Surface Heat Budget of the Arctic Ocean (SHEBA)

Rotation 1: Fall, 1997

Finally, on Sep 27 we helicoptered out to the ships, and were soon underway. I was aboard the Des Grosielliers, which was crewed mostly by Quebecois. They turned out to be an excellent fit for the science party (much more so than the English-speaking crew of the Louis). I had several friends aboard, and there were many new faces, some who had not been in the Arctic before. I was fortunate to have Tom Lehman, my trusted companion on previous projects, as my main assistant. Andy Hieberg, the main logistics manager from Polar Science Center, accompanied us during the setup phase. John "Jumper" Bitters, whom I had known since FRAM I, was also aboard in a logistics capacity. With a strong personality and an inexhaustible store of fascinating life experiences that he was glad to share, he quickly won over the "newbies."

In the days sailing toward our target location, those of us who had worked in the Beaufort previously were amazed at how thin the ice was, with the ships often gliding through ice, a meter or less thick. We began to wonder about finding a site with decent prospects of lasting a year, but eventually found a floe roughly 2 m thick in the target region. At a science meeting that evening, it was decided that the ship would be driven to the center of the floe, anchoring to the ice there. I voiced an objection based mostly on previous experience in the Antarctic, during which we had found that floes survived better when we moored at the floe edge. Perhaps I should have been a bit more forceful, since it turned out that the following March the floe did split along an axis adjacent and parallel to the ship, causing serious disruption. Unfortunately, that occurred during my stint as on-site chief scientist.

As with most projects, the first few days were a blur of activity, erecting shelters, drilling hydroholes, stringing power lines, assembling workstations, etc. We had remarkable cooperation from the Des Grosielliers crew, getting equipment out of the hold, providing tools where needed, in general being helpful wherever they could. At one point, I remarked about that to Andy, who said "Why don't you tell that to the skipper?" So, I did.

Three things stand out to me during the initial weeks of SHEBA. First, for me it was the first time establishing an ice station at the end of the melt season. By this time in September, most of the summer melt ponds had frozen, so the ice surface was hummocky, with a fair amount of small scale relief. When we drilled into the ice we would encounter alternate layers of water and solid ice, in the lower part of the column. This seemed curious at the time, but would make sense later in an investigation of "false bottom" formation with Dirk Notz and Grae Worster

Second, I was asked to sit for an interview with reporters and a camera operator from a network morning show, Good Morning America. They were among a fairly large contingent of press people who had accompanied us out in the two icebreakers, and were intent on capturing "life at an icestation," including filming Jackie Richter-Menge brushing her teeth in the morning! My part was a bit different: a sitdown interview. I did not necessarily relish the idea of taking the better part of a morning away from deploying my project, but I also realized it would be important to explain as clearly as possible why we were there, and what we hoped to find. I carefully answered the questions, trying to explain for example, the albedo feedback, and trying to avoid "uhs" and "you know's" as much as possible. Then, since there was only one camera, they repeated the whole session with the camera operator behind me, filming the reporters asking the same questions. When it was finally over, I felt I had done a pretty decent job.

As an aside, the GMA segment did eventually air the following December. I was on my way to a meeting and during a stopover in Portland asked a bartender in PDX to tune it in. My interview was sandwiched between a tooth-brushing episode and the inevitable talk of polar bears. My entire interview was cut to about 15 seconds and comprised mainly two questions: "Have you ever fallen into the Arctic Ocean?" "Yes." "Was it cold?" "Yes." So much for my teaching millions about the impact of albedo feedback on climate!

The third event during the SHEBA ramp up was much more significant. Shortly after the interview and after most of the media had departed with the Louis St. Laurent to return south, we obtained the first profiles from Jamie Morison's SHEBA ocean profiler. I plotted them out and noticed immediately that the upper well mixed layer was much fresher than we had observed in the past. I had brought with me data from AIDJEX obtained at a nearby location in the same season twenty-two years earlier (1975) that I had studied extensively. I knew that before melting began in early summer, the mixed layer was generally at its deepest and saltiest. As the melt season progresses, a thinner, fresher, seasonal mixed layer would form over the winter mixed layer, incorporating the melt. This separated the lower part of the winter mixed layer from surface mixing, so it retained its properties until fall freezeup. A measure of ice melt could then be computed by comparing the change in freshwater content of the summer mixed layer at its maximum to the properties it had at the beginning of the melt season, retained in the lower, remnant winter mixed layer. It was obvious from comparing the SHEBA and AIDJEX profiles from 1975 that there had been a much more massive melt in this region during the summer of 1997, consistent with the unexpectedly thin ice we had encountered on the voyage in. I concluded that a powerful albedo feedback had indeed occurred during that summer.

I tossed and turned in my bunk for hours that night. Just days before, I had tried to explain to what I thought might be a large television audience that many of us believed that the Arctic was the "canary in the coal mine" for climate, and that the albedo-feedback effect was a critical component. Now very real evidence of that was staring me in the face, and suddenly the idea that the permanent Arctic ice could disappear in the lifetime of my children or grandchildren did not seem so far-fetched. Could my species actually change one of the distinguishing features of the planet, a polar ice cap, in the span of a few decades? Maybe so.

My main objective in SHEBA was to use a mast lowered in a hydrohole to measure turbulence properties along with velocity, temperature and salinity at several levels in the upper ocean throughout the year-long experiment. The main component was a cluster of instruments with small current meters measuring in three direction mounted near very accurate Sea-Bird Electronics temperature and conductivity sensors. The system had evolved over several previous projects, and provided robust measurements of turbulent stress and heat flux at each level on the mast.

As it got darker as fall progressed, we got all the gear checked out and running. We encountered a problem with electronic noise interference that was somehow connected to ship power through our stepdown tranformer. Tom consulted with one of the Scripps wizards and came up with a way of wiring the transformer to eliminate the noise. I never could figure out what it did, but it worked!

At the end of the first field exercise, we flew by Twin Otter back to Barrow, and home the next day. I immediately set to work on a manuscript for Geophysical Research Letters describing the freshening we had observed that fall and its possible implications, encapsulated in the title, Freshening of the upper ocean in the Arctic: Is perennial sea ice disappearing? The paper, published the following March, generated some controversy since up until that time there was little publicly available evidence showing that ice was in fact decreasing. However, not long afterward, release of previously classified US Navy submarine data did indeed show that Arctic ice had thinned substantially since the 1950s, and subsequent events have certainly justified the concern that kept me awake that night in my bunk aboard the Des Grosielliers.

Rotation 2: Spring 1998

I was slated to return to the ice in March for the late winter rotation. In February, Saundie and I took an actual vacation in New Zealand. We split our three weeks between north and south islands, spending several delightful days at Tim Stanton's summer home near Leigh, an hour north of Auckland. We thoroughly enjoyed both the beautiful scenery and the New Zealanders. At a stop in Dunedin on the South Island, we met up with Vernon Squire, a friend and colleague from MIZEX days, who chaired the Physics Dept. at the University of Otago. He pointed us to a spectacular hike in Mt. Cook National Park. We felt particularly at home in Dunedin, perhaps because the phone book had at least two pages of McPhee listings!

Then it was back to the reality of returning to the Arctic. Sometime during the winter, Andy Heiberg had called asking if I would serve as Chief Scientist for the leg starting in March. Despite some misgivings about the complex politics of SHEBA, I figured the Arctic is usually quiet in March and besides it meant a private cabin, so I agreed.

I flew via Twin Otter out to the ice on Mar 11 and soon realized that things were not going to be as laid back as I had imagined. A new lead had formed adjacent to the ship a day or two earlier and the camp had been rearranged considerably from how I had left in November. In addition, a new ridge had formed radiating to the SE from forward of the ship, which was now oriented with the bow pointing north. The lead on the starboard side complicated matters greatly, threatening to cut ship power to the other side where most of the science program was sited. Getting to the other side meant walking or snowmobiling south to a point where it was safe to cross. Part of the CS duties was keeping the shore apprised of our situation with phone calls to Andy in Barrow and weekly situation reports back to NSF in Arlington.

I also began deploying an additional project from my helo hut out near the runway, removed from the main camp. The object was to test a new instrument, an Acoustic Doppler Velocimeter, that sensed three-dimensional current by measuring the Doppler shift of high frequency sound waves with three strategically arranged receivers. SHEBA was the last project where I used the venerable "Smith-rotor" current meter triplets to measure 3-D velocities.

Ice conditions near SHEBA (which had drifted far to the northwest by then) were anything but sedate, as I had envisioned when I agreed to be CS. According to my notes at the time, I was continuously on the go, averaging 15 to 17 hours a day. Several noteworthy events happened. One began at about five one morning with a call from the bridge suggesting that I come up to see what had transpired overnight. The ice had ridged heavily just north of the ship, threatening at least a couple of huts, including the garage for our snowmachines. We quickly mobilized a salvage crew and were able to recover everything important. When it starts piling up in big blocks even relatively thin ice (~2 m), can present significant challenges!

Having a lead separating the ship from the main science camp presented many problems. As a precaution we moved a 12KW generator to the other side of the lead, anticipating that ship power might be interrupted. We parked the snowmachines in the limited space between the ship and the lead. One morning I went down to start a snowmachine at first light. Looking north-east there was a strange lighted object on the horizon, that appeared for the world like a ship, with lights broken up in a pattern you would expect from lights on different decks, etc. I really wondered if a Russian icebreaker was coming to visit us unannounced. I radiod the bridge asking if they were seeing the same thing. They answered that yes, it was an impressive full moon. They probably thought I was losing it. I think what was happening was that in the strong Arctic temperature inversion, light was being refracted differentially, creating the checkered pattern. At the higher level on the bridge, they were seeing the moon as it actually was.

We parked the snowmachines facing away from the ship. On another morning I went through the standard drill of starting in -30 degrees, priming the carburetor and giving several pulls on the starter cord. Suddenly the machine was dragging me forward at high speed as I hung onto the handlebar, which fortunately included the brake. I managed to slow the machine enough to reach over and hit the kill button before it plunged into the lead. Whew! I learned later that a machine had been lost in the same circumstance. It had something to do with the throttle freezing on the Scandia snowmobiles.

Ice movement on Mar 17 interrupted ship power to the main camp, which was restored via the 12 KW generator we had moved into place earlier. Then early on Mar 18 (UT) we had a major ice movement event. A timelapse video from the ship (sidebar) illustrates that across the lead, ice containing most of the science programs shifted north by several hundred meters in the span of a few hours, temporarily preventing access. Fortunately, I had my turbulence mast system running on power from a small portable generator, and was able to capture some of the most interesting data I obtained during the whole project. When it was safe to cross to the other side, it was possible to restore power to most of the science programs within a day using the 12KW generator. Access from the ship remained difficult, entailing detours of some distance to find safe crossings.

It was clear that if SHEBA was to survive into and through the following summer, we would have to relocate science activities closer to the ship. Over the course of the winter, snow drift had masked expression of frozen melt ponds that had existed when we left in the fall. But we knew that ice in those locations would be thinner and less likely to survive a second summer. We found there was sort of a bimodal distribution of ice thicknesses, so I organized parties to drill in a pattern and indentify hummocks beneath the snow, which would be where we would locate huts and equipment for the new camp. In one instance, a young woman who was part of Curry's group and had spent little time actually on the ice, apparently wrenched her back (for which I felt bad), and the ship's nurse ordered her to stay on the ship for a few days. The next day she was sighted scrambling around atop the nonconsolidated ridge forward of the bow, an inherently dangerous place. So the ship's nurse ordered her ashore on the next flight. She objected strenously which fomented discussions among nurse, captain, me, and Andy ashore, all of which seemed unnecessary.

We had several discussions about where and how the the new camp would be located, some getting fairly heated because the met contingent insisted on no upstream obstacles in all directions, which seemed neither feasible nor scientifically necessary. As I heard it (I wasn't there) discussion continued in the ship's bar, which was opened Thursday evenings. At one point, one of the newbies (or FNGs) stuck a video camera right in Tom Lehman's face, which landed on the floor after Tom batted it away. This led to another complaint to the captain, which I had to defuse by arguing that indeed Tom occasionally was hot headed, but that he was by far the best and most competent assistant I had ever had, and was of much value to many others in the project as well.

The question of where the camp would be, either to the starboard (east) or port of the ship, occupied much discussion. The ice around us still seemed pretty unstable. In fact, Andy had held the next crew rotation, which again included several media people, in Barrow waiting for things to settle down. I argued that since we had scouted out the suitable hummocks on the starboard side, it would be best to remain in that configuration. Others, including Jumper Bitters, thought that the ice on the port side was thicker and would make it much easier to set up camp, since we still had the starboard lead to contend with. I didn't trust it-- especially after Tom and I drilled in several locations, finding large variation in thickness. To me this indicated consolidation of a rubble field, which I thought would eventually become unstable. I called a PI meeting to discuss the issue, and although most agreed with Jumper that we should immediately set up off the port side, I exercised my prerogative as Chief Scientist to decide we would continue our efforts to efforts across the lead on the starboard side. Needless to say, given the many undercurrents that already existed in SHEBA, the decision was not greeted with whole hearted support. Nevertheless, we continued in that direction.

Over the next few days, I prepared the main turbulence project in the new location, and packed my sonic velocimeter gear in preparation for the next rotation. Soon the ice around the runway stabilized enough to shuffle crews, and I was replaced as CS by Don Perovich. As a coda to the whole camp replacement saga, after our Twin Otter flight took off, we circled back across the ship and I could see that during the night the ice on the port side of the ship had broken up completely, and was a jumbled mess. I don't know if anyone else on the flight wondered why I was giving myself a fist pump! I remain convinced that the work we did to identify and occupy hummocks that had existed at the end of the previous summer was instrumental in the project's survival through the following summer.