Rapid Coastal Erosion Correlated to Diminishing Sea Ice

December 16, 2009

Retreating sea ice leaves the Alaskan coast vulnerable to the full force of the ocean. Photo: Benjamin Jones, USGS

Rapid erosion of the northern coastline of Alaska midway between Point Barrow and Prudhoe Bay is accelerating at a steady rate of 30 to 45 feet a year, according to CPS-supported scientists presenting a study at the annual American Geophysical Union meeting this week in San Francisco. As the coast erodes, frozen blocks of silt and peat that contain 50 to 80 percent ice topple from bluffs into the Beaufort Sea during the summer.

The acceleration is caused by a combination of large waves pounding the shoreline and warm seawater melting the base of the bluffs, said CU-Boulder Associate Professor Robert Anderson, a co-author on the study. Once the blocks fall they melt within days and sweep silt material out to sea.

Anderson, along with collaborators Cameron Wobus of Stratus Consulting and Irina Overeem of CU’s Institute of Arctic and Alpine Research (INSTAAR) have studied the coastline for the past two summers with Office of Naval Research support. Equipped with two meteorology stations, a weather station, time-lapse cameras, detailed GPS and wave sensors outfitted with temperature loggers, they documented the summer ocean/shore dynamic.

Triple Whammy

Declining sea ice, warming sea water, and increased waves create a “triple whammy” that expedites erosion. For the majority of the year, the Beaufort Sea is covered with sea ice that disconnects from the coast during the summer. These ice-free summer conditions are lasting for longer periods of time, allowing warmer ocean water to lap the coast and weaken the frozen ground. And the longer that sea ice is not connected to the coastline, the further the distance grows between the ice and the shore.  This open-ocean distance between the sea ice and the shore, known as “fetch,” increases both the energy of waves crashing into the coast and the height to which warm seawater can come into contact with the frozen bluffs, said Anderson.

The shoreline bluffs are made up of contiguous, polygon-shaped blocks, primarily made of permafrost and measuring roughly 70 to 100 feet across. Ice “wedges” (created by seeping summer surface water that annually freezes and thaws) are driven deep into the cracks between individual blocks each year. The blocks closest to the sea are undermined as warm seawater melts their base, and eventually split apart from neighboring blocks and topple during stormy conditions, said Anderson.

Impacts of Erosion

As the coastline submits to the ocean, old whaling stations, military and oil related infrastructure and entire towns threaten to fall into the sea. In addition, the loss of sea ice alters ocean systems and diminishes habitat for creatures like the polar bear.

According to a 2009 CU-Boulder study, Arctic sea ice during the annual September minimum is now declining at a rate of 11.2 percent per decade. This year, only 19 percent of the ice cover was more than two years old — the least ever recorded in the satellite record and far below the 1981-2000 summer average of 48 percent.


November Arctic Sea Ice Extent Third Lowest On Record

December 14, 2009

Reductions in arctic sea ice during the past decade have elevated scientific and societal questions about the likelihoods of future scenarios. Photo courtesy USGS

Arctic sea ice levels over the Barents Sea and Hudson Bay were the third lowest on record since officials began monitoring the area by satellite in 1979, according to the National Snow and Ice Data Center (NSIDC). Last month the sea ice extent averaged 3.96 million square miles, 405,000 square miles less than the average from the period between 1979 and 2000.

Monthly November ice extent for 1979 to 2009 shows a decline of 4.5% per decade. Source: NSIDC

Arctic sea ice experiences significant melting during the summer months. By November, darkness sweeps the Arctic, air temperatures plummet, and sea ice grows rapidly. However, both the Barents Sea and Hudson Bay experienced a slow freeze-up this fall.

In the Barents Sea, ice growth was slowed by winds that pushed the ice northwards into the central Arctic. The deepest of the Arctic’s coastal seas, the Barents Sea is open on its southern and northern boundaries, which creates a significant wind corridor. Southerly winds created a high-pressure area over Siberia and low pressure in the northern Atlantic Ocean in November. Those winds transported warm air and water from the south, and pushed the ice edge northwards out of the Barents Sea.

The map of sea level pressure (in millibars) for November 2009, shows low pressure in the North Atlantic and high pressure over Russia, which led to winds that brought warmth to the Barents Sea and pushed the ice northward. Source: NSIDC

By contrast, the Hudson Bay is a nearly enclosed, relatively shallow body of water that tends to capture ice. The lack of ice is likely related to warmer-than-normal air temperatures in the region.

The map of air temperature anomalies for November 2009. Source: NSIDC

Sea ice in the Arctic is now declining at a rate of about 4.5 percent per decade, according to researchers.


A NIMBY Polar Bear?

September 18, 2009

Back in 2007, an International Polar Year (IPY) project  to establish a network of continuous GPS stations (dubbed “GNET”) in Greenland was launched as part of the U.S. contribution to the international Polar Earth Observing Network (POLENET) consortium (Mike Bevis, Ohio State University, is the Lead PI). In addition to the GPS stations, the PIs of the project set out to collect seismic data. They plan to integrate it with GPS data and use the information to help scientists model Arctic ice loss over the past 10,000 years—since the last major ice age.

This map shows the GNET stations ringing Greenland. Read on to find out what happened to KAGZ, near the northwestern corner of the island. Image by GNET

This map shows the GNET stations ringing Greenland. Read on to find out what happened to KAGZ, near the northwestern corner of the island. Image by GNET

It is an ambitious project that enjoys wide support—with the exception of the local fauna. It appears that a resident polar bear at a GNET site established in 2007 called KAGZ didn’t want it in his “back yard.” Specifically, the bear preferred to munch on the highly technical equipment instead of let it do its job and indirectly work toward protecting the bear’s melting habitat.

A mangled antenna reveals a polar bear visit. Photo: Mike Willis

A mangled antenna reveals a polar bear visit. Photo: Finn Bo Madsen

There was evidence the bear tried to smash the powercables from the solar panels with his paw. Photo: Mike Willis

There was evidence the bear tried to smash the power cables from the solar panels with his paw. Photo: Finn Bo Madsen

Marks on the there were marks on the antenna radome indicate the bear either scratched his back on or had been trying to hug the antenna. Photo: Mike Willis

Marks on the antenna radome indicate the bear either scratched his back on or had been trying to hug the antenna. Photo: Finn Bo Madsen

And though it may not be apparent to the untrained eye, the bear also tinkered with the power cables from the auxiliary battery boxes. Said Danish colleague Finn Bo Madsen of Technical University of Denmark, who traveled to the site to install a gravity meter and subsequently was able to bring KAGZ back online: “My compliments to the cable design and make since they hold and were still working.”

Finally, we don’t really think the bear had a grudge against the site—or even the intellectual capacity to understand its function. Most likely, it had an itch and found a place to scratch it.


Ice, Ice, Baby!

August 28, 2009

Over a mile of ice core taken at the NEEM camp, which sets a new drilling record.

Cores taken from deep in the ice sheet are under enormous pressure. When brought to the surface where pressure is much less, they can shatter. To avoid this, deep ice cores are stored in a buffer to 'relax' before they are moved. NEEM cores may rest in the buffer for up to a year before being moved. Photo: Sune Olander Rasmussen. NEEM ice core drilling project, www.neem.ku.dk.

Cores taken from deep in the ice sheet are under enormous pressure. When brought to the surface where pressure is lower, they can shatter. To avoid this, deep ice cores are stored in a buffer to 'relax' before they are moved. NEEM cores may rest in the buffer for up to a year. Photo: Sune Olander Rasmussen. NEEM ice core drilling project, http://www.neem.ku.dk.

Congratulations to chief scientist Dorthe Dahl-Jensen (University of Copenhagen) and the international NEEM team on a dream season!

Read the National Science Foundation press release.


Glacier Quakes

August 18, 2009

Meredith Nettles of Lamont-Doherty Earth Observatory, a scientist studying glacier dynamics in Greenland, sent a link to her project Web site the other day. There, in addition to basic information on her NSF-funded study, you can find a few pictures from the first of two field trips this year and a sheaf of photos from previous years as well.

The team accesses its monitoring sites via helicopter, landing on the scarred surface of the glacier. Source: Nettles Web site

The team accesses its monitoring sites via helicopter, landing on the scarred surface of a southern Greenland glacier. Source: Nettles Web site

Nettles and colleagues Gordon Hamilton (University of Maine) and Jim Davis (Smithsonian), along with Danish and Spanish colleagues and technical experts from UNAVCO, have placed Global Positioning Systems (GPS) networks on two of Greenland’s most active outlet glaciers, Helheim and Kangerdlugssuaq, both on the island’s southeastern coast.  These glaciers dump massive quantities of fresh water into the Arctic Ocean, and back around 2005 scientists noticed that they (and other glaciers in Greenland’s south) seemed to be flowing a lot faster all at once:  a statue placed on Helheim Glacier in January 2002 would have advanced an impressive six kilometers toward the ocean by year’s end; but during 2005 the same statue would have raced seaward some 11 kilometers—about half a football field a day, Gordon Hamilton estimated.  In addition to accelerated advance, the science team observed that the glacier—about 700 meters (nearly half a mile) thick from muddy bottom to tumbled top, seemed to be thinning rapidly as well, which suggested further destabilization.

The calving front of Helheim Glacier, 2006. Photo: Meredith Nettles

The calving front of Helheim Glacier, 2006. Photo: Meredith Nettles

The seasonal processes driving these changes are what the Nettles collaboration is attempting to discover. For the past few years, researchers have gone to one or both of the glaciers and placed GPS instruments on the ice to create the monitoring networks. (On the Helheim, the team has also placed time-lapse cameras and instruments to monitor climate, seismic and tidal activity.)  These have then collected precise information about the glaciers’ movements, sending data via radio signal to a collecting station on a rock outcrop which in turn sends data back to the Nettles lab via Iridium phone.

Here researchers install a GPS instrument in the middle of nowhere--actually a northern section of the Helheim). Photo: J. Vilendal Petersen

Here researchers install a GPS instrument in the middle of nowhere--a northern section of the Helheim). Photo: J. Vilendal Petersen

The networks have captured information about so-called glacier quakes, phenomena discovered less than a decade ago by Nettles and colleagues monitoring other seismic information. The team noticed that seismic signals were being recorded in clusters around the coast of southern Greenland, an area traditionally associated with little seismic activity. Further study revealed that the seismic activity was caused by sudden, fierce movement of glaciers lurching forward, but the physical processes where not known.

Since then, Nettles and others have learned a bit about these quakes. Nettles talked with Popular Mechanics earlier this year, explaining how glacier quakes work:

“We saw a couple last summer from our helicopter, near the calving front. We were at the outlet to the Helheim glacier, in a system of fjords with sheer rock walls that are 500 meters [more than 1600 ft] tall. Typically, you start to see a rift open up in the glacier and then this big block of ice starts to roll over. The block that breaks off might be a couple of kilometers long and it’s the full thickness of the glacier, which is about seven hundred meters—mainly underwater. . . . It takes a couple of minutes to fall, and as it’s rolling, it has to move this thick melange of ice and water that’s in front of it out of the way. You start to see the icebergs moving very, very fast down the fjord or, if they’re close to the calving front, you see them being popped up, straight towards the helicopter. Then you see just tons of water streaming off of the new iceberg as it is being formed. We have instruments to detect the resulting tsunami about 35 or 40 kilometers away.”

Not for the faint of heart.

Instruments located on Helheim Glacier, Greenland.

Instruments located on Helheim Glacier, Greenland.

After capturing a season’s worth of data on the GPS networks, the Nettles team is back in the field this week removing the Kangerdlugssuaq network and winterizing that on the Helheims. She indicated that she is pleased with the data capture. See for yourself by clicking “Telemetry Status” on the project Web page.


That Dam Glacier

August 11, 2009

There are a few once-in-a-lifetime natural events some of us are lucky to witness—like the sighting of the Hale-Bopp comet, or the longest solar eclipse of the century. Most awe-inspiring natural events, though, occur in remote obscurity, remaining unknown to all but the few people who study them and usually discover them after the fact.

And then there’s southeastern Alaska’s Hubbard Glacier, the fastest-moving, largest tidewater glacier in North America. The glacier is on the verge of damming adjacent Russell Fjord at Gilbert Point. When the glacier seals the entrance it will create a 64-kilometer lake, a natural event that has rarely been observed as it happens.

The rapidly advancing Hubbard Glacier. Source: U.S. Forest Service

The rapidly advancing Hubbard Glacier. Source: U.S. Forest Service

Daniel Lawson of the Cold Regions Research and Engineering Laboratory will be there to document it thanks to a recent National Science Foundation grant.  He and several field researchers will visit the glacier to collect a variety of information about the lead up, the damming event itself, and its aftermath. They will use remote sensing information and a suite of sensors placed on the glacier surface to gather their data. The team will also visit observation points via helicopter or boat and will take several fixed-wing over-flights for aerial photography.

It's easy to see why the glacier is a cruise-ship favorite. Photo: Richard Wainscoat, http://www.wainscoat.com

It's easy to see why the glacier is a cruise-ship favorite. Photo: Richard Wainscoat, http://www.wainscoat.com

Completely closing Russell Fjord could devastate the salmon fisheries in the adjacent Situk River, an economic lifeblood for the city of Yakutat. According to a 2007 Forest Service report, closing the Hubbard-Russell ice dam will increase the river’s daily flows from 3 to 11 cubic meters per second (cms) to more than 566 cms if the lake flows over the glacial moraine. In addition to its prolific salmon fishery, the river draws myriad tourists to the region each year.

Located near Yakutat, the Hubbard Glacier encompasses an area of ~3900 square km, flowing 120 kilometers from the flanks of Mt. Logan (5959 meters and located in the Wrangell – St. Elias Mountains) to sea level, where its terminus widens to over 13 kilometers across the head of Disenchantment Bay and the entrance to Russell Fjord.

hubbard_glacier_map_locaterUnlike most southeastern Alaskan glaciers, Hubbard is thickening and advancing, most recently at an average rate of 35 meters per year for the last 15-16 years. The high accumulation area ratio (0.95) of Hubbard Glacier suggests that it will continue to advance for a hundred years or more, barring any significant changes in climate raising its Equilibrium Line Altitude (ELA) by nearly 1000 meters.


In the NEEM Tunnels

July 13, 2009

The process of taking several kilometers of core out of the middle of a great ice sheet is a gigantic undertaking. There’s the frosty landscape, barren of infrastructure and the seemingly interminable logistics chain, both of which drive the stakes high and require a lot of commitment.  And then there’s the fragile treasure—the ice itself, worth its weight in gold by the time it sees daylight given the cost of its capture.

"The main NEEM building, the dome, is just beautiful inside," Robbie Score commented. There's a lot of ambient light, comfortable furniture, well-organized space." Robbie managed to take a quick tour of the dome after touring the ice coring facilities under ground.

"The main NEEM building, the dome, is just beautiful inside," Robbie Score commented. There's a lot of ambient light, comfortable furniture, well-organized space." Robbie managed to take a quick tour of the dome after touring the ice coring facilities under ground.

CPS staffers Robbie Score and Ed Stockard visited the NEEM drilling camp recently with a group of media, and were treated to a tour of the ice coring and processing facilities located below ground. “It almost felt like a science fiction experience,” Robbie recalled. “We were six meters underground, surrounded by all this activity. The international flavor of it added to the energy—there were people from Korea, Denmark, Germany, the US and other places, all working on various elements of the project.” Robbie says that the coring team has to pipe surface air down into the underground rooms to offset the heat from so many bodies, instruments, machines, and computers at work.

This is the drilling station. The tower apparatus in the center of the room is the drill rig. The spool, front center, holds the cable on which the drill itself travels up and down the casing. The NEEM drill, newly engineered, is working gorgeously, and the researchers are also delighted with the new, plant-derived fluid used to keep the hole from freezing.

This is the drilling station. The tower apparatus in the center of the room is the drill rig. The spool, front center, holds the cable on which the drill itself travels up and down the casing. The NEEM drill, newly engineered, is working gorgeously, and the researchers are also delighted with a biodegradable, plant-derived fluid used to keep the hole from freezing or collapsing.

Per the NEEM Web site, the drill can hold about four meters of core, and each run takes somewhere between 40 minutes and several hours, depending on how deep the drill has to descend to reach ice. The NEEM team will need to make about 800 runs to reach the muddy bottom 2.5 km below the surface, so spring/summer drilling operations will continue at least into late 2010.

Ed Stockard got this shot of ice core coming out of the drill barrel.

Ed Stockard got this shot of ice core coming out of the drill barrel.

When it is brought up, the core is taken to a second underground room connected to the drilling area itself by a subterranean tunnel:

There is so much activity that the drilling room is separated from the processing room by a long tunnel.

There is so much activity that the drilling room is separated from the processing room by this long tunnel.

About half of the core is stabilized, packed, archived, and stored for shipment to ice core storage facilities. The rest is analyzed over in the NEEM tunnel, subjected to a series of increasingly destructive measurements: The core is first polished to create the smooth surface needed for some of the optical measurements; the process continues with conductivity tests, which can point to material in the core that provides evidence of big events like volcanoes; after several more tests,  the core is melted for isotopic analysis.

In the science room: Some of the core runs a gamut of tests in the science room, giving up its secrets to scientists without ever leaving Greenland.

Some of the core runs a gamut of tests in the science room, giving up its secrets to scientists without ever leaving Greenland.

On-site processing saves some of the huge logistics costs involved in shipping the core, and it also provides insurance against the risk of catastrophic failure during core transport. Given the planning and effort this frozen treasure demands of the NEEM team, a little insurance is a very good thing.

Pictures by Robbie Score unless otherwise identified.