Basal melt of the southern Filchner Ice Shelf, Antarctica

Basal melt of ice shelves is a key factor governing discharge of ice from the Antarctic Ice Sheet as a result of its effects on buttressing. Here, we use radio echo sounding to determine the spatial variability of the basal melt rate of the southern Filchner Ice Shelf, Antarctica along the inflow of Support Force Glacier. We find moderate melt rates with a maximum of 1.13 m a−1 about 50 km downstream of the grounding line. The variability of the melt rates over distances of a few kilometres is low (all but one < 0.15 m a−1 at < 2 km distance), indicating that measurements on coarse observational grids are able to yield a representative melt rate distribution. A comparison with remote sensing based melt rates revealed that, for the study area, large differences were due to inaccuracies in the estimation of vertical strain rates from remote sensing velocity fields. These inaccuracies can be overcome by using modern velocity fields.

A Note about Crosslinking Density in Imprinting Polymerization

Imprinting polymerization is an exciting technique since it leads to specific binding sites, which are the basis of a variety of applications, such as sensors, detectors, and catalysts. The specific binding sites are created using templates and then fixing the structure of the binding site with crosslinking. The literature review of imprinting polymerizations shows that the crosslinking density governs the physical properties of the resulting molecularly imprinted polymer (MIP). It is also a factor governing the capacity and the selectivity of MIPs. Reviewing polymer science data and theory, the crosslinking density commonly used in MIP synthesis is unusually high. The data reviewed here suggest that more research is needed to determine the optimal crosslinking density for MIPs.

Heat Stress and Rumen Microbial Ecology: Novel Insights Into Goat Adaptation

Establishing the functional significance of rumen microbiome during heat stress may provide crucial information for elucidating climate resilience in goat. The current study was thus designed with an aim to assess the impact of heat stress on the rumen microbiome across three indigenous goat breeds. To prove this hypothesis, six experimental groups were chosen as follows: Osmanabadi Control (n=6), Osmanabadi Heat (n=6), Malabari Control (n=6), Malabari Heat (n=6), Salem Black Control (n=6) and Salem Black Heat (n=6). The study, being first of its kind, provides novel insights into influence of both genetic and environmental interaction on rumen microbial diversity in goats. An evident variation in the rumen microbial abundance was established during heat stress across all three goat breeds. The decreased Firmicutes and higher Bacteroides abundance in Salem Black goats could indicate the better protein and polysaccharide degrading ability of Salem Black breed. Further, the number of unique OTUs in the Salem Black heat group was higher as compared to both Osmanabadi and Malabari heat groups. In addition, the lower abundance of both KEGG as well as COG pathways indicated the sub-threshold level of heat stress experienced by this breed. Moreover, the histomorphometric changes in the rumen also pointed towards the better adaptive ability of Salem Black breed. This result point towards the genetic factor governing the rumen microbial diversity in goats during heat stress exposure. The findings provide substantial evidence on the genetic superiority of Salem Black breed in altering the rumen microbial population which could impart them the potential to thrive well in harsh environmental conditions.

Rising ecosystem water demand exacerbates the lengthening of tropical dry seasons

The timing and length of the dry season is a key factor governing ecosystem productivity and the carbon cycle of the tropics. Mounting evidence has suggested a lengthening of the dry season with ongoing climate change. However, this conclusion is largely based on changes in precipitation (P) compared to its long-term average (P ̅) and lacks consideration of the simultaneous changes in ecosystem water demand (measured by potential evapotranspiration, Ep, or actual evapotranspiration, E). Using several long-term (1979-2018) observational datasets, we compared changes in tropical dry season length (DSL) and timing (dry season arrival, DSA, and dry season end, DSE) among three common metrics used to define the dry season: P < P ̅, P < Ep, and P < E. We found that all three definitions show that dry seasons have lengthened in much of the tropics since 1979. Among the three definitions, P < E estimates the largest fraction (49.0%) of tropical land area likely experiencing longer dry seasons, followed by P < Ep (41.4%) and P < P ̅ (34.4%). The largest differences in multi-year mean DSL (> 120 days) among the three definitions occurred in the most arid and the most humid regions of the tropics. All definitions and datasets consistently showed longer dry seasons in southern Amazon (due to delayed DSE) and central Africa (due to both earlier DSA and delayed DSE). However, definitions that account for changing water demand estimated longer DSL extension over those two regions. These results indicate that warming-enhanced evapotranspiration exacerbates dry season lengthening and ecosystem water deficit. Thus, it is necessity to account for the evolving water demand of tropical ecosystems when characterizing changes in seasonal dry periods and ecosystem water deficits in an increasingly warmer and drier climate.

From Forest Soil to the Canopy: Increased Habitat Diversity Does Not Increase Species Richness of Cercozoa and Oomycota in Tree Canopies

Tree canopies provide habitats for diverse and until now, still poorly characterized communities of microbial eukaryotes. One of the most general patterns in community ecology is the increase in species richness with increasing habitat diversity. Thus, environmental heterogeneity of tree canopies should be an important factor governing community structure and diversity in this subsystem of forest ecosystems. Nevertheless, it is unknown if similar patterns are reflected at the microbial scale within unicellular eukaryotes (protists). In this study, high-throughput sequencing of two prominent protistan taxa, Cercozoa (Rhizaria) and Oomycota (Stramenopiles), was performed. Group specific primers were used to comprehensively analyze their diversity in various microhabitats of a floodplain forest from the forest floor to the canopy region. Beta diversity indicated highly dissimilar protistan communities in the investigated microhabitats. However, the majority of operational taxonomic units (OTUs) was present in all samples, and therefore differences in beta diversity were mainly related to species performance (i.e., relative abundance). Accordingly, habitat diversity strongly favored distinct protistan taxa in terms of abundance, but due to their almost ubiquitous distribution the effect of species richness on community composition was negligible.

How much snow falls in the world's mountains? A first look at mountain snowfall estimates in A-train observations and reanalyses

CloudSat estimates that 1773 km3 of snow falls, on average, each year over the world's mountains. This amounts to 5 % of the global snowfall accumulations. This study synthetizes mountain snowfall estimates over the four continents containing mountains (Eurasia, North America, South America and Africa), comparing snowfall estimates from a new satellite cloud-radar-based dataset to those from four widely used reanalyses: Modern-Era Retrospective analysis for Research and Applications (MERRA), MERRA-2, Japanese 55-year Reanalysis (JRA-55), and European Center for Medium-Range Weather Forecasts Re-Analysis (ERA-Interim). Globally, the fraction of snow that falls in the world's mountains is very similar between all these independent datasets (4 %–5 %), providing confidence in this estimate. The fraction of snow that falls in the mountains compared to the continent as a whole is also very similar between the different datasets. However, the total of snow that falls globally and over each continent – the critical factor governing freshwater availability in these regions – varies widely between datasets. The consensus in fractions and the dissimilarities in magnitude could indicate that large-scale forcings may be similar in the five datasets, while local orographic enhancements at smaller scales may not be captured. This may have significant implications for our ability to diagnose regional trends in snowfall and its impacts on snowpack in rapidly evolving alpine environments.

Dielectric Properties of Binary Solvent Mixtures

The relative permittivity is a measure of the solvent’s ability to insulate opposite charges from each other and has a very significant effect on the strength of the interactions between ions especially in dilute solution. I describe the relative permittivities, εr(sln) of nonaqueous mixtures as a function of the composition at 25 ºC. Experimental data were fitted with the Redlich-Kister equation. I explained the deviation from the ideal solution in terms of the magnitude of the coefficient a0. a0 is a dominant factor governing the Redlich-Kister equation. The decrease in a0 made a plot of εr(sln) vs. x2 close to a straight line, which corresponded to the ideal solution. The cohesive forces between dissimilar components resulted in the increased effective dipole moment and, consequently, in the small negative value of a0.