Ocean Variability and Climate Impacts in the California Current System

The California Current System (CCS) is a major eastern boundary upwelling ecosystem extending from southern British Columbia to Baja California. Its circulation is driven by equatorward winds that induce coastal upwelling of cold, nutrient-rich waters, supporting high biological productivity and diverse fisheries. Superimposed on this seasonal cycle are interannual and decadal variations linked to El Niño–Southern Oscillation and Pacific Decadal Oscillation, which modulate sea-surface temperature, stratification, oxygen levels and biogeochemical cycles. Episodic events such as marine heatwaves and anomalous salinity intrusions alter the depth of the thermocline and the intensity of mixing, with cascading effects on plankton communities, higher trophic levels and coastal economies. Mesoscale eddies and filaments further redistribute heat, nutrients and oxygen, influencing larval transport and recruitment. Advances in autonomous platforms, regional modelling and forecast systems now enable more precise mapping of these processes and more skilful projections of physical and chemical conditions. Improved understanding of CCS variability underpins sustainable management of fisheries, mitigation of hypoxia and adaptation to climate change, with lessons applicable to other eastern boundary currents worldwide.

Research from Nature Portfolio

Recent studies have documented unprecedented extremes of temperature and salinity in the CCS following the marine heatwave of 2014–2016. High-resolution observations from ships, gliders and floats revealed a distinct high-salinity anomaly advected from the North Pacific Subtropical Gyre, altering near-surface density and stratification. Separate experiments with a dynamical downscaling system have demonstrated that seasonal forecasting of temperature, oxygen and carbonate chemistry is feasible when global forecast output is combined with a high-resolution regional model and real-time observations. These experiments underline the potential for tailored seasonal outlooks to inform fisheries management and ecosystem resilience.

Ocean Variability and Climate Impacts in the California Current System publication trend

The graph below shows the total number of articles in ocean variability and climate impacts in the california current system across all publications each year (not limited to Nature Index journals).

Technical terms

Upwelling: The upward movement of deep, cold, nutrient-rich water toward the surface driven by coastal wind forcing.

Thermocline: A subsurface layer characterised by a rapid change in temperature with depth, separating warmer surface water from cooler deep water.

Mesoscale eddy: A rotating body of water, typically 10–100 km in diameter, that redistributes heat, nutrients and biota across the ocean.

Marine heatwave: A prolonged period of anomalously high sea-surface temperatures relative to long-term climatology, persisting for days to months.

Stratification: The vertical layering of water masses of different densities, which influences mixing, nutrient availability and oxygen distribution.

References

1. Downscaled seasonal forecasts for the California Current System: Skill assessment and prospects for living marine resource applications. PLOS Climate (2023).
2. The 2014–2015 warming anomaly in the Southern California Current System observed by underwater gliders. Geophysical Research Letters (2016).
3. Experiments with Seasonal Forecasts of ocean conditions for the Northern region of the California Current upwelling system. Scientific Reports (2016).
4. Temperature and salinity extremes from 2014-2019 in the California Current System and its source waters. Communications Earth & Environment (2021).
5. On the skill of seasonal sea surface temperature forecasts in the California Current System and its connection to ENSO variability. Climate Dynamics (2017).