Disaster!

By David Ho, LDEO

Being out at sea requires that we adapt to different situations and adjust our plans accordingly. Some of these adjustments are expected, while others are genuine surprises.

For instance, when we inject the tracer patch, we select an area that is relatively stable so we don’t end up chasing the tracer patch around the Southern Ocean. However, because there’s no guarantee that winds and currents won’t change, we really don’t know where the patch is going to go. As a result, we don’t have fixed survey lines and have to adjust them minute by minute. That’s expected.

During this cruise, we’ve had some surprises. For instance, what happened to the SuperSoar was a surprise (see Burke’s blog), but given the fact that they are pushing the cutting edge of water sampling technology, it’s not difficult to accept that it could happen.

What happened to us today topped that.

It was about 9:00 am, and time for our morning CTD. Paul and I were discussing something in the Hydro Lab and getting ready for sampling when we heard a loud thud. I said to him facetiously, “I hope that wasn’t the CTD going into the screws [the propellers].” I went to the Staging Bay to check things out, and ran into Carlos on the way who said to me with a panicked voice, “we just lost the CTD.”

I once heard an episode of WNYC’s Radio Lab about Stress, where they talked about what happens to us when we’re under stress. One of the common experiences that people under extreme stress has is that time slows down and thoughts become clear and lucid.

In the few steps that it took to get to the Staging Bay, all the different scenarios under which we could have “lost the CTD” crossed my mind. I was expecting to see the end of a frayed cable dangling in front of me; what I saw was more surprising.

The CTD was hanging off the side of the ship, and the block that used to hang from the CTD boom was laying on the deck. See pictures below for what I fail to convey with words. Apparently, the rosette was accidentally pulled into the block, breaking the block and sending the CTD crashing approximately 20 feet into the side of the ship. Disaster!

The good news out of all this is that nobody was hurt and the rosette/CTD package was eventually recovered. However, the rosette frame was severely damaged and eight sample bottles were crushed.

For the 9:00 am station, we adapted and went to our storm contingency plan, when we expected not to be able to deploy the CTD: Submersible pump. Even though the pump only had enough hose and cable to sample down to about 40 m, it was better than nothing. It was a nice sunny day and a communal atmosphere on deck as we took turns sampling water pumped up to the surface.

We’re working hard to put another rosette/CTD package together, but it will not be ready in time for the upcoming 9:00 pm station. This will be another pumped sampling station. We hope to have the CTD ready for the morning station tomorrow.

Damaged rosette/CTD hanging off the side of the ship

The broken block on deck

Recovering the damaged rosette/CTD

Close-up of the damage

Preparing the submersible pump

Sampling from the submersible pump

A new rosette/CTD being assembled in the Staging Bay

UPDATE: Sara, Geoff, Jonathan, Clay, and Bob worked hard all day and assembled a new rosette/CTD in time for the 9 am morning cast the next day. We’re back in business. Nice going!

The newly assembled rosette/CTD package, ready for the next cast

Pump and Dump

By Dale Hubbard, Oregon State University

There are approximately 60 people, including the crew and the science party, aboard the Ronald H. Brown. The good folks in the galley serve three meals each day, there are snacks available after hours, and there’s a seemingly unlimited supply of things to drink. This is a very good thing (it certainly beats going hungry and being dehydrated), yet it poses a quandary: once we’ve metabolized all of that food & drink, what to do with all of our waste?

There are basically two types of sewage generated aboard the vessel: grey water, which originates from sinks, showers, laundry, and the dishwasher; and black water, which originates from the toilets. (The engines also generate wastewater of a more industrial nature, e.g. oily waste, but this is contained separately and later pumped ashore when the ship is in port, as oily waste is illegal to discharge at sea.) Aboard the Ronald H. Brown gray water and black water are commingled and contained within a holding tank of approximately 5000 gallons capacity. Sewage aboard the Ronald H. Brown is not treated—it is mechanically ground up en route to the tank, then the contents are pumped overboard. Once the sewage tank has accumulated 4400 gallons, it’s time to break off from our study site and make a run for it.

Since our project involves continuously observing a relatively small patch of water in order to collect time-series measurements, we must move at least 3 nautical miles off-site before the ship evacuates the contents of its sewage tank. Sewage contains an assortment of compounds that serve as phytoplankton nutrients, so dumping the holding tank inside of our study area would drastically alter the biological and chemical processes within. Therefore, at least twice each day we must leave the patch to undertake what many aboard refer to as a “Pump and Dump.”

Unfortunately, several times during the course of a Pump & Dump, the ship’s underway seawater line entrained some of the sewage. This caused caused a great deal of excitement in the lab, as steaming through this particular hydrographic feature generates some of the most dramatic measurements observed during the cruise. This secondary “patch” is exemplified by elevated pCO2 and nitrate (both byproducts of the degradation of metabolic waste) and elevated temperature (see pictures below).

On at least one occasion we’ve been able to resolve a sewage signal in the data from our underway transmissometer, an instrument which essentially measures water clarity (or lack thereof) by passing a beam of light through a sample stream of water. Eeeewwww…

In order to pick these Pump and Dump events out when we’re processing the data long after the cruise is over, it’s important that we remember to log them carefully.

Effect of “Pump & Dump” on pCO2 and temperature. Pump and dump signal, from approximately 12:00-12:30, manifested in approximately 20 ppm increase in pCO2 (white trace) and approximately 0.5o C increase in surface seawater temperature (red). “H2O” parameter is water vapor measured inside of shipboard pCO2 equilibrator and also reflects higher surface seawater temperature. The surface salinity values are highly variable (and rather irrelevant) because it had been raining.

Effect of “Pump & Dump” on NO3 concentration. “Amplitude” values represent voltage generated by photodiode detector (note scale is reversed). The ~0.1 V decrease between approximately 12:00 -12:30 represents an approximately 3mM increase in NO3. The variation in amplitude at approximately 13:30 is a standard sequence—a blank, 20 mM, and 9.5 mM KNO3 solutions.