Wednesday, September 21, 2016

Sea levels increase in stairstep fashion--slow, then real fast.

Sea levels are on the rise pretty much everywhere, but not at the same rate.

There is new information coming out of the University of Hawaii that suggests that in areas where the rise has been smallest, it can accelerate quickly.

An example: In the 1990s, the North Indian Ocean didn’t rise much at all. But since 2003 it is catching up—rising at twice the global rate.

That’s from a paper in the Journal of Geophysical Research, written by a team including Philip Thompson, of the University of Hawai`i Sea Level Center in the School of Ocean and Earth Science and Technology, and Mark Merrifield, Eric Firing, Christopher Piecuch and Julian McCreary.

The changes are due to a combination of winds and water temperatures.

“Wind blowing over the ocean caused changes in the movement of heat across the equator in the Indian Ocean. This led to suppression of sea level rise during the 1990s and early 2000s, but now we are seeing the winds amplify sea level rise by increasing the amount of ocean heat brought into the region,” Thompson said.

Hawai`i has similarly experienced less sea level rise than the global average. And that could also come to an end with faster-than-expected rising following the slow period. We reported on that last year in RaisingIslands. 

Thompson called this a staircase effect.
“What we are learning is that the interaction between the ocean and atmosphere causes sea level to rise like a staircase instead of a straight line – starting and stopping for many years at a time. What we’ve done here is described one stair, which will help us better understand and plan for the future,” he said.

© Jan TenBruggencate 2016

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