Triple oxygen isotope composition of CO<sub>2</sub> in the upper troposphere and stratosphere
<p>High-precision measurements of the triple oxygen isotope composition of CO<span class="inline-formula"><sub>2</sub></span> (<span class="inline-formula">Δ<sup>′17</sup></span>O) can be used to estimate biosphere–atmosphere...
Saved in:
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-06-01
|
| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/18/2701/2025/amt-18-2701-2025.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | <p>High-precision measurements of the triple oxygen isotope composition of CO<span class="inline-formula"><sub>2</sub></span> (<span class="inline-formula">Δ<sup>′17</sup></span>O) can be used to estimate biosphere–atmosphere exchange of CO<span class="inline-formula"><sub>2</sub></span>, the residence time of tropospheric CO<span class="inline-formula"><sub>2</sub></span>, and stratosphere–troposphere exchange. In this study, we report measurements of the <span class="inline-formula">Δ<sup>′17</sup></span>O(CO<span class="inline-formula"><sub>2</sub></span>) from air samples collected during two aircraft-based programmes, CARIBIC and StratoClim. CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) provided air samples from numerous transcontinental flights in the upper troposphere–lower stratosphere region. StratoClim (Stratospheric and upper tropospheric processes for better climate predictions) conducted intensive campaigns with the high-altitude aircraft M55 <i>Geophysica</i> during the Asian summer monsoon anticyclone (ASMA), providing air samples from altitudes up to 21 km.</p>
<p>Using high-precision <span class="inline-formula">Δ<sup>′17</sup></span>O measurements of the CARIBIC samples, we show that the N<span class="inline-formula"><sub>2</sub></span>O–<span class="inline-formula">Δ<sup>′17</sup></span>O correlation, previously observed in the stratosphere, extends to the upper troposphere. Moreover, we found no significant spatial or hemispheric differences in <span class="inline-formula">Δ<sup>′17</sup></span>O(CO<span class="inline-formula"><sub>2</sub></span>) for the upper-tropospheric samples collected during the CARIBIC programme. However, in many of the StratoClim samples, with significant stratospheric contributions, we observed a much lower <span class="inline-formula">N<sub>2</sub>O</span>–<span class="inline-formula">Δ<sup>′17</sup></span>O slope compared to CARIBIC samples and previous publications. This deviation is attributed to change in eddy diffusion above the tropopause within the ASMA, confirming previously published model calculations. These samples provide the first experimental evidence that differences in vertical mixing/transport can lead to significantly different <span class="inline-formula">N<sub>2</sub>O</span>–<span class="inline-formula">Δ<sup>′17</sup></span>O slopes. High-precision <span class="inline-formula">Δ<sup>′17</sup></span>O measurements can identify ejections of tropospheric air into the stratosphere based on the slope of the <span class="inline-formula">N<sub>2</sub>O</span>–<span class="inline-formula">Δ<sup>′17</sup></span>O correlation, as both tracers have chemical lifetimes longer than their transport times.</p>
<p>Furthermore, we use the <span class="inline-formula">Δ<sup>′17</sup></span>O measurements from the lower stratosphere and the upper troposphere to estimate global stratospheric production and surface removal of the isotope tracer <span class="inline-formula">Δ<sup>′17</sup></span>O. The removal estimate is then used to derive an independent estimate of global vegetation exchange of CO<span class="inline-formula"><sub>2</sub></span>, confirming earlier estimates based on surface level <span class="inline-formula">Δ<sup>′17</sup></span>O measurements.</p> |
|---|---|
| ISSN: | 1867-1381 1867-8548 |