L. Wacker

L. Wacker
ETH Zurich | ETH Zürich · Department of Physics

About

441
Publications
146,508
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
22,910
Citations
Additional affiliations
February 2003 - present
ETH Zurich
Position
  • Senior Researcher

Publications

Publications (441)
Preprint
Full-text available
A radiochemical method for the isolation of plutonium isotopes from environmental samples, based on the use of specific chromatography resins for actinides (TEVA, Eichrom Industries), has been set up in our laboratory and optimised for their posterior determination by alpha spectrometry (AS) or accelerator mass spectrometry (AMS). The proposed radi...
Article
Full-text available
Radiocarbon ( ¹⁴ C) measurements on dissolved inorganic carbon (DIC) are a powerful tool to trace water masses and carbon cycling in the ocean. Existing methodologies to determine the ¹⁴ C content of seawater DIC requires large volumes of sample (usually >100 mL) and specialized graphitization techniques to achieve the accuracy and precision needed...
Article
Full-text available
Radiocarbon (¹⁴C) is an optimal tracer of methane emissions, as ¹⁴C measurements enable distinguishing between fossil methane and biogenic methane (CH4). However, ¹⁴C measurements in atmospheric methane are still rare, mainly because of the technical challenge of collecting enough carbon for ¹⁴C analysis from ambient air samples. In this study, we...
Article
Full-text available
The Sun drives Earth’s energy systems, influencing weather, ocean currents, and agricultural productivity. Understanding solar variability is critical, but direct observations are limited to 400 years of sunspot records. To extend this timeline, cosmic ray-produced radionuclides like ¹⁴C in tree-rings provide invaluable insights. However, few recor...
Article
Full-text available
Plain Language Summary Mineral protection of organic carbon (OC) by reactive metal (mainly iron and aluminum) (hydr) oxides is one of the key mechanisms promoting the long‐term stabilization of soil organic carbon (SOC). However, the sources and turnover of (metal‐) bound OC in natural soils remain poorly constrained, hampering our understanding of...
Article
Full-text available
Mollusk shells are often found in archeological sites, given their great preservation potential and high value as a multipurpose resource, and they can often be the only available materials useful for radiocarbon ( ¹⁴ C) dating. However, dates obtained from shells are often regarded as less reliable compared to those from bones, wood, or charcoals...
Article
Full-text available
This study suggests that there may be considerable difficulties in providing accurate calendar age estimates in the Roman period in Europe, between ca. AD 60 and ca. AD 230, using the radiocarbon calibration datasets that are currently available. Incorporating the potential for systematic offsets between the measured data and the calibration curve...
Article
Full-text available
We report 27 planktonic and 21 benthic radiocarbon ages from the subtropical marine sediment core ODP Site 1063 (Bermuda Rise) for the time range between 30 and 14 ka before present. Despite low abundances of benthic specimens, it was possible to measure radiocarbon ages down to ∼10 µg carbon using a MICADAS and the gas ion source developed at ETH...
Article
In 2015, a new accelerator mass spectrometry facility (AMS), the ECHoMICADAS (Environnement, Climat, Homme, MIni CArbon DAting System), was installed in the Laboratoire des Sciences du Climat et de l’Environnement (LSCE). Equipped with a hybrid source, it allows the analysis of solid or gas samples for ¹⁴ C measurement. Here, we summarize the equip...
Article
Full-text available
Cellulose of tree rings is often assumed to be predominantly formed by direct assimilation of CO 2 by photosynthesis and consequently can be used to reconstruct past atmospheric ¹⁴ C concentrations at annual resolution. Yet little is known about the extent and the age of stored carbon from previous years used in addition to the direct assimilation...
Technical Report
Full-text available
Four groups of worked wood exposed at –1.61mOD by aggressive tidal scour on the open foreshore at Point Clear on the River Colne, Essex were surveyed and sampled by CITiZAN and local volunteers. Radiocarbon dating and chronological modelling estimates that the three dated features groups (1–3) were constructed in the second half of the sixth centur...
Preprint
Full-text available
Radiocarbon (14C) is an optimal tracer of methane emissions, as 14C measurements enable distinguishing fossil from biogenic methane (CH4). However, 14C measurements in atmospheric methane are still rare, mainly because of the technical challenge of collecting enough carbon for 14C analysis from ambient air samples. In this study we address this cha...
Article
Full-text available
Abrupt radiocarbon (¹⁴C) excursions, or Miyake events, in sequences of radiocarbon measurements from calendar-dated tree-rings provide opportunities to assign absolute calendar dates to undated wood samples from contexts across history and prehistory. Here, we report a tree-ring and ¹⁴C-dating study of the Neolithic site of Dispilio, Northern Greec...
Technical Report
Full-text available
The Must Farm pile-dwelling site is an extraordinarily well-preserved Late Bronze Age settlement in Cambridgeshire built over a freshwater palaeochannel that was destroyed by a catastrophic fire shortly after its construction. Predating the settlement was a double-alignment of massive oak piles. This technical archive report on the tree-ring and ra...
Article
Full-text available
Plain Language Summary Strong Earth‐directed solar eruptions can cause ¹⁴C concentration spikes in the atmosphere. Large enough events may leave a signal in the annually grown tree‐rings as they capture the isotopic carbon fingerprint through photosynthesis. Such rapid ¹⁴C increases have been detected, for instance, starting in years 774 and 993 CE...
Article
Full-text available
Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear when this phase of significant melting initiated. We analyzed the marine sedimentary record to reco...
Article
Full-text available
Placing the origin of an undeciphered script in time is crucial to understanding the invention of writing in human history. Rapa Nui, also known as Easter Island, developed a script, now engraved on fewer than 30 wooden objects, which is still undeciphered. Its origins are also obscure. Central to this issue is whether the script was invented befor...
Article
Full-text available
A better understanding of past extent and dynamics of the Greenland Ice Sheet (GrIS) is required to provide context for present-day observations, to constrain numerical climate models and to predict future scenarios of ice-sheet response to recent climatic change. The presence of a grounded GrIS on the NE Greenland shelf during the Last Glacial Max...
Article
Full-text available
The Middle to Upper Palaeolithic transition in Europe is associated with the regional disappearance of Neanderthals and the spread of Homo sapiens. Late Neanderthals persisted in western Europe several millennia after the occurrence of H. sapiens in eastern Europe¹. Local hybridization between the two groups occurred², but not on all occasions³. Ar...
Technical Report
Full-text available
Radiocarbon wiggle-matching of undated site chronology KNWCSQ08 suggests its final ring formed in cal AD 1553–1573 (95% probability) probably in cal AD 1557–1565 (68% probability), with the timber having an estimated felling date in the range cal AD 1567–1605 (95% probability) probably cal AD 1573–1591 (68% probability). Other timbers used in the G...
Article
Full-text available
Tree-ring chronologies form the backbone of high-resolution palaeoclimatology. However, their number declines drastically prior to medieval times, and only a few such records worldwide extend back to the mid-Holocene. Here, we present a collection of more than 400 subfossil yew (Taxus baccata L.) trees excavated from near sea-level peat-rich sedime...
Article
Full-text available
Cosmogenic nuclides—14C from tree rings and 10Be & 36Cl from ice cores serve as an effective proxy for past extreme solar energetic particle (SEP) events. After identifying the first signature of an extreme SEP event in 774 CE, several candidates have been found in these proxy archives, such as 993 CE, 660 BCE, and 7176 BCE. Their magnitudes have b...
Article
Full-text available
While simultaneous radiocarbon and δ ¹³ C measurements have been available for organic materials (by accelerator mass spectrometry, AMS, and isotope ratio mass spectrometry, IRMS, respectively), this has not been possible for carbonates until now. Using an existing interface for gas ion source AMS measurements, we developed a prototype for a univer...
Article
Full-text available
CH 4 is the second most important anthropogenic greenhouse gas and originates from different sources. The use of radiocarbon ( ¹⁴ C) analysis of CH 4 opens up the possibility to differentiate geological and agricultural origin. At the CologneAMS facility, the demand for ¹⁴ C analysis of CH 4 required the development of a sample handling routine and...
Article
Full-text available
The Sun is magnetically active and often produces eruptive events on different energetic and temporal scales. Until recently, the upper limit of such events was unknown and be- lieved to be roughly represented by direct instrumental observations. However, two types of extreme events were discovered recently: extreme solar energetic particle events...
Article
Full-text available
Radiocarbon (¹⁴C) is a critical tool for understanding the global carbon cycle. During the Anthropocene, two new processes influenced ¹⁴C in atmospheric, land and ocean carbon reservoirs. First, ¹⁴C-free carbon derived from fossil fuel burning has diluted ¹⁴C, at rates that have accelerated with time. Second, ‘bomb’ ¹⁴C produced by atmospheric nucl...
Preprint
Full-text available
The discovery of abrupt radiocarbon ( ¹⁴ C) excursions (Solar Energetic Particle events, or Miyake events) in sequences of radiocarbon measurements from calendar dated tree-rings, has yielded new opportunities to assign absolute, calendar dates to undated wood samples from widely ranging contexts in history and prehistory. We report on an important...
Article
Full-text available
A newly developed compact AMS, LEA (Low Energy Accelerator), is tested and compared with a state-of-the-art AMS system MICADAS (Mini Carbon Dating System), which has a precision performance of better than 1‰ for modern ¹⁴ C. The main difference between these two systems is the acceleration voltage, which has been reduced from 200 kV with the MICADA...
Article
Full-text available
The IntCal family of radiocarbon ( ¹⁴ C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the ¹⁴ C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access dat...
Article
Full-text available
Nowadays, most radiocarbon ( ¹⁴ C) laboratories can reliably avoid and remove any possible sample contamination during the pretreatment of organic samples (e.g., bones, charcoal, or trees) thanks to a series of methods commonly used by the radiocarbon community. However, what about the final step, the storage of graphite? Rarely do the laboratories...
Article
Full-text available
Radiocarbon dating provides a key chronological framework for studying past environmental changes. Raw radiocarbon ages measured in samples must be converted to calendar ages using an appropriate calibration curve. Tree-ring datasets provide the gold-standard for developing a precise curve of atmospheric radiocarbon levels over long-time scales. He...
Technical Report
Full-text available
Independent validation of tentative tree-ring dating for a previously undated site chronology, BEVFSQ02, from Monks Walk, Beverley, East Riding of Yorkshire, has been obtained by radiocarbon wiggle-matching and it can now be considered as a radiocarbon-supported dendrochronological date, that spans AD 1142–1300DR. The three-bay front range to Monks...
Article
Full-text available
A high-resolution multiproxy lake sediment dataset, comprising lithology, radiography, μXRF elemental, magnetic susceptibility (MS), δ ¹³ C, and δ ¹⁸ O measurements since ca. AD 400 is presented in this study. Changes in lithology, radiography, magnetic susceptibility (MS), δ ¹³ C, and δ ¹⁸ O reflect wet/dry climate periods, whereas variability in...
Article
Full-text available
To provide insights into glacier-climate dynamics of the South Shetland Islands (SSI), NW Antarctic Peninsula, we present a new deglaciation and readvance model for the Bellingshausen Ice Cap (BIC) on Fildes Peninsula and for King George Island/Isla 25 de Mayo (KGI) ~62°S. Deglaciation on KGI began after c. 15 cal. ka BP and had progressed to withi...
Article
Full-text available
Climate projection requires an accurate understanding for soil organic carbon (SOC) decomposition and its response to warming. An emergent view considers that environmental constraints rather than chemical structure alone control SOC turnover and its temperature sensitivity (i.e., Q10 ), but direct long-term evidence is lacking. Here, using compoun...
Article
Full-text available
Radiocarbon observations (Δ14C) in dissolved inorganic carbon (DIC) of seawater provide useful information about ocean carbon cycling and ocean circulation. To deliver high-quality observations, the Laboratory of Ion Beam Physics (LIP) at ETH-Zurich developed a new simplified method allowing the rapid analysis of radiocarbon in DIC of small seawate...
Article
Full-text available
Radiocarbon dating is the most widely applied dating method in archaeology, especially in human evolution studies, where it is used to determine the chronology of key events, such as the replacement of Neanderthals by modern humans in Europe. However, the method does not always provide precise and accurate enough ages to understand the important pr...
Article
Full-text available
The timing and impact of deglaciation and Holocene readvances on the terrestrial continental margins of the Antarctic Peninsula (AP) have been well-studied but are still debated. Potter Peninsula on King George Island (KGI) (Isla 25 de Mayo), South Shetland Islands (SSI), NW Antarctic Peninsula, has a detailed assemblage of glacial landforms and st...
Book
Full-text available
Summary: When a Middle Neolithic site was found on the shallow of Cham-Eslen in Lake Zug in 1996, this opened up a new perspective with regards to underwater archaeology for the Canton of Zug. This was for two main reasons: firstly, the conservation of the finds was relatively good and, secondly, they were, at the time, the Canton’s oldest finds a...
Preprint
Full-text available
Thermokarst lakes are important conduits for organic carbon (OC) sequestration, soil organic matter (SOM) processing and atmospheric greenhouse gas (GHG) release in the Arctic. They can be classified as either floating-ice lakes, which sustain a zone of unfrozen sediment (talik) at the lakebed year-round, or as bedfast-ice lakes, which freeze all t...
Preprint
Full-text available
The timing and impact of deglaciation and Holocene readvances on many ice-free terrestrial continental margins of the Antarctic Peninsula have been long-studied but remain debated. Potter Peninsula on King George Island (Isla 25 de Mayo), South Shetland Islands (SSI), NW Antarctic Peninsula has a detailed assemblage of glacial landforms, geomorphol...
Preprint
Full-text available
The timing of mid–late Holocene deglaciation and glacier readvances on the South Shetland Islands, northern Antarctic Peninsula has been long debated. We used a combined geomorphological, chronological, and palaeolimnological approach to develop a new readvance model for the Bellingshausen Ice Cap (BIC) on the Fildes Peninsula, King George Island/I...
Technical Report
Full-text available
Radiocarbon wiggle-matching of undated ring-width site chronology HEDMSQ02 from Headstone Manor, Pinner View, Harrow, London suggests its final ring formed in cal AD 1630-1650 (95% probability), probably in cal AD 1634-1645 (68% probability). Its timbers are likely to represent two phases of felling; the first with an estimated felling date in the...
Article
Full-text available
The melting of marine terminating glaciers in Northeast Greenland is a visible sign that our climate is changing. This melt has been partly attributed to changes in oceanic heat fluxes, particularly warming of Atlantic Water (AW). Yet our understanding of the interaction between glaciers and the ocean is limited by the length of instrumental record...
Article
Constraining the origins, transport history, and burial efficiency of terrestrial organic carbon (OCterr) accumulating in marine sediments is of fundamental importance for understanding the carbon cycle on a range of spatial and temporal scales. While there is abundant evidence that OC composition and age influences the sequestration of OCterr in s...
Article
Full-text available
Subglacial meltwater drainage can enhance localized melting along grounding zones and beneath the ice shelves of marine-terminating glaciers. Efforts to constrain the evolution of subglacial hydrology and the resulting influence on ice stability in space and on decadal to millennial timescales are lacking. Here, we apply sedimentological, geochemic...
Article
Full-text available
The term ‘Little Ice Age’ (LIA) is classically used to define a period of repeated and extensive glacier advances during the last millennium. In the meanwhile, this term is also used to address the period of relatively low temperatures between the Medieval Climate Anomaly (MCA), or Medieval Warm Period, and present-day warming. The end of the LIA i...
Technical Report
Full-text available
Radiocarbon wiggle-matching of three undated ring-width site chronologies, STHASQ01, STHASQ02, and STHASQ03, from Southall Manor House, London, suggests their final rings formed in cal AD 1606-1633 (95% probability), probably in cal AD 1614-1628 (68% probability); cal AD 1602-1620 (95% probability), probably in cal AD 1604-1613 (68% probability), a...
Article
Full-text available
The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produ...
Article
Plasma oxidation for ¹⁴ C sampling utilizes low-pressure (133 Pa), low-energy (<50 W), and low- temperature (<50°C) Ar- and O 2 -plasmas generating CO 2 for AMS dating. O 2 -plasmas on empty chambers remove organic contamination. When clean, a new specimen is inserted and Ar-plasmas dislodge adsorbed atmospheric CO 2 from surfaces. Finally, O 2 -pl...
Article
Full-text available
During solar storms, the Sun expels large amounts of energetic particles (SEP) that can react with the Earth’s atmospheric constituents and produce cosmogenic radionuclides such as ¹⁴C, ¹⁰Be and ³⁶Cl. Here we present ¹⁰Be and ³⁶Cl data measured in ice cores from Greenland and Antarctica. The data consistently show one of the largest ¹⁰Be and ³⁶Cl p...
Article
An early 1980s University of Texas (UT) radiocarbon (¹⁴C) decay-based assay of colon contents from mummy SMM recovered from southwest Texas (41VV656) placed the death at 1150 ± 70 ¹⁴C years ago. This mummy of a “relatively tall, gracile adult male” was discussed in some detail in a comprehensive paper on Late Archaic mortuary practices in the Lower...
Article
Using carbon-14 Carbon-14 or radiocarbon, a radioactive isotope produced in the upper atmosphere by cosmic rays, is rapidly incorporated into the terrestrial carbon cycle and provides a way to calculate the age of carbon-bearing materials as old as 55,000 years. Heaton et al . review recent progress that has allowed the construction of better radio...
Article
Full-text available
Rapid and continuous analysis of radiocarbon (14C) concentration in carbonate samples at spatial resolution down to 100 µm has been made possible with the new LA-AMS (laser ablation accelerator mass spectrometry) technique. This novel approach can provide radiocarbon data at a spatial resolution similar to that of stable carbon (C) isotope measurem...
Article
Full-text available
Radiocarbon dating of Arctic marine sediment is often challenging due to the low availability of calcareous fossils. Consequently, bulk organic matter dating has at times been used to establish sediment core chronologies. Yet, radiocarbon dates based on bulk organic matter often appear to deviate vastly from dates based on fossils, mainly caused by...