Abstract

Climate change is expected to warm, deoxygenate, and acidify ocean waters. Global climate models (GCMs) predict future conditions at large spatial scales, and these predictions are then often used to parameterize laboratory experiments designed to assess biological and ecological responses to future change. However, nearshore ecosystems are affected by a range of physical processes such as tides, local winds, and surface and internal waves, causing local variability in conditions that often exceeds global climate models. Predictions of future climatic conditions at local scales, the most relevant to ecological responses, are largely lacking. To fill this critical gap, we developed a 2D implementation of the Regional Ocean Modeling System (ROMS) to downscale global climate predictions across all Representative Concentration Pathway (RCP) scenarios to smaller spatial scales, in this case the scale of a temperate reef in the northeastern Pacific. To assess the potential biological impacts of local climate variability, we then used the results from different climate scenarios to estimate how climate change may affect the survival, growth, and fertilization of a representative marine benthic invertebrate, the red abalone Haliotis rufescens, to a highly varying multi-stressor environment. We found that high frequency variability in temperature, dissolved oxygen (DO), and pH increases as pCO 2 increases in the atmosphere. Extreme temperature and pH conditions are generally not expected until RCP 4.5 or greater, while frequent exposure to low DO is already occurring. In the nearshore environment simulation, strong RCP scenarios can affect red abalone growth as well as reduce fertilization during extreme conditions when compared to global scale simulations. With ocean temperatures expected to continue to rise, and dissolved oxygen (DO) and pH to decrease, due to climate change, there is an urgent need to understand how marine ecosystems will respond to future ocean conditions 1-3. While the biological impacts of future variability in these, and other, co-occurring environmental drivers are not well understood, the few studies available suggest that understanding variability and covariation of multiple environmental stressors are important for predicting organism responses in marine ecosystems 4,5. Currently, climate model predictions are generally global or regional in scale. However, the consequences of future environmental variability on species and ecological processes are predicated on local exposure regimes, which often exhibit higher temporal and spatial variability 6-9 relative to global estimates. Therefore, there is a critical need to downscale global forecasts to biologically relevant local scales. Global climate models (GCMs) predict increases in surface ocean temperature of up to 4 °C, declines in oxygen of up to 0.78 mg L −1 , and reduction in pH of up to 0.35 units by 2100 10-12. One approach to understand how future global or regional predictions may manifest at local scales is to obtain higher spatio-tempo...

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Internal wave generation due to semi‐diurnal tides (M2) through the acceleration of barotropic tidal flow over sloped topography has received considerable attention over the past several decades. However, the contribution of other tidal constituents and their interactions with M2 have not been as extensively evaluated. Moreover, on the inner shelf, the cross‐shore wind, which is often neglected in the energy conversion studies, dominates the cross‐shore transport and can also affect the energy conversion process. This study addresses this gap by including a diurnal (K1) tidal component and a shoreward diurnal sea breeze in an idealized model of southern Monterey Bay as it represents a highly stratified system that experiences active surface and internal tides. Our simulations demonstrate the role of the K1 tide and its interaction with M2, which is constructive and insensitive to the initial phase lag. Wind‐induced perturbations grow with the wind speed and enhance M2 conversion. On the other hand, the wind interaction with the K1 and M2K1 tides highly depends on the timing with constructive (destructive) conversion occurring when the shoreward wind intensifies during the ebb (flood) tide. Interactions among tides and winds lead to highly variable conversion rates, changes in timing and location of peak conversion, and a range of internal wave frequencies. Such a dynamic alone can be responsible for the complex internal wave environments often observed in the nearshore.