Climate-carbon feedback of the high latitude ocean

Thesis

The warming induced by anthropogenic carbon emissions affects the climate system through a multitude of physical mechanisms. Changes in the dynamics, thermodynamics and biogeochemistry of the ocean alter the different ocean carbon reservoirs, potentially resulting in further carbon emissions and a climate- carbon feedback. Surface wind stress and surface warming are two of the most influential forcings acting on the ocean carbon system in past, present and future climates due to their influence on the mixed layer dynamics and the large scale ocean circulation.

This thesis quantifies the climate-carbon feedback of wind stress and surface warming, with a particular focus on the mechanisms driving the feedbacks and the role of the Southern Ocean and the North Atlantic. To study the feedbacks, a set of theoretical scalings and a hierarchy of numerical simulations are used. Of the climate feedbacks examined, increased surface warming is likely to result in large atmospheric CO₂ anomalies while the effects of North Atlantic wind stress are likely to be negligible. The atmospheric feedback of surface warming is constrained by compensating changes in separate ocean carbon reservoirs as a result of warming-induced circulation changes. Southern Ocean winds affect atmospheric CO₂ through both local upwelling of carbon as well as the remote modification of Equatorial and North Atlantic chemistry. As a result, the net Southern Ocean wind stress feedback could be significant and even comparable to the temperature feedback. This thesis provides a quantification of regional and global climate-carbon feedbacks due to ocean dynamics. The estimates of carbon-climate feedbacks are useful tools for understanding past, present and future climates.

Authors: Bronselaer, B

• DOI: 10.5287/ora-8nx6qpwkb
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford