Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond.
Greetings! Well, last week we had good news, and now, I’m afraid it’s time for some bad news. The global warming file is getting bigger. We’re all familiar with news about giant icebergs calving off the coasts of Antarctica, but it’s August, and we all saw the news release that Greenland has calved a hundred square mile iceberg from its northwestern shore that may choke an island-filled strait and cause other problems. But that’s not all that’s been going on in Greenland. So, screw your courage to the sticking place and read on!
Ice loss from the Greenland ice sheet, which has been increasing during the past decade over its southern region, is now moving up its northwest coast, according to a new international study.
Researchers from the Denmark Technical Institute’s National Space Institute in Copenhagen and the University of Colorado at Boulder have conducted a study that indicates ice-loss acceleration began moving up the northwest coast of Greenland starting in late 2005. The team drew their conclusions by comparing data from NASA’s Gravity and Recovery Climate Experiment satellite system, or GRACE, with continuous GPS measurements made from long-term sites on bedrock on the edges of the ice sheet.
The data from the GPS and GRACE provided the researchers with monthly averages of crustal uplift caused by ice-mass loss. The team combined the uplift measured by GRACE over California-sized chunks of Greenland while the GPS receivers monitor crustal uplift on scales of just tens of miles.
The team found that uplift rates near Thule Air Base on Greenland’s northwest coast rose by roughly 1.5 inches, or about 4 centimeters, from October 2005 to August 2009. Although the low resolution of GRACE — a swath of about 155 miles, or 250 kilometers across — is not precise enough to pinpoint the source of the ice loss, the fact that the ice sheet is losing mass nearer to the ice sheet margins suggests the flows of Greenland outlet glaciers there are increasing in velocity, said the study authors. They speculate that some of the big glaciers in this region are sliding downhill faster and dumping more ice in the ocean.
Another study published in 2009 showed that between April 2002 and February 2009, the Greenland ice sheet shed roughly 385 cubic miles of ice. The mass loss is equivalent to about 0.5 millimeters of global sea-level rise per year.
The changes on the Greenland ice sheet are happening fast, and the researchers say they are seeing more ice mass loss than they anticipated. The ice mass loss is also occurring in Antarctica, a sign that warming temperatures really are having an effect on ice in all of Earth’s cold regions.
Researchers have been gathering data from GRACE since NASA launched the system in 2002. Two GRACE satellites whip around Earth 16 times a day separated by 137 miles and measure changes in Earth’s gravity field caused by regional shifts in the planet’s mass, including ice sheets, oceans and water stored in the soil and in underground aquifers.
In addition to monitoring the Thule GPS receiver in northwest Greenland as part of the new GRL study, the team also is taking data from GPS receivers in southern Greenland near the towns of Kellyville and Kulusuk. An additional 51 permanent GPS stations recently set up around the edges of the Greenland ice sheet should be useful to measure future crustal uplift and corresponding ice loss.
If the activity in northwest Greenland continues and really accelerates some of the major glaciers in the area — like the Humboldt Glacier and the Peterman Glacier — Greenland’s total ice loss could easily be increased by an additional 50 to 100 cubic kilometers (12 to 24 cubic miles) within a few years.
Greenland is about one-fourth the size of the United States and the massive ice sheet covers about 80 percent of its surface. It holds about 20 percent of the world’s ice, the equivalent of about 21 feet of global sea rise. Air temperatures over the Greenland ice sheet have increased by about 4 degrees Fahrenheit since 1991, which most scientists attribute to a build-up of greenhouse gases in the atmosphere.
A 2006 study using the GRACE satellite indicated that Greenland lost roughly 164 cubic miles of ice from April 2004 to April 2006 — more than the volume of water in Lake Erie.
The Peterman Glacier is the one that lost that 100 square mile ice sheet last month so things (like icebergs) are indeed accelerating! And that’s not all that’s happening as Greenland loses its ice cover!
The island of Greenland is currently covered with a thick layer of ice and snow that’s over a mile thick. That much ice weighs a lot and it presses down on the land beneath and compresses it and lowers its elevation. Now, scientists at the University of Miami say Greenland’s ice is melting so quickly that the land underneath is rising at an accelerated pace.
According to the study, some coastal areas are rising by an inch per year and if current trends continue, that number could accelerate to as much as two inches per year by 2025.
Tim Dixon, a geophysics professor says, "It’s been known for several years that climate change is contributing to the melting of Greenland’s ice sheet. What’s surprising, and a bit worrisome, is that the ice is melting so fast that we can actually see the land uplift in response. Even more surprising, the rise seems to be accelerating, implying that melting is accelerating."
Using specialized global positioning system (GPS) receivers stationed on the rocky shores of Greenland, the scientists looked at data from 1995 onward. The raw GPS data were analyzed for high accuracy position information, as well as the vertical velocity and acceleration of each GPS site.
The measurements are restricted to places where rock is exposed, limiting the study to coastal areas. However, previous data indicate that ice in Greenland’s interior is in approximate balance: yearly losses from ice melting and flowing toward the coast are balanced by new snow accumulation, which gradually turns to ice. Most ice loss occurs at the warmer coast, by melting and iceberg calving and where the GPS data are most sensitive to changes. In western Greenland, the uplift seems to have started in the late 1990’s.
Melting of Greenland’s ice contributes to global sea level rise. If the acceleration of uplift and the implied acceleration of melting continue, Greenland could soon become the largest contributor to global sea level rise. The team plans to continue its studies, looking at additional GPS stations in sensitive coastal areas, where ice loss is believed to be highest.
This is a satellite image of Western Greenland, acquired by NASA’s MODIS satellite. The narrow grey band in the center of the image is melting ice, between the rocky coast to the left (west) and thicker, non-melting, higher altitude ice to the right (east). The arrow points to a darker grey zone of rapidly thinning ice near the outlet of Jacobshavn glacier, which also loses mass due to iceberg calving. (Credit: Courtesy of NASA)
Melting and rising, melting and rising. So . . . if that’s what’s going on in Greenland, what’s happening over the rest of the Arctic Ocean in this summer of incredible heat?
Less ice covers the Arctic today than at any time in recent geologic history.
Go ahead, read that sentence again. If it doesn’t send cold chills down your spine, it should. It’s the conclusion of an international group of researchers, who have compiled the first comprehensive history of Arctic ice.
For decades, scientists have strived to collect sediment cores from the difficult-to-access Arctic Ocean floor, to discover what the Arctic was like in the past. Their most recent goal: to bring a long-term perspective to the ice loss we see today.
Now, a team led by researchers at Ohio State University has re-examined the data from past and ongoing studies — nearly 300 in all — and combined them to form a big-picture view of the pole’s climate history stretching back millions of years.
Their conclusion? The ice loss that we see today — the ice loss that started in the early 20th Century and sped up during the last 30 years — appears to be unmatched over at least the last few thousand years according to the lead author of the paper.
Satellites can provide detailed measures of how much ice is covering the pole right now, but sediment cores are the fossils of the ocean’s history. Sediment cores are a record of everything that settled at the sea floor, layer by layer. They record the conditions of the ocean system during the time they settled. When scientists look at the various chemical and biological components of the sediment, and how the sediment is distributed, they can with a certain amount of luck reconstruct the conditions at the time the sediment was deposited.
For example, scientists can search for a biochemical marker that is tied to certain species of algae that live only in ice. If that marker is present in the sediment, then that location was likely covered in ice at the time. Scientists call such markers "proxies" for the thing they actually want to measure — in this case, the geographic extent of the ice in the past.
While knowing the loss of surface area of the ice is important, unfortunately sediment research can’t reveal an even more important fact: how the total volume of ice — thickness as well as surface area — has changed over time.
To review and combine the data from hundreds of studies, the researchers had to combine information on many different proxies as well as modern observations. They searched for patterns in the proxy data that fit together like pieces of a puzzle.
Their conclusion: the current extent of Arctic ice is at its lowest point for at least the last few thousand years.
During the summer of 2011, the team hopes to draw cores from beneath the Chukchi Sea, just north of the Bering Strait between Alaska and Siberia. The Kyushu Current delivers tropically warmed waters that may play an important role in melting the ice across the Arctic. The researchers expect that the ice history of this location will prove very important. They hope to drill cores that date back thousands of years at the Chukchi Sea margin, providing a detailed history of interaction between oceanic currents and ice.
Pack ice near the Arctic island Spitsbergen/Svalbard. (Credit: iStockphoto/Michel De Nijs)
So why was this section titled “Oceanfront Property”? Because the big message of this whole article is “Don’t buy any!”