Sea-Level Rise Tipping Point of Delta Survival

Abstract

The estimated rate of global eustatic sea-level rise (RSLR) associated with the formation of 36 of the world's coastal deltas was calculated for the last 22,000 years. These deltas are located in a variety of environmental settings with respect to tidal range, isostasy, and climate. After correcting the original uncalibrated radiocarbon age estimates to calibrated years, 90% of the deltas appear to have formed at an average age of 8109 ± 122 before present (BP) and a median age of 7967 BP. This age corresponds to a period of significant deceleration in the RSLR to between 5 mm y-1 and 10 mm y-1, and is in agreement with two regional estimates of vegetation growth limits with respect to RSLR. This RSLR tipping point for delta formation can be used to inform forecasts of delta resiliency under conditions of climate change and concomitant SLR. The RSLR is accelerating and will likely be several times higher than the formation tipping point by the end of this century. Hence, the world's deltaic environments are likely to be lost within the same time frame.