Oceanography

 Highlights of Gary’s progress on the

Our Far South Expedition

February 29, 2012

So what have we learnt? 

Oceanography

At 68° South, we have just crossed through the Antarctic Divergence and left most of the floating icebergs behind on our way north to Campbell Island. With a few days of steaming ahead, it is time to take stock and assess what we have learnt along the way. 

Oceanographically, this is a very unique part of the world. Because Antarctica is separated from all the other Southern Hemisphere continents by ocean, it allows a circum Antarctic ocean current to develop between the Antarctic Divergence and the Subantarctic Front buffering the Antarctic Continent from external influences. This current, known as the Antarctic Circumpolar Current or ACC washes along the southern margin of New Zealand’s subantarctic and then sweeps up past Dunedin to the Chatham Rise before heading east, which explains why Dunedin was witness to those ice-bergs a few years ago. The ACC effectively regulates temperatures at the southern end of New Zealand. Closer to Antarctica, and within the Antarctic Divergence, cold and saline water sinks to the ocean floor and also flows along the bottom of the ocean past the eastern seaboard of New Zealand, effectively driving global ocean circulation. Together, these two ocean currents form the main engine room of the global ocean system transferring heat around the planet and New Zealand’s subantarctic is in the firing line so to speak. 

So, what? Well the recent evidence is that Antarctica is warming up and with the melting and loss of ice shelves, a major concern is how will these major currents respond and what will be the effect on New Zealand? Changing temperature gradients across New Zealand? Different storm and rainfall patterns? A move in fishing grounds? Sea level rise? How much? How fast? It’s clear that our back yard does not end at Stewart Island, in fact one of the most significant part of the country is further south yet.

Coming up …. global warming and CO₂