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Poster presented at European Geosciences Union General Assembly 2011.

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  1. 1. Correlations between δ(D,H2) and methane (CH4) in the UTLS region obtained from CARIBIC samples A.M. Batenburg1, T.J. Schuck2, A. Baker2, C.A.M. Brenninkmeijer2 and T. Röckmann1 1 Institute for Marine and Atmospheric Research, Utrecht University, Utrecht, the Netherlands 2 Max Planck Institute for Chemistry, Atmospheric Chemistry Division, Mainz, Atmospheric H2 and the CARIBIC project Flights to Caracas If H2 comes into wide use as a fuel, its atmospheric levels may In total, 490 samples from 21 return flights rise (due to leakage) above present-day levels (≈ 0.5 ppm). This have been analyzed for H2 mixing ratios may affect the atmosphere’s oxidative capacity and stratospher- (m(H2)) and δ(D,H2) at the IMAU isotope labo- ic ozone chemistry. Unfortunately, large uncertainties still exist ratory. Fig. 2 shows results of 7 flights with in the global H2 budget. destination Caracas. The different sources and sinks of H2 have distinct isotope ef- Some samples seem affected by pollution (a fects. Therefore, measurements of isotopic composition high m(H2) and low δ(D,H2) value). This tends (deuterium content, expressed as δ(D,H2)) are a promising tool to occur in samples that were taken around to constrain the terms in the global budget. take-off and landing of the aircraft (e.g. flight The CARIBIC project uses an automated instrument container 286 and 266, values are off the figure scale).Fig.1: The aircraft (Lufthansa on board of a commercial passenger aircraft to carry out in-situAirbus A340-600) and the at- With meteorological and chemical data, sam-tached inlet system used for measurements and collect air samples. The resulting samples ples with stratospheric influence can beCARIBIC. are mostly from the Upper Troposphere-Lower Stratosphere identified. These samples often show a clear (UTLS) region, an interesting, but little studied, part of the at- Fig.2: m(H2) (a) and δ(D,H2) (b) data from flights to Caracas, Venezuela. Stratosphere- elevation in δ(D,H2) . mosphere. influenced samples are shown with open symbols. CH4 oxidation Stratosphere data Monsoon flights Conclusions 156 samples contain air from the lower stratosphere. Previ- Schuck et al. (2010) found A large number of CARIBIC samples D-enriched H2: H2 δ(D,H2) increase ously it was found that in the stratosphere, the competing increased levels of CH4 in were analyzed for m(H2) and δ(D,H2). production production and destruction processes for H2 balance out, flights to India during • For the stratosphere the number of but that these do cause a strong deuterium enrichment summer monsoon. available δ(D,H2) observations has in- H2 with δ(D,H2) (Fig.3). δ(D,H2) shows a compact correlation with methane No enhancement was creased fivefold, and they provide in- (CH4), which is destroyed as H2 is produced. found in m(H2), but the formation about the stratospheric H2 H2 Preferential re- In the CARIBIC data, δ(D,H2) is also strongly correlated with samples with increased cycle. destruction moval of H over D: δ(D,H2) increase CH4, whereas m(H2) is not (Fig. 4 (a)). The correlation’s slope is methane showed a de- • First observations of δ(D,H2) in the very similar to the one found in a stratospheric balloon flight crease in δ(D,H2) that is cor- summer monsoon were made. These oxidation by OH (Röckmann et al., 2003) (Fig. 4(b)). That this effect is found in related to m(CH4) (Fig.5 contain an interesting correlation samples from different geographic locations and altitudes and 6). with the CH4 increase in this season,Fig.3: A cartoon representation ofthe the stratospheric H2 cycle shows that this correlation likely holds globally. This δ(D,H2)decrease in the which may point to an as yet unstud- `Monsoon plume’ is prob- Fig.5: m(CH4) (a) and δ(D,H2)(b) measured on tropospheric ied microbial H2 source. ably caused by increased samples from flights to India south of 400 N in the summer • These samples from the UTLS region convection, bringing H2 monsoon (July-Sept,green shades) and after monsoon (Okt-Nov, reddish colors). are complementary to observations that is depleted in D from from ground stations and ship cruises surface sources to cruising and will help in constraining the un- altitude. certainties in the H2 budget and vali- That no simultaneous H2 dating models. increase is seen, may indi- cate a contribution from a very depleted source. In- References creased microbial produc- - Röckmann et al., Heavy hydrogen in the strato- sphere, Atmos. Chem. Phys 3, 2015-2023, 2003 tion in the wet season is - Schuck et al, Greenhouse gas relationships in the much more strongly de- Indian summer monsoon plume measured by the pleted than combustion CARIBIC passenger aircraft, Atmos. Chem. Phys. 11, sources (≈ -700‰, resp. 503-518, 2011 Fig.4 (a): m(H2) and δ(D,H2) plotted against methane mixing ratio (m(CH4)), with fits through the data. (b): δ(D,H2) Fig.6: δ(D,H2) plotted against m(CH4) for the monsoon plotted against m(CH4) for the CARIBIC samples and literature values (Röckmann et al., 2003) ≈ -200‰). samples in Fig.5, with linear fit. Questions: