Ocean Offshore Research Articles

Nearshore and offshore co-occurrence of marine heatwaves and cold-spells

A changing global climate places shallow water ecosystems at more risk than those in the open ocean as their temperatures may change more rapidly and dramatically. To this end, it is necessary to identify the occurrence of extreme ocean temperature events – marine heatwaves (MHWs) and marine cold-spells (MCSs) – in the nearshore (<400m from the coastline) environment as they can have lasting ecological effects. The occurrence of MHWs have been investigated regionally, but no investigations of MCSs have yet to be carried out. A recently developed framework that defines these events in a novel way was applied to ocean temperature time series from (i) a nearshore in situ dataset and (ii) 14° NOAA Optimally Interpolated sea surface temperatures. Regional drivers due to nearshore influences (local-scale) and the forcing of two offshore ocean currents (broad-scale) on MHWs and MCSs were taken into account when the events detected in these two datasets were used to infer the links between offshore and nearshore temperatures in time and space. We show that MHWs and MCSs occur at least once a year on average but that proportions of co-occurrence of events between the broad- and local scales are low (0.20–0.50), with MHWs having greater proportions of co-occurrence than MCSs. The low rates of co-occurrence between the nearshore and offshore datasets show that drivers other than mesoscale ocean temperatures play a role in the occurrence of at least half of nearshore events. Significant differences in the duration and intensity of events between different coastal sections may be attributed to the effects of the interaction of oceanographic processes offshore, as well as with local features of the coast. The decadal trends in the occurrence of MHWs and MCSs in the offshore dataset show that generally MHWs are increasing there while MCSs are decreasing. This study represents an important first step in the analysis of the dynamics of events in nearshore environments, and their relationship with broad-scale influences.

A Zona de Convergência do Atlântico Sul: uma visão e revisão críticas

A Zona de Convergência do Atlântico Sul (ZCAS) é uma alongada e persistente banda de intensa convecção que na época de verão e com certa frequência se estende da Amazônia ao oceano ao largo das costas brasileiras, exercendo papel significativo no regime pluviométrico do País. Juntamente com suas congêneres do Pacífico e do Índico, constitui uma nova categoria de organismo meteorológico de larga escala, identificado a partir da década de 1970 através da análise de observações de satélite. A explicação do fenômeno é ainda um desafio para a meteorologia e climatologia; essencialmente, resulta de uma intensa interação entre sistemas tropicais e de latitude média. Neste trabalho, recapitulamos uma parte da evolução histórica dos conhecimentos sobre o assunto, incluindo, além das contribuições de pesquisadores brasileiros, os providenciais estudos japoneses comparando a ZCAS com a Baiu, e apresentamos descrições resumidas de eventos de ZCAS no Brasil. Como complemento, reportamo-nos a dois eventos de precipitações destrutivas no Estado de São Paulo, de natureza frontal, a comparar com a atuação da ZCAS.

Understanding the nature of atmospheric acid processing of mineral dusts in supplying bioavailable phosphorus to the oceans.

Acidification of airborne dust particles can dramatically increase the amount of bioavailable phosphorus (P) deposited on the surface ocean. Experiments were conducted to simulate atmospheric processes and determine the dissolution behavior of P compounds in dust and dust precursor soils. Acid dissolution occurs rapidly (seconds to minutes) and is controlled by the amount of H+ ions present. For H+ < 10-4 mol/g of dust, 1-10% of the total P is dissolved, largely as a result of dissolution of surface-bound forms. At H+ > 10-4 mol/g of dust, the amount of P (and calcium) released has a direct proportionality to the amount of H+ consumed until all inorganic P minerals are exhausted and the final pH remains acidic. Once dissolved, P will stay in solution due to slow precipitation kinetics. Dissolution of apatite-P (Ap-P), the major mineral phase in dust (79-96%), occurs whether calcium carbonate (calcite) is present or not, although the increase in dissolved P is greater if calcite is absent or if the particles are externally mixed. The system was modeled adequately as a simple mixture of Ap-P and calcite. P dissolves readily by acid processes in the atmosphere in contrast to iron, which dissolves more slowly and is subject to reprecipitation at cloud water pH. We show that acidification can increase bioavailable P deposition over large areas of the globe, and may explain much of the previously observed patterns of variability in leachable P in oceanic areas where primary productivity is limited by this nutrient (e.g., Mediterranean).

Precessional control on ocean productivity in the Western Pacific Warm Pool for the last 400 kyr: Insight from biogenic magnetite

AbstractsThe Western Pacific Warm Pool plays a significant role in large‐scale atmospheric circulation and global hydrology. We conducted an environmental magnetic study of two late Pleistocene sediment cores from the western equatorial Pacific Ocean offshore of New Guinea in order to better constrain climatic and oceanographic variability, particularly spatiotemporal ocean productivity variations. Magnetic property measurements and transmission electron microscopy reveal that the magnetic mineral assemblages in the studied sediments are a mixture of biogenic and terrigenous magnetite. Variations in the acid soluble sediment component, interpreted as carbonate content, and the proportion of biogenic to terrigenous magnetite estimated from the ratio of anhysteretic to saturation remanent magnetizations are in‐phase with northern hemisphere summer insolation variations. We interpret that ocean productivity increased during insolation maxima, which induced higher populations of magnetotactic bacteria through a larger nutrient supply to the seafloor. This interpretation assumes that magnetotactic bacterial populations are greatest in sediments just below the seafloor. Precessional frequencies in magnetic mineral concentration variations are suppressed after correction for carbonate dilution, whereas cyclic changes with a ∼100 kyr periodicity remain in carbonate‐free magnetic concentration variations. Glacial/interglacial changes in bottom water currents may have influenced transportation and deposition of magnetic minerals. We demonstrate the usefulness of magnetic proxies for paleoceanographic studies, particularly of biogenic magnetite proxies for estimating paleoproductivity variations.

Late Quaternary fingerprints of precession and sea level variation over the past 35 kyr as revealed by sea surface temperature and upwelling records from the Indian Ocean near southernmost Sumatra

Abstract We report high-resolution paleoclimatic reconstructions using isotope, alkenone sea surface temperature (SST), productivity, and terrigenous proxy variations over the past 35 kyr from core SO184-10043 (07°18.57′S, 105°03.53′E) in the eastern tropical Indian Ocean offshore of southernmost (S) Sumatra. The core was retrieved at 2171 m water depth, from the monsoon driven seasonal upwelling area off southernmost Sumatra. Our paleoclimatic reconstructions show that an enhanced marine productivity was closely linked to strengthening of coastal upwelling during the increases of boreal summer insolation and associated southeastern (SE) monsoon strength, with pronounced semi-precession cycles (∼11 kyr). In contrast, our record of alkenone SSTs shows glacial to interglacial, a sea-level variation, but this fluctuates at dominant precession cycles (∼21 kyr). We also observed four SST “plateaus” with relatively warmer hydrographic stability in our records over the past 35 kyr: 32-27 ka, 24-20 ka, 17-12 ka, and 9-4 ka. The time scale of each plateau is ∼4-6 kyr. Our study indicates that since the last glacial maximum (LGM), the sea level rise has been responsible for the Sunda shelf flooding and the Indonesian Throughflow (ITF) from the South China Sea (SCS) to the eastern Indian Ocean, leaving a dominant fingerprint of a glacial to interglacial increase in SSTs since ∼9.5 ka We further argue that the a most recent centennial to millennial scale cooling at ∼3.5 ka observed in our SST record is a widespread event in the tropical Pacific, which has implications for advancing our understanding of the climate dynamics of the tropical oceans at these time scales.

Drivers of spring and summer variability in the coastal ocean offshore of Cape Cod, MA

AbstractThe drivers of spring and summer variability within the coastal ocean east of Cape Cod, Massachusetts, a critical link between the Gulf of Maine and Mid‐Atlantic Bight, are investigated using 2 years of shipboard and moored hydrographic and velocity observations from 2010 and 2011. The observations reveal sharp differences in the spring transition and along‐shelf circulation due to variable freshwater and meteorological forcing, along with along‐shelf pressure gradients. The role of the along‐shelf pressure gradient is inferred using in situ observations of turbulent momentum flux, or Reynolds stresses, estimated from the ADCP‐based velocities using recently developed methods and an inversion of the along‐shelf momentum balance. During spring, the locally relevant along‐shelf pressure gradient contains a sizable component that is not coupled to the along‐shelf winds and often opposes the regional sea level gradient. Together with the winds, local pressure gradients dominate along‐shelf transport variability during spring, while density‐driven geostrophic flows appear to match the contribution of the local winds during summer. These results suggest that local effects along the Outer Cape have the potential to cause significant changes in exchange between the basins.

Stirring by deep cyclones and the evolution of Denmark strait overflow water observed at line W

Shipboard velocity and water property data from 18 transects across the North Atlantic Deep Western Boundary Current (DWBC) near 40 °N are examined to study the evolution of the Denmark Strait Overflow Water (DSOW) component of the DWBC and mixing between DSOW and the interior. The examined transects along Line W – which stretches from the continental shelf south of New England to Bermuda – were made between 1994 and 2014. The shipboard data comprise measurements at regular stations of velocity from lowered acoustic Doppler current profilers, CTD profiles and trace gas chlorofluorocarbon (CFC) concentrations from bottle samples at discrete depths. Comparison of the Line W velocity sections with concurrent sea surface height maps from satellite altimetry indicates that large cyclones in the deep ocean accompany intermittent quasi-stationary meander troughs in the Gulf Stream path at Line W. A composite of 5 velocity sections along Line W suggests that a typical cyclone reaches swirl speeds of greater than 30cms−1 at 3400-m depth and has a radius (distance between the center and the maximum velocity) of 75km. Tracer data suggest that these cyclones affect not only the deep velocity structure along Line W, but also provide a mechanism for water exchange between the DWBC's DSOW and the interior. Vigorous exchange is corroborated by a mismatch in the CFC-11:CFC-12 and CFC-113:CFC-12 ratio ages calculated for DSOW at Line W. During the most recent 5-year period (2010–2014), a decrease in DSOW density has been driven by warming (increasing by almost 0.1°C) as salinity has increased only slightly (by 0.003, which is close to the 0.002 uncertainty of the measurements). The abyssal ocean offshore of the DWBC and Gulf Stream and deeper than 3000-m depth has freshened at a rate of 6×10−4yr−1 since at least 2003. Density here remains nearly unchanged over this period, due to temperature compensation, though a linear cooling trend in the abyssal ocean (to compensate the freshening) is not statistically significant.

Cross-shelf exchanges between the Coral Sea and the Great Barrier Reef lagoon determined from a regional-scale numerical model

Analyses of the variability in a 3.5-year run of a hydrodynamic model developed for simulating the circulation of the Great Barrier Reef (GBR) are presented. Sea-surface temperature, salinity, currents and cross-shelf transports between the GBR lagoon and the deep ocean offshore are investigated and compare well to available observations. Water mass intrusions and flushing events are critical factors in determining the health of coral reef and continental shelf ecosystems. Results from tracer release experiments provide a synoptic view of the variability of residence times within the GBR and identify critical regions of shelf-ocean exchange. One such region of significant tracer contribution to the shelf is identified in the vicinity of the Pompey Reefs in an area characterised by increased frequency of upslope transported water. Another location of enhanced flux on to the shelf exists in the region bracketing Palm Passage, where the reef matrix is very open, and provides little obstacle to cross-shelf exchange. The Palm Passage location is the origin of a northwards plume of elevated concentration. The model circulation provides a robust and useful picture of the Great Barrier Reef, rendering the model suitable for providing input to biogeochemical and sediment models to simulate, at a broad scale, the ecosystem health, water quality, transport and fate of water and waterborne material, moving through catchments and into the GBR lagoon.

Main eddy vertical structures observed in the four major Eastern Boundary Upwelling Systems

AbstractIn the four major Eastern Boundary Upwelling Systems (EBUS), mesoscale eddies are known to modulate the biological productivity and transport near‐coastal seawater properties toward the offshore ocean, however little is known about their main characteristics and vertical structure. This study combines 10 years of satellite‐altimetry data and Argo float profiles of temperature and salinity, and our main goals are (i) to describe the main surface characteristics of long‐lived eddies formed in each EBUS and their evolution, and (ii) to depict the main vertical structure of the eddy‐types that coexist in these regions. A clustering analysis of the Argo profiles surfacing within the long‐lived eddies of each EBUS allows us to determine the proportion of surface and subsurface‐intensified eddies in each region, and to describe their vertical structure in terms of temperature, salinity and dynamic height anomalies. In the Peru‐Chile Upwelling System, 55% of the sampled anticyclonic eddies (AEs) have subsurface‐intensified maximum temperature and salinity anomalies below the seasonal pycnocline, whereas 88% of the cyclonic eddies (CEs) are surface‐intensified. In the California Upwelling System, only 30% of the AEs are subsurface‐intensified and all of the CEs show maximum anomalies above the pycnocline. In the Canary Upwelling System, ∼40% of the AEs and ∼60% of the CEs are subsurface‐intensified with maximum anomalies extending down to 800 m depth. Finally, the Benguela Upwelling System tends to generate ∼40–50% of weak surface‐intensified eddies and ∼50–60% of much stronger subsurface‐intensified eddies with a clear geographical distribution. The mechanisms involved in the observed eddy vertical shapes are discussed.

Long‐period ground motion simulation of a subduction earthquake using the offshore‐onshore ambient seismic field

AbstractLarge earthquakes that occur in subduction zones are likely to generate long‐period ground motions that can cause severe damage even at great distances from the epicenter. We extracted surface‐to‐surface impulse response functions from the ambient seismic field recorded by offshore ocean bottom seismometers located atop the Nankai subduction zone and onshore stations. We showed that these offshore‐onshore impulse response functions can be used to accurately simulate the long‐period ground motions generated by an offshore moderate subduction earthquake. Moreover, we also found that the distributions of the earthquake and impulse response function pseudovelocity response spectra have similar maximum amplifications in the same area close to the earthquake epicenter. This suggests that the ambient seismic field recorded by the increasing number of ocean bottom seismometers around the world can be used to assess seismic hazard related to offshore subduction earthquakes without prior knowledge of the velocity structure.

Spinning in different directions: western rock lobster larval condition varies with eddy polarity, but does their diet?

Larvae of the western rock lobster (Panulirus cygnus) that occur in the south-east Indian Ocean offshore of Western Australia have been found to be in poorer nutritional condition in anticyclonic compared with cyclonic mesoscale eddies. The reason for this is unknown, but culture-based experiments have shown that diet composition and water temperature are key determinants of phyllosoma health and survival. Whether differences in prey composition are the cause of poor phyllosoma condition in situ was tested in the present study by high-throughput sequencing of 18S rDNA amplified from the gut contents of 48 lobster larvae from two cyclonic and two anticyclonic eddies. We determined that phyllosoma prey composition did not vary significantly between anticyclonic and cyclonic eddies and that any variation was at the level of sample site (permutational multivariate analysis of variance F2,35 = 5.12, P < 0.0001). We therefore reject the hypothesis that prey composition alone during the late larval phase determines larval condition. This indicates that the competing hypotheses are more likely: for example, that eddy water temperature is responsible for reducing the condition of phyllosomas directly, or indirectly by impoverishing the nutritional value of their foodweb.

Routing Protocols in Underwater Acoustic Sensor Networks: A Quantitative Comparison

Underwater Acoustic Sensor Networks (UASNs) have drawn great attention for their potential value in ocean monitoring and offshore exploration. In order to make the underwater application possible, the unique characteristics of underwater acoustic channels and continuous node movement inspired the emergence of routing protocols for underwater environment. In this paper, we introduce and compare four prominent routing protocols proposed for UASNs, namely, H2-DAB, GEDAR, E-PULRP, and PER. Performances of the routing protocols are evaluated in terms of the average number of control packets, end-to-end delay, data delivery ratio, and total energy consumption. The impact of water currents on the routing algorithms is also analyzed in our simulation. Experimental results demonstrate that E-PULRP provides high data delivery ratio at the cost of end-to-end delay. H2-DAB has better real-time performance for minimal delay transmission. GEDAR efficiently addresses the problem of void region without introducing extra energy. PER requires the most control packets in the process of routing establishment. Our work aims to provide useful insights to select appropriate routing protocols to fulfil different application requirements in UASNs.

One-year, regional-scale simulation of &amp;lt;sup&amp;gt;137&amp;lt;/sup&amp;gt;Cs radioactivity in the ocean following the Fukushima Dai-ichi Nuclear Power Plant accident

Abstract. A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant following the Great East Japan Earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean by two major pathways: direct release from the accident site and atmospheric deposition. A 1 yr, regional-scale simulation of 137Cs activity in the ocean offshore of Fukushima was carried out, the sources of radioactivity being direct release, atmospheric deposition, and the inflow of 137Cs deposited into the ocean by atmospheric deposition outside the domain of the model. Direct releases of 137Cs were estimated for 1 yr after the accident by comparing simulated results and measured activities adjacent to the accident site. The contributions of each source were estimated by analysis of 131I/137Cs and 134Cs/137Cs activity ratios and comparisons between simulated results and measured activities of 137Cs. The estimated total amounts of directly released 131I, 137Cs, and 137Cs were 11.1 ± 2.2 PBq, 3.5 ± 0.7 PBq, and 3.6 ± 0.7 PBq, respectively. Simulated 137Cs activities attributable to direct release were in good agreement with measured 137Cs activities not only adjacent to the accident site, but also in a wide area in the model domain, therefore this implies that the estimated direct release rate was reasonable. Employment of improved nudging data by JCOPE2 improved both the offshore transport result and the reproducibility of 137Cs activities 30 km offshore. On the other hand, simulated 137Cs activities attributable to atmospheric deposition were low compared to measured activities. The rate of atmospheric deposition into the ocean was underestimated because of a lack of measurements of deposition into the ocean when atmospheric deposition rates were being estimated. Simulated 137Cs activities attributable to the inflow of 137Cs deposited into the ocean outside the domain of the model were in good agreement with measured activities in the open ocean within the model domain after June 2012. The consideration of inflow is important to simulate the 137Cs activity in this model region in the later period of the simulation. The contribution of inflow increased with time and was dominant (more than 99%) by the end of February 2012. The activity of directly released 137Cs, however, decreased exponentially with time and was detectable only in the coastal zone by the end of February 2012.

Comparison of organic (UK'37, TEXH86, LDI) and faunal proxies (foraminiferal assemblages) for reconstruction of late Quaternary sea surface temperature variability from offshore southeastern Australia

Several proxies have been developed to reconstruct past sea surface temperature (SST), but different proxies may reflect temperatures of different seasons and each proxy is characterized by certain uncertainties. Therefore, a multiproxy approach is preferred to precisely reconstruct SST. Here, we reconstruct SST of the ocean offshore southeastern Australia (Murray Canyons area) for the last ~135 ka using three independent organic proxies (TEXH86 based on glycerol dialkyl glycerol tetraethers (GDGTs), UK'37 based on alkenones, and LDI based on long‐chain diols) in addition to foraminiferal faunal assemblages. The organic proxy records show similar trends, with the highest temperature (21°C for UK'37 and TEXH86, and 25°C for LDI) during the last interglacial and lowest temperature (8°C for TEXH86, 10°C for UK'37, and 12°C for LDI) during the Last Glacial Maximum. However, the differences in absolute SST estimates obtained by the organic proxies varied over time with differences of up to 9°C between LDI and TEXH86. The seasonal SST reconstructions based on the modern analogue of foraminiferal assemblages also show similar trends as the organic proxies with highest temperatures during the last interglacial (23°C for the warmest month SST, 20°C for mean annual, and 18°C for the coolest month) and lowest temperature during the Last Glacial Maximum (14°C for the warmest month, 11°C for mean annual, and 9°C for the coolest month). Down core comparison between the reconstructed SSTs of the organic and inorganic proxies shows that LDI‐inferred temperatures compare well with the temperature of the warmest month, TEXH86 with the temperature of the coolest month, and UK'37 with mean annual temperature. An increase in TEXH86 SST estimates relative to those of other proxies during deglaciations and interglacials suggests that either winter temperatures rapidly warmed, possibly due to an invigoration of the Leeuwin Current over the core site, or there was a change in the growth season of the Thaumarchaeota, the source organism of GDGTs. Our study shows the benefits of a multiproxy approach in the interpretation of SST proxies, leading to a more robust knowledge of past ocean temperature changes.

Technical feasibility of using gallery intakes for seawater RO facilities, northern Red Sea coast of Saudi Arabia: the King Abdullah Economic City site

The Kingdom of Saudi Arabia is dependent on desalination of seawater to provide new water supplies for the future. Desalination is expensive and it is very important to reduce the cost and lower the energy consumption. Most seawater reverse osmosis facilities use open-ocean intakes, which require extensive pretreatment processes to remove particulate and biological materials that cause operating problems such as membrane fouling or shutdown during algal blooms. Subsurface systems, using the concept of riverbank filtration, can be used as intakes. These systems include wells of various designs and galleries that provide natural filtration and biological treatment to improve the quality of feed water before it enters the desalination plant. This reduces operating cost, lowers chemical and energy consumption, and reduces environmental impacts. Technical feasibility of gallery-type intakes, beach and seabed types, for use as intakes to seawater reverse osmosis (RO) facilities was evaluated along the northern Red Sea shoreline of Saudi Arabia. The geological characteristics of the offshore ocean bottom were found to be favorable for the development of seabed gallery systems, but the shoreline geology was not adequate for the development of beach gallery intakes. One of the potentially favorable sites for a seabed gallery system was located in the nearshore area at King Abdullah Economic City (KAEC). Detailed investigation of the site hydrology (tides and wave action), sediment grain size characteristics, and sediment hydraulic conductivity, and access for construction were assessed. It was determined that seabed gallery development is favorable at the site. Based on the seawater that has a salinity of about 41,000 mg/L and a conversion rate of 40%, a conservatively designed gallery cell with dimensions of 100 by 50 m would produce about 25,000 m3/day of filtered seawater and seven cells (6 primary and 1 standby) could support a 60,000 m3/day (permeate) seawater RO plant.

係留浮体の波浪中応答解析に対するMPS法の適用性に関する研究（第二報）

For advancing ocean development, it is important to estimate response of moored floating structures in order to ensure the safety because they are placed on severe environment for a long time. Moored floating structures show complex motion at offshore ocean. The moving particle simulation (MPS) method is suitable to simulate the non-linear phenomena and the interaction of fluid and structures. In this study a improved MPS method which has an algorithm to solve pressure oscillation of particles and attenuation of wave height has been developed. The authors examined the applicability of the two-dimensional MPS method to response analysis of moored floating structure in regular waves. The numerical results have good agreement with laboratory data in term of time histories, spectra and frequency response, and the allow ability of the improved MPS method is indicated.

Submarine melt rate estimates for floating termini of Greenland outlet glaciers (2000–2010)

AbstractThe rate of mass loss from the Greenland ice sheet has increased over the past decade due, in large part, to changes in marine-terminating outlet glacier dynamics. These changes are attributed to increased submarine melt rates of floating ice tongues and submerged calving faces resulting from increased coastal ocean heat transport. We use remotely sensed data to calculate submarine melt rates for 13 marine-terminating outlet glaciers in Greenland on a semi-annual basis between 2000 and 2010. We assess temporal and spatial variability in the calculated submarine melt rates and compare those variabilities to concurrent glacier change and offshore ocean temperatures. Over the period of study, average melt rates ranged from 0.03 to 2.98 m d−1 and account for 5–85% of the total volume loss from the floating ice tongue, with no clear spatial pattern. Only four glaciers show substantial interannual variability in melt rate during the decade. Melt rates were uncorrelated with front retreat, speed and changes in ocean temperature. Although the small sample size limits our analysis of the relationship between oceanographic forcing and glacier response, these data suggest that the calving rate may vary with discharge but that submarine melt rates are independent of grounding line discharge.

Technology Focus: Offshore Drilling and Completion (April 2012)

Technology Focus In the 2 years since the Macondo incident, we have seen a lot of action toward new regulations, procedures, and norms to be implemented in an attempt to reduce the risks of those tragic events happening again. But the industry did not stop working; wells were drilled and completed, even in the Gulf of Mexico after the long period of inactivity. As expected, we saw a big focus on subsea-equipment testing and procedures and on needed equipment improvements. But we also saw many reports highlighting improved operational performance, confirming that the industry continues with significant activity. We should work proactively with the public and regulators to bring a framework that will lead to a safer environment for everyone. And we should not be happy with just more paperwork that may not bring needed effective improvement. For obvious reasons, the first step has been focused on the equipment responsible for providing the last barrier of protection, the blowout preventer (BOP). One paper describes BOP upgrades, and another one discusses software-based deepwater-BOP testing. We all must recognize that there has not been a significant advance in terms of BOP testing in the last 30 years. We are still relying, most of the time, on the old paper disks to record tests and on forms filled in by hand to confirm the pressure and duration of the tests prepared on each component tested. We should do much better than that. The third paper highlights the drilling campaign in a promising offshore area in Brazil. But do not forget the underground blowout that leaked oil into the ocean offshore Brazil a few months ago, reminding us that continuous improvement of all offshore operations must take place. The alternative is that we again will face setbacks like those in the Gulf of Mexico after the Macondo accident. Recommended additional reading at OnePetro: www.onepetro.org. IPTC 14868 RasGas Rigless Drift Experience: New Technology and Evolving Best Practice—North Field, Qatar by Russell R. Van Nuis, RasGas Company, et al. OTC 21925 Large-Bore Expandable Liner Hangers Significantly Improve Operational Cost in a Deepwater Gulf of Mexico Well by Michael Johnson, Halliburton, et al. SPE 145876 Temporary Storm/Cyclone Well Suspension Using Inflatable-Packer Systems by Colin Ingram, SPE, TAM International

Comparison of Fault Detection Techniques for an Ocean Turbine

The Southeast National Marine Renewable Energy Center at Florida Atlantic University, which supersedes the Center for Ocean Energy Technology (Driscoll et al., 2008), is conducting research and development to support the implementation of ocean current and ocean thermal energy technologies for a low environmental-impact extraction of energy. Fault detection capability is needed for these offshore ocean turbines (and other systems) because access to these machines for maintenance is difficult and costly. Techniques that offer reliable and early (incipient) detection allow for preventive maintenance to prevent the development of secondary faults that may be generated by the primary faults. Several methods for processing and displaying vibration data are compared and evaluated relative to synergistic detection utilizing data from a prototype (dynamometer) of an ocean current turbine. The results may generically apply to other machines, such as wind turbines.

Transport of reef lizardfish larvae by an ocean eddy in Hawaiian waters

Competent (settlement-stage) larvae of the lizardfish, Trachinocephalus myops were collected from one ocean location (near a coral reef) at times before and during a mesoscale ocean eddy event. Mesoscale ocean eddies occur periodically at this location, offshore of the island of Hawaii. Larval age was younger ( t-test, P < 0.0001) for lizardfish collected at the time when a cyclonic mesoscale eddy dominated the offshore ocean flow field. This result supports two important notions: (1) that reef fish larvae have flexibility in the age at which they can transition to the reef habitat and (2) that offshore deep-sea ocean currents can be influential in larval reef fish recruitment.