# Effect of destroying the Antarctic Circumpolar Current?

The Antarctic Circumpolar Current is a current which endlessly circles around Antarctica. (Deets: https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current ) The key factors I want to highlight are:

• This current isolates A. from warm waters which might otherwise melt those huge ice shelves

• There is a great phytoplankton zone around the edge of the current where it meets warmer waters

• It flows from west to east

So far so good. Now some aliens want to use a very intricate machine to raise a mountain range to block off the ocean between the Palmer Peninsula and South America. Look here:

What I expect to happen is that the cold current hits the mountains and turns north along the coast of Chile, and a warm one flows down Argentina and thaws Antarctica.

Here's the question... What will the impact to Chilean climate be? I'm concerned that the cold current will make the subpolar climate extend much further north, thus ruining the lives of Chileans and their agriculture. Will Chile be destroyed by my geoengineering hubris?

# Globally: There is debate

On the science front, you can find arguments that either the decline in CO$_2$ during the Eocene-Oligocene transition (about 34 million years ago) or the opening of the Drake passage (anywhere from 17-41 million years ago, depending on the source) is the primary culprit. Probably, both were involved.

There are a lot of interlocking theories about the connections between CO$_2$ levels, ice ages, and the isolation of Antarctica by the circumpolar current that are, at best, not fully explained. From a scientific point of view, it is probably best to say that we don't realy know what the effect on world climate would be.

# Locally: No change

The Humboldt current that dominates Chilean climate is caused by the 'point' of South America blocking cold circumpolar water and driving it north. Along the coast of Chile it causes upwelling currents which leads to both rich marine productivity, and a specific sequence of coastal climactic zones: temperate rain forest, Mediterranean, and desert.

The climactic sequence is seen on the West coast of all continents. In South America, there are the Valdivian temperate rain forests, the Mediterranean region around Santiago and Valparaiso, and then the Atacama desert. A very similar combination is seen in North America, with the temperate rain forests of the Pacific Northwest, the Mediterranean climate of California, and then the deserts of Baja California. The west coast of Africa doesn't extend far enough south to get the temperate rain forests, but there is the Mediterranean region around Cape Town folowed by the Namibian desert. Europe is a bit different, because of the geometry of the continent and the Gulf Stream, but you can still see a similar pattern. Ireland, Brittany, and Galicia Spain have a climate similar to a temperate rainforest, while the actual Mediterranean is Mediterranean and the Sahara is the desert.

Since this pattern is general, whether an Antartic circumpolar is being deflected towards the equator or not, it is safe to assume that the climate in Chile won't be changed too much by the closure of the Drake Passage...that is unless that closure causes the ice age we are in to end or something drastic.

• Hmm ... from your map, note that the ACC splits into the Cape Horn current which still goes through the gap between continents, and the Humboldt current. Closing the Cape Horn current should make the Humboldt current far mightier; wouldn't this have an impact on Chile? Awesome map by the way, wish I'd used that one for the Q! ;D – akaioi Nov 22 '17 at 4:56
• @akaioi If you close the Drake passage, you still get cold water going north. Strength of the cold current is not important, as explained and defended in my answer. Since you get the same climate effects from a strong pole-> equator cold current (Humboldt in Chile) or weak (Europe), why would there be any change in climate from closing the Drake passage? – kingledion Nov 22 '17 at 5:13
• this may sound naive, but we're now shipping a much larger amount of cold water north; this water will now warm more slowly and (presumably?) carry the cold current effect further north than it goes now. Not really sure, but it seems ... suspicious that doubling the current would have no effect at all. – akaioi Nov 22 '17 at 5:26
• @akaioi As I am trying to argue, the change will be global, and significant. We just can't be sure what the change will be. – kingledion Nov 22 '17 at 5:28