Common Era sea-level budgets of North America

A sea-level budget improves understanding of driving processes and their relative contributions. However, most sea-level budget assessments are limited to the 20^th and 21^st centuries and are global in scale. Here, we estimate the sea-level budget on centennial to millennial timescales of the Common Era (last 2000 years). We expand upon previous analysis of sites along the U.S. mid-Atlantic coast (Walker et al., 2021) and produce site-specific sea-level budgets for all of the eastern and western North American coastlines and Gulf coast. This broader scope further improves understanding of the temporal evolution and variability of driving processes of sea-level changes in the past and present, and which will shape such changes in the future.

To produce the sea-level budgets, we use an updated global database of instrumental and proxy sea-level records coupled with a spatiotemporal model. Using the unique spatial scales of driving processes, we separate relative sea-level records into global, regional, and local-scale components. Preliminary results along the eastern North American coastline reveal that each budget is dominated by regional-scale, temporally-linear processes driven by glacial isostatic adjustment until at least the mid-19^th century. This signal exhibits a spatial gradient, ranging from 1.0 ± 0.02 mm/yr (1σ) in Newfoundland to a maximum of 1.6 ± 0.02 mm/yr in southern New Jersey to 0.5 ± 0.02 mm/yr in Florida. Non-linear regional and local-scale processes, such as ocean/atmosphere dynamics and groundwater withdrawal, are smaller in magnitude and vary temporally and spatially. The most significant change to the budgets is the increasing influence of the global signal due to ice melt and thermal expansion since ~1800 CE, which reaches a 20^th century rate of 1.3 ± 0.1 mm/yr, accounting for 43-65% of each budget.