Why are we collecting seawater samples from the World’s oceans?
The Southern Ocean is key
|The overturning circulation in the Southern Ocean. |
The circulation around the Antarctic enables deep waters rise
to the surface, allowing new water masses to form and sink
back into the ocean interior taking heat and carbon with it.
A key region in this context is the Southern Ocean, the vast sea that encircles Antarctica. The Southern Ocean occupies around 20% of the total ocean area, but absorbs about three-quarters of the heat that is taken into the ocean, and approximately half of the CO2. This is because of its unique pattern of ocean circulation: it is the main region where deep waters rise to the surface, allowing new water masses to form and sink back into the ocean interior. This exposure of “old” waters to the atmosphere, and the production of new waters at the surface, is fundamental to the exchanges of heat and carbon with the atmosphere.
Despite knowing the key role that the Southern Ocean plays in global climate, there are many important unknowns. These include how exactly heat and carbon are taken up by the oceans and how fast this occurs (especially important because of the Anthropocene period we are living in), and how much heat and carbon is currently stored in the oceans. These questions are being addressed using various chemical and physical measurements of the ocean, including the stable isotope composition of the seawater (which we are responsible for at the BGS). Oxygen isotopes will tell us about how much freshwater to seawater there is at particular locations (which will help us understand melting of the Antarctic ice mass and therefore heat) and carbon isotopes will tell us where the carbon is formed and how the ocean uses the carbon.
|The James Clarke Ross.|
I will be tweeting @MelJLeng and @ORCHESTRAPROJ and Facebooking (Orchestra project) along the way, as well as updating the BGS Geoblogy and drakepassageblog.wordpress.com when I have time.
Melanie Leng is the Science Director for Geochemistry at the BGS and the BGS lead scientist for ORCHESTRA.