Atmospheric CO<sub>2</sub> observations and models suggest strong carbon uptake by forests in New Zealand
A regional atmospheric inversion method has been developed to determine the spatial and temporal distribution of CO<sub>2</sub> sinks and sources across New Zealand for 2011–2013. This approach infers net air–sea and air–land CO<sub>2</sub> fluxes from measurement records, us...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/47/2017/acp-17-47-2017.pdf |
| Summary: | A regional atmospheric inversion method has been developed to determine the
spatial and temporal distribution of CO<sub>2</sub> sinks and sources across New
Zealand for 2011–2013. This approach infers net air–sea and air–land
CO<sub>2</sub> fluxes from measurement records, using back-trajectory simulations
from the Numerical Atmospheric dispersion Modelling Environment (NAME)
Lagrangian dispersion model, driven by meteorology from the New Zealand
Limited Area Model (NZLAM) weather prediction model. The inversion uses
in situ measurements from two fixed sites, Baring Head on the
southern tip of New Zealand's North Island (41.408° S,
174.871° E) and Lauder from the central South Island
(45.038° S, 169.684° E), and ship
board data from monthly cruises between Japan, New Zealand, and Australia. A
range of scenarios is used to assess the sensitivity of the inversion method
to underlying assumptions and to ensure robustness of the results. The
results indicate a strong seasonal cycle in terrestrial land fluxes from the
South Island of New Zealand, especially in western regions covered by
indigenous forest, suggesting higher photosynthetic and respiratory activity
than is evident in the current a priori land process model. On the
annual scale, the terrestrial biosphere in New Zealand is estimated to be a
net CO<sub>2</sub> sink, removing 98 (±37) Tg CO<sub>2</sub> yr<sup>−1</sup> from the
atmosphere on average during 2011–2013. This sink is much larger than the
reported 27 Tg CO<sub>2</sub> yr<sup>−1</sup> from the national inventory for the same
time period. The difference can be partially reconciled when factors related
to forest and agricultural management and exports, fossil fuel emission
estimates, hydrologic fluxes, and soil carbon change are considered, but
some differences are likely to remain. Baseline uncertainty, model transport
uncertainty, and limited sensitivity to the northern half of the North Island
are the main contributors to flux uncertainty. |
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| ISSN: | 1680-7316 1680-7324 |