RV Pelagia Cruise 64PE372, 27 Jun - 11 Jul 2013. Flow dynamics and sedimentation in an active submarine channel: a process-product approach

Novel technologies are providing new opportunities to study the structure and dynamics of submarine sediment-gravity flows; these flows are the dominant process for transfer of sediment into the deep ocean, but are very hard to monitor due their destructive and unpredictable character. The primary aim of 64PE372 was to image the 3D structure of submarine flows passing though a rare example of an active submarine channel system in the southeast Black Sea. The channel system is maintained by through-flow of relatively dense, saline water coming from the Bosporus Strait outflow. ADCP mapping of internal flow structure within and outside the channel was achieved using the NERC Autosub3 Autonomous Underwater Vehicle (AUV), supplemented by vertical, vessel-based, CTD profiling, and a fixed CTD mooring in the proximal channel for the duration of the cruise. Sedimentary features associated with the channel were imaged using towed high-resolution sidescan sonar, supported by vessel-based multibeam bathymetry and backscatter, AUV subbottom profiler data, and gravity cores. The 64PE372 cruise built upon a previous cruise to the study area in spring 2010, but was far more successful due to the increased capability of the barter vessel and the improved performance of the AUV

RRS James Cook Cruise 124-125-126 09 Aug-12 Sep 2016. CODEMAP2015: Habitat mapping and ROV vibrocorer trials around Whittard Canyon and Haig Fras

The main aim of JC125 was to carry out habitat mapping work in the Whittard Canyon, NE Atlantic, in order to obtain a better insight in the biodiversity patterns, benthic habitat distributions and sediment transport processes of submarine canyons. At the same time, the objective was also to test a number of novel habitat mapping techniques, including sideways multibeam mapping of steep and overhanging cliffs using the Autosub6000 AUV (Autonomous Underwater Vehicle), which was specifically adapted for this task. The four-week expedition was the second cruise of the CODEMAP project (COmplex Deep-sea Ecosystems: Mapping habitat heterogeneity As Proxy for biodiversity), funded by the European Research Council (Grant No 258482). Two short ‘tag-on’ cruises were added to this main expedition: JC124 covered four days of seabed monitoring in the Haig Fras and Canyons Marine Conservation Zones as part of the DEFRA-funded project “Novel AUV and Glider deployments to inform future MPA and MSFD monitoring strategy in UK shelf waters?”. JC126 consisted of three days of ROV vibrocorer trials for the NERC-funded technology grant NERC Grant NE/0176581. Together, the five-week voyage was nick-named ‘CODEMAP2015’. To achieve its goals, CODEMAP2015 made extensive use of deep-water marine robotics: in a first for UK science, the Autosub6000 AUV, the Isis ROV (Remotely Operated Vehicle) and a Seaglider provided by the University of East Anglia were operating in the canyon, simultaneously, deployed from the RRS James Cook. They provided an unprecedented insight in the structure and processes of the submarine canyon. The nested survey design that was adopted throughout the cruise combined canyon-wide shipboard and glider surveys with AUV-based acoustics and ROV-based multibeam and HD video recordings. This enabled the integrated observation of different canyon processes at the scale they occur, ranging from 10s of km to a few mm

First direct measurements of hydraulic jumps in an active submarine density current

For almost half a century, it has been suspected that hydraulic jumps, which consist of a sudden decrease in downstream velocity and increase in flow thickness, are an important feature of submarine density currents such as turbidity currents and debris flows. Hydraulic jumps are implicated in major seafloor processes, including changes from channel erosion to fan deposition, flow transformations from debris flow to turbidity current, and large-scale seafloor scouring. We provide the first direct evidence of hydraulic jumps in a submarine density current and show that the observed hydraulic jumps are in phase with seafloor scours. Our measurements reveal strong vertical velocities across the jumps and smaller than predicted decreases in downstream velocity. Thus, we demonstrate that hydraulic jumps need not cause instantaneous and catastrophic deposition from the flow as previously suspected. Furthermore, our unique data set highlights problems in using depth-averaged velocities to calculate densimetric Froude numbers for gravity currents

Basic Methods for Computing Special Functions

This paper gives an overview of methods for the numerical evaluation of special functions, that is, the functions that arise in many problems from mathematical physics, engineering, probability theory, and other applied sciences. We consider in detail a selection of basic methods which are frequently used in the numerical evaluation of special functions: converging and asymptotic series, including Chebyshev expansions, linear recurrence relations, and numerical quadrature. Several other methods are available and some of these will be discussed in less detail. We give examples of recent software for special functions where these methods are used. We mention a list of new publications on computational aspects of special functions available on our website

RRS James Cook Cruise 27, 05 AUG-03 SEP 2008. Investigating landslide and gravity flow geohazards along the northeast Atlantic continental margin

The primary aim of JC027 was to collect sediment cores from a series of deep-water basinsalong the northeast Atlantic continental margin, in order to determine the character, frequencyand potential geohazard of landslides and gravity flows in the region. Target areas included thesubmarine slopes north of the Canary Islands, the Agadir Basin, the Seine, Horseshoe, Tagus,Iberia and Biscay Abyssal Plains, and a series of feeder canyons and channels. In addition,Autosub6000 was deployed on its first scientific missions in order to investigate the erosivepower of large-scale gravity flows in canyon mouth environments.Despite a late change to the schedule, JC027 proved to be a highly successful cruise. A totalof 63 stations were visited, with deployments including five Autosub6000 dives, fivemegacores and 55 piston cores. There was very little weather or technical downtime, whichensured that all of the main objectives were achieved.Cruise highlights included 1) recovery of sufficient core data to allow development of adetailed chrono-stratigraphy for all of the major basins between the Canary Islands and the UK,aiding identification of areas where landslides and gravity flows may pose a potentialgeohazard to European coastlines, 2) collection of a series of spectacular high-resolutionmultibeam bathymetry images of giant erosional scours (using Autosub6000), which areproviding new insights into scour formation and the flows that formed them, 3) new dataillustrating the complexity of sedimentary processes and deposits in deep-water environments,including flow transformations, and 4) new discoveries about seabird distribution andbehaviour in deep-water regions of the northeast Atlantic

RRS "Charles Darwin" Cruise CD166, 29 Oct - 22 Nov 2004. Sedimentary processes and deposits in the Agadir Basin and Gulf of Cadiz

The primary aim of CD166 was to undertake intensive coring in the Agadir Basin on the Northwest African margin, with the intention of characterising deep-water gravity flow processes and deposits at a basin-wide scale. In addition, it was hoped that sampling of volcaniclastic turbidites derived from Canary Islands landslides would provide insights into landslide processes and aid assessment of potential tsunami hazards. In addition, the first two days of the cruise were assigned to piston coring of a small, deep-water sand lobe in the Gulf of Cadiz, off southern Spain.In the event, CD166 proved to be a highly successful cruise. In the Agadir work area a total of 50 piston cores was collected, up to 8 m in length. Most of the cores successfully penetrated through the target turbidite units 1-14, providing sedimentological and stratigraphical data for the last 200,000 years. The piston coring mechanism was extremely reliable throughout this extensive coring effort. In the Speculobe work area, a total of 11 piston cores was collected, up to 7.7 m in length. The seabed environment in this region was highly challenging for coring, although several of the cores did recover crucial sediment sequences. The insights gained from these two datasets are likely to substantially alter current thinking on large-scale deep-water gravity flows.Wildlife observations were dominated by a variety of disoriented migrant landbirds and even a Migratory Locust arrived on board. Of scientific interest was the unusually large number of Leach’s Storm-petrels Oceanodroma leucorhoa recovered on the deck of the ship at night