A102-02
CarbonWatchNZ: Regional to National Scale Inverse Modelling of New Zealand’s Carbon Balance

Thursday, 10 December 2020: 16:18
Virtual
Beata Bukosa1, Sara E Mikaloff-Fletcher1, Gordon W Brailsford1, Colin Nankivell1, Dan Smale2, Elizabeth D. Keller3, Jocelyn C Turnbull3, Kay Steinkamp1, Mike Harvey1, Peter Sperlich1, Rowena Claire Moss1, Sally Gray1, Stuart Moore1, Sylvia Nichol1 and Zoe Buxton1, (1)National Institute of Water and Atmospheric Research (NIWA), Wellington, New Zealand, (2)National Institute of Water and Atmospheric Research (NIWA), Lauder, New Zealand, (3)GNS Science, Lower Hutt, New Zealand
Recorded Presentation
Abstract:
Atmospheric observations of CO2 and other greenhouse gases have been widely used to constrain estimates of terrestrial and oceanic CO2 fluxes through atmospheric inverse modelling. Yet, applying these methods at national scale to verify and improve the National Inventory Report (NIR) and support the Paris agreement remains at the frontier of CO2 science.

We use inverse modelling to estimate New Zealand’s carbon uptake and emissions using atmospheric measurements and model. This effort is part of a five year CarbonWatch-NZ research programme, which aims to develop a complete top-down picture of New Zealand's carbon balance using national inverse modelling and targeted studies of New Zealand’s forest, grassland and urban environments. In addition to quantifying New Zealand’s carbon emissions on a national scale, we also focus on identifying the prevailing processes driving CO2 changes in New Zealand to support climate mitigation.

In an initial study based on the inversion system used in CarbonWatch-NZ, a significantly stronger (30-60 %) sink was found relative to the NIR (Steinkamp et al., 2017), suggesting a strong CO2 uptake in Fiordland, a region covered by indigenous temperate rainforest in New Zealand's South Island. Here, we present new results of CarbonWatch-NZ by expanding the studied time period from 2011-2013 to 2020, expanding our atmospheric observing network from two (Baring Head, 41.41°S, 174.87°E and Lauder, 38.33°S, 176.38°E) to a total of eleven in situ greenhouse gas measurement sites, and improving our atmospheric model resolution by roughly a factor of ten (NAME model, 1.5 km).

Our new results suggest that the strong sink observed in 2011-2013 did not diminish, but for recent years we have found an even stronger sink than for before. Additional measurements collected in the Fiordland region (i.e., CO2 isotopes, carbonyl sulphide) also suggest a stronger CO2 uptake, supporting our inversion results. Implementing observations from an additional site in the North Island (Maunga Kakaramea, 45.034°S, 169.68°E) have additionally increased the strength of the sink, pointing to additional strong sink region at the top of the North Island.

Ref: Steinkamp et al, Atmospheric CO2 observations and models suggest strong carbon uptake by forests in New Zealand, Atmospheric Chemistry and Physics, 2017.

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