The marine environmental evolution in the northern Norwegian Sea revealed by foraminifera during the last 60 ka
at : Jul 02, 2021 09:14:29  (view:263)

The marine environmental evolution in the northern Norwegian Sea revealed by foraminifera during the last 60 ka

WANG Weiguo1, ZHAO Mengwei2*, YANG Jichao3, XIAO Wenshen4, WANG Haoyin5 & LIU Yang 6

1 Third Institute of Oceanography, Ministry of Natural Resources, P.R.C., Xiamen 361005, China;

2 Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China;

3 Shandong University of Science and Technology, Qingdao 266590, China;

4 State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China;

5 School of Marine Science and Technology, Hainan Tropical Ocean University, Sanya 572000, China;

6School of Earth Sciences, Lanzhou University, Lanzhou 730000, China

Abstract: Both planktonic and benthic foraminifera were identified in a sediment core collected from the northern Norwegian Sea to reconstruct the paleoceanographic evolution since the last glaciation. The assemblages and distribution patterns of dominant foraminiferal species with special habitat preferences indicated that three marine environments occurred in the northern Norwegian Sea since 62 ka BP: (1) an environment controlled by the circulation of the North Atlantic Current (NAC); (2) by polynya-related sinking of brines and upwelling of intermediate water surrounding the polynya; (3) by melt-water from Barents Sea Ice Sheet (BSIS). At 62–52.5ka BP, a period with the highest summer insolation during the last glaciatial period, intensification of the NAC led to higher absolute abundances and higher diversity of foraminiferal faunas. The higher abundance of benthic species Cibicidoides wuellerstorfi indicates bottom water conditions that were well-ventilated with an adequate food supply; however, higher abundances of polar planktonic foraminiferal species Neogloboquadrina pachyderma (sin.) indicate that the near-surface temperatures were still low. During mid-late MIS 3 (52.5–29 ka BP), the marine environment of the northern Norwegian Sea alternately changed among the above mentioned three environments. At 29–17 ka BP during the last glacial maximum, the dominant benthic species Bolivina arctica from the Arctic Ocean indicates an extreme cold bottom environment. The BSIS expanded to its maximum extent during this period, and vast polynya formed at the edge of the ice sheet. The sinking of brines from the formation of sea ice in the polynys caused upwelling, indicated by the upwelling adapted planktonic species Globigerinita glutinata. At 17–10 ka BP, the northern Norwegian Sea was controlled by melt-water. With the ablation of BSIS, massive amounts of melt water discharged into the Norwegian Sea, resulting in strong water column stratification, poor ventilation, and an oligotrophic bottom condition, which led to a drastic decline in the abundance and diversity of foraminifera. At 10–0 ka BP, the marine environment was transformed again by the control of the NAC, which continues to modern day. The abrupt decrease in relative abundance of Neogloboquadrina pachyderma (sin.) indicates a rise in near-surface temperature with the strengthening of the NAC and without the influence of the BSIS.

Keywords: Norwegian Sea, foraminifera, North Atlantic Current, Barents Sea Ice Sheet, marine environments, last glaciation