Interannual Variability of Seasonally Influenced Playa Lake Inundation in Northern Mexico: Possible Analogs for Wetter Holocene Climates

Playa lakes in the Chihuahuan Desert, northern Mexico respond to regional climatic signals and display large interannual variability in the timing and duration of flooding. These playas, located on the boundary of the summer North American monsoon system and the winter frontal system, are in a critical location for understanding the variability of these two precipitation modes during past and future climate change. During the Holocene, elevated beach ridges along the edges of these playas indicate the existence of at least three periods with perennial lakes and therefore effectively wetter than modern climates. Increased winter precipitation has been suggested as a mechanism for Holocene lake highstands from the Mojave Desert in the southwestern United States with similar ages to those lakes in northern Mexico. The Mojave Desert is not currently influenced by the North American monsoon, so it is important to understand the interaction between summer monsoonal versus winter frontal precipitation in maintaining wetter than modern climates in northern Mexico. We use a time series of modern playa inundation events from remotely sensed data and concurrent precipitation records to examine the relative contributions of summer and winter precipitation to playa filling. This modern precipitation-inundation analysis may aid in the interpretation of the Holocene lake highstands in northern Mexico. Playas are generally inundated with water by late summer and dry out by early to late winter. Data in a long time series derived from Landsat imagery extends into 1984 and shows a shift from larger, long-lived playa lakes toward smaller, shorter lakes following 1994. The Atlantic Multidecadal Oscillation undergoes a phase shift at the same time. The persistent El-Nino events of the early 1990s occurred at the same time as the only multi-year playa lake in the record. Data from the Moderate Imaging Spectroradiometer (MODIS) satellite has allowed the creation of a more detailed data set of the flooding and subsequent evaporation of the ephemeral lakes with a high temporal resolution. The dynamic response of the playa inundation pattern to the seasonality of regional precipitation is evident in the timing of the initial flooding event, the extent of inundation and the duration of standing water. The three playas receive inflow from separate sub-basins and are unequally affected by each seasonal precipitation regime. The analysis of the relationship of gridded precipitation data with the detailed inundation time series was used to quantify interannual variability for the period between 2000 and 2008. The high temporal resolution of the MODIS record allows us to connect the dynamics of annual playa inundation with specific precipitation events.