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  • 1
    Keywords: Erlebnisbericht ; Polargebiete ; Erwärmung ; Meereis ; Abschmelzen ; Klimatologie
    Description / Table of Contents: Weniger als 25 Jahre geben Wissenschaftler*innen ihm noch, dann wird es so weit sein: Bis 2050 wird das Eis der Arktis mindestens einmal im Sommer vollständig abgeschmolzen sein, und unser Planet, den Generationen nur mit von Eis bedeckten Polkappen kennen, wird sich für immer verändern. Welche Folgen wird das Schwinden des Eises für die Menschheit haben? Wie wirkt es sich auf unser Wetter, die Meere und das Ökosystem der Polarregionen aus? Stefanie Arndt erzählt von den tiefgreifenden Veränderungen, die sie auf ihren Expeditionen beobachten konnte, von ihrer Arbeit als Polarforscherin und von der zarten Schönheit eines schwindenden Lebensraums. Was so fern scheint, rückt dabei ganz nahe: Können wir die unumkehrbaren Auswirkungen, die ein Abschmelzen der Polkappen nach sich zöge, noch aufhalten?
    Type of Medium: Book
    Pages: 221 Seiten, 16 ungezählte Seiten , Illustrationen, 2 Karten , 21 cm x 13.5 cm
    Edition: Originalausgabe
    ISBN: 9783499008665
    DDC: 500
    RVK:
    Language: German
    Note: Quellen: Seite 197-222
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  • 2
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (47 Seiten, 1,77 MB) , Illustrationen, Diagramme
    Language: German
    Note: Förderkennzeichen BMWi 0324029C , Verbundnummer 01169010 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
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  • 3
    Publication Date: 2024-04-05
    Description: The Arctic Ocean is an exceptional environment where hydrosphere, cryosphere, and atmosphere are closely interconnected. Changes in sea-ice extent and thickness affect ocean currents, as well as moisture and heat exchange with the atmosphere. Energy and water fluxes impact the formation and melting of sea ice and snow cover. Here, we present a comprehensive statistical analysis of the stable water isotopes of various hydrological components in the central Arctic obtained during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019–2020, including the understudied Arctic winter. Our dataset comprises >2200 water, snow, and ice samples. Snow had the most depleted and variable isotopic composition, with δ18O (–16.3‰) increasing consistently from surface (–22.5‰) to bottom (–9.7‰) of the snowpack, suggesting that snow metamorphism and wind-induced transport may overprint the original precipitation isotope values. In the Arctic Ocean, isotopes also help to distinguish between different sea-ice types, and whether there is a meteoric contribution. The isotopic composition and salinity of surface seawater indicated relative contributions from different freshwater sources: lower δ18O (approximately –3.0‰) and salinities were observed near the eastern Siberian shelves and towards the center of the Transpolar Drift due to river discharge. Higher δ18O (approximately –1.5‰) and salinities were associated with an Atlantic source when the RV Polarstern crossed the Gakkel Ridge into the Nansen Basin. These changes were driven mainly by the shifts within the Transpolar Drift that carried the Polarstern across the Arctic Ocean. Our isotopic analysis highlights the importance of investigating isotope fractionation effects, for example, during sea-ice formation and melting. A systematic full-year sampling for water isotopes from different components strengthens our understanding of the Arctic water cycle and provides crucial insights into the interaction between atmosphere, sea ice, and ocean and their spatio-temporal variations during MOSAiC.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 4
    Publication Date: 2014-09-24
    Description: The Arctic Ocean is currently undergoing a dramatic change. Decreasing sea-ice extent, thickness and age are changing important processes in the climate system. An increasing coverage of the sea ice by melt ponds and an increased amount of light transmitted to the upper ocean are also affecting the ice associated ecosystem. To document these changes, we operated different remotely operated vehicles (ROV) underneath the drifting sea ice of the Central Arctic Ocean. The newest underwater technology combined with a highly interdisciplinary sensor suite was successfully used for scientific investigations directly under the sea ice. The unique dataset of novel observations provided insights into the partitioning of solar shortwave radiation in and under sea ice, the deformation and topography of the ice cover, the distribution of sea-ice algae and ice algal aggregates and the ice associated primary production. The large range covered by the ROV surveys enabled us to quantify the spatial variability of physical as well as habitat properties. Despite the harsh climatic conditions and logistical difficulties in the high Arctic, the latest ROV technology proved to be a valuable tool for interdisciplinary sea-ice research.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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  • 5
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    AMER GEOPHYSICAL UNION
    In:  EPIC3Geophysical Research Letters, AMER GEOPHYSICAL UNION, ISSN: 0094-8276
    Publication Date: 2019-07-17
    Description: In the paper “Changes in Arctic sea ice result in increasing light transmittance and absorption” by Nicolaus et al. (Geophysical Research Letters, 39(24), L24501, doi:10.1029/2012GL053738, 2012), the presented data on solar surface irradiance are erroneous. In order to generate monthly means of the solar heat input into the Arctic Ocean, among others, the ERA interim (European Centre for Medium-Range Weather Forecasts) data set of solar surface irradiance was used. The original data set consists of eight time slices with integrated fluxes over 3 h each. But in the presented results, only the mean (not sum) of two slices (from 00:00 to 03:00 and from 12:00 to 15:00) was considered, resulting in too low fluxes, approx. by a factor of eight. As a consequence, two text passages (in paragraph 3.1 and 3.3) and three figures (Figure 4 of the main article and Figures S3 and S6 of the auxiliary material) contain too low fluxes. However, the main conclusions of the manuscript remain completely valid and unchanged, since those are only based on relative fluxes, which are not affected by this mistake.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 6
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    In:  EPIC3Polar2018, Davos, Switzerland, 2018-06-19-2018-06-23
    Publication Date: 2018-12-19
    Description: Snowmelt processes on sea ice are the key drivers determining the seasonal sea-ice energy and mass budgets. While there is strong surface melt on Arctic sea ice, snowmelt on Antarctic sea ice is weak with most snow surviving the summer. Here, we compile time series of snowmelt onset dates on perennial Antarctic sea ice from 1992 to 2014 using active microwave observations from European Remote Sensing Satellite (ERS-1/2), Quick Scatterometer (QSCAT) and Advanced Scatterometer (ASCAT) radar scatterometers. Describing snow melt processes, we define two transition stages: A weak backscatter rise indicating the initial warming and metamorphosis of the snowpack (pre-melt), followed by a rapid rise indicating the onset of thaw-freeze cycles (snowmelt). Results show large interannual variability with average pre-melt and snowmelt onset dates of 29 November and 10 December, respectively, without any significant trends over the study period. Related to different signal frequencies, we show that QSCAT Ku-band (13.4 GHz signal frequency) derived pre-melt and snowmelt onset dates are earlier by 25 and 11 days, respectively, than ERS and ASCAT C-band (5.6 GHz) derived dates. This offset has been considered when constructing the time series. As different signal frequencies result in different penetration depths, we hypothesize that the different sensors respond to typical snowmelt processes in different depths within the snow cover.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 7
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    In:  EPIC3DFG Schwerpunktprogramm 1154: Ankarktis , Koordinationsworkshop 2018, 2018-09-11-2018-09-14
    Publication Date: 2019-03-29
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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  • 8
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    Wiley
    In:  EPIC3Journal of Geophysical Research-Oceans, Wiley, 123(12), pp. 8862-8876, ISSN: 0148-0227
    Publication Date: 2019-01-25
    Description: The snow cover on Antarctic sea ice persists during most of the year, contributing significantly to the sea ice mass budget due to comprehensive seasonal transition processes within the snowpack as well as at the snow/ice interface. Consequently, snow on sea ice varies not only in depth but also in particular in its physical characteristics such as snow density and stratigraphy. In order to quantify the heterogeneous nature of the Antarctic snowpack on different spatial scales, that is, small (〈10 m), floe‐size (1‐2 km), and regional (seasonal/perennial ice) scales, we present here a case study of snow analyses in the Weddell Sea in austral winter 2013. The resulting high variability of snow parameters in the basal snow layer reveals the need to distinguish between seasonal and perennial ice regimes, when retrieving, for example, snow depth using satellite microwave radiometry. Considering the full vertical snow column, a more detailed distinction of the perennial sea ice regime into, for example, more ice classes is suggested in order to represent the high variability range. For the internal snowpack variability, however, we identify the grain size variability as the main driver, while snow density variations can be neglected. Moving from regional to floe‐size scales, a similar variability range of the studied snow properties is found, suggesting that a large number of snow samples on a few floes is more crucial than covering a large region with fewer floe‐scale measurements. The spatiotemporally heterogeneous variability in snow accumulation, redistribution, and metamorphism is, however, too large to upscale the given findings beyond regional scale.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 9
    Publication Date: 2017-04-03
    Description: The surface properties of sea ice dominate many key processes and drive important feedback mechanisms in the polar oceans of both hemispheres. Examining Arctic and Antarctic sea ice, the distinctly different dominant sea-ice and snow properties in spring and summer are apparent. While Arctic sea ice features a seasonal snow cover with widespread surface ponding in summer, a year-round snow cover and strong surface flooding at the snow/ice interface is observed on Antarctic sea ice. However, substantial knowledge gaps exist about the spatial distribution and temporal evolution of these properties, and their impacts on exchange processes across the atmosphere/ocean interface. This thesis aims to overcome these limitations by quantifying the influence of surface properties on the energy and mass budgets in the ice-covered oceans. Remote sensing data and in-situ observations are combined to derive the seasonal cycle of dominant sea-ice surface characteristics, and their relation to the transfer of solar radiation from the atmosphere through snow and sea ice into the upper ocean. This thesis shows that characteristics of the solar radiation under Arctic sea ice can be described directly as a function of sea-ice surface properties as, e.g., sea-ice type and melt pond coverage. Using this parameterization, an Arctic-wide calculation of solar radiation through sea ice identifies the surface melt onset as the main driver of the annual sea-ice mass and energy budgets. In contrast, an analysis of the spring-summer transition of Antarctic sea ice using passive microwave satellite observations indicates widespread diurnal freeze-thaw cycles in the top snow layers. While the associated temporary thawing is identified as the predominant melt process, subsequent continuous melt in deeper snow layers is rarely found on Antarctic sea ice. Instead of directly influencing the snow depth on Antarctic sea ice, these melt processes rather modify the internal stratigraphy and vertical density structure of the snowpack. An additional analysis of satellite scatterometer observations reveals that snow volume loss on Antarctic sea ice is mainly driven by changes in the lower snowpack, due to the widespread presence of sea-ice surface flooding and snow-ice formation prior to changes in the upper snowpack. As a consequence, the largely heterogeneous and metamorphous Antarctic snowpack prevents a direct correlation between surface properties and the respective characteristics of the penetrating solar radiation under the sea ice. However, surface flooding is identified as the key process governing the variability of the under-ice light regime on small scales. Overall, this thesis highlights that the mass and energy budgets of Antarctic sea ice are determined by processes at the snow/ice interface as well as the temporal evolution of physical snowpack properties. These results are in great contrast to presented studies on Arctic sea ice, where seasonally alternating interactions at the atmosphere/snow- or atmosphere/sea-ice interface control both the energy and mass budgets. An improved understanding of the seasonal cycle of dominant sea-ice and snow surface characteristics in the Arctic and Antarctic is crucial for future investigations retrieving sea-ice variables, such as sea-ice thickness and snow depth, from recent microwave satellite observations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Thesis , notRev
    Format: application/pdf
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  • 10
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    In:  EPIC3IGS Sea Ice Symposium 2019, Winnipeg, Manitoba, Canada, 2019-08-18-2019-08-23
    Publication Date: 2019-09-17
    Description: Snowmelt processes on sea ice are the key drivers determining the seasonal sea-ice energy and mass budgets. Around Antarctica, snowmelt on pack ice is weak and very different than in the Arctic, with most snow surviving the summer. It is therefore important to understand the mechanisms that drive snowmelt, both at different times of the year and in different regions around Antarctica. Doing so, we compile time series of snowmelt onset dates on perennial Antarctic sea ice from 1992 to 2014 using active microwave observations from European Remote Sensing Satellite (ERS-1/2), Quick Scatterometer (QSCAT) and Advanced Scatterometer (ASCAT) radar scatterometers. Describing snow melt processes, we define two transition stages: A weak backscatter rise indicating the initial warming and metamorphism of the snowpack (pre-melt), followed by a rapid rise indicating the onset of thaw-freeze cycles in the interior snowpack (snowmelt). We compare these with pan-Antarctic temporary snowmelt onset dates in the uppermost snowpack retrieved from diurnal variations in the brightness temperatures from passive microwave (PMW) observations. Results show that QSCAT Ku-band (13.4 GHz signal frequency) derived pre-melt and snowmelt onset dates are earlier by 25 and 11 days, respectively, than ERS and ASCAT C-band (5.6 GHz) derived dates. Snowmelt onset dates from the shortwave PMW observations (37 GHz) are later by 13 and 5 days than those from the scatterometers, respectively. Based on the observed successive timing of melt events retrieved from different sensors and microwave bands, we developed a conceptual model of the temporal evolution of snow temperature and metamorphism and their effect on different microwave wavelengths during the spring/summer transition. These results suggest that future multi-frequency microwave satellite missions could be used to resolve melt processes throughout the vertical snow column. Overall, results show that the magnitude and timing of seasonal and diurnal variations in Antarctic snow on sea ice are highly dependent on latitude, with earlier and more frequent snowmelt in the north. All retrieved melt onset dates show large interannual variability but no significant decadal trends.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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