Emerging trends in landfalling atmospheric rivers over the South Pacific

Abstract Global climate models project that the South Pacific will be a hotspot for some of the largest atmospheric river (AR) changes. Thus, there is an urgent need to review both historical trends and updated high-resolution climate projections tailored to this region. Here we show that significant trends in AR frequency from reanalysis are mostly still constrained to the ocean (~45–60°S). For landfalling ARs, trends in synoptic-scale features are not yet considered robust, whereas percentile-based moisture transports show stronger increases over parts of southern New Zealand and Tasmania. Furthermore, high-resolution downscaled climate projections indicate that landfalling AR trends should become much more widespread and robustly detectable (5 of 6 models) in the next 10–20 years, first appearing across regions of southern New Zealand during spring and winter. Even under a moderate emissions scenario, projections indicate that the frequency of extreme landfalling ARs could double before mid-century, carrying significant societal impacts.