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32 Research products, page 1 of 4

  • European Marine Science
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  • 2018-2022
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  • Open Access English
    Authors: 
    Stockner, William Fatum; Langer, Jonatan Heine;
    Country: Denmark

    The effects of antifreeze proteins (AFPs) on the freezing temperatures of water is well studiedand known today. Studies of the affects of antifreeze proteins on glass transition and melting tem-peratures have been conducted on samples containing relatively high concentrations of glyceroland water. In this paper we conduct experiments with antifreeze proteins in water-dominatedglycerol water mixtures to determine how AFPs affect the glass transition and melting temper-atures of these samples. We present theory behind the various interactions that occur betweencomponents of the various mixtures studied and provide mathematical background and proofsto verify our methods. We discuss the hardware and software setups, experimental procedure,preparation of samples and analysis of the gathered data. The experimental results obtained fromthe raw data is presented as well as information on how the data was interpreted. Our analysisof a 23% glycerol water mixture with varying concentrations of teleost fish type III anti-freezeproteins suggest that there is a lowering effect to the glass transition temperature. Uncertainties,arbitrary choices and areas of future research are established for suggestions of the continuedresearch of these phenomena.i

  • Open Access English
    Authors: 
    Paskett, Wesley Allan;
    Country: Denmark
  • Open Access English
    Authors: 
    Plach, Andreas; Vinther, Bo M.; Nisancioglu, Kerim H.; Vudayagiri, Sindhu; Blunier, Thomas;
    Project: EC | ICE2ICE (610055)

    This study presents simulations of Greenland surface melt for the Eemian interglacial period (∼130 000 to 115 000 years ago) derived from regional climate simulations with a coupled surface energy balance model. Surface melt is of high relevance due to its potential effect on ice core observations, e.g., lowering the preserved total air content (TAC) used to infer past surface elevation. An investigation of surface melt is particularly interesting for warm periods with high surface melt, such as the Eemian interglacial period. Furthermore, Eemian ice is the deepest and most compressed ice preserved on Greenland, resulting in our inability to identify melt layers visually. Therefore, simulating Eemian melt rates and associated melt layers is beneficial to improve the reconstruction of past surface elevation. Estimated TAC, based on simulated melt during the Eemian, could explain the lower TAC observations. The simulations show Eemian surface melt at all deep Greenland ice core locations and an average of up to ∼30 melt days per year at Dye-3, corresponding to more than 600 mm water equivalent (w.e.) of annual melt. For higher ice sheet locations, between 60 and 150 mmw.e.yr-1 on average are simulated. At the summit of Greenland, this yields a refreezing ratio of more than 25 % of the annual accumulation. As a consequence, high melt rates during warm periods should be considered when interpreting Greenland TAC fluctuations as surface elevation changes. In addition to estimating the influence of melt on past TAC in ice cores, the simulated surface melt could potentially be used to identify coring locations where Greenland ice is best preserved.

  • Open Access English
    Authors: 
    Stedmon, Colin A; Amon, Rainer M W; Bauch, Dorothea; Bracher, Astrid; Gonçalves-Araujo, Rafael; Hoppmann, Mario; Krishfield, Richard A; Laney, Samuel; Rabe, Benjamin; Reader, Heather E; +1 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | CarbEx (839311), NSF | Collaborative research: D... (1504469)

    Here we present a merged and calibrated dataset of temperature, practical salinity and dissolved organic matter (DOM) fluorescence obtained from several Ice Tethered Profilers (ITPs) deployed across the central Arctic (2011-2016). The data offer a unique spatial coverage of the distribution of DOM in the surface 800 m below Arctic sea ice. A total of 5044 profiles are gathered. The ITP data are level 3 data products pressure-bin-averaged at 1-db vertical resolution with depth down to either 200 or approximately 750 m. Data (max 800m depth) from CTD casts made during two oceanographic cruises are also included. These were used as part of the calibration and validation of the ITP calibration routines. The cruises were PS94 (ARK-XXIX/3) with POLARSTERN in 2015 and NAACOS with DANA in 2012. The presented DOM fluorescence data are smoothed, corrected for instrument drift and calibrated to provide intercomparable data across the sensors. Fluorescence is reported in Raman Units (nm-1), and comparable to laboratory measurements conducted according to current community recommendations.

  • Open Access English
    Authors: 
    Lee, James E.; Brook, Edward J.; Bertler, Nancy A. N.; Buizert, Christo; Baisden, Troy; Blunier, Thomas; Ciobanu, V. Gabriela; Conway, Howard; Dahl-Jensen, Dorthe; Fudge, Tyler J.; +7 more
    Project: NSF | Collaborative Research: D... (0944307), NSF | Collaborative Research: D... (0944021), NSF | Collaborative Research: A... (0837883), NSF | Roosevelt Island Climate ... (1042883), EC | ICE2ICE (610055)

    In 2013, an ice core was recovered from Roosevelt Island in the Ross Sea, Antarctica, as part of the Roosevelt Island Climate Evolution (RICE) project. Roosevelt Island is located between two submarine troughs carved by paleo-ice-streams. The RICE ice core provides new important information about the past configuration of the West Antarctic Ice Sheet and its retreat during the most recent deglaciation. In this work, we present the RICE17 chronology and discuss preliminary observations from the new records of methane, the isotopic composition of atmospheric molecular oxygen (δ18O-Oatm), the isotopic composition of atmospheric molecular nitrogen (δ15N-N2) and total air content (TAC). RICE17 is a composite chronology combining annual layer interpretations, gas synchronization, and firn modeling strategies in different sections of the core. An automated matching algorithm is developed for synchronizing the high-resolution section of the RICE gas records (60–720 m, 1971 CE to 30 ka) to corresponding records from the WAIS Divide ice core, while deeper sections are manually matched. Ice age for the top 343 m (2635 yr BP, before 1950 C.E.) is derived from annual layer interpretations and described in the accompanying paper by Winstrup et al. (2017). For deeper sections, the RICE17 ice age scale is based on the gas age constraints and the ice age-gas age offset estimated by a firn densification model. Novel aspects of this work include: 1) stratigraphic matching of centennial-scale variations in methane for pre-anthropogenic time periods, a strategy which will be applicable for developing precise chronologies for future ice cores, 2) the observation of centennial-scale variability in methane throughout the Holocene which suggests that similar variations during the late preindustrial period need not be anthropogenic, and 3) the observation of continuous climate records dating back to ∼ 65 ka which provide evidence that the Roosevelt Island Ice Dome was a constant feature throughout the last glacial period.

  • Open Access English
    Authors: 
    Thyrring, Jakob; Wegeberg, Susse; Blicher, Martin E.; Krause-Jensen, Dorte; Høgslund, Signe; Olesen, Birgit; Wiktor Jr, Jozef; Mouritsen, Kim N.; Peck, Lloyd S.; Sejr, Mikael K.;
    Publisher: Zenodo
    Project: EC | EdgeStress (797387), EC | EdgeStress (797387)

    The data contains three supporting datasets: 1. Mid-intertidal data 2. Vertical transect data 3. GPS coordinates for all sites

  • Open Access English
    Authors: 
    Maffezzoli, Niccolò; Vallelonga, Paul; Edwards, Ross; Saiz-Lopez, Alfonso; Turetta, Clara; Kjær, Helle Astrid; Barbante, Carlo; Vinther, Bo; Spolaor, Andrea;
    Project: EC | CLIMAHAL (726349), EC | ICE2ICE (610055)

    Although it has been demonstrated that the speed and magnitude of the recent Arctic sea ice decline is unprecedented for the past 1450 years, few records are available to provide a paleoclimate context for Arctic sea ice extent. Bromine enrichment in ice cores has been suggested to indicate the extent of newly formed sea ice areas. Despite the similarities among sea ice indicators and ice core bromine enrichment records, uncertainties still exist regarding the quantitative linkages between bromine reactive chemistry and the first-year sea ice surfaces. Here we present a 120 000-year record of bromine enrichment from the RECAP (REnland ice CAP) ice core, coastal east Greenland, and interpret it as a record of first-year sea ice. We compare it to existing sea ice records from marine cores and tentatively reconstruct past sea ice conditions in the North Atlantic as far north as the Fram Strait (50–85∘ N). Our interpretation implies that during the last deglaciation, the transition from multi-year to first-year sea ice started at ∼17.5 ka, synchronously with sea ice reductions observed in the eastern Nordic Seas and with the increase in North Atlantic ocean temperature. First-year sea ice reached its maximum at 12.4–11.8 ka during the Younger Dryas, after which open-water conditions started to dominate, consistent with sea ice records from the eastern Nordic Seas and the North Icelandic shelf. Our results show that over the last 120 000 years, multi-year sea ice extent was greatest during Marine Isotope Stage (MIS) 2 and possibly during MIS 4, with more extended first-year sea ice during MIS 3 and MIS 5. Sea ice extent during the Holocene (MIS 1) has been less than at any time in the last 120 000 years.

  • Open Access English
    Authors: 
    Fischer, Delmarie; Annegarn, Harold; Lochner, Paul;
    Publisher: Taylor & Francis
    Country: South Africa

    Criteria for the evaluation of the effectiveness of Strategic Environmental Assessment (SEA) have evolved internationally from the requirement for mere procedural effectiveness, to include criteria such as substantial and incremental effectiveness. This paper provides an overview of the international evolution of effectiveness evaluation for SEA and its parallel progression in South Africa. Within this context, the effectiveness of the two SEA case studies conducted in support of national-scale renewable energy planning in South Africa was reviewed against internationally recognised effectiveness criteria to test their ability to influence decision making for renewable energy projects in the country. The evaluation was informed by the role of the first author as the project director in the case studies. The review found the SEAs to be partially effective, mainly through the introduction of new legislation, processes and systems at the national level that operationalise the outcomes of the SEA. A fundamental limitation emerged in determining whether incremental effectiveness had been achieved as it is too soon to evaluate the effectiveness of the recently promulgated legislation and instruments. The paper builds on previous work on effectiveness evaluations and provides the perspective of an administrative implementer

  • Open Access English
    Authors: 
    Holme, Christian; Gkinis, Vasileios; Lanzky, Mika; Morris, Valerie; Olesen, Martin; Thayer, Abigail; Vaughn, Bruce H.; Vinther, Bo M.;
    Project: EC | ICE2ICE (610055)

    This study examines the stable water isotope signal (δ18O) of three ice cores drilled on the Renland peninsula (east Greenland coast). While ice core δ18O measurements qualitatively are a measure of the local temperature history, the δ18O variability in precipitation actually reflects the integrated hydrological activity that the deposited ice experienced from the evaporation source to the condensation site. Thus, as Renland is located next to fluctuating sea ice cover, the transfer function used to infer past temperatures from the δ18O variability is potentially influenced by variations in the local moisture conditions. The objective of this study is therefore to evaluate the δ18O variability of ice cores drilled on Renland and examine the amount of the signal that can be attributed to regional temperature variations. In the analysis, three ice cores are utilized to create stacked summer, winter and annually averaged δ18O signals (1801–2014 CE). The imprint of temperature on δ18O is first examined by correlating the δ18O stacks with instrumental temperature records from east Greenland (1895–2014 CE) and Iceland (1830–2014 CE) and with the regional climate model HIRHAM5 (1980–2014 CE). The results show that the δ18O variability correlates with regional temperatures on both a seasonal and an annual scale between 1910 and 2014, while δ18O is uncorrelated with Iceland temperatures between 1830 and 1909. Our analysis indicates that the unstable regional δ18O–temperature correlation does not result from changes in weather patterns through strengthening and weakening of the North Atlantic Oscillation. Instead, the results imply that the varying δ18O–temperature relation is connected with the volume flux of sea ice exported through Fram Strait (and south along the coast of east Greenland). Notably, the δ18O variability only reflects the variations in regional temperature when the temperature anomaly is positive and the sea ice export anomaly is negative. It is hypothesized that this could be caused by a larger sea ice volume flux during cold years which suppresses the Iceland temperature signature in the Renland δ18O signal. However, more isotope-enabled modeling studies with emphasis on coastal ice caps are needed in order to quantify the mechanisms behind this observation. As the amount of Renland δ18O variability that reflects regional temperature varies with time, the results have implications for studies performing regression-based δ18O–temperature reconstructions based on ice cores drilled in the vicinity of a fluctuating sea ice cover.

  • Open Access English
    Authors: 
    Seroussi, Hélène; Nowicki, Sophie; Simon, Erika; Abe-Ouchi, Ayako; Albrecht, Torsten; Brondex, Julien; Cornford, Stephen; Dumas, Christophe; Gillet-Chaulet, Fabien; Goelzer, Heiko; +29 more
    Project: EC | ACCLIMATE (339108), EC | NACLIM (308299), NSF | The Management and Operat... (1852977), ANR | TROIS-AS (ANR-15-CE01-0005), NSF | Collaborative Research: E... (1443229)

    Ice sheet numerical modeling is an important tool to estimate the dynamic contribution of the Antarctic ice sheet to sea level rise over the coming centuries. The influence of initial conditions on ice sheet model simulations, however, is still unclear. To better understand this influence, an initial state intercomparison exercise (initMIP) has been developed to compare, evaluate, and improve initialization procedures and estimate their impact on century-scale simulations. initMIP is the first set of experiments of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6), which is the primary Coupled Model Intercomparison Project Phase 6 (CMIP6) activity focusing on the Greenland and Antarctic ice sheets. Following initMIP-Greenland, initMIP-Antarctica has been designed to explore uncertainties associated with model initialization and spin-up and to evaluate the impact of changes in external forcings. Starting from the state of the Antarctic ice sheet at the end of the initialization procedure, three forward experiments are each run for 100 years: a control run, a run with a surface mass balance anomaly, and a run with a basal melting anomaly beneath floating ice. This study presents the results of initMIP-Antarctica from 25 simulations performed by 16 international modeling groups. The submitted results use different initial conditions and initialization methods, as well as ice flow model parameters and reference external forcings. We find a good agreement among model responses to the surface mass balance anomaly but large variations in responses to the basal melting anomaly. These variations can be attributed to differences in the extent of ice shelves and their upstream tributaries, the numerical treatment of grounding line, and the initial ocean conditions applied, suggesting that ongoing efforts to better represent ice shelves in continental-scale models should continue.