Summer temperature variability in the Western Balkans during the Late Glacial and Early Holocene – New results from Lake Prokoško
The Late Glacial and Early Holocene periods were characterized by abrupt, high-amplitude climate oscillations; however, high-resolution, quantitative temperature reconstructions have thus far been lacking from the Western Balkan region. Our new study, published in the prestigious journal Palaeogeography, Palaeoclimatology, Palaeoecology, explores the changes in the mean July temperature of the subalpine Lake Prokoško (1670 m a.s.l.) in the Vranica Mountains of Bosnia and Herzegovina during the period between 18,000 and 9,870 years ago. The publication's first author is Eszter Tombor, a PhD student at our department who has obtained her pre-degree certificate (absolutorium), and the research group's work was coordinated by Dr. Enikő Magyari, professor at the Department of Environmental and Landscape Geography, ELTE. During the research, realized through international collaboration, we reconstructed the evolution of the lake ecosystem and local climate based on chironomid (non-biting midge) remains preserved in the lake sediment, alongside comprehensive geochemical (XRF, LOI) and palynological (pollen) analyses. Based on the investigations, we identified the following distinct historical periods of the lake:
- Before ~14.6 thousand years ago: Lake Prokoško was a cold, oligotrophic glacial environment, where the mean July temperature remained below 8.0 °C. Cold-tolerant taxa (such as Pseudodiamesa) dominated the sediment.
- Bølling–Allerød interstadial (~14.6–13.07 thousand years ago): This period was characterized by rapid warming; the summer temperature increased by 2.6 °C, reaching ~10.2 °C. Driven by the warmer climate, aquatic productivity increased and the lake's catchment area stabilized.
- Younger Dryas (~13.07–11.61 thousand years ago): Temperatures fell again, and the mean July temperature decreased by approximately 2.3 °C (to ~7.9 °C). This period was accompanied by increased soil erosion, catchment instability, and the return of cold-water fauna.
- Early Holocene (from 11.61 thousand years ago): The onset of the Holocene brought an abrupt, further warming of 2.9 °C (>12.0 °C mean summer temperature). This resulted in stable summer stratification, hypolimnetic (bottom-water) oxygen depletion, and a highly productive, mesotrophic-eutrophic lake state.
Examined on a regional scale, our results highlighted that the ~2.3 °C cooling observed during the Younger Dryas at Lake Prokoško represents a transition between the stronger Alpine (>3.0–4.0 °C) and the weaker Eastern Carpathian (<1.0 °C) climate responses. Our research supports the premise that a west-to-east decreasing summer cooling gradient characterized Europe during the Younger Dryas (cooling was more drastic in the west and milder in the east), because the North Atlantic cold influence, triggered by the weakening of the AMOC (Atlantic Meridional Overturning Circulation), progressively diminished towards the continental interior.
Further details can be read in our published study: https://doi.org/10.1016/j.palaeo.2026.114115
The research was supported by the NKFIH "Frontline" Research Excellence Programme (144209: DOMINO-CLIMATE) and the National Multidisciplinary Laboratory for Climate Change (RRF-2.3.1-21-2022-00014).
