AMLR 2005 Weekly Report No. 6

20 February 2005

1. Our current position is south bound in the Drake Passage in transit to the South Shetland Islands. The ship fetched Punta Arenas, Chile late in the evening on 16 February. During a three-day import in Punta Arenas, AMLR personnel was exchanged, provisions and fuel were supplied to the ship. The ship then departed on time at 0500 on the 19th.

2. First item of business for this second leg of the AMLR field season will be a call on Cape Shirreff field camp. Personnel J. Hinke, provisions, propane fuel and mail will be transferred to the shore camp via zodiac. Directly after finishing the resupply of Cape Shirreff the ship began the second survey-D of bio-oceanographic conditions in the vicinity of the South Shetland Islands. The survey area consists of four strata: the West Area north of King George and Livingston Islands; the Elephant Island Area encompassing the northern portion of the South Shetland archipelago; the Joinville Island Area in the western portion of Bransfield Strait; and the South Area in the central portion of Bransfield Strait south of King George and Livingston Islands. Planned order of coverage will be the West Area followed by the Elephant Island Area, the Joinville Island Area, and the South Area.

3. Oceanography and meteorology. The Antarctic Polar Front was crossed between Latitudes 58° 30 S and 57° 50 S on the northbound crossing to Punta Arenas, with the sea surface temperature rising from 3.04°C to 6.22°C and a corresponding increase in salinity from 33.65 PPT to 34.05 PPT. After crossing the Antarctic Polar front the air temperature increased from 4.1°C to 8.3°C. Crossing the Drake Passage the Barometric Pressure steadily increased from 964 to 1004 millibars, associated with strong Westerly to Northwesterly winds, averaging around 25 knots and peaking at over 40 knots. On departure from Punta Arenas at the end of the week, for the second leg of the AMLR 2005 season, sunny and warm weather was experienced with air temperature reaching over 12°C and the Barometric Pressure peaking at 1014 millibars. Winds were moderate, around 10-15 knots, from the Northwest.

4. Bird and marine mammal observations. Observations of seabirds and marine mammals were conducted while underway to the AMLR study area, starting at the east end of the Strait of Magellan. As in past years, seabird data was collected using a 300-meter strip transect, while those of marine mammals were more opportunistic. Overall densities were fairly low although species diversity was comparable to previous years. Unexpected were the high numbers of Common Diving-Petrels off the east side of Tierra del Fuego as well as lesser numbers farther south. Many Thin-billed Prions were also in the former area suggesting a concentration of surface zooplankton. Several Soft-plumaged Petrels were seen, with an increase in numbers during the approach to the Polar Front. Noteworthy were 3 Mottled Petrels, having been last reported on an AMLR cruise in March 1995. There were very few marine mammals, likely a result of unfavorable sea conditions. Peale's Dolphins, several unidentified large whales and 3 small whales, likely beaked whales of the genus Mesoplodon, where the only cetaceans seen.

Submitted by A. Jenkins.