Sánchez, A. & M., Juarez (2025). Chlorins and sea surface temperature in the transitional zone of the northeastern Pacific Ocean during the last 1350 years. Palaeogeography, Palaeoclimatology, Palaeoecology. 661: 112704. DOI: 10.1016/j.palaeo.2024.112704.
Alberto Sánchez 1 y Miryam Juarez 1
Biogeochemical tracers of marine productivity and sea surface temperature (SST) are widely used to reconstruct conditions associated with upwelling systems. The connection of these tracers is complex; thus, it is necessary to use several locations or multiproxy approaches to understand upwelling system processes. In the present work, chlorin concentrations were used as tracers of chlorophyll-a to determine marine productivity and the alkenone Uk´37 index was used to calculate SST for the last 1350 years. This was done to understand the evolution of upwelling systems in the southern region of the California Current and the possible external factors responsible for its changes in the transitional zone of the Eastern Tropical North Pacific (ETNP). This new data set was contrasted with biogenic opal (BO) and organic carbon (OC) data quantified in the same multicore collected in the Magdalena margin. Chlorin concentrations ranged from 11.3 to 26.8 µg g-1 from 650 to 2010 CE. Its continuous increase in the last 1350 years was interrupted by two decreases in 1100 to 1200 CE and 1700 to 1800 CE. SST varied from 23.2 to 26 °C along the record. In the Medieval Warm Period (MWP), consistently low SSTs were interrupted by an increase to a maximum of 26.1 °C at ~1200 years. In comparison, SST showed a centennial variability, but no discernable trend in the Little Ice Age (LIA), rapidly decreasing towards the Current Warm Period (CWP). Chlorins, BO and OC suggested that primary productivity increased steadily. SST was relatively cooler in the MWP relative to the LIA, except for a 2 °C increase during the middle stage of the MWP and then decreased by 2 °C over the last 160 years. The trend of increasing chlorins, BO, and OC suggests that primary productivity was maintained under a predominant regime of La Niña-like oceanographic conditions during the MWP, LIA, and CWP, except for the intervals from 1100 to 1200 CE and 1650 to 1850 CE. Both tracers suggested a reduction in primary productivity. These results demonstrated the complexity of the oceanographic processes that controlled the upwelling system to maintain high marine productivity in the California Current system during the last 1350 years.
Palabras clave: Chlorins; Alkenone; Sea surface temperature; Upwelling; California Current
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