1,721,673 research outputs found
Data to carbon cycle model simulations for the late Pleistocene by considering solid Earth processes
No full textThe global carbon cycle box model BICYCLE is enhanced by a process-based sediment module and the consequences from prescribed fluxes of volcanic outgassing, carbonate and silicate weathering, and coral reef growth on the carbon cycle as a whole and on atmospheric CO2 in detail for the last 800 kyr are analysed. The scenarios for prescribing the fluxes are taken from the literature. Other carbon cycle processes within the ocean and terrestrial biosphere are taken as previously considered in a study published as Köhler et al. (2010, doi:10.1029/2008PA001703)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Simulated change in the future carbon cycle under high CO2 emission and ocean alkalinization
No full textThe CO2 removal model inter-comparison (CDRMIP) has been established to approximate the usefulness of climate mitigation by some well defined negative emission technologies. I here analyze ocean alkalinization in a high CO2 world (emission scenario SSP5-85-EXT++ and CDR-ocean-alk within CDRMIP) for the next millennia using a revised version of the carbon cycle model BICYCLE, whose long-term feedbacks are calculated for the next 1 million years. The applied model version not only captures atmosphere, ocean and a constant marine and terrestrial biosphere, but also represents solid Earth processes, such as deep ocean CaCO3 accumulation and dissolution, volcanic CO2 outgassing and continental weathering. In the applied negative emission experiment, 0.14 Pmol/yr of alkalinity - comparable to the dissolution of 5 Pg of olivine per year — is entering the surface ocean starting in year 2020 for either 50 or 5000 years. I find that the cumulative emissions of 6740 PgC emitted until year 2350 lead to a peak atmospheric CO2 concentration of nearly 2400 ppm in year 2326, which is reduced by only 200 ppm by the alkalinization experiment. Atmospheric CO2 is brought down to 400 or 300 ppm after 2730 or 3480 years of alkalinization, respectively. Such low CO2 concentrations are reached without ocean alkalinization only after several hundreds of thousands of years, when the feedbacks from weathering and sediments bring the part of the anthropogenic emissions that stays in the atmosphere (the so-called airborne fraction) below 4%. The efficiency of carbon sequestration by this alkalinization approach peaks at 9.7 PgC per Pmol of alkalinity added during times of maximum anthropogenic CO2 emissions and slowly declines to half this value 2000 years later due to the non-linear marine chemistry response and ocean-sediment processes. In other words ocean alkalinization sequesters carbon only as long as the added alkalinity stays in the ocean. To understand the basic model behavior I analytically explain why in the simulation results a linear relationship in the transient climate response to cumulative emissions (TCRE) is found for low emissions (similarly as for more complex climate models), which evolves for high emissions to a non-linear relation
Carbon cycle model simulations using BICYCLE-SE over the last 5 millions years with focus on the 405-kyr periodicities in 13C
No full textUsing the carbon cycle model BICYCLE-SE I simulated carbon cycle changes that tried to agree with marine δ13C reconstructions. In doing so the model is in some scenarios prescribed with δ13C data, or nudged to δ13C data. Necessary corrections in the model-internal 13C cycle can in post-processing be used to evaluate if the δ13C signature of geological carbon sources (volcanic CO2 or carbonate rock weathering) external to the model might be responsible for the necessary changes that align the model with the data. The data are obtained from 9 simulation scenarios, which are between 210 kyr and 5 Myr long
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Deep Atlantic Ocean 14C for 21 and 42 kcal BP according to simulations using INTCAL20
No full textRadiocarbon distributions in the past deep Atlantic ocean at 21,000 cal BP (around the Last Glacial Maximum, file = MRA_21000_calBP_30W.nc) and 42,000 cal BP (the onset of the Laschamps Geomagnetic Excursion, file = MRA_42000_calBP_30W.nc) according to simulations running from 55,000 cal BP to 0 cal BP carried out with the LSG ocean general circulation model (Butzin et al., 2020) forced with IntCal20 atmospheric Δ14C and ice core CO2. Each data set displays the median of nine simulation results. Shown is the depletion of dissolved 14C with respect to the contemporaneous atmosphere expressed in terms of 14C age. Low 14C concentrations translate to high 14C ages and vice versa. In both data sets the average ocean circulation is the same. The differences between 21,000 cal BP and 42,000 cal BP are rather due to changes in atmospheric Δ14C levels, and different leads and lags between this atmospheric 14C and its oceanic uptake and dispersal. Data contain marine reservoir age (MRA) which is calculated out of oceanic and atmospheric D14C according to Eq 1 in Butzin et al (2017)
Simulating atmospheric CO2 concentration for the Plio-Pleistocene using a new set of temperature and sea level reconstruction
No full textIn contrast to previous approaches, new reconstructions of changes in global mean surface temperature (Clark et al., 2024, doi: 10.1126/science.adi1908) and global mean sea level (Clark et al., 2025, doi: 10.1126/science.adv8389) include large variability in global mean sea level throughout the Pleistocene. Here we use them to force the global carbon cycle model BICYCLE-SE in different scenarios that capture the spread in existing CO2 reconstructions.
This data set contains:
- important otherwise not yet available data (4.5 Ma long time series of regional SST split by latitude (65°S-30°S | 30°S-30°N | 30°N-65°N) which have been used to force the model;
- resulting major changes in the simulated carbon cycle (mean ocean salinity; Atlantic meridional overturning strength; Southern Ocean vertical mixing; global sea ice area);
- simulated atmospheric CO2 in 3 scenarios that differ in volcanic CO2 outgassing and weathering strength
- …
