29 November 2005

Sea Level Rise Accelerating

by Kate Melville

Rutgers University scientists, reporting in the journal Science, say that global ocean levels are rising twice as fast today as they were 150 years ago, and warming from human activities appears to be the culprit. The speed of the rise today is two millimeters per year, compared to one millimeter annually for the past several thousand years. While the figures may not sound dramatic, it seemingly confirms scientific concerns of acceleration in global warming.

The findings are based on drilling studies along the New Jersey coast, tidal gauges and satellite images. They establish a steady millimeter-per-year rise from 5,000 years ago until about 200 years ago. "With solid historical data, we know it is definitely a recent phenomenon," said Rutgers researcher Kenneth G. Miller. "The main thing that's changed since the 19th century and the beginning of modern observation has been the widespread increase in fossil fuel use and more greenhouse gases," he added.

Interestingly, the findings by Miller's team argue against some widely held tenets of geological science. Miller claims, for example, that ocean heights 100 million years ago and earlier were 150 to 200 meters lower than scientists had previously thought. Changes at these levels can only be caused by the Earth's crust shifting on the ocean floor. Miller's findings, therefore, imply less ocean-crust production than scientists had widely assumed.

During the last days of the dinosaurs (Late Cretaceous), frequent sea-level fluctuations of tens of meters suggest that the Earth was not always ice-free as previously assumed. Miller claims that ice-volume changes are the only way that sea levels could change at these rates and levels. This suggests small- to medium-sized but short-lived ice sheets in the Antarctic region, and casts doubt whether any of the Earth's warmer eras were fully ice-free.

Source: Rutgers University