bluuebunny/crossref_metadata_2025 huggingface dataset:
Artificial neural networks and multiple linear regression model using principal components to estimate rainfall over South America
Authors: Soares dos Santos T. , Mendes D. , Rodrigues Torres R.
Published: January 2016

Abstract. Several studies have been devoted to dynamic and statistical downscaling for analysis of both climate variability and climate change. This paper introduces an application of artificial neural networks (ANNs) and multiple linear regression (MLR) by principal components to estimate rainfall in South America. This method is proposed for downscaling monthly precipitation time series over South America for three regions: the Amazon; northeastern Brazil; and the La Plata Basin, which is one of the regions of the planet that will be most affected by the climate change projected for the end of the 21st century. The downscaling models were developed and validated using CMIP5 model output and observed monthly precipitation. We used general circulation model (GCM) experiments for the 20th century (RCP historical; 1970–1999) and two scenarios (RCP 2.6 and 8.5; 2070–2100). The model test results indicate that the ANNs significantly outperform the MLR downscaling of monthly precipitation variability.
Impact of variable seawater conductivity on motional induction simulated with an ocean general circulation model
Authors: Irrgang C. , Saynisch J. , Thomas M.
Published: January 2016

Abstract. Carrying high concentrations of dissolved salt, ocean water is a good electrical conductor. As seawater flows through the Earth's ambient geomagnetic field, electric fields are generated, which in turn induce secondary magnetic fields. In current models for ocean-induced magnetic fields, a realistic consideration of seawater conductivity is often neglected and the effect on the variability of the ocean-induced magnetic field unknown. To model magnetic fields that are induced by non-tidal global ocean currents, an electromagnetic induction model is implemented into the Ocean Model for Circulation and Tides (OMCT). This provides the opportunity to not only model ocean-induced magnetic signals but also to assess the impact of oceanographic phenomena on the induction process. In this paper, the sensitivity of the induction process due to spatial and temporal variations in seawater conductivity is investigated. It is shown that assuming an ocean-wide uniform conductivity is insufficient to accurately capture the temporal variability of the magnetic signal. Using instead a realistic global seawater conductivity distribution increases the temporal variability of the magnetic field up to 45 %. Especially vertical gradients in seawater conductivity prove to be a key factor for the variability of the ocean-induced magnetic field. However, temporal variations of seawater conductivity only marginally affect the magnetic signal.
Temporal evolution of the momentum balance terms and frictional adjustment observed over the inner shelf during a storm
Authors: Grifoll M. , Aretxabaleta A. L. , Pelegrí J. L. , Espino M.
Published: January 2016

Abstract. We investigate the rapidly changing equilibrium between the momentum sources and sinks during the passage of a single two-peak storm over the Catalan inner shelf (NW Mediterranean Sea). Velocity measurements at 24 m water depth are taken as representative of the inner shelf, and the cross-shelf variability is explored with measurements at 50 m water depth. During both wind pulses, the flow accelerated at 24 m until shortly after the wind maxima, when the bottom stress was able to compensate for the wind stress. Concurrently, the sea level also responded, with the pressure-gradient force opposing the wind stress. Before, during and after the second wind pulse, there were velocity fluctuations with both super- and sub-inertial periods likely associated with transient coastal waves. Throughout the storm, the Coriolis force and wave radiation stresses were relatively unimportant in the along-shelf momentum balance. The frictional adjustment timescale was around 10 h, consistent with the e-folding time obtained from bottom drag parameterizations. The momentum evolution at 50 m showed a larger influence of the Coriolis force at the expense of a decreased frictional relevance, typical in the transition from the inner to the mid-shelf.
The challenge and future of rocky desertification control in karst areas in southwest China
Authors: Zhang J. Y. , Dai M. H. , Wang L. C. , Zeng C. F. , Su W. C.
Published: January 2016

Abstract. Karst rocky desertification occurs after vegetation deteriorates as a result of intensive land use, which leads to severe water loss and soil erosion and exposes basement rocks, creating a rocky landscape. Karst rocky desertification is found in humid areas in southwest China, the region most seriously affected by rocky desertification in the world. In order to promote ecological restoration and help peasants out of poverty, the Chinese government carried out the first phase of a rocky desertification control project from 2006 to 2015, which initially contained the expansion of rocky desertification. Currently, the Chinese government is prepared to implement the second phase of the rocky desertification control project, and therefore it is essential to summarise the lessons learned over the last 10 years of the first phase. In this paper, we analyse the driving social and economic factors behind rocky desertification, summarise the scientific research on rocky desertification in the region, and finally identify the main problems facing rocky desertification control. In addition, we put forward several policy suggestions that take into account the perspective of local peasants, scientific research, and China's economic development and urbanisation process. These suggestions include promoting the non-agriculturalization of household livelihoods, improving ecological compensation, strengthening the evaluation of rocky desertification control and dynamic monitoring, and strengthening research on key ecological function recovery technologies and supporting technologies.
The impact of ancestral heath management on soils and landscapes: a reconstruction based on paleoecological analyses of soil records in the middle and southeast Netherlands
Authors: Doorenbosch M. , van Mourik J. M.
Published: January 2016

Abstract. The evolution of heath lands during the Holocene has been registered in various soil records. Paleoecological analyses of these records enable to reconstruct the changing economic and cultural management of heaths and the consequences for landscape and soils. Heaths are characteristic components of cultural landscape mosaics on sandy soils in the Netherlands. The natural habitat of heather species was moorland. At first, natural events like forest fires and storms caused small-scale forest degradation, in addition on the forest degradation accelerated due to cultural activities like forest grazing, wood cutting and shifting cultivation. Heather plants invaded on degraded forest soils and heaths developed. People learned to use the heaths for economic and cultural purposes. The impact of the heath management on landscape and soils was registered in soil records of barrows, drift sand sequences and plaggic Anthrosols. Based on pollen diagrams of such records we could reconstruct that heaths were developed and used for cattle grazing before the Bronze Age. During the Late Neolithic, the Bronze Age and Iron Age, people created the barrow landscape on the ancestral heaths. After the Iron Age people probably continued with cattle grazing on the heaths and plaggic agriculture until the Early Middle Ages. After AD 1000 two events affected the heaths. At first deforestation for the sale of wood resulted in the first regional extension of sand drifting and heath degradation. After that the introduction of the deep stable economy and heath sods digging resulted in acceleration of the rise of plaggic horizons, severe heath degradation and the second extension of sand drifting. At the end of the 19th century the heath lost its economic value due to the introduction of chemical fertilizers. The heaths were transformed into "new" arable fields and forests and due to deep ploughing most soil archives were destroyed. Since AD 1980, the remaining relicts of the ancestral heaths are preserved and restored in the frame of the programs to improve the regional and national geo-biodiversity.
Tillage-induced short-term soil organic matter turnover and respiration
Authors: Fiedler S. R. , Leinweber P. , Jurasinski G. , Eckhardt K.-U. , Glatzel S.
Published: January 2016

Abstract. Tillage induces decomposition and mineralisation of soil organic matter (SOM) by the disruption of macroaggregates and may increase soil CO2 efflux by respiration, but these processes are not well understood at the molecular level. We sampled three treatments (mineral fertiliser = MF, biogas digestate = BD, unfertilised control = CL) of a stagnic luvisol a few hours before and directly after tillage, and four days later from a harvested maize field in Northern Germany and investigated these samples by pyrolysis-field ionization mass spectrometry (Py-FIMS) and hot-water extraction. Before tillage, BD showed much more volatilised matter (VM) during pyrolysis, indicating an increased amount of SOM. The Py-FIMS mass spectra revealed distinct differences in relative ion intensities of undisturbed soil compared to BD most likely attributable to the cattle manure used for the biogas feedstock and to relative enrichments during anaerobic fermentation. After tillage, the CO2 effluxes were increased in all treatments, but this increase was less pronounced in BD. We explain this by a restricted availability of labile carbon and, possibly an inhibitory effect of sterols from digestates. Despite high spatial variability, significant changes in SOM composition were observed following tillage. In particular, lignin decomposition and increased proportions of N-containing compounds were detected in BD. In MF, lipid proportions increased at the expense of carbohydrates and peptides, indicating an enhanced microbial activity. SOM composition in CL was unaffected by tillage. In summary, combining all analyses data provided strong evidence for significant shortterm SOM changes due to tillage in fertilized soils.
Feasibility of improving a priori regional climate model estimates of Greenland ice sheet surface mass loss through assimilation of measured ice surface temperatures
Authors: Navari M. , Margulis S. A. , Bateni S. M. , Tedesco M. , Alexander P. , Fettweis X.
Published: January 2016

Abstract. The Greenland ice sheet (GrIS) has been the focus of climate studies due to its considerable impact on sea level rise. Accurate estimates of surface mass fluxes would contribute to understanding the cause of its recent changes and would help to better estimate the past, current and future contribution of the GrIS to sea level rise. Though the estimates of the GrIS surface mass fluxes have improved significantly over the last decade, there is still considerable disparity between the results from different methodologies (e.g., Rae et al., 2012; Vernon et al., 2013). The data assimilation approach can merge information from different methodologies in a consistent way to improve the GrIS surface mass fluxes. In this study, an ensemble batch smoother data assimilation approach was developed to assess the feasibility of generating a reanalysis estimate of the GrIS surface mass fluxes via integrating remotely sensed ice surface temperature measurements with a regional climate model (a priori) estimate. The performance of the proposed methodology for generating an improved posterior estimate was investigated within an observing system simulation experiment (OSSE) framework using synthetically generated ice surface temperature measurements. The results showed that assimilation of ice surface temperature time series were able to overcome uncertainties in near-surface meteorological forcing variables that drive the GrIS surface processes. Our findings show that the proposed methodology is able to generate posterior reanalysis estimates of the surface mass fluxes that are in good agreement with the synthetic true estimates. The results also showed that the proposed data assimilation framework improves the root-mean-square error of the posterior estimates of runoff, sublimation/evaporation, surface condensation, and surface mass loss fluxes by 61, 64, 76, and 62 %, respectively, over the nominal a priori climate model estimates.
Climatic controls and climate proxy potential of Lewis Glacier, Mt. Kenya
Authors: Prinz R. , Nicholson L. I. , Mölg T. , Gurgiser W. , Kaser G.
Published: January 2016

Abstract. The Lewis Glacier on Mt. Kenya is one of the best studied tropical glaciers and has experienced considerable retreat since a maximum extent in the late 19th century (L19). From distributed mass and energy balance modelling, this study evaluates the current sensitivity of the surface mass and energy balance to climatic drivers, explores climate conditions under which the L19 maximum extent might have been sustained, and discusses the potential for using the glacier retreat to quantify climate change. Multi-year meteorological measurements at 4828 m provide data for input, optimization, and evaluation of a spatially distributed glacier mass balance model to quantify the exchanges of energy and mass at the glacier–atmosphere interface. Currently the glacier loses mass due to the imbalance between insufficient accumulation and enhanced melt, because radiative energy gains cannot be compensated by turbulent energy sinks. Exchanging model input data with synthetic climate scenarios, which were sampled from the meteorological measurements and account for coupled climatic variable perturbations, reveals that the current mass balance is most sensitive to changes in atmospheric moisture (via its impact on solid precipitation, cloudiness, and surface albedo). Positive mass balances result from scenarios with an increase of annual (seasonal) accumulation of 30 % (100 %), compared to values observed today, without significant changes in air temperature required. Scenarios with lower air temperatures are drier and associated with lower accumulation and increased net radiation due to reduced cloudiness and albedo. If the scenarios currently producing positive mass balances are applied to the L19 extent, negative mass balances are the result, meaning that the conditions required to sustain the glacier in its L19 extent are not reflected in today's meteorological observations using model parameters optimized for the present-day glacier. Alternatively, a balanced mass budget for the L19 extent can be achieved by changing both climate and optimized gradients (used to extrapolate the meteorological measurements over the glacier) in a manner that implies a distinctly different coupling between the glacier's local surface-air layer and its surrounding boundary layer. This result underlines the difficulty of deriving palaeoclimates for larger glacier extents on the basis of modern measurements of small glaciers.
Sea ice cover in Isfjorden and Hornsund, Svalbard (2000–2014) from remote sensing data
Authors: Muckenhuber S. , Nilsen F. , Korosov A. , Sandven S.
Published: January 2016

Abstract. A satellite database including 16 555 satellite images and ice charts displaying the area of Isfjorden, Hornsund, and the Svalbard region has been established with focus on the time period 2000–2014. 3319 manual interpretations of sea ice conditions have been conducted, resulting in two time series dividing the area of Isfjorden and Hornsund into "fast ice" (sea ice attached to the coastline), "drift ice", and "open water". The maximum fast ice coverage of Isfjorden is  >  40 % in the periods 2000–2005 and 2009–2011 and stays  <  30 % in 2006–2008 and 2012–2014. Fast ice cover in Hornsund reaches  >  40 % in all considered years, except for 2012 and 2014, where the maximum stays  <  20 %. The mean seasonal cycles of fast ice in Isfjorden and Hornsund show monthly averaged values of less than 1 % between July and November and maxima in March (Isfjorden, 35.7 %) and April (Hornsund, 42.1 %), respectively. A significant reduction of the monthly averaged fast ice coverage is found when comparing the time periods 2000–2005 and 2006–2014. The seasonal maximum decreases from 57.5 to 23.2 % in Isfjorden and from 52.6 to 35.2 % in Hornsund. A new index, called "days of fast ice" (DFI), is introduced for quantification of the interannual variation of fast ice cover, allowing for comparison between different fjords and winter seasons. Considering the time period from 1 March until end of the sea ice season, the mean DFI values for 2000–2014 are 33.1 ± 18.2 DFI (Isfjorden) and 42.9 ± 18.2 DFI (Hornsund). A distinct shift to lower DFI values is observed in 2006. Calculating a mean before and after 2006 yields a decrease from 50 to 22 DFI for Isfjorden and from 56 to 34 DFI for Hornsund. Fast ice coverage generally correlates well with remote-sensing sea surface temperature and in situ air temperature. An increase of autumn ocean heat content is observed during the last few years when the DFI values decrease. The presented sea ice time series can be utilized for various climate effect studies linked to, e.g. glacier dynamics, ocean chemistry, and marine biology.
Halogen-based reconstruction of Russian Arctic sea ice area from the Akademii Nauk ice core (Severnaya Zemlya)
Authors: Spolaor A. , Opel T. , McConnell J. R. , Maselli O. J. , Spreen G. , Varin C. , Kirchgeorg T. , Fritzsche D. , Saiz-Lopez A. , Vallelonga P.
Published: January 2016

Abstract. The role of sea ice in the Earth climate system is still under debate, although it is known to influence albedo, ocean circulation, and atmosphere–ocean heat and gas exchange. Here we present a reconstruction of 1950 to 1998 AD sea ice in the Laptev Sea based on the Akademii Nauk ice core (Severnaya Zemlya, Russian Arctic). The chemistry of halogens bromine (Br) and iodine (I) is strongly active and influenced by sea ice dynamics, in terms of physical, chemical and biological process. Bromine reacts on the sea ice surface in autocatalyzing "bromine explosion" events, causing an enrichment of the Br / Na ratio and hence a bromine excess (Brexc) in snow compared to that in seawater. Iodine is suggested to be emitted from algal communities growing under sea ice. The results suggest a connection between Brexc and spring sea ice area, as well as a connection between iodine concentration and summer sea ice area. The correlation coefficients obtained between Brexc and spring sea ice (r  =  0.44) as well as between iodine and summer sea ice (r  =  0.50) for the Laptev Sea suggest that these two halogens could become good candidates for extended reconstructions of past sea ice changes in the Arctic.
Comparison of multiple glacier inventories with a new inventory derived from high-resolution ALOS imagery in the Bhutan Himalaya
Authors: Nagai H. , Fujita K. , Sakai A. , Nuimura T. , Tadono T.
Published: January 2016

Abstract. Digital glacier inventories are invaluable data sets for revealing the characteristics of glacier distribution and for upscaling measurements from selected locations to entire mountain ranges. Here, we present a new inventory of Advanced Land Observing Satellite (ALOS) imagery and compare it with existing inventories for the Bhutan Himalaya. The new inventory contains 1583 glaciers (1487 ± 235 km2), thereof 219 debris-covered glaciers (951 ± 193 km2) and 1364 debris-free glaciers (536 ± 42 km2). Moreover, we propose an index for quantifying consistency between two glacier outlines. Comparison of the overlap ratio demonstrates that the ALOS-derived glacier inventory contains delineation uncertainties of 10–20 % which depend on glacier size, that the shapes and geographical locations of glacier outlines derived from the fourth version of the Randolph Glacier Inventory have been improved in the fifth version, and that the latter is consistent with other inventories. In terms of whole glacier distribution, each data set is dominated by glaciers of 1.0–5.0 km2 area (31–34 % of the total area), situated at approximately 5400 m elevation (nearly 10 % in 100 m bin) with either north or south aspects (22 and 15 %). However, individual glacier outlines and their area exhibit clear differences among inventories. Furthermore, consistent separation of glaciers with inconspicuous termini remains difficult, which, in some cases, results in different values for glacier number. High-resolution imagery from Google Earth can be used to improve the interpretation of glacier outlines, particularly for debris-covered areas and steep adjacent slopes.
Effects of Stratified Active Layers on the High-Altitude Permafrost Warming: A Case Study on the Qinghai-Tibet Plateau
Authors: Pan X. , Li Y. , Yu Q. , Shi X. , Yang D. , Roth K.
Published: January 2016

Abstract. Seasonally variable thermal conductivity in active layers is one important factor that controls the thermal state of permafrost. The common assumption is that this conductivity is considerably smaller in the thawed than in the frozen state, λt/λf < 1. Using a 9-year dataset from the Qinghai-Tibet Plateau (QTP) in conjunction with the GEOtop model, we demonstrate that the ratio λt/λf may approach or even exceed 1. This can happen in thick active layers, with thicknesses larger than some 1.5 m, with strong seasonal liquid water content changes. It is additionally furthered by typical soil architectures that may lead to a dry inter-layer. These findings suggest that, given the increase in air temperature and precipitation, soil hydraulic properties, particularly soil architecture in those thick active layers must be taken into account properly in permafrost models.
The impact of melt ponds on summertime microwave brightness temperatures and sea ice concentrations
Authors: Kern S. , Rösel A. , Pedersen L. T. , Ivanova N. , Saldo R. , Tonboe R. T.
Published: January 2016

Abstract. The sea ice concentration (SIC) derived from satellite microwave brightness temperature (TB) data are known to be less accurate during summer melt conditions – in the Arctic Ocean primarily because of the impact of melt ponds on sea ice. Using data from June to August 2009, we investigate how TBs and SICs vary as a function of the ice surface fraction (ISF) computed from open water fraction and melt pond fraction both derived from satellite optical reflectance data. SIC is computed from TBs using a set of eight different retrieval algorithms and applying a consistent set of tie points. We find that TB values change during sea ice melt non-linearly and not monotonically as a function of ISF for ISF of 50 to 100 %. For derived parameters such as the polarization ratio at 19 GHz the change is monotonic but substantially smaller than theoretically expected. Changes in ice/snow radiometric properties during melt also contribute to the TB changes observed; these contributions are functions of frequency and polarization and have the potential to partly counter-balance the impact of changing ISF on the observed TBs. All investigated SIC retrieval algorithms overestimate ISF when using winter tie points. The overestimation varies among the algorithms as a function of ISF such that the SIC retrieval algorithms could be categorized into two different classes. These reveal a different degree of ISF overestimation at high ISF and an opposite development of ISF over-estimation as ISF decreases. For one class, correlations between SIC and ISF are ≥ 0.85 and the associated linear regression lines suggest an exploitable relationship between SIC and ISF if reliable summer sea ice tie points can be established. This study shows that melt ponds are interpreted as open water by the SIC algorithms, while the concentration of ice between the melt ponds is in general being overestimated. These two effects may cancel each other out and thus produce seemingly correct SIC for the wrong reasons. This cancelling effect will in general only be "correct" at one specific value of MPF. Based on our findings we recommend to not correct SIC algorithms for the impact of melt ponds as this seems to violate physical principles. Users should be aware that the SIC algorithms available at the moment retrieve a combined parameter presented by SIC in winter and ISF in summer.
Calibration of a non-invasive cosmic-ray probe for wide area snow water equivalent measurement
Authors: Sigouin M. J. P. , Si B. C.
Published: January 2016

Abstract. Measuring snow water equivalent (SWE) is important for many hydrological purposes such as modeling and flood forecasting. Measurements of SWE are also crucial for agricultural production in areas where snowmelt runoff dominates spring soil water recharge. Typical methods for measuring SWE include point measurements (snow tubes) and large-scale measurements (remote sensing). We explored the potential of using the cosmic-ray soil moisture probe (CRP) to measure average SWE at a measurement scale between those provided by snow tubes and remote sensing. The CRP measures above ground moderated neutron intensity within a radius of approximately 300 m. Using snow tubes, surveys were performed over two winters (2013/2014 and 2014/2015) in an area surrounding a CRP in an agricultural field in Saskatoon, Saskatchewan, CAN. The raw moderated neutron intensity counts were corrected for atmospheric pressure, water vapor, and temporal variability of incoming cosmic ray flux. The mean SWE from manually measured snow surveys was adjusted for differences in soil water storage before snowfall between both winters because the CRP reading appeared to be affected by soil water below the snowpack. The SWE from the snow surveys was negatively correlated with the CRP-measured moderated neutron intensity, giving Pearson correlation coefficients of −0.92 (2013/2014) and −0.94 (2014/2015). A linear regression performed on the manually measured SWE and moderated neutron intensity counts for 2013/2014 yielded an r2 of 0.84. Linear regression lines from the 2013/2014 and 2014/2015 manually measured SWE and moderated neutron counts were very similar, thus differences in antecedent soil water storage did not appear to affect the slope of the SWE vs. neutron relationship. The regression equation obtained from 2013/2014 was used to model SWE using the moderated neutron intensity data for 2014/2015. The CRP-estimated SWE for 2014/2015 was similar to that of the snow survey, with a RMSE of 7.7 mm. The CRP-estimated SWE also compared well to estimates made using snow depths at meteorological sites near (< 10 km) the CRP. Overall, the empirical equation presented provides acceptable estimates of average SWE using moderated neutron intensity measurements. Using a CRP to monitor SWE is attractive because it delivers a continuous reading, can be installed in remote locations, requires minimal labour, and provides a landscape-scale measurement footprint.
Application of GRACE to the evaluation of an ice flow model of the Greenland Ice Sheet
Authors: Schlegel N.-J. , Wiese D. N. , Larour E. Y. , Watkins M. M. , Box J. E. , Fettweis X. , van den Broeke M. R
Published: January 2016

Abstract. Quantifying the Greenland Ice Sheet’s future contribution to sea level rise is a challenging task that requires accurate estimates of ice ﬂow sensitivity to climate change. Forward models of ice ﬂow dynamics are promising tools for estimating future ice sheet behavior, yet conﬁdence is low because evaluation of historical simulations is so challenging due to the scarcity of highly-resolved (spatially and temporally) continental-wide validation data. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained mass concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of estimated monthly global gravity ﬁelds. Speciﬁcally, the Jet Propulsion Laboratory’s JPL RL05M GRACE mascon solution (GRACE-JPL) now offers an opportunity for ice sheet model evaluation within independently resolved 300 km mascons. Here, we investigate how Greenland Ice Sheet mass balance captured through observations - GRACE-JPL - differs from that simulated by the ice ﬂow model - the Ice Sheet System Model (ISSM). For the years 2003-2012, ISSM is forced with regional climate model (RCM) surface mass balance (SMB), and resulting mass balance is directly compared against GRACE-JPL within individual mascons. Overall, we ﬁnd good agreement in the Northeast, Southwest, and the interior of the ice sheet, where mass balance is primarily controlled by SMB. In the Northwest, seasonal amplitudes match well, but trends in ISSM are muted relative to GRACE-JPL. In the Southeast, GRACE-JPL exhibits larger seasonal amplitude than that predicted by SMB while simultaneously having more pronounced trends. These results indicate that discrepancies in the Northwest are controlled by changes in ice dynamics that are not currently modeled by ISSM, i.e. transient processes driven by ice sheet hydrology and ice-ocean interaction, while discrepancies in the Southeast are controlled by a combination of these missing dynamics and errors in modeled SMB. Along the margins, we ﬁnd that transient dynamics are responsible for consistent intra-annual variations in regional mass balance that ultimately contribute to the steeper negative mass trends observed by GRACE-JPL. Consequently, ice-ocean interactions and hydrologically-driven processes at relatively high (monthly-to-seasonal) temporal resolutions must be considered for improving upon ice ﬂow models.
MABEL photon-counting laser altimetry data in Alaska for ICESat-2 simulations and development
Authors: Brunt K. M. , Neumann T. A. , Amundson J. M. , Kavanaugh J. L. , Moussavi M. S. , Walsh K. M. , Cook W. B. , Markus T.
Published: January 2016

Abstract. Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) is scheduled to launch in 2017 and will carry the Advanced Topographic Laser Altimeter System (ATLAS), which is a photon-counting laser altimeter and represents a new approach to satellite determination of surface elevation. Given the new technology of ATLAS, an airborne instrument, the Multiple Altimeter Beam Experimental Lidar (MABEL), was deployed in July 2014 to Alaska to provide data needed for satellite-algorithm development, simulating key elements of the photon-counting sampling strategy, and assessing elements of the resulting data that may vary seasonally. Here, we compare MABEL lidar data to in situ observations in Southeast Alaska to assess instrument performance in summer conditions and in the presence of glacier surface melt ponds and a wet snowpack. Results indicate that: 1) the ATLAS 90 m beam-spacing strategy will provide a robust assessment of across-track slope that is consistent with shallow slopes (<1°) of an ice-sheet interior over 50 to 150 m length scales; 2) the dense along-track sampling strategy of photon counting systems provides crevasse detail; and 3) MABEL 532 nm wavelength light may be sampling the surface and subsurface of shallow (approximately 2 m deep) supraglacial melt ponds.
Similitude of ice-sheet dynamics against scaling of geometry and physical parameters
Authors: Feldmann J. , Levermann A.
Published: January 2016

Abstract. The concept of similitude is commonly employed in the ﬁelds of ﬂuid dynamics and engineering where scaling laws are derived from the governing equation of ﬂow dynamics, e.g., the Navier-Stokes equation. Here we transfer this method to the problem of ice-sheet ﬂow to examine the dynamic similitude of ice sheets against the scaling of their geometry and physical parameters. Carrying out a dimensional analysis of the stress balance for isothermal ice sheets in shallow-shelf approximation we obtain dimensionless numbers that characterize the ﬂow, similar to the Reynolds or Froude numbers in ﬂuid dynamics. Requiring that these numbers remain constant under scaling we obtain conditions that relate the geometric scaling factors, the parameters for the ice softness, surface mass balance and basal friction as well as the ice-sheet intrinsic response time to each other. We demonstrate that these scaling laws are the same for both the (two-dimensional) ﬂow-line case and the threedimensional case and that they are consistent with ﬂow-line boundary-layer theory. The theoretically predicted ice-sheet scaling behavior agrees with results from numerical simulations that we conduct in ﬂow-line and three-dimensional conceptual setups. In a set of experiments the setup geometry is scaled systematically and the physical parameters are prescribed according to the derived scaling laws. We further investigate analytically the implications of geometric scaling of ice sheets for their response time under constant basal conditions ﬁnding that thicker (thinner) ice sheets have a shorter (longer) response time and that the opposite holds for the horizontal ice-sheet extent. With this study we provide a framework which, under several assumptions, allows for a fundamental comparison of the ice-dynamic behavior across different scales. It proofs to be useful in the design of conceptual model setups but might also be applied to real-world systems, e.g., to examine the response times of glaciers, ice streams or ice sheets to climatic perturbations.
Sea ice diffusion in the Arctic ice pack: a comparison between observed buoy trajectories and the neXtSIM and TOPAZ-CICE sea ice models
Authors: Rampal Pierre , Bouillon Sylvai , Bergh Jon , Ólason Eina
Published: January 2016

Abstract. Due to the increasing activity in Arctic, sea ice–ocean models are now frequently used to produce operational forecasts, for oil spill trajectory modelling and to assist in offshore operations planning. In this study we propose a method based on a Lagrangian diffusion analysis to evaluate the sea ice drift properties simulated by two sea ice models, TOPAZ-CICE and neXtSIM, used in two different sea ice–ocean systems developed for such applications. We compare their results to the buoy trajectories of the International Arctic buoy Program (IABP) data set and we find that neXtSIM performs better than TOPAZ-CICE in simulating the mean and fluctuating sea ice velocities over the central Arctic in winter. Our analyses indicate that both TOPAZ-CICE and neXtSIM are able to simulate two distinct sea ice diffusion regimes depending on the time scale considered, similarly to what is predicted by the steady and homogenous turbulent flow theory. However, the basin-averaged absolute diffusion computed from the analysis of drifters trajectories simulated with TOPAZ-CICE is almost twice as high as the value estimated from both the corresponding drifters trajectories simulated with neXtSIM and from observed buoy trajectories. Also, the mean Arctic pattern of absolute diffusion obtained from TOPAZ-CICE shows large differences from the one obtained from the observed buoy trajectories, while the neXtSIM results are much more consistent with the results from the buoy trajectories. The information on the mean drift and diffusivity fields provided by our analysis can be used in an advection/diffusion equation or with Lagrangian passive tracers models to study the drift of e.g. pollutants or micro-organisms moving with the ice. More generally, the analysis presented in this paper should be seen as a useful evaluation metric of coupled sea ice–ocean models that aim at being used in operational forecasting platforms, for process and climate studies.
Grounding and Calving Cycle of Mertz Ice Tongue Revealed by Shallow Mertz Bank
Authors: Wang Xianwei , Holland David M. , Cheng Xiao , Gong Peng
Published: January 2016

Abstract. A recent study, using remote sensing, provided some evidence that a seafloor shoal influenced the 2010 calving event of the Mertz Ice Tongue (MIT), by partially grounding the MIT several years earlier. In this paper, we propose a method to calculate firn air content (FAC) around Mertz from seafloor-touching icebergs. Our calculations indicate the FAC around Mertz region as 4.87 ± 1.31 m. We design an indirect method of using freeboard and sea level data extracted from ICESat/GLAS, FAC, and highly accurate seafloor topography to detect grounding sections of the MIT between 2002 and 2008 and analyze the process of grounding before the calving. By synthesizing remote sensing data, we point out that the grounding position was just localized northeast of the Mertz ice front close to the Mertz Bank. The grounding outlines of the tongue caused by the Mertz Bank are extracted as well, however the length is only limited in several kilometers since late 2002. From 2002 to 2008, the grounding area increased and the grounding became more pronounced. Additionally, the ice tongue could not climb over the Mertz Bank in following the upstream ice flow direction and that is why MIT rotated clockwise after late 2002. Furthermore, we demonstrate that the area-increasing trend of the MIT changed little after calving (~36 km2/a), thus allowing us to use remote sensing to estimate the elapsed time until the MIT can reground on the shoal. This time period is approximately 70 years. The calving of MIT can be repeatable because of the shallow Mertz Bank and the calving cycle of the MIT explains the cycle of sea-surface condition change around Mertz. Keywords: Mertz Ice Tongue, Firn air content, iceberg grounding, Mertz Bank, iceberg scouring, calving cycle.
Composition and microstructure alteration of triticale grain surface after processing by enzymes of cellulase complex
Authors: Kuznetsova Elena , Motyleva Svetlana , Mertvischeva Maria , Zomitev Vladislav , Brindza Jan
Published: January 2016

It is found that the pericarp tissue of grain have considerable strength and stiffness, that has an adverse effect on quality of whole-grain bread. Thereby, there exists the need for preliminary chemical and biochemical processing of durable cell walls before industrial use. Increasingly used in the production of bread finds an artificial hybrid of the traditional grain crops of wheat and rye - triticale, grain which has high nutritional value. The purpose of this research was to evaluate the influence of cellulose complex (Penicillium canescens) enzymes on composition and microstructure alteration of triticale grain surface, for grain used in baking. Triticale grain was processed by cellulolytic enzyme preparations with different composition (producer is Penicillium canescens). During experiment it is found that triticale grain processing by enzymes of cellulase complex leads to an increase in the content of water-soluble pentosans by 36.3 - 39.2%. The total amount of low molecular sugars increased by 3.8 - 10.5 %. Studies show that under the influence of enzymes the microstructure of the triticale grain surface is changing. Microphotographs characterizing grain surface structure alteration in dynamic (every 2 hours) during 10 hours of substrate hydrolysis are shown. It is found that the depth and direction of destruction process for non-starch polysaccharides of grain integument are determined by the composition of the enzyme complex preparation and duration of exposure. It is found, that xylanase involved in the modification of hemicelluloses fiber having both longitudinal and radial orientation. Hydrolysis of non-starch polysaccharides from grain shells led to increase of antioxidant activity. Ferulic acid was identified in alcoholic extract of triticale grain after enzymatic hydrolysis under the influence of complex preparation containing cellulase, xylanase and β-glucanase. Grain processing by independent enzymes containing in complex preparation (xylanase and β-glucanase) shows that more significant role in polysaccharide complex composition and grain surface microstructure alteration belongs to xylanase. Grain processing by independent of cellulolytic enzymes may decrease the strength of pericarp tissue of grain and improved sensory characteristics of the bread.
Redistribution of mineral elements in wheat grain when applying the complex enzyme preparations based on phytase
Authors: Kuznetsova Elena , Cherepnina Ludmila , Motyleva Svetlana , Brindza Ján
Published: January 2016

Biogenic minerals play an important role in the whole human nutrition, but they are included in the grain of the phytates that reduces their bioavailability. Whole wheat bread is generally considered a healthy food, but the presence of mineral elements in it is insignificant, because of weak phytate degradation. From all sources of exogenous phytase the most productive are microscopic fungi. To accelerate the process of transition hard mineral elements are mobilized to implement integrated cellulolytic enzyme preparation based on the actions of phytase (producer is Penicillium canescens). Phytase activity was assessed indirectly by the rate of release of phosphate from the substrate. It has been established that the release rate of the phosphoric acid substrate is dependent on the composition of the drug and the enzyme complex is determined by the presence of xylanase. The presented experimental data shows that a cellulase treatment of the grain in conjunction with the β-glucanase or xylanase leading to an increase in phytase activity could be 1.4 - 2.3 times as compared with the individual enzymes. As a result of concerted action of enzymes complex preparation varies topography grain, increase the pore sizes in seed and fruit shells that facilitate the penetration of the enzyme phytase in the aleurone layer to the site of phytin hydrolysis and leads to an increase in phytase activity. In terms of rational parameters of enzymatic hydrolysis, the distribution of mineral elements in the anatomical parts of the grain after processing complex enzyme preparation with the help of X-ray detector EMF miniCup system in a scanning electron microscope JEOL JSM 6390 were investigated. When processing enzyme preparation wheat trend in the distribution of mineral elements, characteristic of grain - the proportion of these elements in the aleurone layer decreases, and in the endosperm increases. Because dietary fiber and phytate found together in the peripheral layers of fiber-rich grains, it is difficult to separate the effects of degradation processes nonstarch polysaccharides and fiberphytate redistribution of polyvalent metal ions. However, studies have shown that phytase - an effective mechanism for regulating mineral nutrient diet. Application of phytase in grain bakery technology will increase the biological value of the product.
RAPD analysis of the genetic polymorphism in european wheat genotypes
Authors: Kuťka Hlozáková Tí­mea , Gálová Zdenka , Gregová Edita , Vivodí­k Martin , Balážová Želmí­ra , Miháliková Dana
Published: January 2016

Wheat (Triticum aestivum L.) is one of the main crops for human nutrition. The genetic variability of grown wheat has been reduced by modern agronomic practices, which inturn prompted the importance of search for species that could be useful as a genepool for the improving of flour quality for human consumption or for other industrial uses. Therefore, the aim of this study was to analyze the genetic diversity among 24 European wheat genotypes based on Random Amplified Polymorphism (RAPD) markers. A total of 29 DNA fragments were amplified with an average 4.83 polymorphic fragments per primer. The primer producing the most polymorphic fragments was SIGMA-D-P, where 7 polymorphic amplification products were detected. The lowest number of amplified fragments (3) was detected by using the primer OPB-08. The size of amplified products varied between 300 bp (OPE-07) to 3000 bp (SIGMA-D-P). The diversity index (DI) of the applied RAPD markers ranged from 0.528 (OPB-07) to 0.809 (SIGMA-D-P) with an average of 0.721. The polymorphism information content (PIC) of the markers varied from 0.469 (OPB-07) to 0.798 (SIGMA-D-P) with an average 0.692. Probability of identity (PI) was low ranged from 0.009 (SIGMA-D-P) to 0.165 (OPB-07) with an avarage 0.043. The dendrogram based on hierarchical cluster analysis using UPGMA algorithm was prepared. Within the dendrogram was separated the unique genotype Insegrain (FRA) from the rest of 23 genotypes which were further subdivided into two subclusters. In the first subclaster were grouped 13 genotypes and the second subcluster involved 10 genotypes. The first subcluster also included the genotype Bagou from France, in which were detected novel high - molecular - weight glutenin subunits using SDS-PAGE. Using 6 RAPD markers only two wheat genotypes have not been distinguished. Through that the information about genetic similarity and differences will be helpful to avoid any possibility of elite germplasm becoming genetically uniform.
Molecular characterization of rye cultivars
Authors: Balážová Želmí­ra , Petrovičová Lenka , Gálová Zdenka , Vivodí­k Martin Vivodí­k
Published: January 2016

The results of molecular analysis of 45 rye taxa (Secale cereale L.) represented by agricultural varieties originated from Central Europe and the Union of Soviet Socialist Republics (SUN) are presented. The genetic diversity of rye cultivars by 6 SSR markers was evaluated. Six specific microsatellite primer pairs produced 58 polymorphic alleles with an average of 9.7 alleles per locus. The number of alleles ranged from 6 (SCM2) to 14 (SCM86). Genetic polymorphism was characterized based on diversity index (DI), probability of identity (PI) and polymorphic information content (PIC). The diversity index (DI) of SSR markers ranged from 0.5478 (SCM2) to 0.887 (SCM86) with an average of 0.778. The lowest value of polymorphic information content was recorded for SCM2 (0.484) and the highest value for SCM86 (0.885) of PIC was detected in SCM86 with an average of 0.760.The dendrogram of genetic similarity was constructed, based on UPGMA algorithm. The hierarchical cluster analysis divided rye genotypes into 4 main clusters. The first cluster of 14 genotypes was subdivided in two subclusters (1a and 1b) where 50% of genotypes were Czechoslovak origin. The second cluster contained four genotypes were three (75%) of them had Czech or Czechoslovak origin. In the third subcluster separated three rye genotypes of different origin. The rest (24) of rye genotypes in the fourth cluster were divided into two subclusters (4a and 4b) where clearly separated group of Polish (4aa) and Czech and Czechoslovak (4ab) genotypes. Two genotypes of 4aa subcluster (Wojcieszyckie and Dankowskie Nowe) from Poland were genetically the closest. In the dendrogram alle genotypes were differentiated and clustering partially reflects geographic origin of studied rye genotypes. In this experiment, SSRs markers proved to be a high informative and usefull tool in genetic diversity research for the distinguishing and characterization of close related varieties.