Report of Activities on the RVIB N.B. Palmer Cruise 02-04

16 August 2002


There is a saying in Maine (“Burt and I”) that was very appropriate for 16 August.  “You can't get there from here.”  We left station 72 in the wee hours headed for station 67 on survey line 9, a location to the northeast that we were destined never to reach.  We also never got to Station 66, which was on the schedule for sampling after station 67.  When we left the large lead that we had been working in around 0200, we immediately ran into pack ice that was difficult to traverse. By 0800, we had only gone about 4 nm on the northeasterly course. The ice, as shown by the ships bright flood lights, revealed an incredible jumble of broken slabs of ice and small flat one-year-old floes covered with snow. The ridges were everywhere and only a short distance apart.  Clearly the ice pack in this area had been or was under a lot of pressure, and the floes had buckled and over-ridden one another until it became a rather impenetrable mess.  In addition, the visibility was poor because of fog, which made it difficult for the bridge to pick a path of least resistance and picking a good route was critical to making good progress.  With the route northeast blocked, the Palmer took to steaming along leads that led to the northwest in hopes of finding a way to the north that might at least allow us to get to station 66, since station 67 was out of reach. But the pack ice to the north and east of the leads always presented an impenetrable obstacle.  Being in leads allowed us to deploy BIOMAPER-II for an hour and a half while en route during the early afternoon. A substantial krill patch was observed during the towyoing.


The course made good during the day in fact retraced the one taken from station 73 toward station 72 and probably followed the same system of leads. During the daylight hours, seabird and marine mammal observations were made.  An under-ice dive was schedule to be done at station 66 in the mid-afternoon, and in spite of the fact that the Palmer was not close to that station, BIOMAPER-II was retrieved and the dive was done while there was still daylight. The dive actually took place at the location of station 73.  A seal joined the divers and provided some interesting underwater video images.  Later in the evening while still following the system of leads to the northwest on the way to station 65, BIOMAPER-II was again deployed for an hour and a half and more krill-dominated high volume backscattering layers were encountered. The towyoing ended when the need to back and ram became incessant.


There was an unusual fogginess to the atmosphere in the early morning in spite of the air temperature being about -7 C with clear skies over head.  There was speculation that there must be a large area of open water somewhere nearby to cause all the moisture to be in the air because the nearby leads did not seem sufficient.  This was an ice fog that caused ice crystals to form on the metal surfaces especially the hand rails on the ladder ways. The fog remained for much of the day, although the sun shone through, making it a fairly bright day.  The air temperature decreased during the day until near midnight it was -12.8ºC. The barometric pressure continued its slow increase, started the day before, until noon and then held at 1006 mb for the rest of the day. Winds were light (< 10 kts) for most of the day and predominately out of the northwest to northeast. 


CTD Group report (Baris Salihoglu, Eileen Hofmann, Bob Beardsley, Chris MacKay,  Francisco (Chico) Viddi, Sue Beardsley)

The cruise science activities on 16 August were focused on biological studies that involved under-ice diving, net tows, and surveys with BIOMAPER-II. The remaining time was spent in transit to station 65, which is at the outer end of survey transect 9.  As a result, no CTD casts were done in the past 24 hours.


The CTD group spent the time processing discrete salinity samples, titrating the discrete dissolved oxygen samples, and analyzing the results to develop calibration curves for the CTD-mounted conductivity and oxygen sensors, respectively.  Preliminary results of bottle-CTD conductivity comparisons indicate that the primary sensor may have a slight offset and that the secondary sensor is working well.


The oxygen comparisons suggest that the CTD-mounted oxygen sensor is reading low relative to the titrated values and that the offset for the CTD-derived surface oxygen values is greater than that for deeper values.  If this trend continues as more samples are added to the data set, it may indicate that a nonlinear calibration curve is needed to correct the oxygen values.  We will continue to refine the comparisons and calibrations during the next few weeks as more CTD casts are made and more samples are acquired. 


Nutrients (Yulia Serebrennikova and Steve Bell)

Nutrient analyses for lines 10, 11, and 12 of the GLOBEC grid have been completed. The nutrient distribution is essentially the same as found a year ago during GLOBEC II in this area. Nitrate and phosphate showed maximal concentrations of 34 and 2.35 micromolar, respectively, between 200 and 300 meters. The concentrations of both nutrients decreased slightly below these depths at greater distances offshore and substantially in the upper mixed layer (50-100 m) at all locations along lines 10,11, and 12. The mixed-layer displayed an offshore to inshore gradient. The concentrations changed from 31 to 28 micromolar for nitrate and from 2.1 to 1.95 micromolar for phosphate.  Nitrite and ammonia were detectable only in the upper mixed layer. Nitrite had a maximum of 0.2 micromolar on the shelf break and decreased both offshore and inshore. Ammonium concentrations were 0.4-0.5 micromolar for most shelf stations except 72 and 77 where ammonium concentrations were 0.8 and 1 micromolar respectively, the highest found so far. Silicic acid had 75-80 micromolar concentrations in the upper mixed layer and gradually increased with depth. Interestingly, offshore deep water at 900-1000 meters had the same 110 micromolar silicic-acid concentration as the bottom water on the shelf at 400-500 m.


Sea Birds (Chris Ribic and Erik Chapman)

Surveys were conducted for almost 5 hours on 16 August as the ship backed and rammed in an attempt to reach station 67.  The ice proved to be too thick for us to continue trying to get to station 67, and the ship doubled back on its path and began to move toward station 73.  Ice covered 9 to 10/10ths of the ocean's surface within 1km of the ship.

Very few birds were observed, only 2 Snow Petrels and a single Emperor Penguin were recorded in the survey.  Crabeater seals were relatively uncommon compared to previous days, with just 13 individuals observed during the entire day.  As we leave the southern sector of the grid, it is interesting to note that we have already seen 198 Crabeater seals during this cruise after seeing just 50 during the entire winter cruise last year.  This change in abundance suggests that the seals are responding to a change in the abundance and distribution under the ice of their primary prey, Antarctic Krill.  It will be interesting to see if studies of the zooplankton communities in the study area also detect a dramatic shift from last year's winter cruise results.


A summary of the birds and marine mammals observed on 16 August (YD 228) during 4 hours 52 minutes of survey time as the ship traveled between stations 72 and 73 is the following:


Species (common name)

Species (scientific name)

Number observed

Snow Petrel

Pagedroma nivea


Emperor Penguin

Aptenodytes forsteri                    


Crabeater Seal

Lobodon carcinophagus




Marine Mammal report (Chico Viddi)

On August 16, a total of 109 hours of observation have been accumulated since the start of the cruise, of which 51 hours were “effective effort”.  Effective effort observations of marine mammals were made for 4.5 hours today, out of 7.1 total hours of observation. Viewing conditions were mainly affected by dense fog patches. This was a day with partly cloudy sky and ice floes of first year ice, about 80 to 100 cm thick. Coverage was 8 to 10/10ths, with variable sized open water leads covered with a thin layer of ice. More Crabeater seals (Lobodon carcinophagus) were counted on 16 August than previously - a total of 120 individuals. In only one hour, from 1400 (-68º 27.96′S; -74º 37.45′W) to 1500 (-68º 26.55′S; -74º 46.04′W), 98 seals were counted.  Only two seals were seen in the water. Two sightings of minke whales (Balaenoptera acutorostrata) were made. A single whale was seen at 1114, (-68º 31.02′S; -74º 10.59′W) 8º to port and 0.27 nm away from the ship. The second sighting was made at 1431 (-68º 27.27′S; -74º 41.69′W), at 8º to port and 0.67 nm from the vessel in which three minke whales were swimming in circles for a couple of minutes until the vessel was too close to them. Interestingly, this sighting was made at the time when most of the Crabeater seals were counted (between 1400 and 1500).  The area where most seals and the three whales were seen was characterized by many leads of open water.


MOCNESS/ADCP/OPC Report (Phil Alatalo, Ryan Dorland, Peter Wiebe, Dicky Allison, Scott Gallager, Gareth Lawson)

MOCNESS tow #4 was conducted in much milder weather conditions on 16 August at 0045, but towing within a lead was not as successful as with the previous deployments.  Thick ice at Station 72 caused the ship to slow and the MOCNESS frame, with net 4 open, dropped below its intended sampling depths by 45 meters.  Otherwise, tow intervals were regular.  An electrical re-termination improved, but did not solve the communication problem and battery voltages dipped very low twice, but recovered.


The 300-m layer from the SIMRAD proved to be mostly copepods and chaetognaths.  Other than nets 1(450-350m) and 2 (350-202m), biomass was very low.  The broad layer between 50 and 100m, imaged by the ADCP appeared to be composed primarily of copepods with krill furcilia, chaetognaths, and amphipods also present.  This composition described the surface nets as well.  The Optical Plankton Counter (OPC) recorded high surface counts during the oblique haul. This catch (net 0) was diverse: krill, chaetognaths, ostracods, larval shrimp, radiolarians, siphonophores, salps, and copepods.  The presence of a single fish larva in a low-volume surface net further substantiates the ROV's observations of fish larvae associated with the under-ice surface.


BIOMAPER II group report (Gareth Lawson, Peter Wiebe, Scott Gallager, Phil Alatalo  Dicky Allison, Alec Scott)

The overall goal of our group is to quantify the horizontal and vertical distribution of adult and larval krill and other zooplankton taxa, using as our primary tool the BIo-Optical Multi-frequency Acoustical and Physical Environmental Recorder (BIOMAPER-II). BIOMAPER-II is a towed system consisting of a multi-frequency sonar system, a video plankton recorder (VPR), and an environmental sensor package (CTD, fluorometer, transmissometer).  The acoustic system collects backscatter data from a total of ten transducers (five pairs with center frequencies of  43 kHz, 120 kHz, 200 kHz, 420 kHz, and 1 MHz), half of which are mounted on the top of the tow-body looking upward, while the other half look downward. This arrangement enables acoustic scattering data to be collected for much of the water column as the instrument is towyoed up and down between the surface and deeper depths. The VPR is an underwater video microscope that images and identifies plankton and seston in the size range 0.5-25 mm and quantifies their abundances, often in real time. 


Together, the acoustic and VPR systems allow high-resolution data to be obtained on adult and larval krill and their prey. The acoustic data provide distributional data at a higher horizontal resolution than is possible with the towyoed VPR, while the video data provides taxa-specific abundance patterns along the towpath of the BIOMAPER-II. The VPR also allows for direct identification, enumeration, and sizing of objects observed in acoustic scattering layers, such that the VPR data are used to ground-truth the acoustical data.


As was mentioned briefly in a previous report, the BIOMAPER-II was deployed in Crystal Sound for calibration of the acoustic system on August 5. Although we were able to calibrate the down-looking 43 and 120 kHz transducers, the 420 and 1000 kHz transducers stopped transmitting soon after we began the calibration. The BIOMAPER-II team, led by electrical wizards Scott Gallager and Alec Scott, therefore spent the next 95 hours identifying and remedying the problem. The system was then deployed on August 11 for a second calibration, during which we managed to calibrate only the up-looking 120 kHz, due to problems with positioning the calibration ball under the transducers.


In the morning of August 12, we deployed the BIOMAPER-II twice, first between stations 76 and 77 for an along-transect tow, and second at station 77 for a stationary cast while the divers were in the water. Although during the first deployment we observed a very nice patch of high backscatter (ca. -60 dB) between the surface and 150m, it also became evident that the 43 kHz transducers had ceased transmitting. By the next day, all of the transducers were either not transmitting, or transmitting only at a very low level. Long hours of trouble-shooting identified three problems: a burned-out resistor on the high frequency transmit board, a malfunctioning chip on the 43 kHz receiver board, and an as-yet-unidentified malfunction in the multiplexor board. As of today, only the last of these problems has been fixed, and so we can collect acoustic data only at 120 and 200 kHz. Given the long hours we've spent trouble-shooting this system over the past week we're ecstatic to have even those two frequencies functioning.


Since getting the system back up and running, we've managed a number of highly successful BIOMAPER-II tows. Early in the morning of August 15, en route to station 72, we had the tow-body in the water for 45 minutes.  During this time we observed a very dense patch between the surface and 100m, with backscattering levels as high as -58 dB. Later that morning, while still in transit, we got the BIOMAPER-II in for another two hours of surveying, but observed only very low levels of backscatter. In the afternoon of August 16, towing in the vicinity of station 73, we observed between 100 and 150 m one of the densest patches of backscatter seen on all four GLOBEC cruises, and certainly the densest this far out on the shelf. It is worth noting that this is also the same area where Chico Viddi observed a large number of seals. A deployment later that evening in the same area, but now in transit to station 65 again revealed a highly dense layer in the same depth range, and images captured by the VPR indicated that the layer was composed of adult krill.


Current Position and Conditions

The second rendezvous with the L.M. Gould took place earlier in the evening and the two ships are now convoying to the northeast toward SO GLOBEC grid station 41 where the Gould will make their second time-series station. Our current position is (17 August - 2301 hrs) -68º 52.866′S; -74º 23.794′W). Air temperature is -7.6ºC and the barometric pressure is 999.9 mb..  Winds were out of 260º (west) at 6 kts. High thin clouds veil, but do not totally obscure, the waxing moon and stars.


Cheers, Peter