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Archive February 2013

Antarctic voyage: Mud, mud, glorious mud Guest Work Feb 28

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Date: 27/2/2013
Location: 66.5914˚S, 148.064901˚E
Weather: 10 knots and clear
Sea state: Calm

…Nothing quite like it for cooling the blood. Especially when the air temperature is below freezing.

Multibeam data for canyons. [Helen Bostock; data supplied by Alix Post,Geoscience Australia]

We have successfully collected a couple of cores from the Antarctic slope in between some of the CTD stations. The slope is made up of canyons and ridges, some of which have been previously mapped by other voyages using the multibeam (see blog post 6: Multibeam mapping of the seafloor). We have been filling in some of the gaps in the multibeam coverage and mapping new areas, where previously there was only limited bathymetry (depth) data.

We’ve been targeting the flanks of the ridges, rather than the canyons, for the cores because the bottoms of the canyons are often highly eroded by the water and sediment pouring down off the shelf. Some of this sediment settles out of the water on the flanks.

3.5khz chirp section. [Helen Bostock]

As well as using detailed multibeam maps to target the core sites, we also use a sub-bottom profiler or chirp system. This also works like an echosounder, but the frequency of the chirp system allows it to penetrate the upper sea bed and bounce back off any layers that have a change in density (which cause a change in sound velocity, a type of seismic line). We pick coring locations where we can see lots of layers in the sub-bottom profiler. Unlike most of our sounders the chirp system is audible to humans, so the “chirping” has become a constant companion on the ship.

The gravity corer has a 6.5 m barrel (pipe) on it and the longest core we have recovered on the slope has been a whopping 6.2 m – a new record!

Once the gravity core is on board the boat, we remove the plastic liner with the mud inside from the metal core barrel, and measure the total length.

We then cut the core up into sections of about 1 m and split each section lengthways so that we can visually describe (log) the core. We describe the colour, texture (grain size – mud, sand or gravel),and  any fossils or structures (laminations, deformation, erosional features or burrows) that we can see. We also make a note if the changes in the core are abrupt or gradual transitions.

Molly Paterson and Courtney Derriman measuring the magnetic susceptibility of the cores. [Helen Bostock]

Next we measure the sediment in the core for its magnetic susceptibility. This gives a relative measure of the changes in the amount of grains that are magnetic (so it picks out iron or magnetic rich layers). We use a long probe that looks like a ray gun straight out of a Star Wars movie, and we analyse the core every 2 cm down its length. This gives us an idea of changes in the amount of sediment that has come off the adjacent coast (or evidence for volcanic ash), as these layers often have more iron in them than the carbonate or silicate marine microfossils that make up the rest of the sediment.

The cores are then wrapped up and stored in a fridge to stop them drying out. When we get back to the laboratory we will undertake a whole suite of analyses on the cores. The exact analyses that we undertake on the core will depend on the question that we are trying to answer, but can include: X-rays (same as you get when you break an arm of leg ) to look for structures that are not always evident to the eye ; detailed grain size; carbonate and opal (biogenic silica) content; density; visual identification of microfossils or other grains down the microscope; and a whole array of geochemical proxies such as organic biomarkers, rare earth elements and stable isotopes.

We hope that the analyses on these cores from the slope of Wilkes/Adelie Land will reveal natural changes such as the extent of sea ice and amount of Antarctic bottom water formation (see blog post 21: The formation of the Antarctic bottom water) over glacial/interglacial cycles (which occur approximately every 100,000 years).

Timing is everything. How old is a 6.2 m core? We won’t know until we date the sediment. Hopefully we can date the cores using biostratigraphy (fossils that are known to originate, or go extinct, at a certain time), or radiocarbon dating (if there is sufficient organic carbon or carbonate and it is younger than 50,000 years).  Once we know the age of the major changes in the cores we can determine if they are simultaneous with other cores analysed from around Antarctica and the rest of the world. In this way we provide a small piece of information to the giant 4 dimensional puzzle of understanding earth’s ever-changing oceans and climate.

And who wouldn’t want to play with mud? It’s every little kid’s dream.

Antarctic Voyage: The biological pump – the importance of microscopic phytoplankton Guest Work Feb 27

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Writtenby  Helen Bostock (Marine Geologist, NIWA) and Elizabeth Shadwick (ACE CRC)

Date: 26/2/2013
Location: 65.111248°S, 146.056312°E
Weather: Sunny, less than 20 knots

Simplified Antarctic food web. [Courtney Derriman]

Sea state: 1-3 m swell

Phytoplankton are microscopic plants that live at the surface of the ocean.

There are billions of them in ocean surface waters, which are then grazed upon by millions of zooplankton (including krill), which are eaten by fish, which are eaten by bigger fish, which are eaten by seals and penguins (actually the Adelie penguins eat krill, just like the whales), which are eventually eaten by just a few top predators.

Thus, phytoplankton form the base of the marine food web.

Diatoms under a microscope – Odontella weissflogii, Corethron pennatum, Corethron sp., Asteromphlaus hookeri, Thalssiosira spp. [Leanne Armand, Macquarie University]

Phytoplankton photosynthesise, just like land plants, using sunlight to convert CO2 into organic carbon and oxygen (see blog post 13: The carbon team). The organic carbon is then used by the whole marine food web, and a small fraction of it eventually ends up in the deep ocean. This process of transferring carbon from the atmosphere to the deep ocean is called the biological pump.

As the sea ice melts back each summer in the Mertz Polynya, the surface waters are exposed to sunlight and there is an intense phytoplankton bloom. Due to the upwelling of nutrient-rich deep waters on to the shelf there is no shortage of nutrients (nitrate, phosphate, silicate) to feed this bloom.

The phytoplankton also need minor amounts of iron.  The iron is locally sourced from upwelling waters, dust (although this is minor in this region, it can be a major component in other areas of Antarctica) and coastal sediment.

Some of the resulting biomass then sinks to the sea floor. Thus during the brief Antarctic summer the biological pump is active in this region, transferring atmospheric CO2 to the deep ocean, via the formation of the Antarctic bottom water (see blog post 21: The formation of the Antarctic bottom water).

In the Southern Ocean and around Antarctica, the primary producers are diatoms. As well as organic carbon, these also produce a skeleton made out of silica. These silica skeletons are very intricate and beautiful under a microscope.

The filtering set up – the water is filtered through a 20mm, 5mm, 2mm and 0.45mm filter. [Courtney Derriman]

We have been filtering sea water to collect some of these diatoms (and other phytoplankton). We have also been deploying a plankton net – just like a fine meshed fishing net – to see if we can collect any zooplankton. The different species will be identified under a microscope to determine the abundance and changes in the diversity of the assemblage.

We will also use the filtered and towed plankton samples to test out some new geochemical proxies on the carbonate and silica skeletons. By comparing the geochemical values with modern environmental data (temperature, CO2, nutrients, salinity), we can produce a calibration. We can then analyse the geochemistry of the silica skeletons of the diatoms, which accumulate in the sediment cores, to interpret environmental changes over time (see blog posts 8: The geology team and coring and 22: Could the past be the key to the present).

So while plankton are not quite as photogenic as seals, penguins or whales – at least not with a regular camera as they require a high magnification microscope to view them – these creatures play an central role in the marine food web and global carbon cycle.

Ian Smith (crew) holding up the collection of plankton collected using the plankton net. [Courtney Derriman]



Antarctic Voyage: The discovery of the Mertz Region Guest Work Feb 26

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Written by Dr Helen Bostock  (Marine Geologist, NIWA).

Date: 25/2/2013
Location: 65.507326°E, 143.982206°S
Weather: Cloudy and foggy, gentle wind (<20 knots)
Sea State: 2-3 m swell

Given the issues we are having with accessing the coast due to the sea ice this year, it seems incredible that just over 100 years ago an Australian expedition landed in this region and spent a couple of years exploring.

In 1910, Australian geologist Douglas Mawson began organising a voyage to explore and chart the essentially-unknown Antarctic coastline directly south of Australia. At the time very little was known about the area between Cape Adare, lying to the south of New Zealand, and Gauss Berg, south of the Indian Ocean.

An American expedition in 1839, under the leadership of Wilkes, had previously reported land. Subsequent exploration, however, showed that most of these landfalls were incorrect and they had probably only encountered the pack ice.

A year later, Dumont D’Urville came within sight of the Antarctic Coast and named the area Adélie Land after his wife.

Mawson was well known, and had proved himself as an explorer during Ernest Shackleton’s 1907-1909 Nimrod Expedition to find the Magnetic South Pole, which was still on land a century ago (see blog post 16: The South Pole).

The Australian Association for the Advancement of Science gave their approval to Mawson’s plans and pledged a significant sum of money towards the cost of the expedition. Large amounts of funding for the expedition was provided by Australian Commonwealth and State Governments, the British Government and the Royal Geographical Society, with the rest made up of donations from the public.

Mawson’s expedition team of 35 individuals was selected primarily from young graduates from Australian and New Zealand universities. It also included a couple of previous acquaintances from his past adventures, including Frank Wild and Frank Hurley, and he recruited Lieutenant Belgrave Edward Sutton Ninnis of the Royal Fusiliers and Dr. Xavier Mertz, an expert Swiss glaciologist, mountaineer and explorer.

The expedition vessel, SY Aurora, was originally built in Dundee, Scotland, and came from the Newfoundland sealing fleet. The Captain of the ship, and second in command, was John King Davis, whom Mawson had known during the Nimrod expedition.

After being refitted in London and sailing to Australia, the Australasian-Antarctic voyage finally left Hobart in December 1911.

They initially stopped at Macquarie Island southeast of Tasmania, and dropped off a team to set up a base. The main scientific objectives were to carry out geographical exploration, biological and geological collections, and undertake meteorological and magnetic observations. As well as land-based field work on Macquarie Island and Antarctica, the expedition also sampled the ocean and seafloor during the voyage.

In early 1912 they first sighted land, which Mawson named Commonwealth Bay. On the far side of the bay was a cape, presumed to be Cape Découverte, the most easterly extension of Adélie Land. Mawson named the adjoining region King George V Land, after the British King.

They established several bases in Antarctica.

Mawson’s hut at Cape Denison, outside – taken during the centenary voyage on the RV Aurora Australis. [Nick Roden, University of Tasmania]

The main base was at Cape Denison in the middle of Commonwealth Bay. After a long winter trapped inside their hut by raging blizzards, several expeditions were sent off to explore in November 1912.

Mawson led a 3 man sledging team to the east with Mertz and Ninnis and a team of Greenland husky sledge dogs. After 3 weeks of excellent progress the party was crossing a large glacier, when Ninnis, 6 dogs, most of the rations, tents and other supplies fell through a snow covered crevasse and were lost. Mawson and Mertz rationalised their gear to just the basics and with 10 days food immediately turned around and started to head back to Cape Denison.

Mawson’s hut at Cape Denison, inside – taken during the centenary voyage on the RV Aurora Australis. [Nick Roden, University of Tasmania]

They supplemented their food supply by eating the 6 remaining dogs. However, after a couple of days Mertz began to deteriorate and died a few days later. It was unknown at the time that huskydogs’ livers contain extremely high levels of vitamin A, which is poisonous to humans.

Mawson continued pulling a sled with geological specimens (a true dedicated scientist) and the last of the food the final 160 km back to the base at Cape Denison. Unfortunately he was too late as SY Aurora had departed just a few hours before he returned. They used the radio to recall the ship, but bad weather prevented any rescue attempt; and Mawson, and six men who had remained behind to look for him, wintered a second year until December 1913.

The large glaciers in the region were named by Mawson after his companions Ninnis and Mertz. Many other geographical features were also named after members of the expedition and the ship. I recommend reading Douglas Mawson’s book “The Home of the Blizzard” to appreciate the conditions they endured on this expedition, and while others were racing to the poles, they dedicated their efforts to scientific exploration.

Mawson is considered the grandfather of Australian Antarctic and Southern Ocean Science, with a large celebration held last year on the centenary of this scientifically successful expedition.


 

 

 

Antarctic Voyage: Hump day – half way through the trip Guest Work Feb 25

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Written by Dr Helen Bostock  (Marine Geologist, NIWA).

Date: 22/2/2013
Location: 64.838758°S, 142.310661°E
Weather: 20 knots, cloudy
Sea state: 2-3 m swell

Humpback whales

We are now half way through the voyage…. it seems to be going by quickly. While most people were at lunch today, we were visited by 5 or 6 large humpback whales (12-16 m in length): very appropriate for hump day!

The whales ended up swimming and playing around the ship for a couple of hours, putting on a spectacular display for us – breaching, flipper slapping and diving. Several of our photographers got some fantastic images and videos. We will provide these to the whale experts to help them identify the individuals; the experts have named many individuals from their distinct scars and black and white markings on the underside of their tails (also called flukes), and over many years have built up a database of pictures with which they compare whale sightings.

Humpback fluke. [Sue Reynolds]

Humpback breaching. [Sue Reynolds]

Humpback snout. [Sue Reynolds]

 

Aurora australis

Clear skies over several nights this week have treated those of us on the night shift to views of the aurora australis, or southern lights.

The aurora occurs within 10° to 20° of the magnetic pole (see blog post 16: The South Pole), although during geomagnetic storms it expands into lower latitudes. It is caused by the collision of particles and atoms high up in the atmosphere: the particles originate in the magnetosphere and the solar wind and are then deflected by the Earth’s magnetic field into the atmosphere.

Interestingly, NIWA’s atmospheric research station in Lauder, Central Otago, was originally established in the early 1960s to study the aurora australis.

Aurora australis. [Mark Fenwick]

Antarctic Voyage: Could the past be the key to the present? Guest Work Feb 25

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Written by Molly Paterson (PhD student, Antarctic Research Centre, VUW).

Date:21/2/2013
Location: 65.17903°S, 141.413812°E
Weather: Cloudy with winds up to 30 knots
Sea state: 3-4 m swell

Molly logging a sediment core. [Helen Bostock]

Over the last week, while the oceanographers have been studying the hydrology of the slope, the geologists have recovered two cores.

We hope that by analysing the sediment in the cores for different proxies (see blog post 8: The geology team and coring) we will learn about past changes in the Antarctic bottom water formation and flow over glacial/interglacial cycles (several hundred thousand years).

I am a PhD student from the Antarctic Research Centre, Victoria University in Wellington and interested in much longer time scales. I am studying the evolution of Antarctic Ice volume throughout the Cenozoic (the last 65 million years). My PhD focuses on understanding of the physical mechanisms driving Antarctic ice volume and the downstream influence on bottom water circulation and sea level change.

A central question facing society today is what the potential implications of anthropogenic global warming on Earth’s climate system are. In order to help answer this question, I am examining Earth’s history during periods when atmospheric CO2 concentrations were similar to today, and global mean temperatures were in the range of those predicted by climate models for the end of the century. The Pliocene Epoch (~5.3 to 2.6 million years ago) represents the last time Earth’s climate met these criteria, particularly the warmest interval from 4.3 to 3.0 million years.

Geological drilling by the ANDRILL program (ANtarctic geological DRILLing) documented frequent collapses of the marine-based (i.e. grounded below sea level) Ross Ice Shelf, part of the West Antarctic Ice Sheet throughout the Pliocene.

The Wilkes/Adelie Land region of the East Antarctic Ice Sheet, the region which includes the Mertz Polynya, is also largely grounded below sea level. It has therefore been suggested that this region of the EAIS will be sensitive to similar processes regulating the WAIS. It is thought that the melting of these marine-based ice shelves is dominated by warming of the ocean temperatures – resulting in melting from below – with only minor contributions from the warming of the atmosphere (melting from above).

Part of my PhD focuses on understanding the processes off the Wilkes Land margin by looking at data from sediments in long drill cores that were collected by the Integrated Ocean Drilling Program (IODP) in 2010. We are interested in what the sediments can tell us about changes in the ice sheets and their sensitivity to insolation changes (solar radiation – heating by the sun). The sensitivity of the ice sheets to insolation appears to have changed as the Earth went through a relatively warmer period with higher atmospheric CO2.

So it is great to visit my study area during the voyage and get a feel for what the modern system is like. It has been good to get some hands-on field experience of marine geology – especially coring. I also hope to learn more about the polynya system from the oceanographers on board, as it is central to understanding the stability and changes in the ice shelves.

This voyage is in stark contrast to my previous field work. This time last year I was sleeping in shearer’s quarters, dodging cows and sheep, tramping through rivers, climbing up, down and over Pliocene rocks in order to collect geological samples in the Wanganui Basin, New Zealand.  These rocks provide a record of sea level changes, which were up to 7 m higher during the warmest Pliocene intervals. These sea level changes are directly linked to the ice sheet, and associated volume, changes we see in the cores from the Wilkes Land margin, Antarctica.

Antarctic voyage: The formation of the Antarctic bottom water Guest Work Feb 22

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Written by Emmanuelle Sultan and Helen Bostock (NIWA)

Date: 20/2/2013
Location: 65.114305°S, 142.304997°E
Weather: Cloudy and calm
Sea state: Calm

One of the primary aims of this voyage has been to monitor the formation of High Salinity Shelf Water at the Wilkes/Adelie Land shelf and its end product, the Antarctic bottom water.

The Antarctic bottom water can be found at the very bottom of the ocean, directly overlaying the sea floor. This cold, salty, and therefore dense water spreads across the very deep, abyssal (greater than 3000 m) plains of the global ocean and can be found as far north as the equator.

This water, which has recently been in contact with the atmosphere, helps ventilate the deep ocean by delivering oxygen to the abyss. It also plays an important role in the carbon cycle with the uptake of carbon via the biological pump (more on this in future blog posts).

Bottom waters are formed in the high latitudes of both hemispheres. In the Northern Hemisphere the densest waters are formed in the North Atlantic Ocean, in the Labrador and Greenland seas. They export the cold water from the arctic ocean into the deep ocean, which travels south via bottom currents through the Atlantic Ocean, eventually mixing with other deep waters in the Southern Ocean.

In the Southern Hemisphere, several different formation spots exist for Antarctic bottom water.

The major sources are the Weddell and Ross Sea, but there are several other source areas around Antarctica. A combination of several factors is required to make a suitable source region: the shape of the coastline, a deep basin acting as a pool or a long thin plateau, and a polynya system (see previous blog post ‘What is a polynya?’).

The Mertz Glacier polynya is a very important location for the production of the dense salty waters. Strong katabatic winds along an L-shaped polynya, over the Adelie Depression, act as a factory for High Salinity Shelf Water during sea ice formation. The High Salinity Shelf Waters pool in the underlying basin, before overflowing and cascading down the Antarctic continental slope, feeding the Antarctic bottom water. It is the third biggest source of Antarctic bottom water after the Weddell and Ross Seas.

Any change to one of the physical parameters may change the rate of Antarctic bottom water production.

The Mertz Glacier Tongue calving that occurred in February 2010 has completely changed the coastline and the ice conditions in this region. The size, shape and location of the polynya has been altered, with a resulting reduction in the High Salinity Shelf Waters that form the Antarctic bottom waters. This will have downstream effects on deep water circulation, the carbon cycle and the climate system.

As the sea ice is currently preventing us from getting on to the Antarctic continental shelf to directly measure the water in the polynya (and retrieve the moorings – see previous blog post ‘What is a polynya?’), we are now focussing our efforts on the continental slope.

We are undertaking a hydrology (water mass) survey using the CTD to look for the outflow of the high salinity, cold, dense waters flowing off the shelf down a series of canyons. We are finding evidence in the CTD profiles for these salty, cold, oxygen-rich waters just above the sea bed. The challenge now is to discriminate between locally formed dense waters from Antarctic bottom water formed in the Ross Sea and then transported west in to this region by the Antarctic Current.

We are still hoping that the sea ice might open up and let us make a dash for the moorings! Keep your fingers crossed for us.

CTD coming up. [Jill Scott]

Analysing the water for nutrients in the lab – Peter Hughes. [Helen Bostock]

CTD in the snow with Ian Smith, on the deck of RV Tangaroa. [Helen Bostock]

Antarctic voyage: What is a polynya? Guest Work Feb 21

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Written by Dr Beatriz Pena-Molino (ACE CRC)

Date: 19/2/2013
Location: 65.395795°S, 142.682921°E
Weather: Sunny
Sea State: Calm

If you have been following this voyage for the last fortnight then you may well be wondering “what is a polynya?”

Polynya is a Russian word used to describe areas of open water surrounded by ice. They occur both in the Arctic and Antarctic oceans and they are often found around the coast. These were once believed to be rare, but are now known to exist all around the Antarctic continent.

How do we know this? The answer is up there, in the sky. With the help of satellite images, our ability to say when and where polynyas occur has increased enormously. So, unlike early Antarctic explorers, we now have the assistance of daily satellite images like the in this blog post to help guide the RV Tangaroa. The only problem is that clouds can sometimes mask the underlying water.

NASA MODIS Satellite image of the Mertz Polynya area from 15th February, 2013. Location of the moorings shown by blue stars. [NASA MODIS]


But why do we care so much about polynyas?

During the winter it is not uncommon for temperatures to go down to -40 °C around Antarctica. When this cold air is blown over the frozen surface of the ocean, the sea ice insulates the water below from these extreme temperatures. However, in certain parts of the coast, some very strong “katabatic” winds blow from the land towards the ocean and push the ice away from the coast, creating the open patches of water we call polynyas.

Once the polynya has been created, the water is no longer protected by the ice and is exposed to the extreme Antarctic air temperatures. The surface waters freeze and form more sea ice, but the katabatic winds blow the ice away from the coast, allowing yet more sea ice to form. In this way the polynya becomes a very effective sea ice factory.

Sea ice formation not only shapes the upper part of the ocean around the Antarctic continent, but also affects the characteristics of the water below.

As sea ice forms, the salt crystals dissolved in the water are left behind, increasing the salinity of the surrounding water. As a result the water in the polynya is now much denser than the surrounding water and called High Salinity Shelf Water. This dense water sinks to the bottom, eventually forming Antarctic Bottom Water (see future blog posts).

Even though polynyas are a very persistent feature throughout the Antarctic coastline, they are rather delicate. Changes in the wind and distribution of ice can effectively shut down these ice factories. An example of this was the calving of the Mertz Glacier in 2010.  Since the breaking of the Mertz Glacier Tongue, the former Mertz Polynya area has been covered by some very thick ice – making it very difficult for us to get in on the ship in the last couple of years.

While satellite measurements show us the location of the polynyas around Antarctica, sea-going oceanographers still need to get in and physically measure them to understand why they occur. We need to measure temperature, salinity and current speed and direction using a CTD and ADCP (see blog post 5: The Oceanography Team).  This will provide some very valuable information about the current state of the polynyas around the Mertz glacier.

But we are here in summer and most of the “action” happens during the winter time, when the temperatures are the coldest and the Antarctic coastline is virtually inaccessible. This means that for us to measure this part of the ocean even when we can’t actually get there, moored instruments are the solution. These instruments are anchored to the bottom of the ocean and left for a year or two to record what is happening in the polynya. We still hope to retrieve a series of moorings that have been deployed in the region for the last couple of years, to download this important data.

Sea ice and icebergs. [Adrian Bass]


Antarctic voyage: Q and A Guest Work Feb 20

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Written by Helen Bostock  (Marine Geologist, NIWA) . Additional answers provided by Courtney Derriman, Jill Scott and Mike Williams

Date: 16/2/2013
Location: 65.184442°S,143.517782°E
Weather: Cloudy, then clearing to a beautiful day
Sea State: calm, 10 knots of wind, very cold!

We have received a number of questions from students at Wellington East Girls’ College and Nelson College for Girls, which we will attempt to answer in this blog post.

Image: Common dolphin. [Adrian Bass]

Typical Day at Sea

The first question we were sent by the students at Wellington East Girls’ College was “what do you do in a typical day at sea?”

Courtney Derriman (MSc Student, Macquarie University, Sydney) endeavours to explain:

My day begins at 11:30pm. That’s right; I am one of the unfortunate souls that got landed with the night shift (12 hours from 12 am to 12 pm).  I swat at my alarm to make it be quiet and then attempt to roll out of my comfy, warm bunk – thankfully I scored the bottom bunk so there is limited risk of injury. It’s then up to the ‘mess’ (dining room) to have my breakfast just before midnight.  It’s shift changeover time, so we catch up with those working during the day to work out where we are in the voyage plan.

I check my emails (my only link to the outside world) and then hopefully there is some work for me to do. Yesterday morning it was a plankton tow, so I got all dressed up in my various layers to go outside. It’s cold and snowing, and it takes about two hours to finish and clean up after the two tows.

And then, smoko time! Not that I smoke, but it is back to the mess for a cup of tea – desperately required to warm up my hands – while others such as Helen are on to their second or third breakfast for the day.

While most of the other people on my shift are involved with the CTD that is currently being deployed, I don’t have that much to do. I read for a while or watch TV until I feel like I should probably be doing something else (the guilt is killer). I update my data sheets, which are in multiple locations: like the majority of the scientists I am paranoid about losing six weeks’ worth of data. While we are on a 12 hour shift, we are not working 12 hours solidly and there is some down time between stations.

6:30am comes and it’s breakfast time (or in our case more like lunch), then back outside again to start filtering some seawater in the hopes of getting diatoms, a type of phytoplankton. The cold waters of the Antarctic are so nutrient rich that diatoms are abundant and the filters quickly begin to clog; I get out my book and wait patiently for gravity and the pump to get the job done. Then I label everything and move on to the next task.

Thankfully, it is now nearly midday and lunch time (or dinner for the night shift). With my twelve hour shift over it’s time for a shower.

Having a shower is not as easy as you think. When it is rough it is very hard to hold on to the rail in the shower and wash without falling over when the ship rolls. While we don’t have to cook and wash the dishes (thanks to Kim and Kris the cooks and Gemma the steward), we do have to make our beds and do our own washing.

I try to unwind by watching a movie or reading a book, and climb in to bed around 3pm, so I can do it all over again tomorrow.  At first trying to get my eight hours sleep at that time of day was impossible, but as week two of our voyage comes to a close, it is beginning to feel normal. Nothing exhaustion and a pair of ear plugs can’t overcome!

Food glorious food….

After mentions of the fantastic food on board, we were not surprised that we got a question about food from the Wellington East Girls College students: “What was it like for the cooks having to plan what food to take for a 6 week trip?”

RV Tangaroa cook Kim. [Jill Scott]

Jill Scott (IT support, NIWA) went to the kitchen to find out more.

The kitchen crew for this voyage consist of two cooks, Kim Ashby and Kris Solly, who work long and hard to ensure that three large meals and numerous snacks are provided for the crew and scientists every day. Being a 24/7 ship means they also leave plenty of food in the fridge for the midnight shift to eat in the early hours of the morning.

The third member of their team is Gemma Charlett, the Steward.  She assists in the mess with continual dishes and cleaning up after meals, as well as general helping, washing and cleaning around the communal areas of the ship.

So, how do the cooks plan and order the food for the six week voyage?

Chief Cook Kim Ashby started cooking on the Tangaroa 10 years ago – with 5 Antarctic voyages already under her belt she is very experienced in cooking and catering for a 6 week voyage.  When she finds out how many people will be going on the voyage, her first step is to work out how much food will be used each day. She needs to allow for any special dietary requests for vegetarians or those on a gluten- or lactose-free diet, and the gender balance as men generally eat a lot more than women. It’s then a quick calculation to multiply everything by the number of days we are at sea for, and voilà, Kim has her shopping list and the food is ordered. During mobilisation the crew spend an afternoon loading up the storage, chiller and freezer….

The day-to-day menus are then planned on a weekly basis during the voyage. With 3 vegetarians and one vegan on this voyage, Kim has tried to ensure there are plenty of salads.

RV Tangaroa’s kitchen. [Jill Scott]

According to Kim, the fresh food will last right till we get back to Wellington. The chiller is filled with boxes and boxes of fresh fruit and vegetables. By the time we are on the homeward stretch we will still be eating carrots, kumara, pumpkins, potatoes and cabbages. The iceberg lettuces have been bagged and amazingly we will still be eating them too. While bits will go ‘yucky’, we eat the good bits.  There are also lots of frozen veggies to supplement the meals.

Are there any challenges in cooking at sea?

Says Kim: While it is lovely on a calm day, rough conditions can make it quite challenging to continue to produce the same high quality meals.  However the kitchen has been modified to keep the pots on the stove and they are always on the alert to watch out for hazards in the rough. For example, there are bars on the stove to stop the pots from moving around in the roughest of conditions, and they use high pans etc.

A day in the life of a cook

RV Tangaroa cook Kris. [Jill Scott]

Kris Solly is enjoying his first Antarctic trip on the RV Tangaroa. As well as assisting Kim in the kitchen, he contributes to keeping up morale on the voyage, collaborating with Gemma to play the odd practical joke on the unsuspecting scientists and crew.

His impression of Antarctica to date is “Cool!”

Kris’s day starts at 5am with preparations for breakfast to be served at 7am. By 8am he has cooked breakfast, made some goodies and fresh bread for morning tea and prepared the vegetables for lunch. Work continues in the kitchen assisting Kim where he can. After serving lunch, he has a bit of a break and returns between 2:30 and 3pm to start preparations for dinner, making salads and cooking vegetables. He manages to fit in two half-hour workouts in the gym each day, while we are eating lunch and then before bed, and in the rest of his spare time he plays a few games.

RV Tangaroa’s chiller. [Jill Scott]

What happens to all the food waste?

According to Gemma, once we are in Antarctic waters (south of 60°S), all food waste is stored in a large, heavy blue box called a dolav (a large bin) that sits out on the deck aft of the kitchen and is returned to Wellington for disposal. Gemma is responsible for emptying the food bin after each meal.  She is on her first voyage to the ice and discovered that it is not quite as easy in the Antarctic conditions.

Gemma has to suit up to go outside, traversing the deck in the cold, windy and sometimes rough and bleak conditions. Even taking the lid off the dolav can be challenging. She will often wait and choose the right moment, waiting for the wind to die down a bit.

Have you noticed any changes now we are in Antarctic waters?

Says Gemma: “Yes. I used to hate going into chiller and freezer. Now they feel quite warm!”

 

Questions from Nelson College for Girls

1. Isabella: Are the conditions onboard, such as seasickness and cramped conditions, detrimental to the efficiency of the scientists’ mental capacity when conducting experiments?

I don’t think that anyone functions at 100% while they are at sea as all the motion (sea sickness), noise, and lack of sleep make for non-ideal conditions.  Most of the work we are doing is fairly routine, though, so even though we don’t feel our best we can still get our work done.

2. Yulan: What is the hardest part of working (doing science – my words) in Antarctica and why?

The hardest part is probably the funding and logistics.

Once you are in Antarctica, the most difficult problem that makes doing science hard is the cold temperatures. The low temperatures affect the gear, for example icing up mechanical equipment, water freezing in instruments, expanding and potentially breaking them, and batteries generally don’t like the cold.

We also have to make sure we have everything we can possibly need for the voyage as there is no chance to run out to buy stuff along the way that we have forgotten.

3. Unnamed: Do you ever get sick of seeing sea?

Currently the icebergs and sea ice are very cool. But the sea is constantly changing and even when you are a long way out to sea you usually see birds. The sunsets and sunrises can be spectacular.

4. Caitlin: How do you pick where and how far apart you put your devices?

It is a balance between time and the type, and scale, of information that you need to answer your question. So it varies all the time…

On the transit south our stations were roughly 30 nautical miles (55 km) apart – every half a degree of latitude. While on the Antarctic continental shelf, which is shallower (<1000 m), the stations are around 10 km or less apart, as they take less time and the ocean processes are smaller in scale.

5. Shannon: Where does your septic tank empty?

South of 60°S nothing can be thrown overboard. So we just have to store it and take it all back to Wellington. North of 60°S treated greywater can be discharged in to the ocean.

6. Is the boat noisy? Is there a captain constantly driving the ship? Even at night?

Yes the boat is noisy, and because it is so expensive to run a ship we work 24/7 to make the most of the time we have. The captain and 2 officers (or mates) take it in turns to drive the ship, working 4 hour shifts. The scientists and the other crew work 12 hours shifts.

7. Ella: Do weather conditions ever affect your experiments?

Weather plays a large role in our experiments. Currently the sea ice is affecting where we can go in the Mertz Polynya (see the blog post on sea ice, and future blog posts). But in general on research voyages, if the wind gets too strong, and the sea conditions too bad, then it is dangerous to deploy our instruments. Some instruments can only be deployed in really calm weather, while others can be used in reasonably rough conditions.

8. Michelle and Hannah: How do you get chosen to take part in this voyage?

If you are a student, it is studying the right subjects. Then you need to do a postgraduate degree and pick the right supervisor (usually someone who knows someone who knows someone). You also have to be willing to learn and do anything!

Otherwise, for many of us it is part of our job and we go on voyages fairly regularly. Many of the technicians go to sea a couple of times a year and have been to Antarctica many times.

9. Do you have to take the whole supply of freshwater for the trip with you from NZ?

No. We have two distillation plants, which boil and condense water to make freshwater, and one reverse osmosis plant to make fresh water from sea water. Occasionally we get told we need to take short showers and go easy on the water supply as it doesn’t always keep up with demand.

10. Tiana: Does the temperature vary much in Antarctica?

In this region of Antarctica it gets as cold as -30°C in the winter and about 0 in the summer. This morning the air temperature was -8°C, while the ocean is warmer at only -1.5°C. We have had quite a few snow flurries over the last few days, despite its being the middle of summer.

11. Nikita and Clare: Why are the surface waters constantly being checked for CO2 and plankton?

The surface waters vary due to the amount of CO2 in the atmosphere, the temperature of the ocean, the amount of biological productivity, and the windiness (which results in waves).

The oceans buffer the amount of CO2 in the atmosphere, reducing the effects of climate change. But CO2 also reacts with the water and forms carbonic acid, which reduces the pH, a process called ocean acidification. There will be a blog post about this later.

12. Does the condition of the surface water indicate the health of the rest of the ocean?

The surface waters change rapidly, and these changes are transported down into the deep waters (especially in the Southern Ocean). So yes, in some ways the surface waters tell us how the rest of the ocean is going to change.

However, higher pressures, lower temperatures, and slower circulation mean that the deeper waters are quite different and also need to be studied.

13. How expensive is the continuous plankton recorder to build and run?

They are about $40,000 to build, but they are pretty robust and last a long time. The CPR is usually run opportunistically on research voyages, and also on other ships like fishing vessels. So in theory there is minimal cost to actually collecting the plankton as the ships are already going out to sea.

The largest cost is employing the technical experts to analyse the silks and count the plankton, as this is very time consuming.

13. On the map of NZ showing the undersea floor, what are the river- like forms?

These are large canyons – or underwater rivers. They sometimes form just offshore from large onshore rivers. They form when sea level is lower and the rivers continue out to the edge of the continental shelf. Others form because of underwater landslides, while for others we have no idea why they have formed.

They are not all active – some are very old features that formed a long time ago.

14. Is it true that after a long sea voyage you become seasick from the lack of sea motion?

Yes, this is true. I personally struggle more with land sickness when I get off the ship than with sea sickness at the start of a voyage.

When I get back on land the stairs feel like they are moving under me for the first few days, and I have fallen over in the shower my first night back home on solid ground.

Wildlife

And finally, another question from Wellington East Girls’ College students asks “Have you seen much wildlife on the voyage?”

After being escorted out of Wellington Harbour by a pod of dolphins, we have only seen a few sea birds during most of the transit – although there was a rumour that someone spotted a penguin swimming when we were east of Macquarie Island.

Over the last few days, as we have been approaching the Antarctic Shelf, there has been an increase in the abundance of wildlife. The bridge of the RV Tangaroa has been buzzing with scientists and crew with binoculars and cameras at the ready. Minke and humpback whales have been spotted from a long distance, with some curious ones coming up close to the ship (and recorded on the whale record sheets in the bridge). But yesterday when we first encountered the sea ice we got the complete tourist experience.

We have also discovered that we have a talented wildlife photographer on board, Dr Adrian Bass (also masquerading as a chemist). So I will let his photos tell the rest of the story.

Orca. [Adrian Bass]

Bird. [Adrian Bass]

Seal. [Adrian Bass]

Birds. [Adrian Bass]

 

Antarctic voyage: Sea ice Guest Work Feb 20

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Written by NIWA oceanographer and voyage leader Dr Mike Williams.

Date: 18/02/2013
Location: 65.225487°S, 143.020138°E
Weather: Small storm clearing
Sea state: 3-4 m swell improving to 1-2 m

Over the last few days the sea ice has given us some of the highs and lows of the voyage.

RV Tangaroa in the sea ice. [Helen Bostock]

Antarctica has showed its treasures as we travel through the ice under a blue sky, with seals and penguins occasionally dotted on the sea ice. The photographers on board have been making the most of this photogenic scenery and charismatic wildlife (see our upcoming Q&A blog post).

We are here at the end of summer and our hope was that the ice would be at its minimum extent, with open passages (or leads) for us to get through to the coast.  In winter this isn’t an option as the sea ice is at its maximum extent. At that time, it nearly doubles the size of Antarctica – the largest annual change of any natural system on the planet.

Sea ice forms from freezing sea water. Once thick enough, it insulates the ocean from the atmosphere. This limits the ocean to a chilling temperature of -1.9°C (it’s colder than fresh water because of the salt in the ocean), while the atmosphere above cools to -40°C or colder during winter.

Pancake ice. [Helen Bostock]

The first ice to form is frazil ice. These are individual crystals of ice that are only microns in size, but they grow rapidly and form into small discs, called pancake ice. The pancakes grow by waves splashing over them, and more water freezing onto the bottom.  Eventually these grow together dampening out the waves that would break them apart. Once glued together the ice thickens to as much as 2 m for first-year ice near the coast, and around 0.5 -1 m out at the edge of the pack ice.

In winter the loose floes of the marginal ice zone (MIZ ) lie further north. Here the ice is unable to form a solid sheet, as the swell rolling in from the Southern Ocean bends and breaks the floes. As summer comes the ice starts to melt, mainly from underneath as the water warms faster than the air in the sun. The MIZ moves south, allowing the swell and the warming water to break and melt the rest of the pack ice.

By the end of summer the MIZ has retreated significantly. Much of what is left is multi-year ice. Some is first-year ice, but if that lasts another month of summer it will become multi-year ice as well.

The multi-year ice is thicker and more convoluted in shape, the result of wind, which pushes one floe over the top of another. This is then covered with snow, leaving the multi-year ice up to several metres thick.

It’s the MIZ we had hoped to sail through to get in to the Mertz Polynya (see upcoming blog posts). On Saturday night, however, the captain announced that the ice was too bad. We won’t be going any further south unless the situation changes significantly. This was the low the sea ice delivered. We are unlikely to be working on the continental shelf this year. The ice has put plans A and B (see blog post 2) out the window.

So we have moved to Plan C. This will focus on the continental slope looking for the outflow of heavy dense water which overflows from the continental shelf down the canyons (see future blog posts).

The first discussion about Plan C was at 4 am. Now, in daylight a couple of days later, and with more satellite images of the current sea ice situation, we can see it is the best decision, particularly as we struggle to slowly move north at 1 knot, the ship shuddering as we push aside the ice floes.

Also in amongst the first year and multi-year ice there are patches of pancake ice starting to form. We don’t want to get trapped. Better to be safe than sorry.

Antarctic voyage: Sailing through thin ice Guest Work Feb 19

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Written by Helen Bostock (marine geologist, NIWA)

Date: 17/02/2013
Location: 65.627268°S, 144.277825°E
Weather: Cloudy, calm and very cold
Sea State: Calm

Over the last few days we have seen a lot of icebergs and have been skirting along the edge of the sea ice.

‘Patience….’ is the main advice of our Danish ice pilot, Arne Sorensen, when sailing the ship through areas with sea ice.

‘Slow and steady. The force of the impact if we hit the ice is related to the square of the speed that the ship is travelling at. So the faster you go, the more likely you will damage the ship.’

sea ice

Sea ice [Adrian Bass]

The RV Tangaroawas built in Bergen, Norway, in 1991. She is not an ice breaker. But she has an ice strengthened hull, and is an ice 1C class ship. This means that she can push her way through light ice floes of up to 0.4 m thick.Arne has been to Antarctica 20 times and the Arctic over a dozen times on a wide range of ships, with different missions. He has spent the last few years working specifically as an ice pilot, advising and training ship’s officers to negotiate icy conditions.Arne started going to sea when he was 16 years old as a cadet for a Danish shipping company. His father had been a sailor and then worked in the lighthouse, and his older brother was already working on ships. As a cadet he had to work on the deck, as well as learning how to be an officer. In Denmark they have compulsory national service: naturally, Arne spent his with the navy. After that he continued working on supply ships as a mate and then a Captain, and spent a couple of years working in eastern Greenland. Then he started coming down to Antarctica.

He says there are some differences between the sea ice in the Arctic and Antarctic. There is more multiyear ice in the Arctic (sea ice that hasn’t melted during the summer). First year ice has more salt in it and is “spongier”, while multiyear ice is harder and thicker.

Sea ice

Sea ice [Adrian Bass]

 In the Antarctic there are a lot more large icebergs, some of which get grounded on the shallow banks on the continental shelf. The icebergs affect the distribution of the sea ice. The east of an ice tongue, or ice berg, is usually iced up with “fast ice” (unlikely to break up and melt). This is due to the direction of the winds which transport ice from east to west. But you can’t assume that it will be the same every year, and the conditions can change very quickly.Arne is now retired. He chose to come on this voyage as he is interested in the science and still enjoys the challenge of navigating through the ice. “It is a balance between being cautious and trying to get the job done.”Evan Solly, the master, has been down to Antarctica 8 times, 7 times on the RV Tangaroa, while first mate Ian Popenhagen has been 6 times. So between them and the ice pilot they have 35 years of experience working in these icy conditions. Second mate Daniel Hayward, who is on his first trip to Antarctica, will benefit with expert training from them all.

Many of the crew have also been down to Antarctica before. Mike Steele, the bosun for the last 36 years, has been down many times. He is thankful for the improved clothing that they now have to cope with the extreme conditions, though he still isn’t completely satisfied with the gloves… Despite this, I feel we are in good hands.

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