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

表征海洋温度变化和极端情况是了解海洋生态系统适应的热界限的基础。虽然有越来越多的证据表明海洋热浪如何威胁海洋生态系统，但长期极冷的海洋温度、海洋寒冷天气在全球范围内受到的关注较少。我们综合了有关寒冷海洋极端温度及其生态影响和物理机制的文献。在一系列物种和生物物理过程中观察到这些事件的生态影响，包括大规模死亡、范围变化、海洋栖息地丧失和物候变化。海洋寒潮的发展通常是由于风引起的海洋过程，但文献中记录了一系列物理机制。鉴于需要对海洋寒冷天气进行一致的比较，我们制定了一个定义，用于从温度时间序列中检测这些事件并将它们分为四类。该定义用于通过卫星记录在全球范围内一致地检测海洋寒冷天气，并比较显着寒冷事件的特征。在全球范围内，海洋寒潮的发生、持续时间和强度都在下降，在过去的 15 年中，南大洋等部分地区出现了增加的迹象。所有海洋冷系咒语类别都受到这些减少的影响，但“IV 极端”事件除外，这些事件非常罕见，几乎没有减少。虽然减少海洋寒冷天气的发生可以被视为为海洋生态系统减少寒冷压力提供了有益的帮助，