C.S.U.F. expert explains relationship between the Pacific Ocean and California's drought history
January 9, 2017
Although gold might be California’s most famous natural resource, water is by far its most important. Without freshwater, California’s agricultural economy would collapse. Unfortunately, California’s freshwater availability is highly variable from year to year and 100 percent dependent on one season’s input, winter.
As we enter year six of our epic drought, we are reminded just how exposed our state is to its precious water resources. For Southern California it’s even worse than its northern counterparts – Southern California is largely a desert and local freshwater is highly stressed, even before its population ballooned. We manage this problem through groundwater extraction, water reclamation and water importation from Northern California and the Colorado River. Nonetheless, water management depends on knowledge of how water availability changes through time. Knowing how often, and for how long, dry and wet periods occur in the past is critical. This includes knowledge of past floods, which represent a serious socioeconomic threat to Southern California. Even more important than our water history is an understanding of why it rains more some times than at other times. And, is the reason for this change predictable? If yes, can this climate predictability help manage present and future water resources? These questions cannot be answered using merely 50-100 years of meteorological data. These questions require a deeper time perspective. I argue that we need to understand at least the past 10,000 years of California’s water history – since the end of the Last Glacial Period – to develop a statistically robust baseline understanding of why and how water varies in California.
Here at California State University, Fullerton, my research team and I dig – literally – into Southern California’s past to reconstruct the history of drought, floods, fires, and vegetation. To do this, we collect long tubes of mud from the bottom of lakes such as Lake Elsinore, Crystal Lake, Dry Lake, Baldwin Lake, Lower Bear Lake (aka Big Bear Reservoir), Silver Lake, Zaca Lake and Abbott Lake. Like pages in a history book, each layer of mud contains information about the past. This information is extracted using a variety of techniques such as the size of the mud particles, pollen, charcoal, and chemical analyses. For example, to reconstruct the history of drought and floods, we examine the amount of sand in the mud. Sand requires a lot of energy to move from its source (i.e., the mountains) to its sink (i.e., the ocean or a lake basin). As a result, the amount of sand in any given mud layer tells us something about how wet (or dry) it was in the past. To be sure, we often examine various components of the mud from each layer to confirm or refute our interpretations.
Thanks to many, many Cal State Fullerton Geology students, we have learned a lot over the last 14 years. Here at CSUF, the Department of Geological Sciences requires every BS student to complete a research proposal and thesis to graduate. This a huge task for the faculty and students. However, it represents something extremely rare in a university our size – the opportunity for a student to pursue real field and lab based research. Consequently, we send our students into the work force with real, practical critical thinking and communication skills.
What have we learned? Perhaps our most interesting results are evidence for a consistent link between sea surface conditions in the tropical and north Pacific Oceans and how wet it is here in Southern California. We observe this link going back nearly 15,000 years. When the eastern tropical Pacific is warm (El Nino-like conditions), it is generally wetter here in southern California. The same is observed for conditions in the north Pacific. Most recently, this relationship is observed here in southern California during the wet Little Ice Age (1450-1850 AD) and the dry Medieval Climatic Anomaly (900-1300 AD).
Well, you might say `whom cares.’ True, but how the climate system behaves in the past gives us insight to how it might behave in the future. Much like a stock investor, knowledge of how a stock performed in the past tells you something about how it may perform in the future. The wise investor studies the past to make the best decision. So, too, should water managers. And, as I noted, water management practices depend on at least a modicum of climate predictability. As the worlds’ oceans warm in response to global warming, it raises the question, how will the climate of the western United States change? The answer remains a matter of debate with climate models predicting drier conditions, slightly wetter conditions, and/or drier conditions with infrequent but larger intensity storms.
As time passes, models will improve and narrow the range of possibilities. However, our data provides one important piece to the puzzle now. Clearly, what happens in the Pacific matters to the climate of the Western U.S. and, by extension, Southern California. This Pacific–Southern California climate connection is 15,000 years strong. My guess is that it won’t simply disappear. Rather, the future of water in California, in general, and Southern California, specifically, will likely reflect conditions as they change in that big pool of water to our west – the Pacific. Stay tuned. Climate change is our planet’s great experiment. Unfortunately, we are both the cause, and subject, of its effects.