Comparison of qualitative and quantitative dinoflagellate cyst approaches in reconstructing glacial-interglacial climate variability at West Iberian Margin IODP ‘Shackleton’Site U1385

• Main Authors: Datema, Mariska, Sangiorgi, Francesca, de Vernal, Anne, Reichart, Gert-Jan, Lourens, Lucas J., Sluijs, Appy
• Other Authors: Marine Palynology, Marine palynology and palaeoceanography, Stratigraphy and paleontology
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: Dinoflagellate cysts; Shackleton Site; Integrated Ocean Drilling Program; Last glacial transition; Sea surface temperature and salinity; Modern analogue technique; Taverne; Greenland; Shackleton; Greenland ice core; ice core
• Online Access: https://dspace.library.uu.nl/handle/1874/356014

Dinoflagellate cysts (dinocysts) are commonly used to reconstruct past environmental conditions at the sea surface, such as primary production, temperature and salinity. Abundances of selected dinocyst taxa are used in qualitative indices, whereas the modern analogue technique (MAT) is used for quantitative reconstructions. Qualitative indices use process-based knowledge of present-day relations between the environmental variables and the distribution of dinocysts, whereas the MAT is based on the assumption that past assemblages have modern counterparts that correspond to similar sea-surface conditions. Here we explore the potential of both approaches to reconstruct sea surface temperature (SST), production (SSP), salinity (SSS) and seasonality during the last 22 thousand years along the West Iberian Margin (WIM), at Integrated Ocean Drilling Program (IODP) Site U1385. We compare results to published paleoclimatic reconstructions. Our SST and SSS reconstructions provide the first continuous dinocyst MAT-based SST and SSS records for this area and time interval. Qualitative and quantitative dinocyst-based SST estimates from the WIM are similar and resemble previous SST estimates from dinocysts, alkenones and foraminifers from nearby sites. The surface temperature trends and millennial-scale variations largely match those from the Greenland ice core records. Quantitative MAT-based SST estimates show increased seasonality in the glacial stage resulting from strong winter cooling. Dinocyst MAT-based salinity decreases concomitantly with cooling during the Younger Dryas and Heinrich Stadial 1 (HS1), likely related to the melting of icebergs that reached the region during HS1. Our qualitative and quantitative SSP estimates show higher values in the glacial stage compared to the Holocene, which is consistent with published records and supports the usefulness of both approaches. Small differences between SST tracer records may be explained by the limited number of modern analogues from warm ocean regions in the dinocyst ...