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Abstract Small freshwater tundra ponds are hotspots for greenhouse gas release into the atmosphere. As the Arctic warms, thermokarst processes drive changes in tundra pond geomorphology, with implications for their contribution to carbon cycling in these regions. To understand how these morphological changes affect pond biogeochemistry, we compared low‐centered polygonal (LCP) ponds and thermokarst trough (TKT) ponds that are formed through ice‐wedge permafrost thaw. We found substantially higher levels of carbon, nutrients, and algal biomass in TKT ponds as compared to LCP ponds located in the Arctic Coastal Plain near Utqiaġvik, AK. These differences were likely driven by TKT ponds receiving increased terrestrial inputs due to discrete thermokarst events and slumping, lateral inflow of carbon and nutrients from surrounding soils, higher lability of TKT carbon, and greater rates of benthic respiration. Together, these factors create ponds that are more productive and greater sources of CO₂to the atmosphere than LCPs. During the peak growing season (July‐August), CO₂uptake from macrophyte‐dominated habitat in LCP ponds compensates for CO₂release from open water, making LCP ponds net CO₂sinks (−4 ± 3 gCO₂/m²/d), whereas TKT ponds are CO₂sources (3 ± 6 gCO₂/m²/d), despite TKT macrophyte‐dominated habitat also being a site of CO₂uptake. The net atmospheric greenhouse gas contribution of these ponds will likely be altered with high latitude warming, as air temperature influenced factors including vegetation cover, precipitation, water temperature, and thermokarsting alter rates of CO₂flux from tundra ponds. 

Permafrost thaw exhibits an array of spatially heterogenous patterns. As the Arctic continues to warm, those spatial patterns of permafrost thaw, or degradation, are becoming increasingly intricate and dynamic. In particular, ice-wedge permafrost degradation contains a high degree of spatial heterogeneity as ice wedges transition through undegraded, degraded, and stabilized stages. Developing accurate remote sensing methods for characterizing degradation will better allow us to monitor and forecast Arctic landscape evolution and associated land-atmosphere carbon-climate interactions. In this study, we (i) characterized ice-wedge degradation stages across a regional scale using a novel hydrogeomorphic approach. Then, we (ii) assessed the heterogeneity of degradation from meter- to kilometer-scales, and (iii) identified landscape properties associated with degradation patterns. We leveraged the unique spectral and geometric properties of ice-wedge degradation stages to map those stages across 366 km2 of the Arctic Coastal Plain near Prudhoe Bay, Alaska in sub-meter resolution Worldview-2 satellite imagery. Then, we validated the maps with in-situ observations, airborne LIDAR, and drone multispectral surveys. We evaluated spatial heterogeneity in ice-wedge degradation through a clustering approach. Specifically, we grouped regions into hydrogeomorphic clusters defined by similarities in trough widths and flooding, which reflect distinct degradation stages. This analysis revealed that ice-wedge degradation is heterogeneous across both meter and kilometer scales. At the meter scale, a single ice-wedge polygon is generally bounded by varied degradation stages. In addition, the most advanced stages of degradation occur in areas of low trough relative elevation and at the junctions between troughs. At the kilometer-scale, distinct clustering of degradation stages was identified across the region and linked to spatial patterns in topography: regional clusters of advanced degradation occurred in higher elevation areas. The millennial-scale evolution of the landscape has resulted in heterogeneous topographic, hydrologic, and cryogenic characteristics; these varied features exhibit diverse responses to warming events, which reflect the dynamic interplay that occurs between permafrost landscapes and climate change. 

Abstract Model-observation comparisons of type-I X-ray bursts (XRBs) can reveal the properties of accreting neutron star systems, including the neutron star compactness. XRBs are powered by nuclear burning, and a handful of reactions have been shown to impact the model results. Reactions in the NiCu cycles, featuring a competition between⁵⁹Cu(p,γ)⁶⁰Zn and⁵⁹Cu(p,α)⁵⁶Ni, have been shown to be among the most important reactions as they are a critical checkpoint inrp-process flow and significantly impact the light curves and burst ashes. We report a direct measurement of⁵⁹Cu(p,α)⁵⁶Ni, bringing stringent constraints on this reaction rate. New results rule out a strong NiCu cycle in XRBs, with a negligible degree of recycling, ≤5% up to 1.5 GK. The new reaction rate, when varied within new uncertainty limits, shows no impact on one-zone XRB model light curves tailored for clocked-bursterGS1826–24, hence removing an important nuclear physics uncertainty in the model-observation comparison. 

PAX6 is well known as a transcription factor that drives eye development in animals as widely divergent as flies and mammals. In addition to its localization in eyes, PAX6 expression has been reported in the central nervous system, the pancreas, testes, Merkel cells, nasal epithelium, developing cells of the inner ear, and embryonic submandibular salivary gland. Here we show that PAX6 also appears to be present in the mechanosensory neuromasts of the lateral line system in paedomorphic salamanders of the genusEurycea. Using immunohistochemistry and confocal microscopy to examine a limited number of larvae of two species, listed by the United States of America’s federal government as threatened (E.nana) or endangered (E.rathbuni), we found that anti-PAX6 antibody labeled structures that were extranuclear, and labeling was most intense in the apical appendages of the hair cells of the neuromast. This extranuclear localization raises the possibility of an as yet undescribed function for PAX6 as a cytoskeleton-associated protein.