Description: Highlights • Exchange between pore and bottom water with sediment affects authigenic REE in the Labrador Sea (LS). • REE-based correction allows reconstruction of past bottom water ϵNd signatures. • Evidence for lack of southern sourced water in the LS through the last 35 ka. • Glacial LS bottom waters were less radiogenic than today with ϵNd = −16 ± 1. • Similarity to Nordic Seas ϵNd record suggests uninterrupted supply of overflow waters. Abstract Deep waters of the Labrador Sea (LS) are important contributors to the Atlantic Meridional Overturning Circulation, but their water mass structure has been highly variable and sensitive to climatic changes on different time scales. The LS is also an area of intense exchange of rare earth elements (REE) between seawater and the underlying sediments, which complicates the reconstruction of past deep water provenance based on radiogenic neodymium (Nd) isotopes. Most notably, Northwest Atlantic Bottom Water exchanges Nd with Archaean age Laurentian detritus, resulting in a significant shift to less radiogenic Nd isotope signatures before it enters the North Atlantic to form the deep part of North Atlantic Deep Water. Here we show that the authigenic fractions of LS core top sediments carry Nd isotope signatures intermediate between bottom water and detritus and thus reflect pore waters that incorporate a mixture of both signatures. We furthermore find that detrital imprints on pore waters led to shifts of REE patterns in the authigenic fraction towards detrital signatures in the past during times of enhanced supply of glacially eroded material from Hudson Bay to the LS, as recorded by radiogenic lead isotopes. This allows an estimation of the intensity of past benthic REE exchange inside the LS. We exploit variations in the mid REE enrichment in the authigenic phase to propose a correction to one LS Nd isotope record for detrital imprints originating from pore water exchange. The corrected ϵNd signatures are argued to more accurately reflect those of past bottom waters. This correction results in past LS bottom water signatures of −16 ± 1 during MIS 2 and 3, considerably less radiogenic than today. This implies that no southern sourced waters advanced into the LS during the last 35 ka and instead supports continuous bottom water sourcing from the Nordic Seas. It thus seems likely that LS bottom waters supplied unradiogenic Nd to abyssal Glacial North Atlantic Bottom Water in the Northwest Atlantic, as was previously hypothesized.

Description: Dust storms are an important component of the global climate system. At the same time, they also bear a risk for human health by causing pulmonary diseases. Today, East Asian dust storms account for as much as half of the global dust emissions and temporarily affect highly populated areas. Therefore, understanding their mechanisms and predicting their evolution under warmer near-future climate conditions is of major interest. The mid-Pliocene Warm Period (mPWP; 3.264–3.025 Ma) is considered one of the best analogues from the past for anthropogenic climate change. Consequently, understanding the climate dynamics and associated environmental change during the mPWP can help with predicting the environmental effects of warmer-than-present climates. In order to reconstruct Asian dust storm evolution during the mPWP we have analyzed a sediment core from the northern South China Sea (SCS) for its elemental composition, grain-size variations and radiogenic isotope signature for the interval spanning from 3.69 to 2.96 Ma. We show that shortly after the first strong northern hemisphere glaciation (Marine Isotope Stage [MIS] M2; 3.25 Ma) atmospherically transported dust appeared in the northern SCS and this dust deposition prevailed throughout the mPWP. Atmospheric dust input further intensified with the onset of the MIS KM2 glaciation at 3.15 Ma, with distinct and strong dust storms occurring periodically from that time onwards. The increase in atmospherically transported dust can be attributed to the cooling and drying of interior Asia over the course of the mPWP along with an intensification of the East Asian Winter Monsoon and a potential southward shift of the westerlies.