12 Mar 2021

12 Mar 2021

Review status: this preprint is currently under review for the journal ACP.

Spatial distributions of XCO2 seasonal cycle amplitude and phase over northern high latitude regions

Nicole Jacobs1, William R. Simpson1, Kelly A. Graham2, Christopher Holmes2, Frank Hase3, Thomas Blumenstock3, Qiansi Tu3, Matthias Frey3,4, Manvendra K. Dubey5, Harrison A. Parker5,6, Debra Wunch7, Rigel Kivi8, Pauli Heikkinen8, Justus Nothold9, Christof Petri9, and Thorsten Warneke9 Nicole Jacobs et al.
  • 1Department of Chemistry and the Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA
  • 2Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL, USA
  • 3Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 4National Institute for Environmental Studies, Tsukuba, Japan
  • 5Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, NM, USA
  • 6California Institute of Technology, Pasadena, CA, USA
  • 7Department of Physics, University of Toronto, Toronto, Canada
  • 8Finnish Meteorological Institute, Sodankylä, Finland
  • 9Institute of Environmental Physics, University of Bremen, Germany

Abstract. Satellite-based observations of atmospheric carbon dioxide (CO2) provide measurements in remote regions, such as the biologically sensitive but under sampled northern high latitudes, and are progressing toward true global data coverage. Recent improvements in satellite retrievals of total column-averaged dry air mole fractions of CO2 (XCO2) from the NASA Orbiting Carbon Observatory 2 (OCO-2) have allowed for unprecedented data coverage of northern high latitude regions, while maintaining acceptable accuracy and consistency relative to ground-based observations, and finally providing sufficient data in spring and autumn for analysis of the satellite-observed XCO2 seasonal cycles across a majority of terrestrial northern high latitude regions. Here, we present an analysis of XCO2 seasonal cycles calculated from OCO-2 data for temperate, boreal, and tundra regions, subdivided into 5° latitude by 20° longitude zones. We quantify the seasonal cycle amplitudes (SCA) and the annual half drawdown day (HDD). OCO-2 SCA is in good agreement with ground-based observations at five high latitude sites and OCO-2 SCA show very close agreement with SCA calculated for model estimates of XCO2 from the Copernicus Atmospheric Monitoring Services (CAMS) global inversion-optimized greenhouse gas flux model v19r1. Model estimates of XCO2 from the GEOS-Chem CO2 simulation version 12.7.2 with underlying biospheric fluxes from CarbonTracker2019 yield SCA of larger magnitude and spread over a larger range than those from CAMS and OCO-2; however, GEOS-Chem SCA still exhibit a very similar spatial distribution across northern high latitude regions to that from CAMS and OCO-2. Zones in the Asian Boreal Forest were found to have exceptionally large SCA and early HDD, and both OCO-2 data and model estimates yield a distinct longitudinal gradient of increasing SCA from west to east across the Eurasian continent. Longitudinal gradients in both SCA and HDD are at least as pronounced as meridional gradients (with respect to latitude), suggesting an essential role for global atmospheric transport patterns in defining XCO2 seasonality. GEOS-Chem surface contact tracers show that the largest XCO2 SCA occurs in areas with the greatest contact with land surfaces, integrated over 15–30 days. The correlation of XCO2 SCA with these land contact tracers are stronger than the correlation of XCO2 SCA with the SCA of CO2 fluxes within each 5° latitude by 20° longitude zone. This indicates that accumulation of terrestrial CO2 flux during atmospheric transport is a major driver of regional variations in XCO2 SCA.

Nicole Jacobs et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-185', Anonymous Referee #1, 11 Apr 2021
  • RC2: 'Comment on acp-2021-185', Anonymous Referee #2, 07 Jun 2021

Nicole Jacobs et al.

Data sets

Fairbanks, AK EM27/Sun observations of XCO2, XCH4, and XCO with GGG2014 N. Jacobs, W. R. Simpson, F. Hase, T. Blumenstock, Q. Tu, M. Frey, M. K. Dubey, and H. A. Parker

Model code and software

GEOS-Chem 12.7.2 The international GEOS-Chem Community

Nicole Jacobs et al.


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Short summary
Spatial patterns of carbon dioxide seasonal cycle amplitude and summer drawdown timing derived from the OCO-2 satellite over northern high latitudes agree well with corresponding estimates from two models. The Asian Boreal Forest is anomalous with the largest amplitude and earliest seasonal drawdown. Modeled land contact tracers suggest that accumulated CO2 exchanges during atmospheric transport play a major role in shaping carbon dioxide seasonality in northern high latitude regions.