Hypoxia has spread in Tiefer See (NE Germany) due to increased human activity. The onset of hypoxia indicated by varve preservation is dated to ~1920 at the lake’s depocenter, which responds faster and more severely to the reduction in oxygen level. The spread of hypoxic conditions is a gradual process that has lasted nearly 100 years, and the chemistry of the sediments shows that the depletion of oxygen in the lake started several decades before the onset of varve preservation.

The lake drilling project at Lake Hallstatt (Austria) successfully cored 51 m of lake sediments. This was achieved through the novel drilling platform Hipercorig. A core-log seismic correlation was created for the first time of an inner Alpine lake of the Eastern Alps. The sediments cover over 12 000 years before present with 10 (up to 5.1 m thick) instantaneous deposits. Lake Hallstatt is located within an UNESCO World Heritage area which has a rich history of human salt mining.

This paper focuses on volcanic ash (tephra) in European annually laminated (varve) lake records from the period 25 to 8 ka. Tephra enables the synchronisation of these lake records and their proxy reconstructions to absolute timescales. The data incorporate geochemical data from tephra layers across 19 varve lake records. We highlight the potential for synchronising multiple records using tephra layers across continental scales whilst supporting reproducibility through accessible data.

Radiocarbon dating is a widely used tool to establish chronologies for sediment records. We show that modern aquatic plants in the Laguna del Peinado lake system (Altiplano–Puna Plateau) give overestimated ages due to reservoir effects from the input of old groundwater and volcanic CO₂. Our results reveal a spatial variability in the modern reservoir effect within the lake basin, which has implications for radiocarbon-based chronologies in paleoclimate studies in this (and similar) regions.

Productivity increases in Lake Kälksjön sediments during the last 9600 years are likely driven by the progressive millennial-scale winter warming in northwestern Europe, following the increasing Northern Hemisphere winter insolation and decadal to centennial periods of a more positive NAO polarity. Strengthened productivity variability since ∼5450 cal yr BP is hypothesized to reflect a reinforcement of NAO-like atmospheric circulation.