Palaeoceanographic changes in the North Atlantic during the Mid‐ Pleistocene Transition ( MIS 31–19) as inferred from planktonic foraminiferal and calcium carbonate records

• Published in: Boreas
• Main Authors: Hernández‐Almeida, Iván, Sierro, Francisco Javier, Flores, José‐Abel, Cacho, Isabel, Filippelli, Gabriel Michael
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2012
• Subjects: Foraminifera*; North Atlantic; Planktonic foraminifera; Sea ice
• Online Access: http://dx.doi.org/10.1111/j.1502-3885.2012.00283.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1502-3885.2012.00283.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1502-3885.2012.00283.x

Marine sediments from the I ntegrated O cean D rilling P roject ( IODP ) S ite U 1314 (56.36° N , 27.88° W ), in the subpolar N orth A tlantic, were studied for their planktonic foraminifera, calcium carbonate content, and N eogloboqudrina pachyderma sinistral (sin.) δ 13 C records in order to reconstruct surface and intermediate conditions in this region during the M id‐ P leistocene T ransition ( MPT ). Variations in the palaeoceanography and regional dynamics of the A rctic F ront were estimated by comparing CaCO 3 content, planktonic foraminiferal species abundances, carbon isotopes and ice‐rafted debris ( IRD ) data from S ite U 1314 with published data from other N orth A tlantic sites. Site U 1314 exhibited high abundances of the polar planktonic foraminifera N . pachyderma sin. and low CaCO 3 content until M arine I sotope S tage ( MIS ) 26, indicating a relatively southeastward position of the A rctic F ront ( AF ) and penetration of colder and low‐salinity surface arctic water‐masses. Changing conditions after MIS 25, with oscillations in the position of the AF , caused an increase in the northward export of the warmer N orth A tlantic C urrent ( NAC ), indicated by greater abundances of non‐polar planktonic foraminifera and higher CaCO 3 . The N . pachyderma sin. δ 13 C data indicate good ventilation of the upper part of the intermediate water layer in the eastern N orth A tlantic during both glacial and interglacial stages, except during Terminations 24/23, 22/21 and 20/1. In addition, for N . pachyderma (sin.) we distinguished two morphotypes: non‐encrusted and heavily encrusted test. Results indicate that increases in the encrusted morphotype and lower planktonic foraminiferal diversity are related to the intensification of glacial conditions (lower sea‐surface temperatures, sea‐ice formation) during MIS 22 and 20.