Today (30 May) we have started a series of short transects to define the coastal current off the southwestern portion of Adelaide Island using CTDs at point locations and BIOMAPER-II towyos along the trackline. The survey had to be discontinued, however, when word was received late yesterday that the software in the AWS on Kirkwood Islands that logs the wind speed was faulty and needed to be fixed to enable wind speeds above 5 m/sec (10 kts) to be recorded. Earlier this morning, we received code to be inserted into the data acquisition code and so we are currently steaming for the Kirkwoods. Our current position is -68 04.989°S; -69 16.864°W. The wind is between 10 and 16 kts out of the south-southeast (130) and the air temperature is -4.5°C.
Between midnight and 0500 on 29 May, the krill patch study was concluded with the completion of two additional MOCNESS tows. Then the ship steamed over to the eastern side of Marguerite Bay to the San Martin Station manned by Argentina. Two days earlier, we received an invitation to visit the Station by Base Leader, Captain Carlos Martin. They had discovered our presence in the area by chance and welcomed the opportunity to have us see their Station. We arrived around 1030, anchored about a mile from the Station, and then the Zodiacs were used to ferry most of the scientists and a number of the crew to the base for 3 to 4 hour visit. The winds were quite light and the sea nearly smooth. But we could not see much of the mountains around the station because of the snow, which was coming down in a light to moderate fashion.
The Station has a series of reddish buildings, which serve a variety of purposes and there are a number of antennas distributed as an array throughout the station area. It has been in existence since 1951. The work of the Station is mainly geophysical and astrophysical. The nineteen personnel, all male, are there for a year, and they had just completed the first two months of their stay, which ends next March. Most are in the military and the two civilians present represent the scientific contingent. The others provide support and maintain the station. Communication now is by radio, but a satellite system will be in place by July to enable data telemetry and voice communication.
Our hosts gave us a tour of the Station that included the science laboratory space, living quarters, the game room, the food storage buildings (freezer and dry stores), the garage with the skidoos and 4-wheel drive snowmobile, the carpentry shop, and the helicopter pad. All of their supplies come in once a year when the exchange of personnel takes place. There is also a medium-sized two-story structure which the Captain referred to as their "House". The downstairs had a "mud" room for taking off boots and winter outer clothing, an exercise room, and other storage spaces. Upstairs was a cozy environment for eating, socializing, and entertainment (movie viewing etc). Wood lined ceiling and walls gave the place a warm feeling. And in the middle of the biggest room, was a table filled with plates of especially prepared foods and an assortment of drinks. Filling this room were about 35 visitors from the Palmer and 15 or so of the residents. Our host, described highlights of Argentina (which he called our temptation), the history of the Station, and its mission today. Then about 1300, there was an exchange of small gifts, the eating of the food, and the cutting of a cake made for the occasion. It was a very good time and it was clear that they were very happy to have had us accept their invitation. Likewise, our group very much enjoyed their hospitality and the opportunity to visit their station.
With the light fading fast, the group started moving down to shore, a boatload at a time, and by 1530 or so, all had returned to the Palmer and the anchor was hauled up. By 1600, we were back to steaming for the next station and the final couple of days of work before we head for Punta Arenas.
We steamed about 40 nm over to just north of the Faure Island group and began a CTD/BIOMAPER-II section that was intended to sample the coastal current along the southern end of Adelaide Island. The CTD was done at Consecutive Station 91 first in about 200 m of water and then BIOMAPER-II was put into the water for towyoing to the next station about 8 nm away. The bottom topography, as we steamed to station 92, became like a roller coaster, and it was very shallow. Much of the shallow topography was not on the charts and it was slow going. We reached the second CTD site around midnight on 28th of May.
Eileen Hofmann reports that After a delightful and welcome visit to the Argentine base, San Martin, we began a transect of nine closely spaced (about 8 nm) CTD stations along the western side of Adelaide Island. The station spacing is designed to capture the southwesterly flowing coastal current as it turns into Marguerite Bay. After occupying four of the stations, we stopped the transect to return to the Kirkland Islands to repair the AWS.
Combining the data from the four new CTD stations with that from previous
CTD and XBT casts shows that the coastal current around Adelaide Island
is narrow (10-15 km) as it enters Marguerite Bay. This is similar to what
was observed for the coastal current that exits the southern side of Marguerite
Bay around Alexander Island. Once we return to the transect and complete
the remaining stations, we will be able to provide a more complete description
of the coastal current.
Bob Beardsley's Drifter Note 149 (May 29)
A Figure (not shown in this report) shows the drifter tracks for the period starting yd 140 through 147.75, the most recent update. The red asterisk at the head of each track is the last position, indicating the direction of the drifter motion. Blue circles are plotted every 2 days along each track.
Points to note:
1. There are now four drifters on the mid-shelf west of Alexander Island, all moving down shelf towards the west to southwest. Drifter 3, originally in the coastal flow around the northern tip of Alexander Island, moved offshore near Lazarev Bay to join drifter 2.
2. Drifter 10 quit transmitting on yd 142, presumably having gotten trapped in ice and submerged.
3. Drifters 8 and 9 continue to move southward deep in Marguerite Bay. I expected drifter 9 to enter the current leaving the Bay along the northeast side of Alexander Island, but it turned back east instead.
4. Drifters 12 and 13 were deployed on yd 147. Drifter 13 immediately started to move into Marguerite Bay, suggestive of the coastal flow into the Bay around the southern end of Adelaide Island.
5. Drifter 5 is slowly moving west and north towards the shelf break. In the 58 days since being deployed, this drifter has moved a net 57 km towards the WNW, with an average vector speed of 1.2 cm/s and an average scalar speed of 5.8 cm/s.
The drifter data collected to date suggests that there is surface flow
into Marguerite Bay around the southern end of Adelaide Island. This area
was not adequately sampled during the large-scale hydrographic survey,
so additional CTD stations will be made around the southwestern end of
Adelaide in the next few days. We plan to deploy the last drifter near
mooring A1 as the NB Palmer departs this area for the return to Punta Arenas.
Catherine Berchok summarized her Sonabuoy listening activities for
the past three days:
On May 27th in anticipation of installing an AWS on one of the Faure Islands, she was up early to throw in a sonobuoy before arriving at the islands. The first one was deployed at 0650 local, but did not transmit. Recovery of BIOMAPER-II, thwarted her deployment of another one until 0729. Humpback sounds were heard, so a third buoy was put out to try to get a cross bearing of the position. Unfortunately, that buoy was flaky and she could not get a bearing fix from it. The one working buoy gave bearings to two separate groups of whales at 1300. One was at ~190 degrees from the heading of the ship and there seemed to be two at approximately 110 degrees.
Two more sonobuoys were deployed after the work on the AWS installation was completed and BIOMAPER-II was again deployed and started on a series of transects defined by four way points in Labeuf Fjord. One was at 5 nm and the other at 3 nm from BIOMAPER-II way point #3. Humpbacks were heard and a cross bearing between the two channels located the whales in the vicinity of the krill patch that was defined around midnight. In total, five sonobuoys were deployed and 13 hours of recordings were made.
Recordings were started at 0849 on May 28th and continued until 0637 on the following morning. A total of six sonobuoys were deployed (five difars and one omni). One of the difars failed. A couple of cross bearings and triangulations were done with the difars - and placed the vocalizing whales (humpbacks) below the bottom line of a northern survey triangle that BIOMAPER-II ran during the afternoon of the 28th, and between the middle of the line and the right triangle turning point. The vocalizations did not seem to be in the form of song, so perhaps they were feeding calls. More analysis will be needed to answer that question. Also, since there are almost 24 hours of recordings, it may be possible to determine if there is a daily pattern to humpback vocalizations in this area.
Only one sonobuoy was deployed at 2000 on May 29th, about
3 nm from the CTD at station 91. The boat noise was still quite loud, but
it was possible to get a fix on a vocalizing humpback whale - which appeared
to be in the general direction of the patch of krill that was the focus
of the surveys in Labeuf fjord yesterday.
BIOMAPER-II/MOCNESS report (P. Wiebe, C. Ashjian, S. Gallager and C. Davis):
The krill patch experiment continued into the first portion of the 29th of May. During the midnight to four watch, another strobe light experiment was completed with the MOCNESS towed horizontally between 50 and 90 meters (tow # 23). Another quick turn-around was done to load the nets and process the samples. Then the four to eight watch came on and they did an oblique tow from close to the bottom (600 m) to the surface. This second tow (#24) ended about 0445 and the net was on board by the 0500 time on the schedule as the starting point for the steam over to San Marin Station. A paper output from the Simrad sonar system was collected with both tows. Copepods were found at depth, with a few krill (600-300 m), coincident with a scattering layer. Adult krill were abundant from 100-50 m, also coincident with a strong scattering layer. The upper 50 m contained larval krill, copepods, and small minnow like fish (25-0). A weak scattering layer also was found in the upper 50 m.
Around 2230 just north of the Faure Island group, BIOMAPER-II was deployed after at CTD profile to begin a towyo section that was intended to sample the coastal current along the southern end of Adelaide Island. During the early part of the transit to the next CTD station, the bottom topography was so variable that the towyos had to be kept within the upper 50 meter for the most part.