Landsat-derived map of Larsen B showing field sites. Colors indicate ocean depths derived from sonar data: red for shallow areas and blue for deep areas. (Courtesy Eugene Domack and Caroline Lavoie, Hamilton College)
Zoomed-in version of a Landsat-derived map of LARISSA field sites on the Larsen B Ice Shelf. The map shows all the AMIGOS (blue asterisks) and cGPS (red circle and black square) sites visited by Terry Haran in November and December 2012. Cape Disappointment is shown but doesn’t have a blue asterisk, and AMIGOS-6 is located on the small black outcrop just below and to the left of the black circle. Colors indicate ocean depths derived from sonar data: red for shallow areas and blue for deep areas. For scale, Flask Glacier is about 4 miles across at the location of the AMIGOS-3 blue asterisk. (Courtesy Eugene Domack and Caroline Lavoie, Hamilton College)
Both the 0900 and 1100 UTC AMIGOS images from Flask Glacier and Scar Inlet showed good contrast at both sites, and satellite images looked good as well. We took off at 9:32 a.m with six people on board: pilot Al Howland, myself, field assistants Ian (Cheese) Rudkin and Ash Fusiarski (who spent the entire previous day with Daniel Farinotti man-hauling radar equipment on Flask Glacier), and builders Jim Scott and Phil Harle. Got lots of good pictures on the way to Cape Disappointment, particularly of the shear zone running along the northwestern side of Scar Inlet.
Ice-capped Bildad Peak at an elevation of 2,600 feet rises some 1,300 feet above Flask Glacier and is visible in some AMIGOS-3 images. View is toward the northwest.
The northwest edge of Scar Inlet ice shelf, the last remnant of the Larsen B Ice Shelf, is being ripped open due to the increasingly large difference in velocity between slower moving ice northwest of the shear margin, and faster moving ice to the southeast emanating from Flask Glacier
Shear zone middle
Shear zone south
The collapsed AMIGOS-6 tower (middle, left) as seen during one of three passes made over Cape Disappointment just before landing.
After three passes around Cape Disappointment, including two touch-and-go landings, Al set us down at 11:14, about a mile northwest of the AMIGOS-6 site.
The team gathers materials and then rope up in anticipation of hiking out about a mile to the AMIGOS-6 site. (Courtesy Jim Scott, British Atlantic Survey)
Field assistant Cheese Rudkin at the toppled AMIGOS-6 tower on Cape Disappointment.
Seals (probably Weddell) resting on the banks of a sea ice lead extending south from Cape Disappointment. (Courtesy of Jim Scott, BAS)
We donned crampons and harnesses, roped up, split into two groups of three, led by Cheese and Ash each pulling a sled full of equipment, and left the plane at noon. Cheese, myself, and Al arrived at AMIGOS-6 at 12:50, followed closely by Ash, Phil, and Jim. Al, who used to work as a “rigger,” led the group raising the tower, installing the new three-pole outrigger arrangement, and securing the poles to the wire basket rock anchors.
Phil and Ash work on attaching the AMIGOS-6 electronics and high resolution camera enclosure to the now erect and pole-strengthened tower. (Courtesy Jim Scott, BAS)
The upwind anchor which had failed was rebuilt, and strengthened with an additional new wire basket rock anchor. The rock anchor surrounding the tower, which also had failed, was disassembled but not rebuilt. The consensus was that installation of the new poles and strapping the battery box to the tower were providing a sufficient tower anchor. Jim Scott rewired the solar power input and 12-volt output lines to the solar charger assembly, while I added a fourth battery to the battery box and tested the system.
Terry talks to Ted Scambos at NSIDC in Boulder to verify that at least some valid data are being received, so the Iridium cable and antenna seem to be working correctly. (Courtesy of Jim Scott, BAS)
I was dismayed that AMIGOS-6 wasn’t connecting to the internet through the NSIDC FTP server — until I remembered that I had seen an email a couple of days earlier indicating that the server and its associated disks would be down for maintenance all day on December 19. I called Ted who verified that, but who then suggested that he would ask the system administrators if FTP could be brought back up for my test. We started packing up, I called Ted back who said the FTP server was back up, and I then verified that AMIGOS-6 was connecting correctly. We were also able to verify that weather and GPS data were being received via email correctly, but we were unable to verify that images were being correctly received since the FTP disks were still down.
The repaired AMIGOS-6 tower stands ready to record and transmit weather and image data. (Courtesy Jim Scott, BAS)
But since all this had been working correctly in Rothera, albeit with a different Iridium cable and antenna, we felt that it the system was working okay. We started walking back to the plane at 4:30 p.m., arrived at 5:00 p.m., and took off for Leppard Glacier at 5:30 p.m.
After taking off from Cape Disappointment, a final view of the now repaired AMIGOS-6 tower.
After taking off from Cape Disappointment at 5:30 p.m., and before proceeding to Leppard Glacier, we made a slight diversion over Exasperation Inlet and part way up Crane Glacier. Ted Scambos wanted us to obtain some aerial photos of the lower part of the glacier which we did.
Composite image of Exasperation Inlet from Exasperation Point. Cape Fairweather is on the left. Crane Glacier enters the inlet far to the left and out of the frame. The foreground view is entirely sea ice, at most a few meters thick. There are a few icebergs in the foreground and many more as we approached the glaciers from which most of the visible icebergs have been calving. Prior to the disintegration event in February 2002, the entire foreground view of this image would have been of the Larsen B Ice Shelf which was several hundred meters thick.
The calving front of Mapple Glacier. Crane Glacier enters Exasperation Inlet
far to the right of this image.
The calving front of Crane Glacier is at the far left of the image and Exasperation Point is at the far right. The flat large tabular iceberg in the foreground has probably drifted into Exasperation Inlet from a glacier far to the south.
The 2.5-mile wide Crane Glacier calving front is heavily crevassed. The crevasses appear to extend to great depth causing virtually all icebergs that calve off to be very narrow relative to their total thickness. Such icebergs cannot float upright, and so either they immediately lay down on their side or they crumble into bergy bits. Thus most of the horizontal surfaces of the large flat icebergs in this image were originally the vertical surfaces of crevasses in the the glacier before calving.
Composite image of the northern side of the Crane Glacier calving front and the iceberg melange just downstream. The calving front is about 150 feet high and the largest icebergs are over 1,000 feet across. The Crane Glacier surface has lowered by several hundred feet since 2002. A small terrace of stranded glacial ice just above where the calving front meets the rock wall stands about 500 feet above the surface of the melange.
A side glacier about 2 miles across flows into Crane Glacier about 9 miles upstream of the calving front. A relatively uncrevassed area on the surface of Crane is visible in the lower left corner of the image and may suitable for some future instrument installation via Twin Otter.
About 20 minutes after taking off, Al announced it was time to exit Crane and head over to Leppard. We flew over the upper reaches of Mapple, Melville, Pequod, and Starbuck Glaciers, and crossed Flask Glacier just upstream of the AMIGOS-3 site where Ash and Daniel had been collecting radar data just the day before.
A panorama taken where we exited Crane Glacier fjord en route to Leppard Glacier. A pressure ridge marks the confluence of the left (southwest) and right (west) branches of Crane Glacier. Another side glacier can be seen entering the fjord from the right (northwest).
Bildad Peak and Flask Glacier, this time looking southeast. AMIGOS-3, though not visible here, is located near the right edge of the image.
Panorama of Flask Glacier from Spermwhale Ridge on the left to Pip Cliffs on the right.
Due west view looking up Flask Glacier which is almost 3 miles wide at
Another five minutes brought us within sight of the LPRD cGPS on Leppard Glacier. We made a touch-and-go landing, and then a final landing at 6:15 p.m.
Images of the Leppard Glacier continuous GPS system before and after
a touch-and-go landing
The goal at this site was to simply raise the solar panels. This required first re-excavating the hole dug during our previous visit three weeks earlier. Then more snow and ice covering the two solar panel poles below the floor of the hole needed to be chipped away so that the overlapped section of pole extension installed two years earlier could be fully exposed. Then the now useless guy wires extending to the deadman snow anchors needed to be cut, the clamps binding the extension needed to be loosened, the extension slid up about three feet, and the clamps re-tightened.
Images of the Leppard Glacier continuous GPS system before and after
being raised about 3 feet.
Image of the Leppard Glacier continuous GPS system’s GPS antenna located
2.12 meters (about 7 feet) above the snow surface.
All this was done as planned, but unfortunately the cable to the weather station was accidentally damaged in the process. However Ash Fusiarski was able to repair the damaged cable, and Seth White of UNAVCO in Boulder was able to verify that the system was posting good GPS data, although confirmation from Seth of the posting of good weather data had to wait until the next day.
Ash Fusiarski repairing the damaged weather station cable after the solar panels had been raised.
We finished the repairs and took off for Rothera at 8:15 p.m. arriving at 9:30 p.m. After scarfing down the dinners that had been saved for us, I bought a round of beer in the bar for the entire crew. I didn’t go to bed that night since I had to unpack all our gear, separate out the BAS gear that needed to stay in Rothera, and then repack all my gear for the Dash-7 flight in the morning.