Our run South with calm seas has continued. The Southern Ocean is usually described as being filled with huge waves and strong winds, but not this time. This good fortune has enabled us to make an excellent start on one of the newer components of the voyage – looking at how biology and physics interact at the Antarctic Polar Front.
The Front is where cold Antarctic waters meet the warmer waters to the north. It is described in textbooks with nice bold lines, but the reality is that it can be a complex mix of eddies and subducting layers beneath the ocean surface. This is made even more intricate because the Campbell Plateau at the southern bound of Zealandia - the submerged continent that Aotearoa New Zealand is part of - is one of the major pinch points for the Front. So as the ACC flows to the east, it has to squeeze past the Plateau, getting very messy and nothing at all like the text-book bold line on a map.
This complexity gets amplified when you add in biology and how living things survive in this environment. NIWA’s Dr Alina Madita Wieczorek conceived a pilot experiment to sample biophysical properties across the Antarctic Polar Front with the Conductivity Temperature Depth package (CTD)*- an ocean profiler and water sampler - and then use eDNA to see if there is a connection between physical structure and measured ecosystem properties when viewed through residual DNA.
This helps us connect between the physical setting, the plankton-filled background biology, the larger fish and marine mammals. Critically, we know that this frontal structure will change with a warming ocean, but not the details of how, or what the impacts will be.
It was great to see the CTD come up on deck and the team swarm around the sample bottles to get processing going – all at 3am. It is noted the University of Genoa’s Marco Grillo gets the MVP award for enthusiastic sampling.
This was immediately followed by Dr Svenja Halfter’s net-tows to get samples of some of the larger species affected by the changing water. The sorting of the sample species ends up looking like a bento box, and the successful sampling made for a nice birthday present for me 😊.
Work continued as we then hunted for the southern side of the Polar Front, which took much longer than we anticipated. The ocean surface temperature stubbornly stayed warm (~3.5 °C) but then after twelve hours we sailed into ~ 2.5 °C water and we knew we were into Antarctic waters. At that point Alina, Svenja and team repeated the sampling of the previous night – the main difference being everyone was wearing more layers!
Alina’s experiment evolved out of the 2024 Joint Italy-New Zealand Laura Bassi voyage, funded by the Antarctic Science Platform (ASP), where we got to shake down the approach. Unfortunately, on that voyage the conditions over the Antarctic Polar Front were not good for sampling.
So now, a year later, with the ASP again supporting a voyage, and additional funding from NIWA’s SSIF Strategic Voyage Fund and collaborative support from India’s Centre for Marine Living Resources and Ecology, Alina was able to give it a proper go.
An additional milestone was achieved as we sailed south – we “Crossed the Line”. On this ship the line is 60 degrees south. It is a tradition to award first-timers with a ceremony, costumes and a certificate as they do at the equator (but colder). With a large part of our contingent students, or more used to working further north, we had a good number of first-timers. What I wasn’t aware of was that I had to wear a Superman costume.
This northernmost part of our work programme emphasises the Southern Ocean aspect of the research. It is easy to be captured by the amazing Antarctic scenery and discoveries, but, as our primary strategic guide, the Ministry of Foreign Affairs and Trade Aotearoa New Zealand Antarctic and Southern Ocean Research Directions and Priorities 2021–2030 document points out, there are many things about the Southern Ocean still to be determined, not the least of which is the changes coming for the primary absorber of heat and carbon dioxide on the planet.
We continue south to our next sampling station. Oh, and we spotted our first iceberg!
Craig Stevens & Denise Fernandez – Co-voyage Leads
