Version 1 of a sea ice module for the physics-based, detailed, multi-layer SNOWPACK model

Sea ice is an important component of the global climate system. The presence of a snowpack covering sea ice can strongly modify the thermodynamic behavior of the sea ice, due to the low thermal conductivity and high albedo of snow. The snowpack can be stratified and change properties (density, water content, grain size and shape) throughout the seasons. Melting snow provides freshwater which can form melt ponds or cause flushing of salt out of the underlying sea ice, while flooding of the snow layer by saline ocean water can strongly impact both the ice mass balance and the freezing point of the snow. To capture the complex dynamics from the snowpack, we introduce modifications to the physics-based, multi-layer SNOWPACK model to simulate the snow-sea-ice system. Adaptations to the model thermodynamics and a description of water and salt transport through the snow-sea-ice system by coupling the transport equation to the Richards equation were added. These modifications allow the snow microstructure descriptions developed in the SNOWPACK model to be applied to sea ice conditions as well. Here, we drive the model with data from snow and ice mass-balance buoys installed in the Weddell Sea in Antarctica. The model is able to simulate the temporal evolution of snow density, grain size and shape, and snow wetness. The model simulations show abundant depth hoar layers and melt layers, as well as superimposed ice formation due to flooding and percolation. Gravity drainage of dense brine is underestimated as convective processes are so far neglected. Furthermore, with increasing model complexity, detailed forcing data for the simulations are required, which are difficult to acquire due to limited observations in polar regions

Snow Cover Impacts on Antarctic Sea ice

The snow cover on Antarctic sea ice impacts the energy, mass, and momentum balance of the sea ice cover, which in turn strongly influences fluxes between ocean, sea ice, and atmosphere. Despite the fact that snow depth is qualified as an Essential Climate Variable, the knowledge of the snow cover distribution and properties is still mostly vague and no large-scale (e.g. Antarctic wide) snow depth data product is available. Snow on Antarctic sea ice is characterized through a high spatial and temporal variability, and shows a highly heterogeneous internal stratification. This poses a challenge to air or space borne snow depth retrieval algorithms. Similarly, sea ice models are not yet able to resolve snow processes with enough accuracy. Here we present measurements of snow depth and physical snow properties along drift trajectories of autonomous Snow Buoys, which were deployed during several Polarstern cruises in the Weddell Sea since 2014. Resulting time series of snow depth show an event driven snow accumulation even during austral summer, whereas melting and a significant decrease of snow depth is only observed along the marginal sea ice zone. Additional analysis with the 1D multi-layer thermodynamic snow model SNOWPACK provides insights into internal processes such as snow to ice development cover along the trajectories. For these studies, SNOWPACK, which was previously used for land-based snow, has been extended with a sea ice module and is forced with re-analysis data. Comparisons between model and in-situ measurements show the capability of the model to reproduce the prevalent snow stratigraphy

Observations of snow cover processes on Antarctic sea ice from in-situ and model studies

The snow cover on Antarctic sea ice impacts the energy, mass, and momentum balance of the sea ice cover, which in turn strongly influences fluxes between ocean, sea ice, and atmosphere. Despite the fact that snow depth is qualified as an Essential Climate Variable, the knowledge of the snow cover distribution and properties is still mostly vague and no large-scale (e.g. Antarctic wide) snow depth data product is available. Snow on Antarctic sea ice is characterized through a high spatial and temporal variability, and shows a highly heterogeneous internal stratification. This poses a challenge to air or space borne snow depth retrieval algorithms. Similarly, sea ice models are not yet able to resolve snow processes with enough accuracy. Here we present measurements of snow depth and physical snow properties along drift trajectories of autonomous Snow Buoys, which were deployed during several Polarstern cruises in the Weddell Sea since 2014. Resulting time series of snow depth show an event driven snow accumulation even during austral summer, whereas melting and a significant decrease of snow depth is only observed along the marginal sea ice zone. Additional analysis with the 1D multi-layer thermodynamic snow model SNOWPACK provides insights into internal processes such as snow to ice development cover along the trajectories. For these studies, SNOWPACK, which was previously used for land-based snow, has been extended with a sea ice module and is forced with re-analysis data. Comparisons between model and in-situ measurements show the capability of the model to reproduce the prevalent snow stratigraphy

Phylogeny of Parasitic Parabasalia and Free-Living Relatives Inferred from Conventional Markers vs. Rpb1, a Single-Copy Gene

Parabasalia are single-celled eukaryotes (protists) that are mainly comprised of endosymbionts of termites and wood roaches, intestinal commensals, human or veterinary parasites, and free-living species. Phylogenetic comparisons of parabasalids are typically based upon morphological characters and 18S ribosomal RNA gene sequence data (rDNA), while biochemical or molecular studies of parabasalids are limited to a few axenically cultivable parasites. These previous analyses and other studies based on PCR amplification of duplicated protein-coding genes are unable to fully resolve the evolutionary relationships of parabasalids. As a result, genetic studies of Parabasalia lag behind other organisms.Comparing parabasalid EF1α, α-tubulin, enolase and MDH protein-coding genes with information from the Trichomonas vaginalis genome reveals difficulty in resolving the history of species or isolates apart from duplicated genes. A conserved single-copy gene encodes the largest subunit of RNA polymerase II (Rpb1) in T. vaginalis and other eukaryotes. Here we directly sequenced Rpb1 degenerate PCR products from 10 parabasalid genera, including several T. vaginalis isolates and avian isolates, and compared these data by phylogenetic analyses. Rpb1 genes from parabasalids, diplomonads, Parabodo, Diplonema and Percolomonas were all intronless, unlike intron-rich homologs in Naegleria, Jakoba and Malawimonas.The phylogeny of Rpb1 from parasitic and free-living parabasalids, and conserved Rpb1 insertions, support Trichomonadea, Tritrichomonadea, and Hypotrichomonadea as monophyletic groups. These results are consistent with prior analyses of rDNA and GAPDH sequences and ultrastructural data. The Rpb1 phylogenetic tree also resolves species- and isolate-level relationships. These findings, together with the relative ease of Rpb1 isolation, make it an attractive tool for evaluating more extensive relationships within Parabasalia

Priorities for research in soil ecology

The ecological interactions that occur in and with soil are of consequence in many ecosystems on the planet. These interactions provide numerous essential ecosystem services, and the sustainable management of soils has attracted increasing scientific and public attention. Although soil ecology emerged as an independent field of research many decades ago, and we have gained important insights into the functioning of soils, there still are fundamental aspects that need to be better understood to ensure that the ecosystem services that soils provide are not lost and that soils can be used in a sustainable way. In this perspectives paper, we highlight some of the major knowledge gaps that should be prioritized in soil ecological research. These research priorities were compiled based on an online survey of 32 editors of Pedobiologia – Journal of Soil Ecology. These editors work at universities and research centers in Europe, North America, Asia, and Australia. The questions were categorized into four themes: (1) soil biodiversity and biogeography, (2) interactions and the functioning of ecosystems, (3) global change and soil management, and (4) new directions. The respondents identified priorities that may be achievable in the near future, as well as several that are currently achievable but remain open. While some of the identified barriers to progress were technological in nature, many respondents cited a need for substantial leadership and goodwill among members of the soil ecology research community, including the need for multi-institutional partnerships, and had substantial concerns regarding the loss of taxonomic expertise