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  • 1
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    AMER GEOPHYSICAL UNION
    In:  EPIC3Journal of Geophysical Research-Oceans, AMER GEOPHYSICAL UNION, 118, ISSN: 0148-0227
    Publication Date: 2017-01-20
    Description: This study deals with observations and simulations of the evolution of coastal polynias focusing on the Ronne Polynia. We compare differences in polynia extent and ice drift patterns derived from satellite radar images and from simulations with the Finite Element Sea Ice Ocean Model, employing three atmospheric forcing data sets that differ in spatial and temporal resolution. Two polynia events are analyzed, one from austral summer and one from late fall 2008. The open water area in the polynia is of similar size in the satellite images and in the model simulations, but its temporal evolution differs depending on katabatic winds being resolved in the atmospheric forcing data sets. Modeled ice drift is slower than the observed and reveals greater turning angles relative to the wind direction in many cases. For the summer event, model results obtained with high-resolution forcing are closer to the drift field derived from radar imagery than those from coarse resolution forcing. For the late fall event, none of the forcing data yields outstanding results. Our study demonstrates that a dense (1–3 km) model grid and atmospheric forcing provided at high spatial resolution ( 〈 50 km) are critical to correctly simulate coastal polynias with a coupled sea-ice ocean model.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Impact of West Antarctic Ice Shelf melting on the Southern Ocean Hydrography, Cryosphere, COPERNICUS GESELLSCHAFT MBH, ISSN: 1994-0416
    Publication Date: 2020-07-08
    Description: Previous studies show accelerations of West Antarctic glaciers, implying that basal melt rates of these glaciers were previously small and increased in the middle of the 20th century. This enhanced melting is a likely source of the observed Ross Sea (RS) freshening, but its long-term impact on the Southern Ocean hydrography has never been investigated. Here, we conduct coupled sea-ice/ice-shelf/ocean simulations with different levels of ice shelf melting from West Antarctic glaciers. Freshening of RS shelf and bottom water is simulated with enhanced West Antarctic ice shelf melting, while no significant changes in shelf water properties are simulated when West Antarctic ice shelf melting is small. We further show that the freshening caused by glacial meltwater from ice shelves in the Amundsen and Bellingshausen Seas propagates further downstream along the East Antarctic coast into the Weddell Sea. Our experiments also show the timescales for the freshening signal to reach other regions around the Antarctic continent. The freshening signal propagates onto the RS continental shelf within a year of model simulation, while it takes roughly 5–10 years and 10–15 years to propagate into the region off Cape Darnley and into the Weddell Sea, respectively. This advection of freshening signal} possibly modulates the properties of dense shelf water and impacts the production of Antarctic Bottom Water.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
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    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Ocean Science, COPERNICUS GESELLSCHAFT MBH, 13, pp. 765-776, ISSN: 1812-0784
    Publication Date: 2017-09-25
    Description: The Regional Antarctic ice and Global Ocean (RAnGO) model has been developed to study the interaction between the world ocean and the Antarctic ice sheet. The coupled model is based on a global implementation of the Finite Element Sea-ice Ocean Model (FESOM) with a mesh refinement in the Southern Ocean, particularly in its marginal seas and in the sub-ice shelf cavities. The cryosphere is represented by a regional setup of the ice flow model RIMBAY comprising the Filchner-Ronne Ice Shelf and the grounded ice in its catchment area up to the ice divides. At the base of the RIMBAY ice shelf, melt rates from FESOM's ice-shelf component are supplied. RIMBAY returns ice thickness and the position of the grounding line. The ocean model uses a pre-computed mesh to allow for an easy adjustment of the model domain to a varying cavity geometry. RAnGO simulations with a 20th-century climate forcing yield realistic basal melt rates and a quasi-stable grounding line position close to the presently observed state. In a centennial-scale warm-water-inflow scenario, the model suggests a substantial thinning of the ice shelf and a local retreat of the grounding line. The potentially negative feedback from ice-shelf thinning through a rising in-situ freezing temperature is more than outweighed by the increasing water column thickness in the deepest parts of the cavity. Compared to a control simulation with fixed ice-shelf geometry, the coupled model thus yields a slightly stronger increase of ice-shelf basal melt rates.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 4
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    AMER GEOPHYSICAL UNION
    In:  EPIC3Journal of Geophysical Research-Oceans, AMER GEOPHYSICAL UNION, 116(C12038), pp. 1-18, ISSN: 0148-0227
    Publication Date: 2019-07-17
    Description: The polynyas of the Laptev Sea are regions of particular interest due to the strong formation of Arctic sea-ice. In order to simulate the polynya dynamics and to quantify ice production, we apply the Finite Element Sea-Ice Ocean Model FESOM. In previous simulations FESOM has been forced with daily atmospheric NCEP (National Centers for Environmental Prediction) 1. For the periods 1 April to 9 May 2008 and 1 January to 8 February 2009 we examine the impact of different forcing data: daily and 6-hourly NCEP reanalyses 1 (1.875° × 1.875°), 6-hourly NCEP reanalyses 2 (1.875° × 1.875°), 6-hourly analyses from the GME (Global Model of the German Weather Service) (0.5° × 0.5°) and high-resolution hourly COSMO (Consortium for Small-Scale Modeling) data (5 km × 5 km). In all FESOM simulations, except for those with 6-hourly and daily NCEP 1 data, the openings and closings of polynyas are simulated in principle agreement with satellite products. Over the fast-ice area the wind fields of all atmospheric data are similar and close to in situ measurements. Over the polynya areas, however, there are strong differences between the forcing data with respect to air temperature and turbulent heat flux. These differences have a strong impact on sea-ice production rates. Depending on the forcing fields polynya ice production ranges from 1.4 km3 to 7.8 km3 during 1 April to 9 May 2011 and from 25.7 km3 to 66.2 km3 during 1 January to 8 February 2009. Therefore, atmospheric forcing data with high spatial and temporal resolution which account for the presence of the polynyas are needed to reduce the uncertainty in quantifying ice production in polynyas.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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