Mine Burial Observations During the 2003–2004 U.S. Office of Naval Research Experiment

During the 2003-2004 winter season, the U.S. Office of Naval Research (ONR, Arlington, VA), sponsored a detailed in situ study of the mine burial process resulting from wave-seafloor-mine interaction at Martha´s Vineyard Coastal Observatory (MVCO, Edgartown, MA). In total, 16 mine shapes were deployed. Six were the Forschungsanstalt der Bundeswehr fur Wasserschall und Geophysik (FWG, Kiel, Germany) burial registration mines using optical sensors, four others were equipped with acoustical sensors, and six were simple shapes. Repeated acoustic surveys and detailed sediment sampling were conducted to characterize the site and the burial status of all objects. This paper focuses on data from three recovered optical systems. The records show three roll events at all three registration mines, which are necessary for scour burial. Two systems experienced a fourth roll event. Results from earlier experiments suggest only three (four) stages of progressively increasing burial despite frequent successive burial and exposure cycles (some as short as 1 h). During these burial-exposure cycles changes of buried mine volume reached up to 80%. The only reasonable explanation is a change of sediment height of up to 40 cm relative to the stably lying mines. This requires new concepts. Cyclic burial changes that were observed simultaneously at different positions cannot be explained with existing models. The least difficult explanation is ldquounderwater sand stormsrdquo which are characterized by a high sediment suspension.