Browsing by Subject "RADIOCARBON"

Sort by: Order: Results:

Now showing items 1-7 of 7
  • Miyake, Fusa; Panyushkina, Irina; Jull, Tim; Adolphi, Florian; Brehm, N; Helama, Samuli; Kanzawa, K; Moriya, T; Muscheler, Raimund; Nicolussi, K; Oinonen, Markku; Salzer, M; Takeyama, M; Tokanai, F; Wacker, Lucas (2021)
    The annual C-14 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 similar to 660 BCE. Here, we report another rapid increase of C-14 concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These C-14 data series show a significant increase of similar to 6 parts per thousand in 5411-5410 BCE. The signature of C-14 variation is very similar to the confirmed three SEP events and points to an extreme short-term flux of cosmic ray radiation into the atmosphere. The rapid C-14 increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand C-14 excursion during 5481-5471 BCE. The similarity of our C-14 data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.
  • Mueller, Daniela; Tjallingii, Rik; Plociennik, Mateusz; Luoto, Tomi P.; Kotrys, Bartosz; Plessen, Birgit; Ramisch, Arne; Schwab, Markus J.; Blaszkiewicz, Miroslaw; Slowinski, Michal; Brauer, Achim (2021)
    The sediment profile from Lake Goscia(z) over dot in central Poland comprises a continuous, seasonally resolved and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation. This provides a unique opportunity for detailed investigation of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination). The new varve record of Lake Goscia(z) over dot presented here spans 1662 years from the late Allerod (AL) to the early Preboreal (PB). Microscopic varve counting provides an independent chronology with a YD duration of 1149+14/-22 years, which confirms previous results of 1140 +/- 40 years. We link stable oxygen isotopes and chironomid-based air temperature reconstructions with the response of various geochemical and varve microfacies proxies especially focusing on the onset and termination of the YD. Cooling at the YD onset lasted similar to 180 years, which is about a century longer than the terminal warming that was completed in similar to 70 years. During the AL/YD transition, environmental proxy data lagged the onset of cooling by similar to 90 years and revealed an increase of lake productivity and internal lake re-suspension as well as slightly higher detrital sediment input. In contrast, rapid warming and environmental changes during the YD/PB transition occurred simultaneously. However, initial changes such as declining diatom deposition and detrital input occurred already a few centuries before the rapid warming at the YD/PB transition. These environmental changes likely reflect a gradual increase in summer air temperatures already during the YD. Our data indicate complex and differing environmental responses to the major climate changes related to the YD, which involve different proxy sensitivities and threshold processes.
  • Piilo, Sanna; Zhang, Hui; Garneau, Michelle; Gallego-Sala, Angela V.; Amesbury, Matthew; Väliranta, Minna (2019)
    Peatland ecosystems are important carbon sinks, but also release carbon back to the atmosphere as carbon dioxide and methane. Peatlands therefore play an essential role in the global carbon cycle. However, the response of high-latitude peatlands to ongoing climate change is still not fully understood. In this study, we used plant macrofossils and peat property analyses as proxies to document changes in vegetation and peat and carbon accumulation after the Little Ice Age. Results from 12 peat monoliths collected in high-boreal and low-subarctic regions in northwestern Quebec, Canada, suggest high carbon accumulation rates for the recent past (post AD 1970s). Successional changes in plant assemblages were asynchronous within the cores in the southernmost region, but more consistent in the northern region. Average apparent recent carbon accumulation rates varied between 50.7 and 149.1 g C m(-2) yr(-1) with the northernmost study region showing higher values. The variation in vegetation records and peat properties found within samples taken from the same sites and amongst cores taken from different regions highlights the need to investigate multiple records from each peatland, but also from different peatlands within one region.
  • Palonen, Vesa; Pumpanen, Jukka; Kulmala, Liisa-Maija; Levin, Ingeborg; Heinonsalo, Jussi; Vesala, Timo (2018)
    We present a radiocarbon (C-14) dataset of tropospheric air CO2 forest soil air CO2, and soil CO2 emissions over the course of one growing season in a Scots pine forest in southern Finland. The CO2 collection for C-14 accelerator mass spectrometry (AMS) analysis was done with a portable, suitcase-sized system, using molecular sieve cartridges to selectively trap CO2 The piloting measurements aimed to quantify the spatial, seasonal and diurnal changes in the C-14 content of CO2 in a northern forest site. The atmospheric samples collected above the canopy showed a large seasonal variation and an 11 parts per thousand difference between day and nighttime profiles in August. The higher Delta C-14 values during night are partly explained by a higher contribution of C-14-elevated soil CO2, accumulating in the nocturnal boundary layer when vertical mixing is weak. We observed significant seasonal trends in Delta C-14-CO2 at different soil depths that reflected changes in the shares of autotrophic and heterotrophic respiration. Also the observed diurnal variation in the Delta C-14 values in soil CO2 highlighted the changes in the origin of CO2, with root activity decreasing more for the night than decomposition.
  • Uusitalo, J.; Arppe, L.; Hackman, T.; Helama, S.; Kovaltsov, G.; Mielikäinen, K.; Mäkinen, H.; Nöjd, P.; Palonen, V.; Usoskin, I.; Oinonen, M. (2018)
    Recently, a rapid increase in radiocarbon (C-14) was observed in Japanese tree rings at AD 774/775. Various explanations for the anomaly have been offered, such as a supernova, a gamma-ray burst, a cometary impact, or an exceptionally large Solar Particle Event (SPE). However, evidence of the origin and exact timing of the event remains incomplete. In particular, a key issue of latitudinal dependence of the C-14 intensity has not been addressed yet. Here, we show that the event was most likely caused by the Sun and occurred during the spring of AD 774. Particularly, the event intensities from various locations show a strong correlation with the latitude, demonstrating a particle-induced C-14 poleward increase, in accord with the solar origin of the event. Furthermore, both annual C-14 data and carbon cycle modelling, and separate earlywood and latewood C-14 measurements, confine the photosynthetic carbon fixation to around the midsummer.
  • Holmqvist, Elisabeth; Larsson, Åsa M.; Kriiska, Aivar; Palonen, Vesa; Pesonen, Petro; Mizohata, Kenichiro; Kouki, Paula; Räisänen, Jyrki (2018)
    The Neolithic Corded Ware Culture (CWC) complex spread across the Baltic Sea region ca. 2900/2800-2300/2000 BCE. Whether this cultural adaptation was driven by migration or diffusion remains widely debated. To gather evidence for contact and movement in the CWC material culture, grog-tempered CWC pots from 24 archaeological sites in southern Baltoscandia (Estonia and the southern regions of Finland and Sweden) were sampled for geochemical and micro-structural analyses. Scanning electron microscopy with energy dispersive spectrometry (SEM-EDS) and particle-induced X-ray emission (PIXE) were used for geochemical discrimination of the ceramic fabrics to identify regional CWC pottery manufacturing traditions and ceramic exchange. Major and minor element concentrations in the ceramic body matrices of 163 individual vessels and grog temper (crushed pottery) present in the ceramic fabrics were measured by SEM-EDS. Furthermore, the high-sensitivity PIXE technique was applied for group confirmation. The combined pot and grog matrix data reveal eight geochemical clusters. At least five geochemical groups appeared to be associated with specific find locations and regional manufacturing traditions. The results indicated complex inter-site and cross-Baltic Sea pottery exchange patterns, which became more defined through the grog data, i.e., the previous generations of pots. The CWC pottery exhibited high technological standards at these latitudes, which, together with the identified exchange patterns and the existing evidence of mobility based on human remains elsewhere in the CWC complex, is indicative of the relocation of skilled potters, possibly through exogamy. An analytical protocol for the geochemical discrimination of grog-tempered pottery, and its challenges and possibilities, is presented. (C) 2018 Elsevier Ltd. All rights reserved.
  • Solly, Emily F.; Brunner, Ivano; Helmisaari, Heljä-Sisko Marketta; Herzog, Claude; Leppälammi-Kujansuu, Jaana; Schöning, Ingo; Schrumpf, Marion; Schweingruber, Fritz H; Trumbore, Susan E.; Hagedorn, Frank (2018)
    Fine roots support the water and nutrient demands of plants and supply carbon to soils. Quantifying turnover times of fine roots is crucial for modeling soil organic matter dynamics and constraining carbon cycle–climate feedbacks. Here we challenge widely used isotopebased estimates suggesting the turnover of fine roots of trees to be as slow as a decade. By recording annual growth rings of roots from woody plant species, we show that mean chronological ages of fine roots vary from <1 to 12 years in temperate, boreal and sub-arctic forests. Radiocarbon dating reveals the same roots to be constructed from 10 ± 1 year (mean ± 1 SE) older carbon. This dramatic difference provides evidence for a time lag between plant carbon assimilation and production of fine roots, most likely due to internal carbon storage. The high root turnover documented here implies greater carbon inputs into soils than previously thought which has wide-ranging implications for quantifying ecosystem carbon allocation.