English
norskBlar i forfatter "Johansson, Malin"
Viser treff 21-36 av 36
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Multi-frequency polarimetric SAR signatures of lead sea ice and oil spills
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)Synthetic aperture radar is used to identify and monitor oil spills. Separation from oil spill look-alikes is an important part of a fully automatic oil spill detection scheme. Here we investigate the polarimetric signatures for oil spills and newly formed sea ice (a well-known look-alike) in fully polarimetric Radarsat-2 satellite scenes. Using the fully polarimetric scenes we calculate four different ... -
Multi-mission remote sensing of low concentration produced water slicks
(Journal article; Tidsskriftartikkel, 2021-04)Produced water is legally released from oil platforms and often detected by oil spill detection services despite their low oil concentrations. Using fully-polarimetric RADARSAT-2 and dual-polarimetric Sentinel-1 data we investigate their synthetic aperture radar (SAR) characteristics. Detectability ranges within the SAR and optical Sentinel-2 and PlanetScope images are assessed and compared to in-situ ... -
Newly-formed sea ice distinction near the oil platform Prirazlomnaya in the Pechora Sea using polarimetric Radarsat-2 SAR observations
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-01)A polarimetric approach developed to discriminate oil slicks and look-alikes was used to study the polarimetric properties of newly-formed ice (NFI) observed near the Prirazlomnaya oil platform. This approach is based on the multipolarization parameter called Resonant to Non-resonant signal Damping (RND), which is related to the ratio between the ice damping and the short wind waves and wave breakings. ... -
Observing Oil Releases from Platforms Using Synthetic Aperture Radar
(Conference object; Konferansebidrag, 2018)Synthetic aperture radar (SAR) is used for operational surveillance of ocean areas and oil spill detection. Oil spills are frequently detected around oil platforms due to the releases of so-called produced water (PW), which is water containing low concentrations of oil that can form surface slicks similar to other oil spills. PW releases are legal within given limits. Understanding the signatures ... -
Performance Analysis of Roll-Invariant PolSAR Parameters from C-band images with Regard to Sea Ice Type Separation
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06)The Polarimetric Synthetic Aperture Radar (PolSAR) backscatter from a target is dependent on the incidence angle. Consequently, the associated roll invariant parameters are affected by changes in incidence angle. In this work, we identify a few of these parameters that remain robust in identifying sea ice features even under large incidence angle variations. We conclude that the helicity angle ... -
A red tide in the pack ice of the Arctic Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-02)In the Arctic Ocean ice algae constitute a key ecosystem component and the ice algal spring bloom a critical event in the annual production cycle. The bulk of ice algal biomass is usually found in the bottom few cm of the sea ice and dominated by pennate diatoms attached to the ice matrix. Here we report a red tide of the phototrophic ciliate <i>Mesodinium rubrum</i> located at the ice-water interface ... -
Report From Surveys To Assess Harp And Hooded Seal Pup Production In The Greenland Sea Pack-Ice In 2022
(Research report; Forskningsrapport, 2022-06-07)Cruise no.: 2022703 : The 2022 survey of harp and hooded seal pup production in the Greenland Sea was carried out to obtain updated estimates to be used to assess current status of these two seal stocks. Since a similar survey in 2018 indicated a 40% reduction in harp seal pup production since the 2012 survey, and the continued lack of increase in pup production of the severely depleted hooded ... -
Robustness of SAR Sea Ice Type classification across incidence angles and seasons at L-band
(Journal article; Tidsskriftartikkel, 2020-11-16)In recent years, space-borne synthetic aperture radar (SAR) polarimetry has become a valuable tool for sea ice type retrieval. L-band SAR has proven to be sensitive toward deformed sea ice and is complementary compared with operationally used C-band SAR for sea ice type classification during the early and advanced melt seasons. Here, we employ an artificial neural network (ANN)-based sea ice type ... -
Sea ice classification of TerraSAR-X ScanSAR images for the MOSAiC expedition incorporating per-class incidence angle dependency of image texture
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-16)We provide sea ice classification maps of a subweekly time series of single (horizontal–horizontal, HH) polarization X-band TerraSAR-X scanning synthetic aperture radar (TSX SC) images from November 2019 to March 2020, covering the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This classified time series benefits from the wide spatial coverage ... -
Separation and characterisation of mineral oil slicks and newly formed sea ice in L-band synthetic aperture radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-14)Maritime activities in the Arctic Ocean is increasing and consequently the risk for an oil spill there is rising. Synthetic Aperture Radar (SAR) is used operationally to detect and monitor oil slicks and for sea ice monitoring and observations. Leads are often used for ship routing and within the leads newly formed sea ice is often present. Separation between the low backscatter areas that constitutes ... -
Synthetic Aperture Radar Remote Sensing of Operational Platform Produced Water Releases
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-03)Oil spill detection services based on satellite synthetic aperture radar (SAR) frequently detect oil slicks close to platforms due to legal releases of produced water. Separating these slicks from larger releases, e.g., due to accidental leakage is challenging. The aim of this work is to investigate the SAR characteristics of produced water, including the typical appearance in HH/VV data, possible ... -
Towards automatic detection of dark features in the Barents Sea using synthetic aperture radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-17)Increased human presence and commercial activities in the Barents Sea (fishing, offshore oil and gas exploration) are amplifying the need for large-scale operational ocean monitoring of the eventual oil spills in the region. The geographical location and climate impose additional constraints on satellite-based monitoring, making it necessary to use Synthetic Aperture Radar (SAR). Dark features or ... -
Towards operational sea ice type retrieval using L-band Synthetic aperture radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-14)Operational ice services around the world have recognized the economic and environmental benefits that come from the increased capabilities and uses of space-borne Synthetic Aperture Radar (SAR) observation system. The two major objectives in SAR based remote sensing of sea ice is on the one hand to have a large areal coverage, and on the other hand to obtain a radar response that carries as much ... -
Winter storms accelerate the demise of sea ice in the Atlantic sector of the Arctic Ocean
(Journal article; Peer reviewed, 2019-06-25)A large retreat of sea-ice in the ‘stormy’ Atlantic Sector of the Arctic Ocean has become evident through a series of record minima for the winter maximum sea-ice extent since 2015. Results from the Norwegian young sea ICE (N-ICE2015) expedition, a five-month-long (Jan-Jun) drifting ice station in first and second year pack-ice north of Svalbard, showcase how sea-ice in this region is frequently ... -
X-, C-, and L-band SAR signatures of newly formed sea ice in Arctic leads during winter and spring
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-02)We examine an extensive synthetic aperture radar (SAR) data set from the Arctic Ocean spanning a time period from January to June 2015, with the aim of identifying multi-polarization parameters that can be used to accurately separate newly formed sea ice from the surroundings. Newly formed sea ice areas both provide favourable routing for ship traffic, and are key to Arctic climate science because ... -
Year-around C- and L-band observation around the MOSAiC ice floe with high spatial and temporal resolution
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-12)In September 2019, the German research icebreaker Polarstern started the largest multidisciplinary Arctic expedition, the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift experiment. Being moored to ice floes at high Arctic for a whole year, thus including the winter season, the main goal of the expedition is to better understand and quantify relevant processes ...
