Fastest sea-level rise in two millennia linked to increasing temperatures
An international research team has shown that the rate of sea-level rise along the U.S. Atlantic coast is greater now than at any time in the past 2,000 years and have shown a consistent link between changes in global mean surface temperature and sea level.
− Sea-level rise is a potentially disastrous outcome of climate change, as rising temperatures melt land-based ice and warm ocean waters, one of the authors (Horton) said. − Scenarios of future rise are dependent upon understanding the response of sea level to climate changes. Accurate estimates of past sea-level var
In the new study, researchers provided the first continuous sea-level reconstruction for the past 2,000 years and compared variations in global temperature to changes in sea level over this time period.
The team found that sea level was relatively stable from 200 BC to 1,000 AD. Beginning in the 11th century sea level rose by about half a millimeter per year for 400 years associated with a warm climate period known as the Medieval Climate Anomaly. There was a second period of stable sea level associated with a cooler period called the Little Ice Age that persisted until the late 19th century. Since the late 19th century sea level has risen by more than 2 millimeters per year on average, which is the steepest rate for more than 2100 years.
To reconstruct sea level, the research team used microfossils called foraminifera preserved in sediment cores from coastal salt marshes in North Carolina. The age of these cores was estimated using radiocarbon dating and several other complementary techniques.
To ensure the validity of their approach, the team confirmed their reconstructions against tide-gauge measurements from North Carolina for the past 80 years, and global tide-gauge records for the past 300 years. A second reconstruction from Massachusetts confirmed their findings. The records were corrected for contributions to sea-level rise made by vertical land movements.
The team show that the reconstructed changes in sea level over the past millennium are consistent with past global temperatures and can be described using a model relating the rate of sea level rise to global temperature. −The data from the past help to calibrate our model and will improve sea-level rise projections under scenarios of future temperature rise, another of the authors (Rahmstorf) stated.
The research will be published in the journal Proceedings of the National Academy of Sciences on June 20th and was conducted by Andrew Kemp (Yale University), Benjamin Horton (University of Pennsylvania), Jeffrey Donnelly (Woods Hole Oceanographic Institution), Michael Mann (Pennsylvania State University), Martin Vermeer (Aalto University School of Engineering, Finland), and Stefan Rahmstorf (Potsdam Institute for Climate Impact Research, Germany).
Support for this research was provided by the National Science Foundation, the National Oceanic and Atmospheric Administration, United States Geological Survey, the Academy of Finland, the European Science Foundation through European Cooperation in Science and Technology (COST), and the University of Pennsylvania.
Aalto University School of Engineering
tel. 050 357 4139, martinus.vermeer [at] aalto [dot] fi