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Geophysics

KNIPSEIS 2019

The aim of this project is to better understand the lithospheric structure beneath the rare ultraslow, oceanic spreading ridges, using as example the Knipovich Ridge

KNIPSEIS 2019 map illustration
Localization of the transect. 20090200 profile acquired by AWI in 2009: triangles - AWI OBSs, light line – air-gun shooting. KNIPSEIS 2019 profile: light green stars - Polish OBSs (1st deployment), red stars - Norwegian OBSs (one long deployment), dark blue stars - Polish OBSs (2nd deployment), black line – air-gun shooting.
Photo:
Rolf Mjelde, UiB

Ultraslow spreading ridges are characterized by a low melt supply. At spreading rates below 20 mm/y, conductive cooling effectively reduces the mantle temperature and results in less melt produced at larger depths. Ultraslow spreading ridges; the Arctic ridge system with the Gakkel Ridge, Lena Trough and Knipovich Ridge and the Southwest Indian Ridge (SWIR), therefore greatly differ in their morphology from faster spreading ridges.

Ocean Bottom Seismometer (OBS) data along a 280 km long refraction/reflection profile crossing the Knipovich Ridge off the western Barents Sea was acquired by use of RV G.O. Sars on July 24 - August 6, 2019. The project partners are the Department of Earth Science, University of Bergen, Institute of Geophysics, Polish Academy of Sciences, and Hokkaido University. The acoustic energy was emitted every 200 m by an array of air-guns with total volume of 80 l. To receive and record the seismic waves at the seafloor, ocean bottom seismometers were deployed along the highly oblique spreading direction at 12 positions with about 15 km spacing in 2 deployments. All the stations were recovered and correctly recorded data. Clear seismic energy from air-gun shots were obtained up to 50 km from the OBSs. The profile provides information on the seismic crustal structure of the Knipovich Ridge and oceanic and continental crust in the transition zone. With this survey we have to some extent overlapped the previously performed Alfred Wegener Institute (AWI) profile 20090200. Together, they constitute one joined transect crossing the Knipovich Ridge from the American to the European plate.