21 November 2004
Too Much Fresh Water
We woke up to a couple of visitors - Adelie penguins who are not quite in the right place. They appear very tired and rest on their bellies on the ice in the moat. One has a flipper tag and with Mike's huge zoom lens we can read the number and send it off to the penguin research group headed by David Ainley. The other seems pretty skinny (for a penguin) and when they disappear we hope they have gone towards Cape Royds, where the colony is, instead of up the delta, where occasionally the dessicated carcasses of lost penguins are found.
Mornings are starting slow these days. We take the time for pancakes this morning, with fruit and Canadian maple syrup on top. Eventually the coffee, tea or chocolate (or some combination thereof) kicks in and Jennifer, Andrew and Kathy are ready for a dive at Circus. Some of the sponges are so large that we need to take images from further away than we usually do to get a single organism in the photo frame. We want precise measurements of the size of these animals, and how much they have grown in the last 30 years. Plus, there is such an abundance of individuals to image, we need this dive to be sure we have gotten them all. And we also are collecting some of the scallops, Adamussium colbecki, for Paul Ulbrich, a scientist who is back at McMurdo where the scallops do not live. The presence/absence of scallops is just one of the many differences between the east and the west sides of McMurdo Sound. The differences are what make this area an interesting contrast to our work around McMurdo, and will help us determine if the ecological processes of recovery we are following at McMurdo can be extrapolated to recovery processes elsewhere in the Antarctic.
| Two visiting Adelie penguins...
|| And their audience.
There is a thick freshwater lens that extends to the bottom of the ice (19 ft thick), and this water is murky and green. The hole at Circus is keyhole shaped so you have to be sure that you feel your way down the larger part of the keyhole. When you finally reach the seawater it takes a minute for your vision to clear from the mixing of fresh and salt water before you can see the bottom 100 ft below, dotted with large volcano sponges. The freshwater has refrozen into a perfectly clear 2 inch layer of ice, and when Andrew surfaces he rests underneath it for a moment, enjoying the altered view.
| Jennifer slipping into her drysuit (okay, maybe there is a bit of struggling involved).
|| Andrew and Kathy wading across the rapidly melting moat to get to the dive site.
We spend some time getting gear together for a helicopter flight tomorrow - a group of carpenters will be coming out to take down the dive Jamesway and we will have the chance to send things back in the empty returning helo. That and camp chores, packing trash, emptying gray water tubs, sweeping, fetching ice to melt, and of course eating mini pizzas for lunch, took us into the afternoon.
| Jennifer rests like an otter in the huge dive pool at Circus,
|| while Andrew papers himself under the clear ice layer at the end of the dive.
Bob and I do an afternoon dive at the Ice Wall, since it is our last chance to get in there before the Jamesway is removed. There is a short frozen cliff of ice about 30 ft high, and two years ago there were "black pools of death" near at the base. These pools are formed where the salty brine from freezing seawater puddles in small indentations on the seafloor. When seawater freezes, it squeezes the salts out of the crystal lattice of water molecules. The extra salty solution left behind is denser than seawater and sinks, and if there are no currents, stays in one place. Most animals can’t handle the extra salt and die, but there are bacteria that can live in brines and degrade the tissues of the larger animals, but use up all the oxygen in the process. This makes the brine pools black and anoxic, full of decomposing carcasses - hence the name black pools of death. Rikk Kvitek has published a paper on this phenomenon in the Arctic, and though we have seen it down here in the Antarctic we have not documented it. That is our goal for this dive. However, as luck would have it, this year we find only 1 tiny pool about 5 cm across, not enough to satisfy our scientific curiosity. But we do get some good things anyway – we recover a dive bag that the last group accidentally left at the bottom of their hole nearby, and in the distance we see the lonely sentinal light of Romeo, an underwater timelapse camera that will be spending the next several months monitoring a 15 cm square patch of seafloor. One of the frustrations of working in this habitat is that we have so little information on what happens during the winter months, when humans are absent. This camera, deployed by Sam Bowser's group, is a step towards expanding our knowledge to encompass the winter season.
Fortunately, Bob does not have any further surprises for me on this dive. They are very bad for my air consumption rate.
| Even sorting our trash is not such a bad job with such a beautiful background!
| The Romeo underwater camera flag flying over New Harbor.
After an excellent chicken dinner and a surprise dessert (the surprise was how quickly the sauce hardened in the pan, leading to us having to remove it with a chisel – it was still very yummy though!) Jennifer and Andrew were still energetic enough to go and clear all the leftover bits of equipment out of the Jamesway and attempt some more plankton tows. The freshwater layer is causing us problems in that anything that comes out of the water instantly freezes, not good for nets that are supposed to let water through, or for the CTD that we would like to do some casts with. The conductivity sensor that is the "C" in CTD (the other letters stand for temperature and depth), incorporates a thin membrane that is easily fractured by freezing. So far we have not been able to get any CTD casts done safely, though we have, on the warmer days, gotten in a few plankton tows. As always, there is still so much to do!
| More of the challenges caused by the warm weather - the moat is now over bunny boot height, leaving us crossing in our drysuits or on the ATV.