<b>: A novel GDGT-based proxy for reconstructing subsurface temperature in oceanic (sub-)tropical OMZs</b>

The TEX86 proxy, based on the distribution of archaeal isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGT) in marine sediments, is widely utilized for reconstructing sea surface/subsurface temperatures. However, its application in oxygen minimum zones (OMZs) frequently yields substantial warm biases, underscoring the need for systematic evaluation of TEX86 accuracy in low-oxygen environments. Here, we compiled a (sub-)tropical isoGDGT dataset from suspended particulate matter (SPM), surface sediments and sediment cores across OMZs and non-OMZs, alongside influencing parameters including temperature, dissolved oxygen, ammonia oxidation rates. Our analysis reveals substantial deviations between TEX86-derived and in situ or export-layer temperatures, with offsets amplified under low-oxygen conditions. This highlights dissolved oxygen as a key factor influencing isoGDGT composition within the export layer. To address this bias, we propose a new OMZ-specific calibration, TEX86_OMZs, optimized for subsurface temperature reconstructions. Validation against Holocene WOA data and foraminiferal δ18O-based paleotemperature records from the PETM and OAEs confirms its improved accuracy, providing a robust tool for paleotemperature reconstructions in low-oxygen marine environments.