Potential controls on millennial and multicentennial time scales of the North American Monsoon: a 6 Ky record from the lower Gulf of California

Abstract:

The Western North American climate is influenced by the sea surface temperatures in the NE tropical Pacific, the summer expansion of the subtropical high, the mid-latitude Westerlies and land snow covering. The interplay of these features of the climate exert further control to the largest phenomenon of convective summer precipitation in NW Mexico and SW US: the North American Monsoon (NAM) which is the most important source of fresh water for the region. There is a pressing need to better understand especially in times of rapid warming how this monsoonal system is going to respond. Here we explore on the different modes of variability of the monsoonal regime in high-resolution reconstructions of the marine sediment record and their possible controls during the Holocene. The role of the teleconnections between the high and low latitudes climate, the interaction with the ITCZ, ENSO, PDO and AMDO are critical for the understanding of global climate.

We produced an XRF record of the relative abundance of Si and Al in high resolution laminated sediments obtained from the western margin of Pescadero basin (24N,108W) in the southern domain of the Gulf of California as proxies of terrigenous input. The laminated nature of this deposits at intermediate depths on its slopes sets the foundation for a potentially good record of changes in the transfer of lithogenic materials between the continent and the ocean in this region. Here we present recently acquired data from the terrigenous fraction on the marine sediment composite record from Pescadero basin (522 m water depth / 220 cm long). We determined the relative abundance of Si and Al from X-ray fluorescence from records that were absolutely dated with the aid and eight radiocarbon ages, which allowed us to produce a continuous record with a decadal temporal resolution. The time series analysis of the entire record of Si and Al show significant periodicities which were further cross-correlated with other paleoclimate proxy records like ice core, speleothems, lake and marine sediments records with the aim of explain the evolution of the NAM and the links between external and internal feedback effects.