Export 5 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N O P Q R S [T] U V W X Y Z   [Show ALL]
Stephens, BB, Keeling RF, Heimann M, Six KD, Murnane R, Caldeira K.  1998.  Testing global ocean carbon cycle models using measurements of atmospheric O2 and CO2 concentration. Global Biogeochemical Cycles. 12:213-230.   10.1029/97gb03500   AbstractWebsite

We present a method for testing the performance of global ocean carbon cycle models using measurements of atmospheric O-2 and CO2 concentration. We combine these measurements to define a tracer, atmospheric potential oxygen (APO approximate to O-2 + CO2), which is conservative with respect to terrestrial photosynthesis and respiration. We then compare observations of APO to the simulations of an atmospheric transport model which uses ocean-model air-sea fluxes and fossil fuel combustion estimates as lower boundary conditions. We present observations of the annual-average concentrations of CO2, O-2, and APO at 10 stations in a north-south transect. The observations of APO show a significant interhemispheric gradient decreasing towards the north. We use air-sea CO2, O-2, and N-2 fluxes from the Princeton ocean biogeochemistry model, the Hamburg model of the ocean carbon cycle, and the Lawrence Livermore ocean biogeochemistry model to drive the TM2 atmospheric transport model. The latitudinal variations in annual-average APO predicted by the combined models are distinctly different from the observations. All three models significantly underestimate the interhemispheric difference in APO, suggesting that they underestimate the net southward transport of the sum of O-2 and CO2 in the oceans. Uncertainties in the model-observation comparisons include uncertainties associated with the atmospheric measurements, the atmospheric transport model, and the physical and biological components of the ocean models. Potential deficiencies in the physical components of the ocean models, which have previously been suggested as causes for anomalously large heat fluxes out of the Southern Ocean, may contribute to the discrepancies with the APO observations. These deficiencies include the inadequate parameterization of subgrid-scale isopycnal eddy mixing, a lack of subgrid-scale vertical convection, too much Antarctic sea-ice formation, and an overestimation of vertical diffusivities in the main thermocline.

Newman, S, Xu XM, Gurney KR, Hsu YK, Li KF, Jiang X, Keeling R, Feng S, O'Keefe D, Patarasuk R, Wong KW, Rao P, Fischer ML, Yung YL.  2016.  Toward consistency between trends in bottom-up CO2 emissions and top-down atmospheric measurements in the Los Angeles megacity. Atmospheric Chemistry and Physics. 16:3843-3863. AbstractWebsite

Large urban emissions of greenhouse gases result in large atmospheric enhancements relative to background that are easily measured. Using CO2 mole fractions and delta C-14 and delta C-13 values of CO2 in the Los Angeles megacity observed in inland Pasadena (2006-2013) and coastal Palos Verdes peninsula (autumn 2009-2013), we have determined time series for CO2 contributions from fossil fuel combustion (C-ff) for both sites and broken those down into contributions from petroleum and/or gasoline and natural gas burning for Pasadena. We find a 10 % reduction in Pasadena C-ff during the Great Recession of 2008-2010, which is consistent with the bottom-up inventory determined by the California Air Resources Board. The isotopic variations and total atmospheric CO2 from our observations are used to infer seasonality of natural gas and petroleum combustion. The trend of CO2 contributions to the atmosphere from natural gas combustion is out of phase with the seasonal cycle of total natural gas combustion seasonal patterns in bottom-up inventories but is consistent with the seasonality of natural gas usage by the area's electricity generating power plants. For petroleum, the inferred seasonality of CO2 contributions from burning petroleum is delayed by several months relative to usage indicated by statewide gasoline taxes. Using the high-resolution Hestia-LA data product to compare C-ff from parts of the basin sampled by winds at different times of year, we find that variations in observed fossil fuel CO2 reflect seasonal variations in wind direction. The seasonality of the local CO2 excess from fossil fuel combustion along the coast, on Palos Verdes peninsula, is higher in autumn and winter than spring and summer, almost completely out of phase with that from Pasadena, also because of the annual variations of winds in the region. Variations in fossil fuel CO2 signals are consistent with sampling the bottom-up Hestia-LA fossil CO2 emissions product for sub-city source regions in the LA megacity domain when wind directions are considered.

Keeling, RF, Peng TH.  1995.  Transport of heat, CO2 and O2 by the Atlantic's thermohaline circulation. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences. 348:133-142.   10.1098/rstb.1995.0055   AbstractWebsite

We estimate transport of heat, CO2 and O-2 by the Atlantic's thermohaline circulation using an approach based on differences in the chemical and physical characteristics of North Atlantic Deep Water (NADW), Antarctic Intermediate Water (AAIW), and the northward return flow across the equator. The characteristics of the return-flow waters are constrained by imposing conservation of phosphate in the North Atlantic as a whole. Based on a total equatorial return flow of 13 x 10(6) m(3) s(-1), we find that the Atlantic north of the equator is a source of 7.7 +/- 1.4 x 10(14) W to the atmosphere, a sink of 0.51 +/- 0.21 x 10(14) mol of O-2, and preindustrially was a sink of 0.33 +/- 0.15 x 10(14) mol of CO2. Uptake of O-2 and CO2 by the North Atlantic is driven mainly by thermal, as opposed to biological processes.

Keeling, RF.  2009.  Triage in the greenhouse. Nature Geoscience. 2:820-822.   10.1038/ngeo701   AbstractWebsite

The path towards mitigating global warming is going to be tortuous. capturing carbon dioxide and pumping it directly into the deep ocean to avoid atmospheric build-up is an option that has been dismissed prematurely.

Le Quere, C, Aumont O, Bopp L, Bousquet P, Ciais P, Francey R, Heimann M, Keeling CD, Keeling RF, Kheshgi H, Peylin P, Piper SC, Prentice IC, Rayner PJ.  2003.  Two decades of ocean CO2 sink and variability. Tellus Series B-Chemical and Physical Meteorology. 55:649-656.   10.1034/j.1600-0889.2003.00043.x   AbstractWebsite

Atmospheric CO2 has increased at a nearly identical average rate of 3.3 and 3.2 Pg C yr(-1) for the decades of the 1980s and the 1990s, in spite of a large increase in fossil fuel emissions from 5.4 to 6.3 Pg C yr(-1). Thus, the sum of the ocean and land CO2 sinks was 1 Pg C yr(-1) larger in the 1990s than in to the 1980s. Here we quantify the ocean and land sinks for these two decades using recent atmospheric inversions and ocean models. The ocean and land sinks are estimated to be, respectively, 0.3 (0.1 to 0.6) and 0.7 (0.4 to 0.9) Pg C yr(-1) larger in the 1990s than in the 1980s. When variability less than 5 yr is removed, all estimates show a global oceanic sink more or less steadily increasing with time, and a large anomaly in the land sink during 1990-1994. For year-to-year variability, all estimates show 1/3 to 1/2 less variability in the ocean than on land, but the amplitude and phase of the oceanic variability remain poorly determined. A mean oceanic sink of 1.9 Pg C yr(-1) for the 1990s based on O-2 observations corrected for ocean outgassing is supported by these estimates, but an uncertainty on the mean value of the order of +/-0.7 Pg C yr(-1) remains. The difference between the two decades appears to be more robust than the absolute value of either of the two decades.