Frequency of marine heatwaves in the North Atlantic and North Pacific since 1950

Extreme and large-scale warming events in the ocean have been dubbed marine heatwaves,and these have been documented in both the Northern and Southern Hemispheres. This paper examinesthe intensity, duration, and frequency of positive sea surface temperature anomalies in the North Atlanticand North Pacific Oceans over the period 1950–2014 using an objective definition for marine heatwavesbased on their probability of occurrence. Small-area anomalies occur more frequently than large-areaanomalies, and this relationship can be characterized by a power law distribution. The relative frequencyof large- versus small-area anomalies, represented by the power law slope parameter, is modulated bybasin-scale modes of natural climate variability and anthropogenic warming. Findings suggest that theprobability of marine heatwaves is a trade-off between size, intensity, and duration and that region specificvariability modulates the frequency of these events.

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