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  • 1
    Monograph available for loan
    Monograph available for loan
    Hydrogeologische Karte von Baden-Württemberg, Heibronner Mulde (1995)
    Freiburg : Selbstverlag
    Details Availability
    Call number: PIK N 453-02-0108
    Type of Medium: Monograph available for loan
    Location: A 18 - must be ordered
    Branch Library: PIK Library
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    BOOK
    Link to Library Catalog
    get availability status
  • 2
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    The effect of stochastically perturbed parametrisation tendencies (SPPT) on rapidly ascending air streams (2022)
    John Wiley & Sons, Ltd | Chichester, UK
    Details
    Publication Date: 2022-10-06
    Description: The stochastically perturbed parametrisation tendency (SPPT) scheme is a well‐established technique in ensemble forecasting to address model uncertainty by introducing perturbations into the tendencies provided by the physics parametrisations. The magnitude of the perturbations scales with the local net parametrisation tendency, resulting in large perturbations where diabatic processes are active. Rapidly ascending air streams, such as warm conveyor belts (WCBs) and organized tropical convection, are often driven by cloud diabatic processes and are therefore prone to such perturbations. This study investigates the effects of SPPT and initial condition perturbations on rapidly ascending air streams by computing trajectories in sensitivity experiments with the European Centre for Medium‐Range Weather Forecasts (ECMWF) ensemble prediction system, which are set up to disentangle the effects of initial conditions and physics perturbations. The results demonstrate that SPPT systematically increases the frequency of rapidly ascending air streams. The effect is observed globally, but is enhanced in regions where the latent heating along the trajectories is larger. Despite the frequency changes, there are only minor modifications to the physical properties of the trajectories due to SPPT. In contrast to SPPT, initial condition perturbations do not affect WCBs and tropical convection systematically. An Eulerian perspective on vertical velocities reveals that SPPT increases the frequency of strong upward motions compared with experiments with unperturbed model physics. Consistent with the altered vertical motions, precipitation rates are also affected by the model physics perturbations. The unperturbed control member shows the same characteristics as the experiments without SPPT regarding rapidly ascending air streams. We make use of this to corroborate the findings from the sensitivity experiments by analyzing the differences between perturbed and unperturbed members in operational ensemble forecasts of ECMWF. Finally, we give an explanation of how symmetric, zero‐mean perturbations can lead to a unidirectional response when applied in a nonlinear system.
    Description: The stochastically perturbed parametrisation tendencies (SPPT) scheme is used at ECMWF to perturb the model physics and introduces state‐dependent perturbations into the parametrisation tendencies. The frequency of rapidly ascending air streams is systematically enhanced when SPPT is active. This effect is stronger when the latent heating is large (panel a), and is therefore more pronounced in the Tropics than in the Extratropics. In contrast, the impact of SPPT on the physical properties of the air streams, such as the latent heat release, is very small (panel b).
    Description: Helmholtz Young Investigator Group ‘Sub‐ Seasonal Predictability: Understanding the Role of Diabatic Outflow’
    Keywords: ddc:551.5
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 3
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    Niedersächsischer Demokratie-Monitor 2021 (2022)
    Universitätsverlag Göttingen
    Details
    Publication Date: 2022-02-14
    Keywords: Corona pandemic ; Political attitude ; Lower Saxony ; bic Book Industry Communication::J Society & social sciences
    Language: German
    Format: image/jpeg
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    E-BOOK
  • 4
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    A comparison between multi-proxy and historical data of drift-ice conditions on the East Greenland shelf
    PANGAEA
    In:  Supplement to: Alonso-Garcia, Montserrat; Andrews, John T; Belt, Simon T; Cabedo-Sanz, Patricia; Darby, Dennis A; Jaeger, John (2013): A comparison between multiproxy and historical data (AD 1990-1840) of drift ice conditions on the East Greenland Shelf ( 66 N). The Holocene, 23(12), 1672-1683, https://doi.org/10.1177/0959683613505343
    Details
    Publication Date: 2023-05-12
    Description: The reduction in sea ice along the SE Greenland coast during the last century has severely impacted ice-rafting to this area. In order to reconstruct ice-rafting and oceanographic conditions in the area of Denmark Strait during the last ~150 years, we conducted a multiproxy study on three short (20 cm) sediment cores from outer Kangerdlugssuaq Trough (~300 m water depth). The proxy-based data obtained have been compared with historical and instrumental data to gain a better understanding of the ice sheet-ocean interactions in the area. A robust chronology has been developed based on 210Pb and 137Cs measurements on core PO175GKC#9 (~66.2°N, 32°W) and expanded to the two adjacent cores based on correlations between calcite weight percent records. Our proxy records include sea-ice and phytoplankton biomarkers, and a variety of mineralogical determinations based on the 〈2 mm sediment fraction, including identification with quantitative x-ray diffraction, ice-rafted debris counts on the 63-150 µm sand fraction, and source identifications based on the composition of Fe oxides in the 45-250 µm fraction. A multivariate statistical analysis indicated significant correlations between our proxy records and historical data, especially with the mean annual temperature data from Stykkishólmur (Iceland) and the storis index (historical observations of sea-ice export via the East Greenland Current). In particular, the biological proxies (calcite weight percent, IP25, and total organic carbon %) showed significant linkage with the storis index. Our records show two distinct intervals in the recent history of the SE Greenland coast. The first of these (ad 1850-1910) shows predominantly perennial sea-ice conditions in the area, while the second (ad 1910-1990) shows more seasonally open water conditions.
    Type: Dataset
    Format: application/zip, 7 datasets
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    DATA PANGAEA
  • 5
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    Sedimentological and geochemical investigation of Denmark Strait sediments (2017)
    PANGAEA
    In:  Supplement to: Andrews, John T; Cabedo-Sanz, Patricia; Jennings, Anne E; Olafasdottir, Saedis; Belt, Simon T; Geirsdóttir, Áslaug (2017): Sea ice, ice-rafting, and ocean climate across Denmark Strait during rapid deglaciation (~16 to 12 cal ka BP) of the Iceland and East Greenland shelves. Journal of Quaternary Science, https://doi.org/10.1002/jqs.3007
    Details
    Publication Date: 2023-01-13
    Description: Geophysical data from the Kangerlussuaq Trough, E Greenland (Dowdeswell et al., 2010; Stein, 1996), and from the West Iceland shelf (Syvitski et al., 1999) indicate that there are sites where pre Last Glacial Maximum (LGM) sediments exist, but no such sites have been successfully cored. However, a significant number of cores have been recovered that penetrate a basal diamicton, sometimes containing shells and foraminifera, and which are overlain by glacial marine sediments rich in ice rafted debris (IRD) (Jennings et al., 2000; Olafsdottir, 2004). At the LGM, reconstructions and marine field data (Andrews, 2008; Andrews et al., 1998, 2000; Dunhill, 2005; Funder et al., 2004; Hubbard et al., 2006; Vasskog et al., 2015) indicate that the Iceland and Greenland ice sheets were terminating at their shelf breaks with deposition on the slopes above the Denmark Strait. Active sediment deposition ceased on the Kangerlussuaq Trough Mouth Fan (KTMF) ca. 15.3 ka 14C BP (Andrews et al., 1998; Dunhill, 2005) and retreat to the present coastline occurred prior to deposition of the Vedde tephra (Jennings et al., 2006). There is strong evidence that a major change in deep-water circulation at ~15 cal ka BP resulted in abrupt warming at the onset of the Bølling/Allerød (B/A) interstadial (Thiagarajan et al., 2014; Thornalley et al., 2011). Syvitski et al (1999) and Norddahl and Ingolfsson (2015) argued that the Iceland Ice Sheet retreated rapidly during this time, driven by a rapid rise in relative sea level. Jennings et al. (2006) also presented radiocarbon evidence from marine cores for a rapid retreat of the Greenland Ice Sheet along Kangerlussuaq Trough (KT, Fig. 1).
    Type: Dataset
    Format: application/zip, 9 datasets
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    DATA PANGAEA
  • 6
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    Absolute sedimentary concentrations of highly branched isoprenoids, PIP25 indices with derived spring sea ice concentrations, and classification tree predictions of sea ice conditions in three Barents Sea sediment cores (2018)
    PANGAEA
    In:  Supplement to: Köseoğlu, Denizcan; Belt, Simon T; Husum, Katrine; Knies, Jochen (2018): An assessment of biomarker-based multivariate classification methods versus the PIP25 index for paleo Arctic sea ice reconstruction. Organic Geochemistry, 125, 82-94, https://doi.org/10.1016/j.orggeochem.2018.08.014
    Details
    Publication Date: 2023-01-13
    Description: The development of various combinative methods for Arctic sea ice reconstruction using the sympagic highly-branched isoprenoid IP25 in conjunction with pelagic biomarkers has often facilitated more detailed descriptions of sea ice conditions than using IP25 alone. Here, we investigated the complementary application of the Phytoplankton-IP25 index (PIP25) and a recently proposed Classification Tree (CT) model for describing shifts in sea ice conditions to assess the consistency of both methods. Based on biomarker data from three downcore records from the Barents Sea spanning millennial timescales, we showcase apparent and potential limitations of both approaches, and provide recommendations for their identification or prevention. Both methods provided generally consistent outcomes and, within the studied cores, captured abrupt shifts in sea ice regimes, such as those evident during the Younger Dryas, as well as more gradual trends in sea ice conditions during the Holocene. The most significant discrepancies occurred during periods of highly unstable climate change, such as those characteristic of the Younger Dryas-Holocene transition. Such intervals of increased discrepancy were identifiable by significant changes of HBI distributions and correlations to values not observed in proximal surface sediments. We suggest that periods of highly-fluctuating climate that are not represented in modern settings may hinder the performance and complementary application of PIP25 and CT-based methods, and that data visualisation techniques should be employed to identify such occurrences in downcore records. Additionally, due to the reliance of both methods on biomarker distributions, we emphasise the importance of accurate and consistent biomarker quantification for future investigations.
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
  • 7
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    Biomarker and temperature and sea ice proxy data for TEX86 calibration in sediment core B997-316 (2019)
    PANGAEA
    In:  Supplement to: Harning, David J; Andrews, John T; Belt, Simon T; Cabedo-Sanz, Patricia; Geirsdóttir, Áslaug; Dildar, Nadia; Miller, Gifford H; Sepúlveda, Julio (2019): Sea Ice Control on Winter Subsurface Temperatures of the North Iceland Shelf During the Little Ice Age: A TEX86 Calibration Case Study. Paleoceanography and Paleoclimatology, 34(6), 1006-1021, https://doi.org/10.1029/2018PA003523
    Details
    Publication Date: 2023-02-12
    Description: Holocene paleoceanographic reconstructions along the North Iceland Shelf have employed a variety of sea surface temperature and sea ice proxies. However, these surface proxies tend to have a seasonal bias toward spring/summer and thus only provide a discrete snapshot of surface conditions during one season. Furthermore, sea surface temperature proxies can be influenced by additional confounding variables resulting in markedly different Holocene temperature reconstructions. Here, we expand Iceland's marine paleoclimate toolkit with TEX86 L: a temperature proxy based on the distribution of archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids. We develop a local Icelandic calibration from 21 surface sediment samples covering a wide environmental gradient across Iceland's insular shelves. Locally calibrated GDGT results demonstrate that (1) TEX86 L reflects winter subsurface (0-200 m) temperatures on the North Iceland Shelf and (2) our calibration produces more realistic temperature estimates with substantially lower uncertainty (S.E. ±4 °C) over global calibrations. We then apply this new calibration to a high‐resolution marine sediment core (last millennium) collected from the central NIS with age control constrained by 14C‐dated mollusks. To test the veracity of the GDGT subsurface temperatures, we analyze quartz and calcite wt% and a series of highly branched isoprenoid alkenes, including the sea ice biomarker IP25, from the same core. The sediment records demonstrate that the development of thick sea ice during the Little Ice Age warmed the subsurface due to winter insulation. Importantly, this observation reflects a seasonal component of the sea ice/ocean feedback to be considered for the nonlinear cooling of the Little Ice Age in and around Iceland.
    Keywords: (9Z)-2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyliden)pentadeca-9-ene per unit sediment mass; 2,6,10,14-Tetramethyl-7-(3-methylpent-4-enyl)pentadecane per unit sediment mass; Acyclic glycerol dialkyl glycerol tetraether; Age; AGE; B997-316; Crenarchaeol; Crenarchaeol regio-isomer; DEPTH, sediment/rock; Dicyclic glycerol dialkyl glycerol tetraether; Diene II per unit sediment mass; GGC; Giant gravity corer; Glycerol dialkyl glycerol tetraethers; Monocyclic glycerol dialkyl glycerol tetraether; North Icelandic Shelf; Sample ID; Temperature, water, winter; Tetraether index of 86 carbon atoms, low-temperature region; Tricyclic glycerol dialkyl glycerol tetraether
    Type: Dataset
    Format: text/tab-separated-values, 490 data points
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    DATA PANGAEA
  • 8
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    Variation in sedimentation sources on the East Greenland Shelf
    PANGAEA
    Details
    Publication Date: 2023-05-12
    Keywords: Age; AGE; Ratio
    Type: Dataset
    Format: text/tab-separated-values, 184 data points
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    DATA PANGAEA
  • 9
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    (Table III) Correlations between the first two environmental PC and the proxies
    PANGAEA
    Details
    Publication Date: 2023-05-12
    Keywords: Description; Factor 1; Factor 2
    Type: Dataset
    Format: text/tab-separated-values, 51 data points
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    DATA PANGAEA
  • 10
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    (Table 7) Sedimentology, mineralogy and geochemistry of sediment core B997-338 (2017)
    PANGAEA
    Details
    Publication Date: 2023-06-09
    Keywords: Astrononion gallowayi; B997-338; Buccella frigida; Buccella frigida var. calida; Calcite; Calendar age; Carbon, organic, total; Carbonates; Cassidulina neoteretis; Cassidulina obtusa; Cassidulina reniforme; Cibicides lobatulus; Cibicides lobatulus, δ13C; Cibicides lobatulus, δ13C standard deviation; Cibicides lobatulus, δ18O; Cibicides lobatulus, δ18O standard deviation; Confusion Index; DEPTH, sediment/rock; Diene II per unit sediment mass; Dry unit; Elphidium excavatum; Ice rafted debris; Islandiella norcrossi; Kalifeldspar; Magnetic susceptibility, mass; Median, grain size; Mode, grain size, description; Neogloboquadrina pachyderma sinistral; Nonion labradoricum; PC; Piston corer; Quartz; Sediment type; Size fraction 〈 0.002 mm, clay; Size fraction 0.004-0.002 mm, 8.0-9.0 phi, very fine silt; Size fraction 0.008-0.004 mm, 7.0-8.0 phi, fine silt; Size fraction 0.016-0.008 mm, 6.0-7.0 phi, medium silt; Size fraction 0.032-0.016 mm, 5.0-6.0 phi, coarse silt; Size fraction 0.063-0.032 mm, 4.0-5.0 phi, very coarse silt; Size fraction 0.125-0.063 mm, 3.0-4.0 phi, very fine sand; Size fraction 0.250-0.125 mm, 2.0-3.0 phi, fine sand; Size fraction 0.500-0.250 mm, 1.0-2.0 phi, medium sand; Size fraction 1.000-0.500 mm, 0.0-1.0 phi, coarse sand; Size fraction 2.000-1.000 mm, (-1.0)-0.0 phi, very coarse sand
    Type: Dataset
    Format: text/tab-separated-values, 1308 data points
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    DATA PANGAEA
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