TITLE: HOT and COLD: A trapper's tale of two oceans AUTHOR: D M Karl JOURNAL: US JGOFS News Palmer LTER Contribution No. 57 DATE: 1995 Text: HOT & COLD: A trapper's tale of two oceans by David M. Karl I have great admiration and respect for the sediment trap pioneers, Sus Honjo, Werner Deuser, Wilf Gardner and George Knauer, to name a few. The particle flux research programs that they began nearly two decades ago continue to provide exciting and unexpected data that have improved our understanding of global biogeochemical processes in the world ocean. It is quite apparent that deployments of sophisticated sediment trap moorings have become an integral component of the JGOFS field research effort. What is not quite so apparent is the incredible amount of stress and anxiety that is inherent in this research; the so-called "thrill of victory and the agony of defeat" -- to borrow an old ABC sports slogan. Just reflect for a moment on the high stakes that are involved with long-term sediment trap deployments. In addition to the non-trivial financial investments in hardware and shiptime, the results obtained from most U.S.-JGOFS trap deployments (e.g., North Atlantic Bloom and Equatorial Pacific studies) are used to extrapolate the observations made during the relatively brief duration process studies to much longer (1 yr) time scales. Failure to recover the moored traps would be an unmitigated disaster for these programs. For the much longer term time series programs, a missing one year data set that just happened to coincide with a rare El Nino-Southern Oscillation event or with the 6-7 yr maximum extent in the Antarctic ice pack could set that program back by a decade. That's why most of the "experts" hire a Steve Manganini or a Craig Hunter to take on the burden of responsibility for the deployment and recovery details and to commiserate the occasional failure. By comparison to these sediment trap hall of famers, I am a relative novice in the sediment trap business. Among other things that means I am still crazy enough to worry about nearly every detail of trap deployment and recovery myself -- I'll have to work on that in 1995. However, even with a full-time assistant to absorb much of the stress, anyone who routinely deploys long-term sediment traps (or any oceanographic mooring or free-vehicle technology, for that matter) must have nerves of steel. As the motto of this business reads: "The fecal pellets stop here!" By now most of you already know about the JGOFS/WOCE sponsored oceanographic time-series research program "HOT" (Hawaii Ocean Time-series), but you may know less about our complementary long-term Antarctic research program "COLD" (Coupled Ocean-ice Linkages and Dynamics). In 1992 we established sediment trap moorings in conjunction with these NSF- sponsored research programs (HOT: 22o 45'N, 158o W; COLD: 64o 30'S, 66o W and 66o 10'S, 66o 25'W). To date we have a perfect track record, but as the following two cruise summaries suggest, there is a very thin line between success and failure in this business. NORTH PACIFIC SUBEQUATORIAL GYRE: R/V MOANA WAVE, OCT 1994 Four MK-21 "Honjo" traps were successfully deployed on a 4 km mooring in Oct 1993 and they were scheduled for recovery a year later. This was to be our second turnaround (recovery and redeployment) for the ALOHA mooring, and we had prepared everything well in advance. Unfortunately, we had no control over the weather and as anyone who has worked extensively in Hawaiian waters will agree, the name "Pacific" is a gross misnomer. When we arrived on station we had poor visibility, strong NE trade winds (30 kts) and rough seas. The main deck was awash and most of the scientists were in the rack. The forecast was for "more of the same." We quickly established acoustic contact with the release mechanism and confirmed the position of the mooring. During breakfast we discussed our options and decided to proceed with recovery operations despite marginal wind and sea conditions. We knew that it was going to be a long day, but we were not quite prepared for the events that followed. At 0800 hr on 20 Oct the release command was sent and we received an encoded acoustic signal confirming that the command had been enacted. I announced that the mooring should be on the surface within the hour. In the meantime, all hands were mobilized to help with last minute preparations. The spar buoy was equipped with both a VHF radio and strobelight so, normally, the array is easily located once it is on the surface. We waited, and waited, and waited.... At 1030 hrs we returned to the precise mooring location to repeat the interrogation protocols in the event that there might have been a failure in the release mechanism. Fortunately we had adopted the "Deuser- design" dual-release mechanism so the mooring might still be recovered even in the event of a total failure with one of the two releases. This redundancy essentially amounts to a $12,000 insurance policy against loss, or so we thought. To our dismay, repeated attempts to establish contact with either acoustic release failed, so we left to speculate on the fate of our derelict array. After some discussion we concluded that the trap array must already be on the surface but out of VHF radio range (20 nmiles). Based upon our best knowledge of the surface currents (from the hull mounted ADCP data) and the prevailing wind and swell directions, we established a "most probable location grid" and immediately began to conduct a comprehensive search pattern. Time, of course, was of the essence and the weather remained miserable. For the next 18 hr we searched, in and out of the troughs, for the drifting array but it was all to no avail. At 1830 on 21 Oct we reluctantly decided to end our search and to declare the mooring a total loss. The Moana Wave set a course for Honolulu and I retired to my bunk with full appreciation of the agony of defeat. To date, this was the low point of the otherwise successful HOT program. En route to Honolulu, and well outside our "most probable" search area the mate called to announce that the VHF signal was audible and within an hour the mooring strobelight was visible against the dark horizon. The weather was still bad but the forecast was no better -- we decided to make a midnight recovery. By breakfast we had the entire array and 81 out of 84 samples safely aboard. We were elated, but very tired after our nearly 48-hr ordeal on the high seas. An initial inspection of the collected sample materials confirmed the unusual seasonal flux pattern reported in a previous issue of this Newsletter ( ), with particle export pulses centered during late winter and late summer. This should be a very interesting data set once all the analyses have been completed. CRYSTAL SOUND, ANTARCTICA: R/V POLAR DUKE, DEC 1994 The coastal regions of the Antarctic Peninsula are among the most productive waters in the world ocean yet the dynamics of the spring-summer phytoplankton blooms remain poorly described. As one component of the Palmer Long-Term Ecological Research (LTER) program, we deployed year-round sediment trap moorings to document the development and demise of the bloom and to measure particle fluxes during the austral winter. Crystal Sound was selected as a site that might be representative of the extensive ice-covered habitats in this part of the world. When we began this experiment in Jan 1994, we had no idea that this would be one of the heaviest ice years of modern time. That would, however, be fully appreciated during the sediment trap recovery leg, scheduled for Dec 1994. Approximately 25 nmiles from our station we first encountered the heavy pack ice. From that point to the trap deployment site the pack averaged 9/10ths (9/10ths of the sea surface had ice), with generally poor visibility. Our forward progress was down to <1 nmile/hr. We finally arrived on Station at about 1300 hr on 17 Dec and immediately established contact with the acoustic release. Unfortunately, the study area was completely covered by ice, making recovery of the bottom-moored array difficult to impossible. Our fallback position would be to recover the array during the Jan 1995 LTER cruise. We discussed the options and then decided to proceed with recovery operations. The Captain attempted to clear a "recovery area" by breaking up large ice floes. This was largely successful but the pack was already tight and could not be permanently cleared. On an impulse and with a prayer I sent the release command and hoped for the best. It was not to happen. The sediment trap was nowhere to be seen. By acoustic triangulation technique we eventually located the culprit floe and the bridge carefully honed it until the bright yellow floats of success emerged from the abyss. We lowered a workboat to assist in recovery and by 2000 hrs the array and collected sample materials were safely aboard. It was a long, stressful but exciting day for science. We decided against a second one-year deployment in Crystal Sound, opting instead to use the mooring for short-term particle collections in Paradise Harbor. Nevertheless, the sample set that was collected should provide useful information on under-ice processes that will undoubtedly direct our future field experiments.