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ESRL/GMD 2012 poster

Anneke Batenburg
Anneke Batenburg

This document summarizes measurements of hydrogen (H2) mixing ratios and isotopic composition (隆D(H2)) taken from six stations in the EUROHYDROS network over at least one year. The data show larger variability in H2 and 隆D(H2) in the Northern Hemisphere compared to the Southern Hemisphere. Seasonal averages of both H2 and 隆D(H2) are higher in the Southern Hemisphere. Apparent fractionation factors were calculated for some stations, providing insight into the relative contribution of soil uptake and OH oxidation as H2 sinks. The regular observations help constrain global H2 budgets and distributions through comparison with modeling.

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Temporal and spatial variability of 隆D(H2) from six EUROHYDROS stations A. M. Batenburg, S. Walter, G. Pieterse, I. Levin, M. Schmidt, A. Jordan, S. Hammer, C. Yver, and T. R旦ckmann Worldwide (H2) and 隆D(H2) observations Present atmospheric molecular hydrogen (H2) mixing ratios ((H2)) are around ~0.5 ppm. In the coming decades, H2 levels are expected to rise due to use of hydrogen as an energy carrier. This may affect greenhouse gas lifetimes and stratospheric ozone depletion. Unfortunately, large uncertainties still exist in the global H2 budget. The different sources and sinks of H2 have very distinct isotopic signatures and fractionation coefficients, respectively. Therefore, measurements of isotopic composition (隆D(H2)) are a promising tool to gain insight into H2 source and sink processes and to constrain the terms in the global budget. Weekly to monthly air samples from six locations in the EUROHYDROS network have been analysed for 隆D(H2) with a GC-IRMS system. The time series thus obtained now stretch over at least a year for all stations. This is the largest set of ground station observations of 隆D(H2) so far. Fig 1: Locations of the EUROHYDROS flask sampling stations discussed here. Time series Fig. 2 shows the time series of (H2) and 隆D(H2) for the different stations. These data clearly show that the (H2) and 隆D(H2) variability is much larger in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). The NH stations Alert, Mace Head and Cape Verde show clear cycles in both (H2) and 隆D(H2) that are 5-6 months out-of-phase. This phase difference is due to accumulation of H2 from D-depleted (combustion) sources in winter and strong sinks (soil uptake and OH oxidation) in summer that preferentially remove the light hydrogen. For Schauinsland and Neumayer, cycles are observed in (H2) but not in 隆 D(H2). There is large scatter in the Schauinsland 隆D(H2) data, possibly due to the continental location close to source regions. The Amsterdam Island (H2) cycle is weak and no cycle is observed in 隆D(H2). Fig 2: (H2) (blue squares, by UHEI-IUP, LSCE and MPI-BGC) and 隆D(H2) (red circles, by IMAU) measured on samples from the six stations. Solid lines represent harmonic best fits, error bars represent one standard error, open circles represent data that were affected by a system bias, open stars represent other outliers (some in Amsterdam Island are off the scale). Data denoted with open symbols are not used in the calculations. Latitude gradient Sinks In Fig. 3, the seasonal averages If a seasonal cycle is assumed are plotted against station to be driven mainly by sinks, latitude. In all seasons, both an apparent fractionation (H2) and 隆D(H2) are higher in factor (留app) can be calculated the SH than in the NH. from a Rayleigh fractionation Surprisingly, the minimum in 隆 plot. Good fits were obtained D(H2) is not found in Alert, but for three stations only (Fig. at one of the lower-latitude 4(a)). From 留app, the relative stations. As H2 from contribution of the two H2 anthropogenic sources is sinks can be estimated (Fig. D-depleted, this minimum 4(b)). This shows that the may be a result of relative importance of the anthropogenic influence. uptake by soil increases with Fig 3: Seasonal averages of (H2) latitude (i.e. with larger land and 隆D(H2), plotted against station mass and lower OH levels). latitude. Error bars indicate one standard deviation Fig 4: (a) Apparent fractionation factors (留app) for the NH plotted against station latitude. (b) Relative contribution of soil uptake and OH oxidation to the total sinks, assuming 留app is a mass-weighted average of 留s of the two sinks. Conclusions/Outlook These regular observations of (H2) and 隆D(H2) provide insight into the seasonal and latitudinal distribution of H2 and its isotopic composition. Read more Tentative conclusions can be drawn about the geographical variations These data were published in in its sources and sinks. These data have been used with the global - A. M. Batenburg et al., Temporal and spatial variability of the stable isotopic chemical transport model TM5 and help to distinguish between composition of atmospheric molecular hydrogen, ACP, 11, 6985-6999, 2011 different source/sink scenarios. TM5 model results were published in Acknowledgements: We thank our EUROHYDROS partners for this pleasant and - G. Pieterse et al., Global modelling of H2 mixing ratios and isotopic compositions productive cooperation. EUROHYDROS is funded by the EU. with the TM5 model, ACP, 11, 7001-7026, 2011

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ESRL/GMD 2012 poster

  • 1. Temporal and spatial variability of 隆D(H2) from six EUROHYDROS stations A. M. Batenburg, S. Walter, G. Pieterse, I. Levin, M. Schmidt, A. Jordan, S. Hammer, C. Yver, and T. R旦ckmann Worldwide (H2) and 隆D(H2) observations Present atmospheric molecular hydrogen (H2) mixing ratios ((H2)) are around ~0.5 ppm. In the coming decades, H2 levels are expected to rise due to use of hydrogen as an energy carrier. This may affect greenhouse gas lifetimes and stratospheric ozone depletion. Unfortunately, large uncertainties still exist in the global H2 budget. The different sources and sinks of H2 have very distinct isotopic signatures and fractionation coefficients, respectively. Therefore, measurements of isotopic composition (隆D(H2)) are a promising tool to gain insight into H2 source and sink processes and to constrain the terms in the global budget. Weekly to monthly air samples from six locations in the EUROHYDROS network have been analysed for 隆D(H2) with a GC-IRMS system. The time series thus obtained now stretch over at least a year for all stations. This is the largest set of ground station observations of 隆D(H2) so far. Fig 1: Locations of the EUROHYDROS flask sampling stations discussed here. Time series Fig. 2 shows the time series of (H2) and 隆D(H2) for the different stations. These data clearly show that the (H2) and 隆D(H2) variability is much larger in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). The NH stations Alert, Mace Head and Cape Verde show clear cycles in both (H2) and 隆D(H2) that are 5-6 months out-of-phase. This phase difference is due to accumulation of H2 from D-depleted (combustion) sources in winter and strong sinks (soil uptake and OH oxidation) in summer that preferentially remove the light hydrogen. For Schauinsland and Neumayer, cycles are observed in (H2) but not in 隆 D(H2). There is large scatter in the Schauinsland 隆D(H2) data, possibly due to the continental location close to source regions. The Amsterdam Island (H2) cycle is weak and no cycle is observed in 隆D(H2). Fig 2: (H2) (blue squares, by UHEI-IUP, LSCE and MPI-BGC) and 隆D(H2) (red circles, by IMAU) measured on samples from the six stations. Solid lines represent harmonic best fits, error bars represent one standard error, open circles represent data that were affected by a system bias, open stars represent other outliers (some in Amsterdam Island are off the scale). Data denoted with open symbols are not used in the calculations. Latitude gradient Sinks In Fig. 3, the seasonal averages If a seasonal cycle is assumed are plotted against station to be driven mainly by sinks, latitude. In all seasons, both an apparent fractionation (H2) and 隆D(H2) are higher in factor (留app) can be calculated the SH than in the NH. from a Rayleigh fractionation Surprisingly, the minimum in 隆 plot. Good fits were obtained D(H2) is not found in Alert, but for three stations only (Fig. at one of the lower-latitude 4(a)). From 留app, the relative stations. As H2 from contribution of the two H2 anthropogenic sources is sinks can be estimated (Fig. D-depleted, this minimum 4(b)). This shows that the may be a result of relative importance of the anthropogenic influence. uptake by soil increases with Fig 3: Seasonal averages of (H2) latitude (i.e. with larger land and 隆D(H2), plotted against station mass and lower OH levels). latitude. Error bars indicate one standard deviation Fig 4: (a) Apparent fractionation factors (留app) for the NH plotted against station latitude. (b) Relative contribution of soil uptake and OH oxidation to the total sinks, assuming 留app is a mass-weighted average of 留s of the two sinks. Conclusions/Outlook These regular observations of (H2) and 隆D(H2) provide insight into the seasonal and latitudinal distribution of H2 and its isotopic composition. Read more Tentative conclusions can be drawn about the geographical variations These data were published in in its sources and sinks. These data have been used with the global - A. M. Batenburg et al., Temporal and spatial variability of the stable isotopic chemical transport model TM5 and help to distinguish between composition of atmospheric molecular hydrogen, ACP, 11, 6985-6999, 2011 different source/sink scenarios. TM5 model results were published in Acknowledgements: We thank our EUROHYDROS partners for this pleasant and - G. Pieterse et al., Global modelling of H2 mixing ratios and isotopic compositions productive cooperation. EUROHYDROS is funded by the EU. with the TM5 model, ACP, 11, 7001-7026, 2011