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.