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Date: Mon, 24 Jul 1995 17:29:18 +0000 (GMT)

Process Cruise #4 (P4) left Muscat at 2000 on 17 July 95 and began work on the northern U.S. JGOFS line in the early morning of 18 July. P4 concentrates on chemistry, geochemistry and lower food web processes. Translated that means more than half the people are working on phytoplankton processes. P4 was delayed getting underway because of isotope delivery problems; the labeled leucine for bacterial production and labeled carbonate were still being held in Boston when we sailed after a 12-hr delay. There was enough 14C carbonate on hand for primary productivity work to be done as scheduled (all that was required was for Barber to give Balch a promise written in blood that the borrowed label would be replaced in time for Process #6); labeled leucine was not available from any source, so Helen Quinby and Gary Schultz (who work with Hugh Ducklow) could not begin their work. THOMPSON sailed with a plan to ask the NASA-P3B aircraft to drop the isotope to us. Martin Bowen set to work to make an airdrop possible. More on that later. The NASA-P3B flew the U.S. JGOFS box on 17 July and we started to sample the northern line stations about 12 hr after they flew the line. Near Sta 1 of the northern line there was a cold wall with temp. on the inshore side about 23.3 degrees. Sta. 1 of P4 was made in this cool, high chl, and high nutrient water. Nitrate was about 12 micromolar, silicate about 6, chl about 4.0 mg/m3, and prim. prod. about 4 gC/m2/d. The station was within sight of the Omani coast and was flat calm. The water obviously was not upwelling at Sta. 1, but it was recently upwelled further to the south. In the NASA flights before P4, Paula Coble saw evidence of a jet of cool water that may extend from the active upwelling site to the northern line. Sta. 2 was warmer with much lower nutrients and by Sta. 3 SST was 28 deg and nitrate was 0.1 micromolar. Conditions from Sta. 3 to Sta. 7 were typical of tropical, oligotrophic waters. The SW monsoon was evident between Sta. 3 and 7. Winds were usually about 30 knots. Conditions on the northern line were much more moderate than we had expected. And the crew repeatedly emphasized that sea state on the northern line from 17 to 24 July was much better than that experienced by Ken Brink's party on the southern line two weeks earlier, from 1 to 14 July. The SST at Sta. 3 to 7 was 27 to 28 deg, nutrients were close to detection levels, and a typical tropical chl max was present. There was not a hint of offshore upwelling (on the northern line). Meanwhile the NASA aircraft data showed inshore and offshore temp and chl signals, but even on 20 July the two regions were separated by a swath of 28 deg water about 100 km wide. By late July the two upwelling sites had not merged together. Work on THOMPSON went very smoothly up to Sta. 7. The chemical crew does a very impressive number of analyses; the oxygen prim. prod. folks require many extra oxygen analyses for their incubations. The CTD technicians are smooth, efficient, and never nonplussed by the requests of the scientific party. At Sta. 7 we planned to remain on station until the NASA aircraft dropped the isotopes. As we worked on Sta. 7 on 21 July, we heard that quick action by Omani customs and Martin Bowen had gotten the leucine into Martin's hands, and he was to drive it overland for 12 hr in a 4-wheeldrive vehicle to deliver it to the NASA base in Salalah in southern Oman. Then on 22 July the sky opened and Oman had torrential rains, roads were closed and bridges washed out. Martin could not get through to the Salalah airport to put the isotope on the aircraft. We were greatly disappointed to have missed so narrowly. As it turned out, the aircraft had a mechanical problem and was not able to overfly our position, so even if Martin had gotten through we wouldn't have gotten the isotope. But read on. On the last Trace Metal Clean (TM) rosette deployment, the ship rolled as the rosette went into the water. The resulting roll snap when the ship rolled back broke the Kevlar cable cleanly and our beloved TM rosette disappeared in a flash. I was watching the cable and saw it part. The winch operator was being very alert and careful and stopped lowering when the roll started, but the cable went slack a little bit regardless. We have been taking 15deg rolls regularly, and have gotten used to them. I had lots of thoughts as the TM rosette vanished, but my strongest was how will I ever be able to face Craig Hunter (father of the TM). In summary, 23 July at Sta. 7 on the northern line was not a good day, with loss of the TM, failure of the isotope delivery, and mechanical problems on the NASA aircraft. After such a series of failures, you all will probably be surprised to hear that in general everything (else) is going well. The phytoplankton people switched over to the CTD rosette and never missed a beat. We are now at Sta. 10, one station from our easternmost station. The mixed layer is 70 m at Sta. 10 and is very well mixed. The winds have been weaker on the easternmost stations, but are still steady around 25 knots. We are talking with the METEOR and hope to rendezvous with them on the southern line. In the next prog. rpt. I'll provide more results. Regards, Dick Barber Richard T. Barber is