I. LMG 01-06
a. Mission statement:
Overall goal is to elucidate shelf circulation processes and their
effect on sea ice formation and Antarctic krill distribution, and to examine
the factors that govern krill survivorship and availability to higher trophic
levels, including seals, penguins, and whales.
b. Projects represented on the process cruise
BG-232-0 Costa/Burns/Crocker - Foraging Ecology of Crabeater seals
BG-234-0 Fraser - Winter Foraging Ecology of Adelie Penguins
BG-235-0 Fritsen - Sea Ice Microbial Communities
BG-237-0 Harvey- Biochemical Determination of Age and Dietary History
in the Krill Euphasia superba
OG-241-0 Smith/Martinson/Perovich Optical Environment of the Western
Antarctic Peninsula Region
BG-244-0 Quetin/Ross- Winter Ecology of Larval Krill: Quantifying their
interaction with the Pack Ice habitat
c. Cruise overview to date
2 August: The LMG continued to operate in open water/ice edge
region to the south of Adelaide Island. Seals were sighted, including
a few Weddell seals, but very few Crabeaters were hauling out on floes
accessible to the scientists. Nevertheless, we handled and tagged
our second seal of the cruise yesterday. We also completed a CTD
cast, collected ice, and completed a MOCNESS cast. The weather conditions
continued to be good.
3 August: The LMG occupied an area near the southern end of Adelaide Island. We sent a shore party to Emperor Island, part of the Dion Islands, to census an Emperor penguin colony there. This is the northernmost known breeding colony of emperor penguins and the only place where that species is known to breed on land. Ten males, nine with eggs were sighted; the females are at sea feeding this time of year. This is approximately half the number of birds seen in the same place two years ago. Workable seal sightings remained few and far between.
4 August: Sustained winds of 50 knots with gusts to 60+ forced us to suspend science operations for the day. We sought refuge via invitation at Rothera Station and received a warm welcome - literally: air temperatures were several degrees above freezing! Our stay in the banana belt of the peninsula lasted only about 4 hours before we were underway again. However, several scientific collaborations with the BAS were hatched during our visit. As we departed the area we completed a CTD cast east of Jenny Island as part of Rothera's long term monitoring project. We then steamed towards a rendezvous with the NBP.
5 August: In the morning the LMG and NBP made a rendezvous off the southwest coast of Adelaide Island. The LMG transferred two "simple" CRREL ice buoys to the NBP for placement at locations that the LMG will not visit. The NBP then assisted in placing the LMG at Process Station #2, which is near GLOBEC Survey station #42, in the mouth of Marguerite Bay and situated over the submarine canyon leading into the Bay. Once in place the scientists put in a full afternoon's work with one crabeater seal being tagged, and one scuba dive and a full ice transect completed.
6 August: The LMG remained on station at Process Site #2 throughout the day. Ice conditions were such that we were able to put the gangway out and parties have been able to come and go at will. 30-40 cm of ice was overlaid with 10 cm of heavy wet slush and 20 cm of snow. Science operations began at around 9:00 in the morning and the last groups returned to the ship from the ice at about 21:00. Every group was able to collect samples except for those seeking penguins or needing to tow the MOCNESS. We even cut a hole in the ice to allow a CTD cast to be completed. A precipitous drop in air temperature and wind speed helped make operations more comfortable today than yesterday. A number of crabeater seals remained in the area, allowing the seal team to deploy two additional satellite linked time-depth recorders, giving them a total of 5 tags deployed so far.
7 August: The LMG continued to occupy GLOBEC Process Station #2. The past 24 hours have brought highly variable winds and dropping temperatures. Colder weather was a blessing because since it allowed sampling of ice throughout the freezing process. It also froze the 10 cm slush layer on top of the ice so we didn?t have to slog through ankle-deep slop to get to the sampling sites. However, ice and wind conditions prevented us from using the CTD hole that was cut in the ice yesterday. This was because we were unable to reliably keep the hole aligned with the Baltic door. It was a rather slow science day with the ice collectors being the most active group. No workable seals or penguins were sighted. One significant problem developed today in that due to the very cold weather, the Radvan turned into a freezervan as it was no longer capable of maintaining proper temperature. In fact the temperature dropped to less than -10oC. This caused a number of stock solutions to freeze! All experiments for primary production secondary bacterial production were halted until we were able to solve this problem. Fortunately, a temporary fix was achieved by installing an additional wall heater along with several space heaters. These heaters coupled with warmer temperatures has at least for now solved the problem.
8 August: The LMG remained on site at Process Site #2. Continued cold temperatures with wind chill occasionally dropping below -50oC kept outdoors operations somewhat to a minimum yesterday, though things began to slowly warm up with a northerly wind. Science proceeded well, and our challenge was to keep lab spaces at their proper temperatures. We anticipate spending at least two more days at this location before moving to the southwest.
9 August: The LMG is still making productive use of our time at Process Site #2 with diving and ice sampling operations occurring during daylight hours. The air temperatures have risen considerably but snow is accumulating. This depresses the ice under its weight and leads to intrusion of seawater and re-formation of a slush layer between the dry snow and the sea ice. Due to limitations on the LMG we have altered our science plan so that we will move to the northeast of here rather than the southwest in about 2.5 days. The ice sampling crew sighted a seal in the afternoon. This allowed the seal team to successfully deploy their 6th satellite time depth recorder on a male crabeater seal. This was done while the wind was blowing 30 knots with the air temperature a balmy -2.0oC.
d. Individual group reports.
BG-232 Costa, Burns and Crocker. Field team D. Costa, N. Gales,
S. Trumble & B. McDonald. Our research focuses on how crabeater seals
forage within the seasonal winter pack ice. Since our last report we spent
the 2-4 August looking for crabeater seals in the northern reaches of Marguerite
Bay. Although we spotted several leopard and Weddell seals hauled out,
we saw very few crabeater seals and those that we did see were either in
the water or immediately went into the water as we approached. However,
on 5 August, we proceeded to Process Station #2 where we really didn?t
expect to see any crabeater seals. The information from our tagged seals
indicated a consistent movement to the north, with no animal remaining
in the southern reaches of Marguerite Bay. In fact only 1 of our 10-tagged
seals even remained in Marguerite Bay, while all the others had moved north
along Adelaide Island to Crystal Sound. However, we were pleasantly surprised
that upon arriving at Process Site #2, we discovered at least 13 animals
hauled out when we arrived. At least one was close to the ship. The
ice was very slushy with at least 2 ft of snow over 6 inches of water before
you hit ice. This made walking any distance with gear very difficult.
Most of the seals were about a mile or so away. At this time we were in
the middle of a low pressure system the barometer dropped to 951.2 with
the winds out of the north at 30 -34 knots. Fortunately the air temp
was only -1.0oC. Given that it took some time to get the ship
into position and ice condition confirmed, we were not able to get out
onto the ice until the afternoon. In the afternoon we tagged our first
seal at this location. It was a large 307 kg female. As we got a rather
late start, this was the only animal we were able to do that day. However,
on the next day 6 August, we awoke to at least 4 seals on relatively nearby
ice. We headed out to the closest one, which was a lot farther than we
originally thought. We had to carry a substantial amount of gear at least
1 km over rather rough and slushy ice. Nonetheless, we were able to successfully
tag our 4th seal, a 288 kg female. A second seal sat about 2
meters away during the whole procedure and didn?t leave until we had completed
working on the first seal. To our relief a second seal hauled out while
we were working half way between the ship and us. We then stashed our heavy
gear, returned to the ship, to replenish our field kits and ourselves.
Later that afternoon we returned and tagged our 5th seal, a
234 kg male. We looked forward to continued success at this process site.
However, a high pressure system came over the area changing the wind direction
to the South making the conditions much colder (temperature below -20oC
-50oC with wind chill) under these conditions the seals apparently
preferred to stay in the water and for the next several days we did not
see any seals around. Finally late in the day on 9 August, the weather
warmed up to a balmy -2.0oC with the wind coming out of the
North and/or West. As the wind picked up and the visibility declined due
to snowfall, a seal was spotted by the Ice Coring team about 400 m from
the ship. We immediately got prepared and set off to instrument our 6th
crabeater seal. This animal was a 284kg male. The procedure went extremely
well and the total time from capture to release was less than 50 minutes.
We are now quite excitedly receiving updates on the progress of the 14 crabeater seals we have tagged to date. Eight on the first cruise and now 6 on this cruise. Seven of the eight tags continue to transmit excellent data and all of our 6 tags are functioning perfectly! The maximum dive depths for our 5 animals (the 6th was just put out) shows animals diving to maximum depths of 270 m, 445 m, 485 m, 270 m, and 405 m. However, their routine diving depth is shallower, working anywhere from 150-300m. The three seals that were tagged at Process Site 2 continue to work the same general area. However, the two animals that were tagged farther north along the west coast of Adelaide Island are showing considerable movement. The first seal that was tagged half way up the coast of Adelaide Isld has moved way to the north into Crystal Sound, while the second animal tagged off the south coast of Adelaide Isld has moved into the general vicinity of Process Station 2 where our other seals are currently working.
BG-234 Fraser. Field team W. Fraser & S.Muth. With the generous and able assistance of Dan Costa and his group, we instrumented another four Adélie penguins with PTTs on the evening of 3 August. Like the six PTTs deployed previously, these were also placed on birds found near the south coast of Adelaide Island. We were quite fortunate in finding these birds, as the transit south of Adelaide Island to our current position has been through an area that is almost completely devoid of penguins. We have, as a result, been unsuccessful in obtaining Adélie penguin diet samples thus far. On a more positive note, however, the 10 PTTs now deployed are all operational and providing excellent data. An analysis of these data through 5 August indicates that Adelie penguins are foraging along the edges of a polynya south of Adelaide Island much in accordance with the hypotheses guiding our research. Equally interesting is that these birds are focusing their foraging efforts between the 200-500 m contours in an area that surveys during the May cruises indicated were rich in fish and krill. We hope to return to the Adelaide region in the next week or so to obtain penguin diet samples. An additional activity also undertaken by the predator group is that on the morning of 3 August we successfully landed on Emperor Island and obtained a census of breeding Emperor penguins. This rare colony is unfortunately continuing to decrease. In June 1999, when we last surveyed the island, 14 breeding males were observed at the colony. The current census showed 10 males, only 9 were breeding.
BG-235 Fritsen. Field team C. Fritsen, S. Marschall & J. Memmott. While operating in the vicinity of Rothera station BG-235 conducted at CTD profile to document vertical profiles of nutrients and size fractionated chlorophyll a at one of Rothera's long term monitoring sites. Through further communications with Rothera personnel we established a plan to record a time series of ice and snow thickness. Currently Rothera Station conducts ice thickness monitoring in support of their logistics.
After leaving the vicinity of Rothera station we conducted hourly ice observations in transit between the polyna south of Adelaide Island and the ice station located at survey station #42 (done in conjunction with OG-441). Observations documented the distinct ice edge that had set up due to the prevailing northerly winds and steep gradient from open water to ten tenths ice coverage over a 40 km distance.
At station #42, two ice buoys were transferred to BG-235 personnel on the NBP for deployment at stations #40 and 49. The first has been deployed on 6 August along with a snow and ice thickness array that will be used to measure net snow deposition and ice growth/decay if the buoy is recovered during the LTER ice cruise.
Moving on a few miles distant to station #42, a floe measuring ca. 200-500 m in diameter was chosen for extensive time-series studies of ice characteristics and dynamics that would be coordinated with the diving and krill work. Fortuitously, this platform also was in an area where crabeater seals were hauling out (see Costa's report). Unfortunately, the flightless birds have not been very abundant.
At this ice station (informally named ice station "Robert") we have been conducting extensive ice sampling and characterizations in conjunction with BG-244 and OG-041. A 100 meter ice and snow thickness transect was conducted during the first day of studies. Subsequent sampling at 0, 50 and 100 meters along the transect facilitated characterization of the snow, ice, slush water, brine and seawater at the ice water interface. These samples are part of our coordinated sampling design that will document the variability in ice structure, temperatures and salinities at spatial scales ranging from 1 meter up to 100 meters within this ice floe.
Extensive flooding with seawater has created 10-20 centimeters of slush (snow mixed with seawater) on the surface of the sea ice (sea ice is ca. 35 to 100 cm thick) over large areas (~100,000 m2 areas) of this floe. This environment has been sampled for determinations of microbial biomass, activity and nutrients. Since the surface of the ice was extensively flooded with seawater we also deployed short (20 cm) thermistor strings within the slush layer. Air temperatures have dropped from near freezing to -20°C over the last 36 hours that has initiated the freezing of the slush layer and the production of snow ice. With the short-term (3 day) deployment of these slush thermistors and documentation of the ice thickness changes we hope to derive estimates of ocean heat flux and net ice production during this flooding and freezing cycle. Such information aids in validating existing models on flood-freeze cycles and the development of sea-ice microbial communities in pack ice.
Along with ice sample collections we have been conducting photosynthesis and bacterial production measurements. Findings thus far indicate the ice is enriched in algal biomass over the water column by at least 10 fold on average. Water column chlorophyll a concentrations typically average 0.02 ug/l while sea ice chla concentrations average > 0.5 ug/l. Bacterial production rates are difficult to measure in the water column even when incubated over 24 hours. Bacterial production within ice samples and brine are easily detectable and are at least 2 fold higher than in the water column.
To date, the synthesis of existing physical and biological information on the winter pack ice suggest that this winter's pack ice is enriched in microbes over that in the water column. However, we have not yet seen indictors that significant growth of microbiota has occurred or that significant amounts of biomass was incorporated within the ice during its formation stages. This may be indicative of the fact that this ice pack formed well into the winter months. As we head south within the survey grid it will be interesting to see if we encounter older ice that may be more productive and/or have more biomass.
BG-237 Harvey. Field team R. Harvey and S. Ju. A MOCNESS tow on 7/31 southeast of Adelaide Island (vicinity of station 32) collected an initial set of adult krill and other size classes to allow sorting and dissection of eye stalks for onboard analysis of age markers. After several days of significant ice cover, an additional tow was conducted at night in open water leads over depths from 200 meters to near surface. Despite some technical problems with MOCNESS sensors (subsequently corrected by the fabulous ET Peter Martin), significant numbers of adults were collected. Animals were concentrated at deeper depths, but found throughout the water column based on stratified sampling conducted. A night tow in the vicinity two days later collected additional animals, which have been sorted and dissections started for age marker analysis. To date almost 500 adult animals >30 mm are now in hand, providing an adequate number to begin analysis. Surface water samples from CTD casts have also been collected and are being analyzed on-board for pigments to provide information on phytoplankton distributions and comparative information with ice algal communities.
BG-244 Quetin and Ross. Field Team: L. Quetin, C.Boch, S.Dovel, A. Gibson, T.Newberger, S.Oakes, M.Thimgan, J.Watson. During the past week we have moved from the southern end of Adelaide Island to process station #42 near the mouth of Marguerite Bay, where we are presently. We have found krill larval abundance on the underside of the ice similar to our observations at previous locations. Larval aggregations are patchy and occur predominantly in over-rafted areas on upward facing ice surfaces. We are on our fourth experiment on larval growth, continue to analyze larvae for stage and length frequency analysis and freeze samples to analyze larval condition. We have completed two preliminary feeding experiments and have sampled larvae for fluorescence. Unfortunately, progress on larval feeding experiments was delayed when the refrigerated van and incubator on board quit cooling. Phytoplankton cultures and feeding experiments have now been shifted to the aquarium room. Despite that setback, we expect to make better progress with the feeding experiments in the next few weeks.
Ice Processing:
Cores for vertical and horizontal profiles have been collected both
for preservatives and microscopy of the last two stations. Ice-water interface
water had been collected consistently at each site.
Microscopy:
Over a hundred epifluorescent slides have been made for later analysis
of the algal community, though counts have started from these slides. No
cultures are being made at this time due to lack of a dependable incubator.
In addition, a hundred slides for bacteria were made for group #325.
The ship's crew and RPSC personnel continue to provide the best service possible, and we thank them for their continued efforts to ensure our success.
OG-241 Martinson, Perovich, Smith. Field team B. Elder, S. Stammerjohn
& K. Claffey. Ice observations while under way to Ice station Robert
(process site 2, station #42). This brings a total of 730 km of hourly
ice observations. In the last week we have drilled another 108 meters of
ice for ice thickness transects for a total of 160 meters of line. At each
site we measured the ice thickness, free board, snow thickness, liquid
water on the surface and wicked layer before drilling the hole. At Ice
station Robert we have re-measured 30 meters of the line to study the freeze
back of the lower portion of the snow/slush that is now considered ice.
Thus ice is growing faster on the top of the ice due to snow load flooding
than thermal growth on the bottom of the ice sheet. Ice core processing
continues for ice structure and grain size by making both thin and thick
ice sections. Here at ice station Robert we have processed ice cores from
11 sites for temperature, salinity, d18O profiles in 5 cm vertical
sections. The ice coring is done in conjunction with ice biology groups
and we together have cored a total of 74 cores. We deployed our most complex
drifting ice buoy that measures 42 temperatures from the air through the
snow, ice and into the water column. Also on this buoy we have acoustic
devices to measure snow accumulation, and one under the ice to measure
ice growth/melt. There is a flourometer at 3 m depth and a radiometer in
the air, 1 at the bottom of the ice and the last is 4 meters below the
bottom of the ice sheet. This buoy gives us position such that we can watch
the same ice floe as it drifts around the Marguerite Bay area . Due to
ice conditions we passed some of our buoys over to the NBP and they have
deployed one of our simple buoys at station #40 inside Marguerite Bay.
We performed optics measurements at 2 different sites on Ice Station Robert.
In doing so we have measured snow albedo and snow/ice transmission measurements.
Our plans had been to move from Process Site #2 (survey site #42) and establish Process Site #3 (survey site #74) on 13 August. However, given our current situation Captain Verret has indicated that we have now exceeded the capabilities of the LMG and that we could not go any further south than we already have. Simply put, the LMG is operating beyond the conditions it was designed for, and the weather and ice situation have started to cause serious maintenance problems. We currently have sufficient potable water for 7-10 days providing that we don't have any more catastrophic losses. Once we are able to steam at full power then we will be back up to full water-making capacity, which should allow us to complete the remainder of the cruise. We are not under any ice pressure, so the LMG is not in any danger.
Earlier today the LMG PIs, the Chief Scientist, the MPC and Captain Verret met to discuss our options. After considerable discussion we came up with a plan that will result in little loss of the science objectives. The major component is to have the NBP deploy the CRREL complex buoy at or near survey station #74. Our change of plans, which will retain most of the science objectives has been communicated to and agreed upon by the NBP is as follows. The LMG will remain at Process #2 for ~2-3 more days until the afternoon of 12 August or so continuing with our science program. At that time we will move away from the study site by a few hundred meters to open up sufficient water to complete a CTD cast. Meanwhile, the NBP will continue along its survey grid towards station #52, which is about 20 miles from our current location. Late on the 12th or early on the 13th, the two ships will rendezvous and we will send one of the "complex" CRREL buoys and two personnel to the NBP. These two people will complete the cruise on the NBP and will be responsible for placing the buoy at or near survey site #74. They will assist elsewhere as needed.
After this transfer, the LMG will attempt to steam approximately 30 miles to the northeast to get to the southern end of Adelaide Island. The NBP will stand by to assist as needed. Once we reach our target location the NBP will break off and continue with their survey grid in numerical order towards the southwest. The LMG will conduct MOCNESS tows and hopefully find some seals and penguins to handle in open water or thinner ice. After about 4-5 days there, the LMG will proceed under its own power to near survey site #20 and establish Process Site #3 that we hope to occupy for 4-5 days.
At the end of this time we anticipate that the NBP will be finishing their grid and proceeding northward to pick up missed activities/stations from earlier in the cruise. In this way the NBP would be generally heading towards the LMG to assist us out of the ice if necessary. The LMG will stop at Palmer Station on the way back to Punta Arenas, while the NBP can continue their clean-up efforts and return to port on time.
The advantages of this plan are that there will be minimal direct interactions of the two ships after the next rendezvous and transfers. This saves time and uncertainty for the NBP, which allows them to finish their grid without the need to plan for assisting the LMG. It also ensures that the complex CRREL buoy gets deployed in the desired location without the LMG having to go further south. The liability is that the two ships will be decoupled so that if the LMG does get stuck en route to survey #20/Process #3 there will be a significant delay in receiving assistance. However, the exact location of Process #3 is not critical from a scientific standpoint, and we could conduct science wherever the ice might stop us.
Submitted by:
Daniel Costa
Chief Scientist
Karl Newyear
Marine Projects Coordinator