20th Century sea-level change along the eastern US: Unravelling the contributions from steric changes, Greenland ice sheet mass balance and Late Pleistocene glacial loading

We have considered the influence of ocean temperature and salinity changes, mass changes of the Greenland ice sheet (GIS) and the isostatic response of the solid earth to the most recent glacial cycle on 20th century sea-level change along the US east coast with the intention of better understanding the observed signal as well as determining the potential of the tide gauge data for constraining the recent (past 50–100 yr) mass balance of the GIS and earth viscosity structure. Our results show that the signal due to steric changes is large and displays a complex spatial variation which can account for a significant portion of the observed signal. In contrast, that due to changes in the GIS is relatively small and insensitive to the specific geometry of the mass balance model adopted. As a consequence, the tide gauge data alone are not capable of providing useful constraints on either the magnitude or form of recent GIS mass balance. Our inference of mantle viscosity structure based on the tide gauge data was affected dramatically when the steric effect was accounted for: An earth model with an upper mantle viscosity of 8 × 10¹⁹ Pa s and a lower mantle viscosity of 5 × 10²² Pa s produced the best fit to the steric-corrected data; the optimal fit to the uncorrected data was obtained for upper and lower mantle viscosities of 5 × 10²⁰ Pa s and 10²² Pa s, respectively.