Abstract: A Geological Perspective on Sea-level Rise and Its Impacts: Past, present and future

The geologic record places the modern sea-level rise into an historical context and can help inform discussions of the rates and magnitudes of future sea-level rise. During the Pliocene, CO2 levels were similar to 2014 (400 ppm), yet temperatures were globally 2°C warmer and global average sea level stood globally 22±10 m above present.

With the development of large Northern Hemisphere ice sheets at 2.7 Ma, amplitudes of sea-level change increased, reaching over 100 m at times. A globally average sea-level rise of ~130 m followed the last ice age, with rates that at times exceeded by ten times the modern rate of rise (> 40 mm/yr versus ~ 3 mm/yr). Rates of rise along the U.S. Gulf and much of the U.S. Atlantic coasts were higher due to Glacial Isostatic Adjustment and local subsidence.

The rate of relative sea-level rise in the U.S. mid-Atlantic region decreased from 3.5±1.0 m/yr at 7.5-6.5 ka, to 2.2±0.8 mm/y at 5.5-4.5 ka, to a minimum of 0.9±0.4 mm/yr at 3.3-2.3 ka. Relative sea level rose at a rate of 1.6±0.1 mm/yr from 2.2 ka to 1.2 ka (750 CE) and 1.4±0.1 mm/yr from 800-1800 CE. Geological and tide-gauge data show that sea-level rise was more rapid throughout the region since the Industrial Revolution (19th century = 2.7±0.4 mm/yr; 20th century = 3.8±0.2 mm/yr).

There is a 95% probability the 20th century rate of sea-level rise was faster than it was in any century in the last 4.3 kyr. These records reflect global rise (~1.7±0.2 mm/yr since 1880 CE) and subsidence from glacio-isostatic adjustment (~1.3±0.4 mm/yr) at bedrock locations (e.g., New York City, Philadelphia, Baltimore, and Washington D.C.). At coastal plain locations, the rate of rise is 0.3-1.3 mm/yr higher due to groundwater withdrawal and compaction.

We construct 21st century relative sea-level rise scenarios including global, regional, and local processes. We project a 22 cm rise at bedrock locations by 2030 (central scenario; low- and high-end scenarios with a range of 16-38 cm), 40 cm by 2050 (range 28-65 cm), and 96 cm by 2100 (range 66-168 cm), with coastal plain locations having higher rises (3, 5-6, and 10-12 cm higher, respectively). By 2050 CE in the central scenario, a storm with a 10-year recurrence interval will exceed all historic storms at coastal locations.

Comments (0)


Distinguished Lecturer

Kenneth G. (Ken)

Kenneth G. (Ken) Miller

Dean A. McGee Distinguished Lecturer

Distinguished Professor

Rutgers, The State University of New Jersey