Causes of accelerating sea level on the East Coast of North America

The tide-gauge record from the North American East Coast reveals significant accelerations in sea level starting in the late twentieth century. The estimated post-1990 accelerations range from near zero to approximate to 0.3mmyr(-2). We find that the observed sea level acceleration is well modeled using several processes: mass change in Greenland and Antarctica as measured by the Gravity Recovery and Climate Experiment satellites; ocean dynamic and steric variability provided by the GECCO2 ocean synthesis; and the inverted barometer effect. However, to achieve this fit requires estimation of an admittance for the dynamical and steric contribution, possibly due to the coarse resolution of this analysis or to simplifications associated with parameterization of bottom friction in the shallow coastal areas. The acceleration from ice loss alone is equivalent to a regional sea level rise in one century of 0.2m in the north and 0.75m in the south of this region. Plain Language Summary We describe a new analysis of sea level accelerations derived from tide-gauge data along the East Coast of North America. Previous analyses of acceleration in this region have focused on ocean dynamics as the cause of recent rapid sea level changes. We have included a number of sources of sea level acceleration, including not only ocean dynamics but also ice-mass loss from Greenland and Antarctica and atmospheric pressure. By focusing on accelerations we are able to remove one of the greatest sources of uncertainty in the sea level budget, postglacial rebound. We have devised an approach wherein data from previous decades (during which the long-term variation is assumed linear) are included, thereby improving the accuracy of estimated post-1990 accelerations by a factor of 3. We conclude that the spatial variability of sea level acceleration is well modeled using these multiple processes. The results indicate that multiple physical processes must be considered to understand changing sea level. We also conclude that the acceleration from Antarctic and Greenland ice loss alone is equivalent to a sea level rise in one century of 0.2m in the north and 0.75m in the south of this region.