I like to inform you that we have finished the pilot eddy cruise on 23 April. We made 76 stations with CTD and bottle sampling located in the Peter the Great Bay and over the Japan Basin. The scheme is attached. We had a delay with the cruise however we managed to find -1.2 C dense water in the bay and slope and some cold and slightly fresh water at a very bottom layer (2800 m) just below the slope. We will wait for results of chemical analysis to make conclusions. We crossed 3 eddies of different life duration and found them pretty strong and tracing down to bottom with a few low potential vortisity layers. Even the last eddy was hardly visible at the IR images it had a comparable density gradient with the yonger one. I hope we will manage to see the evolution of at least one of them by samling in summer and winter cruises. We had a good training of the team in the conditions of very hard work. Luckily the weather was quite slow.
To implement the cuise we used Rusian Ministry of Science grants for Ecosystem sudies and the World ocean program wich we luckily received in early April. Unfortunately it was impossible to use our vessels at that period, so we organized the cruise as joint expedition with Hydromet institute (FERHRI) on r/v Pavel Gordienko. Thank you very much for your support.
We made salinity measurement by Autosal at major part of the stations. However to be proved with the data I would like to make a calibration of our CTD. This would also allow us to compare our measurements with the data of coming summer and winter cruises. Could you advise me how to do this.
(text deleted)
Best regards,
Slava
The LINKS 1 cruise, part of an NRL program to study the linkage between east Asian marginal seas, was carried out in Korea/Tsushima Strait from 05-13 May 1999 on the R/V Roger Revelle. Six bottom-mounted ADCPs and Wave-Tide Gauges were deployed along each of two lines, one line at each end of the Strait. Instrument locations are indicated as sites N1- N6 and S1-S6 on the accompanying map. Mooring operations were greatly facilitated by the Revelle's p-code GPS navigaton and dynamic positioning systems and by exceptionally calm weather throughout the cruise. The instruments will be recovered and redeployed in October, with final recovery in March 2000.
CTD stations were made at and between each ADCP site and water samples for chemical analysis were taken by participants from KORDI. The ship's hull-mounted ADCP provided current measurements along the mooring lines lines during deployments and during post-deployment runs along the two lines. Additional ADCP sections were made along two short sections closer to Tsushima Island.
We completed the first mesoscale survey and executed another long north-south SeaSoar tow from 40 10 N to 38 00 N along 135 10 E (southbound) and 134 42 E (northbound). The strong subsurface front seen in the section to the west was not present in the eastern section, and was weak in the western one. Following this, we started on the second pass over the survey pattern. Near the end of the first leg, SeaSoar collided with something large and rigid. Fishing gear had been extremely light (we've seen very little gear since we left the Korean coast- even the front is uncluttered), but is still the most likely suspect. No surface expression of the obstacle was seen. When we brought the fish aboard, the stainless steel nose cone had a deep horizontal crease across the brow, both sides of the upper tail fin had been sheared off and a couple of the impeller blades had been bent. The largest loss was the Hydroscat. One of it's underwater connectors was sheared off by the impact, allowing water into the pressure case. Luigi (our electrical engineer) cracked the case, broke down the components and cleaned and packed them for shipment back to the US.- we cannot effect repairs here.
While repairs were being made to SeaSoar, we began executing a cross-front hydrographic survey originally planned for later in the cruise. This has been an all-hands drill due to the tight station spacing and the intensive nature of the water sampling, and everyone has been responding wonderfully. We are currently half way through the survey, which will provide valuable in-situ data to help us interpret the SeaSoar observations. Both CTD casts and optical profiles are being collected. SeaSoar required approximately 12 hours to repair, including a change of nose-cone to compensate for the loss of Hydroscat. The repaired system has been checked out and tested, and will be redeployed following the completion of this hydro line. Because we were at the end of a survey line and immediately switched to hydrocast mode, we will not loose much sampling time to this incident. I anticipate that we will still be able to execute two more repeats of the frontal survey and one or two sections off the Korean coast. If time allows, we will also do a long SeaSoar section on the steam back to Korea.
Weather-wise we have been very fortunate. We've had mostly clear skies (and thus good remote sensing) for most of the cruise. A low pressure system passed over us yesterday, bringing about 12 hours of bumpy riding. Seas picked up quickly but calmed within hours of the time the winds relaxed. Just a taste of the fun to come in January.
That's about all for now...
(text deleted)
... the last part of our cruise went well. We did another
pass of the frontal survey, a set of sections spanning an interesting
loop-current like feature to the south and a cross-shelf section at 36 10 N.
I'll write something more detailed in the next few days and mail it to you
when
I get back to the states.
The third in a sequence of R/V Roger Revelle cruises in the Sea of Japan
(known as the East Sea in Korea) is nearly completed. The principal
activity is deployment of an array of 25 pressure-sensor-equipped inverted
echo sounders (PIES) and 13 current-meter moorings (CM) in the Ulleung Basin,
which covers roughly a 250-km square region between Korea and Japan. Thanks
to a very efficient and helpful ship's crew, a well-equipped ship, and nearly
ideal weather conditions (plus a little help from Lady Luck), we are well
ahead of schedule: after one week at sea we've successfully deployed all but
three PIES and one CM. Prior to deployment, all CM releases have been
wire-lowered to 1000 m to pretest their performance at cold temperatures and
great depths. Following each deployment we acoustically tracked each mooring
to the bottom and communicated with it to verify its performance. We've also
carried out two test deployments of a new model PIES (with extra help from the
Chief, P. Mauricio in fabricating a part). An XBT has been launched after
each PIES deployment.
This joint project between the Univ. of Rhode Island (URI, Watts and Wimbush)
and the Naval Research Laboratory (NRL, Teague) is benefitting in several ways
from collaboration with Korean and Japanese oceanographers at the Korean Ocean
Research and Development Institute, (KORDI, Suk) and the Research Institute
for Applied Mechanics at Kyushu University (RIAM, Yoon). Incidentally, the
expedition name itself, "HAHNARO," is a Korean word meaning "all pulling
together." The full CM array of 18 moorings includes four Korean moorings
(from KORDI) and one Japanese mooring (from RIAM). Moreover, two scientists
from Korea and two from Japan have been with us on this cruise and have been
valuable participants.
It has been particularly important to coordinate our mooring positions with
Korean deep-crab fishing captains. There is intense fishing and crabbing in
the Ulleung Basin, including bottom fishing at depths as great as 2,000
meters. So we and the local fishermen have a mutual concern about
interference from the other's activities. KORDI scientists, led by Dr.
Moon-Sik Suk, kindly arranged a meeting with the fishing captains union
earlier this year, and we hope to have another such meeting after the cruise.
During this cruise we've encountered concerned fishermen in their boats;
having Dr. Suk on board has been extremely valuable for on-site negotiations
and real-time decision-making in these situations, allaying the fishermen's
fears or repositioning moorings.
If our success continues, we anticipate finishing the cruise early.
We greatly appreciate the efforts of everyone on board, and especially
the competent and willing support of the R/V Roger Revelle officers and crew
(Capt. T. Desjardins), and from Koonce and Jacobson, the marine technicians
aboard.
Randy Watts and Mark Wimbush / URI
Watts and Wimbush: deployment of IES and current meter array in the
Ulleung Basin - email report
R/V Roger Revelle, Weekly Scientific Report,
Hahnaro Leg 6, June 13, 1999
L. Talley -
June-July, 1999.Hydrographic observations of the JES.
Complete cruise report.
The first week of work on this leg on the Revelle finally brought together all of the planning for this very international project. The completely full science crew includes two large groups from the Russian Academy of Sciences (7) and from the Russian hydrometeorological agency (5), both in Vladivostok, a group from Seoul National University (2), and groups from SIO (8), WHOI (6) and UW (2). Three main science projects are aboard - hydrographic/CTD profiling at about 120 stations in the Japanese and Korean sectors of the East/Japan Sea, towed video plankton recording (VPR), and bio-optical profiling. At the end of the first week, we have completed over 40 stations covering the Korean sector - Korea/Tsushima Strait and the Ulleung Basin. The bridge reports more fishing boats here than they've ever encountered anywhere - some nights there have been brightly lit boats at every location around us and over a hundred boats on the radars. Encounters with the Korean marine patrol and Navy were a little less welcome given our clearance status. In Japanese waters, the daily P3 flyover checking our reported position reminds us that our presence is noted.
The hydrographic data sets are a real breakthrough, providing for the first time complete coverage of the deeper waters, particularly for nutrients, oxygen, CFC's, alkalinity and pH. The chemical properties are defining deep circulation features that have not been described before. The VPR tows and supporting plankton net tows are showing this area to be much more productive and diverse than expected.
Lynne Talley (chief scientist)
We have just passed the end of our second week of hydrography, bio-optics and towing
a video plankton recorder in the Japan (East) Sea. We celebrated a breezy July 4
with a barbecue during a long steam in Russian waters. We have just spent a
spectacularly beautiful day along the northern coast of Honshu and outside Tsugaru
Strait with a series of many shallow stations to capture the flow through the Strait.
We have completed 91 stations as of now, with about 20 more to go before we return
to Pusan, to arrive next Thursday. The weather and our equipment has held, the
ship rides beautifully and we have lost no station time. CTD and chemistry analysis
operations are gradually being turned over to our Russian colleagues who are aboard
as they will be operating our equipment on the Russian research vessel Khromov,
sampling the northern Japan Sea starting on July 21.
Lynne Talley (chief scientist)
News: 16 January 2000
After three days of intensive set-up, we sailed at 16:00 today. All
systems are operational. SeaSoar sits on the fantail ready for
deployment. Installation of the additional meteorological sensors went
well, and all are now logging data as we cruise north. The sonic
anemometer's GPS returns time but no position, but this will be
rectified by integrating the ship's P-code GPS stream in
post-processing. Rob Pinkle is testing his two new sonar systems,
which may give us velocities to 1000 m. The NRL group is receiving
real-time AVHRR and SeaWiFS imagery. Unfortunately, we forgot to
request a cloud-free central basin, so coverage over the study area
has been limited. A rencent image provided partial coverage of the
subpolar front between 134 E and 135 E, essentially the same region we
sampled in spring 1999. The image reveals sharp sea surface
temperature contrasts near 40 N, with considerable small-scale
structure in and around the front. Our current plan is to steam
northward along the Korean coast to 37 45' N, at which point we will
deploy SeaSoar and continue directly eastward. Unless tomorrow's
images compell us otherwise, we will turn north at 134 E to make our
intial section of the front. The weather remains quite good- hopefully
everyone will have an opportunity to get their sea legs before we face
our first storm.
At 134 E, we turned north to make our initial section across the front. SeaSoar experienced mechanical difficulties as we neared the subpolar front, forcing a recovery near 39 45' N. Given an estimated 6-10 hours on deck for diagnosis and repair, we elected to steam southward back along the sampling line, executing four hydrographic casts between the recovery point and 39 N. These casts revealed a subsurface oxygen maximum/salinity minimum near 80 m, well beneath the surface mixed layer. A thin salinity maximum resided just beneath this. We traced SeaSoar's problems to a hydraulic unit leak. The component was replaced with a spare and a second dissolved oxygen sensor (Seabird SBE-23) was added to supplement the Langdon unit. SeaSoar was redeployed at 39 N following completion of the fourth hydrographic cast. That evening, winds picked up and temperatures dropped- the start of our first cold air outbreak.
We spent the next two days executing an intensive survey of the subpolar front in rough, cold conditions. Wind speeds reached 40 knots, with 4-5 m seas and air temperatures well below freezing. Crew and science weathered the conditions well, though the weather certainly took its toll on general energy levels. Revelle was easily able to maintain the required 8 knot towing speed, and SeaSoar performed well despite the rough conditions. Extreme pitching of the ship impacted SeaSoar's perfomance, resulting in a slightly reduced profiling range when the waves were largest.
Between 134 E and 135 E, the subpolar front sat near 39 50' N with surface temperature gradients of 3 C in 20 km. Mixed layers south of the front were typically 20-40 m deep, with strong stratification at the base. In contrast to our expectations, waters north of the front were warm (5-6 C) with relatively shallow, 50-70 m deep mixed layers. North of 41 N, surface waters cooled to 3 C and the mixed layer deepened considerably. Stratification at the mixed layer base was weaker north of the front than south, but was extremely weak north of 41 N. Subsequent surveys will allow us to explore how the region around the front evolves in response to cold air outbreak events.
Today dawned on calmer seas, sunshine (!) and much, much weaker winds. Many in the science party spent part of the morning enjoying the ice sculptures left behind by the wind and spray of the last two days. A couple of calm days and several hours of undisturbed sleep will be welcome by all. We are currently finishing the first intensive survey, after which we will recover SeaSoar and execute a high-resolution hydrographic/bio-optical section across the front.
At the end of the initial survey, we recovered SeaSoar in preparation for an intensive series of hydrographic and optical stations. Recovery revealed extensive fairing (small drag-reduction fins attached to the sea cable) damage, likely caused by rough operating conditions during the previous cold air outbreak. As usual, fairing repair was a lengthy endeavor, this time undertaken at night with air temperatures well below freezing. A large number of the science party turned out for this exercise, and we of the SeaSoar team are very grateful for their help. Had it not been for all the extra hands, it would have been a miserable, all-night affair.
With SeaSoar aboard, we began a highly resolved section of CTD and optical casts, running from 39 to 41 15" N along 134 28" E. The start of this section coincided with the onset of our second cold air outbreak, with winds gusting to 40 knots, 4-5 m seas and temperatures hovering near -11 C. This event produced a thick coat of ice over the bow, on the bulwark and across the fantail. Revelle provided a stable platform, enabling us to operate despite the conditions. The extreme cold played mischief with several aspects of CTD operations and taught us a few memorable lessons. Problems included frozen plumbing, frozen plugs clogging Nisken bottle drains and general icing of all of our handling gear. Nonetheless, we were able to sample all stations as planned.
Following the hydro section, we redeployed SeaSoar and begun our second intensive survey. This pattern focuses on the region directly around the front, reoccupying the sections sampled by the first survey but staying between 39 10" and 40 10" N. Shortly after deployment, the SeaSoar CTD ceased telemetering data, forcing us to recover for troubleshooting and repair. After an initial scare over shorting in the sea cable, Paul Fucile quickly tracked the fault to arcing in the winch's slip rings. Following slip ring replacement we redeployed SeaSoar and continued with the second intensive survey.
Our second cold air event ended the following day. Temperatures remained quite cold, but the sun reappeared and both winds and seas settled down. Various members of the science party joined the Revelle's crew to help chip and clear ice from Revelle's heavily encrusted bow.
The second survey was completed on 28 January in the calm between cold air outbreaks. In general, mixed layers appear to have deepened and surface waters have cooled considerably since the initial survey, consistent with the response one might expect from several days of strong winds and intense net surface cooling.