March 8, 2013
Record Warming Will Lead To Faster Melting Glaciers And The Loss Looks Irreversible
April Flowers for redOrbit.com - Your Universe Online
In the next few centuries, Canada's Arctic Archipelago glaciers will melt faster than ever, according to a new study. Research has revealed that 20 percent of the Canadian Arctic glaciers may have disappeared by the end of our current century, leading to an additional sea level rise of 1.4 inches.The findings, funded in part by EU's ice2sea program, are available online and will be published in an upcoming issue of Geophysical Research Letters.
The research team, led by Dr Jan Lenaerts from the Institute for Marine and Atmospheric Research (IMAU) at the University of Utrecht, created a climate model for the northern Canadian island group that simulated the shrinking and growing of glaciers in the region. According to the team, the model correctly "predicted" the ice mass loss recorded over the past decade, and then it was used to project the future effects of climate change on Canada's Arctic Archipelago glaciers.
According to Lenaerts, the most important result of this study is that it shows the probable irreversibility of the melting process. He notes, "Even if we assume that global warming is not happening quite so fast, it is still highly likely that the ice is going to melt at an alarming rate. The chances of it growing back are very slim."
One major reason for the irreversibility is the fact that snow melting on tundra, and sea-ice loss from around the glaciers, actually reinforce regional warming. This has a significant impact on the glaciers of Northern Canada. Sea ice and snow reflect sunlight, acting as a shield against rising temperatures. As the snow and sea ice disappear, the sunlight will be absorbed by the land and the oceans, significantly increasing the local temperature.
In one scenario from the model, 20 percent of the glaciers' volume disappears by the end of this century, the average global temperature rises by 5.4 degrees Fahrenheit, and the temperature around Canadian ice caps rises by 14.4F. The team cautions that this is not an extreme scenario.
After Greenland and the Antarctic, Canada's Arctic Archipelago glaciers represent the third largest ice body in the world. The global average sea level will rise by approximately 8 inches if the Canadian ice caps melt completely. Temperatures in this region have risen by 1.8 to 3.6F since the year 2000, and the ice volume has already decreased by a significant amount. If by the end of this century, one-fifth of the ice caps have melted, it will lead to another sea-level rise of 1.4 inches.
Study coauthor Professor Michiel van den Broeke of Utrecht says, "Most attention goes out to Greenland and Antarctica which is understandable because they are the two largest ice bodies in the world. However, with this research we want to show that the Canadian ice caps should be included in the calculations."
Professor David Vaughan, program leader of ice2sea, who is based at the British Antarctic Survey in Cambridge, says, "The Canadian archipelago is an area where climate is changing rapidly, and the glaciers here contain enough ice that we should not ignore their contribution to sea-level rise. Added to glaciers in Alaska, the Russian Arctic and Patagonia, these apparently small contributions add up to significant sea-level rise. A key success of this study was in showing that the model performed well in reproducing recently observed changes. That success gives us confidence in how the model predicts future changes."
11,300 YEARS OF TEMPERATURE RECORDS
In a related study, published this past week in the journal Science, researchers reveal that the Earth is on track to becoming the hottest it has been at any time in the past 11,300 years.
The research team from Oregon State University and Harvard University collected fossil samples and other data from 73 sites globally to reconstruct the history of the planet's temperature from the end of the last Ice Age to the present. The data were gathered from marine fossils, pollen records from lakes and ice cores from Greenland, to create a global picture of temperature records. Previously, studies have been more locally centered.
Ars Technica reports that Earth's climate has been dominated by glacial cycles for millions of years. These cycles are driven by changes in the planet's orbit and reinforced by greenhouse gases, which can be both natural and manufactured. These changes happen over tens of thousands of years, and mankind has only been keeping written temperature records for approximately 1,500 years. This leaves a large gap in our data, which this study attempts to fill.
Cyclical changes, called Milankovitch cycles, occur in both the Earth's orbit and axis causing changes to the amount and distribution of sunlight that strikes the Earth's surface. These changes can raise or lower the average temperature of the planet, resulting in what is called an "orbital forcing." Orbital forcing can drive long-term climate changes, controlling the entry and exit into glacial periods. The timing of glacial and interglacial periods, however, can be affected by many factors including volcanic activity, aerosols, and ocean currents. The new study seeks to better understand our current interglacial period by creating a complete picture.
AFP reports that the team determined that the past decade has been hotter than 80 percent of the last 11,300 years; and temperatures are still rising. Nearly every climate model evaluated by the International Panel on Climate Change (IPCC) predicts that the Earth's atmosphere will be hotter in the coming decades than at any point since the end of the Ice Age. The study explains that this is true no matter what greenhouse gas emission scenario is used.
"We already knew that on a global scale, Earth is warmer today than it was over much of the past 2,000 years," said Shaun Marcott, who is a post-graduate paleoclimatology researcher at Oregon State. "Now we know that it is warmer than most of the past 11,300 years. This is of particular interest because the Holocene spans the entire period of human civilization."
Over the past 5,000 years, the data show that temperatures cooled by about 1.5F. They have been rising again, though, in the past 100 years, especially in the Northern Hemisphere where land masses and population centers are larger.
Average global temperatures will rise by 2 to 11.5 degrees Fahrenheit by the end of the century, according to the climate model predictions. The range is based on the level of CO2 emissions resulting from human activities.
"What is most troubling is that this warming will be significantly greater than at any time during the past 11,300 years," said Peter Clark, a paleoclimatologist at Oregon State.
During that time, the main natural factor affecting temperatures was the Earth's position with respect to the Sun.
"During the warmest period of the Holocene, the Earth was positioned such that Northern Hemisphere summers warmed more," Marcott said. "As the Earth's orientation changed, Northern Hemisphere summers became cooler, and we should now be near the bottom of this long-term cooling trend -- but obviously, we are not."
According to the Wall Street Journal, the research team was also seeking to understand if this shift in temperatures in the past 150 years was unusual–the result of greenhouse-gas emissions from human activity — or can it be explained as part of natural, long-term variations in temperature? The study seems to point to a human culprit because of the suddenness of the shift, which appears to be out of sync with longterm trends.
"What's different is the rate of change," said Marcott.
"This paper throws down the gauntlet by showing that Earth is on its way to being warmer," added David M. Anderson, who heads the paleoclimatology program at the US National Oceanic and Atmospheric Administration (NOAA). "By 2100, it will be a heck of a lot warmer than it was 11,000 years ago."
Anderson warns the insights that can be gained by studying ancient temperature trends are limited, however.
"It's a weakness to look at the world 11,000 years ago, because those were sunlight-driven changes and not CO2-driven changes," Dr. Anderson said. Sunlight-related changes are gradual and vary across different parts of the globe; greenhouse-gas emissions trigger warming everywhere.
Paleoclimatology is a challenging discipline that seeks to estimate Earth's ancient climate relying on proxy measurements taken from such sources as marine fossils or ice cores. These sources offer physical records of past temperatures. To confirm a finding, paleoclimatologists typically check the temperature records from one source with those derived from another, unrelated source.
These new studies could become a focal point in the longstanding debate over the cause of rising temperatures, with many scientists blaming increased emissions of greenhouse gases such as CO2. Other contingents disagree, believing that natural factors, like an increase in cloud cover, are at fault.