A Glimpse into the DIC Lab: An Interview with Dana Greeley

Author: Kathryn Williams

The sea was angry that day, my friends – like an old man trying to send back soup in a deli. So I went to talk to Dana Greeley about DIC… Here is that “conversation”.

Kathryn: What is DIC?

Dana: DIC is an acronym that stands for Dissolved Inorganic Carbon. It is also referred to as Total CO2 (carbon dioxide). It is the sum of the dissolved carbonate species in the seas: carbon dioxide, carbonic acid, bicarbonate, and carbonate. DIC is a key parameter when making measurements related to pH and carbon dioxide flux estimates.  But do most of the readers of this blog really want to hear about this? Can’t we talk about the nice sunsets we’ve had recently? Here give them the link to DIC from Wikipedia. Then we can use your blog post to talk about something more entertaining.

Sunset
Sunset on the Indian Ocean from the NOAA Ship Ronald H. Brown

Kathryn: OK then, when did you start sailing and why do you still go out to sea to measure DIC?

Dana:  A few of my favorite literary quotes might explain my motivation: “Of all the things that drive men to sea, the most common disaster, I’ve come to learn, is women.1” But that was not the case with me. “If you really want to hear about it, the first thing you’ll probably want to know is where I was born, and what my lousy childhood was like, and how my parents were occupied and all before they had me, and all that David Copperfield kind of crap, but I don’t feel like going into it, if you want to know the truth.2” “Some years ago – never mind how long precisely – having little or no money in my purse, and nothing particular to interest me on shore, I thought I would sail about a little and see the watery part of the world.3

Kathryn: OK, alright, hold it right there! Back to the interview… How do you measure DIC?

Dana: Aarrgh, alright. But you’re going to lose your readers if we go into this full on. Send the scientists to read The Handbook and I’ll give you the layman’s version here. We collect seawater from each niskin and take those back into our 20’ shipping container that has been modified as a sea-going laboratory. Inside that lab we hook up the seawater sample to our equipment and withdraw a measured volume. That volume then drops down into a test tube shaped piece of glass (stripper) where we add a small amount of dilute acid and bubble CO2 free air through the seawater so that it resembles a nice freshly poured glass of Fresca. You know what a Fresca is don’t you Mr. Scholarship winner? The (stripped) gas from that Fresca is then sent to a cell (picture a glass beaker with side arm) which contains a blue pH reactive solution that turns clear with the addition of CO2. The cell sits in an analyzer (coulometer) which sends a light path through this (blue) solution and on the other side sits a detector which collects the light and counts the coulombs and with some additional bells and whistles we determine the total CO2 (aka DIC) within that seawater sample. You’re losing your readers here. Seriously, if you want to know more, read the Handbook.

DICE system
DICE: Dissolved Inorganic Carbon Extraction. System used by the DIC Lab to extract DIC out of water samples

Hey, did you know the captain spotted a falcon back a week ago? Turns out it was an Amur Falcon, late returning migrant to its breeding grounds.

Amur Falcon
Amur Falcon on the NOAA Ship Ronald H. Brown

Kathryn: OK, back to the interview… Why are you out here measuring DIC; what is it used for?

Dana: Knowledge is Power! More data means more knowledge which yields a greater understanding.  These GO-SHIP cruises are a continuation of the CLIVAR/WOCE lines and this repeat hydrography helps to improve our understanding of the ocean carbon cycle and how it is changing over time. Data from those previous hydrographic cruises show that the ocean is not evolving with smooth decadal trends. Therefore we need to continue to go to sea to make these carbon measurements until an Argo type float can replace us humans. The old saying still holds true, “Don’t send a buoy to do a man’s job.”  Our DIC analysis helps climate scientists study climate change and predict future climate states with different climate scenarios. Speaking of, can you believe how hot it is outside today? I wish we could package up this heat and save it for the next time someone back home says, “It’s really cold outside, they are calling it a major freeze, weeks ahead of normal!”

Any last comments?

Yes, did you know we have now crossed into the Arabian Sea? It will be interesting to see what the Oxygen Minimum Zone holds in store for us as we continue north. I expect it will be a CO2 maximum, but that’s why we come to measure.

1 Charles Johnson, Middle Passage

2 J. D. Salinger, The Catcher in the Rye

3 Herman Melville, Moby Dick

The Biome Beneath the Surface

Author: Victoria Coles

Inhaling and exhaling, the ocean trades gases with the atmosphere; carbon dioxide, oxygen, chlorofluorocarbons and more. Different scientists on IO7 measure each of them. But what happens to the gases away from the sea surface? In the sunlit ocean, phytoplankton busily use energy from the sun to create more oxygen gas, and to convert carbon dioxide gas to plant mass. Equally active are the bacteria and animals who devour the plants as well as each other, respiring, or turning carbon biomass back to carbon dioxide while using up oxygen. The water here all looks blue to us (Fig 1).

2019_Victoria_OceanShades
Figure 1: Different shades of blue ocean on IO7.

From one day to the next there might be more or fewer whitecaps or torrential rain or fierce sun, but the water looks the same. Below the surface however, there is a hidden world with huge variability in plants and animals. Recently, we have begun to learn that the specific types of plant and animal food webs affect how gasses are processed in the ocean. So, we expect changes in the ecology to influence how much carbon or oxygen the ocean stores, and how much it passes back to the atmosphere.

And this brings us back to how we measure the plant and animal world at and beneath the ocean’s surface.  In the Bio Lab on the ship, Hannah Morrissette (MS student at University of Maryland Center for Environmental Science) and I are working with collaborators (Greg Silsbe, Raleigh Hood, and Joaquim Goes) using funding from NASA to understand the plant and animal communities that lie at the surface where satellites can see them, as well as below where they cannot. This is Hannah’s first time at sea, and I am continually reminded of how lucky we are to be here by experiencing this adventure through her eyes. For NASA, the satellites are our eyes; they measure the wavelength of the light reflected from the sea surface, then convert this to measures of chlorophyll content that can tell us both how many plants are present (Fig 2) and how fast they are growing. These are key measures of the health and state of the ocean, used for managing fisheries (like the tuna industry here in the Indian Ocean), as well as for understanding changes in the ocean’s exhalation of oxygen and carbon dioxide.

2018_Victoria_chlorophyll
Figure 2: Ocean chlorophyll-a composite map using NOAA VIRS and NASA MODIS satellites. (Credit: Dr. Greg Silsbe)

But the satellite measurements of plankton growth must be confirmed and improved using direct measurements from a ship because the equations that convert the satellite reflectance to plankton biomass and growth depend on atmospheric conditions that are changing as well as the specific makeup of the plants that live in a region which is also changing. Here, on the Ronald H. Brown, we filter a lot of water (more than 2600 gallons so far; fig 3) to detect different pigments that each have a unique signature in the wavelengths the satellites measure. From this, we’ll improve the satellite maps to learn how the base of the food web responds to changing climate. We also continuously photograph the plankton community using a FlowCam (fig 4), and measure the size and shape of the cells as well as how they photosynthesize in response to light (using a FIRe instrument; fig 5). Each morning, we also sample the water column to learn how fast the plants and animals are growing by looking at changes in oxygen over time in sealed bottles (fig. 6). This will help us to develop estimates of how much plant based carbon sinks into the deep ocean – affecting the carbon and oxygen breath of the water when it ultimately returns to the surface.

We also tow nets in the upper ocean to learn more about the small animal or zooplankton communities that likely create the fastest source of sinking carbon to the deeper ocean. The water all looks blue, but the plants and animals have been changing radically over the different areas of the Indian Ocean (Figs 4 and 7); from the deserts of the subtropics, to the fertile tropical upwelling areas. These zooplankton samples get photographed and stored at sea for later analysis. Some animals will be examined to learn whether their shells are dissolving in waters with acidic pH. Other samples will be counted (old school) to learn who is there. Some samples will get analyzed with new genetic barcoding techniques (high tech) to find out which DNA occurs in each region. Using old and new school measurements allows us to compare this section with the last one 20 years ago while still staying up to date with modern technologies.

2018_Victoria_SmallAnimals
Figure 7: Some of the animals collected across our net tows.

As we steam through these hidden plant and animal habitats we are continually reminded of how little we know about the diverse organisms below the surface that alternately fuel and steal the ocean’s breath (Fig 7).

I07N 101: Intro to Oceanography

Author: Holly Westbrook

Hello! My name is Holly and I am a scientist. When you read the word “scientist” you might imagine a person in a white lab coat, goggles, and gloves, swirling a flask of strange colored liquid, or maybe frowning at a clipboard. Now, sometimes science does look like that, but other times it looks like this:

ARGO_Deployment
From left to right, Ian, Andy, and Christian deploying an ARGO float.

The scientists onboard the Ronald H. Brown are “oceanographers,” scientists who study the ocean. It can be a tricky field to study because we have to collect samples from places that can’t be easily reached (for example, the middle of the Indian Ocean).

We collect water samples from the bottom of the ocean all the way up to the top using a piece of equipment called a “rosette.” The rosette has many different things attached to it, to bring up water we use “Niskin bottles” (the gray bottles in the next picture). Once the rosette is on deck and secured we can start sampling. There are many different people who need to get water samples. We have a specific order of who goes when to make sure things stay organized and all the time-sensitive samples are collected quickly. Still, things can get a little crowded.

Close_Quarters
From left to right, Chuck, Leah, CFCs Chuck, and Ian working in close quarters to get their water samples.

There are a couple of different ways to collect water, many of us use plastic tubes and glass bottles, some use plastic bottles, some use glass syringes, and one person has a bit more of an involved method:

Christian
Christian sampling black carbon, looks like a pretty involved process.

A lot of the scientists work 12 hour shifts, we usually have another person who will take over our shift when we are done. That means that no matter the time of day there is always research being done! My shift is from 11:30 pm to 11:30 am. It was a little rough adjusting at first, but by now I’ve gotten used to it. Plus I’ve seen some pretty great sunrises.

Sunset
A beautiful sunrise I got to see while waiting for my turn at the rosette.

When we’re not working, how we use our time is up to us. We can read outside, watch movies in the lounge, play card games, go to the gym, or talk to friends online—there’s a surprising number of ways to occupy your time!

Breakfast, lunch, and dinner are prepared by the stewards and they are at the same time every day. But there is always something to eat, which is good because I sleep through dinner and wake up several hours before breakfast. There’s things like oatmeal and cereal, but also daily snacks and ice cream at any time.

The days can be repetitive and tend to blend together but the importance of the work and the company we keep makes it all worthwhile!

Water_Taxi
From left to right: Bonnie, Myself Amanda, Catherine, Carmen, Annelise, and Jenna on a water taxi to Mahé.

A Peek into the Life of a CTD Watch Stander

Author: Yashwant Meghare

“DON’T PANIC” are the words I have written in big letters on my notes for how to operate a CTD. My excellent teacher, Kristene McTaggart (Kristy) laughs and agrees that it is indeed a very good thing to keep in mind.

Two days later, I have a dream that I let the CTD hit the bottom while going on an unapproved bathroom break. I woke up, very disappointed with my-dream-self.

May 5th, 2018

CTD: stands for conductivity, temperature and depth, and refers to a package of electronic instruments that measure these properties. Often, CTD is attached to a rosette that holds Niskin bottles for water sampling.

Somewhere in the middle of the Indian Ocean, at the so called “Station 22” I am sitting next to the person who operates CTD when I am off my watch- which goes from midnight to noon.

– Survey. Computer. Deploy the CTD.

– Winch. Computer. Down at 30 m/min. Target depth … (well whatever the depth is at that station)

The communication is very short and limited in order to avoid miscommunication or any kind of confusion. But as the CTD goes down to the unexplored abysmal depths of the ocean, it’s not the just the CTD that’s under pressure. The operator experiences the same feeling of increasing pressure.

– Quick instrument check for any signs of technical error. All good. (Well, at least that’s what we like to see.)

As the CTD goes deeper and deeper and things start to get more consistent, the operator is relieved. (or are they?)

 

 

FAST FORWARD >> 3 hours

The process of driving a CTD down to the depth can seem very uneventful. You will have to power through with a cup of coffee or some music that will bang you awake. (Or in my case, once when Kristy hid behind the door to scare me. I didn’t need much coffee after that.)

You keep increasing the speed from 30 meters per minute to 45 and then to 60. While it does seem like an uneventful job, there are spurts of times when there’s a bunch of tasks. Keeping a log of things at the beginning is important to have the final file tell you what data is important and what can be discarded. Keeping an eye for any system errors to mark them in the log is necessary. This works much like a checkpoint system in race. Anytime there’s an issue, flag it to check it later. So, even though there’s no consistent activity, it does require your attention all the time for quality data. This includes several markers in the data file to mark the beginning of the activity, the moment when CTD is underwater, when CTD is at maximum depth, and when it is going up.

The rosette hosting the CTD is not just working to measure the salinity, temperature and depth. It is an assorted set of instruments. It has a transmissometer to measure the clarity of the water, fluorometer, LADCP, oxygen sensors, altimeter that measures the height from bottom.

The altimeter activates when the CTD is within 100 meters of the seafloor. The goal is to keep the CTD off the bottom, but just close enough that the sediments don’t get sucked up into the pump (which can cause trouble).

– All stations, CTD is at maximum depth.

 

 

FAST FORWARD >> 3 hours

The journey back up involves collecting water samples at every few hundred meters.

– Winch, standby. Winch, slowdown. Winch stop. Collect water sample.

– Winch, up.

Once the CTD is back on deck, the bottles are checked for any leaks and made sure they had been fired. The real-time data collected is copied and saved on the system. The CTD operator helps with any sampling if needed.

Once all the samples have been collected, there are other simple tasks to take care of such as setting up the CTD for the next cast. There are small details that one must pay attention to for a successful cast. Andrew Stefanick (Andy), who seems like a pro with the CTD instruments helps with and teaches me all the fine details. Uncorking the bottles and cleaning the optical sensors needs to be done in a certain manner so that the equipment is not damaged.

The wording makes it sound like the CTD is some small fragile object, but in reality, it can’t be moved without the help of electrical pulley.

The purpose of GO-SHIP cruises is to observe changes in our oceans over time and this can be done only if we have quality data. From the Niskin bottles, the water is collected to do various types of analysis. Dissolved organic radiocarbon analysis, CO­2 levels, radiometric dating, nutrient concentrations, particulate organic matter, pH and alkalinity levels, dissolved oxygen concentration, CFC gas analysis, calcium analysis and density profiling are all performed on the water collected in the bottles on the CTD. So, this makes CTD a crucial part of the cruise and puts a lot of responsibility on CTD operators. With 132 CTD casts planned between Durban and Goa, this cruise will explore the Western Indian Ocean after a very long time and look for any changes that have occurred over the decades.

 

 

Behind the Science: Dissolved Oxygen

Author: Leah Chomiak

Hello from the middle of the Indian Ocean! The skies are blue, the seas are calm, the air is fresh and full of oxygen (O2)… and so is the water column! My name is Leah, one of the scientists onboard I07N running dissolved oxygen analyses along with my counterpart, Sam. Together, we are in charge of sampling, assessing, and quantifying the amount of gaseous oxygen dissolved in the seawater from every bottle of every station… coming to a grand total of 3,432 samples once we close out the transect in India. Wowza!

o2

Dissolved oxygen, the same stuff you and I breathe each second of the day, is crucial to the marine environment; whether that be oceans, lakes, rivers, or ponds, for obvious reasons. Oxygen is essential for life and is taken up by organisms through a process termed cellular respiration where oxygen is taken in and carbon dioxide is spit out in return. The reverse process, photosynthesis, results in the generation of oxygen through the uptake of carbon dioxide. Just like on land, plant cells fill the oceanic environment in the form of plankton, where oxygen is produced. All remaining organisms of the sea, from fish and sharks to corals and giant squids, rely on the presence of dissolved oxygen in the water column just as we rely on oxygen in our atmosphere – to survive! We measure the dissolved oxygen to understand not only the biological and chemical aspects of seawater, but also for understanding the physical movement of currents and water masses too.

o2 titrationWe start by first collecting a sample of seawater out of a Niskin bottle that is closed at a certain depth in the water column from a CTD rosette, yielding samples from 24 different depths spanning the surface to the ocean floor. Immediately after collecting the seawater sample, the sample is ‘fixed’ with two reagents that react to form a precipitate – in simplest terms, all of the dissolved oxygen reacts to form a solid and is suspended in solution. By performing this reaction, we essentially have the power to “freeze” all oxygen in the sample at that given moment, meaning photosynthesis and respiration are halted and no further O2 is produced or consumed. Once the entire CTD has been sampled, the O2 samples are brought back to our lab inside the ship, where we then give them a shot of strong acid to dissolve the precipitate (turning the sample a cool yellow color) and at last perform a titration to determine the amount of oxygen present in the sample.

Since the surface ocean and the atmosphere are in constant exchange with each other, oxygen from the atmosphere is assimilated into the surface waters, and we tend to see high oxygen near the surface for this reason. Due to the availability of sunlight near the surface, plankton aggregate and help to contribute to the surface oxygen levels through photosynthesis. Samples taken near the bottom of the ocean also tend to have high oxygen levels, one being because the extreme pressure and cold temperatures facilitate the dissolution of gas in seawater, and two, certain water masses, such as the cold and dense Antarctic Bottom Water are known to have high O2 content due to recent exposure with the atmosphere. Central in the water column is where the oldest water lies, and oxygen tends to be lacking due to uptake by biological organisms. Not only is oxygen useful in assessing biological productivity, its also a great parameter to use when observing global ocean circulation!

The outflow of the Arabian Sea/northern Indian Ocean is observed as one of the largest and most distinctive oxygen minimum zones (OMZ) in the world, where oxygen concentrations are extremely low due to high biologic consumption and other chemical factors. As we continue to head north along the I07N transit line, it will be very interesting to see how our oxygen profiles change as we enter the OMZ. It has been 23 years since this hydrographic line was last sampled; I wonder what we will observe this time around!