A nutrient effect on the TEX86 paleotemperature proxy

However, archaeal culture experiments show that nutrient stress elevates TEX 86 values by increasing glycerol dialkyl glycerol tetraether (GDGT) cyclization. Here, we demonstrate that this “nutrient effect” is also recorded in sedimentary GDGTs.

Using an expanded core‐top database, we find a significant negative correlation between TEX 86 and nitrate concentrations (ρ = 0.31; P < 0.001) once the thermal effect is removed. There are stronger correlations (ρ 0.73 to 0.91; P < 0.001) in regions with steep nitrate gradients. Comparisons between TEX 86 and UKʹ37 ‐based reconstructions from the Arabian Sea and Tasman Sea suggest that nutrient stress influenced GDGT distributions during glacial‐interglacial cycles.