A discrete technique of the Schwarz alternating method is presented in this last chapter, to combine the Ritz-Galerkin and finite element methods. This technique is well suited for solving singularity problems in parallel, and requires a little more computation for large overlap of subdomains. The convergence rate of the iterative procedure, which depends upon overlap of subdomains, will be studied. Also a balance strategy will be proposed to couple the iteration number with the element size used in the FEM. For the crack-infinity problem of singularity the total CPU time by the technique in this chapter is much less than that by the nonconforming combination in Chapter 12.

Schwarz Alternating Method

Wind Generated Ocean Waves

Groundwater is projected to become an increasing source of freshwater and nutrients to the Arctic Ocean as permafrost thaws, yet few studies have quantified groundwater inputs to Arctic coastal waters under contemporary conditions. New measurements along the Alaska Beaufort Sea coast show that dissolved organic carbon and nitrogen (DOC and DON) concentrations in supra-permafrost groundwater (SPGW) near the land-sea interface are up to two orders of magnitude higher than in rivers. This dissolved organic matter (DOM) is sourced from readily leachable organic matter in surface soils and deeper centuries-to millennia-old soils that extend into thawing permafrost. SPGW delivers approximately 400–2100 m3 of freshwater, 14–71 kg of DOC, and 1–4 kg of DON to the coastal ocean per km of shoreline per day during late summer. These substantial fluxes are expected to increase as massive stocks of frozen organic matter in permafrost are liberated in a warming Arctic. In this study, the authors show that water flowing through thawed soils below the tundra surface (supra-permafrost groundwater) can be a major source of dissolved organic matter (DOM) to Arctic coastal waters during the summer. This DOM contains leachates from old soil carbon stocks, including potential contributions from thawing permafrost.

/pdf/groundwater-as-a-major-source-of-dissolved-organic-matter-to-2vvr5edrc9.pdf

Groundwater as a major source of dissolved organic matter to Arctic coastal waters

Permafrost thaw has been widely observed to alter the biogeochemistry of recipient aquatic ecosystems. However, research from various regions has shown considerable variation in effect. In this paper, we propose a state factor approach to predict the release and transport of materials from permafrost through aquatic networks. Inspired by Hans Jenny's seminal description of soil-forming factors, and based on the growing body of research on the subject, we propose that a series of state factors—including relief, ice content, permafrost extent, and parent material—will constrain and direct the biogeochemical effect of thaw over time. We explore state-factor-driven variation in thaw response using a series of case studies from diverse regions of the permafrost-affected north, and also describe unique scaling considerations related to the mobile and integrative nature of aquatic networks. While our cross-system review found coherent responses to thaw for some biogeochemical constituents, such as nutrients, others, such as dissolved organics and particles, were much more variable in their response. We suggest that targeted, hypothesis-driven investigation of the effects of state factor variation will bolster our ability to predict the biogeochemical effects of thaw across diverse and rapidly changing northern landscapes.

/pdf/landscape-matters-predicting-the-biogeochemical-effects-of-29euorlhyx.pdf

Landscape matters: Predicting the biogeochemical effects of permafrost thaw on aquatic networks with a state factor approach

Drivers, dynamics and impacts of changing Arctic coasts

https://iopscience.iop.org/article/10.1088/1748-9326/aae35d/pdf

Watershed slope as a predictor of fluvial dissolved organic matter and nitrate concentrations across geographical space and catchment size in the Arctic.

Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)

Sea level rise due to climate change will expose Hudson River tidal marshes to chronic shifts in salinity, thus altering habitat conditions and biogeochemical processes. Increased salt intrusion may affect macroinvertebrate and microbial communities that are important in the decomposition of a dominant, invasive plant species Phragmites australis. We hypothesized that increased salinity intrusion will negatively affect macroinvertebrate and microbial litter breakdown processes. Field and laboratory experiments were conducted to test the effect of salinity on Phragmites decomposition. Leaf packets were incubated among tidal wetlands along a salinity gradient and used to compare microbial respiration, fungal biomass, and mass loss. In addition, salinity tolerance of a freshwater isopod (Caecidotea sp.) and heterotrophic microbes were examined using laboratory bioassays. Salinity negatively affected isopod survivorship and microbial activity in controlled laboratory experiments; however, salinity did not significantly account for in situ variation in Phragmites mass loss, microbial respiration, and fungal biomass among wetlands. Future studies need to include litter from additional wetland species and consider alternative controls on decomposition (e.g., variation in temperature or inorganic nutrients) in order to best forecast the long-term impact of sea-level rise and salinity increases among tidal freshwater wetlands.

Salinity Effects on Phragmites Decomposition Dynamics Among the Hudson River’s Freshwater Tidal Wetlands

This appendix document describes the mechanical material model and the adaptive meshing for the Arctic coastal erosion project and its implementation in the ALBANY finite element code.

Craig T. Connolly

Papers

Groundwater as a major source of dissolved organic matter to Arctic coastal waters

Watershed slope as a predictor of fluvial dissolved organic matter and nitrate concentrations across geographical space and catchment size in the Arctic.

Geometric morphometric and phylogenetic analyses of Arizona Sky Island populations of Scaphinotus petersi Roeschke (Coleoptera: Carabidae)

Salinity Effects on Phragmites Decomposition Dynamics Among the Hudson River’s Freshwater Tidal Wetlands

Arctic Coastal Erosion: Modeling and Experimentation