Recent additions

  • Retrieval of Snow Depth on Arctic Sea Ice From Surface-Based, Polarimetric, Dual-Frequency Radar Altimetry 

    Willatt, Rosemary; Stroeve, Julienne; Nandan, Vishnu; Newman, Thomas; Mallett, Robbie; Hendricks, Stefan; Ricker, Robert; Mead, James; Itkin, Polona; Tonboe, Rasmus; Wagner, David N.; Spreen, Gunnar; Liston, Glen; Schneebeli, Martin; Krampe, Daniela; Tsamados, Michel; Demir, Oguz; Wilkinson, Jeremy; Jaggi, Matthias; Zhou, Lu; Huntemann, Marcus; Raphael, Ian A.; Jutila, Arttu; Oggier, Marc (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-18)
    Snow depth on sea ice is an Essential Climate Variable and a major source of uncertainty in satellite altimetry-derived sea ice thickness. During winter of the MOSAiC Expedition, the “KuKa” dual-frequency, fully polarized Ku- and Ka-band radar was deployed in “stare” nadir-looking mode to investigate the possibility of combining these two frequencies to retrieve snow depth. Three approaches ...
  • A long-term proxy for sea ice thickness in the Canadian Arctic: 1996-2020 

    Glissenaar, Isolde A.; Landy, Jack Christopher; Babb, David G.; Dawson, Geoffrey J.; Howell, Stephen E. L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-15)
    . This study presents a long-term winter sea ice thickness proxy product for the Canadian Arctic based on a random forest regression model – applied to ice charts and scatterometer data, trained on CryoSat-2 observations, and applying an ice type–sea ice thickness correction using the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) – that provides 25 years of sea ice thickness ...
  • Comparing elevation and backscatter retrievals from CryoSat-2 and ICESat-2 over Arctic summer sea ice 

    Dawson, Geoffrey J.; Landy, Jack Christopher (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-27)
    The CryoSat-2 radar altimeter and ICESat-2 laser altimeter can provide complementary measurements of the freeboard and thickness of Arctic sea ice. However, both sensors face significant challenges for accurately measuring the ice freeboard when the sea ice is melting in summer months. Here, we used crossover points between CryoSat2 and ICESat-2 to compare elevation retrievals over summer sea ...
  • The weakening AMOC under extreme climate change 

    Madan, Gaurav; Gjermundsen, Ada; Iversen, Silje Christine; Lacasce, Joseph Henry (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-06)
    Changes in the Atlantic Meridional Overturning Circulation (AMOC) in the quadrupled CO<sub>2</sub> experiments conducted under the sixth Coupled Model Intercomparison Project (CMIP6) are examined. Increased CO<sub>2</sub> triggers extensive Arctic warming, causing widespread melting of sea ice. The resulting freshwater spreads southward, frst from the Labrador Sea and then the Nordic Seas, and ...
  • The Detection and Attribution of Northern Hemisphere Land Surface Warming (1850–2018) in Terms of Human and Natural Factors: Challenges of Inadequate Data 

    Soon, Willie; Connolly, Ronan; Connolly, Michael; Akasofu, Syun-Ichi; Baliunas, Sallie; Berglund, Johan; Bianchini, Antonio; Briggs, William M.; Butler, C.J.; Cionco, Rodolfo Gustavo; Crok, Marcel; Elias, Ana G.; Fedorov, Valery M.; Gervais, François; Harde, Hermann; Henry, Gregory W.; Hoyt, Douglas V.; Humlum, Ole; Legates, David R.; Lupo, Anthony R.; Maruyama, Shigenori; Moore, Patrick; Ogurtsov, Maxim; ÓhAiseadha, Coilín; Oliveira, Marcos J.; Park, Seok-Soon; Qiu, Shican; Quinn, Gerré; Scafetta, Nicola; Solheim, Jan Erik; Steele, Jim; Szarka, László; Tanaka, Hiroshi L.; Taylor, Mitchell K.; Vahrenholt, Fritz; Velasco Herrera, Víctor M.; Zhang, Weijia (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-28)
    A statistical analysis was applied to Northern Hemisphere land surface temperatures (1850–2018) to try to identify the main drivers of the observed warming since the mid-19th century. Two different temperature estimates were considered—a rural and urban blend (that matches almost exactly with most current estimates) and a rural-only estimate. The rural and urban blend indicates a long-term warming ...
  • Demonstrating low Raman background in UV-written SiO2 waveguides 

    Jensen, Mathias Novik; Gates, James C.; Flint, Alex I.; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-06)
    Raman spectroscopy can give a chemical ’fingerprint’ from both inorganic and organic samples, and has become a viable method of measuring the chemical composition of single biological particles. In parallel, integration of waveguides and microfluidics allows for the creation of miniaturized optical sensors in lab-on-a-chip devices. The prospect of combining integrated optics and Raman spectroscopy ...
  • Barents-2.5km v2.0: an operational data-assimilative coupled ocean and sea ice ensemble prediction model for the Barents Sea and Svalbard 

    Röhrs, Johannes; Gusdal, Yvonne; Rikardsen, Edel S. U.; Durán Moro, Marina; Brændshøi, Jostein; Kristensen, Nils Melsom; Fritzner, Sindre Markus; Wang, Keguang; Sperrevik, Ann Kristin; Idzanovic, Martina; Lavergne, Thomas; Debernard, Jens Boldingh; Christensen, Kai Håkon (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-22)
    An operational ocean and sea ice forecast model, Barents-2.5, is implemented for short-term forecasting at the coast off northern Norway, the Barents Sea, and the waters around Svalbard. Primary forecast parameters are sea ice concentration (SIC), sea surface temperature (SST), and ocean currents. The model also provides input data for drift modeling of pollutants, icebergs, and search-and-rescue ...
  • Change in Climate Sensitivity and Its Dependence on the Lapse-Rate Feedback in 4 x CO2 Climate Model Experiments 

    Eiselt, Kai-Uwe; Graversen, Rune Grand (Journal article; Tidsskriftartikkel, 2022-04-19)
    Robust estimates of climate sensitivity are important for decision-making on mitigation of climate change. However, climate sensitivity and its governing processes are still subject to large uncertainty. Recently it has been established that climate sensitivity changes over time in numerical climate model experiments with abrupt quadrupling of the CO<sub>2</sub> concentration. Here we conduct an ...
  • Selective Imputation for Multivariate Time Series Datasets with Missing Values 

    Blazquez-Garcia, Ane; Wickstrøm, Kristoffer Knutsen; Yu, Shujian; Mikalsen, Karl Øyvind; Boubekki, Ahcene; Conde, Angel; Mori, Usue; Jenssen, Robert; Lozano, Jose A. (Journal article; Tidsskriftartikkel, 2023-01-31)
    Multivariate time series often contain missing values for reasons such as failures in data collection mechanisms. Since these missing values can complicate the analysis of time series data, imputation techniques are typically used to deal with this issue. However, the quality of the imputation directly affects the performance of downstream tasks. In this paper, we propose a selective imputation ...
  • Assimilation of high-resolution ice charts in a coupled ocean-sea-ice model 

    Fritzner, Sindre Markus; Christensen, Kai Håkon; Graversen, Rune; Wang, Keguang (Journal article; Tidsskriftartikkel, 2019)
    In this study, we show assimilation results from a coupled ocean sea-ice model. The model has a horizontal resolution of 2.5 km. In the assimilation system, we assimilate high-resolution ice charts, structured on a 1 km grid. We compare the assimilation of passive microwave observations with the assimilation of ice charts. It is shown that the ice charts have a larger impact on the assimilation ...
  • Image analysis and segmentation of polar mesospheric summer echoes 

    Jozwicki, Dorota (Conference object; Konferansebidrag, 2022-07)
  • Structured Illumination Microscopy of Biological Structures 

    Wolfson, Deanna; Villegas, Luis; Opstad, Ida Sundvor; Birgisdottir, Åsa birna; Øie, Cristina Ionica; Ahluwalia, Balpreet Singh (Conference object; Konferansebidrag, 2018)
    <p>Resolution in optical microscopy has long been limited to the Abbe diffraction limit, i.e. about 250 nm laterally for visible wavelengths on a very good microscope. In the last two decades several techniques have been devised to circumvent this limit: an achievement which was recognized with the 2014 Nobel Prize in Chemistry. Structured Illumination Microscopy (SIM) was the first of these techniques ...
  • Observing Oil Releases from Platforms Using Synthetic Aperture Radar 

    Skrunes, Stine; Johansson, Malin; Brekke, Camilla (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 ...
  • Selecting principal attributes in multimodal remote sensing for sea ice characterization 

    Khachatrian, Eduard; Chlaily, Saloua; Eltoft, Torbjørn; Marinoni, Andrea (Chapter; Bokkapittel, 2021)
    Automatic ice charting cannot be achieved using only SAR modalities. It is fundamental to combine information from other remote sensors with different characteristics for more reliable sea ice characterization. In this paper, we employ principal feature analysis (PFA) to select significant information from multimodal remote sensing data. PFA is a simple yet very effective approach that can be applied ...
  • Detecting the linear and non-linear causal links for disturbances in the power grid 

    Foldvik Eikeland, Odin; Bianchi, Filippo Maria; Holmstrand, Inga Setsa; Bakkejord, Sigurd; Chiesa, Matteo (Chapter; Bokkapittel, 2021)
    Unscheduled power disturbances cause severe consequences for customers and grid operators. To avoid suchevents, it is important to identify the causes and localize the sources of the disturbances in the power distribution network. In this work, we focus on a specific power grid in the Arctic region of Northern Norway that experiences an increased frequency of failures of unspecified origin.
  • Learning nanoscale motion patterns of vesicles in living cells 

    Sekh, Arif Ahmed; Opstad, Ida Sundvor; Birgisdottir, Åsa Birna; Myrmel, Truls; Ahluwalia, Balpreet Singh; Agarwal, Krishna; Prasad, Dilip K. (Chapter; Bokkapittel, 2020)
    Detecting and analyzing nanoscale motion patterns of vesicles, smaller than the microscope resolution (~250 nm), inside living biological cells is a challenging problem. State-of-the-art CV approaches based on detection, tracking, optical flow or deep learning perform poorly for this problem. We propose an integrative approach, built upon physics based simulations, nanoscopy algorithms, and shallow ...
  • A Kernel to Exploit Informative Missingness in Multivariate Time Series from EHRs 

    Mikalsen, Karl Øyvind; Ruiz, Cristina Soguero; Jenssen, Robert (Chapter; Bokkapittel, 2020)
    A large fraction of the electronic health records (EHRs) consists of clinical measurements collected over time, such as lab tests and vital signs, which provide important information about a patient’s health status. These sequences of clinical measurements are naturally represented as time series, characterized by multiple variables and large amounts of missing data, which complicate the analysis. ...
  • A Protocol for Single-Molecule Translation Imaging in Xenopus Retinal Ganglion Cells 

    Ströhl, Florian; Lin, Julie Qiaojin; Tartwijk, Francesca W. van; Wong, Hovy Ho Wai; Holt, Christine E.; Kaminski, Clemens F. (Chapter; Bokkapittel, 2020-04-29)
    Single-molecule translation imaging (SMTI) is a straightforward technique for the direct quantification of local protein synthesis. The protein of interest is fused to a fast-folding and fast-bleaching fluorescent protein, allowing one to monitor the appearance of individual fluorescence events after photobleaching of pre-existing proteins in the cell under investigation. The translation of individual ...
  • Unsupervised Band Selection for Hyperspectral Datasets by Double Graph Laplacian Diagonalization 

    Khachatrian, Eduard; Chlaily, Saloua; Eltoft, Torbjørn; Gamba, Paolo; Marinoni, Andrea (Journal article; Tidsskriftartikkel, 2021)
    The vast amount of spectral information provided by hyperspectral images can be useful for different applications. However, the presence of redundant bands will negatively affect application performance. Therefore, it is crucial to select a relevant subset that preserves the information of the original set. In this paper, we present an automatic and accurate band selection method based on Graph ...
  • Explaining doping in material research (Hf substitution in ZnO films) by directly quantifying the van der Waals force 

    Lai, Chia-Yun; Santos Hernandez, Sergio; Moser, Toni; Alfakes, Boulos; Lu, Chun-Yu; Olukan, Tuza Adeyemi; Rajput, Nitul; Boström, Tobias; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-04)
    Non-monotonic behavior has been observed in the optoelectronic properties of ZnO thin films as doped with Hf (HZO). Here we propose that two competing mechanisms are responsible for such behaviour. Specifically, we propose that provided two crystal orientations dominate film growth, only one of them might be responsible for direct Hf substitution. Nonmonotonic behaviour is expected at once by ...

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