ICOS Science Conference, Session 6

1. Beata Bukosa, Sara Mikaloff Fletcher, Gordon Brailsford, Colin Nankivell, Dan Smale,
Elizabeth Keller, Jocelyn Turnbull, Kay Steinkamp, Mike Harvey, Peter Sperlich, Rowena
Moss, Sally Gray, Stuart Moore, Sylvia Nichol, and Zoe Buxton
Regional to National Scale Inverse Modelling
of New Zealand's Carbon Balance

3. National scale CO2
uptake/emission estimates
and national carbon reporting
based on atmospheric data

4. – Pilot Study
Annual mean CO2 fluxes, Steinkamp et al. (2017)
National Inventory vs inversion results
(bottom up) (top down)

5. Inversion 30-60% larger CO2 sink
– Pilot Study
Annual mean CO2 fluxes, Steinkamp et al. (2017)

6. Region 2011 2012 2013
NZ Total -132(36) -97(36) -64(40)
North Island
North
South
18(28)
5(25)
13(17)
-40(28)
-10(25)
-30(17)
-1(30)
7(25)
-8(19)
South Island
East
West
Fiordland
-149(22)
-37(17)
-113(17)
-68(13)
-56(23)
9(18)
-65(16)
-22(12)
-63(28)
-10(23)
-52(17)
-31(14)
Annual mean CO2 flux with uncertainty (1σ) for NZ regions
Steinkamp et al. (2017)
Stronger CO2 sink
MfE, 2017
MfE – Ministry for the Environment

7. • Methodology
• Inversion Setup
• Results
• Carbon exchange for recent years, still a sink?
• Inversion improvements
Higher model resolution
Impact of measurements from a new site
Talk Overview

8. How the inversion works

9. • 25 regions
𝐽 =
1
2
𝑇𝑥 − 𝑑 𝑇
𝐶 𝑑
−1
𝑇𝑥 − 𝑑 +
1
2
𝑥 − 𝑥 𝑜
𝑇
𝐶 𝑜
−1
(𝑥 − 𝑥 𝑜) +
1
2
𝑆𝑥 𝑇
𝐶𝑠
−1
(𝑆𝑥)
Methodology - Bayesian approach
minimized
analytically
𝑥 = 𝐶(𝑇 𝑇 𝐶 𝑑
−1
𝑑 + 𝐶 𝑜
−1 𝑥 𝑜)
𝐶 = (𝑇 𝑇
𝐶 𝑑
−1
𝑇 + 𝐶 𝑜
−1
)−1
The posterior & error covariance matrix

10. What do we see from the measurements?
13-14, 15-16 LT – well mixed air
Baseline – predominantly oceanic air
Inversion data = measurements – baseline – anthropogenic signal
LT – local time

11. Methodology
=
?
Year
CO2(ppm)CO2(ppm)
Year

12. Methodology
= +
? Transport model
NAME III Lagrangian dispersion model
+
NZLAM (12 km) / NZCSM (1.5 km) meteorology
(Local configuration of the UK Met Office Unified
Model)
Year
CO2(ppm)CO2(ppm)
Year

13. Methodology
?
= + +
Prior flux
Biosphere – BIOME-BGC v4.2
Ocean – Takahashi et al. (2009)
Anthropogenic – EDGAR v4.2
Transport model
NAME III Lagrangian dispersion model
+
NZLAM (12 km) / NZCSM (1.5 km) meteorology
(Local configuration of the UK Met Office Unified
Model)
Prior terrestrial
model output
Year
CO2(ppm)CO2(ppm)
Year

14. Results

15. Annual fluxes

16. Annual fluxes
2014 & 2015 work in progress

17. Important model improvement!
NZLAM (12 km) NZCSM (1.5 km)

18. Impact on inversion results, 2018
NZLAM NZCSM
(12 km) (1.5 km)

19. Annual fluxes – sink location
Near neutral Strong sink

20. North Island
Indigenous & planted, exotic
forests
vs
South Island
Mature, indigenous forests
New site, Maunga Kākaramea
Better CO2 flux estimates
&
Better understanding of the CO2 exchange
between different forest types

21. What do we expect? Even larger sink?
Additional significant
CO2 sink in the North
Island?

22. Annual fluxes with new data
2 sites
3 sites
Additional significant
CO2 sink in the North
Island!

23. Monthly fluxes, CO2 variability
Southern Hemisphere seasons!

24. Monthly fluxes, CO2 variability
2 sites

25. Monthly fluxes, CO2 variability
Stronger CO2 uptake during summer
2 sites

26. 2 sites
3 sites
Monthly fluxes, CO2 variability

27. Monthly fluxes, CO2 variability, 2018 – 2 sites
CO2 uptake present in winter also

28. CO2 tracer measurements, Fiordland
Data from Peter Sperlich & Stephen Montzka
CO2 isotopes (δ13C and Δ14C) and Carbonyl sulphide (COS) flask measurements in Fiordland
CO2 (ppm) Uptake Respiration
Autumn -26.4 23.4
Winter -42.9 43.0
Terrestrial biosphere signal Respiration PhotosynthesisCO2 signal

29. 13 sites in total - GHG measurements + isotopes + COS + flux tower
3 long running sites with continuous measurements
9 new sites with in situ measurements
8 new sites with discrete measurements
+ smaller scale studies:
Forests
Grasslands
Urban areas
- Future directions
Fiordland
Auckland
Lake Taupo
Raukumara
Manukau Heads
Winchmore

30. Thank you
Beata.Bukosa@niwa.co.nz
More Info: https://niwa.co.nz/climate/research-projects/carbon-watch-nz #CarbonWatchNZ
Acknowledgements
• CarbonWatchNZ Team at NIWA, GNS Science,
Manaaki Whenua Landcare Research, and
University of Waikato
• UK Met Office and NIWA weather and Lagrangian
modelling teams
• New Zealand eScience Infrastructure (NeSI)
• MBIE, Marsden Fund, and NIWA for funding
• NIWA in situ measurements team
• Recent flux NZ picture: 2016-2019 CO2 sink still present
• New measurements suggest even larger sink
Work in progress, sensitivity tests, uncertainty quantification
Summary

31. Baring Head and Lauder Baring Head, Lauder and Maunga Kakaramea
Modelled footprints
Flux uncertainties in the
North Island

32. Residuals