Paleoceanographic Reconstruction of Surface Water Characteristics in the Northern North Atlantic During the Holocene and MIS 5 Using Planktic Foraminifera

• Main Author: Zhuravleva, Anastasia
• Format: Thesis
• Language: English
• Published: 2011
• Subjects: Arctic; Norwegian Sea; Foraminifera*; Iceland; Nordic Seas; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/28362/; https://oceanrep.geomar.de/id/eprint/28362/1/2011_Zhuravleva-Anastasia_MSc-Thesis.pdf

Paleoceanographic changes of surface water characteristics have been studied in the Nordic Seas during the Holocene and the Eemian warm periods as well as during late phases of preceding glacial periods based on a sediment core from the Iceland Sea. The age model is constrained for the Holocene by three accelerator mass spectrometry (AMS) 14C dates, correlation of some distinct and easily defined age points, obtained from the visual comparison of studied records with NPGRIP core and some tephra markers. The age model for MIS 5e is based on correlation of δ18O record to SPECMAP alongside with tephrochronolgy. Planktic foraminiferal assemblages were analyzed using the >150μm size fraction, foraminiferal δ13C and δ18O stable isotopes were measured on the polar planktic foraminifera N. pachyderma (s) for the Eemian period. According to high proportions of subpolar planktic forminifera (T. quinqueloba, G. bulloides, B. megastoma) during the late MIS 6, the presence of huge meltwater lids on the shelf of the Norwegian Sea was assumed resulting in deflecting of warm Atlantic water masses from its present circulation pattern towards the Iceland Sea. The proximity of the core to the Arctic and Polar fronts give possibility for their migration reconstruction. Hence, proxy records bear witness to the influence of cold fresh Polar water at the 6/5e boundary. The concomitant T. quinqueloba and B. megastoma (species that have different salinity tolerance) appearance alongside with low δ13C values evidence for subduction of warm and saline Atlantic water under fresh and cold surface water during the early part of the Last Interglacial. The same pattern is observed for the Holocene at about 10 ka cal. BP, corroborated by later T. quinqueloba appearance than G. bulloides, species that reflect Atlantic water masses. Cooling events during the periods of high solar insolation were noted and described in the current study for both interglacials. The observed reservoir ages for 8.2 – cold event is higher, by up to 200 years, than ...