Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder

Caroline B. Alden

Research Interests

My work focuses on using trace gas measurements in the atmosphere to address carbon monitoring and carbon-climate mitigation challenges.

At regional to global scales, I use inverse modeling with atmospheric measurements of trace gases and stable isotopes to understand atmosphere-biosphere fluxes and biogeochemical cycling. At local scales, I am developing similar techniques to identify and characterize greenhouse gas emissions from industrial sources, for example, methane emissions from oil and gas infrastructure. 

Prior to joining CIRES, I worked on connecting climate extremes in the Amazon Basin to variations in net biosphere exchange of CO2 with the atmosphere as a postdoctoral fellow with Prof. Noah Diffenbaugh at Stanford University. For my PhD, I worked with Prof. Jim White and Dr. John B. Miller (NOAA/ERSL) to develop an inversion framework for delta13C of atmospheric CO2, and explore its potential as a tracer for regional drought stress in North America. I have also published work on global CO2 sink strength and on atmospheric 13CO2 as a potential indicator of global terrestrial carbon exchange, water stress, and the partitioning of C3/C4 plant productivity.

Teaching Profile

I have taught as a visiting professor at Colorado College and Quest University Canada, and helped develop curriculum for science writing at CU Boulder.

Current Research

My current research projects fall into three main categories.

I work with Greg Rieker in the Mechanical Engineering Department at CU, along with colleagues at the NIST Engineering Laboratory and NOAA, to develop tools for the detection, quantification, and attribution of leaks of methane and other hydrocarbons during natural gas production, distribution and storage. Our team deployed the first fielded dual frequency comb spectrometer for the monitoring of trace gases. We currently have four deployments with industry partners in oil and gas production and underground natural gas storage for testing and prototyping of the observing system. These four systems operate autonomously, providing continuous and low-cost monitoring of active natural gas facilities. This work has resulted in a successful technology transfer to industry with the launching of LongPath Technologies, Inc., which will continue to carry out monitoring and emissions quantification activities in the private sector after the completion of research and development at CIRES and CU's Mechanical Engineering Department.

I also work with the Carbon Cycle Group at NOAA/ESRL in the Global Monitoring Laboratory to better understand what can be learned about regional CO2 fluxes from measurements made aboard the Orbiting Carbon Observatory 2 (OCO-2) satellite. We are working with colleagues at the University of Illinois and the Carnegie Institution at Stanford to reconcile high-resolution top-down and bottom-up estimates of carbon fluxes across the US corn belt, as part of a NASA Carbon Monitoring System development effort. The results of this effort will be the inclusion of satellite-based observations in the CT-Lagrange inversion framework, and better understanding of information content offered and bias corrections needed when assimilating in situ and remotely sensed information in a regional inversion. This effort will also result in a decadal-length analysis of carbon sequestration in the US corn belt.

Finally, I work with colleagues at CIRES and in the NOAA/ESRL Carbon Cycle Group to investigate global biogeochemical cycling using stable isotope measurements made at the INSTAAR Stable Isotope Laboratory. This global-scale analysis will identify large-scale trends and signals of water use efficiency via a data-constrained model.

View Publications

  • Rastogi B; Miller JB; Trudeau M; Andrews AE; Hu L; Mountain M; Nehrkorn T; Baier B; McKain K; Mund J. (Sep 2021). Evaluating consistency between total column CO<sub>2</sub> retrievals from OCO-2 and the in situ network over North America: implications for carbon flux estimation. Atmospheric Chemistry and Physics , 21(18), 14385-14401. 10.5194/acp-21-14385-2021
  • Rybchuk A; Alden CB; Lundquist JK; Rieker GB. (Mar 2021). A Statistical Evaluation of WRF-LES Trace Gas Dispersion Using Project Prairie Grass Measurements. Monthly Weather Review. 10.1175/mwr-d-20-0233.1
  • Alden CB; Wright RJ; Coburn SC; Caputi D; Wendland G; Rybchuk A; Conley S; Faloona I; Rieker GB. (Nov 2020). Temporal Variability of Emissions Revealed by Continuous, Long-Term Monitoring of an Underground Natural Gas Storage Facility. Environmental Science and Technology (Washington) , 54(22), 14589-14597. 10.1021/acs.est.0c03175
  • Cassol HLG; Domingues LG; Sanchez AH; Basso LS; Marani L; Tejada G; Arai E; Correia C; Alden CB; Miller JB. (Oct 2020). Determination of Region of Influence Obtained by Aircraft Vertical Profiles Using the Density of Trajectories from the HYSPLIT Model. Atmosphere , 11(10), 1073-1073. 10.3390/atmos11101073
  • Wang C; Guan K; Peng B; Chen M; Jiang C; Zeng Y; Wu G; Wang S; Wu J; Yang X. (May 2020). Satellite footprint data from OCO-2 and TROPOMI reveal significant spatio-temporal and inter-vegetation type variabilities of solar-induced fluorescence yield in the US Midwest. Remote Sensing of Environment: an interdisciplinary journal , 241. 10.1016/j.rse.2020.111728
  • Alden, CB; Coburn, SC; Wright, RJ; Baumann, E; Cossel, K; Perez, E; Hoenig, E; Prasad, K; Coddington, I; Rieker, GB. (Mar 2019). Single-Blind Quantification of Natural Gas Leaks from 1 km Distance Using Frequency Combs. ENVIRONMENTAL SCIENCE & TECHNOLOGY , 53(5). 10.1021/acs.est.8b06259
  • Coburn, S, CB Alden, R Wright, K Cossel, E Baumann, GW Truong, F Giorgetta, C Sweeney, NR Newbury, K Prasad, I Coddington and GB Rieker. (Apr 2018). Regional trace-gas source attribution using a field-deployed dual frequency comb spectrometer. OPTICA , 5(4). 10.1364/OPTICA.5.000320
  • Alden, CB, S Ghosh, S Coburn, C Sweeney, A Karion, R Wright, I Coddington, GB Rieker and K Prasad. (Mar 2018). Bootstrap inversion technique for atmospheric trace gas source detection and quantification using long open-path laser measurements. ATMOSPHERIC MEASUREMENT TECHNIQUES , 11(3). 10.5194/amt-11-1565-2018
  • Alden, CB, JB Miller, LV Gatti, MM Gloor, K Guan, AM Michalak, IT van der Laan-Luijkx, D Touma, A Andrews, LS Basso, CSC Correia, LG Domingues, J Joiner, MC Krol, AI Lyapustin, W Peters, YP Shiga, K Thoning, IR van der Velde, TT van Leeuwen, V Yadav and NS Diffenbaugh. (Oct 2016). Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange. GLOBAL CHANGE BIOLOGY , 22(10). 10.1111/gcb.13305
  • Ballantyne AP; Andres R; Houghton R; Stocker BD; Wanninkhof R; Anderegg W; Cooper LA; DeGrandpre M; Tans PP; Miller JB. (Jan 2015). Audit of the global carbon budget: estimate errors and their impact on uptake uncertainty. Biogeosciences , 12(8), 2565-2584. 10.5194/bg-12-2565-2015
  • Ballantyne, AP, CB Alden, JB Miller, PP Tans and JWC White. (Aug 2012). Increase in observed net carbon dioxide uptake by land and oceans during the past 50 years. NATURE , 488(7409). 10.1038/nature11299
  • Townsend, AR, CC Cleveland, BZ Houlton, CB Alden and JWC White. (Feb 2011). Multi-element regulation of the tropical forest carbon cycle. FRONTIERS IN ECOLOGY AND THE ENVIRONMENT , 9(1). 10.1890/100047
  • Alden, CB, JB Miller and JWC White. (Nov 2010). Can bottom-up ocean CO2 fluxes be reconciled with atmospheric 13C observations?. TELLUS SERIES B-CHEMICAL AND PHYSICAL METEOROLOGY , 62(5). 10.3402/tellusb.v62i5.16581