Into the field at last! After missing a chance to go out Monday due to continued storminess, the weather began to clear a bit during the evening, and we woke to find Tuesday morning relatively clear and flyable. Since the condition of the sea ice between Ross Island and Beaufort Island has deteriorated somewhat, we were scheduled to fly in the Coast Guard’s HH-16 "Dolphin" helicopter, a ship that is allowed to fly over open water because it has a limited ability to float in a crash landing (I don’t want to test this concept!). See: USCG fact sheet for details. Our helo pilot Wendy (seen here flying past Castle Rock), and her crew chief Monica, introduced us to the sophisticated ship, and I was allowed to sit in the co-pilots seat so I could scout the landing site and access to the beach. This is a bit of a daunting privilege, as you are wrapped around a set of the dual controls for the ship, and you do not want to interfere with the pilot by putting your foot in the wrong place (the rudder pedals), bump the stick, or set your camera bag on the collective (which I did!). As we headed north, scuddy clouds became thicker, and our first view of Beaufort Island was of a dark smudge on the horizon, slightly darker than the clouds covering the summit peak. We flew past the main Adelie colony, eyed the tricky traverse to reach it from the landing zone, made a turn around the northern tip of the island and set up for landing. The glacier is sloping and bumpy, so Wendy took her time to find a suitable landing zone. We off-loaded our field packs and survival bags (in case the ship couldn’t return for weather or other reasons) and waved as Wendy lifted off for the return flight to McMurdo.
I scouted ahead to check for crevasses or other dangers, but found the route down to the beach simple. We carried our gear down and started down the northwestern coast from the northern tip of the island. The new satellite colony that David Ainley had told us about was settled onto the lowest beach terrace, too low an elevation for colonies of any antiquity, but above the modern beach lies a high terrace, rising to the west, that is truncated by wave erosion and mass wasting below, and is emerging from the receding glacier above. To our surprise, we found this terrace covered with pebble mounds, evidence of previous occupation by Adelies. Along the seaward edge, these mounds are being bisected by erosion, so the bright red ornithogenic soils clearly show between a half a meter and a meter of old deposits. Interestingly, it appears that the receding glacier is exposing undisturbed mounds that were hidden beneath it, an idea that we need to research further. The views from this high terrace were tremendous, with the lengthy but narrow splinter of Iceberg B15K dominating the western horizon, complete with huge bergs calving off from stress zones. As the island rises up to the southwest, the bulk of the glacier covers the slopes, and streams from melting snow cascade over basalt cliffs. And as I looked out across the sea ice, I saw an unlikely group of travellers- a troupe of Adelies being followed by a lone Emperor penguin!
Our main objective is to locate the site described by Rodney Seppelt (Seppelt et al., 1999), the famous Antarctic botanist that Jurek met last season, who described an exposure where penguin bones were eroding out of the hillside. Armed with a photo Xeroxed from his paper, I surveyed the beach terminus below the terrace and quickly found the site. In a horizon far below the terrace surface, a half-meter thick layer is exposed that is dense with bone, but the deposit is very different from the mound deposits as it is full of bone and dense with feathers, but contains no shells or ornithogenic soil. It appears that this is a deposit preserving a molt site of unknown age, containing bones of almost all adult-sized birds and feathers, but no nests. Steve sampled the site, collecting bones from the lowest, middle, and highest levels, as it’s important to find out how old the deposit is, and how it relates in time to the pebble mounds on the terrace above. But the size of the colony that must have covered the upper terrace was the biggest surprise, it was apparently once a very large colony. While we investigated the Seppelt exposure, Jurek was sampling the lush vegetation on the slopes above.
Our next step was to excavate a test pit in the terrace
colony site. Steve chose one of the deepest parts of the bisected deposit
for Beaufort Island Site
1. The terraces are covered with roosting skuas, and this lone
sentinel stood guard as we dug. As we screened the sediments, I was
once again struck with the amazing natural
sculptures surrounding us that form from a stew of icebergs, sea ice,
and sea water. As a final task for our first field day, we entered the
colony to collect eggshells for isotope work. This colony
is small, but seems to be doing well with a large number of healthy-looking
chicks, including this content
mother (father?), and relatively close access to open water regardless
of the presence of B15K. Too quickly our day was gone, and Wendy and
Monica flew in right on time. In the afternoon sun, the views of the cloud-shrouded
peaks on Ross Island were spectacular, such as Mount
Bird and Mount
Erebus. Our speedy flight
quickly returned us to McMurdo,
and we were back in plenty of time for dinner. Although we hoped to return
to Beaufort today, the weather was alas uncooperative again, with fog,
clouds, and a bit more snow. As I write this, the clouds seem to be lifting
and the afternoon conditions improving, so hopefully tomorrow………
Addendum, Thursday, January 13, 2005
Well, the forecast was a bit off, with more foggy/snowy/cloudy weather today prohibiting the helos from flying. But there is a good bit of buzz going on down here about a big collision that is about to take place. The largest part of the iceberg that broke off the Ross Ice Shelf a couple of years ago, Iceberg B15A, has been drifting northward and will be running into the massive Drygalski Ice Tongue any day now. See this NASA web page for more details, but the date for the impact is now predicted to be Saturday, the 15th, and we are scheduled to fly up to Mario Zucchelli Station on Monday the 17th, so we will fly right over the impact zone and should get a chance to see what happened. I'll post some images of this and more as soon as I get a chance.
Reference: Seppelt, R., Green, T. G. A., and Skotnicki, M. (1999). Notes on the flora, vertebrate fauna and biological sigificance of Beaufort Island, Ross Sea, Antarctica. Polarforschung 66, 53-59.
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