Neodymium isotope variability in the Chukchi Sea during the Holocene

Abstract

The Chukchi sea is an important region to understand the oceanographic and climatic changes in the western Arctic observed on the late Quaternary glacial-interglacial cycles. Large amounts of relatively fresh water from the North Pacific flow into the western Arctic Ocean through the Bering Strait, consequently affecting the Atlantic Meridional Overturning Circulation (AMOC) according to opening or closing mode of the Bering Strait. The study area, Chukchi sea, overlies where the East Siberian Slope Current meets the Beaufort Gyre. It has been well known that the Arctic Oscillation is linked to changes in the strength of the Beaufort Gyre and the Transpolar Drift. In order to unravel Chukchi Sea water mass composition during the Holocene, seawater-derived neodymium isotope of authigenic fraction in marine sediments has been used. A sediment core ARA02B-GC01A was collected from the northern shelf of the Chukchi Sea with a water depth of 111 m during 2nd RV Araon expedition (ARA02B) in 2011. Based on 7 AMS 14C ages of molluscan shells, the age of bottom core has been extrapolated to ca. 9.31 ka BP. The εNd results might show a general pattern of increasing radiogenic εNd values from -7.23 εNd at ca. 8.86 ka BP to -4.03 ε_Nd at ca. 0.60 ka BP. It implies that the unradiogenic source from the Atlantic Ocean (~ -11 εNd) and Mackenzie river (~ -13 εNd) has been overwhelmed by the radiogenic Bering Strait inflow (~ -5 εNd) after flooding of the strait, at ca. 11 ~ 12 ka BP. The pattern of the εNd results also resemble a quartz/feldspar ratio record of the same core which suggests a consistent decrease in the Beaufort Gyre circulation during the Holocene.