unit is generally observed below a very thick unit of postglacial sediments that can reach >250 m in the St. Lawrence Estuary, leaving it very difficult to be reached by conventional coring operations. Here, we reveal how we were able to trace and core this seismic unit in an area where it lays closer to the seafloor near the southern wall of the Laurentian Channel in the Lower St. Lawrence Estuary. This seismic unit consists of two sedimentary facies: sandy mud including <span class="hlt">ice</span> rafted debris (IRD) underlying faintly laminated to homogenous and plastic silty clays. Based on the sedimentary facies, we interpret the upper clays as <span class="hlt">ice</span>-distal glaciomarine sediments and the lower sandier sediments as <span class="hlt">ice</span>- proximal glaciomarine sediments. Seismic unit 2 is highly disturbed by iceberg scouring in the Gulf of St. Lawrence where it is found at shallower depths, indicating that it was deposited during deglaciation. The available AMS 14C dates obtained in the <span class="hlt">ice</span>-proximal glaciomarine sediments indicate that the lower part of seismic unit 2 was deposited during local re-advances of the Laurentide <span class="hlt">Ice</span> Sheet <span class="hlt">margin</span> in the Goldthwait Sea that began at or before the Younger Dryas cold event (11 100 to 10 000 yr BP) and that seismic unit 2 can be used as a chronostratigraphic marker throughout the St. Lawrence Estuary and northwestern Gulf of St. Lawrence. Moreover, because the seismic character of the sediments below seismic</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ1058214.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ1058214.pdf"><span id="translatedtitle">Breaking the <span class="hlt">Ice</span>: Career Development <span class="hlt">Activities</span> for Accounting Students</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Kilpatrick, Bob G.; Wilburn, Nancy L.</p> <p>2010-01-01</p> <p>This paper describes two co-curricular career development <span class="hlt">activities</span>, mock interviews and speed networking that we provide for accounting majors at our university. The driving force behind both <span class="hlt">activities</span> was to increase comfort levels for students when interacting with professionals and to enhance their job interview and networking skills.…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25345526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25345526"><span id="translatedtitle">Immersion freezing of supermicron mineral dust particles: freezing results, testing different schemes for describing <span class="hlt">ice</span> nucleation, and <span class="hlt">ice</span> nucleation <span class="hlt">active</span> site densities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wheeler, M J; Mason, R H; Steunenberg, K; Wagstaff, M; Chou, C; Bertram, A K</p> <p>2015-05-14</p> <p><span class="hlt">Ice</span> nucleation on mineral dust particles is known to be an important process in the atmosphere. To accurately implement <span class="hlt">ice</span> nucleation on mineral dust particles in atmospheric simulations, a suitable theory or scheme is desirable to describe laboratory freezing data in atmospheric models. In the following, we investigated <span class="hlt">ice</span> nucleation by supermicron mineral dust particles [kaolinite and Arizona Test Dust (ATD)] in the immersion mode. The median freezing temperature for ATD was measured to be approximately -30 °C compared with approximately -36 °C for kaolinite. The freezing results were then used to test four different schemes previously used to describe <span class="hlt">ice</span> nucleation in atmospheric models. In terms of ability to fit the data (quantified by calculating the reduced chi-squared values), the following order was found for ATD (from best to worst): <span class="hlt">active</span> site, pdf-α, deterministic, single-α. For kaolinite, the following order was found (from best to worst): <span class="hlt">active</span> site, deterministic, pdf-α, single-α. The variation in the predicted median freezing temperature per decade change in the cooling rate for each of the schemes was also compared with experimental results from other studies. The deterministic model predicts the median freezing temperature to be independent of cooling rate, while experimental results show a weak dependence on cooling rate. The single-α, pdf-α, and <span class="hlt">active</span> site schemes all agree with the experimental results within roughly a factor of 2. On the basis of our results and previous results where different schemes were tested, the <span class="hlt">active</span> site scheme is recommended for describing the freezing of ATD and kaolinite particles. We also used our <span class="hlt">ice</span> nucleation results to determine the <span class="hlt">ice</span> nucleation <span class="hlt">active</span> site (INAS) density for the supermicron dust particles tested. Using the data, we show that the INAS densities of supermicron kaolinite and ATD particles studied here are smaller than the INAS densities of submicron kaolinite and ATD particles</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25345526','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25345526"><span id="translatedtitle">Immersion freezing of supermicron mineral dust particles: freezing results, testing different schemes for describing <span class="hlt">ice</span> nucleation, and <span class="hlt">ice</span> nucleation <span class="hlt">active</span> site densities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wheeler, M J; Mason, R H; Steunenberg, K; Wagstaff, M; Chou, C; Bertram, A K</p> <p>2015-05-14</p> <p><span class="hlt">Ice</span> nucleation on mineral dust particles is known to be an important process in the atmosphere. To accurately implement <span class="hlt">ice</span> nucleation on mineral dust particles in atmospheric simulations, a suitable theory or scheme is desirable to describe laboratory freezing data in atmospheric models. In the following, we investigated <span class="hlt">ice</span> nucleation by supermicron mineral dust particles [kaolinite and Arizona Test Dust (ATD)] in the immersion mode. The median freezing temperature for ATD was measured to be approximately -30 °C compared with approximately -36 °C for kaolinite. The freezing results were then used to test four different schemes previously used to describe <span class="hlt">ice</span> nucleation in atmospheric models. In terms of ability to fit the data (quantified by calculating the reduced chi-squared values), the following order was found for ATD (from best to worst): <span class="hlt">active</span> site, pdf-α, deterministic, single-α. For kaolinite, the following order was found (from best to worst): <span class="hlt">active</span> site, deterministic, pdf-α, single-α. The variation in the predicted median freezing temperature per decade change in the cooling rate for each of the schemes was also compared with experimental results from other studies. The deterministic model predicts the median freezing temperature to be independent of cooling rate, while experimental results show a weak dependence on cooling rate. The single-α, pdf-α, and <span class="hlt">active</span> site schemes all agree with the experimental results within roughly a factor of 2. On the basis of our results and previous results where different schemes were tested, the <span class="hlt">active</span> site scheme is recommended for describing the freezing of ATD and kaolinite particles. We also used our <span class="hlt">ice</span> nucleation results to determine the <span class="hlt">ice</span> nucleation <span class="hlt">active</span> site (INAS) density for the supermicron dust particles tested. Using the data, we show that the INAS densities of supermicron kaolinite and ATD particles studied here are smaller than the INAS densities of submicron kaolinite and ATD particles</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMOS51A1233L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMOS51A1233L"><span id="translatedtitle">Comparison of Sedimentary Processes on Adjacent Passive and <span class="hlt">Active</span> Continental <span class="hlt">Margins</span> Offshore of Southwest Taiwan Based on Echo Character Studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, C.; Chiu, J.</p> <p>2008-12-01</p> <p>Echo character recorded on Chirp sub-bottom sonar data from offshore area of southwest Taiwan were analyzed to examine and compare the sedimentary processes of adjacent passive and <span class="hlt">active</span> continental <span class="hlt">margin</span> settings. Seafloor echoes in the study area are classified into four types: (1) distinct echoes, (2) indistinct echoes, (3) hyperbolic echoes, and (4) irregular echoes. Based on the mapped distribution of the echo types, the sedimentary processes offshore of southwest Taiwan are different in the two tectonic settings. On the passive South China Sea <span class="hlt">margin</span>, slope failure is the main process on the upper continental slope, whereas turbidite deposits accumulate in the lower continental slope. In contrast, the submarine Taiwan orogenic wedge is characterized by fill-and-spill processes in the intraslope basins of the upper slope, and mass-transport deposits are observed in the canyons and on the lower Kaoping slope. This difference is largely caused by the huge influx of terrigenous sediments into the submarine Taiwan orogenic wedge province compared to the passive South China Sea continental <span class="hlt">margin</span>. In the passive South China Sea <span class="hlt">margin</span>, loading and movement of the Taiwan orogenic wedge has had significant effect on the seafloor morphology, and triggered retrogressive failures. Gas hydrate dissociation may have enhanced the slope failure processes at some locations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014DSRII.104...83H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014DSRII.104...83H"><span id="translatedtitle">Hanging canyons of Haida Gwaii, British Columbia, Canada: Fault-control on submarine canyon geomorphology along <span class="hlt">active</span> continental <span class="hlt">margins</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harris, Peter T.; Barrie, J. Vaughn; Conway, Kim W.; Greene, H. Gary</p> <p>2014-06-01</p> <p>Faulting commonly influences the geomorphology of submarine canyons that occur on <span class="hlt">active</span> continental <span class="hlt">margins</span>. Here, we examine the geomorphology of canyons located on the continental <span class="hlt">margin</span> off Haida Gwaii, British Columbia, that are truncated on the mid-slope (1200-1400 m water depth) by the Queen Charlotte Fault Zone (QCFZ). The QCFZ is an oblique strike-slip fault zone that has rates of lateral motion of around 50-60 mm/yr and a small convergent component equal to about 3 mm/yr. Slow subduction along the Cascadia Subduction Zone has accreted a prism of marine sediment against the lower slope (1500-3500 m water depth), forming the Queen Charlotte Terrace, which blocks the mouths of submarine canyons formed on the upper slope (200-1400 m water depth). Consequently, canyons along this <span class="hlt">margin</span> are short (4-8 km in length), closely spaced (around 800 m), and terminate uniformly along the 1400 m isobath, coinciding with the primary fault trend of the QCFZ. Vertical displacement along the fault has resulted in hanging canyons occurring locally. The Haida Gwaii canyons are compared and contrasted with the Sur Canyon system, located to the south of Monterey Bay, California, on a transform <span class="hlt">margin</span>, which is not blocked by any accretionary prism, and where canyons thus extend to 4000 m depth, across the full breadth of the slope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....8730C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....8730C"><span id="translatedtitle">Crustal structure at the Gulf of Guayaquil <span class="hlt">active</span> <span class="hlt">margin</span> (Ecuador), from multichannel seismic reflection data.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calahorrano, A.; Collot, J.-Y.; Sage, F.; Ranero, C.</p> <p>2003-04-01</p> <p>During the SISTEUR cruise, multichannel seismic reflection lines were shot across the Ecuador trench-<span class="hlt">margin</span> system, off the Gulf of Guayaquil. Line SIS-72, which cuts through the <span class="hlt">margin</span>, immediately north of the Ecuador-Peru border, has been fully processed through pre-stack depth migration to reveal the inter-plate contact geometry, sediment subduction/underplating processes, and a thick fore-arc basin. Strong reflectors allow to identify the top of the Nazca plate oceanic crust (TOC), the inter-plate décollement (ID) and the top of the <span class="hlt">margin</span> basement (TB). The TOC is imaged by a continuous, low frequency reflector, and shows a rough surface that dips ~4° landward for 24 km from the trench axis. Further to the East, the TOC reflector becomes discontinuous and shows a slope break from 4° to 10°, at a 10-km-depth. West of the trench, the TOC is overlain by a 200-m-thick, transparent unit of pelagic deposits, and 600 m of horizontally stratified trench turbidites. The ID reflector is relatively continuous and roughly reflects the TOC geometry. ID and TOC reflectors define a ~600-m-thick subduction channel, which terminates some 24 km landward from the trench, where the ID reflector steps down to join the TOC. Some reflections from the subduction channel appear to be shaped as the casing reflectors, while others have sigmoid shapes with landward dips associated with small oceanic highs of TOC. The ID crops out at the front of a 8-km-wide accretionary wedge, which encompasses ~4 trusts. The accretionary wedge has developed recently against a sharp-pointed buttress formed by the <span class="hlt">margin</span>'s rock framework as indicated by its reflection characteristics. The TB reflector is discontinuous and separates the basement from overlaying stratified sequences. The TB reflector extends from the toe of the <span class="hlt">margin</span> to ~75 km landward, where it abruptly drops from a depth of 4 to 11 km, at the base of a 10-km-thick forearc basin. This basin, bounded by doming structures interpreted</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...592A..68C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...592A..68C"><span id="translatedtitle">Negligible photodesorption of methanol <span class="hlt">ice</span> and <span class="hlt">active</span> photon-induced desorption of its irradiation products</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cruz-Diaz, G. A.; Martín-Doménech, R.; Muñoz Caro, G. M.; Chen, Y.-J.</p> <p>2016-07-01</p> <p>Context. Methanol is a common component of interstellar and circumstellar <span class="hlt">ice</span> mantles and is often used as an evolution indicator in star-forming regions. The observations of gas-phase methanol in the interiors of dense molecular clouds at temperatures as low as 10 K suggest that non-thermal <span class="hlt">ice</span> desorption must be <span class="hlt">active</span>. <span class="hlt">Ice</span> photodesorption has been proposed to explain the abundances of gas-phase molecules toward the coldest regions. Aims: Laboratory experiments were performed to investigate the potential photodesorption of methanol toward the coldest regions. Methods: Solid methanol was deposited at 8 K and UV-irradiated at various temperatures starting from 8 K. The irradiation of the <span class="hlt">ice</span> was monitored by means of infrared spectroscopy and the molecules in the gas phase were detected using quadrupole mass spectroscopy. Fully deuterated methanol was used for confirmation of the results. Results: The photodesorption of methanol to the gas phase was not observed in the mass spectra at different irradiation temperatures. We estimate an upper limit of 3 × 10-5 molecules per incident photon. On the other hand, photon-induced desorption of the main photoproducts was clearly observed. Conclusions: The negligible photodesorption of methanol could be explained by the ability of UV-photons in the 114-180 nm (10.87-6.88 eV) range to dissociate this molecule efficiently. Therefore, the presence of gas-phase methanol in the absence of thermal desorption remains unexplained. On the other hand, we find CH4 to desorb from irradiated methanol <span class="hlt">ice</span>, which was not found to desorb in the pure CH4 <span class="hlt">ice</span> irradiation experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A11Q..05S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A11Q..05S"><span id="translatedtitle">Characterizing <span class="hlt">Ice</span> Nucleating Particles Emitted from Agricultural <span class="hlt">Activities</span> and Natural Landscapes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suski, K. J.; Levin, E. J.; DeMott, P. J.; Kreidenweis, S. M.; Hill, T. C. J.</p> <p>2015-12-01</p> <p>Soil dust and plant fragment emissions from agricultural harvesting and natural ecosystems are two potentially large, yet unquantified and largely uncharacterized, sources of <span class="hlt">ice</span> nucleating particles (INPs). Both organic and mineral components have been shown to contribute to the <span class="hlt">ice</span>-nucleating ability of soil dust, but apart from the likely presence of <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria, little is known about the <span class="hlt">ice</span> nucleating potential of plant tissues. This work aims to identify and differentiate the organic and inorganic contributions of soil and plant INP sources emitted from harvesting <span class="hlt">activities</span> and natural landscapes. For this purpose, the CSU Continuous Flow Diffusion Chamber (CFDC) and the <span class="hlt">Ice</span> Spectrometer (IS) were utilized in a combination of ambient measurements and laboratory studies. Small variability and low INP numbers (< 10 L-1 at -30 °C) characterized measurements made in air over the grazed Pawnee National Grassland in Colorado, while more variable INP over croplands around the DOE-ARM SGP site in Oklahoma appear linked to regional wind, humidity, and rainfall conditions. Harvesting of milo (grain sorghum), soybean, and wheat at an experimental research farm in Kansas resulted in spikes of INPs, with wheat harvesting producing the largest INP concentrations (up to 100 L-1 at -30 °C). In-situ use of heating tubes upstream of the CFDC to deactivate organic INP showed that milo and wheat harvest emissions showed a stronger reduction of INPs at warm temperatures than soybean emissions, suggesting a larger contribution of organics to their INP <span class="hlt">activity</span>. Further characterization of the sources and organic and inorganic contributions to terrestrially emitted INPs by comparison to laboratory studies on collected soil dust and plant samples will also be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22576115','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22576115"><span id="translatedtitle">A new quantitative method to measure <span class="hlt">activity</span> of <span class="hlt">ice</span> structuring proteins using differential scanning calorimetry.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hassa-Roudsari, Majid; Goff, H Douglas</p> <p>2012-01-01</p> <p>There are very few quantitative assays to measure the <span class="hlt">activity</span> of antifreeze proteins (AFPs, or <span class="hlt">Ice</span> Structuring Proteins, ISPs) and these can be prone to various inaccuracies and inconsistencies. Some methods rely only on unassisted visual assessment. When microscopy is used to measure <span class="hlt">ice</span> crystal size, it is critical that standardized procedures be adopted, especially when image analysis software is used to quantify sizes. Differential Scanning Calorimetry (DSC) has been used to measure the thermal hysteresis <span class="hlt">activity</span> (TH) of AFPs. In this study, DSC was used isothermally to measure enthalpic changes associated with structural rearrangements as a function of time. Differences in slopes of isothermal heat flow vs. time between winter wheat ISP or AFP type I containing samples, and those without ISP or AFP type I were demonstrated. ISP or AFP type I containing samples had significantly higher slopes compared to those without ISP or AFP type I. Samples with higher concentration of ISP or AFP type I showed higher slope values during the first hour and took up to 3 hr to attain equilibrium. Differences were attributed to <span class="hlt">activity</span> of the proteins at the <span class="hlt">ice</span> interface. Proteinaceous <span class="hlt">activity</span> of ISPs or AFP type I was confirmed by loss of <span class="hlt">activity</span> after treatment with protease.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/16347741','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/16347741"><span id="translatedtitle">Effect of Plant Species and Environmental Conditions on <span class="hlt">Ice</span> Nucleation <span class="hlt">Activity</span> of Pseudomonas syringae on Leaves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>O'brien, R D; Lindow, S E</p> <p>1988-09-01</p> <p>Selected plant species and environmental conditions were investigated for their influences on expression of <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> by 15 Pseudomonas syringae strains grown on plants in constant-temperature growth chamber studies. <span class="hlt">Ice</span> nucleation frequencies (INFs), the fraction of cells that expressed <span class="hlt">ice</span> nucleation at -5 or -9 degrees C, of individual strains varied greatly, both on plants and in culture. This suggests that the probability of frost injury, which is proportional to the number of <span class="hlt">ice</span> nuclei on leaf surfaces, is strongly determined by the particular bacterial strains that are present on a leaf surface. The INFs of strains were generally higher when they were grown on plants than when they were grown in culture. In addition, INFs in culture did not correlate closely with INFs on plants, suggesting that frost injury prediction should be based on INF measurements of cells grown on plants rather than in culture. The relative INFs of individual strains varied with plant host and environment. However, none of seven plant species tested optimized the INFs of all 15 strains. Similarly, incubation for 48 h at near 100% relative humidity with short photoperiods did not always decrease the INF when compared with a 72 h, 40% relative humidity, long-photoperiod incubation. Pathogenic strains on susceptible hosts were not associated with higher or lower INFs relative to their INFs on nonsusceptible plant species. The <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of individual bacterial strains on plants therefore appears to be controlled by complex and interacting factors such as strain genotype, environment, and host plant species. PMID:16347741</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.C53A0814B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.C53A0814B"><span id="translatedtitle">South Pole <span class="hlt">ice</span> stream temporal and spatial evolution in the last glacial cycle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blankenship, D. D.; Cavitte, M. G.; Young, D. A.; Carter, S. P.; Gutowski, G.; Bingham, R. G.; Siegert, M. J.</p> <p>2012-12-01</p> <p>While considered to be the most stable part of the Antarctic continent, recent studies show East Antarctic <span class="hlt">ice</span> sheet has a high potential for rapid change and significant sea level contribution. Airborne radar sounding has shown that major <span class="hlt">ice</span> stream tributaries have disrupted <span class="hlt">ice</span> at the South Pole, portraying a complex evolution for the East Antarctic <span class="hlt">ice</span> sheet. We confirm the temporal and spatial extent of these flow regime changes through the analysis of dated internal layers observed using airborne sounding data. Layering is time-registered to the local dust record from <span class="hlt">ICE</span> CUBE boreholes and the SPRESSO core, which constrains <span class="hlt">ice</span> stream transient penetration between 50 ka and about 10 ka, corresponding to the last glacial maximum. The <span class="hlt">ice</span> stream <span class="hlt">margin</span> position has migrated through time, initially at 10 km grid north of the South Pole, and migrated to the grid south by 40km before shutting off. The <span class="hlt">active</span> portion of the <span class="hlt">ice</span> sheet has undergone significant melting, bringing <span class="hlt">ice</span> from the MIS 5e interglacial very close to the bedrock with respect to the inactive portion to the grid north. Shear heating from the <span class="hlt">ice</span> stream <span class="hlt">margin</span> migration is consistent with subglacial lakes previously observed in the area (Peters et al, 2008). This <span class="hlt">ice</span> stream is further evidence for a substantial, rapid sea level contribution from the deep interior of the East Antarctic <span class="hlt">Ice</span> Sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/11513659','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/11513659"><span id="translatedtitle">Hypervalent iodine compounds as potent antibacterial agents against <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA) Pseudomonas syringae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Menkissoglu-Spiroudi, U; Karamanoli, K; Spyroudis, S; Constantinidou, H I</p> <p>2001-08-01</p> <p>Twenty-three hypervalent iodine compounds belonging to aryliodonium salts, 1, aryliodonium ylides, 2, and (diacyloxyiodo)arenes, 3, were tested for their antibacterial <span class="hlt">activities</span> against <span class="hlt">ice</span> nucleation <span class="hlt">active</span> (INA) Pseudomonas syringae, and the MIC and EC(50) values were determined. All of the compounds examined caused a dose-dependent decrease in bacterial growth rates. Aryliodonium salts, especially those with electron-withdrawing groups, exhibit higher antibacterial <span class="hlt">activities</span> with MIC = 8-16 ppm, whereas the nature of the anion does not seem to affect the <span class="hlt">activities</span> of the diaryliodonium salts. PMID:11513659</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6575B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6575B"><span id="translatedtitle">Morphotectonic evolution of passive <span class="hlt">margins</span> undergoing <span class="hlt">active</span> surface processes: large-scale experiments using numerical models.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beucher, Romain; Huismans, Ritske S.</p> <p>2016-04-01</p> <p>Extension of the continental lithosphere can lead to the formation of a wide range of rifted <span class="hlt">margins</span> styles with contrasting tectonic and geomorphological characteristics. It is now understood that many of these characteristics depend on the manner extension is distributed depending on (among others factors) rheology, structural inheritance, thermal structure and surface processes. The relative importance and the possible interactions of these controlling factors is still largely unknown. Here we investigate the feedbacks between tectonics and the transfers of material at the surface resulting from erosion, transport, and sedimentation. We use large-scale (1200 x 600 km) and high-resolution (~1km) numerical experiments coupling a 2D upper-mantle-scale thermo-mechanical model with a plan-form 2D surface processes model (SPM). We test the sensitivity of the coupled models to varying crust-lithosphere rheology and erosional efficiency ranging from no-erosion to very efficient erosion. We discuss how fast, when and how the topography of the continents evolves and how it can be compared to actual passive <span class="hlt">margins</span> escarpment morphologies. We show that although tectonics is the main factor controlling the rift geometry, transfers of masses at the surface affect the timing of faulting and the initiation of sea-floor spreading. We discuss how such models may help to understand the evolution of high-elevated passive <span class="hlt">margins</span> around the world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26310455','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26310455"><span id="translatedtitle">Solar PAR and UVR modify the community composition and photosynthetic <span class="hlt">activity</span> of sea <span class="hlt">ice</span> algae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Enberg, Sara; Piiparinen, Jonna; Majaneva, Markus; Vähätalo, Anssi V; Autio, Riitta; Rintala, Janne-Markus</p> <p>2015-10-01</p> <p>The effects of increased photosynthetically <span class="hlt">active</span> radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic <span class="hlt">activity</span> were studied in fast <span class="hlt">ice</span> algal communities. The experimental set-up consisted of nine 1.44 m(2) squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free <span class="hlt">ice</span> covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly Scrippsiella hangoei, Biecheleria baltica and Gymnodinium corollarium) showed UV sensitivity in the top 5-cm layer, whereas Heterocapsa arctica ssp. frigida and green algae showed sensitivity to both PAR and UVR. The photosynthetic <span class="hlt">activity</span> was highest in the top 5-cm layer of the PAR treatment, where the biomass of the pennate diatom Nitzschia frigida increased, indicating the UV sensitivity of this species. This study shows that UVR is one of the controlling factors of algal communities in Baltic Sea <span class="hlt">ice</span>, and that increased availability of PAR together with UVR exclusion can cause changes in algal biomass, photosynthetic <span class="hlt">activity</span> and community composition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26310455','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26310455"><span id="translatedtitle">Solar PAR and UVR modify the community composition and photosynthetic <span class="hlt">activity</span> of sea <span class="hlt">ice</span> algae.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Enberg, Sara; Piiparinen, Jonna; Majaneva, Markus; Vähätalo, Anssi V; Autio, Riitta; Rintala, Janne-Markus</p> <p>2015-10-01</p> <p>The effects of increased photosynthetically <span class="hlt">active</span> radiation (PAR) and ultraviolet radiation (UVR) on species diversity, biomass and photosynthetic <span class="hlt">activity</span> were studied in fast <span class="hlt">ice</span> algal communities. The experimental set-up consisted of nine 1.44 m(2) squares with three treatments: untreated with natural snow cover (UNT), snow-free (PAR + UVR) and snow-free <span class="hlt">ice</span> covered with a UV screen (PAR). The total algal biomass, dominated by diatoms and dinoflagellates, increased in all treatments during the experiment. However, the smaller biomass growth in the top 10-cm layer of the PAR + UVR treatment compared with the PAR treatment indicated the negative effect of UVR. Scrippsiella complex (mainly Scrippsiella hangoei, Biecheleria baltica and Gymnodinium corollarium) showed UV sensitivity in the top 5-cm layer, whereas Heterocapsa arctica ssp. frigida and green algae showed sensitivity to both PAR and UVR. The photosynthetic <span class="hlt">activity</span> was highest in the top 5-cm layer of the PAR treatment, where the biomass of the pennate diatom Nitzschia frigida increased, indicating the UV sensitivity of this species. This study shows that UVR is one of the controlling factors of algal communities in Baltic Sea <span class="hlt">ice</span>, and that increased availability of PAR together with UVR exclusion can cause changes in algal biomass, photosynthetic <span class="hlt">activity</span> and community composition. PMID:26310455</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70044168','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70044168"><span id="translatedtitle">Late Pleistocene and Holocene uplift history of Cyprus: implications for <span class="hlt">active</span> tectonics along the southern <span class="hlt">margin</span> of the Anatolian microplate</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Harrison, R.W.; Tsiolakis, E.; Stone, B.D.; Lord, A.; McGeehin, J.P.; Mahan, S.A.; Chirico, P.</p> <p>2013-01-01</p> <p>The nature of the southern <span class="hlt">margin</span> of the Anatolian microplate during the Neogene is complex, controversial and fundamental in understanding <span class="hlt">active</span> plate-<span class="hlt">margin</span> tectonics and natural hazards in the Eastern Mediterranean region. Our investigation provides new insights into the Late Pleistocene uplift history of Cyprus and the Troodos Ophiolite. We provide isotopic (14C) and radiogenic (luminescence) dates of outcropping marine sediments in eastern Cyprus that identify periods of deposition during marine isotope stages (MIS) 3, 4, 5 and 6. Past sea-levels indicated by these deposits are c. 95±25 m higher in elevation than estimates of worldwide eustatic sea-level. An uplift rate of c. 1.8 mm/year and possibly as much as c. 4.1 mm/year in the past c. 26–40 ka is indicated. Holocene marine deposits also occur at elevations higher than those expected for past SL and suggest uplift rates of c. 1.2–2.1 mm/year. MIS-3 marine deposits that crop out in southern and western Cyprus indicate uniform island-wide uplift. We propose a model of tectonic wedging at a plate-bounding restraining bend as a mechanism for Late Pleistocene to Holocene uplift of Cyprus; uplift is accommodated by deformation and seismicity along the <span class="hlt">margins</span> of the Troodos Ophiolite and re-<span class="hlt">activation</span> of its low-angle, basal shear zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2001M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2001M"><span id="translatedtitle">Reconstructing the last Newfoundland <span class="hlt">Ice</span> Sheet,Canada.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McHenry, Maureen; Dunlop, Paul</p> <p>2015-04-01</p> <p>The Newfoundland <span class="hlt">Ice</span> Sheet which formed part of the North American <span class="hlt">Ice</span> Sheet Complex was situated on the <span class="hlt">margins</span> of the northwest Atlantic Ocean during the Wisconsinan glaciation (~80ka BP to 10ka BP). This complex consisted of the Laurentide, the Cordilleran and Innuitian <span class="hlt">Ice</span> Sheets, the Canadian Maritime Provinces <span class="hlt">Ice</span> Cover and the Newfoundland <span class="hlt">Ice</span> Sheet (NIS). Although all were confluent at the last glacial maximum, the NIS is known to have supported independent <span class="hlt">ice</span> centres with advances from the Laurentide <span class="hlt">Ice</span> Sheet being restricted to Newfoundland's northern and western <span class="hlt">margins</span>. Given its distinctive position, it is likely the evolution of the NIS through the last glacial cycle was influenced by a number of external and internal drivers including configuration changes in the Laurentide <span class="hlt">Ice</span> Sheet, <span class="hlt">ice</span> stream initiation and shutdown, changes in oceanic circulation and fluctuating sea levels and climate signals from the wider Amphi-North Atlantic. As such Newfoundland is a key location for investigating <span class="hlt">ice</span> sheet response to a number of internal and external forcing mechanisms during glacial cycles. An established technique for reconstructing former <span class="hlt">ice</span> sheet behaviour is the mapping and spatial analysis of glacial landforms. This provides a valuable record of former <span class="hlt">ice</span> sheet extent and behaviour through time as well as <span class="hlt">ice</span> sheet retreat during deglaciation. Here we present new mapping based on our interpretation of SPOT satellite imagery and Digital Elevation Models of the entire Island of Newfoundland as well as swath bathymetric imagery from several locations offshore. Our new database consisting of ~150,000 individually mapped subglacial bedforms that includes drumlins, crag and tails, glacially moulded bedrock lineations and ribbed moraines significantly increases the known landform record in this region. The new database shows Newfoundland has a complex palimpsest landscape that records multiple <span class="hlt">ice</span> sheet events across the island. Here we report our</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211532P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211532P"><span id="translatedtitle">10Be in <span class="hlt">ice</span> at high resolution: Solar <span class="hlt">activity</span> and climate signals observed and GCM-modeled in Law Dome <span class="hlt">ice</span> cores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pedro, Joel; Heikkilä, Ulla; van Ommen, T. D.; Smith, A. M.</p> <p>2010-05-01</p> <p>Changes in solar <span class="hlt">activity</span> modulate the galactic cosmic ray flux, and in turn, the production rate of 10Be in the earth's atmosphere. The best archives of past changes in 10Be production rate are the polar <span class="hlt">ice</span> cores. Key challenges in interpreting these archives as proxies for past solar <span class="hlt">activity</span> lie in separating the useful solar <span class="hlt">activity</span> (or production) signal from the interfering meteorological (or climate) signal, and furthermore, in determining the atmospheric source regions of 10Be deposited to the <span class="hlt">ice</span> core site. In this study we use a new monthly resolution composite 10Be record, which spans the past decade, and a general circulation model (ECHAM5-HAM), to constrain both the production and climate signals in 10Be concentrations at the Law Dome <span class="hlt">ice</span> core site, East Antarctica. This study differs from most previous work on 10Be in Antarctica due to the very high sample resolution achieved. This high resolution, through a time period where accurate instrumental measurements of solar <span class="hlt">activity</span> and climate are available, allows us to examine the response of 10Be concentrations in <span class="hlt">ice</span> to short-term (monthly to annual) variations in solar <span class="hlt">activity</span>, and to short-term variations in climate, including seasonality. We find a significant correlation (r2 = 0.56, P < 0.005, n = 92) between observed 10Be concentrations and solar <span class="hlt">activity</span> (represented by the neutron counting rate). The most pervasive climate influence is a seasonal cycle, which shows maximum concentrations in mid-to-late-summer and minimum concentrations in winter. Model results show reasonable agreement with observations; both a solar <span class="hlt">activity</span> signal and seasonal cycle in 10Be are captured. However, the modeled snow accumulation rate is too high by approximately 60%. According to the model, the main atmospheric source region of 10Be deposited to Law Dome is the 30-90°S stratosphere (~50%), followed by the 30-90°S troposphere (~30%). An enhancement in the fraction of 10Be arriving to Law Dome from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DPS....4822022H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DPS....4822022H"><span id="translatedtitle">Synoptic Traveling Weather Systems on Mars: Effects of Radiatively-<span class="hlt">Active</span> Water <span class="hlt">Ice</span> Clouds</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hollingsworth, Jeffery L.; Kahre, Melinda A.; Haberle, Robert; Atsuki Urata, Richard</p> <p>2016-10-01</p> <p>Atmospheric aerosols on Mars are critical in determining the nature of its thermal structure, its large-scale circulation, and hence the overall climate of the planet. We conduct multi-annual simulations with the latest version of the NASA Ames Mars global climate model (GCM), gcm2.3+, that includes a modernized radiative-transfer package and complex water-<span class="hlt">ice</span> cloud microphysics package which permit radiative effects and interactions of suspended atmospheric aerosols (e.g., water <span class="hlt">ice</span> clouds, water vapor, dust, and mutual interactions) to influence the net diabatic heating. Results indicate that radiatively <span class="hlt">active</span> water <span class="hlt">ice</span> clouds profoundly affect the seasonal and annual mean climate. The mean thermal structure and balanced circulation patterns are strongly modified near the surface and aloft. Warming of the subtropical atmosphere at altitude and cooling of the high latitude atmosphere at low levels takes place, which increases the mean pole-to-equator temperature contrast (i.e., "baroclinicity"). With radiatively <span class="hlt">active</span> water <span class="hlt">ice</span> clouds (RAC) compared to radiatively inert water <span class="hlt">ice</span> clouds (nonRAC), significant changes in the intensity of the mean state and forced stationary Rossby modes occur, both of which affect the vigor and intensity of traveling, synoptic period weather systems. Such weather systems not only act as key agents in the transport of heat and momentum beyond the extent of the Hadley circulation, but also the transport of trace species such as water vapor, water <span class="hlt">ice</span>-clouds, dust and others. The northern hemisphere (NH) forced Rossby waves and resultant wave train are augmented in the RAC case: the modes are more intense and the wave train is shifted equatorward. Significant changes also occur within the subtropics and tropics. The Rossby wave train sets up, combined with the traveling synoptic-period weather systems (i.e., cyclones and anticyclones), the geographic extent of storm zones (or storm tracks) within the NH. A variety of circulation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16346129','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16346129"><span id="translatedtitle">Plants as sources of airborne bacteria, including <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lindemann, J; Constantinidou, H A; Barchet, W R; Upper, C D</p> <p>1982-11-01</p> <p>Vertical wind shear and concentration gradients of viable, airborne bacteria were used to calculate the upward flux of viable cells above bare soil and canopies of several crops. Concentrations at soil or canopy height varied from 46 colony-forming units per m over young corn and wet soil to 663 colony-forming units per m over dry soil and 6,500 colony-forming units per m over a closed wheat canopy. In simultaneous samples, concentrations of viable bacteria in the air 10 m inside an alfalfa field were fourfold higher than those over a field with dry, bare soil immediately upwind. The upward flux of viable bacteria over alfalfa was three- to fourfold greater than over dry soil. Concentrations of <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria were higher over plants than over soil. Thus, plant canopies may constitute a major source of bacteria, including <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria, in the air.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19727498','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19727498"><span id="translatedtitle">Cloud condensation nuclei and <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> of hydrophobic and hydrophilic soot particles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koehler, Kirsten A; DeMott, Paul J; Kreidenweis, Sonia M; Popovicheva, Olga B; Petters, Markus D; Carrico, Christian M; Kireeva, Elena D; Khokhlova, Tatiana D; Shonija, Natalia K</p> <p>2009-09-28</p> <p>Cloud condensation nuclei (CCN) <span class="hlt">activity</span> and <span class="hlt">ice</span> nucleation behavior (for temperatures<or=-40 degrees C) of soot aerosols relevant for atmospheric studies were investigated. Soots were chosen to represent a range of physico-chemical properties, from hydrophobic through a range of hydrophilicity, to hygroscopic. These characteristics were achieved through generation by three different combustion sources; three soots from natural gas pyrolysis (original: TS; graphitized: GTS; and oxidized: TOS), soot from a diffusion flame in an oil lamp burning aviation kerosene (TC1), and soot from a turbulent diffusion flame in an aircraft engine combustor (AEC). All of the samples exhibited some heterogeneity in our experiments, which showed evidence of two or more particle sub-types even within a narrow size cut. The heterogeneity could have resulted from both chemical and sizing differences, the latter attributable in part to particle non-sphericity. Neither GTS nor TS, hydrophobic particles distinguished only by the lower porosity and polarity of the GTS surface, showed CCN <span class="hlt">activity</span> at or below water supersaturations required for wettable, insoluble particles (the Kelvin limit). TC1 soot particles, despite classification as hydrophilic, did not show CCN <span class="hlt">activity</span> at or below the Kelvin limit. We attribute this result to the microporosity of this soot. In contrast, oxidized, non-porous, and hydrophilic TOS particles exhibited CCN <span class="hlt">activation</span> at very near the Kelvin limit, with a small percentage of these particles CCN-<span class="hlt">active</span> even at lower supersaturations. Due to containing a range of surface coverage of organic and inorganic hydrophilic and hygroscopic compounds, up to approximately 35% of hygroscopic AEC particles were <span class="hlt">active</span> as CCN, with a small percentage of these particles CCN-<span class="hlt">active</span> at lower supersaturations. In <span class="hlt">ice</span> nucleation experiments below -40 degrees C, AEC particles nucleated <span class="hlt">ice</span> near the expected condition for homogeneous freezing of water from aqueous solutions. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6747620','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6747620"><span id="translatedtitle">Cenozoic evolution of the Antarctic Peninsula continental <span class="hlt">margin</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Anderson, J.B. )</p> <p>1990-05-01</p> <p>Cenozoic evolution of the Antarctic Peninsula continental <span class="hlt">margin</span> has involved a series of ridge (Aluk Ridge)-trench collisions between the Pacific and Antarctic plates. Subduction occurred episodically between segments of the Pacific plate that are bounded by major fracture zones. The age of ridge-trench collisions decreases from south to north along the <span class="hlt">margin</span>. The very northern part of the <span class="hlt">margin</span>, between the Hero and Shackleton fracture zones, has the last surviving Aluk-Antarctic spreading ridge segments and the only remaining trench topography. The sedimentary cover on the northern <span class="hlt">margin</span> is relatively thin generally less than 1.5 km, thus providing a unique setting in which to examine <span class="hlt">margin</span> evolution using high resolution seismic methods. Over 5,000 km of high resolution (water gun) seismic profiles were acquired from the Antarctic Peninsula <span class="hlt">margin</span> during four cruises to the region. The <span class="hlt">margin</span> is divided into discrete fracture-zone-bounded segments; each segment displays different styles of development. Highly tectonized <span class="hlt">active</span> <span class="hlt">margin</span> sequences have been buried beneath a seaward-thickening sediment wedge that represents the passive stage of <span class="hlt">margin</span> development <span class="hlt">Ice</span> caps, which have existed in the Antarctic Peninsula region since at least the late Oligocene, have advanced onto the continental shelf on numerous occasions, eroding hundreds of meters into the shelf and depositing a thick sequence of deposits characterized by till tongues and glacial troughs. Glacial erosion has been the main factor responsible for overdeepening of the shelf; isostasy is of secondary importance. As the shelf was lowered by glacial erosion, it was able to accommodate thicker and more unstable marine <span class="hlt">ice</span> sheets. The shelf also became a vast reservoir for cold, saline shelf water, one of the key ingredients of Antarctic bottom water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3341045','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3341045"><span id="translatedtitle">9,400 years of cosmic radiation and solar <span class="hlt">activity</span> from <span class="hlt">ice</span> cores and tree rings</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Steinhilber, Friedhelm; Beer, Jürg; Brunner, Irene; Christl, Marcus; Fischer, Hubertus; Heikkilä, Ulla; Kubik, Peter W.; Mann, Mathias; McCracken, Ken G.; Miller, Heinrich; Miyahara, Hiroko; Oerter, Hans</p> <p>2012-01-01</p> <p>Understanding the temporal variation of cosmic radiation and solar <span class="hlt">activity</span> during the Holocene is essential for studies of the solar-terrestrial relationship. Cosmic-ray produced radionuclides, such as 10Be and 14C which are stored in polar <span class="hlt">ice</span> cores and tree rings, offer the unique opportunity to reconstruct the history of cosmic radiation and solar <span class="hlt">activity</span> over many millennia. Although records from different archives basically agree, they also show some deviations during certain periods. So far most reconstructions were based on only one single radionuclide record, which makes detection and correction of these deviations impossible. Here we combine different 10Be <span class="hlt">ice</span> core records from Greenland and Antarctica with the global 14C tree ring record using principal component analysis. This approach is only possible due to a new high-resolution 10Be record from Dronning Maud Land obtained within the European Project for <span class="hlt">Ice</span> Coring in Antarctica in Antarctica. The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar <span class="hlt">activity</span> to identify the solar imprint in an Asian climate record. Though generally the agreement between solar forcing and Asian climate is good, there are also periods without any coherence, pointing to other forcings like volcanoes and greenhouse gases and their corresponding feedbacks. The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate. PMID:22474348</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7896G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7896G"><span id="translatedtitle">Relationship between early autumn Arctic sea <span class="hlt">ice</span> and East Asian wintertime transient eddy <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gu, Sen; Zhang, Yang; Wu, Qigang</p> <p>2015-04-01</p> <p>The Arctic sea <span class="hlt">ice</span> is suggested with wide impacts on the winter climate over East Asia. In this study, the relationship between the early autumn Arctic sea <span class="hlt">ice</span> and the wintertime transient eddy <span class="hlt">activity</span> over East Asia is investigated. Our singular value decomposition (SVD) analysis between the Arctic sea <span class="hlt">ice</span> concentration (SIC) and transient eddy kinetic energy (EKE) shows that with the decrease in SIC over the Siberia coast, Kara sea and Barents sea, the EKE around the Tibetan Plateau and the downstream regions increase significantly. This leading mode indicates that more than 60% variance of the wintertime East Asian transient eddy <span class="hlt">activity</span> can be predicted from the SIC three month earlier. Possible dynamical processes responsible for the linkage between SIC and EKE are investigated. In the upstream of Tibetan Plateau, a branch of anomalous wave train is detected propagating southward from Ural Mountains to the North China and Tibet. In the downstream region of Tibetan Plateau, with the decrease in SIC, anomalous increase in synoptic eddy generation is found with the enhanced baroclinicity over the north slope of the Tibetan Plateau, which can result in the increase in EKE as well. Those two dynamical processes both act to enhance the transient eddy <span class="hlt">activity</span> over East Asia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22474348','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22474348"><span id="translatedtitle">9,400 years of cosmic radiation and solar <span class="hlt">activity</span> from <span class="hlt">ice</span> cores and tree rings.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Steinhilber, Friedhelm; Abreu, Jose A; Beer, Jürg; Brunner, Irene; Christl, Marcus; Fischer, Hubertus; Heikkilä, Ulla; Kubik, Peter W; Mann, Mathias; McCracken, Ken G; Miller, Heinrich; Miyahara, Hiroko; Oerter, Hans; Wilhelms, Frank</p> <p>2012-04-17</p> <p>Understanding the temporal variation of cosmic radiation and solar <span class="hlt">activity</span> during the Holocene is essential for studies of the solar-terrestrial relationship. Cosmic-ray produced radionuclides, such as (10)Be and (14)C which are stored in polar <span class="hlt">ice</span> cores and tree rings, offer the unique opportunity to reconstruct the history of cosmic radiation and solar <span class="hlt">activity</span> over many millennia. Although records from different archives basically agree, they also show some deviations during certain periods. So far most reconstructions were based on only one single radionuclide record, which makes detection and correction of these deviations impossible. Here we combine different (10)Be <span class="hlt">ice</span> core records from Greenland and Antarctica with the global (14)C tree ring record using principal component analysis. This approach is only possible due to a new high-resolution (10)Be record from Dronning Maud Land obtained within the European Project for <span class="hlt">Ice</span> Coring in Antarctica in Antarctica. The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar <span class="hlt">activity</span> to identify the solar imprint in an Asian climate record. Though generally the agreement between solar forcing and Asian climate is good, there are also periods without any coherence, pointing to other forcings like volcanoes and greenhouse gases and their corresponding feedbacks. The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFM.B43E1655N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFM.B43E1655N&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Active</span> Venting Sites On The Gas-Hydrate-Bearing Hikurangi <span class="hlt">Margin</span>, Off New Zealand: ROV Measurements And Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naudts, L.; Poort, J.; Boone, D.; Linke, P.; Greinert, J.; de Batist, M.; Henriet, J.</p> <p>2007-12-01</p> <p>During R.V. Sonne cruise SO191-3, part of the "New (Zealand Cold) Vents" expedition, RCMG deployed a CHEROKEE ROV "Genesis" on the Hikurangi <span class="hlt">Margin</span>. This accretionary <span class="hlt">margin</span>, on the east coast of New Zealand, is related to the subduction of the Pacific Plate under the Australian Plate. Several cold vent locations as well as an extensive BSR, indicating the presence of gas hydrates, have been found at this <span class="hlt">margin</span>. The aims of the ROV-work were to precisely localize <span class="hlt">active</span> methane vents, to conduct detailed visual observations of the vent structures and <span class="hlt">activity</span>, and to perform measurements of physical properties and collect samples at and around the vent locations. The three investigated areas generally have a flat to moderate undulating sea floor with soft sediments alternating with carbonate platforms. The different sites were sometimes covered with dense fields of live clams or shell debris, often in association with tube worms, sponges and/or soft tissue corals. <span class="hlt">Active</span> bubble- releasing seeps were observed at Faure's site and LM-3 site. Bubble-releasing <span class="hlt">activity</span> was very variable in time, with periods of almost non-<span class="hlt">activity</span> alternating with periods of violent outbursts. Bubble release occurred mainly from prominent depressions in soft-sediment sea floor. Bottom-water sampling revealed sometimes high concentrations of methane. Sediment-temperature measurements were largely comparable with the bottom- water temperature except for a "raindrop site" (with dense populations of polychaetes), where anomalous low sediment-temperature was measured. Further analysis of the ROV data together with the integration of other datasets will enable us to produce a model characterizing seep structure and environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFMED33B1216R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007AGUFMED33B1216R&link_type=ABSTRACT"><span id="translatedtitle">Online Classroom Research and Analysis <span class="hlt">Activities</span> Using <span class="hlt">MARGINS</span>-Related Resources for the Izu-Bonin-Mariana Subduction System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ryan, J. G.</p> <p>2007-12-01</p> <p>Students today have online access to nearly unlimited scientific information in an entirely unfiltered state. As such, they need guidance and training in identifying and assessing high-quality information resources for educational and research use. The extensive research data resources available online for the Izu-Bonin-Mariana (IBM) subduction system that have been developed with <span class="hlt">MARGINS</span> Program and related NSF funding are an ideal venue for focused Web research exercises that can be tailored to a range of undergraduate geoscience courses. This presentation highlights student web research <span class="hlt">activities</span> examining: a) The 2003-2005 eruptions of Anatahan Volcano in the Mariana volcanic arc. <span class="hlt">MARGINS</span>-supported geophysical research teams were in the region when the eruption initiated, permitting a unique "event response" data collection and analysis process, with preliminary results presented online at websites linked to the <span class="hlt">MARGINS</span> homepage, and ultimately published in a special issue of the Journal of Volcanology and Geothermal Research. In this <span class="hlt">activity</span>, students will conduct a directed Web surf/search effort for information on and datasets from the Anatahan arc volcano, which they will use in an interpretive study of recent magmatic <span class="hlt">activity</span> in the Mariana arc. This <span class="hlt">activity</span> is designed as a homework exercise for use in a junior-senior level Petrology course, but could easily be taken into greater depth for the benefit of graduate-level volcanology or geochemistry offerings. b) Geochemical and mineralogical results from ODP Legs 125 and 195 focused on diapiric serpentinite mud volcanoes, which erupt cold, high pH fluids, serpentine muds, and serpentinized ultramafic clasts at a number of sites in the forearc region of the Mariana subduction zone. The focus of this <span class="hlt">activity</span> is an examination of the trace element chemistry of the forearc serpentines and their associated upwelling porefluids as a means of understanding the roles of ionic radius, valence, and system</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26889747','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26889747"><span id="translatedtitle">Inhibition of <span class="hlt">ice</span> recrystallization and cryoprotective <span class="hlt">activity</span> of wheat proteins in liver and pancreatic cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chow-Shi-Yée, Mélanie; Briard, Jennie G; Grondin, Mélanie; Averill-Bates, Diana A; Ben, Robert N; Ouellet, François</p> <p>2016-05-01</p> <p>Efficient cryopreservation of cells at ultralow temperatures requires the use of substances that help maintain viability and metabolic functions post-thaw. We are developing new technology where plant proteins are used to substitute the commonly-used, but relatively toxic chemical dimethyl sulfoxide. Recombinant forms of four structurally diverse wheat proteins, TaIRI-2 (<span class="hlt">ice</span> recrystallization inhibition), TaBAS1 (2-Cys peroxiredoxin), WCS120 (dehydrin), and TaENO (enolase) can efficiently cryopreserve hepatocytes and insulin-secreting INS832/13 cells. This study shows that TaIRI-2 and TaENO are internalized during the freeze-thaw process, while TaBAS1 and WCS120 remain at the extracellular level. Possible antifreeze <span class="hlt">activity</span> of the four proteins was assessed. The "splat cooling" method for quantifying <span class="hlt">ice</span> recrystallization inhibition <span class="hlt">activity</span> (a property that characterizes antifreeze proteins) revealed that TaIRI-2 and TaENO are more potent than TaBAS1 and WCS120. Because of their ability to inhibit <span class="hlt">ice</span> recrystallization, the wheat recombinant proteins TaIRI-2 and TaENO are promising candidates and could prove useful to improve cryopreservation protocols for hepatocytes and insulin-secreting cells, and possibly other cell types. TaENO does not have typical <span class="hlt">ice</span>-binding domains, and the TargetFreeze tool did not predict an antifreeze capacity, suggesting the existence of nontypical antifreeze domains. The fact that TaBAS1 is an efficient cryoprotectant but does not show antifreeze <span class="hlt">activity</span> indicates a different mechanism of action. The cryoprotective properties conferred by WCS120 depend on biochemical properties that remain to be determined. Overall, our results show that the proteins' efficiencies vary between cell types, and confirm that a combination of different protection mechanisms is needed to successfully cryopreserve mammalian cells.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.P72C..06R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.P72C..06R"><span id="translatedtitle">Seasonally-<span class="hlt">Active</span> Water on Mars: Vapour, <span class="hlt">Ice</span>, Adsorbate, and the Possibility of Liquid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richardson, M. I.</p> <p>2002-12-01</p> <p>Seasonally-<span class="hlt">active</span> 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 <span class="hlt">ice</span> 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 <span class="hlt">ice</span> cap. The southern summer residual carbon dioxide <span class="hlt">ice</span> 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 <span class="hlt">ice</span> in the northern hemisphere by tropical water <span class="hlt">ice</span> 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 <span class="hlt">ice</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21235213','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21235213"><span id="translatedtitle">Homogeneous <span class="hlt">ice</span> nucleation from aqueous inorganic/organic particles representative of biomass burning: water <span class="hlt">activity</span>, freezing temperatures, nucleation rates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Knopf, Daniel A; Rigg, Yannick J</p> <p>2011-02-10</p> <p>Homogeneous <span class="hlt">ice</span> nucleation plays an important role in the formation of cirrus clouds with subsequent effects on the global radiative budget. Here we report on homogeneous <span class="hlt">ice</span> nucleation temperatures and corresponding nucleation rate coefficients of aqueous droplets serving as surrogates of biomass burning aerosol. Micrometer-sized (NH(4))(2)SO(4)/levoglucosan droplets with mass ratios of 10:1, 1:1, 1:5, and 1:10 and aqueous multicomponent organic droplets with and without (NH(4))(2)SO(4) under typical tropospheric temperatures and relative humidities are investigated experimentally using a droplet conditioning and <span class="hlt">ice</span> nucleation apparatus coupled to an optical microscope with image analysis. Homogeneous freezing was determined as a function of temperature and water <span class="hlt">activity</span>, a(w), which was set at droplet preparation conditions. The <span class="hlt">ice</span> nucleation data indicate that minor addition of (NH(4))(2)SO(4) to the aqueous organic droplets renders the temperature dependency of water <span class="hlt">activity</span> negligible in contrast to the case of aqueous organic solution droplets. The mean homogeneous <span class="hlt">ice</span> nucleation rate coefficient derived from 8 different aqueous droplet compositions with average diameters of ∼60 μm for temperatures as low as 195 K and a(w) of 0.82-1 is 2.18 × 10(6) cm(-3) s(-1). The experimentally derived freezing temperatures and homogeneous <span class="hlt">ice</span> nucleation rate coefficients are in agreement with predictions of the water <span class="hlt">activity</span>-based homogeneous <span class="hlt">ice</span> nucleation theory when taking predictive uncertainties into account. However, the presented <span class="hlt">ice</span> nucleation data indicate that the water <span class="hlt">activity</span>-based homogeneous <span class="hlt">ice</span> nucleation theory overpredicts the freezing temperatures by up to 3 K and corresponding <span class="hlt">ice</span> nucleation rate coefficients by up to ∼2 orders of magnitude. A shift of 0.01 in a(w), which is well within the uncertainty of typical field and laboratory relative humidity measurements, brings experimental and predicted freezing temperatures and homogeneous <span class="hlt">ice</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C53A0289B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C53A0289B"><span id="translatedtitle">Towards remote sensing of Arctic <span class="hlt">ice</span> roads and associated human <span class="hlt">activities</span> using SUOMI NPP night light images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bennett, M.; Smith, L. C.; Stephenson, S. R.</p> <p>2014-12-01</p> <p><span class="hlt">Ice</span> roads are often the only cost-effective means of transporting goods and supplies to communities, mines, and other sites in remote parts of the Arctic. Yet, there is no global dataset for Arctic <span class="hlt">ice</span> roads. However, remotely sensed images from the SUOMI NPP day/night band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) may allow for the construction of such a dataset. The DNB's high sensitivity to low-level light suggests that while it is not feasible to view <span class="hlt">ice</span> roads at night per se, other prominent features associated with <span class="hlt">ice</span> roads can serve as proxies. Using a time series of images taken in winter 2012, 2013, and 2014, SUOMI NPP images are compared with Landsat 8 images and an existing map of the Tibbitt to Contwoyto <span class="hlt">ice</span> road in the Northwest Territories and Nunavut, Canada. First results reveal that while the <span class="hlt">ice</span> road's exact path cannot be discerned, key points of human <span class="hlt">activity</span> along the way can be made out. This bodes well for future applications of DNB imagery to detect <span class="hlt">ice</span> roads in places like the Russian Federation, for which there is a dearth of publicly available maps. Knowing the location of <span class="hlt">ice</span> roads is important for two reasons. First, these data can signal sites of natural resource extraction in places for which information is not widely disseminated, such as in the Russian Far East. Second, new geospatial datasets for <span class="hlt">ice</span> roads can be combined with models assessing impacts of climate change on circumpolar land accessibility (Stephenson et al. 2011) in order to understand where the structural integrity of <span class="hlt">ice</span> roads may be at risk. As warming temperatures threaten to shorten the season for <span class="hlt">ice</span> roads, communities and mines alike will need to prepare for changes to their transportation infrastructure, made out of the changing landscape itself.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013CRGeo.345..373M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013CRGeo.345..373M&link_type=ABSTRACT"><span id="translatedtitle">Is earthquake <span class="hlt">activity</span> along the French Atlantic <span class="hlt">margin</span> favoured by local rheological contrasts?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mazabraud, Yves; Béthoux, Nicole; Delouis, Bertrand</p> <p>2013-09-01</p> <p>The seismological study of recent seismic crises near Oleron Island confirms the coexistence of an extensional deformation and a transtensive regime in the Atlantic <span class="hlt">margin</span> of France, which is different from the general western European stress field corresponding to a strike-slip regime. We argue that the switch of the principal stress axes σ1/σ2 in a NW-SE vertical plane is linked with the existence of crustal heterogeneities. Events of magnitude larger than 5 sometimes occur along the Atlantic <span class="hlt">margin</span> of France, such as the 7 September 1972 (ML = 5.2) earthquake near Oleron island and the 30 September 2002 (ML = 5.7) Hennebont event in Brittany. To test the mechanism of local strain localization, we model the deformation of the hypocentral area of the Hennebont earthquake using a 3D thermo-mechanical finite element code. We conclude that the occurrence of moderate earthquakes located in limited parts of the Hercynian shear zones (as the often reactivated swarms near Oleron) could be due to local reactivation of pre-existing faults. These sporadic seismic ruptures are favoured by stress concentration due to rheological heterogeneities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/9099634','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/9099634"><span id="translatedtitle">The presence of complete but masked freezing nuclei in various artificially constructed <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> proteobacteria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yankofsky, S A; Nadler, T; Kaplan, H</p> <p>1997-05-01</p> <p>Disparate gamma-subdivision proteobacteria artificially endowed with the same <span class="hlt">ice</span> gene of enteric origin acquired water-freezing potential at -12 degrees C, but expressed it to varying extents under identical conditions of culture as well as after being subjected to certain post-culture treatments. Varying rates of cell-bound <span class="hlt">ice</span> nucleus synthesis were probably not the root cause of these observed interspecies differences in nucleation-<span class="hlt">active</span> cell frequency because potentially functional but masked <span class="hlt">ice</span>-forming templates were found in the outer cell envelope of even initially inactive individuals taken from physiologically uniform populations of virtually all tested species. We therefore propose that the extent of bacterial <span class="hlt">ice</span> nucleation generally reflects species-specified extent of <span class="hlt">ice</span> nucleus sequestration. PMID:9099634</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8913P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8913P"><span id="translatedtitle"><span class="hlt">Ice</span> nucleation <span class="hlt">active</span> particles in continental air samples over Mainz, Germany</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pummer, Bernhard G.; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine</p> <p>2016-04-01</p> <p>Aerosol particles are of central importance for atmospheric chemistry and physics, climate and public health. Some of these particles possess <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> (INA), which is highly relevant for cloud formation and precipitation. In 2010, air filter samples were collected with a high-volume filter sampler separating fine and coarse particles (aerodynamic cut-off diameter 3 μm) in Mainz, Germany. In this study, the INA of the atmospheric particles deposited on these filters was determined. Therefore,they were extracted with ultrapure water, which was then measured in a droplet freezing assay, as described in Fröhlich-Nowoisky et al. (2015). The determined concentration of <span class="hlt">ice</span> nucleators (INs) was between 0.3 and 2per m³ at 266 K, and between5 and 75 per m³ at 260 K. The INs were further characterized by different treatments, like heating (308 K, 371 K), filtration (0.1 μm, 300 kDa), and digestion with papain (10 mg/ml). We further investigated, which atmospheric conditions (e.g. weather) and distinguished events (e.g. dust storms, volcanic eruptions, and pollen peaks) influenced the number and nature of these INs. Fröhlich-Nowoisky, J., Hill, T. C. J., Pummer, B. G., Yordanova, P., Franc, G. D., and Pöschl, U.: <span class="hlt">Ice</span> nucleation <span class="hlt">activity</span> in the widespread soil fungus Mortierella alpina, Biogeosci., 12, 1057-1071, doi:10.5194/bg-12-1057-2015, 2015.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/7656570','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/7656570"><span id="translatedtitle">Isolation of <span class="hlt">ice</span>-nucleating <span class="hlt">active</span> bacteria from the freeze-tolerant frog, Rana sylvatica.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, M R; Lee, R E; Strong-Gunderson, J M; Minges, S R</p> <p>1995-08-01</p> <p><span class="hlt">Ice</span>-nucleating <span class="hlt">active</span> (INA) bacteria were isolated from the gut of field-collected freeze-tolerant wood frogs (Rana sylvatica) collected in winter. Thirteen strains of Pseudomonas fluorescens, four strains of Pseudomonas putida, and two strains of Enterobacter agglomerans had <span class="hlt">ice</span>-nucleating <span class="hlt">activity</span>. Each of the INA pseudomonad strains was psychrophilic. P. putida strains were differentiated from P. fluorescens strains by gelatinase, lecithinase, and lipase production. The maximum nucleation temperatures (Tmax) of aqueous suspensions (10(9) bacteria/ml) of the four INA P. putida strains ranged from -1.6 to -3.0 degrees C, which places this INA species among the most potent known biological nucleators. Ingestion of INA P. putida isolated from R. sylvatica by another freeze-tolerant frog. Pseudacris crucifer, decreased the capacity of this frog to supercool and remain unfrozen at -2 degrees C. This is the first report of INA bacteria isolated from a vertebrate, and suggests that, as part of the gut flora in some posthibernation freeze-tolerant wood frogs, these bacteria may play a role in enhancing winter survival by promoting <span class="hlt">ice</span> nucleation at high subzero temperatures (ca. -2 degrees C). PMID:7656570</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003PCE....28.1273G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003PCE....28.1273G"><span id="translatedtitle">Extremophilic fungi in arctic <span class="hlt">ice</span>: a relationship between adaptation to low temperature and water <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gunde-Cimerman, N.; Sonjak, S.; Zalar, P.; Frisvad, J. C.; Diderichsen, B.; Plemenitaš, A.</p> <p></p> <p>Little is known about fungal diversity in extremely cold regions. Low temperatures induce the formation of <span class="hlt">ice</span> crystals and therefore also the creation of low water <span class="hlt">activity</span> ( aw). These are the dominant factors in external chemistry that influence microbial biota in cold regions. Therefore, we have used selective low water <span class="hlt">activity</span> media plus low incubation temperatures for the isolation of fungi from an Arctic environment. In comparison with the highest values of colony forming units (CFU) obtained on mesophilic media, considerably higher fungal CFU per litre of water were detected on low aw media, ranging from 1000 to 3000 l -1 in seawater, 6000 to 7000 l -1 in melted sea <span class="hlt">ice</span> and up to 13,000 l -1 in melted glacier <span class="hlt">ice</span>. The dominant taxa were ascomycetous and basidiomycetous yeasts, melanized fungi, mainly represented by the genera Cladosporium and Aureobasidium plus different species of the genus Penicillium. Preliminary taxonomic analyses revealed several new species and varieties. Further characterisations are needed to determine whether this diversity is due to geographic isolation, ecological conditions or independent evolutionary origin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17936742','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17936742"><span id="translatedtitle">Anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> in xylem extracts from trees that contain deep supercooling xylem parenchyma cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kasuga, Jun; Mizuno, Kaoru; Arakawa, Keita; Fujikawa, Seizo</p> <p>2007-12-01</p> <p>Boreal hardwood species, including Japanese white birch (Betula platyphylla Sukat. var. japonica Hara), Japanese chestnut (Castanea crenata Sieb. et Zucc.), katsura tree (Cercidiphyllum japonicum Sieb. et Zucc.), Siebold's beech (Fagus crenata Blume), mulberry (Morus bombycis Koidz.), and Japanese rowan (Sorbus commixta Hedl.), had xylem parenchyma cells (XPCs) that adapt to subfreezing temperatures by deep supercooling. Crude extracts from xylem in all these trees were found to have anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> that promoted supercooling capability of water as measured by a droplet freezing assay. The magnitude of increase in supercooling capability of water droplets in the presence of <span class="hlt">ice</span>-nucleation bacteria, Erwinia ananas, was higher in the ranges from 0.1 to 1.7 degrees C on addition of crude xylem extracts than freezing temperature of water droplets on addition of glucose in the same concentration (100 mosmol/kg). Crude xylem extracts from C. japonicum provided the highest supercooling capability of water droplets. Our additional examination showed that crude xylem extracts from C. japonicum exhibited anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> toward water droplets containing a variety of heterogeneous <span class="hlt">ice</span> nucleators, including <span class="hlt">ice</span>-nucleation bacteria, not only E. ananas but also Pseudomonas syringae (NBRC3310) or Xanthomonas campestris, silver iodide or airborne impurities. However, crude xylem extracts from C. japonicum did not affect homogeneous <span class="hlt">ice</span> nucleation temperature as analyzed by emulsified micro-water droplets. The possible role of such anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> in crude xylem extracts in deep supercooling of XPCs is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17936742','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17936742"><span id="translatedtitle">Anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> in xylem extracts from trees that contain deep supercooling xylem parenchyma cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kasuga, Jun; Mizuno, Kaoru; Arakawa, Keita; Fujikawa, Seizo</p> <p>2007-12-01</p> <p>Boreal hardwood species, including Japanese white birch (Betula platyphylla Sukat. var. japonica Hara), Japanese chestnut (Castanea crenata Sieb. et Zucc.), katsura tree (Cercidiphyllum japonicum Sieb. et Zucc.), Siebold's beech (Fagus crenata Blume), mulberry (Morus bombycis Koidz.), and Japanese rowan (Sorbus commixta Hedl.), had xylem parenchyma cells (XPCs) that adapt to subfreezing temperatures by deep supercooling. Crude extracts from xylem in all these trees were found to have anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> that promoted supercooling capability of water as measured by a droplet freezing assay. The magnitude of increase in supercooling capability of water droplets in the presence of <span class="hlt">ice</span>-nucleation bacteria, Erwinia ananas, was higher in the ranges from 0.1 to 1.7 degrees C on addition of crude xylem extracts than freezing temperature of water droplets on addition of glucose in the same concentration (100 mosmol/kg). Crude xylem extracts from C. japonicum provided the highest supercooling capability of water droplets. Our additional examination showed that crude xylem extracts from C. japonicum exhibited anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> toward water droplets containing a variety of heterogeneous <span class="hlt">ice</span> nucleators, including <span class="hlt">ice</span>-nucleation bacteria, not only E. ananas but also Pseudomonas syringae (NBRC3310) or Xanthomonas campestris, silver iodide or airborne impurities. However, crude xylem extracts from C. japonicum did not affect homogeneous <span class="hlt">ice</span> nucleation temperature as analyzed by emulsified micro-water droplets. The possible role of such anti-<span class="hlt">ice</span> nucleation <span class="hlt">activity</span> in crude xylem extracts in deep supercooling of XPCs is discussed. PMID:17936742</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70015975','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70015975"><span id="translatedtitle">Neogene paleoceanographic events recorded in an <span class="hlt">active-margin</span> setting: Humboldt basin, California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McCrory, P.A.</p> <p>1990-01-01</p> <p>Recognition of North Pacific paleoceanographic events in the <span class="hlt">marginal</span> Humboldt (Eel River) basin of northern California enables correlation of stratigraphic sections and development of a chronostratigraphy. Paleoclimatically related coiling shifts in Neogloboquadrina pachyderma (Ehrenberg) and benthic foraminiferal datums form the basis of the chronostratigraphy. Benthic foraminiferal datums are defined by the occurrence of selected benthic species and abundance maxima of benthic biofacies. The compiled chronostratigraphy is used to refine reconstructions of the depositional history of Humboldt basin. Paleoceanographic events, recognized by the distribution of benthic foraminiferal biofacies, are used to infer paleoceanographic history along the northeastern Pacific <span class="hlt">margin</span>. The similarity in coiling curves of N. pachyderma from the marine sequence at DSDP Site 173 and the coastal Centerville Beach section of Humboldt basin and at other independently dated sites along the northeastern Pacific <span class="hlt">margin</span> demonstrates that matching records of climatic oscillations is a reliable method of correlating marine sequences. Benthic fauna from the Centerville Beach section vary in phase with climatically related coiling shifts in N. pachyderma. In particular these data show an increase in displaced neritic fauna during inferred warm intervals and resurgence of deeper bathyal fauna during inferred cool events. Similar data are observed from the inland Eel River section, demonstrating that benthic foraminiferal trends recognized at Centerville Beach can be identified elsewhere in Humboldt basin. This in-phase benthic response to climatic fluctuations probably results from changes in vertical depth range of many benthic species in response to paleoclimatically related vertical changes in water-mass position. Depositional histories reconstructed for two key sites in southern Humboldt basin indicate low rates of sediment accumulation during early basin filling with hemipelagic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860021653','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860021653"><span id="translatedtitle">Late cretaceous extensional tectonics and associated igneous <span class="hlt">activity</span> on the northern <span class="hlt">margin</span> of the Gulf of Mexico Basin</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bowen, R. L.; Sundeen, D. A.</p> <p>1985-01-01</p> <p>Major, dominantly compressional, orogenic episodes (Taconic, Acadian, Alleghenian) affected eastern North America during the Paleozoic. During the Mesozoic, in contrast, this same region was principally affected by epeirogenic and extensional tectonism; one episode of comparatively more intense tectonic <span class="hlt">activity</span> involving extensive faulting, uplift, sedimentation, intrusion and effusion produced the Newark Series of eposits and fault block phenomena. This event, termed the Palisades Disturbance, took place during the Late Triassic - Earliest Jurassic. The authors document a comparable extensional tectonic-igneous event occurring during the Late Cretaceous (Early Gulfian; Cenomanian-Santonian) along the southern <span class="hlt">margin</span> of the cratonic platform from Arkansas to Georgia.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/404379','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/404379"><span id="translatedtitle">Fusion of satellite <span class="hlt">active</span> and passive microwave data for sea <span class="hlt">ice</span> type concentration estimates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Beaven, S.G.; Gogineni, S.; Carsey, F.D.</p> <p>1996-09-01</p> <p>Young first-year sea <span class="hlt">ice</span> is nearly as important as open water in modulating heat flux between the ocean and atmosphere in the Arctic. Just after the onset of freeze-up, first-year <span class="hlt">ice</span> is in the early stages of growth and will consist of young first-year and thin <span class="hlt">ice</span>. The distribution of sea <span class="hlt">ice</span> in this thickness range impacts heat transfer in the Arctic. Therefore, improving the estimates of <span class="hlt">ice</span> concentrations in this thickness range is significant. NASA Team Algorithm (NTA) for passive microwave data inaccurately classifies sea <span class="hlt">ice</span> during the melt and freeze-up seasons because it misclassifies multiyear <span class="hlt">ice</span> as first-year <span class="hlt">ice</span>. The authors developed a hybrid fusion technique for incorporating multiyear <span class="hlt">ice</span> information derived form synthetic aperture radar (SAR) images into a passive microwave algorithm to improve <span class="hlt">ice</span> type concentration estimates. First, they classified SAR images using a dynamic thresholding technique and estimated the multiyear <span class="hlt">ice</span> concentration. Then they used the SAR-derived multiyear <span class="hlt">ice</span> concentration constrain the NTA and obtained an improved first-year <span class="hlt">ice</span> concentration estimate. They computed multiyear and first-year <span class="hlt">ice</span> concentration estimates over a region in the eastern-central Arctic in which field observations of <span class="hlt">ice</span> and in situ radar backscatter measurements were performed. With the NTA alone, the first-year <span class="hlt">ice</span> concentration in the study area varied between 0.11 and 0.40, while the multiyear <span class="hlt">ice</span> concentration varied form 0.63 to 0.39. With the hybrid fusion technique, the first-year <span class="hlt">ice</span> concentration varied between 0.08 and 0.23 and the multiyear <span class="hlt">ice</span> concentration was between 0.62 and 0.66. The fused estimates of first-year and multiyear <span class="hlt">ice</span> concentration appear to be more accurate than NTA, based on <span class="hlt">ice</span> observations that were logged aboard the US Coast Guard icebreaker Polar Star in the study area during 1991.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AtmEn.109..105S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AtmEn.109..105S"><span id="translatedtitle">Characterization of airborne <span class="hlt">ice-nucleation-active</span> bacteria and bacterial fragments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Šantl-Temkiv, Tina; Sahyoun, Maher; Finster, Kai; Hartmann, Susan; Augustin-Bauditz, Stefanie; Stratmann, Frank; Wex, Heike; Clauss, Tina; Nielsen, Niels Woetmann; Sørensen, Jens Havskov; Korsholm, Ulrik Smith; Wick, Lukas Y.; Karlson, Ulrich Gosewinkel</p> <p>2015-05-01</p> <p>Some bacteria have the unique capacity of synthesising <span class="hlt">ice-nucleation-active</span> (INA) proteins and exposing them at their outer membrane surface. As INA bacteria enter the atmosphere, they may impact the formation of clouds and precipitation. We studied members of airborne bacterial communities for their capacity to catalyse <span class="hlt">ice</span> formation and we report on the excretion of INA proteins by airborne Pseudomonas sp. We also observed for the first time that INA biological fragments <220 nm were present in precipitation samples (199 and 482 INA fragments per L of precipitation), which confirms the presence of submicron INA biological fragments in the atmosphere. During 14 precipitation events, strains affiliated with the genus Pseudomonas, which are known to carry ina genes, were dominant. A screening for INA properties revealed that ∼12% of the cultivable bacteria caused <span class="hlt">ice</span> formation at ≤-7 °C. They had likely been emitted to the atmosphere from terrestrial surfaces, e.g. by convective transport. We tested the ability of isolated INA strains to produce outer membrane vesicles and found that two isolates could do so. However, only very few INA vesicles were released per INA cell. Thus, the source of the submicron INA proteinaceous particles that we detected in the atmosphere remains to be elucidated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19880033433&hterms=Hydrogen+chloride&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3D%2528Hydrogen%2Bchloride%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19880033433&hterms=Hydrogen+chloride&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3D%2528Hydrogen%2Bchloride%2529"><span id="translatedtitle">Antarctic stratospheric chemistry of chlorine nitrate, hydrogen chloride, and <span class="hlt">ice</span> - Release of <span class="hlt">active</span> chlorine</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Molina, Mario J.; Tso, Tai-Ly; Molina, Luisa T.; Wang, Frank C.-Y.</p> <p>1987-01-01</p> <p>The reaction rate between atmospheric hydrogen chloride (HCl) and chlorine nitrate (ClONO2) is greatly enhanced in the presence of <span class="hlt">ice</span> particles; HCl dissolves readily into <span class="hlt">ice</span>, and the collisional reaction probability for ClONO2 on the surface of <span class="hlt">ice</span> with HCl in the mole fraction range from about 0.003 to 0.010 is in the range from about 0.05 to 0.1 for temperatures near 200 K. Chlorine is released into the gas phase on a time scale of at most a few milliseconds, whereas nitric acid (HNO3), the other product, remains in the condensed phase. This reaction could play an important role in explaining the observed depletion of ozone over Antarctica; it releases photolytically <span class="hlt">active</span> chlorine from its most abundant reservoir species, and it promotes the formation of HNO3 and thus removes nitrogen dioxide from the gas phase. Hence it establishes the necessary conditions for the efficient catalytic destruction of ozone by halogenated free radicals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.H44B..02M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.H44B..02M"><span id="translatedtitle">Repeated remobilisation of submarine landslide debris on an <span class="hlt">active</span> subduction <span class="hlt">margin</span> interpreted from multibeam bathymetry and multichannel seismic data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mountjoy, J. J.; Barnes, P. M.; McKean, J.; Pettinga, J. R.</p> <p>2008-12-01</p> <p>EM300 multibeam and multichannel seismic data reveal a 230 square kilometre submarine landslide complex which exhibits many of the characteristic features of equivalent terrestrial creeping earthflow complexes. Slope failures are sourced from the shelf edge/upper slope of the Poverty Bay reentrant on the <span class="hlt">active</span> Hikurangi subduction <span class="hlt">margin</span> of New Zealand where tectonic deformation, via major thrust faults with slip rates of c. 3-4 mm/yr, exerts a controlling influence on seafloor physiography. Individual landslides within this submarine complex are up to 14 km long over a vertical elevation drop of 700 m. Debris streams are in excess of 2 km wide with a debris thickness of 100 m. While multibeam data is limited to c. 10 m resolution, the scale of submarine landslide features allows us to resolve internal debris detail equivalent to terrestrial landslide examples using terrestrial techniques (e.g. airborne lidar). DEM derivative surface roughness techniques are employed to delineate the geomorphic expression of features including <span class="hlt">active</span> and abandoned lateral shears, and contractional and extensional deformation of the landslide debris. From these interpretations multiple internal failures are recognised along the length of the landslide debris. Debris deformation is also imaged in high fold multichannel seismic data and correlated to the imaged surface geomorphic features, providing insight into the failure mechanics of the landslides. Failures initiate and evolve within the quasi-stable prograding sediment wedge built onto the upper slope during lowstand sealevels. Landslides within the greater complex are at different stages of development providing information on their spatial and temporal evolution headward and laterally along the transition from shelf to upper slope <span class="hlt">margin</span>. We infer that failures are triggered and evolve in response to sealevel rise, and/or the frequent occurrence large earthquakes along the <span class="hlt">margin</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....4849L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....4849L"><span id="translatedtitle">Sonic images of submarine landscape evolution on an <span class="hlt">active</span> convergent <span class="hlt">margin</span>, Poverty re-entrant, New Zealand</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lewis, K.; Orpin, A.</p> <p>2003-04-01</p> <p>Seabed bathymetric and backscatter images were collected using a Simrad EM300 multibeam from the Poverty indentation off Gisborne, on the <span class="hlt">active</span> convergent <span class="hlt">margin</span> of the New Zealand East Coast. The 1,500 km square Poverty indentation is a major depression of continental <span class="hlt">margin</span> extending from a re-entrant in the deformation front at the Hikurangi Trough, which coincides with the mouth of the Poverty Canyon. The indentation outlines a triangular, enclosed depression, bounded along its landward flank by a high scarp incised by more than a dozen regularly-spaced, V-shaped, upper slope gullies that cut into the shelf break. The indentation has been partly in-filled by debris flow and avalanche deposits, which range from a few hundred metres to more than 25 km down-slope. At some places, cracks and scarps in the slopes indicate incipient avalanches. The indentation has been simultaneously eroded by a canyon system that exhibits many of the complexities of incised river systems onshore, including offset, capture and slump dams. At the mouth of the Poverty Canyon, scour holes are visible where hydraulic jumps have eroded the sea floor. A new canyon system appears to be in the process of forming a separate northern route to the Hikurangi Trough. On the lower slope, slumping seaward of a bulge indicates collapse in the wake of a small, subducting seamount. There is little evidence of sediment escaping the slope to form fan deposits along the Hikurangi Trough. These data are currently being used to assist in the structural and stratigraphic analysis of the <span class="hlt">margin</span>. The high-resolution maps produced prompt a thorough re-interpretation of the Late Pleistocene "landscape evolution" of the Poverty indentation and highlight the complex interaction of tectonics and deformation with sea floor morphology along <span class="hlt">active</span> plate boundaries in general.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.3856H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.3856H"><span id="translatedtitle">Cellulose and Their Characteristic <span class="hlt">Ice</span> Nucleation <span class="hlt">Activity</span>- Freezing on a Chip</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Häusler, Thomas; Felgitsch, Laura; Grothe, Hinrich</p> <p>2016-04-01</p> <p>The influence of clouds on the Earth's climate system is well known (IPCC, 2013). Cloud microphysics determines for example cloud lifetime and precipitation properties. Clouds are cooling the climate system by reflecting incoming solar radiation and warm its surface by trapping outgoing infrared radiation (Baker and Peter, 2008). In all these processes, aerosol particles play a crucial role by acting as cloud condensation nuclei (CCN) for liquid droplets and as an <span class="hlt">ice</span> nucleation particle (INP) for the formation of <span class="hlt">ice</span> particles. Freezing processes at higher temperatures than -38°C occur heterogeneously (Pruppacher and Klett 1997). Therefore aerosol particles act like a catalyst, which reduces the energy barrier for nucleation. The nucleation mechanisms, especially the theory of functional sites are not entirely understood. It remains unclear which class of compound nucleates <span class="hlt">ice</span>. Here we present a unique technique to perform drop- freezing experiments in a more efficient way. A self-made freezing- chip will be presented. Measurements done to proof the efficiency of our setup as well as advantages compared with other setups will be discussed. Furthermore we present a proxy for biological INPs, microcrystalline cellulose. Cellulose is the main component of herbal cell walls (about 50 wt%). It is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose can contribute to the diverse spectrum of <span class="hlt">ice</span> nucleation particles. We present results of the nucleation <span class="hlt">activity</span> measurements of MCCs as well as the influence of concentration, preparation or chemical modification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24317082','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24317082"><span id="translatedtitle">Measurement of <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria on plants and in precipitation by quantitative PCR.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hill, Thomas C J; Moffett, Bruce F; Demott, Paul J; Georgakopoulos, Dimitrios G; Stump, William L; Franc, Gary D</p> <p>2014-02-01</p> <p><span class="hlt">Ice</span> nucleation-<span class="hlt">active</span> (INA) bacteria may function as high-temperature <span class="hlt">ice</span>-nucleating particles (INP) in clouds, but their effective contribution to atmospheric processes, i.e., their potential to trigger glaciation and precipitation, remains uncertain. We know little about their abundance on natural vegetation, factors that trigger their release, or persistence of their <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> once airborne. To facilitate these investigations, we developed two quantitative PCR (qPCR) tests of the ina gene to directly count INA bacteria in environmental samples. Each of two primer pairs amplified most alleles of the ina gene and, taken together, they should amplify all known alleles. To aid primer design, we collected many new INA isolates. Alignment of their partial ina sequences revealed new and deeply branching clades, including sequences from Pseudomonas syringae pv. atropurpurea, Ps. viridiflava, Pantoea agglomerans, Xanthomonas campestris, and possibly Ps. putida, Ps. auricularis, and Ps. poae. qPCR of leaf washings recorded ∼10(8) ina genes g(-1) fresh weight of foliage on cereals and 10(5) to 10(7) g(-1) on broadleaf crops. Much lower populations were found on most naturally occurring vegetation. In fresh snow, ina genes from various INA bacteria were detected in about half the samples but at abundances that could have accounted for only a minor proportion of INP at -10°C (assuming one ina gene per INA bacterium). Despite this, an apparent biological source contributed an average of ∼85% of INP <span class="hlt">active</span> at -10°C in snow samples. In contrast, a thunderstorm hail sample contained 0.3 INA bacteria per INP <span class="hlt">active</span> at -10°C, suggesting a significant contribution to this sample. PMID:24317082</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24317082','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24317082"><span id="translatedtitle">Measurement of <span class="hlt">ice</span> nucleation-<span class="hlt">active</span> bacteria on plants and in precipitation by quantitative PCR.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hill, Thomas C J; Moffett, Bruce F; Demott, Paul J; Georgakopoulos, Dimitrios G; Stump, William L; Franc, Gary D</p> <p>2014-02-01</p> <p><span class="hlt">Ice</span> nucleation-<span class="hlt">active</span> (INA) bacteria may function as high-temperature <span class="hlt">ice</span>-nucleating particles (INP) in clouds, but their effective contribution to atmospheric processes, i.e., their potential to trigger glaciation and precipitation, remains uncertain. We know little about their abundance on natural vegetation, factors that trigger their release, or persistence of their <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> once airborne. To facilitate these investigations, we developed two quantitative PCR (qPCR) tests of the ina gene to directly count INA bacteria in environmental samples. Each of two primer pairs amplified most alleles of the ina gene and, taken together, they should amplify all known alleles. To aid primer design, we collected many new INA isolates. Alignment of their partial ina sequences revealed new and deeply branching clades, including sequences from Pseudomonas syringae pv. atropurpurea, Ps. viridiflava, Pantoea agglomerans, Xanthomonas campestris, and possibly Ps. putida, Ps. auricularis, and Ps. poae. qPCR of leaf washings recorded ∼10(8) ina genes g(-1) fresh weight of foliage on cereals and 10(5) to 10(7) g(-1) on broadleaf crops. Much lower populations were found on most naturally occurring vegetation. In fresh snow, ina genes from various INA bacteria were detected in about half the samples but at abundances that could have accounted for only a minor proportion of INP at -10°C (assuming one ina gene per INA bacterium). Despite this, an apparent biological source contributed an average of ∼85% of INP <span class="hlt">active</span> at -10°C in snow samples. In contrast, a thunderstorm hail sample contained 0.3 INA bacteria per INP <span class="hlt">active</span> at -10°C, suggesting a significant contribution to this sample.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3911041','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3911041"><span id="translatedtitle">Measurement of <span class="hlt">Ice</span> Nucleation-<span class="hlt">Active</span> Bacteria on Plants and in Precipitation by Quantitative PCR</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Moffett, Bruce F.; DeMott, Paul J.; Georgakopoulos, Dimitrios G.; Stump, William L.; Franc, Gary D.</p> <p>2014-01-01</p> <p><span class="hlt">Ice</span> nucleation-<span class="hlt">active</span> (INA) bacteria may function as high-temperature <span class="hlt">ice</span>-nucleating particles (INP) in clouds, but their effective contribution to atmospheric processes, i.e., their potential to trigger glaciation and precipitation, remains uncertain. We know little about their abundance on natural vegetation, factors that trigger their release, or persistence of their <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> once airborne. To facilitate these investigations, we developed two quantitative PCR (qPCR) tests of the ina gene to directly count INA bacteria in environmental samples. Each of two primer pairs amplified most alleles of the ina gene and, taken together, they should amplify all known alleles. To aid primer design, we collected many new INA isolates. Alignment of their partial ina sequences revealed new and deeply branching clades, including sequences from Pseudomonas syringae pv. atropurpurea, Ps. viridiflava, Pantoea agglomerans, Xanthomonas campestris, and possibly Ps. putida, Ps. auricularis, and Ps. poae. qPCR of leaf washings recorded ∼108 ina genes g−1 fresh weight of foliage on cereals and 105 to 107 g−1 on broadleaf crops. Much lower populations were found on most naturally occurring vegetation. In fresh snow, ina genes from various INA bacteria were detected in about half the samples but at abundances that could have accounted for only a minor proportion of INP at −10°C (assuming one ina gene per INA bacterium). Despite this, an apparent biological source contributed an average of ∼85% of INP <span class="hlt">active</span> at −10°C in snow samples. In contrast, a thunderstorm hail sample contained 0.3 INA bacteria per INP <span class="hlt">active</span> at −10°C, suggesting a significant contribution to this sample. PMID:24317082</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JSAES...4..171B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JSAES...4..171B"><span id="translatedtitle">Paleozoic evolution of <span class="hlt">active</span> <span class="hlt">margin</span> basins in the southern Central Andes (northwestern Argentina and northern Chile)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bahlburg, H.; Breitkreuz, C.</p> <p></p> <p>The geodynamic evolution of the Paleozoic continental <span class="hlt">margin</span> of Gondwana in the region of the southern Central Andes is characterized by the westward progression of orogenic basin formation through time. The Ordovician basin in the northwest Argentinian Cordillera Oriental and Puna originated as an Early Ordovician back-arc basin. The contemporaneous magmatic arc of an east-dipping subduction zone was presumably located in northern Chile. In the back-arc basin, a ca. 3500 meter, fining-up volcaniclastic apron connected to the arc formed during the Arenigian. Increased subsidence in the late Arenigian allowed for the accomodation of large volumes of volcaniclastic turbidites during the Middle Ordovician. Subsidence and sedimentation were caused by the onset of collision between the para-autochthonous Arequipa Massif Terrane (AMT) and the South American <span class="hlt">margin</span> at the Arenigian-Llanvirnian transition. This led to eastward thrusting of the arc complex over its back-arc basin and, consequently, to its transformation into a marine foreland basin. As a result of thrusting in the west, a flexural bulge formed in the east, leading to uplift and emergence of the Cordillera Oriental shelf during the Guandacol Event at the Arenigian-Llanvirnian transition. The basin fill was folded during the terminal collision of the AMT during the Oclóyic Orogeny (Ashgillian). The folded strata were intruded post-tectonically by the presumably Silurian granitoids of the "Faja Eruptiva de la Puna Oriental." The orogeny led to the formation of the positive area of the Arco Puneño. West of the Arco Puneño, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresión Preandina, and Precordillera. The corresponding deep marine turbidite basin was located in the region of the Cordillera de la Costa. Deposition continued until the basin fill was folded in the early Late Carboniferous Toco Orogeny. The basin</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PApGe.173.3291M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PApGe.173.3291M"><span id="translatedtitle">Flare-Shaped Acoustic Anomalies in the Water Column Along the Ecuadorian <span class="hlt">Margin</span>: Relationship with <span class="hlt">Active</span> Tectonics and Gas Hydrates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Michaud, Francois; Proust, Jean-Noël; Dano, Alexandre; Collot, Jean-Yves; Guiyeligou, Grâce Daniella; Hernández Salazar, María José; Ratzov, Gueorgui; Martillo, Carlos; Pouderoux, Hugo; Schenini, Laure; Lebrun, Jean-Frederic; Loayza, Glenda</p> <p>2016-10-01</p> <p>With hull-mounted multibeam echosounder data, we report for the first time along the <span class="hlt">active</span> Ecuadorian <span class="hlt">margin</span>, acoustic signatures of water column fluid emissions and seep-related structures on the seafloor. In total 17 flare-shaped acoustic anomalies were detected from the upper slope (1250 m) to the shelf break (140 m). Nearly half of the flare-shaped acoustic anomalies rise 200-500 m above the seafloor. The base of the flares is generally associated with high-reflectivity backscatter patches contrasting with the neighboring seafloor. We interpret these flares as caused by fluid escape in the water column, most likely gases. High-resolution seismic profiles show that most flares occur close to the surface expression of <span class="hlt">active</span> faults, deformed areas, slope instabilities or diapiric structures. In two areas tectonic deformation disrupts a Bottom Simulating Reflector (BSR), suggesting that buried frozen gas hydrates are destabilized, thus supplying free gas emissions and related flares. This discovery is important as it opens the way to determine the nature and origin of the emitted fluids and their potential link with the hydrocarbon system of the forearc basins along the Ecuadorian <span class="hlt">margin</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PApGe.tmp...16F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PApGe.tmp...16F"><span id="translatedtitle">Flare-Shaped Acoustic Anomalies in the Water Column Along the Ecuadorian <span class="hlt">Margin</span>: Relationship with <span class="hlt">Active</span> Tectonics and Gas Hydrates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Francois, Michaud; Noël, Proust Jean; Alexandre, Dano; Yves, Collot Jean; Daniella, Guiyeligou Grâce; José, Hernández Salazar María; Gueorgui, Ratzov; Carlos, Martillo; Hugo, Pouderoux; Laure, Schenini; Frederic, Lebrun Jean; Glenda, Loayza</p> <p>2016-01-01</p> <p>With hull-mounted multibeam echosounder data, we report for the first time along the <span class="hlt">active</span> Ecuadorian <span class="hlt">margin</span>, acoustic signatures of water column fluid emissions and seep-related structures on the seafloor. In total 17 flare-shaped acoustic anomalies were detected from the upper slope (1250 m) to the shelf break (140 m). Nearly half of the flare-shaped acoustic anomalies rise 200-500 m above the seafloor. The base of the flares is generally associated with high-reflectivity backscatter patches contrasting with the neighboring seafloor. We interpret these flares as caused by fluid escape in the water column, most likely gases. High-resolution seismic profiles show that most flares occur close to the surface expression of <span class="hlt">active</span> faults, deformed areas, slope instabilities or diapiric structures. In two areas tectonic deformation disrupts a Bottom Simulating Reflector (BSR), suggesting that buried frozen gas hydrates are destabilized, thus supplying free gas emissions and related flares. This discovery is important as it opens the way to determine the nature and origin of the emitted fluids and their potential link with the hydrocarbon system of the forearc basins along the Ecuadorian <span class="hlt">margin</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70022547','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70022547"><span id="translatedtitle">Classification methods for monitoring Arctic sea <span class="hlt">ice</span> using OKEAN passive/<span class="hlt">active</span> two-channel microwave data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Belchansky, Gennady I.; Douglas, David C.</p> <p>2000-01-01</p> <p>This paper presents methods for classifying Arctic sea <span class="hlt">ice</span> using both passive and <span class="hlt">active</span> (2-channel) microwave imagery acquired by the Russian OKEAN 01 polar-orbiting satellite series. Methods and results are compared to sea <span class="hlt">ice</span> classifications derived from nearly coincident Special Sensor Microwave Imager (SSM/I) and Advanced Very High Resolution Radiometer (AVHRR) image data of the Barents, Kara, and Laptev Seas. The Russian OKEAN 01 satellite data were collected over weekly intervals during October 1995 through December 1997. Methods are presented for calibrating, georeferencing and classifying the raw <span class="hlt">active</span> radar and passive microwave OKEAN 01 data, and for correcting the OKEAN 01 microwave radiometer calibration wedge based on concurrent 37 GHz horizontal polarization SSM/I brightness temperature data. Sea <span class="hlt">ice</span> type and <span class="hlt">ice</span> concentration algorithms utilized OKEAN's two-channel radar and passive microwave data in a linear mixture model based on the measured values of brightness temperature and radar backscatter, together with a priori knowledge about the scattering parameters and natural emissivities of basic sea <span class="hlt">ice</span> types. OKEAN 01 data and algorithms tended to classify lower concentrations of young or first-year sea <span class="hlt">ice</span> when concentrations were less than 60%, and to produce higher concentrations of multi-year sea <span class="hlt">ice</span> when concentrations were greater than 40%, when compared to estimates produced from SSM/I data. Overall, total sea <span class="hlt">ice</span> concentration maps derived independently from OKEAN 01, SSM/I, and AVHRR satellite imagery were all highly correlated, with uniform biases, and mean differences in total <span class="hlt">ice</span> concentration of less than four percent (sd<15%).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRF..117.2029B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRF..117.2029B"><span id="translatedtitle">In situ cosmogenic radiocarbon production and 2-D <span class="hlt">ice</span> flow line modeling for an Antarctic blue <span class="hlt">ice</span> area</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buizert, Christo; Petrenko, Vasilii V.; Kavanaugh, Jeffrey L.; Cuffey, Kurt M.; Lifton, Nathaniel A.; Brook, Edward J.; Severinghaus, Jeffrey P.</p> <p>2012-06-01</p> <p>Radiocarbon measurements at <span class="hlt">ice</span> <span class="hlt">margin</span> sites and blue <span class="hlt">ice</span> areas can potentially be used for <span class="hlt">ice</span> dating, ablation rate estimates and paleoclimatic reconstructions. Part of the measured signal comes from in situ cosmogenic 14C production in <span class="hlt">ice</span>, and this component must be well understood before useful information can be extracted from 14C data. We combine cosmic ray scaling and production estimates with a two-dimensional <span class="hlt">ice</span> flow line model to study cosmogenic 14C production at Taylor Glacier, Antarctica. We find (1) that 14C production through thermal neutron capture by nitrogen in air bubbles is negligible; (2) that including <span class="hlt">ice</span> flow patterns caused by basal topography can lead to a surface 14C <span class="hlt">activity</span> that differs by up to 25% from the <span class="hlt">activity</span> calculated using an ablation-only approximation, which is used in all prior work; and (3) that at high ablation <span class="hlt">margin</span> sites, solar modulation of the cosmic ray flux may change the strength of the dominant spallogenic production by up to 10%. As part of this effort we model two-dimensional <span class="hlt">ice</span> flow along the central flow line of Taylor Glacier. We present two methods for parameterizing vertical strain rates, and assess which method is more reliable for Taylor Glacier. Finally, we present a sensitivity study from which we conclude that uncertainties in published cosmogenic production rates are the largest source of potential error. The results presented here can inform ongoing and future 14C and <span class="hlt">ice</span> flow studies at <span class="hlt">ice</span> <span class="hlt">margin</span> sites, including important paleoclimatic applications such as the reconstruction of paleoatmospheric 14C content of methane.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMOS33A2014G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMOS33A2014G"><span id="translatedtitle">Carbonate Chemistry Dynamics in an Area of <span class="hlt">Active</span> Gas Seepage: the Hudson Canyon, US Atlantic <span class="hlt">Margin</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Garcia-Tigreros Kodovska, F.; Kessler, J. D.; Leonte, M.; Chepigin, A.; Kellermann, M. Y.; Arrington, E. C.; Valentine, D. L.</p> <p>2015-12-01</p> <p>The fate of oceanic methane and its impact on the global climate has been of particular interest to the global community. The potential for vast amounts of methane to be emitted from the seafloor into the atmosphere due to gas hydrate decomposition has been under scientific evaluation. However, despite the great extent of these geological reservoirs, much of the methane released from the seafloor in deep ocean environments does not reach the atmosphere. Once dissolved in ocean water, the emitted methane can be microbially converted to either carbon dioxide or assimilated to biomass. Here, we will present results from a research cruise to the Hudson Canyon, northern US Atlantic <span class="hlt">Margin</span>, where we investigated changes in ocean water carbonate chemistry induced by the oxidation of methane released from gas seeps. We will be presenting high precision pH data as well as methane and DIC concentrations, natural stable isotopes, and methane oxidation rates collected inside and adjacent to the Hudson Canyon in the summer of 2014.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17314977','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17314977"><span id="translatedtitle">Large subglacial lakes in East Antarctica at the onset of fast-flowing <span class="hlt">ice</span> streams.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bell, Robin E; Studinger, Michael; Shuman, Christopher A; Fahnestock, Mark A; Joughin, Ian</p> <p>2007-02-22</p> <p>Water plays a crucial role in <span class="hlt">ice</span>-sheet stability and the onset of <span class="hlt">ice</span> streams. Subglacial lake water moves between lakes and rapidly drains, causing catastrophic floods. The exact mechanisms by which subglacial lakes influence <span class="hlt">ice</span>-sheet dynamics are unknown, however, and large subglacial lakes have not been closely associated with rapidly flowing <span class="hlt">ice</span> streams. Here we use satellite imagery and <span class="hlt">ice</span>-surface elevations to identify a region of subglacial lakes, similar in total area to Lake Vostok, at the onset region of the Recovery Glacier <span class="hlt">ice</span> stream in East Antarctica and predicted by <span class="hlt">ice</span>-sheet models. We define four lakes through extensive, flat, featureless regions of <span class="hlt">ice</span> surface bounded by upstream troughs and downstream ridges. Using <span class="hlt">ice</span> velocities determined using interferometric synthetic aperture radar (InSAR), we find the onset of rapid flow (moving at 20 to 30 m yr(-1)) of the tributaries to the Recovery Glacier <span class="hlt">ice</span> stream in a 280-km-wide segment at the downslope <span class="hlt">margins</span> of these four subglacial lakes. We conclude that the subglacial lakes initiate and maintain rapid <span class="hlt">ice</span> flow through either <span class="hlt">active</span> modification of the basal thermal regime of the <span class="hlt">ice</span> sheet by lake accretion or through scouring bedrock channels in periodic drainage events. We suggest that the role of subglacial lakes needs to be considered in <span class="hlt">ice</span>-sheet mass balance assessments. PMID:17314977</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013BGD....1010125P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013BGD....1010125P"><span id="translatedtitle">Spores of most common airborne fungi reveal no <span class="hlt">ice</span> nucleation <span class="hlt">activity</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pummer, B. G.; Atanasova, L.; Bauer, H.; Bernardi, J.; Druzhinina, I. S.; Grothe, H.</p> <p>2013-06-01</p> <p>Fungal spores are ubiquitous biological aerosols, which are considered to show <span class="hlt">ice</span> nucleation (IN) <span class="hlt">activity</span>. In this study the respective IN <span class="hlt">activity</span> was tested in oil emulsion in the immersion freezing mode. The focus was laid on species of economical, ecological or sanitary significance. For the first time, not only common moulds, but also edible mushrooms (Basidiomycota, Agaricomycetes) were investigated, as they contribute massively to the total amount of fungal spores in the atmosphere. Only Fusarium avenaceum showed freezing events at low subzero-temperatures, while the other investigated fungal spores showed no significant IN <span class="hlt">activity</span>. Furthermore, we selected a set of fungal strains from different sites and exposed them to occasional freezing stress during cultivation. Although the total protein expression was altered by this treatment, it had no significant impact on the IN <span class="hlt">activity</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A31E3070S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A31E3070S"><span id="translatedtitle">Molecular Study of the Effects of Chemical Processing on Heterogeneous <span class="hlt">Ice</span> Nucleation: Role of <span class="hlt">Active</span> Sites and Product Formation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sihvonen, S.; Schill, G. P.; Murphy, K. A.; Mueller, K.; Tolbert, M. A.; Freedman, M. A.</p> <p>2014-12-01</p> <p>Mineral dust aerosol is the largest global source of <span class="hlt">ice</span> nuclei, but the identity of the <span class="hlt">active</span> sites for nucleation is unknown. During atmospheric transport, mineral dust aerosol can encounter and react with sulfuric acid, which affects the <span class="hlt">ice</span> nucleation <span class="hlt">activity</span> either due to changes to reactive surface sites or product formation. In this study, we reacted two types of clays found in mineral dust, kaolinite and montmorillonite, with sulfuric acid. Variation in the mineral due to acid treatment was separated from product formation through rinsing techniques. The samples were subsequently reacted with a probe molecule, (3,3,3-trifluoropropyl)dimethylchlorosilane, that selectively binds to edge hydroxyl groups that are bonded to a silicon atom with three bridging oxygens. Hydroxyl groups are considered potential <span class="hlt">active</span> sites, because they can hydrogen bond with water and facilitate <span class="hlt">ice</span> nucleation. Attachment to these sites was quantified by 19F magic angle spinning nuclear magnetic resonance (MAS NMR) of the 19F atoms on the probe molecule, which provided a direct correlation of the number of hydroxyl groups. Our results indicate that the number of edge-site hydroxyl groups increases with exposure to acid. <span class="hlt">Ice</span> nucleation measurements indicate that the sulfuric acid-treated mineral is less <span class="hlt">ice</span> <span class="hlt">active</span> than the untreated mineral. Surprisingly, no difference between the nucleation <span class="hlt">activity</span> of the untreated mineral and acid-treated, rinsed mineral is observed. As a result, we hypothesize that once a critical density of <span class="hlt">active</span> sites is reached for <span class="hlt">ice</span> nucleation, there is no further change in nucleation <span class="hlt">activity</span> despite a continued increase in <span class="hlt">active</span> sites. We additionally propose that the reduced <span class="hlt">activity</span> of the acid-treated mineral is due to product formation that blocks <span class="hlt">active</span> sites on the mineral, rather than changes to <span class="hlt">active</span> sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22275469','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22275469"><span id="translatedtitle"><span class="hlt">Ice</span>Cube expectations for two high-energy neutrino production models at <span class="hlt">active</span> galactic nuclei</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Argüelles, C.A.; Bustamante, M.; Gago, A.M. E-mail: mbustamante@pucp.edu.pe</p> <p>2010-12-01</p> <p>We have determined the currently allowed regions of the parameter spaces of two representative models of diffuse neutrino flux from <span class="hlt">active</span> galactic nuclei (AGN): one by Koers and Tinyakov (KT) and another by Becker and Biermann (BB). Our observable has been the number of upgoing muo