242 / 2024-09-12 15:19:50

Implications and application of UK'37 and TEX86H paleothermometer in the Taiwan Strait

UK’37, TEX86H, Paleotemperature l reconstruction, Channel-type marginal seas, Taiwan Strait

Session 66 - Biomarkers in the sea: the tracers of key biogeochemical processes in the ocean’s past, present and future

This study investigates the application potential of the U^K'₃₇ and TEX⁸⁶_H proxies in a subtropical, high-energy, channel-type marginal sea system by analyzing 58 surface sediment samples from the Taiwan Strait (TS). We conducted a correlation analysis between the U^K'₃₇ and TEX⁸⁶_H index and the mean sea surface temperature (SST) data obtained from the MODIS database over a 15-year period (2002-2017), along with temperature measurements from various depths during the sampling period. The aim was to explore the implications of the two paleotemperature proxies in surface sediments and their regional applicability for paleoenvironment reconstruction. The TEX⁸⁶_H index exhibited a strong linear positive correlation with SST in the sediments, with no depth or seasonal bias in the reconstructed temperatures, reflecting the annual average sea temperature signal in the strait. This makes it an effective proxy for reconstructing ancient SST in the region. The regional calibration formula for TEX⁸⁶_H -SST in the TS is: TEX⁸⁶_H = 0.018 × SST - 0.662 (R = 0.69, n = 43). In contrast, the U^K'₃₇ proxy showed a poor correlation with SST in the sediments; however, a significant nonlinear positive correlation was observed between the U^K'₃₇ index extracted from suspended particulate matter and modern temperature measurements. This suggests that the U^K'₃₇ index remains a valid indicator for reconstructing SST. The regional calibration formula for U^K'₃₇-SST in the TS is: U^K'₃₇ = -2.427 + 0.233 × SST - 0.004 × SST² (R² = 0.84, n = 63). Nonetheless, the strong vertical mixing effects and seasonal lateral transport caused by the "narrow channel effect" in the TS have led to a deterioration in the coupling between the U^K'₃₇ index in sediments and SST. Therefore, when conducting modern calibration studies of the U^K'₃₇ index in surface sediments of high-energy channel-type marginal sea systems, it is essential to consider the impacts of sediment transport and redistribution processes, which can cause distortions in the biogeochemical signals within the sediments due to vertical biological pumping effects. Additionally, this study found that the spatial distribution of the U^K'₃₇ index in surface sediments closely aligns with areas of warm current intrusion. Given the ecological niche characteristics of the producer of C₃₇ alkenones, the thermophilic and halophilic dinoflagellate, we propose that the U^K'₃₇ index in this region may primarily reflect SST signals associated with warm current intrusion in the southern TS.