Recent increases in the seasonal amplitude of atmospheric carbon dioxide (CO2) at high latitudes suggest a widespread biospheric response to high-latitude warming. The seasonal amplitude of net ecosystem carbon exchange by northern Siberian ecosystems is shown to be greater in disturbed than undisturbed sites, due to increased summer influx and increased winter efflux. Increased disturbance cou...

It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weather...

Introduction The Department of Energy (DOE) Energy Information Administration estimates atmospheric greenhouse gas releases may exceed 8 billion metric tons by the year 2010 heightening its international environmental concern. Carbon dioxide will dominate the greenhouse gases (Kane and Klein, 1997) and the majority of these results from the use of fossil fuels. With viable replacement of fossil...

Organic carbon buried under the great ice sheets of the Northern Hemisphere is suggested to be the missing link in the atmospheric CO2 change over the glacial-interglacial cycles. At glaciation, the advancement of continental ice sheets buries vegetation and soil carbon accumulated during warmer periods. At deglaciation, this burial carbon is released back into the atmosphere. In a simulation o...

We present a framework for interpreting the carbon isotopic composition of sedimentary rocks, which in turn requires a fundamental reinterpretation of the carbon cycle and redox budgets over Earth's history. We propose that authigenic carbonate, produced in sediment pore fluids during early diagenesis, has played a major role in the carbon cycle in the past. This sink constitutes a minor compon...

Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of atmospheric CO2 that do not show large tropical uptake. Ou...

Title of Document: CARBON CYCLE DATA ASSIMILATION USING A COUPLED ATMOSPHEREVEGETATION MODEL AND THE LOCAL ENSEMBLE TRANSFORM KALMAN FILTER Ji Sun Kang, Doctor of Philosophy, 2009 Directed By: Professor Eugenia Kalnay Department of Atmospheric and Oceanic Science We develop and test new methodologies to best estimate CO2 fluxes on the Earth’s surface by assimilating observations of atmospheric ...

[1] The remarkable correspondence between glacialinterglacial changes in atmospheric CO2 levels and global climate over much of the Pleistocene suggests that CO2 is also a key climate change driver. However, there is as yet no widely accepted explanation of the low glacial CO2 levels. Here I use an intermediate-complexity climate model to show that glacial cooling, acting on the rates of organi...