The University of Southampton
University of Southampton Institutional Repository

On the role of the Southern Ocean in the global carbon cycle and atmospheric CO2 change

On the role of the Southern Ocean in the global carbon cycle and atmospheric CO2 change
On the role of the Southern Ocean in the global carbon cycle and atmospheric CO2 change
Uncertainty about the causes of glacial-interglacial CO2 variations demonstrates our incomplete grasp of fundamental processes that govern our climate and thus one of the foremost problems in palaeoceanography and Earth System Science regards the mechanism(s) responsible for natural changes in atmospheric CO2 concentration. It is becoming clear that the Southern Ocean overturning circulation plays an important role in the global carbon cycle because altered communication between the atmosphere and abyss in the Southern Ocean is relatively well documented and often implicated in explanations of past and future climate changes, but the ambiguity of the paleoceanographic record defies interpretation of the mechanisms involved.

Using a coarse resolution ocean general circulation model and coupled biogeochemistry code, an ensemble of idealised perturbations to external forcing and internal physics of the Southern Ocean is examined to explain the processes that link ocean circulation, nutrient distributions and biological productivity, and determine the extent to which the Southern Ocean governs the partitioning of CO2. Strengthened or northward-shifted winds result in oceanic outgassing and increased atmospheric carbon dioxide levels, while weakened or southward-shifted winds cause oceanic carbon uptake and reduced atmospheric carbon dioxide concentration. Driven by the work done on the ocean by the winds, changes in the rate or spatial pattern of the Southern Ocean residual overturning circulation lead to alteration of upper ocean stratification and the rate and depth from which carbon and nutrient-rich deep waters are upwelled to the surface. These surface waters, imprinted with the pattern of air-sea gas exchange, are subducted to intermediate depths in the ocean interior, not the abyss as previous suggested.

These results are robust to significant alterations to surface heat and freshwater boundary conditions, mesoscale eddy activity and rates of air-sea gas exchange and represent a significant proportion of the change in glacial-interglacial CO2 that can be currently generated by altered ocean circulation in a variety of models, revealing that the upper limb of the Southern Ocean overturning circulation is important in determining atmospheric CO2 levels.
Lauderdale, Jonathan Maitland
e1acdd43-c687-4b07-b1e9-13a344410c7c
Lauderdale, Jonathan Maitland
e1acdd43-c687-4b07-b1e9-13a344410c7c

Lauderdale, Jonathan Maitland (2010) On the role of the Southern Ocean in the global carbon cycle and atmospheric CO2 change. University of Southampton, School of Ocean and Earth Science, Doctoral Thesis, 259pp.

Record type: Thesis (Doctoral)

Abstract

Uncertainty about the causes of glacial-interglacial CO2 variations demonstrates our incomplete grasp of fundamental processes that govern our climate and thus one of the foremost problems in palaeoceanography and Earth System Science regards the mechanism(s) responsible for natural changes in atmospheric CO2 concentration. It is becoming clear that the Southern Ocean overturning circulation plays an important role in the global carbon cycle because altered communication between the atmosphere and abyss in the Southern Ocean is relatively well documented and often implicated in explanations of past and future climate changes, but the ambiguity of the paleoceanographic record defies interpretation of the mechanisms involved.

Using a coarse resolution ocean general circulation model and coupled biogeochemistry code, an ensemble of idealised perturbations to external forcing and internal physics of the Southern Ocean is examined to explain the processes that link ocean circulation, nutrient distributions and biological productivity, and determine the extent to which the Southern Ocean governs the partitioning of CO2. Strengthened or northward-shifted winds result in oceanic outgassing and increased atmospheric carbon dioxide levels, while weakened or southward-shifted winds cause oceanic carbon uptake and reduced atmospheric carbon dioxide concentration. Driven by the work done on the ocean by the winds, changes in the rate or spatial pattern of the Southern Ocean residual overturning circulation lead to alteration of upper ocean stratification and the rate and depth from which carbon and nutrient-rich deep waters are upwelled to the surface. These surface waters, imprinted with the pattern of air-sea gas exchange, are subducted to intermediate depths in the ocean interior, not the abyss as previous suggested.

These results are robust to significant alterations to surface heat and freshwater boundary conditions, mesoscale eddy activity and rates of air-sea gas exchange and represent a significant proportion of the change in glacial-interglacial CO2 that can be currently generated by altered ocean circulation in a variety of models, revealing that the upper limb of the Southern Ocean overturning circulation is important in determining atmospheric CO2 levels.

Text
Lauderdale_2010_PHD.pdf - Other
Download (30MB)

More information

Published date: November 2010
Organisations: University of Southampton

Identifiers

Local EPrints ID: 191935
URI: http://eprints.soton.ac.uk/id/eprint/191935
PURE UUID: faeec94b-cc52-4034-a37a-238aa3448db2

Catalogue record

Date deposited: 28 Jun 2011 10:19
Last modified: 22 Jul 2022 17:44

Export record

Contributors

Author: Jonathan Maitland Lauderdale

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×