keck_ams

W. M. Keck Carbon Cycle Accelerator Mass Spectrometer

	In 2001, ESS/CGECR researchers Ellen Druffel, John Southon and Susan Trumbore were awarded $2 million by the W.M. Keck Foundation in 2001 for the development of an accelerator mass spectrometry (AMS) facility for radiocarbon measurements in support of carbon cycle research at UC Irvine. Picture of the spectrometer we are purchasing
	The amount of carbon dioxide in the atmosphere today is higher than that at any time in the last 420,000 years. While the roughly 30% increase in CO₂ concentration observed over the past 150 years is traceable to human activities such as fossil fuel burning and clearing of forests for agriculture, significant changes in CO₂ also occurred in the past, presumably related to shifts in global climate. Carbon dioxide in the atmosphere exchanges dynamically with carbon dissolved in oceans and stored in plants and soils on land, and changes in atmospheric CO₂ clearly must be explained by repartitioning of carbon among these three reservoirs. However, scientists do not yet understand the fundamental processes controlling this carbon “cycle” well enough to either explain past changes in CO₂ or to predict with confidence how CO₂ will change in the future, given continued fossil fuel emissions.
	Radiocarbon (¹⁴C), a rare isotope of carbon, is used to determine rates of exchange of carbon between the ocean, land and atmosphere. For exchanges on time scales of less than a human life span, ¹⁴C produced by atmospheric weapons testing as it dissolves in surface oceans and is taken up and respired by land plants. On longer timescales, the radioactive decay of ¹⁴C provides information on slower exchanges with the much larger stores of carbon in the deep ocean and stabilized in soils and sediments. Radiocarbon is the best and often the only way to quantify rates of exchange of carbon among reservoirs, and hence is key to achieving predictive understanding of the carbon cycle.