On these long cruises to the Antarctic Western Peninsula, we typically budget five days for steaming from Punta Arenas, Chile to the work site. Good weather allows for a faster passage and foul weather or significant areas of sea ice makes the passage slower. On this cruise, we will need the five days because we are now in the northern portion of a large area of sea ice that, from the satellite imagery we have been receiving, appears to cover the entire survey area. We are currently (26 July, 1030) about 90 miles from our first station, steaming on a southerly course at about 6-7 kts. There are large areas of pancake ice interspersed with open leads. Seas are smooth with the ice cover even though there is a southerly wind blowing in the low 20's kt range. The air temperature has fallen dramatically and is now about -9.0°C. A thick low cloud cover makes the scene a bit gloomy. Snow is coming down lightly.
The 25th of July was another day of steaming with winds and seas somewhat higher than the previous day. Strong westerlies in the range of 30 to35 kts prevailed most of the day and seas were running 12 to 15 feet. The skies were partly cloudy with some occasional light snow in squalls that passed by. The work schedule was again light with XBT's, a couple of sonabuoy deployments, and bird and mammal observations the order of the day.
Around 2145, the ship abruptly slowed when we encountered the northern edge of the first year pack ice. Our position when we encountered the sea ice was -62° 46.707S; -68° 35.801W. Once we were into the sea ice, the high waves and swells were dramatically damped and the ship's ride significantly improved. Our time to the first station, however, was lengthened, because the ship's speed had to be lowered from around 10 to11 kts down to between 6 and 8 kts.
The physical oceanographic work on this cruise is being done by a group led by John Klinck. This work includes the use of the CTDs, XBTs, ADCP (Acoustic Doppler Current Profiler), and the meteorological sensors. John reports that XBT measurements of temperature began just after midnight on July 25 as we left the Argentine 200 mile limit. We used T5 probes at 10 nm spacing and were able to get data down to about 1300-1400 m depth. The upper 100 m of the water column is cold, being mainly below -1°C. However, between 61°S and 61.5°S, surface temperatures were up to 0°C. The southernmost measurements show a clear winter mixed layer to about 100 m with temperatures around -1.5°C. Water warms below 150 m with a layer of 2°C or warmer water starting at 400 m depth and extending to 1000 m or below. This layer has had consistent thickness throughout the measurements so far. We are still north of the Polar front, in the Polar Frontal zone. So far, we have had two probe failures and one bad temperature record.
Ari Friedlaender reported that marine mammal sighting conditions had diminished from the previous day, but incidental observations were made from 1000 until 1600. No whales were seen during watch hours.
The calls of marine mammals are also the subject of study on the cruise and sonabuoys, which are deployed from the Palmer, are being used by Ana Serovic to receive and transmit the sounds to the ship. On 25 July, she deployed one difar and one omni sonobuoy. She reports that no biological sounds were recorded on either one. The major reason for deploying the buoys, though, was to test the range of Yaggi directional antenna (a new antenna mounted on the science mast for this cruise). So far the range, approximately 16 nm, seems satisfactory, especially considering that it was tested in rough seas. This practically doubles the range of the Sinclair antenna used on the previous cruises. Both antennae will be used during this cruise since the Sinclair is omnidirectional and should prove the better of the two while we are on station and the Yaggi will be better while we're steaming on a straight course.