Posts Tagged ‘LARISSA’

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A short weather window for station repair

November 10, 2011
antarctic peninsula, moutnains, glaciers, and clouds

The mountains of the Antarctic Peninsula peek through the clouds. Photo courtesy Ted Scambos.

Ted writes:

As mentioned, this year’s expedition is all about repairing existing stations and setting up one new one; yesterday we completed the first of these repair missions. The site in question is arguably at the eye of the storm for ice shelf break-up, near the center of the Scar Inlet Ice Shelf, a remnant of the Larsen B ice shelf that disintegrated in 2002. Since the 2002 break-up, this shelf has calved at least three major icebergs, developed several huge cracks, and has sped up, as the obstruction of the Larsen B ice shelf plate was removed. Behind it, dammed up by the Scar shelf, lie two very large glaciers, Flask and Leppard.  The idea for this part of the LARISSA venture is to set up a series of stations to record the events leading up to the next break-up. If it happens, the Scar Inlet site is going to be a very exciting place. Briefly.

The weather window to do the work yesterday was rather short. An intense storm gathered offshore of Rothera, with contour lines of pressure resembling a large dirty fingerprint on the map. Already as we were taking off, the wind coming off the ocean was brisk, and from the ground I could see dark chunky clouds skulking around the nearby ridges, spoiling for a fight.

But from up above, as always, it was spectacular. It is the undersides of clouds that are fearsome. The upper sides are glorious, and in Antarctica you have a sun-splashed pallet of azure blue, wispy and sculptured white, ethereal cyan, and impossibly sharp black-brown, as sky, cloud, windswept or fractured ice, and rock form an ever-changing composition. A moonscape dressed in lace.The Antarctic Peninsula will someday be a world park of some kind, I am sure of it. It is breathtaking, and beautiful, and dynamic, and solemn all at once.

We flew past both the Larsen C and Larsen B ice shelves. Koni Steffen (a.k.a. Fearless Leader, and both words apply fully), graduate student Dan McGrath, and Chilean scientist Gino Casassa are now camped on the Larsen C, surveying the ice there at an earlier stage of response to climate change (the Larsen C is south of the Larsen B, and slightly cooler).

The Larsen B is closer to the point of destruction, and you can tell just by looking at it. I mentioned the huge cracks already, and there are massive crevasse trains where the large glaciers emerge from the mountains. But it’s more than that: the entire central shelf is a fine network of narrow fissures and slots, and in warm summers the entire area is covered with shallow melt ponds. The last intense melt season was 2006. If that season happened now, with the additional cracks and faster flow, I think we would see a disintegration.

Our pilot, Doug Cochran, flew several circles around our station; it was surrounded by these narrow spiderweb cracks. Last year, with less snow and more early melting, it was impossible to land here. Exposed cracks were everywhere. This year, the crevasses were still covered by icy spring snow. Eventually we gambled on one path, right along a flag line that we had installed when we first put in the station, in early 2010. It worked. Malcolm Airey,a BAS general field hand, and an expert climber and outdoorsman and I skied 300 yards to the site, roped and loaded with “jingly-janglies” (the UK slang for climbing gear: they say this phrase with complete British seriousness). We replaced the weather station and the main processing box including a much better communications system for getting the data off in a hurry, and we were done: 90 minutes.

True to forecast, the storm broke upon Rothera just as we were landing. Within minutes, we had 50-knot winds and clouds of blowing snow everywhere. Dragging our gear back the short distance to the base was far more arduous than the real work on Scar Inlet. This evening, the wind is howling, ice-choked waves are crashing against the coast, and the building is shaking (60-knot gusts, I’m told).

But we’re in the pub, enjoying the events of the day.  And fearing the walk back to the dorm building.

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One last look

November 24, 2010

Ted writes:

On Saturday, weather again looked to be clearing over the area of our lost “Site Beta” AMIGOS station, as well as over the Larsen C, so I joined a flight that was planned for another group (Dan McGrath and ‘Puma’, a Chilean graduate student) to get an overflight of our last unvisited site. The flight included the chief pilot for BAS/Rothera, Alan Meredith, and several BAS staff hands, Ben Tibbetts and Ian, to assist with the main objective, raising a Larsen C AWS station managed by Dr. Koni Steffen (also of the University of Colorado) higher to keep it from suffering the same fate as Site Beta. The difference is that the Site 108 AWS received about 2 feet of snow since last year. Site Beta received 30.

As we left Rothera behind us, we could see clearing ahead, and soon we were flying over the crest of the Peninsula. But below us the situation still was not good. Long streamers of blowing snow trailed off the surface, and from every rocky ridge. As we turned, I could see that the snow was moving about half the speed of the plane–and the plane was moving at 120 kts. Alan turned to me and said, “I’m sorry Ted, it’s just not going to happen.” I had to agree. We were still 20 miles from the site, and already there were low clouds building in addition to the snow streamers.

The plane turned east, and landed a short while later, in surprisingly calm air on the eastern side. “That turbulence we passed through on the way down,” (it was just a bit of bumpiness) “was the shear layer in the air. The high winds are above us now.” We spent the afternoon refurbishing a full weather station, raising it 3 meters higher so that it will survive at least 3-4 more years.

The team headed north on Sunday, November 21, arriving in PA around 6 pm. We’re now en route home, just in time for Thanksgiving, with several repaired stations and a plan to return next year.

The LARISSA AMIGOS Team of 2010/2011 wishes to thank AGUNSA, NSF, and especially BAS in Rothera for the excellent support we received, and for pitching in to help when needed.

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A taste of success

February 11, 2010

Ted writes (via Iridium modem):

On Saturday, a long-awaited spell of clear weather threw the LARISSA Glaciology Team into fast action. Three of the five stations we hope to put in this are now up and running. Our highest-priority site, Flask Glacier, which flows into the last remaining part of the Larsen B Ice Shelf, is now fully instrumented.

Clear weather over Flask Glacier allowed the team to fly to several sites to set up AMIGOS stations.

The weather was spectacular for nearly three days, beginning on Saturday. With our first flight, our pilots, Richie Cameron and Dave, brought out the GPS system, a continuously operating precision GPS designed to record any subtle changes in the ice flow, even ones at a tiny scale, occurring on a daily or monthly basis. The GPS will also provide a detailed record of any general acceleration if the ice shelf thins and breaks apart.

Every time the plane engines rev, and the plane starts to move, a song just jumps out of my head, like a second heartbeat; Satisfaction by the Rolling Stones for the first flight; Ode to Joy later that day; Ring of Fire by Mr. Johnny Cash on the way back from the ice core camp.

Setting up the Flask GPS took us about 4 hours, and in a second flight, we moved down-glacier to the Flask AMIGOS site. AMIGOS is a heavily instrumented science station, sort of a super weather station with measurements of the ice added in. Terry and Ronald began to assemble the station even before the tents were set up, and had the basic framework laid out by evening. All five of us then set the lower Flask camp, still basically a mountaineering setup with backpack tents and few luxuries. But with five of us now in the cook tent, there was a camaraderie that made up for some of the tough conditions. For dinners lately, we’ve had chili, pan-grilled steak, tofu thai curry, and tonight, with luck and a bit of imagination, jambalaya.

A day trip on Sunday back to the Ice Core Camp got the AMIGOS station there stood up and operational (we had it running, but not erected, for about a week), and on Monday we finished the Lower Flask AMIGOS, the most sophisticated yet. It contains a full-precision GPS (from the GRS-1 board built by TopCon Inc.), a steerable camera system, a full weather station, a sun and reflectivity sensor, and a thermistor string extending 12 meters into the snow. We worked 13 hours that day, until darkness came.. Darkness and night have begun to return here.

As we worked on Monday evening, the fog and snow returned. Tuesday we managed to survey several short radar lines, but fog and poor lighting conditions made it risky to explore too far; the camp is surrounded by huge crevasses. Wednesday we returned to our waiting-for-sunshine mode, that is, looking over the data, sorting the food, reading books, walking short distances for exercise, quoting old movie lines and other trivia games, and just generally hanging around, until the next break.

And with the end of southern summer coming on, we need that break soon. One last push to go.

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The Palmer Departs

January 5, 2010

Ted writes:

The Palmer slipped the surly bonds of the Punta Arenas pier at 5:20 p.m. yesterday, in a beautiful evening sun. The gear was stowed, labs secured, and a full compliment of staff and scientists were aboard. The temperature was about 62 degrees F, and there was a 15-knot breeze. We ate dinner at 6, and after a day of rushing to do the final shopping and securing, the adventurers relaxed, talked with energetic anticipation of the plans ahead and the past cruises that they’d enjoyed.

The AMIGOS crew–Ted, Terry, Ronald, Erin, and Martin–were continuing to build the system software, especially for the new GPS boards, and improve the radar acquisition and analysis software as well. I downloaded our image collection for the survey regions and re-evaluated our selected sites with respect to crevasses, using MODIS, Landsat-7, ASTER, Formosat-2, and other data.

Some early adjustments to the plans included adding a reconnaissance flight to evaluate as many of the sites as possible prior to any deployment of GPS or AMIGOS. We’re planning a loop flight across the Crane and Flask Glaciers, to literally see the lay of the land and the potential risks. Current heavy sea ice conditions  in the western Weddell Sea mean that other science operations may be delayed or progress more slowly than planned, so the AMIGOS team may see a lot of action in the early part of the cruise. We are planning to install three to four sites  between January  10th and 20th.

The sun set off the stern starboard bow. The Palmer is sailing east and north, towards the Atlantic, before a hard starboard turn towards the Drake Passage.

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