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

Abstract

[1] Guaymas Basin, Gulf of California, is a restricted basin located under the present-day wet/dry subtropical divide (~27 N) 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~33-16.5000 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.

Comparisons between marine productivity and terrestrial input records in the Gulf of California over the last 28 ka

“…Based on radiocarbon calibrated ages (Table 1 and Fig. 3) the core spans ~28 ka and shows average sedimentation rates of 65.12 cm ka −1 in agreement with previous studies (Barron et al ., 2005; Cheshire & Thurow, 2013; McClymont et al ., 2012; Pride et al ., 1999). The AMS 14 C dates fall within the Younger Dryas (YD) and Heinrich 2 stadial cold events, and near the base of the interstadial Bølling–Allerød (B/A) warm event.…”

“…(2005) (Barron et al ., 2004; Keigwin & Jones, 1990; Pride et al ., 1999); data from Core MD02‐2515 as in Chang et al . (2015) (Cheshire & Thurow, 2013; Pichevin et al ., 2014), Core JPC20 data ( this study ) show a 3‐point running average. Black arrows show increases/decreases in percentages of biogenic components during stadial events.…”

“…1C) and thus influenced by greater inputs of coarser terrigenous material transferred from the shelf of Carmen Island to the Carmen Basin. Overall, the establishment of wetter conditions could be due to the southward migration of the polar jet front and the high subtropical jet, forced by the size of the Laurentide ice sheet (Cheshire & Thurow, 2013; Roy et al ., 2010). At 21 ka, ~100 lakes existed in the basin of Mojave which led to positive regional feedback of runoff and riverine discharges into the ocean (Smith & Street‐Perrott, 1983).…”

“…However, interlaboratory comparisons suggest that no significant differences exist when this widely used technique is applied to quantify biogenic silica in sediment (Conley, 1998). Furthermore, the Mortlock and Froelich (1989) wet digestion technique has been commonly and successfully used to measure biogenic silica in sediment from the GC (Chang et al ., 2015; Cheshire & Thurow, 2013; Douglas et al ., 2007; Keigwin & Jones, 1990; Pride et al ., 1999; Thunell, 1998).…”

“…Numbers show rivers along the coast. Red star indicates the location of Core AII‐125‐8‐JPC20 and green symbols show the location of other cores previously studied (Barron et al ., 2004; Chang et al ., 2015; Cheshire & Thurow, 2013; Keigwin & Jones, 1990; Pichevin et al ., 2014; Pride et al ., 1999; Staines‐Urías et al ., 2015). (C) Location of Core AII‐125‐8‐JPC20 in the Carmen Basin (latitude 26.039°N, longitude 110.93°W), bathymetric features, depth (m) and distance scale (km).…”