We are now at -67 16.11°S; -69 32.19°W (23:41 local - 2 May)
and steaming on southerly course (190) towards
Station #16 at about 5 kts. The wind has slacked significantly over the previous highs in the 30 kt range during much
of the previous days and is now in the 5 to 10 kt range out of the west northwest (310 degrees). Large swells have
continued to make working on the stern difficult and wet, but with the reduced winds, they are beginning to diminish.
The air temperature is about -0.1°C.
Yesterday and today were good days all around. We completed work at
4 stations on May 1 and 3 stations on May 2.
The work included eight CTD profiles, three 1- m2 MOCNESS tows, twelve Sonabuoy deployments and three
BIOMAPER II deployments. In addition, both the bird and mammal survey groups made a number of sightings as
reported below. During the late afternoon at Station #15, we could see the rugged mountains of the western edge of
Adelaide Island off to the east.
The water samples are being analyzed for oxygen concentration, salinity,
nutrients, and chlorophyll. The primary
production group also takes water for analysis and Scott Gallagher takes samples for microplankton analyses.
The CTD group has completed a preliminary analysis of the data from
the first two survey transects. The water
mass distributions show Antarctic Surface Water in the upper 50-60 m, Winter Water at 65-80 m, and modified Upper Circumpolar Deep Water below 100 - 120 m. At the innermost stations on the first two transects, the Winter Water
layer is eroded, probably due to strong mixing. At these stations, the surface waters are warm, which suggests mixing
with the deeper warmer waters. At the outermost stations on the second survey transect, the Antarctic Surface Water
is reduced and is being replaced by colder water as the seasonal stratification breaks down and winter cooling begins.
At the outermost stations on the second transect, we encountered what
appears to be an onshelf intrusion of Upper
Circumpolar Deep Water. At the last station on the second transect the CTD cast was deep enough to sample Lower
Circumpolar Deep Water (about 500-600 m).
The nutrient samples from the first transect are now analyzed and we
will begin merging these data with the CTD
measurements. This will allow us to look at regions of potential upwelling.
All members of the CTD group are now checked out on deploying and retrieving
the CTD and on acquiring the data on
the computer system. There have been some exciting times in the Baltic room dodging waves and exciting times in the
dry lab avoiding hitting the bottom with the CTD.
May 1: Observations began at 0900 when the ship began steaming to station
#11. Sighting conditions were moderate;
skies were partly cloudy, bss5. On the leg to stations #11 three whales were seen. The first was a humpback that
appeared to avoid the vessel as it approached within 400 meters of the animal. The second animal was logged in as a
"like humpback", as a species confirmation could not be made. The third animal on the leg was also a humpback.
Observation effort ceased at station #11 and began again at 1427 local time when the leg to station #12 began.
Observations effort continued until 1625 when light was too diminished. During this leg 3 sightings of 4 humpback
whales were made. For the day, a total of 6 sightings were made, 5 of which were of humpback whales, and 1 was
logged as a "like humpback". In addition, 5 fur seals were counted between the bird and whale observation teams.
May 2: The watch began this morning at 0912 local time, once the snow
and fog had lifted. Winds and swell were light,
making sighting conditions good. During the transit to station #14, one minke whale was seen (0927 local time), and
a large unidentified whale was also seen (1015 local time). The watch ceased at station #14 and resumed for the
transit to station #15. We reached the station at 1557 local time. No whales were seen during this leg. Throughout
the day 4 fur seals were counted.
Catherine Berchok has been deploying Sonobuoy's whenever whales have
been sighted or as we approached a station.
She reports her activities for the last three days:
April 29: One DiFaR Sonobuoy was deployed over the SIO S3 mooring. Recorded
were very nice, clear finback pulse
calls for about 20 minutes.
May 1: Four DiFaRs were deployed today on the way to station 14. No
less than 2 hours of solid humpback moans
were heard. Also there was a small (<10 minutes) amount of humpback quasi-singing (like little snippets of song)
mostly from the first buoy deployed today (NBP12101.012), which was at 66 12.234 S; 71 03.541 W. In the morning
one DiFar sonobuoy was deployed in the presence of a minke whale. Another unidentified whale was seen around
3-4 miles later, but no marine mammal sounds heard.
May 2: This evening, upon arriving at station 15, 2nd Mate Marty Galster,
who was on the bridge, reported seeing a
minke whale just in front of the bow. A DiFaR sonobuoy was deployed and for close to 2 hours humpbacks in the
1-3 kHz range were heard quite loudly. I also heard odontocetes echolocating and whistling which were likely orcas
(not 100% certain about this). I also deployed an omnidirectional (10 Hz - 40 kHz range) sonobuoy, in order to record
the higher frequency sounds more clearly because the DiFar's have a low pass filter at 2.5 kHz.
Chris Ribic and Erik Chapman reported that on 1 May they surveyed from
the bridge for 5 hours 38 min between CTD
stations 459.250, 419.247 and 420.225 (Stations # 10,11,12). Outside of periodic snow squalls, light winds and calm
seas made for excellent observation conditions today. We found species composition to be similar to previous surveys
although more individuals were observed as we traveled along and across the shelf break. We recorded feeding behavior
among Antarctic and Cape Petrels during the transects. This marked the first observations of feeding during the cruise.
The following species were recorded today:
|Southern Giant Petrel||1|
May 2: We surveyed for 5 hr 12 min today during transects between stations
420.180, 420.145 and 420.125 (Stations
#13, 14, 15). More species were recorded than on any previous day. We observed several groups of between 4 and 14
Antarctic Petrels making this species the most abundant in today's transects. The following is a list of species and
numbers of birds observed today:
|Antarctic Petrel (Thalassoica antarctica)||56|
|Cape Petrel (Daption capense)||14|
|Southern Fulmar (Fulmarus glacialoides)||32|
|Blue Petrel (Halobaena caerulea)||4|
|Southern Giant Petrel (Macronectes giganteus)||5|
|Snow Petrel (Pagrodoma nivea)||5|
|Kelp Gull (Larus dominicanus)||2|
|Unidentified Storm Petrel||1|
BIOMAPER-II deployments (P. Wiebe, C. Ashjian, S. Gallager and C.
The electrical problems plaguing BIOMAPER-II since the start of the survey were finally resolved on the evening of 30 April and since early on the
morning of 1 May, BIOMAPER-II has been towyoing between each of the stations. During the past couple of days,
we have seen a rich variation in the patterns of volume backscattering throughout the water column. Distinct layers
have been observed between the surface and 500 meters, especially with the 43 and 120 kHz frequencies. Large
individual targets (probably fish) often reside above an intense layer between 200 and 300 m of smaller targets
(probably krill). Within the "krill" layer there is strong variation horizontally. We have seen distinct patches that are
several hundred meters across and fifty meters in vertical extent. At other times the layer is much more diffuse, but
with areas of particularly intense backscattering. When the bottom is present in the echogram, we have seen individual
targets aggregated above peaks in the topography. The MOCNESSS net tows have catching very high numbers of
larval krill in the upper 50 meters of the water column and at the higher frequencies (200 and 420 kHz), this zone also
has intense backscattering. Early on in the towyo near the edge of the continental shelf (between stations 10 and 11),
an internal wave with an amplitude of about 30 meters was observed more than 100 meters below the sea surface.
The pattern of sampling on the broad-scale survey has begun to take
on a rhythm that enables all of the scientists
to work together effectively. The breath of scientific observations on the Palmer extends from the primary producers
(the phytoplankton) to the ultimate consumers (the birds and mammals) with our target species (the krill) a vital link
in between. In a few days, first looks at the data sets will help guide our sampling for the rest of the expedition.