Operating an Acoustic Doppler Current Profiler aboard a Container Vessel

Since October 1992 an acoustic Doppler current profiler (ADCP) has been in near-continuous operation on board a 118-m-long container vessel, the container motor vessel Oleander, which operates on a weekly schedule between Port Elizabeth, New Jersey, and Hamilton, Bermuda. The ADCP collects information on currents from the surface to depths as great as 404 m depending on zooplankton concentrations, ship’s speed, sea state conditions, and the ship’s load factor. The southbound transits provide more and better data because the ship is loaded and rides deeper resulting in less bubble formation and entrainment underneath the vessel. Installation and operation of an ADCP on a cargo ship has involved a number of factors not typical of research vessels. Providing a data acquisition system that could operate on its own without assistance from the ship’s officers and that could recover from problems was the first issue. Isolating and removing electrical transients from the ship’s electrical system was extremely challenging. The presence of bubbles underneath the vessel due to variable draft and in heavy weather conditions significantly limits the performance of the ADCP. These difficulties not withstanding, the system is working well and is delivering good data on the southbound legs in most weather conditions and on the northbound legs under more favorable weather conditions. Starting in 1995, differential and attitudinal global positioning system enhancements have made significant improvements to navigational accuracy and ship’s heading data

Directly Measured Currents and Estimated Transport Pathways of Atlantic Water between 59.5°N and the Iceland–Faroes–Scotland Ridge

Using vessel-mounted acoustic Doppler current profiler data from four different routes between Scotland, Iceland and Greenland, we map out the mean flow of water in the top 400 m of the northeastern North Atlantic. The poleward transport east of the Reykjanes Ridge (RR) decreases from ~8.5 to 10 Sv (1 Sverdrup=106 m3 s−1) at 59.5°N to 61°N to 6 Sv crossing the Iceland–Faroes–Scotland Ridge. The two longest ~1200 km transport integrals have 1.4–0.94 Sv uncertainty, respectively. The overall decrease in transport can in large measure be accounted for by a ~1.5 Sv flow across the RR into the Irminger Sea north of 59.5°N and by a ~0.5 Sv overflow of dense water along the Iceland–Faroes Ridge. A remaining 0.5 Sv flux divergence is at the edge of detectability, but if real could be accounted for through wintertime convection to \u3e400 m and densification of upper ocean water. The topography of the Iceland Basin and the banks west of Scotland play a fundamental role in controlling flow pathways towards and past Iceland, the Faroes and Scotland. Most water flows north unimpeded through the Iceland Basin, some in the centre of the basin along the Maury Channel, and some along Hatton Bank, turning east along the northern slopes of George Bligh Bank, Lousy Bank and Bill Bailey’s Bank, whereupon the flow splits with ~3 Sv turning northwest towards the Iceland–Faroes Ridge and the remainder continuing east towards and north of the Wyville-Thomson Ridge (WTR) to the Scotland slope thereby increasing the Slope Current transport from ~1.5 Sv south of the WTR to 3.5 Sv in the Faroes–Shetland Channel

AXIS—an Autonomous Expendable Instrument System

Author Posting. © American Meteorological Society, 2017. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 34 (2017): 2673-2682, doi:10.1175/JTECH-D-17-0054.1.Expendable bathythermographs (XBT) to profile upper-ocean temperatures from vessels in motion have been in use for some 50 years now. Developed originally for navy use, they were soon adapted by oceanographers to map out upper-ocean thermal structure and its space–-time variability from both research vessels and merchant marine vessels in regular traffic. These activities continue today. This paper describes a new technology—the Autonomous Expendable Instrument System (AXIS)—that has been developed to provide the capability to deploy XBT probes on a predefined schedule, or adaptively in response to specific events without the presence of an observer on board. AXIS is a completely self-contained system that can hold up to 12 expendable probes [XBTs, XCTDs, expendable sound velocimeter (XSV)] in any combination. A single-board Linux computer keeps track of what probes are available, takes commands from ashore via Iridium satellite on what deployment schedule to follow, and records and forwards the probe data immediately with a time stamp and the GPS position. This paper provides a brief overview of its operation, capabilities, and some examples of how it is improving coverage along two lines in the Atlantic.Initial development of AXIS mechanical design elements wasmade possible by awards from the Cecil H. and Ida M. Green Technology Innovation Fund and the Sealark Foundation to the team of Dave Fratantoni, Keith von der Heydt (WHOI), and Terry Hammar (WHOI). Construction of the first full AXIS prototype was supported by a technology grant from the National Science Foundation (OCE-0926853) and the second one through an NSF-funded (OCE-1061185) subcontract from the University of Rhode Island.2018-06-2

Wavenumber Spectrum in the Gulf Stream from Shipboard ADCP Observations and Comparison with Altimetry Measurements

The wavenumber spectra for velocity and temperature in the Gulf Stream region are calculated from a decade (1994–2004) of shipboard acoustic Doppler current profiler (ADCP) measurements taken as part of the Oleander Project. The velocity and temperature spectra have comparable magnitude, in terms of the kinetic and potential energy, and both indicate a k−3 slope in the mesoscales. In contrast, the corresponding velocity spectrum determined from satellite altimetry sea surface heights yields a significantly higher energy level and a k−2 slope. The discrepancy between altimeter-derived and directly measured velocity spectra suggests that altimetric velocity probably is contaminated by noise in sea surface height measurement. Also, the k−3 slope, which appears to be in agreement with two-dimensional quasigeostrophic turbulence theory, does not support the contemporary surface quasigeostrophic theory. These results highlight large gaps in the current understanding of the nature of surface geostrophic turbulence

Oleander is more than a flower twenty-five years of oceanography aboard a merchant vessel

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rossby, T., Flagg, C. N., Donohue, K., Fontana, S., Curry, R., Andres, M., & Forsyth, J. Oleander is more than a flower twenty-five years of oceanography aboard a merchant vessel. Oceanography, 32(3), (2019): 126-137, doi:10.5670/oceanog.2019.319.Since late fall 1992, CMV Oleander III has been measuring upper ocean currents during its weekly trips between Bermuda and Port Elizabeth, New Jersey, by means of an acoustic Doppler current profiler installed in its hull. The overarching objective of this effort has been to monitor transport in the Gulf Stream and surrounding waters. With 25 years of observation in hand, we note that the Gulf Stream exhibits significant year-to-year variations but no evident long-term trend in transport. We show how these data have enabled studies of oceanic variability over a very wide range of scales, from a few kilometers to the full 1,000 km length of its route. We report that the large interannual variations in temperature on the continental shelf are negatively correlated with flow from the Labrador Sea, but that variability in the strength of this flow cannot account for a longer-term warming trend observed on the shelf. Acoustic backscatter data offer a rich trove of information on biomass activities over a wide range of spatial and temporal scales. A peek at the future illustrates how the new and newly equipped Oleander will be able to profile currents to greater depths and thereby contribute to monitoring the strength of the meridional overturning circulation.First and foremost we extend our heartfelt thanks to the Bermuda Container Line/Neptune Group Management Ltd for permission to operate an acoustic Doppler current profiler on board CMV Oleander III, a 150 kHz ADCP between 1992 and 2004, and a 75 kHz ADCP between 2005 and 2018. Their interest and support is gratefully acknowledged. Cor Teeuwen, our initial contact in Holland while the ship was still under construction, played an important role in facilitating the original ADCP installation. His evident interest to make this concept work has stimulated similar activities on other commercial vessels. The interest and willingness of the shipping industry to be supportive of science has been a very positive experience for all of us who have ventured in this direction. Initial funding came from NOAA and the Office of Naval Research. Since 1999, the National Science Foundation has supported the project through funding to the University of Rhode Island and Stony Brook University, and now also to the Bermuda Institute of Ocean Sciences (BIOS), which will be taking over the Oleander operation. NSF is also funding the current transition to the new CMV Oleander. In the early years, G. Schwartze and E. Gottlieb were very helpful with technical support for the project. This included frequent visits to the ship before we had the capability to transfer the data through the Ethernet. We thank Jules Hummon and Eric Firing for adapting the UNOLS-wide UHDAS ADCP operating system to the merchant marine environment. We thank E. Williams and P. Ortner at the Rosenstiel School of Marine and Atmospheric Science, University of Miami, for making the 38 kHz ADCP data from Explorer of the Seas available to us. We also want to thank the NOAA Ship Of Opportunity Program for continued interest in and support of XBT operations along the Oleander section. That support started over 40 years ago and is now stronger than ever. All ADCP data from 1992 through 2018 have been archived at the Joint Archive for Shipboard ADCP (JASADCP), established at the University of Hawaii by NOAA’s National Centers for Environmental Information (NCEI). Averaged yearly data sets can be downloaded in ASCII text or NetCDF formats (http://ilikai.soest.hawaii.edu/​sadcp/main_inv.html). We thank Patrick Caldwell, JASADCP’s manager, for his assistance. All ADCP and XBT data can be obtained at the Stony Brook website: http://po.msrc.sunysb.edu/Oleander/. The URL to the project website is http://oleander.bios.edu—an updated data portal and products will soon be accessible here. An ERDDAP server for Oleander data (in the process of being configured) is at this address: http://erddap.​oleander.​bios.edu:​8080/​erddap/. The following link to BIOS lists over 40 publications that have used the ADCP data one way or another: http://oleander.bios.edu/publications/. We thank the two reviewers for their many interesting and helpful comments and suggestions

Non-resonant dot-cavity coupling and its applications in resonant quantum dot spectroscopy

We present experimental investigations on the non-resonant dot-cavity coupling of a single quantum dot inside a micro-pillar where the dot has been resonantly excited in the s-shell, thereby avoiding the generation of additional charges in the QD and its surrounding. As a direct proof of the pure single dot-cavity system, strong photon anti-bunching is consistently observed in the autocorrelation functions of the QD and the mode emission, as well as in the cross-correlation function between the dot and mode signals. Strong Stokes and anti-Stokes-like emission is observed for energetic QD-mode detunings of up to ~100 times the QD linewidth. Furthermore, we demonstrate that non-resonant dot-cavity coupling can be utilized to directly monitor and study relevant QD s-shell properties like fine-structure splittings, emission saturation and power broadening, as well as photon statistics with negligible background contributions. Our results open a new perspective on the understanding and implementation of dot-cavity systems for single-photon sources, single and multiple quantum dot lasers, semiconductor cavity quantum electrodynamics, and their implementation, e.g. in quantum information technology.Comment: 17 pages, 4 figure

Widely tunable, efficient on-chip single photon sources at telecommunication wavelengths

We demonstrate tunable on-chip single photon sources using the Stark tuning of single quantum dot (QD) excitonic transitions in short photonic crystal waveguides (PhC WGs). The emission of single QDs can be tuned in real-time by 9 nm with an applied bias voltage less than 2V. Due to a reshaped density of optical modes in the PhC WG, a large coupling efficiency \beta>65% to the waveguide mode is maintained across a wavelength range of 5 nm. When the QD is resonant with the Fabry-Perot mode of the PhC WG, a strong enhancement of spontaneous emission is observed leading to a maximum coupling efficiency \beta=88%. These results represent an important step towards the scalable integration of single photon sources in quantum photonic integrated circuits.Comment: 15 pages, 5 figue