This was another day for observing the grandeur of the Antarctic ice-scape. In the pre-sunrise light, we steamed towards the Wilkins Ice Shelf between the northern part of Charcot Island and the Southern end of Rothschild Island. The first light was before 0900 and the glow in the sky was just behind the mountains of Rothschild Island, so that the mountains were silhouetted as black against a rose hued band of light just above their crests and the dark grey of the water leading up to their base. The visibility was very good with high thin clouds overhead and even a bit of clear sky. The winds remain light and out of the southeast and these conditions persisted the rest of the day. We are now steaming towards a rendezvous point with the R/V Gould in Lazarev Bay on the North side of Rothschild Island. Our current position on 22 May at 2122 local time is -69 29.451°S; -73 42.054°W. Winds are out of the southwest (230) at less than 10 kts and the air temperature is -5.3°C
Yesterday was an equally nice day, during which most of the effort was devoted to finding a site where bird and mammal observations could be made from Zodiac inflatable boats and where the first of the ROV deployments could take place for under ice krill studies. The area chosen was the embayment bounded by Charcot Island on its north, the Wilkins Ice Shelf to the east, and Latady Island to the south. We had intended to do a station in the vicinity of the Wilkins Ice shelf edge where it was hoped that we might find whales and penguins, as well as do a CTD survey along its face. In the early morning of the 21st of May, however, we found ourselves ploughing ahead at about 3.5 knots into heavier and heavier pack ice and we were still some distance from our intended destination. Earlier in the transit as we entered the ice field around midnight, there were a lot of sea birds in the high intensity spot lights which are always on and focused ahead of the ship after dark, but in the early morning light we were not seeing any birds or mammals. The bird and mammal researchers did not see any sense in going further, so after entering a lead that had probably recently opened and then frozen, we stopped to take an XBT and get ice samples. The latter were obtained by putting the personal carrier with three people aboard over the side with the large main crane and landing it on the ice. Then we turned around and headed back the way we came, but a mile or two to the north. By about 1100 hours, we again reached open water and the ice edge. The zodiacs were readied and then the first was deployed for the whale group to use and the second ferried the bird party, after some delaying outboard engine problems were resolved. During the Zodiac deployments, the ROV was being readied and upon their return, the ROV was deployed for testing and trial runs under the ice late in the afternoon. Unfortunately, a leak developed in the underwater unit of the ROV and fried some of the electronics. Fortunately, the parts that fried were not essential and could be by-passed. By late evening as we were steaming to a new sampling location on the North side of the Wilkins Ice Shelf, the ROV was repaired and ready to again be used.
Eileen Hofmann reports that around mid-day on 20 May (two days ago), the CTD group completed the last cast for the survey grid at station 84. Everyone was very pleased that the survey was finished and that we were able to obtain good quality hydrographic data throughout the entire time. Congratulations to the CTD team for a job well done.
The temperature maximum distribution below 200 m for the completed survey grid shows complex circulation dynamics on the west Antarctic Peninsula and in Marguerite Bay. In particular the current flowing out of the southern end of Marguerite onto the continental shelf and the northeastward flowing current inshore of this are of interest. The dynamics underlying these currents are unclear and must await further analyses.
After completing survey station 84, the decision was made to transit around Charcot Island to the Wilkins Ice Shelf. This transit took us near a site where hydrographic observations were made in March-April 1994 by Stan Jacobs. Thus, we set a cruise track that would take us south from survey station 84 to this site (at 70°S 37.99, 77°W 37.32). Half way to this site we did a CTD cast and then another CTD cast after arriving at the site. By re-occupying the station done by Jacobs we hope to be able to merge our data set with some of the historical hydrographic observations made south of our study area. After completing the CTD station at the previous station site, we did a straight transit into the Wilkins Ice Shelf. Along this transit, we dropped XBT probes at 10 nautical mile intervals.
The additional observations obtained during the transit to the Ice Shelf show that Circumpolar Deep Water is present to the west of Alexander Island. This water appears to be connected with the northeasterly flowing inner shelf current that was observed south and west of Marguerite Bay. Again the dynamics producing this current are unclear and need further study.
During 21 May, the focus of the scientific activities centered on obtaining data for the top predator components of the program. As a result, the CTD group did not do any XBTs or CTDs during the day. Rather, the time was spent catching up on running salinity, oxygen and nutrient samples, plotting data, and doing data analysis.
Chris Ribic and Erik Chapman report that on 21 May, they were able to get into the Zodiac to try to diet sample petrels at the edge of brash ice and first year floes south of Charcot Island. During the hour that they had before they lost light, they managed to attract Snow and Antarctic Petrels near the zodiac using a cod liver oil-soaked red cloth. They nearly captured several birds using this technique and they look forward to refining their methods and giving it another shot where bird densities are higher during the remaining days of the cruise.
Ari Freidlander reported that on 21 May observations began at first light as the ship moved back out of the ice, towards open water, from the Wilkins Ice Shelf. No whales were sighted before we reached open water. However, twenty-two crabeater seals were counted on ice floes during this time. Zodiacs were deployed at 1245 for whale biopsy work. The ship was at the ice edge between young pancake and brash ice, and open water. No whales were sighted and as a result no biopsy attempts were possible. We did encounter four crabeater seals that were active at the surface. When we went for a closer look, we were approached by a single leopard seal. The seal swam under the zodiac several times and surfaced within two meters. The seal then stayed behind the zodiac for several minutes as we moved away in search of whales.
BIOMAPER-II/MOCNESS report (P. Wiebe, C. Ashjian, S. Gallager and
There were no BIOMAPER-II or MOCNESS tows done on 21 May. Most of the work associated with these instruments involved data archiving, and analyses of the video images and the environmental data, and post-processing the high frequency acoustics data.