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The southern westerly wind belt (SWW) interacts with the Antarctic Circumpolar Current and strongly impacts the Southern Ocean carbon budget, and Antarctic ice-sheet dynamics across glacial-interglacial cycles. We investigated precipitation-driven sediment input changes to the Southeast Pacific off the southern margin of the Atacama Desert over the past one million years, revealing strong precession (19/23-ka) cycles. Our simulations with 2 ocean-atmosphere general circulation models suggest that observed cyclic rainfall changes are linked to meridional shifts in water vapor transport from the tropical Pacific toward the southern Atacama Desert. These changes reflect a precessional modulation of the split in the austral winter South Pacific jet stream. For precession maxima, we infer significantly enhanced rainfall in the southern Atacama Desert due to a stronger South Pacific split jet with enhanced subtropical/subpolar jets, and a weaker midlatitude jet. Conversely, we derive dry conditions in northern Chile related to reduced subtropical/subpolar jets and an enhanced midlatitude jet for precession minima. The presence of precessional cycles in the Pacific SWW, and lack thereof in other basins, indicate that orbital-scale changes of the SWW were not zonally homogeneous across the Southern Hemisphere, in contrast to the hemispherewide shifts of the SWW suggested for glacial terminations. The strengthening of the jet is unique to the South Pacific realm and might have affected winter-controlled changes in the mixed layer depth, the formation of intermediate water, and the buildup of sea-ice around Antarctica, with implications for the global overturning circulation and the oceanic storage of atmospheric CO2.

In this study we present data collected between August 2017 and December 2018 from submarine sediment trap M1 located in the eastern tropical North Atlantic and determine lithogenic and biogenic fluxes, and grain-size distributions of aerosol dust. An unprecedented high sampling resolution of four days in combination with satellite imagery allowed the identification of thirteen major dust events of two types within the 468-day series. Seven dust events were classified as high-flux events identified by a deposition of >=25 mg m-2 d-1. The average dust deposition rate increased by 461.3% during these types of events. The remaining six events were characterized by a high composition of giant particles (>7.3 vol%). Seasonal variations of dust flux were recorded, with highest fluxes observed in spring at an average deposition rate of 14.8 mgm-2 d-1, and lowest fluxes in fall with an average rate of 8.6 mg m-2 d-1. The estimated total dust flux in the tropical North Atlantic was 4040.02 mg m-2 y-1. We suggest that most of the summer dust was likely transported over the sampling site at high altitudes while winter transport occurred closer to the sea surface, resulting in generally higher background fluxes. Grain-size distributions exhibited seasonal variations with increased occurrences of giant particles (>62.5 mm) in fall 2017 and spring, and less occurrences in winter and fall 2018. Grain-size sorting was high in spring and most variable in summer. Precipitation did not affect depositional fluxes or grain-size distributions of the aeolian dust significantly. Organic matter was deposited continuously at the sampling site with a deposition rate ranging from 14.4-862.25 mg m-2 d-1. Organic matter fluxes increased by 199.5% during high-flux dust events but decreased by 13.6% during anomalous grain-size events. Spring experienced the highest number of dust events (n=5). This unprecedented high-resolution dataset of dust deposition in marine sediment-traps enabled the distinction of dust events and their relation to organic matter flux. This suggests the possibility of a dust fertilization or mineral ballasting effect. [ABSTRACT FROM AUTHOR]

Mineral dust accumulated on the ocean floor is an important archive for reconstructing past atmospheric circulation changes and climatological conditions in the source areas. Dust emitted from Southern Hemisphere dust sources is widely deposited over the oceans. However, there are few records of dust deposition over the open ocean, and a large need for extended geographical coverage exists. We present a large data set (134 surface sediment samples) of Late Holocene dust deposition from seafloor surface sediments covering the entire South Atlantic Ocean. Polymodal grain‐size distributions of the lithogenic fraction indicate that the sediments are composed of multiple sediment components. By using end‐member modeling, we attempt to disentangle the dust signal from non‐aeolian sediments. Combined with 230Th‐normalized lithogenic fluxes, we quantified the specific deposition fluxes for mineral dust, crrent‐sorted sediments and ice‐rafted debris (IRD). Although the method could not completely separate the different components in every region, it shows that dust deposition off the most prominent dust source for the South Atlantic Ocean—southern South America—amounts up to approximately 0.7 g cm−2 Kyr−1 and decreases downwind. Bottom‐current‐sorted sediments and IRD are mostly concentrated around the continental margins. The ratio of the coarse to fine dust end members reveals input from north African dust sources to the South Atlantic. The majority of the observations are in good agreement with new model simulations. This extensive and relevant data set of dust grain size and deposition fluxes to the South Atlantic could be used to calibrate and validate further model simulations. Plain Language Summary: Ocean records of mineral dust can be used to reconstruct past climatic changes such as wind strength and aridity in the source regions, and also marine biological productivity. However, in the remote open ocean, dust samples are difficult to obtain and therefore records are sparse. We present a large data set of dust deposition, determined from the top centimeter of ocean floor sediments, covering the entire South Atlantic Ocean. These appeared to be complex mixtures of different sediment types, which we attempted to unmix mathematically. This resulted in four individual components, which are fine and coarse mineral dust, current‐sorted sediments and ice‐rafted debris (IRD). Although the unmixing has its limitations, it shows that the dust deposition off the most prominent dust source for the South Atlantic Ocean—southern South America—is significant and decreases downwind as dust settles during transport across the ocean. Current‐sorted sediments and IRD are mostly concentrated around the continental margins. The results also reveal dust transport across the equator from north African dust sources and show similarities with new model simulations. This extensive and relevant data set of dust grain size and deposition fluxes to the South Atlantic can be used to calibrate and validate further model simulations. Key Points: End‐member (EM) modeling is used to disentangle different sediment components from polymodal grain‐size distributionsCombined with 230Th‐normalized lithogenic fluxes, specific fluxes for dust, current‐sorted sediments and ice‐rafted debris are obtainedThis independent quantification provides more specific dust fluxes compared to global compilations of lithogenic fluxes [ABSTRACT FROM AUTHOR]

X‐ray fluorescence, grain‐size and oxygen and carbon stable isotope measurements of a 33 m long piston core, recovered from the Pen Duick drift located at the foot of the prominent Pen Duick Escarpment (Atlantic Moroccan margin), are combined to decipher past oceanographic conditions. The data indicate that, similar to the northern Gulf of Cádiz, the Azores Front exerts a major control on the palaeoclimatology of the region. Contrasting the northern Gulf of Cádiz, where Mediterranean Outflow Water is the main water mass at similar water depths, the palaeoceanography of the studied area is mostly influenced by the amount of Antarctic Intermediate Water advected from the south. The density contrast between the Antarctic Intermediate Water and the overlying North Atlantic Central Water determined the strength of the prevailing internal tides and corresponding high current speeds, which drastically impacted the sedimentary record. The most notable impact is the presence of a 7.8 kyr condensed section (30.5–22.7 ka bp). The formation of the Pen Duick sediment drift was not just controlled by the strength of the bottom currents and the intensity of the internal tides, but also by the amount of (aeolian) sediment supplied to the region. Although variable, drift‐growth phases seem to mainly occur during colder periods of the last glacial, that is Heinrich and Dansgaard‐Oeschger events during Marine Isotope Stage 3 and late Marine Isotope Stage 2. These periods, characterised by increased aeolian dust supply and higher bottom currents, coincide with a phase of prolific cold‐water coral growth and enhanced coral mound formation as recorded in numerous cores obtained from the southern Gulf of Cádiz. This implies that both records (on and off mound cores) are pivotal to provide the complete picture of the palaeoclimatic and palaeoceanographic conditions in the region. [ABSTRACT FROM AUTHOR]