Anomalous diurnal currents in the vicinity of the Yermak Plateau

Abstract

Unexpectedly strong diurnal tidal currents, in a region dominated by semi-diurnal tidal surface displacements, were observed in the ARCTEMIZ 86 and 87 and CEAREX 89 records of buoy drift over the Yermak Plateau, submarine feature north of Svalbard. Similar diurnal currents were observed during the FRAM III, FRAM IV experiments. Data Analysis of the positions of the thirty satellite-tracked drifting buoys provides a description of the diurnal current field with good spatial coverage. This statistical description shows that tidal diurnal currents are enhanced over the entire plateau region. However, specific smaller regions above the plateau (order of 90 km) exhibit locally an even stronger and highly polarized response to the tide that has not been explained until now. Firstly, a simple analytic model is used to show that the variation in the steepness of the slopes of the plateau could be responsible for significant spatial variations in the diurnal current field. Secondly, a numerical model shows that the variation in the curvature of the plateau is also important. Furthermore, the numerical model shows that the curvature of the topography causes the Yermak Plateau to act like a filter, responding resonantly to forcing with periods ranging from approximately 20 to 35 hours

Unexpected strong diurnal tidal currents, in a region dominated by semi-diurnal tidal surface displacements, were observed in the ARCTEMIZ 86 and 87 and CEAREX 89 records of buoy drift over the Yermak Plateau, a submarine feature north of Svalbard. Similar diurnal currents were observed during the FRAM III and FRAM IV experiments. Data analysis of the positions of the thirty satellite-tracked buoys provides a description of the diurnal current field with good spatial coverage. This statistical description shows that tidal diurnal currents are enhanced over the entire plateau region. However, specific smaller regions above the plateau (order of 90 km) exhibit locally an even stronger and highly polarized response to the tide that has not been explained until now. Firstly, a simple analytic model is used to show that the variation in the steepness of the slopes of the plateau could be responsible for significant spatial variations in the diurnal current field. Secondly, a numerical model shows that the variation in the curvature of the plateau is also important. Furthermore, the numerical model shows that the curvature of the topography causes the Yermak Plateau to act like a filter, responding resonantly to forcing with periods ranging from approximately 20 to 35 hours.