Half-precession signals in Lake Ohrid (Balkan) and their spatio-temporal relations to climate records from the European realm

Abstract

The nature of half-precession (HP) cycles (∼9000–12,000 years), although identified in numerous records, is still poorly understood. Here we focus on HP signals in Lake Ohrid and in a variety of different marine and terrestrial proxy records from Europe and the Northern Atlantic region. Our study examines the temporal evolution of the HP signal from the early/middle Pleistocene to the present, discusses the results across the latitudes of the Mediterranean and Europe, and assesses the potential of the HP to reflect the connectivity of climate systems over time.We apply filters on the datasets that remove the classical orbital cycles (eccentricity, obliquity, precession) and high frequency signals to focus exclusively on the bandwidth of the HP signal. Evolutionary wavelet spectra and correlation techniques are used to study the evolution of frequencies through the different records.Next to a connection of HP cycles to interglacials, we see a more pronounced HP signal in the younger part of several proxy records. Although the HP signal is present in all of the investigated sites, we observe a more pronounced HP signal in the southeast compared to records from the north. The latter is consistent with the assumption that HP is an equatorial signal and can be transmitted northward via various pathways. The appearance of HP signals in mid- and high-latitude records can thus be an indicator for the intensity of the mechanisms driving these pathways. The African Monsoon probably plays a major role in this context, as its magnitude directly influences the climate systems of the Mediterranean and Southern Europe.