Ocean oxygen in a warming world
Observations indicate that the ocean is losing oxygen and models suggest that this will accelerate under persistent climate warming. Current indications are, however, that CMIP5 models under-estimate the magnitude of ocean oxygen loss relative to our best observational estimates.
Oxygen loss as a function of temperature change between 1970 and 2014.
The models suggest that warming-driven reductions in solubility are reinforced by increases in AOU in the extra-tropics, leading to large oxygen loss and relatively robust multi-model prediction. Oxygen loss in the tropics is more complicated, however, as changes in tropical ventilation lead to reductions in AOU that partially or wholly compensate for the direct effects of warming on solubility. The competition between these drivers yields divergent predictions across the models and contributes to ambiguous results at the global scale. Tropical ventilation, however, is poorly simulated in many (most?) models, so it is difficult to assess confidence in these results.
This project will aim for as near-comprehensive characterization of CMIP6 oxygen projections as possible in the 3-day timeframe. We will seek to produce compelling visualizations of trends and phenomenology and aim to bundle a collection of Jupyter Notebooks into an accessible, reproducible computational narrative.
Here are some example research questions that will guide the analysis.
How well do the models simulate the mean state and observed trends in upper ocean dissolved oxygen?
What are the trajectories of future ocean oxygen loss and how do these manifest regionally from solubility, circulation, and oxygen utilization rate (OUR) drivers?
What are the projected change in hypoxic and anoxic volumes globally? How much will the vertical extent of viable pelagic habitat be compressed by thermocline O2 loss?
Can we explain AOU-driven changes in tropical oxygen loss in terms of ventilation dynamics? Do we expect that these dynamics are well simulated by the models?
What is the value of climate mitigation to avoiding impacts of oxygen loss?
Is it possible to develop emergent constraints or other clever means of reducing uncertainty in future oxygen projections via exploiting interannual to decadal variability, for instance? Are there relationships between simulated decadal variability and the forced response?
Anticipated Data Needs
- (0th order) Ocean annual 3D fields: potential temperature, salinity, oxygen, oxygen saturation,…
- Additional fields to look at ventilation question…
Anticipated Software Tools
We will use the standard suite of Python analysis tools: xarray, dask, etc.
We will rely on packages like xgcm, esmlab, etc. to enable concise expressions for operations like integrals, etc. It is possible shortcomings in these packages will need to be addressed to enable writing elegant, performant, exemplary notebooks.
People with interest and expertise in ocean biogeochemistry and tropical ocean circulation.