In the early morning of 27 August, low clouds and a light snow kept the mountains of surrounding Paradise Harbor hidden as we turned east out of the Gerlache Straits and went into to it to conduct a series of calibrations on the high frequency acoustical systems used to survey zooplankton during the cruise. This harbor also provided an opportunity for the marine mammal surveyors to use the zodiac to see if whales were in the vicinity. By noon, however, the clouds lifted and provided a breath taking view of snow capped peaks and glaciers running down the slopes to the water's edge. Most of the daylight period was spent doing the calibrations and we did not get leave the area until late afternoon. We are currently steaming out onto the open waters of the continental shelf, now headed for La Maire Straits and our first point of land on the tip of South America. During the transit across the Drake Passage and until we reach the 200-mile limit of Argentina, an XBT survey and passive listening with sonabouys will be done. Our position at 0009 (28 August) is -63° 39.284S; -61° 26.080W. The winds are light (10 kts) out of the west-northwest (297). Air temperature is -3.0°C and the barometer is falling slowly at 977.6 mlb.
The 26th of August was largely a day of steaming. There was a brief stop at broad-scale survey station #4 to do a 1-m2 MOCNESS tow to replace the one that had failed early in the cruise. The intended survey area, the marginal ice edge zone, was some distance from the survey grid and it took the morning to get up into a region where the pack ice was significantly different in character. The hope on the part of the bird and mammal researchers, was that there would be significantly more birds and mammals especially whales. There was a change in the sightings of seals, with elephant seals and leopard seals included in the mix. But no whales were sighted. Although it was cloudy all day, visibility remained good for the surveying until mid-afternoon when it began to snow. Our trackline took us up the middle of the continental shelf until we reached latitude -65°S and then we turned to steaming more to the east so that we reached the Bismark straits in the evening and the Gerlache Straits in the late night.
King Neptune arrived on the Palmer with an entourage of court members in the early evening of 26 August. He held court and sought out the polliwogs in the scientific party, those who had never crossed the Antarctic Circle. After various and sundry rituals, the polliwogs earned the right to be called shellbacks.
John Klinck reports that on 26 August, the CTD group did one XBT today in response to a high temperature and high salinity event on the along track thermosal. Surface salinity increased to 34.1 and the surface temperature approached -1°C. A fast response XBT was launched. The XBT trace showed a normal profile with freezing water near the surface. Since the first 5 to 6 m of the cast are not reliable, the top few meters can not be seen in any case. Perhaps the event had passed by the time the XBT was launched.
The other activity of the CTD group was to finish calibrating the CTD sensor against salinity and oxygen samples. The details of this comparison will be provided in the cruise report. As a quick summary, the oxygen sensor agreed with titrated samples without a bias or time trend. The CTD dual temperature and conductivity sensor agreed to an average difference of 0.000055°C and 0.001. Sensor T1 read persistently higher than T0 by about .001°C. The conductivity comparison changes over the cruise with S1 reading about 0.003 higher than S0 at the beginning of the cruise and shifting to reading lower by about 0.003 at the end. Both conductivity sensors read higher than the AutoSal. Sensor S0 was only slightly higher than the AutoSal at the beginning, but the difference increased over the cruise to about 0.005. The average difference was 0.0042. Sensor S1 started with the same positive offset as S0, but over the cruise it drifted slightly closer to the AutoSal values. The average different was 0.0030. These differences are very close to the stated accuracy of 0.003 for salinity measurements. The salinity values are not likely to be changed in response to these differences.
Chris Ribic and Erik Chapman reported that on 26 August, they surveyed
for 6 hours as the Palmer approached the ice edge. Most of the survey
was still within the pack, but with significantly larger leads than we
have seen on the grid with loose pancake ice and cake floes. As the Palmer
got closer to the ice edge, it began to snow and visibility was not good
enough to see our 300-m transect area. The usual birds were seen in the
leads, mainly Snow Petrels and a few Antarctic Petrels. Just three Adélie
Penguins were seen during the survey, so there have still not been any
large groups of Adélies observed during
this cruise. They still have not surveyed close to land in open water.
It will be interesting to see if more birds are seen during our transit
tomorrow inside Anvers Island.
Ari Friedlaender reports that on 26 August, marine mammal observations began this morning at 0800 from station #4, north towards the ice edge. Starting position was -65° 47.160S, -69° 05.03W. Skies were overcast, yet visibility was between 1.5-2 nm. Ice coverage began as 8/10 of cemented cakes and small floes with rubble between and small open leads. At 1040, we noticed that several cakes that were overturned in our wake, were dirty with algae. Near this time as well, 6 unidentified seals, 2 leopard seals, 2 Weddell seals, one crabeater seal, and 2 elephant seals were observed, all hauled out on floes. The sightings of elephant seals on floes, and during this time of year, seems remarkable. By 1145, the ice conditions had loosened to 6/10 unconsolidated cakes and extensive patches and leads of open water. This trend continued until visibility closed in at 1530 and effort was ceased. Position at the end of observations was -65° 08.254S, -66° 43.913W. No cetaceans were seen today.
On 27 August, the N.B. Palmer was situated, at anchor, in Paradise
Harbor at first light, with the intention of doing calibration runs on
some of the acoustic machinery. After a brief move to a better location,
the Palmer remained stationary until 1600. However, from 1020-1130,
the marine mammal group ventured around the area in a zodiac in an attempt
to locate and possibly biopsy whales. Conditions were poor with 20 knots
of wind, snow fog, and poor visibility. By the time the Palmer began
steaming at 1600, the skies had cleared and visibility was excellent. The
waters in the area had a small chop and were strewn with small patches
of brash ice and small cakes. The course took the Palmer first to
the northwest and then cut to the northeast into the Gerlache Strait. Before
observations were ended due to fading light at 1730, 4 leopard seals were
seen on floes, all situated near a small island that was covered with Adélie
penguins (see bird report). Later on, at 1500, 3 orcas were sighted travelling
south and west in the main channel of the Gerlache. One of the animals
was noticeably smaller than the other two. No mature males were seen in
the group. This sighting was a warm affirmation of the thought that there
is some amount of productivity and available nutrition to support both
predatory pinnipeds and cetaceans. A fine way to leave the Antarctic Peninsula
for the first year of the Southern Ocean GLOBEC cruises. Our kind thanks
to everyone on board the N.B. Palmer, especially Captain Joe and
the officers and crew, for their support and maintenance of a safe, comfortable,
working vessel in the ice. Thanks for the efforts and work produced by
the various science groups on board for this and the first GLOBEC cruise.
And a final bow in thanks to our chief scientist, Peter Wiebe, for his
hard work in organizing so many science projects and for his willingness
to compromise and create equitable vessel time for each of the different
scientific investigations on board.
Ana Sirovic report that on August 26 she deployed 2 difar sonobuoys. The first one was deployed on our way to the ice edge. It was monitored for 44 min. The second one was deployed in a big lead and was monitored for 1h 12min. No biological noise was heard on either of the buoys.
The first sonobouy of 27 August was a difar deployed off the Zodiac while surveying for whales in Paradise Harbor. It was monitored it for a long time since we remained in the area for several hours: 6 h 45 min. The second sonobuoy was an omni deployed after 3 killer whales were sighted. She believes a few short killer whale calls were recorded during the life of that buoy, which was 38 minutes. The third sonobuoy was again a difar and it was deployed as the Palmer was leaving the Gerlache Strait. Seal calls were heard on that sonobuoy, most probably from a leopard seal. This was an excellent day for transmission for the difars: the first one trasmitted over a range of 17.5 mi and the second one transmitted over 13.7 mi. The performance of the omni wasn't as great, as it only trasmitted to a range of 6.5 mi.
Jay Peterson reports that on 26 August, the penultimate day of science off the back-deck, we managed to successfully complete one more OPC/MOCNESS tow. At the beginning of the cruise in late July, a twist of fate caused some last minute cross-talk problems between the OPC and the MOCNESS, resulting in the OPC being removed from the MOCNESS. During that tow the MOCNESS went through a disastrous turn of events resulting in a lost tow and much damage to the frame. In order to maintain as complete coverage of the survey grid as possible, we revisited station #4 in the last 24 hours and successfully completed the 15th OPC cast (and the 17th MOCNESS cast, as described below).
Results of the cast indicate that this region has one of the lower abundances
of zooplankton on our survey grid. Maximum abundance (600 m-3)
was found between 100 - 125 m depth with an average abundance of 400 m-3
for the water column. No distinct scattering layers were apparent on the
ADCP or SIMRAD systems during the tow. The relatively low abundance of
zooplankton at station #4 follows the trend of the survey grid where zooplankton
abundance is highest in Marguerite Bay near Adelaide Island and in the
southern portion of the mid-shelf region west off Lazarev Bay. Zooplankton
abundance decreased off-shelf (West) and towards the north.
BIOMAPER-II/MOCNESS report (P. Wiebe, C. Ashjian, and S. Gallager):
BIOMAPER-II was not deployed on 26 August. During the morning of 27
August, the towed body was hung just below the sea surface off the stern
of the Palmer while it was station keeping in Paradise Harbor. Three
calibration spheres, two Beryllium/steel and one ping-pong ball were suspended
so that they were spaced at 5, 6, and 7 meters below the transducers. The
currents set up by the ship's bow thruster while station keeping made it
difficult to keep the spheres within the acoustic beams, but eventually
sufficient pings were acquired to complete the data collections. Upon completion
of the calibration, BIOMAPER-II was brought back on deck after the calibration
and disassembled in preparation for shipment back to the U.S. at the end
of the cruise.
MOCNESS tow 17 was conducted at station #17 on 26 August at 0306-0414 local time. The tow was a resounding success because of the teamwork of the watch and the outstanding driving of the ship by Marty, the second mate. Upon arrival at station #4, we could not find a lead in which to conduct the tow, so we elected to turn around and tow back along our path through the ice. We launched the net at low ship speed so that few ice floes were advected near the net mouth and frame. The ship speed then was brought up to 1.8 knots. The bottom depth was 346 m, so 330 m of wire was paid out. Once we had finished paying out wire, the ship speed was lowered to less than a knot and the net continued to fall through the water column. Once the net reached 300 m, the ship speed was brought back up to 1.8 knots and the net was drawn back up through the water column. Wire was recovered once the ship speed had ceased to influence the depth of the net. Although ice floes swirled around the wire with alarming regularity, the wire snagged ice seriously only a few times.
The Catch: Thysanoesssa and copepods were present at most depths of the water column. Chaetognaths were present from 150-300 m. Large copepods were seen at depth (>150 m). Pteropods were present in the upper 100 m. Furcilia were seen only in the 50-75 m depth interval, along with copepods and pteropods. Abundances were not high.
This will be the last daily report of the cruise and now the job of putting together the cruise report will be pursued. Captain Joe, the officers and crew of the N.B. Palmer and the Raytheon Marine technical staff provided excellent support for every aspect of our scientific endeavors. A can-do spirit was present from the start to the finish of the work and, in many ways, the success of the cruise is due to the collective efforts of all of these individuals. Thanks also are due to all the scientific members of the different groups that made up the scientific party. The spirit of cooperation and collaboration that pervaded the different groups made my job, as coordinator for the group as a whole, a pleasure.
Cheers, Peter