Tree Ring-Based Historic Hydroclimatic Variability of the Baja California Peninsula

The Baja California Peninsula is one of the most arid regions in Mexico, receiving an average of only 168 mm of precipitation annually. Climate change scenarios project drier and warmer conditions in the region at the end of this century driven by anthropogenic emissions of greenhouse gases. The growing demand for limited water supplies and the impacts of climate change pose a challenge to manage the already scarce water resources in the Peninsula. Analysis of historical hydroclimatic variability in the Peninsula is limited because most of the early instrumental climate data collection started only in the 1950s. In this study, we reconstruct past precipitation variability for the Peninsula using two tree ring chronologies from northern (Pinus monophylla) and southern (Pinus lagunae) Baja California. Our two reconstructions document multicentury hydroclimatic variability in the Peninsula, including events that turned out to be more extreme than those captured by modern instrumental records. Drought episodes are longer, more frequent, and more intense in the northern peninsula compared to the southern region. Multiyear dry and wet events in our two reconstructions exhibit broad spatial extent, affecting most of northwest Mexico and the western United States, which are mainly caused by broad-scale atmospheric circulation patterns such as El Niño–Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO). The results of this study allow framing current and projected droughts in a longer-term context, thus providing a better understanding of past climate variability and a basis for robust water resource management in the region.