ABSTRACT

Marine heatwaves (MHWs) have increased worldwide in intensity, frequency, and duration, often with severe impacts on ecologically and socio-economically important coastal habitats. Most MHW studies have focused on summer events in specific regions or global open-water analyses with little consideration to seasonality or spatial biogeography of the nearshore zone. We address this research gap by analysing changes to MHWs across seasons and ecoregions, within 12 nautical miles (NM) of New Zealand’s coastline, an area with high biodiversity and endemism. We used season-specific linear trend analysis with temporal breakpoints between 1982 and 2021 to identify the number of MHW events and MHW days, and mean, maximum, and cumulative intensity of MHWs for New Zealand coastal ecoregions. Across ecoregions, 69.5% of 200 trend analyses increased significantly whereas the remaining 30.5% were unaffected. For the significant increases, temporal breakpoints occurred between 1994 and 2012. We conclude that MHWs have become stronger, longer and more frequent across coastal New Zealand, but with some variability within and between regions. Our trend-analyses could enable retrospective analyses of biological tipping-points and inform management practices that may enhance the resilience of ecoregions yet to face MHW breakpoints or those in the initial stages of major climatic changes.

摘要

全球海洋热浪 (MHW) 的强度、频率和持续时间不断增加，往往对生态和社会经济重要的沿海栖息地造成严重影响。大多数 MHW 研究都集中在特定地区的夏季事件或全球开放水域分析，很少考虑近岸区域的季节性或空间生物地理学。我们通过分析新西兰海岸线 12 海里 (NM) 范围内的 MHW 跨季节和生态区域的变化来弥补这一研究空白，该地区具有高度的生物多样性和特有性。我们使用 1982 年至 2021 年间时间断点的特定季节线性趋势分析来确定新西兰沿海生态区的 MHW 事件数量和 MHW 天数，以及 MHW 的平均值、最大和累积强度。跨生态区，69。200 个趋势分析中有 5% 显着增加，而其余 30.5% 未受影响。对于显着增加，时间断点出现在 1994 年至 2012 年之间。我们得出的结论是，新西兰沿海地区的 MHW 变得更强、更长、更频繁，但区域内和区域之间存在一些差异。我们的趋势分析可以对生物临界点进行回顾性分析，并为管理实践提供信息，从而增强尚未面临 MHW 断点或处于重大气候变化初始阶段的生态区域的恢复力。