Controls on the spatial distribution of oceanic delta C-13(DIC)

P. B. Holden*, N. R. Edwards, S. A. M. Uller, K. I. C. Oliver, R. M. Death, A. Ridgwell

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

16 Citations (Scopus)

Abstract

We describe the design and evaluation of a large ensemble of coupled climate-carbon cycle simulations with the Earth system model of intermediate complexity GENIE. This ensemble has been designed for application to a range of carbon cycle questions, including the causes of late-Quaternary fluctuations in atmospheric CO2. Here we evaluate the ensemble by applying it to a transient experiment over the recent industrial era (1858 to 2008 AD). We employ singular vector decomposition and principal component emulation to investigate the spatial modes of ensemble variability of oceanic dissolved inorganic carbon (DIC) delta C-13, considering both the spun-up pre-industrial state and the transient change. These analyses allow us to separate the natural (pre-industrial) and anthropogenic controls on the delta C-13(DIC) distribution. We apply the same dimensionally-reduced emulation techniques to consider the drivers of the spatial uncertainty in anthropogenic DIC. We show that the sources of uncertainty related to the uptake of anthropogenic delta C-13(DIC) and DIC are quite distinct. Uncertainty in anthropogenic delta C-13 uptake is controlled by air-sea gas exchange, which explains 63% of modelled variance. This mode of variability is largely absent from the ensemble variability in CO2 uptake, which is rather driven by uncertainties in thermocline ventilation rates. Although the need to account for air-sea gas exchange is well known, these results suggest that, to leading order, uncertainties in the ocean uptake of anthropogenic C-13 and CO2 are governed by very different processes. This illustrates the difficulties in reconstructing one from the other, and furthermore highlights the need for careful targeting of both delta C-13(DIC) and DIC observations to better constrain the ocean sink of anthropogenic CO2.

Original languageEnglish
Pages (from-to)1815-1833
Number of pages19
JournalBiogeosciences
Volume10
Issue number3
DOIs
Publication statusPublished - 2013

Keywords

  • EARTH SYSTEM MODEL
  • CARBON-CYCLE
  • ATMOSPHERIC CO2
  • CLIMATE MODEL
  • EFFICIENT
  • C-13
  • TERRESTRIAL
  • VARIABILITY
  • FEEDBACK
  • DIOXIDE

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