Thursday, 13 March 2014

So, why are we here?

 The global oceans form a vital part of the Earth’s infrastructure. At the sea surface they absorb properties like heat and carbon dioxide from the atmosphere, and transport them around the globe in a fast network of currents. 

 One such current, which you are probably familiar with, is the Gulf Stream. This current flows across the North Atlantic bringing warm waters and our famously lovely weather to the British coast. The oceans do not only transport water across the Earths surface, they also work vertically, constantly pumping water from the surface thousands of kilometers down to the bottom of the sea and back again. This global overturning circulation is a slow process which stores surface waters rich in greenhouse gases deep in the ocean for thousands of years. Previous large-scale changes in the Earths climate, such as the ice ages, have been linked to changes in ocean circulation patterns.

The global ocean current network. Red colours show surface waters and blue colours deeper waters.
Note how most of the upwelling happens in the Southern Ocean. (Adapted from Speer & Marshall,
2012).

The Southern Ocean


I am guessing there are some cynics out there who might think we choose to come here for the penguins and icebergs..... So lets talk about the Southern Ocean; why is it important and what do we hope to learn by coming here?

The Southern Ocean plays a particularly important role in the global current system. It is geographically different to all the other ocean basins, because it is not bounded by continents. It provides a unique route for waters to flow uninterrupted around the globe, linking the Indian, Pacific and Atlantic oceans together. The Antarctic Circumpolar Current or ACC, which circulates Antarctica forms the largest current on Earth, transporting some 150,000,000 m3 of water every second – that’s like 2 million Thames Rivers. It is VERY energetic and this drives the vertical exchange of deep and surface waters in the ocean


 
The braided current patterns which flow around Antarctica (the ACC). Picture from M. Mazloff at SCRIPPS, US.
 
Despite its importance, the Southern Ocean is the least understood of any of the world’s oceans. For instance, we still don’t have an agreed theory for the overall circulation here. Although a remote and hostile place to work, oceanographers are keen to measure how quickly the Southern Ocean is able to transport and mix seawater from the deep back to the surface. This is where the DIMES project comes in…..check out tomorrows post.

The Southern Ocean is renowned to host the biggest seas in the world


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