Preprints
https://doi.org/10.5194/esd-2023-14
https://doi.org/10.5194/esd-2023-14
12 May 2023
 | 12 May 2023
Status: this preprint is currently under review for the journal ESD.

Estimating freshwater flux amplification with ocean tracers via linear response theory

Aurora Basinski-Ferris and Laure Zanna

Abstract. Accurate estimation of changes in the global hydrological cycle over the historical record is important for model evaluation and understanding future trends. Freshwater flux trends cannot be accurately measured directly, so quantification of change often relies on trends in ocean salinity. However, anthropogenic forcing has also induced ocean transport change, which imprints on salinity. We find that this ocean transport affects the surface salinity of the saltiest regions (the subtropics), while having little impact on the surface salinity in other parts of the globe. We present a method based on linear response theory which accounts for the regional impact of ocean circulation changes while estimating freshwater fluxes from ocean tracers. Testing on data from the Community Earth System Model large ensemble, we find that our method can recover the true amplification of freshwater fluxes, given thresholded statistical significance values for salinity trends. We apply the method to observations and conclude that over the period 1975 to 2019, the hydrological cycle has amplified by 4.52 ± 1.21 % per degree of surface warming.

Aurora Basinski-Ferris and Laure Zanna

Status: open (until 13 Jul 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Aurora Basinski-Ferris and Laure Zanna

Model code and software

Code: Freshwater flux estimation with linear response theory Aurora Basinski-Ferris https://zenodo.org/record/7853128

Aurora Basinski-Ferris and Laure Zanna

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Short summary
Under anthropogenic climate change, the hydrological cycle is expected to intensify. However, it is difficult to directly measure the amplification that has occurred over the past decades. Generally, ocean salinity patterns are used to infer this change in the hydrological cycle. Here, we present a new method to do this inference based on linear response theory. We find that over the period 1975 to 2019, the hydrological cycle has amplified by 4.52 ± 1.21 % per degree of surface warming.
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