ALBERT

Description: Reconstructions of global hydroclimate during the Common Era (CE; the past ∼2000 years) are important for providing context for current and future global environmental change. Stable isotope ratios in water are quantitative indicators of hydroclimate on regional to global scales, and these signals are encoded in a wide range of natural geologic archives. Here we present the Iso2k database, a global compilation of previously published datasets from a variety of natural archives that record the stable oxygen (δ18O) or hydrogen (δ2H) isotopic compositions of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 759 isotope records from the terrestrial and marine realms, including glacier and ground ice (210); speleothems (68); corals, sclerosponges, and mollusks (143); wood (81); lake sediments and other terrestrial sediments (e.g., loess) (158); and marine sediments (99). Individual datasets have temporal resolutions ranging from sub-annual to centennial and include chronological data where available. A fundamental feature of the database is its comprehensive metadata, which will assist both experts and nonexperts in the interpretation of each record and in data synthesis. Key metadata fields have standardized vocabularies to facilitate comparisons across diverse archives and with climate-model-simulated fields. This is the first global-scale collection of water isotope proxy records from multiple types of geological and biological archives. It is suitable for evaluating hydroclimate processes through time and space using large-scale synthesis, model–data intercomparison and (paleo)data assimilation. The Iso2k database is available for download at https://doi.org/10.25921/57j8-vs18 (Konecky and McKay, 2020) and is also accessible via the NOAA/WDS Paleo Data landing page: https://www.ncdc.noaa.gov/paleo/study/29593 (last access: 30 July 2020).

Description: Landfast sea ice (fast ice) is an important component of the Antarctic nearshore marine environment, where it strongly modulates ice sheet–ocean–atmosphere interactions and biological and biogeochemical processes, forms a key habitat, and affects logistical operations. Given the wide-ranging importance of Antarctic fast ice and its sensitivity to climate change, improved knowledge of its change and variability in its distribution is a high priority. Antarctic fast-ice mapping to date has been limited to regional studies and a time series covering East Antarctica from 2000 to 2008. Here, we present the first continuous, high-spatio-temporal resolution (1 km, 15 d) time series of circum-Antarctic fast-ice extent; this covers the period March 2000 to March 2018, with future updates planned. This dataset was derived by compositing cloud-free satellite visible and thermal infrared imagery using an existing methodology, modified to enhance automation and reduce subjectivity in defining the fast-ice edge. This new dataset (Fraser et al., 2020) has wide applicability and is available at https://doi.org/10.26179/5d267d1ceb60c. The new algorithm presented here will enable continuous large-scale fast-ice mapping and monitoring into the future.