Radiative Impacts of Volcanic Aerosol in the Arctic

High latitude volcanic eruptions are high-frequency and intensity events capable of releasing large amounts of aerosols into the environment. Studies have shown that the Arctic is particularly sensitive to radiative perturbations due to aerosols, and a high sensitivity to volcanic aerosols would be expected. Despite the potential for volcanic aerosols to significantly perturb the Arctic radiation balance, the radiative impacts of volcanic aerosols in the Arctic are poorly understood and have received less attention than the effects of other aerosol types that are often present in the region, both natural and anthropogenic. A novel review of this topic is presented in detail in this chapter, focusing on the current state of the knowledge and the natural complexities involved with the problem, the important research tools, and the improvements that can be made over the status quo. The Arctic environment is both unique and complicated, and the perturbations caused by volcanic aerosol need to be examined in a regional context. An introduction to remote sensing and data collection in the Arctic is provided because there are often specific challenges, including high surface reflectivities, persistent meteorological clouds, the lack of winter daylight, and harsh conditions that hamper both in situ and remote data collection. Methods for tracking both aerosol and gas plumes in the Arctic that can help mitigate these issues are introduced. In addition to the physical constraints of data collection presented by the Arctic environment, volcanic aerosol is a complex mixture of varying aerosol compositions and sizes. Dealing with the nature of volcanic aerosol for optical calculations is further described, leading into a detailed discussion of the radiative impacts of volcanic plumes in the atmosphere. Radiative forcing comparisons of other aerosol types with comparable plume characteristics (e.g., thicknesses and optical depths) suggest that aerosol layers composed of significant proportions of volcanic ash can dominate the aerosol forcing in the region. Similar comparisons for ash deposits with other types of deposits that can be present in the region emphasize the ability of volcanic ash to produce large, and in some cases extreme, loadings that reduce albedo, which can have profound impacts on the Arctic radiation balance and hydrological cycle. The strengths and shortcomings of volcanic ash transport and dispersion models are reviewed and recommendations are made for future research that would strengthen the use of these models in Arctic environments. In particular, ash aggregation (or the sticking together of ash particles) is often not considered fully in transport modeling, and the consequences of this are discussed. Finally, we present a review of secondary volcanic impacts to oceans and ecosystems that have not been constrained in an Arctic context but are potentially important to the Arctic environment and the global CO2 cycle

Specific Biarsenical Labeling of Cell Surface Proteins Allows Fluorescent- and Biotin-tagging of Amyloid Precursor Protein and Prion Proteins

Fluorescent tagging is a powerful tool for imaging proteins in living cells. However, the steric effects imposed by fluorescent tags impair the behavior of many proteins. Here, we report a novel technique, Instant with DTT, EDT, And Low temperature (IDEAL)-labeling, for rapid and specific FlAsH-labeling of tetracysteine-tagged cell surface proteins by using prion protein (PrP) and amyloid precursor protein (APP) as models. In prion-infected cells, FlAsH-labeled tetracysteine-tagged PrP converted from the normal isoform (PrPsen) to the disease-associated isoform (PrPres), suggesting minimal steric effects of the tag. Pulse-chase analysis of PrP and APP by fluorescent gel imaging demonstrated the utility of IDEAL labeling in investigating protein metabolism by identifying an as-yet-unrecognized C-terminal fragment (C3) of PrPsen and by characterizing the kinetics of PrPres and APP metabolism. C3 generation and N-terminal truncation of PrPres were inhibited by the anti-prion compound E64, a cysteine protease inhibitor. Surprisingly, E64 did not inhibit the synthesis of new PrPres, providing insight into the mechanism by which E64 reduces steady-state PrPres levels in prion-infected cells. To expand the versatility of tetracysteine tagging, we created new Alexa Fluor- and biotin-conjugated tetracysteine-binding molecules that were applied to imaging PrP endocytosis and ultrastructural localization. IDEAL-labeling extends the use of biarsenical derivatives to extracellular proteins and beyond microscopic imaging