More Than Marine Heatwaves: A New Regime of Heat, Acidity, and Low Oxygen Compound Extreme Events in the Gulf of Alaska

• Published in: AGU Advances
• Main Authors: Claudine Hauri, Rémi Pagès, Katherine Hedstrom, Scott C. Doney, Sam Dupont, Bridget Ferriss, Malte F. Stuecker
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2024
• Subjects: climate change; ocean acidification; extreme events; ecosystem; Geology; QE1-996.5; Geophysics. Cosmic physics; QC801-809; Ocean acidification; Alaska
• Online Access: https://doi.org/10.1029/2023AV001039; https://doaj.org/article/7332805725e84998b920cf0387f0ff42

Abstract Recent marine heatwaves in the Gulf of Alaska have had devastating impacts on species from various trophic levels. Due to climate change, total heat exposure in the upper ocean has become longer, more intense, more frequent, and more likely to happen at the same time as other environmental extremes. The combination of multiple environmental extremes can exacerbate the response of sensitive marine organisms. Our hindcast simulation provides the first indication that more than 20% of the bottom water of the Gulf of Alaska continental shelf was exposed to quadruple heat, positive hydrogen ion concentration [H+], negative aragonite saturation state (Ωarag), and negative oxygen concentration [O2] compound extreme events during the 2018–2020 marine heat wave. Natural intrusion of deep and acidified water combined with the marine heat wave triggered the first occurrence of these events in 2019. During the 2013–2016 marine heat wave, surface waters were already exposed to widespread marine heat and positive [H+] compound extreme events due to the temperature effect on the [H+]. We introduce a new Gulf of Alaska Downwelling Index (GOADI) with short‐term predictive skill, which can serve as indicator of past and near‐future positive [H+], negative Ωarag, and negative [O2] compound extreme events near the shelf seafloor. Our results suggest that the marine heat waves may have not been the sole environmental stressor that led to the observed ecosystem impacts and warrant a closer look at existing in situ inorganic carbon and other environmental data in combination with biological observations and model output.