Identifying imprints of externally derived dust and halogens in the sedimentary record of an Iberian alpine lake for the past ∼13,500 years – Lake Peixão, Serra da Estrela (Central Portugal)

• Published in: Science of The Total Environment
• Main Authors: Moreno, J., Ramos, A. M., Raposeiro, P. M., Santos, R. N., Rodrigues, T., Naughton, F., Moreno, F., Trigo, R. M., Ibañez-Insa, J., Ludwig, P., Shi, X., Hernández, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2023
• Subjects: Lacustrine sediments; Geochemical proxies; Northern African dust; Westerly Atlantic airflow; Lateglacial/Holocene transition; (Hydro)climatic changes; Alpine Lake; North Atlantic; Sea ice
• Online Access: http://hdl.handle.net/10400.1/20134; https://doi.org/10.1016/j.scitotenv.2023.166179

Iberian lacustrine sediments are a valuable archive to document environmental changes since the last glacial termination, seen as key for anticipating future climate/environmental changes and their far-reaching implica -tions for generations to come. Herein, multi-proxy-based indicators of a mountain lake record from Serra da Estrela were used to reconstruct atmospheric (in)fluxes and associated climatic/environmental changes over the last similar to 13.5 ka. Depositions of long-range transported dust (likely from the Sahara) and halogens (primarily derived from seawater) were higher for the pre-Holocene, particularly in the late Bolling-Allerod-Younger Dryas period, compared to the Holocene. This synchronous increase could be related to a recognized dust-laden at-mosphere, along with the combined effect of (i) an earlier proposed effective transport of Sahara dust for higher latitudes during cold periods and (ii) the progressive Polar Front expansion southwards, with the amplification of halogen activation reactions in lower latitudes due to greater closeness to snow/sea ice (halide-laden) surfaces. Additionally, the orographic blocking of Serra da Estrela may have played a critical role in increasing precipi-tation of Atlantic origin at higher altitudes, with the presence of snow prompting physical and chemical processes involving halogen species. In the Late Holocene, the dust proxy records highlighted two periods of enhanced input to Lake Peixao, the first (similar to 3.5-2.7 ka BP) after the end of the last African Humid Period and the second, from the 19th century onwards, agreeing with the advent of commercial agriculture, and human contribution to land degradation and dust emission in the Sahara/Sahel region. The oceanic imprints throughout the Holocene matched well with North Atlantic rapid climatic changes that, in turn, coincided with ice-rafted debris or Bond events and other records of increased storminess for the European coasts. Positive parallel peaks in halogens were found in recent times, ...