NOAA/WDS Paleoclimatology - Gulf of California Deglacial Biogenic SST Reconstructions

STUDY NOTES: Sea surface temperature (SST) reconstructions for the Gulf of California (GOC) based on two organic geochemical proxies, the UK37' index and the TEX86H index. Data cover the deglacial interval from roughly 25 - 6 ka. Giant Calypso core MD02-2515 was collected from Guaymas Basin in the central GOC during the 2002 IMAGES-MONA expedition Core MD02-2515: 27°29.01'N, 112°04.46'W, 881 m water depth.
ABSTRACT SUPPLIED BY ORIGINATOR: Centennial-scale records of sea-surface temperature and opal composition spanning the Last Glacial Maximum and Termination 1 (circa 25-6 ka) are presented here from Guaymas Basin in the Gulf of California. Through the application of two organic geochemistry proxies, the UK37'index and the TEX86H index, we present evidence for rapid, stepped changes in temperatures during deglaciation. These occur in both temperature proxies at 13 ka (~3°C increase in 270 years), 10.0 ka (~2°C decrease over ~250 years) and at 8.2 ka (3°C increase in <200 years). An additional rapid warming step is also observed in TEX86H at 11.5 ka. In comparing the two temperature proxies and opal content, we consider the potential for upwelling intensity to be recorded and link this millennial-scale variability to shifting Intertropical Convergence Zone position and variations in the strength of the Subtropical High. The onset of the deglacial warming from 17 to 18 ka is comparable to a "southern hemisphere" signal, although the opal record mimics the ice-rafting events of the north Atlantic (Heinrich events). Neither the modern seasonal cycle nor El Niño/Southern Oscillation patterns provide valid analogues for the trends we observe in comparison with other regional records. Fully coupled climate model simulations confirm this result, and in combination we question whether the seasonal or interannual climate variations of the modern climate are valid analogues for the glacial and deglacial tropical Pacific.