309 research outputs found

    The complementarity of SuperB with the LHC

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    The complementarity between results anticipated from SuperB with those from the LHC experiments is discussed here. SuperB can contribute to searches for new physics using indirect constraints via precision tests of the standard model. In addition to the indirect constraints, there are a number of direct searches that can be performed at low energy. There is a well motivated programme of measurements to make at SuperB, the results of which will add to our understanding of possible scenarios of physics beyond the standard model.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 4 page

    Strong Ocean Melting Feedback During the Recent Retreat of Thwaites Glacier

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    TermPicks: a century of Greenland glacier terminus data for use in scientific and machine learning applications

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    Marine-terminating outlet glacier terminus traces, mapped from satellite and aerial imagery, have been used extensively in understanding how outlet glaciers adjust to climate change variability over a range of timescales. Numerous studies have digitized termini manually, but this process is labor intensive, and no consistent approach exists. A lack of coordination leads to duplication of efforts, particularly for Greenland, which is a major scientific research focus. At the same time, machine learning techniques are rapidly making progress in their ability to automate accurate extraction of glacier termini, with promising developments across a number of optical and synthetic aperture radar (SAR) satellite sensors. These techniques rely on high-quality, manually digitized terminus traces to be used as training data for robust automatic traces. Here we present a database of manually digitized terminus traces for machine learning and scientific applications. These data have been collected, cleaned, assigned with appropriate metadata including image scenes, and compiled so they can be easily accessed by scientists. The TermPicks data set includes 39 060 individual terminus traces for 278 glaciers with a mean of 136 ± 190 and median of 93 of traces per glacier. Across all glaciers, 32 567 dates have been digitized, of which 4467 have traces from more than one author, and there is a duplication rate of 17 %. We find a median error of ∼ 100 m among manually traced termini. Most traces are obtained after 1999, when Landsat 7 was launched. We also provide an overview of an updated version of the Google Earth Engine Digitization Tool (GEEDiT), which has been developed specifically for future manual picking of the Greenland Ice Sheet

    Calving Dynamics and the Potential Impact of Mélange Buttressing at the Western Calving Front of Thwaites Glacier, West Antarctica

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    The western region of the wide Thwaites Glacier terminus is characterized by a near‐vertical calving front. The grounding line at this western calving front (WCF) rests on a relatively high ridge, behind which exists a reverse‐sloping bed; retreat of the grounding line into this over‐deepening basin could therefore expose deep calving faces that may be subject to ice‐cliff failure. Here, we use the 3D Helsinki Discrete Element Model to identify the factors that control the calving dynamics in this location. We then focus on the ability of mélange to influence these dynamics given the wide embayment in which Thwaites Glacier terminates. We find that calving along the WCF is currently influenced by ice flow across the grounding line and consequent longitudinal tensile stress and rift formation. Calving is slowed in simulations that are initiated with a highly constricted mélange, with a thicker mélange suppressing calving entirely. We liken the constrained simulations to a scenario in which mélange piles behind a large grounded iceberg. In a future which may see calving become a more dominant control on the retreat of Thwaites Glacier, this type of blockage will be necessary for robust force chains to develop and transmit resistive forces to the terminus. The ability of the mélange to hinder calving at this location will be determined by the presence and rigidity of binding land‐fast sea ice and iceberg keel depths. Therefore, it is necessary to represent calving, mélange and sea ice in a single framework to predict the fate of Thwaites Glacier
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