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  • 1
    Online Resource
    Online Resource
    [Bremerhaven] : [Alfred-Wegener-Institut für Polar- und Meeresforschung]
    Keywords: Forschungsbericht ; Polargebiete ; Satellitenfernerkundung ; Radarfernerkundung ; Satellitenaltimetrie
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (74 Seiten, 23,4 MB) , Diagramme, Karten
    Language: German
    Note: Förderkennzeichen BMBF 50EE1331. - Verbund-Nummer 01150613 , Paralleltitel dem englischen Berichtsblatt entnommen , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Sprache der Zusammenfassung: Deutsch, Englisch
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  • 2
    Publication Date: 2015-08-03
    Description: The Soil Moisture and Ocean Salinity (SMOS) mission observes brightness temperatures at a low microwave frequency of 1.4 GHz (L-band) with a daily coverage of the polar regions. L-band radiometry has been shown to provide information on the thickness of thin sea ice. Here, we apply a new emission model that has previously been used to investigate the impact of snow on thick Arctic sea ice. The model has not yet been used to retrieve ice thickness. In contrast to previous SMOS ice thickness retrievals, the new model allows us to include a snow layer in the brightness temperature simulations. Using ice thickness estimations from satellite thermal imagery, we simulate brightness temperatures during the ice growth season 2011 in the northern Baltic Sea. In both the simulations and the SMOS observations, brightness temperatures increase by more than 20 K, most likely due to an increase of ice thickness. Only if we include the snow in the model, the absolute values of the simulations and the observations agree well (mean deviations below 3.5 K). In a second comparison, we use high-resolution measurements of total ice thickness (sum of ice and snow thickness) from an electromagnetic (EM) sounding system to simulate brightness temperatures for 12 circular areas. While the SMOS observations and the simulations that use the EM modal ice thickness are highly correlated (r2=0.95), the simulated brightness temperatures are on average 12 K higher than observed by SMOS. This would correspond to an 8-cm overestimation of the modal ice thickness by the SMOS retrieval. In contrast, if the simulations take into account the shape of the EM ice thickness distributions (r2=0.87), the mean deviation between simulated and observed brightness temperatures is below 0.1 K.
    Type: Article , PeerReviewed
    Format: text
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  • 3
    Publication Date: 2014-08-28
    Description: The large-scale thickness distribution of sea ice was measured during several campaigns in the European Arctic north of Svalbard from 2007 using an airborne electromagnetic induction device. In August 2010 and April–May 2011, this was complemented by extensive on-ice work including measurements of snow thickness and freeboard. Ice thicknesses show a clear difference between the seasons, with thicker ice during spring than in summer. In spring 2011, negative freeboard and flooding were observed as a result of the extensive snow cover. We find that the characteristics of the first-year sea ice allow combining observations from different years. The ice thickness in the marginal ice zone increases with increasing latitude and increasing distance to the ice edge; however, in the inner ice pack from ∼100 km from the ice edge the thickness remains almost constant. Modal ice thickness in spring reaches 2.4 m whereas in summer it is 1.0–1.4 m. Our study provides new insight into ice thickness distributions of a typical ice cover consisting of mainly first- and second-year ice, which may become the dominant ice type in the Arctic in the future.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2019-12-31
    Description: Sea ice is an important climate variable and is also an obstacle for marine operations in polar regions. We have developed a small and lightweight, digitally operated frequency-domain electromagnetic-induction (EM) system, a so-called EM bird, dedicated for measurements of sea ice thickness. It is 3.5 m long and weighs only 105 kg, and can therefore easily be shipped to remote places and operated from icebreakers and small helicopters. Here, we describe the technical design of the bird operating at two frequencies of f1 = 3.68 kHz and f2 = 112 kHz, and study its technical performance. On average, noise amounts to ± 8.5 ppm and ± 17.5 ppm for f1 and f2, respectively. Electrical drift amounts to 200 ppm/h and 2000 ppm/h for f1 and f2, during the first 0.5 h of operation. It is reduced by 75% after 2 h. Calibration of the Inphase and Quadrature ppm signals varies by 2 to 3%. A sensitivity study shows that all these signal variations do affect the accuracy of the ice thickness retrieval, but that it remains better than ± 0.1 m over level ice in most cases. This accuracy is also confirmed by means of comparisons of the helicopter EM data with other thickness measurements. The paper also presents the ice thickness retrieval from single-component Inphase data of f1.
    Type: Article , PeerReviewed
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  • 5
    Publication Date: 2019-09-23
    Description: Understanding and responding to the rapidly occurring environmental changes in the Arctic over the past few decades require new approaches in science. This includes improved collaborations within the scientific community but also enhanced dialogue between scientists and societal stakeholders, especially with Arctic communities. As a contribution to the Third International Conference on Arctic Research Planning (ICARPIII), the Arctic in Rapid Transition (ART) network held an international workshop in France, in October 2014, in order to discuss high-priority requirements for future Arctic marine and coastal research from an early-career scientists (ECS) perspective. The discussion encompassed a variety of research fields, including topics of oceanographic conditions, sea-ice monitoring, marine biodiversity, land-ocean interactions, and geological reconstructions, as well as law and governance issues. Participants of the workshop strongly agreed on the need to enhance interdisciplinarity in order to collect comprehensive knowledge about the modern and past Arctic Ocean's geo-ecological dynamics. Such knowledge enables improved predictions of Arctic developments and provides the basis for elaborate decision-making on future actions under plausible environmental and climate scenarios in the high northern latitudes. Priority research sheets resulting from the workshop's discussions were distributed during the ICARPIII meetings in April 2015 in Japan, and are publicly available online.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2023-02-08
    Description: In September 2019, the research icebreaker Polarstern started the largest multidisciplinary Arctic expedition to date, the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift experiment. Being moored to an ice floe for a whole year, thus including the winter season, the declared goal of the expedition is to better understand and quantify relevant processes within the atmosphere–ice–ocean system that impact the sea ice mass and energy budget, ultimately leading to much improved climate models. Satellite observations, atmospheric reanalysis data, and readings from a nearby meteorological station indicate that the interplay of high ice export in late winter and exceptionally high air temperatures resulted in the longest ice-free summer period since reliable instrumental records began. We show, using a Lagrangian tracking tool and a thermodynamic sea ice model, that the MOSAiC floe carrying the Central Observatory (CO) formed in a polynya event north of the New Siberian Islands at the beginning of December 2018. The results further indicate that sea ice in the vicinity of the CO (〈40 km distance) was younger and 36 % thinner than the surrounding ice with potential consequences for ice dynamics and momentum and heat transfer between ocean and atmosphere. Sea ice surveys carried out on various reference floes in autumn 2019 verify this gradient in ice thickness, and sediments discovered in ice cores (so-called dirty sea ice) around the CO confirm contact with shallow waters in an early phase of growth, consistent with the tracking analysis. Since less and less ice from the Siberian shelves survives its first summer (Krumpen et al., 2019), the MOSAiC experiment provides the unique opportunity to study the role of sea ice as a transport medium for gases, macronutrients, iron, organic matter, sediments and pollutants from shelf areas to the central Arctic Ocean and beyond. Compared to data for the past 26 years, the sea ice encountered at the end of September 2019 can already be classified as exceptionally thin, and further predicted changes towards a seasonally ice-free ocean will likely cut off the long-range transport of ice-rafted materials by the Transpolar Drift in the future. A reduced long-range transport of sea ice would have strong implications for the redistribution of biogeochemical matter in the central Arctic Ocean, with consequences for the balance of climate-relevant trace gases, primary production and biodiversity in the Arctic Ocean.
    Type: Article , PeerReviewed
    Format: text
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  • 7
    Publication Date: 2023-02-08
    Description: The gridded sea ice thickness (SIT) climate data record (CDR) produced by the European Space Agency (ESA) Sea Ice Climate Change Initiative Phase 2 (CCI-2) is the longest available, Arctic-wide SIT record covering the period from 2002 to 2017. SIT data are based on radar altimetry measurements of sea ice freeboard from the Environmental Satellite (ENVISAT) and CryoSat-2 (CS2). The CCI-2 SIT has previously been validated with in situ observations from drilling, airborne remote sensing, electromagnetic (EM) measurements and upward-looking sonars (ULSs) from multiple ice-covered regions of the Arctic. Here we present the Laptev Sea CCI-2 SIT record from 2002 to 2017 and use newly acquired ULS and upward-looking acoustic Doppler current profiler (ADCP) sea ice draft (VAL) data for validation of the gridded CCI-2 and additional satellite SIT products. The ULS and ADCP time series provide the first long-term satellite SIT validation data set from this important source region of sea ice in the Transpolar Drift. The comparison of VAL sea ice draft data with gridded monthly mean and orbit trajectory CCI-2 data, as well as merged CryoSat-2–SMOS (CS2SMOS) sea ice draft, shows that the agreement between the satellite and VAL draft data strongly depends on the thickness of the sampled ice. Rather than providing mean sea ice draft, the considered satellite products provide modal sea ice draft in the Laptev Sea. Ice drafts thinner than 0.7 m are overestimated, while drafts thicker than approximately 1.3 m are increasingly underestimated by all satellite products investigated for this study. The tendency of the satellite SIT products to better agree with modal sea ice draft and underestimate thicker ice needs to be considered for all past and future investigations into SIT changes in this important region. The performance of the CCI-2 SIT CDR is considered stable over time; however, observed trends in gridded CCI-2 SIT are strongly influenced by the uncertainties of ENVISAT and CS2 and the comparably short investigation period.
    Type: Article , PeerReviewed
    Format: text
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  • 8
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    Elsevier
    In:  Cold Regions Science and Technology, 65 (3). pp. 308-313.
    Publication Date: 2021-12-31
    Description: We present the prototype of a simplified photogrammetric system (HELicopter-borne Ice Observation System, HELIOS) and demonstrate how it can be used to document ground-based and airborne sea ice surveys. The aerial unit consists of a nadir-looking digital camera mounted on a gimbal, a GPS receiver and a computer. It is of low-cost and weight and is designed such that it withstands low temperatures, operates autonomously and fits to any standard helicopter skid. The accuracy of the georeferenced photographs is about ± 15 m for a flight height of 85 m, flight speed of 130 km/h and a GPS sampling rate of 4 Hz. Systematic errors arise from the GPS-based determination of the camera position, the pointing accuracy of the gimbal, and the camera alignment in flight direction. Because most sea ice mapping projects require lesser accuracies than conventional mapping standards (e.g. ≤ 0.5 m for a map scale of 1:600, ASPRS (1994)), HELIOS offers a broad range of applications. This includes the photogrammetric documentation of experimental sites as well as the verification of satellite-, and model-based estimates of sea ice and snow cover properties. Images taken simultaneously with other airborne observations provide a valuable tool to assess the accuracy of those measurements.
    Type: Article , PeerReviewed
    Format: text
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  • 9
    Publication Date: 2024-02-07
    Description: The Earth climate system is out of energy balance, and heat has accumulated continuously over the past decades, warming the ocean, the land, the cryosphere, and the atmosphere. According to the Sixth Assessment Report by Working Group I of the Intergovernmental Panel on Climate Change, this planetary warming over multiple decades is human-driven and results in unprecedented and committed changes to the Earth system, with adverse impacts for ecosystems and human systems. The Earth heat inventory provides a measure of the Earth energy imbalance (EEI) and allows for quantifying how much heat has accumulated in the Earth system, as well as where the heat is stored. Here we show that the Earth system has continued to accumulate heat, with 381±61 ZJ accumulated from 1971 to 2020. This is equivalent to a heating rate (i.e., the EEI) of 0.48±0.1 W m−2. The majority, about 89 %, of this heat is stored in the ocean, followed by about 6 % on land, 1 % in the atmosphere, and about 4 % available for melting the cryosphere. Over the most recent period (2006–2020), the EEI amounts to 0.76±0.2 W m−2. The Earth energy imbalance is the most fundamental global climate indicator that the scientific community and the public can use as the measure of how well the world is doing in the task of bringing anthropogenic climate change under control. Moreover, this indicator is highly complementary to other established ones like global mean surface temperature as it represents a robust measure of the rate of climate change and its future commitment. We call for an implementation of the Earth energy imbalance into the Paris Agreement's Global Stocktake based on best available science. The Earth heat inventory in this study, updated from von Schuckmann et al. (2020), is underpinned by worldwide multidisciplinary collaboration and demonstrates the critical importance of concerted international efforts for climate change monitoring and community-based recommendations and we also call for urgently needed actions for enabling continuity, archiving, rescuing, and calibrating efforts to assure improved and long-term monitoring capacity of the global climate observing system. The data for the Earth heat inventory are publicly available, and more details are provided in Table 4.
    Type: Article , PeerReviewed
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  • 10
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    PANGAEA
    In:  Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven
    Publication Date: 2023-03-16
    Keywords: Arctic Ocean; ARK-XXVI/3; ICE; Ice station; Ice station #2; Polarstern; PS78/203-1; PS78 TransArc
    Type: Dataset
    Format: unknown
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