Atmospheric d13C-CH4 data from the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado, Boulder in cooperation with NOAA Global Monitoring Laboratory
Authors
* corresponding author for atmospheric data. Email: sylvia.michel@colorado.edu

Abstract
NOAA's Cooperative Global Air Sampling Network has been monitoring the abundance of atmospheric CH4 since 1983. Weekly flask-air samples are collected from the network sites and sent to NOAA in Boulder, Colorado for CH4 analysis. Since 1998, a subset of NOAA's flask-air samples is analyzed for the ratio of stable carbon isotopes of CH4 ( 13C/ 12C), denoted by δ13C-CH4 , at the Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, Boulder. The methane mole fraction data show decadal and interannual variations in the growth rate of CH4 : a large rise in CH4 burden in the 1980s and 1990s, a stabilization period between 1999 to 2006, followed by a period of renewed increase since 2007. The driver behind these variations are still unclear. Around the same time that the renewed CH4 increase started, δ13C-CH4 started to decrease after two centuries of increase [Ferretti et al., 2005; and data presented here]. Since different CH4 sources have distinct δ13C-CH4 signatures over large spatial scales, atmospheric δ13C-CH4 data can provide strong constraints on CH4 emissions and sinks.

This atmospheric δ13C-CH4 dataset was compiled for the study of 'Improved constraints on global methane emissions and sinks using δ13C-CH4 ' (Lan et al. 2021) to provide observation-based global mean δ13C-CH4 and their latitudinal gradients from the Marine Boundary Layer surface (https://www.esrl.noaa.gov/gmd/ccgg/mbl/mbl.html). We also estimate realistic and robust uncertainties for them, which include uncertainties related to the distribution of sampling sites (network), synoptic variability in air masses (atmospheric) and the possibility of unknown bias in measurement (bias). Details regarding the methods used are documented in Lan et al. (2021) (see following citation). δ13C-CH4 signatures from different CH4 sources are often used together with atmospheric δ13C-CH4 data to better allocate different CH4 emissions, as in Lan et al. (2021). An updated version of the δ13C-CH4 source signatures is also complied by Lan et al. (2021) and available here: Source signature inventory 2020


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Globally averaged atmospheric δ13C-CH4 (a) and latitude gradients (b for 2006 and c for 2012 as examples) from INSTAAR/NOAA Global Greenhouse Gas Reference Network; in (a) the blue curves are approximately weekly data and the red shaded areas are their uncertainty bounds, and the black curves are annual means; in (b) and (c) the shaded area around the observations in black are estimated uncertainty bounds. See Lan et al. (2021) for uncertainty calculation.



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This database is made freely available to the scientific community and is intended to stimulate and support global methane cycle and other modeling studies. We rely on the ethics and integrity of the user to assure that the authors receive fair credit for their work. Fair credit will depend on the nature of the work and the requirements of the institutions involved. Your use of this database implies an agreement to contact the database co-authors to discuss the nature of the work and the appropriate level of acknowledgement. If the database is essential to the work, or if an important result or conclusion depends on the database, co-authorship may be appropriate.
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Required Citation

The database has a Digital Object Identifier (DOI) registered with the International DOI Foundation. In addition to the conditions of fair use as stated above, users must also include the following paper and database citation in any publication or presentation using the product:

Lan, X., Basu, S., Schwietzke, S., Bruhwiler, L. M. P., Dlugokencky, E. J., Michel, S. E., Sherwood, O. A., Tans, P. P., Thoning, K., Etiope, G., Zhuang, Q., Liu, L., Oh, Y., Miller, J. B., Petron, G., Vaughn, B. H., Andrews, A., Crippa, M.: Improved constraints on global methane emissions and sinks using d13C-CH4, Global Biogeochemical Cycles, 35, https://doi.org/10.1029/2021GB007000

Database DOI: https://doi.org/10.15138/79jq-qc24


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Atmospheric d13C-CH4 data from the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado, Boulder in cooperation with NOAA Global Monitoring Laboratory

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