High-resolution UK’37 sea surface temperature reconstruction in the southwestern Atlantic Ocean during the Holocene

Abstract

Modern sea surface temperatures (SST) were assessed using the alkenone calibration index (UK′37; SST-UK′37) values from twenty-one core-top sediment samples collected along the Southwestern Atlantic Ocean and validated by comparison with satellite-derived SSTs. The SST-UK′37 values revealed an annual signal between 28 and 30°S and a winter signal (83% of the region samples) between 30 and 34° S, with deviations falling within the UK′37 calibration error range. The paleotemperature (SST-UK′37) reconstruction through the Holocene was performed using two high-resolution marine sediment cores from 33 to 34°S latitude band. Millennial-scale variations dominate most of the SST-UK′37 results with changes up to ∼6 °C. Considering the modern ocean circulation dynamics, the SST-UK’37 in our records likely stems from the combined influence of the Subtropical Shelf Front (STSF) position and the interaction between the warm, salty, and nutrient-poor Subtropical Shelf Water (STSW) and the cold, fresh, and nutrient-rich Subantarctic Shelf Water (SASW). Our SST-UK’37 results also suggest that the northernmost position limit of the STSF reached around 33°S during the mid-to-late Holocene, while after ∼5500 cal yr BP the Plata Plume Water became the dominant influence on the regional SST-UK’37 signal. Spectral analyses revealed statistically significant oscillations of ∼8600 and ∼ 2250 years in record MDBT 557, and ∼ 5300 and ∼ 2600 years in record MDBT 561 which suggests the influence of Southern Westerly Winds (SWW) on the SST-UK’37, and therefore, on the STSF dynamic through the Holocene.