Synchronized records of Holocene Circum-Baltic environmental change

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The Circum-Baltic ecosystem is highly sensitive to both natural climate forcing and human impact. Its evolution since the last deglaciation is well-documented in sediments from the Baltic Sea itself, as well as in surrounding terrestrial environmental archives. Existing studies point to substantial environmental variability with strong spatial gradients working on inter-annual to millennial time-scales, triggered by a complex interplay of internal and external forcing mechanisms.Despite the diversity of existing paleoenvironmental information, a comprehensive understanding of the Holocene development of the coupled marine-terrestrial Baltic ecosystem is still limited. Main causes are a wide temporal and spatial range of forcing mechanisms and different timings, magnitudes and thresholds of proxy responses in different types of environmental archives. The BaltRap network aims at integrating marine-, annually laminated (varved) lake sediment and tree ring records from the southern Baltic realm for a comprehensive understanding of archive-specific proxy responses to short and long-term climate variations and oscillations as well as the distinction of natural variability from the increasing human impact, at up to the highest possible 'seasonal' resolution.However, since BaltRap focusses on the southern Baltic region, a complete understanding of Circum-Baltic ecosystem responses requires a northward extension of the approach based on varved lake sediment and tree ring records from the Scandinavian Peninsula. This is vital since the northern Baltic realm experienced a substantially different climatic and human development, compared to the South. Moreover, multi-archive investigations of leads and lags of proxy responses necessitate a climate-independent synchronization of the considered archives, minimizing individual chronological uncertainties. Within this proposal, we aim at establishing new seasonally resolved Holocene proxy records of climate and human activity using varved lake sediment and tree ring records from Lake Kälksjön and its catchment (central Sweden), to distinguish the unique Scandinavian influence on the Circum-Baltic ecosystem and extend the BaltRap approach northward. We apply the novel 10Be synchronization tool for a precise synchronization of the Scandinavian Lake Kälksjön record to the existing southern Baltic marine and varved lake sediment archives. Ultimate goal of the research is the first investigation of environmental gradients in the Baltic region during the Holocene based on synchronous multi-archive proxy records. The work will improve our understanding of temporal and spatial ecosystem responses to climatic and human forcing on a new transbaltic North-South transect and provides a step towards a more comprehensive knowledge of Circum-Baltic environmental dynamics, helping to better anticipate future 21st century change.