Bayesian age–depth modelling applied to varve and radiometric dating to optimize the transfer of an existing high-resolution chronology to a new composite sediment profile from Holzmaar (West Eifel Volcanic Field, Germany)

This study gives an overview of different methods to integrate information from a varve chronology and radiometric measurements in the Bayesian tool Bacon. These techniques will become important for the future as technologies evolve with more sites being revisited for the application of new and high-resolution scanning methods. Thus, the transfer of existing chronologies will become necessary because the recounting of varves will be too time consuming and expensive to be funded. We introduce new sediment cores from Holzmaar (West Eifel Volcanic Field, Germany), a volcanic maar lake with a well-studied varve record. Four different age–depth models have been calculated for the new composite sediment profile (HZM19) using Bayesian modelling with Bacon. All models incorporate new Pb-210 and Cs-137 dates for the top of the record, the latest calibration curve (IntCal20) for radiocarbon ages as well as the new age estimation for the Laacher See Tephra. Model A is based on previously published radiocarbon measurements only, while Models B–D integrate the previously published varve chronology (VT-99) with different approaches. Model B rests upon radiocarbon data, while parameter settings are obtained from sedimentation rates derived from VT-99. Model C is based on radiocarbon dates and on VT-99 as several normal distributed tie points, while Model D is segmented into four sections: sections 1 and 3 are based on VT-99 only, whereas sections 2 and 4 rely on Bacon age–depth models including additional information from VT-99. In terms of accuracy, the parameter-based integration Model B shows little improvement over the non-integrated approach, whereas the tie-point-based integration Model C reflects the complex accumulation history of Holzmaar much better. Only the segmented and parameter-based age integration approach of Model D adapts and improves VT-99 by replacing sections of higher counting errors with Bayesian modelling of radiocarbon ages and thus efficiently makes available the best possible and most precise age–depth model for HZM19. This approach will value all ongoing high-resolution investigations for a better understanding of decadal-scale Holocene environmental and climatic variations.</p

Time Domain Characterization of Light Trapping States in Thin Film Solar Cells

Spectral interferometry of the backscattered radiation reveals coherence lifetimes of about 150 fs for nanolocalized electromagnetic modes in textured layered nanostructures as they are commonly used in thin film photovoltaics to achieve high cell efficiencies

Early human impact in the Azores Archipelago: A Late Holocene high-resolution paleoecological analysis from Lake Peixinho, Pico Island, Portugal

Human arrival on oceanic islands causes large-scale habitat alterations and extinctions of local flora and fauna. Understanding the processes of how humans transformed island environments soon after colonization is critical to current conservation and restoration strategies. Only a few islands worldwide provide the opportunity to examine island colonization within a period of recorded history. Such islands enable us to calibrate paleoecological methods and perform comparative analyses with other locales. According to the written sources, the Portuguese officially colonized the Azores Archipelago in the North Atlantic Ocean in the 15th century providing a well-documented history of human impact. Paleoecological reconstructions from the Azores thus allow us to compare ecosystem processes and dynamics before and after colonization. A high-resolution pollen record from Lake Peixinho (Pico Island) provides novel insights into early human impacts in the Azores from the 13th century – two centuries prior to the official historical colonization of the archipelago. In addition, the record highlights the role of tephra sedimentation from proximal volcanic eruptions as natural driver of ecosystem dynamics. We compared palynological results to diatom, chironomid, Cladocera and geochemical records from the same lake, as well as other sedimentary records from Pico Island and existing pollen records from other Azorean islands. Ongoing analyses of paleoecological records from other islands in the Azorean Archipelago (Corvo, Flores, Sao Miguel, and Terceira) will help pinpoint the timing and impact of human colonization in the Azores.This research is funded by the Juan de la Ciervaformacion postdoctoral grant (FJCI-2015-26199), the Fundacao LUSO-Americana, and through the Spanish funded research projects PaleoNAO (CGL2010-15767), RapidNAO (CGL2013- 40608-R) and PaleoModes (CGL2016-75281-C2).Peer Reviewe

The North Atlantic Oscillation in the Azores archipelago: a Holocene high-resolution and multiproxy limnological approach. Comunicación en panel.

The two main centers of action associated with North Atlantic Oscillation (NAO) climate variability occur over the Azores archipelago (high) and Iceland (low), respectively. In this context, high-resolution multiproxy haracterization of lacustrine sedimentary records can provide useful insights into the NAO evolution at ifferent temporal scales throughout the Holocene. While the Icelandic Low is relatively stable the oscillatory behavior of Azores High is relatively large and, consequently, this displacement tends to define the NAO state and impacts through time. Other atmospheric and oceanic variability modes like the East Atlantic and Scandinavian patterns, and the Atlantic Multidecadal Oscillation, also play a significant role in climate fluctuations of the european North Atlantic region. The coupling and uncoupling of these atmospheric and oceanic modes have shaped the climate variability of Southern Europe for the last 2,000 years (Sánchez-López et al., 2016 QSR, 149: 135¿150), however, little is known beyond the Common Era. In order to capture the mid-to-late Holocene evolution of the NAO southern center of action and its potential interactions with other climate modes, we have recovered sediments from lakes over a large transect that spans four of the nine Azorean islands: Lagoa Caldeirão (Corvo), Lagoas Funda, Lomba, and Negra (Flores), Lagoas Caveiro and Peixinho (Pico), and Lagoas Azul and Empadadas (São Miguel). We present preliminary results from high-resolution multiproxy haracterizations of these lacustrine sequences. These results suggest complex non-stationary interlinkages between the NAO and other atmospheric and oceanic climate modes on different time-scales, likely reflecting the spatial and temporal displacements of their centers of action. To fully document spatial and temporal shifts throughout the Holocene, it is crucial to study the southern NAO center of action using multiple paleo-records from this area. This research is funded through the PaleoNAO (CGL2010-15767), RapidNAO (CGL2013-40608-R) and PaleoModes (CGL2016-75281-C2) Spanish projects, and the Fundacao USO -AmericanaThis research is funded through the PaleoNAO (CGL2010-15767), RapidNAO (CGL2013-40608-R) and PaleoModes (CGL2016-75281-C2) Spanish projects, and the Fundacao USO -AmericanaPeer Reviewe