http://hdl.handle.net/2122/129 2013-05-23T12:37:37Z http://hdl.handle.net/2122/8391 Title: Calving
 event 
detection 
by
 observation 
of 
seiche 
effects 
on 
the
 Greenland 
fjords Authors: Walter, F.; Swiss
 Seismological 
Service, 
ETH 
Zürich,
 Switzerland; Laboratory
 of
 Hydraulics,
 Hydrology 
and
 Glaciology,
 ETH
 Zürich,
 Switzerland; Olivieri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Clinton, J.; Swiss
 Seismological 
Service, 
ETH 
Zürich,
 Switzerland Abstract: With mass loss from the Greenland ice sheet accelerating and spreading to higher latitudes, the quantification of mass discharge in the form of icebergs has recently received much scientific attention. Here, we make use of very low frequency (0.001-0.01 Hz) seismic data from three permanent broadband stations installed in the summers of 2009/2010 in northwest Greenland in order to monitor local calving activity. At these frequencies, calving seismograms are dominated by a tilt signal produced by local ground flexure in response to fjord seiching generated by major iceberg calving events. A simple triggering algorithm is proposed to detect calving events from large calving fronts with potentially no user interaction. Our calving catalogue identifies spatial and temporal differences in calving activity between Jakobshavn Isbræ and glaciers in the Uummannaq district some 200 km further north. The Uummannaq glaciers show clear seasonal fluctuations in seiche-based calving detections as well as seiche amplitudes. In contrast, the detections at Jakobshavn Isbræ show little seasonal variation, which may be evidence for an ongoing transition into winter calving activity. The results offer further evidence that seismometers can provide efficient and inexpensive monitoring of calving fronts. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7248 Title: Getting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year Authors: Bindschadler, R.; Code 614.0, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; Choi, H.; SAIC, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Wichlacz, A.; SAIC, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Bingham, R.; School of Geosciences, University of Aberdeen, Aberdeen, AB24 3FX, UK; Bohlander, J.; National Snow and Ice Data Center, University of Colorado, Boulder CO 80309-0449, USA; Brunt, K.; Code 614.1, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Corr, H.; British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK; Drews, R.; Alfred Wegener Institut for Polar and Marine Research, Postfach 12 01 61, 27515 Bremerhaven, Germany; Fricker, H.; Scripps Institute of Oceanography, University of California at San Diego, 9500 Giman Drive, La Jolla CA 92093, USA; Hall, M.; Climate Change Institute, University of Maine, Orono ME 04469, USA; Hindmarsh, R.; British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK; Kohler, J.; Norwegian Polar Institute, Polar Environmental Centre, 9296 Tromso, Norway; Padman, L.; Earth and Space Research (ESR), 3350 SW Cascade Ave., Corvallis, OR 97333-1536, USA; Rack, W.; Gateway Antarctica, University of Canterbury, Private Bag, Christchurch 8140, New Zealand; Rotschky, G.; Norwegian Polar Institute, Polar Environmental Centre, 9296 Tromso, Norway; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Vornberger, P.; SAIC, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA; Young, N.; Australian Antarctic Division, University of Tasmania, Kingston, Tasmania 7050, Australia Abstract: Two ice-dynamic transitions of the Antarctic ice sheet – the boundary of grounded ice features and the freelyfloating boundary – are mapped at 15-m resolution by participants of the International Polar Year project ASAID using customized software combining Landsat-7 imagery and ICESat/GLAS laser altimetry. The grounded ice boundary is 53 610 km long; 74% abuts to floating ice shelves or outlet glaciers, 19% is adjacent to open or sea-ice covered ocean, and 7% of the boundary ice terminates on land. The freelyfloating boundary, called here the hydrostatic line, is the most landward position on ice shelves that expresses the full amplitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma) accuracies of the grounded ice boundary vary an order of magnitude ranging from ±52m for the land and open-ocean terminating segments to ±502m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevations along each line are selected from 6 candidate digital elevation models based on their agreement with ICESat elevation values and surface shape inferred from the Landsat imagery. Elevations along the hydrostatic line are converted to ice thicknesses by applying a firn-correction factor and a flotation criterion. BEDMAP-compiled data and other airborne data are compared to the ASAID elevations and ice thicknesses to arrive at quantitative (one-sigma) uncertainties of surface elevations of ±3.6, ±9.6, ±11.4, ±30 and ±100m for five ASAID-assigned confidence levels. Over one-half of the surface elevations along the grounded ice boundary and over one-third of the hydrostatic line elevations are ranked in the highest two confidence categories. A comparison between ASAID-calculated ice shelf thicknesses and BEDMAP-compiled data indicate a thin-ice bias of 41.2±71.3m for the ASAID ice thicknesses. The relationship between the seaward offset of the hydrostatic line from the grounded ice boundary only weakly matches a prediction based on beam theory. The mapped products along with the customized software to generate them and a variety of intermediate products are available from the National Snow and Ice Data Center. 2011-06-30T22:00:00Z http://hdl.handle.net/2122/6870 Title: A dynamic Biologically-Active Layer for numerical studies of the sea ice ecosystem. Authors: Tedesco, L.; CMCC; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Haapala, J.; FMI; Stipa, T.; FMI Abstract: This work introduces a novel approach for the modelling and coupling of sea ice biology to sea ice physics. The central concept of the coupling is the definition of the Biologically Active Layer, which is the time-varying fraction of sea ice that is connected to the ocean via brine pockets and channels, and acts as a rich habitat for many microorganisms. A simple but comprehensive physical model of the sea ice thermohalodynamics is coupled to a novel sea ice microalgal model of growth in the framework of the Biogeochemical Flux Model. The physical model provides the key physical properties of the Biologically Active Layer and the biological model simulates the physiological and ecological response of the algal community to the physical environment. Numerical simulations of chl-a were compared with observations at two different ice stations, in the Baltic and off the coast of Greenland, showing that this new coupling structure is sufficiently generic to represent well the temporal and spatial distribution of sea ice algae during the whole ice season at both sites. This model implementation and coupling structure is viable as a new component of General Circulation Models, allowing for estimates of the role and importance of sea ice biology in the local and global carbon cycle. 2009-12-31T23:00:00Z http://hdl.handle.net/2122/5956 Title: BFM-SI: A new implementation of the biogeochemical flux model in sea ice Authors: Tedesco, Letizia; CMCC; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia Abstract: This work describes a novel implementation of the Biogeochemical Flux Model (BFM) in a sea ice system (BFMSI). The chosen representative groups of the sea ice food web rely on the same dynamics as the BFM. The main differences between BFM and BFMSI stand in the type and number of functional groups, in the parameters assigned to several physiological and ecological processes and in the dimensional size classes they represent. The differential equations of BFMSI are written here according to the nomenclature associated to the new sea ice state variables. At the boundaries, the sea ice system is also coupled to the atmosphere and to the ocean through the exchange of organic and inorganic matter. This is done by computing the entrapment of particulate and dissolved matter and gases when sea ice grows and release to the ocean when sea ice melts to ensure mass conservation. The implementation of the BFM in sea ice and the coupling structure in General Circulation Models will add a new component that may provide new adequate estimate of the role and importance of sea ice biogeochemistry in the global carbon cycle. 2010-02-28T23:00:00Z http://hdl.handle.net/2122/4082 Title: Analysis of bottom morphology of the David Glacier-Drygalski Ice Tongue, East Antarctica Authors: Tabacco, I. E.; Sezione Geofisica, Dipartimento di Science della Terra, Università degli Studi di Milano, I-20129 Milano, Italy; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Data from radio-sounding measurements have been analysed to determine the ice thickness and the bottom morphology of Drygalski Ice Tongue, Antarctica. The morphology and the structure of the bottom surface has been studied through an electromagnetic interpretation. A function that includes the gain/loss due to the geometrical shape of the reflecting surfaces has been calculated. Such a function has been evaluated assuming some physical electromagnetic quantities (the temperature of the glacier, the complex dielectric permittivity of ice, sea ice and sea water). The ice-water interface shows both concave and convex faces toward the sounding system, producing a focusing or defocusing effect, detected as absolute (or relative) amplitude variation in the echo signal. It is shown that the calculated function follows quite well the observed bottom rippled surface of the glacier tongue estimated from the time-arrival measurements of the echo signal. 1999-12-31T23:00:00Z http://hdl.handle.net/2122/3435 Title: Development of a numerical model of sea ice for biogeochemical studies. Part 1: Sea-ice thermodynamics Authors: Tedesco, L.; CMCC; Vichi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Haapala, J.; Finnish Institute of Marine Research, Helsinki, Finland; Stipa, T.; Finnish Institute of Marine Research, Helsinki, Finland Abstract: A fully prognostic 1-D thermodynamic model, functional for studies of sea-ice biogeochemistry is developed to better understand the physical processes and the interactions between the environment and the sea-ice ecosystem. The physical model is capable of simulating seasonal changes of snow and ice thickness. Particular attention is paid to reproduce the snow-ice and the superimposed ice formation which play important roles in the dynamics of sea ice algae. The assessment of the model capabilities is done in 1979--1993 at four different stations in the Baltic Sea. A sensitivity analysis stresses the importance of adequate surface forcing functions to properly simulate the onset of sea ice. Our results show that thickness of the ice layers and timing of the melting are in good agreement with the observed data and confirm that one of the key variables in modelling sea-ice thermodynamics is the snow layer and its metamorphism. 2006-12-31T23:00:00Z