Dr. Julia K Parrish, Associate Dean, College of the Environment, University of Washington; Executive Director, Coastal Observation and Seabird Survey Team (COASST)
Marine Heatwaves, ENSO, and a Warming Arctic: The "New Normal" of Seabird Mass Mortality Events
Recent research has highlighted that the frequency and magnitude of animal mass mortality events (MMEs) have increased over the last half a century, and that mortality events are likely to become more frequent with an increasingly variable climate. Since 2014 the North Pacific has experienced 7 seabird mass mortality events, starting with Cassin's Auklets along the West Coast in 2014-15 through a suite of species (chiefly murres and fulmars) in the Bering Strait region in 2018. In total, these events resulted in millions of mortalities. Although the North Pacific and northern Alaskan coastal regions have experienced MMEs in the past, the frequency, duration and magnitude of MMEs increased sharply following the onset of a series of warming forces, including the northeast Pacific marine heatwave, a weak El Niño, and continued Arctic warming (indicated by reductions in sea ice extent, alterations to the extent of the Bering Sea cold pool, and overall warmer sea surface temperatures compared to climatological averages). Despite the general linkage between a warmer ocean and seabird MMEs, the operational relationship between elevated sea temperatures and the observed effects on seabirds is currently poorly understood. Causative factors are likely to be multifactorial, including but not limited to: (1) Prey Base - shifts in the diversity, energy content, abundance, spatial distribution and phenology of prey populations; (2) Disease; (3) Harmful Algal Blooms; (4) Extreme Weather; and (5) Shifting Physical Cues (e.g. freeze-up and break-up). We used data from a citizen science program focused on beached birds (COASST), as well as information from coastal communities; state, federal and tribal agencies; and other beached bird programs to provide an overview of seabird mortality events affecting the North Pacific and Alaska over the last 16 years.