AGU Journal Highlights -- May 14, 2008

1. Did global sea level rise start centuries ago?

Global sea level rise, an important consequence of climate change, will likely affect the lifestyles of people living in coastal communities. Yet controversy and uncertainty cloud discussion of how fast sea level is rising, and why. To learn more, Jevrejeva et al. are the first to reconstruct global sea level since 1700 using tide gauge records from around the world. The authors then analyze the evolution of sea level changes for the past 300 years and present observational evidence that recent global sea level acceleration may have started at the end of the eighteenth century. They also find that sea level rose by 6 centimeters (2.4 inches) during the nineteenth century and 19 cm (7.5 in) during the twentieth century. If the conditions that established the acceleration continue, sea level will rise 34 cm (13 in) over the 21st century. The authors conclude that sea level acceleration will depend on the actual rate of temperature increase in the 21st century and that the latest Intergovernmental Panel on Climate Change estimates of sea level rise for the 21st century are probably too low.

Title: Recent global seal level acceleration started over 200 years ago"

Authors: S. Jevrejeva and P. L. Woodworth: Proudman Oceanographic Laboratory. Liverpool, U.K.;

J. C. Moore and A. Grinsted: Arctic Centre, University of Lapland, Rovaniemi, Finland; Moore also at Thule Institute, University of Oulu, Oulu, Finland.

Source: Geophysical Research Letters (GRL) paper 10.1029/2008GL033611, 2008; http://dx.doi.org/10.1029/2008GL033611

2. Clues suggest U.S. east coast subsided

At midmantle depths beneath eastern North America, the remnants of the subducted Farallon plate create a broad mantle downwelling. Spasojević et al. seek to investigate how such a mantle downwelling has influenced surface topography and regional sea level. Using mantle models and an analysis of paleo shorelines, they find that the U.S. east coast experienced dynamic subsidence since about 40 million years ago, concurrent with the global sea level fall. Superimposing dynamic subsidence and global sea level change (the latter having a larger magnitude than the former) explains how paleo shorelines along the U.S. east coast are lower than those predicted by global sea level changes, and why regional maximum sea level for New Jersey is significantly lower than global predictions.

Title: The case for dynamic subsidence of the U.S. east coast since the Eocene

Authors: Sonja Spasojević, Lijun Liu, and Michael Gurnis: Seismological Laboratory, California Institute of Technology, Pasadena, California, U.S.A.;

R. Dietmar Müller: School of Geosciences, University of Sydney, Sydney, Australia.