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Abstract An important role in the cycling of marine trace elements is scavenging, their adsorption and removal from the water column by sinking particles. Boundary scavenging occurs when areas of strong particle flux drive preferential removal of the trace metals at locations of enhanced scavenging. Due to its uniform production and quick burial via scavenging,²³⁰Th is used to assess sedimentary mass fluxes; however, these calculations are potentially biased near regions where net lateral transport of dissolved²³⁰Th violates the assumption that the flux of particulate²³⁰Th to the seabed equals its rate of production in the water column. Here, we present a water column transect of dissolved²³⁰Th along 152° W between Alaska and Tahiti (GEOTRACES GP15), where we examine²³⁰Th profiles across multiple biogeochemical provinces and, novelly, the lateral transport of²³⁰Th to distal East Pacific Rise hydrothermal plumes. We observed a strong relationship between the slope of dissolved²³⁰Th concentration‐depth profiles and suspended particle matter inventory in the upper‐mid water column, reinforcing the view that biogenic particle mass flux sets the background²³⁰Th distribution in open ocean settings. We find that, instead of the region of enhanced particle flux around the equator, hydrothermal plumes act as a regional boundary sink of²³⁰Th. At 152° W, we found that the flux‐to‐production ratio, and thereby error in²³⁰Th‐normalized sediment flux, is between 0.80 and 1.50 for hydrothermal water, but the error is likely larger approaching the East Pacific Rise. 

The last glacial period is characterized by abrupt climate oscillations, also known as Dansgaard-Oeschger (D-O) cycles. However, D-O cycles remain poorly documented in climate proxy records covering the penultimate glacial period. Here we present highly resolved and precisely dated speleothem time series from Sofular Cave in northern Türkiye to provide clear evidence for D-O cycles during Marine Isotope Stage (MIS) 6 as well as MIS 2-4. D-O cycles are most clearly expressed in the Sofular carbon isotope time series, which correlate inversely with regional sea surface temperature (SST) records from the Black Sea. The pacing of D-O cycles is almost twice as long during MIS 6 compared to MIS 2-4, and could be related to a weaker Atlantic Meridional Overturning Circulation (AMOC) and a different mean climate during MIS 6 compared to MIS 2-4, leading most likely to a higher threshold for the occurrence of D-O cycles. 

Abstract A paradigm in paleoclimatology holds that shifts in the mean position of the Intertropical Convergence Zone were the dominant climatic mechanism controlling rainfall in the tropics during the last glacial period. We present a new paleo-rainfall reconstruction based on speleothem stable oxygen isotopes record from Colombia, which spans most of the last glacial cycle. The strength and positioning of the Intertropical Convergence Zone over northern South America were more strongly affected by summer insolation at high northern latitudes than by local insolation during the last glacial cycle, resulting in an antiphased relationship with climate in the Cariaco Basin. Our data also provide new insight into how orbital forcing amplified/dampened Intertropical Convergence Zone precipitation during millennial-scale events. During Greenland Stadial events, the Intertropical Convergence Zone was positioned close to the latitude of El Peñon, as expressed by more negative δ¹⁸O values. Greenland Interstadial events are marked by relatively high stable oxygen isotope values and reduced rainfall in the El Peñon record, suggesting a northward withdrawal of the Intertropical Convergence Zone. During some Heinrich Stadial events, and especially Heinrich Stadial 1, the Intertropical Convergence Zone must have been displaced away from its modern location near El Peñon, as conditions were very dry at both El Peñon and Cariaco. 

The five interglacials before the Mid-Brunhes Event (MBE) [c.430 thousand years (ka) ago] are generally considered to be globally cooler than those post-MBE. Inhomogeneities exist regionally, however, which suggest that the Arctic was warmer than present during Marine Isotope Stage (MIS) 15a. Using the first speleothem record for the High Arctic, we investigate the climatic response of northeast Greenland between c.588 and c.549 ka ago. Our results indicate an enhanced warmth of at least +3.5°C relative to the present, leading to permafrost thaw and increased precipitation. We find that δ 18 O of precipitation was at least 3‰ higher than today and recognize two local cooling events (c.571 and c.594 ka ago) thought to be caused by freshwater forcing. Our results are important for improving understanding of the regional climatic response leading up to the MBE and specifically provide insights into the climatic response of a warmer Arctic. 

Abstract In this study, we present a Holocene rainfall index based on three high‐resolution speleothem records from the Western Mediterranean, a region under the influence of the westerly winds belt modulated by the North Atlantic Oscillation (NAO). On centennial to millennial timescales, we show that the North Atlantic ice‐rafting events were likely associated with negative NAO‐like conditions during the Early Holocene and the Late Holocene. However, our data reveal that this is not clearly the case for the mid‐Holocene ice‐rafting events, during which we also show evidence of positive NAO‐like patterns from other paleo‐oceanographic and paleo‐atmospheric data. Hence, contradictory mechanisms involving prolonged periods of both north and south shifts of the westerly winds belt (resembling positive and negative NAO‐like patterns) might at least partially trigger or amplify the ice‐rafting events and the slowdown of the Atlantic Meridional Overturning Circulation.