IceTrek Mid-Size Deployment (AMIGOSberg): 2 March - 6 March
Please credit the National Snow and Ice Data Center for image or content use.
Today, the IceTrek team wrote back with news that their Saturday afternoon ended in a deployment to AMIGOSberg. Below are their experiences during the deployment. See the Research Updates section for more photographs and an explanation of how the AMIGOSberg deployment adds to the big picture of scientific understanding of icebergs.
At 1:30 on March 4, the IceTrek team’s logistics coordinator came to Pedro and Ted with a proposition to solve the problem of the disappearing window in the weather: Would we accept a 6 p.m. deployment and spend the night on the iceberg?
Liftoff occurred at 5:30, with high thin clouds and lowering light--marginal from the start. These are gigantic Sea King helos; they can carry all the gear and all of us in one flight, with six others as flight crew and photographers. The flight plan called for a survey of almost half the iceberg edge, to be sure of the orientation, and to see as much of the edge (with its fracture pattern) as possible. We planned to set two flag lines from the camp to two separate edges, so a survey of both edges was needed.
We turned to get onto the path to the AMIGOSberg tripod site, but as soon as we got over the iceberg, we saw that the light over the huge, very smooth berg was almost hopelessly flat—no features at all, like flying over an infinite bowl of milk. How do you land in this? Even the purple smoke flares seemed like they were floating in a fog—no reference. But finally, the pilot fixed his gaze between both flares and landed smoothly.
There is a unique kind of chaos during an offload: engines screaming, snow blowing, and we got another surprise. Unlike the tempanito, or “chip” iceberg, the surface was covered in thick soft snow. Instead of the usual Antarctic packed “foam” snow, we had something like white peanut butter covering everything. Stumbling, wading, breathing diesel smoke, heaving heavy crates—perhaps we have a new level for Dante.
We got unloaded and put the gear in a pile, and with several of us draped over it to keep it from blowing away, the helicopter took off. We pushed hard for three hours until darkness fell and we got to our projected site. We erected the tower, but didn’t have time to test it; we also set the flag line directions and finished the pits and cores before crawling into our sleeping bags.
March 5, we were up five hours later at 4:30 am, the time of dawn twilight now. We got underway again. Rob and Ted set up to do one flag line, Pedro and Juan Carlos another; Jonathan and Ronald worked to get the tripod electronics going and well tested.
The snow was extremely difficult—even 2.4 km seemed like forever; what’s more, we could not see any sign of the edge from that point. Light was flat, with intermittent thin fog. But we kept going thinking that the edge was just ahead. About 800 m on, as the fog began to lift, we approached the edge.
AMIGOSberg has several “push mounds,” first seen on the Ross Sea icebergs, indicating where an iceberg has crushed against ice shelves or other icebergs during its drift. These were our first sign of the edge, beginning approximately 400 m from the edge itself. The steep roll-off we saw in ICESat was there. If anything, the satellite data under-represent the roll-off. It is as much as 10 m where the satellite shows no more than 3 m; but unlike the tempanito, or "chip" iceberg, there were no cracks until within 20 to 30 meters of the edge. We picked a site where we could get quite close, set an anchor at 30 m from the edge, and walked over.
From over the edge, we could see a thin stringer of fast ice, very little evidence of a submerged bench, and not much of a water-line cavern. The iceberg had a freeboard of approximately 30 m.
The hike back was epic for both groups. Post-holing into the snow made for heavy going progress, and we knew that crew aboard the Irizar was anxious to get going again. The weather cleared, and we knew they would want to launch, but we simply could not move quickly. It required two full hours of hard hiking to retrace the 3 km to camp.
When the two flag teams finally arrived, Ronald and Jonathan had the tower up and running properly, as well as camp broken down. The Irizar launched the helo within minutes of our getting back to camp—their original plan had given us one extra hour to complete our deployment.
That evening, back aboard the Irizar and the ship on its way again, we looked at images from the tripod camera. It stood on its own, alone on the ice of AMIGOSberg. We hope that all of our efforts will take us one step further in understanding how icebergs disintegrate as they float into warmer temperatures—and, by extension, how ice shelves break up as temperatures rise.
One final note: None of this could have been possible without the support of the Captain and crew of the Irizar; as well as the outstanding job that the pilots did under tough weather conditions. Everyone has committed a great deal of ship time to putting us on AMIGOSberg and being supportive of our project. They came up with a plan—our overnight stay—that worked.
Ted writes, "We arrived at the iceberg early late on March 3. This morning, we woke up and there on the radar screen was the edge of AMIGOSberg that we had hoped to see—rotated a bit more than the estimate, but from the edge in the radar, we could orient the older images. We knew where our site was.
Now, the issue is weather. In the met office, the map shows a gang of underachieving low-pressure cells that is kicking the forecast around like a tin can, but to the west we can see a huge area of clear sky. If we don't get away by 3 p.m., we won't have the 5-hour window we need to deploy the equipment today, and that is supposed to be our only chance. But the forecast break in the clouds keeps getting pushed later and later--noon, 2 pm...4 pm."
While the team awaits news of the weather, they have spent the morning in the machine shop. The drill bit on the ice corer, the PICO auger, suffered damage en route, and the team repaired it with help from the ship's heavy machinery group. Ted writes, "The machine shop is an interesting place: spare piston heads the size of oil barrels and valve-and-shaft assemblies the size of mammoth bones sit bolted to the hallway wall like the Borg subunits, waiting for any emergency."
Great news! The IceTrek team has successfully boarded the icebreaker Irizar. Rob says, "The weather is closing in and there is a ton of ice--the ship is just crushing and crunching through ice."
The team hopes to land on AMIGOSberg tomorrow morning; they aren't yet sure what conditions will be like on the iceberg. But they are ready to go, and excited to get down to the work they went such a long way to undertake.
Ted sent these details later in the day:
The A.R.A. Irizar departed Marambio Station and proceeded south-west along the coast of Snow Hill Island towards Matienzo Station. Unfortunately, the past several days of storms had shifted the ice, and several areas were blocked with very thick (2m to 3m) multiyear floes from the southern Weddell Sea. This required many more hours of slow ice-breaking en route. Furthermore, the weather continued rather marginal for flying, and the forecast was more of the same.
However, aboard ship, things went quite well. In the hold of the ship, we reorganized our gear, checked it for problems, and practiced using items such as the ice corer. The crew has generously given us a section of an oceanography lab to set up some equipment.
The ship arrived at Matienzo Station, where the camp was being broken up for the season and the personnel were being brought aboard. We took the opportunity to consolidate our gear for the AMIGOSberg deployment. We also turned our attention to figuring out where AMIGOSberg was and how the iceberg was oriented. This was not easy. Days and days of bad weather had rendered the MODIS satellite tool, our most useful information-gatherer, almost useless. Further, some glitches in our early communications setup on the ship meant that we had almost no access to the outside electronic world.
Our objective was a particular corner of the roughly square AMIGOSberg, the corner that had previously been in the thickest part of the ice shelf. The earlier images that Terry Haran, back at NSIDC, had provided us for download gave us an idea of both drift direction, speed, and rotation rate. By early evening, we had a good estimate of where the iceberg would be on March 3 and 4—our best chance of landing on AMIGOSberg--and how it would be oriented. With this less than certain estimate, an officer translated our request and the captain turned the ship.