This Year’s El Niño and its Impacts

Governor Gavin Newsom declared a state of emergency for the state of California on Sept. 21, to bolster preparedness for this upcoming winter’s El Niño storm season. For long-time residents, strong El Niño events recall visions of heavy rainstorms and potential flooding compared to our normally mild winters.

This upcoming El Niño is predicted to be stronger than any we have experienced in recent history. With impacts already being felt in Southern California that brought about this emergency declaration, why should we be concerned about this year’s climate event?

Let us take a step back and explore what an El Niño climate pattern is and what we would normally expect. An El Niño is identified by a warm patch of surface water in the Eastern Pacific Ocean near the Equator. This warm patch combined with the East-West trade winds around the Equator slowing the push of warm water westward that would normally bring colder deeper waters up to the surface creates a feedback loop that drives more moisture into the atmosphere. Cycling every few years between this warming event and its counterpart cooling event, La Niña, these complex climate events are engines of atmospheric moisture throughout the Pacific. So how does a patch of warm water down by the Equator lead to an emergency declaration in California?

While these are vast simplifications, the heavy rains of winter storms are driven mostly by the moisture content in the atmosphere that depending on the climate cycle can fall harmlessly back into the ocean or get squeezed out as it attempts to cross the Rockies. But the coastal risk that drives this emergency declaration is magnified by oceanographic factors unique to El Niño. The same warm water that drives moisture into the atmosphere also physically expands in the normally cooler Eastern Pacific. Along with altered ocean currents due to lessened trade winds there are Kelvin Waves that are large scale pulses combined with this thermal expansion that can raises the baseline sea level along the California coast by up to a foot during a strong El Niño year.

For the past few winters, I’ve been taking advantage of the mild winters and the King Tides to do a little bit of tidepool foraging. This is another confounding factor that could make these coming winter storms a larger danger to our coastline. While these can be predicted with a strong degree of accuracy, their true magnitudes will not be known until the winter storms develop. Even in non-El Niño years, a combined winter storm and King Tide event has led to strong coastal erosion events and even near over-toppings of the seawalls around San Francisco.

The multi-agency report from 2012, the Ocean Beach Master Plan, only analyzed four potential over-topping events out to 2100 as 100-year events. With our present day knowledge of accelerating climate change, these previous assumptions begin to appear woefully inadequate for how El Niño events are likely to become even more severe than predicted. The Ocean Beach Institute has been studying the shifting dunes to better understand how these erosion patterns can be mitigated in the face of these climate driven events. While our idea of sea level rise may be a slow barely perceptible change every year, the reality is these combination of events can lead to sudden and drastic changes to the coastline.

Continuous heavy rainfall saturates coastal bluffs, followed by large swells during an already elevated baseline sea level with storm surges riding higher up than normal creates ideal conditions for coastal erosion that eats large chunks out of the dunes and roadway. As can be seen at the Upper Great Highway extension, managed shore retreat and realignment is the only feasible long term solution. Even the Ocean Beach Master Plan recognizes this: “With the Great Highway closed south of Sloat, and with signage and other measures, a portion of that traffic could be induced to use more appropriate routes such as Sunset Boulevard. Mitigation measures to prevent aggressive cut-throughs in adjacent neighborhoods (already a problem during frequent road closures) would be essential, as would coordination with ongoing planning for circulation throughout the west side.”

Fortunately we have not put much infrastructure in the path of coastal erosion like Pacifica. One of the expected 100-year over-topping events could potentially occur during this El Niño or we could get lucky like we have in cycles past. The challenge we face is how much to invest in the changes needed to prepare for more worst-case climate scenarios. However, I don’t want this to be all doom and gloom around climate change. If you have talked with fishermen friends, the warmer Pacific waters have led to the expansion of the Bluefin Tuna range with charter boats having hauled in a few not too far off the San Francisco coastline.

Brian Quan is a Richmond District native, co-leader of Grow the Richmond, member of the Park Presidio-Sunset Lions Club and leads a monthly Refuse Refuse S.F. street clean-up.