Key facts
- A 'Kelvin wave,' a massive underwater band of warm water, is approaching California.
- The wave is expected to cause sea levels to rise by up to a foot along the California coast.
- Scientists warn that the Kelvin wave's effects can be amplified by high tides and storm surges.
- A 'super' El Niño is brewing in the Pacific, increasing the likelihood of severe storms overlapping with higher sea levels.
- Coastal flooding is considered practically certain in many areas of California this winter.
- The winter of 1997-1998, which had similar hazards, resulted in massive coastal erosion and widespread disaster declarations in California.
California is bracing for the imminent arrival of a massive underwater warm water band, known as the 'Kelvin wave,' which scientists warn could significantly exacerbate sea level rise and coastal flooding. The wave is currently nearing southern California and is projected to reach the San Francisco Bay Area by early October, with potential for a foot of sea level rise along the coast. This phenomenon, driven by El Niño conditions, swells tides from beneath the surface and can linger, creating conditions for prolonged higher sea levels.
While Kelvin waves on their own may not always be hazardous, their effects can be amplified when coinciding with high tides or storm surges. Scientists, including Dr. Jonathan Warrick of the US Geological Survey, are concerned about the potential for these events to align with major storms and large tides in January, February, and March, leading to compounded and devastating impacts. The current 'super' El Niño brewing in the Pacific is expected to supercharge weather events, increasing the likelihood of severe storms coinciding with the elevated sea levels.
Coastal flooding is considered highly probable, with Daniel Swain, a climate scientist, noting that the damage could be devastating, especially where freshwater outflows mingle with saltwater inflows. He pointed to the winter of 1997-1998 as a precedent, where similar conditions caused massive coastal erosion, landslides, overwhelmed seawalls, and led to 21 of California's 58 counties being declared disaster areas. Current ocean temperatures are warmer than they were before the 1997-1998 event.
Emergency managers and local governments are already undertaking preparations, including supplying sandbags and securing infrastructure. Nick Brubaker, chief resilience officer for Marin County's emergency management office, stated that the incoming wave changes baseline assumptions for planning, noting that flooding from high tides occurred earlier this year even without the Kelvin wave's effects. Engorged creeks and streams may struggle to drain effectively with rising sea levels, potentially leading to significant flooding. Efforts are underway to clear drains, evaluate infrastructure, and implement temporary mitigation measures, though uncertainty remains regarding the exact unfolding of events.