Posts Tagged Antarctic voyage

Antarctic voyage: Back in Wellington Guest Work Mar 14

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Date: 13/3/2013
Location: 41.52247˚S, 174.772597˚E
Weather: Sunny
Sea state: Calm

The day started early with a 6:30am breakfast, arriving in to Wellington Harbour at 8am – a beautiful day coming in to the harbour!

RV Tangaroa looks very small compared to the large cruise ships (that’s Tangaroa on the left hand side, compared with the Queen Mary 2) that are docked on either side of us. It will be a long day of unloading and transporting our gear off the ship and back to the office and stores, or into containers to be shipped to Australia and France.

We are still disappointed about not achieving the main aim of the voyage, which was to recover the oceanographic moorings in the Mertz Polynya (see blog post 20: What is a polynya?). But we have collected a lot of other data in order to answer other questions about the Wilkes/Adélie Land region of Antarctica.

Along with help from colleagues and students, this data will take several months (or years) of hard work in the laboratories and offices to analyse and write up as scientific papers. So this voyage is only the start of a long road ahead.

There are a lot of acknowledgments and thanks required after a long voyage.

Thanks to the agencies in New Zealand, Australia and France that funded the voyage and made it possible.

Thanks to everybody who has been on board for making the voyage as enjoyable as possible, with good humour. This has made it a truly team effort. We would like to especially thank the captain, Evan Solly, and the crew of the RV Tangaroa that have fed and looked after us and helped to achieve the science by deploying our gear, often in unpleasant conditions. They have kept us safe and the doctor has fortunately had very little to do. We have all come home with all our fingers and toes intact.


Team photo. [Adrian Bass]

Team photo. [Adrian Bass]

Thanks to Mike Williams, the leader who has done a great job of organising, communicating and keeping the scientific team on track through the many decisions and changes during the voyage.

Thanks to all the family and friends who have sent regular emails to keep us updated with what has been going on in the world and not feeling quite so isolated out here. I cannot imagine how Mawson and his crew coped 100 years ago with no communication to the rest of the world (see blog post 24: The discovery of the Mertz Region).

Finally, I would like to thank all of you who have been reading the blog posts over the last few weeks and sent in questions. I would also like to thank all the writers and photographers who have contributed to the blogs and helped to provide different perspectives on the science and life on board during the voyage. Most were very willing, while others offered without even being asked! I have certainly learnt a lot by writing and editing the blogs.

Thanks to Aimee Whitcroft and the Science Media Centre for getting the blogs up on the Sciblogs website. I look forward to reading about other scientists’ fieldwork adventures and discoveries!

Antarctic voyage: Are we there yet? Guest Work Mar 13

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Date: 12/03/2013
Location: 43.292704°S, 173.575944°E
Weather: Sunny
Sea state: Calm

The last couple of days we have been making our way up the east coast of the South Island back to Wellington.

While it hasn’t been blue skies and calm seas, we have had a good trip home, with no delays from wild weather. As we approached Auckland Island (south of New Zealand), we realised that we hadn’t used our “bad weather day” and found ourselves with an extra day to get some more science done as we headed north. So we took the opportunity to tidy up a couple of things that we hadn’t quite finished on a previous voyage in 2011.

The extra science has mainly involved multibeaming some interesting features. One of these features looks like a field of small volcanic cones, while another could be a potential reef to the east of Auckland Island.  Further work sampling these features will be required to find out more and to determine their origins. I guess the undersea world is one of the last unexplored wildernesses on earth, where you still find new features every time you go out and take a look….

Multibeam image of several small volcanic cones up to 300 m high. Colours represent different depths. [NIWA]

Multibeam image of several small volcanic cones up to 300 m high. Colours represent different depths. [NIWA]

Tomorrow we will get back to Wellington. So today everyone is finishing up the work, analysing the last samples, packing and cleaning up their gear, cabins and laboratories. Many of the samples are being sent back to Australia for analysis, so there is a lot of extra packing, permits and logistics required to make sure they get to the right laboratories.

We are also writing up a voyage report. This documents everything that we have done and why. A very useful reference for when you are trying to make sense of why and where you sampled when you are analysing the data several months from now.

None of this is helped by the fact that most of us are struggling to get over our jet lag from being on shift (see blog post 17: Q and A (the first one)). We are trying to adjust our body clocks before we get back to New Zealand. Our poor French colleagues on board will have to do this all over again when they get back to France in a few days time.

The idea of the real world, and catching up with life after putting it on hold for almost 6 weeks, seems rather daunting – can we turn around and go back south again? I am, however, looking forward to sleeping in my own bed and making the most of the last days of the New Zealand summer.

Look out for tomorrow’s blog post, which will be the final one in this series!

Antarctic voyage: Student experience Guest Work Mar 12

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Written by Antoine Martin (PhD student from LOCEAN)

Date: 11/03/2013
Location: 46.21046°S, 170.330154°E
Weather: Cloudy
Sea State: Calm, 1 m swell

I am a first year PhD student in the LOCEAN (French oceanographic laboratory). I have been part of the RV Tangaroa Mertz Polynya Voyage 2013 science team because my research topic is oceanic circulation on the Adélie shelf.

During the voyage I have learnt a lot from the experienced scientists on board. I have been on the CTD night watch; my shift mates taught me the important steps for collecting a successful CTD cast (see blog post 29: The CTD) and I have learnt how to take water samples – it’s not as simple as you think! I was also responsible for the LADCPs on the CTD, during the night watch. These instruments allow us to get a snapshot of the current during the CTD cast based on the Doppler Effect (see blog post 29: The CTD).

Antoine learning to knit. [Jill Scott]

Antoine learning to knit. [Jill Scott]

While we are sometimes serious and talk about science during our CTD watch, we have also spent some of the time singing along to the guitar or ukulele, learning to knit and crochet, and improving my English.

A ship is a kind of little self-contained town for 6 weeks. An oceanographic ship is an entire ecosystem of people chosen for their different expertise and skills and who want to understand a region of the ocean – they all share the aim of achieving good science. As you will have read on the previous blog posts, a large number of science activities have been done on board during the voyage: water sampling, coring, chemistry, mapping of the sea floor, cooking, engineering, winching…I have enjoyed discovering how each of the activities contributes to answering the different scientific questions we have about the region.

 Antoine looking at one of the plankton tows being held up by Helen Bostock. [Courtney Derriman]

Antoine looking at one of the plankton tows being held up by Helen Bostock. [Courtney Derriman]

Although the crew and scientists form a good team, in reality the weather and the sea ice have controlled the voyage activities. Unfortunately the sea ice barred our way; it stopped the ship from getting in to the Mertz Polynya and forced us to change our plans. It was a big disappointment not to be able to reach the Australian and French moorings. I have discovered how difficult it is to get any oceanographic data, especially south of the polar circle. Fortunately for my PhD I will also be working on an existing dataset that has been collected by the French oceanographic team since 2007.

However, due to the sea ice affecting our initial plans, I have also learnt a lot about the logistics, and ideas that go into planning new stations. When the decision was taken to do science in the canyons on the Wilkes/Adélie Margin (see blog post 26: Mud, mud, glorious mud), we looked at the work which had already been done in the area to choose important sites to get new profiles. I have also got a better understanding of the huge change in the sea ice distribution due to the Mertz glacier tongue calving. I will analyse the oceanographic data from the Adélie shelf with new insights and a better understanding of the region.

I hope I will return to the Southern Ocean and next time get on to the Antarctic shelf.

Antarctic voyage: Q and A Guest Work Mar 11

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Date: 10/03/2013
Location: 49.181135°S, 166.812487°E
Rain and up to 40 knots
Sea state: 3 to 4 m swell

The last few days of the voyage, and some final questions answered!

Firstly, from Greytown School years 4 and 5.

What clothing and special gear do you need to wear when you are on deck on the ship in the icy wind?

We talked about this back in blog post 12: Cold weather protection. And here is a photo of Mark Fenwick (the father of Ella, from Nelson College for Girls) dressed up in his cold weather gear.

 Mark Fenwick in his mullion suit. [Helen Bostock]

Mark Fenwick in his mullion suit. [Helen Bostock]

How far in km is Antarctica from Wellington and how long does it take you to travel to Antarctica by boat in good weather conditions and in bad weather conditions?

Wellington is 2500 nautical miles – about 4630 km – from the Mertz Glacier Tongue.

In good conditions it takes about 9-10 days to get to Antarctica on the RV Tangaroa, going at an average speed of 10 knots (10 nautical miles/hour). In bad weather it can take much longer, depending on how bad the conditions are. …

What is it like to see a polynya?

I am not sure as we didn’t really get to one on this trip because of the large amount of sea ice. It is just an open expanse of water that is surrounded on all sides by sea ice or glaciers, so I imagine that depending on how big it is, you would just see the sea with ice in the distance.

How close to home are you now?

We are just approaching Auckland Island, 700 nautical miles (about 1300km) south of Wellington, so just a couple of days to go.

Have you tested any new equipment while being there, and if so what was it and how did it perform?

We had a new underwater camera setup which can be attached to the CTD frame. We have had a few minor problems with learning how to use it, for example, we were not charging the batteries enough. But in general we think it worked pretty well and we got some good images from it (see blog post 28: It is all about the critters! for a little movie from the camera).


And from Nelson College for Girls…

From Dasha: How do animals react or adapt to the seasonal change in daylight hours – 24 hours light vs 24 hours night?

Large animals either hibernate or migrate to more tropical climates during the winter, so whales go up to places like Tonga. Small phytoplankton can’t photosynthesise if it is dark, so they go into a resting state and wait out the winter until there is enough light in summer.

Ella: Are the events which occurred on the tongue of the Erebus glacier of the same interest to the scientific community as the breaking off of the Mertz Glacier tongue?

Glaciers are not created equally. The Mertz Glacier Tongue had a big impact, because of its location and its size. The Erebus Glacier Tongue is quite small, and although it will have some local effects it won’t really change how the ocean flows through McMurdo Sound.

Fliss and Tiana: Throughout the voyage, has there been an area where the temperature has risen a significant amount in the sea?

We see significant changes in sea surface temperatures when we cross ocean fronts. There are several major fronts between New Zealand and Antarctica – the subtropical front, subantarctic front and the polar front.

Between our northern-most station, near New Zealand, and Antarctica the temperature change was about 13°C at the surface, from 11°C near the Auckland Islands to about -2°C near Antarctica. This is not as large as the temperature change in the atmosphere, though – it was about 23°C when we left Wellington, and as cold as -10°C near Antarctica.

Many of the CTD stations are repeats of previous stations that have been measured over the last couple of decades (see blog post 32: Sections through the ocean), so when we get back we will compare the data over time. There is a lot of variability in the ocean from one year to the next, so only by comparing many years of data will we know if the oceans are really warming up over time.

Katelyn: How deep are you sending your GoPro cameras to get footage? What cameras do you use to get a view of the ocean floor?

The GoPro camera can go to 2000m water depth, and it is not the only camera that we use to get footage of the sea floor. In the past we have used another camera system called the DTIS (Deep Towed Imaging System). The GoPro system we have been trialling is more of an opportunistic camera that can be attached to other gear and therefore it doesn’t give images which are quite as good as we would expect from the DTIS.

Anne: Would you put a trip like this on your CV?

For many of us we will add it to our list of voyages already on our CV. But for most of the students it is their first voyage, and I am sure they will include it on their CVs when they are looking for a job after they have finished their studies.

And – what part of the voyage was the most enjoyable?

Definitely the part in the sea ice. The sea ice is beautiful, but with the added benefit of regularly spotting seals and penguins. The sea was also much calmer in the sea ice – so several members of the team weren’t suffering from sea sickness. Thank you for giving us another opportunity to show yet another picture of a seal playing around the sea ice…


Seal swimming in the sea ice. [Adrian Bass]

Seal swimming in the sea ice. [Adrian Bass]

And a few questions on how scientists work……

How much of the data you collect on this voyage will be analysed immediately, and how much can’t be analysed until much later?

We are constantly monitoring the data to check that the quality is good and that there are no blockages or breakages in the equipment. We will have a look at all of the data before we get off the ship, so that we can write some preliminary results for our voyage report.

However, most of the detailed analyses of the data won’t be done until we are back in the laboratory or office and it can take many years. This is especially true for the sedimentary cores as there is a lot of processing and laboratory analyses to be done. I probably won’t need to go to sea to collect more cores for quite a few years after this.

Most of your equipment must be very expensive and the conditions harsh. Is there a trade-off between how much data you can collect and the ideal amount of data?

Most of the equipment is expensive, but it is built for harsh conditions. One of the main issues we have experienced has been the freezing up of the water in the CTD sensors when it comes back on deck as the air temperature is much colder than the water temperature. We have to make sure the sensors are all dried out and we have little heaters ready to stop them freezing in between the stations.

Time is the biggest factor affecting how much data you can collect. While we do work 24 hours a day, 7 days a week while we are on the voyage, there is a lot of time in transit between stations, and also time lost due to bad weather (although we have been pretty lucky with that so far this trip).

Our biggest challenge has been the sea ice as this restricts where we can go, and has caused several changes of plan on this voyage. Ideally for our science we would like to collect a lot more data, but practically this would also mean a lot more processing and analysis back in the laboratory, too…and that would probably require several lifetimes, or a lot of students to help.

Do you often have to have several trips to gain enough data to put into climate models etc.? 

Yes.  It requires many voyages, over many years, to start to understand the oceanography of a region, especially changes that happen over timescales longer than a year, e.g., natural oscillations like El Niño or the Southern Annular Mode. Climate change is also causing the ocean to change, so we need to keep monitoring it to understand how it is changing, and how rapidly these changes are occurring.

We don’t put our data directly into climate models. However, the data will be used to test models, by seeing how well they predict the present before we rely on them to predict the future

There are many different types of models and they all have subtle differences in their physics (and in biogeochemical models – also the biology and chemistry). Usually, several different models are run for the same scenario and then the model outputs are compared. Ideally the models will provide similar outputs which match the current datasets. These models can then be used to predict future changes given certain scenarios and similar starting conditions.

There are always approximations that need to be made in models, as computers just aren’t powerful enough to include every little thing. But models can be useful to understand the interactions and feedbacks in the system. They are also the only way we can forecast and plan for potential future changes.

The scientists on this voyage are from several different countries. How do they work together on the same project when they are living in different countries?

Scientists rarely work on their own. Most projects involve a team of several researchers, technicians and students, each doing a small part of the bigger project. This is especially the case for multidisciplinary projects, which require the expertise of several areas of science. This means that scientists have to be good at working in a team and communicating with other researchers from different backgrounds.

For some of these projects there may not be anyone suitable at your own institution, and so you need to find collaborators from different universities or research laboratories. In small countries like New Zealand you may have to link up with overseas researchers that have the skills and the equipment (and funding) that you need to work on a particular problem. With modern communication via e-mail, skype and video conferencing, it has become much easier to collaborate with colleagues that aren’t in an office down the corridor.

Most good collaborations come down to trust. A lot of new friendships and possible future collaborations have developed on the voyage as the researchers have got to know each other and have been discussing their shared scientific interests.


Finally we will let you in to a little secret for coping with sea sickness…written by Jill Scott (IT, NIWA)

Sometimes being on the ship in the rocky ocean swells reminds me of the poem by AA Milne –“when she was good, she was very very good, but when she was bad she was horrid”.

One thing that improves the life for us when the seas are being “horrid” is the humble beanbag. It allows you to continue to work rather than have to retreat to your bunk when your sealegs have abandoned you.

Two days into the voyage, it suddenly turned rough around dinner time. Out came my beanbag and quickly became the popular sitting spot while I was looking after the multibeam.  It wasn’t unknown to sit in the multibeam lab in greater than 30 knot winds watching 6 screens from the comfort of a bright red beanbag on the floor.  The beanbag somehow cushions you from the movement of the ship and when it gets really bad, you can just snuggle down and close your eyes for a few minutes’ nap.

While we were in the sea ice, when the large ocean swells are absorbed by the sea ice, the beanbags were abandoned.  But on our voyage home, the rocking and rolling seas have tested our sea legs again, leading to several of us retreating back to the beanbags.  In fact, a couple of nights were tough with the ship continuously rolling from side to side. It is hard to sleep when you are trying to wedge yourself in to your bunk and much easier to sleep in the beanbag.

And when we get home, my beanbag is coming home with me as a spare seat in the lounge. After this voyage I have a new appreciation for it – although it might put me to sleep while I am watching my favourite TV shows!

Kate Berry and Aitana Forcen taking refuge in the beanbag. [Jill Scott]

Kate Berry and Aitana Forcen taking refuge in the beanbag. [Jill Scott]

Antarctic voyage: Sections through the ocean Guest Work Mar 08

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Written by NIWA oceanographer and voyage leader Dr Mike Williams.

Date: 7/3/2013
Location: 58.600213°S, 158.239401°E
Weather: Cloudy, rain, 20-30 knots wind
Sea state: 2-3 m swell

Both on our transit to Antarctica, and on our way home, we have repeated lines of CTD stations know as sections.  On our way south we occupied the southern part of a section known as SR3 (from Tasmania to Antarctica along 139°51S), and on the way north a section called 150°E (unsurprisingly along longitude 150°E).

This is not the first time either of these sections has been measured. SR3 was first occupied in 1991, and has seen 9 full repeats (all the stations along the section between Tasmania and Antarctica) and 6 partial repeats.  150°E has only been measured a couple of times.

As for the section names, they are historical. In the late 1980s and throughout the 1990s a bold attempt was made to understand the ocean circulation around the whole globe. Named WOCE (World Ocean Circulation Experiment), it consisted of a set of oceanographic sections along which standard measurements would be made. There were too many sections to do all at once, so they were undertaken over a 10 year period. To understand if there were any changes some sections were repeated. This is what gives SR3 its name – S for Southern Ocean, R for repeat, and 3 for the third section in the Southern Ocean.

For oceanographers these sections provide us with a way to understand the ocean. Some of these sections form the side of a box in the ocean, and we are able to compare the sides and learn something about the changes within the box. By repeating the sections we can also monitor changes in the ocean over time.

Our two sections have been chosen as they lie to the east and west of the Mertz Polynya region.  Between them we are looking for changes in the deepest waters in the ocean, a water mass called Antarctic bottom water (see blog post 21: The formation of the Antarctic bottom water). Water masses form at the surface of the ocean where interaction with the atmosphere sets their temperature, salinity, and other chemical properties. These properties allow the water mass to be tracked through the ocean.

On 150°E we expect to see bottom water that has formed in the Ross Sea. While along SR3 we should see a combination of Ross Sea water and bottom water formed in the Mertz Polynya Region.  These can be identified by their subtle differences in salinity and temperature, as well as dissolved oxygen and CFCs.


Temperature, salinity and oxygen data from the SR3 section. [Beatriz Pena-Molino, ACE CRC]

A few years ago these repeats of SR3 and 150°E found that the properties of the Antarctic bottom water mass, the coldest, densest water in the deep ocean, are changing. It is not as dense, or salty, as it was 10 years earlier, and is much fresher than it was in the 1970s.  This suggests there have been major changes around Antarctica. Whether this is less sea ice, or more melt water is hard to tell, and the challenge that we need to tease apart.

Antarctic voyage: Photographic tips and advice Guest Work Mar 07

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Written by Adrian Bass

Date: 6/3/13
Location: 60.015577°S, 154.067054°E
Weather: cloudy, 20 knot winds
Sea state: 1-2 swell

I am a scientist, so my main aim on this expedition was to collect some good data for my research.

But a close second is the opportunity to photograph what is certainly one of the most breathtaking places I have visited. While I am far from being a professional, I like to think I have a basic grasp of photography. So I will attempt to share my experience of photographing the views and wildlife in the ice.

Basic equipment list: I am shooting with a Canon 5D Mark III, a 17-40mm 4.5L, 70-200mm 2.8L II and a 400mm 5.6L.

I suppose you can’t really ask for a better start to a trip than the dusky dolphins on the very first day. This gave me my first lesson for the trip! You never know when the animals will appear, so keep the big zoom on the camera ready to go! Fortunately, the dolphins stuck around long enough that I had time to change from my wide angle lens and get a few shots. I use burst mode at 6 frames a second to shoot fast moving wildlife and probably get about 1 good shot for every 10 photos.

Dusky dolphins . [Adrian Bass]

Common dolphins . [Adrian Bass]

One of my goals on this trip was to try my hand at taking photos of birds in flight, an area I’ve never really explored before. Spending two hours on the stern taught me a few more things, the most important being that birds can be very inconsiderate with their flight paths! Would flying in a straight line really kill them? However, after the first hour or so I managed to get my eye in, and after that I can honestly say it was great fun. Frustrating, but fun!

Bird. [Adrian Bass]

Giant petrel. [Adrian Bass]

Living in the tropics I have apparently forgotten how to dress correctly to photograph in cold conditions. This lead to probably the most frustrating lesson of the trip – always dress for the conditions and make sure your shooting finger does not freeze! My first foray into the frigid Antarctic wind taught me this, and just happened to be the first time a pod of Orcas swam past. While I got a shot, it was pretty average. A real missed opportunity. After learning this lesson both my camera, and cold weather gear sit ready and waiting on the bridge. My mistake was not repeated for the humpback whale and when we encountered a second pod of orcas a few days ago.

Orcas in the Antarctic ocean. [Adrian Bass]

Orcas in the Antarctic ocean. [Adrian Bass]

The landscape here is quite remarkable. In a way you can look out the window and wonder how you could possibly take a bad picture. While it’s true, I’ve found it equally challenging to take what I would consider a really ‘good’ landscape picture. While I have a tripod with me and would always use one on land, it has been no use on the constantly moving ship. So you have to be on your feet and have a steady hand – much easier when the seas are calm.

The daytime light can be harsh and sap away all but the smallest amount of colour and contrast, but the addition of the ship or people can give the shot a sense of depth. The long sunsets and sunrises on those rare clear days make up for all the problems, and give an opportunity to really show the beauty of the area.

Ice in the Antarctic ocean. [Adrian Bass]

Ice in the Antarctic ocean. [Adrian Bass]

Ice in the Antarctic ocean. [Adrian Bass]

Ice in the Antarctic ocean. [Adrian Bass]

Conclusions so far: photography from a research vessel is 90% frustration and 10% exhilaration. But what a 10% it is!

Adrian Bass. [Helen Bostock]

Adrian Bass. [Helen Bostock]

Antarctic Voyage: Ocean Acidification Guest Work Mar 06

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Written by Elizabeth Shadwick (ACE CRC)

Location: 62.803893°S, 147.03681°E
Weather: Cloudy, 25-30 knots
Sea state: 3-4 m swell

Pink Errina fissurata attached to pebbles on the Ross Sea slope, Antarctica at 470 m depth. Other invertebrates visible in the image are a variety of sponges and the white spiky brittle star Ophiacantha pentactis. [ DTIS camera, IPY-CAML 2008 Ross Sea voyage, LINZ]

The release of CO2 into the atmosphere by the combustion of fossil fuels (coal, gas, petrol) over the past several centuries has increased its atmospheric concentration from roughly 280 parts per million (ppm) to present day levels of nearly 390 ppm. This rise in atmospheric CO2has been partially offset by the ocean’s uptake of this greenhouse gas.

When CO2 dissolves in seawater, a number of chemical changes take place. There is an increase in the concentration of hydrogen ions (H+), which corresponds with a decrease in the pH of the seawater (or an increase in acidity). This process has recently been coined ‘ocean acidification’.

During the 20th century, the uptake of CO2 by the surface ocean decreased the pH by 0.1 units. This may not seem like very much, but we measure pH on a log scale. Should atmospheric CO2 concentration continue to rise, by the end of this century the surface ocean will have experienced larger, and also faster, pH changes than at any time in geological history.

The deepsea coral Errina fissurata, collected from the Eastern Ross Sea shelf, from 321 m, during the IPY-CAML 2008 Ross Sea voyage. [Peter Marriott]

The reaction between atmospheric CO2 and seawater also reduces the availability of carbonate. So, acidification will directly impact a wide range of marine organisms that use carbonate to build calcium carbonate (CaCO3) shells, from tiny zooplankton, to shellfish (like oysters and scallops), to corals. While there are no tropical corals in the Antarctic, deep sea corals have been found on the seafloor of the Mertz Polynya region (see blog post 28: It’s all about the critters!). Experiments on corals in aquariums have shown that increasing the CO2in seawater decreases coral growth as it becomes harder for them to make their skeletons due to the lower concentration of carbonate in the water.

The carbonate saturation state (Ω) is a threshold that determines the likelihood of a carbonate mineral dissolving. With a decrease in carbonate concentrations there is a decrease in Ω. In regions where Ω > 1.0, the formation of skeletons and shells is possible. But if Ω < 1.0, the water is corrosive and the dissolution of carbonate shells can occur. In many areas of the ocean, different water properties (volcanic gases, upwelling of deep water) cause the natural values of Ω to be quite low.

The close-up image shows pin prick-sized pores on the branches of the Errina fissurata colony. [Peter Marriott]

CaCO3 is a very interesting mineral. It is naturally more soluble at lower temperature (cold water) and higher pressure (deep water), which is very different from most salts – you will have noticed it is easier to dissolve salt (or sugar) in warm water than in cold water. This means that high latitude and deep-water ecosystems (like the ones we are studying in the Southern Ocean) are more vulnerable to the added stress of ocean acidification. This is especially true for the early life stages (larvae), which often have thinner, more fragile CaCO3shells, potentially making them more vulnerable to changing environmental conditions.

Measuring changes in the pH of the ocean is more complicated than using litmus paper and checking the colour on a chart, like you may have done at school with vinegar and milk. We are trying to detect very small changes over large areas of the ocean and from one decade to the next. This requires very careful measurements of the water properties over time. We also need to understand and separate the natural pH changes that occur seasonally (caused by a variety of processes like biological activity, mixing, sea-ice melt, and changes in temperature), from the decreases in pH that are a result of the uptake of fossil fuel CO2 from the atmosphere. Understanding how these changes in pH could influence the organisms that live in the sea is even more complicated.

See also:

Ocean Acidification video from NIWA on Vimeo.

Antarctic Voyage: The CTD Guest Work Mar 05

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Written by NIWA oceanographer and voyage leader Dr Mike Williams.

Date: 4/03/2013
Location: 63.394131°S, 149.553421°E
Weather: Cloudy, snow and rain, 25 knots of wind
Sea state: 3-4 m swell

CTD about to be deployed. [Jill Scott]

With 10 days left of the voyage we are now heading north, starting to make our way back to Wellington. As with our trip south, we are undertaking some sampling with the CTD (see previous blog posts) along the way.

The CTD is the primary research tool for oceanographers. At the heart of it are the probes which measure pressure, temperature, conductivity, and dissolved oxygen. From temperature and conductivity, we calculate salinity (i.e. how salty the ocean is). Around the CTD sits the ‘Rosette’, with up to 24×10 litre water sampling bottles. On this trip, however, we have removed 2 of these bottles so that we can mount a lowered Acoustic Doppler Current Profiler (LADCP) and Tiny oceanographic gyroscope system (TOGS).

The LADCP sends out a high frequency sound which bounces off particles in the ocean and is reflected back. It uses the return signal to determine the speed of the water going past, and so it gives us measurements of the ocean currents.

TOGS is a gyrocompass that tells us direction, without requiring a magnetic field to determine compass direction. This is particularly important this close to the south magnetic pole (see blog post 16: The South Pole). Unfortunately, this particular instrument is only rated to 3000m water depth, so it cannot be used on the really deep stations (3000 to 4500m).

The 10 litre sample bottles are open at both ends and can be triggered remotely to close at different depths. Once released the ends close, trapping the water inside the bottle so it can be brought to surface for sampling.

As the ship nears each CTD station we turn all the instruments on and reset all the bottles on the CTD, and it is moved into the cutaway – an area of the ship which has a low side for launching and retrieving equipment. After it is launched by the crew, it will take about three hours to go down to the seafloor and back again for a station of 3000 m water depth, as it takes roughly one hour for each 1000 m of water.

While the CTD is in the water several of the scientists will watch the numbers coming back from the CTD sensors, mainly to check it’s working but also to communicate with the crew, who drive the winch, about where we need to stop. The first stop is at about 15m to wait for the pumps on the CTD to turn on. The pumps make sure we have an even flow of water over the sensors. Once the pumps are on, it’s back to surface, then straight down to the bottom.

To make sure we don’t actually hit the seafloor with the CTD, it has an altimeter. This tells us how far we are off the bottom once we are less than 50m from the seafloor. We aim to sit the CTD between 5 and 10m off the bottom. If we hit the bottom we could stir up mud that might block the sensors, or if the bottom is rocky and we crash into it, we might damage the expensive instruments.

On the way back up to the surface we trigger the bottles on the rosette, allowing them to spring closed. We sample at the most interesting parts of the temperature, salinity and dissolved oxygen profiles that we have measured on the way down. The water samples are important because they give us the water we can analyse either in the laboratories on the ship, or back on shore. Although we measure dissolved oxygen and salinity electronically, the sensors are often not accurate enough. So some of the water is used to measure salinity and dissolved oxygen to check the sensors. The rest of the water is used to undertake measurements that we don’t have sensors.

The weight of the water at 3000m is 3000 times the weight of the water at 1m depth and the pressure is 300 times greater. So if we sampled surface water on the way down and took it down to the bottom of the ocean the extreme pressure would crush the full sample bottle. Empty ones don’t get crushed as the pressure inside the open bottle is the same as on the outside. The bottles are made strong enough to cope with 10 litres of water under pressure coming up, but can’t go the other way.

Antoine Martin sampling the CTD. [Aitana Forcen]

Once all the bottles have been fired, we bring the CTD out of the water and collect samples from each of the 10 litre bottles for all the different analyses. There is a strict order in which water samples are taken. Dissolved gases are taken first as they can escape into the atmosphere once the bottles are opened. So we have been taking dissolved oxygen, total carbon, alkalinity, salinity, nutrients (phosphate, nitrate and silicate) and then carbon and oxygen isotopes.

It takes about an hour to sample for all these different analyses from the bottles on the rosette, and download the data from the LADCP, TOGS and camera. While we are doing this the ship moves on to the next station. Often there is just enough time to sample before we are on the next station, then we start all over again…unless the geologists are deploying a core, in which case we might have time for a cup of tea.


Antarctic Voyage: It is all about the critters! Guest Work Mar 04

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Written by Mark Fenwick (NIWA)

Date: 3/3/13
Location: 64.92023°S, 150.066839°E
Weather: Sunny, with a few clouds
Sea state: 2 m swell coming in from the Southern Ocean

Molly Patterson (VUW) adjusting the GOPRO camera unit pre-deployment. [Mark Fenwick]

It is nearly the end of the trip and they finally let the token biologist loose to write a blog about the really important stuff: the critters!

Although the primary focus of this voyage is physical and chemical oceanography and geology (see previous blog posts), there is lots of biology to talk about. Many of the physical and chemical processes that the scientists are studying have an influence on Antarctic phytoplankton productivity (see blog post 25: The biological pump – the importance of microscopic phytoplankton), but also have knock-on effects on both local and global biological systems.

From a biologist’s point of view, understanding the drivers of any environment is very important.

GoPro video frame grab – asteroids, hydroids, coral rubble, quill worms, crinoid (sea lily). [Mark Fenwick]

Simply put, if there is no ocean, rocks, nor mud, then there are no animals. If you have been following the blog posts from this voyage, you will have seen images from our brief encounters with some of the large and small animals that inhabit this region. We have encountered whales, seals and penguins along the way, while also sampling tiny plankton. These organisms are great to see but they all inhabit the water above the sea floor. While we were on the shallower Antarctic continental shelf in water depths of 500-800m (see blog post 27: On the shelf at last!), we took the opportunity to attach a small video camera to the CTD unit.

We are using a Go Pro video camera mounted inside a purpose-built metal housing (rated to 2000m) and a set of three spot lights. We simply turn the camera and the lights on just before the CTD is deployed and then video footage is collected continuously. To get footage of the sea floor we are reliant on the CTD getting close enough (within a few metres), which requires very careful winch driving, as the CTD can get blocked by mud if it touches the sea floor.

GoPro video frame grab – crinoid (sea lily), sponges, coral rubble and quill worms. [Mark Fenwick]

The video footage helps us to ground truth our interpretations of the seafloor from the multibeam and chirp data (see blog post 26: Mud, mud, glorious mud), but the main reason for shooting the video is to get a glimpse of the fauna. The undersea fauna of the Antarctic region is diverse and is dominated by invertebrates. Already in our short “snapshot” videos of the sea floor we have seen sponges, holothurians (sea cucumbers), asteroids (star fish) and corals and a swimming crinoid (see this video we prepared)*.

The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) was set up to ensure that the unique ecosystems in the Antarctic region are not adversely affected by activities such as fishing.  Our video data will be used to report the presence of deep-sea communities to CCAMLR. The data will be added to the existing knowledge of this region, which will be used to make future management decisions.


* See the NIWA Invertebrate Collection’s Critter of the Week series, on Facebook, for examples of these creatures and more!

Antarctic Voyage: On the shelf at last! Guest Work Mar 01

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Date: 28/2/2013
Location: 66.170212°S, 147.947581°E
Weather: Cloudy with the odd sunny spell, a light breeze and very cold
Sea state: Calm and icy

Sea ice image from 26th February 2013. [NASA MODIS satellite]

Sunny, clear days definitely make this region look less formidable and give it a magical glow.

They also provide us with good sea ice images, clear of cloud, from the NASA satellite MODIS. Every day we scrutinize the new satellite image that is sent through to the ship in the hope that the area near the moorings has opened up enough to get in and retrieve them. No luck so far.

A few days ago, after a beautiful, cloudless day, we got a new image that did show an opening up of the sea ice over to the east of the Mertz Glacier, although unfortunately nowhere near the moorings. So we have made a bee-line (dodging a few ice streams) for this opening and are steaming south over the shelf to get some samples before we have to turn around and start heading home.

Iceberg scours from the multibeam. [Helen Bostock]

As we came up the slope and on to the shelf we started to see iceberg scours in the multibeam data. The iceberg scours are caused by the keel of the deep icebergs scraping along the sea floor. The scours criss-cross in different directions. As we get further on to the shelf we also see glacial lineations (lines). These are different from the scours as they are more regular and only flow perpendicular to the shelf (generally south to north). These are relics from when sea level was lower and the Mertz and Ninnis Glaciers flowed all the way out across the continental shelf. Previously, detailed mapping in this area has also found evidence of glacier grounding lines (where the snout of the glacier has been stuck on the bottom), and moraines (mounds of sediment pushed up at the side and the end of the glacier).

However, the main reason for making this effort to get up on to the shelf is to study biological productivity. While there are lots of nutrients out in the open ocean for the phytoplankton to use, they are limited by the lack of iron. In this region iron is sourced from the coastal sediments and local upwelling (see blog post 25: The biological pump – the importance of microscopic phytoplankton). Therefore, there are usually higher concentrations of phytoplankton in the surface waters over the shelf than on the slope. This increase in phytoplankton productivity will draw down the CO2 (and the nutrients) from the surface waters, which is what the chemists are measuring (see blog post 13: The carbon team).  We can also see evidence for this increased phytoplankton productivity across the shelf when we have been filtering (see blog post 25: The biological pump – the importance of microscopic phytoplankton).

Now that we are on the shelf we are able to use the underwater GoPro video camera, which has a special housing and lights that allows it to go down to water depths of less than 2000 m (unfortunately on the slope all of our stations were deeper than this). The camera is attached to the CTD frame, so the video footage is collected opportunistically at the same time as the water data. We get video of the water column, sediment on the sea floor, and also any deep-sea creatures that live down there. After the first few stations we have already seen krill swimming in the water, sea pens, sea stars, and a couple of sponges (more on the underwater critters in a future blog post).

For the above-water photographers there has also been an increase in wildlife again. We have even seen some Emperor penguins, as well as the more common Adelie penguins, and there was a pod of up to 24 orcas around the ship last night.

Emperor Penguin. [Adrian Bass]

Orcas. [Adrian Bass]

Some of you may have noticed that we crossed the Antarctic Circle yesterday. This is the southern-most latitude where, on the longest day in summer, the sun stays above the horizon.  Unfortunately we don’t have 24 hours daylight as we are well past the summer solstice. This makes it a lot harder for the officers on the bridge, trying to steer the ship in between the sea ice in the dark.

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