Impact of a long-lived anticyclonic mesoscale eddy on seawater anomalies in the northeastern tropical Pacific Ocean: a composite analysis from hydrographic measurements, sea level altimetry data, and reanalysis model products

Using observational data, satellite altimeters, and reanalysis model products, we have investigated eddy-induced seawater anomalies and heat and salt transport in the northeastern tropical Pacific Ocean. An eddy detection algorithm (EDA) was used to identify eddy formation at the Mexican Tehuantepec Gulf (TT) in July 2018 during an unusually strong summer wind event. The eddy separated from the coast with a mean translation velocity of 11 cm s−1 and a mean radius of 115 km and traveled 2050–2400 km westwards off the Central American coast, where it was followed at approx 114∘ W and 11∘ N for oceanographic observation between April and May 2019. The in situ observations show that the major eddy impacts are restricted to the upper 300 m of the water column and are traceable down to 1500 m water depth. In the eddy core at 92 m water depth an extreme positive temperature anomaly of 8.2 ∘C, a negative salinity anomaly of −0.78 psu, a positive fluorescence anomaly of +0.8 mg m−3, and a positive dissolved oxygen concentration anomaly of 137 µmol kg−1 are observed. Compared with annual climatological averages in 2018, the water trapped within the eddy is estimated to transport an average positive westward zonal heat anomaly of 85×1012 W and an average westward negative salt anomaly of  kg s−1. The heat transport is the equivalent of 1 % of the total annual zonal eddy-induced heat transport at this latitude in the Pacific Ocean. Understanding the dynamics of long-lived mesoscale eddies that may reach the seafloor in this region of the Pacific Ocean is especially important in light of potential deep-sea mining activities that are being targeted on this area

Workshop on 3D mapping of habitats and biological communities with underwater photogrammetry

For the past decades, photogrammetry has been increasingly used for monitoring spatial arrangement or temporal dynamics of submerged man-made structures and natural systems. As photogrammetry remains a nascent technique for data collection in the underwater environment, acquisition workflows have evolved constrained by specific methodological practicalities (e.g. euphotic environments vs. deep-sea waters). The annual GeoHab conference gathers a world-wide range of scientists interested in mapping and is, therefore, an adequate event to set up a state-of-the-art workshop on (underwater) photogrammetry. More specifically, a preliminary survey identified the overall lack of photogrammetry knowledge from the audience. A programme was conceptualised to explore within a day theoretical concepts, sampling design and practicalities and a wide range of case studies in various underwater environments. Furthermore, we provided manual training on data acquisition and processing. In overall, a post-survey demonstrated the audience’s satisfaction despite a remaining lack of confidence for implementing their own photogrammetry studies. As this workshop gathers a diversity of materials and a training relevant for a scientific audience, it sets the stage for a reproducible event and leaves room for future improvements. Finally, it provided relevant materials and discussions that enabled us to identify the aspects limiting photogrammetry methodology across scientific applications and institutes, in order to work towards standardisation

Monitoring of Anthropogenic Sediment Plumes in the Clarion-Clipperton Zone, NE Equatorial Pacific Ocean

The abyssal seafloor in the Clarion-Clipperton Zone (CCZ) in the NE Pacific hosts the largest abundance of polymetallic nodules in the deep sea and is being targeted as an area for potential deep-sea mining. During nodule mining, seafloor sediment will be brought into suspension by mining equipment, resulting in the formation of sediment plumes, which will affect benthic and pelagic life not naturally adapted to any major sediment transport and deposition events. To improve our understanding of sediment plume dispersion and to support the development of plume dispersion models in this specific deep-sea area, we conducted a small-scale, 12-hour disturbance experiment in the German exploration contract area in the CCZ using a chain dredge. Sediment plume dispersion and deposition was monitored using an array of optical and acoustic turbidity sensors and current meters placed on platforms on the seafloor, and by visual inspection of the seafloor before and after dredge deployment. We found that seafloor imagery could be used to qualitatively visualise the redeposited sediment up to a distance of 100 m from the source, and that sensors recording optical and acoustic backscatter are sensitive and adequate tools to monitor the horizontal and vertical dispersion of the generated sediment plume. Optical backscatter signals could be converted into absolute mass concentration of suspended sediment to provide quantitative data on sediment dispersion. Vertical profiles of acoustic backscatter recorded by current profilers provided qualitative insight into the vertical extent of the sediment plume. Our monitoring setup proved to be very useful for the monitoring of this small-scale experiment and can be seen as an exemplary strategy for monitoring studies of future, upscaled mining trials. We recommend that such larger trials include the use of AUVs for repeated seafloor imaging and water column plume mapping (optical and acoustical), as well as the use of in-situ particle size sensors and/or particle cameras to better constrain the effect of suspended particle aggregation on optical and acoustic backscatter signals

Processed EM122 multibeam swath bathymetry collected during SONNE cruise SO268/1 inside the German License Area in Clarion Clipperton Zone, Pacific

The processed dataset is delivered in .GeoTIFF raster format projected in UTM11N coordinate system. The data acquisition was part of the international project JPI Oceans - MiningImpact Environmental Impacts and Risks of Deep-Sea Mining

Processed AUV multibeam swath bathymetry collected during SONNE cruise SO268/1 inside the German License Area in Clarion Clipperton Zone, Pacific

The processed dataset is delivered in .GeoTIFF raster format projected in UTM11N coordinate system. The data acquisition was part of the international project JPI Oceans - MiningImpact Environmental Impacts and Risks of Deep-Sea Mining

Processed EM122 multibeam swath bathymetry collected during SONNE cruise SO268/1 inside the Belgian License Area in Clarion Clipperton Zone, Pacific

The processed dataset is delivered in .GeoTIFF raster format projected in UTM10N coordinate system. The data acquisition was part of the international project JPI Oceans - MiningImpact Environmental Impacts and Risks of Deep-Sea Mining

Swath sonar multibeam EM122 water column data of R/V SONNE cruises SO268/1 and SO268/2 with links to wcd data files

Data acquisition was performed using the multibeam echosounder Kongsberg EM122. Raw data are delivered in Kongsberg .wcd format. The data acquisition was part of the international project JPI Oceans - MiningImpact Environmental Impacts and Risks of Deep-Sea Mining

Shipboard ADCP data during R/V SONNE cruises SO268/1 and SO268/2 with links to raw data files

Data acquisition was performed using the hull-mounted Teledyne Ocean Surveyor/Observer ADCP in 38kHz (SO268/1) and 75kHz (SO268/2). Raw data are delivered in .ENR format together with their auxiliary files. The data acquisition was part of the international project JPI Oceans - MiningImpact Environmental Impacts and Risks of Deep-Sea Mining

Summary of sizes, weights, counts and coverage of poly-metallic nodules from box cores taken during SONNE cruises SO268/1 and SO268/2

Aggregation of single nodule measurements (see https://doi.pangaea.de/10.1594/PANGAEA.904962) to values describing the entire box corer: - Nodules [#]: Total number of nodules sampled in the box corer (N). Includes surface nodules (N_s) and those from deeper layers (N_d) - Nodules [#](buried): Number of nodules from deeper layers (N_d) in the box corer that were not visible on the sea floor surface - Nodules size [cm^2]: The area A_i [cm^2] of an individual nodule n_i was computed from its two main axes (a_i [mm] & b_i [mm]) and the ellipsoidal formula (A_i = pi * a_i/2 * b_i/2 * 0.01). The value given here represents the median value of all nodule sizes in this box corer (Nodules size [cm^2] = MEDIAN(A_i,i=1..N) - Nodules m [kg]: Sum of the weights w_i [g] of all nodules in the box corer (surface and deeper layers; Nodules m [kg] = SUM(n_i,i=1..N)) * 0.001. To quantify nodule abundance per square meter, multiply this value by 4! - Nodules [%]: The sum of all nodule sizes A_i [cm^2] (i=1..N_s) visible at the seafloor, divided by the area of the box corer (50x50 cm^2): Nodules [%] = SUM(A_i,i=1..N_s) / 250

Profiles of vertical fish echo sounder Simrad EK60 during R/V SONNE cruises SO268/1 and SO268/2 with links to raw data files

Data acquisition was performed using the Simrad EK60. Raw data are delivered in .raw format together with their auxiliary files in .idx and .bot format. The data acquisition was part of the international project JPI Oceans - MiningImpact Environmental Impacts and Risks of Deep-Sea Mining