Millennial-scale surface and subsurface paleothermometry from the northeast Atlantic, 55–8 ka BP

• Published in: Paleoceanography
• Main Authors: Peck, Victoria Louise, Hall, Ian Robert, Zahn, Rainer, Elderfield, H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2008
• Subjects: QE Geology; Ice Sheet; Neogloboquadrina pachyderma; North Atlantic; Northeast Atlantic
• Online Access: https://orca.cardiff.ac.uk/id/eprint/11280/; https://doi.org/10.1029/2008PA001631; https://orca.cardiff.ac.uk/id/eprint/11280/1/Peck%202008.pdf

We present high-resolution records of upper ocean temperatures derived from Mg/Ca ratios of surface-dwelling Globigerina bulloides and subsurface-dwelling Neogloboquadrina pachyderma sinistral and the relative abundance of N. pachyderma sinistral for the period 55–8 ka BP from NE Atlantic sediment core MD01-2461. Millennial-scale temporal variability and longer-term trends in these records enable us to develop a detailed picture of past ocean conditions such as a weakening of thermocline intensity from marine isotope stage 3 (MIS 3) to the last glacial maximum (LGM). The correspondence of all temperature proxies and convergence of paired oxygen isotope (δ 18O) records from both planktonic species implies a breakdown in the thermocline and year-round mixing of the upper water column through the LGM, perhaps related to decreasing insolation and additional cooling in association with the expansion of the circum–North Atlantic ice sheets. Millennial-scale divergence in surface and subsurface temperatures and δ 18O across the last glacial correspond to meltwater release and the development of a strong halocline associated with both Heinrich (H) events and instabilities of the NW European ice sheet. During such episodes, G. bulloides Mg/Ca appears to record ambient, even warming summer sea surface temperatures across H events while the other proxies record maximum cooling.