12-13 May 2001
N.B. Palmer

Today (14 May), is another of the classic Antarctic roaring 40's. In the early morning, the winds and seas again built up and our work schedule has been curtailed. We are currently approaching Station # 63 with winds out of the Northwest (345) at 30 to 35 kts down from highs in the mid-40s. Our current positions is -67 30.121°S; -75 7.725°W (1746 local).

12 May began with calm conditions and the steam between Stations 52 and 53, which took about nine hours was marked by sea ice, bergie bits, and icebergs. By Mid-afternoon, we had arrived at Station 53 - right in the middle of the most impressive ice field with huge icebergs that we have seen thus far this cruise. The ship had to thread its way through the monster icebergs for several hours and they increased with the approach to Station 53. Captain, Mike Watson, expressed the possibility that there might be a need to change the station location because of the "wall" of ice we seemed to be coming to. But we were able to reach the position and conduct the planned work. As described below, in addition to a CTD, the Zodiac was used in an attempt to get close to one of the minke whales sighted in the area and to collect ice samples. During the steam to Station 54 towyoing BIOMAPER-II, the calm conditions gave way to increasing winds and seas. By the time we reached Station 54, conditions had deteriorated to such a degree that we were unable to recover the towed body safely or to do a CTD and MOCNESS tow. Only an XBT and surface water sample was taken and BIOMAPER-II was put down to a safe depth and the ship commenced to steam into the seas for about 12 hrs while waiting for the gale (sustained winds of 40 to 45 kts) to go through.

In the early morning on 13 May, the winds had come down to a point where the ship could be turned and headed to Station 55, although the recovery of BIOMAPER-II had to wait until we had nearly reached the station. At Station 55, we were able to do a CTD and MOCNESS tow, and then re-deploy BIOMAPER-II for the transit to Stations 56 and 57.

In spite of the closely spaced wind events and a significant amount of down time, during the 12th and 13th, we were able to do five CTD casts, twelve sonabuoy drops, one MOCNESS tow, two surface water collections, and two ring net tows for phytoplankton. Between stations, we continued to acquire acoustic, video, and environmental data with BIOMAPER-II, and bird and mammal observations.

Eileen Hofmann reports that late on 12 May, the CTD work was suspended due to bad weather conditions and as a result, at survey station 54 we did a XBT in place of a CTD cast. About mid day on 13 May, the weather improved and we resumed CTD work after returning to survey station 55. After this cast it was determined that the hydro wire on the CTD was frayed and would need to be cut off. This entailed re-terminating the CTD between survey stations 55 and 56. Many thanks to Raytheon personnel Matt Burke, Jesse Doren and Jan Szelag for getting this done.

The temperature and salinity data along the inner part of survey transect eight suggest that an intrusion of Upper Circumpolar Deep Water is overlying the west Antarctic Peninsula shelf in the southern portion of the study area. This intrusion is a different feature than the one observed in the northern portion of the study area. The outer portion of survey transect eight consists of several closely spaced CTD stations. These will provide the data that will allow us to determine if this portion of the shelf is a preferred site for intrusions of UCDW.

At the inner-most portion of survey transect eight, we crossed a sharp frontal feature that is likely associated with the coastal current that flows out of Marguerite Bay. Surface salinity in this region is the lowest encountered so far on the survey. This may be due to freshwater input from the many glaciers on Alexander Island. The inner stations of survey transects nine and ten should provide an estimate of the along-shelf extent of this current.

Chris Ribic and Erik Chapman reported that on 12 May they surveyed for 4 hours 19 minutes during the day as we transited between stations 52 and 53. They surveyed through the area with large, grounded icebergs. The icebergs were being weathered by waves which created large channels of brash ice streaming downwind from the bergs. The surface waters were cold enough so that new ice was forming in association with the brash. They observed a large concentration of birds associated with these ice conditions. Snow Petrels were the most abundant species observed and they saw most of these in close association with the brash or new ice streams. Southern Fulmars were also relatively abundant. They recorded feeding behavior among both Snow Petrels and Southern Fulmars. Hydrography (see Eileen's results) suggests that a cold water current is concentrated along the coastline in this transect area and may be responsible for bringing the ice-bergs to this shallow area where they become grounded. The weathering of the icebergs create brash and bergy bits which are probably cooling the surface waters facilitating the formation of new ice. The high bird and mammal abundance (see Ari's mammal results) in this area suggests important biological processes with this type of physical structure. In particular, we observed Crabeater Seals, Minke Whales, and Snow Petrels in close association with the brash and bergy bits within the survey area. This may be an interesting location for investigation of surface zooplankton communities associated with this type of conditions using the ROV if we return to this area. One anomaly was the absence of Adelie penguins from the area.

On 13 May, they did surveys for 2 hours on our way back to the transect line at station 55 after being displaced during last night's storm. They once again found open water birds in this area with the Blue Petrel being the most common sighting. Overall, bird observations were low during the survey.

They did not conduct evening surveys last night or this morning due to stormy conditions. Here is a summary of results from JD 132 and 133's (12 and 13 May) daytime surveys.
Species Number (JD132) Number (JD133)
4 hr 19 min 2 hr
Antarctic Petrel (Thalassoica antarctica) 9 1
Cape Petrel (Daption capense) 18 3
Southern Fulmar (Fulmarus glacialoides) 48 4
Blue Petrel (Halobaena caerulea) 0 8
Southern Giant Petrel (Macronectes giganteus) 5 1
Snow Petrel (Pagrodoma nivea) 170 2
Kelp Gull (Larus dominicanus) 1 0
Unidentified Storm Petrel  1 0

Ari Frielander reports that the watch began this morning at 0950 local time (12 May) en route to station #53, and at first light and conditions were moderate for viewing. Winds soon increased the seas to a bss6. At 1130 local time, the ship entered an area of more concentrated, shuga, grease, and loose pancake ice. This area also housed many small and medium sized bergs. The winds eased soon after and the ice coverage was between 4-7/10ths. From 1230 local time until 1410, when we reached station, a significant amount of faunal activity was observed. Over 100 crabeater seals were counted, 60 of which were seen in a single group swimming in the wash of a small iceberg. A dozen or so of these animals raced over to the ship and proposed along side for 5 minutes. Also of note were 3 leopard seals. These animals were seen at the surface, probably feeding. There were at least 10 petrels flying around the seals while they were at the surface. As well, 10 sightings of minke whales were made. Seven of these were single animals, two groups of two whales were seen, and one group of three whales was also counted. All but one of these sightings was characterized as ship attraction. Several of the whales approached the ship to within 100 metres. One of the groups was seen lunging out of waves ahead of the ship, and then swam parallel to the ship, down the starboard side at a distance of 50 metres. All sightings of whales and seals were made once the ship was in close proximity to the iceberg fields, and in loose, thin, new ice coverage. Once the ship stopped at station #53, the zodiac was lowered in an attempt to find whales and collect biopsy samples. Light was very poor and no whales were found in the 30 minutes away from the Palmer. Hopefully, we will find similar conditions again, with more time and light to collect samples. Ari thinks we have found a winter dining spot.

Catherine Berchock reports that May 10th she deployed one difar sonabuoy on route to Station 44. Nothing was heard, except for some faint humpback type of calls that need verification.

On May 11th she deployed a difar upon leaving station 49, throwing it into the slush. Even though it did not go straight through, she still picked up a signal from it. No sounds were heard from it and the signal was lost very quickly (in less than 4 miles). She switched the antennae cables again, but the dipole was worse than the stick antennae.

Another difar was deployed on the way to Station 50. A couple of moans were heard, possibly from seals. The ship noise was very loud at the time. This buoy was also lost after three or so miles, but it came back again later on for just a little while longer. Still the range was no more than 4 miles.

The last difar on May 11th went in between Station 50 and 51, so that its signal could be picked up again as the Palmer steamed on a nearby trackline on the way to Station 52. Well, the same problem as before turned up - a strange pulsed static started when we were more than 2.5 nm away. She listened nevertheless, pausing during the MOCNESS tow. The signal occurred again on the way to Station 52 as we passed within 1.5 nm of the sonabuoy. The signal was quickly lost after that. During this period, she may have heard some seal moans again.

On the way to Station 53 on May 12th, a difar sonabuoy was deployed. Some 300 Hz downsweeps were heard, but there was uncertainty about where the sounds originated, possibly seals. As was true the day before, this signal was also lost signal quickly, so the antennas were switched again at the 04 deck, but this did not help.

Another difar was thrown out in the vicinity of some minke whales and seals on the way to Station 53. Catherine heard moans and upsweeps/ downsweeps that might have been from the seals, but this needs additional reference to the literature on seal sounds to confirm it. The sounds were not ones that has been documented from minkes. The signal was lost in less than 3.5 nm from buoy. Another difar was deployed following the sighting of 10 or so minkes. She also went out in the Zodiac with Ari Friedlander to try to deploy some sonabuoys close to a minke, but no minkes were found. During the Zodiac trip, ET's Jeff Otten and Jim Doren were up on the science mast and moved both loops of the dipole antennae aft. Later in the evening, the last difar of the day was deployed on route to station 54. Some downsweeping moans were heard through the ship noise. When the signal was dropping out and the annoying pulsed static started, she switched to the newly configured dipole antennae. The signal came in loud and clear and she was able to record for another 2 hours. The down sweeping moans were heard at least 10 more times. The stick antennae was good while it lasted - but it only lasted 2 days.

May 13th turned out to be a very good day for Catherine. Both difars that were deployed got more than 10 nm of range, and the pulsed static was absent. The first one went out at 68 07.0°S; 71 54.6°W, on route to Station 55 from our course into the wind. Some seal moans like those heard yesterday were recorded, but the show-stoppers were the ten or more infrasonic upsweeps that occurred over the course of about 40 minutes. From the frequency range (18-36 Hertz), they were either finback or blue whale calls. From their length (more than 2 seconds), it is more likely they are from blues.

The second difar went out about 6 miles from station 55. Only seals were heard or observed on the computer screen. They were same moan sounds as yesterday. The literature available on the ship suggest that they may be leopard seals. Weddell and Crabeater seal moans are much higher in frequency, but lack of information about the sounds made by Ross and Fur seals leaves the interpretation open to question.

The use of the dipole antennae was a success and the source of the source of the pulsed static was determined to be originating from the GUV (ultra-violet sensor) up on the science mast. The interference from the GUV may no longer be a problem with the new dipole antenna with its strong signal.

BIOMAPER-II/MOCNESS report (P. Wiebe, C. Ashjian, S. Gallager and C. Davis):
About 0050, on 12 May, the fish was again deployed and towyoing began at the end of Station 52. The transit to Station # 53 was a longer than normal nine hours and along the course the some very large icebergs were past by. Coming out of Marguerite Bay and around the northern tip of Alexander Island, there was some incredible variation in topography. At one point, depths reached 1500 meters and 30 minutes later, they were up around 200 m. Needless to say, we were quite conservative about how deeply we towyoed BIOMAPER-II. The calm sea conditions, however, made the towyoing easy.

By mid-afternoon, we had arrived at Station 53, amidst huge icebergs and the large number of mammals and birds described above. There was very intense volume backscattering on the 43 kHz and 120 kHz echograms in a layer from 190 to 230 m, but little back scattering above 80 meters. In contrast, the 200 kHz echogram had high scattering from 100 to 180 meters, with some bands of stronger scattering.

Late in the afternoon after the zodiac had returned to the Palmer and the CTD cast had been completed, we towyo'd the fish towards station 54. The wind started building soon after we got underway and by the time we reached the Station location, winds were already over 40 kts and the seas were building rapidly. Since a MOCNESS was scheduled for this station, the first order of business was to pull BIOMAPER-II. But with conditions getting worse by the minute, the decision was made to scrub the MOCNESS tow. An attempt was made to bring BIOMAPER-II on board and with ship on course and making about 2 kts into the sea, we started bringing the fish up. But two very large waves came over the stern rail and deck crew went for cover. The big waves were too frequent and it quickly became too dangerous to get the towed body on board. So it was put down to a depth of about 90 m and after abbreviated station work, the Palmer steamed into the wind and seas, which continued to build into another gale, with BIOMAPER-II in tow. All night, the ship steamed about 5 kts into the wind, which was coming out of the north-northeast. Every so often, the stern would dip way down and waves would come pouring over the aft deck flooding the entire area.

Morning (13 May), brought reduced winds and seas making it possible to change to a reciprocal course that took us back to Station 55, but it was still too rough to attempt to bring the fish on board. The ride was smoother, however, and towyoing resumed. This continued until about 1500 when the wind had shifted directions to the west-northwest and had come down into the 20 kt range. In order to get to Station 55 faster and get the station work back on track, the ship was stopped to get the towed body on board. There was still a big sea with swells of 15' or more, but the ship was brought onto a course that minimized the pitching. There was an agonizing period when the fish was just below the surface and a couple of big waves came by, but finally the go was given and BIOMAPER-II was quickly hauled up to the docking mechanism, the tag lines attached, and the towed body safely brought back on board.

We steamed at 11.6 knots for a little over an hour and arrived at Station 55 about 1630. By 1730, the CTD was back on board and the MOCNESS was in the water for a tow to about 350 m. The tow went smoothly in spite of rough seas, but the catch was a bit skimpy. Large copepods were caught down deep, numerous pteropods were present at mid-depths (100-150m), and juvenile krill were in the upper 50 m.

At the end of the station activities, BIOMAPER-II was redeployed for towyoing along the transect to Station 56.

Cheers, Peter