| 1. |
- Czymzik, Markus, et al.
(författare)
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Synchronizing 10Be in two varved lake sediment records to IntCal13 14C during three grand solar minima
- 2018
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 14:5, s. 687-696
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Tidskriftsartikel (refereegranskat)abstract
- Timescale uncertainties between paleoclimate reconstructions often inhibit studying the exact timing, spatial expression and driving mechanisms of climate variations. Detecting and aligning the globally common cosmogenic radionuclide production signal via a curve fitting method provides a tool for the quasi-continuous synchronization of paleoclimate archives. In this study, we apply this approach to synchronize Be-10 records from varved sediments of Tiefer See and Lake Czechowskie covering the Maunder, Homeric and 5500 a BP grand solar minima with C-14 production rates inferred from the IntCal13 calibration curve. Our analyses indicate best fits with C-14 production rates when the Be-10 records from Tiefer See were shifted for 8 (-12/+4) (Maunder Minimum), 31 (-16/+12) (Homeric Minimum) and 86 (-22/+18) years (5500 a BP grand solar minimum) towards the past. The best fit between the Lake Czechowskie Be-10 record for the 5500 a BP grand solar minimum and C-14 production was obtained when the Be-10 time series was shifted 29 (-8/+7) years towards present. No significant fits were detected between the Lake Czechowskie Be-10 records for the Maunder and Homeric minima and C-14 production, likely due to intensified in-lake sediment resuspension since about 2800 a BP, transporting "old" Be-10 to the coring location. Our results provide a proof of concept for facilitating Be-10 in varved lake sediments as a novel synchronization tool required for investigating leads and lags of proxy responses to climate variability. However, they also point to some limitations of Be-10 in these archives, mainly connected to in-lake sediment resuspension processes.
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| 2. |
- Brehm, Nicolas, et al.
(författare)
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Tree-rings reveal two strong solar proton events in 7176 and 5259 BCE
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- 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 produced measurable signals in cosmogenic radionuclides such as 14C, 10Be and 36Cl have been found. Analyzing annual 14C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric 14C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric 14C recorded for both events exceed all previously known 14C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.
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| 3. |
- Czymzik, Markus, et al.
(författare)
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A varved lake sediment record of the Be-10 solar activity proxy for the Lateglacial-Holocene transition
- 2016
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 153, s. 31-39
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Tidskriftsartikel (refereegranskat)abstract
- Solar modulated variations in cosmogenic radionuclide production provide both information on past changes in the activity of the Sun and a global synchronization tool. However, to date the use of cosmogenic radionuclides for these applications is almost exclusively based on Be-10 records from ice cores and C-14 time-series from tree rings, all including archive-specific limitations. We present the first Be-10 record from annually laminated (varved) lake sediments for the Lateglacial-Holocene transition from Meerfelder Maar. We quantify environmental influences on the catchment and, consequently, Be-10 deposition using a new approach based on regression analyses between our Be-10 record and environmental proxy time-series from the same archive. Our analyses suggest that environmental influences contribute to up to 37% of the variability in our Be-10 record, but cannot be the main explanation for major Be-10 excursions. Corrected for these environmental influences, our Be-10 record is interpreted to dominantly reflect changes in solar modulated cosmogenic radionuclide production. The preservation of a solar production signal in Be-10 from varved lake sediments highlights the largely unexplored potential of these archives for solar activity reconstruction, as global synchronization tool and, thus, for more robust paleoclimate studies.
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| 4. |
- Erhardt, Tobias, et al.
(författare)
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High-resolution aerosol data from the top 3.8kyr of the East Greenland Ice coring Project (EGRIP) ice core
- 2023
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Ingår i: Earth System Science Data. - 1866-3508. ; 15:11, s. 5079-5091
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Tidskriftsartikel (refereegranskat)abstract
- Here we present the high-resolution continuous flow analysis (CFA) data from the top 479m of the East Greenland Ice coring Project (EGRIP) ice core covering the past 3.8kyr. The data consist of 1mm depth-resolution profiles of calcium, sodium, ammonium, nitrate, and electrolytic conductivity as well as decadal averages of these profiles. The nominally 1mm data represent an oversampling of the record as the true resolution is limited by the analytical setup to approximately 1cm. Alongside the data we provide a description of the measurement setup, procedures, the relevant references for the specific methods as well as an assessment of the precision of the measurements, the sample-to-depth assignment, and the depth and temporal resolution of the data set. The error in absolute depth assignment of the data may be on the order of 2cm; however, relative depth offsets between the records of the individual species are only on the order of 1mm. The presented data have sub-annual resolution over the entire depth range and have already formed part of the data for an annually layer-counted timescale for the EGRIP ice core used to improve and revise the multi-core Greenland ice-core chronology (GICC05) to a new version, GICC21 . The data are available in full 1mm resolution and decadal averages on PANGAEA (10.1594/PANGAEA.945293, ).
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| 5. |
- Mekhaldi, Florian, et al.
(författare)
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Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴅ 774/5 and 993/4.
- 2015
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Mekhaldi, Florian, et al.
(författare)
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Radionuclide wiggle matching reveals a nonsynchronous early Holocene climate oscillation in Greenland and western Europe around a grand solar minimum
- 2020
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Ingår i: Climate of the Past. - : COPERNICUS GESELLSCHAFT MBH. - 1814-9324 .- 1814-9332. ; 16:4, s. 1145-1157
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Tidskriftsartikel (refereegranskat)abstract
- Several climate oscillations have been reported from the early Holocene superepoch, the best known of which is the Preboreal oscillation (PBO). It is still unclear how the PBO and the number of climate oscillations observed in Greenland ice cores and European terrestrial records are related to one another. This is mainly due to uncertainties in the chronologies of the records. Here, we present new, high-resolution Be-10 concentration data from the varved Meerfelder Maar sediment record in Germany, spanning the period 11 310-11 000 years BP. These new data allow us to synchronize this well-studied record, as well as Greenland ice core records, with the IntCal13 timescale via radionuclide wiggle matching. In doing so, we show that the climate oscillations identified in Greenland and Europe between 11 450 and 11 000 years BP were not synchronous but terminated and began, respectively, with the onset of a grand solar minimum. A similar spatial anomaly pattern is found in a number of modeling studies on solar forcing of climate in the North Atlantic region. We further postulate that freshwater delivery to the North Atlantic would have had the potential to amplify solar forcing through a slowdown of the Atlantic meridional overturning circulation (AMOC) reinforcing surface air temperature anomalies in the region.
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| 7. |
- O'Hare, Paschal, et al.
(författare)
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Multiradionuclide evidence for an extreme solar proton event around 2,610 BP (similar to 660 BC)
- 2019
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 116:13, s. 5961-5966
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Tidskriftsartikel (refereegranskat)abstract
- 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 (C-14)] and ice cores [beryllium-10 (Be-10), chlorine-36 (Cl-36)]. Here, we show evidence for an extreme solar event around 2,610 years B.P. (similar to 660 BC) based on high-resolution Be-10 data from two Greenland ice cores. Our conclusions are supported by modeled C-14 production rates for the same period. Using existing Cl-36 ice core data in conjunction with Be-10, 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.
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| 8. |
- Paleari, Chiara I., et al.
(författare)
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Cosmogenic radionuclides reveal an extreme solar particle storm near a solar minimum 9125 years BP
- 2022
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- 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 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 36Cl/10Be 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 10Be-based evidence that, contrary to expectations, the SEP event occurred near a solar minimum.
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| 9. |
- Paleari, Chiara I., et al.
(författare)
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Evaluating the 11-year solar cycle and short-Term 10Be deposition events with novel excess water samples from the East Greenland Ice-core Project (EGRIP)
- 2023
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Ingår i: Climate of the Past. - 1814-9324. ; 19:11, s. 2409-2422
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Tidskriftsartikel (refereegranskat)abstract
- 10Be is produced by the interaction between galactic cosmic rays (GCRs) and solar energetic particles (SEPs) with the Earth's atmospheric constituents. The flux of GCRs is modulated by the varying strength of the magnetic fields of the Earth and the Sun. Measurement of 10Be concentrations from polar ice cores is thus a valuable tool to reconstruct the variations in the geomagnetic field and solar activity levels. The interpretation of 10Be records is, however, complicated by non-production-related effects on the 10Be deposition rate caused by climate-or weather-induced variability. Furthermore, volcanic eruptions have been proposed to lead to short-Term 10Be deposition enhancements. In this study, we test the use of excess meltwater from continuous flow analysis (CFA) to measure 10Be, allowing less time-consuming and more cost-effective sample preparation. We compare two records obtained from CFA and discrete samples from the East Greenland Ice core Project (EGRIP) S6 firn core, reaching back to 1900gCE. We find that the two records agree well and that the 10Be record from CFA samples agrees as well as the discrete samples with other records from Greenland. Furthermore, by subtracting the theoretically expected GCR-induced signal, we investigate the high-frequency variability in the 10Be records from Greenland and Antarctica after 1951gCE, focusing on SEP events and volcanic eruptions. Finally, we use the 10Be records from Greenland and Antarctica to study the 11-year solar cycles, allowing us to assess the suitability of the CFA samples for the reconstruction of solar activity. This result opens new opportunities for the collection of continuous 10Be records with less time-consuming sample preparation, while saving an important portion of the ice cores for other measurements.
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| 10. |
- Zheng, Minjie, et al.
(författare)
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Modeling Atmospheric Transport of Cosmogenic Radionuclide 10Be Using GEOS-Chem 14.1.1 and ECHAM6.3-HAM2.3 : Implications for Solar and Geomagnetic Reconstructions
- 2024
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Ingår i: Geophysical Research Letters. - 0094-8276. ; 51:2
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Tidskriftsartikel (refereegranskat)abstract
- A prerequisite to applying 10Be in natural archives for solar and geomagnetic reconstructions is to know how 10Be deposition reflects atmospheric production changes. However, this relationship remains debated. To address this, we use two state-of-the-art global models GEOS-Chem and ECHAM6.3-HAM2.3 with the latest beryllium production model. During solar modulation, both models suggest that 10Be deposition reacts proportionally to global production changes, with minor latitudinal deposition biases (<5%). During geomagnetic modulation, however, 10Be deposition changes are enhanced by ∼15% in the tropics and attenuated by 20%–35% in subtropical and polar regions compared to global production changes. Such changes are also hemispherically asymmetric, attributed to asymmetric production between hemispheres. For the solar proton event in 774/5 CE, 10Be shows a 15% higher deposition increase in polar regions than in tropics. This study highlights the importance of atmospheric mixing when comparing 10Be from different locations or to independent geomagnetic field records.
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| 11. |
- Hayakawa, Hisashi, et al.
(författare)
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The extreme space weather event in 1903 october/november : An outburst from the quiet sun
- 2020
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 897:1
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Tidskriftsartikel (refereegranskat)abstract
- While the Sun is generally more eruptive during its maximum and declining phases, observational evidence shows certain cases of powerful solar eruptions during the quiet phase of solar activity. Occurring in the weak Solar Cycle 14 just after its minimum, the extreme space weather event in 1903 October-November is one of these cases. Here, we reconstruct the time series of geomagnetic activity based on contemporary observational records. With the mid-latitude magnetograms, the 1903 magnetic storm is thought to be caused by a fast coronal mass ejection (≈1500 km s-1) and is regarded as a superstorm with an estimated minimum of the equivalent disturbance storm time index (Dst') of ≈-531 nT. The reconstructed time series has been compared with the equatorward extension of auroral oval (≈44. 1 in invariant latitude) and the time series of telegraphic disturbances. This case study shows that potential threats posed by extreme space weather events exist even during weak solar cycles or near their minima.
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| 12. |
- Koldobskiy, Sergey, et al.
(författare)
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Multiproxy Reconstructions of Integral Energy Spectra for Extreme Solar Particle Events of 7176 BCE, 660 BCE, 775 CE, and 994 CE
- 2023
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Ingår i: Journal of Geophysical Research: Space Physics. - 2169-9380. ; 128:3
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Tidskriftsartikel (refereegranskat)abstract
- Extreme solar particle events (ESPEs) are rare and the most potent known processes of solar eruptive activity. During ESPEs, a vast amount of cosmogenic isotopes (CIs) 10Be, 36Cl, and 14C can be produced in the Earth's atmosphere and deposited in natural stratified archives. Accordingly, CI measurements in these archives allow us to evaluate particle fluxes during ESPEs. In this work, we present a new method of ESPE fluence (integral flux) reconstruction based on state-of-the-art modeling advances, allowing to fit together different CI data within one model. We represent the ESPE fluence as an ensemble of scaled fluence reconstructions for ground-level enhancement (GLE) events registered by the neutron monitor network since 1956 coupled with satellite and ionospheric measurements data. Reconstructed ESPE fluences appear softer in its spectral shape than earlier estimates, leading to significantly higher estimates of the low-energy (E < 100 MeV) fluence. This makes ESPEs even more dangerous for modern technological systems than previously believed. Reconstructed ESPE fluences are fitted with a modified Band function, which eases the use of obtained results in different applications.
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| 13. |
- Mekhaldi, Florian
(författare)
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Cosmogenic radionuclides in environmental archives – A paleo-perspective on space climate and a synchronizing tool for climate records
- 2018. - Lundqua Theses
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Sun is the primary source for Earth’s climate system. Its fluctuations in irradiance are also known to have an impact on climate. In addition, changes in solar activity modulate the atmospheric production rates of cosmogenic radionuclides (e.g. 10Be, 14C, 36Cl) that all eventually deposit to different environmental archives. The signal of the changing solar activity through time can thus be retrieved and measured from these archives, such as ice cores, tree rings, or lake sediments. The Sun can also display a more chaotic behavior by erupting flashes of light, plasma and magnetic fields whereby energetic particles can be accelerated, and sometimes hit Earth. These all can damage our spacecraft technologies, harm astronauts, and also affect transformer, electric, and electronic infrastructures on the ground. In the case of extreme events, they may also pose a challenge to air-travel safety. At the same time, when solar energetic particles enter the atmosphere, they can enhance the production rate of cosmogenic radionuclides. The objectives of this thesis are twofold. First, the potential of using 10Be, 14C, and 36Cl as tracers of extreme solar storms is explored in depth. Second, the common production signal of 10Be and 14C caused by the longer term changes in solar activity is used to synchronize climate records from different environmental archives from different regions in order to assess the relative timing of a prominent climate oscillation, over 11,000 years before present. Two large signatures of cosmic-ray increase date to AD 774/5 and AD 993/4 are conclusively attributed to extreme solar energetic particle events that have hit Earth and left a clear imprint on the production rates of 14C as measured in tree rings all around the world, and of 10Be and 36Cl in ice cores from Greenland and Antarctica. The inferred energy spectrum and flux of particles of these events indicate that they were an order of magnitude stronger than any solar high-energy event observed during the space era. To infer the energy spectrum of ancient events, it is shown that the relative differences in the energy dependency of the production rates of 10Be and 36Cl by solar particles can be used. An additional, and similarly extreme, solar storm is also suggested to have hit Earth 2,610 years BP. The events from AD 774/5 and AD 993/4 are further explored to test, and thereafter reject, the hypothesis that nitrate enhancements in ice cores can be reliably linked to the occurrence of solar storms or to assess their magnitude. Two high resolution and continuous records of ice-core 36Cl concentration spanning the past several centuries are also presented. They show several increases in 36Cl possibly linked to solar energetic particle events including one that is coeval with the geomagnetic storm of September 1909 CE. These records also show that there is no enhancement in 36Cl production rate following the Carrington event of 1859 CE. A theoretical experiment also proposes that it is possible that major solar storms with a large flux of lower energy particles could lead to a significant increase in ice-core 36Cl concentrations but not in 10Be. Finally, it is shown that wiggles in cosmogenic radionuclides caused by longer-term changes in solar activity can be used to synchronize lake sediment records from Europe to Greenland ice cores. The investigation of both archives on the same time-scale suggests that the climate oscillations observed in Greenland, and subsequently in Western Europe could be attributed, in part, to solar forcing.
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| 14. |
- Nguyen, Hoang Long, et al.
(författare)
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The potential for a continuous 10Be record measured on ice chips from a borehole
- 2021
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Ingår i: Results In Geochemistry. - : Elsevier BV. - 2666-2779. ; 5
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Tidskriftsartikel (refereegranskat)abstract
- Ice cores are excellent archives for obtaining long and continuous 10Be records. However, traditional ice core 10Be measurements required a lot of ice (0.5–1kg) and often needed to be connected to a large and costly ice core project. These reasons have been the factors limiting the number and variety of 10Be projects and data. In this paper, we show measurements of 10Be on small samples (∼45g) of continuous auger ice chips from a borehole at Little Dome C (LDC), East Antarctica. The sample preparation method for 10Be accelerator mass spectrometry (AMS) was tested and optimized using test samples (∼50g) including well-mixed surface ice chips from the LDC site, snow collected in Lund (Sweden) and frozen Milli-Q water. The results show that our small ice samples should be processed without ion exchange filtration of the melt water and cleaning the subsequent Be(OH)2 precipitate. In addition, co-precipitating Be with Fe led to more reproducible measurement currents and offer the potential for higher efficiency and precision via longer measurement time. We applied the established preparation method to measure 10Be on 76 samples of the auger ice chips. The resulting 10Be concentration record for the period from 1354 to 1950 CE agrees well with the 10Be concentration in a South Pole ice core and the global 14C production rate and thus reflects well the atmospheric production signal of 10Be. We also observed insignificant mixing among the ice chip samples during the process of drilling and retrieving the ice. Therefore, the new ice chip samples are promising for assessing the long-term changes in 10Be deposition at different ice core sites. A wide application of this novel ice chip samples will increase the variety of 10Be records which will help to improve the assessment of long-term solar and geomagnetic shielding of galactic cosmic rays.
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| 15. |
- Sigl, M., et al.
(författare)
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Timing and climate forcing of volcanic eruptions for the past 2,500 years
- 2015
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 523:7562, s. 543-549
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Tidskriftsartikel (refereegranskat)abstract
- Volcanic eruptions contribute to climate variability, but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings. Here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual-to-decadal temperature variability in the Northern Hemisphere during the past 2,500 years. Our results are based on new records of atmospheric aerosol loading developed from high-resolution, multi-parameter measurements from an array of Greenland and Antarctic ice cores as well as distinctive age markers to constrain chronologies. Overall, cooling was proportional to the magnitude of volcanic forcing and persisted for up to ten years after some of the largest eruptive episodes. Our revised timescale more firmly implicates volcanic eruptions as catalysts in the major sixth-century pandemics, famines, and socioeconomic disruptions in Eurasia and Mesoamerica while allowing multi-millennium quantification of climate response to volcanic forcing.
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| 16. |
- Usoskin, Ilya, et al.
(författare)
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Extreme Solar Events : Setting up a Paradigm
- 2023
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Ingår i: Space Science Reviews. - 0038-6308. ; 219:8
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Forskningsöversikt (refereegranskat)abstract
- 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 believed to be roughly represented by direct instrumental observations. However, two types of extreme events were discovered recently: extreme solar energetic particle events on the multi-millennial time scale and super-flares on sun-like stars. Both discoveries imply that the Sun might rarely produce events, called extreme solar events (ESE), whose energy could be orders of magnitude greater than anything we have observed during recent decades. During the years following these discoveries, great progress has been achieved in collecting observational evidence, uncovering new events, making statistical analyses, and developing theoretical modelling. The ESE paradigm lives and is being developed. On the other hand, many outstanding questions still remain open and new ones emerge. Here we present an overview of the current state of the art and the forming paradigm of ESE from different points of view: solar physics, stellar–solar projections, cosmogenic-isotope data, modelling, historical data, as well as terrestrial, technological and societal effects of ESEs. Special focus is paid to open questions and further developments. This review is based on the joint work of the International Space Science Institute (ISSI) team #510 (2020–2022).
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