Geological information from telecommunications cable route surveys of the continental shelf

Several burial assessment surveys using a seabed plough have been carried out along routes on the United Kingdom continental shelf to assess their potential for cable burial. Detailed information on sediment thicknesses and characteristics within the top meter of the seabed was collected using a survey tool called the Plough Surveyor. Geophysical surveys along these routes have enabled correlation with the plough data. Results include the range of tensions, tension trace characteristics, and typical penetration, and these have been correlated with seabed types and thickness of sediment.     

A New Methodology for Incorporating Tide Gauge Data in Sea Surface Topography Models

As part of the Vertical Offshore Reference Frames (VORF) project sponsored by the U. K. Hydrographic Office, a new model for Sea Surface Topography (SST) around the British Isles has been developed. For offshore areas (greater than 30 km from the coast), this model is largely derived from satellite altimetry. However, its accuracy and level of detail have been enhanced in coastal areas by the inclusion of not only the 60 PSMSL tide gauges with long-term records around the coasts of the United Kingdom and Ireland but also some 385 gauges established at different epochs and for different observation spans by the U. K. Admiralty. All tide gauge data were brought into a common reference frame by a combination of datum models and direct GPS observations, but a more significant challenge was to bring all short-term sea level observations to an unbiased value at a common epoch. This was achieved through developing a spatial-temporal correlation model for the variations in mean sea level around the British Isles, which in turn meant that gauges with long-term observation spans could be used as control points to improve the accuracy of Admiralty gauges. It is demonstrated that the latter can contribute point observations of mean sea level (MSL) with a precision of 0.078 m. A combination of least squares collocation and interpolation was developed to merge the coastal point and offshore gridded data sets, with particular algorithms having to be developed for different configurations of coastal topology. The resulting model of sea surface topography is shown to present a smooth transition from inshore coastal areas to offshore zones. Further benefits of the techniques developed include an enhanced methodology for detecting datum discontinuities at permanent tide gauges.     

Assessment of the impact of the planetary scale on the decay of blocking and the use of phase diagrams and enstrophy as a diagnostic

It was shown that abrupt changes in the large-scale structure of atmospheric flows may lead to the rapid decay of blocking. Analysis of phase diagrams made it possible to identify when sharp changes occurred in the dynamics of the system. The connection of these changes to the decay of blocking was estimated for three blocking events in the Southern Hemisphere. In addition to phase diagrams, enstrophy was used as a diagnostic tool for the analysis of blocking events. From the results of this analysis, four scenarios for the decay mechanisms were determined: (i) decay with a lack of synoptic-scale support, (ii) decay with an active role for synoptic processes, and (iii–iv) either of these mechanisms in the interaction with an abrupt change in the character of the planetary-scale flow.     

Controls on crustal accretion along the back-arc East Scotia Ridge: constraints from bathymetry and gravity data

This study investigates crustal accretion processes along the East Scotia Ridge (ESR), an intermediate-rate back-arc spreading center with ten segments (E1–E10) that strike north–south. Mantle Bouguer anomaly (MBA) was calculated for the ESR region using satellite-derived and shipboard data sources. De-trended MBA (MBA_det) was determined by removing a residual plane from the MBA map, and ΔMBA_det was defined as the along-segment change in MBA_det. ΔMBA_det, as well as segment-averaged values of Na₈, Fe₈, and ⁸⁷Sr/⁸⁶Sr obtained from the published literature, generally appear to be better correlated with dist_sst (the distance from each segment center to the nearest point on the South Sandwich Trench) than with spreading rate. For each of the northern segments E2 through E6, MBA_det has a central low. MBA_det values also form a broad, longer-wavelength low from segments E2 through E6. Generally speaking, these findings are consistent with earlier studies such as Livermore et al. (Earth Planet Sci Lett 150:261–275, 1997) in suggesting that the region around segment E2 is a center for focused accretion along the ESR. On the other hand, southern segments E7 and E8 have central MBA_det highs, and MBA_det decreases somewhat linearly from segment E7 to E9, notwithstanding intrasegment variations. The quasi-linear MBA_det trend along these ESR segments is similar to that observed for the southernmost Lau spreading centers (e.g., Martinez and Taylor in Nature 416:417–420, 2002). Overall, plate boundary geometry and three-dimensional mantle flow may play a significant role in melting processes along the ESR, especially if the spreading center is processing geochemically heterogeneous South Atlantic mantle.     

Offshore wind capital cost estimation in the U.S. Outer Continental Shelf—A reference class approach

Offshore wind power developed rapidly in Northern Europe in the first decade of the 21st century and is expected to spread to Southern Europe, North America and Asia before 2020. To date, no projects have been built offshore North America because of the high development costs and economic risk and uncertain profitability. The purpose of this paper is to review the development cost of constructing offshore wind farms to inform the U.S. market. The capital expenditures of a reference class of 18 European wind farms constructed after 2005 with monopile foundations are normalized to proxy U.S. capital cost. Regression models are developed to investigate the physical features that influence expenditures. U.S. capital costs are expected to range between $4 and $5.6 million/MW for projects built between 2012 and 2015. Capital costs increase with increasing water depth and steel prices. For most farm components, capital expenditures are expected to be similar in Europe and the U.S., but the installation markets differ and this may impact the reliability of the reference class approach.     

A tool for site prioritisation of marine protected areas under data poor conditions

A challenge of managing data poor fisheries lies in overcoming uncertainties associated with a lack of information on biological and socio-economic conditions. This paper focuses on site prioritisation for marine protected areas, a process that usually imposes moderate to heavy demands on data, time, local expertise, and funds. A fuzzy logic decision support tool for zoning marine areas that is suitable for use in data poor conditions is developed. This tool, the Protected Area Suitability Index (PASI), assesses the suitability of sites for protection based on fishers’ preferences for that site and the site’s conservation value. Only eight input attributes are required to run the PASI, which operates on a series of heuristic rules to estimate a site suitability score that ranges from 0 to 10, where 10 indicates that a site is highly suitable for being protected from fishing. Sensitivity analysis reveals that the PASI is relatively robust, and produces reliable results even as the system is degraded by the loss of data. Eighteen actively fished sites and 11 sites that are closed to fishing are assessed to evaluate how well the PASI is able to distinguish differences between sites. The estimated scores are significantly different (p<0.05), whereby non-fished sites are scored as being more suitable for protection than fished sites. The PASI can be used as a decision support tool to facilitate systematic marine spatial management under data poor conditions, especially in the task of identifying suitable sites for protection.     

Age and growth of the elephant fish. callorhinchus milii (Elasmobranchii: Callorhynchidae)

A method of aging the elephant fish Callorhinchus milii Bory de St Vincent 1823, is described. Alternating light and dark layers, seen in cross‐sections of the dorsal spine, are assumed to be laid down annually as in other fish. Ages obtained from spine sections are identical with ages obtained from interpretation of modal peaks in the length‐frequency graphs. Males mature at 3 y old, at approximately 50 cm fork length; females at 4.5 y old and 70 cm. The significance of this in relation to the New Zealand fishery for elephant fish is discussed.     

Further birth records of elephant seals Mirounga leonina in New Zealand (note)

The second and third recorded births of southern elephant seals Mirounga leonina on the mainland of New Zealand occurred at Kaikoura in mid‐October 1976. One female pup died within 14 d of birth and the other (sex unknown) disappeared from the region with its mother on 19 November 1976.     

Depth of settlement of two mussel species on suspended collectors in Marlborough Sounds,New Zealand (Note)

The preferred depth of settlement and settlement period of two species of mussel spat were monitored at Yncyca Bay (NZMS1 S15 220460) and Wet Inlet (NZMS1 S16 265432) in the Marlborough Sounds on collectors suspended in 0–4 m of water between 20 October 1975 and 4 April 1976. Peak settlement of Mytilus edulis aoteanus was between 20 October 1975 and 4 January 1976, and decreased with increasing depth. Peak settlement of Perna canaliculus was between 16 February 1976 and 12 April 1976, and showed no preferred depth of settlement.

Capture of wild stocks of Mytilus edulis aoteanus and Perna canaliculus spat for use in aquaculture has become more reliable through accurate forecasting of peak settlement periods, and knowledge of preferred depth of settlement of the two species.

Preferred depth of settlement of spat may affect the shore zonation of mussels.     

Hooker's sea lions in southern New Zealand

The discovery at Stewart Island of a hauling‐out ground regularly used by Hooker's sea lions (Phocarctos hooked) is described, and recent sightings of sea lions in southern New Zealand are reported. An attempted copulation between a male Hooker's sea lion and a dead female fur seal (Arctocephalus forsteri) is also described.