Towards Uncovering Arctic Marine Heatwaves

Marine heatwaves (MHWs) are intensifying globally, and have become more frequent in the Arctic under ongoing climate warming. Yet, they remain little studied in the high Arctic, despite rapid environmental changes and distinctive regional features such as extensive sea ice and strong salinity stratification. These conditions likely produce polar-specific driving mechanisms and impacts, which are especially unclear for MHWs occurring below the Arctic surface.Here, we review and synthesise scattered yet valuable insights from across disciplines to address two key questions: (i) What are the drivers of Arctic MHWs, and (ii) what are their ecological and biogeochemical impacts? We extend this review beyond the surface to the largely overlooked subsurface dimension. We clarify where knowledge is well-established, and where knowledge remains speculative but supported by indirect evidence. In particular, we highlight Arctic-specific processes associated with MHWs, and outline plausible yet undocumented feedback mechanisms. We conclude by offering methodological and scientific recommendations to guide future research.By integrating cross-disciplinary information, we aim to advance a more comprehensive understanding of Arctic MHWs and their potential consequences for this rapidly changing ocean.