High-resolution migration history of the Subtropical High/Trade Wind system of the northeastern Pacific during the last ~ 55 years: Implications for glacial atmospheric reorganization

<p>Guaymas Basin, Gulf of California, is a restricted basin located under the present-day wet/dry subtropical divide (~27\textdegreeN) and is ideally circumstanced for detecting variations in the North Pacific Subtropical High (NPSH)/Trade Wind system. Controlled by climate cell boundary displacement, NPSH midwinter location was the primary influence on timing and intensity of upwelling seasons in Guaymas Basin. Analysis of high-resolution X-ray fluoresence data and sediment fabric log from 75\% laminated Core MD02-2517/2515, western Guaymas Basin, reveals systematic changes in NPSH behavior over the last ~55 kyr BP. Southward displacement of the wet/dry subtropical divide controlled upwelling-related diatom productivity, while sea level and regional rainfall controlled terrigenous supply. The basin was oxic during the glacial, and preservation was ensured by high burial rate due to the increased deposition of terrigenous sediment. Sediment fabric style (number and/or thickness of laminae, plus color banding and homogeneous intervals) changes systematically through the core and gives insights into the number of seasons occurring in Guaymas Basin, and the occurrence and intensity of the upwelling season. Five millennial-scale low flux events with close timing to Heinrich events and ten decadal/centennial-scale low biogenic silica events occurring in the interval ~33\textendash16.5000 years Before Present (kyr BP) are interpreted as times of extreme aridity. At ~16.5 kyr BP, a regime shift from terrigenous-dominated oxic to evenly balanced biogenic-terrigenous dysoxic conditions occurred. Although there was a further extreme arid event at ~11.5 kyr BP, ~16.5 kyr BP was essentially the beginning of the interglacial.</p>