We have another mechanism conspiring to launch our planet into abrupt climate change. The Great Southern Ocean, or the Antarctic ocean is the culprit this time. Work out of the University of Zurich, Switzerland, Columbia University, Cambridge and Princeton has taken a million year look at sediment two sediment cores from the Antarctic. They found that every time the world warmed, upwelling ocean currents in the Antarctic increased.
The Great Southern Ocean is the largest biofactory on the planet. It makes plankton. As the plankton die, they sink to the ocean floor and take carbon with them, so in essence, it is the largest carbon sink on the planet outside of the ocean as a whole that absorbs CO2 all over.
Why? Not real sure, but we know it happens. Part of the reason may be increased winds around the Antarctic. The winds help stir up the ocean and increase the rate of upwelling of deep ocean waters. These deep ocean waters are enriched in Co2 and when they get to the surface, the extra CO2 comes out into the atmosphere. Or it may be that, the increase in meltwater happening now as those increased ocean currents bump up against the bottom of the Antarctic ice shelves and melt more, a layer of fresh water “floats” on the surface of the ocean.
The fresh water is less dense than salt water allowing it to float and keeping it from mixing with the underlying salt water. As it cools in the late summer, sea ice can form faster as fresh water freezes at 32 degrees but salt water freezes at 28 degrees. the faster freezing sea ice increases the amount of sea ice around Antarctica diminishing the amount of dust that falls in the ocean to “fertilize” the plankton. This reduces the sequestration capacity of the southern ocean.
Now, are you beginning to see what I mean about we don’t’ exactly know why? We do know what happens though, and this is that the Antarctic Ocean changes from a sink to source with warming, every time. So as it warms the Great Southern Ocean will add to the greenhouse gas load in the sky.
And unfortunately we may be seeing this already as winds have increased around Antarctica, increasing upwelling, increasing under ice melt, increasing sea ice formation and likely, increasing CO2 emissions.
And btw, this is one of those things that models can’t get. unfortunately, climate deniers use this sort of thing to discredit climate models altogether. they do not tell folks that the rest of climate modeling is fantastically accurate, they simply let the public believe that climate modeling is the same thing as weather modeling that they say things like ”everybody knows the weather models can’t forecast their way out of a wet paper bag”.
And in case you don’t know the models are basically the same model, there is always some truth to a myth. But this is where it ends. Weather models are loaded with the specific weather happening right now, the trends of the last few days or weeks and then they are run into the future to “predict” the weather. Their results fall apart as we all know after three to seven days, hence the myth.
The great difference with climate models is that the modelers load them with random climate data, lots of them, and then run them all off into the future. The results are totally random as you might expect. The modelers then take the random results and average them all together and this is what we are presented as the climate projections for the next hundred years. See the difference? They are simply totally unrelated, yet the deniers would have us believe they are the same.
Jaccard, et al., Two Modes of Change in Southern Ocean Productiviy over the Past Million Years, Science, March 25, 2013