We’re hiding from the storm in the sea ice. Open water is on the horizon beneath the bruised clouds. Photo: Craig Stevens
Ross Sea Voyage Update #9: Sheltering in sea ice
At the end of the last update, we’d headed for shelter along the Victoria Land Coast. Now we’re sitting in pack ice a few kilometres off Coulman Island (a little south of Cape Hallett) waiting, again*, for weather to improve.
More about weather
The Southern Ocean is typically a sequence of major weather systems circling the planet at around 60’S, with brief periods of respite in between. Much of the energy passes by to the north of us but we’re not protected from some events, especially big southerly fronts that come across the Ross Ice Shelf and channel up the Victoria Land Coast.
On the ship, we have information at our finger-tips – weather forecasts, sea ice maps, GIS tools, Argo data – plus a wealth of experience. Plus, with the improved internet connectivity, we all have access to tools we’d use back home. However, none of this was much help with the present storm, which came from a direction that left us with nowhere to hide. We ended up squeezed into the edge of the pack ice, pointed into the waves. While designed for moving cargo and breaking ice, it’s fair to say the Laura Bassi is not designed for riding waves in anything like comfort. Scientifically, there’s lots of interest is seeing how waves penetrate into pack ice….less so when it’s you that’s rolling back and forth!
*A note on the weather: while we've had a few delays of bad weather, they've been short and sharp and well-signalled in the forecasts, so we've been able to maximise sampling. On balance I think we are doing generally okay in terms of operational time.
Mt Herschel across the sea ice. Photo: Craig Stevens
Italian moorings
The location where we chose to lodge in the pack ice is offshore from Cape Hallett on the Victoria Land Coast. Cape Hallett has been the scene of significant science activity, including a substantial base occupied until the early 1970s, and is overlooked by the very substantial Mount Herschel (3335m).
The Italians maintain a mooring deep within Edisto Inlet, the bay tucked in behind Cape Hallett, at the foot of Mt Herschel, as part of the excellently named LASAGNE program. It will require some shifts in sea ice to access this mooring. We’ll see how conditions evolve but continue to hope.
It’s been very useful participating in the voyage to see how the Italian science projects are structured. The Italian MORSEA programme is long-term and sustains most of their moorings in the region, whereas much of the rest of the activity is built around year-to-year project work. A PNRA (Programma Nazionale di Ricerche in Antartide) voyage is a combination of projects – there are five on this present one. They have a separate “Party Chief” to coordinate and act as a focal point between the science priorities (including the New Zealand team’s activities) and the bridge operations.
Mooring deployment. Photo: Lana Young
Early Career Researchers
The MAC3 Impact Philanthropies cohort of Early Career Researchers (ECR) have been meeting regularly to develop a framework for collaboration and sample design for future expeditions. Not only are they looking at how the present work might be developed, but they’re also discussing very ambitious singular ideas that might suit a high-profile new science initiative. It’s a work in progress, as there are confident ECRs mixing ideas with early-stage PhD students, plus different languages (mindful that the New Zealand team is very international in composition too).
It's been a very restorative experience for me, watching the ECR team build confidence and develop their ways of interacting to bring the most from each of their strengths. This is a model that I think could be rolled out for future voyages that have a substantial student cohort.
Cross shelf, collaborative ocean research
We departed the relative shelter of the Victoria Land Coast for around 36 hours of sample activity before arrival of the next weather front.
We traversed the Drygalski Trough; this deeper passage extends from the grounding line of the Drygalski Ice Tongue and the David Glacier to the continental shelf break, so the ocean water takes a journey of around 450 km. As such, it’s a conduit of cold, salty, oxygenated water that finds its way into the cascade point, where much of the water draining off the continental shelf enters the global thermohaline system. This is a critical monitoring point for so many processes in the region.
Another great aspect of the improved communication is being able to contact colleagues on other research voyages and check in with what they’re seeing in terms of ocean properties. Work seeking to understand this cross-shelf transition along the sequence of north-south troughs requires stitching a lot of different data together. This is where FAIR data principals come into play (Findability, Accessibility, Interoperability, and Reusability). The Southern Ocean Observing System (SOOS) plays a highly visible role in this, developing tools and awareness around what data exist.
In the case of the Drygalski Trough, there are Italian moorings at key locations in the western Ross Sea. New Zealand has hydrographic data from a number of key locations, including the Drygalski Ice Tongue and the continental shelf break near Cape Adare. Korean work includes substantial hydrographic surveys in key regions.
SOOS works to raise awareness of these datasets and to promote findability tools. Three members of the SOOS Ross Sea Working Group are aboard – Paola Rivaro, Pierpaolo Falco and myself (Craig Stevens). We work with several other working group members, including New Zealand based co-Chair Michelle LaRue (University of Canterbury). One of the initiatives the working group has taken recently is to conduct a search for an ECR member to revitalise the perspectives of the team.
Recovering the sediment trap. Photo: Craig Stevens
Sediment trap recovery
We headed a little north of the continental shelf break to recover a sediment trap from Wilson’s Canyon. This had been deployed a year earlier by RV Tangaroa as part of an Antarctic Science Platform-funded opportunity project led by Dr Katie Maier (NIWA). The project looks at flows down submarine canyons i.e. the cascading described above.
A sediment trap is about as difficult as you can get on an ocean mooring – it’s large, cumbersome, involves mechanical operation and generates physical samples. Deploying these moorings in canyons at depths of 2km is challenging. Care is needed for it to land where you want and not drag down the side of a rock face. And recovery can be equally testing. As it was, when we passed over the mooring location with our echo sounder on, we couldn’t spot the moored gear and feared it had been buried in a mudslide.
Nevertheless, the NIWA moorings team (Jasmin McInerney and Craig Stewart with PhD student Liv Cornelissen) tried signalling to the mooring with an acoustic transponder to check if it was there. No response. They then tried a second transponder/release pair, with the same result. The ship repositioned. Again, no good. Then, finally, a combination of position, transponder and jiggling the line got a response back from the seafloor equipment and the mooring was released to begin its 20-minute journey to the surface.
We all lined the windows of the bridge to spot where the floats would surface. Liv Cornelissen spotted it first, only a hundred and fifty metres away. The skilled Italian deck crew made short work of the recovery and we sent Katie the good news. There’s nothing like participating in these operations to bring a new perspective on the hard-won nature of ocean data, especially in Antarctic oceans.
Anthoathecata (thecate hydroids) that had grown on the mooring gear at 2 km depth. Image ~5cm across. Photo: Craig Stevens
Once the gear was aboard, the University of Otago team attempted a multicore at the site, but were thwarted by the subtly declining weather conditions. A later attempt is planned.
With more success, Dr Svenja Halfter (NIWA) and Georgia Pollard (University of Waikato) were able to take another plankton net trawl. Then we ran a line of CTDs along the shelf edge for the Italian sampling. We now head south for shelter from the next weather front.
This update was sent from the ship by Prof. Craig Stevens, New Zealand voyage leader and revised by the New Zealand-based communications team.
Map showing recent activities and locations mentioned in this update.