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
C,
Be and
Cl. Here ...we present
Be and
Cl data measured in ice cores from Greenland and Antarctica. The data consistently show one of the largest
Be and
Cl production peaks detected so far, most likely produced by an extreme SEP event that hit Earth 9125 years BP (before present, i.e., before 1950 CE), i.e., 7176 BCE. Using the
Cl/
Be ratio, we demonstrate that this event was characterized by a very hard energy spectrum and was possibly up to two orders of magnitude larger than any SEP event during the instrumental period. Furthermore, we provide
Be-based evidence that, contrary to expectations, the SEP event occurred near a solar minimum.
•Review on technical developments in AMS over the past 35 years.•Basic principles of AMS technology.•State-of-the-art AMS instrumentation.•Latest developments in AMS.
This report attempts to ...summarize the technical evolution of accelerator mass spectrometry (AMS) instrumentation over the last thirty-five years. The related impact of the AMS measurement technology to the wide variety of applications of long-lived radionuclides in modern research is not covered. The accompanying article by W. Kutschera overviews these applications. Here, I am providing an introduction to the basics principles of AMS measurement technology, describe the set-up of a typical AMS instrument, and discuss in general specific requirements to reach sensitivity as it is required to measure long-lived radionuclides at their natural levels in the environment. A retrospective view is given on the major development steps of AMS instruments and measurement technique. Special attention is paid to the simplification of AMS systems by reducing their size and complexity. These developments have launched the wide spread use of AMS in modern research fields. Today, commercially available high-performance instruments are standard for more than 100 AMS facilities around the World. There are a number of primary important radionuclides in focus of AMS measurement procedures but radiocarbon is still of paramount importance. Consequently, I will summarize the latest developments in radiocarbon AMS.
MICADAS: A new compact radiocarbon AMS system Synal, Hans-Arno; Stocker, Martin; Suter, Martin
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
June 2007, 2007-06-00, Letnik:
259, Številka:
1
Journal Article
Recenzirano
A novel tabletop AMS system with overall dimensions of only 2.5×3m2 has been built and tested. The mini radiocarbon dating System (MICADAS) is based on a vacuum insulated acceleration unit that uses ...a commercially available 200kV power supply to generate acceleration fields in a tandem configuration. At the high-energy end, ions in charge state 1+ are selected and interfering molecules of mass 14 amu are destroyed in multiple collisions. The new system is now fully operational. It is the prototype of a new generation of radiocarbon spectrometers which fulfill the requirements for radiocarbon dating applications as well as for the less demanding 14C/12C isotopic ratio measurements as needed, e.g. in biomedical applications. A detailed description of the system is given and results of performance tests are discussed.
Within the project AEROWOOD (Aerosols from wood burning versus other sources), particulate matter was collected at two Swiss Alpine valleys during winter. Apportionment of aerosols from transit ...traffic and residential wood burning was performed using radiocarbon (14C) determinations of the organic carbon (OC) and elemental carbon (EC) fractions. On daily average, 88% and 65% of the total carbonaceous matter (including all other atoms than carbon) originated from non‐fossil sources inside and outside of the village, respectively, which is mainly attributed to wood burning. These proportions were generally higher during the evening compared to morning hours, when traffic intensity waned and heating activities increased. 14C measurements of EC indicated episodes of both nearly pure traffic and wood‐burning sources, respectively, of which the latter extreme has not been observed for EC under ambient conditions before. Results show that regulatory measures for the improvement of air quality must consider residential wood burning as an important source even in industrialized countries.
The origin of two large peaks in the atmospheric radiocarbon (14 C) concentration at AD 774/5 and 993/4 is still debated. There is consensus, however, that these features can only be explained by an ...increase in the atmospheric 14 C production rate due to an extraterrestrial event. Here we provide evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved 10 Be measurements from both Arctic and Antarctic ice cores. Using ice core 36 Cl data in pair with 10 Be, we further show that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100 MeV. These results imply that the larger of the two events (AD 774/5) was at least five times stronger than any instrumentally recorded solar event. Our findings highlight the importance of studying the possibility of severe solar energetic particle events.
Recently, it has been confirmed that extreme solar proton events can lead to significantly increased atmospheric production rates of cosmogenic radionuclides. Evidence of such events is recorded in ...annually resolved natural archives, such as tree rings carbon-14 (14C) and ice cores beryllium-10 (10Be), chlorine-36 (36Cl). Here, we show evidence for an extreme solar event around 2,610 years B.P. (∼660 BC) based on high-resolution 10Be data from two Greenland ice cores. Our conclusions are supported by modeled 14C production rates for the same period. Using existing 36Cl ice core data in conjunction with 10Be, we further show that this solar event was characterized by a very hard energy spectrum. These results indicate that the 2,610-years B.P. event was an order of magnitude stronger than any solar event recorded during the instrumental period and comparable with the solar proton event of AD 774/775, the largest solar event known to date. The results illustrate the importance of multiple ice core radionuclide measurements for the reliable identification of short-term production rate increases and the assessment of their origins.
We present a new glacier chronology from one of the major end moraine systems of the Southern Alps. Timing and extent of the Last Glacial Maximum (LGM) advance of the Ticino-Toce glacier were ...reconstructed in detail based on landform relationships and surface exposure dating. 10Be and 36Cl ages from 41 erratic boulders constrain the last maximum of the Ticino-Toce glacier to have lasted from 25.0 ± 0.9 ka to 19.9 ± 0.7 ka. Over this period of ca. 5000 years the Ticino-Toce glacier underwent only minor oscillations, during which the glacier front remained close to its LGM maximum position. Underpinned by our detailed geomorphological reconstruction, the ages further demonstrate that the Verbano piedmont lobe was significantly larger (about 200 km2) than shown on recent maps. A short-lived glacier readvance around 19.7 ± 1.1 ka terminated internal to the LGM maximum margins. Collapse of the Verbano lobe must have set in soon after and final withdrawal from the foreland occurred no later than 19 ka. The new Ticino-Toce chronology matches temporal constraints of major glacier systems emerging from adjacent Alpine accumulation areas. This points to in-phase glacier advances across the Western Alps, apart from the southwestern massifs for which a slightly earlier reaching of the Late Pleistocene maximum position of the Lyon lobe was shown recently. A two- potentially three-fold LGM advance structure with intervening retreat intervals, as reported for two major amphitheatres (Garda, Tagliamento) to the east is distinctly not supported by our data for the Ticino-Toce glacier. This contrast in glacier behaviour between the central and eastern Southern Alps is ascribed to shifting precipitation patterns after ca. 23–22 ka, away from southern to predominantly northwestern air flow and a greater independence of southerly moisture transport for the central Southern Alps.
•Last Glacial Maximum of Ticino-Toce glacier was ∼200 km2 larger than thought.•From ∼25 to 19.9 ka Ticino-Toce glacier oscillated close to its maximum position.•A glacier readvance around 19.7 ± 1.1 ka was short-lived.•Ticino-Toce glacier was in phase with other glacier systems of the Western Alps.•Central southern Alpine glaciers may have been less dependent on southerly moisture.
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