North American Monsoon

Above: A photograph of 8 different total lipid extract (TLE) samples in a fume hood. These TLEs are a mixture of lipids (fats), including the alkenones and leaf waxes I analyyzed.

Master's Research

The North American Monsoon is a complex land-ocean-atmosphere dynamic that many people and ecoosystems heavily rely on in the southwestern United States and Mexico. The monsoon's future in our warming world is uncertain, so gaining as much information about it's past as possible is important for us to understand how it works - it's natural variability. For my master's work, I extracted different biomakers including alkenones and leaf waxes from a sediment core in the Gulf of California. These biomarkers give us clues about how the monsoon behaved in the past, since warmer ocean temperatures allow for a stronger monsoon. 

My master's thesis is titled, "Sea Surface Temperature Variability in the Gulf of California over the last 1,300 years," and focuses on the alkenone-based sea surface temperature reconstruction (link). A future publication, including updated radiocarbon dates, will describe both the alkenone and leaf wax records. 

Thesis Abstract: The North American Monsoon is a crucial component of the ecology and hydrology of the southwestern United States and northwestern Mexico. Sea surface temperatures in the Gulf of California (GoC) are linked to the strength of the monsoon and therefore understanding their variability in this region is essential. However, there are limited instrumental observations and a persistent lack of high resolution paleoclimate records from the core monsoon region. This prevents a better understanding of the behaviors and drivers of this system on time scales from decades to millennia and limits the accuracy of local paleo-temperature estimates. Here we generate a new record of warm season SST using the alkenone-based, UK′37 paleotemperature proxy from sediments cores spanning 695 to 1980 CE. Spectral analyses of our reconstruction show a prominent bicentennial oscillation and multidecadal variability throughout the record. There is a slight cooling trend over the entire reconstruction, but the record lacks a clearly delineated Medieval Climate Anomaly or Little Ice Age. Colder periods in our record appear to be associated with reduced solar forcing and periods of increased volcanism, similar to Northern Hemisphere temperature reconstructions. Multidecadal SST variability in the GoC is likely linked to broader patterns of unforced variability in the Pacific. Our SST record provides novel temperature information that can be used to investigate the link between marine conditions and regional terrestrial precipitation during the Common Era.