Abstract Greater ocean export productivity fueled by enhanced delivery of iron to the Sub‐Antarctic Zone (SAZ) of the Southern Ocean is hypothesized to play an important role in reducing atmospheric CO 2 during Pleistocene glaciations. However, spatial variability in iron input and nutrient availability complicates quantifying the integrated impact of iron‐fertilization on carbon export. We reconstruct preserved carbon export and iron input across the central Indian sector of the Southern Ocean with a latitudinal transect of sediment cores. 230 Th‐normalized fluxes of organic and inorganic productivity proxies are compared to bulk sedimentary redox‐sensitive trace metal concentrations to investigate preservation bias related to glacial‐interglacial changes in bottom water oxygenation. Across the last 28 ka, a strong relationship is observed between iron fluxes and export productivity across the SAZ, suggesting enhanced iron delivery during the Last Glacial Maximum (LGM) strengthened the biological carbon pump. Changes in bottom water oxygenation influenced the preservation of organic‐based productivity proxies, while excess barium fluxes reliably record carbon export. The southern SAZ (44.7°S) received ∼8× more iron during the LGM than the central SAZ (42.3°S). This pronounced iron flux gradient suggests terrigenous inputs from the Kerguelen Plateau entrained in the Antarctic Circumpolar Current delivered greater volumes of iron to the southern SAZ, relative to the northern SAZ dominated by aeolian input. These results, alongside previous studies, demonstrate iron fertilization increased export productivity across large swathes of the SAZ during the LGM. However, spatial heterogeneity in iron supply led to regional differences in the magnitude of glacial‐interglacial shifts in productivity.

AbstractMultiple expressions of climate change, in particular warming‐induced reductions in the type, extent and thickness of sea ice, are opening access and providing new viable development opportunities in high‐latitude regions. Coastal margins are facing these challenges, but the vulnerability of species and ecosystems to the effects of fuel contamination associated with increased maritime traffic is largely unknown. Here, we show that low concentrations of the water‐accommodated fraction of marine fuel oil, representative of a dilute fuel oil spill, can alter functionally important aspects of the behaviour of sediment‐dwelling invertebrates. We find that the response to contamination is species specific, but that the range in response among individuals is modified by increasing fuel concentrations. Our study provides evidence that species responses to novel and/or unprecedented levels of anthropogenic activity associated with the opening up of high‐latitude regions can have substantive ecological effects, even when human impacts are at, or below, commonly accepted safe thresholds. These secondary responses are often overlooked in broad‐scale environmental assessments and marine planning yet, critically, they may act as an early warning signal for impending and more pronounced ecological transitions.

Abstract Climate change is known to affect the distribution and composition of species, but concomitant alterations to functionally important aspects of behaviour and species-environment relations are poorly constrained. Here, we examine the ecosystem ramifications of changes in sediment-dwelling invertebrate bioturbation behaviour—a key process mediating nutrient cycling—associated with near-future environmental conditions (+ 1.5 °C, 550 ppm [pCO2]) for species from polar regions experiencing rapid rates of climate change. We find that responses to warming and acidification vary between species and lead to a reduction in intra-specific variability in behavioural trait expression that adjusts the magnitude and direction of nutrient concentrations. Our analyses also indicate that species behaviour is not predetermined, but can be dependent on local variations in environmental history that set population capacities for phenotypic plasticity. We provide evidence that certain, but subtle, aspects of inter- and intra-specific variation in behavioural trait expression, rather than the presence or proportional representation of species per se, is an important and under-appreciated determinant of benthic biogeochemical responses to climate change. Such changes in species behaviour may act as an early warning for impending ecological transitions associated with progressive climate forcing.

The skeletons of long-lived bamboo coral (Family Keratoisididae) are promising archives for deep-water palaeoceanographic reconstructions as they can record environmental variation at sub-decadal resolution in locations where in-situ measurements lack temporal coverage. Yet, detailed three dimensional (3D) characterisations of bamboo coral skeletal architecture are not routinely available and non-destructive investigations into microscale variations in calcification are rare. Here, we provide high-resolution micro-focus computed tomography (µCT) data of skeletal density for two species of bamboo coral (Acanella arbuscula: 5 specimens, voxel size, 15 µm (central branch scans) and 50 µm (complete structure scan); Keratoisis sp.: 4 specimens, voxel size, 15 µm) collected from the Labrador Sea and Baffin Bay deep-water basins, Eastern Canadian Arctic. These data provide reference models useful for developing methods to assess structural integrity and other fine-scale complexities in many biological, geological, and industrial systems. This will be of wider value to those investigating structural composition, arrangement and/or composition of complex architecture within the fields and subdisciplines of biology, ecology, medicine, environmental geology, and structural engineering.

The impact of warming, acidification, and deoxygenation on deep-sea environments is a growing concern. Historical records are sparse, particularly at high latitudes, making climate change projections challenging. Indirect proxies, such as trace element composition of marine carbonates, such as coral skeletons, can offer an alternative method to fill data gaps but have not been realised. Here, using Laser Ablation Triple-Quadrupole Inductively Coupled Plasma Mass Spectrometry (LA-QQQ-ICP-MS), we examined micrometre-scale element variation within and between individual colonies of the bamboo coral Keratoisis sp. obtained from the Eastern Canadian Arctic. These data are used to assess the influence of biological variability on geochemical tracers for reconstructing past environmental conditions (temperature: Mg/Ca, Li/Mg, Sr/Ca, Ba/Ca, U/Ca; [Ba](SW): Ba/Ca). We place these data into context, based on a survey of literature data, using refined calibrations for high-Mg calcitic Octocorals. We find reproducible (2 sigma relative coefficient of variation) values of Mg/Ca (3%) and Ba/Ca (6%) along the radial growth axis of all colonies and internodes of Keratoisis sp., indicating that these signals are likely suitable for environmental reconstructions. After revising the available multi-taxa calibrations for Mg/Ca (0.316 +/- 0.026 degrees C/mmol/mol, R-2 = 0.87, p < 0.001) and Ba/Ca ([Ba/Ca mu mol/mol] = 0.148 +/- 0.005 [Ba-SW nmol/kg], R-2 = 0.97, p < 0.001), we show that vital effects within and among Keratoisis sp. colonies strongly influence reconstructed temperature and [Ba](SW), but this can be somewhat mitigated by combining multiple internode transects from one colony into a single composite series. Despite the ontogenetic variability, all colonies reveal a gradual deep-water cooling trend since the early 21st century and synchronised, multi-year spikes in Ba/Ca (and hence [Ba](SW)) that suggest substantial and coherent barium inputs to the seafloor. Our study confirms the reliability of Mg/Ca and Ba/Ca proxies in high-Mg bamboo corals for detecting multi-annual temperature and seawater barium variations in cold-water environments, but further investigation into micro-scale element behaviour influenced by biotic processes in these corals is needed to enhance confidence in reconstructions at finer spatial and temporal resolutions. We conclude that employing empirical calibrations based on multi-taxa approaches can increase the certainty of capturing regional changes in the environment more accurately than a single species calibration, while leveraging multiple element series to account for biological-induced variability improves single colony reconstructions.

The Southern Ocean is an important regulator of global CO 2 levels and likely had a key role in lowering atmospheric CO 2 levels during the Last Glacial Maximum (LGM) and driving the subsequent increase during the following deglaciation. Nonetheless, debate continues surrounding the relative importance of Northern versus Southern Hemisphere forcing during deglacial events. In this Review, we compare modern Southern Ocean conditions with those in the LGM and deglacial period, identifying factors that were critical in initiating the glacial termination. During the LGM, North Atlantic sourced waters appear to have shoaled and were largely absent from the glacial Southern Ocean. Increased ocean stratification, shoaling of the chemical divide and increased nutrient utilization at the surface contributed to glacial carbon sequestration in deep waters. Warming at mid-latitudes of the Southern Hemisphere and the Southern Ocean began at ~21 ka, preceding deglaciation, indicating insolation changes could have driven early atmosphere–ocean warming that initiated the shifting of ocean fronts leading to the release of carbon sequestered in the LGM. Southern Ocean dynamics appear to have been substantial, or even the critical, factors initiating the termination of the LGM before deepening of North Atlantic sourced waters. Future research should focus on better resolving deglacial chemical and physical changes in Southern Ocean waters and their representation in numerical models.

A closed-system batch reaction experiment was conducted for 270 days to evaluate the effects of inter-action between Gulf of Mexico (GOM) seawater and Mississippi River sediments on the system's dis-solved rare earth elements (REE) concentrations and neodymium isotopic compositions (eNd). This study specifically focuses on geochemical reactions involving silicic sediments derived from weathering of the North American continent as they affect the REEs and eNd of seawater along continental margins, in contrast to previous studies that investigated the influence of basaltic rocks and sediments on REEs and eNd in the ocean. Our results show that the dissolution of labile phases of lithogenic Mississippi River sediments leads to an approximately 100-fold increase in dissolved REE concentrations within the first 33 days of the experiment. Secondary mineral precipitation appears to lower the REE concentrations between days 33 and 270 of the experiment, although seawater REE concentrations remain elevated compared to initial values. The two-way elemental transfer involving dissolution and precipitation results in a net increase by a factor of 24 +/- 12 (mean +/- 1r) in the dissolved REE concentrations by the end of the experiment (i.e., day 270). The dissolved REE concentration maxima observed after 33 days of the experiment represent the mobilization of approximately 0.37 % of the REE content of the opera-tionally defined "exchangeable " fraction of the riverine sediments. The eNd values of the reactive lithogenic components were-9.77 and-9.95, which are similar to the GOM value of-9.81 +/- 0.36. Because of the similarity between eNd values, changes in the seawater Nd isotope value throughout the experiment were subtle (mean +/- std, reacted seawater eNd of-9.87 +/- 0.17). The highest REE concentrations coin-cided with the most radiogenic eNd (-9.65 & PLUSMN; 0.23; day 33), which suggests that REE concentrations and eNd compositions of the GOM may be buffered by fluxes from sediments in the system. Our results are comparable to previous studies involving basaltic rocks and/or sediments of basaltic composition in that they demonstrate that silicic, river sediments are highly reactive in marine environments with regard to REE mobilization. The experimental results further suggest that "boundary exchange " plays an important role in influencing the eNd of seawater along continental margins dominated by large river systems, although the impacts of boundary exchange will be most profound where ambient seawater and river sediments have distinct Nd isotopic compositions (e.g., basaltic, or Precambrian shield material). Finally, our results indicate that the eNd value of GOM seawater is largely controlled by the lithogenic sediment delivered to the basin by the Mississippi River.(c) 2022 Elsevier Ltd. All rights reserved.

Neodymium (Nd) isotopes have been utilized as a tracer of water mass source in the modern ocean and in palaeoceanographic studies, though the oceanic cycling of Nd is not yet fully constrained. Recent studies have highlighted the importance of processes that occur near the seawater – sediment interface in altering the Nd isotopic composition of bottom waters. The two major observed processes “boundary exchange” and “benthic flux” have been suggested as playing an important role in setting water mass compositions, however, more studies are needed to constrain their chemical mechanism and the extent to which these processes set the composition of deep waters. The Antarctic continental margin is an important place to study these processes because Antarctic-sourced waters dominate the Southern Ocean and ventilate the global deep ocean. This study is the first to measure and compare seawater, porewater and sediment data from along the margin of Antarctica to examine the nature of potential boundary processes. We show that a process similar to boundary exchange seems to be occurring within porewaters, modifying porewater chemistry by shifting its Nd isotopic ratios to more radiogenic values without significantly increasing the concentration of dissolved Nd. We hypothesize that this shift results from partial dissolution of radiogenic detrital particles, such as smectite, amphibole and/or volcanic glass, while re-scavenging maintains low Nd concentrations. We infer the existence of benthic flux of porewaters to deep waters by examining chemical gradients in porewaters and show that it is much lower on the Antarctic margin compared to other studies. Benthic flux appears to be slightly higher along the Antarctic Peninsula than in the Bellingshausen Sea due to partial degradation of organic matter and associated dissolution of Fe-Mn oxyhydroxides. Taken together, boundary processes do not significantly change the Nd isotopic composition of Antarctic margin seawater because while the porewaters have an altered Nd isotopic composition the Nd concentration of these porewaters is low compared to other settings.

The chain of events surrounding the initiation and intensification of the last glacial cycle remain relatively poorly understood. In particular, the role of Southern Ocean paleocirculation changes is poorly constrained, in part, owing to a paucity of sedimentary records from this region. In this study we present multiproxy data - including neodymium isotope and sortable silt measurements - for paleocirculation changes within the deep (3167 mwater depth) Indian sector of the Southern Ocean from a new sediment core, TT1811-34GGC (41.718 degrees S, 80.163 degrees E). We find a tight coupling between circulation changes, Antarctic climate, and atmospheric CO2 concentrations throughout the last 118,000 years, even during the initial stages of glacial inception of Marine Isotope Stage (MIS) 5.4 to 5.1. We find that periods of cooling correspond to reductions in the entrainment of North Atlantic-sourced waters within the deep Southern Ocean, as evidenced by more radiogenic neodymium isotope values of deep water bathing our core site. Cooling also corresponds to generally slower bottom water flow speeds, as indicated by finer sortable silt size fractions. A reduction in entrainment of North-Atlantic sourced waters occurred during MIS 5.4-5.1, when Atlantic circulation was strong, suggesting a Southern hemisphere control on paleocirculation changes at that time. We hypothesise that expanded Southern Ocean sea-ice during MIS 5.4 increased the density of the deep Southern Ocean, reducing the ability of Atlantic-sourced waters to mix into Lower Circumpolar Deep Water. This led to an expanded contribution of Pacific Deep Water within the lower circulation cell and increased stratification within the deep Southern Ocean. These paleocirculation changes can help account for the reduction in atmospheric CO2 across the MIS 5.5 to 5.4 transition, and in doing so help explain the chain of events surrounding the decent into the last glacial period. (C) 2021 Elsevier Ltd. All rights reserved.

Abstract The decrease in δ13C of dissolved inorganic carbon (δ13CDIC) owing to uptake of anthropogenic CO2 (the oceanic 13C Suess effect) in the Southeastern Indian Ocean over the last decade was calculated using an extended multiparameter linear regression technique. Samples collected on the CROCCA‐2S (Coring to Reconstruct Ocean Circulation and Carbon Dioxide Across 2 Seas) cruise in November–December 2018 were compared to samples from the CLIVAR (Climate and Ocean: Variability, Predictability, and Change) and OISO (Océan Indien Service d'Observation) programs from 2007 to 2009. Surface ocean δ13CDIC decreased by an average of −0.53 ± 0.04‰ across this period, at an average rate of −0.053 ± 0.004‰ per year. This rate of δ13CDIC change is an increase from −0.021 ± 0.024‰ per year between 1994 and 2008. We find that the interior water mass most impacted by the oceanic 13C Suess effect between 2008 and 2018 was Subantarctic Mode Water (SAMW), within which δ13CDIC decreased by −0.044 ± 0.002‰ per year. Using previously published relationships between the oceanic 13C Suess effect and anthropogenic carbon, we estimate the annual storage of anthropogenic carbon within SAMW in the southeastern Indian Ocean has increased from ∼2.0 ± 0.2 μmol/kg per year between 1994 and 2008 to 5.5 ± 0.6 μmol/kg per year between 2008 and 2018.

The Antarctic Peninsula's Pacific margin is one of the best studied sectors of the Antarctic continental margin. Since the 1990s, several research cruises have targeted the continental rise with geophysical surveys, conventional coring and deep-sea drilling. The previous studies highlighted the potential of large sediment drifts on the rise as high-resolution palaeoenvironmental archives. However, these studies also suffered from chronological difficulties arising from the lack of calcareous microfossils, with initial results from geomagnetic relative palaeointensity (RPI) dating promising a possible solution. This paper presents data from new sediment cores recovered on cruise JR298 from seven continental rise sites west of the Antarctic Peninsula and in the Bellingshausen Sea with the objectives to (i) seek calcareous foraminifera, especially at shallow drift sites, to constrain RPI-based age models, and (ii) investigate the depositional history at these locations. We present the results of chronological and multiproxy analyses on these cores and two cores previously collected from the study area. We establish new age models for the JR298 records and compare them with published RPI-based age models. In addition, we evaluate the reliability of different palaeoproductivity proxies and infer depositional processes. Planktic foraminifera are present in various core intervals. Although their stable oxygen isotope (delta O-18) ratios, tephrochronological constraints and glacial-interglacial changes in sediment composition provide age models largely consistent with the RPI chronologies, we also observe distinct differences, predominantly in the Bellingshausen Sea cores. Enrichments of solid-phase manganese together with evidence for "burn-down" of organic carbon in late glacial and peak interglacial sediments document non-steady-state diagenesis that may have altered magnetic mineralogy and, thus, RPI proxies. This process may explain discrepancies between RPI-based age models and those derived from delta O-18 data combined with tephrochronology. The data also indicate that organic carbon is a much less reliable productivity proxy than biogenic barium or organically-associated bromine in the investigated sediments. In agreement with previous studies, sediment facies indicate a strong control of deposition on the rise by bottom currents that interacted with detritus supplied by meltwater plumes, gravitational downslope transport processes and pelagic settling of iceberg-rafted debris (IRD) and planktic microfossils. Bottom-current velocities underwent only minor changes over glacial-interglacial cycles at the drift crests, with down-slope deposition only rarely affecting these shallow locations. Maximum concentrations of coarse IRD at the seafloor surfaces of the shallow sites result predominantly from upward pumping caused by extensive bioturbation. This process has to be taken into account when past changes in IRD deposition are inferred from quantifying clasts >1 mm in size. (C) 2021 The Author(s). Published by Elsevier Ltd.

In previous work, researchers in Human-Robot Interaction (HRI) have demonstrated that user trust in robots depends on effective and transparent communication. This may be particularly true forrobots used for transportation, due to user reliance on such robots for physical movement and safety. In this paper, we present the design of an experiment examining the importance of proactive communication by robotic wheelchairs, as compared to non-vehicular mobile robots, within a Virtual Reality (VR) environment. Furthermore, we describe the specific advantages – and limitations – of conducting this type of HRI experiment in VR.

This paper explores the tradeoffs between different types of mixed reality robotic communication under different levels of user workload. We present the results of a within-subjects experiment in which we systematically and jointly vary robot communication style alongside level and type of cognitive load, and measure subsequent impacts on accuracy, reaction time, and perceived workload and effectiveness. Our preliminary results suggest that although humans may not notice differences, the manner of load a user is under and the type of communication style used by a robot they interact with do in fact interact to determine their task effectiveness

The performance of human-robot teams depends on human-robot trust, which in turn depends on appropriate robot-to-human transparency. A key way for robots to build trust through transparency is by providing appropriate explanations for their actions. While most previous work on robot explanation generation has focused on robots’ ability to provide post-hoc explanations upon request, in this paper we instead examine proactive explanations generated before actions are taken, and the effect this has on human-robot trust. Our results suggest a positive relationship between proactive explanations and human-robot trust, and reveal fundamental new questions into the effects of proactive explanations on the nature of humans’ mental models and the fundamental nature of human-robot trust.

Most conceptual models of ocean circulation during past glacial periods invoke a shallowed North Atlantic-sourced water mass overlying an expanded, poorly ventilated Southern Ocean (SO)-sourced deep water mass (Southern Component Water or SCW), rich in remineralized carbon, within the Atlantic basin. However, the ventilation state, carbon inventory, and circulation pathway of SCW sourced in the Pacific sector of the SO (Pacific SO) during glacial periods are less well understood. Here we present multiproxy data-including delta O-18 and delta C-13 measured on the benthic and planktic foraminifera Cibicidoides wuellerstorfi, and Neogloboquadrina pachyderma, and productivity proxies including percent CaCO3, total organic carbon, and Ba/Ti-from a sediment core located in the high-latitude (71 degrees S) Pacific SO spanning the last 800 kyr. Typical glacial delta C-13 values of SCW at this core site are similar to 0%o. We find no evidence for SCW with extremely low delta C-13 values during glacials in the high-latitude Pacific SO. This leads to a spatial gradient in the stable carbon isotope composition of SCW from the high-latitude SO, suggesting that there are different processes of deep- and bottom-water formation around Antarctica. A reduced imprint of air-sea gas exchange is evident in the SCW formed in the Atlantic SO compared with the Pacific SO. A spatial delta C-13 gradient in SCW is apparent throughout much of the last 800,000 years, including interglacials. A SO-wide depletion in benthic delta C-13 is observed in early MIS 16, coinciding with the lowest atmospheric pCO(2) recorded in Antarctic ice cores.

DIARC has been under development for over 15 years. Different from other cognitive architectures like SOAR or ACT-R, DIARC is an intrinsically component-based distributed architecture scheme that can be instantiated in many different ways. Moreover, DIARC has several distinguishing features, such as affect processing and deep natural language integration, is open-world and multi-agent enabled, and allows for "one-shot instruction-based learning" of new percepts, actions, concepts, rules, and norms. In this chapter, we will present an overview of the DIARC architecture and compare it to classical cognitive architectures. After laying out the theoretical foundations, we specifically focus on the action, vision, and natural language subsystems. We then give two examples of DIARC configurations for "one-shot learning" and "component-sharing". We also briefly mention different use cases of DIARC, in particular, for autonomous robots in human-robot interaction experiments and for building cognitive models.