How Did the 2017/2018 Heat Wave Over the Tasman Sea Affect Ocean Carbon Uptake and Biogeochemistry?

The Tasman Sea experienced a record-breaking heat wave during the austral summer of 2017/8. The October-January average sea surface temperatures in this region were 2°C or more above average over most of the Tasman Sea south of 35°S, and peak temperatures exceeded 6°C in places. How did this extreme event impact ocean carbon uptake and biogeochemistry, and what are the implications in a changing climate where extreme events become more frequent?

Analysis of preliminary atmospheric measurements of CO₂and related gases, including N₂O, O₂/N₂ratios, radiocarbon and ¹³C/¹²C carbon isotopes suggests that the heat wave had a significant impact on air-sea CO₂exchange in the Southwest Pacific. We use satellite observations of sea surface temperatures and chlorophyll to assess the link between surface temperature changes and biology and Argo float data to delve beneath the surface. Ship based observations of DIC/CO₂, N₂O, and N₂/O₂from research voyages during 2017/8 have been analysed to investigate the role of upwelling. Subsurface observations of mixed layer depth, temperature, and other physical parameters from Argo floats will be presented. Atmospheric simulations connect the changes we find in the ocean with the atmospheric data. Finally, we will link the findings of this study to future projections from CMIP to explore what lessons the 2017/8 heat wave might teach us about the future of Tasman Sea carbon exchange and biogeochemistry.