It would appear that the recent panic about being thrown from my bunk in heavy seas was a little premature. The low pressure system is crossing our transect but it will be quite a bit further north east of our location when it produces its 9 metre swell. It’s back to 4 metres tomorrow, but considering that we have only just crossed the Polar Front we still may feel the fury of the 50’s over the following week. The icebergs are now a thing of the past, and beneath the vessel the currents are changing marking our exit from the westward flow that hugs closer to the Antarctic continent, to the eastward flow known as the Antarctic Circumpolar Current. We are back in open water.
The Antarctic Circumpolar Current is the largest current on earth carrying about 150 million cubic metres of water each second from west to east around Antarctica, which according to Dr Rintoul is around 150 times the flow of all the world’s rivers combined.
This massive current system is very important to the “conveyor belt” circulation that I previously described. This is because it connects the ocean basins i.e. the Pacific, the Indian and the Atlantic oceans, allowing the transfer of heat, energy and nutrients. One of the main aims for the physical oceanographers on board is to determine exactly how strong the Antarctic Circumpolar Current is.
And in other news I feel the need to make something clear, although I have the feeling it is only going to make things more unclear. There is much talk of the decreasing pH of the oceans and the susceptibility of the Polar Regions to ocean acidification due to the uptake of CO2 from the burning of fossil fuels etc. While it is true that gas is more soluble at cold temperatures (warm beer losing the bubbles etc), this is not the reason that polar waters are the first to be impacted by the effects of ocean acidification. The important concept when discussing the Polar Regions is “buffering”. A solution is able to resist changes to pH if it contains any chemical species that can neutralize the effect of the offending acid or base. In seawater, it is the ratio of the dissolved inorganic carbon species (dissolved carbon dioxide, bicarbonate and carbonate) to alkalinity (which is a measure of the charge balance of chemicals in the ocean) that determines the buffering capacity. So if you ever hear someone saying the oceans are turning to battery acid, this is nonsense as they are neglecting the buffering capacity of seawater.
So what am I trying to clarify, for fear that Dr Elizabeth may beat me to death with her laptop or worse wag her finger at me, is that there is a weaker buffering capacity in the polar regions. And this is why the Polar Regions are the first to be impacted by increased levels of anthropogenic CO2. Is that clear? Of course not, but it’s the best I can do in less than 500 words.