The Effects of Transient Rheology on the Interpretation of Lower Mantle Viscosity

We have reexamined the role played by transient rheology in the interpretation of mantle viscosity. This investigation has been carried out by comparing the amplitude responses with the data of secular variation of J2, the relative sea-level histories at sites well within the ice margins and at the ice margin like the city of Boston. A linear Burgers' body theology has been assumed in the lower mantle. The data near the edge of the ice load proves most sensitive to the transient viscosity structure. The non-monotonic behavior of sea-level data near Boston can be explained both by a steady-state lower mantle viscosity of 10=P with a thick lithosphere and also by a transient lower mantle theology but with a thin lithosphere. The longterm viscosity of the lower mantle in this second model has a steady-state value of around 5x 10•3P.