Sea-surface temperature records of Termination 1 in the Gulf of California: Challenges for seasonal and interannual analogues of tropical Pacific climate change

摘要

Centennial-scale records of sea-surface temperature and opal composition spanning the Last Glacial Maximum and Termination 1 (circa 25-6ka) are presented here from Guaymas Basin in the Gulf of California. Through the application of two organic geochemistry proxies, the U _(37) ~K index and the TEX _(86) ~H index, we present evidence for rapid, stepped changes in temperatures during deglaciation. These occur in both temperature proxies at 13ka (～3C increase in 270years), 10.0ka (～2°C decrease over ～250years) and at 8.2ka (3C increase in <200years). An additional rapid warming step is also observed in TEX _(86) ~H at 11.5ka. 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 18ka 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 Nio/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.