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  • 1
    Online Resource
    Online Resource
    MAP-BORealis - Assistierte Schiffsführung im Meereis auf Arktischen Passagen durch Berechnung optimaler Routen mittels satellitenbasierter Fernerkundungsdaten : Schlussbericht : Laufzeit des Vorhabens: 01.07.2019-30.06.2021 (2021)
    Bremen : Drift + Noise Polar Services GmbH
    Details Availability
    Keywords: Forschungsbericht ; Schiffsführung ; Meereis ; Arktis ; Fernerkundung ; Reiseweg ; Planung ; Radar ; Synthetische Apertur
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (34 Seiten, 10,45 MB) , Illustrationen, Diagramme, Karten
    URL: https://doi.org/10.2314/KXP:1837736162
    DOI: 10.2314/KXP:1837736162
    Language: German
    Note: Förderkennzeichen BMWi 50RP1935B , Verbundnummer 01192078 , Literaturverzeichnis: Seite 33-34 , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden
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  • 2
    Online Resource
    Online Resource
    MAP-BORealis - assistierte Schiffsführung im Meereis auf Arktischen Passagen durch Berechnung optimaler Routen mittels satellitenbasierter Fernerkundungsdaten : Schlussbericht : Laufzeit des Vorhabens: 01.07.2019-30.06.2021 (2021)
    Bremen : [Universität Bremen]
    Details Availability
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (36 Seiten, 1,35 MB) , Illustrationen, Diagramme
    URL: https://doi.org/10.2314/KXP:1841799459
    DOI: 10.2314/KXP:1841799459
    Language: German , English
    Note: Förderkennzeichen BMWi 50RP1935A , Verbundnummer 01192078 , Autoren und durchführende Institution dem Berichtsblatt entnommen , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden , Sprache der Zusammenfassung: Deutsch, Englisch
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  • 3
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    Sea ice lead fractions from multiple sensors in the Transpolar Drift during MOSAiC 2019/2020 (2024)
    PANGAEA
    Details
    Publication Date: 2024-04-20
    Description: Divergent sea ice motion breaks the ice and opens fractures and leads. Depending on the air temperature, those open-water areas can quickly refreeze. The open water or thin ice in leads play a crucial role in the heat and gas exchange between the ocean and the atmosphere, impacting atmospheric, ecological, and oceanic processes. Leads can be detected from space, using different types of instruments, e.g., thermal infrared, passive microwave, active microwave, or optical sensors. The retrieval methods have different sensitivities, especially concerning the minimum lead width and the maximum ice thickness, different spatial resolutions, and different limits. We presented a time series of lead fractions from different lead products (Oct 2019 - May 2020) along the drift of the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the Transpolar Drift. We compared 7 different lead products based on 1. accumulated divergence derived from SAR images, 2. divergence in linear kinematic features, 3. classified SAR data, 4. thermal infrared data from MODIS, 5. passive microwave data from AMSR-2, 6. radar altimetry from CryoSat-2 (lead fractions and total lead count), and 7. thermal infrared data from helicopter surveys. We extracted daily lead fractions in a circle with a radius of 50 km along the drift of MOSAiC. Data is available from 5 October 2019 to 15 May 2020 with shorter time series for some of the sensors. We found that the mean lead fractions varied by 1 magnitude across different lead products due to different physical lead and sea ice properties observed by the sensors and methodological factors such as spatial resolution. Thus, the choice of lead product should align with the specific application. Each file contains time and lead fraction for a circular area (radius 50 km) around the MOSAiC position of the particular time stamp. The thermal infrared data from helicopter surveys are available from doi:10.1594/PANGAEA.951569.
    Keywords: Arctic Ocean; CSV text file; CSV text file (File Size); CSV text file (MD5 Hash); CT; File content; leads; MOSAiC; MOSAiC20192020; Multidisciplinary drifting Observatory for the Study of Arctic Climate; Ocean-ice-atmosphere interaction; Open-water fraction; Polarstern; PS122/1; PS122/1-track; PS122/2; PS122/2-track; PS122/3; PS122/3-track; PS122/4; PS122/4-track; PS122/5; PS122/5-track; sea ice deformation; Underway cruise track measurements
    Type: Dataset
    Format: text/tab-separated-values, 14 data points
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    DATA PANGAEA
  • 4
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    Binary sea ice lead maps derived from Sentinel-1 SAR images during MOSAiC expedition (2023)
    PANGAEA
    Details
    Publication Date: 2024-04-20
    Description: During winter, a significant part of the Arctic Ocean is covered with sea ice. Sea ice works as an insulation layer between the ocean and the atmosphere. The presence of leads is an important feature of the Arctic sea ice cover. Leads are areas with open water or thin ice, which are usually of elongated shape. Leads regulate the heat, gas, and moisture fluxes between the ocean and the atmosphere and are places of increased sea ice production, during periods of freezing conditions. Here binary lead maps derived from Sentinel-1 SAR images covering the MOSAiC expedition, which took place in the Central Arctic in 2019-2020, are presented. The data set contains 1596 classified Sentinel-1 scenes acquired in the extra wide swath (EW) mode with 400 km swath width and 40 meters pixel spacing. The maps are produced with a binary classification algorithm based on a convolutional neural network. Results are provided as geotiff images in the SAR geometry with the native SAR 40 meters pixel size. Georeferencing is done with ground control points corresponding to the ground control points provided with Sentinel-1 images.
    Keywords: Arctic Ocean; Binary Object; Binary Object (File Size); Binary Object (MD5 Hash); CT; DATE/TIME; LATITUDE; leads; LONGITUDE; Mosaic; MOSAiC; MOSAiC20192020; Multidisciplinary drifting Observatory for the Study of Arctic Climate; Polarstern; PS122/1; PS122/1-track; PS122/2; PS122/2-track; PS122/3; PS122/3-track; PS122/4; PS122/4-track; PS122/5; PS122/5-track; SAR; Sea ice; Sentinel-1; Synthetic Aperture Radar (SAR), Sentinel, 1A/B; Underway cruise track measurements
    Type: Dataset
    Format: text/tab-separated-values, 1596 data points
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    DATA PANGAEA
  • 5
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    Method for detection of leads from Sentinel-1 SAR images (2018)
    INT GLACIOL SOC
    In:  EPIC3Annals of Glaciology, INT GLACIOL SOC, ISSN: 0260-3055
    Details
    Publication Date: 2018-03-15
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 6
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    The 2018 North Greenland polynya observed by a newly introduced merged optical and passive microwave sea-ice concentration dataset (2019)
    In:  EPIC3The Cryosphere, 13(7), pp. 2051-2073, ISSN: 1994-0424
    Details
    Publication Date: 2020-05-06
    Description: Observations of sea-ice concentration are available from satellites year-round and almost weather-independently using passive microwave radiometers at resolutions down to 5 km. Thermal infrared radiometers provide data with a resolution of 1 km but only under cloud-free conditions. We use the best of the two satellite measurements and merge thermal infrared and passive microwave sea-ice concentrations. This yields a merged sea-ice concentration product combining the gap-free spatial coverage of the passive microwave sea-ice concentration and the 1 km resolution of the thermal infrared sea-ice concentration. The benefit of the merged product is demonstrated by observations of a polynya which opened north of Greenland in February 2018. We find that the merged sea-ice concentration product resolves leads at sea-ice concentrations between 60 % and 90 %. They are not resolved by the coarser passive microwave sea-ice concentration product. The benefit of the merged product is most pronounced during the formation of the polynya. Next, the environmental conditions during the polynya event are analysed. The polynya was caused by unusual southerly winds during which the sea ice drifted northward instead of southward as usual. The daily displacement was 50 % stronger than normal. The polynya was associated with a warm-air intrusion caused by a high-pressure system over the Eurasian Arctic. Surface air temperatures were slightly below 0 ∘C and thus more than 20 ∘C higher than normal. Two estimates of thermodynamic sea-ice growth yield sea-ice thicknesses of 60 and 65 cm at the end of March in the area opened by the polynya. This differed from airborne sea-ice thickness measurements, indicating that sea-ice growth processes in the polynya are complicated by rafting and ridging. A sea-ice volume of 33 km3 was produced thermodynamically.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
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    Same same, but different: Lead Fractions from divergence (2022)
    In:  EPIC3ESA Living Planet Symposium 2022, Bonn, 2022-05-23-2022-05-27
    Details
    Publication Date: 2022-06-07
    Description: In the polar oceans in winter, fractures and leads are the hotspots of exchange between the ocean and atmosphere which are otherwise well separated by sea ice. By altering the heat, gas, and momentum fluxes they play a crucial role in atmospheric, ecological, and oceanic processes. At the same time, leads represent a part of the present state of strain of the ice cover, opening up the possibility to study ice rheology. The transient nature of leads and their narrow appearance has set limits to the detection of leads from satellites. Different approaches using active and passive sensors from the microwave and infrared spectrum are employed so far to observe leads by means of satellite data. They make use of the strong contrast between leads and the surrounding ice pack in (i) surface temperature, (ii) microwave backscatter, (iii) emission or (iv) a change in ice drift speed. With the increasing availability of high-resolution SAR data for the Arctic, we explored the potential to use SAR derived sea ice deformation to estimate lead fractions. We calculated sea ice drift and divergence with a spatial resolution of 1.4 km from daily Sentinel-1 scenes. We obtained the divergence-based lead fraction of a region by summing up all positive divergence pixels multiplied by the respective time step length. We derived a second lead fraction product from the deformation fields that calculates the position of linear kinematic features (LKFs) first. The advantage is a skilled noise reduction, and a tracking algorithm of the deformation zones. We compared divergence- and LKF-based lead fractions to several other established lead fraction products in the Transpolar Drift along the drift track of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) between October 2019 to April 2020. We used lead fractions from helicopter-borne infrared surveys at a grid resolution of 5 m, classified Sentinel-1 (SAR) scenes at 80 m, MODIS (thermal infrared) at 1 km, AMSR2 (passive microwaves) at 3.25 km, and CryoSat-2 (altimeter in Ku-band) at 12.5 km. Since the methods rely on different physical properties of the water and ice in leads and are affected by different constraints, derived mean lead fractions vary by 1-2 magnitudes between the products. For example, infrared, SAR and microwave radiometer-based algorithms do not only detect open-water leads but also leads with thin ice up to a certain thickness, which differs between the products. Common lead events were identified across products. The time series mostly indicated a phase of increased lead activity during freeze-up in autumn 2019 and spring 2020. We used the different lead fraction time series to estimate new ice formation in the leads and compared the results to ice thickness and oceanographic measurements obtained during the MOSAiC campaign. Results yield lower and upper bounds for ice formation and brine expulsion in and from leads. Due to the wide range of lead fractions obtained from different methods, we conclude that the specific lead fraction product must be chosen depending on research question. Divergence- and LKF-based lead fractions provide valuable information in addition to established lead fraction products at high spatial resolution and independent of cloud coverage.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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  • 8
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    Lead fractions from SAR-derived sea ice divergence during MOSAiC (2024)
    Copernicus Publications
    In:  EPIC3The Cryosphere, Copernicus Publications, 18(3), pp. 1259-1285, ISSN: 1994-0416
    Details
    Publication Date: 2024-05-01
    Description: Leads and fractures in sea ice play a crucial role in the heat and gas exchange between the ocean and atmosphere, impacting atmospheric, ecological, and oceanic processes. We estimated lead fractions from high-resolution divergence obtained from satellite synthetic aperture radar (SAR) data and evaluated them against existing lead products. We derived two new lead fraction products from divergence with a spatial resolution of 700mcalculated from daily Sentinel-1 images. For the first lead product, we advected and accumulated the lead fractions of individual time nstances. With those accumulated divergence-derived lead fractions, we comprehensively described the presence of up to 10 d old leads and analyzed their deformation history. For the second lead product, we used only divergence pixels that were identified as part of linear kinematic features (LKFs). Both new lead products accurately captured the formation of new leads with widths of up to a few hundred meters. We resented a Lagrangian time series of the divergence-based lead fractions along the drift of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the central Arctic Ocean during winter 2019–2020. Lead activity was high in fall and spring, consistent with wind forcing and ice pack consolidation. At larger scales of 50–150 km around the MOSAiC expedition, lead activity on all scales was similar, but differences emerged at smaller scales (10 km). We compared our lead products with six others from satellite and airborne sources, including classified SAR, thermal infrared, microwave radiometer, and altimeter data. We found that the mean lead fractions varied by 1 order of magnitude across different lead products due to different physical lead and sea ice properties observed by the sensors and methodological factors such as spatial resolution. Thus, the choice of lead product should align with the specific application.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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