Marine cold-spells

Characterising ocean temperature variability and extremes is fundamental for understanding the thermal bounds in which marine ecosystems have adapted. While there growing evidence of how heatwaves threaten ecosystems, prolonged periods extremely cold temperatures, cold-spells, received less global attention. We synthesize literature on their ecological impacts physical mechanisms. Ecological these events were observed across a range species biophysical processes, including mass mortalities, shifts, habitat loss, altered phenology. The development cold-spells often due to wind-induced but mechanisms are documented literature. Given need consistent comparison we develop definition detecting from time series classifying them into four categories. This used consistently detect globally over satellite record compare characteristics notable events. Globally, cold-spells’ occurrence, duration, intensity decreasing, with some areas, such as Southern Ocean, showing signs increase past 15 years. All cold-spell categories affected by decreases, exception “IV Extreme” events, so rare that has been little decrease. decreasing occurrences could be viewed providing beneficial reduction stress fewer spells will alter regime experience important consequences structure function.