Sea-Surface Characteristics of the Newfoundland Basin of the Northwest Atlantic Ocean during the Last 145,000 Years: A Study Based on the Sedimentological and Paleontological Proxies

Harunur Rashid,Yang Wang,Min Zeng,Qian Qian Lu,Zhao Wu Zhang

doi:10.3390/app11083343

Harunur Rashid, Yang Wang + Show 3 more

Open Access

https://doi.org/10.3390/app11083343

Copy DOI

Abstract

Dramatic changes occur in the sea-surface characteristics (i.e., temperature and salinity) and freshwater input due to the interaction of cold and fresh Labrador Current and warm and salty North Atlantic Current (NAC) on the southeast Grand Banks. As a result, the biological productivity and seasonal stratification of the upper water masses are intensified. Such changes must have been more dramatic during the glacial times due to the penetration of the Polar and Arctic fronts and southward migration of the Gulf Stream/NAC. However, the extent to which such changes impacted the sea-surface characteristics in the Newfoundland Basin is poorly known. We report changes in the sea-surface characteristics using a piston core (Hu9007-08) collected from the Milne seamount during the last 145,000 years. Heinrich layers H1, H2, H4, and H5 and H11 within the MIS3 and at the penultimate deglaciation were identified by the ice-rafted detritus (IRD) and Neogloboquadrina pachyderma peaks and lighter oxygen isotopes. Rapid turnover by the foraminiferal species with distinct depth habitats and ecological niches in the mixed-layer and thermocline suggests an interplay between the polar and subpolar water masses during the Heinrich and non-Heinrich periods. Only two North Atlantic-wide cooling events, C24 and C21, in which the latter event linked to the minor IRD event during the marine isotope stage (MIS) 5 in Hu90-08, compared to the eight events in the eastern subpolar gyre (e.g., ODP site 984). Millennial-scale N. pachyderma variability in the western subpolar gyre appears to be absent in the eastern subpolar gyre during the MIS3 suggesting the occasional presence of salty and warm water by the NAC inflow, implying a different climate state between the western and eastern subpolar gyre. Although T. quinqueloba data are fragmentary, there are differences between the western and eastern subpolar gyre in addition to the differences within the western subpolar gyre during MIS5 that might imply a variable influence by the subpolar water. This finding suggests that the influence by the NAC outweighs the impact of cold and fresh polar water in the northern northwest Atlantic during the MIS5.

Highlights

IntroductionDuring the last glacial cycle, enormous amounts of icebergs, sediments, and meltwater were discharged to the neighboring Labrador Sea and the North Atlantic [1]
Due to the periodic expansions and contractions of the Laurentide Ice Sheet (LIS)during the last glacial cycle, enormous amounts of icebergs, sediments, and meltwater were discharged to the neighboring Labrador Sea and the North Atlantic [1]
The foraminiferal assemblages data linked to Heinrich or other high-frequency ice-rafted detritus (IRD) events are lacking, preventing assessing perturbation in the surface water properties

Summary

Introduction

During the last glacial cycle, enormous amounts of icebergs, sediments, and meltwater were discharged to the neighboring Labrador Sea and the North Atlantic [1]. These discharge events, known as the Heinrich events (H-events), are recorded as ice-rafted detritus (IRD). The foraminiferal assemblages data linked to Heinrich or other high-frequency IRD events are lacking, preventing assessing perturbation in the surface water properties. The existing Labrador Sea records lack the integrated foraminiferal census data with δ18 O to assess the impact of abrupt ice-rafting events

Objectives

Methods

Findings

Discussion

Conclusion