LARISSA - LARsen Ice Shelf System, Antarctica, a NSF-funded project.

LARISSA - LARsen Ice Shelf System, Antarctica, a NSF-funded project.
We are conducting an integrated, multi-disciplinary field program to address the rapid and fundamental changes occurring in the Antarctic Peninsula region as a consequence of the abrupt collapse of the Larsen B Ice Shelf in the fall of 2002. A profound transformation in ecosystem structure and function is occurring in coastal waters of the western Weddell Sea. This transformation appears to be yielding a redistribution of energy flow between chemoautotrophic and photosynthetic production, and to be causing the rapid demise of the extraordinary seep ecosystem discovered beneath the ice shelf, providing an ideal opportunity to test fundamental paradigms in ecosystem evolution.

Thursday, March 4, 2010

Non-programmed camping in James Ross Island

10 - 14 Feb With heavy hearts we have headed northward from Lockyer Station
and out through the Antarctic Sound to the west side of the Antarctic
 Peninsula. Unusually heavy sea ice, including floes (or floating ice slabs)
 several years old and meters thick have forced us to abandon our plan to
 work in the Larsen B area. Although our vessel, the NB Palmer, is an 
icebreaker, it cannot safely smash its way through multiyear sea ice
 because of high pressure ridges (compressed areas of sea ice 3-4 meters 
high). It is clearly unsafe to linger longer on the eastern side of the 
Antarctic Peninsula this high ice year, and even our offshore oceanographic
 sites are now covered solidly with the pack ice. 

Satellite image showing heavy sea-ice cover throughout our
 desired study area in the Larsen B vicinity (dashed circle). Flat whit areas are sea ice and ice shelves; ruffled areas throwing shadow are
 clouds. In most years, the circled area is clear of sea ice by the end of
 January. The heavy sea conditions this year illustrate the high
 interannual variability in weather conditions in the Antarctic – even
 though climate warming continues at a very fast rate in this region, during 
some years, sea ice may still persist throughout the summer due to
 stochastic weather processes.

Before leaving Lockyer Station, we had a bit of a scare, and a reminder 
that the Antarctic is still a remote and potentially dangerous environment.
 Two of our party, a geologist and writer for National Geographic, were
 flown by helicopter to a site on the Antarctic Peninsula 25 miles away to
 collect glacial erratics (rocks dropped by glaciers far from their site of 
origin). As they were working, the weather began to close in so they
 helicopter flew out the pick them up and return them to the ship. During
 the return flight (only about 15 minutes), the weather closed in even 
further, and whiteout conditions forced the helicopter, with three aboard,
 to land on a beach on James Ross Island only 6 miles from the ship. A snow 
storm ensued for the next three days, grounding the scientist,
 writer and helicopter pilot in two small tents for three days. The
 helicopters always travel with emergency rations for 6 days, sleeping bag s
and tents, so the stranded party was is in no immediate danger. However,
 it was sobering to realize that while they were only 6 miles from us, there
 was nothing we or anyone else on earth could do for them until the snow
 storm abated. After 3 days, we finally had a patch of blue sky in which to 
recover our now smelly shore party. They had spent their time digging a
 latrine, building snow walls to protect the tents from the 30 inches of 
snow fall, and reading and dozing in their sleeping bags. The National 
Geographic writer now has quite a story to tell about forced camping in the
 Antarctic wilderness, an experience somewhat reminiscent of the stranding
 of Shackleton’s shore party on Elephant Island, 180 miles north of here.

The snow storm that stranded three of our expedition members on 
James Ross Island for three days.

Following recovery of our wayward three, the NB Palmer crashed northward
 through very thick sea ice, making only 2-4 knots for 26 hours. 
As we entered the Antarctic Sound, the strait between the Weddell and
 Scotia Seas at the north end of the Antarctic Peninsula, the sea ice 
thinned and we were able to make much better time. By evening of the 13th 
we were in position for an ROV dive on a recently discovered submerged
 volcano in the Antarctic Sound, to search for hydrothermal vents to provide 
study organisms for David Honig and Mike McCormick. The ROV dive found no
 vents, but did reveal dense communities of sponges, crinoids (see lilies),
 brittle stars and other suspension feeders characteristic of
 the Antarctic seafloor. It is thought that such communities can thrive in
 the Antarctic only because large crushing predators, such as king crabs and
 bottom feeding sharks, are excluded by the very cold Antarctic waters 
(below 0 centigrade). Such communities of exposed suspension feeders 
occurred worldwide in the ancient ocean, but apparently were eliminated
 with the evolution of large crabs and bottom-feeding sharks. The lack of
 these large, skeleton-crushing (or duraphagous) predators in the Antarctic 
has allowed the radiation of a diverse assemblage of suspension feeders 
unique to Antarctic waters. As climate change brings warmer waters to the
 Antarctic, skeleton-crushing predators, especially king crabs, threaten to
 invade shallow waters around the Antarctic Peninsula, potentially leading
 to the extinction of many unique Antarctic species. During the dive we 
also observed giant “barrel” sea anemones that apparently roll along
 the seafloor without a permanent attachment. This may be an 
adaptation to utilize habitats newly exposed by the bulldozing of the
 seafloor by grounding icebergs, a major source of disturbance for seafloor 
habitats at depths less than 300 m in Antarctica.

The NB Palmer breaking its way though multi-year sea ice south
 of the Antarctic Sound.

A dense assemblage of suspension feeding sea lilies (crinoids, 
plumose yellow animals), brittle stars, sponges (white blobs and shapes),
 and octocorals (pink trees) on the seafloor at 500 m depths on the
 submerged volcano in the Antarctic Sound. This is classic, high-biomass,
 exposed Antarctic benthic assemblage is likely to be very susceptible to
 predation from invading king crabs. 

Barrell anemone approximately 30 cm (12 inches) long rolling 
along the seafloor on the Antarctic Sound submerged volcano.

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