Western Ross Sea – NBP15–02, 2015

From January–March 2015, the US icebreaker and research vessel Nathaniel B Palmer will be home to marine geologists, geophysicists and palaeo-glaciologists on expedition in the western Ross Sea, Antarctica. The expedition objectives are to decipher how the Antarctic ice sheets behaved during their previous glacial expansion onto the continental shelf, the interplay between the outlets of the Western and Eastern ice sheets, and the dynamics and stability of ice sheet retreat during climate and ocean warming following the last glacial maximum. The Palmer sails from McMurdo Station, on Ross Island, Antarctica on January 23rd, for 40+ days of geophysical survey and sediment coring of the glaciated seafloor shaped by the past activity of the Antarctic ice sheets. Sarah Greenwood from IGV is participating in the expedition.

 Sara will be writing a field blog starting January 18

 

Last night at sea
Land is in sight! The transit has been remarkably kind to us, the weather seeming to behave more or less as forecast. We’ve ducked and weaved and zigzagged our way between the pressure systems that line up to batter ships daring to sail this part of the ocean, and emerged relatively unscathed. We entered Australian waters mid-afternoon yesterday, and 24 hours later we were creeping into a broad, cliff-lined bay from where we’ll sail into Hobart with daybreak tomorrow. The air smells of salt and land, and humidity is an odd sensation.

Science has been packed up, boxes and hard drives filled, and papers planned (started, even!). Hallway conversations continue to strike up with suddenly remembered ideas to pass on. Transit time has been no less busy than science time. Old routines die hard, and I’ve stayed on a night pattern. After days of fog, the winds swept the skies clear and brought out the stars and, more than I’d hoped for, a dancing aurora over the last 3–4 nights.

Tomorrow: land. This experience has been like no other, I can’t even begin to sum it up.

Aurora australis. Photo by B. Demet

 

Science is over!
At 5am on Monday, 45 days of Science came to an end. We’d shifted our plans with the winds in our final survey area, and I guess someone had a word with the sea gods because the waters calmed down enough to get some decent multibeam data in the end. The weather gods had other ideas, throwing a snowstorm our way in the pitch dark, reducing visibility and the ship’s speed, 2 hours out from our final core site with the clock ticking down to handover. Another quick change of plans and, fortunately, a short-lived snowstorm (though one that had me pretty worried!) and our final core came up on deck at 04.40. Perfect timing!

The tally:

  • 15042 km survey lines
  • 980 hours of multibeam collection
  • 420 GB raw, unprocessed geophysical data
  • 66 kasten cores
  • 7 jumbo piston cores and trigger cores
  • 1 jumbo gravity core
  • 1 box core and 7 grab samples
  • >134m of mud


So now we’re in transit, and in transition. Hobart beckons, 8 days away across the raging Southern Ocean. Routines are no longer, the normal structure of a science day is broken. Most people have transitioned from shifts to a normal working day, and this will hopefully be a time to finalise datasets, prepare all our samples and geophysical data to take away from the boat with us and, with a bit of luck, discuss our interpretations and plans for paper writing. Science acquisition might be over, but there’s still a lot to do. Seasickness depending...

I’m in fact still working through the night. In practical terms, it relieves pressure on the geophysics computers. Mostly though, there’s a calm about the night shift that I’m not quite ready to give up. It has been the time of the most spectacular vistas, and I wouldn’t change those magical moments for anything. Two days of fog hasn’t granted me any more starry night views, yet, but I’m still hoping!

Night-shift.

Night-shift.

Night-shift.

 

Be careful what you wish for
I asked for some wind, to disturb the forming sea ice and give us some open water and clean data. 40 knot winds and breaking waves was not what I had in mind. The blue and white skies and seas look beautiful outside; my multibeam computer screen is not, however, a pretty sight. I guess I should have been more specific in my request.

 

Shelves, tongues, bergs and pancakes
You may think ice is just ice. White(ish). Frozen(ish). In the last six weeks (yes, six weeks today!) we’ve seen a whole host of many weird and wonderful forms that ice takes in and around the oceans. The giant, imposing Ross Ice Shelf, a floating body fed from the interior grounded ice sheet, nearly half a million square kilometres, the size of France. The bergs that calve from it, sculpted by the waters and the weather, some huge and immovable and others bobbing along by the ship. The solid plates of last winter’s frozen seas back in the early days of the cruise, and now in the last 48 hours we’ve seen grease, sugar, new grey plates, fingers and pancake ice forming. Today on a stunningly beautiful morning, the ice sheet’s outlet glaciers through the TransAntarctic Mountains loom shining in sunshine on the horizon, whilst we creep past the frankly freakish Drygalski Ice Tongue, an 80 km long tongue of ice that protrudes essentially unsupported from the David Glacier, over water >1000m deep. Gone are the open oceans and easy multibeaming of the Eastern Ross Sea. We’re back to easing our way around the sea ice, but Antarctica feels more present over here.

It’s crunch time now. Science is due to end at midnight Sunday night, and almost every hour there are calculations being done, planned tracklines re-measured, the absolute necessity of every track and every remaining core re-evaluated. All the while the season is closing in on us, the seas are freezing up before our eyes.

Drygalski ice tongue in front of the TransAntarctic Mountains.

Pancake ice. 

All Change
We’re back in the West (or East, depending on which way you look at things). The 2nd leg of my part of the cruise has begun. The internet has returned. The Sun’s made an appearance for the first time in a couple of weeks... and begun setting and rising. Nights are becoming night. We’ve left behind the calm winds and seas of the LSU group’s survey area and found ourselves in some sort of perpetual choppy water. Science “plans” are consequently in constant flux. Welcome to the Antarctic!

Sunshine It' s been a while.

 

JPCs, KCs, XBTs, MTs, ETs, MMOs & OCD
Just as there’s a whole new way of life on this boat, there’s a whole new language. Acronyms just start rolling off the tongue.

We’re wrapping up the huge area of multibeam survey now, and a lot of people are rather happy they have something active to do again! It’s coring time: 6 Kasten Cores and 4 Jumbo Piston Cores in 24 hours. We’re not processing the JPCs on board, but there’s still a lot of mud on the table in the Lab to be cleaned up, described, logged, sampled and archived. And the MTs on the back deck have been working flat out to turn around core after core after core. We’re targeting various grounding zone wedge surfaces in the complex that we’ve mapped with the multibeam, with our key aims being i) to recover enough material for radiocarbon dating of the timing of ice retreat from the continental shelf, and ii) to determine the development of an ice shelf and its relationship to the retreat dynamics, based on the types of sediments we recover.

When the JPC operation is all wrapped up, we’ll be heading out to the continental shelf edge to re-start the aborted seismic line. We’ll do some final patching up of a few multibeam holes en route: my neurotic tendencies regarding systematic (or lack thereof) data acquisition have been widely noted...

The JPC deploys and a mud coated barrel returns.

Scraping mud off the JPC barrel.Capping the JPC trigger core.

Scraping mud off the JPC barrel./Capping the JPC trigger core.

Routines
I guess before I left I’d been worried life on board would get monotonous. There is a world of difference, though, between routine and monotony. It’s true: every day is essentially a copy of the previous. I come on shift at midnight. Take a look at where we are, what we’ve covered in the hours I’ve been asleep. Though it’s only ocean and more ocean and more ocean around us, for some reason it’s still important for my brain to know whether I’m looking out to the north or south. I check where we’re at with data import, processing, multibeam editing. There is always multibeam editing to do. Dot killing, as the students refer to it. All the early geophys data is processed and finalised now, so we can begin to work with it: landform mapping, stratigraphy mapping, building interpretations, and fixing up our plans for the 2nd leg in the Western Ross Sea. At some point in the early hours I head up to the Bridge with a cup of coffee for an injection of light, vista, the perspective that being on the 5th floor gives you rather than down in our lab right in the belly of the boat. These early to middle hours of the shift are peaceful, when the majority of day shifters have gone to bed and before the non-shift, normal working day folk get up for breakfast. After breakfast is always an energetic time. People are getting up, wanting to know where we are, what’s come in overnight. This is talking time, and science time. Look at this here, what do you think about that there?...

It’s always the same, and yet every day is different. Each ‘morning’ the sea and the sky look new. The light (or even the dimness that’s building in the early hours now) that streams in through the Bridge windows is always different. The data’s only a continuation of the patch we just covered, but it’s brand new, not seen before, and always throws up new questions, ideas, points for discussion, things to cross-reference between our different datasets. Routine, but definitely not monotonous. 

 
Never get tired of these.

Never get tired of these.
 

Multibeaming
After the first week or so, when objectives, locations, methods deployed, not to mention sleep patterns were in a state of constant change, we’ve now settled into a phase of steady geophysics survey. The seismic survey was called to a halt prematurely, half way down the final line, by a sudden explosion of a kind that’s not supposed to happen on the airgun. The streamers were hauled in, and we began a large multibeam survey area a little earlier than anticipated while the MTs (marine techs) fix the problem.

We’ll come back to finish the seismic line later, and in the meantime are painting the seafloor with the multibeam over a large area of the outer continental shelf. I think there’s quite a few folk itching to do something other than sweep back and forth, back and forth, but from my perspective it’s immensely satisfying to record such a large area with continuous data. With fantastic data quality (much better than I’d expected) and extensive coverage we really have a spectacular – and unprecedented – view of the last glacial grounding zone system here in the Whales Deep.

Our first taste of stormy weather at the end of last week inflicted a few casualties (to both personnel and data quality). The Dry Lab took on a slightly different outlook, with bodies on the floor, trying to keep Watch with as little movement as possible. Others explored various vantage points on the ship to look out over the spectacle, the dark swirling seas and 15–20 ft waves crashing on us from all around (and yes, in 2½ weeks of being on an American ship I’ve lost the ability to speak metric). It was pretty impressive. But if that’s all the weather we get during this trip, I’d be ok with that.

The Lows seem to be leaving us alone right now. The Sun’s out, the water’s flat and littered with organic-looking patches of ‘sugar ice’, the data’s coming in beautifully, England kicked off this year’s Six Nations rugby with a win in Wales... all is right with the World.

Stormy seas.

 

More important than Science?: the Superbowl
BBQ lunch, and an afternoon gathering up on the Bridge while we get play commentary over the phone. The internet’s down, you know...

 

Time travel Pt 2
Travelled a little too far it would seem: back to an internet-less World. We’ve entered the absolute epicentre of a satellite no-coverage zone, stuck between the Americas and Asia-Pacific, and we’re set to be here for some time. Conversation around the ship invariably comes back to ‘well if we had the internet...’. Or simply dwelling on ‘29 days...’. Trials and tribulations of being at sea in the 21st century; how will we possibly cope?! I’ll keep on writing – at some stage this will make it into the Outside World.

Deploying the seismic airgun.

Science continues relatively unabated. We’re a few days into Phil’s project now, and the next suite of techniques for studying the seafloor has been deployed. After playing for an hour or so with an underwater camera deployed almost down to the seabed off the ship deck (amazing quality of images of the modern ecosystem at the sediment surface) we got into position for three long seismic lines across the whole span of the continental shelf. Seismic signals penetrate deeper down into the substrate than the chirp acoustic subbottom profiler we’ve been using in the western Ross Sea, so we can record reflections from strata buried much deeper (and therefore older), albeit at a lower resolution. And in contrast to the chirp and multibeam, which are mounted on the ship’s hull and emit a short clicking sound, the seismic pulse is fired from an airgun towed ~60 m behind the ship. I think those of us who’ve never been involved in seismic collection before naïvely thought we’d hear something. But instead, we see only the faintest illumination and shudder of the buoys that keep the airgun just below the water surface.

Our long lines bring us relatively close up to the front of the Ross Ice Shelf. It’s a formidable sight, the solid white wall rising up out of the waters, even though it’s relatively lowlying. Turn around, your path is blocked here.

 

 

Glacial lineations and marginal landforms in our multibeam dataset.

The Ross Ice Shelf looms through sea smoke.
 

Time travel
Travelled East, and woke up in yesterday. We’re in the Eastern Ross Sea, one of the westernmost parts of the World: we just crossed the 180 longitude line, and therefore the International Date Line. The ship’s operating on New Zealand time, and the geophysical equipment is operating on GMT. I’m working the night shift in broad daylight. Confused? Good. You’re not alone.

 

Sea ice and science
The sea ice is not part of our science. Though perhaps no one’s told it so – it seems to want to creep up on us from any direction, at any moment. Sea ice has been a tale of our first couple of days’ science, chasing us out of open water embayments and leads. We lasted 10 hours before having to change our course, and our plans! Although we’re on an icebreaker ship which can easily get through the summer sea ice, the ice interferes badly with the two types of sonar we’re running, and there’s simply no point in collecting bad data if we can be at all flexible about exactly where we survey. Having said that, where we’ve found open water (and the ship’s crew have been excellent at steering us into the best areas possible to collect the best data we can – and putting up with our last minute requests and changes), we pieced together a great patch of data over southern Drygalski Trough in the first 48 hours of the cruise, and I’m very happy with the quality of data collected: long may it last!  

Kasten coring in the Drygalski Trough.

Our primary targets are the glacial deposits of the last (de)glaciation that cover and form the seafloor here on the continental shelf. My group is using multibeam sonar (to generate a high resolution depth model of the sea floor), chirp sonar (to ‘see through’ and record the stratigraphy of the upper ~20m or so of sediment) and we’re taking a large number of sediment cores to directly sample the surface and up to 6m of buried sediment. The sonars have been logging since we left McMurdo and will do so for the remainder of the cruise, more or less, and we’ve 5 cores in the bag to keep those folk who like to play with mud and bugs happy. Grounding zone wedges have been the story of these first survey days: large deposits which accumulate at the front of the ice sheet, at the point at which ice no longer sticks to the seafloor but begins to float. We’ve recorded these in all manner of forms and positions in and around southern Drygalski, an area that’s been very poorly surveyed until now. Our data should give us a great handle on retreat of the last ice sheet here. It looks like our cores reached down to the sediments deposited at or close to the time/position of ungrounding, which will give us even better insight into the sediment processes and environments at the grounding zone and, we hope, the timeframes for retreat across our study area.

Drygalski’s done – for now. We’re running a line down Joides and then Pennell troughs to get preliminary survey coverage for this first part of my group’s cruise time, before we head East to Phil’s area. We’ll be back here in a month or so, and have plenty of food for thought in the meantime.

Ruthie Lauren from Rice Univ. looking at the chirp sonar output coming in.

Sea ice.

Next stop: Hobart
We’ve been at sea for two days now. At sea and at science: we turned the multibeam on as soon as we had got through the sea ice around McMurdo and had open water beneath us – a couple of hours after the crew hauled in the ropes at the station. We're collecting data! For the next 42–43 days we will be traversing back and forth across various sectors of the Ross Sea (see the updated maps on this post). In our planning we’ve identified key areas based on pre-existing data, based on the lack of pre-existing data, and based on our hypotheses of past glacial dynamics in these areas, where we want to collect new geophysical data and sediment cores.
 
“We” is a group predominantly based at Rice University, in Houston in the US (the project I’m a part of, focussing on the Western Ross Sea with Principal Investigator John Anderson: www.earthscience.rice.edu ) and a group from Louisiana State Univ, working in the Eastern Ross Sea with the Chief Scientist on board the ship, Phil Bart (www.geology.lsu.edu ). We’re a small group – just 15 scientists – and since we have rather similar scientific themes for this cruise, we’ve joined forces and all hands are working shifts together.

These first few days, we’re working in my group’s area in the Western Ross Sea. Late tomorrow we shall head out east, to the Whales Deep in the Eastern Ross Sea where Phil and his group will work for the next 3–4 weeks before we head back west for the final couple of weeks of the cruise. It’s begun!


(Click on the images for larger images)

 

McMurdo
We made it! Boomerang bags were not needed, though it was apparently a close call. We landed on McMurdo Ice Shelf (a tongue of floating ice, a couple of hundred metres' thick over nearly a kilometre of water to the ocean floor) in snowfall and pretty sketchy visibility.

With smiles and excitement all round – even the old hands, I suspect – we piled out onto the snow. ‘Town’ was fairly bewildering at first. “It’s just round that khaki coloured building over there”... as I looked out on a mass of brown industrial looking sheds and containers and dorm buildings.

Two days later and it feels like I’m getting the hang of things, and it’s a shame we’re not here for longer – there’s hikes to do, ski trails to explore, penguins to track down... they are noticeably absent around the station right now, just some seals lazing the days away out on the ice.

The station area is a strange mix of industrial drab, engineering surpassing the challenges of the wilderness, and breathtakingly beautiful, depending on which way you’re looking (literally and metaphorically). The view from the library window of the Crary Lab is simply captivating, it draws you in and doesn’t let go. Mt Discovery and the Royal Society range loom in the distance across the white plain of sea ice, with wispy banks of cloud drifting around through the day so the view never seems to look the same – there’s always a glimpse of something new. My office view back at IGV just isn’t going to cut it!

We’ve spent the last couple of days checking sea ice conditions, rehearsing plans and strategies, discussing lab space and geophysics protocols. Tomorrow we move from our dorms on the station down onto the boat. Time to finally move on from the planning, and get to work!

Boarding in Christchurch. TransAntarctic Mountains from
the inbound flight.
The Palmer breaking ice
on the way into McMurdo to meet us.
 

The Waiting game...
We should have flown to McMurdo today. Instead: another baking hot summer’s day in Christchurch. Our shuttle to the US Antarctic Program base out at the airport was due to pick us up at 6.15 this morning... then it was 8.15... 11...   “I’m sorry, you won’t be flying today”.

We’d been warned this could happen. We fly on a US airforce C130 Hercules, on a journey which will take around 8 hours across the Southern Ocean and down along the TransAntarctic Mountains. Any sign of bad weather, and the plane will turn around and come back (‘boomerang’) to where we started. Or, in our case, won’t even leave. So instead we’ve spent the day catching up on work, planning, catching the last of some summer sunshine...waiting...


Over the past 2–3 days, our team has assembled here in New Zealand, along with various other groups of cruise support staff and folks heading to McMurdo. USAP runs a fairly large operation here in Christchurch with, it seems, a number of groups deploying and returning on a weekly basis at this time of year.

Yesterday was kit issue and flight orientation day: a couple of hours at the USAP base form filling, watchinga series of video briefings (“when you get to McMurdo you’ll get yet another briefing: that one will be shorter and more to the point”) and, with a fair degree of amusement, trying on our flight clothing – the extreme weather gear that we have to have with us at all times. ‘Michelin Man’ doesn’t even come close.

6.15 tomorrow morning is our latest departure info. Boomerang bags are packed. Let’s hope we don’t use them.

Expedition Log
by Sarah Greenwood
Department of Geological Sciences
Svante Arrhenius väg 8, SE-106 91 Stockholm, Sweden | Phone: +46 (0)8 16 20 00 | Web administrator ines.jakobsson[at]geo.su.se
In case of emergency call (08) 16 22 16 or (08) 16 42 00