Rising oceans guaranteed: Arctic land ice loss and sea level rise

Purpose of Review This paper reviews sea level contributions from land ice across the Arctic, including Greenland. We summarize ice loss measurement methods, ice loss mechanisms, and recent observations and projections, and highlight research advances over the last 3-5 years and remaining scientific challenges. Recent Findings Mass loss across the Arctic began to accelerate during the late twentieth century, with projections of continued loss across all future greenhouse gas emission scenarios. Recent research has improved knowledge of ice hydrology and surface processes, influences of atmospheric and oceanic changes on land ice, and boundary conditions such as subglacial topography. New computer models can also more accurately simulate glacier and ice sheet evolution. Summary Rapid Arctic ice loss is underway, and future ice loss and sea level rise are guaranteed. Research continues to better understand and model physical processes and to improve projections of ice loss rates, especially after 2050

MPAS-Albany Land Ice (MALI): a variable-resolution ice sheet model for Earth system modeling using Voronoi grids

We introduce MPAS-Albany Land Ice (MALI) v6.0, a new variable-resolution land ice model that uses unstructured Voronoi grids on a plane or sphere. MALI is built using the Model for Prediction Across Scales (MPAS) framework for developing variable-resolution Earth system model components and the Albany multi-physics code base for the solution of coupled systems of partial differential equations, which itself makes use of Trilinos solver libraries. MALI includes a three-dimensional first-order momentum balance solver (Blatter–Pattyn) by linking to the Albany-LI ice sheet velocity solver and an explicit shallow ice velocity solver. The evolution of ice geometry and tracers is handled through an explicit first-order horizontal advection scheme with vertical remapping. The evolution of ice temperature is treated using operator splitting of vertical diffusion and horizontal advection and can be configured to use either a temperature or enthalpy formulation. MALI includes a mass-conserving subglacial hydrology model that supports distributed and/or channelized drainage and can optionally be coupled to ice dynamics. Options for calving include eigencalving, which assumes that the calving rate is proportional to extensional strain rates. MALI is evaluated against commonly used exact solutions and community benchmark experiments and shows the expected accuracy. Results for the MISMIP3d benchmark experiments with MALI's Blatter–Pattyn solver fall between published results from Stokes and L1L2 models as expected. We use the model to simulate a semi-realistic Antarctic ice sheet problem following the initMIP protocol and using 2&thinsp;km resolution in marine ice sheet regions. MALI is the glacier component of the Energy Exascale Earth System Model (E3SM) version 1, and we describe current and planned coupling to other E3SM components.</p

DFT investigation of 3d transition metal NMR shielding tensors in diamagnetic systems using the gauge-including projector augmented-wave method

We present a density functional theory based method for calculating NMR shielding tensors for 3d transition metal nuclei using periodic boundary conditions. Calculations employ the gauge-including projector augmented-wave pseudopotentials method. The effects of ultrasoft pseudopotential and induced approximations on the second-order magnetic response are intensively examined. The reliability and the strength of the approach for 49Ti and 51V nuclei is shown by comparison with traditional quantum chemical methods, using benchmarks of finite organometallic systems. Application to infinite systems is validated through comparison to experimental data for the 51V nucleus in various vanadium oxide based compounds. The successful agreement obtained for isotropic chemical shifts contrasts with full estimation of the shielding tensor eigenvalues, revealing the limitation of pure exchange-correlation functionals compared to their exact-exchange corrected analogues.Comment: 56 page

Compensating errors in inversions for subglacial bed roughness: same steady state, different dynamic response

Subglacial bed roughness is one of the main factors controlling the rate of future Antarctic ice-sheet retreat and also one of the most uncertain. A common technique to constrain the bed roughness using ice-sheet models is basal inversion, tuning the roughness to reproduce the observed present-day ice-sheet geometry and/or surface velocity. However, many other factors affecting ice-sheet evolution, such as the englacial temperature and viscosity, the surface and basal mass balance, and the subglacial topography, also contain substantial uncertainties. Using a basal inversion technique intrinsically causes any errors in these other quantities to lead to compensating errors in the inverted bed roughness. Using a set of idealised-geometry experiments, we quantify these compensating errors and investigate their effect on the dynamic response of the ice sheet to a prescribed forcing. We find that relatively small errors in ice viscosity and subglacial topography require substantial compensating errors in the bed roughness in order to produce the same steady-state ice sheet, obscuring the realistic spatial variability in the bed roughness. When subjected to a retreat-inducing forcing, we find that these different parameter combinations, which per definition of the inversion procedure result in the same steady-state geometry, lead to a rate of ice volume loss that can differ by as much as a factor of 2. This implies that ice-sheet models that use basal inversion to initialise their model state can still display a substantial model bias despite having an initial state which is close to the observations.</p

Increasing mass loss from Greenland's Mittivakkat Gletscher

Warming in the Arctic during the past several decades has caused glaciers to thin and retreat, and recent mass loss from the Greenland Ice Sheet is well documented. Local glaciers peripheral to the ice sheet are also retreating, but few mass-balance observations are available to quantify that retreat and determine the extent to which these glaciers are out of equilibrium with present-day climate. Here, we document record mass loss in 2009/10 for the Mittivakkat Gletscher (henceforth MG), the only local glacier in Greenland for which there exist long-term observations of both the surface mass balance and glacier front fluctuations. We attribute this mass loss primarily to record high mean summer (June–August) temperatures in combination with lower-than-average winter precipitation. Also, we use the 15-yr mass-balance record to estimate present-day and equilibrium accumulation-area ratios for the MG. We show that the glacier is significantly out of balance and will likely lose at least 70% of its current area and 80% of its volume even in the absence of further climate changes. Temperature records from coastal stations in Southeast Greenland suggest that recent MG mass losses are not merely a local phenomenon, but are indicative of glacier changes in the broader region. Mass-balance observations for the MG therefore provide unique documentation of the general retreat of Southeast Greenland's local glaciers under ongoing climate warming

Dendritic Cells Activate and Mature after Infection with Mycobacterium tuberculosis

<p>Abstract</p> <p>Background</p> <p>Dendritic cells (DCs) can take up an array of different antigens, including microorganisms which they can process and present more effectively than any other antigen presenting cell. However, whether the interaction between the human DC and <it>Mycobacterium tuberculosis </it>represents a defense mechanism by the invaded host, or helping the invader to evade the defense mechanism of the host is still not clearly understood.</p> <p>Findings</p> <p>To analyze the interactions between <it>M. tuberculosis </it>and immune cells, human peripheral blood monocyte-derived immature DCs were infected with <it>M. tuberculosis </it>H37Rv wild type strain and flow cytometry was used to analyse cell surface expression markers. The ability of the <it>M. tuberculosis </it>infected DC to induce T cell proliferation using 5 and 6-carboxyfluorescein diacetate succinimidyl ester (CFSE) dilution technique was also investigated. DCs were found to internalize the mycobacteria and show dose dependent infection and necrosis with different multiplicity of infection. Flow cytometry analysis of cell surface expression markers CD40, CD54, CD80, CD83, CD86 and HLA DR in infected DC revealed significant (p < 0.05) up regulation following infection with <it>M. tuberculosis </it>in comparison to immature DC with no stimulation. Lipopolysaccharide (LPS) from <it>Salmonella abortus equi</it>, a known DC maturation agent, was used as a positive control and showed a comparable up regulation of cell surface markers as observed with <it>M. tuberculosis </it>infected DC. It was revealed that the <it>M. tuberculosis </it>infected DC induced T cell proliferation.</p> <p>Conclusion</p> <p>These data clearly demonstrate that <it>M. tuberculosis </it>induces activation and maturation of human monocyte-derived immature DC as well as induces T cell proliferation <it>in vitro</it>.</p

Murfreesboro Addresses

https://digitalcommons.acu.edu/crs_books/1086/thumbnail.jp

Absence of p300 induces cellular phenotypic changes characteristic of epithelial to mesenchyme transition

p300 is a transcriptional cofactor and prototype histone acetyltransferase involved in regulating multiple cellular processes. We generated p300 deficient (p300−) cells from the colon carcinoma cell line HCT116 by gene targeting. Comparison of epithelial and mesenchymal proteins in p300− with parental HCT116 cells showed that a number of genes involved in cell and extracellular matrix interactions, typical of ‘epithelial to mesenchyme transition' were differentially regulated at both the RNA and protein level. p300− cells were found to have aggressive ‘cancer' phenotypes, with loss of cell–cell adhesion, defects in cell–matrix adhesion and increased migration through collagen and matrigel. Although migration was shown to be metalloproteinase mediated, these cells actually showed a downregulation or no change in the level of key metalloproteinases, indicating that changes in cellular adhesion properties can be critical for cellular mobility

Superhard Phases of Simple Substances and Binary Compounds of the B-C-N-O System: from Diamond to the Latest Results (a Review)

The basic known and hypothetic one- and two-element phases of the B-C-N-O system (both superhard phases having diamond and boron structures and precursors to synthesize them) are described. The attention has been given to the structure, basic mechanical properties, and methods to identify and characterize the materials. For some phases that have been recently described in the literature the synthesis conditions at high pressures and temperatures are indicated.Comment: Review on superhard B-C-N-O phase