I looked into it a bit.
There is an article by EarthEclipse (calling itself a paper) that summarizes the Southern Ocean. The most pertinent to operating in the Southern Ocean is "...The area of the ocean that ranges the latitude 40 south traveling to the Antarctic circle is said to have the strongest average winds found anywhere on Earth." It also notes later in the article of complex current systems, but I'm not a sailor so I don't know how that affects ships. What is clear is that there is very limited and distributed support infrastructure, with ports in Australia and New Zealand being the only major ones.
Southern Ocean can influence the global climate as it connects to the three major oceans: Indian, Atlantic and Pacific Oceans. It stores the huge amount of heat, carbon dioxide, and nutrients and helps to drive the currents of the Ocean all around the world.
www.eartheclipse.com
There is also the "The International Antarctic Weather Forecasting Handbook." I haven't read through a great deal of it, but it is a decent reference despite it's age (2004). I found this quote interesting:
"As the cold air from the south moves over the warmer, oceanic surface to the north strong baroclinic instabilities and convection occur, which together with the high cyclonic vorticity result in the formation of
numerous mesoscale and synoptic scale cyclonic systems around the edge of the Antarctic domain." I have a friend who went through the Drake Passage between Argentina and Antarctica a few years ago. It's about as far away from the AAT as you can get in the Southern Ocean but for reference, he said it was some of the worst waters he has ever gone through.
Nothing on 48 degrees South
specifically, however.
On a side note I'd argue there is not a current or near future need for OPV in the Southern Ocean, so long as the treaty remains current and relatively understood.
An ocean going vessel like the Nuyina is certainly more suitable for operating in the Southern Ocean. It is better suited to more extreme latitudes and with greater self-sufficiency than anything an OPV can provide. Whilst it can't conduct security operations, the size and capacity of the vessel is certainly a clear message to any foreign competitors with the benefit of actually being able to support scientific activity in the Antarctic. This is combined with recent demonstrations of C-17 and C-130 capability of Antarctic support (however limited). The OPV fleet is going to be of more use in North Australia, the South Pacific and SE Asia - as evidenced by defence interests in mine warfare, unmanned systems and constabulary roles, all three of which are far more prevalent in the North rather than in the South.
For the time being, so long as the treaty is still in effect, it is better to show influence in the AAT via major soft power (airlift, Nuyina, the AAD, etc) as opposed to minor hard power (OPV patrols, etc). In terms of stopping illegal fishing, I'd argue that a soft power approach may be more effective here. Stopping whaling would require standing up to Japan politically, which I don't see happening anytime soon. With this happening the only way to stop protest ships is to crack down on them, which may come with some public backlash (the Sea Shepherds have at least notable support in Tasmania, at the very least). Toothfish poachers are a more conventional constabulory challenge but there have been some notable ideas floated about recently. There are substantial seabird populations across the South, for use by these ideas:
Fishermen illegally trawling the Indian Ocean might soon find they have more to worry about than the proverbial albatross around their neck—real bad luck might now lurk in the form of one of the birds spying on them from the sky.
phys.org
If it does come to be a major issue, then maritime patrol/surveillance and space based sensors could also be of use, with the OPV fleet (or more major fleet assets) or DFAT then being directed to intercept. Illegal fishermen do have to come above latitude 50 at some point, after all.
A two cents, again.
en.wikipedia.org
www.defenceconnect.com.au