The Iso2k Database: A global compilation of paleo-δ<sup>18</sup>O and δ<sup>2</sup>H records to aid understanding of Common Era climate

Abstract

Abstract. 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 composition of environmental waters, which reflect hydroclimate changes over the CE. The Iso2k database contains 756 isotope records from the terrestrial and marine realms, including: glacier and ground ice (205); speleothems (68); corals, sclerosponges, and mollusks (145); 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 non-experts 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/10.6084/m9.figshare.11553162 (McKay and Konecky, 2020).

Data‐Model Comparisons of Tropical Hydroclimate Changes Over the Common Era

“…The remainder of the records (51 out of 67; 76%) are water isotope‐based records, which reflect the isotopic composition (δ 2 H or δ 18 O) of precipitation, groundwater, lake water, or near‐surface seawater, and as such track numerous aspects of the hydrologic cycle. δ 2 H and δ 18 O records from closed lake systems generally reflect the local water balance of the lake (i.e., precipitation minus evaporation), while open lake, speleothem, and glacier ice records generally reflect the isotopic composition of precipitation, which integrates information about precipitation and evaporation rates, seasonality of precipitation, moisture sources, transport, and water recycling over land (Konecky et al., 2020). In the tropics, lower (higher) δ 2 H and δ 18 O values in meteoric water generally occur during periods of regionally wetter (drier) conditions, as described by the “amount effect,” which is an empirical relationship in which the isotopic composition of precipitation in the tropics is negatively correlated with the amount of precipitation on monthly or longer time scales (Dansgaard, 1964; Risi et al., 2008).…”

“…However, the efficacy of the climate models used to project future climate can be tested against past records. In particular, the last 2,000 years, known as the Common Era, has been a major reconstruction target for the paleoclimate community over the last decade (Konecky et al., 2020; PAGES 2k Consortium, 2013, 2019; PAGES 2k‐PMIP3 Group, 2015; Tierney et al., 2015) given its relative abundance of data and the similarity of the Earth's boundary conditions to present.…”

A multiproxy database of western North American Holocene paleoclimate records

“…The database includes a large variety of metadata ( Supplementary Table 1) to facilitate analyses and re-use. The metadata included in this database are largely consistent with those developed and used in the Temperature 12k database (Kaufman et al, 2020), with some refinement for hydroclimate related records. Predominant metadata are subdivided into the following categories:…”

Expression of the “4.2 ka event” drought in the southern Rocky Mountains, USA

“…Given the growing evidence of drought within the southern Rocky Mountains associated with the widespread climatic anomaly at 4.2 ka, a lack of d 18 Ocarb records of the event in the region, or in North America entirely, is surprising (Anderson et al, 2016b;Konecky et al, 2020).…”

“…S1). Downcore shifts in d 18 Ocarb produced by seasonal changes in the timing and rate of carbonate formation have been proposed as potential sources of variability within individual records (Fronval et al, 1995;Lamb et al, 2007;Steinman et al, 2012;Steinman & Abbott, 2013;Tyler et al, 2007) and could play a role in the record at HL, but such differences could also generate the variability in the long-term trends observed among records from the southern Rocky Mountains and elsewhere (Bini et al, 2019;Konecky et al, 2020;Roberts et al, 2008).…”