The effect of a 170m sea level rise on today's continents (dark blue), based on combined changes in ocean basin volume and the melting of icesheets
What the world may look like 80 million years from now, with sea levels 120 m lower (exposed land shown in dark green). Images courtesy of R. Dietmar
Sea levels were 550 feet (170 m) higher in the late Cretaceous period, about 80 million years ago, than today, shows a new reconstruction of historic ocean basins published in the journal Science. The authors say the work may help model current global warming-driven sea level change.
Analyzing data on ocean crust production, ocean sediment buildup and tectonic plate boundaries to reconstruct ancient ocean basins, R. Dietmar Muller of the University of Sydney and colleagues modeled a late Cretaceous sea level that was 550 feet (276-878 feet) [170 (85 to 270) meters] higher than it is today.
The estimates center around geological changes near New Jersey, where plate movement might have pulled the Jersey coast downward by 340-585 feet (105 to 180 meters) in the past 70 million years. Muller and colleagues says the results "could help reconcile different Cretaceous sea level estimates from the area" as well as improve forecasting for sea level change due to warming climate.
"A combination of a global ocean basin volume analysis with modern geodynamic models provides a powerful tool for discriminating eustasy from regional, time dependent sea-level variations caused by mantle convection. Our global sea-level curve calibration provides an improved framework for sequence stratigraphy, resource exploration, and models for long-term climate change," the authors write.
The study suggests that the current rise attibuted to thermal expansion of sea water and melting ice is but a brief interruption of an broader geological trend toward deeper oceans. Overall the authors forecast a sea level decline of 120 meters over the next 80 million years.
R.D. Muller et al (2008). Long-Term Sea-Level Fluctuations Driven by Ocean Basin Dynamics. Science 07 March 2008.