The weather has changed dramatically from yesterday. There have been thick clouds and a heavy snowfall - blizzard conditions - today (8 August). The pack ice has been much thinner during the past 24 hours, making for much better steaming and working conditions, and one indicator of this is the fact that the Palmer has been running on two engines rather than four. We have been working in the northern end of Marguerite Bay in an area known as Le Beuf Fjord. Currently (1604), we are at (-67° 57.163 S; -68° 37.144 W). The wind is out of the northeast (030) at 30 to 35 kts and the air temperature is -8.6°C. The barometric pressure is 983.6 mlb.
Yesterday (August 7) was a beautiful, but cold workday with partly cloudy skies and lots of sunshine. The ice pack was not as resistant to our passage and there were many more open leads that made towing of BIOMAPER-II between stations possible. We passed a number of large icebergs during our transits between station locations and at station #37, we did the CTD and phytoplankton ring net tow within a few hundred meters of one giant just as the sun was setting. This was a particularly spectacular sunset because a sun dog appeared and stayed to the right of the setting sun for half an hour or more. On 7 August, we completed work at stations #38, 37, and 36 that included 3 CTDs, 3 phytoplankton net tows, BIOMAPER-II towoying between stations, and some bird and mammal observations.
John Klinck reports that on 7 August, the CTD group did two station deep in the far reaches of Marguerite Bay (a third was done near Le Beuf Fjord). Ice was a significant problem for both of these stations. At the first, pack ice crowded the ship causing us to stop closing bottles at about 30 m. After a bit of effort, a sufficient clearing was created to lift the CTD back into the Baltic Room. Near surface nutrient and chlorophyll, among other measurements, were thus lost. But, we got the CTD back. Heavy ice prevented us from reaching the second station in a reasonable amount of time, so we made the measurements a few miles away from the planned station and headed off to continue the survey.
Station #38 (426m) had a uniform mixed layer to 70 m. Considerable temperature and salinity layering is occurring throughout the pycnocline, but most vigorously in the upper pycnocline. Below about 250 m, water properties are rather uniform with slowly increasing temperature (around 1.0°C) and salinity, and nearly uniform oxygen (around 3.9 ml-1).
Station #37 (555 m) has a mixed layer to about 105 m with a clear linear increase in temperature and salinity from the surface to the bottom of the mixed layer. Some layering is occurring in the upper pycnocline. Below 400 m, dissolved oxygen increases giving rise to an O2 minimum layer between 200 and 400 m. Both temperature and salinity rise monotonously below 200 m.
Jason Hyatt reports on ten days of Meteorological Data gathered during the cruise thus far for the Western Antarctic Peninsula (Yeardays 209 to 219). A quick look at an animation generated from isobar images (which is on the Palmers net work computer - P:\Temp\hyattjapics\isobar219.avi) shows a series of low pressure systems meandering eastward around the Continent. These lows, and the high pressure ridges between, characterize the weather patterns we have been experiencing. The following pattern has happened twice thus far:
1. Start with some
high pressure, low winds, and colder clearer atmosphere with relatively
low moisture, as on July 29.
2. Now a low approaches from the east, causing the winds to shift to the north and bring down warmer, moister air, and often snowfall as on 31 July and 1 August. We actually experienced above freezing conditions!
3. As the low pressure continues its eastward motion, its center can pass almost directly overhead, as on 1 August. After this, the slightest increase in pressure signals that the low has passed and the winds shift around to the east, bringing very cold dry air off of the continent.
4. The low passes, followed by another high pressure ridge, clear skies, and some light southerly winds bringing cold dry air.
This cycle repeated itself from 2 August to the present time, with the strong low passing over us just after at 0103 GMT (2103 local) on 6 August, and a temperature drop of 20°C in about 5 hours, the first half of which occurred in less than one hour.
We should have a day or so of the current high pressure system, great weather for some photography of the awesome scenery we should witness as we skirt the southern coast of Adelaide Island. It remains to be seen if this progression repeats itself, with the low passing nearly overhead. The next low does not appear to have as tightly packed isobars as the last one, so it could be less dramatic.
Ari Friedlaender reports that on 7 August, observations were made from 1130 until 1500 as we steamed mostly through freshly frozen leads towards station #37. Conditions were excellent; high visibility, light winds, and some recently frozen leads that still contained small patches of open water. While the habitat was promising from an observational point of view, no whales were sighted. However, one emperor penguin and two crabeater seals were spotted. Spirits are up, however, as we should be entering some open and productive waters tomorrow.
Ana Sirovic reports that on 7 August, she deployed 1 omni sonobuoy as we entered the big lead. The open water was a good opportunity for an omni, and she wanted to be able to pick up killer whale calls, in case there were any around. The buoy was monitored for 2 h 40 min and got a range of 10 nm. No whales were heard.
Chris Ribic and Erik Chapman report that on 7 August (JD-219), they
surveyed for 3 hours and 31 minutes on our way to station #36. They saw
Snow Petrels and a few Antarctic Petrels in the lead that the ship followed
at the beginning of the transect. As we left the lead and entered 10/10ths
ice concentration, a single Emperor Penguin was sighted. Once in the dense
ice-pack, birds were no longer seen. A summary of the bird observations
is the following:
BIOMAPER-II/MOCNESS report (P. Wiebe, C. Ashjian, and S. Gallager):
BIOMAPER -II has been towyoed between all of the stations in the northern reaches of Marguerite Bay without difficulty. There was a strong backscattering layer which began about 160 meters and went down to the bottom (as deep as 600 meters). In fact, the strongest backscattering seen on this cruise thus far has been in Marguerite Bay. Between stations #38, 37, and 36, there was extremely variable topography with the bottom depths changing as much as 200 meters in only a minute or two. At a towing speed of four to five knots (120-150 m/minute), this change in depth means that the variations were due to cliff-like structures. The topography change was too great to allow us to towyo down into the hollows between the shallow peaks where the backscattering was high. So at station #36 after the CTD was completed, BIOMAPER-II was lowered vertically down to within 50 meters of the bottom, which was at 389 meters. A few krill were observed with the VPR, but mostly the VPR images were of copepods or detrital particles. We suspect there were more krill down at depth, but that they were avoiding the towed body and as a result the VPR cameras missed seeing them. The MOCNESS tow taken a station later, caught significant numbers of adult krill in the 250 to 350 m net.