Sunday, March 13, 2016

Sea Level Rise Is Accelerating; How Much It Costs Is Up to Us

The Perito Moreno Glacier’s ice bridge collapses into Lake Argentina, at Los Glaciares National Park, near El Calafate, in Argentina’s Patagonia region, Thursday, March 10, 2016. (Photograph Credit: Francisco Munoz/AP) Click to Enlarge.
Important new research shows that sea levels are rising at unprecedented rates, and will have tremendous costs if we don’t slow them

As humans emit heat-trapping gases into the atmosphere, it’s causing the Earth to warm.  It’s also causing the ocean waters to rise.  In fact, water rise is one of the clearest signatures of a warming world.  The questions we want to answer are, how much will sea levels rise, and how fast? 

The answers to this have large implications on what societies should do.  It isn’t just coastal communities that will be affected.  While there are approximately 150 million people worldwide that live within 3 feet of today’s water levels, because of the interconnected economies and societies, ocean rise will affect us all.

The prestigious Proceedings of the National Academy of Sciences recently published a series of sea level rise papers.

One paper covers the Antarctic ice sheet, and the authors look back in time at the world’ largest ice sheet.  The authors use three tools to advance our knowledge of the ice.  First, they use a very accurate calculation approach to quantify how the ice sheet interacts with the atmosphere. Second, they incorporate potential ice fractures into their analysis.  Finally, they use information about changes to oxygen isotopes to improve their calculations.  What they find is that the atmospheric concentration of carbon dioxide will soon be at levels not encountered since the Miocene period (23 million to 5 million years ago).  They also find that newer computer calculations do a better job of quantifying changes to the ice sheet.

A second paper published by Roelof Rietbroek and colleagues looked at the sources of sea level rise.  They wanted to know how much of the current rise is from water that is warming and expanding, how much is from melting of ice sheets in Greenland and Antarctica, how much is from melting glaciers, how much is from shifting continents, etc. 

This study measured the mass of water in various regions of the Earth through special gravity-sensitive satellites that orbit the Earth.  They conclude that the sea level rise from thermal expansion is higher than previously reported.  The also find the water rise from melting of ice is consistent with measurements taken of ice melt around the world.  Finally, they find that while the global oceans are rising steadily, there is tremendous regional variation so that some areas have very fast ocean water rise while others have slow ocean rise (or even ocean drop). 

Read more at Sea Level Rise Is Accelerating; How Much It Costs Is Up to Us

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