Fram Strait Bathymetry
The study area can be divided in a complex sequence of transform faults and spreading centers. Outstanding morphological features exist along with the Hovgaard Fracture Zone (FZ), the Molloy FZ and the Spitsbergen FZ (south to north). Figure 1 shows a perspective view of the investigation area based on the new bathymetric data. View direction is from north to south.
In the north of the study area and vicinal to the Spitsbergen continental margin, the Spitsbergen FZ links with the Lena Trough located between the Yermak Plateau in the east and the Greenland shelf (Ob Bank) in the west. The Lena Trough is congruent with the Gakkel Ridge in the Arctic Basin. Morphologically the Spitsbergen FZ is characterized by a depression reaching depths of over 4500 m. The "Spitsbergen Trough" follows a northwest-southeast direction that is characteristic for most morphological and geological features in the Fram Strait region.
The Molloy FZ is located about 100 km south of the Spitsbergen FZ following the same direction. The central Molloy Fracture Zone is characterized by the Molloy Ridge, an area of complex morphology, particularly composed of a series of three seamounts reaching heights of 1600 m over the surrounding seafloor with depths ranging from 2500 m to 3500 m. Recently we submitted feature name proposals to SCUFN in order to name these seamounts: Atla Seamount, Eistla Seamount and Gjalp Seamount (Figure 1).
The most significant morphologic feature in the Fram Strait is located at the intersection of the Molloy Transform Fault and the Molloy Ridge system: the Molloy Hole is a nodal deep (Thiede et al. 1990) reaching a depth of 5669 m according to our investigation. This is the deepest known depression of the Arctic Ocean, the Norwegian-Greenland Sea and the Atlantic Ocean north of 60° latitude. It has an almost circular shape with a diameter of about 30 km. At the steepest slopes in the south the seafloor plunges down from 2500 m to 5400 m over a horizontal distance of only 10 km. Local slopes reach values of nearly 100% (42°).
The Greenland-Spitsbergen Sill is bounded by the Molloy FZ in the north and the Hovgaard FZ in the south. The sediment-covered plateau has a southeast-northwest trend with a width of about 60 km. Depths increase slightly from southeast (2300 m) to northwest (2600 m). The northeast region of the sill close to the Molloy FZ is almost flat while the southwest part near the Hovgaard Ridge shows undulations of the sediment cover due to buried geologic structures and probably current effects.
The Hovgaard FZ is dominated by the elongated Hovgaard Ridge. The structure has a southwest-northeast axis of about 60 km length with minimum depth of 1200 m in the southwestern part slightly tilting towards northeast. Flanks are steep while the ridge top is relatively flat. The rise is bordered by the 2500 m contour at the edge of the Greenland-Spitsbergen sill and the 2800 m contour in the southwest where it faces the Boreas Abyssal plain. East of the main ridge is a smaller structure with an axis length of 25 km and a minimum depth of about 1300 m.