L. Wacker

ETH Zurich | ETH Zürich · Department of Physics

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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 are 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 produced me...

The Laacher See eruption (LSE) in Germany ranks among Europe’s largest volcanic events of the Upper Pleistocene1,2. Although tephra deposits of the LSE represent an important isochron for the synchronization of proxy archives at the Late Glacial to Early Holocene transition³, uncertainty in the age of the eruption has prevailed⁴. Here we present de...

The African baobab, Adansonia digitata L., has great paleoclimatological potential because of its wide distributional range and millennial length life span. However, dendroclimatological approaches are hampered by dating uncertainties due to its unique, parenchyma-dominated stem anatomy. Here, securely dated time series of annual wood increment gro...

The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and ∼660 BCE. Here, we report another rapid increase of 14C concentration in tree rings from California, Switzerland, and Finland around 54...

Burial of terrestrial organic carbon (OCterr) in marginal sea sediments is a key component of the carbon cycle, exerting long-term influence on atmospheric CO2 and climate. Assessment of the burial efficiency of OCterr is of key importance, yet remains poorly constrained due to current gaps in our knowledge of mechanistic controls, including the in...

Baffin Bay hosts the largest and most productive of the Arctic polynyas: the North Water (NOW). Despite its significance and active role in water mass formation, the history of the NOW beyond the observational era remains poorly known. We reconcile the previously unassessed relationship between long-term NOW dynamics and ocean conditions by applyin...

The Chronos ¹⁴ Carbon-Cycle Facility is a new radiocarbon laboratory at the University of New South Wales, Australia. Built around an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) installed in October 2019, the facility was established to address major challenges in the Earth, Environmental and Archaeologica...

Although Accelerator Mass Spectrometry (AMS) offers unparalleled sensitivity by investigating the fate of ¹⁴C-labeled compounds within the organism, its widespread use in ADME (absorption, distribution, metabolism, excretion) studies is limited. Conventional approaches based on Liquid Scintillation Counting (LSC) are still preferred, in particular...

Because ice shelves respond to climatic forcing over a range of time scales, from years to millennia, an understanding of their long-term history is critically needed for predicting their future evolution. We present the first detailed reconstruction of the Larsen C Ice Shelf (LCIS), eastern Antarctic Peninsula (AP), based on data from sediment cor...

Northern and southern hemispheric influences—particularly changes in Southern Hemisphere westerly winds (SSW) and Southern Ocean ventilation—triggered the stepwise atmospheric CO 2 increase that accompanied the last deglaciation. One approach for gaining potential insights into past changes in SWW/CO 2 upwelling is to reconstruct the positions of t...

Thermokarst lakes play an important role in permafrost environments by warming and insulating the underlying permafrost. As a result, thaw bulbs of unfrozen ground (taliks) are formed. Since these taliks remain perennially thawed, they are zones of increased degradation where microbial activity and geochemical processes can lead to increased greenh...

Aims. The 11-year solar cycle (Schwabe cycle) is the dominant pattern of solar magnetic activity reflecting the oscillatory dynamo mechanism in the Sun’s convection zone. Solar cycles have been directly observed since 1700, while indirect proxy data suggest their existence over a much longer period of time, but generally without resolving individua...

The 11-year solar cycle is the dominant pattern of solar activity reflecting the oscillatory dynamo mechanism in the Sun. Solar cycles were directly observed since 1700, while indirect proxies suggest their existence over a much longer period of time but generally without resolving individual cycles and their continuity. Here we reconstruct individ...

A coupled accelerator mass spectrometer–gas interface system has been successfully operating at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary, since 2013. Over the last 6 years more than 500 gas targets were measured below 100 µg carbon content for carbon isotopic composition. The system was tested with blanks, OxII, IAEA-C1...

Significance Terrestrial organic-carbon reservoirs (vegetation, soils) currently consume more than a third of anthropogenic carbon emitted to the atmosphere, but the response of this “terrestrial sink” to future climate change is widely debated. Rivers export organic carbon sourced over their watersheds, offering an opportunity to assess controls o...

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-21647-w

E xcursions in the carbon-14 (14 C) record measured in tree rings are attributed to various high energy but short-lived cosmic effects 1-7. Wang et al. 8 proposed a new event at 3372-3371 BCE based on a single set of annual 14 C data measured on a floating tree rings from a buried specimen of Chinese wingnut (Pterocarya stenoptera). Here we attempt...

The Sun provides the principal energy input into the Earth system and solar variability represents a significant external climate forcing. Although observations of solar activity (sunspots) cover only the last about 400 years, radionuclides produced by cosmic rays and stored in tree rings or ice cores serve as proxies for solar activity extending b...

Thermokarst lakes play an important role in permafrost environments by warming up and insulating the underlying permafrost. As a result, thaw bulbs of unfrozen ground (taliks) are formed. Since these taliks remain perennially thawed, they are zones of increased degradation where microbial activity and geochemical processes can lead to increased gre...

This paper presents an age–depth model based on an ultra‐high‐resolution, 80‐m‐thick sedimentary succession from a marine continental shelf basin, the Kattegat. This is an area of dynamic deglaciation of the Fennoscandian Ice Sheet during the Late Pleistocene. The Kattegat is also a transitional area between the saline North Sea and the brackish Ba...

The Quaternary is well known for being a period of the geological record that saw significant and alternating climatic fluctuations. Here, we concentrate on the last 94 millennia that saw Australia and its surrounding seas undergo significant environmental changes. Importantly also it is during that this period of time includes the arrival and sett...

Many studies have investigated the role of solar variability in Holocene climate. Beyond sunspot observations, solar activity can be reconstructed from 14 C in tree rings. Due to the lack of sub-decadal resolution of 14 C records, these studies focused on long-term processes. In this study, we use an annually-resolved 14 C record to examine solar v...

In Antarctic and Subantarctic environments, ¹⁴C‐based age determination is often challenging due to unknown reservoir effects, low organic carbon contents of sediments, and high contributions of petrogenic (¹⁴C‐free) carbon in ice marginal settings. In this study, we evaluate possible benefits and challenges of compound‐specific radiocarbon analysi...