Renkl, C., H. Seo and A. J. Miller, 2026:
Marine heatwaves in the Northeast
Pacific intensify landfalling
atmospheric rivers on the west
coast of North America.
Scientific Reports, 16, 23097.
Abstract.
Extreme precipitation along the west coast of North America is often associated with atmospheric
rivers (ARs), fueled by evaporation from the ocean. When ARs interact with marine heatwaves (MHWs),
they can form compound extreme events with amplified hydrological impacts. Here, we quantify
how MHWs influence the intensity and precipitation of landfalling ARs through thermodynamic
air–sea interaction processes. We use high-resolution regional coupled ocean–atmosphere ensemble
simulations to isolate the influence of large-scale MHW-related sea surface temperature (SST)
anomalies while constraining the synoptic-scale atmospheric circulation. Focusing on well-documented
AR events during the 2013–16 Northeast Pacific MHW, we show that anomalously warm SSTs enhance
evaporation and lower-tropospheric moisture availability, leading to a robust increase in integrated
vapor transport and intensified landfalling ARs. The enhanced moisture transport results in earlier
onset and substantially increased coastal precipitation, particularly over drought-vulnerable regions
of California. Moisture-budget diagnostics demonstrate that this amplification arises from a direct
thermodynamic response to SST anomalies, rather than indirect modulation through changes in largescale
atmospheric circulation. Insights gained from this case study identify a thermodynamic pathway
linking MHWs and ARs, highlighting the role of persistent oceanic thermal anomalies in shaping
compound hydrological extremes under continued climate warming.
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