Intraseasonal Oscillations of \textasciitilde20 days Revisited: The Jet Stream and its Ecological Implications along the Oregon Coast

Intraseasonal oscillations in the atmosphere-ocean system can affect weather patterns and regional ecosystems. In turn, these oscillations can be affected by climate variability, resulting in additive and/or non-linear responses of regional ecosystems to climate forcing. In the Northern California Current, a strong correlation was identified between the location of the jet stream and planktonic bloom near Newport, Oregon (44.652°N), on time scales of approximately 20 days during the 2001 summer upwelling season (Bane et al., 2007). However, this relationship has not been investigated for years other than 2001. To identify additional years with the \textasciitilde20-day signal, we use remotely-sensed and reanalysis data of geopotential, sea surface temperatures, meridional wind, and chlorophyll-a for the last two decades (2001-2022). We explore the relationship between the atmospheric conditions and primary production using data analysis techniques such as lagged cross correlations, maximum covariance analysis (MCA), and wavelet coherence analysis. The MCA between geopotential and chlorophyll-a displays strong coherence within the 16-to-32-day periodicity band in 2004, 2007, 2014, 2015, 2016, 2018, 2020, and 2021. As 2001, 2007 and 2018 have the strongest coherence at \textasciitilde20 days in the entirety of the upwelling season, whereas other years only contain a strong \textasciitilde20-day signal for part of the upwelling season. The relationship between jet stream position and large-scale atmospheric processes shows that years in a cold phase of Pacific Decadal Oscillation (PDO) and with shifts to a neutral El Niño Southern Oscillation (ENSO) index often contain the \textasciitilde20-day ISO, while presence of a strong El Niño or La Niña appears to suppress the \textasciitilde20-day ISO. Preliminary results of community composition indicate oscillations in plankton size distribution occur with the \textasciitilde20-day jet stream oscillation. Furthering this work can inform ecosystem-based management to prepare for environmental conditions that will enhance or inhibit lower trophic level productivity and subsequent fishery yields during a given year.