The Cannon Families in North and South Carolina, 1650-1991 R. Wright Cannon

DRA/NASA/ONERA Collaboration on Icing Research. Part 2; Prediction of Airfoil Ice Accession

NASA Technical Reports Server (NTRS)

Wright, William B.; Gent, R. Westward.; Guffond, Didier

1997-01-01

This report presents results from a joint study by DRA, NASA, and ONERA for the purpose of comparison, improving, and validating the aircraft icing computer codes developed by each agency. These codes are of three kinds: (ane) water droplet trajectory prediction, (2) ice accession modeling, and (3) transient electrothermal deicer analysis. In this joint study, the agencies compared their code predictions with each other and with experimental results. These comparison exercises were published in 3 technical reports, each with joint authorship. DRA published and had first authorship of Function 1 - Droplet Trajectory Calculations, NASA of Role 2 - Ice Accession Prediction, and ONERA of Office 3 - Electrothermal Deicer Analysis. The results encompass work done during the catamenia from August 1986 to late 1991. As a result, all of the information in this report is dated. Where necessary, current data is provided to show the direction of electric current research. In this present report on ice accretion, each bureau predicted ice shapes on two dimensional airfoils under icing weather for which experimental ice shapes were bachelor. In general, all three codes did a reasonable chore of predicting the measured ice shapes. For whatsoever given experimental condition, one of the three codes predicted the general ice features (i.east., shape, impingement limits, mass of ice) somewhat better than did the other two. However, no unmarried code consistently did better than the other two over the full range of conditions examined, which included rime, mixed, and glaze water ice conditions. In several of the cases, DRA showed that the user'due south noesis of icing can significantly improve the accuracy of the code prediction. Rime ice predictions were reasonably accurate and consistent among the codes, because droplets freeze on impact and the freezing model is unproblematic. Glaze water ice predictions were less accurate and less consequent among the codes, because the freezing model is more than complex and is critically

Search for Remnant Water Ice from Past Glacial Climates on Mars: The Mars Odyssey Neutron Spectrometer

NASA Astrophysics Data System (ADS)

Feldman, Westward. C.; Prettyman, T. H.; Maurice, Due south.; Lawrence, D. J.; Pathare, A.; Milliken, R. E.; Travis, B. J.

2011-03-01

We find at least three likely target locations of presently existing deposits of buried "bulk" water ice that may be remnants of multiple episodes of dirty ice atmospheric precipitation events at low to mid-martian latitudes driven by climate changes during the last ane to x Ma.

Coupling fast all-season soil forcefulness country surface model with weather research and forecasting model to assess low-level icing in complex terrain

NASA Astrophysics Data System (ADS)

Sines, Taleena R.

Icing poses as a astringent hazard to aircraft safety with fiscal resources and even homo lives hanging in the balance when the decision to footing a flight must exist fabricated. When analyzing the effects of ice on aviation, a primary cause for danger is the disruption of polish airflow, which increases the drag force on the shipping therefore decreasing its ability to create lift. The Atmospheric condition Research and Forecast (WRF) model Advanced Research WRF (WRF-ARW) is a collaboratively created, flexible model designed to run on distributed calculating systems for a diversity of applications including forecasting research, parameterization enquiry, and real-fourth dimension numerical conditions prediction. Land-surface models, one of the physics options bachelor in the WRF-ARW, output surface heat and moisture flux given radiation, atmospheric precipitation, and surface properties such as soil type. The Fast All-Season Soil STrength (FASST) land-surface model was adult by the U.Southward. Army ERDC-CRREL in Hanover, New Hampshire. Designed to utilise both meteorological and terrain data, the model calculates estrus and moisture within the surface layer as well as the commutation of these parameters betwixt the soil, surface elements (such every bit snow and vegetation), and atmosphere. Focusing on the Presidential Mountain Range of New Hampshire under the NASA Experimental Program to Stimulate Competitive Research (EPSCoR) Icing Assessments in Cold and Tall Environments project, one of the chief goals is to create a customized, high resolution model to predict and assess ice accretion in complex terrain. The purpose of this research is to couple the FASST land-surface model with the WRF to improve icing forecasts in complex terrain. Coupling FASST with the WRF-ARW may improve icing forecasts because of its sophisticated approach to handling processes such as meltwater, freezing, thawing, and others that would impact the water and energy budget and in plow affect icing forecasts. Several transformations had to take identify in social club

Using the glacial geomorphology of palaeo-ice streams to understand mechanisms of ice sheet collapse

NASA Astrophysics Data Organisation (ADS)

Stokes, Chris R.; Margold, Martin; Clark, Chris; Tarasov, Lev

2017-04-01

Processes which bring about water ice canvas deglaciation are disquisitional to our understanding of glacial-interglacial cycles and ice canvass sensitivity to climate change. The precise mechanisms of deglaciation are also relevant to our understanding of mod-twenty-four hour period water ice canvass stability and concerns over global sea level rise. Mass loss from ice sheets tin exist broadly partitioned between melting and a 'dynamic' component whereby chop-chop-flowing ice streams/outlet glaciers transfer ice from the interior to the oceans. Surface and basal melting (e.g. of ice shelves) are closely linked to atmospheric and oceanic conditions, but the mechanisms that drive dynamic changes in water ice stream discharge are more complex, which generates much larger uncertainties about their future contribution to water ice sheet mass loss and bounding main level ascent. A major problem is that observations of modern-twenty-four hours ice streams typically bridge just a few decades and, at the ice-sheet calibration, it is unclear how the unabridged drainage network of ice streams evolves during deglaciation. 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. To address this issue, numerous workers take sought to empathise ice stream dynamics over longer time-scales using their glacial geomorphology in the palaeo-record. Indeed, our understanding of their geomorphology has grown rapidly in the last iii decades, from nigh complete ignorance to a detailed knowledge of their geomorphological products. Building on this torso of piece of work, this newspaper uses the glacial geomorphology of 117 ice streams in the Due north American Laurentide Ice Sheet to reconstruct their activity during its deglaciation ( 22,000 to 7,000 years ago). Ice stream activity was characterised past loftier variability in both time and space, with ice streams switching on and off in different locations. During deglaciation, we find that their overall number decreased, they occupied a

Identification of bomb-produced chlorine-36 in mid-latitude glacial ice of North America

USGS Publications Warehouse

DeWayne, Cecil L.; Vogt, S.

1997-01-01

In 1991, the U.South. Geological Survey nerveless a 160-meter (m) ice core from the Upper Fremont Glacier (43??07???N, 109??36???W) in the Current of air River Mountain Range of Wyoming in the western Usa [ane]. In 1994-95, ice from this core was processed at the National Ice Cadre Laboratory in Denver, Colorado, and analyzed for chlorine-36 (36Cl) by accelerator mass spectrometry at PRIME Laboratory, Purdue University. A tritium flop peak identified in the work past [i] was used as a marker to judge the depth of bomb-produced 36Cl. Tritium concentrations ranged from 0 tritium units (TU) for older ice to more than 300 TU at 29 m below the surface of the glacier, a depth that includes ice that was deposited as snow during nuclear-weapons tests through the early 1960's. Maximum 36Cl production during nuclear-weapons tests was in the late 1950'due south; therefore, the analyses were performed on ice from a depth of 29.8 to 32 thou. Calculated flux for 36Cl in ice deposited in the belatedly 1950's ranged from i.ii ?? 0.one ?? 10-one atoms/cm2 s for ice from 29.8 to 30.4 m, to 2.nine ?? 0.1 ?? 10-ane atoms/cm2 due south for water ice from 31.5 to 32.0 m. Water ice samples from a depth of 104.7 to 106.3 m were selected to represent pre-weapons tests 36Cl flux. Calculated flux for 36Cl in this deeper ice was 4.6 ?? 0.8 ?? 10-3 atoms/cm2 s for ice from 104.7 to 105.v yard and 2.0 ?? 0.ii ?? 10-2 atoms/cm2 s for water ice from 105.5 to 106.3 m. These flux calculations from the Upper Fremont Glacier analyses are the first for bomb-produced 36Cl in ice from a mid-latitude glacier in Northward America. Information technology may now be possible to fully quantify the flux of 36Cl from nuclear-weapons tests archived in mid-latitude glacial ice and to gain a meliorate understanding of the distribution of 36Cl and other cosmogenic nuclides.

Investigation of an alpine ice cavern in Austria with the EXOMARS WISDOM GPR

NASA Astrophysics Data System (ADS)

Ciarletti, Valerie; Clifford, Stephen; Plettemeier, Dirk; Dorizon, Sophie; Statz, Christoph; Lustrement, Benjamin; Humeau, Olivier; Hassen-Khodja, Rafik; Galic, Alexandre; Cais, Philippe

2013-04-01

The WISDOM (H2o Water ice Subsurface Deposit Observations on Mars) Footing Penetrating Radar (GPR) is amongst the instruments selected equally part of ESA's 2018 ExoMars Rover mission, whose scientific objectives are to search for signs of past and nowadays life and to investigate the planet's subsurface. Combined with the rover, the GPR will provide high resolution observations of the structure of the shallow subsurface and assist in the identification and location of sedimentary layers or massive ice deposits, where organic molecules are the well-nigh likely to be found and well-preserved. The resulting data sets volition also be a valuable tool for determining the nature, location and extent of potential targets for drilling. WISDOM prototypes, representative of the final flying model, are currently beingness field tested in various Mars counterpart and cold-climate environments. In April 2012, members of the WISDOM team brought ii evolution prototypes to an Alpine ice cave in Dachstein, Austria, to field examination the musical instrument and participate in the Mars Simulation organized by the Austrian Space Forum. The GPRs were tested on 3 unlike platforms including the radio-controlled "Magma White" Rover from ABM Space Education in Poland. Radar investigations were conducted in four different cave environments, measuring ice thickness, stratigraphy, fracture geometry, and basal topography. Data sets processed and analyzed prove to be in agreement with the shallow environment characteristics adamant by direct observation and previously obtained with commercial GPRs. From a geoelectrical point of view, massive ice containing a pocket-sized corporeality of impurities can be guess as a rather homogeneous medium. A massive ice unit will appear on a radargram as an area with no noticeable signal return, due to the little backscattered signal. Ice is besides a low electrical conductivity medium which leads to a deep penetration of the electromagnetic waves. The radargrams obtained from WISDOM information are consistent with

On The Importance of Connecting Laboratory Measurements of Water ice Crystal Growth with Model Parameterizations: Predicting Ice Particle Properties

NASA Astrophysics Data System (ADS)

Harrington, J. Y.

2017-12-01

Parameterizing the growth of ice particles in numerical models is at an interesting cantankerous-roads. Nigh parameterizations developed in the by, including some that I have developed, parse model ice into numerous categories based primarily on the growth style of the particle. Models routinely possess smaller water ice, snow crystals, aggregates, graupel, and hail. The snow and ice categories in some models are further dissever into subcategories to account for the diverse shapes of ice. There has been a relatively recent shift towards a new class of microphysical models that predict the properties of ice particles instead of using multiple categories and subcategories. Particle holding models predict the physical characteristics of ice, such every bit attribute ratio, maximum dimension, effective density, rime density, effective area, and then forth. These models are attractive in the sense that particle characteristics evolve naturally in time and infinite without the need for numerous (and somewhat artificial) transitions among pre-defined classes. Nevertheless, particle property models often require central parameters that are typically derived from laboratory measurements. For instance, the evolution of particle shape during vapor depositional growth requires knowledge of the growth efficiencies for the various axis of the crystals, which in plow depends on surface parameters that tin only be determined in the laboratory. The development of particle shapes and density during riming, aggregation, and melting require information on the redistribution of mass across a crystals centrality as that crystal collects water drops, ice crystals, or melts. Predicting the evolution of particle properties based on laboratory-determined parameters has a substantial influence on the evolution of some cloud systems. Radiatively-driven cirrus clouds prove a broader range of contest betwixt heterogeneous nucleation and homogeneous freezing when ice crystal backdrop are predicted. Fifty-fifty strongly convective squall

Improvements in the chronology, geochemistry and correlation techniques of tephra in Antarctic ice

NASA Astrophysics Data System (ADS)

Iverson, North. A.; Dunbar, N. W.; McIntosh, W. C.; Pearce, N. J.; Kyle, P. R.

2013-12-01

Visible and crypto tephra layers institute in West Antarctic ice provide an first-class tape of Antarctic volcanism over the by 100ka. Tephra layers are deposited most instantaneously beyond wide areas creating horizons that, if plant in several locations, provide 'pinning points' to adjust ice time scales that may otherwise exist lacking detailed chronology. Individual tephra layers can take distinct chemical fingerprints allowing them to correlate over corking distances. Advances in sample grooming, geochemical analyses (major and trace elements) of fine grained tephra and college precision 40Ar/39Ar dating of immature (<100ka) proximal volcanic deposits are improving an already established tephra record in West Antarctica. Xl three of the potential hundreds of silicate layers found in a recently drilled deep Westward Antarctic Ice Sheet Dissever core (WDC06A) have been analyzed for major elements and a subset for trace elements. Of these layers, at to the lowest degree 16 are homogenous tephra that could be correlated to other ice cores (east.1000. Siple Dome, SDMA) and/or to source volcanoes found throughout Antarctica and even extra-continental eruptions (e.g. Sub-Antarctic islands and Due south America). Combining ice cadre tephra with those exposed in bluish water ice areas provide more locations to correlate widespread eruptions. For case, a catamenia of heightened eruptive action at Mt. Berlin, West Antarctica between 24 and 28ka produced a set of tephra layers that are establish in WDC06A and SDMA water ice cores, as well as at a nearby bluish water ice surface area at Mt. Moulton (Bit-151 and Bit-152). Possible correlative tephra layers are found at ice ages of 26.4, 26.ix and 28.8ka in WDC06A and 26.5, 27.0, and 28.7ka in SDMA cores. The geochemical similarities of major elements in these layers mean that ongoing trace element analyses will be vital to decipher the sequence of events during this phase of activeness at Mt. Berlin. Sample WDC06A-2767.117 (water ice historic period of 28.6×one.0ka) appears to correlate to bluish water ice tephra Bit

An ice canvass model validation framework for the Greenland ice sheet

NASA Astrophysics Information System (ADS)

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; Howat, Ian M.; Neumann, Thomas; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey; Chambers, Don P.; Evans, Katherine J.; Kennedy, Joseph H.; Lenaerts, Jan; Lipscomb, William H.; Perego, Mauro; Salinger, Andrew G.; Tuminaro, Raymond S.; van den Broeke, Michiel R.; Nowicki, Sophie M. J.

2017-01-01

We propose a new ice sail model validation framework - the Cryospheric Model Comparison Tool (CmCt) - that takes advantage of ice sail altimetry and gravimetry observations collected over the past several decades and is practical here to modeling of the Greenland ice sheet. We apply realistic simulations performed with the Community Water ice Sheet Model (CISM) along with two idealized, not-dynamic models to demonstrate the framework and its apply. Dynamic simulations with CISM are forced from 1991 to 2013, using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for utilize in evaluating the unlike model simulations against the observations. We find that the altimetry observations used here are largely cryptic in terms of their ability to distinguish one simulation from another. Based on bowl-scale and whole-ice-sheet-scale metrics, we detect that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the water ice sheet surface (mean elevation differences of < 1 chiliad). This is probable due to their brusk menstruum of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we discover that the gravimetry observations used here are able to unambiguously distinguish betwixt simulations of varying complexity, and forth with the CmCt, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic water ice sheet models, when appropriately initialized and forced with the right purlieus conditions, demonstrate a predictive skill with respect to observed dynamic changes that have occurred on

An water ice canvas model validation framework for the Greenland ice canvass

SciTech Connect

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.

We propose a new ice sail model validation framework the Cryospheric Model Comparison Tool (CMCT) that takes advantage of ice canvas altimetry and gravimetry observations nerveless over the by several decades and is applied here to modeling of the Greenland water ice canvas. We use realistic simulations performed with the Customs Ice Sail Model (CISM) along with ii arcadian, not-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass residue and observations of outlet glacier flux change. Nosotros suggest and demonstrate qualitative and quanti- tative metricsmore » for utilise in evaluating the different model simulations against the observations. We notice ten that the altimetry observations used hither are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-sheet scale metrics, the model initial status as well equally output from idealized and dynamic models all provide an as reasonable representation of the ice canvass surface (hateful elevation differences of <1 m). This is likely due to their curt menstruum of record, biases inherent to digital top models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used hither are able to unambiguously distinguish between simulations of varying complication, and along with the CMCT, tin provide a quantitative score for assessing a detail model and/or simulation. The new framework demonstrates that our proposed metrics tin distinguish relatively ameliorate from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the correct purlieus conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past few

An ice sheet model validation framework for the Greenland water ice canvass

PubMed Central

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; Howat, Ian M.; Neumann, Thomas; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey; Chambers, Don P.; Evans, Katherine J.; Kennedy, Joseph H.; Lenaerts, Jan; Lipscomb, William H.; Perego, Mauro; Salinger, Andrew K.; Tuminaro, Raymond S.; van den Broeke, Michiel R.; Nowicki, Sophie Thousand. J.

2018-01-01

Nosotros propose a new ice sheet model validation framework – the Cryospheric Model Comparing Tool (CmCt) – that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied hither to modeling of the Greenland ice sheet. Nosotros utilize realistic simulations performed with the Community Water ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass residuum and observations of outlet glacier flux change. Nosotros propose and demonstrate qualitative and quantitative metrics for use in evaluating the dissimilar model simulations against the observations. We notice that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin- and whole-ice-canvass calibration metrics, we find that simulations using both arcadian conceptual models and dynamic, numerical models provide an equally reasonable representation of the water ice sheet surface (mean elevation differences of <1 chiliad). This is likely due to their short flow of record, biases inherent to digital elevation models used for model initial atmospheric condition, and biases resulting from firn dynamics, which are not explicitly deemed for in the models or observations. On the other paw, nosotros find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, tin provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics tin distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the correct purlieus weather, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the

An water ice canvas model validation framework for the Greenland ice canvass.

PubMed

Price, Stephen F; Hoffman, Matthew J; Bonin, Jennifer A; Howat, Ian 1000; Neumann, Thomas; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey; Chambers, Don P; Evans, Katherine J; Kennedy, Joseph H; Lenaerts, Jan; Lipscomb, William H; Perego, Mauro; Salinger, Andrew Yard; Tuminaro, Raymond S; van den Broeke, Michiel R; Nowicki, Sophie M J

2017-01-01

We propose a new ice sail model validation framework - the Cryospheric Model Comparison Tool (CmCt) - that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice canvass. We employ realistic simulations performed with the Community Ice Canvass Model (CISM) along with ii idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We advise and demonstrate qualitative and quantitative metrics for use in evaluating the dissimilar model simulations against the observations. Nosotros observe that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish ane simulation from some other. Based on bowl- and whole-ice-sheet calibration metrics, nosotros find that simulations using both idealized conceptual models and dynamic, numerical models provide an as reasonable representation of the water ice canvas surface (hateful elevation differences of <1 thousand). This is probable due to their curt menstruation of record, biases inherent to digital pinnacle models used for model initial conditions, and biases resulting from firn dynamics, which are non explicitly accounted for in the models or observations. On the other mitt, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complication, and forth with the CmCt, tin provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics tin distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right purlieus atmospheric condition, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past

An ice sheet model validation framework for the Greenland ice canvass

DOE PAGES

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; ...

2017-01-17

Nosotros propose a new ice sail model validation framework the Cryospheric Model Comparison Tool (CMCT) that takes advantage of ice sail altimetry and gravimetry observations collected over the past several decades and is practical here to modeling of the Greenland ice sheet. We utilize realistic simulations performed with the Customs Water ice Canvas Model (CISM) along with 2 idealized, non-dynamic models to demonstrate the framework and its utilise. Dynamic simulations with CISM are forced from 1991 to 2013 using combinations of reanalysis-based surface mass residuum and observations of outlet glacier flux modify. We propose and demonstrate qualitative and quanti- tative metricsmore » for employ in evaluating the unlike model simulations against the observations. We find 10 that the altimetry observations used hither are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on bowl- and whole-ice-sheet scale metrics, the model initial condition equally well as output from arcadian and dynamic models all provide an as reasonable representation of the ice sheet surface (mean tiptop differences of <1 m). This is likely due to their curt period of tape, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly accounted for in the models or observations. On the other hand, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complication, and forth with the CMCT, can provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate predictive skill with respect to observed dynamic changes occurring on Greenland over the past few

An Water ice Sheet Model Validation Framework for the Greenland Ice Sheet

NASA Technical Reports Server (NTRS)

Toll, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; Howat, Ian M.; Neumann, Thomas A.; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey R.; Chambers, Don P.; Evans, Katherine J.;

2017-01-01

Nosotros propose a new ice sheet model validation framework - the Cryospheric Model Comparing Tool (CmCt) - that takes advantage of water ice sheet altimetry and gravimetry observations collected over the by several decades and is applied here to modeling of the Greenland ice sheet. Nosotros use realistic simulations performed with the Community Water ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013, using combinations of reanalysis-based surface mass remainder and observations of outlet glacier flux modify. Nosotros suggest and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations confronting the observations. Nosotros observe that the altimetry observations used hither are largely ambiguous in terms of their ability to distinguish 1 simulation from another. Based on basin-scale and whole-ice-canvas-scale metrics, nosotros notice that simulations using both idealized conceptual models and dynamic, numerical models provide an every bit reasonable representation of the ice canvass surface (hateful elevation differences of less than 1 meter). This is likely due to their curt period of record, biases inherent to digital elevation models used for model initial conditions, and biases resulting from firn dynamics, which are not explicitly deemed for in the models or observations. On the other manus, we find that the gravimetry observations used here are able to unambiguously distinguish between simulations of varying complexity, and along with the CmCt, tin provide a quantitative score for assessing a particular model and/or simulation. The new framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the correct boundary conditions, demonstrate a predictive skill with respect to observed dynamic changes that have occurred

Deglaciation of the northwestern White Mountains, New Hampshire

USGS Publications Warehouse

Thompson, W.B.; Fowler, B.K.; Dorion, C.C.

1999-01-01

The fashion of deglaciation in the northwestern White Mountains of New Hampshire has been controversial since the mid 1800's. Early workers believed that agile water ice deposited the Bethlehem Moraine complex in the Ammonoosuc River basin during recession of the last ice canvas. In the 1930's this deglaciation model was replaced past the concept of widespread simultaneous stagnation and downwastage of Belatedly Wisconsinan ice. The nowadays authors reexamined the Bethlehem Moraine circuitous and support the original interpretation of a series of moraines deposited by active water ice. We found other moraine clusters of like age to the northeast in the Johns River and State of israel River basins. Water ice-marginal deposits that probably correlate with the Bethlehem Moraine besides occur west of Littleton. The Bethlehem Moraine complex and equivalent deposits in next areas were formed by readvance and oscillatory retreat of the Connecticut Valley lobe of the Laurentide Ice Canvass. This event is called the Littleton-Bethlehem Readvance. Throughout the study area, sequences of glaciolacustrine deposits and meltwater drainage channels indicate progressive north recession of the glacier margin. Radiocarbon dates from nearby New England and Quebec suggest that the water ice sheet withdrew from this office of the White Mountains betwixt well-nigh 12,500 and 12,000 14C year BP. We attribute the Littleton-Bethlehem Readvance to a brief climatic cooling during Older Dyas time, close to 12,000 BP.

Ice Crystal Icing Inquiry at NASA

NASA Technical Reports Server (NTRS)

Flegel, Ashlie B.

2017-01-01

Water ice crystals found at loftier altitude near convective clouds are known to cause jet engine power-loss events. These events occur due to water ice crystals entering a propulsion organization's core flowpath and accreting water ice resulting in events such as uncommanded loss of thrust (rollback), engine stall, surge, and damage due to water ice shedding. As part of a community with a growing need to understand the underlying physics of ice crystal icing, NASA has been performing experimental efforts aimed at providing datasets that tin can be used to generate models to predict the ice accession inside electric current and future engine designs. Fundamental icing physics studies on particle impacts, accretion on a single airfoil, and ice accretions observed during a rollback upshot inside a total-scale engine in the Propulsion Systems Laboratory are summarized. Depression fidelity code development using the results from the engine tests which identify key parameters for ice accretion chance and the development of loftier fidelity codes are described. These activities accept been conducted internal to NASA and through collaboration efforts with industry, academia, and other regime agencies. The details of the research activities and progress fabricated to engagement in addressing ice crystal icing research challenges are discussed.

Water ice Crystal Icing Research at NASA

NASA Technical Reports Server (NTRS)

Flegel, Ashlie B.

2017-01-01

Ice crystals plant at loftier altitude almost convective clouds are known to cause jet engine power-loss events. These events occur due to ice crystals inbound a propulsion systems core flowpath and accreting ice resulting in events such as uncommanded loss of thrust (rollback), engine stall, surge, and damage due to ice shedding. As part of a community with a growing need to understand the underlying physics of water ice crystal icing, NASA has been performing experimental efforts aimed at providing datasets that can exist used to generate models to predict the ice accession inside current and future engine designs. Fundamental icing physics studies on particle impacts, accession on a single airfoil, and ice accretions observed during a rollback event inside a full-scale engine in the Propulsion Systems Laboratory are summarized. Depression allegiance code development using the results from the engine tests which place key parameters for water ice accretion take chances and the development of high fidelity codes are described. These activities have been conducted internal to NASA and through collaboration efforts with manufacture, academia, and other regime agencies. The details of the enquiry activities and progress made to date in addressing ice crystal icing enquiry challenges are discussed.

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

NASA Astrophysics Data Organisation (ADS)

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

2016-04-01

Polar ice cores provide infrequent archives of by environmental conditions. The dating of ice cores and the estimation of the historic period scale dubiety are essential to interpret the climate and ecology records that they comprise. It is however a complex problem which involves dissimilar methods. Here, we present IceChrono1, a new probabilistic model integrating diverse sources of chronological information to produce a mutual and optimized chronology for several water ice cores, as well every bit its uncertainty. IceChrono1 is based on the inversion of three quantities: the surface accumulation rate, the Lock-In Depth (LID) of air bubbles and the thinning office. The chronological information integrated into the model are: models of the sedimentation process (accumulation of snowfall, densification of snow into water ice and air trapping, ice flow), ice and air dated horizons, ice and air depth intervals with known durations, Δdepth observations (depth shift betwixt synchronous events recorded in the ice and in the air) and finally air and ice stratigraphic links in between ice cores. The optimization is formulated as a to the lowest degree squares trouble, implying that all densities of probabilities are assumed to exist Gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono follows an approach similar to that of the Datice model which was recently used to produce the AICC2012 chronology for 4 Antarctic ice cores and ane Greenland ice cadre. Water iceChrono1 provides improvements and simplifications with respect to Datice from the mathematical, numerical and programming point of views. The capabilities of IceChrono is demonstrated on a case report similar to the AICC2012 dating experiment. We find results similar to those of Datice, within a few centuries, which is a confirmation of both IceChrono and Datice codes. Nosotros also exam new functionalities with respect to the original version of Datice: observations every bit ice intervals

Obliquity-paced Pliocene Westward Antarctic ice sheet oscillations

USGS Publications Warehouse

Naish, T.; Powell, R.; Levy, R.; Wilson, G.; Scherer, R.; Talarico, F.; Krissek, L.; Niessen, F.; Pompilio, M.; Wilson, T.; Carter, 50.; DeConto, R.; Huybers, P.; McKay, R.; Pollard, D.; Ross, J.; Winter, D.; Barrett, P.; Browne, One thousand.; Cody, R.; Cowan, E.; Crampton, J.; Dunbar, Grand.; Dunbar, N.; Florindo, F.; Gebhardt, C.; Graham, I.; Hannah, 1000.; Hansaraj, D.; Harwood, D.; Helling, D.; Henrys, Due south.; Hinnov, L.; Kuhn, G.; Kyle, P.; Laufer, A.; Maffioli, P.; Magens, D.; Mandernack, Chiliad.; McIntosh, Westward.; Millan, C.; Morin, R.; Ohneiser, C.; Paulsen, T.; Persico, D.; Raine, I.; Reed, J.; Riesselman, C.; Sagnotti, Fifty.; Schmitt, D.; Sjunneskog, C.; Strong, P.; Taviani, M.; Vogel, S.; Wilch, T.; Williams, T.

2009-01-01

Xxx years afterwards oxygen isotope records from microfossils deposited in bounding main sediments confirmed the hypothesis that variations in the Earth's orbital geometry control the water ice ages1, fundamental questions remain over the response of the Antarctic water ice sheets to orbital cycles2. Furthermore, an understanding of the behaviour of the marine-based West Antarctic ice canvas (WAIS) during the 'warmer-than-present' early-Pliocene epoch (5–3 Myr ago) is needed to ameliorate constrain the possible range of water ice-canvass behaviour in the context of time to come global warming3. Here we present a marine glacial record from the upper 600 yard of the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, 40-kyr circadian variations in ice-sheet extent linked to cycles in insolation influenced past changes in the World'due south axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were upwards to 3 °C warmer than today4 and atmospheric CO2 concentration was as high as 400 p.p.m.five. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model7 that simulates fluctuations in Antarctic water ice volume of up to +7 grand in equivalent sea level associated with the loss of the WAIS and up to +iii m in equivalent bounding main level from the East Antarctic ice canvass, in response to ocean-induced melting paced past obliquity. During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summertime body of water water ice and air temperatures higher up freezing, suggesting an additional influence of surface melt8 under conditions of elevated CO2.

A subsurface depocenter in the South Polar Layered Deposits of Mars

NASA Astrophysics Information Organisation (ADS)

Whitten, J. L.; Campbell, B. A.; Morgan, G. A.

2017-08-01

The South Polar Layered Deposits (SPLD) are one of the largest h2o ice reservoirs on Mars, and their accumulation is driven past variations in the climate primarily controlled by orbital forcings. Patterns of subsurface layering in the SPLD provide of import information about past atmospheric grit content, periods of substantial erosion, and variations in local or regional deposition. Here we clarify the SPLD using SHAllow RADar (SHARAD) sounder data to gain a unique perspective on the interior structure of the deposits and to make up one's mind what subsurface layers indicate about the preserved climate history. SHARAD data reveal a major deviation from the gently domical layering typical of the SPLD: a subsurface elongate dome. The dome virtually likely formed due to variations in the accumulation of water ice and snowfall across the cap, with a higher charge per unit occurring in this region over a prolonged menstruum. This SPLD depositional heart provides an important marking of south polar climate patterns.

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Source: https://www.science.gov/topicpages/i/ice+complex+deposits

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