07. Cruise Letter #6

Dong-Ha Min’s cruise letters from P18 CLIVAR/CO2 Repeat Hydrography expedition in the Pacific Ocean (2007/2008)

Letter #6

Sailing Day 9 (12/22/2007, 1400 PST)

12.0 deg N, 110.0 deg W

Holiday must be around the corner. I see more Christmas decorations on board despite the warmer weather outside. Crew set up a Christmas tree in their TV lounge (see picture), and I see the lights tangling on lab ceilings. Also fewer mails coming from outside… we are going to be forgotten for a while.

We saw more creatures during the last few days esp. at nights. We saw congregation of baby jelly fish on the water, squids, and birds. Two nights ago few squids actually came on board along with our rosette sampler package. Two of them suddenly fell on the deck out of blue, and we speculated they might have wrapped themselves around the wire coming up. Most exciting observation was a big yellowish back sea turtle** which popped up in front of us and swam away. I never have seen a sea turtle swim that fast before. Rumor is circulating in the ship that a giant squid might be sabotaging our water sampling mission underneath us…. oh boy…

Our work is in progress. We have occupied 21 full depth stations and deployed many other instruments in the water for satellite communication. They will float in the ocean at depths for number of years following the ocean circulation. About 20 or more different science programs are in action here, and we are busy coordinating them as well as assuring their mission is successfully accomplished.

When we stop at a station (the pre-determined location to work at sea), we lower the rosette package to the bottom of the ocean to obtain continuous profiles of many different ocean properties such temperature, salinity, pressure, and dissolved oxygen besides discrete water samplings for later analysis. Taking the water samples at the deepest part at a certain location in the ocean is always challenging. Just imagine that this big ship constantly maneuvering her position within few meters from its original position at appropriate heading against the winds, waves, and currents. Then we lower the few thousand pound package with a few millimeter diameter metal wire to the bottom at 4000 m ocean bottom. We want to take measurements throughout the water column and at the deepest point but without hitting the ground, otherwise we may damage the instruments, or even worse, can jeopardize the ship’s safety if the package is stuck at the bottom! That would be really bad.

We utilize ship’s wide-angle Seabeam, echo-sounder, and actual water pressure sensor and altimeter mounted on the package to determine the exact bottom depth and height above the bottom for the package. The Seabeam is a wide-angle multi-beam echo sounder that transmits the sound to the ocean bottom from the ship in wide angle so we can get a swath picture of the ocean floor. The echo-sounder is more focused to the bottom directly below us. Its pinger transmits (pings) the sound from the package so we can get more clear topography of the bottom. We constantly monitor the pressure sensor reading for actual depth of the package. Within ~100 m from the bottom, the altimeter automatically kicks in and starts to ping. It gives even more fine reading of distance from the bottom. With coordination of these data we make the bottom approach within 10 m from the ocean floor.

Problem is when there is irregular bottom topography such as sea mount is nearby. The ocean current can cause the package to drop in angle instead of straight down. The bottom can suddenly shoal as ship slightly drifts around in that area. To avoid the crash of the package at the bottom, we have to be on alert at maximum tension during this period. Usually 2-3 people watch the console screen to control this. A grad student operates the electronic deck unit to record the information and trigger the sampling bottles at desired depths. Other person assists as second watchful eyes. I would stand behind them to give direction and sometimes make a critical decision. During the last few nights, we have occupied several locations of which bottom depths varied by few hundred meters within few tens of meters of ship’s movement in few minutes of time scale. We must have stopped on top of narrow valley with steep slopes around it… Lot of swearing and cursing went on. No crash so far. Sweating continues.

We took severe hit on our science program due to the 8 days of time loss at the San Diego port. To accomplish the original goals of our programs with minimum level of compromise, chief scientist and I have spent seemingly endless hours on communicating and figuring out most optimum revision of our plan. After consulting with many high level folks on shore and other colleagues and officers on the ship, we came to a conclusion. Two days of delay in arrival to Easter island, stretching our station spacing from 30 miles to 35 miles, increase ship’s speed to 12 knots from 9 knots, cut down the operation time for buoy team (this is another long story so I spare it for now).

Before we announce this to everyone, chief scientist and I had two ‘long’ meetings with the ship’s officers. It was a quite unusual scene to see chief scientists sit together with CO (commanding officer), XO (executive officer), FOO (field operation officer), NAV (navigation officer), and last but not least, medical officer of the ship. We talked, negotiated, argued, threw chalks to each other (not really), and came to an agreement on ship’s fuel situation and cruise plan.

Changing the plan like this makes a big impact on so many people. Not just us and crew but also the scientists who will come to Easter island to relieve us. Many of us should change our travel schedules (flights and hotels, etc). So basically people would hate us… We tried to look this in positive perspective: everyone gets a Christmas gift. Leg 2 group who comes to Easter Island would get few extra days on Easter island and fewer days in the treacherous Southern Ocean, and Leg 1 people (us) would be privileged to obtain more data. Didn’t go very far… not a very good thought. Chief scientist asked me if he could send this announcement from my e-mail account. I said “no way”. We dreaded but finally hit the ‘send’ button anyway. We made sure we won’t go to an isolated area in the ship alone… Before long, I heard screams from many areas… but so far we are still alive… good sign.

I’ve been managing my daily schedule that I sleep 4 hours a day, and instead I eat 3 meals per every day. I officially work from midnight to noon, but overlap with the chief scientist for few more hours in daytime to relay the information and to provide the extra hands. I may need to change this pattern as I will get more exhausted. The medical officer continually patrols the ship to check all individuals whether anyone shows a sign of severe fatigue or confusion. We would rather suffer quietly rather than seeing him in his office (this story also spared for a later time). I did my first laundry few days ago. See the attached pictures for the ship’s washers and dryers on the bottom deck. It’s not that exciting to explain about the washer and dryer, but I found an interesting thing on this deck: scuttle valve (see picture). This thing can flood the ship and sink her by opening a hole at the bottom of the ship. During the wars, navy ships or submarines used it to scuttle their own ships not to lose the ship and intelligent information to the enemy’s hands. Chilling thought…

More news to follow soon.

Whiskey Tango Echo Charlie out…

Dong-Ha Min

on NOAA ship Ronald H. Brown in the cobalt blue Pacific Ocean

(P.S. from shore) My sea tuttle expoert friend in Texas told me the turle we saw with yellowish back might have been a leatherback, although it is very difficult to identify them from the deck.