PLACING REGIONAL SEA LEVEL CHANGES IN A GLOBAL CONTEXT

Over the last decade, studies of modern sea-level change have moved beyond estimates of globally-averaged trends toward a deeper appreciation of the inherent regional and even temporal variability in sea-level records. This change in focus has been motivated both by the urgency of planning for future sea-level hazards and by geophysical studies that have highlighted the inherent geographic variability of the processes that contribute to sea level change. The latter processes include the ongoing adjustment of the Earth in response to the ice age (or glacial isostatic adjustment, GIA), mass flux in present-day ice reservoirs and dynamic sea-level effects (e.g., ocean circulation changes, thermosteric effects, ocean-atmosphere interactions, etc). These processes need to be understood and quantified before regional sea-level records can be robustly placed into a global context. In particular, to what extent can high resolution, Late Holocene sea-level records in specific geographic regions help to constrain the GIA signal in modern sea-level records from regions without such data? Moreover, what can a GIA-corrected regional sea-level rate inferred from tide gauge records tell us about global ice volumes? As a simple, cautionary example, consider the hypothetical case of a GIA-corrected sea level rate of 0.5 mm/yr along the U.S. east coast. This rate can be reconciled equally well by mass loss from the Antarctic or Greenland ice sheets equivalent to a eustatic (globally averaged) sea-level rise of ~0.4 and ~0.8 mm/yr, respectively. In this talk, I will review recent advances in the modeling of sea-level changes due to both GIA and modern melt events, with emphasis on the implications of these advances for the interpretation of regional sea-level records. I will also report on a "fingerprinting" study of tide gauge records which yields simultaneous estimates of the GIA signal and melting from both the Antarctic and Greenland Ice Sheets.