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Characterizing Carbon-Dioxide Fluxes from Oceans and Terrestrial Ecosystems


Krakauer, Nir Yitzhak (2006) Characterizing Carbon-Dioxide Fluxes from Oceans and Terrestrial Ecosystems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/8B12-1G19.


Understanding the processes that change the amount of carbon stored in the ocean and in the land biota, with their implications for future climate and ecology, is a fundamental goal of earth-system science. I have developed, refined, and applied several approaches that combine data analysis and modeling to better understand processes affecting carbon fluxes.

(1) Using a database of tree-ring widths from some 40,000 trees, I looked at the impact of large volcanic eruptions in the past millennium on tree growth globally. I found a decline in growth north of 45° N lasting for several years after eruptions, presumably due to eruption-associated cooling, and no significant impact at lower latitudes. This argues against the hypothesis that the increased diffuse-light fraction due to volcanic aerosols greatly increased plant carbon uptake after the 1991 Pinatubo eruption, suggesting that other explanations are needed for the slow increase in atmospheric CO2 levels in the early 1990s.

(2) I applied generalized cross-validation (GCV) to the problem of estimating a regional CO2 source/sink pattern consistent with observed geographic variation in atmosphere CO2 levels. I showed that GCV works for selecting data and regional-flux uncertainty levels to assume for this inverse problem; these have usually been estimated rather arbitrarily, though they can have a large impact on the solution.

(3) The air-sea gas transfer velocity determines how fast the surface ocean adjusts to a change in atmospheric composition, and hence is important for understanding ocean CO2 uptake. By modeling the ocean’s adjustment to fluctuations in atmospheric carbon isotope composition and analyzing a variety of atmosphere and ocean bomb-14C and 13C measurements, I estimated regional and global mean gas transfer velocities, concluding that there may be less latitudinal variation in the gas transfer velocity than usually thought – implying, for example, relatively low CO2 uptake in the Southern Ocean.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:air-sea gas exchange; biogeochemistry; carbon sink; climate change; greenhouse gases; interannual variability
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geochemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Schneider, Tapio
Thesis Committee:
  • Schneider, Tapio (chair)
  • Adkins, Jess F.
  • Randerson, James T.
  • Wennberg, Paul O.
  • Yung, Yuk L.
Defense Date:19 May 2006
Non-Caltech Author Email:nir (AT)
Record Number:CaltechETD:etd-05262006-111949
Persistent URL:
Krakauer, Nir Yitzhak0000-0002-4926-5427
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2105
Deposited By: Imported from ETD-db
Deposited On:01 Jun 2006
Last Modified:31 Mar 2020 19:36

Thesis Files

PDF (thesis_nyk.pdf) - Final Version
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