The overwhelming role of soils in the global atmospheric hydrogen cycle T. S. Rhee1,2, C. A. M. Brenninkmeijer1, and T. Röckmann3,4 1Max Planck Institute for Chemistry, Atmospheric Chemistry Division, Mainz, Germany 2Korea Polar Research Institute, Ansan, Korea 3Max Planck Institute for Nuclear Physics, Atmospheric Physics Division, Heidelberg, Germany 4Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands
Abstract. The removal of molecular hydrogen (H2) from the atmosphere is dominated
by the uptake in soils. Notwithstanding, estimates of the magnitude of this
important process on a global scale are highly uncertain. The CARIBIC
aircraft observations of the seasonal variations of H2 and its D/H
isotopic ratio in the Northern Hemisphere allow an independent, better
constrained estimate. We derive that 82% of the annual turnover of
tropospheric H2 is due to soil uptake, equaling 88 (±11)Tg a-1,
of which the Northern Hemisphere alone accounts for 62 (±10)Tg a-1.
Our calculations further show that tropospheric H2
has a lifetime of only 1.4 (±0.2) years – significantly shorter than
the recent estimate of ~2 years – which is expected to decrease in the
future. In addition, our independent top-down approach, confined by the
global and hemispheric sinks of H2, indicates 64 (±12)Tg a-1
emissions from various sources of volatile organic compounds by
photochemical oxidation in the atmosphere. This estimate is as much as up to
60% larger than the previous estimates. This large airborne production
of H2 helps to explain the fairly homogeneous distribution of H2
in the troposphere.
Citation: Rhee, T. S., Brenninkmeijer, C. A. M., and Röckmann, T.: The overwhelming role of soils in the global atmospheric hydrogen cycle, Atmos. Chem. Phys., 6, 1611-1625, doi:10.5194/acp-6-1611-2006, 2006.