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Rivers play a key role in the global carbon cycle by transporting terrestrial organic matter (TerrOM) from land to the ocean. Upon burial in marine sediments, this TerrOM may be a significant long-term carbon sink, depending on its composition and properties. However, much remains unknown about the dispersal of different types of TerrOM in the marine realm upon fluvial discharge since the commonly used bulk organic matter (OM) parameters do not reach the required level of source- and process-specific information. Here, we analyzed bulk OM properties, lipid biomarkers (long-chain n-alkanes, sterols, long-chain diols, alkenones, branched and isoprenoid glycerol dialkyl glycerol tetraethers (brGDGTs and isoGDGTs)), pollen, and dinoflagellate cysts in marine surface sediments along two transects offshore the Mississippi–Atchafalaya River (MAR) system, as well as one along the 20 m isobath in the direction of the river plume. We use these biomarkers and palynological proxies to identify the dispersal patterns of soil–microbial organic matter (SMOM), fluvial, higher plant, and marine-produced OM in the coastal sediments of the northern Gulf of Mexico (GoM). The Branched and Isoprenoid Tetraether (BIT) index and the relative abundance of C32 1,15-diols indicative for freshwater production show high contributions of SMOM and fluvial OM near the Mississippi River (MR) mouth (BIT = 0.6, > 50 %), which rapidly decrease further away from the river mouth (BIT < 0.1, < 20 %). In contrast, concentrations of long-chain n-alkanes and pollen grains do not show this stark decrease along the path of transport, and especially n-alkanes are also found in sediments in deeper waters. Proxy indicators show that marine productivity is highest close to shore and reveal that marine producers (diatoms, dinoflagellates, coccolithophores) have different spatial distributions, indicating their preferred niches. Close to the coast, where food supply

While Pleistocene glacial-interglacial cycles are commonly associated with strong waxing and waning of Northern Hemisphere ice sheets, the response of the Antarctic ice sheet and regional changes in oceanographic and environmental conditions to Pleistocene climate dynamics remain poorly constrained. We present a reconstruction of sea-ice cover, sea surface temperature and primary productivity off the Ross Sea margin (Adare Basin at the slope of the Drygalski Basin) during the marine isotope stages (MIS) 9 to 5 (350–70 thousands years ago, encompassing Terminations IV to II). Our multiproxy study relies on micropaleontology (diatoms, dinoflagellate cysts, benthic foraminifers), organic and inorganic geochemistry proxies (carbon and nitrogen isotopes, lipid biomarkers, XRF-data), and sedimentology (IRD) obtained from deep-sea core AS05-10. For each glacial-interglacial transition a clear succession of events can be observed: (near-)permanent sea ice cover during glacial stages is followed by ice-shelf break-up with episodic ice-free areas and surface water stratification. Notably, ice-shelf break-up precedes the increase in air temperature as measured in the Vostok ice core for each glacial-interglacial transition. Generally, air temperature over Vostok starts rising once sea-ice cover at site AS05-10 has significantly decreased, becoming seasonal, as indicated by the diatom species composition. This is also reflected by the high diatom productivity and increased water mixing at site AS05-10, which is indicative of its proximity to the Marginal Ice Zone. At the onset of Termination II (MIS6 to 5), high export productivity and dysoxic bottom water conditions occurred, while water temperature increased about 5 °C. During each interglacial spring/summer sea-ice cover is most reduced, and highest productivity occurs. Following each interglacial, the warm and cold fluctuations match the sawtooth character of the temperatures over Vostok. This record illustrates that at

mprovements in our capability to reconstruct ancient surface-ocean conditions based on organic-walled dinoflagellate cyst (dinocyst) assemblages from the Southern Ocean provide an opportunity to better establish past position, strength and oceanography of the subtropical front (STF). Here, we aim to reconstruct the late Eocene to early Miocene (37–20 Ma) depositional and palaeoceanographic history of the STF in the context of the evolving Tasmanian Gateway as well as the potential influence of Antarctic circumpolar flow and intense waxing and waning of ice. We approach this by combining information from seismic lines (revisiting existing data and generating new marine palynological data from Ocean Drilling Program (ODP) Hole 1168A) in the western Tasmanian continental slope. We apply improved taxonomic insights and palaeoecological models to reconstruct the sea surface palaeoenvironmental evolution. Late Eocene–early Oligocene (37–30.5 Ma) assemblages show a progressive transition from dominant terrestrial palynomorphs and inner-neritic dinocyst taxa as well as cysts produced by heterotrophic dinoflagellates to predominantly outer-neritic/oceanic autotrophic taxa. This transition reflects the progressive deepening of the western Tasmanian continental margin, an interpretation supported by our new seismic investigations. The dominance of autotrophic species like Spiniferites spp. and Operculodinium spp. reflects relatively oligotrophic conditions, like those of regions north of the modern-day STF. The increased abundance in the earliest Miocene of Nematosphaeropsis labyrinthus, typical for modern subantarctic zone (frontal) conditions, indicates a cooling and/or closer proximity of the STF to the site . The absence of major shifts in dinocyst assemblages contrasts with other records in the region and suggests that small changes in surface oceanographic conditions occurred during the Oligocene. Despite the relatively southerly (63–55∘ S) location

The Dacian Basin was uniquely situated to record late Miocene hydrological changes that influenced depositional environments and faunal dispersal patterns in Central Eurasia's mega-lake Paratethys. Differences between the high strontium isotope ratio (87Sr/86Sr) of the waters from Lake Pannon and local Carpathian rivers and low 87 Sr/86Sr of the Eastern Paratethys (Black Sea ‒ Caspian Sea) allow a thorough investigation of connectivity and water fluxes in the transient Dacian Basin. We present a detailed 87Sr/86 Sr record for the Dacian Basin, which provides an exceptional record of basin connectivity from the latest Tortonian (ca. 7.7 Ma) until the early Pleistocene (ca. 1.8 Ma). Data show that a late Tortonian transgression (7.6–7.4 Ma) started with an incursion of Eastern Paratethys waters into the Dacian Basin, after which local rivers became the dominant source for the mostly freshwater environments of the early Messinian. The regional Maeotian-Pontian transitional interval (6.3–5.9 Ma) records a second incursion of Eastern Paratethys waters, but this time with an additional marine (Mediterranean) influx coinciding with a short-lived salinity incursion. During the Messinian Salinity Crisis of the Mediterranean, the Dacian Basin progressively connected with the Eastern Paratethys (5.9–5.5 Ma), after which it became restricted during the peak Mediterranean lowstand (5.5 Ma) and filled with Lake Pannon and local river water (5.5–5.3 Ma). During the Plio-Pleistocene, the Dacian Basin reconnectedwith the, at that time isolated, Black Sea, which shows similar 87Sr/86Sr as in the Last Glacial Maximum.

Antarctic continental ice masses fluctuated considerably during the Oligocene “coolhouse”, at elevated atmospheric CO2 concentrations of ∼600–800 ppm. To assess the role of the ocean in the Oligocene ice sheet variability, reconstruction of past ocean conditions in the proximity of the Antarctic margin is needed. While relatively warm ocean conditions have been reconstructed for the Oligocene offshore of Wilkes Land, the geographical extent of that warmth is unknown. In this study, we reconstruct past surface ocean conditions from glaciomarine sediments recovered from Deep Sea Drilling Project (DSDP) Site 274 offshore of the Ross Sea continental margin. This site, located offshore of Cape Adare is ideally situated to characterise Oligocene regional surface ocean conditions, as it is situated between the colder, higher-latitude Ross Sea continental shelf and the warm-temperate Wilkes Land margin in the Oligocene. We first improve the age model of DSDP Site 274 using integrated bio- and magnetostratigraphy. Subsequently, we analyse organic walled dinoflagellate cyst assemblages and lipid biomarkers (TEX86, TetraEther indeX of 86 carbon atoms) to reconstruct surfacepalaeoceanographic conditions during the Oligocene (33.7–24.4 Ma). Both TEX 86-based sea surface temperature (SST) and microplankton results show temperate (10–17 ∘C ± 5.2 ∘C) surface ocean conditions at Site 274 throughout the Oligocene. Oceanographic conditions between the offshore Wilkes Land margin and Cape Adare became increasingly similar towards the late Oligocene (26.5–24.4 Ma); this is inferred to be the consequence of the widening of the Tasmanian Gateway, which resulted in more interconnected ocean basins and frontal systems. Maintaining marine terminations of terrestrial ice sheets in a proto-Ross Sea with offshore SSTs that are as warm as those suggested by our data requires a strong ice flux fed by intensive precipitation in the Antarctic h

The fractional abundance of branched glycerol dialkyl glycerol tetraether (brGDGT) membrane lipids in coastal marine sediments has been posited as a proxy for the reconstruction of terrestrial temperatures on the nearby land, based on the assumption that they are produced in soils and delivered to the marine realm by rivers following erosion. Here, we test the suitability of brGDGTs as a continental paleothermometer in Pliocene age sediments from the northern Gulf of Mexico (GoM; speculated Mississippi River input) and the Ceará Rise (speculated Amazon River input). Low branched to isoprenoid tetraether (BIT) index values of 0.00–0.13 and the near absence of pollen and long-chain plant waxes in the GoM sediments suggest that the Mississippi River did not have a strong influence on the delivery of terrestrial organic matter to the site during the Pliocene and soil input was limited. Indeed, the high weighted average of cyclopentane-containing tetramethylated brGDGTs (#ringstetra) in the GoM sediments (0.50 ± 0.09) relative to that of modern soils from the Mississippi catchment (0.25 ± 0.16) indicates that the brGDGTs in the GoM sediments were mostly produced in situ in the marine realm, hampering reliable land temperature reconstruction using the global soil transferfunction. In contrast, high BIT index values (0.46 ± 0.21) and low #rings tetra (0.25 ± 0.15) in sediments from the Ceará Rise suggest that these brGDGTs are primarily derived from soils. However, reconstructed temperatures were 11–18 °C lower than modern Amazon catchment temperatures. The relative abundance of 6-methylated brGDGTs (Isomerisation Ratio; IR) in the sediments is 0.82 ± 0.10, which resembles that of suspended particulate matter (SPM) in the modern Amazon River more than that of catchment soils (IR = 0.18 ± 0.18). This reveals that brGDGTs in the Ceará Rise sediments likely have a freshwater, riverine origin. Thus, the majority of the brGDGTs in both the GoM and Ceará Ri

Coral reef environments are important marine ecosystem and they are in decline due to climate change. Monitoring coral reefs is crucial but has its challenges since coral reefs are dynamic and data is sensitive to weather conditions. This often leads to difficulties for acquiring accurate data. Coral reef surveys are normally done during ideal conditions which are not always available when researchers are present. That is only one of several challenging aspects in coral reef classification. This study explores the possibilities of applying deep learning to classify drone imagery from coral reefs as a promising new approach for coral reef classification, but also as a new approach for producing geophysical output. This study also explores if it is possible to classify non ideal shore imagery. The possibility to work with non ideal imagery would provide more options for the analysis of coral reef surveys. The images are classified using a segmentation approach with a convolutional neural network. The binary classifications achieve high accuracies of 94% and 96% and IoU values of 77% and 71%. From the segmented output a coral density map is derived. The production of the coral density map is the one of the final steps towards producing promising geophysical output. The classification of non ideal imagery led to some difficulties, but it should be possible to fully correctly classify those as well, which can be discussed in further research

Early to Middle Miocene sea-level oscillations of approximately 40-60 m estimated from far-field records(1-3) are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth(2). This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene(4,5). Data and model outputs can be reconciled if a large West Antarctic Ice Sheet (WAIS) existed and expanded across most of the outer continental shelf during the Early Miocene, accounting for maximum ice-sheet volumes. Here weprovide the earliest geological evidence proving large WAIS expansions occurred during the Early Miocene (similar to 17.72-17.40 Ma). Geochemical and petrographic data show glacimarine sediments recovered at International Ocean Discovery Program (IODP) Site U1521 in the central Ross Sea derive from West Antarctica, requiring the presence of a WAIS covering most of the Ross Sea continental shelf. Seismic, lithological and palynological data reveal the intermittent proximity of grounded ice to Site U1521. The erosion rate calculated from this sediment package greatly exceeds the long-term mean, implying rapid erosion of West Antarctica. This interval therefore captures akey step in the genesis of a marine-based WAIS and a tipping point in Antarctic ice-sheet evolution.

A series of papers published shortly after the Integrated Ocean Drilling Program Arctic Coring Expedition (ACEX, 2004) on Lomonosov Ridge indicated remarkably high early Eocene sea surface temperatures (SSTs; ca. 23 to 27 ∘C) and land air temperatures (ca. 17 to 25 ∘C) based on the distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether (isoGDGT and brGDGT) lipids, respectively. Here, we revisit these results using recent analytical developments – which have led to improved temperature calibrations and the discovery of new temperature-sensitive glycerol monoalkyl glycerol tetraethers (GMGTs) – and currently available proxy constraints.The isoGDGT assemblages support temperature as the dominant variable controlling TEX86 values for most samples. However, contributions of isoGDGTs from land, which we characterize in detail, complicate TEX86 paleothermometry in the late Paleocene and part of the interval between the Paleocene–Eocene Thermal Maximum (PETM; ∼ 56 Ma) and the Eocene Thermal Maximum 2 (ETM2; ∼ 54 Ma). Background early Eocene SSTs generally exceeded 20 ∘C, with peak warmth during the PETM (∼ 26 ∘C) and ETM2 (∼ 27 ∘C). We find abundant branched GMGTs, likely dominantly marine in origin, and their distribution responds to environmental change. Further modern work is required to test to what extent temperature and other environmental factors determine their distribution.Published Arctic vegetation reconstructions indicate coldest-month mean continental air temperatures of 6–13 ∘C, which reinforces the question of whether TEX86-derived SSTs in the Paleogene Arctic are skewed towards the summer season. The exact meaning of TEX86 in the Paleogene Arctic thus remains a fundamental issue, and it is one that limits our assessment of the performance of fully coupled climate models under greenhouse conditions.

The number of designated Protected Areas (PAs) worldwide has been increasing fast over the past decades and currently 15.1% of the land and 7.9% of the ocean’s surface are under protection. However, the mere designation of a PA does not guarantee any degree of protection. Where the IUCN Categorizing system classifies PAs solely based on the management strategy on paper, the actual effects of this management remain undetermined. Over the past years, thousands of PA effectiveness methodologies have been developed and applied to PAs from all over the world. However, the majority of the existing assessments are not entirely fit for a quick and easy assessment of the actual quality of the protection in place. Therefore, we propose a new method that assesses the effects of the PA management and thereby reflects the actual degree of protection within the borders of a PA. We present the Protection Level Index (PLI), an index (ranging from 0 to 1) that is based on the scores for 12 equally weighted managerial, socio-economic and ecological sub-indices that are based on both the results from a questionnaire and an analysis of the spatial characteristics of the PA in a GIS. One of the great advantages of PLI is that it omits pre-defining universal optimal conditions and instead allows the PA manager(s) to put numerical quantifications into context. PLI has been tested for 7 European PAs covering a wide range of environmental regimes. The results indicate that some the sub-indices are closely related to each other and that despite the dissimilarities between the 7 PAs, they all have a similar final PLI score in the midrange around 0.63. This emphasizes the unbiased character of PLI, which makes it an ideal protected area management effectiveness method that can be applied to any PA worldwide.

Global climate has been rapidly changing due to on-going anthropogenic CO2 input to the atmosphere, causing the Antarctic Ice Sheet (AIS) to retreat and subsequently cause global sea level rise. AIS melting is heavily dependent on ocean-ice interactions. To be able to more accurately predict the future behaviour of the AIS - with respect to the ocean-driven melting - studying the interactions between AIS and ocean during past intervals of rapid climate warming can provide insights into mechanisms and feedbacks. One interval in the past when climate rapidly warmed is the Miocene Climatic Optimum (18 to 16 Ma), when the Southern Ocean was several degrees warmer in comparison to present sea surface temperatures. This research hence is a palaeoceanographic reconstruction of the Ross Sea in the early to middle Miocene and is performed using samples made into microscopic slides from the Ross Sea at Site U1521, recently retrieved during IODP. Dinoflagellate cyst assemblages suggest a highly dynamic marine-based Ross Sea ice sheet before and throughout the MCO and a clear warming trend towards the MCO. The studied interval starts with the reworking period indicating a period of increased glacial activity. Before the onset of the MCO the Ross Sea is mostly dominated by gonyaulacoid dinocysts suggesting a low SST and a locally ice-free sea to allow light to penetrate and stimulate photosynthesis. The onset of the MCO is indicated by the chert layer with dominance of heterotrophic dinocysts, indicating upwelling of nutrient rich water and ice sheet retreat with a higher Ross Sea SST. A small cooling trend is visible after the onset with fluctuating sea surface temperatures, indicated by autotrophic gonyaulacoid dominance, until the MCO where temperatures rise and heterotrophic dinocysts become abundant again.

The marine-based West Antarctic Ice Sheet (WAIS) is currently locally retreating because of shifting wind-driven oceanic currents that transport warm waters toward the ice margin, resulting in ice shelf thinning and accelerated mass loss. Previous results from geologic drilling on Antarctica’s continental margins show significant variability in ice sheet extent during the late Neogene and Quaternary. Climate and ice sheet models indicate a fundamental role for oceanic heat in controlling ice sheet variability over at least the past 20 My. Although evidence for past ice sheet variability is available from ice-proximal marine settings, sedimentary sequences from the continental shelf and rise are required to evaluate the extent of past ice sheet variability and the associated forcings and feedbacks. International Ocean Discovery Program Expedition 374 drilled a latitudinal and depth transect of five sites from the outer continental shelf to rise in the central Ross Sea to resolve Neogene and Quaternary relationships between climatic and oceanic change and WAIS evolution. The Ross Sea was targeted because numerical ice sheet models indicate that this sector of Antarctica responds sensitively to changes in ocean heat flux. Expedition 374 was designed for optimal data-model integration to enable an improved understanding of Antarctic Ice Sheet (AIS) mass balance during warmer-than-present climates (e.g., the Pleistocene “super interglacials,” the mid-Pliocene, and the Miocene Climatic Optimum). The principal goals of Expedition 374 were to Evaluate the contribution of West Antarctica to far-field ice volume and sea level estimates; Reconstruct ice-proximal oceanic and atmospheric temperatures to quantify past polar amplification; Assess the role of oceanic forcing (e.g., temperature and sea level) on AIS variability; Identify the sensitivity of the AIS to Earth’s orbital configuration under a variety of climate boundary conditions; and Reconstruc

During the last glacial period, climate conditions in the North Atlantic region were determinedby the alternation of relatively warm interstadials and relatively cool stadials, with superimposed rapidwarming (Dansgaard‐Oeschger) and cooling (Heinrich) events. So far little is known about the impact ofthese rapid climate shifts on the seasonal variations in sea surface temperature (SST) within the NorthAtlantic region. Here, we present a high‐resolution seasonal SST record for the past 152 kyrs derived fromIntegrated Ocean Drilling Program“Shackleton”Site U1385, offshore Portugal. Assemblage counts ofdinoflagellates cysts (dinocysts) in combination with a modern analog technique (MAT), and regressionanalyses were used for the reconstructions. We compare our records with previously published SST recordsfrom the same location obtained from the application of MAT on planktonic foraminifera. Ourdinocyst‐based reconstructions confirm the impression of the Greenland stadials and interstadials offshorethe Portuguese margin and indicate increased seasonal contrast of temperature during the cold periods ofthe glacial cycle (average 9.0 °C, maximum 12.2 °C) with respect to present day (5.1 °C), due to strong wintercooling by up to 8.3 °C. Our seasonal temperature reconstructions are in line with previously published data,which showed increased seasonality due to strong winter cooling during the Younger Dryas and the LastGlacial Maximum over the European continent and North Atlantic region. In addition, we show that overlonger time scales, increased seasonal contrasts of temperature remained characteristic of the colder phasesof the glacial cycle.

During the last glacial period, climate conditions in the North Atlantic region were determined by the alternation of relatively warm interstadials and relatively cool stadials, with superimposed rapid warming (Dansgaard‐Oeschger) and cooling (Heinrich) events. So far little is known about the impact of these rapid climate shifts on the seasonal variations in sea surface temperature (SST) within the North Atlantic region. Here, we present a high‐resolution seasonal SST record for the past 152 kyrs derived from Integrated Ocean Drilling Program “Shackleton” Site U1385, offshore Portugal. Assemblage counts of dinoflagellates cysts (dinocysts) in combination with a modern analog technique (MAT), and regression analyses were used for the reconstructions. We compare our records with previously published SST records from the same location obtained from the application of MAT on planktonic foraminifera. Our dinocyst‐based reconstructions confirm the impression of the Greenland stadials and interstadials offshore the Portuguese margin and indicate increased seasonal contrast of temperature during the cold periods of the glacial cycle (average 9.0 °C, maximum 12.2 °C) with respect to present day (5.1 °C), due to strong winter cooling by up to 8.3 °C. Our seasonal temperature reconstructions are in line with previously published data, which showed increased seasonality due to strong winter cooling during the Younger Dryas and the Last Glacial Maximum over the European continent and North Atlantic region. In addition, we show that over longer time scales, increased seasonal contrasts of temperature remained characteristic of the colder phases of the glacial cycle.

Plastic pollution poses one of the most urgent threats of present time to the marine environment. Global plastic production is growing exponentially and causing an unprecedented increase in the amount of mismanaged plastic waste available to enter the world’s oceans. Microplastic particles with a density lower than that of seawater float on the ocean surface and tend to accumulate in the Subtropical Gyres of all ocean basins due to geostrophic and Ekman currents and Stokes drift. This work develops a method to analyse the possible pathways followed by particles that were sampled in the South Atlantic Subtropical Gyre in order to identify their sources. To do so, particle trajectories were computed by means of Lagrangian simulations backward in time and for each particle the probability of being sourced from nine selected cities bordering the South Atlantic Ocean was calculated. Probability calculations were performed following both an exponential and a quadratic modelling approach on two different datasets. Both models were implemented in such a way that the probability decreased with an increase in distance between the particle and the potential source. The probabilities were also a function of the source uncertainty distance, a parameter representing the uncertain distance at which a particle could be identified as being sourced from a given location. The consistency between the results obtained from two modelling approaches and the different datasets allowed to pinpoint the Rio de la Plata estuary (comprising Montevideo and Buenos Aires), Cape Town and Rio de Janeiro as the most likely sources of microplastics to the South Atlantic Subtropical Gyre. Additionally, from sensitivity analysis the most meaningful source uncertainty distance was determined to range between 25 and 100 km. The methodology developed to calculate land source probabilities is fully transferable and could be used regardless of the study domain and the source locations that want to be address

Last time in Earth’s history when atmospheric CO2 was comparable or slightly higher than at present was during the early Late Pliocene (3.6 to 3.0 Ma). During this generally warm period, one intense glaciation occurred (known as M2, lasting between 3.312 and 3.264 Ma), followed by the mid-Piacenzian Warm Period. The transition from M2 to the mid-Piacenzian Warm Period is often seen as an analogue for the climate of our (near) future. The end of the mid-Piacenzian Warm Period started with the less intense G20 glacial (3.025 Ma), followed by other less intense glacials. This study focuses on a marine sediment record from ODP Site 625 taken offshore the Mississippi delta, which is, therefore, expected to contain both marine and terrestrial material. The aim of this study is to reconstruct the terrestrial (hydro)climate and associated Mississippi input into the Gulf of Mexico (GoM) as well as the oceanographic changes in the Gulf of Mexico during two glacial periods: M2 and the less intense G20 using a multi-proxy approach of both lipid biomarkers and palynology. The absence of plant- and soil-derived lipid biomarkers and pollen in the sediments indicate that terrestrial material discharged to the ocean by the Mississippi did not reach the site location during the studied intervals. On the other hand, marine lipid biomarkers and dinoflagellate cysts reveal a strong influence of the Loop Current during the interval preceding M2, transporting warm and salty Caribbean waters into the Gulf of Mexico. During the cold M2 interval, TEX86 sea surface temperatures dropped from 22.7°C to 20.6°C and Uk37 sea surface temperatures from 27.2°C to 26.2°C. During the temperature drop, salinity and stratification of the water column increased, eventually resulting in hyperstratification, as indicated by the presence of P. zoharyi. Hyperstratification still lasted into the following mid-Pliocene Warm Period, at least until 3.247 Ma. Eventually, the change in dinocyst composition shows th