• European Marine Science
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Much of our understanding of Earth's past climate states comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, major intervals in those records that lack the temporal resolution and/or age control required to identify climate forcing and feedback mechanisms. Here we document 66 million years of global climate by a new high-fidelity Cenozoic global reference benthic carbon and oxygen isotope dataset (CENOGRID). Using recurrence analysis, we find that on timescales of millions of years Earth's climate can be grouped into Hothouse, Warmhouse, Coolhouse and Icehouse states separated by transitions related to changing greenhouse gas levels and the growth of polar ice sheets. Each Cenozoic climate state is paced by orbital cycles, but the response to radiative forcing is state dependent.

We used a multibeam echosounder (Reson7125) front-mounted onto the ROV Isis (Dive D333, DY081 expedition) to map the terrain of a vertical feature marking the edge of a deep-sea glacial trough (Labrador Sea, [63°51.9'N, 53°16.9'W, depth: 650 to 800 m]). After correction of the ROV navigation (i.e. merging of USBL and DVL), bathymetry [m] and backscatter [nominal unit] were extracted at a resolution of 0.3 m and different terrain descriptors were computed: Slope, Bathymetric Position Index (BPI), Terrain Ruggedness Index, Roughness, Mean and Gaussian curvatures and orientations (Northness and Eastness), at scales of 0.9, 3 and 9 m. Using a Principal Component Analysis (PCA), the terrain descriptors enabled to retrieve 4 terrain clusters and their associated confusion index, to investigate the spatial heterogeneity of the terrain. This approach also underlined the presence of geomorphic features in the wall terrain. The extraction of the backscatter intensity for the first time considering vertical terrains, opens space for further acquisition and processing development. Using photographs collected by the ROV Isis (Dive D334, DY081 expedition), epibenthic fauna was annotated. Each image was linked to a terrain cluster in the 3D space and pooled into 20-m² bins of images. A Bray-Curtis dissimilarity matrix was constructed from morphospecies abundances. This enabled to test for differences of assemblage composition among clusters. Few species appeared more abundant in particular clusters such as L. pertusa in high-roughness cluster. However, nMDS suggested differences in assemblage composition but these dissimilarities were not strongly delineated. Whereas the design of this study may have limited distinctive differences among assemblages, this shows the potential of this cost-effective method of top-down habitat mapping to be applied in undersampled benthic habitat in order to provide a priori knwoledge for defining appropriate sampling design.

High-resolution 2D seismic reflection data during research cruise MSM63 in April/May 2017 onboard RV Maria S. Merian. The seismic profiles were acquired with a two-105/105-in3-GI-Gun-array shot at 210 bar every 5 seconds and a 150 m-long streamer with 96 channels and 1.5625 m channel spacing. The resulting shot point distance is approximately 8.75-12.5 m at 3.5-5 kn ship speed. The frequency range of the two-GI-Gun-array is 15-500 Hz. The processing included geometry and delay corrections, static corrections, binning to 1.5625 m and bandpass filtering with corner frequencies of 25, 45, 420, and 500 Hz. Furthermore, a normal-move-out-correction (with a constant velocity of 1488 m/s calculated from CTD measurements) was applied and the data were stacked and then migrated using a 2D Stolt algorithm (1500 m/s constant velocity model). Sub-bottom profiler data acquired during cruise MSM63 using Parasound P70 with 4 kHz as the secondary low frequency to obtain seismic images of the upper 100 m below the seafloor with very high vertical resolution (< 15 cm). We applied a frequency filter (low cut 2 kHz, high cut 6 kHz, 2 iterations) and calculated the envelope within the seismic interpretation software IHS Kingdom. Bathymetric data were acquired with the EM712 system mounted to the hull of RV Maria S. Merian. The survey was designed to provide high-resolution bathymetry with 5 x 5 m resolution. We processed the data using MB Systems software (Caress & Chayes, 2017) and included statistical evaluation of soundings that increased the signal-to-noise ratio. The sound velocity profile for multibeam processing was measured at the beginning and at the end of the cruise.

These datasets were used to describe the diversity, ecology and role of non-scleractinian corals on scleractinian cold-water coral carbonate mounds in the Logachev Mound Province, Rockall Bank, NE Atlantic. Cold-water coral carbonate mounds, created by framework-building scleractinian corals, are also important habitats for non-scleractinian corals, whose ecology and role are understudied in deep-sea environments. In total ten non-scleractinian species were identified, which were mapped out along eight ROV video transects. Eight species were identified as black corals (three belonging to the family Schizopathidae, one each to the Leiopathidae, Cladopathidae, and Antipathidae and two to an unknown family) and two as gorgonians (Isididae and Plexauridae). The most abundant species were Leiopathes sp. and Parantipathes sp. 2. Areas with a high diversity of non-scleractinian corals are interpreted to offer sufficient food, weak inter-species competition and the presence of heterogeneous and hard settlement substrates. A difference in the density and occurrence of small vs. large colonies of Leiopathes sp. was also observed, which is likely related to a difference in the stability of the substrate they choose for settlement. Non-scleractinian corals, especially black corals, are an important habitat for crabs, crinoids, and shrimps in the Logachev Mound Province.

An understanding of the balance of interspecific competition and the physical environment in structuring organismal communities is crucial because those communities structured primarily by their physical environment typically exhibit greater sensitivity to environmental change than those structured predominantly by competitive interactions. Here, using detailed phylogenetic and functional information, we investigate this question in macrofaunal assemblages from Northwest Atlantic Ocean continental slopes, a high seas region projected to experience substantial environmental change through the current century. We demonstrate assemblages to be both phylogenetically and functionally under-dispersed and thus conclude that the physical environment, not competition, may dominate in structuring deep-ocean communities. Further, we find temperature and bottom trawling intensity to be amongst the environmental factors significantly related to assemblage diversity. These results hint that deep-ocean communities are highly sensitive to their physical environment and vulnerable to environmental perturbation, including by direct disturbance through fishing, and indirectly through the changes brought about by climate change.

International efforts are underway to establish well-connected systems of marine protected areas (MPAs) covering at least 10% of the ocean by 2020. But the nature and dynamics of ocean ecosystem connectivity are poorly understood, with unresolved effects of climate variability. We used 40-year runs of a particle tracking model to examine the sensitivity of an MPA network for habitat-forming cold-water corals in the northeast Atlantic to changes in larval dispersal driven by atmospheric cycles and larval behaviour. Trajectories of Lophelia pertusa larvae were strongly correlated to the North Atlantic Oscillation (NAO), the dominant pattern of interannual atmospheric circulation variability over the northeast Atlantic. Variability in trajectories significantly altered network connectivity and source-sink dynamics, with positive phase NAO conditions producing a well-connected but asymmetrical network connected from west to east. Negative phase NAO produced reduced connectivity, but notably some larvae tracked westward-flowing currents towards coral populations on the mid-Atlantic ridge. Graph theoretical metrics demonstrate critical roles played by seamounts and offshore banks in larval supply and maintaining connectivity across the network. Larval longevity and behaviour mediated dispersal and connectivity, with shorter lived and passive larvae associated with reduced connectivity. We conclude that the existing MPA network is vulnerable to atmospheric-driven changes in ocean circulation.

The Atlantic meridional overturning circulation (AMOC) is a system of ocean currents that has an essential role in Earth's climate, redistributing heat and influencing the carbon cycle. The AMOC has been shown to be weakening in recent years1; this decline may reflect decadal-scale variability in convection in the Labrador Sea, but short observational datasets preclude a longer-term perspective on the modern state and variability of Labrador Sea convection and the AMOC. Here we provide several lines of palaeo-oceanographic evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately AD 1850) compared with the preceding 1,500 years. Our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the LIA, or as a more gradual, continued decline over the past 150 years; this ambiguity probably arises from non-AMOC influences on the various proxies or from the different sensitivities of these proxies to individual components of the AMOC. We suggest that enhanced freshwater fluxes from the Arctic and Nordic seas towards the end of the LIA—sourced from melting glaciers and thickened sea ice that developed earlier in the LIA—weakened Labrador Sea convection and the AMOC. The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet. Our results suggest that recent decadal variability in Labrador Sea convection and the AMOC has occurred during an atypical, weak background state. Future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the AMOC weakening described here. The data presented here is the supporting data for Thornalley et al. 2018 (see details below) and is derived from cores KNR-178-56JPC and KNR-178-48JPC. It includes the mean sortable silt size, details of radiocarbon dating, the % nps and binned sub-surface temperature reconstructions.

One and two metre snow pit accumulation, density, peroxide and conductivity on a depth and age scale from summer 2019 obtained at 7 ice core drilling sites; NEEM, B16, B19, B22 as well as 3 sites in the vicinity of EastGRIP representing the years 2014 to summer 2019. The data was analysed by means of continuous flow using the Light weight In Situ Analysis (LISA) box (Kjær et al, 2021).

Comparison of the equatorial upwelling system, the northern coastal upwelling system of the Gulf of Guinea and the tropical Angolan upwelling system.

Permafrost thaw and ice wedge degradation lead to drastic landscape changes in the permafrost region. With this data set we investigated the cliff retreat of the Sobo-Sise Cliff (SSC), a high ice-bearing yedoma cliff in the Lena River Delta. The 1,660 m long cliff SSC extends from 72°32'34 N / 128°15'59 E to 72°32'06 N / 128°18'21 E and is located on the Sardakhskaya channel, which is one of the main Lena river branches in the Lena River Delta. Erosion rates for the SSC were determined based on satellite images from different sensors (Corona, Hexagon, Landsat, Planet cube-sat) for the period 1965-2018. Cliff front lines were manually digitized and erosion rates were calculated with the Digital Shoreline Analysis System (DSAS) tool (Himmelstoos et al. 2018). The study Fuchs et al. (2020) (doi:10.3389/feart.2020.00336) shows that the up to 27.7 m high SSC erodes in average 15.7 m yr-1 (2015-2018). During the entire observed time period from 1965-2018, the SSC retreated in average 484 m (ranging from 322 - 680 m). This data set compilation consist of three GIS shapefiles with a corresponding metadata file and a table of the mean annual erosion rates of the yedoma SSC for the time periods 1965-1975, 1975-2000, 2000-2005, 2005-2010, 2010-2015, and 2015-2018, as well as the absolute cliff retreat rates over the entire period 1965-2018, which are derived from remote sensing imagery analyzed with the DSAS tool. In addition, the cliff front lines for each investigated time step are provided as well as the separation between yedoma and alas deposits for each time step. Related trend data for this region, based on Landsat trend analysis are available at: doi:10.1594/PANGAEA.884136 (Nitze, 2018).