ARCTIC-OCEAN GRAVITY-FIELD DERIVED FROM ERS-1 SATELLITE ALTIMETRY

The derivation of a marine gravity field from satellite altimetry over permanently ice-covered regions of the Arctic Ocean provides much new geophysical information about the structure and development of the Ar ctic sea floor. The Arctic Ocean, because of its remote location and p erpetual ice cover, remains from a tectonic point of view the most poo rly understood ocean basin on Earth. A gravity field has been derived with data from the ERS-1 radar altimeter, including permanently ice-co vered regions. The gravity field described here clearly delineates sec tions of the Arctic Basin margin along with the tips of the Lomonosov and Arctic mid-ocean ridges. Several important tectonic features of th e Amerasia Basin are clearly expressed in this gravity field. These in clude the Mendeleev Ridge; the Northwind Ridge; details of the Chukchi Borderland; and a north-south trending, linear feature in the middle of the Canada Basin that apparently represents an extinct spreading ce nter that ''died'' in the Mesozoic. Some tectonic models of the Canada Basin have proposed such a failed spreading center, but its actual ex istence and location were heretofore unknown.