As Glaciers Melt, Science Seeks Data on Rising Seas

[telemann.livejournal.com]

From a helicopter hovering over Greenland, the oceanographer Fiammetta Straneo took measurements to determine how fast the water is melting the nearby Helheim Glacier.

The New York Times on Sunday, had a great article about scientists studying the quickening pace of glacier melt in Greenland. According to climate experts, sea levels are expected to rise significantly due to melting glacial ice; estimates vary from three to six feet by the end of the century.

Climate scientists readily admit that the three-foot estimate could be wrong. Their understanding of the changes going on in the world’s land ice is still primitive. But, they say, it could just as easily be an underestimate as an overestimate. One of the deans of American coastal studies, Orrin H. Pilkey of Duke University, is advising coastal communities to plan for a rise of at least five feet by 2100. “I think we need immediately to begin thinking about our coastal cities — how are we going to protect them?” said John A. Church, an Australian scientist who is a leading expert on sea level. “We can’t afford to protect everything. We will have to abandon some areas.”

While snowfall for Greenland increased during the 1990s, warmer air temperatures, and warm waters penetrating glacial fjords, have accelerated glacier melt and in a significant manner. But not everyone believes global warming is responsible:

John R. Christy, a climatologist at the University of Alabama in Huntsville who is often critical of mainstream climate science, said he suspected that the changes in Greenland were linked to this natural variability, and added that he doubted that the pace would accelerate as much as his colleagues feared. For high predictions of sea-level rise to be correct, “some big chunks of the Greenland ice sheet are going to have to melt, and they’re just not melting that way right now,” Dr. Christy said. Yet other scientists say that the recent changes in Greenland appear more pervasive than those of the early 20th century, and that they are occurring at the same time that air and ocean temperatures are warming, and ice melt is accelerating, throughout much of the world.

To a majority of climate scientists, the question is not whether the earth’s land ice will melt in response to the greenhouse gases those people are generating, but whether it will happen too fast for society to adjust. Recent research suggests that the volume of the ocean may have been stable for thousands of years as human civilization has developed. But it began to rise in the 19th century, around the same time that advanced countries began to burn large amounts of coal and oil.

The sea has risen about eight inches since then, on average. That sounds small, but on a gently sloping shoreline, such an increase is enough to cause substantial erosion unless people intervene. Governments have spent billions in recent decades pumping sand onto disappearing beaches and trying to stave off the loss of coastal wetlands.

Scientists have been struggling for years to figure out if a similar pace of sea-level rise is likely to continue in this century — or whether it will accelerate. In its last big report, in 2007, the United Nations group that assesses climate science, the Intergovernmental Panel on Climate Change, said that sea level would rise at least seven more inches, and might rise as much as two feet, in the 21st century.

But the group warned that these estimates did not fully incorporate “ice dynamics,” the possibility that the world’s big ice sheets, as well as its thousands of smaller glaciers and ice caps, would start spitting ice into the ocean at a much faster rate than it could melt on land. Scientific understanding of this prospect was so poor, the climate panel said, that no meaningful upper limit could be put on the potential rise of sea level.

That report prompted fresh attempts by scientists to calculate the effect of ice dynamics, leading to the recent, revised projections of sea-level rise.

Climate scientists note that while the science of studying ice may be progressing slowly, the world’s emissions of heat-trapping gases are not. They worry that the way things are going, extensive melting of land ice may become inevitable before political leaders find a way to limit the gases, and before scientists even realize such a point of no return has been passed.

“The past clearly shows that sea-level rise is getting faster and faster the warmer it gets,” Dr. Rahmstorf said. “Why should that process stop? If it gets warmer, ice will melt faster.”

Recent analysis of Greenland's glacial melt.


This photo shows the “bathtub ring” above Helheim Glacier. It was created in the middle of the last decade when the glacier sped up and thinned, exposing rock that had once been covered by ice. The light-colored band of rock is about 300 feet thick. The Greenland ice sheet can be seen in the background at the top of the picture.


Summer ponds of melted water on the surface of Helheim Glacier. This kind of melting has accelerated because air temperatures in Greenland are warming.

And before of the denialists come out swinging that ice has been increasing in the Artic or Greenland, please watch this first:

The graph above shows daily Arctic sea ice extent as of November 1, 2010, along with daily ice extents for years with the previous four lowest minimum extents. Light blue indicates 2010, dark blue shows 2009, purple shows 2008, dotted green indicates 2007, and dark gray shows the 1979 to 2000 average. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.


Monthly October ice extent for 1979 to 2010 shows a decline of 6.2% per decade.



It's a fascinating read, extremely well written. I thought I'd pass it along to the community. One worrisome feature is that apparently due to budget constraints, several satellites used by NASA and NOAA for studying glacial ice melt, and water temperatures, etc are being retired with no immediate replacements, due to budget constraints. NASA is using airplane overflies to garner what information it can, but losing satellites at this critical juncture is not good.

I thought this article by Fiammetta Straneo is fascinating as well. It's a study of sea levels during the Roman period and the implications of rising sea levels on modern society. Another resource to check is the The National Snow and Ice Data Center.

Comments

[telemann.livejournal.com]

He never does. Malasadas has pointed it out in several posts this is the SOP for Reality.