Basins and seas


It’s a long, intricate passage to sail non-stop through Indonesia from Darwin, Australia, to northern Borneo. We’d been sailing on our Peterson 44, Oddly Enough, for two weeks. We were two-thirds of the way through when Tom and I stopped in Bitung, Sulawesi, Indonesia, for a quick top-up on our diesel and a bit of a rest. We hadn’t intended to come this way. When we checked out of Darwin, our Australian exit papers listed Palau as next port of call, but once at sea, we were feeling at loose ends and not ready for another Pacific island. So we were heading west instead, to the heart of Southeast Asia.

The first afternoon of our leg out of Bitung, we passed through Selat Bangka and entered the Celebes Sea. The name looked exotic in our logbook, as if a bit of magic clung to it. We would reach Sandakan, on the northeast coast of Sabah, Malaysian Borneo, in less than a week. But when I woke from my second three-hour sleep that night, thunderstorms had replaced gray but benign weather and brought wind from the west right on the nose. We’d also entered a vast field of fishing boats. A pain in the day, harrowing in the darkest of dark, at new moon. Most of the palliative effects of the brief stop vanished with a dull sense of dread taking its place; it had dogged me through the trip, reappearing at times when circumstances seemed to be narrowing options down toward nil. Somehow this trip I’d missed the equilibrium I usually find at sea. I need options. If I know there’s a bailout point, no matter how impractical it might seem, I’ll go into most anything.

By morning we had managed to gain some distance by tacking. Yet as I climbed again into the cockpit, the anxiety bird was fluttering.

“No wind now, huh.”

Tom shook his head.

We’d stopped in Bitung to repair our mainsail and to refuel since we’d run one tank dry in the Molucca Sea. We hadn’t repainted the bottom recently and we were hauling around some growth and burning more fuel than in the past. Two fishermen filled our jerry jugs in exchange for U.S. dollars, a convenience because we didn’t want to check in, but the first lot of fuel they brought was dirty and we’d only filled one tank with good fuel. A friend who sailed this route a month earlier had e-mailed, “Weather map shows headwinds all the way. Take it on the chin. You’ll probably have to motor.” It was about 550 miles to Sandakan, on the northeast coast of Sabah. We could only plan on motoring half that.

I looked at the logbook. For the last two hours I’d been asleep, the wind had been dying and our course had been veering gradually toward the northeast. It looked like we’d picked up a contrary current.

“What do you want me to do?”

Just as he said that, the wind came in very light, on the nose again. I looked out at the featureless sea.

“Turn the engine on,” I said with a sigh.

To help with the helplessness, we set ourselves goals. The first had been to navigate the channels north of Bitung and gain sea room, which we did. The second day’s goal was to make it to less than 240 miles to go to the Sibutu Pass, our exit from the Celebes Sea into Malaysian waters. One positive thing about our passage was we had all the time we needed. No boats in company to make us feel slow; the transitional season between monsoons was just beginning, so we weren’t escaping weather. We were already two and a half weeks out of Darwin, and it mattered little how much longer it took to complete the passage.

Tom kept emphasizing that Oddly Enough is a sailboat, which means, if all else fails, we can sail. On ocean passages, with plenty of sea room, that’s true, but our trip had been akin to coastal passages without stops.

Not only was this a coastal passage, but we were sailing through a surprising number of seas. Since leaving Darwin, we’d been in the Timor Sea, Arafura Sea, Banda Sea, Ceram Sea, Molucca Sea, and now the Celebes Sea, all in the space of 1,000 miles. To our west lay the South China Sea. And come to think of it, what ocean were we in? I went to an oceanography book, which told me the official line between the Pacific and Indian oceans runs from Cape Londonderry in Western Australia to Timor, Java, and Sumatra in western Indonesia, then to the Malay Peninsula. We were sailing from southern to northern limits of the East Indian Archipelago, the maze of seas and islands that makes up east and central Indonesia. The archipelago itself is part of an adjacent sea to the Pacific, just as the Caribbean is an adjacent sea to the Atlantic Ocean.

Topography defines currents
“Sea” is a surface topography term for an isolated body of salt water whose outlets are narrower than its sides. In the bottom topography that maps out the features of the ocean floor, a “basin” is defined as an oval or round depression, as opposed to a trough, or trench. Basins are surrounded by ridges that may or may not rise above sea level. While a basin is an underwater feature, it can coincide with a sea. This is the case in the East Indian Archipelago, where a listing of basins and seas match. Knowing basin topography, and the depth of the “sills” separating them from their sources of water, is important in understanding currents and water qualities and the distribution of marine organisms in a given area.

Major ocean basins have been defined as those with depths exceeding 4,000 meters (13,123 feet). I was surprised to find basins we’d crossed on the major list; the South Banda Basin is 5,400 meters (17,716 feet) deep, and the basin under the Celebes is a whopping 6,280 meters (20,603 feet) deep! Considering the mean depth of the Pacific is 4,282 meters (14,048 feet), this is deep.

A look at a submarine topographic map shows the Celebes Basin to be a rectangle roughly 450 miles by 380 miles. It is fed by North Pacific Ocean water flowing across a sill in the northeast corner, and flowing out via the Makassar Strait in the southwest corner. However, the flow divides at the entrance to the strait, with one branch returning east across the top of Sulawesi. The eastward flow backs up against a ridge of islands and passes which extends from the northeastern tip of Sulawesi (and forms the eastern side of the Celebes Basin). This barrier causes it to turn northward, where it eventually rejoins the water flowing in from the Pacific. The surface currents generally follow the basin flow; though seasons affect the speed, the basic direction of flow stays steady and an eddy-like circulation shows on pilot charts for most of the year.
Transitional weather
October and November are transitional weather months in the equatorial regions. In the Northern Hemisphere a changeover occurs between the southwest monsoon of summer and the northeast winds of winter. (In Asian waters, the monsoon regime is the strongest force, along with land-sea breezes along island coasts and tropical storms.) By early November the GRIB files were showing mild tweaks from the northeast in the northern Celebes Sea, which meant the northeast monsoon was moving south toward us from the Philippines.

Our goal for the trip’s third day was to get through a reasonable number of miles, say 70, which we could do by making three knots. Every mile we made under sail meant one more mile we could motor at the end when we would encounter tricky channels. We angled northwest, pushed partly by course and partly by my hope that we’d encounter the bottom edge of the northeasterlies, though I didn’t have much faith in the GRIBs as they hadn’t accurately predicted the winds we had on any part of our trip so far. Our winds did shift, from west to northwest, then to north, though not strong enough to do much. At least they didn’t push us back.

Around sunset, we were watching fish feeding frenzies and feeling the wind die with sinking hearts. We’d been making good progress under sail all afternoon. At 2000 we rolled in the jib as it was hanging limply, and a half-hour later, we took down the main to keep the slatting from driving us crazy. To our surprise, we’d found we could drift within 10 to 15 degrees of our course, at a couple of knots, even without sails. We had crossed the eddy and were squarely in the west-bound flow.

The morning of our last full day we spotted a string of oil drums tied together. On this trip the universe seemed to be testing us: Are you sure you want to do this? Are you really sure? Pow, here’s another setback. But if you are determined, you can pass into the next phase. We thought the stuff must be jetsam from a ship, but then we saw another, and soon, high-prowed fishing boats nudged up to them. We later found out the drums were floats for fish aggregating devices (FADs). We didn’t dare drift through that field, as the chance of getting snagged was high, so, using precious fuel, we motored all day. We passed the fishing boats, and at night, just as we’d think we had seen the last, a new set of boats would turn their lights on.

The final sea
When we finally left the last FAD it was time to enter Sibutu Pass, which would take us into one final sea, the Sulu. (The Sulu Basin is another major one, 5,580 meters (18,307 feet) at its maximum depth.) Three countries, Indonesia, Philippines, and Malaysia, meet in this area. The Tawi-Tawi islands at the pass are Philippine, part of the Sulu Archipelago. South of Mindanao is pirate territory, and the Sulu name is particularly infamous. The troubles between Malaysia and the Philippines stem from, as is often the case, the divvying up of land by the British colonizers. Our cruising notes dated from the 1990s when few boats traveled here. There were serious problems with Philippine piracy, but most of it was directed at big ships and poor fishermen. The Malaysians don’t take kindly to piracy against their guests, and they have a big naval presence in their waters west of Sibutu. But our friend who’d sailed a month earlier passed a ship navigating the pass with no lights, and we encountered an ore carrier coming up the straits from Australia which did a 180 and turned off its lights when we converged on its path. Maybe it thought we were the pirates.

After Sibutu we were able to sail enough to eke out our fuel. Reflecting on the voyage at the end of two more days from the shelter of Sandakan, it seemed dreamlike. Fishing boats like those that plagued us right to our last night out, raced past all day as we were anchored in the narrow shelf off the yacht club, between the large town mosque and the busy ferry wharves. Outside the harbor, the Sulu Sea is fed not from the Pacific but from the South China Sea, the only one of the seas we’d been through to do so. Asia was truly at our doorstep.

Ann Hoffner has voyaged extensively in the Pacific with her husband Tom Bailey aboard their Peterson 44, Oddly Enough.

By Ocean Navigator