Glacial and environmental changes in northern Svalbard over the last 16.3 ka inferred from neodymium isotopes

摘要

The reconstruction of past ice sheet extents and dynamics in polar regions is essential for understanding the global climate system and obtaining more reliable predictions of future climate change. Here, we present a multiproxy dataset integrating the Nd isotopic compositions (epsilon Nd) of paired detrital and authigenic Fe oxide fractions, grain size distributions, organic geochemistry, and mineral assemblages in a glacimarine sediment core (core HH17-1085-GC) retrieved from the continental shelf off northern Svalbard. Our results indicate variability in sediment provenance and chemical weathering patterns since the last deglaciation, allowing us to distinguish a succession of distinct paleoclimate events: 1) a general retreat of the Svalbard-Barents Sea Ice Sheet (SBIS) from the continental shelf before ca. 16.3 ka BP; 2) an intense episode of meltwater discharge related to massive glacier loss between ca. 12.1-9.9 ka BP; and 3) a period of reduced meltwater input between ca. 9.9 and 2.7 ka BP followed by 4) a phase of glacier re-advance over the last two millennia. Evidence for the prolonged supply of radiogenic detrital epsilon Nd and dolomite at the site of core HH17-1085-GC indicates that the onset of deglaciation offshore northeastern Svalbard may have occurred at least 1 ka later than that at the northwestern shelf, which can be further evaluated by obtaining a more precise end-member determination for the northeastern source with a quantitative epsilon Nd dataset from Nordaustlandet. In the context where both polar sea-ice and oceanic circulation are expected to have played minor roles in determining the sedimentary epsilon Nd compositions, the evidence for pronounced Nd isotopic decoupling between paired authigenic and detrital signatures (Delta epsilon Nd) at ca. 15.2 and 14.1 ka BP is interpreted as reflecting chemical weathering changes following the retreat of the SBIS on northern Svalbard, probably corresponding to punctual episodes of glacial re-advances. Our findings provide a better understanding of the deglacial history of northern Svalbard during and after the last deglaciation and highlight the utility of Nd isotopes as a proxy for reconstructing paleo-cryosphere changes.