Abstract
Abstract. Varved lake sediments provide climatic records with seasonal to annual resolution and low associated age uncertainty. Robust and detailed comparison of well-dated and annually laminated sediment records is crucial for reconstructing abrupt and regionally time-transgressive changes as well as validation of spatial and temporal trajectories of past climatic changes. The VARved sediments DAtabase (VARDA) presented here is the first data compilation for varve chronologies and associated palaeoclimatic proxy records. The current version 1.0 allows detailed comparison of published varve records from 95 lakes. VARDA is freely accessible and was created to assess outputs from climate models with high-resolution terrestrial palaeoclimatic proxies. VARDA additionally provides a technical environment that enables us to explore the database of varved lake sediments using a connected data model and can generate a state-of-the-art graphic representation of a multisite comparison. This allows the reassessment of existing chronologies and tephra events to synchronize and compare even distant varved lake records. Furthermore, the present version of VARDA permits the exploration of varve thickness data. In this paper, we report in detail on the data-mining and compilation strategies for the identification of varved lakes and assimilation of high-resolution chronologies, as well as the technical infrastructure of the database. Additional palaeoclimatic proxy data will be provided in forthcoming updates. The VARDA graph database and user interface can be accessed online at https://varve.gfz-potsdam.de (last access: 15 September 2020), all datasets of version 1.0 are available at https://doi.org/10.5880/GFZ.4.3.2019.003 (Ramisch et al., 2019).
Highlights
A major challenge in simulating climate change is validating model outputs with palaeoclimatic data
We report in detail on the data-mining and compilation strategies for the identification of varved lakes and assimilation of high-resolution chronologies, as well as the technical infrastructure of the database
Laminated lake sediments provide reliable data for such networks because they offer palaeoclimatic information in high temporal resolution with low associated age uncertainty. Due to their annual to seasonal resolution, multisite networks of varved lake sediments enable investigations of abrupt and regionally timetransgressive climate change on the continents (e.g. Lane et al, 2013; Rach et al, 2014), which are fundamental to understanding past climates, especially that of the last glacial cycle (Clement and Peterson, 2008), and to better assess spatial and temporal trajectories of future climate changes
Summary
A major challenge in simulating climate change is validating model outputs with palaeoclimatic data. Networks of varved lake sediments provide means to test contrasted proxy responses to climate change (e.g. Ott et al, 2017; Ramisch et al, 2018; Roberts et al, 2016), further enhancing the robustness of palaeoclimatic reconstructions Despite their usefulness for the generation of highly resolved multisite networks, a global synthesis of varve-related palaeoclimatic data is still not available. Continuous geochronological development results in frequent updates of fundamental methods such as calibration curves (e.g. Reimer et al, 2004, 2009, 2013) and age–depth modelling algorithms (e.g. Bronk Ramsey, 2008; Blaauw and Christen, 2011) Incorporating such changes into existing varve-related datasets requires an interactive approach that is not offered by fixed data structures of standard relational database management systems. We compiled all available and published varved sediment records and developed criteria for how these data are integrated in this database
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